![]() 1b, to mimic the coloration of Morpho butterfly wing scales by a novel process based on electron beam lithography and alternate development/dissolution on PMMA/LOR superlattice multilayers. This paper reports a technical breakthrough, recently achieved in the fabrication of aligned lamellae multilayer on nanopillars, as schematically presented in Fig. ![]() Moreover, most of the mimicked nanostructures uses inorganic materials, resulting in replicas’ displaying color unlike the real Morpho butterfly because optical properties of inorganic materials are different from that of cuticle in the real butterfly wing scales. Unfortunately its optical coloration is not characterized. 40 recently introduces a method for the large area nanofabrication by industrialized techniques and subsequent nanoimprint of 3D butterfly wing scales. However, all the reported approaches were not based on standard top-down nanolithography process with large area, high yield and low cost. 38, 39 used butterfly as bio-templates to synthesize the 3D nanostructures by metal oxides or polydimethylsiloxane (PDMS) and reported that the replica can reflect different colors with various lattice sizes and refractive indices. 32 fabricated replica of Morpho butterfly scales and observed blue color reflection by using focused-ion-beam chemical-vapor-deposition (FIB-CVD). 31 mimicked the blue color with wide angular viewing by multilayer deposition of TiO 2/SiO 2 on irregular substructure. Even though, numerous attempts have been reported. Such kind of nanostructures has been a daunting challenge in replication because of the 3D variations in the profile. Presenting on the sidewall of each ridge is actually lamellar structure consisting of alternate layers of cuticle and air. 1a, the wing scale is covered with parallel ridges with random heights from each other. As schematically shown by the original architecture in Fig. The key to the success in interpreting the coloration precisely is to establish a reliable technical methodology for the architecture of the periodical structure on the micro- and nanoscale on butterfly wing scale, which is also an inevitable step toward its applications in daily life. The anticipated applications include iridescent textile apparel 19, functional coatings 20, unmatchable color security coding 21, efficient solar cells 22, highly selective gas sensors 23, 24, chemical sensors with excellent sensitivity and selectivity 25, 26 and high-speed infrared imaging devices 27, 28, etc. Since the first observation of the inside structure with powerful scanning electron microscope (SEM) 15, substantial researches on the origin of the coloration by the elaborate nanostructures in Morpho butterfly wings have been widely conducted 16, 17, 18, driven by extensively potential applications. The coloration of the butterfly wings exhibits a number unique features such as broad blue iridescence, brilliant luster, speckle-like aspects, high resistance to discoloration, high sensitivity to environment and angle independent spectra 13, 14. Among them, the most widely cited examples are the Morpho butterflies 9, 10, 11, 12, living in South America. Structural color is frequently seen in butterflies 1, 2, 3, 4, 5, beetles 6 and sea animals 7, 8, etc. ![]() In principle, this approach establishes a starting point for mimicking structural colors beyond the blue in Morpho butterfly wings. The effects of the regularity in the replicas on coloration are analyzed. Structural color in blue reflected by the fabricated wing scales, is demonstrated and further extended to green as an application exercise of the new technique. Careful characterization of the mimicked blue by spectral measurements under both normal and oblique angles are carried out. The relationship between the coloration and geometric dimensions as well as shapes is systematically analyzed by solving Maxwell’s Equations with a finite domain time difference simulator. This paper reports a technical breakthrough to mimic the blue color of Morpho butterfly wings, by developing a novel nanofabrication process, based on electron beam lithography combined with alternate PMMA/LOR development/dissolution, for photonic structures with aligned lamellae multilayers in colorless polymers. Although the physics of structural color by the nanophotonic structures built on the wing scales has been well established, replications of the wing structure by standard top-down lithography still remains a challenge. The bright and iridescent blue color from Morpho butterfly wings has attracted worldwide attentions to explore its mysterious nature for long time.
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