MIT Researchers Prototype Reusable N95 Mask


Six months into the COVID-19 pandemic, the world is still short of N95 respirators (i.e. masks) — a product most people probably knew nothing about before this year. Here in California, we’ve been using them for wildfire smoke, but typically only for a few days or weeks each year. In normal times they are used and then thrown away. But shortages have required all sorts of innovative ways to allow them to be sterilized and re-used, up to a point. Now, researchers at MIT and Brigham and Women’s Hospital have come up with a partial solution to the shortage.

The iMASC uses two, small, replaceable filte inserts -- Image Courtesy MIT

The iMASC uses two, small, replaceable filter inserts. Image courtesy of MIT.

They’ve prototyped and are testing an injection molded silicone rubber mask with two replaceable N95-quality filter inserts. Called the iMASC — which stands for Injection Molded Autoclavable, Scalable, Conformable — the rubber portion of the mask can be sterilized in any number of different ways. However, the N95 filter inserts have the same shortcomings as traditional N95 masks. They should really not be re-used, but presumably could be if necessary and appropriately sanitized. The big advantage of the iMASC is that it takes a lot less N95 material to make the two small filters than it does an entire N95 respirator.

3M re-usable respirator with P100 filter cartridgesThe idea of a rubber and plastic respirator with replaceable filters is hardly new. Perusing the 3M site yields literally pages of commercial-grade respirators and dozens of different filter cartridge options — ranging from N95 all the way through P100 and vapor filters. However, they have one big drawback that makes them a problem for use against COVID-19: They filter the air you breathe in, but not air you breathe out. After all, they are made to protect the wearer from the environment, not the other way around. Several of my friends who happen to own them for their business have modified them by adding a filter to the exhaust valve, but that isn’t a great mass-market option.

The team from MIT and Brigham and Women’s Hospital started from the shape and design of a disposable model, 3M’s 1860 N95 respirator, that was already in use at the hospital. Their goal was to get an equivalent fit, but in an inexpensive, reusable form factor.

An initial test with 24 healthcare workers has gone well, with positive feedback on its fit and breathability. It also successfully filtered out a test aerosol. The masks are expected to cost hospitals about $15 each once they are in production, and should be reusable up to 100 times. The team hopes the filters will cost less than a dollar. With the currently-inflated $3-$10 current cost of disposable N95 masks, that sounds like a pretty good option. Of course, back when I bought 3M N95 respirators for wildfire smoke in 2017, they were $0.75 each even in small quantities.

The researchers are working on a new version, and plan to create a company to produce and sell them. Right now that seems like a great idea for a business, but it’s hard to believe that 3M doesn’t have a bunch of similar designs in progress based on minor modifications to their existing offerings. So their startup will clearly have its work cut out for it.

[Featured image credit: MIT]

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