"The
human face is a goldmine for health data, making everyday glasses the perfect
wearable," said Nivedita Arora (pictured), who led the work. Credit:
Northwestern University
From blinking and smiling to jaw
clenching and eyebrow raising, faces are constantly in motion—and generating
tiny amounts of energy along the way. Now, Northwestern University engineers
are putting that energy to work.
The team developed a new type of
smart glasses equipped with tiny sensors that harvest mechanical energy from
facial movements and convert it into electrical power. Even a quick blink or an
artery's faint pulsing provides enough mechanical energy to activate the highly
sensitive sensors.
To put their self-powered sensors
to the test, researchers used the glasses to detect jaw clenching, teeth
tapping, blinking and eyebrow raising. Not only did the glasses distinguish these movements
from everyday activities like talking and eating, but they also recognized
teeth tapping with 99% accuracy and jaw clenching with 96% accuracy.
The advance,
called GlassTENG, could pave the way for ordinary glasses to seamlessly monitor
cardiovascular health, bruxism (inadvertent jaw clenching and teeth grinding),
fatigue, eating behaviors and other activities throughout the day—without bulky
batteries or regular charging.
The research
is published
in the Proceedings of the 2026 ACM International Symposium on Wearable
Computers.
"The
human face is a goldmine for health data, making everyday glasses the perfect
wearable," said Northwestern's Nivedita Arora, who led the work.
"Generally, wearables track health data, like heart rate, through the
wrist. But people have to remember to wear those trackers and take them off to
recharge. Our idea is based on the fact that half the population already wears
glasses. We can turn those glasses into wearables without asking people to
change their habits and behaviors."
An expert in
self-powered electronics, Arora is the Breed Chair assistant professor of
electrical and computer engineering and computer science at Northwestern's
McCormick School of Engineering, where she leads the Vasudhaiva Kutumbakam
(VAK) Embodied Systems Lab. Raj Dave, Jovanis Prodanich and Yung-ching Lai—all
master's students in the VAK Embodied Systems Lab—are the study's co-first
authors.
A little static goes a long way
At the heart
of the new glasses are three paper-thin devices called triboelectric
nanogenerators (TENGs). Although the name sounds complicated, the
phenomenon behind them is familiar: static electricity.
Anyone who has
rubbed a balloon against their hair or petted a cat's fur on a dry winter day
has experienced the triboelectric effect. When two different materials come
into contact and then separate, electrons can transfer from one material to the
other, generating a brief electrical charge.
GlassTENG
takes advantage of that same basic phenomenon. Each flexible sensor contains
layers of materials that repeatedly press together and separate in response to
facial movements. A blink, for example, pushes against one sensor. A clenched
jaw activates another. Even the subtle pressure produced by blood pumping
through an artery can push the sensors.
"As the
layers touch and separate, they generate a tiny voltage," Arora said.
"That means the very movement being measured supplies the mechanical
energy needed to power its detection. In other words, a blink helps power the
sensor that detects the blink."
Three sensors, many signals
To capture as
much information as possible, Arora and her team positioned three sensors at
strategic locations around the glasses frame. One sits at the bridge of the
nose, near the angular artery and muscles surrounding the eyes. There, it can
pick up the pulse as well as blinking and eyebrow movements. Another sensor
sits near the temple, where it detects the superficial temporal artery along
with jaw movements. A third sensor sits closer to the ear, where it detects
movements from chewing and clenching.
Together, the
three sensors give the glasses different vantage points from which to
"feel" the face's movements. And the sensors are sensitive to a range
of forces. An arterial pulse—the lightest force the researchers
tested—generated electrical signals of about 50 to 100 millivolts. Blinks and
eyebrow raises produced roughly 200 to 500 millivolts. Stronger jaw movements,
including chewing and clenching, generated signals as high as 1.5 volts.
"These
differences give various facial activities their own recognizable electrical
signatures," Arora said.
While wearing
GlassTENG, 20 participants performed six activities: blinking, raising their
eyebrows, clenching their teeth, tapping their teeth, eating and talking. The
research team then used machine-learning algorithms to analyze patterns in the
electrical signals and determine which activity each participant performed.
Across the six activities, the system achieved 93.8% accuracy.
"One of
the most exciting possibilities is using this technology to turn unconscious
behaviors into opportunities for meaningful behavior," said study
co-author Nabil Alshurafa, an associate professor of preventive medicine,
computer science and electrical and computer engineering at Northwestern, where
he has appointments at Northwestern University Feinberg School of Medicine and
McCormick.
"Imagine
glasses that recognize when someone is clenching their jaw and gently prompt
them to relax or detect eating and encourage mindful awareness of their habits.
By combining cardiovascular and behavioral sensing within the same
ultra-low-power platform, GlassTENG opens the door to studying how
physiological states and everyday behaviors interact and to delivering
personalized interventions at the moments they may be most helpful."
Ultra-low power, big benefits
Beyond what
GlassTENG can do, another big advantage is what it doesn't need: electricity.
Many existing wearables continuously draw power. Constant power consumption
leads to bigger energy demands that require bigger batteries, which add weight
and bulk. Batteries also need regular recharging, which presents another
barrier to truly continuous health monitoring.
GlassTENG's
three sensors consume just 4.1 microwatts of power combined—orders of magnitude
less power than many conventional sensing technologies. From there, it uses
Bluetooth to stream data straight to a smartphone or tablet.
"In the
long term, we want to do on-device computation," Arora said. "If it
detected a physiological event, it could have on-device intelligence in a
battery-free way that could give immediate feedback. For example, if it
detected jaw clenching, it could immediately alert the user to relax their jaw.
I think it's only a matter of time until the glasses we wear every day can
monitor our health."
"The future isn't just wearables that tell us what we did," Alshurafa said, "but wearables that help us recognize and change what we're doing in the moment."
Provided by Northwestern University
Source: Blink-powered glasses harvest mechanical energy from facial movements to power sensors
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