Dual‐Modal Invisible Photonic Crystal Prints from Photo/Water Responsive Photonic Crystals

Abstract

Invisible photonic crystal prints (IPCPs) are appealing for anti‐counterfeiting and information protection due to their capability in hiding and showing the encrypted information under specific conditions. Herein, the dual‐modal IPCPs based on responsive photonic crystals (PCs) with tunable photoluminescent (PL) and structural colors are reported. The responsive PCs are prepared by the self‐assembly of dyes doped silica particles into non/swellable polymers. The independent design and control over the optical response of the PL of the particles and structural colors of PCs enable the successful encryption of dual‐modal patterns. Under normal conditions, the as‐fabricated IPCP shows a fake pattern with uniform structural colors and thus hides the encrypted pattern due to the similar particles size, lattice constant, and refractive index of each region. In striking contrast, PL and structural colors‐based new patterns can be instantly and reversibly revealed when the IPCP is exposed to UV illumination or soaked in water. This work provides a new concept in designing and fabricating dual‐modal IPCPs, and facilitates their applications in the fields of color display, antifake package, and multilevel anti‐counterfeiting.