Beating the teapot effect

TL;DR

This paper reveals that surface wettability significantly influences liquid dripping in inertial flows, with superhydrophobic surfaces completely preventing dripping, explained by a new hydro-capillary adhesion model and demonstrated via electro-wetting control.

Contribution

It introduces a novel hydro-capillary adhesion framework linking inertial flow and wettability, and demonstrates real-time dripping control using electro-wetting.

Findings

Superhydrophobic surfaces suppress dripping.

Wettability, flow velocity, and edge curvature affect flow separation.

Electro-wetting enables real-time control of dripping.

Abstract

We investigate the dripping of liquids around solid surfaces in the regime of inertial flows, a situation commonly encountered with the so-called "teapot effect". We demonstrate that surface wettability is an unexpected key factor in controlling flow separation and dripping, the latter being completely suppressed in the limit of superhydrophobic substrates. This unforeseen coupling is rationalized in terms of a novel hydro-capillary adhesion framework, which couples inertial flows to surface wettability effects. This description of flow separation successfully captures the observed dependence on the various experimental parameters - wettability, flow velocity, solid surface edge curvature-. As a further illustration of this coupling, a real-time control of dripping is demonstrated using electro-wetting for contact angle actuation.