Harvesting energy from human knee joint through a rope-driven mechanical motion switch

Abstract The knee joint possesses immense biomechanical energy, and harnessing this energy offers the potential to deliver clean and sustainable power for portable wearable devices. Nevertheless, efficient methods for harvesting knee joint energy remain a great challenge. This study introduces a rope-driven energy harvesting device (REH) that employs a mechanical motion switch (MMS) to effectively capture the negative work generated by the knee joint. The MMS-REH utilizes coaxially reverse-wound ropes to drive the MMS, which incorporates a sliding gear, thereby transforming the knee joint's low-frequency oscillatory motion into high-speed unidirectional rotation of an electromagnetic power generation unit. This device is characterized by its simple design, insignificant impact on human motion, and high efficiency in harvesting the knee joint's negative work. Under a 240 Ω load, as human movement speed increases from 1 to 7 km/h, the MMS-REH output voltage rises from 3.6 to 7 V, and the output power increases from 10 to 80.1 mW. By integrating the signal characteristics generated by the MMS-REH with deep learning techniques, the device can not only generate power but also function as a sensor. This dual capability not only presents an innovative energy solution for wearable devices but also highlights its potential applications in motion monitoring, rehabilitation therapy, and elderly health management.