Anti‐Counterfeiting Tags with Camouflaged QR Codes on Nanocavities, Using Polymer‐Dispersed Liquid Crystals

Abstract Counterfeiting poses an ever‐growing challenge, driving the need for innovative anti‐counterfeiting strategies and technologies. Many solutions focus on tags characterized by optical features that are camouflaged to the human eye, thus discouraging scammers. In this paper, a QR code is printed using a commercial printer on a thin plastic foil previously coated by a specific nanocavity consisting of a metal‐insulator‐metal‐insulator (MIMI) multilayer, that possesses unique features in terms of light transmission and reflection, due to its specific design. A thin layer of polymer dispersed liquid crystals (PDLC), is fabricated to camouflage the QR code that becomes, then, readable only under specific thermal conditions. Two anti‐counterfeiting tags were fabricated, each using a distinct nematic liquid crystal (NLC) with its own nematic‐isotropic transition temperature. The combination of the unique optical properties of NLCs and optical nanocavities results in the creation of a new type of tags showing two different encoding levels. Stability tests such as immersion in water, bending test, and prolonged heating have been performed ensuring the long‐term stability of the tags. The realized two security‐level anti‐counterfeiting tags are cost‐effective, straightforward to manufacture and, thanks to their flexibility, can be easily integrated into packaging and products.