Close Integration of a UHF-RFID Transponder Into a Limb Prosthesis for Tracking and Sensing

Abstract

The technology of structural radio systems that is well assessed in the avionic and naval communications is here applied to obtain antenna functionality out of a limb prosthesis with minimal changes to the device, in specific, an orthopedic nail. A microchip transponder based on the ultrahigh frequency-radio-frequency identification (RFID) communication standard is connected to the nail by means of a central notch forming a towel-bar-like antenna. The resulting device, called prosthetic structural tag, is such to preserve the mechanical continuity of the original nail, but it is also capable of energy harvesting and RFID. The electrical and geometrical control parameters for impedance tuning were identified using computer simulation and laboratory tests. The radiation performance is mostly dependent on the geometry of the notch, while it is rather unaffected by the length of the nail, so that the proposed layout may also be applied to different kinds of prosthesis. The experimented read distance at 870-960 MHz was more than 35-cm far from the limb surface. The augmented smart prosthesis is, hence, suitable to be monitored using an external non-contacting antenna for application to tracking and, in the near future, to monitor the prosthesis health status.