Lateral motion of a droplet after impacting on groove-patterned superhydrophobic surfaces

The lateral motion of a droplet after its impact on groove-patterned superhydrophobic surfaces is numerically studied in the present work. Different from previous studies, the wettability gradient is not required to produce lateral motions. Instead, a substrate with two halves decorated with same Cassie area fractions but different length ratios is used and four different motions can be observed by varying the impact velocity. The asymmetrical penetration into the grooves of the substrate is found to be the main reason for triggering the different motions. The penetrated liquid could bring upward momentum to lift the droplet from one side of the substrate, or it could block the retracting contact line from one side. As a result, different oblique motion components are generated and added to the vertical rebound motion, finally leading to the different lateral motions. Our simulation findings provide a fresh idea for the control of droplet motion by coating the solid surfaces.