If you're wondering how power works, one of Praviz's previous projects was a contact lens with a working LED. Power for that was described as being "powered remotely using a 5-millimeter-long antenna printed on the lens to receive gigahertz-range radio-frequency energy from a transmitter placed ten centimetres from the eye." The copper circle around the edge of this lens is most likely an inductive charging coil, so actual use of this will probably require some kind of face-mounted charging antenna.