Hydrogel-based dynamic structural colors for dual-mode image encryption

Overcoming the complexity of multi-mode optical encryption, this work demonstrates a simple approach for dual-mode image encryption that employs configurable hydrogel nanograting arrays, enabling a dynamically tunable structural color. Hydrogel nanograting arrays were fabricated on an aluminum layer, supporting the coupling of surface plasmon polaritons (SPPs) with polarization selectivity for the first-mode encryption. The resonance of SPPs was configurable with periodicity; the coloration was stepwise tunable with the swelling/deswelling of hydrogel nanogratings in response to environmental humidity. Furthermore, a second exposure method is developed to selectively modify the swellability of the hydrogel structures, inducing a second-mode encryption based on distinct humidity-responsive color changes. The self-driven tunability, real-time adjustability, repeatability, and long-term stability of this hydrogel-based dynamic structural color engineer its efficient applications in multispectral camouflage, optical information security, and intelligent anti-counterfeit.