Materials Science

Push both ways to avoid a jam

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Science  14 Oct 2016:
Vol. 354, Issue 6309, pp. 193-194
DOI: 10.1126/science.354.6309.193-d

When subject to shear flow, dense solutions of particles can jam together, dramatically increasing their viscosity. This can be helpful, such as in traction control systems, or it can be harmful, such as when a pipe becomes blocked during industrial processing. During flow, when the stress exceeds a critical value, particle interactions transform from lubricated to frictional, leading to transient force chains. Lin et al. show that this particle jamming transition is not fixed by the suspension formulation, but rather can be dynamically tuned: The trick is to introduce perturbations in an orthogonal direction to break up the force chains before they fully form. This enables control of the thickening viscosity over two orders of magnitude.

Proc. Nat. Acad. Sci. 10.1073/pnas.1608348113 (2016).

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