Micro/nano-robotic medical device: preparation, actuation mechanisms and their applications in medicine.

Hydrogels feature a unique three-dimensional crosslinked network integrated with responsive chemical functional groups, enabling them to undergo structural and functional transitions under various external stimuli, including chemical energy, temperature, light, pH, ultrasound, magnetic fields, and ions. These transformations arise from mechanisms such as molecular conformational changes, bond formation or cleavage, and ion exchange. Recent advances in micro/nanorobotics have led to the development of hydrogel-based micro/nano-robotic medical devices that combine excellent biocompatibility with multi-modal actuation, allowing adaptation to diverse environments and precise task execution. This review summarizes current progress in hydrogel micro/nano-robotic medical device research, with a focus on multi-drive synergistic strategies and advantages of composite hydrogel designs. Fabrication techniques, driving mechanisms, and biomedical applications-including targeted drug delivery, tissue engineering, and in vivo imaging-are discussed. Finally, the major challenges in clinical translation are analyzed, and possible solutions are proposed to facilitate future practical implementation.