Colloidal suspensions under biaxial shear

What is it about?

In this work, we shear a colloidal suspension along two directions to manipulate the suspension structure. We also measure its viscosity along two directions simultaneously. In the explored regime, we find that despite of the anisotropic shear-induced structure of the suspension, its rheological behavior remains isotropic. This implies that the hydrodynamic interactions may have a subtle way to generate an isotropic stress response in an anisotropic structure.

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Why is it important?

Conventional rheometers are only able to probe fluid viscosity unaxially. Here we present a method that provides a way to investigate the anisotropic viscosity of a fluid. We also demonstrate that anisotropic structure does not always guarantee an anisotropic rheological response.