Jumbomask

https://github.com/mcdermatt/n95

Between March and June 2020 I lead a small team of Tufts engineering students to design an open source low cost n95 mask body capable of interfacing with existing 3M filter cartridges. Unlike other designs on the internet, there are no 3D printed parts in our final BOM and all materials are rated to 180° C so that the entire mask body can be sterilized in an autoclave.

The mask body consists of a moldable silicone rubber shaped to form a seal around the mouth and nose of the user. A polycarbonate bayonet mount was CNC’d and locked in place with a matching threaded ring. Pictured below is a cross section of the mask fitted with a pair of custom n95 filter cartridges made with heat blown polypropylene.

The mask body is formed with a 4 part 3D printed mold tool. This tool is designed such that the liquid mask material is mixed and poured until it reaches the top of the pouring tube. A plunger is then used to force all of the rubber into the voids in the mold. The mold includes escape holes so that air does not become trapped in any overhangs. In this final version version, the parting lines of the mold are at rear and underside of the mask body so that there are no visible flashing lines on the completed mask body.

Ultimately, when combined with proper n95 filter cartridges the mask was capable to passing the smell test, meaning that it was able to filter out a significant amount of droplets that could potentially carry covid-19. While I was wearing the mask I was able to inhale with an open bottle of Tabasco sauce an inch from my face without smelling anything, meaning that the mask was able to successfully prevent the droplets from reaching my nose.

By the time the summer came around it was becoming clear that the problem of using masks for COVID-19 was one of community health policy and not mechanical engineering. A low cost open source n95 mask body is still a useful resource for other situations such as mitigating urban air pollution or wildfire smoke. Furthermore, this project was an awesome exercise in leading an engineering team and I learned lots of new skills ranging from project management to designing mold tooling.