Three-Dimensional Printable Color-Modulation and Shape-Programmable Structures: An Encryption Key for Image Recognition Electronic Locks.

Stimuli-responsive materials have shown promising applications in the areas of sensing, bioimaging, information encryption, and bioinspired camouflage. In particular, multi-stimuli-responsive materials represent a hot topic due to their modulated properties under multiple stimuli. Herein, we successfully developed multi-stimuli-responsive inks and a series of complex multi-stimuli-responsive 3-dimensional (3D) structures were fabricated via digital light processing 3D-printing technology. Notably, these complex 3D structures show shape memory, fast-response photochromic and thermochromic behavior, and excellent repeatability due to the combination of photochromic molecules (4-(2,2-bis(4-fluorophenyl)vinyl) benzyl methacrylate) and thermochromic pigments. Furthermore, a programmable encrypted box that changes colors and morphology by controlling temperature and ultraviolet irradiation was designed and printed, and this encrypted box exhibits strong security using OpenCV-based image recognition technology. This strategy provides a promising approach for the design of multi-stimuli-responsive materials and complex encryption systems in the future.