Cholesteric Liquid Crystals Based Micro‐Fingerprints Generator for Anti‐Counterfeiting Labels

Abstract

In this study, a method is presented to fabricate optical fingerprint‐like patterns. The method relies on the use of commercially available chiral nematic liquid crystals (CNLCs) confined in microspheres. The peculiar optical texture is obtained by applying a high‐frequency voltage to the micrometric objects able to distort the molecular director orientation. The texture can be stabilized by doping the CNLC with photosensitive materials. Each microsphere shows a different fingerprint‐like pattern that is generated in a completely random manner making this procedure suitable to create physical unclonable functions (PUFs) keys. The optical patterns can be stored to create an artificial fingerprints database or they can be used to fabricate electroluminescent labels to be exploited as complex anti‐counterfeiting devices. An authentication software is developed and used to test the robustness of the proposed anti‐counterfeiting system.

Flexible Physical Unclonable Functions Based on Non-deterministically Distributed Dye-Doped Fibers and Droplets

“…During the past decade, many efforts have been undertaken to produce strong and attack resistant PUFs using a broad combination of materials and physical phenomena. Such combination has led to the development of composite systems with unique physical and chemical properties that can be detected at different scales and only using specific experimental techniques allowing multilevel encryption. , From the pioneering work of Pappu et al that presented the first example of an optical PUF, a plethora of solutions have been proposed on the basis of organic crystals, photonic crystals, fluorescent materials, perovskites, metamaterials, soft materials, and polymers, which offer peculiar optical properties and random morphologies led, for example, by the self-assembling properties of some materials. ,− Recent technologies based on plasmonic security tags or biomimetic microfingerprints achieved high levels of protection against cloning attacks. , The paradox is, however, that many of the strongest anticounterfeiting systems can be more expensive than the protected products. Moreover, specific and expensive tools are usually required to verify their authenticity.…”