Preparation of a Flexible Superhydrophobic Surface and Its Wetting Mechanism Based on Fractal Theory

Abstract

Substrates of superhydrophobic surface are important for their application. Preparation of a flexible superhydrophobic surface has drawn more and more attention. In this work, a flexible substrate was made using a semi-curing spray method to obtain a flexible superhydrophobic surface with excellent abrasion resistance on the surface of a room temperature vulcanized silicone rubber. Results show that under a bending condition, excellent superhydrophobic properties are still maintained. The Cassie-Baxter model and Wenzel model can be used to estimate the static water contact angle for regular roughness surfaces. There are few numerical theoretical models to predict contact angle or wetting mode for irregular micro-nanostructures superhydrophobic surfaces. The fractal theory can be used to transform the equation of Wenzel model and obtained the fractal wetting theory suitable for fractal structures on irregular rough surfaces. However, this fractal-wetting model cannot be applied to Cassie-Baxter state, which is always suitable for superhydrophobic surfaces. A new method was developed to calculate the static water contact angle of water droplets in the Cassie-Baxter model state. Using image identification and split surface method, a new model is constructed based on the fractal theory. Experimental data for water contact angles on flexible superhydrophobic surface with SiC/CNTs micro-nanostructures is agreement with the simulated values.