Description :
Keywords : fluid mechanics, microfluidics, rheology, soft matter, fluid-structure interactions, multiphase flows.

Backgrounds : master in physics/mechanics or engineer degree even without master. Knowledge in fluid mechanics or soft matter will be appreciated. The candidate has to be opened to interdisciplinarity.

Grant : Program of Excellence of Université de Grenoble-Alpes (Idex)

PhD context : Microcapsules are promising soft microparticles to control the delivery of drugs or nutrients in the human body. These substances are encapsulated in micro-drops, protected from the external fluid by a thin elastic membrane and released by rupture, fusion or cyclic deformations of the membrane.. Microcapsules have the feature to be highly deformable under flow. They are so considered as a simplified model of Red Blood Cells, a micrometric deformable cell. We expect that suspensions of artificial deformable microcapsules should share common physical features with the blood, especially strong structuration (i.e. the spatial organisation of the particles) under flow due to their deformability. Typically, soft cells are concentrated in the centre of the channel, leaving a depletion layer near the walls, where rigid cells are more likely to be found.

PhD Objective : The structuration of suspensions of soft microcapsules, relies to a many-body problem with hydrodynamic interactions which depends on their dynamics of deformation. Contrary to suspensions of rigid particles, the understanding of such soft suspensions in flow is scarce. Only recent numerical simulations begin to capture some fruitful ingredients that have to be confirmed (or not) by experiments. The PhD candidate will explore experimentally the collective dynamics of soft microcapsules in microfluidics flow to gain insight into their rheology, structuration and transition under flow providing a support for further numerical and theoretical progress. In summary, the candidate will tackle this problematic following this plan :


 How flows a suspension of microcapsules ? What is the contribution of the physical properties of suspensions of microcapsules (size, deformability, concentration) on their structuration under flow and their rheology (apparent viscosity) ?


 What is the role of flow confinement ? Can we expect segregation in bidisperse suspension governed by deformability as in blood microcirculation ?

Methods : The PhD candidate will approach this problematic by the fabrication of suspensions of microcapsules with well-defined mechanical properties to experiment their behaviour in shear flows and microfluidic channels coupled to microscopy and high-speed imaging.

References :
Kumar et al. Margination and segregation in confined flows of blood and other multicomponent suspensions. Soft Matter (2012).
Munn, & Dupin, Blood cell interactions and segregation in flow. Ann. Biomed. Eng. (2008) ;
de Loubens, Leonetti, et al.,Tank-treading of microcapsules in shear flow. J. Fluid Mech. (2016).
de Loubens, Leonetti, et al., Stretching of capsules in an elongation flow, a route to constitutive law. J. Fluid Mech. (2015).

Reference :

Date de démarrage : 01 octobre 2017

Durée :

Contacter :
Laboratoire Rhéologie et Procédés
Clément de Loubens
GRENOBLE
email : clement.de-loubens@univ-grenoble-alpes.fr