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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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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Platform Optimization

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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