Rapid fabrication of tunable structural color patterns by spray-coating.

Structural color, a color generated based on physical principles, has broad applications such as displays, optical sensors, and anti-counterfeiting. Traditional methods for producing structural colors are often complex and time-consuming, whereas spray-coating colloidal self-assembly offers a simple and controllable alternative. However, due to the high-pressure atomization process, colloidal inks often form amorphous photonic structures (APSs), making it challenging to precisely control the assembly of colloidal particles on substrates to achieve ordered structures. By rationally designing the composition of colloidal mixed solutions, controlling particle concentration, and adjusting evaporation temperatures, it is possible to effectively regulate the assembly of colloidal particles and obtain angle-dependent iridescent colors. This work proposes a simple spray-coating process that enables the control of both ordered and disordered structures, with tunable optical properties, suitable for colloidal patterning on various substrates. This method not only simplifies the fabrication of photonic crystals (PCs) but also has broad potential, particularly in anti-counterfeiting, where it enables the creation of hard-to-replicate structured patterns with enhanced security.