Instabilities of ring-rivulets: Impact of substrate wettability

TL;DR

This study uses numerical simulations to explore how substrate wettability patterns influence the stability, breakup, and droplet formation of ring-shaped rivulets, revealing controllable dewetting behaviors.

Contribution

It introduces a detailed analysis of how patterned wettability affects rivulet stability and morphology, expanding understanding beyond homogeneous substrates.

Findings

Wettability patterns can control rivulet stability and breakup.

Pattern tuning influences droplet number and position.

Substrate wettability patterns enable manipulation of dewetting dynamics.

Abstract

Rivulets and droplets are naturally appearing shapes when small amounts of liquid are deposited on a partially wettable substrate. Here we study, by means of numerical simulations, the dewetting dynamics of a ring-rivulet on substrates with various contact angles and wettability patterns. In particular, we consider, beyond the homogeous case, an annular band of lower contact angle as compared to the background and a constant radial gradient of contact angle, pointing either inward or outward from the centre. We show that by tuning the parameters characterizing the patterns, it is possible to control not only the stability of the rivulet, i.e. its breakup/collapse dynamics and the associated time scales, but also the dewetting morphology, in terms of number and position of the formed droplets.