Wettability-independent droplet transport by \emph{Bendotaxis}

TL;DR

This paper introduces bendotaxis, a new mechanism for droplet self-transport driven by bending and capillarity in channels, independent of wettability, with potential applications in self-cleaning surfaces.

Contribution

The study presents the concept of bendotaxis, combining experiments and modeling to show how bending-induced pressure gradients can move droplets regardless of surface wettability.

Findings

Droplets move spontaneously in a consistent direction regardless of wettability.

Bendotaxis is driven by a pressure gradient caused by channel bending and capillarity.

Potential applications include self-cleaning surfaces and droplet transport technologies.

Abstract

We demonstrate \textit{bendotaxis}, a novel mechanism for droplet self-transport at small scales. A combination of bending and capillarity in a thin channel causes a pressure gradient that, in turn, results in the spontaneous movement of a liquid droplet. Surprisingly, the direction of this motion is always the same, regardless of the wettability of the channel. We use a combination of experiments at a macroscopic scale and a simple mathematical model to study this motion, focussing in particular on the time scale associated with the motion. We suggest that \emph{bendotaxis} may be a useful means of transporting droplets in technological applications, for example in developing self-cleaning surfaces, and discuss the implications of our results for such applications.