Future Research Projects

Project List

• Shear-induced ordering in a 2-dimensional sandpile
• Dynamic Heterogeneities in Colloidal Glasses

   

  Avalanches in rod-like granular materials

  Avalanches in ordinary sand are widely studied and fairly well-understood. The avalanche begins when the slope reaches a critical angle and stops at another, well-defined, angle. When the particles are long and thin, however, the picture is no longer clear. The pile above shows a complicated surface profile and large voids throughout. Pictured is a snapshot during the collapse of a large void results in motion that occupies a large portion of the pile.

   

  Dynamic Heterogeneities in Colloidal Glasses

  Not much is known about glass. If you look at a snapshot of the molecules, they look just like that of a liquid. Nevertheless, the viscosity is 1000 times greater. How is this possible? It's been theorized that the answer lies in dynamic heterogeneities, the idea that only certain regions of the sample (heterogeneities) are mobile (dynamic). These have never been seen in a real experiment, however, and we can't look directly at the that molecules in a glass as they move around. A good model for a glass is a colloidal suspension — small particles suspended in a fluid. If the number of particles is large, they don't have space to rearrange (even though they're jiggling around due to Brownian motion) and they act very much like a molecular glass. I have some data of colloidal suspensions that I'd like to analyze to see if dynamical heterogeneties exist.