Tech Briefs Magazine - April 2022 - 34

Sensors
way the individual spirals of a Slinky
come out of contact with each other
when you pull both ends. This process
happens even with small amounts of
strain, which is the key to the sensor's
high sensitivity.
Unlike current highly sensitive stretchable
sensors that rely on exotic materials
such as silicon or gold nanowires, this
sensor doesn't require special manufacturing
techniques or even a cleanroom.
It could be made using any conductive
material. The researchers tested the resiliency
of the sensor by stabbing it with
a scalpel, hitting it with a hammer, running
it over with a car, and throwing it in
A close-up view of the sensor's patterned conductive carbon fibers. The fibers are sandwiched between
two pre-strained elastic substrates. The overall electrical conductivity of the sensor changes
as the edges of the patterned carbon fiber come out of contact with each other. (Photo: James
Weaver/Harvard SEAS)
a washing machine 10 times. The sensor
emerged from each test unscathed.
To demonstrate its sensitivity, the researchers
embedded the sensor in a fabric
arm sleeve and asked a participant to
make different gestures with their hand
including a fist, open palm, and pinching
motion. The sensors detected the small
changes in the subject's forearm muscle
through the fabric and a machine
learning algorithm was able to successfully
classify these gestures. Such a sleeve
could be used in everything from virtual
reality simulations and sportswear, to
clinical diagnostics for neurodegenerative
diseases like Parkin son's Disease.
Another aspect that differentiates the
technology is the low cost of the constituent
materials and assembly methods. The
researchers are exploring how the sensor
can be integrated into apparel due to the
intimate interface to the human body it
provides. The sensor could make biomechanical
and physiological measurements
throughout a person's day, which is not
possible with current approaches.
Watch a demo of the sensor on Tech Briefs
TV at www.techbriefs.com/tv/slinky_sensor.
For more information, contact Leah Burrows
at lburrows@seas.harvard.edu; 617-496-1351.
Sensors Integrated in Clothing Monitor Heart Rate
The device ultimately should be able to provide accurate signals from a person who is walking,
running, or climbing stairs.
The Charles Stark Draper Laboratory, Cambridge, MA, and University of Colorado, Boulder, CO
S
tretchable, bendable " smart " textiles
are poised to reshape clothes of all
kinds, creating new opportunities for
integrating advanced monitoring technologies
into everyday items. Researchers
are applying neuroscience and
psychophysiology to build responsive
technologies like those integrated in
smart textiles. They found that wearable
sensor systems don't seem to perform
as well in monitoring heart rates
as traditional electrodes..
To solve the problem, the researchers
tested the feasibility of electrocardiogram
(ECG) monitoring with sewn textile
electrodes instead of traditional gel
electrodes in a three-lead, chest-mounted
configuration. Commercially available
wearables are usually incapable of
detecting the full ECG waveform.
Approahces included conductive inkbased
electrodes printed onto the fabric
surface that tend to crack, causing
34
breaks in the conductive surface and
changes in resistance during movement.
They also explored planar-fashionable
circuit boards (P-FCBs), which similarly
print onto the fabric surface but require
advanced manufacturing methods to
produce the conductive paste.
The solution the team devised involved
fabricating " dry " electrodes that
are directly integrated in clothing. BeThe
new electrode overcomes a deficit common with commercially available wearables in accurately
monitoring heart rates. (Photo: Draper)
www.techbriefs.com
Tech Briefs, April 2022
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Tech Briefs Magazine - April 2022

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