Methods for design and fabrication of bio-inspired nanostructures exhibiting structural coloration

In recent years, structural color has burgeoned into a vibrant and dynamic field of study. Many structurally colored organisms rely on comparatively few materials to create a large diversity of optical responses and a broad array of compelling and functional features. Scientists and engineers often explore such systems as examples of sustainable, robust solutions to complex problems. By looking to existing hierarchical material systems in biological systems, we aim to determine guidelines for fabrication of material structures with pre-determined functionality and properties. Here, we compare approaches for producing surfaces that reflect color and discuss tunable design parameters. Methods discussed include bottom up self assembly, abstracted lithographic replication of structures, and top down systematically designed surfaces. We consider existing techniques and levers available to control output, and present the components of an inverse design approach. We compare different methods on the basis of scalability, tunability, and achievable responses, and provide practical guidelines for producing bio-inspired surface structures. Our proposed designs are constrained for realizable fabrication using additive direct laser writing techniques such as two-photon polymerization that are suitable for producing arbitrary structures with sub-wavelength resolution. These evaluated and characterized structures could eventually be adapted to roll to roll or imprint-based systems for scale-up and manufacturing on a commercial scale. Here we contribute to a broader vision of systematic materials design by exploring tools for generating color.