Structural Color Materials for Optical Anticounterfeiting

Abstract

The counterfeiting of goods is growing worldwide, affecting practically any marketable item ranging from consumer goods to human health. Anticounterfeiting is essential for authentication, currency, and security. Anticounterfeiting tags based on structural color materials have enjoyed worldwide and long‐term commercial success due to their inexpensive production and exceptional ease of percept. However, conventional anticounterfeiting tags of holographic gratings can be readily copied or imitated. Much progress has been made recently to overcome this limitation by employing sufficient complexity and stimuli‐responsive ability into the structural color materials. Moreover, traditional processing methods of structural color tags are mainly based on photolithography and nanoimprinting, while new processing methods such as the inkless printing and additive manufacturing have been developed, enabling massive scale up fabrication of novel structural color security engineering. This review presents recent breakthroughs in structural color materials, and their applications in optical encryption and anticounterfeiting are discussed in detail. Special attention is given to the unique structures for optical anticounterfeiting techniques and their optical aspects for encryption. Finally, emerging research directions and current challenges in optical encryption technologies using structural color materials is presented.

Metal Halide Perovskites Functionalized by Patterning Technologies

“…Counterfeiting puts a great threat to the global economy and causes large financial loss to both individuals and society. [ 18 ] Therefore, anti‐counterfeiting technology is urgently needed to be developed. Fluorescent materials like organic dyes, lanthanide‐doped nanoparticles, colloidal PCs, and semiconductor QDs have emerged as anti‐counterfeiting inks for writing confidential information on different substrates with the help of patterning technologies.…”

Retroreflection and Wettability Controlled Smart Indicator Based on Responsive Bilayer Photonic Crystals for Traffic Warning

“…eff − sin 2 θ) 1/2 for the [111] plane, [62] where θ is 0° for normal incidence. The λ max shows redshift and the wetted area changes from green to red.…”

Optically Ambidextrous Reflection and Luminescence in Self-Organized Left-Handed Chiral Nematic Cellulose Nanocrystal Films

“…[1][2][3][4][5][6][7][8] Among the wide range of optical materials developed so far, photonic crystals with periodic modulation of dielectric functionality display remarkable ability to manipulate light propagation due to photonic bandgaps (PBG). [9][10][11][12][13] Chiral nematic phases are attractive as self-organized, one-dimensional photonic crystals with periodic layered structures and one-dimensional PBG that promise to be useful in photonic technologies. [14][15][16][17][18] In nature, chiral nematic phases often function in the form of structural coloration and polarization-insensitive reflectors; for example, the cuticles of certain beetles show selective reflection of circularly polarized (CP) light with the same helical handedness.…”