Breakup of viscous liquid bridges on solid surfaces

TL;DR

This study investigates the breakup dynamics of viscous liquid bridges on solid surfaces, highlighting the influence of wettability, dissipation mechanisms, and external constraints, and deriving a scaling relation for the minimum width evolution.

Contribution

It introduces a comprehensive analysis of breakup dynamics considering wettability effects and develops a scaling law for the minimum width of liquid bridges.

Findings

Wettability significantly affects breakup dynamics.

A scaling relation accurately predicts minimum width evolution.

External constraints alter behavior differently for various viscosities.

Abstract

The breakup dynamics of viscous liquid bridges on solid surfaces is studied experimentally. It is found that the dynamics bears similarities to the breakup of free liquid bridges in the viscous regime. Nevertheless, the dynamics is significantly influenced by the wettability of the solid substrate. Therefore, it is essential to take into account the interaction between the solid and the liquid, especially at the three-phase contact line. It is shown that when the breakup velocity is low and the solid surface is hydrophobic, the dominant channel of energy dissipation is likely due to thermally activated jumping of molecules, as described by the Molecular Kinetic Theory. Nevertheless, the viscous dissipation in the bulk due to axial flow along the bridge can be of importance for long bridges. In view of this, a scaling relation for the time dependence of the minimum width of the liquid bridge is derived. For high viscosities, the scaling relation captures the time evolution of the minimum width very well. Furthermore, it is found that external geometrical constraints alter the dynamic behavior of low and high viscosity liquid bridges in a different fashion. This discrepancy is explained by considering the dominant forces in each regime. Lastly, the morphology of the satellite droplets deposited on the surface is qualitatively compared to that of free liquid bridges.