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UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE
Towards Wearable Sensors for
Wireless pH Monitoring in Sweat
Giusy Matzeu, Claudio Zuliani, Dermot Diamond
Clarity, Centre for Sensor Web Technology, Dublin City
University, Ireland
Pittcon, 14/03/2012
1
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE 2
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE
Analyte
Chemo/Bio Sensing
Wireless data transmission
Sensors for the Digital World
4
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE
IS-Membrane
Conducting Polymer
Carbon
Resist
Silver
PET
Substrate
Cost
Reproducibility
Compatible with Wearable &
Environmental Applications
Sensors for the Digital World
5
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE
pH ISE – An Initial Design
Sensors and Actuators B,
2010, 146 , 19
2nd calibration after 3days in the
conditioning solution
y = -53.3x + 537.1
R² = 0.970
y = -54.9x + 544.1
R² = 0.972
y = -53.2x + 504.8
R² = 0.9730
150
300
450
2 4 6 8 10
E/
mV
pH
May we improve this limit working
on SPE fabrication ?
6
y = -52.1x + 521.2
R² = 0.994
y = -53.8x + 524.8
R² = 0.996
y = -52.0x + 519.7
R² = 0.996
y = -53.3x + 522.0
R² = 0.9930
150
300
450
2 4 6 8 10
E/
mV
pH
1st calibration after overnight
conditioning
Loss of linearity & offset
change over time.
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE
“Initial” vs “New” SPE
7
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE
“Original” vs “New” SPE
-8
-4
0
4
-0.4 -0.2 0 0.2
i/
uA
E / V
Original SPE y = 21.5x + 1.53
R² = 0.986
y = -52.4x - 0.21
R² = 0.999-80
-40
0
40
80
0 0.5 1
i/
μA
v0.5 / V0.5 s-0.5
0.3 < σ < 0.6
y = 71.9x + 1.27
R² = 0.997
y = -65.1x - 2.71
R² = 0.996-80
-40
0
40
80
0 0.5 1
i/
μA
v0.5 / V0.5s-0.5
σ ≈ 1.6
8
-8
-4
0
4
-0.4 -0.2 0 0.2
i/ A
E / V
New SPE
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE
pH ISEs – Silverless-SPE and
Membrane Thickness
550 μm well allows a better reproducibility !
500 μm PMMA + 50 μm PSA as
masking layer
y = -52.8x + 521.0
R² = 0.995
y = -54.2x + 529.8
R² = 0.996
y = -53.6x + 522.2
R² = 0.996
y = -53.1x + 522.7
R² = 0.99550
150
250
350
3 5 7 9
E / m
V
pH
175 μm PMMA + 50 μm PSA as
masking layer
y = -48.55x + 529.1
R² = 0.988
y = -52.6x + 530.8
R² = 0.973
y = -49.6x + 524.3
R² = 0.989
y = -57.0x + 572.3
R² = 0.998
50
150
250
350
3 5 7 9
E / m
V
pH
10
Carbon prints were masked used PSA and PMMA. PET substrate were laminated
with PSA and PMMA after that tracks carbon was screen printed: Integration of ISE
within microfluidic system
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE
pH ISEs – Performance over
Time & Storage Calibration repeated after 5 days
storage in conditioning solution
y = -55.2x + 563.5
R² = 0.997
y = -54.3x + 552.4
R² = 0.997
y = -57.9x + 579.0
R² = 0.9950
100
200
300
400
3 4 5 6 7 8 9
E/
mV
pH
11
Printing protocols, e.g.,
presence of Ag,, have a
significant impact in sensor
reproducibility over time !
y = -53.5x + 524.3
R² = 0.996
y = -55.8x + 565.0
R² = 0.997
y = -55.8x + 544.6
R² = 0.992
0
100
200
300
400
3 4 5 6 7 8 9
E/
mV
pH• Day 0
• Day 5 (kept in conditioning solution)
• Day 19 (kept in dry conditions)
Dry storage may
preserve sensor
functionality !
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE
Reference Electrodes based
on Lipophilic Salts on SPE U. Mattinen, J. Bobacka, A. Lewenstam,
Electroanalysis 2009, 21, 1955.
-500
-450
-400
-350
0 20 40 60 80
E/
mV
Time / min
SC=PEDOT
0.1 M
KCl
1 mM
KCl
1 mM
NaCl 0.1 M
NaCl 0.1 M
KCl
Cl- ≈ 20 mV/decade
Possibility for RE
where [Cl-] is constant Need
optimisation
• SC=PEDOT
• SC=POT
-250
-200
-150
-100
-50
0 20 40 60 80
E/
mV
Time / min
0.1 M
KCl
1 mM
KCl
1 mM
NaCl
0.1 M
NaCl
0.1 M
KCl
13
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE
Mote Interface and Wireless
Communication
2.5
3.0
3.5
4.0
0 20 40 60 80
Po
ten
tia
l / m
V
Time / s
• Mote 1
• Mote 2
• Mote 3
• 16Ch-
Lawson Labs
Bias between motes and
standard instrumentation < 0.3mV
Bias between motes < 0.1 mV
14
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE
Dual SPE – Integration of pH
& RE on same substrate
The two carbon disks printed
on the PET substrate will be
modified to give a pH and a
reference electrode
The substrate can also be
laminated with PSA and PMMA
for futher integration within
microfluidics.
15
Work currently under progress to
optimize sensor response !!
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE
Wearable pH Sensor –
Concept
Mote Casing
Strap Patch
Sensor +
Microfluidic
16
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE
Wearable pH Sensor –Layers
Microfluidics
pH ISE & RE
Patch
Mote Casing
Mote
17
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE
Acknowledgements
Prof. Dermot Diamond
Dr. Fiachra Collins,
postdoc
Javier Torres,
Tyndall
Giusy Matzeu,
PhD student
Dr. Salzitsa Anastasova,
Dr. Aleksandar Radu,
Dr. Ulriika Mattinen,
Prof. Johan Bobacka
18
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE
SOCIAL/AGENCY
COLLABORATORS
INDUSTRY COLLABORATO
RS
CSET CORE
CLARITY Centre & Ecosystem
16
SOCIAL/AGENCY COLLABORATORS
INDUSTRY COLLABORATORS
SOCIAL/AGENCY COLLABORATORS
INDUSTRY COLLABORATORS
19
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE
Thank You for
Attention
20
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITY TYNDALL NATIONAL INSTITUTE
pH ISEs – Role of SPE Design A comparison between 1°
calibration for (Ag+C) SPE & C
(Batch II) SPE
y = -51.9x + 519.6
R² = 0.997
y = -53.4x + 523.9
R² = 0.996
0
100
200
300
400
3 4 5 6 7 8 9
E/
mV
pH
• (Ag+C) SPE
• C SPE
12