New method for restoring N95 masks to meet COVID demand

A researcher at the University of Tokyo is developing a method for refilling the N95 mask with a van de Graaff generator, which could significantly reduce the lack of high-quality personal protective equipment during the whole disease COVID-19 release. Credit: Institute of Business Science, University of Tokyo

A researcher from the Institute of Industrial Science at the University of Tokyo has unveiled a new method for recovering sterilized N95 masks so that they can be reused. By exposing the masks to 100 kilovolts for 3 minutes after sterilization in hot water or autoclave, they recovered their static charge. This work can be implemented quickly to help meet the high demand for protective equipment that will prevent the spread of the COVID virus.

Through the current COVID pandemic, N95 masks have become essential for keeping health care workers and first responders safe. The name comes from the fact that these masks can filter more than 95% of airborne granules, even though their pore sizes are ten times larger than the tiny aerosol granules that the virus can carry. The trick is that the N95 masks are made of electrospun polypropylene fiber, which retains a static electricity charge that can attract and capture the charged aerosols. However, this static charge cannot withstand conventional sterilization methods, such as hot water washing or automation. Even the moisture in the wearer’s breath can reduce the efficiency of the electric pull. For this reason, the masks are often discarded after a single use, which greatly increases the gap between the number of N95 masks required and the number available.

Now, a researcher at the University of Tokyo has shown that sterilized masks can be returned to use after they have been refilled using a van de Graaff generator. These devices, familiar to many science museum visitors, use the friction from a spinning belt to generate very high voltages between two metal conductors. “Utilizing the high voltage provided by the van de Graaff generator, this method is much faster than other methods,” says study author Kaori Sugihara. To restore a previously sterilized mask, it was attached to the largest metallic globe, while the smaller globe was placed several centimeters away for 3 minutes. The refurbished masks were tested and shown to be comparable in seeding capacity to unused masks.

“We hope this approach will allow many more people access to N95 masks every day, and this is our best line of defense against the spread of COVID,” Sugihara says. Because van de Graaff generators are much cheaper and safer to use than other high voltage sources, this method can be easily applied in hospitals and other places where N95 masks are most needed. The work is published in Soft case such as “Restoring N95 masks with van de Graaff generator for safe recycling. ”

Information: 17 December 2020, Soft case.
DOI: 10.1039 / d0sm02004d