Levich Institute Seminar Announcement, 05/03/2005

Tuesday, 05/03/2005 2:00 PM Steinman Hall, Room #312 (Chemical Engineering Conference Room) Professor Eric Weeks Emory University Department of Physics "Studying the Glass Transition by Poking Colloidal Suspensions" [This is a CCNY/Columbia NSF-IGERT Soft Materials seminar]

ABSTRACT
Are glasses merely extremely slow liquids, and if so, why are they many orders of magnitude slower than conventional liquids? We study concentrated colloidal suspensions, a model system which has a glass transition. We view the motion of these colloidal particles in three dimensions by using an optical confocal microscope. This allows us to directly study the microscopic behavior responsible for the macroscopic viscosity divergence of glasses. In particular we use small magnetic particles to locally "poke" on the colloidal samples. We find a yield force (below which there is no motion), which grows as the glass transition is approached. Above this force, the magnetic particle moves, disturbing the surrounding colloidal particles. We are investigating how the spatial range of the disturbance changes near the glass transition.

BRIEF ACADEMIC/EMPLOYMENT HISTORY

Undergraduate: at the University of Illinois / Urbana-Champaign (1992); Graduate: at the University of Texas / Austin (1997); Postdoctoral work: with Arjun Yodh & David Weitz at the University of Pennsylvania, then continuing with David Weitz at Harvard University (1998-2000); Started at Emory University in the Department of Physics in January 2001.

CURRENT RESEARCH INTERESTS

Colloidal glass transition, microrheology, shear and rheology of complex fluids