Towards Wearable Sensors for Wireless pH Monitoring in...

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


Analyte

Chemo/Bio Sensing

Wireless data transmission

Sensors for the Digital World

4


IS-Membrane

Conducting Polymer

Carbon

Resist

Silver

PET

Substrate

Cost

Reproducibility

Compatible with Wearable &

Environmental Applications

Sensors for the Digital World

5


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.


“Initial” vs “New” SPE

7


“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


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


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 !


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


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


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 !!


Wearable pH Sensor –

Concept

Mote Casing

Strap Patch

Sensor +

Microfluidic

16


Wearable pH Sensor –Layers

Microfluidics

pH ISE & RE

Patch

Mote Casing

Mote

17


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


SOCIAL/AGENCY

COLLABORATORS

INDUSTRY COLLABORATO

RS

CSET CORE

CLARITY Centre & Ecosystem

16

SOCIAL/AGENCY COLLABORATORS

INDUSTRY COLLABORATORS

SOCIAL/AGENCY COLLABORATORS

INDUSTRY COLLABORATORS

19


Thank You for

Attention

20


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

Towards Wearable Sensors for Wireless pH Monitoring in...

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