Levich Institute Seminar – Tuesday, 12/05/2023

Tuesday, 12/05/2023
2:00 PM
Steinman Hall #312 

Professor Daniel Blair
Georgetown University, Physics Department

“Microscopic Origins of Shear Thickening in Colloidal and Active Fluids”


In this talk I will discuss our recent results on the microscopic physical origins of shear thickening in two vastly different materials: colloidal suspensions and active gels. 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 to suspensions undergoing 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 kinesin motor proteins that self-assemble to form complexes that propel themselves through the fluid. What results is a dramatic increase in the viscosity of the material with applied shear rate.
  • MS, Physics, University of Chicago, 2000 — Advisors: Heinrich Jaeger, Sidney Nagel
  • PhD Physics, Clark University, 2003 — Advisor: Arshad Kudrolli
  • Post-Doctoral Fellow, Harvard University — Advisor: David Weitz
  • Professor of Physics, Georgetown University, 2007-Current
  • Co-Founder and Member of The Institute for Soft Matter Synthesis and Metrology, Georgetown University, 2012-Current 
  • Polymerization pathways in reconstituted and natural silk protein solutions
  • Real-Space optical analysis of sheared colloidal dispersions
  • Rheology of active fluids
  • Structural properties of composite biogels for 3D printing applications
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