Engineers are developing sensors for face masks that help measure fit: the system measures biological and environmental changes and detects contact between the mask and the wearer’s skin

There are currently no easy ways to measure a mask’s fit, but a new sensor developed at MIT could make it much easier to ensure a good fit. The sensor, which measures the physical contact between the mask and the wearer’s face, can be applied to any type of mask.

Using this sensor, the researchers analyzed the fit of surgical masks on male and female subjects and found that the masks overall fit much less accurately on women’s faces than on men’s faces.

“By analyzing our data collected from the subjects in the study, we found that the masks we use in daily life are not very suitable for female participants,” says Canan Dagdeviren, LG Career Development Professor of Media Arts and Sciences at MIT and the corresponding author of the study.

The researchers hope their sensor will help people find masks that fit them better and that designers could use it to create masks that fit a wider variety of face shapes and sizes. The sensor can also be used to monitor vital signs such as respiratory rate and temperature, as well as environmental conditions such as humidity.

The study is a collaboration between Dagdeviren’s laboratory; Siqi Zheng, the STL Champion Professor of Urban and Real Estate Sustainability in the Department of Urban Research and Urban Planning; and Tolga Durak, executive director of MIT’s environment, health and safety programs. Jin-Hoon Kim, an MIT postdoc, is the lead author of the paper, which appears in today nature electronics.

fit quality

Researchers began work on this project before mask-wearing became common during the Covid-19 pandemic. Their original intention was to use sensors embedded in masks to measure the effectiveness of mask wearing in areas of high air pollution. However, as the pandemic began, they realized that such a sensor could have broader applications.

With so many different types of masks available during the pandemic, researchers thought this type of sensor could be useful in helping individuals find the mask that would work best for them. Currently, the only way to measure mask fit is to use a device called a mask fit tester, which assesses mask fit by comparing airborne particle concentrations inside and outside the face mask. However, this type of machine is only available in specialized facilities such as hospitals, which use it to assess the fit of masks for medical workers.

The MIT team wanted to create a more user-friendly, handheld device to measure mask fit. Dagdeviren’s lab, the Conformable Decoders Group, specializes in developing flexible, stretchable electronics that can be worn on the skin or embedded in textiles to capture signals from the body.

“In this project we wanted to monitor both biological and environmental conditions at the same time, e.g. B. Breathing patterns, skin temperature, human activity, temperature and humidity inside the face mask, and the position of the mask, including whether people are wearing it correctly or not,” says Kim. “We also wanted to check the fit.”

To integrate their sensors into face masks, the researchers created a device they call a compliant multimodal sensor face mask (cMaSK). Sensors that measure a variety of parameters are embedded in a flexible polymer frame that can be reversibly attached to the inside of each mask at the edges.

To measure fit, the cMaSK has 17 sensors on the edge of the mask that measure the capacitance that can be used to determine if the mask is touching the skin at each of these locations.

The cMaSK interface also has sensors that measure temperature, humidity and barometric pressure and can detect activities such as talking and coughing. An acceleration sensor in the device can detect whether the wearer is moving. All sensors are embedded in a biocompatible polymer called polyimide, which is used in medical implants such as stents.

The researchers tested the cMaSK interface in a group of five men and five women. All subjects wore surgical masks, and the researchers monitored readings from the sensors while participants performed a variety of activities, such as B. Talking, walking and running. They also tested the sensors under different temperature conditions.

Using data obtained from the capacitance sensors, the researchers created a machine learning algorithm to calculate the fit of the mask for each subject in the study. These measurements revealed that women’s mask fit was significantly poorer than men’s due to gender differences in face shape and size. However, the fit for women could be slightly improved by wearing smaller surgical masks. The researchers also found that the mask fit was poor on one of the male subjects with a beard, resulting in gaps between the mask and the skin.

To verify their findings, the researchers also worked with MIT’s Environment, Health, and Safety Office in designing and evaluating the fit and found that the fit results for each study participant were very similar to those they found with the cMaSK .

Tailored fit

The researchers hope their findings will encourage mask makers to design masks that fit a variety of face shapes and sizes, particularly women’s faces. Dagdeviren’s lab plans to work on mass production and large-scale deployment of the cMaSK interface.

“We hope to think about ways to design masks and find the best fit for the individual,” says Dagdeviren. “We have different sizes for shoes and you can even customize your shoes. So why not personalize and personalize your mask, for your own health and for societal benefit?”

The researchers also hope to return to their original idea of ​​studying the effects of air pollution on people who work outdoors.

“Our technology can really help to quantify the social costs of these environmental hazards and also measure the benefits of any kind of political intervention,” says Zheng.

The research was funded by the MIT Media Lab Consortium, the 3M Non-Tenured Faculty Award, and the MIT International Science and Technology Initiative (MISTI) Global Fund.