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Harvesting Personal Power

12 Impacts of the 12th Man: bald man leaning forward, with energy emitting from his head

Researching The Properties Of Piezoelectrics So That Electronic Devices Can Power Themselves

Imagine a self-powering cell phone that never needs to be charged because it converts sound waves produced by the user into the energy it needs to keep running.

It’s not as farfetched as it may seem thanks to the recent work of Tahir Cagin, a professor in the Artie McFerrin Department of Chemical Engineering at Texas A&M University.

Using materials known as piezoelectrics, Cagin, whose research focuses on nanotechnology, has made a significant discovery in the area of power harvesting, a field that aims to develop self-powered devices that do not require replaceable power supplies, such as batteries.

Specifically, Cagin and his partners from the University of Houston have found that a certain type of piezoelectric material can convert energy at a 100 percent increase when manufactured at a very small size — in this case, around 21 nanometers in thickness.

What’s more, when materials are constructed bigger or smaller than this specific size, they show a significant decrease in their energy-converting capacity, he says.

His findings, which were detailed in Physical Review B, the journal of the American Physical Society, could have potentially profound effects for low-powered electronic devices such as cell phones, laptops, personal communicators and a host of other computer-related devices, which everyone from the average consumer to law enforcement officers and even soldiers in the battlefield use.

Key to this technology, Cagin explains, are piezoelectrics. Derived from the Greek word “piezein,” which means “to press,” piezoelectrics are materials (usually crystals or ceramics) that generate voltage when a form of mechanical stress is applied. Conversely, their physical properties change when an electric field is applied.

Discovered by French scientists in the 1880s, piezoelectrics aren’t a new concept. They were first used in sonar devices during World War I. Today they can be found in microphones and quartz watches.
Cigarette lighters in automobiles also contain piezoelectrics. Pressing down the lighter button causes impact on a piezoelectric crystal, which in turn produces enough voltage to create a spark and ignite the gas.

On a grander scale, some nightclubs in Europe feature dance floors built with piezoelectrics that absorb and convert the energy from footsteps in order to help power lights in the club. And a Hong Kong gym is reportedly using the technology to convert energy from exercisers to help power its lights and music.

Although advances in those applications continue to progress, piezoelectric work at the nanoscale is a relatively new endeavor with different and complex aspects to consider, Cagin says.

Tahir Cagin, professor in the Artie McFerrin Department of Chemical Engineering at Texas A&M University.
Tahir Cagin

For example, imagine going from working with a material the size and shape of a telephone pole to dealing with that same material the size of a hair, he says. When such a significant change in scale occurs, materials react differently. In this case, something the size of a hair is much more pliable and susceptible to change from its surrounding environment. These types of changes have to be taken into consideration when conducting research at this scale, he says.

“When materials are brought down to the nanoscale dimension, their properties for some performance characteristics dramatically change,” says Cagin, who is a past recipient of the prestigious Feynman Prize in Nanotechnology. “One such example is with piezoelectric materials. We have demonstrated that when you go to a particular length scale — between 20 and 23 nanometers — you actually improve the energy-harvesting capacity by 100 percent.

“We’re studying basic laws of nature such as physics and we’re trying to apply that in terms of developing better engineering materials, better performing engineering materials. We’re looking at chemical constitutions and physical compositions. And then we’re looking at how to manipulate these structures so that we can improve the performance of these materials.”

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