Researchers at Northwestern University have developed a new concept of face mask that aims to make the wearer less infectious, in addition to protecting others from coronavirus disease 2019 (COVID-19).  

The idea focuses on modifying mask fabrics with antiviral chemicals that can sanitize exhaled, escaped respiratory droplets. By simulating inhalation, exhalation, coughs, and sneezes in the laboratory, the researchers discovered that non-woven fabrics used in most masks work well to demonstrate the concept.

For example, a lint-free wipe with 19% fiber density sanitized up to 82% of escaped respiratory droplets by volume. Such fabrics do not make breathing more difficult since the on-mask chemicals did not detach during simulated inhalation experiments, according to the study.

“Masks are perhaps the most important component of the personal protective equipment needed to fight a pandemic,” said lead researcher Jiaxing Huang, PhD, from Northwestern University, in a press release. “We quickly realized that a mask not only protects the person wearing it, but much more importantly, it protects others from being exposed to the droplets (and germs) released by the wearer.”

Huang and his team designed a mask fabric that would not make breathing difficult, can load molecular antiviral agents—such as acid and metal ions—that can readily dissolve in escaped droplets, and does not contain volatile chemicals or easily detachable materials that could be inhaled by the wearer.

After experimentation, 2 well-known chemicals were chosen: phosphoric acid and copper salt. These non-volatile chemicals were appealing because neither can be vaporized and then potentially inhaled, while both creating a local chemical environment that is unfavorable for viruses, according to the study.

A layer of a conducting polymer polyaniline on the surface of the mask fabric fibers was grown by the research team, as the material adheres strongly to the fibers and acts as a reservoir for acid and copper salts. Even with loose fabrics with low-fiber packing densities of approximately 11%, such as medical gauze, the mask still altered 28% of exhaled respiratory droplets by volume. However, for tighter fabrics, such as lint-free, 82% of respiratory droplets were modified.

Limitations of the study include many researchers having to receive “essential” designation to work throughout Illinois’ “Stay-at-Home” order and the difficulty of how to measure and quantify the degree of chemical modification of escaped droplets, according to the authors.

“For acid-modified droplets, I thought we could do this simply by collecting them on a pH paper and seeing the color changes of the landed droplets,” Huang said in a press release. “I insisted that Haiyue and Hun should try this first, and only to realize that it wasted a few weeks of their time.”

Huang added that the droplets tend to spread out on pH papers, leaving barely detectable drying marks, as the pH dyes do not have enough color intensity to generate a clear contrast of the dried droplets under optical microscope. After discovering the color indicator for acid itself in polyaniline, the research team was able to generate hundreds of microscopy images.

The research team hopes the current work on the mask will provide a scientific foundation for other researchers, particularly in other parts of the world, to develop their own versions of the mask and test it further with viral samples or patients.

REFERENCE
Face mask aims to deactivate virus to protect others. Northwestern University. https://news.northwestern.edu/stories/2020/10/face-mask-aims-to-deactivate-virus-to-protect-others/#:~:text=In%20the%20pandemic%2C%20people%20wear,team%20of%20Northwestern%20University%20researchers.&text=The%20research%20was%20published%20today,29)%20in%20the%20journal%20Matter. Published October 29, 2020. Accessed November 4, 2020.