Tech Briefs Magazine - February 2023 - 34

Sensors
Flexible Sensor for Robotic Sensing and Health Monitoring
It can be used in robotics to perceive surface texture or in wearable health technology devices.
National University of Singapore
R
eal-time health monitoring and sensing
abilities of robots require soft
electronics but a challenge of using such
materials lies in their reliability. Unlike
rigid devices, being elastic and pliable
makes their performance less repeatable.
The variation in reliability is known
as hysteresis. Guided by the theory of
con tact mechanics, a team of re searchers
developed a sensor material that has significantly
less hysteresis. This ability enables
more accurate wearable health
technology and robotic sensing.
When soft materials are used as compressive
sensors, they usually face severe
hysteresis issues. The soft sensor's material
properties can change in between repeated
touches, which affects the reliability
of the data. This makes it challenging
to get accurate readouts every time, limiting
the sensors' possible applications.
The new material has high sensitivity
but with an almost hysteresis-free performance.
The team developed a pro cess to
crack metal thin films into desirable ringshaped
patterns on a flexible material
called polydimethylsiloxane (PDMS).
They integrated this metal/PDMS film
with electrodes and substrates for a
piezoresistive sensor and characterized its
performance. They conducted repeated
TRACE sensor patches can be used on fingers of robotic hands for texture recognition. (Image:
National University of Singapore)
mechanical testing and verified that their
design improved sensor performance.
The Tactile Resistive Annularly Cracked
E-Skin (TRACE) sensor could potentially
be used in robotics to perceive surface texture
or in wearable health technology devices;
for example, to measure blood flow
in superficial arteries for health monitoring
applications. The next step is to further
improve the conformability of the
material for different wearable applications
and to develop artificial intelligence
(AI) applications based on the sensors.
The long-term goal is to predict cardiovascular
health in the form of a tiny, smart
patch that is placed on human skin. Other
applications include uses in prosthetics,
where having a reliable skin interface
allows for a more intelligent response.
For more information, contact Denise
Yuen at denise.yuen@nus.edu.sg; +65
6516 4470.
Standalone Sweat Sensor Provides Immediate Results
A wearable device allows the sensor to operate independently to directly visualize the
measurement's results.
University of California San Diego, LaJolla, CA
E
ngineers at the University of California
San Diego have developed a thin, flexible,
stretchy sweat sensor that can show the
level of glucose, lactate, sodium, or pH of
your sweat - at the press of a finger. It is
the first standalone wearable device that
allows the sensor to operate independently
- sans any wired or wireless connection to
external devices - to directly visualize the
measurement's results.
The small, disk-shaped patch includes
two integrated batteries, a microcontroller,
34
sensors, the circuit, and a stretchable display.
This covers all functionalities essential
for operating a wearable sensor, from powering
up to showing the user the results.
" We are trying to address the issue of
practicality in wearable technologies, "
said Lu Yin, a Nanoengineering Postdoctoral
Researcher at the UC San Diego
Jacobs School of Engineering. " We
have seen so many inventions of wearable
sensors with great novelty but with
limited practicality. "
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Besides the microcontroller, all the
components and interconnections are
fabricated using customized elastomeric
inks, which can be printed with low-cost
and high-throughput screen printing onto
stretchable polymer sheets.
The fabrication of the device involves
the formulation of nine different types
of stretchable inks, which were used to
print the batteries, circuits, display panel,
and sensors. The device is printed by
layer onto stretchable polymer sheets
Tech Briefs, February 2023

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Tech Briefs Magazine - February 2023

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