But, in a new study published in the journal Nature Communications, Wang's team said they had overcome key hurdles to converting a haphazardly-generated electrical charge into current. Their prototype comprises a disc about 10 centimetres (four inches) across, designed to show the potential from a small, portable generator moved by ambient energy.
Inside are two circular sheets of material, one an electron "donor" and the other an electron "receiver," brought together through rotary movement. If the sheets are separated, one then holds an electrical charge isolated by the gap between them.
Sandwiched between the two discs is a third disc with electrodes, which bridges the gap and helps a small current to flow. At a top speed of 3,000 revolutions per minute, the device generated 1.5 watts.
This gave it an energy efficiency of 24 percent, three times greater than piezoelectric, the previously best source of mechanical electricity harvesting -- and as efficient as magnetic-induction turbines.
It can run on a gentle wind or tap water, or "random jerky motions," including human movement, to provide the rotation, Wang said. "As long as there is mechanical action, there is power that can be generated."
The prototype used copper for the rotator and gold for the electrodes in lab tests, but these could easily be substituted for low-cost synthetics, he said. The team is working on ways to scale up tribo-electric energy for harvesting power from the ocean. Watch a video below to see how the technology works.