Orientation-Dependent Reflection of Structurally Coloured Butterflies

Abstract

The photonic structures of butterfly wing scales are widely known to cause angle-dependent colours by light interference with nanostructures present in the wing scales. Here, we quantify the relevance of the horizontal alignment of the butterfly wing scales on the wing. The orientation-dependent reflection was measured at four different azimuth angles, with a step size of 90 • , for ten samples-two of different areas of the same species-of eight butterfly species of three subfamilies at constant angles of illumination and observation. For the observed species with varying optical structures, the wing typically exhibits higher orientation-dependent reflections than the individual scale. We find that the measured anisotropy is caused by the commonly observed grating structures that can be found on all butterfly wing scales, rather than the local photonic structures. Our results show that the technique employed here can be used to quickly evaluate the orientation-dependence of the reflection and hence provide important input for bio-inspired applications, e.g., to identify whether the respective structure is suitable as a template for nano-imprinting techniques.

Light and Autofluorescence, Multitasking Features in Living Organisms

“…In fact, scales are characterized by parallel ridges with an organized series of microribs working as a grating, as assessed in Papilionidae butterflies such as those belonging to Parides genus and Troides magellanus, and in subjects form the genus Morpho [184][185][186][187].…”

Color Modulation in Morpho Butterfly Wings Using Liquid Crystalline Elastomers

“…To characterize the wing iridescence, the sample has been tilted at different angles from 0° to 50° with steps of 10° (Figure a and Figure S5b, Supporting Information), keeping fixed the illumination and collection direction. The sample was always oriented with the scale ridges perpendicular to the plane of incident light because reflectance is higher in this configuration . The wavelength shift and the maximum intensity of the reflectance as a function of the tilting angle show as increasing the angle, a progressive blue shift occurs from 469 ± 1 nm at 0° to 438 ± 1 nm at 50° together with the reflectance reduction from 53% to 26% (Figure b).…”

Nanoimprinting of Biomimetic Nanostructures

“…Structural colors are colors that are not based on pigments but on nanostructured materials [79][80][81][82]. They can be found in insects [83,84] like butterflies [85][86][87] and beetles, spiders [88,89], birds [86,90,91] and fish [92]. Constructive and destructive interference, diffraction and randomness come together to achieve a unique color impression.…”