A device that can wirelessly charge a moving object at close range has been developed by Stanford University scientists. The technology could be used to charge electric cars on the motorway, or medical implants and cell phones as you walk nearby.

“In addition to advancing the wireless charging of vehicles and personal devices like cell phones, our new technology may untether robotics in manufacturing, which also are on the move,” said Professor Shanhui Fan.

To demonstrate the new technology, the team transmitted electricity wirelessly to a moving LED lightbulb.

“In theory, one could drive for an unlimited amount of time without having to stop to recharge,” Prof Fan explained. “A coil in the bottom of the vehicle could receive electricity from a series of coils connected to an electric current embedded in the road.”

Wireless technology could also assist GPS navigation of driverless cars.

According to the researchers, mid-range wireless power transfer is based on magnetic resonance coupling. The continuous flow of electricity can only be maintained, however, if some aspects of the circuits, such as the frequency, are manually tuned as the object moves.

To address the challenge, the Stanford team eliminated the radio-frequency source in the transmitter and replaced it with a commercially available voltage amplifier and feedback resistor. This system automatically figures out the right frequency for different distances without the need for human interference.

“We can rethink how to deliver electricity not only to our cars, but to smaller devices on or in our bodies,” Fan said.