A wireless power transfer system that can charge an LED bulb even as the bulb moves away from the power source is reported in this week’s Nature.

Developments in wireless power transfer have paved the way for applications such as the powering of implantable medical devices and the wireless charging of stationary electric vehicles. However, it has been challenging to create a robust system that maintains efficient transfer of power as the operating conditions - such as the distance between the source and the wirelessly powered device - vary.

Shanhui Fan and colleagues created a wireless power transfer system that can achieve high-efficiency power transfer over varying distances. Using the principle of parity-time symmetry - a concept from quantum mechanics - the authors produced electrical circuitry and were able to demonstrate power transfer efficiency that remains constant over a distance variation of approximately one metre. In experiments involving an LED bulb, the authors demonstrated that the bulb could be powered, producing a constant brightness, as it was moved away from the power source until it reached a separation distance of around one metre.

The authors suggest that their findings could have applications in delivering power to moving devices or vehicles, where the transfer distance and orientation can change continuously.