Capturing the electrical charge between plastics

Researchers have discovered a way of 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).

The triboelectric generator could supplement power produced by nanogenerators that use the piezoelectric effect to create current from the flexing of zinc oxide nanowires.

What we have introduced is a gap separation technique that produces a voltage drop, which leads to a current flow

Because these triboelectric generators can be made nearly transparent, they could offer a new way to produce active sensors that might replace technology now used for touch-sensitive device displays.

“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 and 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 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.

If an electrical load is then connected between the two surfaces, a small current will flow to equalize the charge potential.

By continuously rubbing the surfaces together and then quickly separating them, the generator can provide a small alternating current. An external deformation is used to press the surfaces together and slide them to create the rubbing motion.

The res earch was funded by the National Science Foundation, the Department of Energy and the US Air Force.