Engineers at Northwestern University have designed a "Fitbit for the face," which turns a face mask into a wearable sensor platform — and they've called it, in a fit of inspiration, a "FaceBit."
"We wanted to design an intelligent face mask for health care professionals that does not need to be inconveniently plugged in during the middle of a shift," explains lead developer Josiah Hester, assistant professor 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 FaceBit itself, though, isn't actually a mask: It's a compact sensor, roughly the size of a quarter, which attaches to any mask - from N95 respirators down to simple cloth or surgical masks — via a magnet. Energy sources, meanwhile, include heat from the wearer's breath and the sun - or even the force of the wearer's breathing. The result: an 11-day runtime between charges.
As for what the device can sense, it starts with the ability to detect potentially problematic leaks. "If you wear a mask for 12 hours or longer, sometimes your face can become numb," Hester explains. "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."
The FaceBit also tracks the wearer's physiology, including heart rate and respiration — picking up the former by minute movements in the host mask as the wearer's blood is pumped to the face. All gathered data is then transmitted wirelessly to a smartphone, where it can provide alerts to mask leaks or warn of an increase in apparent stress levels.
The hardware itself includes a u-blox BMD-350 Bluetooth Low Energy (BLE) module, ferromagnetic RAM (FRAM), AC and DC energy harvesting inputs with capacitors for storage, and a suite of sensors offering considerably more capabilities than explored in the team's work: A temperature sensor, magnetometer, six degrees of freedom (6DoF) inertial measurement unit, a barometric pressure sensor, an air quality sensor, and a microphone.
"FaceBit provides a first step toward practical on-face sensing and inference, and provides a sustainable, convenient, comfortable option for general health monitoring for COVID-19 front-line workers and beyond," Hester claims. "I'm really excited to hand this off to the research community to see what they can do with it."
The team's work has been published in the Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies; more information is available on the FaceBit website, while hardware design files and source code for the firmware and companion app are available on the project's GitHub repository under an unspecified open source license.