Engineers at the University of Michigan have now built the first millimeter-scale stand-alone device that speaks BLE. Consuming just 0.6 milliwatts during transmission, it would broadcast for 11 years using a typical 5.8-millimeter coin battery. Such a millimeter-scale BLE radio would allow these ant-size sensors to communicate with ordinary equipment, even a smartphone. In the new circuit, the team used the antenna itself as the inductor in the resonant tank. Because it was acting as an inductor, the antenna radiated using a changing magnetic field instead of an electric field; that meant it could be more compact.