Physics Colloquium
Friday, October 29th, 2004, 4:00 P.M.

Erik Luijten

Department of Materials Science and Engineering,
University of Illinois at Urbana-Champaign

Understanding Colloidal Stabilization: A New Simulation Approach to the Study of Complex Fluids

Colloidal particles find widespread application as precursors for nanostructured materials, including advanced coatings, drug carriers, and colloidal crystals. These materials are frequently fabricated from the liquid phase via hierarchical self-assembly processes that are governed by the interactions of the particles, their shape, and their size. The understanding and prediction of phase behavior and stability of a suspension relies on a fundamental knowledge of the effective forces between colloids. In principle, computer simulations are highly suited to sort out the intricate interplay between energetic and entropic effects responsible for these effective interactions, but the presence of multiple time and length scales poses a major hurdle. We have developed a new simulation method that applies to both colloidal mixtures and large classes of other complex fluids and that mitigates several of the dynamical problems that plague the numerical study of these systems. I will present an introduction to this method that is also accessible to non-specialists. In order to illustrate its capabilities, I will address the underlying mechanism of a recently-discovered and widely-publicized method for colloidal stabilization, in which uncharged micron-sized colloids experience an interaction that is controlled by the presence of highly-charged nanoparticles. Unlike earlier methods, our new approach explicitly takes into account both the colloids and the nanoparticles. The results agree remarkably well with the experimental findings and may provide a guide to optimization of the stabilization mechanism.

http://www.mse.uiuc.edu/faculty/Luijten.html