Controlling deposition and characterising dynamics of thin liquid films with high temporal and spatial resolution

TL;DR

This paper introduces a novel experimental device for precise control and characterization of thin liquid films, enabling high-resolution measurements of film dynamics and thickness with reduced inertia effects.

Contribution

The authors develop a new low-inertia coating device and a high-resolution interferometric method to measure film profiles and dynamics with unprecedented accuracy.

Findings

Film thickness follows Landau-Levich scaling despite accelerations.

Nanometer-per-second resolution in film thinning rates.

Surface tension and gravity effects quantified.

Abstract

The high inertia of classical fluid coating processes severely limits the possibility of controlling the deposited film thickness through the entrainment velocity. We describe and characterize a new experimental device where the inertia is dramatically reduced, allowing for millimeter-scale patterning with micrometer-accurate thickness. Measuring precise film profiles over large spatial extents with high temporal resolution poses a challenge, which we overcome using a custom interferometric set-up coupled with state-of-the-art signal processing. The sensitivity of our method allows us to resolve film thinning rates in the nanometer-per-second range, and to quantify the relative contribution of surface-tension and gravity driven flows. We apply this method by showing that the thickness of the deposited film obeys the classical Landau-Levich scaling even when the meniscus faces important acceleration.