A Streamlined Approach to Anticounterfeiting Technologies: Patterned AAO Membranes Based on Photonic Crystal Effects with Tunable Color Shifts and pH Responsiveness

Anticounterfeiting technologies have become increasingly crucial due to the growing issue of counterfeit goods, particularly in high-value industries. Traditional methods such as barcodes and holograms are prone to replication, prompting the need for advanced, cost-effective, and efficient solutions. In this work, a practical application of anodic aluminum oxide (AAO) membranes are presented for anticounterfeiting, which addresses the challenges of high production costs and complex fabrication processes. Unlike previous approaches requiring metal coatings for color generation, this method uses commercial aluminum foils to produce colorful AAO membranes without metal layers. Elemental mapping suggests that impurities on the aluminum surface contribute to enhanced reflectivity, aiding photonic crystal formation. A two-step anodization process that creates patterned AAO membranes is further introduced, with the pattern clarity controlled by anodization time. Additionally, a pH-responsive film composed of 2-anilino-6-dibutylaminofluoran (ODB-2) and thermoplastic polyurethane (TPU) is integrated, enabling dynamic color changes under varying pH conditions, further enhancing the anticounterfeiting functionality. This streamlined approach provides a scalable and cost-effective solution for developing versatile AAO membranes for industrial anticounterfeiting applications.