Using a simple setup--basically, two metal coils--MIT researchers have demonstrated for the first time that it's feasible to send power wirelessly as far as two meters. The approach might someday make it possible to charge batteries in laptops, cameras, or phones without plugging them in, says MIT physicist Marin ­Soljaˇci´c, who led the research with physicist John Joannopoulos. The technique involved, magnetic inductive coupling, has long been used to transfer power between transformers a few centimeters apart, but the MIT group extended its range by focusing the energy at a specific frequency. Power in a cable (1) is transferred to a copper coil antenna (2) that includes a disclike capacitor (3). The coil produces a magnetic field of around 10 megahertz. Energy (4) is transmitted by the magnetic field and received by an antenna (5) also resonating at around 10 megahertz. Ultimately, such a receiving antenna could be built into consumer electronics.

Credit: John Macneill