Multivariate coupling mechanism of NOCTUIDAE moth wings’ surface superhydrophobicity

Abstract

The surface shape, structure, biomaterial and wettability of moth wings (10 NOCTUIDAE species) from the northeast region of China were qualitatively and quantitatively studied by means of a stereoscopic microscope, a scanning electronic microscope, fourier transform infrared spectroscopy(FT-IR) and the interface contact angle measurement. The observation shows that there are scales arranged like overlapping tiles on the surface of the moth wings. The shapes of the scales are different between species. They overlap horizontally and there is particular space vertically in the direction of the wing veins. The surface of the scale is structured by micron-class grooves and nanometer-class vertical gibbosities. The biomaterial components of the moth wing scale are mostly made up of protein, lipids and chitin. The observation also shows that the contact angle for wings with scales is in the range from 144.8° to 152.9°, while that for those without scales is from 90.0° to 115.9°. It indicates that the surfaces of the wings with scales are more hydrophobic. According as Cassie model, the equation of wettability on the NOCTUIDAE moth wing surface is established and the hydrophobic mechanism is analyzed. It is concluded that the hydrophobicity of the moth wings is induced by the multivariate coupling of the shape, structures and biomaterial of the scales.