Hydrogel-based sensors for multimodal health monitoring: from material design to intelligent sensing

Hydrogels, due to their biocompatibility, tunability, and stimulus responsiveness, are promising materials for flexible health monitoring. However, traditional hydrogel sensors suffer from various limitations in terms of long-term stability, signal fidelity, and integration of advanced functionalities. This review outlines a roadmap for hydrogel-based health monitoring by synthesizing the recent advances in material design and intelligent sensing. We analyze the strategies for enhancing the performance of hydrogels (robustness, conductivity, stability, and biocompatibility) and detail their multimodal sensing mechanisms for physical (strain, pressure, temperature, and fluorescence) and chemical (sweat biomarkers, pH, and oxygen) signals. This review emphasizes the integration of hydrogels with technologies like (1) self-powered sensing via triboelectric nanogenerators for autonomous operation; (2) closed-loop diagnosis-therapy platforms; and (3) artificial intelligence (AI) for advanced signal interpretation and diagnostics. These improvements enable applications in epidermal electronics, smart bandages, and implantable devices. Despite their progress, challenges remain in the environmental stability, integrated multimodal sensing, and clinical translation of implantable systems. Addressing these issues requires interdisciplinary collaboration to advance hydrogel platforms toward autonomous, personalized, and precision medicine.