Researchers and engineers in the United States have designed a new method for generating electricity, which gathers power from lost energy sources such as microwave signals, sounds or even Wi-Fi.

A team at Duke University's Pratt School of Engineering have used inexpensive materials configured and tuned to capture particular signals.

In their recent demonstration, the team used a series of five fibreglass and copper energy conductors wired together on a circuit board to convert microwaves into 7.3V of electrical energy. The standard power supply needed for USB devices is only 5V.

The key to the novel power harvester lies in its application of ‘metamaterials’; engineered structures that can capture wave energy and tune them for useful applications.

Tests have already indicated the technique can achieve results in the range of current solar cells.

“We were aiming for the highest energy efficiency we could achieve,” said undergraduate engineering student Allen Hawkes.

“We had been getting energy efficiency around 6 to 10 percent, but with this design we were able to dramatically improve energy conversion to 37 percent, which is comparable to what is achieved in solar cells.”

“The properties of metamaterials allow for design flexibility not possible with ordinary devices like antennas,” said graduate student Alexander Katko.

“When traditional antennas are close to each other in space they talk to each other and interfere with each other's operation. The design process used to create our metamaterial array takes these effects into account, allowing the cells to work together.”

“Our work demonstrates a simple and inexpensive approach to electromagnetic power harvesting,” said lead investigator Steven Cummer, professor of electrical and computer engineering.

“The beauty of the design is that the basic building blocks are self-contained and additive. One can simply assemble more blocks to increase the scavenged power.”

Full details of the technological breakthrough have now been published online.