Out of the Printer and Up your Nose
Category: Manufacturing Technology • Feb 11, 2021
By Chuck Schroeder, IMTS Media Representative/Owner – Insight Marketing
Millions have cursed while a nasopharyngeal (NP) swab stabbed their brain as part of COVID-19 testing. Although they have a diameter of just 0.15 in., it feels as if most of their 6 in. length goes into the nasal cavity. While unpleasant, consider the blessing of 3D printing and its ability to answer the call for rapid prototyping and large-scale production when it mattered the most.
As with masks, gowns and other healthcare products, NP swabs for virus testing could have been a supply chain casualty because of inadequate stockpiles. One of the companies who stepped into the gap was Formlabs, a 3D printing company with headquarters in Massachusetts and offices in North Carolina, Germany, Japan, China, Singapore, and Hungary. Working in collaboration with healthcare and educational institutions in the United States and Singapore, Formlabs helped develop 3D-printed alternatives in record time.
In just two days, a team from the Clinical Applications Division of USF Health (University of South Florida) and Northwell Health (New York’s largest healthcare provider) developed prototypes using Formlabs’ 3D printers and a biocompatible resin. By late April, Northwell Health was making 5,000 swabs per day.
In Singapore, Dr. Ho Chaw Sing, the managing director of the National Additive Manufacturing Innovation Cluster (NAMIC), called upon the support of Formlabs and its distribution partner, Eye 2 Eye, to quickly develop a clinically validated, cost-effective 3D-printed NP swab. Multiple divisions at National University of Singapore tested 30 prototypes, and in less than two months, Eye 2 Eye had ramped production to 30,000 swabs per day.
While the rapid design and prototyping capabilities of 3D printing have been well documented as part of COVID-19 responses, the availability of biocompatible materials has not been covered as thoroughly.
“Immature material availability is a major issue the additive manufacturing industry needs to address in order to achieve its full potential,” says Dave Burns, Senior Advisor, AMT and Principal and Founder of Global Business Advisory Services. For example, Burns notes that biocompatibility issues created roadblocks for 3D printing of respirator components.
Fortunately, Formlabs had a ready-to-go solution thanks to its “Surgical Guide Resin,” a biocompatible material designed for stereolithography (SLA) 3D printing of Class I devices, such as dental surgical guides, drilling templates, pilot drill guides, and device sizing templates. Formlabs does not disclose the chemical composition of Surgical Grade Resin, but notes that it is non-cytotoxic, non-irritating, not a sensitizer, and complies with ISO 10993-1:2018 Biological evaluation of medical devices. It has been rigorously tested with autoclaves, solvents, and implant systems and was designed to work with Formlabs SLA printers for improved part quality, accuracy, and mechanical properties.
While those with a swab excavating their nasal cavity might not appreciate it, Surgical Guide Resin has a high flexural strength (≥ 70 Mpa) and flexural modulus (≥ 2,000 Mpa) to minimize brittleness and breakage. In fact, companies have to design a break point into the 6-in.-long swabs so that it will fit into the test tube for processing.
Anyone who has had a sunburn, professional manicure, or a dental crown installed has experienced the power of UV light, a form of electromagnetic radiation. UV photons have a shorter and more powerful wavelength than visible light, and they contain enough energy to initiate a range of photochemical reactions, such as turning skin red, quickly setting nail gel, or curing epoxy to set a dental crown in seconds instead of hours.
The SLA process only cures resin to a “green” state. If you select a spot anywhere on a printed part and zoom into the molecular level, you could follow the polymer chain to any other spot on the part. However, a green part still has some open polymer connections (“reactive groups”) that can further cross-link, and closing these connections is required for biocompatibility.
Following an alcohol bath and air drying, curing NP swabs starts with increasing the temperature to 60o C for 30 minutes. Higher temperature promotes molecular mobility and the probability that reactive groups within the resin can link with each another.
The curing machines also use UV light. SLA resins contain compounds called photoinitiators. When exposed to UV light, photoinitiators produce “radicals,” which are atoms or molecules with an open electron shell—think of them as molecular match makers that initiate polymer chain growth. As the radicals cause more crosslinks to form within the polymer network, the part’s strength, stiffness, and temperature resistance improve.
For a further look into the interesting world of NP swab production and 3D printing, follow AMT manufacturing technology analyst Stephen LeMarca on his visit to Formlabs. Part of the Road Trippin’ with Steve series on the IMTS Network, Stephen gets an inside tour of Formlabs’ “printing farm” and research facility in Cambridge, Mass. With millions of NP swabs produced with Formlabs technology, there’s a high probably that your connection with additive manufacturing is right under your nose.