Tesla Revisited: Wireless Devices That Harvest Energy From Thin Air Demonstrated

We might be one step closer to an Internet-of-things reality.

University of Washington engineers have created a new wireless communication system that allows devices to interact with each other without relying on batteries or wires for power, instead harvesting energy directly from the ambient radio-frequency signals that surround us nearly everywhere.

The new communication technique, which the researchers call “ambient backscatter,” takes advantage of these TV and cellular transmissions. Two devices communicate with each other by reflecting the existing signals to exchange information. The researchers built small, battery-free devices with antennas that can detect, harness and reflect a TV signal, which then is picked up by other similar devices.
The technology could enable a network of devices and sensors to communicate with no power source or human attention needed.

“We can repurpose wireless signals that are already around us into both a source of power and a communication medium,” said lead researcher Shyam Gollakota, a UW assistant professor of computer science and engineering. “It’s hopefully going to have applications in a number of areas including wearable computing, smart homes and self-sustaining sensor networks.”

“Our devices form a network out of thin air,” said co-author Joshua Smith, a UW associate professor of computer science and engineering and of electrical engineering. “You can reflect these signals slightly to create a Morse code of communication between battery-free devices.”

Smart sensors could be built and placed permanently inside nearly any structure, then set to communicate with each other. For example, sensors placed in a bridge could monitor the health of the concrete and steel, then send an alert if one of the sensors picks up a hairline crack. The technology can also be used for communication – text messages and emails, for example – in wearable devices, without requiring battery consumption.

The researchers tested the ambient backscatter technique with credit card-sized prototype devices placed within several feet of each other. For each device the researchers built antennas into ordinary circuit boards that flash an LED light when receiving a communication signal from another device.
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