Tunable Shear Thickening in Suspensions

TL;DR

This paper introduces a method to dynamically control shear thickening in suspensions by applying orthogonal high-frequency shear, enabling on-demand viscosity tuning for advanced material applications.

Contribution

The study demonstrates that orthogonal high-frequency shear can effectively suppress shear thickening, providing a new in situ control mechanism for suspension flow properties.

Findings

Viscosity can be reduced by up to two decades using orthogonal shear.

Orthogonal shear acts as an effective regulator for shear thickening.

Transverse agitation induces similar effects as high-frequency shear.

Abstract

Shear thickening, an increase of viscosity with shear rate, is a ubiquitous phenomena in suspended materials that has implications for broad technological applications. Controlling this thickening behavior remains a major challenge and has led to empirical strategies ranging from altering the particle surfaces and shape to modifying the solvent properties. However, none of these methods allow for tuning of flow properties during shear itself. Here, we demonstrate that by strategic imposition of a high-frequency and low-amplitude shear perturbation orthogonal to the primary shearing flow, we can largely eradicate shear thickening. The orthogonal shear effectively becomes a regulator for controlling thickening in the suspension, allowing the viscosity to be reduced by up to two decades on demand. In a separate setup, we show that such effects can be induced by simply agitating the sample transversely to the primary shear direction. Overall, the ability of in situ manipulation of shear thickening paves a route towards creating materials whose mechanical properties can be controlled.