Heterogeneous phase-change polyelectrolyte-based flexible temperature sensors via thermally-driven for tunable wide-range temperature monitoring.

Flexible temperature sensors are key to flexible electronics. To address narrow range, low sensitivity and poor stability, we use poly(n-alkyl acrylate) copolymers and ionic liquids(LiTFSI), propose thermally driven ion transmembrane migration, and design an asymmetric bilayer structure. By regulating the alkyl side-chain length and blending ratio of acrylate monomers according to the specific temperature requirement, the temperature sensing interval of the sensor can be precisely controlled to be approximately 9 °C. Sensors fabricated with different formulations of this series of materials achieve cumulative temperature-range coverage. Sensors prepared from four homologous materials in this work, namely dodecyl acrylate (DA), hexadecyl acrylate (HA), octadecyl acrylate (SA), and butyl acrylate (BA), at varied blending ratios enable continuous temperature detection across a broad range from -20 °C to 70 °C. Under the optimized ionic liquid doping concentration, the sensor obtains an ultrahigh temperature coefficient of resistance (TCR) of -7.51% °C-1, a high detection resolution of 0.1 °C. The sensor maintains stable sensing signals under bending, stretching, twisting and pressure deformation, showing excellent mechanical robustness. It can realize real-time temperature monitoring in various scenarios, including low-temperature cold chain, human body temperature detection, battery overheating and fire hazard early warning, and can be integrated into flexible touch-sensing arrays, which provides a new material system and sensing strategy for high-performance flexible temperature sensors.