Scientists plumb water power for mobiles

The technology is based on the interaction between liquids and solids on a very small scale. The surface of the solid receives a small charge that attracts opposite-charged ions in the liquid and repels like-charged ions. The process creates an electric double layer (EDL)--a thin liquid layer with a net charge that ranges from a thickness of several nanometers to a few micrometers.

Professors Daniel Kwok and Larry Kostiuk from the University of Alberta created channels similar in size to the EDL and forced liquid through the channels, resulting in a movement of net charges downstream. Because the ions that are repelled by the surface move faster than the ions that are attracted to the surface, a current is generated, which leads to a voltage difference across the ends of the channel if the solid is a nonconducting material.

The power generated from a single channel is extremely small--a 30cm column of water will produce one to two microamps (one millionth of an amp)--but the researchers envisage millions of parallel channels being used to increase the power output to a level sufficient to power small electrical devices such as mobile phones and calculators.

The system requires input of energy in the form of applying pressure to the liquid in the channels. Mobiles powered by this method would not be plugged into power mains to recharge, but would require pumping.

"The applications in electronics and microelectronic devices are very exciting," Kostiuk said. "This technology could provide a new power source for devices such as mobile phones or calculators which could be charged up by pumping water to high pressure. What we have achieved so far is to show that electrical power can be directly generated from flowing liquids in microchannels."

The research was published recently in the Journal of Micromechanics and Microengineering published by the Institute of Physics.

James Pearce of ZDNet Australia reported from Sydney.