Non-equilibrium dynamics of a confined colloidal bilayer in planar shear flow

TL;DR

This study uses Brownian dynamics simulations to explore how shear flow affects the structure and dynamics of confined charged colloids, revealing shear-induced order transitions, diffusion behavior, and zig-zag particle motion.

Contribution

It provides new insights into shear-induced structural and dynamical transitions in confined colloidal bilayers, including an analytical model for shear-melted diffusion and observation of zig-zag motion.

Findings

Shear induces translational order transitions in colloidal layers.

Diffusion in shear-melted state modeled by a single particle in a harmonic trap.

Zig-zag oscillations observed in particle motion, matching experimental findings.

Abstract

Using Brownian dynamics (BD) simulations we investigate the impact of shear flow on structural and dynamical properties of a system of charged colloids confined to a narrow slit pore. Our model consists of spherical microions interacting through a Derjaguin-Landau-Verwey-Overbeek (DLVO) and a soft-sphere potential. The DLVO parameters were chosen according to a system of moderately charged silica particles (with valence Z$\sim$35) in a solvent of low ionic strength. At the confinement conditions considered, the colloids form two well-pronounced layers. In the present study we investigate shear-induced transitions of the translational order and dynamics in the layers, including a discussion of the translational diffusion. In particular, we show that diffusion in the shear-melted state can be described by an analytical model involving a single shear-driven particle in a harmonic trap. We also explore the emergence of zig-zag motion characterized by spatio-temporal oscillations of the particles in the layers in the vorticity direction. Similar behavior has been recently observed in experiments of much thicker colloidal films.