Tech Briefs Magazine - May 2024 - 26

Screen-Printed Sensors Allow Earbuds to Record Brain
Activity and Exercise Levels
Capturing valuable physical and chemical signals from the ear canal could pave the way
for new opportunities in the field of wearables.
University of California San Diego, La Jolla, CA
A
pair of earbuds can be turned into a
tool to record the electrical activity
of the brain as well as levels of lactate in
the body with the addition of two flexible
sensors screen-printed onto a stamplike
flexible surface.
The sensors, developed by a team at
the University of California San Diego,
are a lot less cumbersome than state-ofthe-art
devices currently used to sense
the brain's electrical activity and the
body's sweat secretions.
" Being able to measure the dynamics
of both brain cognitive activity and body
metabolic state in one in-ear integrated
device that doesn't intrude on the comfort
and mobility of the user opens up
tremendous opportunities for advancing
health and wellness of people of all ages,
anytime and anywhere, " said Professor
Gert Cauwenberghs.
The screen-printed, flexible sensors are
attached to the earbuds on a flexible,
stamp-like surface. The earbuds are secured
with a silicon hook in order to be
more stable in the ear.
" Earbuds have been around for decades,
and in many ways were one of the
first wearable devices on the market, " said
Professor Patrick Mercier. " This research
takes important first steps to show that impactful
data can be measured from the
human body simply by augmenting the
capabilities of earbuds that people already
use on a daily basis. Since there are no major
frictions to using this technology, we
anticipate eventual wide scale adoption. "
The first step in building the in-ear sensors
was confirming that EEG and lactate
data could be gathered in the ear. Researchers
had to design smaller, more
compact instruments to gather electrophysiological
signals, such as EEG data,
that would fit on an earbud. They also had
to find a suitable material to collect sweat
and sense lactate.
After preliminary experiments on human
subjects, researchers determined
that the best location to collect and record
26
The screen-printed, flexible sensors are attached to the earbuds on a flexible, stamp-like surface.
(Image: UCSD)
lactate data was the tragus, where sweat
accumulates at the entrance of the ear.
The team also knew from previous experience
that to collect EEG data, high-performance
physiological electrodes pointed
toward the temporal lobe were required.
To make sure that the electrophysiological
sensors had firm contact with the ear,
researchers designed 3D, spring-loaded
sensors that hold contact but can adjust as
earbuds move. On the other hand, to improve
sweat collection, researchers covered
the electrochemical sensors with a
see-through hydrogel film.
" This new and powerful in-ear multimodal
wearable bioelectronic platform
offers a rich source of real-time information
on the health of the users, by recording
simultaneously and dynamically physical
and biochemical information, " said
Professor Joseph Wang.
One of the devices' limitations is that to
gather enough lactate to meaningfully analyze
data, subjects need to perform exerwww.techbriefs.com
cise
or other physical activity that get people
to sweat. In future work, researchers
will aim to do away with this requirement.
The team is also working on processing
the data on the device itself. Ultimately,
the goal is to transmit the processed
data wirelessly to a computer or a
smartphone. In-ear sensors could also
gather additional data, such as oxygen
saturation levels and glucose levels.
Throughout the study, researchers conducted
extensive experiments to validate
the efficacy of the sensors.
" The ear canal has been relatively underexplored
within the wearable technology
community, " said Sheng Xu.
" This work demonstrates the potential
of continuous sensing to capture valuable
physical and chemical signals from
the ear canal thereby paving the way for
numerous exciting opportunities in the
field of wearables. "
For more information, contact Ioana
Patringenaru at ipatrin@ucsd.edu.
Tech Briefs, May 2024

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