Scalable, Low‐Cost, Freeze‐Resistant Hydrogels by Alkali‐Polyphenol‐Triggered Polymerization for Low‐Temperature Self‐Powered Triboelectric Sensor

Hydrogels are promising flexible and conductive electrodes for triboelectric nanogenerators (TENGs), but their practical application is limited by cumbersome, high-cost fabrication processes and inferior frost resistance. Herein, a novel multifunctional alkali-polyphenol (DESL-OH^-) self-catalytic system is artfully designed to drive the rapid ambient polymerization of α-methacrylic acid (MAA) and hydroxyethyl acrylate (HEA) monomers, yielding a scalable, low-cost hydrogel with exceptional cryo-tolerance (-40°C), robust interfacial adhesion (0.065 MPa on paper), high conductivity (2.8 mS cm^-1), and optical transparency (>88%) within two min. Its anti-freezing performance stems from alkali-driven HEA hydrolysis to generate ethylene glycol (EG), forming an endogenous EG-water cosolvent system that disrupts the ordered tetrahedral arrangement of water molecules via hydrogen bonding interactions, suppresses ice nucleation, and thus maintains hydrogel functionality at extreme low temperatures. Harnessing these superior attributes, the hydrogel is assembled into a triboelectric nanogenerator (H-TENG) that operates stably at -40°C (open-circuit voltage = 154 V, short-circuit current = 1.00 µA, transferred charge = 34.6 nC), serving as both a reliable power supply for commercial electronics and a high-sensitivity tactile sensor for real-time human motion monitoring. This work establishes an efficient, sustainable fabrication paradigm for designing anti-freezing hydrogels devoid of exogenous cryoprotectants and provides critical insights for the development of next-generation wearable energy harvesters.