Hip Implant Energy Harvester

Abstract

Failed hip replacements have resulted in increased demand for revision hip surgeries and rising costs in healthcare. To mitigate the problem, instrumented hip prostheses have been proposed to detect the early signs and symptoms of failures in vivo. In the main, batteries and an inductive power link are used to power instrumented hip implants. However, batteries are an unattractive option because of their limited lifetime and the replacing of batteries requiring additional surgery. The use of an electromagnetic inductive link is a potential powering method but requires external drivers to activate implant systems, not preferable for home activity monitoring. Therefore, methods of powering instrumented hip implants by human movement are studied in this thesis.

An electromagnetic vibration energy harvester based on magnetic levitation is presented as suitable for low frequency, high amplitude excitation such as that associated with human motion. The constraints on the size of the harvester are due to the volume of the hip prosthesis which makes designing an effective energy harvester operating at a frequency below 10 Hz a significant challenge. To overcome this, a magnetically levitated electromagnetic vibration energy harvester based on coupled levitated magnets is presented with a nonlinear response, to extend operational bandwidth and enhance the power output of the harvesting device. Experiment results have demonstrated a improvement in the performance of a harvester based on coupled levitated magnets compared with that based on a single levitated magnet. The output voltage across the optimal load 2.66kΩ generated from hip movement is 0.122 Vrms (0.66 Vp-p) and 0.314 Vrms (2.54 Vp-p) during walking and running respectively. The power output obtained is 5.61 μW (walking) and 37.07 μW (running). The presented results demonstrate the feasibility of harvesting energy from hip movements to power the instrumentation.

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Identifiers

ORCID for Stephen Beeby: orcid.org/0000-0002-0800-1759

ORCID for Dibin Zhu: orcid.org/0000-0003-0517-3974

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