Filter Test Kits for 3D-printed Reusable Masks

youmagine

The BEmask continues to evolve towards meeting the stringent requirements for a medical N95 mask. Key functional design challenges to overcome include providing an airtight seal around the face and nose for a wide range of users, ensuring user comfort in terms of weight and bulk compared to disposable masks, and guaranteeing effortless breathing with available filter materials that meet N95 standards. The BE masks are being tested in three sizes (S, M, L) using either rigid or flexible materials. PLA is a robust material that is easy to print, while the user can be easily custom-fitted for the nose area by applying heat from hot water. TPU, on the other hand, is compliant and forms a softer interface with the skin of the user, but it is more challenging to print. To address comfort concerns regarding weight and bulk, a 3D printed variation of a head strap arrangement used by 3M for their bulky industrial respirators has been employed. Specifically designed for maximum comfort, this innovative design can be viewed at https://www.youmagine.com/designs/comfortable-head-strap-for-reusable-respirators-and-medical-masks#information. Our filter test kits are custom-designed variations of the BEmasks to study the effects of different filter materials, their thickness, and surface area on breathing ease in a 3D printed mask. We have discovered that commercially available HEPA filters with a MERV rating of 15, found in some vacuum cleaner bags, may require two layers of filtration to meet N95 standards. To determine how large such filters must be for comfortable user breathing, we have designed a filter holding box that can adjust the filter area by masking off a portion with blue tape. This adapter features two filter compartments for standard (2 1/2 inch) filter sizes, allowing users to evaluate breathing comfort with up to double the filter size for single-layer and double-layer filters. The three mask sizes (S, M, L) have been modified to easily accept the filter holding box, making it easy to study this critical design aspect. The evolution of the BEmask design can be followed on our website at https://bemask.org/.