Hydrogel-Based Dynamic Structural Color with Optical Janus Effect for Imaging Encryption/Concealment

Structural colors are widely used due to their eco-friendliness, stability, and precise controllability. However, achieving dynamic structural colors typically requires complex fabrication processes and high-quality material preparation. Here, a simple bilayer structure containing hydrogel micropattern and semi-transparent ultrathin aluminum film is proposed that achieves the dynamic structural color with Janus effect. Combining experimental research and theoretical analysis, it is found that by merely controlling the electron-beam exposure dose, the colors, and patterns with these hydrogel-based Janus structures can be precisely and rationally designed. Additionally, the thickness and swellability of the hydrogel micropattern can be individually regulated, enabling imaging encryption/concealment with the optical Janus effect. The stability and cyclic performance of this structure are verified. The environmental sensitivity, real-time adjustability, and stability of this hydrogel-based Janus structural color make it suitable for applications such as secure information transmission and intelligent anti-counterfeiting labels.