Drop impact of dense suspensions: shear jamming with free surfaces

Dense suspensions exhibit a variety of exotic flow behaviors under high stresses, such as shear thickening and shear jamming. Here, I will show how we can utilize ultrahigh-speed imaging and the free-surface geometry in drop impact as a new tool for studying the flow of dense colloidal suspensions. This system offers a unique lens with which to study shear-thickening fluids, allowing us to obtain flow information in a spatially-localized manner, so that we can observe coexisting solid and liquid phases. Furthermore, we capture shear jamming as it occurs via a solidification front traveling from the impact point, and show that the speed of this front is set by how far the impact conditions are beyond the shear thickening transition. We are currently investigating how jamming and solidification are altered when the suspension is composed of rod-like particles, as well how these jammed systems re-fluidize.