Double permanent magnet vibration power generator for smart hip prosthesis

Ever since the first studies about biomedical implantable devices, the problem of how to energize them has stood out as both important and notoriously difficult to solve. In order to extend the lifetime of implants, it is imperative to develop power generators that are autonomous, safe and maintenance-free. Energy harvesting is a natural way of meeting these requirements. First, the energy source is theoretically everlasting, a fact that helps to guarantee the autonomy. Second, the energy is obtained from the environment of the application itself, contributing to its safety. Finally, a properly designed energy harvesting system is very unlikely to ever require maintenance. This paper follows this line and describes an electromagnetic power transducer that harvests electrical energy from the human gait and stores it. An efficient power management module uses the stored energy to energize the telemetric system of a smart hip prosthesis implant, enabling the early detection of loosening, the target application of this work. The system is able to extract a total 1912.5 mu J of usable energy under normal walking conditions. (C) 2011 Elsevier B.V. All rights reserved.