We live in a gadgets word and forgetting to plug and recharge your favorite device could sometimes mean a real disaster. But maybe soon enough we will have alternatives to the ubiquitous power wire.

A team of scientists form from MIT’s Department of Physics, Department of Electrical Engineering and Computer Science, and Institute for Soldier Nanotechnologies (ISN) has demonstrated a new concept, called “WiTricity”, (an acronym for wireless electricity).

They were able to light a 60W light bulb from a power source seven feet (more than two meters) away; there was no physical connection between the source and the appliance.

According to the MIT’s team WiTricity is based on using coupled resonant objects. Two resonant objects of the same resonant frequency tend to exchange energy efficiently, while interacting weakly with extraneous off-resonant objects.

The team explored a system of two electromagnetic resonators coupled mostly through their magnetic fields; they were able to identify the strongly coupled regime in this system, even when the distance between them was several times larger than the sizes of the resonant objects. This way, efficient power transfer was enabled. Magnetic coupling is particularly suitable for everyday applications because most common materials interact only very weakly with magnetic fields, so interactions with extraneous environmental objects are suppressed even further. “The fact that magnetic fields interact so weakly with biological organisms is also important for safety considerations,” Kurs, a graduate student in physics, points out.

The investigated design consists of two copper coils, each a self-resonant system. One of the coils, attached to the power source, is the sending unit. Instead of irradiating the environment with electromagnetic waves, it fills the space around it with a non-radiative magnetic field oscillating at MHz frequencies. The non-radiative field mediates the power exchange with the other coil (the receiving unit), which is specially designed to resonate with the field. The resonant nature of the process ensures the strong interaction between the sending unit and the receiving unit, while the interaction with the rest of the environment is weak. Moffatt, an MIT undergraduate in physics, explains: “The crucial advantage of using the non-radiative field lies in the fact that most of the power not picked up by the receiving coil remains bound to the vicinity of the sending unit, instead of being radiated into the environment and lost.”

With such a design, power transfer has a limited range, and the range would be shorter for smaller-size receivers. Still, for laptop-sized coils, power levels more than sufficient to run a laptop can be transferred over room-sized distances nearly omni-directionally and efficiently, irrespective of the geometry of the surrounding space, even when environmental objects completely obstruct the line-of-sight between the two coils.