Spontaneous Jumping of Coalescing Drops on a Superhydrophobic Surface

TL;DR

This study investigates the spontaneous out-of-plane jumping of coalescing drops on superhydrophobic and Leidenfrost surfaces, revealing elastic interactions and energy conversion mechanisms that enable autonomous water removal, beneficial for condensation processes.

Contribution

It demonstrates the physical mechanism behind drop coalescence-induced jumping on superhydrophobic surfaces and models the energy transfer involved.

Findings

Jumping motion results from elastic interactions during coalescence.

The kinetic energy of merged drops relates to surface energy released.

This phenomenon enables gravity-independent water removal.

Abstract

When micrometric drops coalesce in-plane on a superhydrophobic surface, a surprising out-of-plane jumping motion was observed. Such jumping motion triggered by drop coalescence was reproduced on a Leidenfrost surface. High-speed imaging revealed that this jumping motion results from the elastic interaction of the bridged drops with the superhydrophobic/Leidenfrost surface. Experiments on both the superhydrophobic and Leidenfrost surfaces compare favorably to a simple scaling model relating the kinetic energy of the merged drop to the surface energy released upon coalescence. The spontaneous jumping motion on water repellent surfaces enables the autonomous removal of water condensate independently of gravity; this process is highly desirable for sustained dropwise condensation.