Mask design limits COVID-19 spread by killing virus in respiratory droplets

A schematic shows how a chemical modulation layer "sanitizes" the face mask wearer's respiratory droplets. Photo courtesy of Northwestern University
A schematic shows how a chemical modulation layer "sanitizes" the face mask wearer's respiratory droplets. Photo courtesy of Northwestern University

Oct. 29 (UPI) -- Researchers at Northwestern University have developed a new concept for a face mask intended to make wearers less infectious if they are sick with a virus, they said in a paper published Thursday by the journal Matter.

The design proposes treating face mask material with anti-viral chemicals to sanitize exhaled, escaped respiratory droplets, which researchers say could help in controlling the spread of COVID-19.


In an analysis that simulated wearers' inhalation, exhalation, coughs and sneezes in the lab, non-woven fabrics used in most masks, and including a lint-free wipe with just 19% fiber density, sanitized up to 82% of escaped respiratory droplets by volume, the researchers said.

Such fabrics do not make breathing more difficult, and the on-mask chemicals did not escape during simulated inhalation experiments, meaning they are unlikely to impact wearers, they said.


The chemicals would "sanitize escaped droplets from masks so that [wearers] -- symptomatic or not -- become less infectious," study co-author Jiaxing Huang told UPI.

"This helps to cut down the sources of the viruses and prevent spread, and it helps to better protect people around them, especially caregivers and healthcare workers," said Huang, a professor of materials science and engineering at Northwestern University's McCormick School of Engineering.

Since early in the pandemic, both the World Health Organization and the U.S. Centers for Disease Control and Prevention have recommended usingface coverings to limit the spread of COVID-19.

Several studies have shown that face coverings can block most respiratory droplets containing the virus from being transmitted by those infected if they are placed over the mouth and nose.

However, surgical masks, N95 masks and other coverings do not kill the virus or stop it from spreading completely, Huang said.

For this project, he and his colleagues sought to design a mask fabric loaded with antiviral agents that would not inhibit breathing. They also wanted to ensure that wearers would not inhale the antiviral chemicals themselves.

After performing multiple experiments, Huang and his team selected two well-known antiviral chemicals: phosphoric acid and copper salt. These non-volatile chemicals were appealing because neither can be vaporized and then potentially inhaled -- and both create a local chemical environment that is unfavorable for viruses, the researchers said.


The team grew a layer of the conducting polymer polyaniline on the surface of the mask fabric fibers and found that even loose fabrics with low-fiber packing densities of about 11%, such as medical gauze, still sanitized 28% of exhaled respiratory droplets.

With tighter fabrics such as lint-free wipes -- the type of fabrics typically used in the lab for cleaning -- 82% of respiratory droplets were sanitized, the researchers said.

For now, the mask design is still in the concept stage, and is some time away from commercial development, Huang said.

However, the findings should provide a platform for future research and development, he said.

"Masks are not just personal protection equipment -- they are more like public health equipment," Huang told UPI.

"The current work is designed to enhance masks' function as public health equipment [and] provides the scientific foundation for enhanced public health equipment function of masks, [so] we welcome anyone who is interested and equipped to commercialize it," he said.

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