Study of Magnetic Hydrogel 4D Printability and Smart Self‐Folding Structure.

4D printing technology offers the potential to create smart structures that respond to external stimuli. This study focuses on a novel magnetic hydrogel with promising applications in 4D printing, particularly for medical devices such as guidewire robots, drug delivery systems, and vascular stents. Magnetic‐responsive hydrogels suitable for 4D printing are scarce, and their complex rheological properties pose challenges for printing. The study investigates these properties and optimizes them through adjustments in ink composition and the application of an external magnetic field, improving printability. Using the direct writing (DLP) method, which allows magnetic programming of individual strands, the study achieves greater flexibility compared to the traditional SLA method. Optimized printing parameters and material ratios produced high‐quality single strands, grids, and sheet‐like structures, demonstrating responsiveness to varying magnetic fields. Results confirm that DLP can be effectively applied to hydrogel 4D printing, achieving flexible structures with tunable mechanical properties. Additionally, magnetic‐responsive, self‐folding hydrogel structures were created, with a response speed of 180 ms under a magnetic field. This research establishes a foundation for magnetic hydrogel 4D printing and offers insights for the development of future smart medical devices. [ABSTRACT FROM AUTHOR]