Researchers at the Institute of Nanotechnology at Sungkyunkwan University in Seoul, South Korea have developed a new technique for turning sound into electricity, allowing a mobile phone to be powered up while its user holds a conversation. The technology would also be able to harness background noise and even music to charge a phone while it is not in use.
Sound power can be used for various novel applications including cellular phones that can be charged during conversations and sound-insulating walls near highways that generate electricity from the sound of passing vehicles. A prototype of the technology was able to convert sound of around 100 decibels – the equivalent of noisy traffic – to generate 50 millivolts of electricity.
The technology uses tiny strands of zinc oxide sandwiched between two electrodes. A sound absorbing pad on top vibrates when sound waves hit it, causing the tiny zinc oxide wires to compress and release. This movement generates an electrical current that can then be used to charge a battery. Even though this is not enough to charge a phone properly, researchers hope that by altering the material the wires are made from they will be able to produce more energy at lower sounds levels. [source]