Smart Flexible Fabrics for Energy Storage, Self‐Heating, Energy Harvesting, and Self‐Powered Motion Sensing at Low Temperatures

Abstract Energy harvesting and storage at extreme temperatures are significant challenges for flexible wearable devices. This study innovatively developed a dynamic‐bond‐cross–linked spinnable azopolymer‐based smart fabric (PAzo‐M/PVA, M = Mg, Ca, Zn) capable of photothermal energy storage, light‐induced self‐heating, mechanical energy harvesting, and self‐powered motion sensing under cold conditions, overcoming issues like low energy density and poor structural stability when azopolymers are combined with other fabrics via impregnation or spraying. PAzo‐Mg, operating without solvents, demonstrated high energy density (264.8 J g ⁻¹ ) and long‐term stability (14 days). Upon light excitation at −20 °C, this fabric achieved the highest temperature increase (9.3 °C) and sustained self‐heating for 45 minutes. A triboelectric nanogenerator based on this fabric achieved a maximum output power density of 3.43 W m ⁻² and demonstrated excellent durability (≈10 000 cycles) at −20 °C, with light‐induced trans/cis isomerization and dynamic bond formation/dissociation affected the electrical output, a phenomenon not previously reported. Moreover, a self‐powered motion sensor embedded with this fabric successfully detected subtle pulse variations during outdoor human activities at −18 to −21 °C. This smart fabric combines energy storage, self‐heating, and triboelectric power generation at low temperatures, providing a feasible solution for creating flexible wearable devices for complex environments.