Technology for Graphene and FET-based SensorsKrishna Persaud*1, Suresh Garlapati1, Sheida Faraji2, Michael Turner2,

Tien-Chun Yu3, Guohua Hu3, Jie Dai3, Tawfique Hasan3,Xiao Huang4

1Department of Chemical Engineering and Analytical Science, University of Manchester2OMIC, Department of Chemistry, University of Manchester

3Cambridge Graphene Centre, Engineering Department, University of Cambridge4Nanyang Technological University, China

Printed Sensors

The market for fully printed sensors is predicted to reach $7.6 billion by 2027.

www.idtechex.com

• Printed disposable glucose sensors currently generate the majority of revenues. • Gas sensors, temperature sensors and photodetectors are moving to mass production.• The next generation of printed sensors will enable new applications, from human-machine interfaces to environmental

sensing.

Source: IDTechEx

• Large area• Conformal• Wearable• Imperceptible • …

• Printed gas sensors play a key role in IoT development.

Printed Gas Sensors

NH3 sensor

Danesh, E., et al. Analytical Chemistry 86 (18) (2014) 8951Seekaew, Y. Organic Electronics 15 (2014) 2971–2981

Jung, Y. Sensors 17(5) (2017) 1182

• Ventilation and air conditioning (HVAC) systems, air purifiers and smart windows will employ gas sensors for air quality monitoring.

• Selective gas sensors are required for detection of atmospheric pollutants, e.g. VOCs, NOx, CO, ammonia, SO2, etc.

GraphClean – Air Quality Monitoring

200 mg/m3 of NO2 is 104 ppb and 40 mg/m3 of NO2 is 21 ppb PM2.5 sensor Gas sensor

10.8 mg/mL FeCl3+

1.66 mg/mL GO

120 ℃

8 h

sonication 60 min

wash with H2O and

IPA

53.3 mg/mL CH3COONa

Water + IPA (6/4 v/v)

redispersed in

IPA+2-butanol (9/1 v/v)

sonication

30 min

Metastable ink

Mass production of Fe2O3/graphene

Figure: Spray coated Fe2O3/graphene sensor arrays on (a) paper and (b)

polystyrene of a scale of A2 (420mm * 594mm). The array integrates 16 * 13

devices. The electrodes are screen-printed silver IDEs. The insets show zoomed-in

images of the sensors.

ba

5mm5mm

Large scale sensor prototyping

Inkjet printed graphene/metal oxide gas sensors on flexible substrates

Metal

electrodes

Connected sensors for environmental monitoring:

Low power, low cost, acceptable accuracy

With Prof X Huang, NTU

500 nm

a

500 nm

c

200 nm

f

200 nm

500 nm

200 nm

b

d

e

G. Hu et al, unpublished.

Inkjet printed graphene/metal oxide gas sensors

0 50 100 1500.0

0.4

0.8

1.2

Time (min)

Resis

tance (

a.u

.)

NO2

N2

0.2

pp

m

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%)

Concentration (ppm)

20.2%/ppm

Room temperature operation

With Prof X Huang, NTUG. Hu et al, unpublished.

Inkjet printed graphene/metal oxide gas sensors

12

34

5

1 2 3 4 5 6 7 8 9 10

Devic

e

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.)

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unt

(%)

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m: 89.1

s: 2.21

23

45

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De

vic

e

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20.2%/ppm(a) Typical measured response under exposure to NO2for thestabilised response after intialsaturated exposure.

(b) The measured response in (a) with respect to the NO2 concentration, showing a sensitivity of 20.2%/ppm.

(c) The measured saturated responsivity of 45 devices of the sensor array. The 5 grey spots correspond to the short-circuited devices.

(d) Gaussian fitting of the measured initial saturated responsivity at 1 ppm N02, showing that 100% are distributed within μ±3σ.

Fitted mean (μ) response: 89.1%, Std dev (σ): 2.2

With Prof X Huang, NTUG. Hu et al, unpublished.

Connected gas sensors

Measurement on an OFET

Situation 5 years ago

Requirements:

• Solution processible to allow large-area production and easily customised sensor arrays.

• Low-voltage operation (< 3 V), low power consumption, integration with silicon microcontroller and portability.

• Good stability and durability (against bias stress, temperature, etc.).

• Sensitivity and Selectivity to a range of analytes, such as VOCs, ammonia, CO, NO2, SO2, etc.

Organic field-effect transistors (OFETs) as sensing platform

Chemiresistor→change in resistance

OFET→Multiparametric outputs,better sensitivity through amplification of current

L. Torsi and A. Dodabalapur, Anal. Chem., 2005, 77, 380A; Wedge et al. Sensors and Actuators B 143 (2009) 365Gromski, P. S. et al. Anal Bioanal Chem 406 (2014) 7581

• High-k dielectric: P(VDF-TrFE-CFE)

• Low-k capping layer: UV-crosslinked PMMA

• Organic semiconductor: DPPTTT 𝑪𝒊 =𝜿

𝒅

PEN

Gate

Dielectric

S DOSC

Fabrication of OFETs

P(VDF-TrFE-CFE) terpolymer:

• High κ (~ 55) due to ferroelectric phase and polar nanodomain.

• However, its polar surface groups tend to trap carriers from the channel or Interaction with water molecules and results in poor device stability.

Stability of OFETs against ‘bias stress’ and ‘temperature’

-500 0 500 1000 1500 2000 2500 3000 3500 4000

-50

0

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Time (Sec)

Uncapped Terpolymer

I DS c

han

ge

(%

)

100% increase in IDS

Non-polar capping layers

0 1000 2000 3000 4000

0

500

1000

1500

2000

2500

3000

3500

<100% increase in IDS

Uncapped Terpolymer

PAMS-capped Terpolymer

PMMA-capped Terpolymer

I DS c

hange (

nA

)

Time (sec)

Dipole field induced localisation of charge carriers and interaction with water

molecules is suppressed.

Improve sensitivity and promote selectivity

Sensitizers as additives to OSC (DPP) solution

(a) Zinc Phthalocyanine (ZnPc)(b)Zinc 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (TTB-ZnPc)(c) Iron phthalocyanine (FePc)(d) 5,10,15,20-Tetraphenyl-21H,23H-porphine copper(II) (CuTTP)(e) and (f) phthalocyanine (Pc1 and Pc2)

Selectivity of semiconductorto different volatile analytes achieved by addition of smallamounts of compoundsthat promote specific analyteinteractions

GraphClean- Improve sensitivity and promote selectivity using sensitizers

Porphyrins

M: metal or empty

Phthalocyanines

-3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0

10-12

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IDS

IGS

I1/2

DS

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S (

A)

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(V)

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A)

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(V)

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DS

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I DS (m

A)

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(V)

Limit of Detection (LoD ~ 20 ppb)

Nitrogen dioxide (NO2)

Limit of Detection (LoD ~ 20 ppb)

Carbon monoxide (CO)

GraphClean – Response to NO2, CO and mixtures

For detection of a certain gas, OFETs with specific recognition element (e.g. metal/metal-free phthalocyanine) can be used.

First NO2 /CO Sensor Module based on Organic Field Effect Transistors

Patented

GraphClean – Field trials in Manchester

UMAN

UCAM

Display Gas inlets

Front view Back view

Connected gas sensors

Manufacturability and device-to-device

consistency is key

Insi

de

offic

e

Insi

de

offic

e

Graphene/Metal oxide Chemoresistors

GraphClean – OFET Devices-Field trials in Manchester

NO2

For all sensors, correlating peaks in NO2 concentration are detected

around evening and morning rush hours .

Two sensor technologies with promise

• Graphene based chemoresistors and Low voltage printable gas sensors based on Organic Field Effect Transistors

• First OFET NO2 and CO Gas Sensor

• Good correlation with conventional environmental gas monitoring systems at a fraction of the cost

Acknowledgements: Innovate UK, EPSRC Centre for Innovative Manufacturing in Large Area Electronics, Partners University of Cambridge, Imperial College London, The University of Manchester, Swansea University

Conclusions