Researchers at Duke University’s Pratt School of Engineering have designed a power-harvesting device with efficiency similar to that of modern solar panels. They used inexpensive materials configured and tuned to capture microwave signals, wirelessly converting the microwave signal to direct current voltage capable of recharging a cell phone battery or other small electronic device.

According to Duke's School of Engineering Web site, the device operates on a similar principle to solar panels, which convert light energy into electrical current. But this energy harvester could be tuned to harvest the signal from other energy sources, including satellite signals, sound signals or Wi-Fi signals.

They used a series of five fiberglass and copper energy conductors wired together on a circuit board to convert microwaves into 7.3V of electricity. By comparison, Universal Serial Bus (USB) chargers for small electronic devices provide about 5V. With additional modifications, the researchers said the power-harvesting metamaterial could potentially be built into a cell phone, allowing the phone to recharge wirelessly while not in use. This feature could, in principle, allow people living in locations without ready access to a conventional power outlet to harvest energy from a nearby cell phone tower instead...(Duke University)