Inkjet Printing as a Tool for the Fabrication of ... · • Low wastage, important for ......

Inkjet Printing as a Tool for the Inkjet Printing as a Tool for the Fabrication of Conducting PolymerFabrication of Conducting Polymer--

Based Sensors & BiosensorsBased Sensors & Biosensors

Dr. Aoife Morrin

The National Centre for Sensor ResearchThe National Centre for Sensor Research1

National Centre for Sensor Research

School of Chemical Sciences

Dublin City University

Ireland

OverviewOverview

1. Introduction

2. Inkjet printing of conducting polymer

3. High specification, flexible, inkjet printed gas sensor platform


3.gas sensor platform

4. Biosensor fabrication & application

OverviewOverview

1. Introduction

2. Inkjet printing of conducting polymer





IntroductionIntroduction

• 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


• ‘Enabling technologies’ are principle drivers in sensor fabrication development

Printed SensorsPrinted 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 of the screen-printed glucose biosensor


• 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•


• 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….


Interesting Functional Materials for Sensing Include:Electroactive/Optically active materials

Conducting PolymersMetallic Inks

Biomolecules for BiosensingMembranes

….

OverviewOverview

1. Introduction

2. Inkjet printing of polyaniline





• Suitable for chemical sensing

of acids and bases through its

excellent doping/dedoping

capabilites

• Desirable material for

Sensor Platforms Based on Sensor Platforms Based on PolyanilinePolyaniline

NH2

Aniline Monomer


• 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

PANIPANI--based Sensor Researchbased Sensor Research


• 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 (for control and analysis of response)


• Works really well, but laborious fabrication procedure

• How to translate into a commercially relevant product??

Potential (V)

-0.4-0.20.00.20.40.60.81.0

Cu

rre

nt (µ

A)

-100

-50

0

50

ScreenScreen--Printing for Electrode Printing for Electrode FabricationFabrication


l Low start up and manufacturing cost

l Mass production

l Disposability

l Platform for glucose biosensor industry

3 cm

1 cm

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

Silver Inter-Digitated Array (IDA) Single Electrode


• Commercial Ag product

• ~ 1 Ω 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 PANIProcessable PANI


• New, processible materials

• Water-soluble, or stable nanodispersions

• High processibility

• Aqueous-based

• Good redox activity and conductivity

PANI Nanodispersion PANI Nanodispersion CharacterisationCharacterisation

0

10

20

30

1 10 100 1000 10000

Diameter (nm)

Volu

me (%

)

< 100 nm diameter


No Stabiliser Present* DBSA Stabiliser Present

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

5821

Inkjet Printing of PANIInkjet Printing of PANIMulti-Head Desktop Epson Inkjet Printer

Commercial Research Fuji Dimatix Printer


Inkjet Printed PANI ElectrodesInkjet Printed PANI Electrodes

•• PANI nanodispersions inkjet printed onto IDAs for gas

sensor platform

• Also printed to carbon paste working electrodes


Resulting ‘Smooth’ MorphologyResulting ‘Smooth’ Morphology

(a) Bare SPE (b) 10 Prints


(c) 20 Prints (d) 30 Prints

MorphologyMorphology

1 print

1 cm1 cm

40 prints

1 cm

10 prints

1 cm1 cm

4000


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

No. of Prints of PANI

1 5 10 20 30 40

Film

Th

ickn

ess (

nm

)0

1000

2000

3000

OverviewOverview

1. Introduction

2. Inkjet printing of conducting polymer-based sensor

3. High specification, flexible, inkjet printed



4. Biosensor Fabrication & application

Ammonia SensingAmmonia 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


Detection Mechanism Detection Mechanism –– Gas SensingGas 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

Hn

N

H

N N N

H

Emeraldine Salt

Deprotonatedby NH3

+ (NH3)n

- (H+)n

+•

•• ••

••


– Decrease in conductivity

• Apply potential to IDA

– current flows through PANI film

– Vapp : step or ramp

• Measure change in current on NH3 exposure

H Hn

Emeraldine Base

Vapp

Imeas

Vapp

Imeas

PANI (ES) PANI (EB)

+ 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

µA

400

500

600

µA

400

500

600


– Begins to plateau above 10 layers (inset)

– Thicker layers do not seriously effect response/recovery times – porous film

No. of PANI layers

0 2 4 6 8 10

Sa

mple

d c

urre

nt /

0

100

200

300

y = 60.4 x - 67.2r ² = 0.9939200x1500 IDAn = 3

No. of Layers

0 5 10 15 20 25

No. of PANI layers

0 2 4 6 8 10

Sa

mple

d c

urre

nt /

0

100

200

300

y = 60.4 x - 67.2r ² = 0.9939200x1500 IDAn = 3

No. of Layers

0 5 10 15 20 25

No

rmalis

ed s

am

ple

d c

urr

en

t

0.6

0.8

1.0 T50

T90

Sensor Response TimesSensor Response Times

• Response times for PANI IDA (n=4)– t50 ~ 15 s

– t100 < 60 s

• ~ 60 ppm NH3

Exposed to

NH3 vapour


Time / s

0 15 30 45 60 75 90 105 120 135 150 165 180

No

rmalis

ed s

am

ple

d c

urr

en

t

0.0

0.2

0.4

• 3

• Response times currently within those specified by ISA (Instrument Society of America)– t50 < 90s

Flexible Heater SubstrateFlexible 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


• Compatible with inkjet printing

• Possibility of printing directly to heater substrate

Inkjet printed PANI

Silver IDA on PET substrate

Flexible heating foil

No

rmalis

ed c

urr

ent

0.6

0.8

1.0Non-heated

50 C

60 C

70 C

80 C

Response Behaviour Using Response Behaviour Using Flexible Heater SystemFlexible Heater System


Time / s

0 500 1000 1500 2000 2500 3000 3500

No

rmalis

ed c

urr

ent

0.0

0.2

0.4

0.6

Increasing temperature reduces sensitivity to increase linearity over relevant range

Sensor Recovery Using Flexible Sensor Recovery Using Flexible Heater SystemHeater System

No

rma

lis

ed

cu

rre

nt

0.6

0.8

1.0

Time / s

0 500 1000 1500

1.0

• Room Temp recovery > hours

• 80°C recovery < seconds


Time / s

-100 0 100 200 300 400

No

rma

lis

ed

cu

rre

nt

0.0

0.2

0.4

No

rma

lis

ed

cu

rre

nt

-2.0

-1.5

-1.0

-0.5

0.0

0.5

log (

ln(I

0 -

I))

0.35

0.40

0.45

0.50

[NH3] / ppm

0 20 40 60 80 100

Cu

rrent /

µA

0.00.20.40.60.81.01.21.41.61.8

r ² = 0.9971

Quantitative AnalysisQuantitative Analysis

PANI IDA sensor is far


[NH3] / ppm

2 4 6 8 20 40 60 801 10 100

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 ArrayGas 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


• Exploit inkjet printing to fabricate arrays of

polymer (polyaniline?) layers modified to be

selective towards specific gases

OverviewOverview

1. Introduction

2. Inkjet printing of conducting polymer-based sensor

3. High specification, flexible, inkjet printed gas




BiosensorBiosensor

Signal Processor

Target Analyte

Induces

Physical

or Chemical


Transducer

Biomolecule

Signal Processor

Digital

Signal

Matrix

or Chemical

Change

Inkjet Printed Biosensor PublicationsInkjet 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’!!!


Field: Publication

Year

RecordCount

% 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 BiosensorThermally 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)


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

Inkjet Printed Inkjet Printed Cantilever Array Cantilever Array

ChipsChips


• 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

ScreenScreen--Printed Carbon Paste Printed Carbon Paste ElectrodeElectrode


Scan Rate Study

Cu

rren

t (m

A)

0.0

0.5

1.0

1.5

Electrochemistry of Inkjet Printed Electrochemistry of Inkjet Printed PolyanilinePolyaniline

Relationship of peak current with scan rate

R2 = 0.9679

-1.00E-03

0.00E+00

1.00E-03

2.00E-03

0 100 200 300 400 500

pe

ak

Cu

rre

nt

(A)

peak anodic currents


Potential (V)

0.20.40.60.81.0

Cu

rren

t (m

A)

-1.5

-1.0

-0.5

0.0

500 mV

300 mV

200 mV

50 mV

25 mV

R2 = 0.9584

-2.00E-03scan 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

0 5 10 15 20 25

(scan rate)1/2

\ (mV.s-1

)1/2

pe

ak

cu

rre

nt

\A peak anodic currents

peak cathodic currents

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