Flexible core-sheath thermochromic phase change fibers for temperature management and electrical/solar energy harvesting

As clean and repeatable thermal energy storage materials, phase change materials (PCMs) exhibit excellent capability in absorption and releasing latent heat for thermal energy storage and thermal management applications. Integrating PCMs in flexible fibers provides new strategy for smart wearable systems. However, though lots of efforts have been made, it is still challenging to design and fabricate phase change fibers with flexibility, high energy storage capacity and good shape stability. Herein, we present a wet-spinning based core-sheath strategy to fabricate smart thermochromic phase change fibers (TPCFs) by directly encapsulating PCMs into flexible fibers in a low-cost, fast and adjustable way using octadecane (OD) as core, PCMs and polyurethane (PU) with thermochromic microcapsules as encapsulation layer. The obtained TPCFs exhibited high enthalpy (185 J/g), excellent mechanical property (elongation of 800%), thermal stability and reliability, outstanding shape stability and temperature responsiveness. Moreover, the materials possess high electrical-thermal and solar-thermal conversion and storage efficiency of 90.2% and 91.4% respectively through integrating with carbon fibers. These attractive features make TPCFs potential materials for wearable thermal management and energy harvesting and storage applications.