Researchers at the University of California, Riverside have developed a nanofiber filter that is highly effective at removing coronavirus aerosols from air. As a major source of COVID-19 transmission, aerosols pose an ongoing threat. Technologies to remove aerosols from the air in buildings or as part of personal protective equipment are being developed for the long-term fight against COVID-19. This latest material contains tiny pores, just micrometers in size, and is highly effective at aerosol capture.
Aerosols are tiny specks of water and other material that remain suspended in the air after people speak, cough, or sneaze. During the current pandemic, they are a major source of COVID-19 transmission, as viral particles can hitch a ride from an infected person to a new victim by attaching to an aerosolized droplet. Wearing a conventional mask helps to reduce aerosol dispersion, but it doesn’t come close to eliminating the risk.
Aerosols are at the heart of the ongoing discussion about masks, ventilation, and air filtration as methods to reduce viral transmission. For air filters and masks, the key component is the material used to filter the aerosols, as they are surprisingly tricky to capture. This new study used coronavirus aerosols to compare various face masks and air filters in their ability to stop aerosols in their tracks.
“Our work is the first study to use coronavirus aerosols for evaluating filtration efficiency of face masks and air filters,” said Yun Shen, a researcher involved in the study. “Previous studies have used surrogates of saline solution, polystyrene beads, and bacteriophages — a group of viruses that infect bacteria.”
The researchers have developed a new filter made using electrospun fibers that are approximately 167 times thinner than a human hair. The network of fibers includes tiny pores that are just a couple of micrometers across. Electrospinning imparts an electrical charge on the fibers, which may increase their ability to capture aerosols. However, while the pores are small, the material is highly porous, which should make breathing through it easy.
To test the new material, the team compared it with surgical and cotton masks, and a neck gaiter, in terms of its ability to capture coronavirus-laden aerosols. The coronavirus in question was one that can infect mice, but is harmless to humans. The neck gaiter and cotton mask removed between 45% and 73% of the aerosols, and the surgical mask removed as much as 98%, but none performed as well as the new electrospun material, which removed 99.9%.
“Electrospinning can advance the design and fabrication of face masks and air filters,” said Shen. “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.”
Study in journal Environmental Science & Technology Letters: Development of Electrospun Nanofibrous Filters for Controlling Coronavirus Aerosols