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Inkjet Printing as a Tool for the Inkjet Printing as a Tool for the Fabrication of Conducting Polymer Fabrication of Conducting Polymer- Based Sensors & Biosensors Based Sensors & Biosensors

• Dr. Aoife Morrin

The National Centre for Sensor Research The National Centre for Sensor Research

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National Centre for Sensor Research School of Chemical Sciences Dublin City University Ireland

Overview Overview

• 1. Introduction
• 2. Inkjet printing of conducting polymer
• 3. High specification, flexible, inkjet printed

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3.

gas sensor platform

• 4. Biosensor fabrication & application

Overview Overview

• 1. Introduction
• 2. Inkjet printing of conducting polymer
• 3. High specification, flexible, inkjet printed

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3.

gas sensor platform

• 4. Biosensor fabrication & application

Introduction Introduction

• Advances in materials and engineering are paving the

way for new and more capable sensors

• Most recent advances are not originating from new

transduction materials, but more from materials and innovations that reduce overall cost and improve quality

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• ‘Enabling technologies’ are principle drivers in sensor

fabrication development

Printed Sensors Printed Sensors

• Mass market application areas
• High demand for low-cost, mass-producible sensor products in specific

key markets such as point-of-care medical diagnostics and smart packaging, remote environmental sensing, etc….

• Early 1980s saw the enormous commercial success
• f the screen-printed glucose biosensor

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• 9 billion glucose tests performed annually
• Inkjet printing – set to surpass

screen-printing???

• Today we have more sophisticated

materials available…

Enabling Technology: Inkjet Enabling Technology: Inkjet Printing…. Printing….

• Rapid, reproducible, cheap way to manufacture sensors
• Easily scaled up, suited to large and small production volumes
• Quality control in real time
• High precision, claiming a resolution of ~ 25 µm
• Thin film deposition (nm). Thinner films can yield faster response

times

• Amenable to simultaneous deposition of more than one material

– multi-component layers, microarrays

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• Sensor optimisation through combinatorial printing
• Non-contact printing (substrate and print head don’t touch),

suitable for fragile substrate e.g., membranes

• Aqueous solution are printable – important for biological species
• Low wastage, important for precious materials
• Flexible design process
• ………..

…..Combined With Processable, …..Combined With Processable, High Quality Sensing Materials…. High Quality Sensing Materials….

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Interesting Functional Materials for Sensing Include:

Electroactive/Optically active materials Conducting Polymers Metallic Inks Biomolecules for Biosensing Membranes ….

Overview Overview

• 1. Introduction
• 2. Inkjet printing of polyaniline
• 3. High specification, flexible, inkjet printed

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3.

gas sensor platform

• 4. Biosensor fabrication & application

• Suitable for chemical sensing
• f acids and bases through its

excellent doping/dedoping capabilites

• Desirable material for

Sensor Platforms Based on Sensor Platforms Based on Polyaniline Polyaniline

NH2

Aniline Monomer

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• Desirable material for

biosensing because of its good redox properties and hence can act as a diffusionless mediator for electron transfer between enzyme centres and the electrode transducer Doped Polyaniline (conductive state)

• Developing various electrochemical sensor/biosensor

platforms using polyaniline-based polymers

• Examining various sensor fabrication approaches such as
• electrochemical deposition
• nano-templating
• printing approaches

PANI PANI-

• based Sensor Research

based Sensor Research

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• printing approaches
• Printing methods permit processability, low cost and

disposability

• Aiming to demonstrate that inkjet printing, combined with the

right materials is a feasible, valid approach to sensor fabrication

Back In The Old Days…. Back In The Old Days….

• Glassy Carbon Electrode Platform
• Traditional 3-electrode cell setup to

electropolymerise PANI films to electrode surface

Auxiliary Electrode Working Electrode Reference Electrode N2 in Supporting electrolyte (with analyte) Potentiostat

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• Works really well, but laborious fabrication

procedure

• How to translate into a commercially relevant

product??

Potential (V)

• 0.4
• 0.2

0.0 0.2 0.4 0.6 0.8 1.0 Current (µA)

• 100
• 50

50

Screen Screen-Printing for Electrode Printing for Electrode Fabrication Fabrication

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• Low start up and manufacturing cost
• Mass production
• Disposability
• Platform for glucose biosensor

industry

3 cm 1 cm

Inkjet Printing of Silver for Inkjet Printing of Silver for Electrode Fabrication Electrode Fabrication

Silver Inter-Digitated Array (IDA) Single Electrode The National Centre for Sensor Research The National Centre for Sensor Research

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• Commercial Ag product
• ~ 1 cm-1 (1 layer)
• Challenge will be to print inert carbon electrode layers

comparable to screen-printed carbon

• Can print gold or platinum as alternatives

Modifcation of Electrode: Modifcation of Electrode:

Processable PANI Processable PANI

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• New, processible materials
• Water-soluble, or stable nanodispersions
• High processibility
• Aqueous-based
• Good redox activity and conductivity

PANI Nanodispersion PANI Nanodispersion Characterisation Characterisation

10 20 30 1 10 100 1000 10000 Diameter (nm) Volum e (% )

< 100 nm diameter

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No Stabiliser Present* DBSA Stabiliser Present

*Jiaxing Huang, Richard B. Kaner, Angew. Chem. Int. Ed. 2004, 43, 5817- 5821

Inkjet Printing of PANI Inkjet Printing of PANI

Multi-Head Desktop Epson Inkjet Printer Commercial Research Fuji Dimatix Printer The National Centre for Sensor Research The National Centre for Sensor Research

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Inkjet Printed PANI Electrodes Inkjet Printed PANI Electrodes

• PANI nanodispersions inkjet printed onto IDAs for gas

sensor platform

• Also printed to carbon paste working electrodes

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Resulting ‘Smooth’ Morphology Resulting ‘Smooth’ Morphology

(a) Bare SPE (b) 10 Prints

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(c) 20 Prints (d) 30 Prints

Morphology Morphology

1 print

1 cm 1 cm

40 prints

1 cm

10 prints

1 cm 1 cm

4000

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Elimination of classic drop-coated ‘coffee-ring effect’

• No. of Prints of PANI

1 5 10 20 30 40

Film Thickness (nm)

1000 2000 3000

Overview Overview

• 1. Introduction
• 2. Inkjet printing of conducting polymer-based

sensor

• 3. High specification, flexible, inkjet printed

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• 3. High specification, flexible, inkjet printed

gas sensor platform

• 4. Biosensor Fabrication & application

Ammonia Sensing Ammonia Sensing

• Ammonia is a highly toxic chemical species
• Classified as a major pollutant
• The ammonia sensing industry spans a wide range of

markets

• Mature market, lacking in innovation
• Niche for low-cost portable sensors e.g., for health & safety

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Detection Mechanism Detection Mechanism – – Gas Sensing Gas Sensing

• Conductimetric mode

– 2 electrode cell

• Ammonia deprotonates

PANI backbone – Emeraldine salt (ES) to emeraldine base (EB) form – Decrease in

N H N N H N H

n

N H N N N H Emeraldine Salt Deprotonated by NH3 + (NH3)n

• (H+)n

+•

• The National Centre for Sensor Research

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– Decrease in conductivity

• Apply potential to IDA

– current flows through PANI film – Vapp : step or ramp

• Measure change in current
• n NH3 exposure

H H

n

Emeraldine Base

• + NH3
• NH3

Increasing Print Layers Increasing Print Layers – – Increasing Increasing Current Current

• Sequential inkjet

printed layers

– Quasi-linear

increase from 1 – 10 layers

– Begins to plateau

400 500 600 400 500 600

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– Begins to plateau

above 10 layers (inset)

– Thicker layers do not

seriously effect response/recovery times – porous film

• No. of PANI layers

2 4 6 8 10 100 200 300 y = 60.4 x - 67.2 r ² = 0.9939 200x1500 IDA n = 3

• No. of Layers

5 10 15 20 25

• No. of PANI layers

2 4 6 8 10 100 200 300 y = 60.4 x - 67.2 r ² = 0.9939 200x1500 IDA n = 3

• No. of Layers

5 10 15 20 25

sampled current

0.6 0.8 1.0

T50 T90

Sensor Response Times Sensor Response Times

• Response times for

PANI IDA (n=4)

– t50 ~ 15 s – t100 < 60 s

• ~ 60 ppm NH3

Exposed to NH3 vapour The National Centre for Sensor Research The National Centre for Sensor Research

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Time / s

15 30 45 60 75 90 105 120 135 150 165 180

Normalised s

0.0 0.2 0.4

• 3
• Response times

currently within those specified by ISA (Instrument Society of America)

– t50 < 90s

Flexible Heater Substrate Flexible Heater Substrate

• MincoTM thermofoil heaters
• Thin and flexible

– fast temperature equilibration

• up to 200°

C

– sub 100° C used for PANI sensors

• Compatible with inkjet printing

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• Compatible with inkjet printing
• Possibility of printing directly

to heater substrate

Inkjet printed PANI Silver IDA

• n PET

substrate Flexible heating foil

rrent

0.6 0.8 1.0 Non-heated 50 C 60 C 70 C 80 C

Response Behaviour Using Response Behaviour Using Flexible Heater System Flexible Heater System

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Time / s

500 1000 1500 2000 2500 3000 3500

Normalised curre

0.0 0.2 0.4 0.6

Increasing temperature reduces sensitivity to increase linearity

• ver relevant range

Sensor Recovery Using Flexible Sensor Recovery Using Flexible Heater System Heater System

ed current 0.6 0.8 1.0

Time / s 500 1000 1500 1.0

• Room Temp recovery > hours
• 80°

C recovery < seconds

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Time / s

• 100

100 200 300 400 Normalised 0.0 0.2 0.4

Normalised current

• 2.0
• 1.5
• 1.0
• 0.5

0.0 0.5

log (ln(I0 - I)) 0.35 0.40 0.45 0.50

[NH3] / ppm 20 40 60 80 100 Current / µA 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

r ² = 0.9971

Quantitative Analysis Quantitative Analysis

PANI IDA sensor is far

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[NH3] / ppm

• 0.20

0.25 0.30

PANI IDA sensor is far superior when compared with a commercial sensor

– Honeywell NH3 sensor – Zellweger Impulse XP – 1 - 100 ppm range

Extension to Inkjet Printed Extension to Inkjet Printed Gas Sensor Array Gas Sensor Array

• Recently received ‘Proof of Concept’ Funding to

build an inkjet printed gas sensor array

• Gases including H2S, CO, Cl2 and NO2
• Exploit inkjet printing to fabricate arrays of

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• Exploit inkjet printing to fabricate arrays of

polymer (polyaniline?) layers modified to be selective towards specific gases

Overview Overview

• 1. Introduction
• 2. Inkjet printing of conducting polymer-based

sensor

• 3. High specification, flexible, inkjet printed gas

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• 3. High specification, flexible, inkjet printed gas

sensor platform

• 4. Biosensor fabrication & application

Biosensor Biosensor

Signal Processor Target Analyte Induces Physical

• r Chemical

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Transducer Biomolecule Signal Processor

Digital Signal

Matrix

• r Chemical

Change

Inkjet Printed Biosensor Publications Inkjet Printed Biosensor Publications

> 13,000 hits for ‘biosensor’ on Web of Science > 500 Peer-Reviewed Publications on ‘screen-printed and biosensor’ Just 10 Peer-Reviewed Publications on ‘inkjet and biosensor’!!!

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Field: Publication Year Record Count % of 10 Bar Chart 2002 1 10.0000 % 2004 4 40.0000 % 2005 3 30.0000 % 2006 1 10.0000 % 2006 1 10.0000 %

biosensor’!!!

Thermally Printed Biosensor Thermally Printed Biosensor

• Horseradish Peroxidase (HRP) and Glucose Oxidase (GOD)-based

biosensors

• Thermal printing does not affect the activity of the enzymes
• PEDOT/PSS electronic communication with enzyme (but

employed a soluble mediator to enhance this)

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Setti et al. (2007). Sens. Actuat. (126) 252

Inkjet Printed Inkjet Printed Cantilever Array Cantilever Array Chips Chips

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• Highly controlled deposition of inkjet printed functional layers
• Demonstrated prototype as a DNA biosensor and a gas sensor array
• Inkjet printing can, uniquely functionalise cantilevers individually very

easily

• Fast, easy to assemble, scalable

Bietsch et al. (2004). Nanotechnology (15) 873 Characterisation of hydrophilic and hydrophobic inkjet printed SAMs 8 inkjet printed polymers on individual cantilevers

Screen Screen-Printed Carbon Paste Printed Carbon Paste Electrode Electrode

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Scan Rate Study

nt (mA)

0.5 1.0 1.5

Electrochemistry of Inkjet Printed Electrochemistry of Inkjet Printed Polyaniline Polyaniline

Relationship of peak current with scan rate

R

• 1.00E-03

0.00E+00 1.00E-03 2.00E-03 100 200 300 400 500

peak Current (A)

peak anodic currents

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Potential (V)

0.2 0.4 0.6 0.8 1.0

Current

• 1.5
• 1.0
• 0.5

0.0 500 mV 300 mV 200 mV 50 mV 25 mV

R

• 2.00E-03

scan rate (mV.s-1)

peak anodic currents peak cathodic currents

Relationship of peak current with (scan rate)1/2

• 2.00E-03
• 1.00E-03

0.00E+00 1.00E-03 2.00E-03 5 10 15 20 25

(scan rate)1/2 \ (mV.s-1)1/2 peak current \A

peak anodic currents peak cathodic currents