52
nanotimes
10-02 :: February 2010
News in Brief
Engineers at the University of California, Berke-
ley, have created energy-scavenging nanofibers
that could one day be woven into clothing and
textiles. These nano-sized generators have „pie-
zoelectric“ properties that allow them to convert
into electricity the energy created through me-
chanical stress, stretches and twists. Because the
nanofibers are made from organic polyvinylidene
fluoride, or PVDF, they are flexible and relatively
easy and cheap to manufacture.
“This technology could eventually lead to wearable
‚smart clothes‘ that can power hand-held elec-
tronics through ordinary body movements,” said
Liwei Lin, UC Berkeley professor of mechanical
engineering and head of the international research
team that developed the fiber nanogenerators.
“We think the efficiency likely could be raised
further,” Lin said. “For our preliminary results, we
see a trend that the smaller the fiber we have, the
Shown is a fiber nanogenerator on a plastic substrate crea-
better the energy efficiency. We don‘t know what
ted by UC Berkeley scientists. The nanofibers can convert
the limit is. And because the nanofibers are so energy from mechanical stresses and into electricity, and
small, we could weave them right into clothes with
could one day be used to create clothing that can power
no perceptible change in comfort for the user.
small electronics. © Chieh Chang, UC Berkeley
The tiny nanogenerators have diameters as small
as 500 nanometers and one-tenth the width of
common cloth fibers. The researchers repeatedly Other research teams have previously made nano-
tugged and tweaked the nanofibers, generating generators out of inorganic semiconducting mate-
electrical outputs ranging from 5 to 30 millivolts rials, such as zinc oxide or barium titanate. „Inor-
and 0.5 to 3 nanoamps. Furthermore, the resear- ganic nanogenerators - in contrast to the organic
chers report no noticeable degradation after stret- nanogenerators we created-— are more brittle and
ching and releasing the nanofibers for 100 minutes harder to grow in significant quantities,“ Lin said.
at a frequency of 0.5 hertz (cycles per second).
The researchers demonstrated energy conversion “Surprisingly, the energy efficiency ratings of the
efficiencies as high as 21.8%, with an average of nanofibers are much greater than the 0.5 to 4%
12.5%. achieved in typical power generators made from
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