Amorphous Photonic Structure Patterns with Thin Film\nInterference Effects for Multilevel Anticounterfeiting

Colloidal\nphotonic structures with the ability to control and manipulate\nlight propagation offer long-term color stability, low optical loss,\nand angle-dependent color properties, while combinations of different\nphotonic structures across multiple scales provide an extensive color\nrange and enhanced optical functionalities, presenting significant\npotential for advanced anticounterfeiting applications. However, the\nproper design or manufacture of such complex structures is still challenging.\nIn this study, amorphous photonic structures (APSs) with thin film\ninterference (TFI) effects were fabricated for multilevel anticounterfeiting.\nThe APSs inherit the isotropic resonant scattering and render partial\nTFI effects, resulting in unprecedented dynamic specular and diffuse\ncolor-shifting features as the viewing or incident direction shifts.\nAdditionally, incorporating a certain concentration of fluorescent\nmicrospheres into the colloidal ink adds a third layer of fluorescent\nanticounterfeiting mode to the APSs. Enabled by infiltration-assisted\n(IFAST) colloidal assembly technologies, the sophisticated color distributions\nand randomly arranged fluorescent microspheres on the microscale of\nAPSs grant unique and inherent fingerprint features. The unique and\nunpredictable optical and structural characteristics of APSs provide\nphysical unclonable functions (PUFs) to prevent replication and tampering,\ndemonstrating their potential as optical PUF security labels for anticounterfeiting\napplications through artificial intelligence (AI) reading and authentication.