Super-hydrophobic/hydrophilic patterning on three-dimensional objects

Abstract

As superhydrophobic/superhydrophilic (SHPo/SHPi) patterned surfaces can be applied in various fields such as boiling heat transfer and water harvesting, many techniques for their fabrication have been developed. A patterned surface in nature generally has three-dimensionally curved surfaces, such as those observed in the banana leaf and Namib desert beetle. However, existing patterned surface fabrication technologies have a limitation in that they can be applied only to flat surfaces because they are based on laser and ultraviolet techniques. In this study, we proposed a SHPo/SHPi patterning method that can be applied to the fabrication of three-dimensional objects using aluminum. The novelty of the method is the fact that the surface coated to achieve SHPo properties does not cause a chemical reaction with the surface treatment solution. A patterned surface with a contact angle of < 10° for the SHPi surface and > 160° for the SHPo surface was successfully realized. Furthermore, this method enabled desired patterning even in areas that laser light cannot reach, such as the inner walls of a tube. This study allows the expansion of the application scope of the SHPo/SHPi surface patterning technique toward the fabrication of three-dimensional structures, thereby overcoming the limitation of previous patterned surface fabrication technologies.