Superhydrophobic surface (coating) plays an irreplaceable role in the fields of drag reduction, energy saving, anti ice and anti biological deposition. Recently, many bottom-up or top-down preparation strategies have been developed to construct functional superhydrophobic coatings with low surface energy and rough surface structure. However, due to the complexity of the micro nano structure surface construction process and the wear characteristics of the micro nano rough structure, the preparation cost and service life of the superhydrophobic coating are greatly restricted. It is an important development direction in this field to develop a simple strategy to realize the functional coating with high wear-resistant, easy to repair and renewable superhydrophobic surface.

Recently, Professor shaker a. Meguid of the University of Toronto, Canada, took nano silica particles and silicone resin as raw materials, and based on simple industrial spraying technology or traditional resin molding technology, simply realized the construction of multifunctional composite superhydrophobic coating. At the same time, the research team carried out a detailed characterization and Analysis on the relationship between the composition of the two kinds of superhydrophobic coating systems and the surface hydrophobicity; the system test shows that the superhydrophobic coating constructed in the research results has excellent elasticity, durability and renewable performance of superhydrophobic surface, and has a broad prospect of practical industrial application.

Schematic diagram of preparation process of superhydrophobic coating or block material. Photo source: ACS appl. Mater. Interfaces

For the preparation of composite super hydrophobic coating by spraying process, the research team systematically studied the super hydrophobic system with different silica doping concentration (0 ~ 33wt%). With the increase of SiO2 doping concentration, the coating gradually presents bright color; when the SiO2 doping concentration is more than 9 wt%, the surface of composite coating reaches super sparse state (water contact angle > 150 °, rolling angle < 10 °); when the SiO2 doping concentration reaches 33 wt%, the water contact angle of coating surface reaches about 171 °, rolling angle is only about 2 °, but the durability of coating decreases significantly.

The influence of silica doping concentration on the surface color and hydrophobicity of the coating. Photo source: ACS appl. Mater. Interfaces

Based on SEM and AFM, the surface morphology of the composite coating is tested. The results show that the micro nano roughness structure is the key factor to realize the superhydrophobic characteristics of the coating surface. When the doping concentration of silica is 7 wt%, the surface roughness and hydrophobicity of the coating are smaller when silica is embedded in the silicone resin; when the doping concentration of silica is 14 wt%, the spherical particles of silica with a diameter of ~ 10-25 μ m are distributed on the surface of the coating to significantly improve the surface roughness and hydrophobicity of the coating.