Tech Briefs Magazine - May 2022 - 27

chloride ion levels can be used to diagnosis
and monitor cystic fibrosis;
and cortisol, a stress hormone, can be
used to assess emotional stress as well
as metabolic and immune functions.
Athletes could monitor a wide range
of markers during physical exertion to
aid in predicting performance peaks
or declines during competition.
The ability to integrate the sensors
into clothing is made possible by flexible
threads coated with conductive inks. Different
coatings alter the functionality of
the threads; for example, lactate can be
detected by coating a thread with an enzymatic
sensing material incorporating
the enzyme lactate oxidase. A pH sensing
thread is coated with polyaniline that
responds to acidity, and so on. The array
of thread sensors is integrated into clothing
or a patch and connected to a miniature
circuit module and microprocessor,
with wireless capability to communicate
with a smartphone.
Researchers tested the device on human
subjects, monitoring their electrolyte
and metabolite response during a
maximum exertion exercise on stationary
bikes. The sensors were able to detect
variation in analyte levels as they moved
up and down, within 5 to 30 second intervals
- sufficient for most real-time
tracking needs. The study established
that the sensor was able to detect consistent
patterns of analyte expression that
could be used for future studies identifying
these correlations.
For more information, contact Mike Silver
at mike.silver@tufts.edu; 617-627-0545.
Liquid Metal Wearable Pressure Sensor
The sensor enables health monitoring and early diagnosis of disease.
Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
S
oft pressure sensors have received
significant research attention in a
variety of fields including soft robotics,
electronic skin, and wearable electronics.
Researchers have developed a highly
sensitive wearable pressure sensor capable
of sensitive, precise, and continuous
measurement of physiological and physical
signals and shows great potential for
health monitoring applications and the
early diagnosis of diseases.
A soft pressure sensor is required to
have high compliance, high sensitivity,
low cost, long-term performance stability,
and environmental stability in order
to be employed for continuous health
monitoring. Conventional solid-state
soft pressure sensors using functional
materials, including carbon nanotubes
and graphene, have showed great sensing
performance; however, these sensors
suffer from limited stretchability, signal
drifting, and long-term instability due
to the distance between the stretchable
substrate and the functional materials.
To overcome these issues, liquid-state
electronics using liquid metal have
been introduced for various wearable
applications. Of these materials, Galinstan
- a eutectic metal alloy of gallium,
indium, and tin - has great mechanical
and electrical properties that can
be employed in wearable applications.
But today's liquid metal-based pressure
sensors have low pressure sensitivity,
limiting their applicability for health
monitoring devices.
The researchers developed a 3D-printed,
rigid microbump array-integrated,
liquid metal-based soft pressure sensor.
With the help of 3D printing, the inteTech
Briefs, May 2022
Liquid Metal
3D-Printed
Microbump Array
Elastomer
Stretching
Bending
Liquid Metal
Folding
Twisting
Highly sensitive liquid-metal-based soft pressure sensor integrated with 3D-printed microbump array.
(Photo: KAIST)
gration of a rigid microbump array and
the master mold for a liquid metal microchannel
could be achieved simultaneously,
reducing the complexity of the
manufacturing process. Through the
integration of the rigid microbump and
the microchannel, the new pressure sensor
has an extremely low detection limit
and enhanced pressure sensitivity compared
to previously reported liquid metal-based
pressure sensors. The proposed
sensor also has a negligible signal drift
over 10,000 cycles of pressure, bending,
and stretching and exhibited excellent
stability when subjected to various environmental
conditions.
www.techbriefs.com
These performance outcomes make
it an excellent sensor for various health
monitoring devices. First, the research
team demonstrated a wearable wristband
device that can continuously monitor
one's pulse during exercise and be employed
in a noninvasive, cuffless blood
pressure monitoring system based on PTT
calculations. Then, they introduced a wireless,
wearable heel pressure monitoring
system that integrates three 3D-BLiPS with
a wireless communication module.
For more information, contact Professor
Inkyu Park, KAIST Micro/Nano Transducers
Laboratory, at inkyu@kaist.ac.kr or visit
http://mintlab1.kaist.ac.kr/.
27
TB Sensors 0522_1.indd 27
Cov
ToC
4/20/22 11:39 AM

http://mintlab1.kaist.ac.kr/ http://www.techbriefs.com http://info.hotims.com/82321-809

Tech Briefs Magazine - May 2022

Table of Contents for the Digital Edition of Tech Briefs Magazine - May 2022