Shear Jamming in Dense Suspensions*

Dense suspensions of hard particles in a simple liquid have become a model system in the soft condensed matter, granular materials, and rheology communities for the investigation of strongly non-Newtonian behaviors. A key aspect underlying the recent surge of activity has been the realization that, in addition to hydrodynamic interactions, frictional contact between particles can occur. In fact, friction forces were found to be essential in order to explain some of the most striking phenomena observed, such as an abrupt, essentially discontinuous onset of shear thickening, whereby the viscosity can jump up by over an order of magnitude as a critical shear rate is exceeded. So far, however, friction has typically been modelled as a parameter without considering its origin. Furthermore, a focus on the steady-state response has prevented most models from capturing transient phenomena, most notably the propagating jamming fronts associated with the transition from a shear-thickened to a solid-like, shear jammed state. Thus, there remain fundamental questions both at the nano-scale about the nature of the frictional interactions, and at the macro-scale about the relation between steady-state and transient dynamic phenomena.

This talk will discuss recent experiments and simulations that address these questions, focusing on the differences between discontinuous shear thickening (DST) and shear jamming (SJ). In particular, I will show how controlling the particles’ shape, their surface chemistry, and the suspending solvent opens up new opportunities for designing the dynamic stress response of dense suspensions as they transform into a shear jammed state.