3Dresyns conductive 3D resins and additives contain micron, and/or submicron, and/or nanoparticles, and/or nanowires, and/or microfibers, which indendently on their shape need to be fully wetted, dispersed (fully uncoiled for nanowires and microfibers), stabilized in suspension, and fully homogenized to ensure maximum conductivity readings for each conductive resin system.

Conductivity basics and requirements

The conductivity results from the interconnection ensurance of individual particles, nanowires, or microfibers, which it is affected by their distribution in the printed 3D resin. Unfortunately, nanowires and microfibers naturally tend to coil, creating webs and clumps among themselves. Agglomeration of nano, micron, and submicron particles, nanowires, and microfibers in clumps or agglomerates occurs naturally due to electrostatic interaction, even in solid form. Gravitational separation and decantation tends to occur due to the high density of metallic materials (silver has a density of 10.49 g/cm³) in comparison to the much lower density of resins (most resins have densities of 0.95-1.05 g/cm³).

Full homogenization and homogeneous distribution of the active conductive material during printing, without settling issues is necessary for achieving conductivity of the prints.

Difficulties and limitations of 3D printable conductive materials 

Unfortunately, ready to use conductive 3D resins based on metallic nanomaterials, such as silver or copper, can gel during transportation since they are prone to polymerize at temperatures above 40-50ºC, reducing their shelf life significantly. Due to this limitation, they cannot be sent predispersed in the 3D resin because silver nanomaterials suffer from premature gelation, specially in summer due to exposure to excessive temperature during shipping. They are also prone to suffer from separation "settling" from the liquid medium, and gelation by "polymerization" and/or by foam formation, when exposed to too high shear and heat in the microscopic and macroscopic level, such as with too high speed mixing and too high sonication power, frequency and time.

Key variables affecting conductivity

The provided conductivity values shown on each product information are achievable conductivities, not fixed values, since final conductivity readings depend on these key variables:

  • the degree of deagglomeration, stabilization, and homogenization of the conductive material in the 3D resin 
  • the chosen resin and its potential contribution to conductivity 
  • the final suspension stability of the conductive additive in the chosen 3D resin, since each one has different viscosity, provide different wetting, and suspension stability
  • dispersion equipment and specifications used since:
    • too low dispersion settings cannot ensure full deagglomeration, stabilization, and homogenization
    • too high dispersion settings can cause gelling of the resin, by excessive foam formation, or by polymerization, as well as breaking the conductive nano and micron materials, specially sensitive to breakage are long and thin nanowires, which upon excessive shear can be broken reducing the conductivity
    • vortex mixers are ideal for dispersing conductive resins at low concentrations and viscosities in test tubes since cross-contamination and excessive heat is prevented because direct contact with the conductive 3D resin system with sharp blades is prevented. Blades can cause excessive heat in the contact area of the blade with the resin inducing premature thermal polymerization. Vortex mixers tend to create excessive foam formation. Use vortex mixers gently. If too much foam is formed, warm it gently to promote foam elimination and use vacuum to remove air bubbles
    • rotary mixers or stirrers are often too big for small mixing quantities, unless small Conn blades are used. Avoid excessive shear to prevent gelation, caused by polymerization due to excessive heat generation, or by foaming. Cowles blades are less prefered than Conn blades because they generate too much friction due to their sharp cutting edges.  
    • magnetic stirrers are not recommended since they cannot fully disperse nanomaterials  at high concentrations or viscosities due to their low mixing yield 
    • high-speed dispersers, also known as high-speed homogenizers, are capable of homogenizing efficiently conductive 3D resins. At too high speed they can cause gelation, due to excessive shear, and local heat generation, causing premature polymerization, excessive foaming, and breaking of delicate nanowires and microfibers, reducing their conductivity. On the other hand, high-speed homogenizers at low speeds can be used efficiently to mix viscous components. Avoid cross-contamination which may reduce the conductivity
    • ultrasonic cleaning machines and ultrasonic probe sonicators (also known as ultrasonic liquid processors) can be used with caution to prevent gelation of the photo and thermally reactive conductive 3D resin. Excessive sonication by too high frequency and time, generate excessive heat, which can promote premature polymerization 
  • Instrumentation and specifications used for measuring conductivity
  • Annealing of the prints by heating them to at least 80-140ºC for eg 30 min promote conductivity. The annealing temperature depends on each conductive material properties

Final conductivity readings depend on the mentioned variables, which are beyond 3Dresyns direct control. Additionally, conductivity values and dosages are generic or typical as highlighted on each product information, since for example, nanowires, due to their relative high length and low thickness tend to coil in webs and clumps, and break with excessive shear. Nanowires length and integrity need to be preserved during processing. They need to be fully deagglomerated, uncoiled, stabilized, and homognized before and during printing to avoid any decrease of conductivity. Similar requirements are needed for conductive materials with particle morphology, since despite not suffering coiling, their agglomerates need to be wetted, deagglomerated, stabilized, and homogenized, and its re-agglomeration and sedimentation prevented, to provide conductivity.   

Recommended additives for 3D printable conductive resins 

The following 3Dresyns additives are recommended for custom design of conductive resin systems:

Conductive additive processing

If conductivity values are lower than the achievable reported ones mentioned on each product information, the whole dispersion, stabilization and homogenization process may need optimisation. Excessive foaming can reduce conductivity readings since entrapped air act as conductivity insulator.

An increase of the conductive additive dosage is recommended since conductivity values are approximate, depend on the specific resin to which the conductive additive is added, and on the overall processing conditions used. If needed increase the dosage of conductive additive as much as needed, and ensure its full dispersion, deagglomeration, stabilization, and homogenization before printing. Without the optimum deagglomeration of agglomerates and clumps conductivity will be significantly reduced. The conductivity depends not only on the degree of dispersion and deagglomeration of the conductive additive but also on its dosage, its suspersion stability, and the potential contribution to conductivity of the chosen 3D resin.

Contact us for consultation before placing your orders at: info@3Dresyns.com