X‐Ray Fluorescence‐Based Spray‐On “Elemental Barcodes”

Abstract A novel spray‐on elemental barcode technology is reported for the secure, permanent, and tamper‐proof identification of polymeric and fiber‐reinforced composite materials. This system utilizes the in situ reduction of metal salts to nanoparticles embedded within a polymer matrix, creating a unique barcode that is detectable through X‐ray fluorescence (XRF). The barcode's composition is based on the metallic nanoparticle mixture and offers a semi‐quantitative, non‐destructive, and thermally stable method for material authentication. The process is straightforward, involving the manual application of metal salt solutions followed by mild heating, ensuring no significant alteration to the material's properties. The barcodes can be read through protective coatings or paints and are robust even under extreme conditions, such as high temperatures. This low‐cost method does not introduce additional manufacturing steps and demonstrates significant potential for anti‐counterfeiting and lifecycle tracking in various industries. Moreover, with an information density of up to 12 bits mm −1 , this elemental barcode significantly surpasses the data storage capabilities of traditional optical barcodes. This approach holds promise for broad substrate applicability and can be expanded to other metals and reduction protocols, making it versatile for diverse material applications.