http://lewisgroup.seas harvard.edu

!

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

Poly

mer

inks

!

!

Broad range of commercial printers and solidification schemes (photocuring, !T, laser sintering, drying, etc.)

Stereolithography 3D Systems

Laser Sintering 3D Systems

Fused Deposition Stratasys

PolyJet Process Objet

Laser Net Shaping Optomec

Electron Beam Melting Arcam

3D Printing Z Corp

Robocasting Robocasting Enterprises

3D Printing – Design, Print, Innovate

Broad range of commercial printers and solidification schemes (photocuring, !T, laser sintering, drying, etc.)

Stereolithography 3D Systems

Laser Sintering 3D Systems

Fused Deposition Stratasys

PolyJet Process Objet

Laser Net Shaping Optomec

Electron Beam Melting Arcam

3D Printing Z Corp

Robocasting Robocasting Enterprises

3D Printing – Design, Print, Innovate

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Several advances needed for 3D printing of high performance, functional materials

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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

Our research focus  

…  expedite  transformation  from  rapid  prototyping    to  manufacturing  of  functional  materials  

10x10x5 cm3 ± 50 nm ! ! !1m2x10 cm ± 5 µm! V = 0.1 -10 mm/s ! ! ! !V = 1 -1000 mm/s !!

Moderate Area, High Precision! Large Area, High Speed Stage!

Custom stages designed for 3D printing

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Ink filament printing! ! continuous filament! is extruded through ! deposition nozzle!

Printing ink filaments (in and out of plane)

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Desired Ink Rheology: •" Shear thinning behavior facilitates flow through fine nozzles without clogging

•" Viscoelastic behavior enables printing of self-supporting (spanning) features

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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

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colloidal inks! sol-gel inks! polyelectrolyte inks!fugitive inks!

nanoparticle inks!

Viscoelastic inks designed for 3D printing

Reactive silver inks for integrated electronics

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Silver particle inks for integrated electronics

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!Silver inks are highly conductive as-printed

Silver particle inks for printed electronics

Solar panels - present design

Rigid, costly, active materials* occupy large area *silicon PV cells and silver interconnects

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100 µm interconnects

78$72)$!78$72)$78$72)$

Printing High Aspect Ratio Silver Microelectrodes! 1 µm nozzle 5 µm nozzle 10 µm nozzle

30 µm nozzle 5 µm nozzle

10 µm nozzle

5 µm nozzle 10 µm nozzle 30 µm nozzle

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Flexible photovoltaics

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30 µm nozzle

610 µm nozzle

Sparse array of PV cells; finer interconnects !Sparse array of PV cells; finer interconnects

g+X!3.11$!

g+%.)3#++.3%$!

10 cmx10 cm

g+!3#1127#)2%*#+!6*%/!Y.-()*8$!2+0!YAgO!

Printing interconnects and bus bars

g+!3#1127#)2%*#+!6*%/!Y.-()*8$!2+0!YAgO!

Printed interconnects are highly flexible and can withstand repeated bending (1000’s cycles) without performance loss

Printed interconnects exhibit excellent I-V response

6” polyimide substrate

Flexible concentrator photovoltaics

"ink~1x10-5 #•cm (after 30 min @ 175°C) Sheet resistance = 30 m#/sq

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Conformal printing of electrically small antennas

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VSWR: a measure of signal reflected at component junctions Ideally, VSWR = 1 (no reflected power, no mismatch loss)

Performance characteristics

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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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For autonomous devices that: 1. Harvest energy

- photovoltaic - thermoelectric - piezoelectric!

2. Store energy

- micro-batteries w/ high energy and power density 3. Perform function

- Mechanical - Sensing - RF

Energy !Harvesting!

Energy !Emission!

Energy !Storage!

Control!

Aim: Print Microbatteries w/ High Power & Energy Density

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Warneke et al., Computer 2001!Lai et al., Adv. Mater. 2010!

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Key Factors Influencing Power & Energy Density

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Printing 3D Interdigitated Microbatteries!

LTO !LFP!

c)

Current collector (Au) !

Glass!

a) Nozzle (30 µm) !

b)

LTO !

Packaging !d)

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Ink Viscosity and Elastic Modulus  

LFP  ink  (cathode)  

LTO  ink  (anode)  

Ink  rheology  tailored  for  3D  filamentary  printing  

K.  Sun,  Lewis,  Dillon  et  al,  Adv.  Mater.  2013  

Printing High Aspect Ratio Structures!

Y2+0!,)2*+$!

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200 µm 300 µm

Printed 3D Interdigitated Microbattery  

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  

Microbattery Performance! Z.5!&S9!O/*2+,!:"gv<!!

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High throughput 3D printing

3;!

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5 mm

1 mm

200 μm

All 64 nozzles are 205±3 µm on a side

Multinozzle design based on Murray’s law: Hierarchical branching network Created by CNC milling

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rparent3 = rbranch _ generation

3"

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High throughput printing of 3D architectures Periodic polymer foam

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3D Interpenetrating Architectures!

!" 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

Summary

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Thank you!

http://lewisgroup.seas harvard.edu

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