Dynamic characteristics of drops on tilted hydrophobic ratchet surfaces

Asymmetric ratchet surfaces are used to manipulate drops which has received extensive attention due to their wide potential applications. In this paper, using aluminum sheets as substrates, some hydrophobic ratchet surfaces with different geometric parameters were prepared. The dynamic behavior of drops in the initial movement stage on the tilted surfaces was captured by a high-speed camera. Compared with the behavior on the flat tilted aluminum sheet, the velocity and acceleration of the drop on the tilted ratchet surfaces exhibit nonlinearly characteristics. The forces acting on the drop was analyzed and a theoretical model was proposed to elucidate the dynamic behavior, which was in agreement with our experimental results. Besides, by changing the tilt angle of the substrate, the geometric parameters of ratchets, and the size of drops, the factors that affect the drop movement were discussed.