Research On Wettability And Its Mechanism Of Moth Wing Surfaces

Wettability is an important characteristic of solid surface, lots of interfacial phenomena in nature and daily life is related to wettability. According to the value of the contact angle of the liquid on the solid surface, the solid surface can be divided into three groups: super-hydrophobic surface, hydrophobic surface and hydrophilic surface. The hydrophobic surface, especially the super-hydrophobic surface are remarkable for their waterproof, pollution prevention, oxidation and self-cleaning and other functions. They have broad application prospects in military, industrial, agricultural production and people's daily life. The purpose of research is to understand the wettability laws of solid wetted by liquid so that we can change the wettability according to our demand. The scientists discovered that super-hydrophobic surface is a common phenomenon in the nature, the lotus leaves, the wing of lepidopterous insects and waterfowl feathers have strong hydrophobic.In order to resisting the rain, fog and dust and other unfavorable factors, the wing surface of moth formed anti-adhesion, non-wettability, super-hydrophobic and self-cleaning functions in long-term evolution. It appears that the wing surface of moth is smooth, but it is a non-smooth surface composing of scales in fact, which can be seen clearly under the microscope. The wettability and its mechanisms are dissertation Wettability of the wing surface of moth are researched in this dissertation, the mechanisms of wettability of the wing surface of moth are also analyzed here.The wing surfaces of kinds of moths are observed under SteREO Discovery.V12 Auto-stereoscopic Microscope and JSM-5600LV Scanning Electron Microcopy. The micron scales bestrew the wing surface of moth, which are composed of several parallel sub-micron ribs and grooves. They are many pores at the bottom of the grooves. The size, spacing of the scales and spacing of ribs and grooves are measured. The result shows that the size, spacing of the scales and spacing of ribs and grooves are different with different moths.Static contact angle and sliding angle of the wing surfaces of kinds of moths are measured by the OCA20 Contact Eagle Measuring System. The contact angle of the wing surfaces of kinds of moths are between 130.7 o～152.9o,which obviously bigger than the contact angle of no-scale wing surfaces(102.4°~133.3°). It shows that the scales play an important role in hydrophobic of the wing surface of moth. The sliding eagle of the wing surface of moth is anisotropy, the positive contact eagles measured by first ramp and then drop method are smaller than 3o, which shows that its surface has a good self-cleaning character.The Cassie Model and the improved Cassie Model are used to analyze the mechanisms of wettability of the wing surface of moth. We analyzed the theoretical contact eagle under the separate action and complex action by micron scales and ribs (grooves). The result indicated that the hydrophobic of the wing surface of moth is the result of complex action by micron scales and ribs (grooves). The calculate value and the experiment value are well consistent. Based on this, we make bionic design of super-hydrophobic surface model.