The milestone could lead to tiny devices that harvest electrical energy from the vibrations of everyday tasks, something that could charge your phone as you walk for example.

Berkley Lab Viurs Electric Piezoelectric Energy Generator

The Berkeley Lab scientists describe their work in the May 13 advance online publication of the journal Nature Nanotechnology.

Seung-Wuk Lee, a faculty scientist in Berkeley Lab’s Physical Biosciences Division and a UC Berkeley associate professor of bioengineering and colleagues wondered if a virus studied in labs worldwide offered a better way. The M13 bacteriophage only attacks bacteria and is benign to people. Being a virus, it replicates itself by the millions within hours, so there’s always a steady supply. It’s easy to genetically engineer. And large numbers of the rod-shaped viruses naturally orient themselves into well-ordered films, much the way that chopsticks align themselves in a box.

These are the traits that scientists look for in a nano building block. But the Berkeley Lab researchers first had to determine if the M13 virus is piezoelectric. Lee turned to Ramamoorthy Ramesh, a scientist in Berkeley Lab’s Materials Sciences Division and a professor of materials sciences, engineering, and physics at UC Berkeley, an expert in studying the electrical properties of thin films at the nanoscale. They applied an electrical field to a film of M13 viruses and watched what happened using a special microscope. Helical proteins that coat the viruses twisted and turned in response – a sure sign of the piezoelectric effect at work.

Next, the scientists increased the virus’s piezoelectric strength. They used genetic engineering to add four negatively charged amino acid residues to one end of the helical proteins that coat the virus. These residues increase the charge difference between the proteins’ positive and negative ends, which boosts the voltage of the virus.

The scientists further enhanced the system by stacking films composed of single layers of the virus on top of each other. They found that a stack about 20 layers thick exhibited the strongest piezoelectric effect.

The only thing remaining to do was a demonstration test, so the scientists fabricated a virus-based piezoelectric energy generator. They created the conditions for genetically engineered viruses to spontaneously organize into a multilayered film that measures about one square centimeter. This film was then sandwiched between two gold-plated electrodes, which were connected by wires to a liquid-crystal display.

When pressure is applied to the generator, it produces up to six nanoamperes of current and 400 millivolts of potential. That’s enough current to flash the number “1″ on the display, and about a quarter the voltage of a triple A battery.

The scientists tested their approach by creating a larger generator that produces enough current to operate a small liquid-crystal display. It works by tapping a finger on a postage stamp-sized electrode coated with the specially engineered viruses. The viruses convert the force of the finger tap into an electric charge.

Their generator is the first to produce electricity by harnessing the piezoelectric properties of a biological material. Piezoelectricity is the accumulation of a charge in a solid in response to mechanical stress.

The research also points to a simpler and very important insight for making microelectronic devices. That’s because the viruses arrange themselves into an orderly film that enables the generator to work. Self-assembly is a much sought after goal in the finicky world of nanotechnology.

Lee said, “More research is needed, but our work is a promising first step toward the development of personal power generators, actuators for use in nano-devices, and other devices based on viral electronics. We’re now working on ways to improve on this proof-of-principle demonstration. Because the tools of biotechnology enable large-scale production of genetically modified viruses, piezoelectric materials based on viruses could offer a simple route to novel microelectronics in the future.”

The piezoelectric effect has a lot of potential, its been known since 1880.  The effect has turned up in crystals, ceramics, bone, proteins, and DNA. It’s already been put to use in simple personal devices like electric cigarette lighters and very high technology scanning probe microscopes that rely on the effect to function. There are more of these simple yet ultra reliable devices about than most folks realize.

Its great to see another route to piezoelectric power and to see the nasty nemesis of humanity, the virus, put to useful work for a change.  But the big clue maybe the potential of self assembly, where virus applications could further miniaturize devices and reduce their need for electric power.

Now if they’d just manage to engineer virus to defeat the viruses of the common cold, herpes and AIDS.

ORNL’s Volker Urban and colleagues at Technical University Aachen in Germany noticed the reverse piezoelectric effect — defined as creating a mechanical strain by applying an electrical voltage — while conducting fundamental research on polymers.  At first they didn’t think about their observations in terms of classic piezoelectric materials, but then they became more curious.

Urban, a member of the Department of Energy lab’s Neutron Scattering Science Division said, “We thought about comparing the effects that we observed to more ‘classic’ piezoelectric materials and were surprised by how large the effects were by comparison. We observed this effect when two different polymer molecules like polystyrene and rubber are coupled as two blocks in a di-block copolymer.”

Piezoelectric Component Stack

This research shows up to 10 times the measured electro-active response as compared to the strongest known piezoelectric materials, typically crystals and ceramics.  Scientists have been thinking that non-polar polymers were not capable of exhibiting any piezoelectric effect, which has been occurring only in non-conductive materials.

Temperature-dependent studies of the molecular structure revealed an intricate balance of the repulsion between the unlike blocks and an elastic restoring force found in rubber. The electric field adds a third force that can shift the intricate balance, leading to the piezoelectric effect.

Urban lists a number of examples for use including sensors, actuators, energy storage devices, power sources and biomedical devices, “The extraordinarily large response could revolutionize the field of electro-active devices,” and also noted that additional potential uses are likely as word of this discovery gets out and additional research is performed. “Ultimately, we’re not sure where this finding will take us, but at the very least it provides a fundamentally new perspective in polymer science,” he said.

This is significant research and a new ground breaking result.  The paper has been published as the cover article in Advanced Materials. This is a paper that might be worth the outrageous price journals demand.

Piezoelectric Cover at Advanced Materials. Click image for more info..

Working with Urban, the other authors are Markus Ruppel and Jimmy Mays of ORNL and Kristin Schmidt of the University of California at Santa Barbara. Authors from Aachen University are Christian Pester, Heiko Schoberth, Clemens Liedel, Patrick van Rijn, Kerstin Schindler, Stephanie Hiltl, Thomas Czubak and Alexander Böker.

So far piezoelectric has been considered a very small generator with uses where very low power or charging would employ the technology.  The costs for a full working kit haven’t been competitive.  That may all be changed now.  A ten-fold increase – the first step in the new discovery bodes well for applications where the power demands are more substantial.

University of Michigan Piezoelectric Energy Harvester. Click image for the largest view. Image Credit: Erkan Aktakka

The UM team has built a complete system that integrates a high-quality energy-harvesting piezoelectric material with the circuitry that makes the power accessible. (Piezoelectric materials allow a charge to build up in them in response to mechanical strain, which in this case would be induced by the machines’ vibrations.)

Called a micro machining piezoelectric or MEMS the unit is packaged with its MEMS together with tiny circuit elements that form a complete vibration energy harvester in just 27 cubic millimeters. The tiny unit harvests vibrational energy between 14-and-155 cycles-per-second (155 Hz is similar to the vibration you’d feel if you put your hand on top of a running microwave oven) and produces about 200 microWatts from 1.5g vibrations.

The energy harvester sends the charge to a supercapacitor up to 1.85 volts, which powers the load. The researchers estimate the energy harvester could repeat this cycle for 10-to-20 years without degradation.

Khalil Najafi, one of the system’s developers and chair of Electrical and Computer Engineering at UM said, “In a tiny amount of space, we’ve been able to make a device that generates more power for a given input than anything else out there on the market.”

The new vibration energy harvester is specifically designed to turn the cyclic motions of factory machines into energy to power wireless sensor networks. These sensor networks monitor machines’ performance and let operators know about any malfunctions.

Erkan Aktakka, one of the system’s developers and a doctoral student in Electrical and Computer Engineering explains, the sensors that do this today get their power from a plug or a battery. They’re considered “wireless” because they can transmit information without wires. Being tethered to a power source drastically increases their installation and maintenance costs.

Aktakka thinks the wireless sensor networks can be expected to grow to $450 million by 2015, “If one were to look at the ongoing life-cycle expenses of operating a wireless sensor, up to 80 percent of the total cost consists solely of installing and maintaining power wires and continuously monitoring, testing and replacing finite-life batteries.”

Perhaps most interesting is the team as come up with a novel silicon micro machining technique that allows the engineers to fabricate the harvesters in bulk with a high-quality piezoelectric material, unlike other competing devices.

Najafi believes these new devices could have applications in medicine and the auto industry, too. They could possibly be used to power medical implants in people or heat sensors on vehicle motors.

The team will present the new harvester at the 16th International Conference on Solid-State Sensors, Actuators, and Microsystems (TRANSDUCERS 2011) in Beijing in June. The research was funded by the Defense Advanced Research Projects Agency and National Nanotechnology Infrastructure Network.

The University of Michigan is pursuing patent protection for the intellectual property, and is seeking commercialization partners to help bring the technology to market.

Stacked up to say nine units would get well past 12 volts, enough for battery charging, or 1000 would get to 2 hundredths of watt, a worthwhile amount of power.

This design is fascinating in its completeness at the diminutive size.  Its quite good voltage and should production get to scale perhaps the price might be low enough that really noticeable wattage production could get to market.  The team’s work might not drive resistance heating or other power hungry loads, but for fast low power needs, remote or high maintenance positions, bursting messaging from low draw sensors, even some micro processors and memory chips, there will be a huge market – if the price can plunge far enough fast enough.

It’s a very interesting engineering effort – but please UM, tell us more about the team’s micro machining technique!  We want to see the rest of the iceberg.

Half-Heusler compounds and the structurally similar Heusler materials are intermetallic compounds made from three elements that form a cubic crystal structure.

The team gained improvement in the half-Heusler material, which has been under study for its thermal stability, mechanical sturdiness, non-toxicity and low cost. But, the application of half-Heusler has been limited because of its poor thermoelectric performance: it previously registered a peak figure of merit of approximately 0.5 at 700º C for bulk ingots.

The goal for efficiency is a value of 1 or more for a performance measurement called the thermoelectric figure of merit or ZT.  ZT combines the electric and thermal conductivities of a material with its capacity to generate electricity from heat.  Getting to this goal has proven extremely difficult because the two parameters are generally interdependent of one another.

BC's New half-Heusler Thermoelectric Material. Click image for more info.

The team’s new process is first forming alloyed ingots using an arc melting technique, then creating nanoscale powders by ball milling the ingots and finally obtaining dense bulk by hot pressing the balls into a whole. The research team loaded the alloyed bulk ingot of a half-Heusler alloy (with a composition of Zr0.5Hf0.5CoSb0.8Sn0.2) into a jar with grinding balls and then subjected to a mechanical ball-milling process. The resulting nanopowder with particles as small as 5 to 10 nanometers were then reconstructed into bulk form by pressing them into pellets with a diameter of 12.7 mm by the direct current induced hotpress method.

Transport property measurements together with microstructure studies on the nanostructured samples, in comparison with that of the bulk ingots shows that the thermoelectric performance improves largely because of low thermal conductivity produced by enhanced phonon scattering at grain boundaries and defects in the material. The material was also found to have a high Seebeck coefficient, a measure of thermoelectric power.

The point is to not let a lot of heat pass through while converting the heat into electricity.  Thermal conductivity isn’t good, the heat is getting away.  If you can keep the heat in and one outside of the device cool the difference will get you more power.

The team’s dramatic increase in the figure of merit, used to measure a material’s relative thermoelectric performance, could pave the way for a new generation of products – from car exhaust systems and power plants to solar power technology –  that run cleaner, according to co-author Xiao Yan, a researcher in the Department of Physics at Boston College.

Yan, working with BC Professor of Physics Zhifeng Ren and MIT’s Soderberg Professor of Power Engineering Gang Chen, have increased the figure of merit value of p-type half-Heusler another step to 0.8 at 700º C. Moreover, the groups’ material preparation methods proved to save time and expense compared with conventional methods.

Ren said, “This method is low cost and can be scaled for mass production. This represents an exciting opportunity to improve the performance of thermoelectric materials in a cost-effective manner.”

Researchers in the BC and MIT labs are still trying to prevent grain growth during the press operation, which accounts for the still large thermal conductivity of half-Heusler.

Ren explains, “Even lower thermal conductivity and improved thermoelectric performance can be expected when average grain sizes are made smaller than 100 nm.”

Thermoelectric is a technology that could catch the massive losses of heat from fuel use.  Perhaps half or more of the fuel used is lost as heat, recovering it to electricity would double the amount of work from fuel or more succinctly, cut fuel use in half.

These are efforts well worth the time and investment.

Alphabet Energy aims to take the decades-old idea of generating electricity from captured heat, and deploy it at massive scale on the cheap with a little help from nanotechnology and the semiconductor industry.  By providing a thermoelectric chip that can be inserted into any exhaust flue or engine to convert heat into electrical power, Alphabet hopes to become the “Intel of waste heat,” a description from Matthew L. Scullin, PhD. the company’s chief executive and co-founder.

A Standard Peltier Element for reference. No Alphabit image seems available. Click image for the largest view.

A thermoelectric device is simply a device that can make use of heat to generate power with no moving parts using the heat just as a solar cell generates electricity from using visible light. It is based on the long-known principle that electrons can be pushed through a material by heat. Alphabet says its innovation is in both the choice of material and proprietary technology that gives it low thermal conductivity, and makes it highly suitable for both scale and miniaturization for use in small devices as well as in large factory flues. The device is connected by wire to the plant’s electrical system or to the grid, so it feeds in power converted by heat in real time.

Alphabet’s efforts come as part of a larger drive by researchers, entrepreneurs, and trade groups to make use of heat energy that’s currently lost to the atmosphere.  Policy making is catching up – Representative Paul Tonko of New York, former head of his state’s public power research authority, introduced a bill that would provide a 30 percent investment tax credit for installation of waste heat recovery systems in industrial settings. At least one Congressman is on his toes.

Waste heat recovery is an old idea; everyone buying fuels and seeing the power disappear into the air has a little bit of financial agony when a fuel is burned without full use.  Cogeneration (also called combined heat and power) systems, can generate electricity or mechanical power and useful heat at a facility that requires thermal energy, or convert waste energy on-site into electricity and mechanical energy. In 2008, the Oak Ridge researchers reported that the 3,300 cogeneration sites in the United States accounted for nearly 9 percent of the country’s total electricity generating capacity, and called for a push to raise that to 20 percent by 2030—a level already exceeded by some European countries.  It’s a big potential field, in 2008 cogeneration accounted for more than half of total national power production in Denmark, nearly 40 percent in Finland and more than 30 percent in Russia.

The catch in the U.S. is another regulation issue that generally bars utilities from reaping financial rewards from efficiency gains – they’re required to pass the savings along to ratepayers, taking out the incentive to invest.

Alphabet claims it can radically change the price point in the heat-power equation by using a relatively abundant, low-cost material that ordinarily wouldn’t be effective as a thermoelectric semiconductor. The company uses technology originally developed at the Lawrence Berkeley National Laboratory by Scullin and Professor Peidong Yang, PhD to adapt this material and lower its thermal conductivity, basically allowing it to produce more electricity with less heat.

Alphabet plans the earliest application of its technology will be in places like factories, where waste heat projects have been concentrated at the largest and hottest sources and at industrial sites and power plants.  Should the firm’s technology work as planned it could be a path for economic recycling of energy in a wider variety of settings, from cell phones to cars. Scullin emphasizes that Alphabet remains in the very early stages of commercializing this technology for mobile applications.

Alphabet’s chip is produced in a way that’s similar to how microchips for electronic devices are made. Using the semiconductor industry’s economies of scale will allow the firm to slash costs enough to install its systems for “well under $1 a watt,” said Scullin in comparing to installation costs double or triple that amount for some competing waste heat recapture systems.

Scullin explains that depending on the flow rate, chemical composition, and temperatures of the exhaust coming out of an industrial flue, Alphabet’s technology could deliver a payback time of two to four years for a manufacturer.

Alphabet plans to complete a pilot installation at an industrial facility with a large waste heat source in 2011, with an aim of winning commercial customers by 2012. Scullin revealed most of the potential customers in discussion with Alphabet are multinational corporations.  Scullin notes that waste heat is one of few power sources that the U.S. government does not subsidize. While fossil and renewable energy projects can benefit from subsidies and tax credits the lack of incentives for waste heat recovery translates to a disincentive for investments in energy-saving technology.

That means the Tonko bill, co-sponsored by Representatives Jay Inslee of Washington Shelly Berkley of Nevada and Texas Representative Ron Paul, could change that.  There is an abundance of energy recycling ideas already proven to work.  By taking out the disincentive and applying a leveling of incentives waste heat technologies could take off.  Remember, in recycling heat the energy is already bought, earned and paid for – the power recovered is fuel cost free.

Miniature Piezoelectric Generator. Click image for more info.

Khalil Najafi, chair of electrical and computer engineering and Tzeno Galchev, a doctoral student at the University of Michigan Engineering Research Center for Wireless Integrated Microsystems have created an energy-harvesting device that is highly efficient at providing renewable electrical power from arbitrary, non-periodic vibrations. This type of vibration for example could be a byproduct of traffic driving on bridges, machinery operating in factories, the refrigerator compressor, water pipes, and people just moving their arms and legs.

The research and engineering pair are calling the new device Parametric Frequency Increased Generators (PFIGs).

Najafi, who is the Schlumberger Professor of Engineering and also a professor in the Department of Biomedical Engineering explains that most similar devices have more limited abilities because they rely on regular, predictable energy sources, “The vast majority of environmental kinetic energy surrounding us everyday does not occur in periodic, repeatable patterns. Energy from traffic on a busy street or bridge or in a tunnel, and people walking up and down stairs, for example, cause vibrations that are non-periodic and occur at low frequencies. Our parametric generators are more efficient in these environments.”

In the course of exploring the field the research team built three prototypes and a fourth is forthcoming. In two of the generators, the energy conversion is performed through electromagnetic induction, in which a coil is subjected to a varying magnetic field using the principle similar to how large-scale generators function in big power plants.

The latest and smallest device, which measures one cubic centimeter, uses a piezoelectric material, which is a type of material that produces charge when stressed. The third version has applications such as infrastructure health monitoring. The tiny generators could one day power bridge sensors that would warn inspectors of cracks or corrosion before human eyes could discern problems or power wireless sensors deployed in buildings to make them more energy efficient, or throughout large public spaces to monitor for toxins or pollutants.  The list could get very long.

The numbers that might matter most is the team has the latest generators demonstrating they can produce up to 0.5 milliwatts (or 500 microwatts) from typical vibration amplitudes found on the human body. That’s more than enough energy to run a wristwatch, which needs between one and 10 microwatts, or a pacemaker, which needs between 10 and 50. A milliwatt is 1,000 microwatts. These numbers are a bit of surprising good news.

Galchev said, “The ultimate goal is to enable various applications like remote wireless sensors and surgically implanted medical devices. These are long lifetime applications where it is very costly to replace depleted batteries or, worse, to have to wire the sensors to a power source.”  Galchev is on the best point – battery oversight and replacement are time consuming and often costly processes when endlessly repeated or running line or transformer power is capital intensive even if the energy use is minimal.

Najafi makes an astute observation, “There is a fundamental question that needs to be answered about how to power wireless electronic devices, which are becoming ubiquitous and at the same time very efficient. There is plenty of energy surrounding these systems in the form of vibrations, heat, solar, and wind.”  The question will be cost.

The university is pursuing patent protection for the intellectual property. Galchev and a team of engineering and business students are at work to commercialize the technology through their new company, Enertia. Enertia recently won first place in the DTE/U-M Clean Energy Prize business plan competition and second place in the U-M Zell Lurie Institute for Entrepreneurial Studies’ Michigan Business Challenge. Other members of the team are Erkan Aktakka, and Adam Carver. Aktakka is an electrical engineering doctoral student. Carver is an MBA student at the Ross School of Business.  Good luck kids.  Get to know your customers and what they need.

Recheck that photo.  At about a third the height and a little more diameter than the AA battery, three of these stacked up would get you 1.5 milliwatts, six 3 milliwatts.  That’s getting somewhere.  With a rechargeable coin size battery for the non-shaking periods the product should have a future.  Now if one could just keep on shakin’.  .  . Couldn’t resist.

A team at the University of Wisconsin-Madison is on it with a new material made from crystals of zinc oxide that, when immersed in water, absorb vibrations and develop areas of strong negative and positive charge. These charges rip apart nearby water molecules, releasing hydrogen and oxygen gas.

Lead researcher Huifang Xu as quoted by Phil McKenna at NewScientist saying, “This is like a free lunch. You are getting energy from the environment just like solar cells capture energy from the sun.”

The material the team designed generates hydrogen using the new take on piezoelectric crystals. Piezoelectrics are a materials that generate a voltage when strained such as being bent or flexed, which are also being investigated as a way to generate electricity from movement.

So where is an abundance of free motion or movement?  Sound.  It’s just that sound doesn’t move molecules very much and the less mass moving the less energy involved.

Xu’s team designed crystals that are submerged in water so the charge they generate instead pulls apart water molecules to release hydrogen and oxygen gas, a mechanism Xu’s team is calling a ‘piezoelectrochemical’ effect. This a completely different take from flexing something for a bit of electrical charge.

Piezoelectrochemical Graphic. Click image for more info.

Xu and his colleagues grow thin microfibers of highly flexible zinc oxide crystals that when subjected to vibration, flex due to sound waves. The team has shown ultrasonic vibrations under water cause the fibers to bend between 5 and 10 degrees at each end, creating enough electrical field with a high enough voltage to split water and release oxygen and hydrogen. There’s a ‘how about that’ moment.

Jinhui Song of Georgia Tech University, also quoted by NewScientist explains because there is no need to wire in an in/out circuit the devices based on the new crystals could be simpler than those based on conventional dry piezoelectrics.  “It’s a good idea. They can reduce the complexity of the device.”

Song offers a cautionary note that submerged devices would not necessarily be more efficient. In principle, says Song, the energy generated by a material should be the same however it is deployed.  Yet the microfiber mechanics compared to current piezoelectric mechanics might offer some form of increase and further research to smaller scales may be worth investigation.

The advantage in device construction costs is intriguing.  Yet the oxygen and hydrogen separation process would need addressed at low cost as well. But there’s an abundance of motion about, even wind might be worth investigation for generating efficient ultrasonic energy.  If a system were cheap enough, the efficiency required wouldn’t be so high.

The team’s research was published on the web March 2nd at The Journal of Physical Chemistry Letters. In the supporting documentation pdf a zinc oxide sample is shown at a remarkable 18% efficiency. This writer suspects the press release would have gotten much more attention if this point were noticed.

There is potential here when considering the energy already just moving around.

Engineers at Leeds in the U.K. are developing a way to capture the kinetic energy produced when soldiers march and use it to power their equipment. The devices will use high tech ceramics and crystals as piezoelectric transducers in order to convert mechanical stress into an electric charge.

Schema of the Piezoelectric Effect. From Wikipedia.

The UH group’s goal is to use piezoelectrics to create nanodevices that can power electronics, such as cell phones, MP3 players and even biomedical implants.  The Leeds group is working toward soldiers one day powering electronic devices such as personal radios using just their own movements on the battlefield.  Soldiers using this technology will not have to carry extra supplies of batteries.

The UH group is addressing a very large sum of power demand.  I did a quick google to see if there is a handy statistic or graph to illustrate the power of charges for small devices to no easy avail, but I did look through the house and found 7 little chargers here.  All of them plugged in is like having just over a 50 watt bulb burning.  They are all unplugged again.  The only “smart” one is for my cell phone that when plugged into the phone scales back as the cell’s battery gets close to full.  The kill-a-watt says it runs at full power though, when its not plugged into the cell phone.  How’s that for engineering?

That sort of makes the case when those stories appear about the hundreds of millions of them in the U.S. alone.  Maybe there are a billion or more of them worldwide.  You can imagine the total draw is going to equal several power plants running full out.  All for lack of a little engineering multiplied millions of times.

Associate professor Pradeep Sharma, one of the creative minds at the Cullen College of Engineering at UH says, “Nanodevices using piezoelectric materials will be light, environmentally friendly and draw on inexhaustible energy supplies.”  Not satisfied with saving a lot of generated power his imagination goes on to, “Imagine a sensor on the wing of a plane or a satellite. Do we really want to change its battery every time its power source gets exhausted?  Hard-to-access devices could be self-powered.”  It’s a little like the potential isn’t even thought through completely.

Sharma explains and expands the topic even more, “Indeed, gas lighters used in most homes are based on this. These future piezoelectric nanodevices will also generate an electrical current in response to mechanical stimuli. Then, the energy will be stored in batteries or, even better, in nanocapacitors for use when needed.”

The UH team is exploring new possibilities by beefing up the effect in natural piezoelectrics. Doing so requires understanding the phenomenon that energizes piezoelectricity, known as “flexoelectricity.”  Sharma says, “Flexoelectricity, at the nanoscale, allows you to coax ordinary material to behave like a piezoelectric one. Perhaps more importantly, this phenomenon exists in materials that are already piezoelectric. You can make the effect even larger.”  For example, the piezoelectricity in barium titanate can be increased by 300 percent when the material is reduced to a 2-nanometer-beam and pressure is applied. “Thus, you’ll take an ordinary piezoelectric material and really give it some juice,” he says.

Sharma underscores the flexoelectric effect is a function of size – and the smaller the better, at least for generating piezoelectric power. Materials with nanoscale features – such as nanoscale thin plates stacked on each other or materials with particles or holes the size of a few nanometers – exhibit a much larger flexoelectric effect, he says.

Ramanan Krishnamoorti, chairman of the department, is working with Sharma to embed classes of nanostructures in polymers to create unusual types of piezoelectrics while Sharma and professor Ken White recently reported that the electrical activity caused by flexoelectricity also affects a material’s resiliency. They tested their theory – that the elasticity of a material would be quite altered by flexoelectricity and caused electrical activity – by poking the material with a sophisticated needle.

Sharma says, “We basically predicted that when you poke it, because of this electrical activity, depending upon how big a crater you create, your elastic behavior will change. It’s not supposed to. Ordinarily, whether you make a big crater or small crater, if you calculate how stiff it is or soft it is, it’ll give you the same answer – a constant.” White and Sharma conducted several experiments on single crystals of materials.  White says, “By monitoring the stiffness of the material as the crater became larger and larger, we discovered a change in elasticity relative to size, which could only be explained by flexoelectric effect.”

The amount of power that can be harvested is still too low to actually power wearable devices unless efficient electric storage solutions, like nanocapacitors are developed.

In the U.K. they seem to be less nano and more micro.  Prof Andrew Bell, director of the Institute for Materials Research at Leeds University and his researchers believe piezoelectric material, which converts movement into electrical energy, may be the portable answer. His group aims to make a wearable device that does not restrict a soldier’s movement on the battlefield.

Bell says, “What this project needs to deliver is not only devices that can harvest the energy, but they must do it with minimal impact to the soldier and the possibly positive impact.”  The team has suggested a device that would mount around the knee and extract energy as a soldier stretches his leg forward and cushion his knee as the leg returns. Bell said electrical engineers working on the project would optimize the electronics so that they take energy out of the device’s transducer during the part of the walking cycle when the leg extends.

‘We need to take energy out of the device at the right part of the cycle so the soldier doesn’t feel it,’ Bell explained.  But when compared to soldiers’ packs of up to 75kg in weight a little counter force might not be so noticeable.

The electricity generated would be distributed through wires weaved across a soldier’s uniform and used to charge up the batteries that power its devices. Such a power distribution system could be avoided if the piezoelectrics were self-contained in the electronic devices. His group aims to develop a personal radio that demonstrates this possibility. “The innards of the radio will move up and down as the soldier walks,” he said. “Kinetic energy can be harvested from that.” A very British perspective.

They are looking at single crystal piezoelectric materials. They have the potential to be 10 times better at energy conversion compared with PZT, the most popular piezoelectric in the world, with the potential to be 10 times better at energy conversion compared with PZT.

Bell said the strength of the material and its flexibility will also be a concern, especially for applications such as the knee-worn device. He added that it is possible to create a composite made of the fibers of the piezoelectric material so that the piezoelectrics could be worn around a soldier’s knee more like an elastic bandage.

One does wonder about the comfort of an elastic bandage, but the Leeds team is still formulating the forward planning.  But what stands out is the likelihood that the current state of the art in materials might just take those batteries of the backs of our service men out on patrol.

Both of these technologies when developed would make it to consumer products offering a relief not just from the task of remembering to charge them, but likely save weight and size.

If any of you have a reliable number on the power drain for all those little chargers of portable devices I’m sure everyone would like to know.  I’ll bet it’s a very interesting amount of power, making these researchers work very worthwhile.