Ionic Hydrogel Triboelectric Sensor for Real-Time Swimming Kinematics Monitoring and Stroke Recognition

Recently, wearable sports electronics have attracted increasing attention for their potential to enable continuous motion tracking and energy-autonomous operation in complex athletic environments. In this work, we present a flexible triboelectric nanogenerator (PAC-TENG) constructed from a PVA/Ala/CaCl₂ ionic hydrogel electrode and a compliant silicone triboelectric layer. The PAC hydrogel provides high stretchability, stable ionic conductivity, and strong deformation tolerance, while the silicone surface ensures efficient and repeatable charge generation. Benefiting from this synergistic design, the PAC-TENG achieves excellent electrical outputs, including a peak voltage of 472.9 V, a short-circuit current of 37.1 µA, and a transferred charge of 104.1 nC, along with high power density under matched load. The device exhibits strong sensitivity to bending angle, applied force, and motion frequency, enabling accurate perception of human biomechanics. When mounted on swimming-related joints, the PAC-TENG can reliably monitor stroke patterns and detect abnormal motion signals, highlighting its promise for self-powered aquatic sports analytics and intelligent safety monitoring.