Possible origin of the crack pattern in deposition films formed from a drying colloidal suspension

The fracture mechanics was usually employed to explain the crack propagation in the deposition produced by drying colloidal suspension. However, more complex than conventional fracture, those cracks periodically distribute and make up a unique pattern. Inspired by the concept of spinodal decomposition, here we develop the theory to illustrate the possible mechanism of the spatial arrangement of the cracks. It indicates that before the cracks develop and propagate in the deposition under the law of fracture mechanics, the periodically distributed flaws are generated by the phase separation of colloidal clusters and solvent. Then the cracks originate at the sites of those flaws in terms of fracture mechanics. It concludes that the crack spacing results from the wavelength of the concentration fluctuation during the phase separation, linearly growing with the increase of the deposition thickness and initial particle concentration, which is consistent with experimental results. DOI: 10.1103/PhysRevE.86.061406