Modelling the formation of structured deposits at receding contact lines of evaporating solutions and suspensions

TL;DR

This paper develops a hydrodynamic model to predict the formation of regular and irregular line patterns during the evaporation of liquid suspensions and polymer solutions, highlighting a self-organized pinning-depinning cycle.

Contribution

It introduces a detailed hydrodynamic model based on a long-wave approximation to explain pattern formation during evaporation, linking it to experimental observations and depinning transitions.

Findings

Pattern properties depend on evaporation rate, solute concentration, and other parameters.

The model predicts a stick-slip contact line motion leading to line pattern formation.

Results relate to experimental data and depinning phenomena in soft matter.

Abstract

When a film of a liquid suspension of nanoparticles or a polymer solution is deposited on a surface, it may dewet from the surface and as the solvent evaporates the solute particles/polymer can be deposited on the surface in regular line patterns. In this paper we explore a hydrodynamic model for the process that is based on a long-wave approximation that predicts the deposition of irregular and regular line patterns. This is due to a self-organised pinning-depinning cycle that resembles a stick-slip motion of the contact line. We present a detailed analysis of how the line pattern properties depend on quantities such as the evaporation rate, the solute concentration, the P\'eclet number, the chemical potential of the ambient vapour, the disjoining pressure, and the intrinsic viscosity. The results are related to several experiments and to depinning transitions in other soft matter systems.