Title: Experimental Studies of Jammed Colloidal Packings: Novel Methods for Imaging Contact Networks using Quantum Dots

Author (Poster): Eru Kyeyune-Nyombi, Levich Institute-City College of New York

Abstract:

Since the time of the Kepler's conjecture on the maximum attainable density of an ordered packing of spheres to the pioneering studies of Bernal and Onsager on disordered packings of spheres and rods, the problem of packing structure has attracted the attention of specialists and laymen alike. Recent theoretical advances in the statistical mechanics of jamming in granular materials, isostatic formulations, and analogies with critical phenomena and the physics of glasses, have provided a new outlook to this long standing problem. Here, we perform systematic experiments with jammed colloidal systems to characterize the nature of the random close packing of spherical particles. Our experiments require detailed examination of the contact network of jammed colloids at high resolution. For this purpose we use a strategy based on fluorophore exclusion from quantum dot nanoparticles. This allows for the detection of contact points between particles at higher resolution than previous work. The experimental data also allow for tests to determine whether the ensemble of volumes can describe the state of randomness in jammed packings through equations of state relating average and local coordination number, entropy, volume fraction, and local Voronoi volumes.