Abstract:
Drop-surface interaction is predominant in nature as well as in many industrial applications. Superhydrophobic surfaces show potential for various applications as they show complete drop rebound.
In a recent work, it has been reported that the drop lift-off time on a superhydrophobic substrate
could be further reduced by introducing a macro-ridge. The macro-ridge introduces asymmetry on
the morphology of drop spreading and retraction on the surface. This changes the hydrodynamics
of drop retraction and reduces the lift-off time. Keeping practical applications in view, we decorate
the surface with multiple ridges. The morphology of the hydrodynamic asymmetry is completely
different for the drops impacting onto the tip of the ridges from those impacting onto the middle of
the valley between the ridges. We show that the morphology forms the key to the lift-off time. We
also show that the outward flow from the ridge triggers a Laplace pressure driven de-wetting on the
tip of the ridge, thus aiding the lift-off time. At the end of this work, we propose a ridge to ridge
separation that effectively reduces the lift-off times for impacts both at the tip of the ridge and offset
from it.
