(July 9, 2012) Researchers
have discovered yet another way to harvest small amounts of electricity from
motion in the world around us – this time by capturing the electrical charge
produced when two different kinds of plastic materials rub against one another.
Based on flexible polymer materials, this “triboelectric” generator could
provide alternating current (AC) from activities such as walking.
The
triboelectric generator could supplement power produced by nanogenerators that
use the piezoelectric effect to create current from the flexing of zinc oxide
nanowires.
The triboelectric
generator operates when a sheet of polyester rubs against a sheet made of
polydimethysiloxane (PDMS). The polyester tends to donate electrons, while the
PDMS accepts electrons. Immediately after the polymer surfaces rub together,
they are mechanically separated, creating an air gap that isolates the charge
on the PDMS surface and forms a dipole moment.
“The fact that an electric charge
can be produced through this principle is well known,” said Zhong Lin Wang, a
Regents professor in the School of Materials Science & Engineering at the
Georgia Institute of Technology. “What we have introduced is a gap separation
technique that produces a voltage drop, which leads to a current flow, allowing
the charge to be used. This generator can convert random mechanical energy from
our environment into electric energy.”
The research was funded by the National
Science Foundation, the Department of Energy and the U.S. Air Force. Details were reported in the June issue of
the journal Nano Letters. In addition to Wang, authors of the paper included
Feng-Ru Fan, Long Lin, Guang Zhu, Wenzhuo Wu and Rui Zhang from Georgia Tech.
Fan is also affiliated with the State Key Laboratory of Physical Chemistry of
Solid Surfaces at Xiamen University in China.