Piezoelectric MEMS Energy Harvesters - BFH · PDF filePiezoelectric MEMS Energy Harvesters Danick Briand, ... Vibration sources ... Exciter Control Type 1050 Resistor High g shaker

PiezoelectricPiezoelectric MEMS MEMS EnergyEnergy HarvestersHarvesters

Danick Briand, D. Isarakorn, J. Pattanaphong, N.F. de Rooij

Team leader EnviroMEMS

Sensors, Actuators and Microsystems LabInstitute of MicroengineeringEPFL STI IMT-NENeuchâtel, Switzerland

http://[email protected]

2Energy Harvesting Workshop | Biel - CH27.10.10| D.Briand

Sources of energy and harvesting approaches

From Dr. C Van Hoof, IMEC - Holst Center


Towards miniaturization

From Dr. C Van Hoof, IMEC - Holst Center


Vibration sources

S. Roundy et al., Computer Communications 26 (2003) 1131–1144


Electrical parameters of energy harvesters

POWER

VOLTAGE

CURRENTLOAD


Three ways to convert vibrationsPiezoelectric

Strain in piezoelectricmaterial causes a charge separation (voltage acrosscapacitor)

Capacitive

Change in capacitance causes either voltageor charge increase.

Inductive

Coil moves through magnetic field causing current in wire.

LoadVs

C RsPiezoelectric generator

Amirtharajah et. al., 1998


Piezoelectric scavengers on silicon

Resonant type and impact type harvesters d31 or d33

Thick PZT sheet - Thick PZT films - Thin films (AlN, PZT)

F33 Mode (longitudinal)

V-

+

3

12

F33 Mode (longitudinal)

V-

+

3

12

V-

+V

-

+

-

+

-

+

3

12

3

12

31 Mode (transverse)

FV+-

3

12

31 Mode (transverse)

FV+-

3

12

FV+-

3

12

FV+-

3

12

3

12

30 µm

80-130 µm

LAAS-FR

InSensor

IMEC

1-10 µm


Piezoelectric micro energy harvesters

1. Impact generators2. Resonant generators

- d31 mode (transverse) - d33 mode (longitudinal)- AlN- Epitaxial films

AlN

Impact

d31

d33

Epi-PZT

Auburn Univ.IMEC

IMTEK

SAMLAB

National Taiwan Univ.


MEMS power generator

Objective

Design and fabricate a MEMS-basedpiezoelectric power generator for the vibrational energy harvesting

Project description•Optimize the structure and load impedance to maximizethe efficiency of the vibration-to-electricity conversion

•Develop microfabrication processes

•Study the effect of viscous air damping on the power generation

•Design a piezoelectric converter circuit

•Develop an experiment set-up for power generating test

Pow

er N

eeds

Pow

er O

utpu

t

TimePresent


Resonant type harvesterStructure design requirementsLow resonant frequency

The frequency range of the ambient vibrations 60-200 Hz

High power generationLarge stress in the PZT film Large deflection

Cantilever with a proof mass

- Heavy proof mass: low resonant frequency and high power generation- Low damping effect- Compactness

Modelling of PZT cantilever with a proof mass(1000um x 2000um) at 1g


Analytical power model (Roundy)

( )

( )( ) ( ) 2231

2231

2

22

2312

2 444

5.1

21

ζωζωζε

ω +++

⎟⎟⎠

⎞⎜⎜⎝

⎛ +

=bb

inb

sppPb

RCkRCk

Al

tttdERC

P

Measured parameters-Frequency-Damping ratio-Coupling factor-Dielectric constant-Piezo coefficient d31

P: output power (bimorph)R: resistive loadCb: PZT capacitanceEp: PZT Young’s modulusd31: piezoelectric coeff.ε: dielectric constanttp: PZT thicknessts: silicon thicknesslb: cantilever lengthAin: accelerationζ: damping ratiok: coupling coeff.ω: angular frequency


Piezoelectric films for energy harvesters

18.20.1823.3110018.2Epi-PZT (20/80)**

120.0130.1690012Poly-PZT (53/47)*

1.050.1000.1110.51.05AlN*

IFVFPFεr-e31 (Cm-2)Piezo material

*S. Trolier-McKinstry and P. Muralt, J. Electroceram. 12, 7 (2004)**Measured data

High piezoelectric coefficientLow dielectric permittivity


Si substrateSTOSRO bottom electrodeSingle crystalline piezoelectric film

SrTiO3: Strontium Titanate Oxide (STO)SrRuO3: Strontium Ruthenate Oxide (SRO)

Uniform control of the piezoelectric response over nanometer length scales

Atomically smooth and exhibit microstructural homogeneities

Very large piezoelectric coefficients

Limited to maximum thickness of 0.5 µm

Epi Piezo MEMS Harvester


Technology platform

Piezo SRO STO Silicon

a)

b)

c)

d)

e)

f)

Au/Cr

Before

After

D. Isarakorn et al. JMM, 2010


Epitaxial PZT cantilevers

Cantilever: 1000×2500×40 μm3

PZT thickness: ~100 nm

d31: ~130-140 pm/V

( )31 2

13 s p s s p

KdVs s h h h Lδ

= −+

3 3 2 4 2 4 2 24 4 6p s s p p s s p p s s p p s s pK s s h h s s h h s h s h s s h h= + + + +

ss : the compliance of the Si layer (7.7 × 10-12 m2/N) sp : the compliance of the PZT film (12.4 × 10-12 m2/N) hs : the thickness of Si layer hp : the thickness of the PZT film

Sensitivity: ~ 5 um/VQ factor: 230 in air

D. Isarakorn et al. JMM, 2010


Experimental setup

Multimeter(Agilent 34411A)

Power AmplifierType 2712

Exciter ControlType 1050

Resistor

High g shakerType 4811

Accelerometer Type 4374

Metallic box

Bruel & Kjaer vibration exciter system- Max acceleration 210g - Maximum displacement 12.7 mm- Frequency 1 Hz – 10kHz - Frequency resolution 1.19 mHz


Experimental results


Epitaxial PZT cantilever with mass: ~500 nm PZT

0 5 10 15 20 25

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

Out

put p

ower

(μW

)

Load resistance (kΩ)

0.1 g 0.3 g 0.5 g

23 nW @ 1 kΩ

160 nW @ 2.2 kΩ

370 nW @ 2.2 kΩ

f=2.3 kHz

Front

Back

Epi PZT MEMS energy harvester

D. Isarakorn et al. Proc. PowerMEMS, 2010


Epi Piezo MEMS Harvester - comparison

SAMLAB

SAMLAB


Epi Piezo MEMS Harvester - Optimisation

3.63.71795370.1578Typ

C (nF)RL (kΩ)f (Hz)Vac (mV)Iac (mA)P (µW)

Simulation results @ 0.5g of acceleration

Base Mass

STOSi PZTSROSiO2

Simulation parametersd31: 130 pC/NDielectric constant: 100PZT thickness: 500 nmk31: 0.23Damping: 0.0004Acceleration: 0.2 and 0.5g

L

W

Length of the beam: 1500 µm

Width of the beam: 750 µm


Thick PZT sheet harvesters

Base

WH

Cantilever: W × L × H µm3

L

Glue

• Cantilever size: 3000 x 5000 x 50 (100 and 150) µm3

• Thickness of PZT sheet : 135 µm• Adhesive bonding• Gap of interdigitated electrodes : 150 - 200 µm

Si PZT Au

1 mm

Thick PZT cantilever


Ouput power measurement on impact mode

Impact type harvester

0.111.5250

0.061.2240

0.030.8530

0.0120.6220

0.0060.410

Max. I @ 10Ω (µA)Max. Vo (Volts)Amplitude (µm)

0 80000 160000 2400000.0

0.8

1.6

2.4

3.2

Out

put p

ower

(nW

)

Load resistance (Ω)

Output power (nW) @ 10 um Output power (nW) @ 20 um Output power (nW) @ 30 um Output power (nW) @ 40 um Output power (nW) @ 50 um

-Max. output power :

3.2 nW @ 267 kΩ

- Optimisation: cantilevers with different stiffness and differentgaps of IDEs on piezo

Open circuit voltage and current measurement

Open circuit voltage waveform

0.0 0.2 0.4 0.6 0.8 1.0 1.2-0.3

0.0

0.3

0.6

0.9

1.2

1.5

Ope

n ci

rcui

t vol

tage

(V)

Time (S)

Vo (V)

0.00 0.05 0.10 0.15 0.20 0.25 0.30-0.3

0.0

0.3

0.6

0.9

1.2

1.5

Ope

n ci

rcui

t vol

tage

(V)

Time (S)

Vo (V)


Conclusions

MEMS based energy scavengers- Resonant and impact types- Modelling, technology platforms, characterisation tools- Variety of materials and characteristics

Potential for:- Compactness, multi-elements: Cost ???- CMOS integration on chip- Autonomous smart systems : no battery !

Application first, solution second !!!


Acknowledgements

Research work

University of Geneva, CH

HES Geneva, CH

University of Yale, USA

Funding:

SNF-NCCR MaNEP program: Materials with Novel Electronic Properties


http://samlab.epfl.ch

Danick Briand : [email protected]

Sensors, Actuators and Microsystems LabInstitute of MicroengineeringEPFL STI IMT-NENeuchâtel, Switzerland

Contact detailsContact details

THANK YOU !

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Piezoelectric MEMS Energy Harvesters - BFH · PDF filePiezoelectric MEMS Energy Harvesters Danick Briand, ... Vibration sources ... Exciter Control Type 1050 Resistor High g shaker