Flexible Hydrogel‐Based Triboelectric Nanogenerator for Self‐Powered Motion Sensing and Intensity Evaluation in Tennis Athletes

Recently, intelligent wearable electronics have received considerable attention for their potential in health monitoring, motion sensing, and human–machine interaction. Here, we developed a montmorillonite (MMT)/polyvinyl alcohol (PVA)/hydroxyethyl cellulose (HEC)‐based triboelectric nanogenerator (MPH‐TENG), where PVA serves as the polymer matrix and MMT nanosheets and HEC chains act as functional fillers to construct a reinforced hydrogel network. The hybrid structure endows the device with high ionic conductivity, mechanical stretchability, and reliable environmental adaptability. The MPH‐TENG delivers outstanding electrical outputs, including a peak open‐circuit voltage ( V OC ) of 188 V, a short‐circuit current ( I SC ) of 28 μA, and a transferred charge ( Q SC ) of 108 nC per cycle, with a maximum power density of ∼1.8 mW (optimal resistance: ∼5 MΩ). Beyond energy harvesting, the MPH‐TENG functions as a robust self‐powered sensor that can capture delicate motions, such as finger flexion for grip adjustments, as well as larger joint activities, including elbow extension and knee bending, which are critical for stroke execution and footwork in tennis. In tennis practice, the MPH‐TENG tracks wrist, grip, and leg motions in real time, enabling both performance optimization and injury prevention. This underscores its role as a robust and multifunctional solution for wearable sports sensing and intelligent monitoring.