Elucidating the mystery of Morpho-blue using in-plane randomness: toward simple nanofabrication

Abstract

Morpho butterflies are well known for their brilliant blue color that has a low angular dependence. This distinctive coloration has long been attributed to the skillful combination of order and disorder in the hierarchical nanostructures, which allows the interference of light to avoid iridescence. However, there remains a fundamental mystery: the artificial Morpho-blue color is successfully obtained despite the lack of vertical randomness. Using a numerical simulation, we found that the three-dimensional randomness can be converted to a two-dimensional randomness. This finding leads to a novel approach for the simple nanofabrication of not only Morpho-blue but also of more general photonic devices.

Development of a High‐Performance, Anti‐Fouling Optical Diffuser Inspired by Morpho Butterfly's Nanostructure

“…In fact, this random arrangement is derived from the top‐view nanostructure of a Morpho butterfly's wing scale and has been applied to the design of our artificial Morpho ‐colored materials. [ 47,52 ] Because they offered uniform light diffusion in reflection without the crossed lines as well as Morpho butterflies, the random arrangement was also applied to the nanopattern design of Morpho ‐type diffusers.…”

“…[50,51] Although the vertical randomness in height is preferable for anti-grating, [46] we previously demonstrated that 2-D randomness combined with binary height also provides sufficient phase variations for anti-grating, allowing for this simplification. [52] Figure 1d illustrates the cross section of the simplified design, wherein 2-D nanopatterns composed of random widths and binary height were created on either surface. The height variation of nanopillars was decreased to four levels (including the two nanopatterns), but instead the pillar widths were rendered random to produce sufficient randomness for anti-grating.…”

Novel optical applications inspired by the Morpho butterfly’s coloration: technology transfer from reflection to transmission

“…Thus, σz, which obstructs artificial reproduction because of its complexity in lithography, can be replaced by or converted to in-plane disorder. 10) This finding gives hope to open the practical and simple processes not only for Morpho-color but also for other applications. In fact, the application of the Morphocolor to transmission-type optical devices is a direct example to show the validity of this design concept, as shown later (Sect.…”

“…Possible solutions were found to avoid the high aspect ratio by a conversion technique between the twodimensional (2D) and three-dimensional (3D) structures. 10) The 3D-2D conversion has been a discovery found in the study on reflective properties of the Morpho-color, whereas it was effectively applied to the research on transmission. The usefulness of this newly designed 2D structure was verified through numerical simulations, and finally, the fabrication was attempted.…”

Optical costs and benefits of disorder in biological photonic crystals

“…Despite the appearance of strong periodic order in these structures, demonstrable structural irregularity and elements of disorder persist in variables associated with the ridge alignment, ridge heights and the lamellar period. [43][44][45][46][47][48] The consequences of these relatively low measures of structural irregularity, or disorder, in Morpho typically translate to lower peak reectance, broader spectral reectance, a wider solid-angle in which light scattering takes place (namely, more diffuse reectance) and a weakening of iridescence, the former two resulting visually in a less saturated colour appearance. Studies conrm that various degrees of disorder prevail, sometimes concurrently, among a range of biological systems.…”