This has been adapted from Berkeley Lab’s Newscenter.
In the early days of the pandemic, amidst all the uncertainty, one thing was for sure: N95 masks – the personal protective respiratory devices that filter out viruses, bacteria, and wildfire smoke – were in short supply. So when materials scientists Jeff Urban and Peter Hosemann heard that a local HMO needed advice on N95 alternatives, they immediately knew what to do: Make a better mask.
Hosemann got on the phone, and discovered that the HMO’s doctors and supply managers wanted to know what makes an effective antiviral mask, and how they could verify whether the masks they found were actually any good.
“It was helpful to learn what their needs were, and how we could fill in and help support their mission,” said Hosemann, who holds titles of faculty scientist in the Materials Sciences Division at Lawrence Berkeley National Laboratory (Berkeley Lab) and Ernest S. Kuh Chair in Engineering at UC Berkeley.
“Fortuitously, Peter and I had just joined forces because we had each started working on similar ideas at the lab level,” said Urban, who directs the Foundry’s Inorganic Nanostructures Facility.
“We, like many others, saw the shortcomings in the PPE (personal protective equipment) supply chain and even in the functionality of what was available, so we felt this was an important area to focus on,” Urban said.
When it comes to protecting you from COVID-19 or other viral infections, N95 masks are the gold standard. They are commonly made from tightly woven layers of polypropylene that filter out at least 95% of very small particles in the submicron (millionth of a meter) range, including coronavirus particles and particulate matter from wildfire smoke. This mishmash of fibers generates an electrostatic charge that attracts and traps virus particles.
But despite their excellent filtering efficiency, N95 masks have their limits. For example, experts advise against reusing N95 masks, especially after wearing them the whole day. That’s because when we exhale, we expel moisture from our mouth and lungs – and if we’re wearing an N95 mask for long durations, that moisture eventually wears down the electrostatic charge on the virus-trapping fibers, Urban said.
Urban and Hosemann say that their joint research effort aims to address such problems with long-term filter efficiency by designing and fabricating a reusable silicone N95 mask with a rechargeable, wire-mesh active filter.
The wire mesh bears an electrostatic charge, which helps to trap and neutralize virus particles, Hosemann explained. “This mesh filter can be recharged, and thus the mask itself can be reusable, a key advantage,” he said. “The ultimate vision is to make a mask with a filter battery cartridge that you could plug in and recharge overnight, like a cell phone.”
To manage problems related to fit and PPE shortages, the scientists are developing a 3D-printable, silicone-cast mold for the body of the mask.
A metal wire incorporated into the silicone cast allows the mask to conform to most faces.
And in the event of a PPE shortage, a 3D-printable mold would allow anyone – from the DIY hobbyist to supply clerks at a school or hospital – to make silicone N95 masks on demand and with short lead times, Hosemann said.
The scientists also designed the silicone masks to interface with commercially available N95 filters or the rechargeable mesh filter.
To test the mask prototype’s impenetrability against small, virus-sized particles, the scientists employed fluorescent particle tests in collaboration with UC Berkeley’s Evan Variano, a professor of environmental engineering, and Simo Mäkiharju, an assistant professor in mechanical engineering. The fluorescent particles track particle distribution in and around the fabricated masks, Hosemann said.
The scientists will use the same fluorescent nanoparticle technology for future filter-efficiency tests in collaboration with Bruce Cohen of Berkeley Lab’s Molecular Foundry.
The 3D-printable silicone-casting mold and rechargeable N95 filters are still in the early stages of R&D, but Urban and Hosemann say they are making progress quickly. The scientists are in the process of developing an on-site N95 quality-assessment test for medical industry researchers and hospitals through the Molecular Foundry’s user program.
Read the full press release.