Top: Professor Zhong Lin Wang holds a prototype microfibre
nanogenerator, which generates power from your clothing.
Scientists in the US have developed a way to generate electricity by
jostling fabric with unbelievably tiny wires woven inside, raising the
prospect of textiles that produce power simply by being stretched,
rustled or ruffled by a breeze.
The
research, described in Thursday’s edition of the journal Nature,
combines the precision nanotechnology with the elegant principle known
as the piezoelectric effect, in which electricity is generated when
pressure is applied to certain materials.
“The fibre-based
nanogenerator would be a simple and economical way to harvest energy
from physical movement,” said Zhong Lin Wang of the Georgia Institute
of Technology, who led the study.
For the research, Wang and his
colleagues covered individual fibres of fabric with nanowires made of
zinc oxide. These wires are only 50 nanometres in diameter - 1,800
times thinner than a human hair. They also coated alternating fibres
with gold.
When
two different nanowires in the fabric – plated with zinc oxide (green)
and gold (golden) – rub against each other, a piezoelectric charge is
created. The gold wire then feeds the charge into a circuit
As one strand of the fabric is stretched against another, the nanowires
on one fibre rub against the gold-coated ones on the other, like the
teeth of two bottle brushes. The resulting tension and pressure
generates a piezoelectric charge that is captured by the gold and can
be fed into a circuit.
The
allure of the idea is that it doesn’t take unusual movement to generate
usable electricity. Pretty much anything someone does while wearing a
piezoelectric shirt would be productive.
“The beauty of this
work is that if you have wind, or you have sonic waves, or you have
vibrations, it works for you,” Wang said. “You do not need a very large
force for that.”
Wang has coaxed the wires to grow around
strands of yarn in a few square millimetres of fabric, but has not made
sizable pieces yet.
“But our estimates show we can have up to 80
milliwatts per square metre of this fabric.. This is enough to power a
little iPod or charge a cell phone battery,” he said.
“This work
represents a significant achievement,” said Charles Lieber, a
researcher at Harvard University who also is pursuing nanotech power
generation and was not involved in Wang’s project.
Lieber noted
that the research could also lead to biological sensors and other
nanoscale devices that produce their own power from movement or sound
waves. For such nanodevices to be feasible, “harvesting energy from the
environment is a key technology,” he said.
Although Wang used
gold in the research, he expects less expensive metals would work just
as well as conductors. Whatever metal is used, it would be laid down in
such tiny increments that he does not believe it would substantially
increase the weight of an article of clothing.
However, there is
one big hurdle to the advent of power shirts. Though zinc oxide makes a
nice sunscreen, it’s not really waterproof. The Georgia Tech team must
figure out how to protectively coat the nanowires – or else a trip
through the washing machine would rob these fabrics of their magic.
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