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BERKELEY SENSOR &

ACTUATOR CENTER

ME 138/238

Flexible Mechanical-Electrical

Transducers for Self-Powered Systems

Dr. Junwen Zhong

Supported by Prof. Liwei Lin

junwenzhong@berkeley.edu

2016/11-Present: Postdoctoral researcher in University of

California Berkeley, USA

2011/09-2016/06: PhD student in Huazhong University of

Science and Technology, China

2014/07-2015/10: Visiting student in Georgia Institute of

Technology, USA

2007/09-2011/06: Undergraduate students in Huazhong

University of Science and Technology, China

Research Projects

Wearable and Paper-Based Devices; Self-Powered Electronics; Electret andPiezoelectret Materials

He has published 11 Chinese patents, 1 USA patent and 29 papers, among which 10papers were published as the first or co-first author in the journals with IF>10(including 2 ESI highly citied papers and 2 cover papers). Some of this papers havebeen published in Energy & Environmental Science, Advanced Materials, ACSNano, and Advanced Functional Materials, with over 1550 citations.

Resume

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The internet of things (IoT) is the network of physical devices, vehicles, buildings and other

items—embedded with electronics, software, sensors, and network connectivity that enables

these objects to collect and exchange data. —— Wikipedia

“IoT will consist of almost 50 billion objects by

2020”.—— Dave Evans, Cisco

2020

Power Sources for Astronomical

Electronics & Sensors in IoT ? No !

Scientific American, Zhonglin Wang3

GeneratorConvert Human Energy to Electricity

Improve the Output Characteristics

EnergyManagement

Energy Storage& Application

Various applications

Self-Power System

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A self-powered sensor system and

its potential applications! Aiming at

entirely replace battery and/or extend

the life time of the

battery for sustainable operation.

Many devices made based on nanotechnology

may need micro- to milli-Watt scale power to operate.

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Mechanical Energy

Mechanical Energy

Ubiquitous & abundant in the ambient

Power & signal sources

Boar frequency & power ranges

Human Body Energy

T. Starner, IBM Syst. J. 1996, 35, 618

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Mechanical-Electrical Energy Conversion

PiezoelectricElectromagnetic

Electrostatic Induction

Flexible Transducers

G. Zhu, et al, Nat. Commum., 2014, 5, 3426

F. Feng, et al, Nano Energy, 2012, 1, 328

Z. L. Wang, et al, EES, 2015, 7, 426

J. Zhong, et al, ACS Nano, 2014, 6, 6273

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Electromagnetic

Ad：Large outputs, Mature technology

DisAd：Non-flexible, Heavy

Piezoelectric Electrostatic

Ad：Flexible, Miniaturize, wearable

DisAd：Little outputs,toxic

Ad：Flexible, Relative large outputs

DisAd：Bad stability, Abrasion

Comparison for 3 Principles

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Flexible Piezoelectric Transducer

Part I:

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Piezoelectricity

Piezoelectric Effect is the ability of certain materials to generate an electric

charge in response to applied mechanical stress.

Active Effect

Negative EffectQuartz

Electrical Dipoles

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Piezoelectric Materials

Single Crystal materials: Electrical Dipoles

are in order configuration to form piezoelectricity. Zinc Oxide

(ZnO), Quartz, Barium Titanate (BaTiO3), etc.

Polycrystal materials: Composed of many single crystal

piezoelectric particles. There is no piezoelectricity before poling.

Piezoceramics (PZT), Piezopolymers (PVDF), etc.

E

Before poling In poling After poling

I II III

Electrical Poling: Applying high electrical field to electrical dipoles be regular

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Material Structure d33 (pC/N)

PMN-PT

PZT

PZT

BaTiO3

ZnO

Quartz

PVDF

Single crystal

Polycrystalline

Thin film

Thin film

Thin film

Thin film

Polymer film

2000 to 3000

250 to 700

60 to 130

191

5.9

2.3

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Piezoelectric Coefficients

Larger d33 coefficients, Larger outputs!12

Inorganic/Non-Flexible

Organic/Flexible

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Polyvinylidene Fluoride (PVDF)

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Piezoelectricity FTIR

High Performance Piezoelectric Devices Based on Aligned Arrays of Nanofibers of PVDF

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Arrays of highly aligned piezoelectric nanofibers of PVDF

400 μm 10 μm

Persano, L.; et al. Nature Com., 2013, 4, 1633

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Experimental and theoretical studies of responses of pressure sensors15

Experimental and theoretical studies of responses of flexural sensors16

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Direct-Write Piezoelectric PVDF Nanogenerator with High Energy Conversion Efficiency

L. Lin, et al., Nano Letters 2010, 10, 726.17

Electric output of a piezoelectric PVDF nanogenerator

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19

c

d

Stability and Energy Conversion Efficiency

Novel “3-D spacer” all fibre piezoelectric textiles for energy harvesting applications

N. Soin, T. H. et al, Energy & Environmental Science 2014, 7, 1670. 20

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Output Performances of 3D Piezoelectric Fabric Power Generator21

Question:

Can the Inorganic Piezoelectric Materials be Used to Fabricate

Flexible Transducers???

Yes!!!!With the Help of Micro-Nano Technology!!!!

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Piezoelectric Nanogenerators Based on Zinc Oxide Nanowire Arrays

Z. L. Wang, J. Song, Science 2006, 312, 242. 23

Transport is governed by a metal-

semiconductor Schottky barrier for

the PZ ZnO NW

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Electromechanically coupled

discharging process of

aligned piezoelectric ZnO

NWs observed in contact

mode.

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Power Generation with Laterally Packaged Piezoelectric Fine Wires

R. Yang, Y. Qin, L. Dai, Z. L. Wang, Nat Nano 2009, 4, 34.

Design of a piezoelectric fine wire (PFW)

generator on a flexible substrate

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Electrical output of a single-wire generator (SWG)

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Connecting two single-wire generators (SWGs) in series.

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Air/Liquid-Pressure and Heartbeat-Driven Flexible Fiber Nanogenerators as a Micro/Nano-Power Source or

Diagnostic Sensor

Z. Li, Z. L. Wang, Advanced Materials 2011, 23, 84. 29

Two normal good working FNGs for

a ‘linear superposition’ test of

output current densities

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Pulse-driven fiber nanogenerator for energy harvesting or strain sensor

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Highly-Efficient, Flexible Piezoelectric PZT Thin Film Nanogenerator on Plastic Substrates

K.-I. Park, et al, Advanced Materials 2014, 26, 2514. 33

Schematics of the working

principle of flexible PZT thin

film NG

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Large-Area and Flexible Lead-Free Nanocomposite Generator Using Alkaline Niobate Particles and Metal Nanorod Filler

C. K. Jeong, et al, Advanced Functional Materials 2014, 24, 2620. 36

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Piezoelectricity of Single-Atomic-Layer MoS2 for Energy Conversion and Piezotronics

W. Wu, et al, Nature 2014, 514, 470.

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Second-Harmonic Generation(SHG)

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Direct-current electrical characterizations of single-layer and

bilayer MoS2 devices under strains. 41

Piezoelectric outputs from single-layer and multi-layer MoS2 devices.

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Reliable Piezoelectricity in Bilayer WSe2 for Piezoelectric Nanogenerators

J.-H. Lee, et al, Advanced Materials, 2016,17, 1606667.

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Investigation of the mechanical stability in mono/bi-layers WSe2.

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Virus-Based Piezoelectric Energy Generation

B. Y. Lee, S.-W. Lee, Nat Nano 2012, 7, 351.

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01/30 Tuesday 1pm: Harrison Khoo, Ian Connett，Martin Xu

01/30 Tuesday 2pm: Dan Xu, Vedang Patankar

01/30 Tuesday 4pm: Margann Rui, Tiffany, Vatsal

01/31 Wensday 3pm: Amruth,Marina Rizk, Lujain Alobaide, Nate

02/01 Thursday 1pm: Neil, Junpyo Kwon

Lab Experiment ScheduleEtcheverry Hall 1113

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Flexible Electrostatic Transducer

Part II:

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Annoying Static Electricity

Static Electricity is Useful!!!

Van de Graaff Electrostatic Generator

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Electrostatic Induction

Electrostatic induction is a method to create or generate static electricity

in a material by bringing an electrically charged object near it. This causes

the electrical charges to be redistributed in the material, resulting in one side

having an excess of either positive (+) or negative (−) charges.

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An electret is a piece of dielectric material exhibiting a quasi‐permanent electric charge

Electrets

J. A. Malecki, PRB 1999, 59, 9954 

Even hundreds of years

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Electrets

[ C C ]

F F

F F

n

Corona charge

A

-15 kV

Electret

Needle

Electrode

Electret material: Teflon (PTFE)

Charges injection

G. M. Sessler, Electrets(2nd ed), Berlin: Springer‐Verlag, 198757

Electrode 1

Electret

0

dd1

d0

d2

Air Gap

x

ε0

εr ε0

ε0

σ1

σ2

E1

Er

E2

U+

-

(1) According to gauss law：

(2) According to kirchhoff's second law：

Combing (1) and (2)：

Surface Charge Density Detection

Electrode 2

Air Gap

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Surface Potential Detection

0 5 10 15 20 25 300

-1

-2

-3

Su

rfac

e P

ote

nti

al (

kV)

Time (Day)

PE

0 5 10 15 20 25 300

-1

-2

-3

-4

Su

rfac

e P

ote

nti

al (

kV)

Time (Day)

pp

PP

0 5 10 15 20 25 300

-2

-4

-6

-8

Su

rfac

e P

ote

nti

al (

kV)

Time (Day)

PTFE

0 5 10 15 20 25 300

-2

-4

Su

rfac

e P

ote

nti

al (

kV)

Time (Day)

PET

0.1‐1 mC/m2

‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐+  +  +  +  +  +  +  +

+                   +

A

R

‐

+d2

1

2

d1

Electrostatic Induction

12

12 dd

d

er

021 Top Electrode

+ + + +

+ +

- - - - - -A

+ + + +

+ +

- - - - - -A

Pressing+ + +

- - - - - -A

+ + +

ReleasingOriginal

Working Mechanism of Flexible Electrostatic Transducer

Bottom Electrode

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Original

Pressing Equilibrium

Releasing

Simulation Results

equivalent circuit

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Pressing

Releasing

-Q (t)

R

+

-

I+Q (t)-Ｔ

V

Q (t)

Ｔ-Q (t)

E1

E2

E+

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0 5 10

0

25

50

Pea

k po

wer

den

sity

(W

/cm

2 )

r

0 5 100

150

300

Pea

k po

wer

den

sity

(W

/cm

2 )

Rx (G)

0 100 200

0

25

50

Pea

k po

wer

den

sity

(W

/cm

2 )

d0 (m)

Dielectric Coefficient of Electret

External Loading

0 5 10

0

40

80

Pea

k po

wer

den

sity

(W

/cm

2 )

v (mm/s)

Pressing Velocity

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Thickness of Electret

Factors Affecting Outputs

Arch-Shaped Flexible Generator

Q

Q2

Q1d1

d2

E1

E2

2 m1 m

Pressing

Releasing

J. Zhong & Q. Zhong et al, Nano Energy, 2013, 2, 491 64

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65

Pressing

Releasing

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Power Shoe

63 LEDs, 157.5 V

0 2 4 6

0

20

40

Cu

rren

t (

A)

Time (s)

Power Textile

IR Wireless sensor

Chinese Paten No. 201320434010.7

Output current > 6 mA

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Paper-Based Flexible Generator

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Paper Metal (M) Polymer

Paper

Coating P@Pre‐Paper

Assembling

Ⅱ Ⅲ ⅣⅠ

100 μm 500 nm

Evaporate M 

Q. Zhong & J. Zhong et al., Energy Environ. Sci., 2013, 6, 1779

Charge Injection

PTFE

(c) (d)

(a) (b)

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NG

Blue LED

Turn over

Turn back

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An important first step in exploring

this power harvesting approach

at macro scale

Prof. G. K. FedderIEEE Fellow

Director of The Robotics Institute

Disney Research Pittsburg

Carnegie Mellon University

Highlight

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