Using a Functional Wool Keratin Photoresist to Build Iridescent and Fluorescent 3D Micro‐Pattern for Dual‐Mode Optical Anti‐Counterfeiting

Abstract The construction of bio‐nanostructures plays a critical role in the advancement of applications across bioelectronics, bio‐optical devices, and biomedicine. Among various fabrication techniques, soft lithography emerges as an efficient and scalable method for producing high‐quality intricate surface micropatterns. Herein, a mild and aqueous approach is developed to endow biocompatible wool keratin (WK) with photoresponsiveness; and utilize the gold nanoclusters (AuNCs) incorporated functional bio‐photoresist to build iridescent and fluorescent micrometer‐scale patterns for dual‐mode optical anti‐counterfeiting. Specifically, the chemical modification of WK is achieved by using glycidyl methacrylate under mild conditions. And then, the modified WK can function as a green bio‐photoresist, which can be cross‐linked via UV light‐initiated radical polymerization. By combining soft lithography, both positive and negative 3D WK micro‐patterns with stability, biocompatibility, and controlled degradability can be facilely fabricated. Notably, the obtained periodic microstructures exhibit typical iridescent behavior with an excellent diffraction efficiency. Interestingly, by using WK as both a reductant and a stabilizer, the AuNCs functional WK resist with significant fluorescence response can be in situ generated. More importantly, through the skillful combination of iridescent micro‐patterns and fluorescence, the WK/AuNCs‐based hybrid micro‐patterns can be further used for dual‐mode optical anti‐counterfeiting, which can significantly enhance information storage and encryption security.