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Masks and PPE with hydrophilic surfaces could reduce infection risk – IIT Bombay research

By Rajeev Chitguppi & Uday Shetty
August 14, 2020

According to the latest research from IIT Bombay, masks and PPE materials with hydrophilic surfaces could help the respiratory droplets dry faster, thus minimising the risk of infection spread.

Evidence shows that SARS-CoV-2 spreads through respiratory droplets expelled from the mouth or nose by coughing, sneezing or talking. However, these droplets lose their infectivity once they dry, thus minimising the chance of further infection spread.

Prompted by these findings, a team of Indian researchers from IIT Bombay conducted a study to explore how these wet droplets dry once they settle on various surfaces like face masks or the other frequently touched surfaces, e.g. door handles or smartphone touch screens etc.

Rajneesh Bhardwaj and Amit Agrawal, two professors from IIT Bombay, have published their study in Physics of Fluids. They state that by reducing the drying time of droplets, one could reduce the risk of SARS-CoV-2 infection.

Their study aimed to quantify the droplet drying time on various surfaces, based on which they could make a recommendation for the ideal types of surfaces for masks and personal protective equipment (PPE). They studied the drying time of a droplet for different contact angles, and then using a mathematical physics model, calculated the expected survival chances of SARS-CoV-2 on a surface.

Drying time of a 5-nanoliter droplet as a function of the contact angle on the surface. Credit: R. Bhardwaj and A. Agrawal (phys.org)

Their calculations of the drying time as a function of contact angle showed that the droplet dries roughly four times faster on hydrophilic surfaces (that attract water) than hydrophobic surfaces (that repel water). Thus, hydrophilic surfaces drastically reduce the chances of virus survival.

Therefore, by modifying the surface wettability and drying time, one can reduce the chances of infection. Making a surface more hydrophilic minimises the drying time, and we can apply this finding to the surfaces of masks and PPE. We can also use this finding on other frequently touched surfaces inside the hospitals, where outbreaks are more likely to occur.

The authors recommend reducing the contact angle of the surface of face masks and frequently touched surfaces. In the case of N95 respirators, surgical masks and PPE bodywear, the contact angle reduction of a hydrophilic surface could reduce the chances of Covid-19 infection by 50%.

This research provides a better understanding of SARS-CoV-2 survival within a drying droplet, which might help us in predicting the survival of other transmissible viruses, e.g. flu virus that spread through respiratory droplets.

On their personal communication to Dr Uday Shetty, implantologist & aesthetic dentist from Mumbai, the authors stated that while they have not tested cotton (which absorbs water) in their study, it is very likely that it helps in faster evaporation. This could have a practical implication in that cotton gowns might prove to be better than the impervious PPE that are in use currently. Though this sounds logical, we may have to wait for confirmatory data to emerge.

Till then one can use cotton masks on top of N95 masks

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Indian Institutes of Technology (IIT) are world-famous institutes because of their top-notch education standards and their illustrious alumni. IIT have made their way into Dilbert, the immensely popular comic strip about the corporate world. IIT graduates hold prominent positions in the US economy. IIT Bombay is ranked 34th among the top 200 Universities in Asia category by the QS Asia Ranking 2020.

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