RectennaDevices that convert the energy from electromagnetic waves (AC) into DC are called rectennas. The researchers have developed a new version (described in Nature), which uses a flexible RF antenna that ‘catches’ electromagnetic waves (including WiFi signals).
A few atoms thickThis antenna is then connected to a circuit that consists of a two-dimentional semiconductor, which is just a few atoms thick. The AC signal runs through the semiconductor, which turns it into a DC voltage that can be used to power electronic devices or charge batteries.
R2RIn this way the circuit passively captures useful energy from the ubiquitous WiFi signals. A big advantage is that the new circuit is flexible and can be manufactured in a roll-to-roll proces (R2R) for large-scale use. A first applications for the new antenna are, for example, powering flexible, wearable, medical devices and sensors for the IoT.
ImplantsIn experiments the new antenna was capable of producing a power of about 40 µW when exposed to a typical WiFi power of 150 µW – more than enough to light up an LED or to power a silicon chip. This opens possibilities for medical implants (including pills that can be swallowed by a patient and which transmit diagnostic information to a receiver).
MolybdenumThe rectifier is made from molybdenum-disulphide (MoS2), that, with a thickness of only three atoms, is one of the thinnest semiconductors in the world. When exposed to certain chemicals a transition from semiconductor to metal is created – in principle a Schottky-diode. The parasitic capacitance of this diode is so small that it is possible to rectify wireless signals up to 10 GHz.