Effect of Evaporation Boundary Condition on The Consolidation and Crack Propagation in Drying Colloidal Films*

We investigate the dynamics of consolidation front growth and the subsequent crack propagation during the directional drying of colloidal film. By varying the geometry of the drying boundary, we observe that the shape of the conslidation front evolve from the shape of the boundary to one with smallest curvature. We also find the direction of the crack propagation keeps perpendicular to the consolidation front, resulting curved cracks. A theoretical model is developed to explane the evolution of consoildation front. Our finding allows us to explore other evaporation boundary conditions, such as temperature and humidity gradient, to control the direction of crack propagation in drying colloidal films.