Excellent Structure-Based Multifunction of Morpho Butterfly Wings： A Review

Morpho butterfly, famous for its iridescence wing scales, has gradually evolved a diversity of functions and has attracted much attention recently. On the other hand, it is known that the wing surface of Morpho butterfly has some complex and so- phisticated structures. In fact, they are composed of an alternating multilayer film system of chitin and air layers, which have different refractive indexes. More importantly, these structures can interact strongly with visible light because the feature size of the structures is in the same order of magnitude with light wavelength. It is noteworthy that it is these optical architectures that cause the excellent multifunction including structural color, antireflection, thermal response, selective vapour response, direc- tional adhesion, superhydrophobicity and so on. This review mainly covers the excellent multifunctional features of Morpho butterfly wings with representative functional structures of multilayer film system, photonic crystal and ridges. Then, the mechanism of the structure-based optical multifunction of Morpho butterfly is analyzed. In order to facilitate mechanism analysis, the models of bionic functional structures are reported, as well as the interaction process between the multiscale structures and the external media It is concluded that these functions of Morpho butterfly wings have inevitable and corre- sponding regularity connection with the structural parameters and the dielectric coefficient of the filled medium. At last, the future direction and prospects of this field are briefly addressed. It is hoped that this review could be beneficial to provide some innovative insoirations and new ideas to the researchers in the fields of engineering, biomedicine, and materials science.

Investigation on color variation of Morpho butterfly wings hierarchical structure based on PCA

Morpho butterfly wings show brilliant blue color,which has a close relationship with the hierarchical micro/nano structures on the surface of scales.When liquids such as methanol,ethanol and isopropanol with different refractive indexes drop onto the scales,the reflectance of wings would decrease.The main peaks of reflectance shift to the right and the scales turn to yel-low-green.After the liquids volatilizes completely,the scales revert to the original blue color.The typical micro/nano struc-tures of Morpho butterfly wing scales are modeled,and the reflectance variation in the course of dropping liquids is simulated.Furthermore,the principal component analysis(PCA) method is employed to analyze the experimental and simulation reflec-tance data,extract principal components and reduce dimensions.As a result,the curves mapping the reflectance variation are clearly shown in the coordinate system consisting of three principal components.The typical color variation of scales during the dropping process could be monitored,and different kinds of liquids could be obviously distinguished according to the dis-tributed regions of mapping points.This study provides guidance to environmental media detecting as well as data processing,and enhances the fabrication and application of the mimic Morpho butterfly wings micro/nano structures.