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SUMMARY:MechE Colloquium: Local Rheological Probes of Stress Heterogeneiti
 es in Active and Passive Fluids
DTSTART:20261027T120000
DTEND:20261027T130000
DTSTAMP:20260930T015950Z
UID:a6171e2d3e0ae25112d98d928788a3f9ed327fdc0bf34bda6b2c186d
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Daniel Blair\, Department of Physics\, University of Geo
 rgetown\, USA\nAbstract: In this talk I will discuss our recent results
  on the microscopic physical origins of shear thickening in two vastly dif
 ferent 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 s
 uspensions undergoing shear thickening. I will present our results on the 
 existence of clearly defined dynamically localized regions of substantiall
 y increased stress that appear intermittently at stresses well above the a
 pplied stress. Surprisingly\, we find that these spatially distinct and dy
 namic phases quantitatively account 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 s
 ystem is composed of microtubules and kinesin motor proteins that self-ass
 emble to form complexes that propel themselves through the fluid. What res
 ults is a dramatic alteration in the measured viscosity. I will provide a 
 simple physical model that fits the rheological response with zero fitting
  parameters. \n\nBiography: Daniel Blair is a Professor of physics and
  a co-founding member of the Institute for Soft Matter Synthesis and Metro
 logy I(SM)2 at Georgetown University. Prior to joining Georgetown in 2007
 \, Professor Blair was a postdoctoral fellow at Harvard University in th
 e Paulson School of Engineering and the Department of Physics. In 2009\, h
 e was awarded the NSF Career Award and has done pioneering work into the s
 tructure and rheology of soft and biological materials. His group has deve
 loped a variety of tools and techniques centered on quantitative 4D micros
 copy coupled with microfluidic and rheometric methods. 
LOCATION:MED 0 1418 https://plan.epfl.ch/?room==MED%200%201418 https://epf
 l.zoom.us/j/61360740951
STATUS:CONFIRMED
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