Levich Institute Seminar Announcement, 10/27/2009
Steinman Hall, Room #312
(Chemical Engineering Conference Room)
Professor Heinrich Jaeger
The James Franck Institute
Center for Integrative Science
"Why Don't All Suspensions Shear Thicken? "
[This is a CCNY/Columbia NSF-IGERT Soft Materials seminar]
Suspensions are of wide interest and form the basis for many smart fluids. For most suspensions, the viscosity decreases with increasing shear rate, i.e. they shear thin. Few are reported to do the opposite, i.e. shear thicken, despite the longstanding expectation that shear thickening is a generic type of suspension behavior. In this talk I discuss how this apparent contradiction might be resolved. Specifically, I will demonstrate that shear thickening can be masked by a yield stress and can be recovered when the yield stress is decreased below a threshold. I then show the generality of this argument and quantify the threshold in rheology experiments with yield stresses arising from a variety of sources, such as attractions from particle surface interactions, induced dipoles from applied electric and magnetic fields, as well as confinement of hard particles at high packing densities. Finally, I will discuss how this opens up possibilities for the design of smart suspensions that combine shear thickening with electro- or magnetorheological response.
BRIEF ACADEMIC/EMPLOYMENT BACKGROUND:
Heinrich Jaeger received his Ph.D. in physics in 1987, having worked on ultrathin superconducting films with Allen Goldman at the University of Minnesota. He then spent 15 months at the University of Chicago as a James Franck Postdoctoral Fellow before accepting a position as a Senior Researcher at the Delft Institute for Microelectronics and Submicrontechnology in The Netherlands. In 1991 he returned to the University of Chicago, joining the faculty where he is now a Professor in the Department of Physics. He directed the Chicago Materials Research Center from 2001 – 2006, and currently is director of the James Franck Institute at the University of Chicago. Jaeger was awarded a David and Lucille Packard Fellowship for Science and Engineering in 1991, an Alfred P. Sloan Fellowship in 1992, and a Research Corporation Cottrell Scholarship in 1994. In 2006 he received a Quantrell Award for Excellence in Undergraduate Teaching.
CURRENT RESEARCH INTERESTS:
Current research involves projects ranging from the self-assembly of nanoparticles to investigations of the complex nonlinear behavior of macroscopic granular materials.