Researchers show homemade COVID face masks work – effectiveness varies by design

Penetration and atomization of cough droplets through single-layer homemade mask fabrics. Credit: Bal Krishan

Three-layer cotton cloth masks were found to be the most effective in blocking the aerosolized virus.

Since the spread of the virus causing COVID-19[female[feminine continues, experts have recommended wearing homemade face masks when surgical or N95 masks are not available to prevent the spread of the pandemic. While such makeshift masks are more economical and accessible in low-capitalization countries, the effectiveness of cloth masks has not been thoroughly studied.

In Fluid physics, by AIP Publishing, researchers at the Indian Institute of Science studied the fate of large surrogate cough droplets at different rates, ranging from mild to severe, while using various locally purchased fabrics as masks.

“Our results show that cotton and towel-based fabrics were the most effective among the fabrics considered and must be sewn together in multiple layers to make homemade masks,” said author Saptarshi Basu. “A homemade mask with three or more layers is recommended because it can significantly remove aerosolization.”

The researchers analyzed the effect of washing on the effectiveness of the mask and the results showed a negligible influence of washing on the effectiveness of the mask for up to 70 wash cycles.

Using a piezoelectric droplet dispenser, the researchers created surrogate cough droplets that impacted a single layer of different tissue samples at different speeds. Fabrics used in the research included single layers of a summer stole, a handkerchief, a cotton towel, and surgical masks.

The specific cotton fabrics were selected based on their daily use and people’s propensity to cover their face with these fabrics. The researchers used high-speed imaging to quantify the penetration threshold and the amount of penetration of droplets at different speeds.

The researchers examined how the properties of the fabric, such as the size and porosity of the pores, influence the penetration of the droplets through the mask.

The findings are relevant to many groups, including policymakers studying how to counter the generation of aerosols by secondary atomization of cough droplets as they enter mask tissue. For mask makers and the general population, it is helpful to know that N95 and surgical masks are the most effective, but when these are not available, some specific cotton materials or homemade fabrics are suitable for masks. effective fortune facials.

The results could also be applicable in applications ranging from agriculture to medical practices, where the placement of a wire mesh or perhaps an engineered cellulose mesh of varying porosity can reduce the momentum of the incoming spray. ‘a nozzle, thus ensuring optimal distribution of nutrients or pesticides to the crops. or better disinfection in the hospital.

Reference: “Effectiveness of Homemade Facial Masks Against Human Cough: Insights into Penetration, Atomization and Aerosolization of Cough Droplets” by Bal Krishan, Dipendra Gupta, Gautham Vadlamudi, Shubham Sharma, Dipshikha Chakravortty and Saptarshi Basu, September 14, 2021, Fluid physics.
DOI: 10.1063 / 5.0061007

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