Enabling Autonomous Moisture Harvesting and Cyclic Transpiration Cooling with MXene-LiBr Functionalized Hydrogels for Advanced Thermal Management

Abstract

Hygroscopic hydrogels offer cyclic transpiration cooling, mitigating local heat accumulation in integrated flexible electronics. However, the low thermal conductivity of traditional hygroscopic hydrogels poses a major challenge in meeting growing heat dissipation demands in electronics. Herein, a strategy for synthesizing hydrogels with highly thermally conductive MXene flakes is introduced enabling dual functions of autonomous moisture harvesting and cyclic transpiration cooling. A lithium bromide–polyacrylamide/MXene (Li-PAAm/MXene) hydrogel is engineered by integrating MXene into polyacrylamide (PAAm) chains via hydrogen bonding, simultaneously enhancing thermal conductivity through microscale thermal bridges and increasing hygroscopic capacity through synergistic effect of MXene and lithium bromide (LiBr), thereby generating more moisture sorption sites and lowering diffusion energy barriers. Morphology, chemical, and thermal characterizations demonstrate the formation of heat-transfer microchannels within the hydrogel, resulting in higher thermal conductivity and enhanced water evaporation. Hygroscopic capacity tests and molecular dynamics simulations further reveal that the synergy between MXene and LiBr increases osmotic pressure and water diffusion rates, leading to more efficient moisture sorption. This highly thermally conductive hygroscopic hydrogel demonstrates efficient cyclic transpiration cooling, outperforming commercial heat dissipation films and conventional hygroscopic hydrogels, making it a promising candidate for advanced thermal management in electronics.