Patterned coating by suspensions

TL;DR

This study explores how suspensions of macroscopic particles behave during coating processes in a rotating cylinder, revealing phase separation driven by capillary attraction and particle clustering.

Contribution

It introduces the first analysis of Landau-Levich flow with macroscopic particles that exceed the film thickness, highlighting capillary effects and phase separation.

Findings

Particles cause excess surface area and capillary attraction.

Suspension separates into dense clusters and clear liquid regions.

Phase separation is driven by capillary forces.

Abstract

This is a fluid dynamics video submitted to the Gallery of Fluid Motion of the 63rd Annual Meeting of the American Physical Society Division of Fluid Dynamics. We examine the Landau-Levich flow of a suspension of neutrally buoyant particles within a rotating glass cylinder. This differs from previously investigated systems in that we deal with macroscopic particles which immediately exceed the thickness of the deposited liquid film. Thus, the presence of particles on the liquid-coated wall creates excess surface area, leading to a capillary attraction between particles. In turn, this capillary attraction induces phase separation of the suspension coating into regions of either dense particle clustering or clear liquid.