Rheology and dynamics of colloidal superballs

Abstract

Recent advances in colloidal synthesis make it possible to generate a wide array of precisely controlled, non-spherical particles. This provides a unique opportunity to probe the role that particle shape plays in the dynamics of colloidal suspensions, particularly at higher volume fractions, where particle interactions are important. We examine the role of particle shape by characterizing both the bulk rheology and micro-scale diffusion in a suspension of pseudo-cubic silica superballs. Working with these well-characterized shaped colloids, we can disentangle shape effects in the hydrodynamics of isolated particles from shape-mediated particle interactions. We find that the hydrodynamic properties of isolated superballs are marginally different from comparably sized hard spheres. However, shape-mediated interactions modify the suspension microstructure, leading to significant differences in the self-diffusion of the superballs. While this excluded volume interaction can be captured with a rescaling of the superball volume fraction, we observe qualitative differences in the shear thickening behavior of moderately concentrated superball suspensions that defy simple rescaling onto hard sphere results. This study helps to define the unknowns associated with the effects of shape on the rheology and dynamics of colloidal solutions.

Interplay of particle shape and suspension properties: a study of cube-like particles

“…56,58 This comparison is shown in Table 1; we found that all the predictions matched the experimental results within the uncertainty bounds. For s = 1.4, [ η ] is quite similar to the value for a sphere, 2.5, such that for the experimental data, the value is the same as a sphere within numerical uncertainty.…”

Relating microstructure and particle-level stress in colloidal crystals under increased confinement

“…Here we study increasingly confined colloidal crystals to investigate how changes in their microstructure affect the microscopic stresses ultimately responsible for their bulk mechanical properties. Such colloidal systems are comprised of particles small enough to undergo Brownian motions that preserve a thermodynamic ensemble, while still large enough to be optically imaged with high temporal and spatial resolutions [19][20][21][22][23][24][25]. As such, colloidal crystals have been widely used as a model system to elucidate many phenomena associated with confinement including crystal growth [26], packing [27][28][29][30][31], and melting mechanisms [32].…”

Effect of acid and temperature on the discontinuous shear thickening phenomenon of silica nanoparticle suspensions

“…The rheological properties of STFs are largely dependent on the particle shape, size and size distribution [10,19,27]. STFs comprising particles with diameter smaller than 1 lm and narrow size distribution often exhibit a shear thickening response [10,28,29].…”