Flexible Ti₃C₂T_<i>x</i> MXene/Polyolefin-Based Phase Change Foaming Film with Solar-Thermal Conversion and Sensitive Motion Detection for Wearable Thermal Management

For wearable thermal management, phase change materials (PCMs) with solar-thermal conversion capacity are highly desired. However, traditional solid–liquid PCMs suffer challenges such as inherent solid stiffness, liquid leakage, and limited motion sensing capability. Herein, the flexible POE elastomer functions as a continuous supporting phase encasing n-octadecane in these innovative Ti3C2Tx MXene/polyolefin elastomer (POE)-based phase change foaming films (FPPMs), which have high flexibility and form stability, superior solar-thermal conversion efficiency, and sensitive motion detection. The supercritical carbon dioxide (scCO2) foaming technique was employed to enhance the flexibility and thermal insulation performance of the synthesized flexible phase change films. The FPPMs demonstrated a relatively high energy storage density (147.6 J/g), excellent form stability, superior thermal management performance, and remarkable flexibility (tensile stress up to 1000 kPa). Additionally, the incorporation of single-layer Ti3C2Tx MXenes significantly enhanced the solar-thermal conversion efficiency (up to 86.94%) and improved the motion detection sensitivity of the PCM films. The FPPMs can be employed as a strain sensor to detect various human motions, including facial expression, wrist bend, elbow bend, and finger bend.