1

CTEA Symposium

Pulin Wang, Ph.D., M.S.Tech.Comm.

pwang22@utexas.edu

Stretch Med, Inc., A spin-off from the University of Texas at Austin

Applications of Skin-Mounted Sensors

Mobile Health

Human-Machine Interface

Bricks-On-Strips Chips-On-Tapes

When Bio Meets Electronics

Skin vs. Silicon

ESi = 130 x 109 Pa ESkin = 130 x 103 Pa

Credit: Intel Credit: ICTGraphicsLab @ USC

Flexible Electronics

Sony, 2007

PolyIC, 2006

Rogers, UIUC, 2008 Lumalive, Philips, 2010

Someya, U of Tokyo, 2005 PowerFilm, 2004

Stretchable Electronics

Science 333, 838 (2011). Nature Materials 10, 316 (2011).

Epidermal Electronics Balloon Catheter Heart “Sock”

Nature Comm. 5, 3329 (2014).

PNAS 108, 1788 (2010).

Tunable Electronic Eyeball

Nature Materials 9, 929 (2010).

Conformal LED Stretchable Transistors

Science 321, 1468 (2008).

e = 100%

3cm

1.04%

0.01%

0.61%

Experiment Numerical Simulation

Stretchable Structure - Serpentine

3cm e = 40%

0.28%

-0.02%

0.13%

e = 30%

3cm

0.36%

0.00%

0.18%

Microfabrication of Stretchable Electronics

Rigid wafer

PI precursor

Flexible

substrate

SOI

PDMS Stamp

Doped Si nanomembrane PI

Au

Si PI

Stretchability & Cycleability

0 50 100 150 2000

2

4

6AlAu RTDEPCoil

R/R

0

Applied Strain (%)

5 mm 0% 30% 90% 199%

0% 30% 90%

30% 90%

115%

68%

2

mm

a

b 0%

c

Coil

EP

RTD 1 10 100 1000 10000

-2

0

2

4

6

8e= 20%

e= 30%

R

/R0 (

%)

Number of Cycles

Apps

Amplifie

r

LED Solar Cell

T Sensor e

Gauge

L Coil

Multi-Functionality

antenna LED

wireless power coil RF coil

temp. sensor strain gauge

RF diode ECG/EMG sensor

0.5mm

Kim*, Lu*, Ma* (*equal contribution), Rogers, et al., Science 333, 838, (2011).

Mounting and Removal of Epidermal Electronics

Epidermal Electronics on A Skin Replica

Yeo, Rogers, et al, Advanced Materials 25, 2773–2778 (2013).

Why Is Conformability Important?

Fully-Conformal (FC)

Non-Conformal (NC)

Partially conformal (PC)

Jeong, et. al., Adv. Mater. 2013, 25, 6839

Conformable contact ensures

• Low interface impedance

higher signal to noise ratio

• Less relative motion less motion

artifacts

• Better heat or mass transfer

Skin

Conventional

Jeong, et. al., Adv. Healthcare Mater. 2014, 3, 642–

648

Epidermal

Skin

Skin

Recent Development in Epidermal Electronics

Kim*, Lu*, Ma* (*equal contribution), Rogers, et al., Science 333, 838, (2011).

Memory & drug delivery

Son et al, Nat. Nanotech. 9, 397 (2014).

Skin temp. mapping

Webb et al, Nat. Mater. 12, 938 (2013).

Jeong et al, Adv. Mater. 25, 6839 (2013).

HMI

Xu et al, Science 344, 70 (2014).

Wireless ECG sensor

Dagdeviren et al, Nat. Mater. 14, 728 (2015).

Skin stiffness

Yeo et al, Adv. Mater. 25, 2773 (2013).

Respiratory rate sensor

Microfabrication of Stretchable Electronics

Rigid wafer

PI precursor

Flexible

substrate

SOI

PDMS Stamp

Doped Si nanomembrane PI

Au

Si PI

Cleanroom, time consuming, low yield, high cost, wafer-based

Cost and Time Effective “Cut-and-Paste” Method

a. APT_Cutting Mat b. Cutting c. Peeling from

mat

d. Removal f. ESS

Au_PET Thermal Release Tape (TRT) Cutting Mat

Deactivated TRT Target Substrate

e. Printing

Yang, et al, Adv. Mater. DOI: 10.1002/adma.201502386 (2015).

Subtractive, dry, desktop, portable, green & roll-to-roll compatible

Multiparametric Epidermal Sensor System

Planar FS coil

RTD

EP sensor

Hydration sensor

20 mm Capacitor

Disposable Epidermal Sensor System (ESS)

Yang, et al, Adv. Mater. DOI: 10.1002/adma.201502386 (2015).

0

10

20

30

Resis

tan

ce

RTD (100)

Before

After

Al Coil ()

Different Types of Substrates

On KRST

On tattoo paper

On Tegaderm

a b c d

e f g h

i j k l

Yang, et al, Adv. Mater. DOI: 10.1002/adma.201502386 (2015).

Multifunctional Epidermal Sensor System (ESS)

ECG

Heart

Muscl

e

0 1 2 3 4-0.8

-0.4

0.0

0.4

0.8 ESS

Conventional

Vo

lta

ge

(m

V)

Time (s)

0 1 2 3 4 5 6-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

Time (s)

Vo

ltag

e (

mV

)

Force 44N

Force 14NEMG

Skin Hydration

0 1 2 3 428.5

29.0

29.5

30.0

30.5

Thermal couple

RTD on ESS

Tem

pe

ratu

re (

oC

)

Time(min)

Skin Temp.

Skin temperature

0 4 8 12 1660

70

80

90

100

110

Time (min)

Hyd

r. L

evel (a

.u.)

H Sensor on ESS

Corneometer

Calm Espresso

0 5 10 15 20-1.0

-0.5

0.0

0.5

1.0

R

/R (

%)

Time (s)Respiration

Respiratory rate

0123

Conventional

ESS

× 10- 4

0 20 40 60 80 1000369

× 10- 12

Frequency (Hz)

Eye open

Eye closed

EEG

a rhythm

FFT

(mV

/Hz)

Brain

Yang, et al, Adv. Mater. DOI: 10.1002/adma.201502386 (2015).

Synchronous Multimodal Measurements

Chen et al, to be submitted (2016).

Core T

Skin T

Skin T

Skin H Heart Rate

ECG by gel electrodes

ECG by EES

Exp. 1 - EMG Sensor on Muscles

Quantification of Muscle Fatigue

EMG for Quantification of Muscle Fatigue &

Recovery Epidermal electrodes Conventional gel electrodes

EM

G (

mV

)

EM

G (

mV

)

2 122 124 0 2 122 124 0 2 122 124

Time (Min)

2 122 124 0 2 122 124 0 2 122 124

Time (Min)

A

B

C

D

E

F

G

H

I

J

Fa

tig

ue

In

de

x

MF (

Hz)

EM

G (

mV

) R

aw

EM

G

(mV

) H

GF (

N)

MF (

Hz)

EM

G (

mV

) R

aw

EM

G

(mV

) H

GF (

N)

Fa

tig

ue

In

de

x

EMG Sensor

Hand

Dynamometer

Exp. 2 - Soft Strain Gauges Measuring Skin Deformation

0 5 10 15 20-1.0

-0.5

0.0

0.5

1.0

R

/R (

%)

Time (s)Respiration

Respiratory rate

Respiratory Rate Sensor

Wireless Tremor Detection and Auto-Warning

Exp. 3 - Skin Mounted Heater

Perioperative Warming

Expedited Transdermal Drug Delivery

Son et al, Nature Nanotechnology 9, 397–404 (2014).

Thermal joint therapy

Epidermal Programmable Heater

Epidermal heater integrated

with T sensor allowed

feedback control

Exp. 4 - Electrotactile Stimulator

10 mm

hand mold

Ying, Bonifas, Lu et al., Nanotech 23, 344004 (2012).

10 mm

finger-

tube

flattened finger-tube

PDMS stamp

gla

ss

device

10 mm

electrotactile stimulator

10 mm

So

urc

e V

olt

ag

e (V

)

Sensation

No

Sensation

28

36

32

0 40 80 120

40

Frequency (Hz)

Exp. 5 Multifunctional Epidermal Glucose

Sensor

B D

A C

Prof. Dae-Hyeong

Kim @ Seoul National

Univ.

pH Correction Is Important

Sensor Is Validated against Gold

Standard

On-Demand Metformin Release

• Multifunctional: sensing, stimulation, therapeutics

• Address challenges in wireless communication and

power supply

• Epidermal sensor is a platform technology

• Initial product offering – ECG patch

What’s Next?

Thank you