Abstract
Cracks in a colloidal film formed by evaporation induced drying can be controlled by changing drying conditions. We show, for the first time that the crack morphologies in colloidal films are dependent on shape of constituting particles apart from the microstructure and particle assembly. In order to investigate the particle shape effect on crack patterns, monodispered spherical and ellipsoidal particles are used in sessile drop experiments. On observing the dried sessile drop we found cracks along the radial direction for spherical particle dispersions and circular crack patterns for ellipsoidal particle dispersions. The change in crack pattern is a result of self assembly of shape anisotropic particles and their ordering. The ordering of particles dictate the crack direction and the cracks follow the path of least resistance to release the excess stress stored in the particle film. Ellipsoids having different aspect ratio (~3 to 7) are used and circular crack patterns are repeatedly observed in all experiments.
Highlights
Cracks in the form of concentric circles
We show the dependence of crack morphology on particle shape anisotropy apart from the particle ordering and their arrangements[25]
The crack formation mechanism during the evaporation of sessile drop consisting of dispersion of spherical particles is fairly well established but for ellipsoid particles it is still not explored
Summary
Cracks in the form of concentric circles. We show the dependence of crack morphology on particle shape anisotropy apart from the particle ordering and their arrangements[25]. The direction of crack propagation is dictated by the direction of propagation of drying fronts and by the particle self-assembly and the cracks propagate through a least resistance path[26]. The effects of particle concentrations and aspect ratios on crack morphologies are studied
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