Masks Made of Nanofibers Nearly 100% Effective Against Coronaviruses

Killian Meara

In the study, cotton masks stopped 45%-73% of coronavirus aerosols. Masks with nanofiber filters blocked 99.9% of the particles.

Not to throw water on all the good news concerning how the United States appears to be emerging from the COVID-19 pandemic, but medical experts have stressed all along that SARS-CoV-2 is here to stay. Hopefully, thanks to vaccinations and an attainment of herd immunity, we will coexist with a declawed COVID-19, in the way we coexist with influenza. But COVID-19 continues to mutate and can be carried by animals. It’s not going anywhere.

Another unfortunate fact that medical experts point out is that the taming of COVID-19 means that medical science has beaten back one—just one—pandemic. There will be others.

The world will need to be prepared for “what we can’t imagine,” as the New York Times recently put it. “We spent decades planning for a pandemic that would resemble the viruses we already knew,” the newspaper states. “We didn’t plan for face masks, mass testing, stay-home orders, politicized decision making or devastating racial disparities. Looking forward, we need to prepare for a much broader range of threats.”

Investigators from the University of California at Riverside, in collaboration with the George Washington University, seem to be doing their part, as they’ve discovered that a filter made from polymer nanothreads can capture up to 99.9% of coronavirus aerosols. Results from the study were published in the journal Environmental Science & Technology Letters.

“Our work is the first study to use coronavirus aerosols for evaluating filtration efficiency of face masks and air filters,” Yun Shen, PhD, a corresponding author on the study said. “Previous studies have used surrogates of saline solution, polystyrene beads, and bacteriophages—a group of viruses that infect bacteria.”

For the study, investigators sent high electrical voltage through a drop of liquid polyvinylidene fluoride to spin threads about 300 nanometers in diameter and created a nanofiber filter. The technique is known as electrospinning and can be a cheap way to mass produce the filters for personal protective equipment and air filtration systems.

“The electrospun air filters showed excellent performance by capturing up to 99.9% of coronavirus aerosols, which outperformed many commercial face masks,” the study states. “In addition, we observed that the same electrospun air filter or face mask removed NaCl aerosols equivalently or less effectively in comparison to the coronavirus aerosols when both aerosols were generated from the same system. Our work paves a new avenue for advancing air filtration by developing electrospun nanofibrous air filters for controlling SARS-CoV-2 airborne transmission.”

Most studies up until now have used other materials to mimic both the size and behavior of coronaviruses, but the investigators in this study use an aerosolized saline solution and an aerosol that contained a coronavirus from the same family as COVID-19.

Findings from the study showed that the cotton mask and neck gaiter removers around 45% to 73% of the aerosols, while the surgical mask removed around 98%. However, the nanofiber filter removed almost all of the coronavirus aerosols, just about 99.9%.

"Electrospinning can advance the design and fabrication of face masks and air filters," Shen said. "Developing new masks and air filters by electrospinning is promising because of its high performance in filtration, economic feasibility, and scalability, and it can meet on-site needs of the masks and air filters."

The original version of this article first appeared in Contagion®.