(529e) Hydrodynamic-Controlled Uniform Crack Spacing Following Convective Deposition

Convective deposition is highly useful for fabricating thin films of well-ordered arrays of monosized particles.  These thin films range from monolayers of hexagonally arranged particles to multilayered colloidal crystals.  Evaporation-driven flow draws particles into a thin liquid film, orders particles through flow steering, and eventually dries.  Near this drying front, highly uniform parallel cracks form propagating in the direction of deposition.  The spacing of these cracks is described by a model developed by Lee and Routh, Langmuir, 2004 where the yielding of the material is a result of capillary pressure generated in the porous thin film.  While the previous theory roughly described millimeter crack spacings in thicker film, a highly linear relationship between micron-scale crack spacing and thin film thickness follows the same trend over roughly 4 orders of magnitude in crack spacing.  Transitions between thinner and thicker films also give clues to the dynamic response of the crack formation.