Programmable Hydrogels: Frontiers in Dynamic Closed-Loop Systems, Biomimetic Synergy, and Clinical Translation

Programmable hydrogels are an emerging class of intelligent materials engineered to respond precisely to specific stimuli, offering tailored functionalities with significant potential for biomedical applications, including drug delivery, tissue engineering, and wound healing. This review comprehensively explores various programmable hydrogels responsive to diverse triggers, including temperature, gene expression, color, shape, and mechanical force. The design and fabrication methods underlying these systems are detailed, highlighting the roles of crosslinkers, adhesion groups, and photosensitive functional groups. Furthermore, the key physical, chemical, and biological properties that govern the performance and functionality of hydrogels are analyzed. The review further examines the mechanisms and recent advancements in self-executing hydrogels, such as self-activated, self-oxygenated, self-expandable, and self-powered systems, demonstrating how these innovative designs drive the development of next-generation programmable hydrogels. The main challenges in hydrogel design, including complexity, reproducibility, and clinical translation, are also addressed. Finally, a perspective on future research directions, highlighting the integration of the latest technologies to realize programmable hydrogels with dynamic closed-loop responsiveness, bionic synergy, and robust clinical applicability, is offered.