A Piezoelectric Electromagnetic Composite Wearable Device for Lower Limb Motion Monitoring

This paper presented a piezoelectric–electromagnetic composite wearable device for lower‐limb motion monitoring (PEW‐LMM), to respond to the need of intelligent health devices for human body movement monitoring. It incorporates a piezoelectric energy harvesting module (PEM) as the primary energy harvesting and sensing unit, and an electromagnetic sensing module (ESM) as an auxiliary self‐powered sensing channel. By integrating piezoelectric and electromagnetic technologies and optimizing structural parameters, the device achieves efficient energy conversion and precise motion monitoring. The optimal configuration was obtained with a spring wire diameter of 0.8 mm and a sphere diameter of 18 mm. At 2 Hz excitation, the upper piezoelectric patches achieved 276.67 V pp and a maximum output power of 129.032 mW. The lower piezoelectric patches produced 149 V pp maximum voltage and 154.88 mW maximum power output. The total power density can reach 9.91 mW/cm 3 . Experiments have demonstrated that the structure is capable of successfully lighting high‐power LEDs of 200 μW and powering electronic devices. In wearable performance testing experiments, the PEW‐LMM can monitor different motion states by outputting voltage signals with different characteristics. It has proven its ability to analyze motion states and provides a new solution for the field of motion rehabilitation.