Organic semiconductor based devices for wearable electronics Piero Cosseddu, Ph. D.

Dept. of Electrical and Electronic Engineering University of Cagliari (Italy) TechOnYou Srl

[email protected] http://www.diee.unica.it/eolab3 http: www.techonyou.com

Advanced Course on ORGANIC ELECTRONICS: Principles, devices and applications

Milano (Italy), 26-29 November, 2013

DIEE - University of Cagliari Prof. Annalisa Bonfiglio Dr. José Saenz, Ph. D. Dr. Monia Demelas, Ph. D. Andrea Spanu, Ph. D. Student Alberto Loi, Ph. D. Student Giulia Casula, Ph.D. Student Stefano Lai, PhD student Organic Thin Film Transistors on flexible substrates • • • • •

Mechanical and bio-chemical sensing Wearable electronics-smart textile Electronic Skin NV-Memory Elements Photodetectors

Outline • Introduction: Wearable Electronics Organic Electronics for Wearable Electronics • Organic semiconductor devices for sensing applications and their integration into clothes Flexible electronics issues:  high operating voltages  mechanical deformation • Electronics embedded in yarns and fibres • OTFTs on yarns for e-textile applications • Playing with natural fibres and nanotechnology: how to make conductive cotton • Applications

Wearable Electronics The concept of wearable electronics has emerged in the last 15 years, as a direct consequence of the intensive miniaturization of silicon technology. In the early years this expression was used in a literal sense to indicate the insertion of any portable electronic system not necessarily in direct contact with clothes Early ninties

2010

early Nineties

Textile PLUS electronic part 2010 textile-adapted

Wearable Electronics: surface mounted electronics Electronic devices fabricated onto highly flexible substrates and mounted on clothes/fabrics

Devices can actively interact with their environment (sensors, actuators and data managements units)

T. Someya et al. Nature 499, 458–463 (25 July 2013)

Textile WITH electronic part textile-integrated

Wearable Electronics: electronics integrated on yarns Fibers are modified in order to confer them electrical properties The integration between electronics and textiles reaches its highest peak, since the yarn itself may act as an electrical/electronic component Passive and active devices can be fabricated directly during the weaving process (e-textile) Organic semiconductors/conductive polymers are suitable for this approach

Textile IS electronic part textile-based special yarns acting as sensors are woven into the fabric of a t-shirt

Why Organic Materials? • Very low cost materials and technologies suitable for

Large Areas Applications • Organic semiconductor devices are particularly suitable for sensing applications • Flexibility  possibility of application to any kind of surfaces (paper, fabric and 3D structures) Thanks to their flexibility properties plastic sensors can be integrated into clothes. Wearable systems are integrated with traditional microelectronics, to enable data processing and transmission via Bluetooth™ or WiFi™

Drawbacks • Flexible structure doesn’t mean flexible electronics • High operating voltages very low portability, step-up conversion needed for battery-operating devices, high power consumption

-175µ

Id[Vgs=60V] Id[Vgs=40V] Id[Vgs=20V] Id[Vgs=0V] Id[Vgs=-20V] Id[Vgs=-40V] Id[Vgs=-60V]

-150µ -125µ -100µ

ID(A)

Electrical behavior is severely affected by mechanical deformation

-75µ -50µ -25µ 0 0

-10

-20

-30 -40 VD(V)

-50

-60

Resistor based temperature sensor Interdigitated platinum electrodes resistance changee according to temperature variations. The sensor geometry was designed to fit onto a stripe with a width of 500 um. Electronic devices were fabricated on flexible substrates. The substrates are cut into narrow stripes (2 mm wide or less) and then weaved into textiles.

T. Kinkeldei et al. IEEE SENSORS 2009 Conference, pp. 1580

Resistor based temperature sensor

RTD resistance is influenced by strain. Up to about 3 % of elongation, the sensor resistance is not influenced much by the deformation. At about 3 % of deformation the resistance starts to increase rapidly, till the breakdown of the resistance at 4 %.

Failure of the device for surfce strain higher than 3% Failure is induced by cracks in the metal layers

T. Kinkeldei et al. IEEE SENSORS 2009 Conference, pp. 1580

Multimodal sensing: temperature and humidity Integration of two resistive based temperature and humidity sensors on a flexible plastic susbstrate. The pattern for the sensor designs consists of (1) a meander shaped resistor structure representing a temperature sensor and (2) an interdigitated finger electrode structure representing a humidity sensor. The sensor system is designed that a single temperature and humidity sensor fit on a strip with a width of 1 mm.

A thin film of conductive polymer PEDOT:PSS (Baytron P AI 4083) is spincoated at 1200 rpm for 60 seconds. The resulting layer serves as conductive bridge over the finger electrode, making it a resistive type humidity sensor. Further the conductive polymer covers the gold structures and improves the electrical conduction during bending and possible crack formation. T. Kinkeldei et al. Proc. 16th Int. Solid-State Sensors, Actuat. Mycrosyst. Conf., Jun. 2011, pp. 1156–1159.

Multimodal sensing: temperature and humidity Integration of a resistive based temperature sensor with ac capacitive based humidity sensor on a flexible plastic substrate

C. Ataman et al. Sensors and Actuators B 177, 1053-1061 (2013)

Why Organic Materials?

C. Ataman et al. Sensors and Actuators B 177, 1053-1061 (2013)

Inkjet printed temperature and humidity sensors

G. Mattana et al. IEEE SENSORS JOURNAL, VOL. 13, pp. 3901 OCTOBER 2013

OTFT based sensors

Can an OFET be used as a sensor? How and Why?

Organic Semiconductor Source

Source

Insulator Gate

OTFT based sensors How an OFET can be used as a sensor? Change of its electrical behaviour (in a reversible way!) when exposed to an external stimulus - FET Amplification - Sensing + switching - Multiple parameters - Mobility - Off Current - Threshold voltage

• Bio-Chemical agent • Mechanical stimulus

Organic Semiconductor Source

Source

Insulator Gate !Different sensing areas!

OFET for chemical sensing External agent

S

D

Insulator G

The direct interaction between an external (bio)chemical agent with the active layer induces a reversible change in the electrical response of the device (multiple parameters!) - Mobility - Off Current - Threshold voltage

OFET for chemical sensing

Ion and mobility decrease when exposed to wet N2 atmosphere Higher sensitivity for thin films The morphology of polycrystalline pentacene films is relatively open, H2O molecules can easily diffuse into these crevices and interact with the trapped carriers by altering the electric field at the grain boundaries

Zheng-Tao Zhu et al. Appl. Phys. Lett. 81, 4643 (2002)

OFET for chemical sensing Bilayer OTFT with calixarene container molecules deposited on the assembled device: OS first layer: 5,50-bis-(7-dodecyl-9H-fluoren-2-yl)-2,20-bithiophene (DDFTTF) Container molecules: calix[8]arene (C[8]A) and C-methylcalix[4]-resorcinarene (CM[4]RA)

Selective molecular uptake!

ppm A. N. Sokolov, et al. Adv. Mater. 2010, 22, 2349–2353

OFET DNA detection

DNA molecules are directly immobilized by physical adsorption in the pentacene film The immobilization can be optimized according to the sizes of DNA molecules by controlling morphology of pentacene films phosphate groups on the DNA backbone are known to be able to attract electrons, leaving more holes than before DNA immobilization  Vt shift

Q. Zhang, et al. Biosens. Bioelectr. 22, 3182 (2007)

Why Organic Materials? • Very low cost materials and technologies suitable for

Large Areas Applications • Organic semiconductor devices are particularly suitable for sensing applications • Flexibility  possibility of application to any kind of surfaces (paper, fabric and 3D structures) Thanks to their flexibility properties plastic sensors can be integrated into clothes. Wearable systems are integrated with traditional microelectronics, to enable data processing and transmission via Bluetooth™ or WiFi™

Drawbacks • Flexible structure doesn’t mean flexible electronics • High operating voltages very low portability, step-up conversion needed for battery-operating devices, high power consumption

-175µ

Id[Vgs=60V] Id[Vgs=40V] Id[Vgs=20V] Id[Vgs=0V] Id[Vgs=-20V] Id[Vgs=-40V] Id[Vgs=-60V]

-150µ -125µ -100µ

ID(A)

Electrical behavior is severely affected by mechanical deformation

-75µ -50µ -25µ 0 0

-10

-20

-30 -40 VD(V)

-50

-60

What can affect the electrical behaviour in OTFTs ? •

Capacitance changes in the gate dielectric S.C.B. Mannsfeld et al., Nature Materials 9 , 859–864 (2010)

•

Interface between gate dielectric and organic semiconductor A. N. Sokolov et al. Adv. Funct. Mater. 22, 175-183 (2012)

•

Morphological changes in the organic semiconductor active layer P. Cosseddu et al. Org. Electr. 14, 206-211 (2013)/ EDL 33, 113 (2012), T. Sekitani et al APL 87, 173502 (2005)

Other issues: Delamination Cracks in the metal layers

not reversible behavior

Organic Semiconductor Source

Source

Insulator Gate

Strain effects on OTFTs Flexible substrate: PET, PEN, Kapton Gate dielectric: Parylene C, PVA, PVP etc. Organic Semiconductors: • P3HT • Pentacene (different morphologies)  d f  ds Strain    2* R





 1  2   2   1   1   

 df   Strain    2* R   

In which dl and ds are the thicknesses of the layer and of the substrate respectively, η is dl/ds, χ is the ratio between the Young moduli of the layer and of substrate (χ =Yl/Ys) and R is the bending radius

Strain effects on the electrical characteristics Strain [%]

3.9

0.2

2.9

0.3

1.9

0.5

1.3

0.7

0.9

1.0

0.4

2.2

0.2

4.4

mobility ID

80 60

1

Irreversible changes

40 20 0 0

1

2 3 Strain [%]

Irreversible changes

0 VT [V]

ID/ [%]

R [cm]

4

5

-1 -2 -3 -4

0

1

2 3 Strain [%]

4

5

OFETs based mechanical sensors

The bending test apparatus with a precision mechanical stage

T. Sekitani et al. Appl. Phys. Lett. 86, 073511 (2005) T. Sekitani et al. Mat. Res. Soc. Symp. Proc. Vol. 814 © 2004 I5.9.1

Strain effects on structure and morphology

Response is more related to MORPHOLOGICAL CHANGES Pentacene film properties are not permanently affected by mechanical deformation V. Scenev, P. Cosseddu, A. Bonfiglio, I. Salzmann, N. Severin, M. Oehzelt, N. Koch, J.P. Rabe, Org. Electr. 14,

1323-1329 (2013)

Effect of strain on OTFTs: Pentacene vs P3HT Pentacene

Well ordered even when deposited on “non ideal” plastic substrates

P3HT

Highly disordered

Effect of strain on OTFTs: Pentacene vs P3HT

P. Cosseddu et al. IEEE Electron Device Letters 33 (2012) 113

Effect of strain on OTFTs depends on morphology

P. Cosseddu et al. IEEE Electron Device Letters 33 (2012) 113

Effect of strain on OTFTs: Pentacene vs P3HT 0.0 0.5 1.0 1.5 2.0 2.5 Strain [%]

60

Pentacene P3HT

ID/ID [%]

40 20 0

1

2

3

Pressure [kPa]

4

5

• Pentacene devices are characterized by a much higher sensitivity • P3HT disordered films, with very small grain dimensions showed a much lower sensitivity

Intensity (a.u.)

0

10

Mylar substrate P3HT on Mylar

5

(100)

10

4

10

3

(200)

5 P. Cosseddu et al. IEEE Electron Device Letters 33 (2012) 113

10

(300)

15

20

 (deg)

25

30

Why Organic Materials? Dynamic response F = 4 Hz

F = 2Hz -1125

-1100

-1150

mV

mV

-1150 -1200

-1175 -1250 -1300 40

-1200 41

42

43

44

45

60

61

62

Seconds

63

64

65

seconds

F = 6 Hz F = 10 Hz

-1190

-1670

-1180

-1680

-1170

-1690

mV

mV

-1200

-1160 -1150 -1140 100

-1700 -1710

101

102 103 Seconds

104

105

-1720 60

61

62

63 Seconds

64

65

Why Organic Materials? Sensor applied to a chest bandage for breathing monitoring

Regular breathing

-7.4n

V D = -5V V G = -40V

-7.6n

I D (A)

-7.8n -8.0n -8.2n -8.4n -8.6n -8.8n 0

10

20 Time (s)

30

40

50

Applications: joints motion and breath rate

Sensor applied onto a ribbon can be transferred onto clothes for joints motion monitoring -29µ

Different bending radii 90°

90°

ID (A)

-30µ 120°

120°

-31µ

150°

150°

180°

-32µ 180° -33µ 20

0,10

100 cycles NO DEGRADATION Sensitivity (I/I0)

-29µ

ID (A)

-30µ

-31µ

-32µ

40

60

180°

80

100

time (s)

0,05

0,00 0

20

40 time (s)

60

80

80

100

120

140

160

bending degree

180

Applications: sensing glove

0.05

-7.5µ

(ID-ID0)/ID0

0.04

-8.0µ

0.03

ID [A]

Different bending radii

-8.5µ -9.0µ

0.02

-9.5µ

0

50 100 time [s]

0.01 0.00

2

3

4 R (cm)

5

6

150

200

Applications: sensing shoesole • Weight distribution  matrix of pressure sensors • Gait phases analysis and fall detection  sensorized shoe sole with 2 sensors Walk

toe heel

1.2 sec

Vout(mV)

1200

1100

1000 25.0

27.5 Time (sec)

30.0 0.66 sec

Run

S1

toe heel

Vout(mV)

1200

1000

S2 800 28

29

30

31 32 Time (sec)

33

34

Applications: Artificial robot skin Develop a highly flexible, compliant system for tactile transduction Inkjet printed matrices and arrays of OTFTs on plastic substrates Skin-based Technologies and Capabilities for Safe, Autonomous and Interactive Robots

200 µm

Applications: Artificial robot skin • • • •

tins = 1.54 μm, εr = 3.15  Cins = 1.8 nF/cm2 μ = 0.1 cm2/Vs VT = 4 ± 5 V ION/IOFF ≈ 105

Strain sensitivity in TIPS based OTFTs Highly crystalline TIPS-Pentacene films TIPS

Flat before bending r=1.3cm [strain=0.69%] r=0.8cm [strain=1.12%]

1.0

0.2

0.6

I/I0

ID/ID0

0.8

0.3 TIPS-pentacene

0.4

0.1

0.2

0.0

0.0 40

20

0 Vg(V)

-20

-40

0

1

2

3

Strain (%)

4

5

Artificial skin: Experimental set up Embedding the organic substrates with elastomers

Mechanical properties and thickness of the elastomer influence the sensitivity (Ecoflex  1 + 1 mm) • Pressure exerted by a mechanical finger • Hemispheric indenter (4 mm radius) • Controlled input: Dz, F • Output: ΔI/I • Increasing pressures • Different configurations

Artificial skin: electro-mechanical characterization

10 8 ID/ID0 %

• Very good repeatability and sensitivity • Working range 0 - 4 N • Resolution = 0.1 N

6 4 2 0 0

A. Loi et al. IEEE Sensors Journal, accepted for publication

1 2 Force (N)

3

Artificial skin: electro-mechanical characterization

Mechanical Stress Tests Applied force=2 N

Output of two different taxels

-13,0µ

-12,0µ -14,0µ

Id [A]

Id [A]

-13,0µ

-15,0µ

-16,0µ

-14,0µ -15,0µ 0

100 200 300 400 500 600 700 Time [sec]

0

100

200

300

Time [sec]

Negligible current shift Reproducible response up to 1000 cycles A. Loi et al. IEEE Sensors Journal, accepted for publication

400

500

Towards flexible devices

Is it possible to minimize the effect of mechanical deformation? • Geometry an layout of the device • Morphological and structural properties of the organic semiconductor layer

Towards flexible devices

Geometry and layout of the device Surface strain depends on the bending radius, but also on the substrate thickness!!!  d f  ds Strain    2* R





 1  2   2   1   1   

Two different approaches: • Neutral strain position • Thin substrates

 df   Strain    2* R   

OTFT in neutral strain position

• T. Sekitani et al. Appl. Phys. Lett. 87, 173502 (2005) • T. Sekitani et al. Nature Mater. 9, 1015 (2010)

Reducing strain by using thin substrates Parylene C films have been deposited on Silicon substrate (low surface corrugation)

After deposition the film can be peeled off Parylene C

Silicon Substrate

Parylene C microstancils S. Selvarasah et al. , Sensors and Actuators A 145 (2008) 306

Parylene C processing  Thin freestanding films that can act at the same time as mechanical support and as gate dielectrics  Two working surfaces, the film can be patterned on both sides  Can be transferred on any kind of surfaces (paper, fabric and 3D structures)  Thickness down to 400nm Thickness [m]

2.0µ 1.6µ 1.2µ 800.0n 400.0n 1 P. Cosseddu, A. Piras and A. Bonfiglio IEEE Transaction on Electron Devices, 58, 3416-3421 (2011)

2

3

Parylene C [g]

4

ID/ID0

Mechanical characterization

Device Active area

1.2 1.0 0.8 0.6 0.4 0.2 0.0 20

flat before bending r=0.75cm r=0.5cm r=0.2cm flat after bending

10

0

-10

VG(V)

b)

-20

-30

Devices fabricated on freestanding thin films are not affected by mechanical deformation Substrate thickness: 400nm vs 175µm  much lower surface strain for the same applied bending radius P. Cosseddu, A. Piras and A. Bonfiglio IEEE Transaction on Electron Devices, 58, 3416-3421 (2011)

Towards flexible devices

Morphological and structural properties of the organic semiconductor layer

Inducing morphological changes Pentacene based devices As sensitivity to strain seems o be related to morphology, we have intentionally modified the morphology by changing the deposition rate

0.08 Å/s a)

0.5 Å/s b)

5 Å/s c) 500 nm

11 Å/s d)

Influence of morphology on the sensitivity 40 ID [%]

30

0.08A/s 0.5A/s 5A/s 11A/s

a)

20 10 0 0.0

0.5 Strain [%]

1.0

Morphological properties strongly influence the sensitivity to strain

Tuning the sensitivity Sensitivity can be finely tuned by setting the deposition parameters 25

DS

High sensitivity 20 Sensor applications

b)

15

Low sensitivity 10 Flexible 5 electronics 0

100

150 200 diameter [nm]

P. Cosseddu et al. Organic Electronics 14 (2013) 206–211

250

Why Organic Materials? • Very low cost materials and technologies suitable for

Large Areas Applications • Organic semiconductor devices are particularly suitable for sensing applications • Flexibility  possibility of application to any kind of surfaces (paper, fabric and 3D structures) Thanks to their flexibility properties plastic sensors can be integrated into clothes. Wearable systems are integrated with traditional microelectronics, to enable data processing and transmission via Bluetooth™ or WiFi™

Drawbacks • Flexible structure doesn’t mean flexible electronics • High operating voltages very low portability, step-up conversion needed for battery-operating devices, high power consumption

-175µ

Id[Vgs=60V] Id[Vgs=40V] Id[Vgs=20V] Id[Vgs=0V] Id[Vgs=-20V] Id[Vgs=-40V] Id[Vgs=-60V]

-150µ -125µ -100µ

ID(A)

Electrical behavior is severely affected by mechanical deformation

-75µ -50µ -25µ 0 0

-10

-20

-30 -40 VD(V)

-50

-60

Towards low voltage OTFTs

Is it possible to scale down the operational voltages in OTFTs? A d

Cins 

 0 r d

A

Increasing gate capacitance is the key factor for realizing low-voltage OFETs

State of the art – SAMs and Polymers

Halik et al., Nature, 2004, 431 H. Klauk, et al. Nature 445, 745 2007 (2007)Zschieschang et al., Adv. Mater. 2010 , 22 Young-geun Ha, et al. JACS, 2010, 132, 17426

Myung-Han Yoon, H. Yan, A. Facchetti, and T. J. Marks, JACS, 2005, 127, 10388

Low voltage OTFTs Bottom gate, bottom contact structure on flexible PET substrate

- Gate: Aluminum - Gate Dielectric:

AlOx

[UV-Ozone treatment at temperature]

room

Parylene C [deposited by CVD] [air-stable, robust, biocompatible and resistant to solvents; can be deposited in very thin films] P. Cosseddu, et al. Appl. Phys. Lett. 100, 093305 (2012)

AlOx/Parylene C Double-Layer Thermally evaporated pentacene as OS Insulating Al 2 O3 Structure

Capacitance

AlOx

3.5 E-6

AlOx + 25nm Parylene

1.3 E-7

[F/cm2]

IG [A] JG[A/cm2]

Vt [V]

µ [cm2/Vs]

S [mV/dec]

Nt [cm-2eV-1]

OTFTs Yield [%]

6 E-6 2.9 E-5

-1.2

3.3 E-3

360

1.1 E14

15%

-0.5

6 E-2

350

4 E12

95%

4 E-10 1.9 E-9

200p

-500n -250n 0 0.0

-0.5 VD(V)

-1.0

1x10

-7

1x10

0

IG(A)

ID(A)

-750n

ID(A)

Vg=0.5V Vg=0.25V Vg=0V Vg=-0.25V Vg=-0.5V Vg=-0.75V Vg=-1V

-1µ

-9

-1.0

-0.5 0.0 VG(V)

0.5

-200p

Towards high frequency: self-alignment 3,5 3,0 2,5

AI [dB]

2,0 1,5

fT,LVSA = 100 kHz

1,0

fT,LV = 100 Hz

0,5 0,0 0

10

1

10

2

10

3

10

Frequency [Hz]

S. Lai, P. Cosseddu, G.C. Gazzadi, M. Barbaro e A. Bonfiglio, Org. Electr. 14, 754-761 (2013)

4

10

5

10

OTFTs on ultrathin substrates Bent Substrate

1,0 Flat R=1.3 cm R=0.9 cm R=0.8 cm

ID/ID0

0,8 0,6 0,4 0,2 0,0 -2

-1 Vg[V]

0

Similar devices have been fabricated on a 175µm thick PET film

ε=d/2R d=substrate thickness R=bending radius

Surface strain depends on substrate thickness It can be dramatically reduced by using ultrathin flexible substrates

Low Voltage OTFTs pressure sensors for e-skin 0.8

0.8

0.6 I/I0

/0

0.6

0.4

0.4

Irreversible changes

0.2

Irreversible changes

0.2 0.0

0.0 1

Strain (%)

2 0.2 N 0.3 N 0.4 N

0.00 (ID-ID0)/ID0

-0.05 -0.10

0

0.10

(ID-ID0)/ID0

0

1 Strain (%)

2

0.8 0.6 F = 0.03 N 0.4 0.2 0.0 60 80 100 120

0.05

-0.15 -0.20

0

50

100 150 200 250 Time (s)

0.00

0.1

0.2

0.3 0.4 Force (N)

0.5

Strain sensitivity in low voltage OTFTs OTFTs fabricated on 175µm PET substrate Vg=0.5V Vg=0V Vg=-0.5 Vg=-1V Vg=-1.5V Vg=-2V

ID(A)

-4µ -3µ -2µ

1.0 0.8 ID/ID0

-5µ

0.6 0.4 0.2

-1µ 0 0.0

Flat before bending Bending @ R=8mm Flat after bending

0.0 -0.5

-1.0 -1.5 VD(V)

-2.0

0.5 0.0 -0.5 -1.0 -1.5 -2.0 VG(V)

OTFTs fabricated on 1.5µm PET substrate 1.0

Flat before bending Bending @ R=1mm

0.8 ID/ID0

Vg=0V Vg=-0.5V Vg=-1V Vg=-1.5V Vg=-2V

ID(A)

-12µ -10µ -8µ -6µ -4µ -2µ 0 0.0

0.6 0.4 0.2 0.0

-0.5

-1.0 VD(V)

-1.5

0.0 -0.5 -1.0 -1.5 -2.0 VG(V)

Towards e-textile Fabricating conductive yarns/fabrics on natural cotton fibers

Electronic yarns Typical OFET structure Source and drain electrodes: Gold Gate dielectric: SiO2 Gate: Highly doped Si substrate

Si acts at the same time as substrate and as gate electrode Typical OFET structure Source and drain electrodes: Gold, PEDOT:PSS Human hair Gate dielectric: Polyimide, Polypyrrole Gate: Cu yarn core Organic Semiconductor: Pentacene

OFET

Gate D=45 to 65 μm, Cu core

Insulator Semiconductor M. Maccioni et al. Applied Physics Letters, 89 (2006) 143515

Gate Drain Source

Organic semiconductor: Pentacene D=45 to 65 μm, Cu core

Atomic Force Microscopy

Focused Ion Beam Cross Section Semiconductor Pentacene

500nm

Copper core

M. Maccioni et al. Applied Physics Letters, 89 (2006) 143515

Insulating layer

Source and drain Patterning Au S and D electrodes Shadow mask  no stable contacts PEDOT:PSS electrodes Softlithography printing  no stable contacts Lamination  stable contact

-800n

Id [ A]

-600n -400n -200n 0

M. Maccioni et al. Applied Physics Letters, 89 (2006) 143515

0

-20

-40

-60

Vds [V]

-80

-100

Ambipolar Organic FET on a yarn Double layer Pentacene/C60 Pentacene buffer layer allows C60 to grow crystalline n-type

ID(A)

4n

Vg=100V Vg=80V Vg=60V Vg=40V Vg=20V Vg=0V Vg=-20V Vg=-40V Vg=-60V Vg=-80V Vg=-100V

-80.0n -60.0n

ID(A)

Vg=20V Vg=40V Vg=60V Vg=80V Vg=100V

-40.0n

2n

-20.0n 0

0.0 0

20

-7

40 60 VD(V)

80

0

100

-20

-40 -60 VD(V)

-80

-100

2x10

Vt=+33.9V -6 1x10 -3 2 n=6.98x10 cm /Vs

-7

2x10 ID(A)

-8

-8

5x10

-8

1x10

-7

1x10

-8

-8

6x10

-ID(A)

1x10

Vt=-26.7V -3 2 =8.88x10 cm /Vs

8x10

-7

-7

1x10

1x10

-8

4x10

-9

1x10

-8

2x10

0 -9

-100

-7

1x10

-50

0 50 VG(V)

100

P. Cosseddu et al. Applied Physics A (2008)

1x10

0

-10

-100

-50

0 VG(V)

50

100

1x10

Low Voltage Organic FET on a yarn Al core (d = 250 um) Gate dielectric AlOx (UV-Ozone grown) Parylene C (30 to 60 nm) -40n V =-6V DS

Id[Vgs=0V] Id[Vgs=-1V] Id[Vgs=-2V] Id[Vgs=-3V] Id[Vgs=-4V] Id[Vgs=-5V] Id[Vgs=-6V]

Id[A]

-30n -20n

0 -1

-2 -3 Vd [V]

-4

-5 -200n Id[Vgs=-8V] Id[Vgs=-10V] Id[Vgs=-6V] Id[Vgs=-4V] Id[Vgs=0V] Id[Vgs=-2V]

-100n

0

2

0

-2

-4 -6 Vd [V]

-8

-10

0

-2 -4 Vg [V]

VDS=-10V

-6

Id[A]

0

Id[A]

-200n

-20n -10n

-10n 0

-30n Id[A]

-40n

-100n

0

2

0

-2

-4 -6 Vg [V]

-8 -10

Why not using a natural fiber (as cotton)? • Relatively cheap fibers • Good mechanical properties • Obtained from the cultivation of plants (potentially unlimited supply) • Almost never cause allergic reactions or other dermatological issues • Unfortunately: cellulose is electrically insulating.

• Common textile materials like cotton, (it can be made also on polyester and Lycra) are treated with the conductive polymer PEDOT:PSS, transforming normally insulating materials into conductors. • Conductive textiles can be manufactured into many shapes, printed, sewn, or knitted into fabrics, or even woven in fiber forms directly into textile structures

Mechanical properties of treated and non-treated cotton yarns Elongation to break (%)

Stress at Young's modulus break (MPa) (MPa)

Non treated

6.23 ± 0.98

170.9 ± 7.5

3711 ± 318

PEDOD:PSS+EG treated

4.58 ± 0.39

69.1 ± 14.6

2987 ± 149

Cotton OTFTs Cotton-based OFET

Cotton-based organic field effect transistor (OFET)

In the cotton-based OFET the gate electrode is represented by a conductive yarn; the gate dielectric, semiconductor and drain/source contacts are deposited around the yarn.

Cotton OECTs Cotton-based organic electrochemical transistor (OECT)

Cotton-based OECT

G. Mattana, P. Cosseddu et al., Organic Electronics, 12, 2033-2039, 2011

Cotton electrodes Non-treated polyester fabric PEDOT:PSStreated polyester fabric

By directly treating common textile materials with a glycerol-doped PEDOT:PSS solution, we obtain very conductive fabrics that, when used as dry surface electrodes, have shown a performance comparable to standard gelled-Ag/AgCl electrodes. Electrode comparison • Commercial Ag/AgCl ECG electrode with gel: Standard disposable electrode for clinical applications • Sewed Ag-coated Nylon yarn electrode: State of the art approach for fabricating dry textile electrodes1 • Conductive polymer treated fabric electrode: Our proposed solution using conventional textile fabrics (like cotton, polyester or polyamide) treated with a conducting polymer

Commercial ECG Ag/AgCl with gel

Sewed Ag-coated Nylon yarn

PEDOT:PSS treated fabric

Conductive fabric electrodes with 16cm2 of active area were used to acquire the ECG signals from a human volunteer at rest and while walking.

For further info: [email protected]; [email protected]

Conducting textile for pressure sensing

For further info: [email protected]; [email protected]

• Measurements were done after 1 and 10 seconds after the onset of the applied pressure. • The behavior is almost linear up to 10N/cm2 of pressure. • Current increase more than 10 times every 1 N/cm2 of pressure along the first 10N/cm2 • Curves are constructed with the mean value and the standard deviation measured for 4 different sensing elements

Conclusions • Electronic devices with different functionalities can be fabricated on highly flexible substrate • The flexible structures can be cut and easily transferred onto clothes for smart clothing applications • The effect of mechanical deformation during normal activities can be minimized by engineering the device architecture • E-Textiles: electrical properties directly in yarns and fabrics • Conductive fibers/fabrics, a step forward towards etextile

Thank you for your kind attention