Technology Innovation Report v17

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Energy Harvesting

Through Piezo-

materialMD AFZALUL KARIM

MEHDI AHMADI

MSES 5060

Technology Innovation

Course coordinator: Dr. Nourredine Boubekri

Submission Date: 12-10-2012


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Executive Summary

Piezoelectric or more generally, electro elastic materials exhibit electromechanical coupling.

They experience mechanical deformations when placed in an electric field and become

electrically polarized under mechanical loads. These materials have been used to make various

electromechanical devices. Examples include transducers for converting electric energy to

mechanical energy or vice versa, resonators and filters for telecommunication and timekeeping,

and sensors for information collection. Piezoelectricity has been a steadily growing field for

more than a century, progressed mainly by researchers from applied physics, acoustics, and

materials science and engineering, and electrical engineering. After World War II,

piezoelectricity research has gradually concentrated in the IEEE Society of Ultrasonic,

Ferroelectrics, and Frequency Control. The two major research focuses have always been the

development of new piezoelectric materials and devices. All piezoelectric devices for

applications in the electronics industry require two phases of design. One aspect is the device

operation principle and optimal operation which can usually be established from linear analyses;

the other is the device operation stability against environmental effects such as a temperature

change or stress, which is usually involved with nonlinearity. Both facets of design usually

present complicated electromechanical problems. Due to the application of piezoelectric sensors

and actuators in civil, mechanical, and aerospace engineering structures for control purposes,

piezoelectricity has also become a topic for mechanics researchers. Mechanics can provide

effective tools for piezoelectric device and material modeling. Mechanics theories of composites

are useful for predicting material behaviors. This paper will give a clear idea about piezoelectric

materials, how it works as an energy harvesting and wide range of applications.


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Table of Contents

Chapter 1 ....................................................................................................................................................... 1

Introduction to Piezoelectricity .................................................................................................................... 1

1.1 Introduction: ....................................................................................................................................... 1

1.2 History: ................................................................................................................................................ 3

Chapter - 2 .................................................................................................................................................... 1

Introduction to piezoelectric energy harvesting........................................................................................... 1

2.1 Piezoelectric Material: ........................................................................................................................ 1

2.2 How Piezoelectricity Works ................................................................................................................ 3

2.3 What is piezoelectric energy harvesting? ........................................................................................... 5

2.4 Piezoelectric energy harvesting with alternatives .............................................................................. 6

2.4.1 Photonic ....................................................................................................................................... 6

2.4.2 Thermal ........................................................................................................................................ 7

2.4.3 Vibrational .................................................................................................................................... 8

3. Piezoelectric as an energy harvester (vibration harvesting) ..................................................................... 9

3.1 Wideband ............................................................................................................................................ 9

3.2 Damping: ........................................................................................................................................... 11

3.3 Remote controllers ........................................................................................................................... 12

Chapter 4 ..................................................................................................................................................... 14

Utilization of New Materials for Piezo-electric energy harvesters ............................................................. 14

4.1 MEMS Piezo-electric energy harvesting ........................................................................................... 14

4.2 MEMS piezoelectric harvester with record power output ............................................................... 16

4.2.1 Record and novel material ......................................................................................................... 16

4.2.2 Vacuum package ........................................................................................................................ 17

4.2.3 Fully Autonomous ...................................................................................................................... 18

4.3 Thermal Acoustic Piezo Energy Conversion ................................................................................... 19

4.3.1 TAPEC Electricity ........................................................................................................................ 20

4.3.2 Advantages of TAPEC ................................................................................................................. 21

4.4 Turning heat into sound, then electricity ......................................................................................... 21


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4.4.1 How to Get Power from Heat and Sound .................................................................................. 22

4.5 Piezoelectric ribbons and fibers ........................................................................................................ 24

4.6 Zinc Oxide (ZnO) nanowire................................................................................................................ 26

4.6 Piezoelectric graphene ...................................................................................................................... 28

4.7 Optimal shape piezoelectric energy harvesters ................................................................................ 29

4.8 technique for fabricating piezoelectric ferroelectric nanostructures .............................................. 30

4.9 Giant piezoelectric effect to improve energy harvesting devices .................................................... 32

4.10 Potential for lead-free piezoelectric ceramics ................................................................................ 34

4.11 Electro-active papers ...................................................................................................................... 36

4.12 Electroactive polymers and piezoelectric Energy harvesting Devices ............................................ 38

4.13 Energy Harvesting from Piezoelectric Polymers ............................................................................. 39

4.13 Piezoelectric fabric that can detect and produce sound ................................................................ 42

4.13.1 Microphone check ................................................................................................................... 42

4.13.2 Sound results............................................................................................................................ 43

Chapter - 5 .................................................................................................................................................. 44

Applications of piezoelectric energy harvesters ......................................................................................... 44

5.1 Consumer Electronics ....................................................................................................................... 44

5.1.1 Energy harvesting Backpack ....................................................................................................... 44

5.1.2 Piezoelectric kinetic energy harvester for mobile phone from Nokia ....................................... 46

5.1.3. Small scale wind turbines (Contact-less Piezoelectric Wind Turbine)................................... 47

5.2 Energy harvesting for vehicles .......................................................................................................... 49

5.2.1 Piezoelectric Power Source for tire pressure monitoring .......................................................... 49

5.2.2 Piezoelectric roads for California ............................................................................................... 51

5.2.3 Energy harvesting for robots ..................................................................................................... 52

5.3. Healthcare ........................................................................................................................................ 56

5.3.1 Breakthroughs with sensing in the human body ....................................................................... 56

Chapter 6 ..................................................................................................................................................... 57

Energy Harvesting Market Shares, Strategies, and Forecasts, Worldwide ................................................. 57

Citation: ......................................................................................................................................................... a


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Chapter 1

Introduction to Piezoelectricity

1.1 Introduction:

Many historical studies have been dedicated to the discovery of novel effects and phenomena.

Following the discovery of a new basic phenomenon and the emergence of a novel field, much

less attention was dedicated to the early development of physical research. This paper will

describe the history of piezoelectricity after the discovery of the effect to its consolidation into an

accepted body of experimental and theoretical knowledge. This process seems to recur in the

establishment of novel scientific subfields and thereby, knowledge. The mere discovery of an

effect (in piezoelectricity that pressure induces electric polarity in crystals) was not enough to

establish a scientific subfield. It could have been left as merely another curious experimental fact

unconnected to any other. A subfield emerged only with subsequent study of the observed effect

and related phenomena under various conditions, which resulted in the knowledge of their

characteristics and laws. Such study is neither self-evident nor inevitable. The subsequent study

depended both on the phenomenon and on a few scientists interested in issues that it raised; the

interest stemming from their own theoretical experimental, or occupational concerns, and their

earlier works. The emergence of a new subfield requires a basic consensus on the phenomena

that it encompasses and their characteristics. As this history shows, such a consensus evolved via

experimental study, theoretical arguments, and controversy. Its evolution was part of a process of

consolidation that the new field underwent in the first two decades after its discovery. At the end

of this process piezoelectricity encompassed an accepted body of knowledge consisting in


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experimental findings and a mathematical theory that accounted for them. Still, many issues

were left open and were the subject of disagreement between scientists. That the subfield of

piezoelectricity was compatible with the general concepts and laws of contemporary science

enabled its consolidation. Discordance with the accepted truths of physics would probably have

precluded a consensus on the theory.

Beyond the interest in the study of mundane gross matter phenomena, there are good specific

reasons to draw historians and philosophers of science to the early history of piezoelectricity.

Though almost unknown outside the professional community, piezoelectric devices are today

ubiquitous. Virtually everyone in the West possesses at least one device based on piezoelectric

technology. Most of us carry at least one piezoelectric device a few millimeters from the skin.

All quartz watches and clocks are based on piezoelectricity. The piezoelectric resonator is the

basis for most electronic time keepers and regulators. Thus, most electronic devices contain such

a resonator, which utilizes the two basic effects of piezoelectricity: the induction of electricity by

changes of pressure and the converse induction of strain by changes in the electric field in

crystals. Yet, time keeping is but one application of the phenomenon, and its scientific study

continues unabated. Transducers, sensors, actuators, pumps, motors, and smart structures are

only some of the central devices that employ the piezoelectric effect. Electric communication,

medical diagnostics, computers, industrial sensors, and micro electromechanical (MEMS)

devices are a few examples for the application of the piezoelectric effect.[1]


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1.2 History:

Piezoelectricity was discovered in 1880 by Jacques and Pierre Curie when studying how pressure

generates electrical charge in crystals (such as quartz and tourmaline). Its use in submarine sonar

in World War 1 generated intense development interest in piezoelectric devices.

Most modern piezoelectric materials are ceramics, although polymeric and single crystals also

exist and are used commercially in many applications.

The term ceramic's meaning has evolved a great deal from its Greek root keramos, meaning

pottery (or potters clay). Ceramic materials can now be broadly considered to be all inorganic

non-metallic materials. However, it is more useful to classify them as polycrystalline non-

metallic materials that acquire mechanical strength through a sintering process. The inherent

physical properties of ceramics have made them desirable for use in a wide range of industries.

The first applications in the electronics sector made use of their inherently high electrical

resistivity, and intrinsic stability for fabrication into insulating bodies needed to carry and isolate

electrical conductors.

However, these immediately apparent properties exploited in the first half of the twentieth

century are only the most obvious of a wide range of properties. Materials with unusually high

dielectric constants (er > 2000-10,000) were used due to the phenomenon of their ferroelectric

nature. These materials where first employed in high-dielectric capacitors (barium titanate

[BaTiO3] based), and later developed into:

piezoelectric transducers positive temperature coefficient (PTC) devices
http://www.piezoinstitute.com/about/piezohistory/index.phphttp://www.piezoinstitute.com/about/piezohistory/index.phphttp://www.piezoinstitute.com/about/piezohistory/index.phphttp://www.piezoinstitute.com/about/piezohistory/index.php


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electro-optic light valves

Some of the more recent developments in the field of ferroelectric ceramics are their use in:

medical ultrasonic composites high displacement piezoelectric actuators thick/thin films

The birth of ferroelectric ceramics as a useful class of materials came about as a result of:

1. Discovery of unusually high dielectric constant in barium titanate

2. Discovery that the origin of this high dielectric constant was due to a permanent internal

dipole momentferroelectricity. This allowed the development of ABO3 structure ferroelectrics

3. Discovery of electrical poling process within the ceramics, giving rise to single-crystal like

properties

Over the next few decades, new piezoelectric materials and applications were explored and

developed. Piezoelectric devices began to emerge in many applications. Ceramic phonograph

cartridges made record players cheaper to maintain and easier to build. Ultrasonic time-domain

reflectometers could find flaws inside cast metal and stone objects, which improved structural

safety.

Other developments included new designs for piezoceramic filters used in radios and televisions,

and the piezoelectric igniter, which generates sparks for gas ignition systems by compressing a

ceramic disc.
http://www.piezoinstitute.com/about/piezohistory/index.phphttp://www.piezoinstitute.com/about/piezohistory/index.phphttp://www.piezoinstitute.com/about/piezohistory/index.phphttp://www.piezoinstitute.com/about/piezohistory/index.php


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The most commonly used ferroelectric materials are PZT (Pb[Zr,Ti]O3) ceramics, which are

based on the cubic perovskite structure. Most commercial materials are based on morphotropic

phase boundary (mpb) compositions. (A mpb separates solid solutions of the same prototype

structure but with different structural distortions.) The mpb in PZT separates rhombohedral and

tetragonal phases.

More recently, using domain engineering in single crystals it is possible by the use of appropriate

crystal cuts to maximize the piezoelectric properties. However, it is not possible to produce

useful size single crystals of PZT because it melts incongruently. However, it is possible to grow

large crystals of PMN-PT and PZN-PT (Pb[Zn1/3,Nb2/3]O3PbTiO3) with mpb compositions.

The pioneering work at Penn State by Tom Shrout has shown that it is possible to achieve

piezoelectric properties that are nearly an order of magnitude greater than those achievable with

PZT ceramics.

The environmentally-focused agenda of most governments includes the legislated reduction in

the industrial use of lead and lead containing materials. For many industrial sectors the use of

lead containing piezoelectric materials (such as PZT, or PMN-PT) is permitted because the

societal advantages outweigh any perceived dangers. The lead in PZT is chemically bound

within its crystalline structure and there is no evidence that this lead can leach out into the

environment. However, this has not stopped the aggressive development of lead-free

piezoelectric materialsnotably by research groups in Japan. Impressive research has uncovered

new lead-free compositions that might one day offer potential replacement strategies for many

applications[2].


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Chapter - 2

Introduction to piezoelectric energy harvesting

2.1 Piezoelectric Material:

Simply stated, piezoelectric materials produce a voltage in response to an applied force, usually a

uniaxial compressive force. Similarly, a change in dimensions can be induced by the application

of a voltage to a piezoelectric material. In this way they are very similar to electrostrictive

materials.

Figure 1: Piezoelectric EffectThese materials are usually ceramics with a perovskite structure (see figure 1). The perovskite

structure exists in two crystallographic forms. Below the Curie temperature they have a

tetragonal structure and above the Curie temperature they transform into a cubic structure. In the

tetragonal state, each unit cell has an electric dipole, i.e. there is a small charge differential

between each end of the unit cell.


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Figure 2: Shows the (a) tetragonal perovskite structure below the Curie temperature and the (b) cubic structure above the

Curie temperature.

The piezoelectric effect occurs only in nonconductive materials. Piezoelectric materials can be

divided in 2 main groups: crystals and cermaics. The most well-known piezoelectric material is

quartz (SiO2).

Crystals1) Quartz (SiO2)2) Aluminum orthophosphate,(AlPO4)3) Gallium orthophosphate (GaPO4)4) Tourmaline

Ceramics1) Barium titanate BaTiO32) Lead zirconate titanate PZT

Other Materials1. Zinc oxide (ZnO)2. Aluminum nitride (AlN)3. Polyvinylidene fluoride (PVDF)


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4. Lithium tantalate5. Polyvinylidene fluoride6. Lanthanum gallium silicate7. Potassium sodium tartrate

Ceramics with perovskite tungsten-bronze structures:1. BaTiO3,2. KNbO3,3. Ba2NaNb5O5,4.

LiNbO3,

5. SrTiO3,6. Pb(ZrTi)O3,7. Pb2KNb5O15,8. LiTaO3,9. BiFeO3,10.NaxWO3

2.2 How Piezoelectricity Works

1. Normally, the charges in a piezoelectric crystal are exactly balanced, even if they're notsymmetrically arranged.


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Figure 3: Balanced charge2. The effects of the charges exactly cancel out, leaving no net charge on the crystal faces.

(More specifically, the electric dipole momentsvector lines separating opposite

chargesexactly cancel one another out.)

Figure 4: Charges cancel one another out3. If someone squeezes the crystal, applying force helps the charges out of balance.

Figure 5: Crystal is squeezed


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4. Now the effects of the charges (their dipole moments) no longer cancel one another outand net positive and negative charges appear on opposite crystal faces. By squeezing the

crystal, a voltage across its opposite faces is produced which is called piezoelectricity.

Figure 6: Generation of piezoelectricity2.3 What is piezoelectric energy harvesting?

The increasing demand for completely self-powered electronics has caused an increase of

research into power harvesting devices over the past decade. With the advances being made in

wireless technology and low power electronics, sensors are being developed that can be placed

almost anywhere. However, because these sensors are wireless, they require their own power

supply which in most cases is the conventional electrochemical battery. Once these finite power

supplies are extinguished of their power, the sensor must be obtained and the battery replaced.

The task of replacing the battery is tedious and can become very expensive when the sensor is

placed in a remote location. These issues can be potentially alleviated through the use of power

harvesting devices. The goal of a power harvesting device is to capture the normally lost energy

surrounding a system and convert it into usable energy for the electrical device to consume. By

utilizing these untapped energy sources, electronics that do not depend on finite power supplies,

such as the battery, can be developed. One source of typically lost energy is the ambient

vibrations present around most machines and biological systems.


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The piezoelectric effect converts mechanical strain into electric current or voltage. This strain

can come from many different sources. Human motion, low-frequency seismic vibrations, and

acoustic noise are everyday examples. Except in rare instances the piezoelectric effect operates

in AC requiring time-varying inputs at mechanical resonance to be efficient.

Most piezoelectric electricity sources produce power on the order of miliwatts, too small for

system application, but enough for hand-held devices such as some commercially available self-

winding wristwatches. One proposal is that they are used for micro-scale devices, such as in a

device harvesting micro-hydraulic energy. In this device, the flow of pressurized hydraulic fluid

drives a reciprocating piston supported by three piezoelectric elements which convert the

pressure fluctuations into an alternating current.

2.4 Piezoelectric energy harvesting with alternatives

The most common types of energy harvesting are photonic, thermal, and vibrational [3].

2.4.1 Photonic

Common photonic harvesters rely on solar energy drawn with the use of photovoltaic.

Photovoltaic convert sunlight into electricity, and are commonly made from semiconductors.

They may be solar cells or panels. A tiny, inexpensive solar cell can generate 150 watts of

energy at noontime, so they can be relatively powerful and plentiful sources of energy.
http://en.wikipedia.org/wiki/Piezoelectric_effecthttp://en.wikipedia.org/wiki/Strain_%28materials_science%29http://en.wikipedia.org/wiki/Strain_%28materials_science%29http://en.wikipedia.org/wiki/Piezoelectric_effect


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Figure 7: Photon energyThe most obvious drawback of photonic harvesting is that sunlight is not on 24 hours a day,

which affects the amount of voltage generated. Voltage is also affected by waning light from

dusk or creeping light from the dawn, both of whihc change the angle of incidence of the light

which hits the device. Susceptibility to pollutants such as dust that blocks light from the cells

may further impede their efficiency. The fragility of photovoltaic devices is still yet another

concern.

2.4.2 Thermal

Unless objects are at absolute zero, they have thermal activity. Differences in temperature

between objects produce thermal gradients that can be used to generate electricity nearly

everywhere on Earth. Of course it is neither feasible nor practical to use any object in existence

to do this, as factors such as durability, cost, and efficiency would need to be factored in.
http://www.brighthubengineering.com/thermodynamics/3422-the-third-law-of-thermodynamics-what-happens-at-absolute-zero-temperature/http://www.brighthubengineering.com/thermodynamics/3422-the-third-law-of-thermodynamics-what-happens-at-absolute-zero-temperature/


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Figure 8: Thermoelectric micro-structures generate high voltagesThermoelectric devices used for energy harvesting convert thermal activity into electricity are

constructed from semiconductors. They don't require generators or pumps or fluids, and don't

require copius amounts of materials to build. The main requirements for operation are a heat

source and a heat sink.

Because thermoelectric elements produce DC power, a further requirement is that of a DC-DC

converter to ensure stability of the potential produced by the power source. One of their

drawbacks is that they are not as efficient as Stirling engines.

2.4.3 Vibrational

Vibrational devices feed off motion produced as a by-product in order to generate power, and so

are natural AC power sources. Because they are AC, they require rectifying and regulatory

circuits. Sources include the human gait, trains, motors, engines, and radio frequencies.

The two most common methods to generate power are that of electromagnetic induction and

piezoelectricity.

Electromagnetic induction is harvested using motors, with the difference being that the magnet

inside the coils moves back and forth instead of just spinning.
http://www.brighthubengineering.com/machine-design/8247-history-and-development-of-stirling-engine/http://www.guardian.co.uk/technology/2006/sep/28/energy.askjackhttp://www.guardian.co.uk/technology/2006/sep/28/energy.askjackhttp://www.brighthubengineering.com/machine-design/8247-history-and-development-of-stirling-engine/


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Figure 9: Volture V25W-ND cantilever piezoelectric energy harvester.Piezoelectric materials produce voltages under pressure changes brought about by sound waves

or touch or mechanical strain. Crystals made from this substance form diaphragms or are linked

to them, and they can function as speakers or microphones. For energy harvesting, piezoelectric

generators are usually cantilevers with masses attached to a free end.

Vibrational harvesting devices are useful monitoring equipment and machinery in industrial

environments without the use of batteries or cables. However, this method is not good to use in

devices where mobility is a requirement, due to concerns with stability and interference that will

impact features such as velocity and noise. They are also best used where the input is at a

consistent, predictable frequency [4].

3. Piezoelectric as an energy harvester (vibration harvesting)

3.1 Wideband

Thin film piezoelectric lead zirconate titanate (PZT) materials offer a number of advantages in

micro electro mechanical systems (MEMS) as such devices provide large motions with low

hysteresis in applications such as actuating mirrors [5], and raster scanning mirrors [6]. They also

provide good signal to-noise ratio in a wide dynamic range [711]. The piezoelectric coefficient

of PZT is more superior than other piezoelectric thin films, such as ZnO and AlN, due to the high


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energy density. Hence, PZT thin films are good transducer materials for MEMS based energy

harvesters [1214]. Vibration-based MEMS energy harvesters have received increasing attention

as a potential power source for microelectronics and wireless sensor nodes [15,16]. To date most

energy harvesters based on piezoelectric, electromagnetic and electrostatic transduction

mechanisms, particularly MEMS-based harvesters, operate at frequencies of more than 100 Hz

[1721]. Increasing compliant spring and bulk movable mass are required to achieve lower

resonant frequency. It is a great challenge to realize small size and low resonant frequency at the

same time due to the limitation of microfabrication processes and brittle properties of silicon

material. The generated power is theoretically proportional to the cube of the operation

frequency and drops dramatically at low frequencies [22]. Thus energy harvesters with low

resonant frequencies would result in reduced power output. However, harvesting energy from

low frequency vibrations, such as human motions (


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Renaud et al. [30] has reported a non-resonant impact-based energy harvester driven by a free

ball moving in a guided channel where top and bottom piezoelectric benders are mounted in

between. The method however does not benefit from the power enhancement of a resonant operation.

Aresonant impact-based energy harvesting prototype which utilizesa low-frequency resonator to directly

impact two high-frequencyPZT bimorphs in order to trigger their self-oscillations and generatepower at

high operation frequencies was also reported by Gu et al. [31]. The prototype suffered from large device

size and has not been realized by MEMS technology. In fact, none of the aforementioned works use

micro-scale approaches [32,33]. For a given acceleration, the vibration amplitude of an oscillator is

inversely proportional to the square of the vibration frequency. A lower resonant frequency requires an

increased displacementspace and mechanical stoppers to prevent damage of the oscillator, thus reducing

the generated power density of the device, though the mechanical stopper does broaden the frequency

bandwidth [34,35]. Instead of increasing the extra space to accommodate the displacement of the LRF

oscillator, by incorporating apiezoelectric HRF cantilever which is excited into self-oscillation

by the impact of the LRF cantilever and at the same time acts as an energy harvester. This will not only

reduce the device space and protect the oscillator, but also realize a wide operation band and FUC

behavior. As a result, additional significant power will be generated and power density of the system will

be improved.

3.2 Damping:

A damping mechanism suitable for use with a vibrating beam accelerometer comprising a

piezoelectric block mounted between the vibrating beam force transducer and the pendulum of

the instrument. The proof mass, or pendulum, is mounted for pendulous motion about a pair of

hinge means. Vibration of the instrument causes opposite charges to appear on electrodes which

are on two opposite faces of the block. These charged electrodes are connected to each other by a
http://pendulum.net/http://pendulum.net/


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resistor and so a current will flow through the resistance to neutralize the charge. The resistor

will then dissipate the vibration energy as heat. This energy dissipation is effectively damping.

3.3 Remote controllers

Piezoelectric film used for new remote that twists and bends September 25, 2011 by Nancy

Owano report Piezoelectric film used for new remote that twists and bends Leaf Grip Remote

Controller using piezoelectric film (sample) (PhysOrg.com) -- Murata Manufacturing Co. is

using high-transparency organic piezoelectric film for its two new devices, a remote control that

works by bending and twisting, and a touch-pressure pad that connects to PCs. Murata will ship

samples of both devices next year. Murata says the film they are using has a high piezoelectric

output constant; high transparency (light beam transmittance of 98% or higher according to the

internal haze measurement) and most notably it is free from the pyroelectric effect. Murata, in

its press release announcing the devices, stresses what is special about its film. Conventional

piezoelectric films are usually subject to a pyroelectric effect. The company says this is a

drawback because they cannot detect bending and twisting vibrations separately from changes in

temperature. Murata instead has developed a high-transparency piezoelectric film that is free

from the pyroelectric effect. Murata developed the film through a joint research effort with

Kansai University and Mitsui Chemicals. Piezoelectric film used for new remote that twists and

bends Enlarge Piezoelectric film used for new remote that twists and bends That bending and

twisting movement is the key feature of its new remote control device for TVs. The device is

called the Leaf Grip Remote Controller, and it can convey the tv users commands by using a

bending and twisting motion. The control device uses two piezoelectric films: one for detecting

bends and the other for detecting twists. Murata further describes the remote as using pigments to


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discharge electrons when it receives light, and is assembled with a photovoltaic cell that converts

light into electricity to provide it with a "battery-less feature." Piezoelectric film used for new

remote that twists and bends Touch pressure pad using piezoelectric film (sample) Piezoelectric

film used for new remote that twists and bends The second device that Murata announced is a

Touch Pressure Pad, which is a panel that can be connected to a PC. The touch panel can detect

vertical and horizontal finger movements and can measure the users pressure strength. For

example, the user can enlarge an image at high speed by pressing the panel firmly and at low

speed by pressing the panel lightly.

Figure 10: Leaf Grip Remote Controller using piezoelectric film


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Chapter 4

Utilization of New Materials for Piezo-electric

energy harvesters

4.1 MEMS Piezo-electric energy harvesting

Micro-Electro-Mechanical Systems, or MEMS, is a technology that in its most general form can

be defined as miniaturized mechanical and electro-mechanical elements (i.e., devices and

structures) that are made using the techniques of microfabrication. The critical physical

dimensions of MEMS devices can vary from well below one micron on the lower end of the

dimensional spectrum, all the way to several millimeters. Likewise, the types of MEMS devices

can vary from relatively simple structures having no moving elements, to extremely complex

electromechanical systems with multiple moving elements under the control of integrated

microelectronics. The one main criterion of MEMS is that there are at least some elements

having some sort of mechanical functionality whether or not these elements can move. The term

used to define MEMS varies in different parts of the world. In the United States they are

predominantly called MEMS, while in some other parts of the world they are called

Microsystems Technology or micromachined devices.

While the functional elements of MEMS are miniaturized structures, sensors, actuators, and

microelectronics, the most notable (and perhaps most interesting) elements are the microsensors

and microactuators. Microsensors and microactuators are appropriately categorized as

transducers, which are defined as devices that convert energy from one form to another. In the


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case of microsensors, the device typically converts a measured mechanical signal into an

electrical signal.

Figure 11: Components of MEMS

In recent years, a great effort has been devoted to the study of self-powered electronics by using

renewable power sources or energy scavengers to replace traditional batteries. Therefore, energy

harvesting technique which is used to collect and convert ambient energy into usable electrical

power has been considered as a promising solution and has attracted noticeable research

interests. Among many energy sources, vibration energy is ubiquitous in numerous applications

ranging from common household devices, trans-portation tools, and industry machines to human

motions. In addition, vibration-based energy harvesters (EHs) using MEMS technology are

reported to generate electricity based on piezoelectric, electromagnetic, electrostatic, and hybrid

mechanisms. Piezoelectric EHs convert mechanical strain into voltage output, i.e., electric field

across the piezoelectric layer, based on the piezoelectric effect. Because of the advantages of

simple configuration and high conversion efficiency, they have received much attention.

Currently, most investigations for power generation of vibration-based piezoelectric EHs focus

on the configuration of cantilever beam with or without proof mass in the form of unimorph,


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series triple layer bimorph, parallel triple layer bimorph in the d31 mode and d33 mode.

However, the performances, such as output voltage and power, of piezoelectric EHs with

piezoelectric elements in series or in parallel connections under similar mechanical strain

conditions, have not been thoroughly studied [36].

4.2 MEMS piezoelectric harvester with record power output

Recent research shows that, a piezoelectric harvesting device fabricated by MEMS technology

generates a record of 85W electrical power from vibrations. A wafer level packaging method

was developed for robustness. The packaged MEMS-based harvester is used to power a wireless

sensor node. Within the Holst Centre program on Micropower Generation and Storage, imec

researchers developed a temperature sensor that can wirelessly transmit data in a fully

autonomous way [37].

Micromachined vibrational energy harvesters operating in the frequency domain between 150

and 1000Hz are ideal devices to convert vibrations from machines, engines and other industrial

appliances into electricity. Thanks to their smaller dimensions, the micromachined devices are

the preferred candidates for powering miniaturized autonomous sensor nodes.

4.2.1 Record and novel material

By using cost-effective, CMOS compatible MEMS processes on 6 silicon wafers, imec

developed piezoelectric energy harvesters capable of generating up to 85W of power.

The harvester consists of a Si mass that is suspended on a beam with Aluminum Nitride (AlN) as


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piezoelectric material. By changing the dimensions of the beam and mass, the resonance

frequency of the harvester can be designed for any value in the 150-1200Hz domain.

Figure 12: Aluminum Nitride (AlN) as piezoelectric material

Not only the record power output, but also the use of AlN as piezoelectric layer, is a notable

achievement. AlN has several advantages in terms of materials parameters and ease of

processing compared to the commonly used PZT (Lead zirconate titanate). Just to name two:

AlN can be deposited up to three times faster while composition control is not an issue, thanks to

the stoichiometric nature of the material.

4.2.2 Vacuum package

Final achievement in the research is the development of a wafer-scale process to protect the

piezoelectric devices by a package. It was shown that the power output significantly increases by

the use of the vacuum package compared to packaging in atmospheric pressure. In a three step

process, glass covers are coated with an adhesive, vacuum bonded on top and bottom of the

processed wafer and diced.


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Figure 13: a): Wafer-scale vacuum package process flow. The wafer with the AlN piezoelectric energy harvester is bonded

between two glass wafers. The cavities in the glass wafer are etched with HF and the SU-8 bonding layer is applied with a

wafer scale roller-co

4.2.3 Fully Autonomous

The piezoelectric harvester was connected to a wireless temperature sensor, built op from of-the-

shelf components. After power optimization, the consumption of the sensor was reduced from

1.5mW to 10W, which is an improvement by three orders of magnitude. When subjected to

vibrations at 353Hz at 0.64g (indicating a realistic amplitude of the vibrations), the system

generated sufficient power to measure the environmental temperature and transmit it to a base

station with an interval of fifteen seconds. The result proves the feasibility of building fully

autonomous harvesters for industrial applications.

Once fully mature, the technology can be used to power sensors in industrial applications such as

tire-pressure monitoring and predictive maintenance of moving or rotating machine parts. Imec


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and Holst Centre do not go to market themselves, but perform the research together with

industrial players interested in commercializing the technology.

The result was obtained within the Micropower Program at Holst Centre, an open-innovation

initiative by imec and TNO[38].

4.3 Thermal Acoustic Piezo Energy Conversion

Thermal Acoustic (or Thermoacoustic) devices are a type of technology capable of either:

Drawing on sound waves to drive heat from location A to location B Capitalising on the difference between two temperatures to create sound which can,

subsequently, be turned into electricity by introducing a piezoelectric device.

Symkos heat to electricity conversion technology involves two processes, then. Firstly,

thermoacoustic devices (known as heat engines) convert heat into sound. Secondly, piezoelectric

devices convert this sound into electricity when pressure is applied to them. Symko himself

Figure 14: Fully autonomous wireless temperature sensor powered by a vibrational energy harvester


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compares the effects of pressure on piezoelectric devices to hitting your elbow a sudden,

painful impulse.

4.3.1 TAPEC Electricity

Professor Symko has drawn attention to how the electricity created as a result of Thermo

Acoustic Piezo Energy Conversion (TAPEC) could actually be used. Potential applications

include a number of areas in the home, where the TAPEC electricity could replace that produced

by household photovoltaic devices, like solar panels, which draw on the energy in the suns rays,

and for which another term is solar electric. Small TAPEC devices could also be incorporated

into PCs or laptops, which could draw on the machines internal heat to produce electricity from

and which, in turn, the PC or laptop could derive power from thus creating a satisfying and

efficient renewable energy circuit.

TAPEC electricity could also have military applications and, recognizing this, the US military is

involved in the Utah teams research - the US Army having injected finance into the venture.

Technology capable of providing a combat edge within a conflict zone could obviously prove

highly advantageous to those that own it and, according to Professor Symko, the US Army is

keen on taking care of waste heat from radar, and producing a portable source of electrical

energy which one can use in the battlefield to run electronics.

Another application is within the manufacturing industry. The purpose of industrial cooling

towers is to remove the heat associated with industrial processes. Rather than have this waste
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heat pass into the atmosphere, however, the Utah scientists propose drawing on it and applying

TAPEC technology in order to create electricity.

We are converting waste heat to electricity in an efficient, simple way by using sound, Symko

says. Itis a new source of renewable energy from waste heat.

4.3.2 Advantages of TAPEC

Among the advantages of TAPEC technology is the fact that it generates little or no noise

pollution. According to Symko, once the devices are able to be made more compact, they will

able to transform heat into sounds that the human ear cannot detect (ultrasonic). Whats more,

the sound-to-electricity conversion processes already involve an inherent loss of volume anyway.

Finally, the sound can be reduced through the application of muffling devices[39].

4.4 Turning heat into sound, then electricity

Figure 15: Physicist Orest Symko works on blowtorch


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University of Utah physicist Orest Symko demonstrates how heat can be converted into sound by using a

blowtorch to heat a metallic screen inside a plastic tube, which then produces a loud tone, similar to when

air is blown into a flute. Symko and his students are developing much smaller devices that not only

convert heat to sound, but then use the sound to generate electricity. The devices may be used to cool

electronics, harness solar energy in a new way, and conserve energy by changing waste heat into electric

power. Credit: (Credit: Image courtesy of University of Utah) University of Utah physicists developed

small devices that turn heat into sound and then into electricity. The technology holds promise for

changing waste heat into electricity, harnessing solar energy and cooling computers and radars [40].

4.4.1 How to Get Power from Heat and Sound

Symko's work on converting heat into electricity via sound stems from his ongoing research to

develop tiny thermoacoustic refrigerators for cooling electronics.

In 2005, he began a five-year heat-sound-electricity conversion research project named Thermal

Acoustic Piezo Energy Conversion (TAPEC). Symko works with collaborators at Washington

State University and the University of Mississippi.

The project has received $2 million in funding during the past two years, and Symko hopes it

will grow as small heat-sound-electricity devices shrink further so they can be incorporated in

micro machines (known as micro electro mechanical systems, or MEMS) for use in cooling

computers and other electronic devices such as amplifiers.

Using sound to convert heat into electricity has two key steps. Symko and colleagues developed

various new heat engines (technically called "thermo acoustic prime movers") to accomplish the

first step: convert heat into sound.
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Then they convert the sound into electricity using existing technology: "piezoelectric" devices

that are squeezed in response to pressure, including sound waves, and change that pressure into

electrical current. Most of the heat-to-electricity acoustic devices built in Symko's laboratory are

housed in cylinder-shaped "resonators" that fit in the palm of your hand. Each cylinder, or

resonator, contains a "stack" of material with a large surface area -- such as metal or plastic

plates, or fibers made of glass, cotton or steel wool -- placed between a cold heat exchangerand

a hot heat exchanger.

When heat is applied -- with matches, a blowtorch or a heating element -- the heat builds to a

threshold. Then the hot, moving air produces sound at a single frequency, similar to air blown

into a flute. "You have heat, which is so disorderly and chaotic, and all of a sudden you have

sound coming out at one frequency," Symko says.

Then the sound waves squeeze the piezoelectric device, producing an electrical voltage. Symko

says it's similar to what happens if you hit a nerve in your elbow, producing a painful electrical

nerve impulse. Longer resonator cylinders produce lower tones, while shorter tubes produce

higher-pitched tones.

Devices that convert heat to sound and then to electricity lack moving parts, so such devices will

require little maintenance and last a long time. They do not need to be built as precisely as, say,

pistons in an engine, which loses efficiency as the pistons wear.

Symko says the devices won't create noise pollution. First, as smaller devices are developed, they

will convert heat to ultrasonic frequencies people cannot hear. Second, sound volume goes down
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as it is converted to electricity. Finally, "it's easy to contain the noise by putting a sound absorber

around the device," he says [41].

4.5 Piezoelectric ribbons and fibers

Nanofiber-based piezoelectric energy generators could be scalable power sources applicable in

various electrical devices and systems by scavenging mechanical energy from the environment.

Piezoelectric nano generators made of PVDF (polyvinyllidenefluoride) or PZT (lead zirconate

titanate) and fabricated by means of electro spinning processes such as conventional, modified or

near-field electro spinning (NFES) are the key focuses of this paper. Material and structure

analyses on fabricated Nano fibers using tools such as XRD(X ray diffraction), FTIR(Fourier

transform infrared), SHG(second harmonic generation), PFM ( piezo response force microscopy)

and Raman spectroscopy toward the fundamental characterizations of piezoelectric Nano fibers

are also described.

Figure 16: Different layers of piezo electric fibers


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After decades of developments in the miniaturization of portable and wireless devices, new

power sources beyond rechargeable batteries have become important topics for current and

future stand-alone devices and systems. Specifically, ideal power sources should be scalable for

power demands of various portable devices without the necessity of a recharging process or

replacement. Recent work in the field of nanomaterials has shown considerable progress toward

self-powered energy sources by scavenging energy from ambient environments (solar, thermal,

mechanical vibration, etc.). In particular, the use of piezoelectric generators by nanomaterials as

a robust and simple solution for mechanical energy harvesting has attracted lots of attentions.

One of the earliest nanogenerators for possible energy scavenging applications from mechanical

strain utilized piezoelectric zinc oxide (ZnO) nanowires . By coupling their semiconducting and

piezoelectric properties, mechanical strains can be converted into electricity. In recent years,

numerous research groups have demonstrated results in the field of mechanical energy

scavenging using nanomaterials with different architectures, including: film- based, nanowire-

based and nano fiber-based nanogenerators. Film-based nanogenerators are often made by the

spin- on or thin-film deposition methods. Mechanical strains due to the bending, vibration or

compression of the thin-film structure can be the source of the energy generation. Nanowire-

based nano generators are typically made of semiconducting materials such as ZnO, ZnS , GaN

or CdS . These piezoelectric nanowires have been demonstrated to build up an electrical

potential when mechanically strained by an AFM tip, zig-zag electrodes or a compliant substrate

to convert mechanical strains into electricity. The third group of nano generators is based on

nanofiber s often constructed by the electro spinning process with piezoelectric materials such

as PZT or PVDF. PZT is a ceramic material exhibiting exceptionally good piezoelectric

properties and is only recently utilized in nanofiber based energy harvesters. Most of PZT- based


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energy harvesters have film-based structures, including the typical design of cantilever structure

with proof mass [42].

4.6 Zinc Oxide (ZnO) nanowire

Zinc oxide (ZnO) nanostructures are generating significant interest due to unique characteristics

that make them good candidates for UV optoelectronic applications such as biosensors and

resonators. These properties are due to the wide band gap of ZnO (3.37eV at room temperature)

and to its large exciton energy (60meV), which makes it possible to employ excitonic

recombination as a UV-lasing mechanism. ZnO is also a piezoelectric and bio-safe material that

has probably spawned the richest family of nanostructures to date. Moreover, the ferromagnetic

properties of ZnO doped with rare earth metals are also of interest for the design of novel devices

that store information as a particular spin orientation (spintronics).

Of the techniques for growing ZnO nanostructures with controlled dimensions, we have been

using two of the most common and cost-effective, namely, the catalytic vapor-liquid-solid (VLS)

method and a low-temperature technique based on chemical engineering. When optimized, both

approaches can be used to produce large-scale wafers and are suitable for commercial

production. Below Figure shows the schematics of the oven used in our VLS growth

experiments. We have generated a wide family of different ZnO nanostructures, including wires

(both vertically aligned and randomly oriented), ribbons, dots, flowers, branched structures, and

leaves, on a variety of substrates with crystalline or amorphous surfaces.
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Figure 17: Fabrication of zinc oxide (ZnO) nanowires using the catalytic VLS growth method. Insert: Transmission electron

microscope image of a nanowire with a gold (Au) particle at the tip. Ar: Argon. The room temperature photoluminescence (PL) spectra of typical ZnO nanowire samples are

characterized by two main emission bands. The first is a sharp free-exciton UV band that usually

centers on () 380nm, and the second is a widerbroad band observed between 420 and 700nm,

historically referred to as the green luminescence or deep-level emission band. Although all ZnO

nanostructures display both bands, their relative intensity varies depending on different growth

methods and parameters. Deep-level emission is the source of observed white light emission.

The assignment of this band is still controversial, and we have attempted to elucidate its origin.

In a recent experiment, different ZnO bulk samples were annealed for 1h at 501050C in the

presence of ZnO powder, metallic zinc, pure oxygen, or air. All the experiments, except

annealing in air, were performed in quartz-encapsulated samples filled with the corresponding

gas or powder. After annealing, PL spectra were recorded in the 27300K temperature range

using the 350nm line from an argon ion laser as the excitation source [43].
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4.6 Piezoelectric graphene

Graphene, the ultra-durable carbon material that holds promise for a range of applications, has

yet another trick up its single-atom-thick sleeve. Engineers at the University of Houston have

used quantum mechanical calculations to show that, merely by creating holes of a certain

configuration in a sheet of graphene, they can coax graphene into behaving like a piezoelectric

material. Piezoelectric substances generate electricity in response to physical pressure, and vice

versa, and scientists can use these materials for applications such as energy harvesting and

artificial muscles, as well as to make precise sensors. Graphene itself is not naturally

piezoelectric. But the Houston engineers reasoned that if they took either a semiconducting or

insulator form of graphene, punched triangle-shaped holes into it, and applied a uniform pressure

to the material, they could make that material act as though it were piezoelectric. The teams

calculations showed that triangular holes did indeed result in piezoelectric behavior, while

circular holes as they predicted did not. They also found that graphenes pseudo-

piezoelectricity was almost as strong as that of well-known piezoelectric substances such as

quartz. The authors suggest that triangular pores could be created in real graphene using

electron-beam radiation in a lab, which means these calculations can be tested using existing

methods. Nature has dealt humankind a very limited choice of effective electromechanical

materials that exhibit piezoelectricity, write the authors in their paper, accepted to the AIPs

Applied Physics Letters. Adding graphene to the list could potentially open new avenues of

use, both for graphene and for applications that rely on piezoelectricity [44].
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Figure 18: This illustration shows lithium atoms (red) adhered to a graphene lattice that will produce electricity when bent,

squeezed or twisted. Conversely, the graphene will deform when an electric field is applied, opening new possibilities in

nanotechnology.

4.7 Optimal shape piezoelectric energy harvesters

We aim at using variable shape cantilever beam to improve the efficiency of energy harvesting

from ambient vibration in wireless grid sensor applications. The cantilever beam is composed of

an active layer composed of a piezoelectric material and a metallic layer (unimorph design). A

tip mass attached to the free end of the cantilever beam is added to increase the inertial forces of

the structure. The introduction of the variable shape design is motivated by the fact that prismatic

shape beams are not efficient since only the part near to the clamped side can produce electrical

power thanks to the presence of stresses. By varying the geometry of the beam we redistribute

the stress along the beams length in order to increase the harvested power. In this work, the

equations of motion and associated boundary conditions are derived using Hamilton Principle.

We analyze the statics and dynamics of the variable geometry beam. In order to maximize the

harvested energy, we discuss the influence of the systems and excitations parameters on the

dynamic problem. Besides, we found that harvested energy is maximized for an optimum electric

load resistance. Concerning the beams shape, this work reveals that it should be as truncated as


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possible. In fact, trapezoidal cantilever with base and height dimensions equal to the base and

length dimensions of a rectangular beam will have a higher strain and maximum deflection for a

given load[45].

Figure 19: Usual structure of a piezoelectric vibration

4.8 Technique for fabricating piezoelectric ferroelectric nanostructures

Researchers have developed a soft template infiltration technique for fabricating free-standing

piezoelectrically active ferroelectric nanotubes and other nanostructures from PZT a material

that is attractive because of its large piezoelectric response. Developed at the Georgia Institute of

Technology, the technique allows fabrication of ferroelectric nanostructures with user-defined

shapes, location and pattern variation across the same substrate.

The resulting structures, which are 100 to 200 nanometers in outer diameter with thickness

ranging from 5 to 25 nanometers, show a piezoelectric response comparable to that of PZT thin

films of much larger dimensions. The technique could ultimately lead to production of actively-

tunable photonic and phononic crystals, terahertz emitters, energy harvesters, micrometers,
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micro-pumps and nano-electro-mechanical sensors, actuators and transducers all made from

the PZT material

Using a novel characterization technique developed at Oak Ridge National Laboratory, the

researchers for the first time made high-accuracy in-situ measurements of the nanoscale

piezoelectric properties of the structures. They are using a new nano-manufacturing method for

creating three-dimensional nanostructures with high aspect ratios in ferroelectric materials that

have attractive piezoelectric properties. They also leveraged a new characterization method

available through Oak Ridge to study the piezoelectric response of these nanostructures on the

substrate where they were produced.

Ferroelectric materials at the nanometer scale are promising for a wide range of applications, but

processing them into useful devices has proven challengingdespite success at producing such

devices at the micrometer scale. Top-down manufacturing techniques, such as focused ion beam

milling, allow accurate definition of devices at the nanometer scale, but the process can induce

surface damage that degrades the ferroelectric and piezoelectric properties that make the material

interesting.

Until now, bottom-up fabrication techniques have been unable to produce structures with both

high aspect ratios and precise control over location. The technique reported by the Georgia Tech

researchers allows production of nanotubes made from PZT (PbZr0.52Ti0.48O3) with aspect

ratios of up to 5 to 1.
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The ferroelectric nanotubes are especially interesting because their properties including size,

shape, optical responses and dielectric characteristicscan be controlled by external forces even

after they are fabricated.

For example, the piezoelectric effect could permit fabrication of nano-muscle tubes that would

act as tiny pumps when an electric field is applied to them. The fields could also be used to tune

the properties of photonic crystals, or to create structures whose size can be altered slightly to

absorb electromagnetic energy of different wavelengths[45].

4.9 Giant piezoelectric effect to improve energy harvesting devices

Researchers in the Department of Materials Science and Engineering and the Materials Research

Institute at Penn State are part of a multidisciplinary team of researchers from universities and

national laboratories across the U.S. who have fabricated piezoelectric thin films with record-

setting properties. These engineered films have great potential for energy harvesting

applications, as well as in micro-electro-mechanical-systems (MEMS), micro actuators, and

sensors for a variety of miniaturized systems, such as ultrasound imaging, microfluidics, and

mechanical sensing.
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Figure 20:Comparison of the figure of merit for PMN-PT film with other reported piezoelectric values for micromachined

actuators and energy harvesting devices

Piezoelectric materials can transform electrical energy into mechanical energy and vice versa.

Most MEMS utilize silicon, the standard material for semiconductor electronics, as the substrate.

Integrating piezoelectric thin films onto silicon-based MEMS devices with dimensions from

micrometers to a few millimeters in size will add an active component that can take advantage of

motion, such as a footstep or a vibrating motor, to generate electric current, or use a small

applied voltage to create micron level motion, such as in focusing a digital camera.

Previously, the best piezoelectric MEMS devices were made with layers of silicon and lead

zirconium titanate (PZT) films. Recently, a team led by Chang-Beom Eom of University of

Wisconsin-Madison synthesized a lead magnesium niobate-lead titanate (PMN-PT) thin film

integrated on a silicon substrate.

The Penn State team, led by Susan Trolier-McKinstry, professor of ceramic science and

engineering, and including research associate Srowthi Bharadwaja, PhD, measured the electrical

and piezoelectric performance of the thin films and compared the PMN-PT films against the

reported values of other micromachined actuator materials to show the potential of PMN-PT for

actuator and energy harvesting applications.


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In a recent article in Science, the team reported the highest values of piezoelectric properties for

any piezoelectric thin film to-date, and a two-fold higher figure of merit than the best reported

PZT films for energy harvesting applications. This increase in the effective piezoelectric activity

in a thin film will result in a dramatic improvement in performance. For example, energy

harvesting using such thin films will provide local power sources for wireless sensor nodes for

bridges, aircraft, and potentially for human-body sensors [46].

4.10 Potential for lead-free piezoelectric ceramics

Scientists are using Diamond Light Source, the UK's national synchrotron facility, to discover

how we can detoxify our electronic gadgets. Results published in the journal Applied Physics

Letters reveal the potential for new artificial materials that could replace lead-based components

in everyday products from inkjet printers to digital cameras.

Researchers from the Institute for Materials Research at the University of Leeds' Faculty of

Engineering used the Diamond synchrotron to investigate the structure and properties of

piezoelectric ceramics in order to develop more environmentally friendly alternatives to the

widely-used but toxic ceramic crystal lead zirconium titanate (PZT)

The team used the I15 Extreme Conditions beamline at Diamond to probe the interior crystal

structure of the ceramics with a high-energy pinpoint X-ray beam and saw changes in the crystal

structure as an electric field was applied. Their results demonstrate that this new material,

potassium sodium bismuth titanate (KNBT), shows the potential to perform the same job as its

lead counterpart.
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Dr Tim Comyn, lead investigator on the project, said: "These results are very encouraging.

Although harmless when in use, at the end of their lifetime these PZT gadgets have to be

carefully disposed of due to their lead content and as a consequence, there is significant interest

in developing lead-free ceramics."

Piezoelectric materials generate an electrical field when pressure is applied, and vice versa. For

example in gas igniters, like those used on ovens and fires, a piezoelectric crystal creates sparks

when hit with the hammer. In an electrical field, it undergoes a phase transition, that is changes

in the crystal structure.

The team will continue to work at Diamond to study the electric field induced transformation at

high speed (1000 times per second) and under various conditions using state of the art detectors.

Adam Royles, PhD student on the project, said: "Not only could a lead-free solution mean safer

disposal of electronic equipment, by virtue of the absence of lead, these new materials are far

lighter than PZT. The piezoelectric market has applications in many fields, where a lighter lead-

free alternative could make quite a difference."


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Figure 21: Crystal structure of KNBT before the application of an electric field (left) and after (right). The purple spheres are

either sodium or potassium atoms, the red spheres are oxygen atoms, the small blue sphere is titanium. The figures show

the arrangemen

In the medical field, PZT is used in ultrasound transducers, where it generates sound waves and

sends the echoes to a computer to convert into a picture. Piezoelectric ceramics also hold great

potential for efficient energy harvesting, a possible solution for a clean sustainable energy source

in the future.

Lead-based electronic ceramics are one of only a few exemptions to the European directive on

the restriction of the use of certain hazardous substances in electrical and electronic components

(2002/95/EC). This exemption will be reviewed again in 2012.

The global market for piezoelectric-operated actuators and motors was estimated to be $6.6

billion in 2009 and is estimated to reach $12.3 billion by 2014[46].

4.11 Electro-active papers

EAPap is a paper that produces large displacement with small force under an electrical

excitation. EAPap is made with a chemically treated paper by constructing thin electrodes on

both sides of the paper. When electrical voltage is applied on the electrodes the EAPap produces
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bending displacement. However, the displacement output has been unstable and degraded with

timescale. To improve the bending performance of EAPap, different paper fiberssoftwood,

hardwood, bacteria cellulose, cellophane, carbon mixture paper, electrolyte containing paper and

Korean traditional paper, in conjunction with additive chemicals, were tested. Two attempts were

made to construct the electrodes: the direct use of aluminum foil and the gold sputtering

technique. It was found that a cellophane paper exhibits a remarkable bending performance.

When 2 MV m1 excitation voltages were applied to the paper actuator, more than 3 mm tip

displacement was observed from the 30 mm long paper beam. This is quite a low excitation

voltage compared with that of other EAPs. Details of the experiments and results are addressed.

Figure 22: Electro active paperThe recent emergence of electro active polymers (EAPs) has received much attention due to their

capability for large displacement actuators. Some of the currently available materials are ionic

polymer metal composites (IPMCs), gel polymers, conductive polymers, electric-field-activated

EAPs such as electron-irradiated P(VDF-TrFE), electrostrictive polymer artificial muscle

(EPAM), electro rheological fluids and so on . EPAM is an elastomeric polymer sandwiched

between two compliant electrodes. When an electric field is applied across the thickness, the


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polymer thickness shrinks, but the area is enlarged due to the electrostatic forces of the free

charges on the electrodes. Diaphragm actuators have been used for pumps, adaptive optics and

loudspeakers . However, these actuators need highly compliant electrodes to be expanded in

plane and pestess to enhance the displacement output. The use of paper as an electrostrictive

EAP actuator has been demonstrated by other reaearcher. Paper is a sheet that is composed of a

multitude of discrete particles,mainly of a fibrous nature, which form a network structure.Since

paper is produced in various mechanical processeswith chemical additives, there is a possibility

of preparing a paper that can meet the requirements for EAP actuators. Such actuators were

prepared by bonding two silver-laminatedpapers with the silver electrodes placed on the outsidesurface. When electric voltage is applied to the electrodes the actuator produces bending

displacement depending onthe excitation voltage, frequencies, type of adhesive and host papers.

This is termed electro-active paper (EAPap). Once EAPaps meet the requirements of EAP

actuators in terms of force and displacement, various applications may be possible, including

active wings for flying objects, active sound absorbing materials, flexible speakers and smart

shape control devices.

4.12 Electroactive polymers and piezoelectric Energy harvesting Devices

This article reviews the state of the art of Electroactive Polymers (EAPs) field, which are also

known as artificial muscles for their functional similarity to natural muscles. The key aspects of

this subject are: available materials, analytical models, processing techniques and

characterization methods. EAPs are plastic materials that change shape and size when given

some voltage or current. They always had enormous potential, but only now this potential

starting to materialize. The most interesting EAP application is a robot arm built with artificial
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Figure 24: Flow chart for EAP

Utilizing intelligent materials to harvest energy from ambient vibrations has been of great

interest over the past few years. Due to the relatively low power output ofpiezoelectric

materials, energy storage devices are used to accumulate harvested energy for intermittent use.

Technology is continuously becoming smaller and smaller. With these advancements, sensors

and other electronics can be used in the most remote locations and transmit information

wirelessly. A great deal of research has repeatedly demonstrated that piezoelectric energy

harvesters hold the promise of providing an alternative power source that can enhance or replace

conventional batteries and powerwireless devices. Also, ambient vibrations have been the focus

as a source due to the amount of energy available in them. By using energy harvesting devices to

extract energy from their environments, the sensors that the power can be self-reliant and

maintenance time and cost can be reduced. To maximize the amount of energy harvested from

the source, generally a resonant mode of the harvester should match one of the dominant

frequencies of the source. Due to inconsistencies in the fabrication of the harvester or variations

in the source, frequency matching can be difficult to achieve. By being able to tune the device
http://void%280%29/http://www.energyharvestingjournal.com/articles/electroactive-polymers-and-piezoelectric-energy-harvesting-devices-00002310.asphttp://void%280%29/http://www.energyharvestingjournal.com/articles/electroactive-polymers-and-piezoelectric-energy-harvesting-devices-00002310.asphttp://void%280%29/http://void%280%29/http://void%280%29/http://void%280%29/http://www.energyharvestingjournal.com/articles/electroactive-polymers-and-piezoelectric-energy-harvesting-devices-00002310.asphttp://void%280%29/http://www.energyharvestingjournal.com/articles/electroactive-polymers-and-piezoelectric-energy-harvesting-devices-00002310.asphttp://void%280%29/


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during fabrication or in real time during operation, a means to meet this criterion during

operation of the device can be provided.

Polyvinylidene fluoride (PVDF) is a semi-crystalline high-molecular weight polymer with repeat

unit (CH2-CF2), whose structure is essentially head-to-tail, i.e., CH2-CF2-(CH2- CF2)n-CH2-CF2.

PVDF is approximately half crystalline and half amorphous. In the semi-crystalline polymers

such as PVDF, there are regions where the chains exhibit a short and long-term ordering

(crystalline regions). A net dipole moment (polar phase) is obtained by applying a strong electric

field at or above Tg. Then, it is frozen in by cooling the material resulting in a piezoelectric-like

effect. PVDF has the advantage that it is mechanically strong, resistant to a wide variety of

chemicals including acids and can be manufactured on a continuous reel basis. Another

important property of PVDF is that it shows a strong piezoelectric response.

Energy Harvesting Journal has shown a list of great applications of piezoelectric energy

harvesters. In the future, most of these examples could be fabricated exclusively by Electroactive

Polymers, such as PVDF and its composites. Below are some examples of piezoelectric energy

harvesters:

Energy harvesting for robots Energy harvesting backpack Harnessing vibrations from raindrops Flapping leaf generator for wind energy harvesting Piezoelectric kinetic energy harvester for mobile phones Breakthroughs with sensing in the human body Harvesting energy from natural motion
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Electroactive Polymers (EAPs) are a promising alternative forenergy harvesting devices, due to

the flexibility, versatility and low cost of these materials. Considering the high degree of

complexity of the current technological context, the development of clear reviews can deeply

help toward the best investments strategy in Renewable Energy in general and also in the

emerging Polymeric Energy Harvesters (PEH) technologies.

4.13 Piezoelectric fabric that can detect and produce sound

Researchers have created new plastic fibers that can detect and produce sound. When stretched,

these strands could be used to make clothes that act as a microphone or generate electricity. "You

can actually hear them, these fibers," said Nomie Chocat, a graduate student in the materials

science department at MIT and co-author of a paper describing the fibers. "If you connected

them to a power supply and applied a sinusoidal current" an alternating current whose period

is very regular"then it would vibrate," Chocat said. "And if you make it vibrate at audible

frequencies and put it close to your ear, you could actually hear different notes or sounds coming

out of it."

4.13.1 Microphone check

The heart of the new acoustic fibers is a plastic commonly used in microphones. By playing with

the amount of the element fluorine in the plastic, the researchers were able to ensure that the

material's molecules remained "lopsided," with the fluorine atoms lining up on one side and

hydrogen atoms on the other. This asymmetry made the plastic "piezoelectric," meaning that it

changes shape when an electric field is applied to it.
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In a conventional piezoelectric microphone, this useful electric field is generated by metal

electrodes. But in a fiber microphone, the drawing process when the strand is pulled into

being from a larger block of materialwould cause metal electrodes to lose their shape.

So the researchers instead used a conducting plastic that contains graphite, the material found in

pencil lead. When heated, the conducting plastic maintains a higher viscosity meaning it

yields a thicker fluid than a metal would. Not only did this prevent the mixing of materials

that might wreck the fibers' properties, but, crucially, it also made for fibers with a regular

thickness.

After the fiber was drawn, the researchers needed to align all the piezoelectric molecules in the

same direction. That required the application of an electric field 20 times as powerful as the

fields that cause lightning during a thunderstorm.

4.13.2 Sound results

In addition to wearable microphones, the fibers could be used as biological sensors for

monitoring bodily functions. The tiny filaments could measure bloo

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