Mobiles can be Charged with the Wave of a Hand

Imagine charging your cell phone or iPod by waving your hand, or stretching your arm, or taking a stroll. Well, it could be a reality soon.

Scientists are mulling a technology which can convert mechanical energy from body movements or the flow of blood in the body into electric energy that may be utilised to power a broad range of electronic devices without batteries.

"This research will have a major impact on defence technology, environmental monitoring, biomedical sciences and even personal electronics," lead researcher Zhong Lin Wang of the Georgia Institute of Technology said.

In fact, the new "nanogenerator" could have countless applications, among them a way to run electronic devices used by the military when troops are far in the field.

According to the researchers, harvesting energy from the environment by converting low-frequency vibrations, like simple body movements, the beating of the heart or movement of the wind, into electricity, using zinc oxide (ZnO) nanowires that conduct the electricity.

The ZnO nanowires are piezoelectric — they generate an electric current when subjected to mechanical stress. The diameter and length of the wire are 1/5,000th and 1/25th the diameter of a human hair.

In generating energy from movement, the researchers concluded that it was most effective to develop a method that worked at low frequencies and was based on flexible materials.

The ZnO nanowires met these requirements. At the same time, they say a real advantage of this technology is that the nanowires can be grown easily on a wide variety of surfaces, and the nanogenerators will operate in the air or in liquids once properly packaged.

Among the surfaces on which the nanowires can be grown are metals, ceramics, polymers, clothing and even tents.

"Quite simply, this technology can be used to generate energy under any circumstances as long as there is movement. The nanogenerator would be particularly critical to troops in the field, where they are far from energy sources and need to use sensors or communication devices," Mr. Wang said.

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