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Abstract Polymer hydrogel materials are increasingly recognized for their potential in various transformative areas including wearable and implantable devices, tissue engineering, drug delivery, and soft robotics. While their intrinsic bulk properties are crucial for advanced applications, surface modifications are indispensable for enhancing their functionality without compromising core characteristics. Recent advances in hydrogel surface engineering have enabled the development of hydrogels with rationally designed surface chemistries, multiscale architectures, structural complexity, and spatial heterogeneity. These engineered surface features have significantly broadened the applicability of hydrogels, unlocking functionalities that are unattainable with conventional bulk materials. Despite this progress, the field of hydrogel surface engineering remains in its early stages, facing challenges such as limited functionality, insufficient control over architecture, and issues with ambient stability. Addressing these challenges will be critical for unlocking the full potential of hydrogels in next‐generation technologies. Herein, this review examines functional hydrogels from the perspective of surface engineering and summarizes the current innovative strategies for functionalizing hydrogel interfaces. These strategies serve as the foundation for following introduction of representative functionalities that rely heavily on the physicochemical properties of hydrogel surfaces, as evidenced by progress in both academic research and commercial applications.
Zhang et al. (Tue,) studied this question.