Testing and Developing DIY Masks

Abstract

The purpose of this design project is to develop a DIY mask to combat the shortage of N95 respirators and medical masks in low resource settings. In the preliminary stages of the project, meetings with stakeholders, mostly in the form of experts in the area of study, were conducted. Research was also done on literature in the area, which led to the development of engineering specifications. The mask should have a low cost of fewer than 2 cedis or 0.34 USD. The mask should be made in less than 30 minutes with fewer than 12 steps of instructions. The mask should filter over 50% of particles over 50 nm in size. The mask should fit well to the face and minimize airflow around the edge with a fit factor greater than or equal to 2. The mask should also be comfortable to wear with average scores greater than 4 on a 6 point Likert scale. Finally, the mask should sustain a long lifespan, supporting over 20 uses with a decontamination cycle in between each use. Using a combination of design heuristics and a morphological matrix, several designs were brainstormed to meet the project requirements. These designs were then filtered using a decision matrix, resulting in the three best designs. Engineering analyses were then developed to further evaluate the mask designs and answer some key design drivers. The first and simplest test was the Mask Fabrication Test, which simply recorded the time it took to create the masks. The test indicated that the three designs had a comparable fabrication time. The next substantial test that was conducted was the Mask Fit Test, which measured airflow around the masks. From this test, various factors of the best performing masks were determined. To help ensure the mask was comfortable, several steps were taken. First, a Comfort Priority Survey was conducted, which helped provide context for the results of the Mask Comfort Test. Then, prototypes of the three mask designs were tried on and rated for various aspects of comfort by people close to team members. From these tests, the nylon design was chosen as the final design, with a few modifications. The final design uses three layers of material -cotton, silk, and nylon- to filter out particles. The nylon layer also acts as the ear straps for comfortability. Wires are sewn inside the top and bottom of the mask to improve fit, and pleats are sewn on the side for flexibility. One final comfort test was conducted with the design, which verified the requirement. The low-cost requirement was verified through calculations, and the “uses available materials requirement” was verified from research. The “is easy to create” requirement was verified with a use test. To verify the lifetime and filtration efficiency requirements, a Mask Filtration Efficiency Test was performed. However, due to a lack of testing time, no conclusive results were obtained from the test, and the lifetime and filtration efficiency requirements were left unverified. An inability to test also left the fit requirement unverified. By the end of the project, a design and instructions on creating the design were created. This design has been verified to fulfill 4 out of 7 requirements. The filtration efficiency, lifetime, and fit requirements all require further testing for verification.