Physics Colloquium: Fluids that Stiffen and Swim
Prof. Daniel Blair, Department of Physics, Georgetown University
In this talk I will discuss our recent results on the microscopic physical origins of shear thickening in sheared colloidal suspensions and the viscoelasticity of active fluids. In the first part of my talk, I will introduce a method we have developed that allows us to resolve the spatial distribution of stresses in sheared soft-materials, known as Boundary Stress Microscopy. We have applied this technique suspensions undergoing continuous and discontinuous shear thickening. I will present our results on the existence of clearly defined dynamically localized regions of substantially increased stress that appear intermittently at stresses well above the applied stress. Surprisingly, we find that these spatially distinct and dynamic phases account quantitatively for the observed shear thickening seen in sheared colloidal dispersions (e.g. Oobleck). In the second part of my talk I will discuss our results on the rheology of active matter. Our system is composed of microtubules and motor kinesin proteins that self-assemble to form complexes that propel themselves through the fluid, resulting in spontaneous “swimming” of the suspended material. What results is an interplay between the internal active stresses and any imposed external stress. I will discuss the impact of the internal flows have on the local and bulk rheological response.
Tuesday, October 2 at 3:15pm
Regents Hall, 351
3700 O St. NW