Universality in dynamic wetting dominated by contact line friction

TL;DR

This study investigates rapid contact line motion during droplet spreading, revealing that contact line friction governs the dynamics and leads to a universal scaling law across various fluids and surfaces.

Contribution

The paper introduces a contact line friction parameter that explains the universal behavior in dynamic wetting, supported by experiments and simulations.

Findings

Contact line friction limits spreading speed.

Universal scaling law for contact line evolution.

Agreement across different fluids and surface properties.

Abstract

We report experiments on the rapid contact line motion present in the early stages of capillary driven spreading of drops on dry solid substrates. The spreading data fails to follow a conventional viscous or inertial scaling. By integrating experiments and simulations, we quantify a contact line friction ($\mu_f$), which is seen to limit the speed of the rapid dynamic wetting. A scaling based on this contact line friction is shown to yield a universal curve for the evolution of the contact line radius as a function of time, for a range of fluid viscosities, drop sizes and surface wettabilities.