Janus-structured phase change film for efficient solar-thermal energy harvesting and real-time motion monitoring

The integration of phase change materials (PCMs) possessing high-efficiency solar-thermal conversion ability into thermoregulation devices holds significant potential to address both thermal energy demands and advance renewable energy utilization. However, the practical application is constrained by inherent limitations including leakage, inadequate light absorption, and structural rigidity in pristine PCMs. In this work, we developed a novel phase change film (PCF) with Janus structure characteristic. This system comprises an energy storage layer made of docosane microcapsule and polyurethane, and a functional layer formed by carboxylated multi-walled carbon nanotube (CNT) deposition. Specifically, the PCF exhibits excellent mechanical properties, which can be easily operated into various shapes without any damage. The phase change enthalpy remains at 120.35 J/g even after 50 thermal cycles, demonstrating superior thermal energy storage capacity. Under an irradiation power of 200 mW/cm 2 , the solar-thermal conversion efficiency can reach 93.8 %, indicating the efficient solar-thermal conversion performance. Additionally, the deposited CNT enable the PCF to generate current signals in response to shape changes in the circuit, making it possible for motion monitoring applications. Therefore, this Janus-architected PCF holds significant potential for the applications in the fields of thermoregulation and smart monitoring. • A Janus-structured phase change film (PCF) was prepared through a facile phase inversion and spraying method. • The obtained PCF exhibits excellent flexibility, adjustability and thermal energy storage capacity. • This PCF can simultaneously achieve efficient solar-thermal energy harvesting and real-time motion monitoring. • This PCF holds significant potential for the applications of thermoregulation and smart monitoring.