Implementation of endurable superhydrophobic surfaces through dilution rate control of the PDMS coating on micro-nano surface structures

Modifying the wettability of engineering surfaces has been widely practiced for several years because changing the surface properties of materials can induce useful functional properties. Superhydrophobic surfaces with maximized hydrophobicity prevent contamination, freezing, and corrosion, and are usually categorized based on the coating solution used. Among the various coating solutions, polydimethylsiloxane (PDMS) has attracted wide attention because it yields fluorine-free superhydrophobic coatings. Herein, fluorine-free superhydrophobic coatings were fabricated by varying the ratio of PDMS and toluene with respect to their viscosity. The roughness, wettability, and durability of the coatings were measured and described in detail. A simple chemical etching and oxidizing process was used to fabricate micro-nanostructures on the hydrophilic surface before hydrophobic coating. The variance in the morphological structure and surface roughness of the yielded micro-nanostructures in accordance with the viscosity control was analyzed using SEM images and surface roughness values, respectively. To measure the contact angle of the water droplet, coating conditions were derived to realize a superhydrophobic surface with a contact angle of over 150 degrees. Furthermore, these superhydrophobic specimens were tested for durability in saline, acidic, and alkaline solutions. The superhydrophobic specimens showed no sign of degradation in brine for 72 h, and some surfaces showed degradation in HCl and NaOH aqueous solutions.