Recent Advances in Flexible Hybrid Hydrogel-Based Sensors for Human Health Monitoring.

The rapid development of flexible health monitoring systems is driven by high-performance functional materials engineered with application-oriented sensing functions. Hybrid hydrogels formed through the organic integration of natural polymers, synthetic polymers, or functional components in various combinations have emerged as one of the most promising candidates for flexible sensing applications. This review summarizes recent advances in the design and application of hybrid hydrogel-based flexible sensors for health monitoring. It first discusses representative natural and synthetic polymers used in hybrid hydrogel construction and their controllable chemical modification strategies for property optimization. Subsequently, various crosslinking mechanisms, including irreversible covalent, reversible covalent, and non-covalent crosslinking, are reviewed in terms of their design principles, structure-property relationships, and roles in achieving specific functions such as self-healing, conductivity, and stretchability through molecular-level synergistic regulation. Furthermore, two typical categories of hybrid hydrogel sensors, double network (DN) hydrogels and nanocomposite hydrogels, are outlined, covering their structural characteristics, fabrication approaches, and functional design strategies. The representative applications of hybrid hydrogels in pressure, strain, and temperature sensing, and wound management are also summarized. Finally, the key challenges facing hybrid hydrogel-based flexible sensors are discussed, along with perspectives on future trends toward health monitoring systems.