Flexible and Stretchable Electronics

and Applications for Biomedical Devices

School of Chemical and Biological Engineering

Seoul National University

Dae-Hyeong Kim

Suffering Patients Doctors

How to bridge?

Bio-Integrated

Electronics ?

Our Goals

* Connect medical doctors and suffering patients By

Using Bio-Integrated Electronic Devices/Systems.

* Develop high performance flexible and stretchable

electronic and optoelectronic devices using high

quality single crystal inorganic materials.

* Apply flexible and stretchable technologies to bio-

integrated electronic devices for the health monitor

and therapy systems.

High Performance Flexible Devices

Polymer Amor. Si Poly. Si Single Si SC III-V

~0.1 ~1 ~100 ~500 ~1000 Electron Mobility (cm2/Vs)

R. Reuss et al. Proc. IEEE (2005)

1 10 100 1000

100KHz

1MHz

100MHz

1GHz

TFT Capability (mobility, cm2/Vs)

Sy

ste

m A

pp

lic

ati

on

s

Organic Semiconductors

α Si

Poly Si

Single Crystal Si

LCD

OLED

RFID

Computer

High Performance

Market Applications

Low Performance

Market Applications

S. Mack et al. Appl.

Phys. Lett. (2006)

Ultrathin Flexible Silicons

300nm thick silicon ribbons

Transfer Printing

Printed surface can be flexible

Area Expansion

Can increase spacing between structures

Flexible Transistors Using Silicon Nanomembranes

100m

IEEE Electron Device Letters 29, 73 (2008)

500m

Transfer Curve

Vg (V)-7 -6 -5 -4 -3 -2 -1 0

- I d

(m

A)

0.0

0.3

0.6

0.9

1.2

1.5

1.8

2m

4m

9m14m19m24m

Vg (V)

-6 -4 -2 0 2

Id (

A)

10-2

10-5

10-8

10-11

Vg(V)

- I d

(A)

-6 -4 -2 0 2

10-2

10-5

10-8

10-11

Typical IV Curve

Vd (V)-3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0

- I d

(m

A)

0.0

0.3

0.6

0.9

1.2

1.5

1.8- 6V

- 5V

- 4V

- 3V

nMOS pMOS

nMOS

pMOS

Flexible Si CMOS Circuits

0.3mm

Vin

VDD Vout

Vin (V)0 1 2 3 4 5

Vo

ut

(V)

0

1

2

3

4

5

6

Gain

0

40

80

120

160

Time (s)-2 -1 0 1 2

Vo

ut

(V)

-6.0

-3.0

0.0

3.0

6.0

0.5mm

VDD Vout

Vin

100m

Metal

Interconnect

NMOS

PMOS

BCB Polyimide

SiO2

Vin

VDD Vout

nMOS

pMOS

CMOS inverter

3 stage CMOS

Ring Oscillator

IEEE Electron Device Letters 29, 73 (2008).

Bending, Folding and Stretching

http://www.nokia.com

stretching Folding (extreme bending)

bending

Robot skin

Smart surgical glove

Wearable computer

Extreme Bendability – ‘Foldability’ – In Ultrathin Circuits

cover slip

etch holeSiO2

metal

PI

Si (p) Si (n)

<1.7m

Science 320, 507 (2008).

thickness

bending radius Strain ~

Conformal Contact to Curvilinear Surfaces

unwrapped

wrapped

unwrapped

unwrapped

‘Wavy’ Silicon Nanoribbons are Stretchable

10 m

Materials

Mechanics

‘Accordion’ Physics

Science 311, 208 (2006).

PNAS 104, 15607 (2007).

Advanced Wavy CMOS ICs

0.5 mm

Science 320, 507 (2008).

Stretching CMOS

Science 320, 507 (2008).

stretching

0% 2.5% 5.0%

releasing

300 m

0% 4.0% 8.8% 0%

0%

stretching releasing

y

x

y

x

300m

Non-Coplanar Serpentine Interconnects

PNAS 105, 18675 (2008).

Stretchable iLED

Nature Materials 9, 929 (2010).

Stretch

Release

0 10 20 30 40 50

0.0

0.2

0.4

0.6

0.8

1.0 Initial X stretch: 60.1 % Diagonal: 57.7 %

Release

Curr

ent (m

A)

Voltage (V)

1 10 100 1000 0

25

30

35

40

Cycle

V a

t I=

20 ㎂

(V

)

200 um 200 um

X-stretch: strain = 30.1 % Initial: Pre-strain = 20.0 %

Island

Pop-up

2 mm

X-direction initial

Diagonal direction initial

Strain = 33.3 %

X-direction stretched

Strain = 45.5 %

Diagonal direction stretched

Stretch

Release

3D Deformations

Nature Materials 9, 929 (2010).

0 degree: Flat

360 degrees

720 degrees

1 mm

0 10 20 30 40 50 60 70 80 90

0.0

0.2

0.4

0.6

0.8

1.0

Flat

360 Degrees 720 Degrees Back to Flat

Curr

ent

(mA

)

Voltage (V)

0 degree: Flat

360 degrees

720 degrees

1 mm Flat Inflated: 29.0 %

Pencil tip

1 mm

Balloon

Inflate

Deflate

Inflate

Deflate

Stretchable Photovoltaic Array

Unpublished

patterning, doping, etching

p+

n+

PDMS

anchors

Si ribbon

Fabricate stretchable -cell

Transfer print silicon solar m-cells Transfer mesh array to biaxially

stretched PDMS substrate

L + ΔL

p+ n+

Stretchable Energy Harvesting Device

Unpublished

x stretching

rele

asin

g

y stretching

rele

asin

g

0% 200m

30%

y

12.5 % Pre-strain

30%

0%

x

30 % stretching

0.0 0.1 0.2 0.3 0.4 0.5

0.0

2.0x10-5

4.0x10-5

6.0x10-5

8.0x10-5

1.0x10-4

1.2x10-4

Cu

rre

nt

(A)

Voltage (V)

0%

y-dir 30%

x-dir 30%

Electronics on Various Substrates

bending

unfolding fo

ldin

g

1cm

1mm

Paper

1 mm

1 mm

Paper

1 mm

1 mm

Al foil

Adv Mater 21, 3703 (2009).

Nature Materials 9, 929 (2010).

Cycle0 250 500 7501000

Gain

0

50

100

150

200

VM

0

2

4

6

stretching

releasing

5mm

1mm

Stretched

5mm

vinyl glove

leather glove

Stretched

3 mm

Fabric

1 mm

Bio-Integrated Electronics

Electrophysiology & Soft, Curvilinear

Tissues – High Performance

Flexible/Stretchable Electronics

Current Technology for Epicardial Mapping

Conventional devices

- Single electrode mapping

- Iterative measurement for 2D map

(Long time EP procedures)

- High risk due to mapping delay

- Low resolution

(cannot pinpoint abnormal tissue)

Device Requirements

- High Resolution 2D Array

- Fast Mapping

- Large Area Coverage

Cardiac Electrophysiology (EP)

- aid diagnosis / guide therapy

for cardiac arrest or other

structural heart disease

Flexible Electronics for Mapping

250 m

1.5 mm

Device Characteristics

- 1618, 800m spacing

- High Speed Silicon TRs

- ~15mm ~13mm

Flexible Electronics

- Conformal contact with

curvilinear, soft cardiac

tissues.

Science Translational Medicine 2, 24ra22 (2010)

In-vivo Experiment with Swine Model

t = ~ 200 ms

1 cm

5 mm

5 mm

80-90 lb male Yorkshire pig

Expose epicardial surface through

sternotomy and pericardiotomy

Science Translational Medicine 2, 24ra22 (2010)

High Resolution, Real-Time Mapping

10 m

V

400 ms

0.3

mV

20 ms

2D Graph 3

X Data

2100 2150 2200

Y D

ata

-0.4-0.20.00.20.40.60.81.0

Col 1

SNR ~ 50

Sci Transl Med 2, 24ra22 (2010)

(s)

0 200 400 600 800 1000 1200 1400 1600 1800-0.01

-0.005

0

0.005

0.01

2 4 6 8 10 12

2

4

6

8

10

12

14

16

0 200 400 600 800 1000 1200 1400 1600 1800-0.01

-0.005

0

0.005

0.01

2 4 6 8 10 12

2

4

6

8

10

12

14

16

0 200 400 600 800 1000 1200 1400 1600 1800-0.01

-0.005

0

0.005

0.01

2 4 6 8 10 12

2

4

6

8

10

12

14

16

0 200 400 600 800 1000 1200 1400 1600 1800-0.01

-0.005

0

0.005

0.01

2 4 6 8 10 12

2

4

6

8

10

12

14

16

-2 mV

+6 mV

-10 mV

800 m

t = 0 ms t = 11.2 ms

t = 14.4 ms t = 24 ms time

Raw data

Neural Interface Application

Clinical mapping application for epileptic

seizure patients

• Diagnose and/or guide epilepsy surgery

• Pinpoint the location of onset of

epilepsy for patients whose epilepsy

location cannot be found with external

imaging techniques, such as MRI or CT

• Mapping brain functions before surgery

BCI neuroprosthetic application for paralyzed

patients with sensory or motor dysfunction

• Mapping and Decoding AP and LFP from

sensory and motor cortex

• Visual cortex/retina implantation

brings light back for blind people

• Cochlear prostheses restore hearing

• Face motor cortex implantation generates

machine languages

• Motor cortex implantation moves computer

cursors (below)

L. R. Hochberg et al., Nature (2006) 2 cm

High Resolution over Large Area: EA with Multiplexers

IEEE Int. Symp. on Circuits and Systems, p 3115 (2007)

How to make a conformal contact??

Long Term Gliosis of Penetrating Electrodes

PNAS 2003, 100, 11041

Advantage

~ High resolution (50~150 m size, 2~10 mm length, ~500 m spacing), Good SNR

Disadvantage

~ Penetration causes mechanical tissue damage → activate immune functions of

brain → cause deposition of astrocytic/inflammatory tissues on electrodes (after

3~6 months)→ poor SNR → difficult long time mapping

Neurosci. Lett. 2006, 406, 81

normal

reactive astrocytic

components of the

scar

Gliosis is a proliferation of astrocytes in damaged areas of the central nervous system (CNS)

High Density Neural Mapping Array

~ 20X18 HDN Sensor Array

~ 300X300µm, 500µm spacing

1 mm

300 m

Kapton (PI) 14.0 m

3.0 m

10.0 m SU8

multiple misaligned via

Si PI

NMP

pt

Pt Contact

Electrodes

Multilayer

Misaligned

Via Structure

Horizontal

/ Vertical

Interconnect

Doped Si

Ribbons on

Polyimide

Pt

Via

1st MT 2nd MT

Si

0.2 mm

Load TR Multiplexer

Output +V Row Slt.

Elect -rode

Vd (V)

0 1 2 3 4

I d (

mA

)

0.0

0.4

0.8

1.2

1.6

Vg (V)

-2 0 2 4 6

I d (

A)

1e-7

1e-6

1e-5

1e-4

Y A

xis

2

0

40

60

I d (

µA

)

20

Nature Neuroscience 14, 1599

(2011).

Seizure Measurement with HDN In-Vivo

Seizure induced (picrotoxin) 2 mm

HDN array on

visual cortex

1 mm

Nature Neuroscience 14, 1599 (2011).

Seizure Mapping : Spiral/Plane Waves

Dela

y in m

s

0

20

40

60

80

100

120

140

160

Counterclockwise spiral delay map

0 ms

165 ms

110 ms

55 ms

Dela

y in m

s

0

10

20

30

40

50

60

70

80

90

Clockwise spiral delay map

0 ms

90 ms

60 ms

30 ms

II IV

I II IV V III III

500 ms

2 m

V

iEEG

Nature Neuroscience 14, 1599 (2011).

Bioresorbable Implantable System

Science 337, 1640 (2012).

c

2 mm

0 min 10 min 5 min

1 cm

top view

Mg electrode

MgO

dielectric

doped Si

silk substrate

Mg

electrode

tilted view

MgO

dielectric

Transient Silicon Electronics

Science 337, 1640 (2012).

3 mm 5 mm

Voltage (V)

Cu

rre

nt

(mA

)

-1.0 -0.5 0.0 0.5 1.0

0.0

0.1

0.2

0.3

0.4

0.5

Diode Resistor 1

Resistor 2

Resistor 3

0 1 2 3 4 50

5

10

15

20

Vd (V) I d

(m

A)

5V

3V

1V

0 1 2 3-40

-20

0

Frequency (GHz)

S2

1 (

dB

)

Inductor

LC oscillator

Capacitor

3 mm S D

G

VDD

VOUT

VIN

VGND

VGND

VDD VIN

VOUT

Mg dep. (shadow mask)

1 mm

1 2 30

1

2

3

0

2

4

6

8

Vin (V)

Vo

ut (V

)

Ga

in

NOR to NAND Time

V (

V)

0

2

4

VB

VA

(0,0)1

(0,1)0 (1,0)0 (1,1)0 0

2

4

Time

V (

V)

(0,0)1 (0,1)1 (1,0)1

(1,1)0

VB

VA VDD VA

VB

VOUT

2 mm

In-vivo Experiment of Transience

Science 337, 1640 (2012).

1 cm

suture

Transistor

Implant Sutured 3 weeks 3 weeks

300 µm

A

B

C

4 mm

1-Re for

inner coil

2-Re for

outer coil

23

26

Turn on both coils

IR image

0 5 10 15 200

2

4

6

8

Time (day)

Q f

ac

tor

experiment

modeling

1 2 3

-12

-8

-4

0

in air

in silk

day 0

day 4

day 8

day 15

Re

fle

cti

on

(S

11

) d

B

Frequency (GHz)

5 mm

Current Non-invasive Skin Electrophysiology

* Current procedure needs cleaning with alcohol wipes and

conductive gel, which is significantly UNCOMFORTABLE.

* Skin electrophysiology using gel is in LIMITED TIME USE

only, since conductive gel dries out over several hours.

* Electrodes and amplifying equipments are BULKY.

www.ucc.ie / openeeg.sourceforge.net

Epidermal Electronic System

Science 333, 838 (2011).

antenna LED

wireless power coil RF coil

temp. sensor strain gauge

RF diode ECG/EMG sensor

0.5mm 0.5cm

undeformed state

stretched

boundary

compressed

Serpentine Functional Units: Non-invasive Sensors,

Wireless Power Supply, Wireless Communications 0.5mm

S

D

G

Si res.

S D G

Si R

0.3mm

Pt CPDMS

cap.

ind.

0.5mm

S

D

G

S D

G

0.3mm

RB

RD

CIN COUT

RIN

ROUT

NMOS

VOUT

VIN

VDD

GND Frequency (GHz)0.0 0.5 1.0 1.5 2.0

Ca

pa

cit

or

S2

1 (

dB

)

-60

-40

-20

0

0.7085nF1.5nF2.204nF2.969nF

Frequency (GHz)0.0 0.5 1.0 1.5 2.0

Ind

uc

tor

S2

1 (

dB

)-30

-20

-10

0

Ind

uc

tor

S1

1 (

dB

)

-15

-10

-5

0

Capacitance (nF)0.5 1.0 1.5 2.0 2.5 3.0

Os

cil

. F

req

. (G

Hz)

0.4

0.5

0.6

0.7

0.8

0.9

0.5mm

Frequency (GHz)0.0 0.5 1.0 1.5 2.0

S11 (

dB

)

-40

-30

-20

-10

0

10

S21 (

dB

)

-120

-90

-60

-30

0

30

S11 fwdS11 rvsS21 fwd S21 rvs

1mm

0.3mm

P N

I

high voltage connection

Si

1 mm

LED

photo- detector

1

3

5

7

10-6

J/m3

Frequency (Hz)10-3 10-1 101 103 105

Ga

in

0.0

0.4

0.8

1.2

1.6

CIN=1F

CIN=220pF

CIN=

Science 333, 838 (2011).

ECG and EMG (Leg and Neck) Recordings

Time (sec)0 5 10 15

Am

plitu

de (

V)

-100

0

100

200

up right

left down

Time (sec)0 5 10 15 20

Am

p. (

V)

-100

0

100

Time (sec)0 5 10 15 20

Am

p. (

V)

-100

0

100EES dry conv.

w/ gel

Time (sec)0.0 0.2 0.4

Am

plitu

de (

V)

-100

0

100

200

Q S

R

base

Time (sec) Time (sec) Time (sec) Time (sec)

up down left right

0 1 2 3 0 1 2 3 0 1 2 3 0 1 2 3

10

100

200

Fre

qu

en

cy (

Hz)

250

150

50

20

20

Fre

qu

en

cy (

Hz)

10

200

10

200

0 10 5 15

active

passive

0 10 5 15

walk stand

walk stand

100

100

Fre

qu

en

cy (

Hz)

Time (sec) 103

Science 333, 838 (2011).

EEG (Forehead) Recordings: Alpha Rhythms

Frequency (Hz)5 10 15 20 25 30

DF

T C

oeff

icie

nt

0

10

20

30

eye close

eye open

103

Fre

qu

en

cy (

Hz)

Time (s) 0 4 8 12 16 20

5

10

20

15

0~10s eye close 10~20s eye open

opening blinking alpha

rhythm

1cm

bare skin

0.5 cm

skin patch

- When large ensembles of neurons fire synchronously, a large electric field is

generated and can be measured on scalp, called Electroencephalography (EEG).

- Alpha range neural activity (8~12Hz) reflects the attention to visual environment.

- When subjects gain visual attention focus, amplitude of alpha oscillation decreases,

while amplitude increases by losing visual attention focus (ex. eye close).

Science 333, 838 (2011).

Suffering Patients Doctors

How to bridge?

Bio-Integrated

Electronics ?