4D‐Printed Fluorescent Hydrogels for Dual‐Encryption: Time‐Gated Hierarchical Morphing With Multicolor Fluorescence

ABSTRACT The development of advanced information storage materials with spatiotemporal security features is critical to address the growing demand for high‐level encryption and anti‐counterfeiting protection. Herein, two types of 4D‐printed fluorescent hydrogels that exhibit time‐gated hierarchical morphing and color‐varying dual functions, driven solely by temperature, have been successfully developed. Specifically, for the first one, the target blooming state of Hydrogels A is realized under 365 nm UV light through synchronized hierarchical morphing and graded fluorescence color transition (orange→blue). For the second one, under 254 nm UV irradiation, doped Hydrogels B exhibit reversible hierarchical state switching between bloomed and closed configurations, accompanied by dynamic multicolor fluorescence modulation. These promising results originate from spatially gradient crosslinking networks precisely engineered via vat photopolymerization (VP) 3D printing, and specially‐designed luminescent chromophores, collectively enabling fluorescent hydrogels to achieve an all‐in‐one stimulus response integrating “shape morphing—multicolor fluorescence—information encryption” under thermal activation. Thus, a unique “codebook”—a time‐dependent dual‐parameter encryption system can be developed using these 4D‐printed fluorescent hydrogels, by dynamically adjusting bending angles and fluorescence ratios, effectively enabling high‐security spatiotemporal information protection. The integration of time‐gated shape‐shifting and multicolor fluorescence enhances encryption complexity through multi‐layered protection. 4D‐printed fluorescent hydrogels enable this bimodal spatiotemporal strategy, preventing unauthorized access while enabling novel secure storage approaches.