Photonic Patterns Printed in Chiral Nematic Mesoporous Resins

Chiral nematic mesoporous phenol‐formaldehyde resins, which were prepared using cellulose nanocrystals as a template, can be used as a substrate to produce latent photonic images. These resins undergo swelling, which changes their reflected color. By writing on the films with chemical inks, the density of methylol groups in the resin changes, subsequently affecting their degree of swelling and, consequently, their color. Writing on the films gives latent images that are revealed only upon swelling of the films. Using inkjet printing, it is possible to make higher resolution photonic patterns both as text and images that can be visualized by swelling and erased by drying. This novel approach to printing photonic patterns in resin films may be applied to anti‐counterfeit tags, signage, and decorative applications. Printing photonic patterns made easy: Using chemical “inks”, latent photonic patterns were written onto chiral nematic mesoporous‐resin films. The patterns are invisible in the dry films, but emerge upon swelling. Inkjet printing of the resin films afforded high‐resolution photonic patterns that can be revealed upon swelling and erased by drying, making them suitable for anti‐counterfeiting applications.