implantable biomedical sensor device for measuring in vivo the presence and / or concentration of physiological substances , such as the concentration of glucose , in a human or animal body . a miniaturized electronic responder arranged in a closed housing of biocompatible material in an electromagnetic interrogation field is capable of contactlessly exchanging binary coded information with a transmitter / receiver , and includes electrical connections passed through the wall of the housing , at least a work electrode , a counter - electrode and preferably also a reference electrode outside the housing . the work electrode includes a membrane with hollow fibers extending transversely to the surface of the membrane and having internal walls coated with a conductive polymer and in which a redox enzyme is disposed . one end of the hollow fibers is in electrical contact with a processing device which converts the signals supplied by the work electrode in operation to binary signals .