Fabrication of superhydrophobic surfaces with Cassie-Baxter state

Abstract

In order to develop a micro-textured surface with Cassie superhydrophobic properties, the influence of different microstructures on the wettability of metal materials was studied, and an optimized structure based on the improvement of the solid-liquid-gas three-phase contact state was proposed. In the experiment, chemical and electrochemical deposition methods were used to prepare microstructure surfaces with three different shapes, namely conical, spherical and pit-shaped. The static contact angle is used to measure the influence of different microstructures on surface hydrophobicity. The wetting model of water droplets on hydrophobic surfaces with different microstructures was established. The theoretical analysis of the three-phase solid-liquid-gas contact state on different microstructure surfaces is carried out. In addition, its effect on improving hydrophobic properties was characterized. Therefore, an efficient micro-scale structure was selected and optimized. The experimental results show that the microstructured surfaces with different morphologies obtained under the same modification conditions have significant differences in improving the hydrophobicity of the substrate surface. The concave structure shows the best hydrophobic effect, and the contact angle of water droplets on its surface corresponds to 165°. The simulation results show that the groove formed by the pit structure can retain nearly 90% of the air, thereby increasing the contact area between air and liquid droplets on the rough surface. In addition, the solid-liquid contact area is smaller than other structures. Through the combination of simulation analysis of the optimized structure, it can be determined that the pit structure with a certain concave radian is more likely to achieve the Cassie-Baxter state. This in turn leads to better hydrophobicity of the metal surface. Hence, the results of the study indicated that the introduction of suitable micrometer-scale pit-shaped structures on the metal substrate has a significant positive effect on the improvement of the surface hydrophobic properties with Cassie state.

Graphical Abstract

Keywords:

• Electrochemistry
• microstructure surface
• static contact angle
• wettability
• Cassie Baxter state

Additional information

Funding

The National Natural Science Foundation of China (approval numbers 51875417 and 51975425) supported this work. The author is very grateful for these supports.