When compared with other forms of face coverings and air filters, a filter produced from polymer nanothreads has been shown to capture almost 100% of coronavirus aerosols – established as a major mechanism of Covid-19 virus transmission.
A study led by Yun Shen, assistant professor of chemical and environmental engineering at UC Riverside, and Danmeng Shuai at The George Washington University, used coronavirus aerosols for evaluating filtration efficiency in polymer nanothread masks and filters.
Other pandemic studies on filter or mask efficiency have used materials thought to resemble coronavirus aerosols in behaviour and size. This time, a virus from the same family as the virus causing Covid-19, but which affects mice only, was tested in an aerosolised saline solution and an aerosol.
Previously, bacteriophages, polystyrene beads and surrogates of saline solution were used but in this study, the scientists utilised an electrospinning process which sent a high electrical voltage through a drop of liquid polyvinylidene fluoride to spin threads of approximately 300nm in diameter. This process created pores on the surface of the nanofibers which, with a diameter of around 2 micrometers, helped catch 99.9% of coronavirus aerosols.
The electrospinning process imparts an electrostatic charge which boosts the ability of the nanofibers to catch aerosols, while elecrospun nanofibre filters are more easily breathed through due to their high porosity.
Yun Shen said,
“Electrospinning can advance the design and fabrication of face masks and air filters. 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.”
So far, attempts to contain aerosol spread of Covid-19 have concentrated on reducing people’s exposure and reducing the overall quantity of aerosols in an environment by improving air filtration systems, increased indoor ventilation and individual mask-wearing.
In tests, a cotton mask and neck gaiters removed 45% – 73% of coronavirus aerosols, a surgical mask removed 98% of coronavirus aerosols while the nanofibre filter removed 99.9% of coronavirus aerosols.