One-step fabrication of flexible superhydrophobic surfaces to enhance water repellency

Abstract

This paper investigates a one-step fabrication method of flexible superhydrophobic surfaces on silicone rubber substrates, which enhance the repellency to both static and impacting water droplets. Grooved structures with hierarchical roughness were constructed directly on intrinsically hydrophobic silicone rubber surfaces using nanosecond ultraviolet laser. The effects of laser parameters, laser scanning speed and number of scans, on surface morphology and wettability were explored. Results show that the scanning speed and the number of scans jointly affect the roughness of the processed surfaces and further the contact angle of static droplets. Due to the anisotropic wettability, the contact angle perpendicular to grooves is generally larger than that in the parallel direction. When the scanning speed is 540 mm/s and the number of scans is 75, the maximum contact angles in the perpendicular and parallel directions are 156.5°, 155.0°, respectively. One of the silicone rubber based superhydrophobic surfaces was then bent into convex shapes with various curvatures and a series of droplet impact experiments were performed on it. Compared to that on a flat superhydrophobic surface, the contact time of impacting droplets on the curved surface is reduced dramatically. It demonstrates that the flexible surfaces can also have improved repellency to dynamic droplets. This work provides an effective approach for repelling water through fabricating flexible superhydrophobic surfaces.