Influence of Particle Size Polydispersity on Dynamical Heterogeneities in Dense Particle Packings

The dynamics of dense particle packings near the jamming transition is characterized by correlated particle motion. The growth of dynamical heterogeneities, or strong spatial variations in the motion of the constituent particles, is a hallmark feature of slow glassy dynamics. We report here a systematic confocal microscopy study that characterizes the cooperative dynamics of fluorescently-labeled colloidal particles in dense aqueous suspensions. Our experiments demonstrate that jammed particulate suspensions can be fluidized by increasing the width of the particle size distribution. Our molecular dynamics simulations, performed to numerically investigate the effects of continuous-size polydispersity (PD) on dense particle packing dynamics, show qualitative agreement with our experimental studies on the PD-dependence of the observed heterogeneity trends. Besides shedding light on the fundamental aspects of particle-scale dynamics at the jamming-unjamming transition, our findings are significant in the fabrication of commonly-encountered dense suspensions such as paints, cosmetics, and foods.