Water-Repellency and Anisotropic Wettability of Micro-Grooved Polymer Surfaces

This is the authors' abstract. We don't add key points for this paper.

Superhydrophobicity and anisotropic wettability can be simultaneously achieved by simple groove pattern on a surface. To verify those characteristics experimentally, we fabricated the micro-grooved surfaces with four different groove widths. Static contact angles were measured with the sessile drop method to investigate the apparent wettability and wetting states. All four surfaces exhibited the static contact angles well fitted to those estimated on the Cassie-Baxter state in which favorable water-repellency was expected. The static contact angles measured perpendicular to grooves were higher than those measured parallel to grooves. This anisotropic wettability was also observed with the sliding angle at the onset of the droplet moving when the surfaces were tilted. The sliding angles measured perpendicular to grooves were much higher than those measured on the smooth surface without micro-grooves. Conversely, the sliding angles measured parallel to grooves were smaller than those measured on the smooth surface. Because the sliding angle as well as the contact angle hysteresis reflect the water-repellency, the micro-grooves clearly made the surfaces anisotropic water-repellent.