Anti-splashing properties of sticky superhydrophobic surfaces

Abstract

We used a high-speed camera to investigate the effect of pore structures on the anti-splashing properties of superhydrophobic surfaces. Zinc oxide (ZnO) nanowires with open air pockets and anodic aluminum oxide (AAO) with sealed air pockets were synthesized and subsequently treated with a low-energy self-assembled monolayer to render their surfaces superhydrophobic. The water contact angle of the superhydrophobic ZnO surface (SH-ZnO) was almost identical to that of the superhydrophobic AAO surface (SH-AAO); however, SH-AAO exhibited greater adhesion than SH-ZnO, which we attributed to the difference in the structures of air pockets. In addition, when a water droplet impacted SH-AAO, the surface effectively suppressed droplet splashing because of high adhesion; by contrast, the conventional superhydrophobic surface (i.e., SH-ZnO) promoted droplet splashing because of the presence of an air layer between the impacting water and the solid surface. The anti-splashing behavior of SH-AAO was observed not only for the impact of a water droplet but also for the impact of a water jet on the surface.