Polymer inks !
Printing Functional Materials
Jennifer A. Lewis
School of Engineering and Applied Sciences
Wyss Institute for Biologically Inspired Engineering
Harvard University
NSF Additive Manufacturing Workshop – 07.11.13
http://lewisgroup.seas harvard.edu
!
3D Printing – Design, Print, Innovate
Broad range of commercial printers and solidification schemes
(photocuring, !T, laser sintering, drying, etc.)
Stereolithography Laser Sintering Fused Deposition PolyJet Process
3D Systems 3D Systems Stratasys Objet
3D Printing Robocasting Laser Net Shaping Electron Beam Melting
Z Corp Robocasting Enterprises Optomec Arcam
3D Printing – Design, Print, Innovate
Broad range of commercial printers and solidification schemes
(photocuring, !T, laser sintering, drying, etc.)
Stereolithography Laser Sintering Fused Deposition PolyJet Process
3D Systems 3D Systems Stratasys Objet
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3D Printing Robocasting Laser Net Shaping Electron Beam Melting
Z Corp Robocasting Enterprises Optomec Arcam
!
Several advances needed for 3D printing of
high performance, functional materials
!
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Our research focus
Ø Broaden materials palette for 3DP
Ø Integration of multiple materials
Ø Digitally specify form and function
Ø Improve feature resolution by 100x
Ø Improve throughput by 100x
…
expedite
transformation
from
rapid
prototyping
to
manufacturing
of
functional
materials
Custom stages designed for 3D printing
Moderate Area, High Precision! Large Area, High Speed Stage!
10x10x5 cm3 ± 50 nm ! ! !1m2x10 cm ± 5 µm!
V = 0.1 -10 mm/s ! ! ! !V = 1 -1000 mm/s !!
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Printing ink filaments (in and out of plane)
Ink filament printing!
!
continuous filament!
is extruded through !
deposition nozzle!
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Desired Ink Rheology:
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$#1*0[1*4.!
"#081*!:X2<!
•" Shear thinning behavior facilitates $/.2)!
flow through fine nozzles without %/*++*+,!
=8*0!!
clogging
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R.6%#+*2+! ""!
•" Viscoelastic behavior enables
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printing of self-supporting
(spanning) features V*12-.+%2)?!()*+%*+,! \+271.!%#!).%2*+!
B12-.+%2)?!$/2(.!
Viscoelastic inks designed for 3D printing
Ink design and deposition
• ink must flow through nozzle without jamming
• ink filaments must form high integrity interfaces
• ink must solidify rapidly (via gelation, coagulation, or evaporation)
• concentrated inks minimize shrinkage during drying
colloidal inks! fugitive inks! nanoparticle inks! polyelectrolyte inks! sol-gel inks!
/01*µ2* /01*(2*
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Reactive silver inks for integrated electronics
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Silver particle inks for integrated electronics
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Silver particle inks for printed electronics
!
Silver inks are highly conductive as-printed
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Solar panels - present design
100 µm
interconnects
78$72)$
78$72)$!
fK!XW!3.11!
Rigid, costly, active materials* occupy large area
*silicon PV cells and silver interconnects
Printing High Aspect Ratio Silver Microelectrodes!
1 µm nozzle 5 µm nozzle 10 µm nozzle
5 µm nozzle 30 µm nozzle
10 µm nozzle 5 µm nozzle
10 µm nozzle
30 µm nozzle
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Flexible photovoltaics
Q>2-(1.9!
Y*!-*3)#3.11$!T!
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Printing interconnects and bus bars
610 µm nozzle
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+#]]1.!
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g+%.)3#++.3%$! 30 µm nozzle
g+X!3.11$!
&D!µ-!!
+#]]1.!
10 cmx10 cm
g+%.)3#++.3%$!
Sparse array of PV cells; finer interconnects
!
g+!3#1127#)2%*#+!6*%/!Y.-()*8$!2+0!YAgO!
Flexible concentrator photovoltaics
"ink~1x10-5 #•cm (after 30 min @ 175°C)
Sheet resistance = 30 m#/sq
6” polyimide substrate
Printed interconnects are highly flexible and can withstand
repeated bending (1000’s cycles) without performance loss
Printed interconnects exhibit excellent I-V response
g+!3#1127#)2%*#+!6*%/!Y.-()*8$!2+0!YAgO!
Conformal printing of electrically small antennas
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Performance characteristics
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VSWR: a measure of signal reflected at component junctions
Ideally, VSWR = 1 (no reflected power, no mismatch loss)
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Embedded Electronics
(carbon ink printed in polymer matrix)
!
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Embedded Electronics
(carbon ink printed in polymer matrix)
Strain
Gage
Length
=
20
mm
All
printed
sequentially
in
1mm
thick
EcoFlex
reservoir
with
the
Wood
group
3D Printed of Strain Gage Arrays
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Printed Three-Layer Stretchable Sensors
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Aim: Print Microbatteries w/ High Power & Energy Density
For autonomous devices that: Energy !
Emission!
1. Harvest energy
- photovoltaic Control!
- thermoelectric
- piezoelectric!
2. Store energy Energy !
- micro-batteries w/ high energy Storage!
and power density Energy !
Harvesting!
3. Perform function
- Mechanical
- Sensing
- RF
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Lai et al., Adv. Mater. 2010! Warneke et al., Computer 2001!
Key Factors Influencing Power & Energy Density
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Printing 3D Interdigitated Microbatteries!
a) b) Nozzle
Current (30 µm) !
collector (Au) !
LTO !
Glass!
c) LTO ! d) Packaging !
LFP!
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Ink Viscosity and Elastic Modulus
LFP
ink
(cathode)
Ink
rheology
tailored
for
3D
filamentary
printing
LTO
ink
(anode)
K.
Sun,
Lewis,
Dillon
et
al,
Adv.
Mater.
2013
Printing High Aspect Ratio Structures!
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Printed 3D Interdigitated Microbattery
200 µm 300 µm
K.
Sun,
Lewis,
Dillon
et
al,
Adv.
Mater.
2013
Printed and Packaged 3D Microbattery
200 µm
K.
Sun,
Lewis,
Dillon
et
al,
Adv.
Mater.
2013
LFP-LTO Full Cell Properties
K.
Sun,
Lewis,
Dillon
et
al,
Adv.
Mater.
2013
Z.5!&S9!O/*2+,!:"gv<!!
Microbattery Performance!
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High throughput 3D printing
5 mm
@'!
3;!
<;!
Multinozzle design based on
Murray’s law: 1 mm
3
rparent = " rbranch
3
_ generation
Hierarchical branching network
Created by CNC milling 200 μm
All 64 nozzles are 205±3 µm on a side
High throughput printing of 3D architectures
Periodic polymer
3D Interpenetrating
foam
Architectures!
h[+#]]1.!2))2?!
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Summary
!" Created model and functional inks with
controlled flow behavior
!" Printed flexible electronics, photovoltaics,
and sensors from conductive inks
!" Printed 3D Li-ion microbatteries
!" Implemented new multimaterial 3D printing
!" Designed and implemented microvascular
nozzle arrays for high throughput printing
.>(.0*%*+,!%)2+$5#)-2%*#+!5)#-!)2(*0!()#%#%?(*+,!!
%#!-2+8523%8)*+,!#5!20H2+3.0!-2%.)*21$!
Thank you!
_.6*$!,)#8(!
http://lewisgroup.seas harvard.edu
!
