Reproduction, mass production, and control of the Morpho butterfly's blue

Abstract

Strucural color of some blue Morpho butterflies has a physically mysterious feature, because it has both high reflectivity (>60%) and a single color in too wide angular range (> ± 40° from the normal), which are contradicting with each other from viewpoint of the interference phenomena. We have recently proven the principle of the mystery by extracting the physical essence, and emulating the nano-structures using nano-fabrication techniques. The key was exquisite combination of regular and random structures at nanometer scale. Such artificial structural color was found to concern wide applications, because the Morpho-color can produce a single color without pigment in wide angular range with high reflectivity. Also it makes colors impossible by pigment, and is resistant to fading due to chemical change over longtime. However, we must overcome several "death valleys" for wide industrial applications. A serious problem was low throughput in the fabrication process of nano-patterning by the conventional lithography, which was solved by use of nano-imprinting technique. Next research step is attempts at a precise control of the optical properties, in both terms of real space and wavelength, i.e. angular distribution and spectrum. We could successfully optimize the optical properties by controlling the parameters of nano-structures in the artificial film. In this process, optical simulations and micro-structural observations were taken in account. The optimization was achieved both theoretically and empirically by comparing a series of films fabricated with different nano-patterns. Also the relationship between the structural parameters and the optical properties was analyzed. The reflective characteristics of the optimized film were found to reproduce the optical properties closer to the natural Morpho-blue than the prototypes.

Engineered biomimicry for harvesting solar energy: a bird's eye view

“…and coefficient of thermal expansion. Randomly sized and spaced pyramids [14,18,19], deep vertical-wall grooves [20], V grooves [21,22], and arrays of nanopillars [6][7][8][9][10][11]23] on the surface of silicon wafers have been widely utilized to reduce optical reflectance. Several surface-texturing techniques [24] including anodization [25] have also been used.…”

“…Such colors are called structural colors and their first description dates back to Isaac Newton [6], who tried to explain the brilliant plumage of the common Indian peafowl (Pavo cristatus) as rising from optical interference from the thin transparent part of the feathers. This research has now been extended to photonic crystals [7] and applied to the manufacture of unpigmented but colored fabrics [8]. Very recently, achromatic waveplates found in the eyes of crustaceans of a certain species inspired the design and fabrication of similarly performing waveplates [9].…”

Designing visual appearance using a structured surface

“…The nanofabrication methods are often highly inventive with different limitations on geometries and materials and, thus, also on obtainable colors and angle dependence. The governing effects for color control are (layered) interference effects possibly combined with randomization [1,5,[7][8][9]11,12,14], structural (particle) scattering [2][3][4]6], and surface plasmon effects [10,13]. The approaches mentioned-which by no means provide an exhaustive list-all have their limitations due to manufacturability, such as good color selectivity but little control of angular reflection, or expensive fabrication and/or design procedures.…”

“…Recently, a range of techniques for creating synthetic structurally colored systems have been reported in the literature. The methods each utilize a very different production technique, ranging from self-assembly [1][2][3][4] to deposition, growth, embossing, and etching techniques [5][6][7][8][9][10][11][12][13][14]. The nanofabrication methods are often highly inventive with different limitations on geometries and materials and, thus, also on obtainable colors and angle dependence.…”

Biomimetic Pieris rapae’s Nanostructure and Its Use as a Simple Sucrose Sensor

“…A particular example in this general area is the case of the Blue Morpho butterfly whose blue iridescent color comes from a natural Bragg reflector formed by stacked layers of cuticle and air [6]. The Blue Morpho butterfly example has led to multiple biomimetic approaches using different types of microfabrication including techniques such as PDMS soft lithography [7] and nano-imprinting technique [8].…”