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MEMS-BASED

ENERGY HARVESTER

“ICT-Energy 2016: Energy Efficiency and Sustainability in ICT“ August 18, 2016

Energy Efficiency and Sustainability in ICT

Cristina Rusu, 18,08.2016

ACREO

Electromagnetic Sensors MEMS Inertial Sensors

Bio & Chemical Sensors

Wireless Systems

ENERGY HARVESTING &

AUTONOMOUS SENSING



Safety & security

Environment

Manufacturing

Automotive

Transport

smart Agriculture

Structural health

monitoring

Medical, sports

Battery

Power- MEMS / Energy Harvesters - A Solution to Battery Problem

• Ultra-low power

• Low data rate

• Low duty cycle

• Inaccessible

• Large quantities

Energy harvesting



Passenger stop button using miniaturized piezo harvester

&

Wireless stop pulse to the bus drivers computer (Volvo bus)

- 40 buttons eliminates 230 metres of cable reduce weight

(hundreds of kg) and fuel consumption (tons of CO2).

EXAMPLES…. Transportation

Only solution is - effective

- low cost small-size & Micro System (MEMS)harvesters

- in large quantities

to be cost effective.



EXAMPLES…. Toys

- VIBRATION HARVESTER

- PZT MATERIAL

- SUPERCAP

- MPU / ASIC

MEMS ENERGY HARVESTING SYSTEM

… with focus on topics where R&D for improvement are / can be done

Smart mems piezo based energy harvesting with

integrated supercapacitor and packaging

EU Horizon 2020 (2014-2018)

© LivaNova

Reproduced with

permission

CHALMERS

MODELLING



Energy flow of Piezoelectric Harvester: 1. Capturing the mechanical stress from the available source 2. Converting the mechanical energy into electrical energy with piezoelectric transducer 3. Processing and storing the generated electrical energy

Losses ….

Enviroment

Excitation Energy

• Mechanical loss Mechanical Vibration

Energy

• Mechanical - Electrical Transduction Loss

Electrical

Energy Generated

• Electrical loss Electrical

Energy Output



Modelling / Simulations ….

Analytical model - physical electro-

mechanical model

Finite element simulation (Comsol,

Ansys, Spice)

Damping mechanisms • Intrinsic

• PZT

• Viscous

o Drag forces (difficult to estimate)

o Squeeze film effects

Intrinsic

damping Molecular

damping

Viscous

damping



Design & Fabrication ….

For IZMs packaging process

min 5 µm Cu UBMs are needed

PZT mech-el cantilever converter

Encapsulated (WLP) low frequency

vibrating mechanical Silicon MEMS resonator

Sil-Via® TSVs for electrical output

to ASIC and rest of the system

Hermetic W2W

metal bond frames



…. and Characterization

Laser Doppler vibrometer + shaker + vacuum chamber

• Mechanical characteristics

• Piezo-mechanical coupling

• Damping / losses - air & vacuum

• Verification of harvester model

PIEZOELECTRIC MATERIAL

- PZT -



Small-size harvesters MEMS

Source: S-G Kim et.al “Piezoelectric MEMS for Energy

Harvesting.” MRS Bulletin 37.11 (2012): 1039–1050

Why Piezoelectric for Energy Harvesting?

• Standard MEMS processes are available

for many piezoelectric materials

• Directly convert mechanical energy into

electrical energy

• Directly integrated into monolithic MEMS-

scale systems



PZT (Lead Zirconate Titanate) film optimization

• FOM (e31)2 / R

• Electro mechanical coupling (e31) is typically higher for <100> PZT than for <111> PZT

• R is normally higher and leakage current lower for <111> PZT and doped PxZT than non doped <100> PZT.



PZT - Microstructural Characterisation

PZT (100)/(001)

Buffer

Pt TiO2

SiO2

0.2 µm

e31 -18 C/m2 (-13 C/m2)



Non destructive poling

and testing on wafer level

Quality control with DBL

- e31 measurements -

Poling and Test Systems

4 point bending setup with heating unit and

Inverse e31 test setup with heating chamber

0 5 10 15 20 25 30 35-16

-15

-14

-13

-12

-11

-10

-9

-8

-7

-6

0

20

40

60

80

100

120

140

W22001W12-Sample1

Poling +20V 120C 450s +600s field cooling

e31av [C/m2]

Bias Voltage [V]

Temperature

time [min]

poling region

field removed, initial decay

increase by poling temperature decay

In-situ measurement of e31 during Tpoling

poling

study

SUPERCAPACITOR

- Renewal sources are not continuous -



Energy storage - Supercapacitor

- Energy is stored electrostatically on surface of material (does not involve

chemical reactions)

Can be charged quickly leading to a very high power density

Do not lose their storage capabilities over time

Can last for millions of charge / discharge cycles without losing energy storage

capability.

Low energy density (the amount of stored energy per unit weight is very small,

compared to batteries).



Energy storage - Supercapacitor

- Development nanomaterials from renewal sources - cellulose

- Build all components: nanostructured carbon electrodes, separators and parts of

electrolyte.



Supercapacitor – Materials

Electrode

3D structured carbon nanofiber / MnO2 composite material

(NCNF / MnO2) exhibits best performance with high specific

capacitance (108.6 F/g @ 0.5A/g) and excellent power

capability (84.3 F/g @ 15 A/g).

Separator

The glass fiber with high thermal stability up to 600 oC,

excellent mechanical property and high uptake of different

electrolytes.

Electrolyte

• High temperature electrolyte EMIM Ac ionic liquid enables

high working voltage window up to 1.5 V and increases

energy density to 21.1 Wh/kg.

• Temperature durable PVA / H3PO4 gel electrolyte with

reduced leakage risk and high package capability. Device

can deliver 82 mF after high temperature exposure.

Energy storage Energy storage - Supercapacitor



Energy storage

Battery and supercapacitor challenges

• Leakage (requires more frequent charging)

• Output impedance limiting drive capability

• Parasitics (charge/energy stored in unwanted caps)

• Ageing, lifetime, reliability

ASIC & Power management



Ultra-low-power integrated power management energy harvesting

Key goal: Efficient extraction of very low power-levels (in the µW range)

Includes:

• Piezoelectric-harvester interface circuits (rectifier) for power-transfer

• DC-DC power conversion

• Voltage regulation

• Control circuitry



Ultra low PMU -

Rectifier must be able to conduct for very low input voltages in

“standard” CMOS technology

Loading conditions

• Impedances and switching affect the harvester

• If you take out all power “at once”, the cantilever stops and needs

new vibration input

• Non-periodical waveforms and transients.

• All power should be taken out before next vibration input



Ultra low PMU -

Effect of and need for regulator



Ultra low PMU – System Overview

SUMMARY


Cristina Rusu, 18,08.2016 This project has received funding from the European Union’s Horizon 2020

research and innovation programme under grant agreement No 644378.

Scaling piezoelectric vibration harvester:

• Resonance frequency 1 / (scaling factor)

• Cpzt scaling factor

• Rload_opt const. (same piezoel. mat. coupling coef = const. and

damping ratio = const.)

• Poutput (scaling factor)4 (acceleration vibr = const.)

• Poutput const. (amplitude vibr = const.)

SUMMARY

Mechanical MEMS harvesters will have to improve the

EFFICIENCY in order to enter the market



Translating the technologies into validated systems

Vibration energy harvesting (TRL2 TRL5)

Challenge

• Low frequency, small vibr. amplitude,

small size

Approach

• Modelling

• Piezoelectric material (quality,

thickness)

Packaging (TRL3 TRL6-7)

Challenge

• Size and reliability

Approach

• Flat panel packaging, 2D / 3D

Energy storage (TRL2 TRL4-6)

Challenge

• Rechargeable, energy density,

maturity

Approach

• Functionalisation of electrode

materials

Tailored ASICs (TRL2 TRL6)

Challenge

• Low energy consumption, small size

Approach

• Efficiency, very low static energy

consumption

This project has received funding from the European Union’s Horizon 2020

research and innovation programme under grant agreement No 644378.



Acknowledgements

Thorbjörn Ebefors, Silex

Jacob Wikner, Linköping University

Tanja Braun, Fraunhofer IZM

Peter Enoksson, Chalmers Technical University

Renzo DalMolin, LivaNova

An Nguyen-Dinh, Vermon

THANK YOU!

Cristina Rusu [email protected] +46 709151826

This work has received funding from:

• The European Union’s Horizon 2020 research and innovation programme under grant

agreement No 644378

• Sweden’s Innovation Agency VINNOVA “Smart energy optimization via energy harvesting

utilizing new Swedish piezo mems technology”

mailto:[email protected]

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