Highly Stretchable Ti3C2Tx MXene-Integrated Phase Change Films for Solar-Thermal Harvesting and Infrared Stealth

Phase change materials (PCMs) with superior solar-thermal harvest and efficient infrared stealth have crucial significance for modern military wearable thermal management but suffer from liquid leakage, poor motion detection, and intrinsic solid rigidity of conventional solid–liquid PCMs. In this work, highly stretchable phase change films (MPSPCFs) with sensitive motion detection, superior solar-thermal harvest, and efficient infrared stealth were designed using Ti3C2Tx MXene nanosheets, silicone rubber elastomers, n-eicosane, and poly(vinyl alcohol). The MPSPCF exhibited excellent energy storage density (107.1 J/g), long-term thermal reversibility (100 cycles), and superior flexibility. The lamination of MPSPCF with natural cotton fabrics enabled effective infrared stealth for thermal targets. Furthermore, due to the introduction of the MXene/PVA layer, the MPSPCF processed excellent solar-thermal conversion efficiency (η = 86.7%) and sensitive strain sensing (GF = 4.45). The MPSPCF-based thermoelectric power generation system was designed, which generated a maximum power of 91.95 mW. The MPSPCF could also be utilized as a strain sensor to detect human movement, including the bending motion of the finger, wrist, elbow, and knee. Combining these multiple functions, the MPSPCF developed in this work has great potential for personal thermal management applications in both military and civil fields, offering new ideas for the design of advanced PCM composites.