Drop deposition on surfaces with contact-angle hysteresis: Liquid-bridge stability and breakup

TL;DR

This study investigates the stability and breakup of liquid bridges on surfaces with contact-angle hysteresis, combining theoretical predictions with experiments to understand how contact angles influence stability and droplet size.

Contribution

It provides new insights into how contact-angle hysteresis affects liquid-bridge stability and breakup, highlighting the role of dynamic contact angles and transition states.

Findings

Stability loss can occur during transition from pinned-pinned to pinned-free interface.

Dynamic contact angles influence contact-line radius after stability loss.

Interface evolution can increase droplet size if contact angle is fixed.

Abstract

We study the stability and breakup of liquid bridges with a free contact line on a surface with contact-angle hysteresis under zero-gravity conditions. Theoretical predictions of the stability limits are validated by experimental measurements. Experiments are conducted in a water-methanol-silicon oil system where the gravity force is offset by buoyancy. We highlight cases where stability is lost during the transition from a pinned-pinned to pinned-free interface when the receding contact angle is approached---rather than a critical state, indicating that the breakup length is not always associated with the static maximum-length stability limit. We demonstrate that the dynamic contact angle controls the contact-line radius following stability loss, and that interface evolution following stability loss can increase the dispensed-drop size if the contact angle is fixed.