Dynamics of particle aggregation in de-wetting films of complex liquids #

James Junzhe Zhang, David Sibley, Dmitri Tseluiko, Andrew Archer

12:10 Monday in 4Q04.

Part of the Droplets and impact session.

Abstract #

We consider the dynamic wetting and de-wetting processes of films and droplets of complex liquids on planer surfaces, focusing on the case of colloidal suspensions, where the particle interactions can be sufficiently attractive to cause agglomeration of the colloids within the film. This leads to complex dynamics within the liquid and of the liquid-air surface. Incorporating concepts from thermodynamics, we construct a model consisting of a pair of coupled partial differential equations that represent the evolution of the liquid film and the effective colloidal height profiles using the thin-film approximation. We determine the relevant phase behaviour of the uniform system, including finding associated binodal and spinodal curves, helping to uncover how the emerging behaviour depends on the particle interactions. Performing a linear stability analysis of our system enables us to identify parameter regimes where agglomerates form, which we independently confirm through numerical simulations. We obtain various dynamics such as uniform colloidal profiles in an unstable situation evolving into agglomerates and thus elucidate the interplay between de-wetting and particle aggregation in complex liquids on surfaces. We verify the code using the numerical and theoretical data. We obtain bifurcation diagrams for various cases, including ones with strong coupling and match with the final profiles of different systems. We also model the system in three dimensions and achieve good agreement with two dimensional simulations.