Characterization of Foot Strike Motion and Biomechanical Energy Harvesting for Footwear

The low frequency of the foot strike motion and the cushioning requirements of the shoe heel pose a significant challenge in the development of energy-harvesting footwear. In this study, we propose an internally threaded sleeve structure to address these challenges through the implementation of a high-performance shoe-heel-mounted energy harvester. Our design tactfully uses a two-stage frequency-up conversion mechanism to capture foot strike energy while enhancing cushioning to improve overall wearing comfort. Additionally, we analyze the acceleration amplitude during the moment of touchdown in walking, examine its frequency response, and create a predictive model to estimate the power output of the energy harvester. Finally, we validate the cushioning functionality of the fabricated prototype and evaluate its power output through testing on treadmill walking conditions. The results demonstrate a 15.6% reduction in acceleration amplitude during heel touchdown in comparison to walking without the device. In terms of power output, the prototype achieves an average peak power of 3.7 W at a stride speed of 6 km/h, exceeding the performance of the previously reported footwear energy harvester.