Masks, PPE materials should be hydrophilic

Date:
August 11, 2020
Source:
American Institute of Physics
Summary:
Making masks and personal protective equipment (PPE) with
hydrophilic surfaces, where droplets of coronavirus spread out
and dry faster, could reduce infection risk, researchers say.



FULL STORY ========================================================================== Since the COVID-19 virus spreads through respiratory droplets, researchers
in India set out to explore how droplets deposited on face masks or
frequently touched surfaces, like door handles or smartphone touch
screens, dry.


========================================================================== Droplets can be expelled via the mouth or nose while coughing, sneezing
or simply talking. These droplets are tiny, around twice the width of
a human hair, and studies have shown a substantially reduced chance of infection once they dry.

In Physics of Fluids, from AIP Publishing, Rajneesh Bhardwaj and Amit
Agrawal, professors at IIT Bombay, publish findings that surface wetting properties to reduce the drying time of droplets could help lessen the
risk of infection from coronaviruses.

"We wanted to quantify the droplet drying time on various surfaces
and make a recommendation for the ideal types of surfaces for masks
and personal protective equipment (PPE) based on the drying time,"
said Bhardwaj.

By studying the drying time of a droplet for different contact angles,
the expected chances of survival of the coronavirus on a surface can be estimated by using a mathematical physics model.

"Our calculations of the drying time as a function of contact angle
show that the droplet dries roughly four times faster on the hydrophilic surface that attracts water than on the one that repels water. This will drastically reduce the chances of virus survival," Bhardwaj said.



========================================================================== Their work also shows that, by tailoring the surface wettability and
drying time, the chances of infection can be reduced.

"Making a surface more hydrophilic reduces the drying time, and it is
advisable to use it for masks, PPE and frequently touched surfaces where outbreaks are most likely to occur, such as the common areas within
hospitals," said Agrawal.

In the case of N95 respirators, surgical masks and PPE bodywear, a
reduction to a contact angle of a hydrophilic surface implies that the
chances of infection of COVID-19 will be cut in half.

"We recommend reducing the contact angle of the surface of face masks
and frequently touched surfaces," Agrawal said.

The biggest surprise was their finding that the maximum drying time
occurs at an intermediate contact angle value of 148 degrees.

"This implies that a superhydrophobic surface needs to be made even
more superhydrophobic to reduce the drying time," Agrawal said. "This
is counterintuitive, because we normally think of making a surface more hydrophilic, reducing the contact angle, to reduce the drying time."
This work provides a better understanding of coronavirus survival within
a drying droplet, which may be helpful for predicting the survival of
other transmissible diseases spread through respiratory droplets, such
as the flu.

The article, "Tailoring surface wettability to reduce chances of infection
of COVID-19 by a respiratory droplet and to improve the effectiveness
of personal protection equipment," is authored by Rajneesh Bhardwaj and
Amit Agrawal. It will appear in Physics of Fluids on Aug. 11, 2020.


========================================================================== Story Source: Materials provided by American_Institute_of_Physics. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Rajneesh Bhardwaj, Amit Agrawal. Tailoring surface wettability
to reduce
chances of infection of COVID-19 by a respiratory droplet and to
improve the effectiveness of personal protection equipment. Physics
of Fluids, 2020; 32 (8): 081702 DOI: 10.1063/5.0020249 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200811120208.htm

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