a 北京航空制造工程研究所 高能束流加工技术国家重点实验室 北京 100024;
b 北京航空航天大学 航空科学与工程学院 北京 100191
Wettability Analysis and Design of Micro-nanostructured Superhydrophobic Surface
Ma Guojiaa, Zheng Haikunb, Chang Shinanb, Wang Shuoshuob
a Science and Technology on Power Beam Processes Laboratory, Beijing Aeronautical Manufacturing Technology Research Institute, Beijing 100024;
b School of Aeronautic Science and Engineering, Beihang University, Beijing 100191
The special wettability of superhydrophobic surface usually has high contact angles (CA > 150°) and low contact angle hysteresis (CAH < 5°), which has been exploited for many potential applications. It is well known that wettability is mainly determined by micro/nano structure and surface composition, and various types of natural superhydrophobic surface could exhibit different wetting states, showing different wetting properties, such as low adhesive lotus leaf; the anisotropic superhydrophobic rice leaf; high adhesive rose petal. Therefore, the relationship between the wetting state and the surface structure should have a deeper understanding, especially in the design preliminary stage. The "droplet-superhydrophobic surface" system is taken as the research objects, four stable wetting state expressions are analyzed based on the principle of minimum energy. Wetting state transitions are studied on superhydrophobic surface coverd with micro/nano structured pillars of different distributions. The calculation formula of intrinsic contact angle is derived and the intrinsic contact angle of common materials is investigated. Based on the four wetting state of apparent contact angle equations, wetting diagrams were drew for investigating the wetting behavior, which include "one point, three lines, six areas, four state". The influence of the relative structure spacing and relative structure height on the wetting state is analyzed. It is found that the larger relative structure height, the smaller relative structure spacing, which can reduce the critical parameters of the transition state of the infiltration state, thereby expanding the range of the superhydrophobic surface, the more design options are available. It is also beneficial to the stability of the superhydrophobic surface, but should be controlled within certain scales because of mechanical stability. The simulation results accurately reflected the wetting state with the changes of the relative structure spacing and relative structure height. Finally, the general design of the superhydrophobic surface is refined. The results can provide theoretical guidance and technical fundament for the design of superhydrophobic surfaces.