Advanced face mask kills bacteria and viruses with sun exposure

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

 While face masks made of various cloth materials have been shown to filter nanoscale aerosol particles such as those released by a cough or sneeze, live bacteria and viruses on the surface of the mask itself still present a contagion risk 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 fabric’s surfaces while being washable, reusable and safe for the wearer.

It allows the face mask to be disinfected by leaving it outside in the sun or by spending a longer period of time under office or building lights with no other special decontamination measures.

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 attached to the DEAE chains by strong electrostatic interactions.

The team found that a fabric made with a dye called rose Bengal as the photosensitiser 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.

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 fabric shows promise for making reusable, antibacterial/antiviral cloth face masks and protective suits, the researchers say.

The research has been published in the American Chemical Society’s Applied Materials & Interfaces.

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