A multidimensional anti-counterfeiting dynamic flexible label based on light/thermal responsive CLC microspheres†

Abstract

Compared to static anti-counterfeiting, polymorphic dynamic anti-counterfeiting typically incorporates additional parameters specifically to increase the complexity of decryption. The development of security in flexible multi-dimensional materials holds significant implications for anti-counterfeiting applications in pharmaceuticals, food, and other products, yet it presents considerable challenges. Here, we propose a composite hydrogel film based on cholesteric liquid crystal (CLC) microspheres with photochromic spiropyran (SP) dyes and sodium alginate/N-isopropyl acrylamide. The film incorporates microspheres capable of synergistic color changes under light/heat stimuli. In the temperature range of 30–12 °C, CLC microspheres can achieve color tuning in the entire visible light band. By incorporating SP, the liquid crystal structural color can overlap with SP fluorescence/dye color. Furthermore, as a soft actuator, the flexible composite hydrogel can achieve a range of predesigned dynamic actuation effects such as biomimetic butterflies and flowers. By integrating the CLC microspheres with actuatable composite hydrogels, a sophisticated multidimensional dynamic anti-counterfeiting flexible label has been successfully realized. This not only enhances security and complexity in multidimensional dynamic anti-counterfeiting but also holds significant potential for applications in dynamic camouflage, bio-inspired actuation, and display sensing.