Flexible and Photothermally active polymer-PCM composite for wearable thermal therapy

Phase change materials (PCMs) offer significant potential for thermal therapy because they can store and release heat within physiologically relevant temperature ranges. However, their application in wearable thermal therapy is hindered by the rigidity of traditional encapsulation methods used to prevent PCM leakage, which limits flexibility and comfort. Integrating photothermal capability offers an attractive route toward passive, light-activated thermal therapy without external energy input. In this work, a flexible, shape-stable, and photothermally active composite was developed for wearable thermal therapy applications. Paraffin wax (PW) was incorporated into a porous polydimethylsiloxane (PDMS) scaffold reinforced with expanded graphite (EG), thereby enhancing thermal conductivity and light-to-heat conversion. The porous EG–PDMS structure was fabricated using a sugar-templating strategy, followed by vacuum-assisted infiltration of PW to ensure uniform loading. An outer EG-modified PDMS coating was applied to suppress leakage while enabling efficient photothermal heating. The resulting composite exhibited excellent mechanical flexibility, strong shape stability, enhanced thermal conductivity (0.506 W/m.K), and high photothermal conversion efficiency of 98.6% under light exposure. These features make the PDMS/EG/PW composite a promising solution for safe and effective wearable thermal therapy devices, combining comfort, durability, and thermal performance.