Angle‐Dependent Dynamic Fluorescent Anti‐Counterfeiting of Multilayer Flexible Structure for High‐Capacity 3D Luminescent Barcodes

Abstract Dynamic fluorescent anticounterfeiting, which converts external stimuli into intuitive color changes, faces challenges due to low encryption levels and complex stimulation requirements. Here, a multilayer flexible structure combining dielectric microsphere cavity arrays (MCA), quantum dot polymer composites films (QDs), and polydimethylsiloxane (PDMS) to enhance anticounterfeiting performance is presented. The MCA/QDs/PDMS/QDs (MQPQ) flexible structure, fabricated by screen printing, exhibits angle‐dependent variations in both color and brightness under ultraviolet excitation. Four distinct MQPQ structures with different quantum dot emissions realize widely tunable hue conversion. Experimental and theoretical investigations reveal that the directional antenna effect significantly contributes to the optically variable mechanism. The MQPQ structure is extended to 3D dynamic fluorescent barcodes, where variations in stripe brightness and color provide enhanced information storage. Up to five distinct barcode patterns can be read from different angles, improving both storage capacity and security. This approach, requiring only a single excitation light, offers simplicity, universality, and advanced anticounterfeiting potential.