Engineers at Northwestern University have created a new smart sensor platform for face masks that they describe as a “Fitbit for the face.”

The lightweight, quarter-sized sensor, dubbed “FaceBit,” attaches to any N95, cloth, or surgical face mask using a small magnet.

It could not only detect the user’s real-time breathing rate, heart rate, and mask wear duration, but it could also be capable of replacing time-consuming testing by monitoring mask fit. This data is then wirelessly transferred to a smartphone app, which includes a display for real-time health monitoring. When problems, such as an increased heart rate or a leak in the mask, occur unexpectedly, the app may promptly notify the user. The physiological data might potentially be utilized to forecast weariness, physical health, and emotional state.

Although the gadget is powered by a small battery, FaceBit is designed to gather energy from a number of ambient sources, including the force of the user’s breathing, motion and heat from the user’s breath, and sunlight. This increases the battery life of the sensor, allowing it to go longer between charges.

“We wanted to design an intelligent face mask for health care professionals that do not need to be inconveniently plugged in during the middle of a shift,” said Josiah Hester, who headed the gadget development at Northwestern. “We augmented the battery’s energy with energy harvesting from various sources, which means that you can wear the mask for a week or two without having to charge or replace the battery.”

The study was published in the Proceedings of the ACM on Interactive, Mobile, Wearable, and Ubiquitous Technologies last week. FaceBit’s accuracy was found to be comparable to clinical-grade devices in the trial, and the battery lasted more than 11 days between charges.

Attempting to approximate the fit test

Hester and his partners initially interviewed physicians, nurses, and medical assistants to better understand their demands for smart face masks before inventing FaceBit. In a series of studies, all physicians agreed that the quality of mask fit was the most critical factor, especially when working directly with patients with viral illnesses.

Health care employees must regularly perform a 20-minute “fit test” to verify that their N95 masks are securely sealed to their faces. During this process, health care workers first put on an N95 respirator, followed by a transparent hood over their entire head. The hood is then sprayed with either sweet or bitter aerosol mists by another worker. The concentration of the aerosol within the hood is progressively raised until it can be recognized by the person wearing the respirator. The mask is not adequately sealed if the wearer tastes bitter or sweet before a specified number of aerosol pumps.

Although Hester’s FaceBit cannot yet replace this time-consuming process, which has long been a difficulty in the medical profession, it can ensure that the mask remains a correct fit between testing events. FaceBit can inform the wearer if the mask gets loose over the day or if the user bumps the mask during an activity, for example.

“If you wear a mask for 12 hours or longer, sometimes your face can become numb,” Hester explained. “You might not even realize that your mask is loose because you cannot feel it or you are too burnt out to notice. We can approximate the fit-testing process by measuring mask resistance. If we see a sudden dip in resistance, that indicates a leak has formed, and we can alert the wearer.”

“Your heart is pushing a lot of blood through the body, and the ballistic force is quite strong,” Hester said. “We were able to sense that force as the blood travels up a major artery to the face.”

FaceBit can utilize this information to advise the user to take a break, go for a walk, or take some deep breaths to calm down because stressful situations can provoke physiological reactions like fast breathing. This data might potentially be used by hospital systems to optimize shift and break plans for their employees. Because heart rate and respiration rate are so inextricably linked, being able to simply monitor both might open up new study avenues.

Future without batteries

Hester, an expert in battery-free technology, expects that his team or others will someday be able to make FaceBit totally battery-free. The wearer’s respiration and motions, as well as the sun, may now be used to increase the battery’s life. However, in the future, captured thermal and kinetic energy might be used to power the gadget entirely.

Despite the fact that his team tested the gadget on volunteers in real-world circumstances, Hester stated that FaceBit still requires clinical studies and validation. The researchers made the project open source and open hardware so that anyone may construct and test the gadget.

“FaceBit provides the first step toward practical on-face sensing and inference, and provides a sustainable, convenient, comfortable option for general health monitoring for COVID-19 frontline workers and beyond,” Hester said. “I’m really excited to hand this off to the research community to see what they can do with it.”

FaceBit: Smart Face Masks Platform was funded by the National Science Foundation’s Grants for Rapid Response Research to combat the COVID-19 epidemic (award number CNS-2032408). FaceBit was developed in partnership with Nabil Alshurafa, an associate professor of preventative medicine at Northwestern University’s Feinberg School of Medicine and computer science at McCormick.


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