WEARABLE CHEMICAL SENSING –
OPTIMIZING PLATFORMS AND SENSITIVITY
FOR REAL-TIME SWEAT ANAYLSIS
Background
Jennifer Deignan1, Larisa Florea1, Shirley Coyle1 and Dermot Diamond1
Measurement Stability
1Insight Centre for Data Analytics, National Centre for Sensor Research, Dublin City University, Ireland.
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V)
Time (min)
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30 mM
60 mM
90 mM
130 mM
Solution In Solution Out
Microchannel
Cover slide
(100µm)
Microelectrode Connection Box
Waste
Syringe Pump
Channel designs were also created in PMMA for increased durability
in wearable applications and increased surface area of the channel
with respect to the sensor.
y = -2.6865x + 2132.7 R² = 0.9849
y = -0.9208x + 2041.3 R² = 0.9933
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V)
Concentration (mM)
Platform Optimization
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mM
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Time (min)
Conclusions The results of this work will be implemented in a real-time, wearable device
for monitoring the sweat conductivity. Such a device may be used to
monitor hydration levels and test the effect of cystic fibrosis medications.
Additionally, optimization of such a platform could allow replacement or
integration of other detection methods for sodium, or integration of
detection methods for other physiological features.
This work presents the optimization of electrical parameters and sampling platforms to maximize the sensitivity of conductivity measurements for
applications in wearable sweat sensing. Capacitively coupled contactless conductivity detection (C4D) was used to test microelectrodes in
preparation for the creation and development of an on-body detection system for sweat analysis. In addition, various polydimethylsiloxane (PDMS)
and poly(methyl methacrylate) (PMMA) microchannels of various configurations were tested for their compatibility with the system and their
enhancement effect on signal sensitivity.
Introduction
Acknowledgments Science foundation Ireland under the Insight initiative, grant SFI/12/RC/2289.
A gold Micrux chip was
calibrated with 10-130 mM
solutions of NaCl with a
flow rate of 20 µL/min.
Two distinct linear ranges
are sustained; 10-50 mM
and 60-130 mM. NaCl
concentration variations
over the normal range
(<60 mM) and elevated
values associated with
cystic fibrosis (>60 mM)
can be clearly
distinguished.
Measurements also showed high repeatability over the calibration
range (relative standard deviation between 0.0087%-0.0726% for
n=3) and high stability over 5 minute measurements (relative
standard deviation between 0.0017%-0.0860% for n=5940). These
measurements may be used to determine the efficacy of therapeutic
interventions to regulate the ion composition towards normal levels,
which is detectable in sweat.
Multiple channel
configurations were
created to optimize the
direction of flow and
surface area of the
channel with respect to
the sensor. The larger
channel surface areas
with respect to the
electrode used in the
PMMA microchannels
dramatically increased
the voltage difference
between [NaCl]
compared to the PDMS
microchanels. In
addition, the durability
of the PMMA channels
makes them desirable
for wearable
applications.
130
mM
A TraceDec C4D system was used to determine the conductivity of a
range of NaCl solutions using a Micrux thin-film interdigitated
microarray electrode.
Multiple channel configurations were created in PDMS to optimize the
design with respect to direction of flow and practical integration into a
wearable device.
C4D Calibration 2
2 m
m
11
mm
10 µm
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