微结构表面Cassie/Wenzel润湿模式转换机制研究

Transition Mechanism of Cassie/Wenzel Wetting Model on Micro Structure Surfaces

粗糙表面固液润湿模式主要有Wenzel、Cassie 2种,Cassie润湿模式有利于微结构表面的超疏水自清洁作用,因而对于超疏水表面需要阻止固液界面从Cassie模式向Wenzel模式转换。探讨Cassie/Wenzel(C/W)润湿模式转换机制以及微结构表面阻止C/W润湿模式转换的条件。研究表明,表面能大小是导致润湿模式转换的决定性要素,要阻止C/W润湿模式转换,应当选择适当的表面微结构几何参数使得Cassie模式的能量比Wenzel模式的低;对于圆柱/方状凹坑、圆柱/方状凸起等单级微观结构表面,可以通过增大凹坑深度比/凸起高度比或者减小凹坑/凸起间距比阻止发生C/W润湿模式转换。而凹坑微观结构有利于防止C/W润湿模式转换,更适合制备超疏水表面。

Wenzel and Cassie models are two main kinds of solid-liquid wetting models on the rough surfaces. Cassie wetting model is helpful to super-hydrophobic and self-clean function of micro-structure surfaces, so that it is a must for super-hydrophobic surfaces to prevent solid-liquid interface transiting from Cassie model to Wenzel model. The transition mechanism of Cassie/Wenzel（C/W） wetting model and the condition to prevent C/W wetting model transition were researched. The results show that the size of surface energy is the decisive factor for wetting model transition. In order to prevent C/W wetting model transition, the suitable micro structural parameters are selected so that the Cassie model＇ s energy is under Wenzel model＇ s. For single grade micro structure surfaces of column/square concave and column/square convex, the C/W wetting model transition can be prevented by increasing the concave depth and convex height or reducing the spacing of concave and convex. The concave micro-structures are helpful to prevent C/W wetting model transition and even more suitable to prepare super-hydrophobic surfaces.