A flexible wearable phase change composite with electro-/photo-thermal heating for personal thermal management and human body motion detection

There is an urgent need to develop flexible materials with electrothermal/photothermal conversion and energy storage/release capabilities to meet the requirement of wearable personal thermal management (PTM) and health monitoring. Here, sandwich-structured phase change composites (SSPCCs) with PTM and health monitoring were prepared through film-forming and pressing process, in which a poly (ethylene vinyl acetate) (EVA)/poly (ethylene glycol) (PEG) composite was the middle layer, and waterborne polyurethane (WPU)/carbon nanotubes (CNTs) films were the top and bottom layers. The electrical conductivity and tensile strength of the two outer layers with 3 phr CNTs can achieve 2.83 S/m and 12.96 MPa, respectively. Due to the multiple synergistic effects of sandwich structure, the SSPCCs exhibit excellent flexibility with an elongation at break of approximately 1173 %, good stability and durability of 500 cycles and admirable electro-/photo-thermal heating performance (∼40 °C at 7 V or NIR light power of 50 mW/cm2). In addition, the inner layer, where the flexible EVA hold PEG well, has a melting latent heat of 71.45 J/g and freezing latent heat of 65.79 J/g in the phase change process as the mass ratio of PEG reached 50 wt%. The prepared composites show good abilities of information encryption and motions monitoring, which turns out great promising applications in wearable personal thermal management and medical devices.