But a new type of power-harvesting device developed at Duke University has been able to capture and convert microwave signals into usable direct current that could charge small electronic devices.

Researchers at Duke's Pratt School of Engineering have configured a wireless power-harvesting device made with inexpensive materials to be able to recapture some of this 'lost' energy and turn it into a viable power source for gadgets. The new device uses a series of conductors connected together on a circuit board, and can put out about 7.3V of electrical energy (compare with a small USB charger with a 5V output).