Fabrication of Novel Stretchable Devices Jeong Sook Ha Department of Chemical and Biological Engineering Korea University 11 th Korea-US Forum on Nanotechnology
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%