Dynamics of particle aggregation in evaporating and dewetting films of complex liquids

We consider the dynamic wetting and dewetting processes of films and droplets of complex liquids on planar surfaces, focusing on the case of colloidal suspensions, where the particle interactions cause agglomeration. This leads to complex dynamics within the liquid and on 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. The model extends to also include mass transfer effects due to solvent evaporation and condensation. The model extends to also include mass transfer effects due to solvent to evaporation and condensation. 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 evaporation, dewetting and particle aggregation in complex liquids on surfaces. Bifurcation analysis was performed to systematically investigate the final profile relate to the system size.

This work has various of potential applications including ink jet printing/coating, printing of electronic components and circuits.