Instructions for Use IFU for biocompatible resins

The printing of biocompatible resins requires appropriate printers, printing and postprocessing settings and equipments (light box and quality control equipments), including well implemented biocompatible manufacturing protocols and workflows.

Ideally, 3D resins need to be designed and tuned in accordance with appropriate printing and postprocessing units, protocols, and workflows for achieving maximum biocompatibility:

3Dresyns offers consulting services to help biomedical device manufacturers to design and implement appropriate protocols and workflows to manufacture biomedical devices compliant with the relevant applicable regulations (FDA and ISO, class I, II, III, IV, etc). For more info read:

Required equipment:

  • high power printers and light boxes which do not suffer from light power decay upon usage are needed to ensure and warranty the quality and safety of 3D printed biomedical devices:
    • printers and light boxes with too low light and variable powers can yield to low polymer conversions leaving excessive unreacted monomers and extractables due to undercuring, which reduce biocompatibility since free unreacted monomers and extractables can leach out and be extracted during usage (eg extracted by saliva in the mouth in dental applications) unless 3D printed biomedical devices are fully cured and free of extractables before commercialisation and usage
  • a thermal oven (optional, needed in method 2 is used)
  • quality control instrumentation to ensure that biomedical devices comply with the relevant quality and safety specifications

Printing

Follow our general Instructions for Use "IFU" and our more specific IFU for different printing technologies, which can be requested by email to info@3Dresyns.com after ordering our 3Dresyns 

Cleaning and postprocessing biocompatible protocols

The following cleaning and postprocessing protocols are required for obtaining maximum biocompatibility of prints. Follow our postprocessing instructions without cutting corners for getting optimum biocompatibility results:

Method 1: Light box post-curing of prints in immersion/dipping  (recommended process)

Features:

  • fast & easy process, recommended with the required usage of Cleaning Fluid NW1 Bio (odorless version yields increased gloss, transparency, and biocompatibility)
  • without the usage of Cleaning Fluid NW1 Bio maximum gloss and transparency of clear resins will not be obtained independently of the resin used, when alcohols, such as ethanol or isopropanol IPA are used for cleaning since they cause whitening and embrittlement of prints

Process:

  • remove prints from the build platform with a spatula
  • cut the supports
    • dip prints inside a washing basket in a washing container filled with warm Cleaning Fluid NW1 Bio:
      • it is odorless, ultra safe and non-flammable
      • warm the Cleaning Fluid NW1 Bio to <65ºC with eg a kettle (always below 65ºC to prevent yellowing)
    • remove any uncured resin from the prints positioned in the basket while stirring the warm Cleaning Fluid NW1 Bio at <65ºC with a magnet stirrer (wash mode of the Wash & Cure machine)
    • once prints and washed and cleaned dip them again in the same (or another) transparent container filled with fresh and clean Cleaning Fluid NW1 Bio**
    • postcure prints at room temperature inside Cleaning Fluid NW1 Bio in the light box for 15-30-45-60 minutes or more (cure mode of the Wash & Cure machine):
      • light box curing times depend on the power and wavelength of your specific light box
      • low light power postcuring units require longer times than high power postcuring units
      • too short light box postcuring can leave a too high concentration of unreacted monomer
    • after light box postcuring remove Cleaning Fluid NW1 Bio from the surface of the prints by spraying isopropanol on its surface to remove any rest of Cleaning Fluid NW1 Bio

    Options and different possible scenarios:

    • if the prints are too sticky, increase the light postcuring time inside clean Cleaning Fluid NW1 Bio
    • once the prints are non-sticky prints can be dipped in warm Cleaning Fluid NW1 Bio for 20-30 minutes or longer to remove hydrophobic extractables, leachables, contaminants, residual uncured monomers, and other hydrophobic byproducts
      • the higher the temperature and dipping time the higher the biocompatibility
      • materials non sensitive to temperature will require dipping temperatures of 90-100ºC
      • materials sensitive to temperature will require dipping temperatures of 60-70ºC
    • followed by a dip in warm*** water for 20-30 minutes or longer to remove hydrophillic extractables, leachables, contaminants, residual uncured monomers, and other hydrophillic byproducts

    *Note: for more info read Do you want to go in depth? Let´s unlock the black box!

    **Note: ideally use fresh unused Cleaning Fluid NW1 Bio to avoid contamination of prints with uncured resin from previous washings.

    ***Note: despite being Cleaning Fluid NW1 Bio ultra safe it has a residual bitter taste, which is transfered to the prints. To remove it, instead of using just warm water, use combinations of water and Cleaning Fluid Bio (version 2) at 50%/50% ratio to remove the bitter taste. Boiling water is ideal for removing extractables, unfortunately, not all 3D printed resins will withstand 100ºC without suffering a decrease of mechanical strength. Decrease and adjust the temperature to 60-70ºC if your prints do not withstand boiling water. Excessive temperature and time of dipped prints in water can decrease their gloss.  

    Method 2: Light box post-curing of dry prints in air atmosphere (also recommended if you have an oven, but do not have Cleaning Fluid NW1 Bio)

    This altenative method does not require the use of any cleaning fluid, but requires the use of a thermal oven for dipping out the uncured resin from the prints after printing and of solvents for removing any residual extractables from prints.

    Features:

    • ideal for dripping out of the uncured resin from the prints by gravity in an oven at 65ºC without the need for using cleaning Fluid NW1 Bio, which despite being ultra safe and biocompatible confers a bit of bitter taste to the prints
    • there is not any residual bitterness caused by Cleaning Fluid but still residual and extractables need to be removed by dipping the prints in hydrophobic solvents and in warm water

    Process:

    • after printing cut the supports and let the uncured resin drip out by gravity from the surface of the prints in the upside down position in an oven heated at <65ºC from 15 to 60 minutes (leave prints upside down, and rotate them for maximum drip out by gravity)
      • the higher the viscosity of the resin the longer time needed for dripping out
      • avoid temperatures above 65ºC to prevent yellowing
    • postcure the dry prints in a normal light box for 15-30-45-60 minutes* at room temperature
    • turn the prints upside down and postcure them for other 15-30-45-60 minutes* 
    • clean and remove any residual stickiness by spraying ispropanol isopropanol IPA on the prints (use a spray bottle to ensure that clean IPA is always used)

    Options and different possible scenarios:

    • if the prints are too sticky increase the light postcuring time
    • once the prints are non-sticky, prints can be dipped in your chosen warm non flammable hydrophobic solvents, or in our recommended Cleaning Fluid NW1 Bio for 20-30 minutes or longer**** to remove hydrophobic extractables, leachables, contaminants, residual uncured monomers, and other hydrophobic byproducts
      • the higher the temperature and dipping time the higher the biocompatibility
      • materials non sensitive to temperature will require dipping temperatures of 90-100ºC
      • materials sensitive to temperature will require dipping temperatures of 60-70ºC
    • followed by a dip in warm**** water for 20-30 minutes or longer to remove hydrophillic extractables, leachables, contaminants, residual uncured monomers, and other hydrophillic byproducts

    ****Note: The optimum time and temperature will need to be determined by experimentation since depends on many variables beyond our control, such as the resin, the printing and light box specifications, light power and wavelength, and your final biocompatibility specifications.

    Discover how method 1 and 2 compare to the cleaning with conventional alcohols which cause matting, whitening, and embrittlement to prints: Comparison of different methods for cleaning and post processing 3D printed resins

    Summary

    When instructions are followed without cutting corners prints with excellent gloss, transparency, surface quality, light fastness, mechanical strength and biocompatibility can be successfully made. The polymer conversion, the removal of extractables, and the overall cleansing yield depend on the cleaning time and chosen temperature of the solvents used for extracting residual monomers and extractables. The higher the temperature the shorter the time needed for fully cleansing the prints. Some 3D resins have been designed to withstand high temperatures (boiling water) without mechanical degradation and yellowing. At the boiling temperature of water the cleansing yield is increased resulting in increased polymer conversion and removal of extractables, leachables, contaminants, and byproducts. Some 3D resins can suffer a significant decrease of mechanical strength when boiled in water. In these cases, use hot water at <70-90ºC and longer cleaning times to prevent any potential decrease of mechanical strength. Excessive temperature and time of dipped prints in water can decrease their gloss.  

    Biocompatible prints will not be ready for usage until maximum polymer conversion and full cleansing are achieved. Biocompatible prints should be free of hydrophillic and hydrophobic extractables and leachables before usage. The safety and biocompatibility of 3D printed biomedical devices are responsibility of medical device manufacturers since quality and safety depend on the quality of their sold products, which depends on the design, implementation, quality assurance and  "in house" production of their products with the right printing and postprocessing protocols and controls.   

    For more info about biocompatible 3D printed resins read:

    Learn more about the effect of printer and printing specifications on the properties of tested standards:

    Learn more about Sterilization of 3D printed resins for medical devices