Multifunctional Hydrogel Interfaces: Reshaping the Future of Flexible Electronics

Flexible electronics is undergoing a transition from single-function devices to intelligent systems capable of multimodal perception and closed-loop operation. Multifunctional hydrogels have emerged as a core platform for next-generation electronics, owing to their structural tailorability, biomimetic compatibility, dynamic responsiveness, and exceptional interfacial properties. This review outlines a cross-scale design pathway of hydrogel electronics spanning molecular strategies and microstructural architectures to macroscopic functionalities (mechano-electro-thermo-chemical responses) and system-level integration. We critically survey recent advancements in hydrogel-based applications, including wearable health monitoring, electronic skin, soft robotics, and self-powered devices, highlighting their unique advantages in high-fidelity signal acquisition, autonomous energy management, and long-term stability under complex conditions. Furthermore, we explore how AI-driven inverse design, digital twins, and in situ characterization are accelerating the shift from empirical to model-driven development of hydrogel electronics. A performance evaluation framework based on the "energy-signal coupling coefficient" is introduced, combining with green design principles promoting circular sustainability. Finally, we outline future challenges and opportunities to achieve extreme environmental adaptability and promote standardization and scalable manufacturing. Interdisciplinary integration and AI-assisted multimodal data analytics will ultimately advance hydrogel electronics from functional devices to fully intelligent bio-integrated systems.