Construction of anti-counterfeiting pattern on the cellulose film by in-situ regulation strategies

Cellulose and its derivatives films are increasingly used in paper, packaging, and other fields, but there is limited research on its films with anti-counterfeiting patterns. Here, we demonstrate an approach to prepare cellulose film with a micro-millimeter scale pattern by lithium chloride (LiCl) crystal template, which grows out by the in-situ generation in the film formation process. The surface morphologies of the as-prepared film were systematically controlled by regulating the solution viscosity (η) and the surrounding temperature. The imprinting of LiCl crystal was retained on the film surface after rinsing. Moreover, the crystallinity of patterned film was significantly improved, and about 62 MPa increased tensile strength than the film without a pattern. Incredibly, these patterns were similar to fingerprint size, which exhibited an excellent function to unlock fingerprint locked phones and showed potential in the anti-counterfeiting yield.