Medical Design Briefs - September 2023 - 40

Researchers Fabricate Health-Monitoring Sensors onto
Ready-Made Wearables
The sensors demonstrate
high flexibility and strain
sensitivity but don't affect
breathability.
Purdue University
West Lafayette, IN
A patent-pending method developed
by Purdue University researchers
brings the public one step closer
to clothes with wearable electronics
that don't affect the wearer's comfort.
The method also simplifies the manufacturing
process and boosts sensing
capability.
Wearable electronics that monitor bioinformation
like blood pressure, body
temperature, and respiratory patterns
have become prominent in research. Traditional
wearable devices such as healthmonitoring
systems, however, are hard
and inflexible, which makes them difficult
to wear for extended periods of time.
Furthermore, fabricating wearable
sensors onto clothing creates different
sets of problems, says Sunghwan
Lee, assistant professor of engineering
technology in the Purdue Polytechnic
Institute. Traditional sensors eliminate
fabric breathability, or the circulation
of air from the inside to the outside.
Breathability allows vapor moisture to
diffuse, which prevents people from overheating
and keeps them comfortable.
" This is significant especially when
sensors have military or medical assistive
rehabilitation applications, " Lee says.
" People need to wear these electronics
for long periods of time. It isn't convenient
to replace them in the middle of a
rehab session or military exercise.
" These limitations are caused by the
traditional method to fabricate sensors
on clothing. It relies on either brittle
and inflexible inorganic materials, which
lack longer-cycle stability, or liquid- phase
processing, which is unable to create
conformal coating on fabrics and hence
makes it difficult to secure the required
breathability. "
Lee and his team have used a techPurdue
researcher Sunghwan Lee and his research team are developing breathable health-monitoring sensors
that can be embedded directly into wearable fabric gloves. In this prototype, sensor strips are embedded in the
fabric above the knuckles and on the wrist below the palm. Researchers use the robot arm to mimic everyday activities
and object manipulation with tactile sensors. (Credit: Purdue University photo/John O'Malley)
nique called oxidative chemical vapor deposition,
or oCVD, to form highly conducting
and mechanically flexible polymer
films conformally coated on every thread
of fabric. It controls the thickness of
the polymer layer, called PEDOT, while
maintaining the fabric's breathability
and flexibility.
Lee and his team demonstrated the
method by directly depositing and patterning
the PEDOT layer on commercially
available disposable gloves and masks
to create blood pressure- and respiratory
rate-monitoring sensors. The team confirmed
the mechanical flexibility of the
conformally vapor-printed PEDOT layer
through cyclic bending tests on fabric
samples coated with various thicknesses
of the films at different temperatures.
" Samples were bent 180 degrees to
generate high stress and strain on the
fabrics. Their electrical conductivity was
measured every cycle, " Lee says. " The
deposited layer was shown to maintain its
conductive performance consistently for
more than 100 bending cycles. This exemplifies
excellent mechanical flexibility
and resilience to bending and strain that
typical wearable fabrics undergo. "
A breathability test determined that the
Using a robotic hand, Jinwook Baek (left), postdoctoral research assistant, and Sunghwan Lee, assistant professor
of engineering technology at Purdue, examine how a flexible and wearable sensor could be used to monitor health
information and manipulate a small object. (Credit: Purdue University photo/John O'Malley)
40
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fabric's air permeability was not compromised
by the coated PEDOT film. There
was a negligible difference in breathability
between bare fabric and an oCVD PEDOTcoated
fabric; there also was no clear difMedical
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Medical Design Briefs - September 2023

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