Design considerations of an electromechanical generator implanted in human total knee prosthesis

The energy generation inside the human body represents a crucial aspect for powering implantable measuring circuits. In this work, a system for the electromagnetic energy harvesting, implantable in a total knee prosthesis (TKP) and capable of generating electricity from the knee movement, is presented. The energy harvesting system (EHS) is composed of two series of NdFeB magnets, located on each condyle, and a coil placed in a pivot of the tibial tray. The operating principles, design considerations and performed simulations are shown. Simulation results demonstrate that it is possible to generate an alternating voltage of maximum 600 mV. The proposed generator eliminates the batteries inside the human body and the use of techniques for the inductive power supply. The structural changes with respect to commercial prosthesis are minimal. Furthermore, the proposed energy harvester allows to generate electricity without changing or hindering the patient natural movement.