Abstract
The specific metallic blue of Morpho butterfly is structural color having high reflectivity produced by an interference effect. However, a single color in too wide angular range (> ± 40° from the normal) contradicts the optical interference. After we have proven the principle of the mystery by reproducing the specific nanostructures of their scales, we found the artificial Morpho-color to serve wide applications, because it can provide a brilliant single color in wide angular range with high reflectivity without chemical pigment, which is resistant to fading caused by chemical change for long time. We have developed various techniques for applications of the specific color, such as mass-production processes, simulation and control of its optical properties, and substrate-free color materials. One of the remaining key issues is to produce the large-area flexible film, because the flexible film was limited to small area, and large-area Morpho-color material have long been accompanied with the solid substrate, which has limited the variety of applications. By combining these processes to fabricate the small flexible film and solid large-area Morpho-color material, we developed a simple process to mass-fabricate the large-area flexible Morpho-color material. The method was quite simple, whereas this process needed to develop a flexible mold for nano-imprint, because the large-area nano-imprint gives serious stress and damage to the solid mold. Finally, by developing a process to produce a large-area flexible mold, we have successfully replicated the flexible large-area Morpho-color film, which can be realized by immersion into hot water. The fabricated large-area Morpho-color film was flexible, resistant against stress and strain, and found to maintain the original optical properties of Morpho-color. This process will expand the applications of the Morpho-color, which enables the coloring without limit of shape and area.
