Hydrogels for robust thermal management: mechanism and applications

The increasing global demand for energy and the growing urgency of environmental concerns have underscored the need for advanced materials capable of efficient thermal regulation. Hydrogels, featuring high water content, structural and mechanical tunability, and biocompatibility, provide a valuable platform for addressing a wide range of thermal management challenges. Unlike conventional thermal management materials, hydrogels can operate through a combination of mechanisms, including evaporative cooling, thermal conduction, heat storage, and radiative cooling, allowing adaptable responses to changing conditions. Besides, they can further incorporate phase-change materials, hygroscopic agents, conductive nanofillers, and structural design to enhance performance in dynamic environments. These advancements have broadened their applicability to areas such as wearable thermoregulation, infrared camouflage, biomedical applications, electronic cooling, and passive building insulation. Despite these advances, key challenges remain, particularly in terms of long-term durability, water retention under low-humidity conditions, and scalable manufacturing. This review provides a comprehensive overview of the underlying physicochemical principles of hydrogel-based thermal regulation, critically examines recent materials and innovative applications, and discusses emerging strategies to address existing limitations. By integrating design strategies with thermal functionality, hydrogels are positioned to play a critical role in the development of next-generation, adaptive thermal management technologies.