Triboelectrics offer step-change in energy generation

Zhong Lin Wang, a professor at the Georgia Institute of Technology, is using the triboelectric effect to create electrical power by rubbing or touching two different materials together.

He believes the research can provide a new way to power mobile devices such as sensors and smartphones by capturing the otherwise wasted mechanical energy from such sources as walking, the wind blowing, vibration, ocean waves or even cars driving by.

In its simplest form, the triboelectric generator uses two sheets of dissimilar materials, one an electron donor, the other an electron acceptor.

When the materials are in contact, electrons flow from one material to the other. If the sheets are then separated, one sheet holds an electrical charge isolated by the gap between them.

If an electrical load is then connected to two electrodes placed at the outer edges of the two surfaces, a small current will flow to equalize the charges.

By continuously repeating the process, an alternating current can be produced.

In a variation of the technique, the materials – most commonly inexpensive flexible polymers – produce current if they are rubbed together before being separated. Generators producing DC current have also been built.

‘The fact that an electric charge can be produced through triboelectrification is well known,’ Wang said in a statement. ‘What we have introduced is a gap separation technique that produces a voltage drop, which leads to a current flow in the external load, allowing the charge to be used. This generator can convert random mechanical energy from our environment into electric energy.’