Lateral migration of particles in square micro-channels at low flow inertia

International audienceControlling the transport of particles inflowing suspensions is relevantin a number of contextsranging from bio-engineering and medicine to food engineering. However, the seemingly simple question, “What are the trajectories ofmicroscopic particles transported in a given flow?” can rarely be answered up to date due to the high complexity of the situations encountered in real conditions. At moderate Reynoldsnumbers, neutrally buoyant spherical particlesare known to migrate laterally in wall bounded flows and concentrate at specific equilibrium positions located near the channel wall.In the present work, a second regime of migration is highlighted: at low flow inertia, particles migrate towards the channel center. This second regime of migration is experimentally studiedthanks to the two experimental set-ups developed and already validated at moderate Reynoldsnumbers[1-2]. The first one, based on classical on-line microscopy is used to visualize in situ the suspensions flowing in micro-channels. In the second one, fluorescent particles are harvested on a plane membrane fixed perpendicularly to the flow direction and further observed by fluorescent microscopy. Fromthe obtained distributions at different distances from channel inlet, Reynolds numbers, particle to channel sizeratios and volume fractions, the competition between the two migration regimes,towards the channel center or towards the channel wall,is analyze