Gleaming and dull surface textures from photonic-crystal-type nanostructures in the butterflyCyanophrys remus

Abstract

Photonic-crystal-type nanostructures occurring in the scales of the butterfly Cyanophrys remus were investigated by optical and electron microscopy (scanning and transmission electron microscopy), reflectance measurements (specular, integrated, and goniometric), by fast Fourier transform analysis of micrographs, by modeling, and by numerical simulation of the measured reflectance data. By evaluating the collected data in a cross-correlated way, we show that the metallic blue dorsal coloration originates from scales which individually are photonic single crystals of 50 x 120 microm2 , while the matt pea-green coloration of the ventral side arises from the cumulative effect of randomly arranged, bright photonic crystallites (blue, green, and yellow) with typical diameters in the 3-10-mum range. Both structures are based on a very moderate refractive index contrast between air and chitin. Using a bleached specimen in which the pigment has decayed with time, we investigated the role of pigment in photonic-crystal material in the process of color generation. The possible biologic utility of the metallic blue (single-crystal) and dull green (polycrystal) textures both achieved with photonic crystals are briefly discussed. Potential applications in the field of colorants, flat panel displays, smart textiles, and smart papers are surveyed.

Structure, function, and self-assembly of single network gyroid ( I 4 1 32) photonic crystals in butterfly wing scales

“…The three-dimensional crystalline complexity of papilionid and lycaenid butterfly scales has been appreciated since the 1970s (8,11,(15)(16)(17)(18)(19)(20)(21)(22)(23)(24). However, most studies have used 2D electron microscopy (EM) to characterize these 3D photonic nanostructures, which is not sufficient to completely resolve their mesoscale features.…”

“…However, most studies have used 2D electron microscopy (EM) to characterize these 3D photonic nanostructures, which is not sufficient to completely resolve their mesoscale features. These structures have been variously characterized as simple cubic (SC) (17), face-centered cubic (FCC) (16), or FCC inverse opal (22,24) orderings of air spheres in chitin. Recently, Michielsen and Stavenga (18) reported qualitative pattern matching between published transmission electron microscope (TEM) images of various papilionid and lycaenid structurally colored wing scales and simulated sections of level set gyroid computer models.…”

Diffractive hygrochromic effect in the cuticle of the hercules beetleDynastes hercules

“…A multilayer stack generally produces a bright metallic-like colour by multiple interferences and usually shows iridescence [18], as the dominant reflected colour is blue-shifted when the angle of incidence increases. This is not observed here, but it is known that structural iridescence can sometimes be avoided by special choices of the multilayer parameters [19,20] or by the introduction of a sufficient level of disorder [21].…”

Natural photonics for industrial inspiration

“…Several recent investigations have revealed further cases of this 'inverse opal' in weevils and butterflies (e.g. Kertész et al 2006).…”

“…However, matt colours, similar to those of pigments, are also known to result from some structures (e.g. Kertész et al 2006). Traditionally, biologists have found helpful the classification of structural colours into the categories of (random) scattering, diffraction gratings, multilayer reflectors and liquid crystals.…”