Ambient Backscatter: Harvesting Power from Thin Air

A new system of wireless communication allows devices to interact and send data from one to another without having any source of power, whether it’s from batteries or a power outlet.
The system is based on the new ambient backscatter technology, which practically harvests all the existing signals in the air and converts them into power for communication devices.
University of Washington researchers created the new system, which absorbs all the different kinds of transmissions all around us in the air, from radio waves, TV and cell signals to mobile networks and Wi-Fi, and transforms them to both a source of electricity and a medium for battery-free communication.

Basically, prototype devices using the technology are equipped with antennas to pick up the signals and reflect them back and forth, in a coded version similar to Morse code. Other devices equipped with similar antennas then intercept and decode the signal and send a response, allowing full communication without any exterior power source and without any human intervention.
Washington University researchers tested the technology with devices the size of credit cards, consisting of circuit boards, antennas and a LED light, without any batteries. The devices were placed within several feet of each other and tested in different urban settings, including on a street corner and in an apartment.

The devices were able to communicate even when 6.5 miles away from a TV tower. The prototypes were able to transmit information at a rate of 1 kilobit per second both outdoors (2.5 feet apart) and indoors (1.5 feet apart). The rate is enough to transmit text messages or relay sensor data.
Researchers believe the technology can have multiple applications, most notably in speeding up the development of what is known as ‘the Internet of Things.’ The concept has to do with interconnecting everything in our environment, but one of the major obstacles is the need to provide every device that would be part of such a network with a sustainable power source.

The ambient backscatter technology could be used in construction, to incorporate sensors in concrete structures so as to monitor the integrity of that structure, without having to worry about the sensor running out of power.  The tech could also be used to allow smartphones to send text messages even if their battery is dead, or to tag various items such as keys, wallet or phone to transmit their location if they are lost.