Crystallization and intermittent dynamics in constricted microfluidic flows of dense suspensions

A strong coupling between shear, confinement and microstructure governs the flow of dense colloidal suspensions through narrow channels. In this paper we explore the additional complexity that arises when the channel is partially blocked by a constriction in the centre of the channel. The reduction of the particle flux due to the constriction induces a densification upstream from the constriction, resulting in the formation of extended crystalline domains. A dynamic equilibrium establishes, which is characterized by large fluctuations in the instantaneous flow velocity and the local density. In some cases, the individual events leading to this intermittent behaviour are clearly visible as transient and localized jamming and unjamming events.