NEW YORK UNIVERSITY MRSEC “Granocentric” view of Random Packing Michael D. Ward, New York University, DMR Packing problems are everywhere, ranging from oil extraction through porous rocks to grain storage in silos and the compaction of pharmaceutical powders into tablets. How polydisperse particles randomly pack into a 3D assembly is an ancient and unsolved question due to the vast complexity of the system. By visualizing a packing of spherical droplets in the confocal microscope, we were able to devise a local statistical model that can describe all the properties of the experimental packing: distributions of contacting and neighboring particles, local densities as well as the global density. Our model considers packing from the perspective of a particle within it, which we coin the “granocentric” view. This approach captures the effect of the particle size distribution on the structure and geometry of packings and predicts the density of the material. MRSEC investigators: Maxime Clusel, Eric I. Corwin, Alexander O. N. Siemens, Jasna Brujic Nature, June 2009 Supported by the MRSEC, DMR

Image Ideas: Real Raw Data from the confocal: 2D slice of droplets; 3D projection of the image; And 3D rendering of the whole volume. Michael D. Ward, New York University, DMR

FUN rendering of OUR REAL DATA + a photograph of chewing gum in a 25 cents bowl Jasna Brujic in the Granocentric view Michael D. Ward, New York University, DMR