ER-000 defines the identity, scope and reading architecture of the ER-001 to ER-200 corpus in its published form. This web hub continues the same numbered Engineering Review sequence through ER-300 and presents ER-001–ER-300 as one continuous current publication map.

Examines how refractive index, transmittance, absorption, surface quality, birefringence and scattering are reported across optical additive-manufacturing studies, and how measurement context affects cross-study comparability.

Keywords: additive manufacturing photopolymers · optical characterisation · refractive index · optical transmittance · reporting practices · cross-study comparability

Examines why working-curve agreement alone does not establish cross-platform process equivalence, organising the discussion around spectral, atmospheric and material-history observation domains and part-level qualification.

Keywords: vat photopolymerization · working curve · cross-platform variability · process equivalence · material qualification · oxygen inhibition · photopolymer cure · additive manufacturing standardisation

Synthesises nanoimprint lithography through three recurring interaction patterns: rheology-compliance during filling, curing-interface coupling during cure and mechanical-energetic coupling during release.

Keywords: nanoimprint lithography · UV-NIL · material-process coupling · demolding mechanics · photopolymer resists · mold materials · interfacial chemistry · anti-stick coatings · microfabrication

Compares spatial selectivity through integrated-dose contrast, chemically gated dual-wavelength coincidence and nonlinear two-photon absorption, linking each mechanism to distinct optical and photochemical constraints.

Keywords: volumetric additive manufacturing · tomographic photopolymerisation · xolography · spatial selectivity · photoswitchable photoinitiator · cumulative exposure · chemical gating · two-photon polymerisation · material development

Synthesises evidence that reported Dp and Ec values depend on source spectrum, irradiance and measurement procedure, and discusses the reporting dimensions needed to interpret and transfer working-curve data.

Keywords: vat photopolymerisation · working curve · Jacobs equation · depth of penetration · critical exposure · interlaboratory variability · spectral bandwidth · reproducibility · characterisation methodology

Reviews biological response as a system-level outcome of formulation chemistry, workflow execution, application context and temporal exposure, with emphasis on residual species, post-cure conversion, extractables and qualification constraints.

Keywords: photopolymer · additive manufacturing · biocompatibility · biological response · dental polymers · orthodontic aligners · denture base · residual monomer · extractables · ISO 10993 · ISO 20795-1 · workflow validation

Compact narrative review of electrically functional VPP materials using the System-Dependent Conductivity Framework to organise chemistry, dispersion, printer optics, exposure, geometry, post-cure and service history.

Keywords: vat photopolymerisation · conductive photopolymer · system-dependent electrical performance · printed electronics · PEDOT:PSS · carbon nanotube composite · electrostatic control · dielectric composite

Proposes a deliberately non-exclusive hypothesis in which negative biodegradation results may reflect intrinsic recalcitrance, specimen geometry, network transport, sample preparation, test conditions or combinations of these factors.

Keywords: photopolymer additive manufacturing · crosslinked thermoset networks · biodegradation testing · structural accessibility · specimen geometry · polymer transport · network deconstruction · enzymatic depolymerisation · OECD 301 · ISO 14855-2

Reviews water-removable sacrificial photopolymers across indirect-manufacturing applications and distinguishes direct molecular dissolution, swelling-dominated removal and hydrolytic disintegration as operational removal pathways.

Keywords: water-removable sacrificial photopolymer · vat photopolymerisation · stereolithography · digital light processing · LCD masked stereolithography · indirect additive manufacturing · photopolymerisation kinetics · polymer dissolution · sacrificial mould · microfluidics

Geometric performance in vat photopolymerisation (VPP) is frequently compressed into terms such as resolution, accuracy and precision even though these descriptors answer different measurement questions. This ambiguity limits comparison across printers, resins, feature scales and studies. This review develops a metrological framework for VPP based on current measurement terminology and additive-manufacturing standards. Resolution is treated as a feature-reproduction capability rather than a synonym for accuracy; accuracy is decomposed into trueness and precision; and realised geometric fidelity is treated as the end result of a multistage chain connecting the digital target, projected optical field, local cure response, layerwise mechanics, post-processing and the measurement system.

Renewable building blocks are increasingly incorporated into photoresins for stereolithography, digital light processing and related vat-photopolymerisation processes. The field is chemically diverse: plant-oil acrylates provide flexible aliphatic segments and adjustable functionality; itaconate polyesters enable systematic control of double-bond density and backbone structure; isosorbide and biomass-derived aromatic units introduce rigidity; lignin-, vanillin-, guaiacol-, cardanol- and rosin-derived structures provide alternative aromatic or polycyclic motifs; and dynamic covalent chemistry adds reprocessability or chemical recovery as an orthogonal network function. Across these families, bio-based content alone does not determine viscosity, cure response, glass-transition temperature, modulus, toughness, resolution or recyclability.

Vat photopolymerisation (VPP) provides a digitally direct route to microfluidic and organ-on-chip (OoC) devices with three-dimensional geometries, rapid design iteration and increasingly accessible equipment. However, the material requirements of OoC systems are substantially more demanding than geometric printability alone. A printed photopolymer may generate fluorescence background, attenuate excitation or emission light, absorb or adsorb test compounds, release residual reactive species, alter oxygen availability, change surface-mediated cell behaviour, or distort the intended channel geometry through cure broadening and trapped-resin effects. This review synthesises primary evidence from VPP microfluidics, cell-culture devices and OoC platforms and organises the field around five qualification domains:

Photopolymer additive manufacturing normally converts a low-viscosity reactive formulation into a permanently crosslinked object. That transformation is advantageous for geometric fidelity and green strength, but it also restricts molecular mobility after cure and can leave layer interfaces, crack surfaces and damaged regions unable to re-establish load-bearing connectivity. A growing literature addresses this limitation through intrinsic dynamic covalent networks, supramolecular interactions, mobile linear-polymer phases, extrinsic healing agents and hybrid elastomer architectures. These approaches are often grouped under the term self-healing even though they solve different problems. Interlayer welding during or after fabrication is not the same experiment as restoring a severed specimen;

Vat photopolymerisation (VPP) enables digitally fabricated polymer parts with controlled geometry, but antimicrobial function introduces an additional set of coupled variables. Metal and metal-oxide fillers can provide ion-mediated or contact-associated activity; covalently incorporated cationic groups can create contact-active surfaces; releasable agents can generate sustained or transient antimicrobial effects; zwitterionic chemistries can reduce fouling without necessarily killing microorganisms; and photosensitising systems can create on-demand activity under a specified illumination protocol. This review organises the field around six qualification questions: what mechanism is intended; what microbial endpoint is measured; whether the activity depends on release; whether the printed state preserves the mechanism;

Vat photopolymerisation enables tissue-engineering scaffolds with designed pore networks, perfusable channels and spatially controlled architectures, but the realised scaffold is governed by coupled material and geometric evolution after printing. Hydration changes dimensions, polymer volume fraction and modulus; molecular transport depends on both intrinsic network mesh size and designed pore connectivity; degradation changes mass, chemistry, pore structure and mechanics; and post-processing establishes the initial crosslink state from which all later behaviour develops. This review organises the evidence around four coupled questions: what is transported, through which length scale; what mechanical function must be retained; what degradation mechanism changes the network; and at what hydrated/degraded state each property is measured.

Electrically functional photopolymers are increasingly used to create geometrically complex components for electronics, sensing and radio-frequency research, but electromagnetic shielding is often inferred too early from conductivity measurements. This Engineering Review separates the formation of a conductive network from the evidence required for an EMI-shielding claim. Shielding effectiveness is treated as a frequency-, thickness-, geometry- and orientation-dependent response measured through transmission/reflection methods rather than as an intrinsic extension of DC conductivity. Published additive-manufacturing studies demonstrate that infill architecture, conductive-filler orientation, cellular geometry and printing direction can materially change shielding behaviour even when feedstock chemistry is unchanged.

Vat photopolymerisation couples liquid photopolymer feedstocks, light-driven conversion, support generation, washing, drying, post-curing and material-management steps that are often omitted or represented inconsistently in environmental assessments. This makes VPP particularly vulnerable to apparently precise but structurally incomparable carbon-footprint results. The present engineering perspective develops a methodology for life-cycle assessment of VPP systems rather than claiming that VPP, bio-based resins or any particular post-processing route is intrinsically sustainable. The framework begins with ISO 14040 and ISO 14044 and incorporates VPP-specific evidence from energy models, reusable unit-process inventories and stereolithography case studies.

Photopolymer formulation is a constrained multi-objective problem in which liquid rheology, cure kinetics, optical attenuation, conversion, dimensional fidelity and final mechanical or functional properties interact. Machine learning can reduce experimental burden, but small datasets, correlated formulation variables, measurement noise and process-dependent labels create substantial risk of overfitting and false optimisation. This review defines an engineering architecture for ML-assisted photoresin development: encode chemically meaningful variables; standardise process and test metadata; use uncertainty to guide experiments; treat feasibility constraints explicitly; optimise Pareto trade-offs rather than a single score; and close the loop with printed validation.

Additive manufacturing enables radiation-functional polymer components with complex geometry, but performance depends on the interaction between active species, polymer optics, filler distribution, cure and geometry. Plastic scintillators require efficient energy transfer and photon collection; photon shields depend on composition, density, thickness and energy spectrum; neutron absorbers require isotope-specific interaction physics and secondary-radiation assessment; dosimetric and radiological phantoms require calibrated response or attenuation; and radiation-hard parts require retained properties after dose. This review organises these functions into separate qualification pathways.

Thermal performance of VPP polymers emerges from network architecture and the cure history imposed by printing, washing and post-curing. HDT, Tg and dynamic-mechanical transitions are related but non-equivalent metrics, and their numerical values depend on test method, applied stress, heating rate, frequency, specimen state and conditioning. Recent work on hot-lithography, heat-assisted VPP, high-viscosity systems and high-Tg interpenetrating networks shows that print temperature and cure strategy can modify conversion, shrinkage, modulus and thermal response.

VPP provides geometric freedom for piezoelectric ceramics and polymer-ceramic composites, but device performance cannot be inferred from filler identity or dielectric permittivity. Ceramic loading affects viscosity, scattering, cure depth and sintering; particle orientation and porosity affect anisotropy; poling determines domain alignment; and electrode, resonance and mechanical boundary conditions determine measured device response. This review develops a qualification framework centred on printable state, polarised state and device state. It separates d33/d31 from permittivity, coupling factor and acoustic response, and requires poling and measurement protocols to be reported explicitly.

VPP has been applied to optical lenses, contact-lens structures, Fresnel optics, gradient-index components and proof-of-concept intraocular-lens geometries. The material requirements differ sharply across these device classes. Optical power depends on geometry and refractive index, while image quality additionally depends on transmission, haze, scatter, surface figure and chromatic dispersion. Contact-lens materials introduce hydration, oxygen transport and surface wetting; intraocular and other implanted optical devices add stringent chemical and biological qualification; all optical polymers require ageing studies because post-cure, water, UV and temperature can change yellowing, transmission and mechanics.

VPP of ceramic-filled resins enables complex zirconia, alumina, hydroxyapatite and related bioceramic geometries, but qualification spans several material states. High-solids slurry must remain printable and homogeneous; the green body must survive cleaning; debinding must remove organics without cracking; sintering must control shrinkage, phase and porosity; and the final ceramic must meet application-specific mechanical, chemical and biological requirements. This review defines a six-state evidence chain from feedstock to final device and separates dense zirconia-type requirements from porous bioactive scaffold requirements.

VPP enables monolithic soft components, complex pneumatic channels and stimuli-responsive architectures, but the relevant material requirements are device-specific. Pneumatic actuators require compliance, tear resistance and low leakage; thermoresponsive or hydrogel actuators additionally require transport kinetics and dimensional stability; self-sensing devices require electrical-mechanical integration; and multi-material robots require durable interfaces between dissimilar networks. This review develops a materials qualification framework based on actuation mode, compliance, fatigue, permeability, hysteresis and interface durability. It separates coupon properties from device outputs and rejects universal bending-angle/pressure maps.

Photopolymer printing plates convert a digital image or pattern into a mechanically loaded transfer surface. This function creates requirements that are not captured by nominal printer resolution, Shore hardness or tensile properties alone. In flexography, a raised relief receives a metered ink film from an anilox roll and transfers it to a substrate under controlled impression; in pad and contact printing, conformity and release govern transfer to flat, curved or microstructured targets; in microcontact printing, stamp deformation, interfacial adhesion and ink mobility can determine the final pattern at micrometre and sub-micrometre scales. This review organises the field around five qualification domains:

Vat photopolymerisation (VPP) can fabricate cellular and TPMS architectures with smooth curved walls, thin features and high geometric complexity. Recent experiments show that the realised mechanical response depends simultaneously on base photopolymer, topology, relative density, number of unit cells, wall-thickness fidelity and loading mode. Large VPP datasets on gyroid lattices further demonstrate that nominal porosity alone does not collapse the response across different photopolymers. This Engineering Review organises the evidence around five distinctions: solid-material state versus architected state; designed versus realised relative density; topology versus scale; tensile versus compressive response; and coupon behaviour versus functional structure.

Vat photopolymerisation converts a spatially patterned light field into a crosslinked network, but the resulting network state is not described completely by cure depth or a pass/fail print. Chemical conversion can vary through thickness, across projected features and during post-cure; different analytical methods also interrogate different volumes and functional groups. Recent DLP research has demonstrated full-field in-situ interferometric monitoring of curing dynamics and has combined interferometry with Raman spectroscopy to relate optical evolution to chemical conversion. This Engineering Review separates five quantities: delivered exposure, geometric solidification, degree of conversion, network/property evolution and residual/leachable chemistry.

Drop-on-demand material jetting converts a liquid photopolymer into a train of discrete droplets before solidification. The governing material state differs sharply from a low-shear benchtop viscosity measurement: the fluid experiences rapid deformation in the nozzle, a newly created interface with microsecond-to-millisecond age, ligament extension, pinch-off, flight, impact and then curing. Recent work with UV-curable acrylate inks shows that high-frequency rheology and dynamic surface tension can be combined with jetting temperature and waveform variables to predict satellite-free operating conditions. This Engineering Review organises those phenomena into a qualification framework spanning material rheology, nozzle/waveform dynamics, droplet breakup, impact/wetting and cure timing.

Two-photon polymerisation (2PP) localises photochemistry within the focal volume of an ultrafast laser, but the eventual polymer voxel is not determined by optics alone. Molecular absorption cross section, excited-state pathways, initiator solubility and efficiency, sensitisation, radical diffusion, oxygen inhibition, resin reactivity and network formation all influence the exposure threshold and the growth of the polymerised region. This Engineering Review develops a material-centred qualification framework separating nonlinear excitation, initiation, polymerisation threshold, voxel growth and final network response.

Competition between radical generation, oxygen transport and radical quenching can alter conversion, cure depth and near-surface mechanical response in vat photopolymerisation. Oxygen-permeable interfaces can also be used deliberately to maintain a liquid region. Filled formulations introduce additional optical, rheological and transport effects. This note maps seven verified sources to a minimum reporting architecture. It does not assign a universal inhibition-zone thickness or infer interface integrity from nominal exposure. The shared evidence-to-decision method is defined in RP-02 and is not reproduced here.

This note distinguishes chemical shrinkage from residual stress and geometry-dependent warpage. Three topical sources support curing-dependent thermoviscoelastic behaviour, grayscale dose-gradient modelling and digital warpage compensation. ISO 291:2008 is identified for conditioning atmosphere, while the exact dimensional, thermal and mechanical methods must be selected for the intended claim. The document is not a quantitative meta-analysis and does not pool values across formulations, machines or geometries. RP-02 defines the shared qualification method.

The retained evidence covers sealed high-temperature storage of a volumetric-additive-manufacturing resin and reincorporation of mechanically recycled cured thermoset into fresh resin. It does not measure light leakage, oxygen ingress, contamination, evaporation, selective depletion or repeated printing in an open vat. Those mechanisms are therefore framed as test requirements, not findings. RP-02 supplies the shared qualification method.

Three topical studies show that postwashing conditions can change residual-monomer elution, degree of conversion, mechanical properties and dimensional or strength outcomes in printed dental materials. They do not establish a universal swelling or drying-gradient model. This note therefore separates evidenced outcomes from qualification requirements. For body-contact articles, chemical characterisation belongs within the applicable biological-evaluation risk process, including ISO 10993-12:2021 with Amendment 1:2025 and ISO 10993-18:2020 with Amendment 1:2022. RP-02 defines the shared qualification method.

Bottom-up vat photopolymerisation requires the newly exposed region to detach from the vat interface without damaging the green part. Recent LCD-VPP studies show that interface flexibility, vat design, surface roughness, temporal irradiance and printing temperature can change separation behaviour. This Engineering Qualification Note maps those topic-specific findings to a minimum reporting set. It is not a quantitative meta-analysis: values from different machines and geometries are not pooled because the source conditions are not interchangeable. The common evidence-to-decision method is defined separately in RP-02.

Critical exposure, Ec, and penetration depth, Dp, are useful working-curve parameters, but their fitted values remain protocol-dependent. This review separates incident and absorbed light, initiating-species formation, inhibitor consumption, functional-group conversion, gelation, dimensional survival and repeated exposure history. It explains why an experimentally fitted Ec need not represent the first molecular initiation event and why a fitted Dp need not be an invariant optical attenuation length. Functionality, reactive-group equivalent weight, viscosity, molecular mobility, oxygen inhibition, photobleaching, absorption, scattering, retained resin and enclosed microfluidic channels are treated as coupled variables.

Primary corpus cluster: Photochemistry, cure-depth interpretation and dimensional verification.

Five verified topical sources address rheology of filled slurries, rheology-linked cure measurement, ultra-high-viscosity VPP, conductive-filler dispersion and optical cure control with photoabsorbing fillers. None directly quantifies sedimentation in an operating photopolymer vat. Sedimentation, stratification and depth-dependent sampling are therefore treated as qualification controls and evidence gaps, not as established quantitative findings. ISO 3219-1:2021 and ISO 3219-2:2021 provide current terminology and general principles for rotational and oscillatory rheometry. RP-02 defines the shared evidence-to-decision method.

Three verified topical studies address rapid debinding of Si3N4 green bodies, cure-depth selection for Al2O3 VPP and pyrolysis-kinetics prediction for ceramic VPP binders. This note maps that evidence to a qualification architecture that retains failed parts and inspects defects before sintering. ISO 11358-1:2022 is identified for general thermogravimetric principles, but the actual formulation, atmosphere, heating rate, gas flow, crucible and sample mass remain part of the result. Generic photopolymer reviews are removed from the topic-specific evidence set. RP-02 defines the shared qualification method.

Three verified topical sources address large-scale VPP master patterns, investment-casting shell/process development and techno-economic comparison of VPP routes. The evidence supports a workflow-level qualification boundary rather than a universal castability claim. Shell composition, thickness and permeability are mapped to the investment-casting review, not to a generic photopolymer source. Thermal analysis is tied to ISO 11358-1:2022 principles and to complete method conditions. The document does not treat an unspecified marketing ash value or a successful print as evidence of casting performance. RP-02 defines the shared qualification method.

This note separates evidence that is present from measurements still required for application release. The cited studies address curing-dependent thermo-viscoelasticity, heat-assisted VPP processing, network development during photopolymerisation and a defined dental fatigue comparison. They do not provide a service-life creep or stress-relaxation dataset for a vat-printed thermoset. Creep and relaxation are therefore treated as qualification requirements and explicit evidence gaps. ISO 899-1:2017, ASTM D2990-17(2025) and, where fibre reinforcement makes it applicable, ISO 13003:2003 provide method anchors. RP-02 defines the shared qualification logic.

Three topical studies address solid-lubricant modification of photocurable VPP resins, printing parameters associated with surface quality and wear resistance, and the effects of washing and curing time on tribological and hardness characteristics. Their results support conditional engineering relationships, not a universal ranking of materials. This note defines the minimum tribosystem and reporting record, identifies ASTM G99-23, ASTM G133-22 and ISO 7148-2:2026 as method anchors within their respective scopes, and separates manufacturer-controlled 3Dresyns implementation candidates from independent evidence. RP-02 supplies the shared qualification method.

Three topical sources address solvent effects on UV-modified printing plates and ink films, mechanical-property changes in 3D-printed dental materials, and postwashing effects on residual-monomer elution, conversion and mechanics. Their conditions and material families are not interchangeable. This note uses ISO 175:2010 and ASTM D543-21 as general method anchors for immersion and chemical-reagent evaluation. Environmental stress cracking is excluded because no cited primary study applies a defined stressed-exposure protocol to a vat-printed photopolymer. RP-02 defines the shared qualification method.

Two primary studies evaluate dimensional accuracy of printed surgical guides or templates after defined sterilisation/disinfection workflows. No source in the retained set reports mechanical, thermal or extractables change as a function of a sterilisation cycle. Those outcomes are therefore qualification requirements, not reviewed findings. Current process anchors are ISO 17665:2024 for moist heat, ISO 11135:2014+A1:2018 for ethylene oxide and ISO 11137-1:2025 for radiation. Biological evaluation belongs to the finished processed and sterilised article within ISO 10993-1:2025 risk management. RP-02 defines the shared qualification method.

Three topical sources address multimaterial VPP architectures, programmed heterogeneous micro-environments and tunable-resin microfluidic actuators. The evidence supports controlled multimaterial and graded structures, but not a universal interface strength or biological-suitability claim. This note defines spatial mapping, geometry-specific adhesion/fracture testing, differential dimensional control and interface-focused durability requirements. Biological evaluation, where relevant, remains a separate finished-article process under ISO 10993-1:2025. RP-02 supplies the shared qualification method.

Three topical studies address photoabsorbing fillers, optical change after thermal treatment and rheological cure-depth measurement. They support optical and cure-response control, but not photochemical-ageing durability. This note narrows the evidence claim and defines optional colorimetry and xenon-exposure gates using current standards. RP-02 supplies the shared qualification method.

Two topical sources demonstrate fire-resistance approaches in a coated photopolymer lattice and a flame-retarded stereolithography resin for printed circuit boards. Their results are not interchangeable. This note defines a test architecture that requires the named fire method, specimen configuration, conditioning and post-ageing retest before any public rating. RP-02 supplies the shared qualification method.

Three topical sources address liquid-resin behaviour under high vacuum and volatile emissions from cured or printed materials. This note distinguishes screening from qualification and clarifies ASTM E595 outputs versus ECSS acceptance limits. RP-02 supplies the shared qualification method.

Three topical studies address hybrid thermally conductive fillers, ZnO-filled DLP resin and high-viscosity VPP processing. This note maps claims to those sources, specifies current diffusivity and conductivity standards and removes unverifiable cross-series dependence. RP-02 supplies the shared qualification method.

Two topical sources report soft or thermoresponsive DLP actuators, while a third studies printing and post-curing of a passive polymeric stent. No retained source demonstrates a vat-printed 4D actuator operating in a biological medium with blocked force or work output and cycle life. This note therefore presents qualification limits, not clinical evidence. RP-02 defines the shared evidence-to-decision and qualification method and is not reproduced here. The corrected public 4Dresyn F-HV1 TDS v1.4 was verified against the controlled local copy on 21 August 2026.

The evidence covers VPP strategies for metals and ceramics, ceramic cure-depth selection, large investment-casting master patterns and one techno-economic comparison of rapid investment casting against VPP routes. This note scopes cost-per-accepted-part accordingly and defines a reproducible route-selection record. RP-02 supplies the shared qualification method.

This published review analyses the relevant material-function and interface variables, separating demonstrated functions from device- and application-level qualification.

Primary corpus cluster: Functional materials and interfaces.

This published review separates literature evidence from finished-article, workflow, exposure and intended-use qualification in the relevant biomedical or hazard domain.

Primary corpus cluster: Biomedical, exposure and hazard.

This published review analyses the relevant reaction pathway, network architecture and qualification boundaries, separating mechanistic evidence from formulation-specific performance.

Primary corpus cluster: Photochemistry and network architecture.

Weak build-platform adhesion can cause early detachment, layer slip or complete print failure, whereas excessive first-layer cure can increase dimensional distortion and make part removal difficult. Beyond the build plate, direct fabrication onto glass, silicon, ITO, metals and polymers requires a different evidence chain because successful printing is only the beginning of the interface life. Recent quantitative two-photon-polymerisation studies show that silanisation, plasma activation and polymeric interlayers can materially alter adhesion, and that geometry, solvent exposure and thermal history can change which treatment remains effective. DLP process studies likewise show that initial adhesion is coupled to exposure and separation loading.

Primary corpus cluster: Process physics, metrology and control.

Vat photopolymerisation can fabricate both gas-permeable and gas-barrier polymer structures, but the underlying transport mechanisms and measurement quantities are often conflated. For dense homogeneous polymers, permeability reflects the combined ability of a penetrant to sorb into and diffuse through the network. Printed parts introduce additional pathways and state variables: conversion gradients, post-cure, residual species, water uptake, layer interfaces, shrinkage, voids, thickness and surface sealing. Direct VPP literature demonstrates highly gas-permeable printed PDMS-like networks, DLP-printed mixed-matrix membranes for H2/CO2 separation, and DLP-printed ionic-liquid-containing membranes with gas-specific permeability.

Primary corpus cluster: Process physics, metrology and control.

Vat photopolymerisation can generate three-dimensional polymer optical paths whose geometry is difficult to obtain by conventional planar photonics. Recent work demonstrates DLP-printed elevated waveguides, DLP-printed photoluminescent waveguides and splitters, stereolithography-printed methacrylate waveguides whose optical output changes after solvent uptake, complex SLA waveguides for three-dimensional light redistribution, and two-photon-polymerised waveguides with sub-micrometre features and engineered core-cladding structures. These demonstrations also expose the qualification problem.

Primary corpus cluster: Functional materials and interfaces.

Vat photopolymerisation can embed molecular dyes, organometallic emitters, carbon dots, nanoparticles and aggregation-induced-emission systems into three-dimensional polymer networks. Primary studies demonstrate fluorescent photopolymer objects with tunable absorption and scattering, phosphorescent DLP resins, red-emitting carbon-dot additives, photoluminescent printed waveguides, and fluorescence changes that can track network formation. These demonstrations do not make photoluminescence a single material property.

Primary corpus cluster: Functional materials and interfaces.

Additive manufacturing is increasingly used to shape carbon-dioxide capture media into monoliths, lattices and structured reactors. The underlying materials, however, span fundamentally different states. Published work includes direct-ink-written silicone/sodium-carbonate composites that retain the polymer matrix, DLP-printed zeolite 13X and Li4SiO4 structures in which a photopolymer enables shaping but is subsequently removed or converted, and 3D-printed activated-carbon monoliths evaluated by adsorption and breakthrough methods. These systems cannot be pooled into a single CO2-capture number.

Primary corpus cluster: Functional materials and interfaces.

This published review analyses the relevant reaction pathway, network architecture and qualification boundaries, separating mechanistic evidence from formulation-specific performance.

Primary corpus cluster: Photochemistry and network architecture.

This published review analyses the relevant reaction pathway, network architecture and qualification boundaries, separating mechanistic evidence from formulation-specific performance.

Primary corpus cluster: Photochemistry and network architecture.

This published review analyses the relevant reaction pathway, network architecture and qualification boundaries, separating mechanistic evidence from formulation-specific performance.

Primary corpus cluster: Photochemistry and network architecture.

This published review analyses the relevant reaction pathway, network architecture and qualification boundaries, separating mechanistic evidence from formulation-specific performance.

Primary corpus cluster: Photochemistry and network architecture.

This published review analyses the relevant reaction pathway, network architecture and qualification boundaries, separating mechanistic evidence from formulation-specific performance.

Primary corpus cluster: Photochemistry and network architecture.

This published review analyses the relevant reaction pathway, network architecture and qualification boundaries, separating mechanistic evidence from formulation-specific performance.

Primary corpus cluster: Photochemistry and network architecture.

This published review analyses the relevant reaction pathway, network architecture and qualification boundaries, separating mechanistic evidence from formulation-specific performance.

Primary corpus cluster: Photochemistry and network architecture.

This published review analyses the relevant reaction pathway, network architecture and qualification boundaries, separating mechanistic evidence from formulation-specific performance.

Primary corpus cluster: Photochemistry and network architecture.

This published review analyses the relevant material-function and interface variables, separating demonstrated functions from device- and application-level qualification.

Primary corpus cluster: Functional materials and interfaces.

This published review analyses the relevant material-function and interface variables, separating demonstrated functions from device- and application-level qualification.

Primary corpus cluster: Functional materials and interfaces.

This published review analyses the relevant reaction pathway, network architecture and qualification boundaries, separating mechanistic evidence from formulation-specific performance.

Primary corpus cluster: Photochemistry and network architecture.

This published review analyses the relevant material-function and interface variables, separating demonstrated functions from device- and application-level qualification.

Primary corpus cluster: Functional materials and interfaces.

This published review analyses the relevant material-function and interface variables, separating demonstrated functions from device- and application-level qualification.

Primary corpus cluster: Functional materials and interfaces.

This published review analyses the relevant process-state, measurement and qualification variables while keeping reported outcomes conditional on formulation, equipment, geometry and workflow.

Primary corpus cluster: Process physics, metrology and control.

This published review analyses the relevant process-state, measurement and qualification variables while keeping reported outcomes conditional on formulation, equipment, geometry and workflow.

Primary corpus cluster: Process physics, metrology and control.

This published review analyses the relevant process-state, measurement and qualification variables while keeping reported outcomes conditional on formulation, equipment, geometry and workflow.

Primary corpus cluster: Process physics, metrology and control.

This published review analyses the relevant reaction pathway, network architecture and qualification boundaries, separating mechanistic evidence from formulation-specific performance.

Primary corpus cluster: Photochemistry and network architecture.

This published review analyses the relevant process-state, measurement and qualification variables while keeping reported outcomes conditional on formulation, equipment, geometry and workflow.

Primary corpus cluster: Process physics, metrology and control.

This published review analyses the relevant process-state, measurement and qualification variables while keeping reported outcomes conditional on formulation, equipment, geometry and workflow.

Primary corpus cluster: Process physics, metrology and control.

This published review analyses the relevant reaction pathway, network architecture and qualification boundaries, separating mechanistic evidence from formulation-specific performance.

Primary corpus cluster: Photochemistry and network architecture.

Color and appearance in vat photopolymerisation are coupled material-process-surface properties. CIELAB coordinates describe a color stimulus under declared measurement conditions, while CIEDE2000 provides a defined color-difference calculation from CIELAB coordinates. Neither quantity is independent of illuminant, observer, measurement geometry, background or specimen state. Additive-manufacturing studies show that printing orientation, layer thickness, post-curing, polishing, glazing, ageing media and surface roughness can alter measured color and translucency. Independent work on 3D-printed polymers also demonstrates that gloss and roughness change with surface finishing, making visual match a broader problem than chromatic coordinates alone.

Primary corpus cluster: Process physics, metrology and control.

Vat photopolymerisation provides geometrically complex polymer substrates and sacrificial mandrels that can subsequently receive metallic layers. Published routes include catalyst-containing stereolithography resins, ZnO-containing DLP resins activated by laser irradiation, grafted interfacial layers for electroless copper on ultra-smooth SLA substrates, selective palladium catalysis in vat-printed plastronic parts, thiol-rich photocurable networks that bind metal ions directly, and self-activating DLP resins containing inexpensive metal precursors.

Primary corpus cluster: Functional materials and interfaces.

This published review analyses the relevant reaction pathway, network architecture and qualification boundaries, separating mechanistic evidence from formulation-specific performance.

Primary corpus cluster: Photochemistry and network architecture.

This published review analyses the relevant reaction pathway, network architecture and qualification boundaries, separating mechanistic evidence from formulation-specific performance.

Primary corpus cluster: Photochemistry and network architecture.

This published review analyses the relevant reaction pathway, network architecture and qualification boundaries, separating mechanistic evidence from formulation-specific performance.

Primary corpus cluster: Photochemistry and network architecture.

This published review analyses the relevant reaction pathway, network architecture and qualification boundaries, separating mechanistic evidence from formulation-specific performance.

Primary corpus cluster: Photochemistry and network architecture.

This published review analyses the relevant reaction pathway, network architecture and qualification boundaries, separating mechanistic evidence from formulation-specific performance.

Primary corpus cluster: Photochemistry and network architecture.

This published review distinguishes process feasibility from accepted-part, lifecycle and application-level qualification for the relevant manufacturing route.

Primary corpus cluster: Indirect manufacturing and lifecycle.

This published review separates literature evidence from finished-article, workflow, exposure and intended-use qualification in the relevant biomedical or hazard domain.

Primary corpus cluster: Biomedical, exposure and hazard.

This published review analyses the relevant material-function and interface variables, separating demonstrated functions from device- and application-level qualification.

Primary corpus cluster: Functional materials and interfaces.

Vat-photopolymerised parts are often described as having smooth or high-quality surfaces, yet published studies show that the realised topography depends on both process physics and measurement method. DLP formulation can change feature size and stair-stepping; LCD projection discontinuities can generate lateral texture; build direction alters roughness; post-curing and polishing change the measured surface state; and finishing can simultaneously change roughness, gloss and other functional outputs. This Engineering Review develops a state-based qualification framework for surface topography of SLA, DLP and LCD/MSLA photopolymers.

Primary corpus cluster: Process physics, metrology and control.

Vat photopolymerisation can fabricate monolithic microfluidic channels, integrated covers, valves, connectors and complex flow paths, but fluidic success cannot be inferred from printability or dimensional accuracy alone. Published SLA and DLP studies report pressure-driven flow, pressure-to-failure tests, leak-free bonded interfaces, reusable connector burst-pressure measurements and, in a recent hydraulic-fitting comparison, failure of printed components to achieve application-level leak tightness despite acceptable dimensional tolerances. This Engineering Review establishes a state-based qualification framework for leak testing and sealing of vat-printed photopolymers.

Primary corpus cluster: Process physics, metrology and control.

Vat-photopolymerised thermosets are frequently described using static tensile modulus, Shore hardness, elongation or impact strength, yet vibration control and dynamic energy dissipation require a different measurement architecture. In linear viscoelastic response, an oscillatory strain produces a phase-shifted stress that can be decomposed into storage and loss components; the ratio of loss to storage response is commonly expressed as tan delta.

Primary corpus cluster: Process physics, metrology and control.

Historical UV printing provides an unusually clear natural experiment in chemical evidence generation. Beginning in the 1970s, dermatitis investigations repeatedly identified multifunctional acrylates including TMPTA, PETA, HDDA and later TPGDA in workers exposed to UV-curing inks and coatings [1-7]. A large UK study subsequently used Graphical, Paper and Media Union membership to quantify skin complaints across printing activities, while current UK HSE guidance continues to identify UV-cured ink use as a printing activity with elevated skin-risk concern [8,15]. These records do not establish a simple intrinsic-hazard ranking between monomers.

Primary corpus cluster: Biomedical, exposure and hazard.

Technical-grade (meth)acrylates are often treated in formulation discussions as single molecular species. Historical analytical work shows why that simplification can fail: commercial patch-test diacrylates were reported at 81–91% purity, with tripropylene glycol diacrylate containing 13% tripropylene glycol monoacrylate, while triacrylates were 82– 86% pure and the corresponding hydroxyacrylates occurred at 1–13% [1]. Clinical evidence demonstrates that an impurity can become the causal sensitizer: acrylic acid present as an impurity in an ECG electrode hydrogel was identified by HPLC and positive patch testing as the cause of allergic contact dermatitis [4].

Primary corpus cluster: Biomedical, exposure and hazard.

Occupational contact dermatitis is a practical failure mode in workflows that handle uncured photo-curable materials. Direct 3D-printing case reports now document allergic contact dermatitis associated with (meth)acrylate-containing printing resins and with epoxy-resin chemistry, while recent UV-printing evidence also demonstrates an airborne allergic-contact-dermatitis route. Historical occupational studies in dental personnel and printing workers show that acrylic monomers can become clinically relevant sensitisers and that safety data sheets may not reveal the compounds implicated by patch testing or chemical analysis.

Primary corpus cluster: Biomedical, exposure and hazard.

Photo-curable (meth)acrylates share structural motifs that invite structure-activity reasoning, particularly the alpha,beta-unsaturated carbonyl system of acrylates and the alpha-methyl substitution of methacrylates. Experimental studies show that electrophilic reactivity toward glutathione can vary by orders of magnitude and that alpha-methyl substitution reduced thiol reactivity for selected acrylate/methacrylate pairs. Guinea-pig sensitisation studies likewise demonstrate meaningful differences between multifunctional acrylates, but they do not support a simple monotonic rule based on functionality count alone.

Primary corpus cluster: Biomedical, exposure and hazard.

Photoinitiators control the conversion of optical dose into reactive species, but unreacted initiator and photolysis products can remain in cured materials and may migrate under use or extraction conditions. This creates a substitution problem with at least four coupled axes: spectral compatibility, initiation efficiency and conversion, residual parent-photoinitiator and photoproduct inventory, and the intended-use interpretation of chemical release. Direct DLP evidence comparing multiple photoinitiator systems shows that changing the photoinitiator can simultaneously alter cytotoxicity, colour, dimensional accuracy, conversion and mechanical properties.

Primary corpus cluster: Photochemistry and network architecture.

Thermomechanical dimensional stability in vat-photopolymerised polymers is controlled by more than a single coefficient of thermal expansion (CTE). Linear expansion can vary with temperature, cure state and network mobility; the response can change near glass transition; repeated heating can reveal residual cure or irreversible strain; and the printed architecture can introduce orientation-dependent behaviour in some systems while other SLA systems show little or no measurable thermal-expansion anisotropy. Direct VPP evidence supports both sides of that boundary. Peterson et al. used thermomechanical analysis in a DLP-printed graded-crosslink system [1]. Sekmen et al.

Primary corpus cluster: Process physics, metrology and control.

Vat photopolymerisation enables monolithic microchannels but also creates process-dependent surfaces whose wetting behaviour can influence filling, droplet motion and two-phase flow. Direct DLP evidence shows that layer thickness and lamination direction can change surface roughness, contact angle, contact-angle hysteresis and capillary movement [1]. A separate SLA study found time-dependent contact-angle change in a printed polymer and linked that evolution to the practical window for self-driven capillary microfluidics [2].

Primary corpus cluster: Process physics, metrology and control.

Charge-transfer complexes, also termed electron donor-acceptor complexes in this context, can form by ground-state association of complementary donor and acceptor molecules and generate an absorption response not present in the separated components. Visible-light excitation can drive electron transfer and create initiating species for radical or cationic photopolymerisation, while some systems also show thermal initiation. A focused 2019-2023 literature set demonstrates additive-manufacturing relevance: phosphine/iodonium CTCs [1], indole/iodonium CTCs [2], a water-compatible dye/triethanolamine CTC used for hydrogel printing [3], and bromoacetophenone/amine CTCs [4] were all taken into 405 nm patterning or 3D-printing demonstrations.

Primary corpus cluster: Photochemistry and network architecture.

High-solids photopolymer formulations require simultaneous control of wetting, particle-particle attraction, suspension rheology, sedimentation, optical transport and photopolymerisation. Historically, dispersant chemistry progressed from low-molecular-weight amphiphiles to oligomeric hydroxy-fatty-acid structures, polymeric anchoring agents, and increasingly defined block, grafted, branched and comb-like architectures. Public patent literature from the 1970s onward documents an important route based on ricinoleic acid and 12-hydroxystearic-acid polyesters, including polyester-polyamine and polyester-polyethyleneimine structures.

Primary corpus cluster: Photochemistry and network architecture.

Engineering Reviews ER-01 to ER-99 cover photopolymer chemistry, vat-photopolymerisation process physics, qualification methods, functional materials, biomedical and occupational constraints, indirect manufacturing and lifecycle questions. This paper treats that sequence as a bounded corpus and asks what engineering logic emerges across it. The corpus reconstruction used the controlled ER-01–ER-49 map, the ER-50–ER-87 publication ledger, final publication manifests for later papers and the public Zenodo community state. Ninety-nine identifiers are represented without a numbering gap, and the current public map assigns an active Zenodo record and permanent concept DOI to every identifier from ER-01 through ER-99.

Primary corpus cluster: Corpus synthesis and evidence architecture.

Vat photopolymerisation can manufacture compliant structures with complex internal channels, thin membranes and fine features, but the formulation requirements for recoating and rapid cure compete with the long, mobile network strands needed for soft and durable elastomeric response. Primary studies from 2017 to 2026 demonstrate several routes for moderating this trade-off, including flexible urethane-acrylate segments, densely entangled networks, reversible hydrogen-bonded physical crosslinks, dynamic covalent topology and sequential or dual cure. Reported formulation-specific tensile results range from sub-megapascal moduli and very high extension to unusually high strength and toughness. These demonstrations establish a broad design space, not a universal property envelope.

Primary corpus cluster: Polymer chemistry and network architecture.

True silicone elastomers derive their material identity from crosslinked polysiloxane chains, most commonly poly(dimethylsiloxane), rather than from softness, Shore hardness or tactile feel alone. Vat photopolymerisation imposes low-viscosity, optical and rapid-gelation requirements that can conflict with the long flexible chains and reinforcing strategies used in conventional silicone rubber. Primary studies demonstrate several routes through this conflict, including thiol-ene crosslinking of vinyl- and thiol-functional polysiloxanes, simultaneous chain extension and crosslinking, sequential photo and thermal cure, and orthogonal silicone double networks. These routes prove that genuine silicone structures can be printed, but their reported properties remain formulation- and process-specific.

Primary corpus cluster: Polymer chemistry and network architecture.

Urethane- and urea-containing photopolymers occupy a large design space between low-viscosity printing resins, soft elastomers and highly crosslinked thermosets. Primary studies demonstrate flexible urethane-acrylate elastomers, multiple-hydrogen-bond poly(urethane–urea) networks, non-isocyanate acrylic polyhydroxy urethanes, dual-curable polyurethane acrylates and urea-containing photocurable monomers. These examples show that segment selection, reactive functionality, association, chain extension and post-cure can alter modulus, extension, toughness, swelling and print resolution. They do not establish a universal polyurethane property envelope. Chemical naming must identify the load-bearing network and the reaction that creates it:

Primary corpus cluster: Polymer chemistry and network architecture.

Fluorinated materials offer combinations of low surface energy, solvent resistance, optical transparency, dielectric response and low friction that are attractive for microfluidics, electronics and demanding interfaces. Their established bulk-processing routes are often incompatible with vat photopolymerisation, so light-based fabrication has followed several chemically distinct strategies: direct curing of perfluoropolyether methacrylates, two-photon structuring of PFPE photoresists, dispersion and subsequent sintering of PTFE particles, vat printing of elastic fluorinated networks, post-print fluoroalkyl surface modification, photoreactive modification of existing fluoropolymers and recyclable thiol–ene fluorinated photoresists.

Primary corpus cluster: Polymer chemistry and network architecture.

All-aromatic polyimides combine thermal stability and mechanical performance with poor melt or solution processability in their final imidised state. Light-based additive manufacturing therefore commonly prints a soluble and photosensitive precursor, fixes geometry by a temporary photocrosslinked scaffold and then uses solvent removal plus thermal imidisation to form the target polyimide. Primary studies demonstrate mask-projection stereolithography of photoacrylated polyamic esters, photocurable polyamic-acid salts, concentrated supramolecular polysalts, two-photon writing of a commercial negative photosensitive precursor and structure–morphology differences between polyimide variants.

Primary corpus cluster: Polymer chemistry and network architecture.

Cyanate-ester, maleimide/bismaleimide and benzoxazine formulations extend vat photopolymerisation toward high-temperature thermosets, but they do not share one cure mechanism. Primary demonstrations include Hot Lithography of an unfilled cyanate-ester formulation through photo-induced catalytic polytrimerisation, stereolithography of a methacrylate-functionalised bismaleimide oligomer, and projection micro-stereolithography of photocurable benzoxazine precursors followed by thermal ring-opening polymerisation. In these routes, light may create the final network, activate a latent catalyst or only establish a shape-retaining intermediate. Post-cure temperature can increase conversion and properties while also causing diffusion, overgrowth, oxidation, warpage, cracking or volatile loss.

Primary corpus cluster: Polymer chemistry and network architecture.

Phenolic and lignin-derived materials enter vat photopolymerisation through several chemically different routes. Primary studies demonstrate photoacid-triggered polycondensation of a pure novolak formulation by Hot Lithography without a binder or matrix polymer; stereolithography of eugenol-, guaiacol- and vanillyl-alcohol-derived (meth)acrylates; direct laser writing of vanillin acrylate networks; Hot Lithography of methacrylated lignin containing more than 30% lignin without reactive diluent; and low-level lignin reinforcement of a methacrylate SLA resin. The native phenolic route produces water and can form bubbles if reaction and evaporation overlap above the stable process window.

Primary corpus cluster: Polymer chemistry and network architecture.

Furan-derived materials enter additive manufacturing through distinct routes that cannot be pooled as one resin family. Primary VPP studies include stereolithography of a 5-hydroxymethylfurfural-derived imine-bearing methacrylate oligomer, DLP printing of a glycerol-diacrylate/tetrahydrofurfuryl-methacrylate vitrimer, and furfuryl-methacrylate photoresins assembled with maleimide partners through Diels-Alder chemistry. These systems fix geometry primarily by radical polymerisation of acrylate or methacrylate groups; the furan-derived structure may alter polarity, rigidity, optical response or later dynamic chemistry but is not automatically the photoreactive bond. Tetrahydrofurfuryl groups no longer contain an aromatic furan ring, and FDCA polyesters reported for thermoplastic 3D printing are adjacent evidence rather than VPP validation.

Primary corpus cluster: Polymer chemistry and network architecture.

Isosorbide-derived photoresins combine a renewable rigid bicyclic core with separately installed photoreactivity. Direct VPP evidence includes DLP processing of isosorbide dimethacrylate blends, isosorbide/vanillin ester and ester-imine thermosets, and thiol-yne networks prepared from dipropargyl derivatives of isosorbide and its epimers. These routes cannot be pooled: methacrylate chain growth and thiol-yne step growth differ in stoichiometry, gelation, oxygen response, residual groups and network defects. In one methacrylate study, neat isosorbide methacrylate was brittle, while furan-derived comonomers reduced viscosity and raised measured fracture energy; the same comonomers changed optical attenuation, conversion and thermal response.

Primary corpus cluster: Polymer chemistry and network architecture.

Itaconic-acid-derived photoresins offer several chemically distinct routes to VPP. The pendant exomethylene can remain along an unsaturated polyester or poly(ester amide), be installed in low-molar-mass itaconate reactive diluents, or be incorporated into amino-acid-derived itaconamides. Direct SLA and DLP studies show that viscosity, wavelength-specific cure, conversion, crosslink density, glass transition, strength and elongation depend strongly on polyester architecture, diluent identity and concentration, and post-cure. Acrylate-free itaconate diluents and high renewable-content formulations are feasible, but these labels do not establish low hazard, complete cure, biodegradability or life-cycle benefit. Recent itaconamide systems expand the design space toward monomers derived from alanine, valine, isoleucine and phenylalanine;

Primary corpus cluster: Polymer chemistry and network architecture.

Dithiolane and lipoate photoresins replace or supplement conventional carbon-carbon-forming vinyl cure with light-driven ring opening of strained cyclic disulfides. The resulting linear disulfides can exchange, relax stress and, under controlled dilution, heat or catalytic conditions, revert toward cyclic monomer. Direct evidence now spans 405 nm DLP, commercial LCD printing and two-photon lithography. Renewably sourced lipoate mixtures have been printed, depolymerised and reprinted across two recovery cycles; tetrafunctional dithiolanes have shown approximately 95% monomer mass recovery; and latent-base formulations provide thermally triggered depolymerisation at macro- and microscales.

Primary corpus cluster: Degradable, reprocessable and bio-derived networks.

Thioester-containing photoresins combine rapid radical cure with post-cure bond exchange. Direct evidence includes masked stereolithography of anhydride-derived reversible thioester networks, SLA composites that degraded with 91% filler recovery, and tough semicrystalline resins that were converted into thiol-functional oligomers and repolymerised into stiff or soft objects. Earlier thiol-X photopolymers established recovery and repolymerisation chemistry but did not by itself qualify a VPP process. The mechanisms are not interchangeable: thiol–thioester transesterification requires a thiolate/nucleophile and retains a thioester, whereas anhydride-derived thioesters can participate in a temperature-dependent network equilibrium. Dissolution is not automatically monomer recovery, and matching modulus does not close a recycling loop.

Primary corpus cluster: Degradable, reprocessable and bio-derived networks.

Hemiacetal-ester (HAE) and N,O-acetal junctions offer two routes to degradable VPP thermosets. HAE-terminated polyurethanes use methacrylate cure for geometry and dilute acid to release a reusable polyurethane diol after poly(methacrylic acid) removal. Oxazolidone N,O-acetals use thiol–ene cure; their exchange and hydrolysis depend on protic species, temperature, base, dynamic-bond fraction and topology. Direct evidence includes CLIP printing, vat working curves, 50 µm layers, acid dissolution, hot-press reprocessing and measured mechanical loss. O,O-acetals, ketals, HAE and N,O-acetals are not interchangeable, and dissolution, recovered polymer, reprocessing and monomer recovery are different endpoints.

Primary corpus cluster: Degradable, reprocessable and bio-derived networks.

PBAE-diacrylate photoresins offer a chemistry-controlled route to hydrolytically degradable micro-stereolithography objects. A systematic primary study synthesised eleven macromers from PEG or butane diacrylates and primary amines or hydrazides under solvent- and catalyst-free aza-Michael conditions. The reported networks ranged from complete mass loss in 90 min to minimal loss at 45 days under accelerated conditions, while all produced 55 µm patterned features and selected formulations printed complex objects with 45 µm features. Hydrophilic networks behaved as bulk-degrading systems; hydrophobic networks could appear surface-like before water penetration caused bulk degradation. These results do not establish universal formulations, surface degradation, biodegradability, biocompatibility or environmental superiority.

Primary corpus cluster: Degradable, reprocessable and bio-derived networks.

PPF photoresins have been processed by layerwise and projection stereolithography as PPF/DEF mixtures or PPF-rich systems. Primary studies show that oligomer number-average molar mass, PPF fraction and resin temperature control rheology; selected cDLP specimens exceeded 15 MPa ultimate tensile strength with elastic moduli of 178–199 MPa. A 308 nm pulsed-projection platform achieved micrometre-scale cure-depth control with 1 wt% BAPO, while initiator absorption, oxygen, interfaces, pulse fluence and bleaching altered the working-curve response. These data are platform-specific. HOS-cell attachment after 48 h, hydrolysable ester linkages and the term resorbable do not establish device biocompatibility, in-vivo resorption or safe degradation products.

Primary corpus cluster: Degradable, reprocessable and bio-derived networks.

Photo-crosslinkable PTMC macromers support flexible and elastic stereolithography networks. Direct studies report tensile moduli from about 3.8 to 7.9 MPa in different formulations, elongation above 900% in selected films, porous structures, five-generation branched channels and PTMC/β-TCP builds. Up to 45 wt% propylene carbonate was used as a non-reactive viscosity reducer in one platform, making extraction and residual-solvent closure integral to identity. Water flow through approximately 224 µm channels and HUVEC attachment demonstrate platform capability, not haemocompatibility or implantation readiness. Filler contents up to 60 wt% were printed in smaller structures, while 51 wt% enabled a large prototype and surface enrichment showed composition nonuniformity.

Primary corpus cluster: Degradable, reprocessable and bio-derived networks.

Direct studies demonstrate three-armed methacrylated PCL scaffolds processed without added solvent by heating the resin, PCLMA networks with modulus and accelerated-degradation rate controlled by degree of methacrylation, GelMA/PCLMA and dECM/PCLMA hybrid stereolithography, and PCLMA/hydroxyapatite gyroids whose pore fidelity depends on optical attenuation. One solvent-free scaffold platform reported 70.5 ± 0.8% porosity and 465 µm average pore size. Another varied Young’s modulus from 0.12 to 3.51 MPa and changed accelerated degradation from complete within 17 days to nonsignificant within 21 days by increasing methacrylation. A 2026 composite study showed that 0.1 wt% Orange II changed the ρ = 0.6 mm gyroid from 29.9% dimensional error for PCLMA10S to 9.6% for PCLMA10SOr. These results are platform-specific;

Primary corpus cluster: Degradable, reprocessable and bio-derived networks.

Direct primary studies demonstrate photocurable PLA derivatives produced through a two-stage urethane/methacrylate route in supercritical carbon dioxide, a one-pot liquid poly(L-lactide)-PETA triacrylate, and a transesterification/methacrylation upcycling route for stereolithography. The first platform reported cured-structure Young’s modulus from 16.9 to 102.5 MPa depending on lamp, LED, two-photon or laser-stereolithography conditions, showing that cure modality is part of material state. The one-pot PLA-PETA platform reported 91% crosslinkage and greater than 90% mean cell viability under its assay. The upcycling platform spanned 33–3911 mPa·s at 30 °C, reached 51 wt% PLA-waste content and reported a best-system storage modulus of 2240 MPa. These values are not transferable between derivatives.

Primary corpus cluster: Degradable, reprocessable and bio-derived networks.

Direct primary studies establish four separate evidence states. A one-step PG6-A resin printed volumetrically at 405 nm with 6.5 Pa·s viscosity and 0.075 wt% LAP, but uncured residue reuse required a changed exposure and unprocessed prints produced cytotoxic extracts; 99% reported degree of cure and non-cytotoxic extracts followed an additional 60-minute post-cure plus sequential water and bicarbonate washes. Acr-PGS extrusion used blended macromers to create a viscosity window: low-viscosity inks flowed, high-viscosity ink fractured, and a 10/90 blend preserved multilayer geometry. PGSA/PEGDA DLP scaffolds linked composition and architecture to hepatocyte culture for up to 16 days without proving liver regeneration.

Primary corpus cluster: Degradable, reprocessable and bio-derived networks.

Primary evidence defines POMaC as a citric-acid/1,8-octanediol/maleic-anhydride polyester with independent photochemical and condensation crosslinking levers. Early thermosets spanned 0.03-1.54 MPa initial modulus and 48-534% elongation at break across controlled states. A later LCD-vat formulation reduced viscosity from 10 136 to 282 cP with 50 wt% PEG400, used TMPTA to reduce gel time from 11 to 7 s, and printed 80 µm positive features, a nominal 100 µm open channel measured at 110 µm and 100 µm gyroid features. Increasing porogen unexpectedly raised compression modulus from 80 to 790 kPa after extraction while increasing brittleness; residual components required extensive washing, and cell viability remained above 80% only for the tested post-treated specimens.

Primary corpus cluster: Degradable, reprocessable and bio-derived networks.

Primary studies demonstrate aqueous DLP printing of glycidyl-methacrylate-functionalised Bombyx mori silk fibroin, with properties altered by GMA feed, measured lysine modification, macromer concentration, photoinitiator and exposure. The founding study reported 141-705 mM GMA feeds, 22-42% lysine modification, 10-30% Sil-MA, 3.5 mW/cm2 and 3 s per layer, but those values describe one controlled route rather than a universal resin. Subsequent cartilage, sealant, protocol and graphene-oxide studies add distinct formulations, article states and biological models. This review defines a traceable chain from protein source through functionalisation, printing, washing, hydration, secondary-structure evolution, mechanics, degradation and biological state, and proposes minimum release gates for silk-derived photocurable constructs.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Primary evidence shows that type-I collagen can be methacrylated while retaining fibrillar self-assembly and enzymatic degradability, but source, extraction, solubilisation, methacrylation and neutralisation remain material-defining. Gaudet and Shreiber reported rapid 365 nm photocrosslinking, a five-fold storage-modulus increase and state-dependent collagenolytic resistance for one collagen methacrylamide route. Han et al. later combined extracted ColMA with PEGDA for DLP printing, creating a hybrid rather than a neat collagen network. This review separates collagen identity, triple-helix/fibril state, derivatisation, formulation, low-temperature handling, optical processing, hydration, mechanics, collagenase degradation and biological evidence, and defines minimum qualification gates.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Chitosan-derived photocurable hydrogels cannot be specified by the word chitosan alone. Molecular-weight distribution, degree and pattern of deacetylation, acid dissolution, neutralisation, derivatisation and purification determine the incoming macromer. Morris et al. demonstrated SLA manufacture of chitosan:PEGDA hybrid gels, while Seo et al. used hydroxybutyl-methacrylated chitosan for temperature-reversible SLA 4D printing. Bucciarelli et al. showed that CsMA concentration, temperature and shear rate govern solution viscosity, while CsMA concentration, photoinitiator concentration and UV exposure jointly alter compression modulus, morphology, degradation and solubilisation. This review separates neat derivatives from PEG hybrids and distinguishes pH/ionic history, temporary shape change and permanent network state.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Hyaluronic-acid methacrylate or methacryloyl is a family of derivatives, not a single photoresin. Biological or fermentation source, molecular-weight distribution, salt form, derivatisation reagent, substitution method, purification and storage define the macromer. HAMA is frequently used in DLP as a component of GelMA, PEG or cleavable hybrid bioinks, so printability and mechanics cannot automatically be assigned to neat HA. This review separates parent-polymer identity, substitution, formulation, exposure, washing, hydration, network contribution and hyaluronidase-sensitive degradation, and withholds universal biological or clinical claims.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Primary studies show that photocrosslinkable alginates are route-specific macromers, not interchangeable grades. Carbodiimide coupling of 2-aminoethyl methacrylate enabled substitution-dependent swelling, modulus and degradation; glycidyl methacrylate, 2-aminoethyl methacrylate and methacrylic anhydride produced derivatives with similar measured substitution but different compressive failure behaviour; functionalisation time and initiator concentration changed a separate photocurable bioink system; oxidation before methacrylation created another degradation coordinate; and light-patterned ionic alginate demonstrated that divalent-cation-bound networks can be fabricated without covalent methacrylate chemistry.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Primary studies show that methacrylated dextran is route-, substitution- and state-specific. Glycidyl methacrylate was coupled to dextran in DMSO with DMAP, with substitution controlled by reagent ratio and aqueous radical polymerisation controlled by initiator and macromer concentration. Glycerol changed chain conformation, optical and mechanical behaviour and crosslinking kinetics in DexMA/gellan systems. A 2025 DLP study printed Dex-GMA/PCL-IEMA hybrids across a defined concentration, LAP, tartrazine, dose and wash window; its results belong to that hybrid and solvent state, not to DexMA alone. GelMA-DexMA and degrading dex-MA studies likewise show that substitution, partner network and enzyme exposure alter swelling, mechanics and transport.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Photocurable starch systems span methacrylic-anhydride starch, glycidyl-methacrylate starch, pentenoate-thiol networks and hybrid bioinks. These are not interchangeable. Noe et al. demonstrated aqueous DLP of methacrylated high-amylose maize starch with LAP, while Hedin et al. established UV crosslinking of GMA-modified cornstarch. Van Nieuwenhove et al. showed that starch-pentenoate/gelatin networks can phase-separate, and Zhou et al. reported that low-substitution methacrylated starch alone printed poorly but improved in a methacrylated-chitosan hybrid. This review separates parent-starch identity, chain processing, substitution, formulation, optical exposure, network attribution, hydration, enzymatic degradation and biological evidence.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Photocurable cellulose-derived systems span dissolved methacrylated carboxymethylcellulose (mCMC), mCMC reinforced with native or methacrylated cellulose nanocrystals (CNCs), and CNCs bearing a covalently attached photoinitiator. Melilli et al. demonstrated aqueous DLP of mCMC, Soullard et al. separated DLP and two-photon polymerisation formulations and their different resolution limits, Soullard et al. also quantified the effect of CNC and mCNC fillers, and Wang et al. used photoactive CNCs as initiator, crosslinker and nanofiller in a methacrylate composite. This review separates parent-cellulose identity, two independent substitution coordinates, nanoparticle functionalisation, optical process, network attribution and article state.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Photocurable pectin-derived systems include methacrylate-modified pectin combined with ionic pre-gelation, norbornene-functionalised pectin crosslinked with thiolated peptides, and hybrid dressings or bioinks in which pectin shares network ownership. Pereira et al. established a low-solids dual ionic-photo bioink and a separate thiol-norbornene platform; Giron-Hernandez et al. linked cocoa-pod extraction and esterification to pectin methacrylate; Bozer et al. studied a pectin/hyaluronic-acid hybrid. This review separates parent identity, derivatisation, formulation, network attribution, optical process, hydration, degradation and biological evidence.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Photocurable kappa-carrageenan systems span methacrylated kappa-carrageenan (MA-kappa-CA) that retains thermoreversible and cation-responsive assembly, dual ionic-photo bioinks, DLP formulations and composites with gelatin methacrylate or hydroxyapatite. Mihaila et al. established the chemically and physically crosslinked derivative; Lim et al. resolved the KCl/UV sequence for extrusion; Kumari et al. transferred the chemistry to DLP; and Kansiz et al. varied methacrylation and mineral loading. This review separates parent identity, substitution, thermal and ionic history, photoconversion, process, hydration, network attribution and biological evidence.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Photocurable gellan-gum systems span gellan gum methacrylate (GGMA), injectable GGMA/PEG-dimethacrylate formulations, ionically or photo-crosslinked cell carriers, and extrusion-printed composites. Pacelli et al. linked functionalisation to solubility, mechanics, swelling and release; Tsaryk et al. compared ionic and photo-crosslinked cell constructs; D'Amora et al. resolved synthesis, printing and post-crosslinking; and Annurakshita et al. added ionic pre-crosslinking and gallol functionality. This review separates parent identity, substitution, thermo-ionic history, photoconversion, process, hydration, network attribution and biological evidence.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Photocurable pullulan systems span methacrylated pullulan (PulMA), methacrylate-bearing multiscale scaffolds, inkjet formulations and norbornene-functionalised pullulan (Pul-NB) for thiol-ene DLP. Bae et al. linked methacrylation and concentration to hydration, mechanics and cell organisation; Della Giustina et al. demonstrated stereolithography and two-photon patterning; Mugnaini et al. analysed self-assembly and inkjet films; Feng et al. established Pul-NB DLP; and Nonsuwan et al. resolved beta-cyclodextrin and curcumin effects. This review separates parent identity, functionalisation, photochemistry, process, hydration and claims.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Photocurable konjac-glucomannan systems span methacrylated KGM (KGMMA) extrusion bioinks, photocrosslinked 3D-culture hydrogels, light-curable microspheres for subcutaneous filling and oxidised KGMMA wound composites. Qin et al. established KGMMA printability; Redondo et al. reported KGM photocrosslinked hydrogels for in-vitro 3D cell culture; Wang et al. reported light-curable methacrylated KGM microspheres for subcutaneous tissue filling; Li et al. combined KGMMA with zinc-induced glycyrrhizic-acid assembly; and Pan et al. used methacrylated oxidised KGM with drug-bearing components. This review separates parent identity, acetylation, oxidation, substitution, cure, article state and claims.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Photocurable xanthan-containing systems include native xanthan rheology modifiers and partner-owned networks in which GelMA, PEGDA/PEGDMA or methacrylated collagen peptide carries the light-triggered cure. Methacrylated xanthan is confirmed as a covalent network participant in one systematically characterised extrusion system, while unsaturated xanthan derivatives remain a separate, source-unconfirmed evidence class. This review keeps polymer identity, rheological function, covalent ownership and article state explicit.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Photocurable guar-derived hydrogels span GG-MA macromonomers, HPG-MA networks, hybrid permanent-reversible networks and cell-laden extrusion inks. Tiwari et al. linked GG-MA molar mass and methacrylation to swelling, enzymatic degradation and endothelial-cell response. Ospennikov et al. combined HPG-MA photochemistry with reversible phenylboronate-diol links. Shang et al. reported a monophasic GG-MA extrusion bioink. Non-photo HPG/borate systems provide essential controls for reversible-network attribution. This review keeps those material and article states separate.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Agarose-enabled fabrication includes methacrylate-modified agarose hydrogels, photoannealable agarose microgels, native agarose used to pregel extrusion inks, agarose support baths for GelMA, and GelMA-agarose composites; the initiation chemistry of the methacrylate-modified route is not established in this corpus. De Paepe et al. established methacrylate-modified agarose. Mukundan et al. converted thermogelling agarose into a jammed microgel bioink with a photoannealing step. Gong et al., Yang et al. and Mokhtarzade et al. instead illustrate physical-matrix, support-bath and partner-owned photocure roles. This review makes polymer identity, thermal history, network owner and article state explicit.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Locust bean gum (LBG) is a carob-seed galactomannan whose hydration and association depend on source, processing, molar mass and galactose distribution. Qu et al. reported directly methacrylated LBG as an injectable UV-crosslinked hydrogel. Cheng et al. used oxidised LBG in a double network whose named radical precursor was methacrylated carboxymethyl chitosan. O'Connell et al., Wirzeberger et al. and Merg et al. define parent-polymer, physical-network and hydrated-rheology controls. This review keeps those evidence classes and their network ownership separate.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Gum arabic (GA) is a structurally heterogeneous Acacia exudate. Kersten et al. quantified variation across twenty Acacia senegal samples. Gerola et al. prepared GMA-modified GA with substitution-dependent swelling and pH response. Ibrahim et al. reported GA/PEGDMA hydrogels formed by chemical free-radical polymerisation. Pandit et al. used periodate-modified GA to crosslink PVA, while Wang et al. reported a gum-Arabic-based three-dimensional printed hydrogel for customizable sensors. This review separates GA identity, derivative state, network ownership, printing mode and the still-unproven photocure/vat-transfer step.

Primary corpus cluster: Photocurable biopolymer and hydrogel systems.

Industrial additive manufacturing spans seven standard process categories and a growing set of adjacent, non-layerwise, direct, indirect and hybrid implementations. Category names alone do not identify the state of the object leaving the machine, the transformations needed to obtain a usable component or the factory evidence required for repeatable production. This qualitative engineering review develops a state-resolved framework for screening additive-manufacturing routes across polymers, metals, ceramics and advanced materials. It separates feedstock state, shape-creation mechanism, usable scale and orientation, support or depowdering strategy, as-built state, mandatory post-processing, delivered material state and intended-use qualification.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Polymer material extrusion includes materially different architectures that share selective deposition through a nozzle. In filament-fed systems, the solid filament is both feedstock and force-transfer element. Pellet-fed systems use a screw to convey, melt, mix and pressurise granules. Reactive thermoset systems within this review use a melt-capable screw or large-format extrusion head to convey, thermally condition and pressurise material before controlled gelation or cure during or after deposition. This qualitative engineering review compares those routes from released feedstock to accepted component.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Polymer powder-bed fusion contains several architectures that share sequential powder spreading but create selective consolidation differently. Laser PBF, commonly called selective laser sintering, scans a focused energy source. Multi Jet Fusion, High Speed Sintering and Selective Absorption Fusion pattern radiation-absorbing or boundary-modifying fluids and use bed-wide infrared exposure within system-specific thermal strategies. This qualitative engineering review follows all four routes from released powder to accepted component.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Industrial vat photopolymerisation includes multiple exposure and interface architectures that must not be collapsed into a single SLA parameter space. Laser-scanned stereolithography delivers a moving optical spot; digital light processing projects a micromirror image; LCD/MSLA masks a light-engine field; and continuous routes maintain an inhibition or mobile liquid interface to reduce discrete separation and recoating pauses. This qualitative engineering review follows each route from released resin to accepted component. It examines resin conditioning, spectral and spatial light delivery, working curves, voxel and feature formation, separation, resin renewal, heat and mass transport, supports, drainage, washing, post-cure, shrinkage, surface state, safety, full-cell throughput and change control.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Material jetting creates three-dimensional objects by selectively depositing build-material droplets. Industrial implementations include piezoelectric drop-on-demand photopolymer systems, phase-change and wax routes, solution or suspension deposition and multimaterial platforms. These routes share droplet placement but not a single fluid window, solidification mechanism, support strategy or delivered material state. This qualitative engineering review follows the complete chain from released feedstock to accepted component.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Direct ink writing and paste extrusion deposit continuous or interrupted filaments from flowable, often non-molten feedstocks. Their material range can include one- and two-part silicones, moisture- or photo-reactive elastomers, hydrogels, adhesives, sealants, thermosets and particle- or fibre-filled polymer pastes. The same breadth makes generic process claims unsafe. This qualitative engineering review follows the complete route from released feedstock to accepted component. Published studies demonstrate useful mechanisms but not universal windows: colloidal, epoxy, silicone, hydrogel and support-bath results remain formulation-, apparatus-, geometry- and state-specific.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Laser-based powder-bed fusion of metals, designated PBF-LB/M by ISO/ASTM and widely called LPBF, SLM or DMLS, selectively melts successive powder layers to create near-net-shape metal components. Its industrial value can include tool-less geometric complexity, internal features, part consolidation, rapid design iteration and high material utilisation relative to subtractive routes for selected geometries. Those benefits are conditional. The deposited layer is a heterogeneous granular state; laser–matter interaction can move among incomplete fusion, stable conduction-like melting and keyhole behaviour; plume, condensate, ejecta and gas flow redistribute energy and material; supports conduct heat and restrain distortion while adding removal and surface burdens;

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Electron-beam powder-bed fusion of metals, designated PBF-EB/M by ISO/ASTM and widely known as EBM or selective electron beam melting, selectively melts successive metal-powder layers using an electronically generated, focused and deflected beam in a low-pressure chamber. Its potential industrial value includes complex near-net metal geometry, rapid beam repositioning, elevated-temperature processing and a process atmosphere distinct from laser powder-bed fusion. Each benefit has a boundary. Electrons can charge electrically isolated powder particles and trigger the rapid particle-ejection instability called smoke. Bed preheating and partial sintering change electrical conduction, thermal conductivity and mechanical stability, but also create a cake whose strength affects depowdering, internal-feature access and powder recovery.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Metal binder jetting selectively deposits a liquid binder into successive metal-powder layers to form a green component, which is subsequently cured, excavated, depowdered, debound and densified. The process can offer parallel layer patterning, dense nesting and freedom from melt-pool residual stresses during printing, while also decoupling the printer from a furnace fleet. Its delivered performance nevertheless emerges from a coupled powder–binder–geometry–thermal route. Particle morphology, size distribution, moisture, spreading and reuse affect bed packing and green density. Droplet formation, wetting, saturation, drying and feature thickness affect edge growth, layer bonding and handling strength.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Bound-metal material extrusion deposits a thermoplastic or otherwise flowable metal-powder/binder compound as adjacent roads and successive layers, producing a green composite that is subsequently debound and sintered or otherwise densified. Filament-fed variants can use familiar FFF-style equipment but require a compound that is both highly filled and mechanically transportable as a stable filament. Pellet-, rod-, piston- or screw-fed variants can bypass filament manufacture and process feedstocks closer to powder-injection-moulding compounds, while introducing distinct dosing, residence-time, segregation and pressure-control burdens.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Lithography-based metal manufacturing uses patterned light to solidify a photoactive metal-powder/binder system layer by layer, producing a green composite that is subsequently cleaned, debound and sintered or otherwise densified. Literature labels such as LMM, LMAM, metal DLP, micro-DLP and metal stereolithography cover related but not necessarily identical material-delivery and exposure architectures. Liquid suspensions, thixotropic pastes and temperature-conditioned feedstocks impose different mixing, sedimentation, recoating, separation and recovery burdens. Increasing metal loading can reduce organic content and support final densification, while increasing viscosity, reducing layer renewal and changing optical attenuation and scattering.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Directed-energy deposition (DED) uses concentrated thermal energy to melt feedstock as it is delivered to a substrate or existing component. The category includes powder-fed and wire-fed laser-beam systems and arc-based wire systems commonly called wire-arc additive manufacturing (WAAM); these architectures cannot share an assumed process window. Powder flow or wire-feed speed, energy delivery, travel, standoff, shielding, bead overlap, substrate heat flow and interpass history jointly determine catchment, melt-pool behaviour, dilution, geometry and defects. A nominal power, current or energy-per-length surrogate does not describe those interactions.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Vat photopolymerisation of ceramics selectively cures a photoactive ceramic-powder suspension or paste to form a polymer-bound green body that is subsequently recovered, cleaned, debound and sintered. Labels including ceramic stereolithography, ceramic DLP, LCD ceramic printing, lithography-based ceramic manufacturing (LCM), CerAM VPP and ceramic direct production (CDP) describe related implementations but do not guarantee an identical optical engine, layer-delivery mechanism, feedstock state or thermal route. Powder refractive index, absorption, particle and agglomerate size, surface chemistry, solids loading, resin spectrum and initiator response govern light transport. Rheology, sedimentation, thixotropic recovery and aging govern layer renewal and composition.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Ceramic direct ink writing (DIW), often called robocasting in ceramic implementations, selectively deposits a particle-loaded ink, slurry or paste through a nozzle as continuous filaments. The filaments must flow under the imposed reservoir, line and nozzle history, form a controlled free surface, contact neighbouring material, resist spreading, sagging and buckling, then survive drying and handling as a green body. Where temporary organics remain, burnout or debinding must remove them without unacceptable pressure, residue or cracking. Sintering changes dimensions, pores, phases and grain structure and may require material-specific atmospheres, setters and finishing.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Binder jetting selectively deposits liquid binder into successive powder layers. The process family can handle ceramics, sands and refractory powders, but the printer normally establishes a porous bonded architecture rather than the final material state. Powder flowability, packing, spreadability and sinterability are distinct coupled properties; no single particle-size, shape or apparent-density measure proves a suitable bed. Binder saturation is an emergent liquid-volume field produced by droplet generation, spacing, powder pores, wetting, capillary flow, evaporation and cure, not an independent quality variable. Printhead addressability is therefore not final resolution.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Ceramic material extrusion with highly filled binder-continuous feedstocks is an indirect additive-manufacturing route. Ceramic powder is compounded with a temporary polymeric or reactive vehicle, delivered as filament, pellets or granules, or a bounded binder-rich paste, and deposited as roads. Cooling, binder solidification or another declared binder-setting mechanism creates a green body; controlled debinding creates a porous intermediate; sintering develops the final ceramic microstructure. Each state has different failure modes and acceptance evidence. Powder chemistry, morphology, surface area, agglomeration and moisture interact with binder wetting, plasticisation, lubrication, solids loading and compounding.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Indirect polymer-binder powder-bed shaping uses selective thermal energy to join binder-bearing particles into a green geometry, followed by depowdering, debinding and densification. The route is variously described as indirect selective laser sintering, indirect laser powder-bed fusion, polymer-assisted powder-bed processing or, in commercial implementations, cold fusion. These names can obscure the essential distinction between the phase that creates the printed bond and the material expected in the final product. This qualitative engineering review follows the complete state chain from released powder-binder feedstock to accepted metal, ceramic, glass, carbide or other advanced material.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

The industrial use of nano-and micron-scale powders, fibres, platelets and dispersions requires more than matching a material name to an additive-manufacturing category. Raw-material identity includes composition, crystalline or molecular state, primary dimensions, morphology, aspect ratio, specific surface area, porosity, surface chemistry, coating, moisture, aggregation, agglomeration, contamination, ageing and package history. Each attribute can change when a sample is split, dispersed for measurement, compounded into a feedstock, pumped, jetted, extruded, recoated, irradiated, cured, dried, debound, sintered or finished. This qualitative engineering review defines a complete chain from supplier lot to accepted 2D trace, coating, retained 3D composite, green body, sintered material or indirectly moulded component.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Nano-and micron-scale carbon, metal, conducting-polymer and ceramic phases can provide electrical conduction, controlled electrostatic dissipation, electromagnetic shielding or heat transport in additively manufactured components. The same constituent can also increase viscosity, cure attenuation, sedimentation, nozzle wear, agglomeration, porosity, contact resistance, anisotropy and occupational-control burden. This qualitative engineering review separates four functions that are frequently collapsed under the word conductive: direct-and alternating-current transport; electrostatic-discharge control; electromagnetic-interference shielding; and thermal conduction or diffusivity.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Nano-and micron-scale dielectric, ferroelectric, piezoelectric and magnetic phases can enable additively manufactured capacitive structures, radio-frequency elements, sensors, actuators, ultrasonic transducers, energy harvesters, permanent magnets, flux guides and magnetically responsive devices. Their value is conditional. High-permittivity particles can raise viscosity, scatter curing light, sediment, concentrate electric field and increase loss. Ferroelectric or piezoelectric ceramics can require debinding, sintering, electrode firing and high-field poling; retained polymer composites can remain printable but dilute active-phase connectivity and transfer stress inefficiently. Permanent-magnet powders can increase melt viscosity, nozzle wear, density gradients and demagnetizing-field sensitivity;

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Additive manufacture can shape fused silica, transparent polymers, high-refractive-index nanocomposites, gradient-index structures, photonic crystals, fluorescent and quantum-dot architectures, scintillators, radiation collimators and mixed-field attenuators. The same interactions that create function also constrain manufacturing. Absorbers and high-index particles reshape the cure field; fluorophores and quantum dots can compete with photoinitiators; interfaces scatter; residual stress creates birefringence; polishing changes both dimensions and optical loss; scintillation output depends on energy deposition, transport, coupling and detector response; high-Z loading can increase photon attenuation while viscosity, voids and spectral hardening change the delivered component.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Vat-photopolymerized thermosets can provide fine geometry and unusual combinations of stiffness, heat resistance, chemical durability, flame retardancy, gas transport and electrical insulation. They also retain linked liabilities: cure gradients, residual reactive species, high crosslink density, brittleness, stress, anisotropic defects, solvent uptake, additive migration, permeation, surface leakage and continuing network evolution. This qualitative engineering review defines six distinct extreme-service functions and the evidence required to close each one. Electrical insulation is assessed after the same thermal, chemical and humidity exposures that define service.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Specialised vat-photopolymerization systems can be designed to move, recover a memorised shape, repair damage, operate as soft elastomers, swell as hydrogels, expand into cellular solids, form enclosed fluidic networks, carry authentication features or process unusually viscous feedstocks. Their apparent diversity conceals a shared engineering problem: the useful response emerges only after a sequence of transformations and is strongly coupled to geometry, transport, network mobility and process history. This qualitative engineering review defines the functional evidence required for eight resin families without transferring vendor specifications or research-paper values across systems. Shape-memory is separated into programming, fixation, storage, activation, recovery and cyclic drift.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Additive-manufacturing (AM) technology selection is often reduced to a comparison of printer categories, nominal resolution, material labels or deposition rate. That shortcut fails when a factory must deliver accepted components rather than merely produce an as-built object. This review converts that principle into a state-resolved factory decision matrix. It compares vat photopolymerisation, material extrusion, powder-bed fusion, material jetting, direct ink writing, binder jetting, bound-powder routes, lithography-based metal or ceramic manufacturing, directed-energy deposition and indirect tooling routes. The matrix does not rank technologies universally.

Primary corpus cluster: Industrial additive-manufacturing routes and material-selection architecture.

Internal channels are frequently presented as a geometric advantage of additive manufacturing. In production, however, an enclosed channel is acceptable only when supports, uncured liquid, loose powder, sacrificial material, gas and cleaning residues can be recovered and when the resulting feature can be verified. This review compares self-supporting orientation, removable solid supports, soluble sacrificial supports, powder-bed self-support, support-bath or embedded printing, and indirect tooling routes. It separates the printed state from the washed, cured, debound, sintered and conditioned states; identifies non-compensatory access and safety gates; and proposes measurable recovery endpoints, worst-case witness geometries and state-specific acceptance records.

Primary corpus cluster: Part, factory and qualification controls.

Non-destructive evaluation is often presented as a capability that a part either has or does not have. For vat-photopolymerised components that framing fails at the first question, because the useful question is not whether a method can image the part but whether it can detect the specific discontinuity that would make the part unacceptable. This review organises non-destructive evaluation of vat-photopolymerised parts around defect class rather than around instrument, and states what the published evidence does and does not support. The central finding is negative and should be read as the paper’s principal contribution:

Primary corpus cluster: Part, factory and qualification controls.

A bonded joint on a printed photopolymer is usually described by a single number in megapascals, and that number is usually a property of the wrong thing. This review treats the joining of vat-photopolymerised components as a problem in which the adherend, not the adhesive, is most often the limiting element, and in which the adherend arrives at the bond line in a state that the printing workflow has determined and that almost nobody records. The controlling variables are the post-cure state, the oxygen-inhibited free surface, the wash-solvent history and the layer geometry — every one of which is set upstream of the joining operation and none of which appears in a conventional adhesive specification.

Primary corpus cluster: Part, factory and qualification controls.

Every printed part that has to carry a load carries it through a small number of discrete places: an insert, a thread, a press fit, a bolted hole. Those places are where the material is most highly stressed, least well characterised and most casually specified. This review takes local load introduction into vat-photopolymerised components as its subject. It located one vat-photopolymerisation insert study with accessible quantitative results, in which the insert was adhesively potted — placing its retention mechanism partly in ER-165 — and a second vat-photopolymerisation pull-out paper whose relevant content could not be obtained and to which no value is attributed.

Primary corpus cluster: Part, factory and qualification controls.

Printed photopolymer parts are routinely reamed, faced, drilled or threaded when printing alone cannot deliver the required feature. A directly relevant bibliographic record has now been identified: Kim, Kim and Kim report a study of curing and machining conditions in post-processing of an SLA-manufactured polymer [26]. Its bibliographic identity is verified, but neither its abstract nor its full text is present in the preserved evidence for this review. It therefore establishes that a directly relevant record exists, while supporting no transferable cutting parameter, cure sequence, numerical outcome, outcome class or universal process window here.

Primary corpus cluster: Part, factory and qualification controls.

Coating a vat-photopolymerised part joins two evolving material systems. The printed substrate may retain an oxygen-affected surface, extractable or migrating species and post-cure capacity, while the applied film brings its own wetting, cure, transport and stress response. This Engineering Review identifies the unresolved coupling among surface cure state, mobile residual species, continuing dimensional evolution, adhesion and barrier response. It defines a minimum state-resolved experiment capable of closing the evidence gap without proposing universal conversion thresholds, waiting times, surface treatments, adhesion values, coating thicknesses, residual-species limits or compatibility rules.

Primary corpus cluster: Part, factory and qualification controls.

This Engineering Review examines in-process insertion of prefabricated functional components into vat-photopolymerised parts through a pause-place-resume route. Direct SLA studies establish technical feasibility for specified printers, transparent methacrylate resins, component preparations and device geometries, while also identifying optical shadowing, local cure inhibition, restart-registration error, resin-flow and separation forces, cleaning challenges, shrinkage and incomplete sealing as qualification risks. The review defines a bounded framework covering component identity and orientation, interface geometry, placement accuracy, optical access, restart alignment, cleaning, post-cure, sealing and retained function. It does not propose universal compatibility, process windows or industrial-readiness claims.

Primary corpus cluster: Part, factory and qualification controls.

Accelerated ageing of a printed photopolymer contains a confound that is easy to miss: the elevated temperature, radiation or humidity intended to accelerate degradation can also continue cure, relax residual state, change free volume or alter transport. A specimen can therefore become stiffer or stronger during an ageing exposure even while another degradation process is occurring. ER-170 does not review the degradation mechanisms themselves; those remain in ER-072 and neighbouring reviews. It asks the narrower qualification question: when does an accelerated exposure preserve enough mechanism and material state that an acceleration factor or service-life claim is defensible?

Primary corpus cluster: Part, factory and qualification controls.

Statistically based material design values are intended to bound population variability with declared confidence, production representativeness and environmental applicability [1,2]. Classical A-basis and B-basis terminology provides a useful model for distinguishing a population-bound value from a mean, but its labels and tabulated values cannot be copied automatically to vat-photopolymerised materials. An interlaboratory study using aliquots from one photopolymer-resin batch found large scatter in working-curve parameters when procedures, light engines and measurement capability varied [3]. This demonstrates that even a nominally common material can produce incompatible parameter populations when state and method are not controlled.

Primary corpus cluster: Part, factory and qualification controls.

Qualification of incoming photoresin raw materials is often compressed into a comparison of supplier identity, CAS identity and certificate-of-analysis values. Those records are necessary for traceability, but they do not answer the same question as functional equivalence in a defined photopolymer system. A 1999 study of neat acrylates outside vat photopolymerisation illustrates both sides of this distinction: deliberate inhibitor addition produced an initial change in a cure-monitor response, while reported post-inhibitor rate parameters showed no continuing difference and the photoDSC heat difference remained within measurement error.

Primary corpus cluster: Part, factory and qualification controls.

This Engineering Review examines routine compounding, homogenisation, deaeration, filtration, transfer and filling of unfilled photoresins as controlled material-state transitions. It distinguishes recorded operations from measured associations and transferable causal claims. The directly read evidence shows that order of addition can be deliberately varied and measured in a ceramic-filled vat-photopolymerisation feedstock, but it does not establish the direction, magnitude or practical consequence of that variable in an unfilled photoresin. The review therefore defines the evidence gap, the batch information that must be declared and a minimum coupled experimental design linking composition or chemical proxy, rheology, cure and printing or part response.

Primary corpus cluster: Part, factory and qualification controls.

This Engineering Review treats the optical state of LCD-based vat-photopolymerisation equipment as a spatial, multidimensional quantity rather than a nominal wavelength and average irradiance. It defines a bounded architecture for baseline mapping and drift detection across irradiance, spectrum and divergence, and distinguishes baseline non-uniformity, temporal drift and ageing attribution. The review explains why grayscale correction can reduce irradiance non-uniformity without correcting divergence and why optical mapping does not replace formulation-specific conversion, dimensional or functional measurement. It does not propose a universal drift threshold, measurement interval, ageing rate, service life, replacement interval or decay model because directly read longitudinal evidence was not recovered.

Primary corpus cluster: Part, factory and qualification controls.

Changing a vat-photopolymerisation system from one resin to another is not merely a housekeeping operation. Residual liquid resin, pigments, fillers, photoinitiator-containing material, cleaner, or particulate can be transferred into the next build and alter the state of the incoming formulation. The resulting defect may be visible, such as colour carryover, or effectively invisible until cure response, dimensional stability, surface quality, mechanics, optics, or biological-contact risk is affected. The engineering question is therefore not whether equipment appears clean, but whether the changeover process has reduced relevant carryover below a scientifically justified and analytically demonstrable acceptance limit for the next material and use case.

Primary corpus cluster: Part, factory and qualification controls.

Photoresin manufacture and use combine reactive unsaturated monomers or oligomers, photoinitiators, inhibitors, pigments, fillers, solvents and, in some systems, thermal initiators or second-stage curing chemistry. The same kinetic features exploited for rapid cure can create process-safety liabilities when reaction rate and heat generation rise faster than heat can be removed. This review develops a qualification framework for reactive safety across compounding, hold, storage excursion, post-cure and printer-adjacent operations. Primary and review evidence from radical-polymerisation runaway and inhibition studies shows that inhibitor state and loss of heat removal can materially change escalation behaviour.

Primary corpus cluster: Part, factory and qualification controls.

Vat photopolymerisation uses liquid reactive formulations and usually requires pouring, printing, resin recovery, washing, drying, post-curing and finishing. Direct chamber studies show that particle and organic-vapour releases occur during SLA and DLP operations, that emission magnitude varies by printer technology and task, and that printing is not necessarily the highest-concentration phase [1,2]. The same studies also show why total volatile organic compound readings and particle counts cannot identify every relevant constituent. Separate permeation studies demonstrate that glove performance depends on the challenged acrylate or methacrylate, formulation, solvent, material, thickness and test method; a generic material name does not establish a universal breakthrough time [3,4].

Primary corpus cluster: Part, factory and qualification controls.

Vat-photopolymerisation operations generate chemically distinct liquid and solid waste streams. Direct evidence recovered for this review is uneven. An abstract-level aquatic-toxicity study and its publisher supplement show that six commercial uncured-resin categories produced formulation-dependent biological responses and distinguishable aqueous HPLC-UV profiles under the study conditions [1]. The evidence supports conservative segregation and a no-discharge posture, but not a universal waste class, toxicity ranking, discharge threshold or treatment endpoint. Two industrial supplier case studies demonstrate that distillation can recover a large solvent fraction from the specific resin-contaminated isopropanol streams and devices tested [2,3]; they do not establish virgin-solvent equivalence, residue classification or legal permission.

Primary corpus cluster: Part, factory and qualification controls.

A photoresin does not stop evolving when it leaves the mixing vessel. The production package remains part of the material state because its polymer grade, wall, colour, closure, liner, gasket, headspace, gas transport, light transmission and thermal history can alter the liquid that later reaches the vat. ER-179 defines qualification of the exact packaged resin and storage-excursion disposition without prescribing one universal container, headspace, oxygen concentration, temperature limit or shelf-life correction factor. It defines the observations, state variables and controls needed to separate present measurements from transferable manufacturing or service claims.

Primary corpus cluster: Part, factory and qualification controls.

This Engineering Review examines the identifiability limits of reconstructing manufacture and service history from a failed vat-photopolymerised component. It separates present observations from historical attribution and explains why continuing cure, ageing and depletion of mobile species can allow different histories to converge on similar measurements. The review defines a bounded framework based on declared candidate histories, discriminating measurements, provenance preservation and known-history validation. It does not support universal reconstruction of cure dose, exposure history, contamination event or manufacturing cause, and it proposes no attribution rule, confidence figure or universal method-capability threshold.

Primary corpus cluster: Part, factory and qualification controls.

Post-curing is often specified as a time and temperature in a named chamber. That description is insufficient for engineering qualification. The printed part does not experience a nominal recipe. It experiences a spatially and temporally varying radiation field, a temperature history and an atmosphere, all filtered by the part geometry, optical state, orientation, loading arrangement and material response. ER-181 treats post-cure as a second manufacturing process rather than a finishing checkbox. It separates commanded settings from delivered dose, chamber capability from part exposure, surface state from through-thickness state, and useful network development from dimensional or appearance penalties.

Primary corpus cluster: Part, factory and qualification controls.

Photopolymer networks are routinely described with a single convenient scalar: degree of conversion, gel fraction, swelling ratio, modulus or an inferred crosslink density. These quantities are related, but they are not interchangeable. A material can reach high double-bond conversion while retaining soluble species, can possess a high gel fraction while remaining weakly crosslinked, or can show a high modulus because it is glassy rather than because its elastically active network density is high. ER-182 defines a metrology architecture for resolving those distinctions. It treats each network-state measurement as a method-dependent observation with a defined specimen state, solvent or temperature history, constitutive assumptions and uncertainty.

Primary corpus cluster: Part, factory and qualification controls.

Mechanical recycling of a cured photopolymer does not reverse thermoset network formation and does not restore the original liquid resin. The experimentally demonstrated route is different: cured material is mechanically reduced to particles and intentionally reincorporated into a liquid photopolymer, creating a particulate composite and therefore a new formulation state. The recycled fraction can change rheology, recoating, optical transport, cure, interface formation and final properties even when the source waste came from the same nominal resin. ER-183 defines the evidence required to qualify that new state. It separates feedstock identity, size reduction, particle characterisation, dispersion, optical and rheological consequences, printing, post-processing and property verification.

Primary corpus cluster: Part, factory and qualification controls.

Visible defects in vat photopolymerisation are rarely unique signatures of a single mechanism. Curl, separation, weak interfaces, dimensional drift, incomplete layers and surface defects can arise from different combinations of optical, chemical, rheological, interfacial, geometric and post-processing states. Treating an observation as its own root cause creates false certainty and can make a corrective action appear successful without establishing why the failure occurred. ER-184 defines a bounded evidence architecture for diagnostic inference. It separates observation, classification, localisation, mechanism attribution, root-cause attribution and corrective-action verification, and it makes an unresolved result an acceptable scientific outcome.

Primary corpus cluster: Part, factory and qualification controls.

Photocuring ceases to be a surface-coating problem when the optical path becomes comparable with the attenuation length of the formulation. In a thick putty, gel, sealant or potting mass, the exposed surface can reach a high apparent cure state while an intermediate layer or core remains chemically and mechanically different. Increasing irradiance or exposure time does not guarantee that this gradient disappears, because absorption, scattering, photoinitiator depletion, photobleaching, oxygen transport, vitrification, heat generation and any secondary cure mechanism evolve during exposure. ER-185 treats through-cure as a spatial qualification problem.

Primary corpus cluster: Radiation-curing extensions and application-specific qualification.

A light-curable adhesive is not qualified merely because an exposed bead becomes hard. In an assembly, the cure-driving spectrum must reach every location whose state matters, while interfacial chemistry, attenuation, oxygen, reaction after irradiation and geometrical shadowing can make the bondline non-uniform. ER-186 provides a bounded engineering framework for connecting formulation, optical access and time-dependent cure-state verification. It separates chemical cure evidence from structural-joint qualification and treats inaccessible or weakly illuminated regions as explicit process states rather than assumed extensions of the visible surface.

Primary corpus cluster: Radiation-curing extensions and application-specific qualification.

Security inks and labels can combine structural colour, fluorescence, photochromic switching and machine-readable patterns. Primary demonstrations show reflective and fluorescent information encoded in the same microstructured label, reversible visible/invisible information under alternating illumination, and fluorescent flexographic printing with measured optical and rub-resistance properties [1-3]. These studies establish feasible multimodal designs, but they do not by themselves prove that every observable response is statistically independent, stable across manufacture or robust throughout service. ER-187 defines a verification architecture that separates feature existence, readable contrast, information integrity, mode independence and lifecycle retention.

Primary corpus cluster: Radiation-curing extensions and application-specific qualification.

Electron-beam curing can initiate acrylic network formation without a deliberately added photoinitiator, but that difference does not make an electron-beam process a direct substitute for an optically qualified cure. Electron energy deposition, dose rate, penetration, atmosphere and formulation state determine a reaction and network history that cannot be reduced to a universal conversion from optical radiant exposure to absorbed dose. ER-188 defines a bounded comparison and a requalification framework. It distinguishes the justified absence of photoinitiator-derived species from the unjustified claim that the cured material contains no residual or mobile species.English

Primary corpus cluster: Radiation-curing extensions and application-specific qualification.

A waterborne radiation-curable coating does not pass directly from liquid formulation to cured network in one step. Water must be redistributed and removed to the degree required by the system, dispersed polymer particles or domains must approach and consolidate, mobile hydrophilic species can redistribute, and reactive groups must then reach a sufficient photochemical state. These events can overlap, compete or arrest one another. A film may look dry while remaining weakly consolidated, may reach substantial chemical conversion while retaining water or morphology defects, or may develop a surface conversion state different from its interior.

Primary corpus cluster: Radiation-curing extensions and application-specific qualification.

A pressure-sensitive adhesive is not qualified by driving its photocure as far as possible. It must remain sufficiently compliant and dissipative to wet a counter-surface and develop tack while retaining enough cohesive network strength to resist shear, edge lifting, transfer and internal failure. In a radiation-curable PSA, cure therefore creates a bounded material-state problem rather than a simple maximisation problem. The useful state depends on formulation, coating weight, irradiation history, network formation and the measurement used to describe that state. Direct UV-PSA studies show that tack, peel adhesion and cohesive/shear performance can move in different directions as crosslinking advances.

Primary corpus cluster: Radiation-curing extensions and application-specific qualification.

A photopolymer that appears radiopaque, radiolucent or approximately tissue-like in one computed-tomography scan is not thereby qualified for a radiographic phantom or X-ray workflow. X-ray attenuation depends on photon energy and composition, while the measured CT number also depends on manufactured density, geometry, scan spectrum and reconstruction. When radiopaque particles are introduced into a photocurable resin, a second coupling appears: the same particles that modify X-ray response can change optical attenuation, scattering, cure depth, dispersion stability and dimensional fidelity during printing. A useful radiographic material therefore cannot be specified by a single Hounsfield-unit value or by filler percentage alone.

Primary corpus cluster: Radiation-curing extensions and application-specific qualification.

Photopolymerised hearing-aid shells and earmoulds combine patient-specific geometry with prolonged local contact, fit, acoustic performance and device-specific mechanics. A primary study demonstrated multi-drug-loaded devices made by digital light processing and reported mechanical, surface, blood-compatibility and antibiofilm measurements for the tested formulations. ER-192 treats that result as a bounded research route rather than general clinical suitability. It separates resin identity, delivered exposure, post-cure, geometry, mechanics, surface and extractable state, microbiological method, fit and acoustic response, requiring each claim to be supported by tests on the relevant material and process state.

Primary corpus cluster: Radiation-curing extensions and application-specific qualification.

Drug-loaded devices produced by vat photopolymerisation couple formulation and geometry with dose, degradation and molecular transport. Two primary studies provide bounded evidence: one varied biodegradable device geometry using a fluorescent surrogate, while another evaluated risperidone-loaded research implants based on PEGDA systems. ER-193 treats these results as distinct feasibility routes, not evidence of an approved medicine, clinically valid dose or universal material suitability. It requires independent control of formulation identity, drug content and uniformity, optical processing, geometry, residual chemistry, stability, analytical method and biological evidence, with no universal resin, dose, exposure model or clinical-performance claim.

Primary corpus cluster: Radiation-curing extensions and application-specific qualification.

Photocuring can manufacture cell-laden structures with controlled external geometry and internal transport features, but a printable research bioink is not thereby a food-qualified manufacturing system. The same formulation and exposure choices that establish shape also influence cell-supporting conditions, residual chemistry, transport architecture and the mechanical state later interpreted as texture. ER-194 defines an evidence-bounded qualification framework that keeps these questions separate. It uses one directly read DLP/GelMA cultured-meat proof of concept as the primary anchor and does not generalise its recipe, equipment settings or biological results into universal food specifications.

Primary corpus cluster: Radiation-curing extensions and application-specific qualification.

Radiation-curable coatings develop internal stress when polymerisation shrinkage is constrained after gelation. The observable consequence depends not only on free shrinkage, but also on the evolving coating modulus, relaxation before vitrification, coating thickness, substrate stiffness, laminate symmetry, cure rate and thermal history. Direct studies show that formulation and irradiation intensity alter gelation, vitrification and stress development in UV-curable acrylates; that coupled kinetic-mechanical models can reproduce some stress regimes while failing in early non-equilibrium or post-vitrification regimes; and that substrate compliance and annealing can strongly change curl in a UV-coated semi-rigid laminate [1-4].

Primary corpus cluster: Radiation-curing extensions and application-specific qualification.

A thin pigmented UV-curable ink can fail at the air interface even when the layer beneath has polymerised substantially. Oxygen continuously competes for radical species at the free surface, while pigment and photoinitiator compete for the incident photons that create those radicals. The practical consequence is that nominal lamp dose, bulk conversion, hardness or apparent dryness cannot be used interchangeably. Graphic-ink qualification must explicitly resolve the surface state, the through-film state and the spectral-optical state that couples them. It links formulation, delivered energy, geometry, interfaces and measurement conditions to the evidence needed for application-specific qualification.

Primary corpus cluster: Radiation-curing extensions and application-specific qualification.

Multimaterial vat photopolymerisation can encode distinct polymer states within one liquid formulation by changing wavelength, dose or the photochemical pathway activated at each location. Direct primary studies demonstrate three relevant strategies: wavelength-selective radical and cationic curing from a multicomponent resin, grayscale control of local conversion and mechanical state in a single-cure resin, and dose-triggered switching between polymerisation mechanisms reported through a photobuffer-mediated system. A recent hybrid epoxy-acrylate study further reports dual-projection fabrication of hard and soft domains from one resin. These demonstrations do not by themselves establish robust material identity, reaction orthogonality or transferable process windows.

Primary corpus cluster: Terminal evidence architectures and programmed material states.

Claims of circular photopolymer additive manufacturing often compress several different operations into one word. Network cleavage or dissolution demonstrates processability of an article, not recovery of a defined material fraction. Isolation of a liquid or oligomeric fraction demonstrates recovery, not its identity or suitability as feedstock. Fabrication of a second object demonstrates reprinting, not equivalence of composition, yield or performance. Similar properties after one cycle do not establish repeatability or an environmentally preferable system.

Primary corpus cluster: Terminal evidence architectures and programmed material states.

Four-dimensional printing of liquid-crystal elastomers combines geometry, anisotropic molecular order and stimulus-dependent mechanics. A successful demonstration can nevertheless conceal several different failures: the printed geometry may be accurate while the director field is wrong; a director field may be present but spatially blurred; a first thermal transformation may resemble the target while later cycles drift; or a programmed shape may result from structural compliance rather than the intended local anisotropy. Primary studies show that orientation may be encoded through extrusion flow, surface shear, electric or magnetic fields, or post-print mechanical deformation followed by a second locking reaction.

Primary corpus cluster: Terminal evidence architectures and programmed material states.

Engineering Reviews ER-101 to ER-199 extend the first corpus from material-family chemistry through industrial process selection, part and factory controls, radiation-curing applications, circularity evidence and programmed material states. This paper treats the sequence as a bounded second qualification corpus. The controlled enumeration contains 99 contiguous identifiers, 99 non-empty controlling titles and 99 named title-source documents, with no duplicate identifier. Forced single-cluster coding assigns 38 identifiers to material, macromer and network families; 24 to industrial process-family and material-selection architecture; 22 to part, factory and qualification controls; 12 to radiation-cure extensions and application-specific qualification; and 3 to terminal evidence architectures and programmed material states.

Primary corpus cluster: Corpus synthesis and evidence architecture.

Molar-mass distribution, functionality, residuals and measurement capability Photopolymer oligomers are distributions rather than single molecules. A material sold under one chemical description can contain chains of different length, branching and end-group state together with unreacted feedstocks, catalysts, stabilisers and synthesis-derived side products. The analytical problem is therefore not solved by obtaining one average molar mass or one chromatogram. It requires a declared measurand, a separation or observation mechanism, calibrated detector response, uncertainty and enough orthogonal information to distinguish a genuine material difference from a method artefact. This review defines a metrology architecture for the chemical identity of photopolymer oligomers.

Absorbed photons, reactive-state formation and cross-laboratory comparability A photoinitiator absorption spectrum identifies wavelengths at which light can be absorbed; it does not by itself measure productive initiation. Between incident photons and polymerisation lie spectral delivery, absorption, excited-state formation, intersystem crossing or electron transfer, bond cleavage, cage escape, quenching, oxygen and inhibitor reactions, addition to monomer and subsequent propagation. Different experiments observe different stages of this chain. Comparing them as though they were one “efficiency” produces false rankings and poor transfer between laboratories. This review defines a measurement hierarchy for photoinitiator action spectra and quantum yields.

Irradiance, spectral dose, geometry and calibration transfer Photopolymer processes are often described by an irradiance, exposure time and nominal wavelength. Those quantities are not sufficient to establish what radiation reached a sample. Detector responsivity, spectral bandwidth, spatial non-uniformity, angle, distance, window transmission, temporal modulation and sample geometry can produce different exposures while the displayed settings remain identical. Chemical actinometers add a valuable reaction-based measurement but do not remove these dependencies; they introduce their own absorption, quantum-yield, conversion and analytical boundaries. This review develops a traceability architecture for radiation used in photopolymer processing.

Exotherm, heat loss, local temperature and state attribution Photopolymerisation couples a light-driven reaction to heat generation, heat transport and temperature-dependent kinetics. A measured temperature trace is therefore neither a direct measure of conversion nor a pure record of reaction enthalpy. It is the result of local heat generation, conduction into tooling and previously cured material, convection in liquid resin, radiation, changing material properties, source heating, sensor response and the location at which temperature is observed. This review defines a measurement architecture for transient thermal history during photopolymerisation. Photo-differential scanning calorimetry, embedded sensors, infrared thermography and inverse heat-conduction models are compared by their measurands and perturbations.

Sampling volume, conversion gradients and calibration boundaries Raman and infrared spectroscopy can map the consumption of reactive groups in photopolymers, but a spectral map is not automatically a map of network state. Each pixel or depth point represents a finite sampling volume shaped by optics, refractive index, absorption, scattering, confocal response, surface contact and data reduction. Reactive-band loss may correlate with conversion while remaining sensitive to band overlap, orientation, baseline, photobleaching and the stability of the chosen internal reference. ATR-FTIR, transmission FTIR and confocal Raman therefore observe different volumes and cannot be merged without a transfer model. This review establishes a measurement framework for spatial cure-state mapping.

Porosity, internal defects, segmentation and detection limits X-ray micro-computed tomography can reveal pores, inclusions, channels and internal geometric departures in printed photopolymers without sectioning the part. Its three-dimensional output is attractive for qualification, but a reconstructed volume is not a direct map of physical truth. Detectability depends on attenuation contrast, source spot, magnification, detector sampling, acquisition noise, reconstruction, artefact correction and the orientation and morphology of each indication. Quantitative porosity additionally depends on the segmentation rule, region of interest and treatment of partial-volume voxels. This review defines a bounded qualification architecture for micro-CT examination of vat-photopolymerised and related printed photopolymers.

Curvature, hole-drilling, diffraction, relaxation and model dependence Residual stress in photopolymerised parts is not observed directly. It is inferred from deformation, strain release, diffraction, optical response or a coupled constitutive model. Each route samples a different spatial scale and stress component, and each embeds assumptions about elastic behaviour, geometry, material symmetry, time dependence and the stress-free reference state. A value obtained from a thin coating on a beam is therefore not interchangeable with a near-surface hole-drilling result or a lattice-strain measurement. This review defines a measurement architecture for residual stress in cured photopolymers and photopolymer-based parts.

XPS, ToF-SIMS, ATR-FTIR, contact angle and contamination attribution The outer surface of a printed photopolymer is not necessarily a representative slice of its bulk network. Oxygen inhibition, contact with a vat film or build platform, washing, secondary exposure, abrasion, migration and storage can produce a chemically and physically distinct interphase. Surface analysis is therefore useful for diagnosing adhesion failures, wetting drift, residues and unexpected functional response, but no single technique can identify all of these causes. This review defines a bounded measurement architecture for mapping the surface chemistry of vat-photopolymerised and related printed photopolymers. X-ray photoelectron spectroscopy provides elemental and chemical-state information from the near surface;

Specimen state, protocol transfer and reproducibility statistics An interlaboratory study can estimate how a material or method behaves when transferred beyond one laboratory, but it can also confound resin state, machine, operator, post-processing and measurement. Vat-photopolymer systems are unusually sensitive to this problem because the test article is created through a coupled chain of liquid-material handling, optical exposure, layerwise manufacture, washing, drying, secondary cure, conditioning and measurement. A nominally shared resin and CAD file do not establish a common measurand. This review develops a round-robin architecture for vat-photopolymer materials.

Measurands, traceability and fitness for purpose Additive-manufacturing test artefacts compress many geometric features into one build, but a dense collection of cones, holes, walls and overhangs is not automatically a qualification method. Each feature needs a declared measurand, a measurement route, an uncertainty compatible with the decision and a reason for occupying a particular position and orientation. Otherwise the artefact is a demonstration piece whose attractive complexity can conceal ambiguous evidence. This review develops a fitness-for-purpose architecture for reference artefacts and benchmark geometries used in additive-manufacturing qualification. It distinguishes a digital nominal definition, a manufactured test artefact, a calibrated reference object and a routine witness feature.

Viscosity, conversion, shrinkage, network state and hazard trade-offs A reactive diluent is not an inert viscosity reducer. It changes the liquid formulation, participates in cure and becomes part of the resulting network or residual-species population. Selection must therefore connect processing viscosity, compatibility, photoreactivity, achievable conversion, shrinkage, network state, volatility and hazard classification. Optimising any one of these dimensions in isolation can displace risk into another: a low-viscosity monomer can increase volatility or alter shrinkage; higher functionality can accelerate gelation yet restrict late conversion; a flexible spacer can reduce shrinkage in one formulation while reducing modulus; and lower nominal hazard cannot be inferred from a structural label alone.

Backbone, functionality, branching, viscosity and network performance Photocurable oligomers are commonly described by a resin family and a nominal functionality, yet those labels do not specify the molecular population that enters the formulation. Backbone chemistry, soft- and hard-segment length, molar-mass distribution, branching, end-group conversion, residual starting materials and hydrogen-bonding capacity can all influence liquid viscosity, compatibility, cure mobility and network performance. Synthesis order and stoichiometry may also change the mixture even when the same reagents are used. This review develops an engineering framework for connecting oligomer molecular architecture to formulation and cured-state evidence.

Oxygen reserve, storage stability, cure delay and thermal risk An inhibitor package in a radical photocurable formulation is not defined adequately by the name or nominal concentration of one stabiliser. The effective state depends on the combined monomers and oligomers, inhibitor identities already carried by raw materials, dissolved oxygen, headspace and container conditions, pigments and fillers, photoinitiator chemistry, thermal history and prior light exposure. The same package must provide sufficient resistance to unintended reaction during manufacture and storage while still allowing the intended photopolymerisation process to reach its required conversion and network state. This review presents a qualification architecture that keeps four questions separate:

Molecular-weight control, stress relaxation, conversion and property retention Chain-transfer agents can regulate radical photopolymer-network formation by terminating or redirecting growing chains, creating a new radical, delaying gelation, altering strand architecture or enabling reversible exchange. These effects can reduce stress or change mechanical response, but the term chain transfer covers chemically distinct mechanisms. Conventional thiol hydrogen transfer, irreversible addition–fragmentation chain transfer and reversible addition–fragmentation chain transfer cannot be assigned one common transfer efficiency or property ranking. This review separates the mechanisms and defines the evidence required to connect transfer chemistry with conversion history, gelation, stress evolution, network state and retained properties.

Sensitisation, latency, dark cure and residual ionic species Hybrid radical–cationic photopolymer formulations combine reaction channels that differ in initiation, propagation, inhibition, termination and post-irradiation behaviour. Iodonium or sulfonium photoacid generators may participate directly or through a sensitiser, while a radical initiator or sensitiser-derived radical supports the radical channel. Nominal component identity does not establish which channel was activated, how efficiently acid was generated, whether conversion continued after irradiation, or which ionic and neutral photolysis products remained in the cured material.

Spectral overlap, inner filtering, surface cure and colour stability Coloured photopolymers contain several wavelength-dependent competitors for the incident light field. Dissolved dyes absorb, pigments absorb and scatter, photoinitiators consume photons, and photoinitiators or colourants may bleach or generate coloured products. The resulting optical state changes with depth, conversion and irradiation history. A bulk spectrum, top-surface conversion or nominal cure depth therefore cannot by itself establish through-cure, surface response, colour retention or dimensional fidelity. This review defines a measurement architecture for separating absorption, scattering, inner filtering, photoinitiator response, depth-dependent conversion, surface cure and colour-state evolution.

Wetting, dispersion, interface formation and cure coupling Surface functionalisation can alter how a nano- or microparticle is wetted by a photocurable resin, how it aggregates, how the formulation flows, how light and reactive species reach the interface, and how the cured network transfers stress across that interface. These outcomes are related but not interchangeable. A supplier treatment label, an infrared band or a stable suspension does not by itself prove covalent grafting, complete surface coverage, network coupling or retained composite performance. This review defines a qualification architecture that follows the particle from incoming surface state through treatment verification, wetting and dispersion, photopolymerisation, cured morphology and interface-sensitive properties.

Phase state, ring opening, dark cure and storage boundaries Water can act as a proton carrier, nucleophile, chain-transfer agent, hydrolysis reactant, plasticiser or separate phase in cationic photoresins. Its effect is therefore not represented adequately by one humidity value or by the statement that moisture inhibits cure. Epoxy, oxetane and vinyl-ether systems differ in monomer structure, basicity, miscibility, propagation route and network development, while formulation components change the amount and state of water that reaches the reactive species. This review defines a comparative moisture-tolerance qualification architecture.

A mass- and species-balanced framework for photocurable formulations Reactive diluents reduce viscosity and participate in network formation, but some can also leave an uncured or curing formulation by volatilisation. The resulting problem is not captured by total mass loss, total volatile organic compound concentration, viscosity or final conversion alone. A defensible assessment must distinguish loss from the liquid formulation, atmospheric transport, chemical conversion, reaction-driven redistribution and later outgassing from the cured article. This review defines a measurement and requalification architecture for volatile reactive-diluent loss during storage-like handling, heating, deposition and cure.

A measurement architecture from absorbed light to reaction-family response Photobase generators and other photolatent base systems are often evaluated through polymer conversion or a colourimetric response. Those observations do not by themselves quantify how much base was generated, released into the matrix, survived neutralisation or remained catalytically active. Optical absorption, cage cleavage, nominal base equivalents, pH, free-base concentration and reaction rate are related but non-equivalent measurands. This review defines a quantitative chain from incident and absorbed light through chemical base release, neutralisation and reaction-family response.

A metal-specific qualification architecture from adherend identity to aged failure locus Adhesion of a photocurable coating or printed feature to a metal is not a property of the resin alone. It is the response of a declared alloy, its near-surface oxide, hydroxide and contamination state, the applied liquid, the evolving cured network, the specimen geometry and the conditioning history. A contact angle, cross-hatch class or pull-off strength can be useful, but none identifies the controlling interface or establishes durability by itself. This review defines a metal-specific qualification architecture. It begins with alloy and surface-state identity, verifies what cleaning, abrasion, activation, conversion or priming changed, and separates wetting, interfacial chemistry, cure conversion, residual stress and mechanical failure.

A substrate-state framework for compatibility, activation, interphase formation and durability Adhesion of a photocurable material to a thermoplastic or thermoset depends on the state of both polymeric materials and the interphase produced between them. Surface energy and solubility parameters can screen candidate pairs, but they do not measure swelling, dissolution, interdiffusion, primer anchoring, cure arrest, environmental stress cracking or durable joint performance. A treatment that initially improves wetting can recover, contaminate or damage the substrate before bonding. This review defines a polymer-substrate qualification architecture. It requires polymer identity, grade, additives, crystallinity or cure state and prior ageing; separates thermodynamic screening from direct interdiffusion and mechanical evidence;

A surface-state and crack-path qualification architecture for hydroxylated inorganic adherends Adhesion of a photocurable coating or bonded feature to glass or ceramic is governed by the declared inorganic composition, phase, finish and hydroxylated surface state together with the coupling layer, photocurable network, cure history, environment and test geometry. A nominally clean glass surface may carry adsorbed water, alkali-rich alteration, organic contamination or a previous silane layer. A ceramic label may conceal a silicate glass, glass-ceramic, zirconia-rich surface or multiphase oxide. These states are not interchangeable. This review defines a qualification architecture that separates cleaning, hydroxylation, roughening and silanisation; verifies coupling-layer chemistry and organofunctional compatibility;

A two-sided interphase qualification framework from deposited film state to locus-resolved recoat performance A primer is not qualified by its name, nominal concentration or initial contact angle. It is an interphase whose substrate-facing anchoring, deposited mass and continuity, drying or condensation state, outward-facing functionality and compatibility with the overlying photocure must all be demonstrated. Time between priming and coating is likewise not a universal open time: the surface changes through reaction, adsorption, migration, contamination and physical ageing. This review defines a state-resolved primer qualification framework. It separates substrate anchoring from coating-facing reactivity; treats thickness, coverage and surface segregation as measured variables;

A state-resolved qualification framework from delivered activation to locus-resolved bond performance Plasma, corona and UV-ozone treatment can change a polymer surface within seconds, but the treatment name does not define the surface delivered to a bonding operation. Gas composition, power coupling, source-to-surface geometry, exposure, temperature and the printed part's wash and post-cure history influence oxidation, chain scission, crosslinking, contaminant removal, roughening and the formation of mobile low-molecular-weight material. The resulting state can then change through hydrophobic recovery, migration, adsorption and handling before a coating or adhesive is applied. This review defines a qualification architecture for already polymerised photocurable surfaces.

A coupled interface, optics, transport and lifecycle qualification framework for photocurable release surfaces A release film, coated vat window or demoulding surface in a photocurable process is a functional interface whose behaviour cannot be reduced to low surface energy. Separation force also depends on cured area and geometry, resin viscosity, degree of conversion, fluid drainage, lift trajectory, support compliance and deformation. Where the window controls light transmission or oxygen delivery, the release construction also alters cure and dimensional fidelity. With use, wear, scratching, swelling, clouding, fouling and additive depletion can change these coupled functions before catastrophic failure occurs.

Abstract 1. Significance and scope 2. Apply the ER-040 tribosystem definition to the lubricious surface state 3. Identify where the lubricating function resides Low friction on a printed photopolymer is not an intrinsic material property. It is the response of a complete tribosystem comprising the printed and post-cured resin, the location and attachment of the lubricating function, the counterface, contact geometry, load, speed, motion, temperature, environment and accumulated sliding history. Bulk solid lubricants, surface-segregated additives, covalently attached brushes, deposited coatings and hydrated layers can all reduce friction, but they replenish, migrate, wear and fail by different mechanisms. This review defines a qualification architecture for low-friction and lubricious printed-photopolymer surfaces.

Abstract 1. Significance and scope 2. Define the printed surface before biological exposure 3. Separate mechanism classes before selecting endpoints An antifouling claim for a printed photopolymer cannot be established by a clean initial surface, a short planktonic kill test or one percentage reduction. Protein and organic conditioning, initial cell attachment, growth, extracellular-matrix development and mature biofilm are different stages. Hydration layers, surface charge, designed topography, contact-active chemistry, leaching agents and photocatalytic surfaces act by different mechanisms and require different controls. This review defines a qualification architecture for antifouling and biofilm-resistant photopolymer surfaces.

Abstract 1. Significance and scope 2. Define the claimed function before selecting a test An anti-icing claim for a printed photopolymer is not established by a high water contact angle, a single freezing-delay experiment or a low initial ice-adhesion result. The service response depends on the printed and post-cured substrate, surface chemistry and texture, humidity, droplet or vapour supply, thermal history, freezing pathway, ice morphology, loading mode and accumulated environmental damage. Condensation can replace an initially non-wetted state with a water-filled texture; frost can form by condensation followed by freezing or by direct vapour deposition; and repeated thermal, icing, deicing, cleaning and wear cycles can alter chemistry, roughness and coating attachment.

Abstract 1. Significance and scope 2. Define the aged substrate as a material state An aged printed photopolymer is not the same bonding substrate as a freshly printed surface. Conversion, oxidation, hydrolysis, contamination, extractive loss, absorbed water, residual stress, cracking and previous service can change surface reactivity and the load-bearing structure. Abrasion, cleaning, plasma or UV-ozone treatment, primer application and a compatible repair resin can improve a particular interface, but no treatment is universally beneficial. A high initial lap, shear or flexural result may reflect cohesive failure outside the interface, favourable specimen geometry or a repair material that has not itself been aged.

Strength scatter in a printed photopolymer is not a single material constant. It reflects the population sampled: resin and batch, printer and build, orientation and position, wash and post-cure, conditioning, specimen geometry, stressed area or volume, loading and failure mode. A Weibull fit can organize a declared population, but it does not by itself prove a weakest-link mechanism, identify the controlling defect, establish a safe threshold or justify transfer to a larger component. This review defines a non-compensatory framework for statistical size effects and Weibull analysis in vat-printed thermosets. It separates central strength, distribution shape and lower-tail reliability; requires the estimator, censoring, confidence intervals and model checks to be reported;

Notch sensitivity in a vat-printed thermoset is not determined by a CAD radius or elastic stress-concentration factor alone. The realised root geometry, notch depth, edge condition, layer arrangement, wash and cure state, conditioning, material strength, fracture resistance, component scale and loading mode jointly determine whether failure is governed by a finite stress gradient, crack-like fracture or another local mechanism. A printed V-notch, printed U-notch, machined notch, razor precrack, central hole and natural process defect are not interchangeable. This review defines a non-compensatory qualification framework for fracture-controlled notch design in printed photopolymers.

A state-resolved framework for dynamic characterization and bounded design transfer Impact resistance and high-rate response are not single properties of a printed photopolymer. Pendulum impact energy, drop-weight force history, rapid servo-hydraulic stress–strain response and split-Hopkinson measurements interrogate different geometries, rate histories and failure processes. Their results depend on resin chemistry, print orientation, exposure, wash, post-cure, conditioning, specimen dimensions, notch state, temperature, stress state and data-reduction assumptions. A higher response at rapid loading does not establish a universal dynamic increase factor, and absorbed impact energy is not interchangeable with a constitutive law.

A mechanism-resolved framework from bulk compression to progressive architectural collapse The compressive response of a printed photopolymer structure is not a single material property. A solid coupon may exhibit elastic deformation, yielding, cracking, barreling or confinement, while a lattice can respond through strut bending, node rotation, local cell buckling, global instability, brittle fracture, progressive crushing and densification. The measured curve also depends on as-built relative density, wall and strut fidelity, skins, platen alignment, friction, aspect ratio, contact, loading rate and the definitions used for stress, strain, plateau and densification.

A state-resolved framework for calibrating and testing failure surfaces The strength of a printed photopolymer under combined loading cannot be reconstructed safely from one tensile strength and one elastic modulus. Tension, compression and shear can activate different deformation and fracture processes, while print orientation, cure, conditioning, temperature, rate, specimen geometry and local stress gradients alter the observed failure state. Familiar criteria such as maximum stress, von Mises, Drucker-Prager, Mohr-Coulomb, Tsai-Hill and Tsai-Wu encode different assumptions. Selecting one by convenience does not establish its applicability, and fitting an interaction coefficient to the same data used for evaluation does not validate prediction.

A coupled stress-environment framework for screening, diagnosis and bounded qualification Environmental stress cracking is a coupled failure process. An environmental agent that produces modest swelling or property drift in an unloaded specimen can accelerate craze initiation or subcritical cracking when tensile stress, residual stress or constraint is present. Conversely, a stressed specimen may survive in air but fail during exposure. Printed photopolymers add orientation, layered defects, wash history, conversion gradients, support scars, surface inhibition and residual stress to this coupling. Unconstrained immersion, ordinary creep and post-exposure strength loss are therefore informative controls but are not, alone, environmental stress cracking tests.

A state-resolved qualification framework for repeated temperature excursions Thermal cycling is not equivalent to storage at one elevated temperature. Each excursion changes modulus, thermal strain, moisture state and residual stress; repeated reversals can accumulate interfacial slip, crazing, microcracking, warpage and loss of preload even when neither temperature extreme causes immediate failure. Printed photopolymers add cure gradients, orientation, layer structure and post-processing history to this problem. Hybrid assemblies add coefficient-of-thermal-expansion mismatch among resin, fillers, coatings, inserts, adhesives and fasteners. This review establishes a non-compensatory framework for thermal-cycling qualification. It requires the real part temperature and dwell history, not chamber setpoints alone;

A state-resolved framework for resonance, power spectral density and prospective validation Random vibration cannot be qualified by quoting an overall acceleration alone. A power spectral density distributes energy across frequency, and the response depends on resonances, damping, boundary conditions, fixture dynamics, preload, temperature and the evolving stiffness of the printed material. Printed photopolymers add orientation, surface state, cure history, ageing and viscoelastic frequency dependence. Consequently, two tests with the same root-mean-square acceleration can produce different stresses and damage. This review defines a non-compensatory framework for vibration and random-fatigue qualification of printed photopolymer components.

Fretting is repeated small-amplitude relative motion between loaded contacts. It is not ordinary sliding wear at reduced stroke. Partial slip can nucleate edge cracks while gross slip can generate a broader wear scar, debris and progressive conformity; transitions depend on pressure, tangential force, displacement amplitude, frequency, surface state, environment and counterface. Printed photopolymers add cure gradients, orientation, pixel or layer texture, residual washing products and viscoelastic time dependence. A friction coefficient or wear volume measured in another polymer cannot therefore be transferred safely. This review defines a non-compensatory qualification framework for fretting and repeated-contact damage.

A printed photopolymer that survives a short tensile test can still lose preload, accumulate strain, buckle or rupture under sustained service load. Creep, stress relaxation and creep rupture are distinct endpoints. Their rates depend on temperature, humidity, absorbed chemicals, cure, orientation, specimen age, stress level and geometry. Physical ageing can reduce short-time compliance while embrittlement or environmental damage reduces rupture resistance. Time-temperature superposition and accelerated ageing are powerful only when the same mechanism and material state persist across the shift. This review defines a non-compensatory framework for long-term load retention. It separates constant-stress, constant-load, constant-strain and structural tests; requires true geometry and evolving stress to be tracked;

Exposure-pattern compensation modifies the image sent to a vat-photopolymerisation system so that the manufactured geometry approaches a target despite optical blur, pixel cross-talk, thresholded polymerisation, cure spread, accumulated dose and deformation. The task is an inverse problem, not a universal XY offset. A pattern that corrects one feature size, resin or projector location can fail on another because the forward response depends on irradiance distribution, spectrum, layer history, resin state, geometry, support and metrology. Positive and negative features can exhibit different bias, and a lower mean dimensional error can coexist with closed channels, missing walls or unacceptable surface shape.

Grayscale vat photopolymerisation uses spatially varied exposure to produce an intended field of conversion, surface height or material response. The digital image is only the first link in a chain. Grayscale code, irradiance, exposure dose, local reaction history, conversion, network state and mechanical property are not interchangeable. Projector nonlinearity, oxygen inhibition, absorption, scattering, diffusion, heat, accumulated layer exposure, shrinkage and post-treatment can make the response nonlocal, nonlinear and history dependent. Equal nominal dose delivered through different intensity-time pairs may not be equivalent, and a conversion gradient does not uniquely establish a modulus, toughness or residual-monomer gradient.

The nominal pixel pitch of a masked vat-photopolymerisation system is not its printable resolution. A commanded mask is sampled on a finite grid, transformed by pixel aperture and fill factor, projector or LCD optics, focus, magnification, distortion, angular distribution, field nonuniformity, resin transport and cure threshold. Raster orientation and neighbouring pixels alter the delivered edge. Anti-aliasing may improve mean edge placement while broadening transitions, changing local dose or erasing small negative features. A visually smoother contour is therefore not sufficient evidence of dimensional fidelity. This review defines a metrology-led framework for qualifying pixel geometry, rasterisation, anti-aliasing and projection optics.

Layer exposure in vat photopolymerisation assumes that liquid resin has replenished the target gap and reached an acceptable fluid state. That assumption fails when blade motion, platform travel, cavity geometry, wetting, viscosity, surface tension or entrained gas create a nonuniform layer. “Settling time” is often used ambiguously for free-surface relaxation, squeeze-flow equilibration, bubble escape and particle sedimentation. These processes have different timescales and acceptance variables. This review defines a qualification framework for recoating and refill of low-viscosity photoresins. It separates bulk refill, meniscus and contact-line motion, residual free-surface waves, local thickness error, bubble entrainment and dispersed-phase sedimentation. Rheology is measured at process-relevant temperature and shear history.

Temperature is a process state, not a secondary environmental note, in vat photopolymerisation. It changes viscosity, refill time, species mobility, photopolymerisation kinetics, dark reactions, volatilisation, optical response and the mechanical condition of the machine. A nominal vat setpoint does not establish the temperature of the exposure region, the incoming feed, the return line or the resin adjacent to a recently cured layer. This review defines a qualification framework for resin-vat and feed-system temperature control. It separates setpoint, sensor reading, local resin temperature and thermal history; maps spatial gradients and transient recovery; couples temperature to rheology, working curves and build duration; and requires independent alarms for over-temperature, unintended polymerisation and material loss.

Vat photopolymerisation consumes and redistributes liquid resin while the optical and mechanical process assumes a stable reference level. Global liquid height sets hydrostatic pressure, immersion depth, refill head and free-surface geometry. Local menisci, waves and constrained gaps can depart from that global state. A level sensor can therefore be accurate yet insufficient, and a fixed refill volume can be repeatable yet wrong after density, temperature or geometry changes. This review defines qualification of resin-level, hydrostatic-pressure and free-surface control. It separates inventory, bulk level, local interface, meniscus, pressure head and dynamic disturbance; establishes calibrated level-volume geometry; accounts for platform displacement and cured-volume removal; and couples make-up dosing to settling and bubble control.

Continuous vat photopolymerisation replaces the repeated separation step of layerwise printing with a maintained liquid interface between the growing part and an optically transparent window or membrane. Continuity is possible only while inhibition, exposure, liquid transport, window condition and heat removal coexist inside a bounded state. A dead zone is therefore not a fixed geometric property. It is an oxygen- and radical-dependent reaction-transport region whose thickness and stability can change with irradiance, resin chemistry, membrane permeability, fouling, pressure, part cross-section, draw speed and temperature. This review defines a qualification method for that coupled state.

Top-down vat photopolymerisation exposes resin at or through an upper liquid interface while the part descends into the vat. The architecture avoids a transparent vat floor and its separation forces, but introduces a coupled free-surface system. Optical path length, meniscus and waves influence exposure; recoating must restore a usable layer; buoyancy and hydrodynamic forces act on the submerged build; supports must resist those loads; and scale-up changes both surface dynamics and resin inventory. This review defines system-level qualification for top-down vat photopolymerisation. It consumes the qualified global-level state from ER-246 and the qualified local surface-readiness state from ER-244, then integrates those inputs with optical and mechanical consequences without redefining either upstream control problem.

Projection vat photopolymerisation can enlarge its build area by translating or multiplexing a finite optical field. Every tile boundary then becomes a coupled geometric and photochemical interface. Registration error creates steps or duplicated features; irradiance non-uniformity changes local conversion; overlap adds dose; gaps subtract dose; resin and machine drift make a calibration unstable over time. A seamless image on a calibration target is therefore not sufficient qualification evidence. This review defines qualification of large-area projection stitching. It separates stage geometry, optical distortion, radiometric response, temporal sequencing and cured-part outcome. It requires boundary-oriented artefacts, field-wide uncertainty, endurance tests and non-compensatory gates.

Supports enable vat-photopolymerised parts to survive printing, but their removal is a separate manufacturing operation. Cutting, peeling, twisting, dissolving or thermal release transfers load into a partially or fully cured network. Fine walls can bend or crack, contact scars can erase functional detail, and inaccessible internal supports can remain undetected. A part that meets dimensional requirements before support removal may fail after it. This review defines qualification of support removal for fine features and internal geometries. It links support design to access, removal sequence, local load path, material state, surface damage and verification. It requires representative destructive trials, inspection sensitivity and explicit acceptance rules.

This Engineering Review examines biological-evaluation planning for photopolymer devices, focusing on material state, contact category, endpoint selection and evidence integration. It frames biological evaluation as a system-level qualification problem linking formulation, processing, post-cure, exposure conditions and the finished article.

This Engineering Review examines common artefacts in cytotoxicity testing of photopolymers, including extraction conditions, dose metrics, controls and interpretation of results. It focuses on how specimen state, extraction design and test configuration can affect the meaning and comparability of cytotoxicity evidence.

This Engineering Review examines analytical evaluation thresholds for photopolymer extractables, with emphasis on analytical coverage, identification, quantitation and uncertainty. It addresses how threshold concepts interact with method capability, unknowns, exposure context and the evidence needed for defensible interpretation.

This Engineering Review examines toxicological risk assessment of photopolymer constituents and leachables, including exposure estimation, hazard information, read-across and margin-of-safety reasoning. It focuses on the evidence chain connecting chemical characterisation with use-specific toxicological evaluation.

This Engineering Review examines skin-contact wearables made from photopolymers, with emphasis on occlusion, sweat, friction, sensitisation and long-term use. It considers how material state, repeated contact, environmental exposure and device geometry can influence biological and mechanical qualification.

This Engineering Review examines mucosal-contact photopolymer devices under saliva exposure, mechanical cycling, biofilm formation and extractables release. It focuses on qualification of the finished use-state rather than treating nominal resin composition as sufficient evidence.

This Engineering Review examines blood-contacting photopolymer devices, with emphasis on haemocompatibility, surface state, flow, thrombosis-related factors and sterilisation. It highlights the need to evaluate material, process, surface and device conditions together when interpreting blood-contact evidence.

This Engineering Review examines bone–implant interfaces for photopolymer-derived devices, focusing on surface chemistry, porosity, mechanics and biological evidence. It considers how bulk material properties, interfacial state and architectural design contribute to qualification of the bone-contacting system.

This Engineering Review examines the durability of antimicrobial claims in photopolymer devices, including depletion, fouling, cleaning, resistance and test design. It distinguishes initial antimicrobial performance from retained function after realistic use, ageing and maintenance cycles.

This Engineering Review examines digital traceability for patient-specific photopolymer devices, covering design input, material lot, process history and release. It focuses on linking the manufactured article to the controlled data, material and process states needed for reproducible qualification and change control.

This Engineering Review examines printed conductors and resistive elements in photopolymer systems, with emphasis on percolation, contact resistance, drift and reliability. It considers how formulation, geometry, interfaces, curing and service history influence realised electrical performance.

This Engineering Review examines capacitive sensors in printed photopolymer structures, focusing on dielectric state, electrode geometry, humidity and calibration. It treats sensor output as a coupled material–geometry–environment response rather than as a property of the resin alone.

This Engineering Review examines dielectric breakdown and insulation ageing in printed photopolymers, including defects, electric-field concentration, temperature and moisture. It addresses the qualification variables needed to connect short-term dielectric measurements with longer-term electrical reliability.

This Engineering Review examines photopolymer-enabled electrochemical electrodes, focusing on surface area, binder state, electrolyte access and cycling stability. It considers how printed architecture, interfaces and electrochemical conditioning affect measured electrode performance and comparability.

This Engineering Review examines photopolymer-derived battery components, including electrodes, separators, current collectors, cure residuals and cell qualification. It focuses on the transition from printable material systems to electrochemically functional components under defined cell and cycling conditions.

This Engineering Review examines photopolymer-derived supercapacitor architectures, with emphasis on porosity, conductivity, electrolyte wetting and cycle life. It links material formulation and printed structure to transport, interfacial behaviour and electrochemical qualification.

This Engineering Review examines electroluminescent and light-emitting photopolymer composites, focusing on field distribution, optical loss, heat generation and ageing. It considers how composition, geometry, interfaces and operating conditions govern realised light-emitting performance.

This Engineering Review examines integration of photodetectors and photosensors with printed photopolymers, including spectral response, encapsulation and signal stability. It focuses on the interaction between optical access, material state, device packaging and long-term measurement reliability.

This Engineering Review examines radiofrequency antennas and transmission structures on printed photopolymers, focusing on dielectric loss, metallisation and geometry. It treats RF performance as a system response controlled by substrate state, conductor quality, architecture and operating frequency.

This Engineering Review examines phase-change and latent-heat materials in printed photopolymer structures, with emphasis on containment, thermal cycling and heat management. It considers how encapsulation, phase transition, leakage control and repeated cycling affect functional thermal performance.

This Engineering Review examines primary-data carbon accounting for photopolymer additive manufacturing, covering energy, material consumption, yield and allocation. It focuses on transparent system boundaries and traceable inventory data rather than generic sustainability assumptions.

This Engineering Review examines solvent-recovery mass balances in photopolymer processing, with emphasis on contaminant build-up, separation efficiency and reuse limits. It frames solvent recovery as a controlled mass-balance problem involving composition, process performance and qualification of the recovered stream.

This Engineering Review examines regeneration and reuse of aqueous and semi-aqueous wash media, including dissolved organics, suspended solids and process control. It focuses on how contamination evolves during reuse and on the evidence needed to define practical regeneration and replacement limits.

This Engineering Review examines recovery of unreacted monomers and photoinitiators from photoresin waste, focusing on separation, chemical identity and requalification. It distinguishes physical recovery from evidence that a recovered component remains suitable for controlled reuse.

This Engineering Review examines purification and reuse of products obtained from triggered photopolymer depolymerisation, with emphasis on composition, functionality and closed-loop evidence. It focuses on demonstrating what is actually recovered and whether the recovered stream can reproduce intended material performance.

This Engineering Review examines recovery and requalification of functional fillers from cured photopolymer composites, focusing on separation, surface state and retained performance. It addresses how recovery processing can alter filler chemistry, morphology, interfaces and suitability for reuse.

This Engineering Review examines particle and microplastic release from printed photopolymers under wear and weathering, with emphasis on measurement and exposure boundaries. It distinguishes generation, detection and exposure assessment and highlights the importance of realistic service and sampling conditions.

This Engineering Review examines aquatic and terrestrial ecotoxicity of uncured photoresin constituents and mixtures, focusing on exposure realism and evidence gaps. It considers how hazard data, formulation context, dilution, environmental fate and actual release scenarios affect interpretation.

This Engineering Review examines analytical monitoring of wastewater contaminated by photopolymer processes, including target species, non-target screening and treatment verification. It focuses on measurement strategies that can distinguish known contaminants from broader chemical change before and after treatment.

This Engineering Review examines end-of-life decision hierarchies for photopolymer products, including reuse, repair, recycling, recovery and disposal. It frames end-of-life selection around retained function, material state, contamination, process feasibility and evidence of actual recovery performance.

This Engineering Review examines vat-printed microreactors for chemical processing, focusing on residence-time distribution, mixing, material compatibility and scale-out. It considers how printed geometry, surface state, transport and chemical resistance influence reactor performance and reproducibility.

This Engineering Review examines printed analytical labware and sample-handling devices, with emphasis on contamination, sorption, cleanliness and measurement bias. It focuses on how the printed material and post-processing workflow can influence analytical background, recovery and result integrity.

This Engineering Review examines vacuum-compatible fluidic and pneumatic components made from photopolymers, focusing on leakage, outgassing, seals and cycling. It distinguishes bulk permeation, through-defects, interfaces and volatile release as separate qualification concerns.

This Engineering Review examines printed composite tooling for lay-up, infusion and cure, focusing on surface quality, permeability, thermal expansion and tool life. It considers how the printed tool state and repeated thermal-mechanical cycles influence dimensional stability and manufacturing performance.

This Engineering Review examines sacrificial mandrels and cores for electroforming and composite manufacture, with emphasis on removal, surface transfer and dimensional control. It focuses on the full process chain from printing through secondary manufacture to clean removal of the sacrificial structure.

This Engineering Review examines printed models for wind-tunnel and flow-visualisation testing, including surface fidelity, inserts, pressure taps and load limits. It considers how dimensional accuracy, finish, instrumentation and mechanical integrity affect the validity of aerodynamic experiments.

This Engineering Review examines cryogenic service of printed photopolymers, focusing on glass transition, thermal shock, permeation, fracture and repeated cycling. It addresses the need to evaluate properties in the actual low-temperature state rather than extrapolating from room-temperature data.

This Engineering Review examines printed fixtures and holders for radiation and sterilisation workflows, with emphasis on dose stability, contamination and reuse. It considers how irradiation, sterilisation and repeated service can change material properties, cleanliness and dimensional performance.

This Engineering Review examines food-contact tooling and process aids made from photopolymers, focusing on migration, cleaning, wear and regulatory boundaries. It separates material performance from food-contact qualification and emphasises the processed article, exposure conditions and intended use.

This Engineering Review examines photopolymer additive manufacturing for cultural-heritage replication and conservation, focusing on fidelity, reversibility and ageing. It considers how material choice, surface reproduction, long-term stability and conservation principles affect appropriate use.

This Engineering Review examines the digital thread for photopolymer manufacturing across requirements, geometry, material, process, inspection and release. It focuses on maintaining traceability between design intent, manufacturing state, verification data and the released article.

This Engineering Review examines requirement traceability for additively manufactured photopolymer parts, including allocation, verification and change impact. It addresses how requirements can be linked to evidence and how design or process changes propagate through the qualification record.

This Engineering Review examines change control and requalification of photopolymer materials and processes, focusing on equivalence, risk and evidence depth. It considers how the significance of a change should determine the scope of comparative testing and requalification.

This Engineering Review examines supplier-quality management for photopolymer raw materials, including specifications, evidence-based audits, deviations and continuity. It focuses on incoming-material control and the traceable evidence needed to manage supplier and lot-to-lot variability.

This Engineering Review examines process failure mode and effects analysis for vat photopolymerisation, focusing on state variables, detection and control priority. It applies structured failure analysis to the coupled material, optical, mechanical and workflow variables that can affect print quality and qualification.

This Engineering Review examines statistical process control for photopolymer manufacturing, including sampling, control charts, drift and multivariate signals. It focuses on distinguishing common variation from meaningful process change and on selecting measurements that reflect the controlled manufacturing state.

This Engineering Review examines calibration management for photopolymer production and testing, focusing on traceability, calibration intervals, guard bands and out-of-tolerance impact. It considers how measurement-system control supports defensible process decisions and retrospective assessment when calibration is lost.

This Engineering Review examines data integrity and FAIR evidence for photopolymer qualification, including raw data, metadata, audit trails and reuse. It focuses on preserving traceability from original observations to processed results so that qualification evidence remains interpretable, reviewable and reusable.

This Engineering Review examines evidence maturity and technology readiness in photopolymer manufacturing, focusing on claims, gates and decision confidence. It distinguishes early evidence from qualification-grade evidence and considers how uncertainty should be carried into technical and manufacturing decisions.

This Engineering Review synthesises the third qualification corpus spanning ER-201 to ER-299, focusing on evidence architecture, state variables, scope boundaries, cross-paper couplings and research priorities. It provides a corpus-level map for reading the individual reviews without replacing their topic-specific evidence.