1. An implantable device comprising: an array of silicon nanowires having a predetermined spatial distribution, density, size and shape, each nanowire having a first end and a second end, the array of nanowires configured to be implanted within a tissue for receiving a triggering signal; an electrical conductor disposed at a the first end of all nanowires in the array of nanowires; a bias source in electrical communication with the electrical conductor for biasing the array; and an electrode disposed on a the second end of each nanowire to define a plurality of electrodes, wherein each nanowire produces a current at a corresponding electrode in response to detection of the triggering signal, wherein the array of nanowires generates an output signal corresponding to the currents produced in response to the triggering signal.