Complex pattern formation in drying dispersions

We investigated the formation of complex aggregation patterns during the drying of nanocolloidal dispersion drops on various surfaces. Our results show that large-scale and well-organized multibranched surface aggregates can form during this drying process. Both the emergence and topological features of these complex patterns were found to be controlled by two parameters: (1) the actual volume fraction of the drop in the late step of the drying and (2) the hydrodynamic shear involved in the rupture-dewetting and receding motion of the residual suspension drop. A simple phenomenological model was proposed, which accounts for the experimental results and their analogy with shear instabilities and structure formation in purposely designed Hele-Shaw cells.