University of Cincinnati Study Suggests Silk Face Masks May Protect Better Than Cotton or Synthetic Masks

“The ongoing hypothesis is that coronavirus is transmitted through respiratory droplets. If you wore layers of silk, it would prevent the droplets from penetrating and from being absorbed."

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click to enlarge UC postdoctoral researcher Adam Parlin holds up a silk mask in a biology lab. - Photo: Joseph Fuqua II/UC Creative
Photo: Joseph Fuqua II/UC Creative
UC postdoctoral researcher Adam Parlin holds up a silk mask in a biology lab.

Due to the continued limited supply of medical-grade personal protective equipment — and the need for the general public to buy/wear/make cloth face masks to stop the spread of COVID-19 — researchers at the University of Cincinnati did their research thing and may have found a new and optimum fabric for masks: silk.

"Next to a single-use N95 respirator or surgical mask, UC found the best alternative could be made by a hungry little caterpillar. Silk face masks are comfortable, breathable and repel moisture, which is a desirable trait in fighting an airborne virus," says a release from UC. "Perhaps best of all, silk contains natural antimicrobial, antibacterial and antiviral properties that could help ward off the virus."

Patrick Guerra, an entomologist and assistant professor of biology at UC’s College of Arts and Sciences, says silk from silk moths contains copper, which "can kill bacteria and viruses on contact"

“Copper is the big craze now. Silk has copper in it. Domesticated silk moths eat mulberry leaves. They incorporate copper from their diet into the silk,” Guerra says.

Guerra's wife is a doctor who says many health care workers are wearing additional protection, like cotton or surgical masks, over their N95 respirators to prolong the life of the N95. Guerra says wearing a traditional cotton mask over the respirator can trap moisture, but that silk is breathable, thinner and dries more quickly. 

To test the theory that silk works better than other fabric masks, UC researchers tested a variety of materials — cotton, polyester, multiple types of silk — to see which would repel or create a barrier against water, a liquid representation of COVID-19 respiratory droplets. 

"UC’s study concluded that silk performs similarly to surgical masks when used in conjunction with respirators but has the added advantages of being washable and repelling water, which would translate to helping to keep a person safer from the airborne virus," reads the release. (The CDC has gone back and forth about the virus' airborne transmission capability, recently publishing new guidelines saying aerosol transmission is the most common way the virus spreads, then retracting that statement.)

“The ongoing hypothesis is that coronavirus is transmitted through respiratory droplets,” Guerra says. “If you wore layers of silk, it would prevent the droplets from penetrating and from being absorbed. Recent work by other researchers also found that increasing layers of silk improves filtration efficiency. This means that silk material can repel and filter droplets. And this function improves with the number of layers.”

Now, Guerra's students are raising Bombyx mori silk months in his biology lab.

“Silk has been with us for a while — since the days of the Silk Road,” Guerra says. “It’s not a new fabric, yet now we’re finding all these new uses for it.”

Read the study results in the peer-reviewed journal PLOS ONE at journals.plos.org.

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