Abstract:

Objective Textile-based personal thermal management systems have emerged as a effective alternative to the conventional technologies for environmental temperature control. Current thermal management textiles primarily focus on cooling or heating functions. However, the dynamic and unpredictable nature of ambient temperature fluctuations necessitates a more flexible approach. Unidirectional thermal regulation methods often fail to meet the complex thermal needs of the human body around the clock. In order to address this challenge, a novel dual-mode thermal management fabric with a three-layer structure is proposed, aiming to overcome the limitations of existing unidirectional thermal management fabrics.

Method This sandwich structured dual-mode thermal management fabric was fabricated by coating one side of a cotton fabric with a mixture solution of polyvinylidene fluoride (PVDF) and titanium dioxide (TiO₂) nano particles to serve as the cooling side, while a novel two-dimensional MXene material, Ti₃C₂T_x, was sprayed onto the other side of the cotton fabric to act as the heating side. The apparent morphology, cooling and heating performance, and underlying mechanisms of this dual-mode thermal management fabric were investigated and analyzed.

Results The results demonstrated that the PVDF-TiO₂/C/Mxene dual-mode thermal management fabric (PTCM) possessed a dual-sided characteristic (with the cooling side being white and the heating side being black), and its radiative cooling side exhibited excellent cooling performance. After conducting temperature tests with a specially constructed testing apparatus in a sunny outdoor environment during summer, it was found that the average temperature on the cooling side of PTCM was 3.9 ℃ lower than that of ordinary cotton fabric. Meanwhile, when tested with the same apparatus in a sunny outdoor environment during spring, the average temperature on the heating side was 11.8 ℃ higher. In terms of electrothermal response and conversion capability, PTCM showed rapid temperature stabilization and efficient heat dissipation. At different test voltages, PTCM reached a stable temperature within 0.5 min and returned to room temperature within 2 min after power-off. At a voltage of 5 V, the stable temperature of PTCM could rise to approximately 60 ℃. In cyclic step-up voltage tests at 2, 3, and 4 V, PTCM reached the same temperature at each voltage level, with highly consistent temperature rise curves. This result demonstrated the excellent Joule heating stability of PTCM at different voltages, which is crucial for maintaining stable performance and extending service life in complex environments. Furthermore, under continuous step-up voltage conditions, when the voltage exceeded 3 V, the temperature of PTCM increased by an average of 10 ℃ for every 1 V increase, indicating that the PTCM has a wide range of temperature change with controllable, sensitive electrothermal conversion capability, that provides flexible thermal compensation for textiles and enhancing wearer comfort. Under summer clear sky conditions, the cooling or heating mode can be switched by flipping the dual-mode thermal management fabric. Observation with a thermal infrared imager revealed that the temperature on the cooling side was 0.9 ℃ lower than that of original cotton fabric, whereas the temperature on the heating side was 5.1 ℃ higher. These results confirm that the dual-mode thermal management fabric integrates radiative cooling and heating functions, effectively addressing the dynamic and unpredictable changes in ambient temperature.

Conclusion The dual-mode fabric PTCM exhibits significant thermal management capabilities, achieving an average cooling effect of 3.9 ℃ under summer sunlight and an average heating effect of 11.8 ℃ under spring sunlight. Moreover, driven by a 6 V voltage, PTCM can self-heat up to 80 ℃. In outdoor thermal infrared imaging tests conducted on sunny summer day, the cooling side temperature of PTCM was 0.9 ℃ lower than that of traditional cotton fabric, while the heating side temperature was 5.1 ℃ higher. PTCM integrates radiative cooling and heating functions, effectively addressing the dynamic and unpredictable nature of ambient temperature changes. Given its multifunctional performance, PTCM has broad application prospects in various fields such as personal thermal management textiles, temperature-regulating car covers, and outdoor tents.

Key words: dual-mode thermal management, titanium dioxide, MXene, polyvinylidene fluoride, radiative cooling, radiative heating, thermal management textiles