Wettability-mediated transition from circular to radial cracks in dried deposit of colloidal ellipsoids

We report a transition in the orientation of primary cracks in colloidal ellipsoid deposits driven exclusively by variations in substrate wettability. On highly wettable substrates, the primary cracks in the deposit of ellipsoids are predominantly along the circumferential direction. In contrast, with decreased substrate wettability, the primary cracks in the particulate deposit are oriented solely along the radial direction. Additionally, decreasing substrate wettability leads to a reduction in total crack length and an increase in both crack spacing and width. These experimental observations are corroborated by taking into account the energy release rate, work of adhesion, and arguments based on an estimation of in-plane stresses in the particulate deposits, providing a mechanistic understanding of the observed crack pattern transition.