Levich Institute Seminar Announcement, 10/16/2012
Tuesday, 10/16/2012
2:00 PM
Steinman Hall, Room #312
(Chemical Engineering Conference Room)

Professor Jay Schieber
Illinois Institute of Technology
Department of Chemical Engineering

"Diffusion and Microrheology in Viscoelastic Media: Effects of Inertia and Non-Conservative Forces"


The dynamic modulus G of a viscoelastic medium is often measured by following the trajectory of a small bead subject to Brownian motion in a method called “passive microbead rheology”. We seek to expand its applicability into higher frequencies and under non-equilibrium circumstances—for example, in an optical trap. However, we discovered several fundamental issues that were not apparent in typical applications. In other words, the typical equation used for data analysis—the Generalized Stokes-Einstein relation— relies on a sort of cancellation of errors. We discuss and resolve these issues, and then show how the analysis can be generalized to our systems of interest. With these issues resolved, we show how one can (1) rigorously include bead inertia, (2) rigorously include fluid inertia, (3) perform Brownian Dynamics simulations to analyze data from microbead rheology at high frequencies or under non-conservative forces, and (4) derive the correct generalized Langevin equation with inertia removed. Our simulations are used to examine the e.ects of bead circulation from non-conservative forces in optical traps recently discovered in David Grier’s group.


Prof. Jay Schieber is currently the director of the Center for Molecular Study of Condensed Soft Matter (µCoSM) at the Illinois Institute of Technology. The center houses faculty from Biology, Chemistry, Physics, and Chemical and Biological Engineering, and Prof. Schieber’s academic appointments are in Chemical and Biological Engineering, and in Physics. He received his Bachelors degree in Chemical Engineering from the University of Illinois-Urbana, and his Ph.D. in Chemical Engineering from the University of Wisconsin-Madison under canoe enthusiast, composer and linguist Prof. R. Byron Bird, who also studies transport phenomena. Afterwards, he was NATO-NSF Fellow at the University of Freiburg, Germany, and then post-doctoral associate at McGill University. After a few years at the University of Houston, he was Assistant, Associate and then full Professor at IIT.


Professor Schieber's research focuses primarily on molecular modeling of concentrated polymers, and the experimental measurement of thermal transport in polymers under deformation.

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