DUKE UNIVERSITY RESEARCHERS CONVERT MICROWAVE SIGNALS TO CHARGE MOBILE PHONE

Researchers claim the technology would allow citizens residing in regions without access to a power outlet to produce energy from a close by cell phone tower

Researchers from the Duke University's Pratt School of Engineering have created a device capable of converting the microwave signal into direct current voltage, which can be used for recharging a cell phone battery or other small electronic devices.

Operating on a similar principle of solar panels which converts light energy into electrical current, the new energy harvester was created using metamaterials that capture diverse forms of wave energy and modify them for other applications.

Duke University graduate student Alexander Katko said that the design could be used for a lot of different frequencies and types of energy, including vibration and sound energy harvesting.

"Until now, a lot of work with metamaterials has been theoretical. We are showing that with a little work, these materials can be useful for consumer applications," Katko said.

"The properties of metamaterials allow for design flexibility not possible with ordinary devices like antennas," said 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."

Researchers used fibreglass and copper conductors on a circuit board to convert microwaves into 7.3 volts of electricity, while the device could also be used to harvest satellite, sound or Wi-Fi signals in future.

Duke University undergraduate engineering student Allen Hawkes said that researchers' team is aiming for the highest energy efficiency they could achieve.

"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," Hawkes said.

Researchers also hoped that the further transformation of the power-harvesting metamaterial would allow building it into a cell phone, which would allow wirelessly recharging the phone when not in use.

Duke University electrical and computer engineering professor, lead investigator Steven Cummer said that the work demonstrates a simple and inexpensive approach to electromagnetic power harvesting.

"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," Cummer said.