Researchers are exploring a phenomenon called "evanescent coupling" as a way to juice up devices powered by rechargeable batteries without connecting them directly to a charger. Unlike electromagnetic induction–the technology that charges electric toothbrushes and early pacemakers–which requires the charger to be very close to the device, this new approach could potentially work at distances of several meters, claim the MIT physicists. From New Scientist:
Evanescent coupling…allows electromagnetic energy "trapped" in a charging device to be tapped by a "drain" mobile device if the two have the same resonant frequency.
"The energy is trapped at source, until I bring a device that has the same resonant frequency close to it. Only then can the energy 'tunnel through'," says (researchers Marin) Soljacic. Crucially, the "charger" only starts powering another device when a compatible gadget comes within range…
Placing one of these wireless chargers in each room of a home or office could provide coverage throughout the building.
