Flexible structural color label with tetra-mode iridescence in full three-dimensional space for sophisticated anti-counterfeiting

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-06, Vol.489, p.151277, Article 151277
• Main Authors: Liu, Tianyi, Meng, Rou, Ren, Jie, Han, Yaqun, Li, Xingzuo, Zhang, Shufen, Wu, Suli
• Format: Article
• Language: English
• Subjects: Sophisticated Anti-counterfeiting; Structural color; Tetra-mode iridescence; Three-Dimensional Space Anti-counterfeiting
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.151277

Utilizing to the coupling of the disordered ZnS spheres with the Al coating, the flexible structural color label provides a unique visual appearance, presenting angle-sensitive dynamic structural colors in 3D space under the light source. The angle dependence of the specular mode and the 3D iridescent of the diffuse mode form a tetra-mode iridescence, which brings sophisticated anti-counterfeiting. [Display omitted] •Flexible anti-counterfeiting labels were prepared by disordered ZnS spheres on aluminized film.•The flexible anti-counterfeiting label displays specular-diffuse dual-mode.•Labels based on the directivity of Mie scattering exhibit bright iridescent color.•Labels have different iridescent colors under incident light in different directions.•A convenient way to verify the authenticity of labels has been developed. The attractive visual appearance provided by disordered surfaces has been proven, which demonstrates great anticounterfeiting potential. However, the real application is challenging due to complex processing and Si substrates. We fabricated flexible structural color anti-counterfeiting labels by printing ZnS spheres onto aluminized flexible films to form a disordered surface, resulting in specular-diffuse dual modes appearances. Especially, based on the directionality of Mie scattering, the diffuse mode displayed three-dimensional (3D) angle-dependent structural colors under ambient light and exhibited angle-sensitive dynamic structural colors in 3D space under the light source. The angle dependence of the specular mode and the 3D iridescent of the diffuse mode form a tetra-mode iridescence, which brings sophisticated anti-counterfeiting. The comprehensive color information is directly determined by the optical properties of ZnS and Al, which pose challenges for replication using alternative methods. Further, labels with multi-color dragon patterns were fabricated using ZnS spheres with different diameters, which greatly improves information security. More importantly, based on the tetra-mode, a verification method compatible with personal terminals has been developed, which can quickly identify authenticity.