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

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.