Drop impact of colloidal suspensions: effect of particle anisotropy

Dense suspension flows are ubiquitous in many industrial and agricultural processes, and drop impact provides a unique method to study these flows at very high shear rates, above the range easily accessible using conventional rheometry.  These extreme shear rates have been recently shown to lead to the appearance of a wide range of elastic behaviors upon impact, from localized jamming to complete solidification.  Here, we present an experimental study of how anisotropy influences impact and spreading dynamics in a dense suspension.  Using highly monodisperse silica rods, we explore how increasing particle aspect ratio influences impact-generated shear jamming.  Our observations suggest that impacting drops of rod-shaped suspensions show thickening and jamming at lower volume fractions as compared to sphere suspensions, in agreement with rheological measurements.  Furthermore, we observe that the extent of jamming behavior is more pronounced for higher impact velocities and higher particle aspect ratios.