“A Stanford engineering team, in collaboration with researchers from the University of California, Berkeley, has built a radio the size of an ant, a device so energy efficient that it gathers all the power it needs from the same electromagnetic waves that carry signals to its receiving antenna – no batteries required.”

Source: news.stanford.edu

Via Gizmag:

http://www.gizmag.com/radio-on-a-chip-transceiver-iot/33797/