Threshold levels for wettability in nano- and micro-meter periodic structures

Abstract

The purposes of this study are to clarify the relationship between surface wettability and the pitch and size of periodic structures on the surface and to determine the thresholds at which the wettability switches from being hydrophobic to hydrophilic. To this various nano- and micro-meter scale periodic structures were fabricated. By applying a fine periodic structure to the surface, the wettability can be controlled between + 50° (hydrophobic) and -55° (hydrophilic). The pitch of the periodic structure at which the wettability switches from hydrophilic to hydrophobic was found to between 500 and 1,000 nm. Additionally, the height of the periodic structure at which the wettability switches from hydrophobic to hydrophilic was found to between 300 and 700 nm.