Center for Mechanics of Solids, Structures and Materials
Center for Mechanics of Solids, Structures and Materials
• Motivation
• Deformability of polymer-supported
metal and silicon thin films
• Case Study – Non-Invasive
• Epidermal electronics
• Electrotactile finger tube
– In Vivo
• Instrumented balloon catheter
• Cardiac web
• Outlook
Roadmap
Center for Mechanics of Solids, Structures and Materials
Bio-Integrated Electronics
3
Health Monitoring
Human-Machine Interface
Assistive Devices
Surgical Tool
Implantable Electronics
Center for Mechanics of Solids, Structures and Materials
Fundamental Challenge
Center for Mechanics of Solids, Structures and Materials
Mechanics
• Conformable
• Stretchable
• Robust binding without
detachment
Materials
• High-performance
• Biocompatible
• Bioresorbable
Functionality
• Electrical, mechanical, thermal,
optical, biomedical
Cost, Power, Weight, Size
• Minimal
Desired Properties
Center for Mechanics of Solids, Structures and Materials
Polymer-Supported Metal and Silicon Films
Ductile
Si film
Si film
polymer substrate
Brittle
Plastic Polyimide
Wheatstone Bridge diode
SiO2
Metal
SU8
Metal
SU8
5mm 200 µm
Won, Kim, Lu, Rogers, IEEE Transactions on Electron Devices 58, 4074 (2011).
Center for Mechanics of Solids, Structures and Materials
Stretchability of Blanket Metal on Polymer
7
aCu/Cr/Kapton 50%
10mm
80mm
Cu/Kapton 20%
Kapton substrate
Cu film
R
L
1mm
13mm
Lu, Wang, Suo, Vlassak, Applied Physics Letters 91, 221909 (2007).
Lu, Wang, Suo, Vlassak, Journal of Materials Research 24(2), 379-385 (2009).
Lu, Suo, Vlassak, Acta Materialia 58, 1679-1687 (2010).
Center for Mechanics of Solids, Structures and Materials
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
1.E-08 1.E-07 1.E-06 1.E-05 1.E-04 1.E-03
Max. B
en
din
g C
urv
atu
re (
m-1
)
Silicon Thickness (m) Nano-membrane Bulk wafer
Bendability of Silicon
+1%
0%
-1%
%12
max h
h
Center for Mechanics of Solids, Structures and Materials
Stretchability of Si-Based Electronics
Buckled
Ribbons
Sun et al., Nature Nanotech. 1, 201 (2006).
2D Wavy
Membrane
Choi et al., Nature Lett. 7, 1655 (2007).
Si Islands +
Interconnects
Kim et al., PNAS 105, 18675 (2008).
Center for Mechanics of Solids, Structures and Materials
Stretchability of Serpentines
Unknowns: w/R, l/R, α
appmax /Constraints: 1). No overlap ( ); 2). Y/w=fixed; 3). Min. 0X
= 40%
0.28%
-0.02%
0.13%
l/R 4.1166
w/R 0.7079
α (°) 8.7039
Y/w 10
R
l α
q
w
X
Y
Widlund, Yang, Lu, to be submitted (2013).
Center for Mechanics of Solids, Structures and Materials
Stretchability of Brittle Islands
Sun, Lu, Suo, Vlassak et al., J. Mater. Res. 24, 3338 (2009).
Center for Mechanics of Solids, Structures and Materials
Electronics On Various Substrates
3 mm
Fabric
1 mm
1 mm
Printing paper
1 mm
1 mm
Al foil
5mm
1mm
vinyl glove
1
mm
Kim, Rogers et al., Adv. Mater. 21, 3703 (2009).
Kim, Rogers et al., Nature Mater. 9, 929 (2010).
Center for Mechanics of Solids, Structures and Materials
Micro-Transfer Printing Technique
13
Flexible
substrate
SOI
PDMS Stamp
Si nanomembrane
Rigid wafer
PI precursor
PI
Au
Si PI
Center for Mechanics of Solids, Structures and Materials
• Non-invasive
– Epidermal Electronics:
extreme compliance,
non-invasive
– Wearable Finger Tube
• In Vivo
– Balloon Catheter:
extreme expandability,
– Cardiac web
Case Study
Tactile sensor
EKG sensor
EKG sensor 1mm
Rabbit heart
Center for Mechanics of Solids, Structures and Materials
Stiff and thick
PDMS E = 145 kPa, h = 0.6 mm
Soft and thin
PDMS E = 19 kPa, h = 0.3 mm
Polymer on Skin
PDMS thickness (mm)0.0 0.3 0.6 0.9 1.2 1.5
Te
ns
ile
Str
ain
(%
)
0
20
40
6050:130:1
Model
PDMS thickness (mm)0.0 0.5 1.0 1.5 2.0C
om
pre
s.
Str
ain
(%
)20
40
60
80 50:130:1
Model
polyester
PDMS
polyester
PDMS
Kim*, Lu*, Ma* (*equal contribution), Rogers, et al., Science 333, 838, (2011).
Center for Mechanics of Solids, Structures and Materials
Au
Ecoflex
PI
30µm
1.4µm
1mm
Compliance and Stretchability
Strain (%)0 5 10 15 20 25 30
Str
es
s (
kP
a)
0
30
60
90skin: 160 kPay: 150 kPax: 130 kPaFEM x FEM y
Ecoflex
0.5mm
EP sensor x
y
Au
Ecoflex
PI
30µm
0.5µm
Kim*, Lu*, Ma* (*equal contribution), Rogers, et al., Science 333, 838, (2011).
0.15%
0.05%
0%
0.1%
xx=30%
yy=
30%
Center for Mechanics of Solids, Structures and Materials
Thinning Down
Ecoflex
Water soluble film (E=2GPa)
0.5 mm
Ecoflex (E=60kPa) 30 mm
Center for Mechanics of Solids, Structures and Materials
Mounting and Removal
Sample credit: Dae-Hyeong Kim, Nanshu Lu
Arm credit: Dae-Hyeong Kim
Video credit: Yun-Soung Kim
Center for Mechanics of Solids, Structures and Materials
Extreme Compliance & Conformability
Yeo, Rogers, et al, Advanced Materials 25, 2773–2778 (2013).
Center for Mechanics of Solids, Structures and Materials
Up
Time (sec)0 1 2 3
Am
plitu
de (
mV
)
-800
-400
0
400
Am
plitu
de (
mV
)
-30
0
30
60
Down
Time (sec)0 1 2 3
Am
pli
tud
e (
mV
)
-800
-400
0
400
Am
pli
tud
e (
mV
)
-30
0
30
60
Left
Time (sec)0 1 2 3
Am
pli
tud
e (
mV
)
-800
-400
0
400
Am
pli
tud
e (
mV
)
-20
0
20
40
60
up down
left
Right
Time (sec)0 1 2 3
Am
pli
tud
e (
mV
)
-800
-400
0
400A
mp
litu
de (
mV
)
-30
0
30
60right
up right
left down
Neck
EMG Sensing In collaboration with Todd Coleman, UCSD BME
Sokoban
Kim*, Lu*, Ma* (*equal contribution), Rogers, et al., Science 333, 838, (2011).
Center for Mechanics of Solids, Structures and Materials
Apps
Amplifier LED Solar Cell
T Sensor Gauge L Coil
Kim*, Lu*, Ma* (*equal contribution), Rogers, et al., Science 333, 838, (2011).
Center for Mechanics of Solids, Structures and Materials
Electrotactile Stimulators on Wearable Finger Tube
Ying, Bonifas, Lu et al., Nanotech 23, 344004 (2012).
So
urc
e V
olt
age
(V)
Sensation
No
Sensation 28
36
32
0 40 80 120
40
1 cm
Frequency (Hz)
Center for Mechanics of Solids, Structures and Materials
Angioplasty balloon catheter Balloon atrial septostomy
Balloon Catheters
Center for Mechanics of Solids, Structures and Materials
Instrumented Balloon Catheter
Catheter
Sensors
ACF film 1
Connector
ACF film 2
5mm
Infla
tion
Defla
tion
3mm
Contacts
Kim*, Lu*, Ghaffari* (*equal contribution), Rogers, et al., Nature Mater. 10, 316 (2011).
Center for Mechanics of Solids, Structures and Materials
Right
atrium
Right atrium
Pig CT
Sensing and Therapeutics
Time (sec)0 1 2 3 4 5
( R- R
0)/
R0 (
%)
0
10
20
30
401
0 m
V
Contact Non-contact
Tactile sensor
EKG sensor
EKG sensor 1mm
Rabbit heart
Kim*, Lu*, Ghaffari* (*equal contribution), Rogers, et al., Nature Mater. 10, 316 (2011).
Time (sec)
0 50 100 150 200
Te
mp
era
ture
(o
C)
15
20
25
30
35
40
45
Po
we
r (m
W)
0
200
400
600
800
Lesion Lesion
5mm
Temp. sensing
body
temp
.
ablation
off
Ablation electrodes
Temp. sensor
ablation on
Ablation electrodes
In collaboration with Marv Slepian, U of Arizona
Center for Mechanics of Solids, Structures and Materials
Stretchable Strain Gauges
0.5mm
Kim*, Ghaffari*, Lu* (*equal contribution), Rogers, et al., PNAS 109, 19910 (2012).
Yang, Lu, Sensors 13, 8577-8594 (2013).
Strain (%)0 2 4 6 8 10
(R-R
0)/
R0 (
%)
-1
0
1
2
3longitud.diagon. trans.
GF = 0.23
Center for Mechanics of Solids, Structures and Materials
In Vivo Epicardial Sensing
2mm
Time (sec)0 1 2 3 4 5
Time (sec)0 1 2 3 4 5
w/o and w/ ischemia
10
%
w/ pacing
10
%
120bpm 200bpm
pacing starts
Kim*, Ghaffari*, Lu* (*equal contribution), Rogers, et al., PNAS 109, 19910 (2012).
Center for Mechanics of Solids, Structures and Materials
What’s Next?
28
• Li-ion battery
• Supercapacitor
• Energy harvesting
• Wireless transmission
Power • Memory
• Near field
• RF (blue tooth)
Data
• Adhesion
• Implantable
• Biochemical
• Actuation
Interface
Center for Mechanics of Solids, Structures and Materials
Acknowledgement
Collaborators:
Prof. Dae-Hyeong Kim, SNU
Prof. Juejun Hu, Univ. of Delaware
Prof. Ken Liechti, UT Austin
Prof. Deji Akinwande, UT Austin
Prof. Edward Yu, UT Austin
Prof. Ken Diller, UT Austin