Article dans Physical Review X : le “Capillarytron”

Media composed of a mixture of fluid and microscopic solid particles are all around us, from mud to fresh concrete to liquid food. Yet, how these media flow is still poorly understood, as illustrated by the familiar and notorious suspension of cornstarch particles, which, liquid at rest, can suddenly turn solid upon impact.

In this study, we develop a new tool – called “the Capillarytron” – that allows us to access for the first time the frictional properties of these microscopic suspensions during flow. We show that, depending on the applied force, the particles of the suspension behave as rubbing or non rubbing solids, a feature that deeply modifies the flowability of the suspension.

These results confirm a mechanism recently proposed to explain the behavior of shear-thickening suspensions, such as the suspension of cornstarch particles, and open the way to characterizing complex suspensions such as those encountered in geophysics and in industry. Based on a new concept in rheometry, the Capillarytron confines the particles in a controlled way using the the air/suspension capillary interface. This fine control of the particle pressure via a soft capillary interface opens the possibility to explore the flow of fragile particles, such as Brownian colloids, active particles and living cells for biomedical applications.

Ref : Bruno Etcheverry, Yoël Forterre & Bloen Metzger « Capillary-stress controlled rheometer reveals the dual rheology of shear-thickening suspensions », to be published in Physical Review X.

Contact : Bloen Metzger (, Laboratoire IUSTI, CNRS UMR 7343, Aix-Marseille Université.

Funding: ERC PLANTMOVE & ANR Science-Friction.