A team of researchers at the Indian Institute of Technology Guwahati (IIT-G) has developed a ‘Nanometer Thick Superhydrophobic Coating’ material to modify ordinary cloth or silk masks, which will maintain its comfort while offering better protection against aerosol-driven infections such as Covid-19.

As per  World Health Organization (WHO) guidelines, N-95 masks or double masking protects people to a great extent from Coronavirus. But the drawback is that people undergo suffocation after wearing them for a long time.

Besides, N-95 masks are costly and thus unaffordable to a large section of the population. Instead, people resort to cheaper and readily-available cloth and silk masks.

To address these challenges and to bring in a safer, economical and comfortable alternative, the researchers at IIT Guwahati have developed a coating material to modify the easily-available cloth mask into a hydrophobic mask to repel virus-laden droplets and avoid breathing difficulties even when worn for a longer period of time.

Another advantage is that these masks are versatile and can be used with other additives such as antibacterial nanomaterial for additional protection against viruses.

“A cloth mask is largely porous to aerosol and thus cannot effectively prevent Covid-19 type infections. Although they are still better than not wearing a mask, an improved version that would prevent the entry or exit of the aerosol from the modified cloth mask was needed,” Arun Chattopadhyay from the Department of Chemistry and Centre for Nanotechnology, IIT-G, said in a statement.

“We have worked on that based on the principle of repulsion of the aerosol by the modified cloth while allowing the air to flow through the mask. A simple coating of the hydrophobic molecule on the silk cloth worked well here,” he said .

The findings have been published in the peer-reviewed journal ‘ACS Applied Bio Materials’.

The breathability was tested by measuring the oxygen permeation through the mask with the help of an instrument called Gas Chromatography. The penetration of oxygen reduces by only 22 per cent for the modified Eri silk mask compared to the natural Eri silk mask, whereas for N-95, the reduction with respect to the natural Eri silk came out to be around 59 per cent.

Hence, the modified silk mask is way more breathable than the N-95 mask, but with almost similar protection against aerosol-driven infections.

The sustainable and durable Eri silk, also referred to as the fabric of peace, is softer than many other silks or cotton and has the unique property of maintaining coolness in summer and providing warmth in winter.

“To attain hydrophobicity, Eri silk fabric was coated with a biocompatible nanometre-thick coating of a chemical called octadecyl trichlorosilane (OTS). OTS, being a fluorine-free chemical after bonding with the fabric, becomes non-hazardous to health and the environment. And the good part is the cloth/silk masks still remain comfortably breathable after the nan-coating,” said Partho S.G. Pattader from the Department of Chemical Engineering, IIT Guwahati.

When any droplet hits the modified Eri silk mask, it bounces back into the air rather than passing through the fabric or getting soaked by the fabric itself. Another added advantage is that these modified Eri silk masks can be reused again after subsequent washing with household detergent and drying, said the researchers.

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