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Fabrication of Novel Stretchable Devices

Jeong Sook Ha Department of Chemical and Biological Engineering

Korea University

11th Korea-US Forum on Nanotechnology

Outline

2. Design concept of novel stretchable devices

1. Introduction

3. Fabrication

4. Stretchable nano-material based devices

5. Summary

Stretchable electronics?

stretchable device

stable operation

interconnection

expansion

compression

under deformation Expandable

Twistable

Compressible

Electronics on curved surfaces

▶Digital cameras with designs inspired by the arthropod eye

Rogers et al., Nature 497, 95 (2013)

Stretchable devices

▶Stretchable batteries with self-similar serpentine interconnects

Rogers et al. Nat. Comm. 4, 1543 (2013)

▶Thin, conformable device softly laminating onto the surface of the skin to enable advanced, multifunctional operation for physiological monitoring in a wireless mode

Rogers et al. Science 344, 70 (2014)

Epithermal electronics & integrated circuits

▶Epidermal Electronics

Rogers et al. Science 333, 838 (2011)

Our recent work on stretchable nanowire devices

1. “Stretchable Field-Effect-Transistor Array of Suspended SnO2 Nanowire”, Small 7, 1181 (2011).

2. “SnO2 Nanowire Logic Devices on Deformable Nonplanar Substrates” , ACS Nano 5, 10009 (2011).

3. “Fabrication of a Stretchable Solid-State Micro-Supercapacitor Array”, ACS Nano 7, 7975 (2013).

4. “Fabrication of Stretchable Single-Walled Carbon Nanotube Logic Devices”, Small 10, 2910 (2014). 5. “Design and Fabrication of Novel Stretchable Device Arrays on a Deformable Polymer Substrate with Embedded Liquid-Metal Interconnections”, Adv. Mater., in press (2014). DOI: 10.1002/adma.201402588 (2014). 6. “High-Density, Stretchable, All-Solid-State Microsupercapacitor Arrays”, ACS Nano, in press (2014). DOI: 10.1021/nn503799j

VDD

Vout

Vin

Ground

S D

Stretchable SnO2 nanowire inverter array

Shin et al. ACS Nano 5, 10009 (2011)

SnO2 NW

(b)

(c)

1 mm 300 μm

1 cm (a)

1 cm

1 cm 1 mm 300 μm

Plane

Convex

Concave

500 μm 200 μm

PI interconnection

230 μm

1 μm

1 μm

1 μm

prestrain: 21 %

prestrain: 28 %

SEM images after deformation

VG (V)

-2 -1 0 1 2

I DS (

A)

1e-12

1e-11

1e-10

1e-9

1e-8

1e-7

1e-6

1e-5

Y A

xis

3

1e-12

1e-11

1e-10

1e-9

1e-8

1e-7

1e-6

1e-5

VDS

(V)

0.0 0.5 1.0 1.5 2.0

I DS (

A)

0

1e-6

2e-6

3e-6

X Data

-2 -1 0 1 2

Y D

ata

-9e-9

-6e-9

-3e-9

0

3e-9

6e-9

9e-9

VDS

(V)

1.5 2.0 0

0

ID

S (μA

)

3

VGS

= 0 ~ 2 V

(0.2 V step)

2

VGS

(V)

1 2 -2 -1 0

ID

S (A

)

10-5

10-7

10-9

10-11

IG

S (A

)

VDS

= 2 V

VDS

= 0 V

(a) (b)

X Data

0.0 0.5 1.0 1.5 2.0

Y Data

0.0

0.5

1.0

1.5

2.0

Vin

(V)

0.5 1.5

Gain ~4.8

1.0

Plane

10

~300 MΩ

~9 GΩ

VDS

(V)

1.0 2.0 -2.0 -1.0 0

0

ID

S (nA

) 6

-3

-6

Before RIE

After RIE

(c)

Gain ~4.7

0

Vo

ut(V

)

1.5

2.0

0.5

1.0

(d)

Convex shape

Concave shape

2.0

Gain ~4.8 3

9

-9

×

1

0.5 1.0

10-5

10-7

10-9

10-11

VDS

= 2 V

(Extremely

stretched)

▶No deterioration of electrical performance upon deformation

Stretchable micro-supercapacitor array

▶micro-supercapacitor with SWNT electrodes and ionic-gel electrolyte

Kim et al. ACS Nano 7, 7975 (2013).

0 1 2 3-200

-150

-100

-50

0

50

100

150

200Strain (0.5V/s)

0%

10%

20%

30%

Potential (V)

Ca

pa

cit

an

ce

(F

/g)

Charging

3 V

Micro-LED(orange)

Discharging

Bent (r ~ 2.5 cm) Stretched (~ 20 %)

▶No noticeable deterioration in electrochemical performance with stretching

2. Design concept of novel stretchable devices

Main concept of our novel stretchable device

Difference in Young’s Modulus → Minimized strain on active device

→ Doubling the fill factor

→ Simple fabrication/ Protection from external impact/ Increase in fill factor

dry transferred device array

2 mm

PDMS (stiff)

ecoflex + PDMS (soft)

5 mm

heterogeneous structure a

embedded EGaIn interconnection

EGaIn 5 mm

b

double integration

upper blue LEDs

lower white LEDs 5 mm

c

silver sticker

d

e

→ Independent fabrication of active devices from the substrate

3. Fabrication

SiO2/Si substrate

PDMS

deviceelectrode

EGaIn

coating of PDMS and half curing

Ag NW solution

drop casting of Ag NW solution attach the sticker betweenthe EGaIn and electrode

PI filmPDMS

SiO2/Si substrate

spin coating of PDMS attachment of PI film device fabrication detachment of device from the substrate

2 mm

1.0 μm

b

c

a

detach the mold from the whole assembly

remove the iron wire & inject the liquid metal

transfer the fabricated device & attach the silver sticker

pour PDMS into a each mold for rigid island & attach both molds

insert the Fe wire into thetop mold

top mold

bottom moldbottom moldinsert the Fe wire into bottom mold for the injection of liquid metal

pour mixture of ecoflexand PDMS to form the soft thin film

Schematics of fabrication process

a. Preparation of deformable substrate

b. Preparation of active device and dry transfer

c. Preparation of Ag nanowire sticker

Yoon et al. Adv. Mater. In press (2014)

4. Stretchable nano-material based devices

Stretchable array of LEDs & strain distribution

d

1 cm 180° twisting

c

1 cm

Bending with r = 13 mm

l li lf

unit module l'

side view b a

applied strain = 60% released

flat bending twisting

1.0 cm

e

1 cm ɛapplied = 30%

50% 25% 0% 180%

→ Stable performance upon deformations of stretching, bending, and twisting → Minimized strain on island (<1%) with concentrated strain on thin film (>100%) upon 30% stretching

area 1

area 2

area 1

area 2

area 1 (island) area 2 (thin film)

180%103%

85%

145%

0.6%

10.5%

10.3%

12.3%

with PI (Ɛapplied = 30%)

without PI (Ɛapplied = 30%)

a b c

area 1 area 2

120%180%

0%

20%

50%

15%20%

0%

5%

10%

150%

100%

180%

60%

130%

120%

110%

140%

area 1

area 2

area 1

area 2

area 1 (island) area 2 (thin film)

180%103%

85%

145%

0.6%

10.5%

10.3%

12.3%

with PI (Ɛapplied = 30%)

without PI (Ɛapplied = 30%)

a b c

area 1 area 2

120%180%

0%

20%

50%

15%20%

0%

5%

10%

150%

100%

180%

60%

130%

120%

110%

140%

I-V characteristics of LED arrays upon deformation

0 10 20 30 40 50 60 700.1

1

10

Rn

orm

ali

zed

applied (%)

Stretching

0% 70%

d

a

-3 -2 -1 0 1 2 3

0.00

0.02

0.04

0.06

0.08

0.10

Cu

rren

t (A

)

Voltage (V)

flat

r = 3 cm

r = 2 cm

r = 1 cm

Bending

c

-3 -2 -1 0 1 2 3

0.00

0.02

0.04

0.06

0.08

0.10

Cu

rren

t (A

)

Voltage (V)

0%

10%

30%

50%

70%

Stretching

-3 -2 -1 0 1 2 3

0.00

0.02

0.04

0.06

0.08

0.10

Cu

rren

t (A

)

Voltage (V)

flat

90o

180o

270o

twisting

b

0 4000 8000 12000 160000.1

1

10

R/R

0

Stretching cycles

f

1.5 2.0 2.5 3.0

10-3

10-2

10-1

Cu

rre

nt

(A)

Voltage (V)

100 cycle

1000 cycle

4000 cycle

8000 cycle

10000 cycle

16000 cycle

e ɛapplied = 60%

→ Stable performance upon bending, twisting, and stretching → Mechanically stable upon repeated stretching cycles of 16,000 under external strain of 60%

Stretchable SnO2 nanowire UV sensor & SWCNT FET

0 300 600 900 1200 1500

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0%

10%

20%

30%

Cu

rren

t (m

A)

Time (sec)

UV ON

UV OFF

SnO2 sensor

a b

200 400 600 800 1000 120010

-1

100

101

102

103

I ph/

I dark

Time (Sec)

UV on UV off

0 100 200 300 400

0.5

1.0

1.5

2.0

2.5

3.0

0%

10%

20%

30%

Cu

rre

nt

(A

)

Time (sec)

-10 -5 0 5 10

0.8

1.0

1.2

1.4

1.6

1.8

2.0

I ds (A

)

Vg (V)

0%

10%

20%

30%

Vds = 1 V

Vds = 1 V

Vg = -10 V

c d

SWCNT FET

→ stable photo-current upon uniaxial stretching → Iph/Idark ~ 60 → stable transfer curve upon stretching → stable Ids value

2㎛

5㎛

SnO2 NW

5 µm

SWCNT

Energy Generation NWs sensor Energy Storage

Solar Cell

Nano-generator

Supercapacitor

SWCNT & solid electrolyte

controller S

D NWs

S D P N

Diode

Resistor

hυ

external vibration

+

- - - -

+ + +

NO2

Stretchable electronics with integrated energy generation and storage devices

Wearable computer

Apple-watch

Metallization

MWNT-COOH/MnOx

Functionalized MWNT

Ti/Au current collector

Layer-by-Layer (LbL) assembly

SiO2/Si substrate

PDMS

PET film Solidification

of solid electrolyte

PVA-H3PO4 gel

200 nm

220nm

Channel length = 150 µm Active area = 0.6 cm2 Thickness = 220 nm Volume = 1.32 x 10-4cm3

5mm

Fabrication of micro-supercapacitor with LbL assembled MWNT/MnOx electrodes

0 1 2 3

-20

-10

0

10

20

Cu

rren

t (

A)

Potential (V)

0%

10%

20%

30%

40%

0 1 2 3

-20

-10

0

10

20

Cu

rren

t (

A)

Potential (V)

1 cycle 100 cycle

500 cycle 1000 cycle

2000 cycle 3000 cycle

0 10 20 30 400.1

1

10

C/C

0

A

Stretching

Releasing

0 1000 2000 30000.1

1

10

C/C

0

Stretching number

0%

10%

20%

136%

45%

c d

e f

a b

Stretching

Releasing

ɛapplied (%)

1 cm

Stretching Releasing

ɛapplied = 40%

200 mV/s

200 mV/s

ɛapplied = 40% ɛapplied = 40%

Stretchable micro-supercapacitor array

Single Array

Ecell 2.6 2.4

Pcell 23 8

(mWh/cm3)

(Wh/cm3)

→ Stable electrochemical performance upon repeated stretching up-to 40%

Hong et al. ACS Nano, In press (2014)

0 10 20 30 400.1

1

10

L/L

0

ɛapplied = 40%

Galinstan

a b

1.8 V 2.0 V

2.2 V 3.3 V

5 mm

ɛapplied (%)

▶ Powering various µ-LEDs with different operating voltages by integrated circuit of MSCs ▶ Stable illumination of µ-LEDs under applied strain of 40%

Integrated energy storage devices

Summary

▶ We present the fabrication of stretchable electronic devices on newly designed deformable substrates. ▶Integrated devices, such as μ-LEDs, SnO2-NW UV sensors, SWCNT FETs, and planar all-solid-state micro-supercapacitors exhibit mechanically stable device performance after bending, twisting, and uniaxial stretching, which corresponds with the FEM analysis of the distribution of strains. ▶This study demonstrates the successful performance of our newly designed deformable device and the potential for its application in the field of wearable nano-electronics.

Acknowledgments

▶This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (Grant No. NRF-2013R1A2A1A01016165).

▶This work was done with Dr. Jangyeol Yoon Ms. Soo Yeoung Hong Ms. Yein Lim Prof. Goangseup Zi Dr. Seung-Jung Lee

http//surfnano.korea.ac.kr

Effective strain

distribution

Simple fabrication

process

Embedded liquid metal

interconnection

Double integration

VS

1st Polyimide Ti/Au

SWCNT bundle

Ionic polymer 2nd Polyimide (encapsulation)

PDMS

2차원

Top device

Bottom device

Polyimide

PDMS EGaIn

interconnect

3차원

Comparison with previous design

Conducting properties of EGaIn upon stretching

-6 -4 -2 0 2 4 6

-0.10

-0.05

0.00

0.05

0.10

Cu

rren

t (A

)

Voltage (V)

0%

10%

20%

30%

40%

50%

60%

70%

0 10 20 30 40 50 60 700.1

1

10

R/ R

0

applied (%)

V

stretching

5 mm

a b

c

2 mm 4 mm

→ Stable conduction upon uniaxial strain up-to 70% (conductivity of EGaIn : 3.4 x 104 S/cm) → No noticeable volume change of EGaIn

Conduction through Ag nannowire sticker upon stretching

0 20 40 60 80 1000.1

1

10

R/R

0

silver sticker ecoflex

copper wire

ɛapplied (%) 0 1 2 3 4 5 6

0

5

10

15

20

25

30

Au electrode

Ag sticker_1

Ag sticker_2

Ag sticker_3

Ag sticker_4

Ag sticker_5

R

number of samples

500 nm 2 mm

V

a b

Ti/Au

S D

V

silver sticker

S D

V

c

d e f

→ Electrical conduction comparable to Au thin film → No change in conductivity upon uniaxial stretching up-to 100%