In exemplary implementations of this invention, an implant device is wholly or partially implanted in a mammal. The implant device includes an antenna, circuitry, a supercapacitor, one or more light sources, and an array of optical fibers or light guides. The antenna and circuitry receive energy by wireless transmission from an external transmit coil. The supercapacitor stores at least a portion of the energy and provides power to one or more light sources. The array of optical fibers or light guides deliver light from the light sources to living tissue of a mammal. The tissue includes light-sensitive, heterologously expressed proteins. The light affects the light-sensitive proteins, triggering a change in all or part of the tissue, such as a change in voltage, pH or a change in function.
