Flexible phase change sensors with improved heat dissipation for wearable thermal management

Phase change materials (PCMs) are extensively utilized as mediums for thermal storage and temperature regulation, owing to their exceptional capacity to absorb or release substantial amounts of latent heat at a constant phase change temperature. However, the intrinsic low thermal conductivity, solid-state rigidity, hydrophilicity, and electrical insulation challenges associated with PCMs significantly restrict their practical applications in the domain of flexible wearable thermal management. In this context, this paper introduces a straightforward yet effective method for fabricating flexible composite PCM films that exhibit enhanced mechanical strength, hydrophobicity, electrical conductivity, and improved thermal conductivity. The polymer matrix employs boronic acid bonding, B-N coordination bonding, and hydrogen bonding interactions as robust physical cross-links. This approach yields composites with impressive mechanical strength (114.0 MPa), notable self-healing capabilities (81.08 % self-healing within 24 h at 80 ℃), and recyclability (94 %). The composites achieved high hydrophobicity (contact angle of 134°) through modulation of the polymer molecular structure. Furthermore, by leveraging the interaction between carbon nanotubes and graphene nanosheets, these composites exhibited an electrical conductivity of 5.56 S/m-effectively addressing the insulating properties inherent to PEG-based materials. Remarkably, the heat dissipation performance of these composites was substantially enhanced-with a thermal conductive efficiency reaching up to 1033 %-following the incorporation of modified hexagonal boron nitride. Additionally, the composite PCM demonstrated excellent Joule heating and photothermal conversion efficiencies (94.31 %, under an input power density of 100 mW·cm⁻²) alongside superior energy storage capabilities. Simultaneously, this composite PCM is capable of rapidly monitoring human motor activities and subtle muscle changes (with a normative factor GF = 7.99). Therefore, integrating solar energy harvesting with Joule heating into a wearable flexible PCM presents promising potential for developing next-generation personal thermal management systems that are adaptable across various weather conditions and seasons while being dual-mode triggered for complex variable applications.