MIT professor pulls plug on cables

New concept resonates with sense for wireless power transmission

A future free of tangled wires and cables could be possible thanks to a development by US researchers.

A team from the Massachusetts Institute of Technology (MIT) has successfully tested an experimental system dubbed Witricity (wireless electricity) that can deliver power to devices without the need for wires, reports the journal Science.

The journal said the setup was able to make a 60W light bulb glow from a distance of 2m (7ft).

Appliances would need to be within range of a Witricity transmitter for this to work; but it opens up the possibility that devices such as notebook PCs, mobile phones and a myriad other electronic gadgets could automatically recharge themselves without needing to be plugged into the electrical supply.

Witricity exploits basic physics making use of "resonance", a phenomenon that causes an object to vibrate when energy of a certain frequency is applied.

When two objects have the same resonance they exchange energy without having an effect on other surrounding objects. There are many examples of resonance such as acoustic resonance.

The Witricity system consists of two copper coils, one sending power, the other receiving it. The receiver is designed to resonate at the same frequency as the magnetic field generated by the transmitter.

MIT physics professor Marin Soljacic, who lead the teams, explained: "If you fill a room with hundreds of identical glasses and you fill each one with a different level of wine each one will have a different acoustic resonance."

If tapped with a spoon, each glass would ring with a different tone.

Professor Soljacic's inspiration for Witricity grew out of his frustration at having to find a plug to charge his mobile phone. "It occurred to me that it would be so great if the thing took care of its own charging," he said.

There should be no adverse health issues because Energy would only be picked up by gadgets designed to "resonate" with the field.

Witricity transmitters could over the next few years eventually replace most power cables, in the same way that mobile and cordless phones had supplanted landlines.