Researchers develop new cotton masks; claim it kills 99.99% viruses, bacteria in an hour of sunlight

Researchers from the University of California, Davis in the United States, have developed a new cotton face mask that can kill up to 99.99 per cent of bacteria and viruses within an hour of exposure to sunlight.

Face masks made of various cloth materials can filter nanoscale aerosol particles - such as those released by a cough or sneeze - potentially helping to reduce the spread of diseases, including COVID19.  However, live bacteria and viruses on the surface of the mask could still be contagious.

A person could disinfect their cloth mask during their lunch hour outside in the sun, or by spending a longer period under office or building lights, which are much less intense than sunlight, they said.

The researchers made their antimicrobial fabrics by attaching positively charged chains of 2-diethylaminoethyl chloride (DEAE-Cl) to ordinary cotton. Then they dyed the modified cotton in a solution of a negatively charged photosensitiser - a compound that releases ROS upon exposure to light - which is attached to the DEAE chains by strong electrostatic interactions.

The team found that a fabric made with a dye called Rose Bengal as the photosensitisers killed 99.9999 per cent of bacteria added to the fabric within 60 minutes of daylight exposure and inactivated 99.9999 per cent of T7 bacteriophage -- a virus thought to be more resistant to ROS than some coronaviruses -- within 30 minutes.

They then dyed the modified cotton in a solution of a negatively charged photosensitiser -- a compound that releases ROS upon exposure to light -- which is attached to the DEAE chains by strong electrostatic interactions.

Further testing showed that the material could be hand washed at least 10 times and constantly exposed to daylight for at least 7 days without losing its antimicrobial activity, the researchers said. The researchers claimed the fabric shows promise for making reusable, antibacterial or antiviral cloth face masks and protective suits.

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