title: Drying paint: from micro-scale dynamics to mechanical instabilities.
abstract: Charged colloidal dispersions make up the basis of a broad range of industrial and commercial products, from paints to coatings and additives in cosmetics. During drying, an initially liquid dispersion of such particles is slowly concentrated into a solid, displaying a range of mechanical instabilities in response to highly variable internal pressures. Here we summarize the current appreciation of this process by pairing an advection-diffusion model of particle motion with a Poisson-Boltzmann cell model of inter-particle interactions, to predict the concentration gradients in a drying colloidal film. We then test these predictions with osmotic compression experiments on colloidal silica, and small-angle X-ray scattering experiments on silica dispersions drying in Hele-Shaw cells. Finally, we use the details of the microscopic physics at play in these dispersions to explore how two macroscopic mechanical instabilities-shear-banding and fracture-can be controlled.This article is part of the themed issue 'Patterning through instabilities in complex media: theory and applications.'
authors.affiliation: School of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham NG11 8NS, UK lucas.goehring@ntu.ac.uk.|Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Göttingen, Germany.
authors.forename: Lucas
authors.identifier: http://orcid.org/0000-0002-3858-7295
authors.initials: L
authors.lastname: Goehring
authors.affiliation: Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Göttingen, Germany.
authors.forename: Joaquim
authors.initials: J
authors.lastname: Li
authors.affiliation: Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Göttingen, Germany.
authors.forename: Pree-Cha
authors.initials: PC
authors.lastname: Kiatkirakajorn
keywords: colloids; drying; fracture; shear bands; small-angle X-ray scattering; solidification