Slip-Mediated Dewetting of Polymer Microdroplets

TL;DR

This study investigates how slip at the solid-liquid interface influences the dewetting dynamics of polymer microdroplets, combining experiments, scaling analysis, and numerical simulations to reveal slip's significant role.

Contribution

It provides experimental evidence and modeling insights into slip-mediated dewetting of microdroplets, highlighting slip's impact on contact line motion and shape evolution.

Findings

Slip significantly affects droplet shape and contact line dynamics.

Experimental results align with numerical simulations using Navier slip boundary conditions.

Slip controls the relaxation process of dewetting microdroplets.

Abstract

Classical hydrodynamic models predict that infinite work is required to move a three-phase contact line, defined here as the line where a liquid/vapor interface intersects a solid surface. Assuming a slip boundary condition, in which the liquid slides against the solid, such an unphysical prediction is avoided. In this article, we present the results of experiments in which a contact line moves and where slip is a dominating and controllable factor. Spherical cap shaped polystyrene microdroplets, with non-equilibrium contact angle, are placed on solid self-assembled monolayer coatings from which they dewet. The relaxation is monitored using \textit{in situ} atomic force microscopy. We find that slip has a strong influence on the droplet evolutions, both on the transient non-spherical shapes and contact line dynamics. The observations are in agreement with scaling analysis and boundary element numerical integration of the governing Stokes equations, including a Navier slip boundary condition.