Since the COVID-19 outbreak, there has been a global shortage of face masks, particularly the N95s worn by healthcare workers, they said.
Although these coatings provide the highest level of protection currently available, they do have limitations, the researchers noted in the journal ACS Nano.
They said that N95 masks filter out about 85 percent of particles less than 300nm.
The researchers noted that SARS-CoV-2, the coronavirus that causes COVID-19, is in the 65-125 nanometer (nm) size range, so some virus particles could slip through these covers.
Due to the shortage, many healthcare workers have had to wear the same N95 mask repeatedly, even though they are intended for single use only.
To help overcome these problems, Muhammad Mustafa Hussain and his colleagues wanted to develop a membrane that would more efficiently filter out SARS-CoV-2-sized particles and could be replaced in an N95 mask after each use.
The researchers first developed a silicon-based porous template using lithography and chemical etching.
They placed the template on a polyimide film and used a process called reactive ion etching to make pores in the membrane, with sizes ranging from 5 to 55 nm.
The researchers then peeled off the membrane, which could be attached to an N95 mask.
To make sure that the nanoporous membrane was breathable, the researchers measured the speed of air flow through the pores.
They found that for pores less than 60nm, the pores had to be placed at a maximum distance of 330nm from each other to achieve good breathability.
The hydrophobic membrane is also cleaned because the droplets slide, preventing pores from clogging with viruses and other particles, according to the researchers.