Analysis of approaches to mathematical description of the characteristics of materials with high hydrophobicity

Abstract

The increasing interest in the superhydrophobic materials in the scientific world leads to the accumulation of a large amount of theoretical models of such surfaces, and the corresponding experimental data. The ordering of such information is required to create a unified approach to modeling surfaces with controlled hydrophobicity. The review includes a classification of the main significant characteristics of the hydrophobic properties of materials, namely, wetting, roll-off, and outflow wetting and inflow wetting angles in applying to smooth, as well as rough surfaces. Two fundamental wetting states of textured materials - Cassie-Baxter and Wentzel are described. Next, a set of mathematical models, which allow to calculate the above parameters based on structural and energy properties of the material surface is given. One of the most important characteristics of superhydrophobic materials - wetting state stability is described in the third part of the review, which presents corresponding analytical models, indicating the possible optimal types of the surface structure to achieve the specified state. For example, using irregularities with a reentrant geometry allows to achieve stable values of the wetting angle above 160°. At the same time, it is shown that for large-scale use of superhydrophobic materials, materials with the hierarchical (micro-nano) structure of irregularities are the most suitable.