Regulatory barriers to face shield production
Given that Health Canada Medical Device Establishment Licence (MDEL) considerations include the processing of a licensing application, as well as in-house production of PPE, we decided to forego licensing in order to meet the direct needs of healthcare workers in a timely manner. Although an MDEL was not obtained, we ensured due diligence in production, decontamination, and communication about the processes involved to ensure that the face shields were reliable and safe for use. In order to do this, the components of the face shield, the 3D printed visor and the plastic sheet, were delivered disassembled to the receiving organization, and a waiver of liability was signed by the organization receiving the donation. Disassembly minimizes further points of contact by volunteers, ensures decontamination is retained, and maximizes the number of face shields that can be transported at a time.
Quality versus production capacity
Print speed is a key variable associated with optimal face shield quality and production capacity. The 3DVerkstan design’s recommended print settings (e.g. 0% infill, 1.6 mm wall thickness) fostered the printing of face shields at stable speeds (40–60 mm/s), while printing at very high speeds to increase production (60–125 mm/s) resulted in issues such as overheating of face shields frames due to insufficient cooling. In addition, other printing errors such as wrapping, ringing, and weak layer adhesion often occurred [26, 27].
Stacking was a means of maintaining quality while increasing production speed. This method was only carried out by advanced printing operators who had the expertise to troubleshoot and conduct experimental runs until optimal print settings for their printers were identified. It was essential for stacks printed at high speeds to maintain quality without resulting in breaks during detachment.
In future endeavors, we recommend that novice printer operators maximize their printer bed by arranging at least 2 shields on the bed, and printing at comfortable speeds (40–50 mm/s) when using simple printers with small print nozzles (0.4 mm). In addition, to optimize time spent managing printing, we suggest alternate modes of production for novice printer operators, such as printing singles during the daytime and printing stacked face shield frames for overnight prints. Furthermore, the use of post-production treatment protocols, such as sanding or an acetone wash, should be performed to remove 3D printing lines that render the face shield as less visually aesthetic to ensure end-user peace of mind.
It is important to note that sterilization and disinfection are both decontamination processes, however, they execute different degrees of organismal destruction. While both are essential for proper healthcare delivery, sterilization destroys all microbial life whereas disinfection eliminates many or all pathogenic microorganisms, with the exception of bacterial spores. In this particular case, sterilization is not essential for safe and effective use of the 3D printed face shields, as per CDC guidelines .
Unsuccessful techniques that were performed included thermal sterilization (i.e. autoclave and dry heat), laboratory glassware washer, and EtO/H2O2 gas sterilization. Each technique presented unique challenges. As previously mentioned, PLA and PETG were chosen as the thermoplastic filaments of choice which have a glass transition temperature of approximately 60–65 °C and 80–85 °C , respectively. Autoclaving is one of the most rigorous and accessible sterilization techniques, requiring elevated pressure and a sustained temperature of 121 °C for a defined period of time . When the 3D printed frames were exposed to the pre-set autoclave dry plastics cycle conditions, the frames warped and fused together. Furthermore, autoclaving and steam sterilization have been found to decrease the mechanical strength of such plastics . The Laboratory Glassware Washer G 7883, Miele Professional was thereby trialed due to its low temperature settings and sanitization capabilities, however, the results were much the same. Finally, a hot air dryer was trialed at the recommended and verified temperature of 65 °C for 60 min to eliminate potential bacteria and viruses present on the surface. While this method was successful, disinfection was limited to the number of frames that could be disinfected at one time and by the longer exposure time . Alternative sterilization methods, such as low-temperature gas sterilization using EtO or H2O2, have been validated for use on 3D printed materials . However, these protocols are not cost-effective nor readily available, as their use had been reserved for re-sterilization of N95 masks used by frontline workers.
Bleach, or 10% sodium hypochlorite, is a commonly utilized disinfectant amongst similar PPE initiatives. However, a concern of using bleach is that if the protocol is not followed precisely (e.g. the frames were not thoroughly rinsed with water, the bleach solution is not diluted correctly, or the frames are submerged for an inappropriate amount of time) the solution can cause potential degradation of the material, effectively altering the integrity of the frames [32, 33]. This is in part a consequence of using Fuse Deposition Modeling, which results in a porous structure of the printed material [34, 35]. Bleach is an extremely corrosive agent that degrades even the most resistant materials (e.g. epoxy), must be remade daily, and must be disposed of carefully as it cannot be poured down the sink . In addition, the use of bleach over time has the potential to cause yellowing of the plastic shield, compromising visibility. Furthermore, we discovered that using bleach incorrectly on these items may also cause skin and eye irritations for the user . Based on these findings, it was necessary to find an alternative disinfection protocol that would have less variability.
Limitations of ethanol
While there are many benefits to using ethanol, there are a few shortcomings that must be taken into consideration. Ethanol is a volatile molecule that evaporates very quickly. Products must be completely submerged for the appropriate amount of time to ensure complete disinfection and should be used in a well-ventilated area. Furthermore, 100% ethanol cannot be obtained by the general public and therefore must be obtained and used in a certified facility. Finally, there are a number of thermoplastics that can degrade from prolonged exposure to various incompatible liquid solvents . For this reason, it is important to select a disinfectant based on the characteristics of the selected plastic.