Overview

The client for this capstone was Dr. Chen, from the Harvard Medical School. He realized that many masks are uncomfortable, and testing for pathogens such as COVID can be time consuming and unpleasant. His task for my team was to create a reusable mask that is comfortable and allows for non-invasive diagnostic testing. Ideally, a person could wear the mask during their work day, a sample would be collected automatically, and at the end of the day, that sample would then be sent off for testing.

Problem

In order for Dr. Chen’s diagnostic test to work, 1 ml of respiratory fluid must be collected. This meant developing a system that could collect respiratory fluid from breathing and storing that fluid until collection. This system also had to be light enough to not be burdensome to wear for extended periods.

Action

While passive collection methods were explored, such as capturing respiratory droplets using nano-scale geometries, these solutions were deemed unfeasible due to our ability to manufacture such geometries with the resources available.

We decided to opt for an electronic solution, utilizing a Peltier tablet. This tablets act as a small refrigeration cycle, creating a hot and cold side. Due to the saturated air present in an enclosed mask, the cold side of the tablet is able to condense respiratory fluid exhaled in the breath. To increase the condensation efficacy, hydrophobic strips were placed on the cold surface.

During use, the condensed droplets flow off of the tablet into a collection container; the container houses a sponge to absorb the fluid until collection. A fan is connected to the hot side of the tablet to aid in heat dispersion. Two filter boxes are present on each side of the clear front, and these filters can be replaced as needed. A rechargeable battery powers the components. Dual adjustable straps with magnetic attachments provides the ergonomic fit required for extended use without strain on the neck.

Figure 3 shows all of the necessary electronics. A temperature and humidity module was also implemented; data collected from this module is recorded on the Rasberry Pi and can be exported for analysis.

Result

Ultimately, we were able to provide our client with a fully functional prototype that met all of the required design criteria. Our tests with the final prototype showed that the 1 ml of fluid can be collected in approximately 8 hours of use with a sedentary activity level. This collection rate means that the mask can collect the required amount of fluid during a normal work day with no change in behavior required from the user. Through proper weight distribution of the electronic components combined with the dual strap design, the mask is also comfortable to wear for the required collection time.