Mie-Resonant Silicon Nanoparticles for Physically Unclonable Anti-Counterfeiting Labels

Security labels produced by nondeterministic processes are a promising platform to shield counterfeiting. Here, we demonstrate the design of a physically unclonable anticounterfeiting label made of clusters of Mie-resonant silicon nanoparticles (NPs) fabricated by the laser-induced forward transfer technique. The number and relative position of clusters form the first security level authenticated by a smartphone with a macro lens. The enhanced optical response from the resonant NPs provides an opportunity to create additional laboratory security levels. These levels are based on spatial and chromatic coordinates as well as NP crystallinity, generating unique cluster fingerprints. The K-means clustering method utilized for the NP dark-field image processing makes it possible to achieve an encoding capacity of 10240000 for a 1000 × 500 pixel image. The widespread material, high-throughput fabrication, and multilevel security make a perfect set for label application in security and tracking of different items from consumer goods to art objects.