Enhanced horizontal mobility of a coalesced jumping droplet on superhydrophobic surfaces with an asymmetric ridge

Enhancing the horizontal mobility of coalesced droplets on a plane could promote droplet jumping. Here, we achieve enhanced horizontal mobility of a coalesced jumping droplet on superhydrophobic surfaces with an asymmetric ridge and investigate the underlying mechanism through experiment and simulation. Results indicate that the coalesced droplet accelerates during the coalescence-induced jumping stage and gains horizontal velocity during the rebound stage. The nondimensional horizontal velocity can reach 0.47, which is about 2.3 times the jumping velocity on the plane. Depending on the height-to-width ratio of the asymmetric ridge, the ratio of the horizontal velocity to the fallen velocity when the fallen droplet makes contact with the ridge is 0.55-0.75. Furthermore, the coalesced droplet can still obtain considerable horizontal velocity on superhydrophobic surfaces with an asymmetric ridge when the initial droplet radius is unequal. This work provides new insights for improving droplet jumping by surface structure in related fields. Published under an exclusive license by AIP Publishing.