Fabrication is a tremendous challenge. We are not yet able to replicate many of these systems in the laboratory; we cannot match nature’s fabrication capability. Fabrication of comparably intricate and complex synthetic structures is tremendously difficult, expensive, and not ready or capable of the scale-up required for commercial application. Developing fabrication techniques as well as new tools to help understand the structures, physics, materials, and function is critical to field. Current fabrication techniques such as top-down lithographic techniques or bottom-up colloidal processes, as well as using actual biostructures as templates, are a solid starting place. Eventually, however, we will need to be able to create these structures at any scale, size, or pattern at low cost and over large areas. Up-and-coming fabrication techniques such as molecular and three-dimensional (3D) printing are still very nascent but may point the way to “fab-less” fab (i.e., the ability to make large amounts of devices without requiring the large fabrication facility [fab] infrastructure). We will want to have extreme local control of inhomogeneity, to control material gradients, and composition even within the nanostructures. We need to be able to build in disorder. Current fabrication techniques are built on the premise that we want perfection. However, biological photonic structures have shown us that disorder can be leveraged to produce desired effects, such as the angle-independent reflection in structural color due to the existence of multidomains. We will want to be able to fabricate these structures out of functional materials, such as optomechanical or electro-optical materials, to create even more functionality. For example, supercrystals have been proposed that incorporate quantum dots into periodic structures.1 It becomes particularly interesting when you think of the nanoparticle microcolloids discussed in Chapter 2. Finally, biological photonic structures have inspired other approaches to structural color that may be easier to fabricate, such as plasmonic nanostructures seen in Figure 9.1 that

have been able to produce a very wide range of colors with high spatial resolution (although only for static images).2