Tuesday, 09/20/2022 2:00 PM Steinman Hall #124 (Exhibit Room) Professor Eric Weeks Emory University, Physics Department “In Sheared Highly Polydisperse Emulsions, Large Droplets Cause Trouble for Smaller Droplets” Simultaneous Zoom Link:  https://ccny.zoom.us/j/82406201095

We study experiments and simulations of highly polydisperse emulsions under shear flow. By highly polydisperse, we mean with the largest droplet diameters being as much as ten times the smallest diameters. We quantify non-affine motion in these highly polydisperse samples — motion where droplets move with displacements distinctly different from their neighbors, or different from the overall imposed shear flow. The largest droplets typically move affinely, as if they are in a simple effective fluid formed by the other droplets. In contrast, the smallest droplets are often forced to move non-affinely by the larger droplets.  The behavior depends on the overall droplet size distribution; in general, the largest droplets are always the troublemakers.  Our main conclusion is that highly polydisperse samples behave qualitatively differently than weakly polydisperse samples.  This is both true microscopically (in terms of droplet motion) and macroscopically (in terms of rheology).

BRIEF ACADEMIC/EMPLOYMENT HISTORY:

Eric got his undergraduate degree in engineering physics from the University of Illinois at Urbana-Champaign in 1992.  In 1997 he earned his PhD in physics from the University of Texas at Austin working with Harry Swinney.  He was a postdoctoral researcher with David Weitz at the University of Pennsylvania and later at Harvard University.  In January 2001 he joined the faculty at Emory University, where he is now a Dobbs Professor of Physics and also Associate Vice Provost for Faculty Affairs.

MOST RECENT RESEARCH INTERESTS:

Colloids, granular materials, emulsions, foams.  In particular, recently I’m studying random close packing; clogging of soft particles; the colloidal glass transition; and colloidal gels.