iTechNote

Imagine a mobile device without the need to recharge ever. BBC News has a report on the work of Assistant Professor Marin Soljacic and his colleagues Aristeidis Karalis and John Joannopoulos about wireless power transfer.

The system is consisted of two antennas - one on the power source, the other on the device - resonating at 6.4MHz. The electromagnetic waves (energy) picked up by the device is used to recharge the battery. Resonance is a natural phenomena visibly observed in musical instruments.

In physics, resonance is the tendency of a system to oscillate when excited by energy at a certain frequency. This frequency is known as the system’s natural frequency of vibration, resonant frequency, or eigenfrequency. A resonant object, whether mechanical, acoustic, or electrical, will be easy to vibrate at resonant frequency, and more difficult to vibrate at other frequencies.

In order for it to work properly, a new class of “non-radiative” material is needed to achieve long-lived resonances. When energy is applied on the material, it does not scatter energy in all directions like normal material. Instead, its “tails” of energy will flicker over space few meters long. Energy not diverted into a mobile device is reabsorbed back to the power source minimizing the energy loss during the transfer.

If the range can be extended to 100 meters (the indoor range of 802.11b Wi-Fi), the technology has great potentials. Power suppliers can setup “hotspots” similar to the one you have for wireless Internet access now. When you are connected to Wi-Fi, your device is also charged at the same time. If the range is extended further over a metropolitan area, it truly achieves the goal of “always on” mobile device.

via BBC