ISM Researchers Investigate Shear-Thickening Suspensions

Graph of viscosity vs flow rate, with S-shaped curve showing increase in viscosity as heterogeneities are observed in thickening regime

A new publication from the ISM post-doctoral researcher Esmaeel Moghimi, who works with Professors Daniel Blair and Jeffrey Urbach, has appeared in the high impact Journal of Colloid and Interface Science. The research probes the phenomenon of shear thickening, where the viscosity of a dense suspension undergoes a dramatic increase when the applied stress surpasses a material-specific threshold. This thickening is thought to involve non-uniform flow and localized stresses. However, some recent research has found evidence of localized stresses in cornstarch but not calcium carbonate, which could indicate that the non-uniformities are only present for certain types of inter-particle interactions. This research used the more sensitive technique of boundary stress microscopy to look at calcium carbonate under stress on the micron scale and was able to find localized regions of elevated stresses, in addition to nonaffine flow at the boundary. This confirms that stress and flow inhomogeneity are inherent to shear-thickening suspensions.