Surfaces designed so that drops do not adhere to them but instead bounce off have received substantial attention because of their ability to stay dry^1–4, self-clean^5–7 and resist icing^8–10. A drop striking a non-wetting surface of this type will spread out to a maximum diameter^11–14 and then recoil to such an extent that it completely rebounds and leaves the solid material^15–18. The amount of time that the drop is in contact with the solid—the ‘contact time’—depends on the inertia and capillarity of the drop¹ , internal dissipation¹⁹ and surface–liquid interactions^20–22. And because contact time controls the extent to which mass, momentum and energy are exchanged between drop and surface²³, it is often advantageous to minimize it. The conventional approach has been to minimize surface–liquid interactions that can lead to contact line pinning^20–22; but even in the absence of any surface interactions, drop hydrodynamics imposes a minimum contact time that was conventionally assumed to be attained with axisymmetrically spreading and recoiling drops^21,24. Here we demonstrate that it is possible to reduce the contact time below this theoretical limit by using superhydrophobic surfaces with a morphology that redistributes the liquid mass and thereby alters the drop hydrodynamics. We show theoretically and experimentally that this approach allows us to reduce the overall contact time between a bouncing drop and a surface below what was previously thought possible.

Paper: James C. Bird, Rajeev Dhiman, Hyuk-Min KwoN, and Kripa K. Varanasi. Nature (Cover Article)

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