3D Printing: Not quite a Star Trek replicator!
When Covid-19 arrived on the scene, many owners of 3D printers came to the rescue. Making a medical device with a 3D printer was clearly child’s play. Headlines were filled with stories of students making face shields and respirator masks in their bedrooms and sending them off to the needy healthcare professionals. There were few if any headlines concerning harms from such homemade medical devices so presumably they worked adequately, or the recipients slipped them quietly into the trash bins.
Rather than sound like a wet blanket, the intention here is to urge budding entrepreneurs to consider the potential risks associated with 3D printed medical products and to use the tips of the trade known to the established medical device 3D manufacturers. These tips are certainly valid for any existing medical device manufacturer employing 3D printers as part of a production program.
Unlike a Star Trek replicator a 3D printer cannot make “Earl Grey Hot”. Most common 3D printers work with polymers, but there are some notable exceptions we will discuss below. Considering the common polymer 3D printers, the most prevalent now use melted polymer resin that cools as it is deployed by one or more printer nozzles. This type of printer known as Fused Deposition Modeling (FDM) works with a filament of the chosen polymer and layered into the desired shape and cured. Stereolithography uses light to cure a resin, usually within an inert fluid, so the device can be formed in fine detail. The 3D printing polymers cover the range of chemistries and properties so the first task you have is to select the material that has the properties your medical product will need in its final form (finished or semi-finished goods.)
Obviously, the final device may make a difference in the optimum processing parameters but another factor affecting safety of the device is the medical suitability of the material after the manufacturing process is complete. You need to be aware that even if your use a “biocompatible material” the production process may render the material unsafe. The completed process of 3D (additive) manufacturing must assure that there are no toxic by-products from the manufacturing steps. Toxic by-products can result from incomplete processing, variations in the manufacturing conditions and errors in handling the formed component in subsequent processing. If you hope to continue manufacturing your 3D printed wonder-device after the Covid-19 “all clear”, you will be responsible for conducting a Biological Risk Assessment which includes a robust risk analysis of the materials and processing parameters and final device testing before marketing the device. (Elsewhere in this website we explain the FDA requirements for FDA market clearance or approval.)
3D Printing Metals
It did not take long once polymer forming with additive manufacturing came into medical device manufacturing that metal forming with similar techniques was available. Metal powder with a “binder” can be formed and then sintered to produce the final shape or metal may be formed in the presence of a high-powered laser directly to the final form. Post-forming processes of metal can, like with the polymer-based form, introduce potentially toxic by-products.
Physical Uniformity and Integrity
Most 3D printed devices include voids within the structure. The voids can assure the lightest possible device and conserve the use of materials. Voids can also weaken the device in ways that are not apparent until the product has been used more extensively. A 3D printed product may look identical to a machined or molded product but be vulnerable to stress fractures from surface defects and thin walls not apparent at the time of formation. Manufacturers must not only design the manufacturing process to optimize the device form, but also understand where these vulnerabilities to static and fatigue forces may develop when used as intended. Initial prototypes may not reveal what happens after multiple runs of the same device. Validation of manufacturing processes is just as important for 3D manufacturing as for other processing methods. The protocol for the process validation must reflect the manufacturing risks associated with both the device form and the manufacturing process drift.
FDA has attempted to provide medical device manufacturers employing 3D manufacturing with guidance on safety and qualification considerations. We highly recommend “Technical Considerations for Additive Manufactured Medical Devices” issued 2017. You may find interesting the video: titled “The 3Rs of 3D Printing: FDA’s Role.
To Boldly Go?
Perhaps an indicator that “bioprinting” with a 3D printer has become common knowledge is when we find a Wikipedia page on the subject. Bioprinting is no longer news. Already the ethics of ownership and the challenges of regulation of “bioprinted” organs and tissues is a concern. Could we soon see, for example, instead of bone graft particulates, a fully shaped bone replacement equipped with its own marrow? And what of making an organ or a portion of an organ using a scaffold upon which cells have been seeded prior to implant? In a Star Trek Next Generation episode Jean Luc Piccard received a replacement heart but it was made from synthetic materials, suggesting that we have leaped past science fiction! We may see “artificial cell lines” for sale which can be manipulated into various organs based upon the “software” encoded into the cells and preprogrammed manufacturing variables. Regardless of the materials and the machines, my bet is on the FDA figuring out how to regulate the safety of 3D bioprinting. When they do Paladin Medical®, Inc. should be right here to help you find the guidance documents you need and the regulatory strategy to pursue.