Visible Frame QR-Coded Microparticles Integrated with an Invisible Layer for Unlocking Hidden Data via Fluorescence

We present an advanced anticounterfeiting strategy utilizing quick-response (QR)-coded microparticles to address the challenges of static data content and ease of replication associated with traditional QR codes. This study integrates openly accessible frame QR codes with hidden content QR codes, visible only under fluorescence microscopy, thereby enhancing security measures against counterfeiting. Microparticles were fabricated using a combination of polyurethane acrylate resin and 2,2-dimethoxy-2-phenylacetophenone, which serves as both a photoinitiator and a photoluminescent material under ultraviolet (UV) light. Leveraging the advantages of QR-coded microparticles, including biofriendliness, potential for mass production, and scalability, the design enables high decodability without fluorescent materials by producing dot-type QR code modules. The fabrication process involves optofluidic maskless lithography for frame QR code formation, followed by postcuring to enhance morphological stability and photolithography to embed the content QR code as additional data. This advanced method enables dynamic control over the visibility of the embedded content QR code by manipulating UV irradiation time, providing customizable content for security by changing the UV exposure pattern without changing the materials. Our findings suggest that these QR-coded microparticles offer a scalable and versatile anticounterfeiting solution capable of incorporating visible and covert security features.