Shape anisotropy enhances the elasticity of colloidal gels through mechanisms that act multiplicatively

Abstract: The physical gelation of colloids produces elastic structures that are commonly used to stabilize complex fluids in multiple industries. However, the ability to control the level of elastic modulus of these materials is limited by the universality of the arrested spinodal decomposition mechanism that governs their formation. We demonstrate that manipulating particle shape can yield very large shifts in gel elasticity relative to this universal behavior, and that these changes are generated by a set of independent mechanisms that act multiplicatively. Modeling demonstrates that this efficient generation of elasticity is the consequence of the combined effects of shape anisotropy on the hierarchical fractal microstructure of the gel network, the anisotropy of the attractive interparticle pair potentials, and the volumetric compactness of the fractal cluster. The findings show how and why particle anisotropy can be exploited to generate elasticity at ultra-low colloidal volume fractions in this important class of soft matter.