Advanced face mask kills bacteria and viruses when exposed to the sun

A cotton face mask that uses a special fabric that can kill 99.99 percent of bacteria and viruses within 60 minutes of daylight exposure has been developed by California researchers.

Although face masks made of various materials have been shown to filter nanoscale aerosol particles, such as those released by coughing or sneezing, live bacteria and viruses on the surface of the mask itself still pose a risk of contamination to the wearer.

Now a team has developed a new cotton fabric that releases reactive oxygen species (ROS) when exposed to daylight, killing microbes attached to the surfaces of the fabric while being washable, reusable and safe for the wearer.

This allows the face mask to be disinfected by leaving it outdoors in the sun or by spending extended periods of time under office or building lighting without other special disinfection measures.

The researchers made their antimicrobials by attaching positively charged chains of 2-diethylaminoethyl chloride (DEAE-Cl) to plain cotton.

They then dyed the modified cotton in a solution of a negatively charged photosensitizer (a compound that releases ROS when exposed to light), which attaches to the DEAE chains through strong electrostatic interactions.

The team found that a fabric made with a dye called Rose Bengal, because the photosensitizer killed 99.9999 percent of the bacteria added to the fabric within 60 minutes of exposure to daylight and inactivated 99.9999 percent of the T7 bacteriophage – a virus believed to be more resistant to ROS than some coronaviruses – within 30 minutes.

Further tests showed that the material could be hand washed at least 10 times and exposed to constant daylight for at least 7 days without losing its antimicrobial activity. The fabric holds great promise for making reusable, antibacterial / antiviral fabric face masks and protective suits, the researchers say.

The research is published in the American Chemical Society’s Applied materials and interfaces.

Since the beginning of the Covid-19 pandemic, research into improving the effectiveness of face masks has stepped up significantly. A battery-powered mask with built-in fans was built by LG, a team at MIT developed a mask with an integrated heated copper mesh, and another team designed a reusable silicone rubber mask with interchangeable N95 filters.

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