Face shield developed by the University of São Paulo is produced by industrial firms

3D printed face shields are worn by frontline health workers over a conventional surgical mask.

By José Tadeu Arantes  |  Agência FAPESP – Face shields have become an extremely important personal protective equipment (PPE) item for frontline health workers fighting COVID-19. Resembling motorcycle helmet visors, they provide physicians, nurses, nurse technicians, physical therapists and other personnel with a first barrier that shields the eyes, nose and mouth against droplets containing the virus expelled by patients. Eye protection and a conventional surgical mask must be worn under the face shield.

The need to produce large numbers of face shields very quickly has mobilized several groups who work with additive manufacturing, which uses a 3D printing technique known as FFF (fused filament fabrication). In recent months, these groups have begun networking globally via digital media and are already turning out “Prusa shields” based on an open-source design created by Czech entrepreneur Josef Prusa.

One of the nodes in this network is the Research Group on Additive Manufacturing and Design for Assistive Technology, led by Zilda de Castro Silveira, a professor in the Mechanical Engineering Department at the University of São Paulo’s São Carlos Engineering School (EESC-USP) in Brazil and researcher in the university’s Center for Advanced Manufacturing (NUMA). NUMA is supported by FAPESP via the Thematic Project “Study, Development and Application of Hybrid Processes: Additive Manufacturing (AM) Plus High Speed Machining/Grinding (HSM/G)”, the principal investigator of which is Reginaldo Teixeira Coelho. The Physical Therapy Department at the Federal University of São Carlos (UFSCar) is also participating in the initiative.

“In our first week, we produced 210 face shields for the Santa Casa hospital in São Carlos. This fast-track initiative inspired the plastics industry to mass-produce shields with the same design to meet demand from many more hospitals,” Silveira told Agência FAPESP.

According to ABINFER, the Brazilian toolmaking industry association, which has companies in six states (São Paulo, Minas Gerais, Paraná, Santa Catarina, Rio Grande do Sul and Amazonas), started producing injection-molded head and chin bands for face shields in late March. ABINFER also estimates that by May 7th, these companies had donated more than 296,000 face shields to institutions all over Brazil, most of which are based in the state of São Paulo (the destination of over 133,000 deliveries) and the three states that form the country’s South Region (approximately 68,000 deliveries).

Silveira says their production capacity is approximately 6,000 units per mold. In São Carlos, she reported that some 1,500 head and chin band sets have been donated to the Santa Casa hospital and USP’s university hospital.

Porosity is an issue for 3D printed shield producers. “Because items produced by additive manufacturing are structured in layers, they’re more porous than products made by conventional techniques. This porosity doesn’t stop the face shield from acting as a physical barrier but makes it more vulnerable to contamination,” Silveira explained. “To compensate for this, we apply acetone, which helps reduce surface porosity by chemical reaction. To reinforce decontamination, we worked with Santa Casa and Sterileno, a firm that specializes in the sterilization of hospital equipment, to test sterilization with hydrogen peroxide [H₂O₂], which proved effective. As a result, the hospitals are using this disinfection procedure for face shields.”

Institutions that receive the items produced by the manufacturers can sterilize them with hydrogen peroxide between uses.