n95 coronavirus face mask health worker

Replaceable facemask membrane designed to resist Covid-19 virus particles

Image credit: Dreamstime

A membrane has been developed to cover N95 face masks used by healthworkers in the coronavirus pandemic which improves their ability to block the minute virus particles.

Since the start of the Covid-19 pandemic, personal protection equipment (PPE) has been in short supply, especially the most effective N95 masks that are required to protect people in healthcare scenarios.

In addition, N95 masks can only filter about 85 per cent of particles smaller than 300nm. The Covid-19 virus ranges in size from 65-125nm, so some virus particles could slip through these coverings.

The newly developed membrane can be attached to a regular N95 mask and replaced when needed and the filter has a smaller pore size than normal N95 masks, potentially blocking more virus particles.

The PPE shortages have meant that many healthcare workers have been forced to reuse the same N95 mask, even though they are only intended for single use. The membrane could also help to improve the safety of these masks as they are worn repeatedly.

To make the membrane, the researchers first developed a silicon-based, porous template using lithography and chemical etching.

They placed the template over a polyimide film and used a process called reactive ion etching to make pores in the membrane, with sizes ranging from 5-55nm.

Then, they peeled off the membrane, which could be attached to an N95 mask. To ensure that the nanoporous membrane was breathable, the researchers measured the airflow rate through the pores.

They found that for pores tinier than 60nm (i.e. smaller than SARS-CoV-2), the pores needed to be placed a maximum of 330nm from each other to achieve good breathability.

The hydrophobic membrane also cleans itself because droplets slide off it, preventing the pores from getting clogged with viruses and other particles.

A report earlier this month recounted the environmental cost of single-use masks and found that reusable masks could avoid 66,000 tonnes of contaminated plastic waste being generated this year.

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