A preliminary study published in ACS Nano led by researchers of Indian origin at University of Chicago and Argonne National Laboratory, suggests that a combination of masks made of high thread-count cotton with natural silk fabric or a chiffon weave can effectively filter out aerosol particles, but only if the fit is good.
“There is a huge interest and need for homemade cloth masks, but we found little data on how good various fabrics are as filters for masks,” according to senior author Professor Supratik Guha of the University of Chicago, is quoted saying in a recent press release from the University.
Guha is recognized as a leading scientist in microelectronics and materials for quantum information, but he prioritized this research to meet a growing need during COVID-19, when masks are being prescribed by all to avoid passing on or breathing in deadly droplets of the virus,
Guha is a professor with UChicago’s Pritzker School of Molecular Engineering and a scientist at Argonne. He and his colleagues wanted to find out how effectively commonly available fabrics could filter out aerosols similar in size to respiratory droplets.
“According to these results, it’s possible to get very good filtering with commonly available fabrics, but the wearer only gets maximum protection if the fit is very close to your face,” Guha said.
The first author on the study was Abhiteja Konda from Argonne National Laboratory. The other authors were Argonne’s Abhinav Prakash as well as Pritzker School of Molecular Engineering graduate student Gregory Grant. The team used the U.S. Department of Energy’s Center for Nanoscale Materials at Argonne National Laboratory, to conduct their experiments, rigging up two plexiglass boxes connected by a tube, using various combinations of fabrics, and pumping aerosol particles to test their resiliency.
According to their results, one layer of a tightly woven cotton sheet, combined with two layers of polyester-based chiffon filtered out the most aerosol particles (80% to 99%, depending on particle size). Substituting the chiffon with natural silk or a polyester-cotton flannel, or simply using a cotton quilt with cotton-polyester batting, produced similar results, they found.
Tightly woven fabrics can act as a mechanical barrier to particles; whereas fabrics that hold a static charge can serve as an electrostatic barrier which serves to suck in and hold the tiniest particles, that might otherwise slip through holes in the cotton.
However, Guha added, even a small gap reduced the filtering efficiency of all masks by half or more, emphasizing the importance of a properly fitted mask.