Highly durable, thermally stable, semi-transparent superhydrophobic surfaces for easy-cleaning of contaminants

Abstract

With the development of smart electronic devices, the importance of surface-protective coatings is rapidly increasing. Superhydrophobic surfaces are promising protective coatings that exhibit potential for anti-wetting, self-cleaning, and antibacterial applications. However, their poor mechanical durability makes their practical application difficult. Additionally, rough surface geometries induce incident light scattering, thereby reducing the transparency and limiting their optical applications. This study describes semi-transparent superhydrophobic surfaces with improved mechanical strength and thermal stability obtained through simple spray coating. We mixed reactive polydimethylsiloxane (PDMS) as a binder with low surface free energy and high thermal resistance with fluorinated silica nanoparticles. PDMS polymers were functionalized to improve their hydrophobicity and adhesion properties through hydrosilylation with acrylate monomers. As a result, our superhydrophobic surfaces had a high-water repellency of above 160° and transparency of approximately 60 % at a wavelength of 550 nm. The coated surfaces exhibited an outstanding pencil hardness of 5H and sufficient clarity to identify objects through them. After heat treatment at 400 °C, the hardness increased to 6H while maintaining superhydrophobicity. Additionally, various contaminants were easily removed with water spraying. Our semi-transparent superhydrophobic surfaces can be widely applied in hard coatings for mobile displays, solar cell panels, self-cleaning paint, and outdoor facilities.