Structural Color from Multi-Bounce Reflection Interference in Metalized Microstructures

The development of materials and methods for controlling iridescent structural color arising from optical interference has attracted considerable attention for a variety of applications ranging from anticounterfeiting to displays. Here, we investigate high-reflectivity structural color generated by multi-bounce reflection interference within metallized microstructures and describe the relationships between coloration, reflection efficiency, and microstructure geometry. Ray tracing simulations are combined with experimental, angularly resolved far-field optical analysis for a detailed understanding of the underlying mechanism. Fabrication of microstructures with grayscale lithography and image patterning using metal masking is demonstrated. We further investigate microstructure geometries combining both concave and convex curvatures for highly diversified and more complex tunable optical interference. These results provide insight into how to control the iridescent properties of microstructures with improved structural color saturation and reflectivity by exploiting a multi-bounce interference optical mechanism.