Interdisciplinary Seminar in Nonlinear Science

Title: How to Stabilize Colloidal Suspensions? Application of a New Algorithm for Complex Fluids
Speaker: Erik Luijten
Speaker Info: University of Illinois
Brief Description:
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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. Colloidal suspensions are typically stabilized by mitigating the ubiquitous attractive van der Waals forces via Coulombic or steric repulsive forces. These mechanisms, however, pose serious problems for the fabrication of close-packed colloidal crystals: the repulsive forces not only prevent gelation, but also increase the lattice spacing of the sedimented colloids. A lattice spacing larger than 1-2% of the particle diameter will lead to cracking of the crystal upon drying. Recently, an alternative method for tailoring the interactions has been discovered, which relies on the addition of highly-charged nanoparticles. Since a convincing theoretical understanding of this new stabilization method is currently lacking, we have employed computer simulations to clarify the underlying mechanism. The disparity in time and length scales, arising from the presence of micron-sized colloids and nanometer- sized particles, requires the use of new simulational algorithms that have rather striking properties. In this seminar, I will discuss these numerical techniques and the advantages they bring to the simulation of complex fluids in general. Subsequently, I will present our findings for the nanoparticle-colloid mixtures.
Date: Friday, October 31, 2003
Time: 2:00PM
Where: Tech M416
Contact Person: Monica Olvera
Contact email: m-olvera@northestern.edu
Contact Phone: 847-491-7801
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