Fine Optimization of Colloidal Photonic Crystal Structural Color for Physically Unclonable Multiplex Encryption and Anti‐Counterfeiting

Abstract

Robust anti‐counterfeiting techniques aim for easy identification while remaining difficult to forge, especially for high‐value items such as currency and passports. However, many existing anti‐counterfeiting techniques rely on deterministic processes, resulting in loopholes for duplication and counterfeiting. Therefore, achieving high‐level encryption and easy authentication through conventional anti‐counterfeiting techniques has remained a significant challenge. To address this, this work proposes a solution that combined fluorescence and structural colors, creating a physically unclonable multiplex encryption system (PUMES). In this study, the physicochemical properties of colloidal photonic inks are systematically adjusted to construct a comprehensive printing phase diagram, revealing the printable region. Furthermore, the brightness and color saturation of inkjet‐printed colloidal photonic crystal structural colors are optimized by controlling the substrate's hydrophobicity, printed droplet volume, and the addition of noble metals. Finally, fluorescence is incorporated to build PUMES, including macroscopic fluorescence and structural color patterns, as well as microscopic physically unclonable fluorescence patterns. The PUMES with intrinsic randomness and high encoding capacity are authenticated by a deep learning algorithm, which proved to be reliable and efficient under various observation conditions. This approach can provide easy identification and formidable resistance against counterfeiting, making it highly promising for the next‐generation anti‐counterfeiting of currency and passports.

Structural Color Enhancement through Synchronizing Natural Convection and Marangoni Flow in Pendant Drops

“…12−17 Based on the coloring mechanisms of structural colors, they can be broadly categorized into plasmonic structural colors of metallic nanostructures, 18 thin-film interference, 19 chiral nematic liquid-crystal structural colors, 20 total internal reflection structural colors, 21,22 and photonic crystal structural colors. 23,24 Among these, colloidal photonic crystals, composed of periodically arranged colloidal nanoparticles, are one of the most extensively studied photonic materials.…”

“…With the continuous advancement of technology, the demand for environmentally friendly materials, especially in the realm of color, is increasing. − Structural colors, originating from physical structures rather than traditional pigments or dyes, have garnered considerable attention due to their potential low toxicity and long-lasting resistance to fading. − Based on the coloring mechanisms of structural colors, they can be broadly categorized into plasmonic structural colors of metallic nanostructures, thin-film interference, chiral nematic liquid-crystal structural colors, total internal reflection structural colors, , and photonic crystal structural colors. , Among these, colloidal photonic crystals, composed of periodically arranged colloidal nanoparticles, are one of the most extensively studied photonic materials.…”

Fast and Accurate Recognition of Perovskite Fluorescent Anti-counterfeiting Labels Based on Lightweight Convolutional Neural Networks

“…Anti-counterfeiting label recognition methods fall into two main categories: traditional computer vision with feature point matching and deep learning approaches. Traditional methods like Oriented FAST and Rotated BRIEF or Scale-Invariant Feature Transform algorithms effectively identify feature points in images to verify labels without extra markings. , Meanwhile, researchers are increasingly exploring deep learning methods, , utilizing neural network architectures to identify subtle differences and complex patterns in labels, thereby verifying their authenticity. However, these methods struggle to balance accuracy with recognition speed.…”