Brilliant hollow SiO2-based structural colors for water infiltration, warning and information encoding

Abstract

A series of functional stimulus-response indicators based on the multi-color regulation mechanisms of Bragg's law were developed. However, they were basically fast-response and high-sensitivity systems. Herein, this paper introduced a novel approach using slow water infiltration to regulate structural color photonic band gaps (PBG), which was more conducive to temporal monitoring, with applications in water penetration, warning systems, and information encoding. The hollow SiO₂ and polyethylene glycol diacrylate (PEGDA) films were employed as structural units, showing that the color-changing ability of the hollow SiO₂-based structural color films was negatively correlated with the SiO₂ thickness. Additionally, the RGB values were analyzed through images, demonstrating the slow color-changing characteristics of these films. The results indicated that both methods exhibited similar trends, confirming that these two characterization techniques effectively reflected the color change under water infiltration conditions. Furthermore, these bright and water-permeable materials, when used in conjunction with inverse PC structures for synergistic water-induced color-change response tags, were effective for reversible information recognition. Moreover, this type of material possessed excellent water-penetration rate adjustment capabilities, which could further enhance its encryption potential. Therefore, the hollow SiO₂-based structural color material was further applied in fields such as large indoor cold storage warehouses and eco-smart aquariums. These tags were able to effectively prevent temperature rise risks in frozen goods due to power outages and served as built-in anti-counterfeiting labels, offering strong anti-counterfeiting capabilities.