Moving contact lines of a colloidal suspension in the presence of drying

This article presents the first experimental study of an advancing contact line for a colloidal suspension. A competition between the hydrodynamic flow due to the drop velocity and the drying is exhibited: drying accounts for particle agglomeration that pins the contact line whereas the liquid flow dilutes the agglomerated particles and allows the contact line to advance continuously. The dilution dominates at low concentration and high velocity, but at high concentration and low velocity, the contact line can be pinned by the particle agglomeration, which leads to a stick-slip motion of the contact line. The calculation of the critical speed splitting both regimes gives an order of magnitude comparable to that of experiments. Moreover, a model of agglomeration gives an estimation of both the size of the wrinkles formed during stick-slip and the force exerted by the wrinkle on the contact line.