Scientists are creeping closer to delivering power without a cord. This would enable truly wireless devices.

MIT researchers are working on the well-known phenomenon of electromagnetic induction, by which a current running in one coil can induce a current in another nearby coil, but now claim to be able to extend this effect over much longer distances than previously thought possible.

At the moment, that is still the length of a room thanks to what's known as a "non-radiative" power transmitter that can generate an electrical field that a specially designed receiver, in a laptop or mobile phone for example, can pick up and use to charge its batteries.

The non-radiative part is important: attempting to transfer energy between two points via electromagnetic radiation is both inefficient and potentially dangerous.

Speaking at the annual 2006 American Institute of Physics' Industrial Physics Forum, MIT's Marin Soljacic and two colleagues, Aristeidis Karalis and John Joannopoulos, explained that they began wrestling with the problem when Soljacic found, yet again, that his mobile phone battery had died in the early hours. "Wouldn't it be great if this thing charged itself?" he had asked himself.

So far, the research consists of theoretical calculations and simulations. But the team did conclude that with such a non-radiative power source, a laptop could recharge itself by being a few metres away.