Drone flight times could soon be unlimited. Researchers believe a technology called inductive coupling can allow drones to recharge midflight.

Inductive coupling is the transfer of electromagnetic energy from one metal coil to another at a specific frequency. The phenomenon was first revealed by Nikola Tesla more than a century ago. While some smartphones and other small electronics can now recharge wirelessly, scientists have so far failed to use the technology to power up flying vehicles.

Scientists at Imperial College London, however, have offered hope of a breakthrough. Recently, researchers successfully charged a battery removed from a drone using inductive coupling. Their success inspired a live experiment.

Engineers at ICL bought a small quadcopter drone, removed its battery and wrapped the craft with a copper wire. They then created a charging station using another copper wire, a circuit board and a power source. Scientists reconfigured the drone's electronics to match the electromagnetic field created by the transmission device.

When the drone was flown over the charging station, its copper wire antenna fielded an alternating current from the magnetic field. The drone's electronics successfully converted the alternating current into a direct current capable of powering the device.

Currently, the technology only works when the drone is within four inches of the transmission device. But researchers are now looking for commercial partners to develop more ambitious wireless recharging devices.

"There are a number of scenarios where wirelessly transferring power could improve drone technology," Samer Aldhaher, a researcher and electrical engineer at ICL, explained in a news release. "One option could see a ground support vehicle being used as a mobile charging station, where drones could hover over it and recharge, never having to leave the air."

Wireless power transmission could allow drones to perform of variety of vital tasks. The technology could allow drones to transmit power to sensors on towers and bridges that monitor structural integrity. The possibilities outside the world of drones are promising, too.

"Another application could include implantable miniature diagnostic medical devices, wirelessly powered from a source external to the body," said Paul Mitchell, a professor of electronic engineering. "This could enable new types of medical implants to be safely recharged, and reduce the battery size to make these implants less invasive."