Title: Experimental Studies of Jammed Colloidal Systems: Novel Methods for Imaging Contact Networks

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

Abstract:

Rocks and soil are examples of naturally occurring granular matter. Many consumer products like powders and facial creams are also composed of granular matter. Researchers endeavor to predict mechanical, thermal, and electrical properties of granular materials from the arrangement of their grains. Unfortunately, the relationship between a material’s physical properties and granular structure is generally not predictable or even the same for every material. This leads researchers to more heavily rely on patented empiricisms and personal experience when designing granular materials or processes like multi-phase reactions that occur in granular media. Recent theoretical advances in the statistical mechanics of jamming in granular materials have provided a new outlook for thermodynamically characterizing packings in granular matter. Here, we perform systematic experiments with jammed colloidal systems to characterize random close packing of spherical particles. High resolution images are obtained by confocal microscopy. And a novel method called fluorophore exclusion is used to verify points of contact between neighboring particles at higher resolution than previous work. This also allows for experimental testing of volume ensembles used to 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.