An In-Shoe Harvester With Motion Magnification for Scavenging Energy From Human Foot Strike

The aim of this study was to develop an in-shoe magnetic harvester that could be embedded in a shoe to scavenge mechanical energy from human foot strike for conversion into electricity, thereby serving as a sustainable power source for portable or wearable electronic devices. The allowed displacement of the shoe heel in the vertical direction was extremely small; therefore, a special trapezoidal slider mechanism was employed to amplify the displacement of a footstep. To compensate for the low-frequency foot strike, a gear train was used to accelerate the motion that finally drove a microgenerator to produce electricity. Two sets of springs were employed to provide a restoring force for the trapezoidal slider mechanism that enabled the harvester to generate electricity during the return trip. The in-shoe harvester could be embedded in a shoe heel such that the human foot step was not hindered during activity. Experiments indicated that the harvester could generate an average power output of approximately 1 W during normal walking. Compared to harvesters from previous studies, the harvester in this study can generate a higher power output.