ScienceDaily (Dec. 2, 2008) — 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
far-fetched 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.
Utilizing materials known in scientific circles 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 covert 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 said.
His findings, which are detailed in an article published this fall in
"Physical Review B," the scientific 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 used by everyone from the
average consumer to law enforcement officers and even soldiers in the
battlefield.
Many of these high-tech devices contain components that are measured in
nanometers – a microscopic unit of measurement representing
one-billionth of a meter. Atoms and molecules are measured in
nanometers, and a human hair is about 100,000 nanometers wide.
Though Cagin's subject matter is small, its impact could be huge. His
discovery stands to advance an area of study that has grown increasingly
popular due to consumer demand for compact portable and wireless devices
with extended lifespans.
Battery life remains a major concern for popular mp3 players and cell
phones that are required to perform an ever-expanding array of
functions. But beyond mere consumer convenience, self-powering devices
are of major interest to several federal agencies.
The Defense Advanced Research Projects Agency has investigated methods
for soldiers in the field to generate power for their portable equipment
through the energy harvested from simply walking. And sensors – such as
those used to detect explosives – could greatly benefit from a
self-powering technology that would reduce the need for the testing and
replacing of batteries.
"Even the disturbances in the form of sound waves such as pressure waves
in gases, liquids and solids may be harvested for powering nano- and
micro devices of the future if these materials are processed and
manufactured appropriately for this purpose," Cagin said.
Key to this technology, Cagin explained, 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, they demonstrate a
change in their physical properties 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 that in turn
produces enough voltage to create a spark and ignite the gas.
On a grander scale, some night clubs 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 it's been
reported that a Hong Kong gym is using the technology to convert energy
from exercisers to help power its lights and music.
While advances in those applications continue to progress, piezoelectric
work at the nanoscale is a relatively new endeavor with different and
complex aspects to consider, said Cagin.
For example, imagine going from working with a material the size and
shape of a telephone post to dealing with that same material the size of
a hair, he said. 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, Cagin noted. These types of changes have to be taken into
consideration when conducting research at this scale, he said.
"When materials are brought down to the nanoscale dimension, their
properties for some performance characteristics dramatically change,"
said 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."
http://www.sciencedaily.com/releases/2008/12/081201162127.htm
Regards
Syed Imran
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