Chargé de Recherche CNRS
LRP, CNRS, Univ. Grenoble-Alpes, Grenoble INP
LRP, CNRS, Univ. Grenoble-Alpes, Grenoble INP
LIPhy, IRPHE, CNRS, Univ. Grenoble-Alpes, Supervised by C. Misbah and M. Léonetti
IRPHE, CNRS, Aix-Marseille Univ., Supervised by M. Léonetti
Digesta Group, Massey University, New-Zealand, Supervised by R. Lentle
GMPA, INRA, AgroParisTech, Supervised by I. Souchon and A. Magnin
PhD in Engineering Science
Master 2 in Rheology and Mechanics of Soft Materials
Master degree in Engineering, Fluid Mechanics
ENSHMG, Grenoble INP
Blood is a suspension of elastic objects, namely Red Blood Cells (RBCs), whose large deformability in the vessels leads to rheological properties of complex fluids and to intriguing structuration phenomena such as margination . It consists in a segregation of blood cells under flow: RBCs are located at the centre of the vessel while White Blood Cells (WBCs) and platelets are at the periphery close to the endothelial cells covering the vessel. While known from many decades in medecine, the detailed mechanisms and modelling of margination are still a challenge despite the numerous numerical investigations and the interest in taking advantage of it for separation purposes.
We propose an experimental investigation of margination phenomena with a simplified blood model containing two populations of RBCs, namely healthy and rigidified.
Encapsulation is a promising technology to control the spatio-temporal delivery of substance. This substance is encapsulated in micrometric drops and protected by a solid membrane with elastic properties. For example, in the food industry, volatile substances (aroma), bacteria or nutrients (iron) are preserved from degradation by the ambient environment during the storage through encapsulation. These substances are delivered directly in the digestive tract with highly beneficial effects on sensory properties and health of consumers. The release of the substance (e.g. drugs, nutrients) may either be instantaneous, by membrane break-up or continuous, by diffusion.
The objective of this proposal is to characterize the break-up properties of self-assembled chitosan / surfactant microcapsules. The break-up will be studied in microfluidic extensional flows. It will so be possible to relate break-up criteria with formulation parameters (concentrations, time of complexation) and the membrane thickness measured by AFM.
Microcapsules know an increasing interest due to the tunability of their mechanical and physico-chemical properties. They are promising objects to control delivery of drugs in the bloodstream or also to develop new multi-functional materials as paints. The challenge is to control the structuration (i.e. the spatial organisation of the microcapsules) in bulk and in surface. Microcapsules are also considered as a model of red blood cells arousing numerous numerical and theoretical studies on the dynamics of isolated capsules in flow.
Our objective is to understand the effects of the deformability of microcapsules on their migration and the structuration of suspensions under flow, i.e. the spatial organisation of the microcapsules. We will design soft microcapsules (size, viscoelascity, plasticity) providing uniform suspensions to experiment their structure and rheology in simple flows.
Controlling the spatio-temporal delivery of drugs or nutrients in the gastro-intestinal tract is of prime importance to improve pharmaceutical treatments or to control the nutritional properties of food products. The major constraints to such mixing are the high viscosity and the non-Newtonian characteristics of the gastro-intestinal content and the low velocity of the active mucosa, which together result in low Reynolds numbers. It is most likely that transfers in the lumen should limit biochemical reactions. Hence, it is essential to understand and model the mixing strategies developed by the digestive tract.
To identify the relevant biomechanical and rheological factors that limit mixing and absorption in the small intestinal lumen, we have developed methods of high fidelity quantification of intestinal motility, coupled to realistic models of intestinal fluid dynamics as well at the scale of smooth muscle activity (1 mm), as at the one of villi, finger-like structures of around 500 μm length covering intestinal mucosa. At macroscopic scale, we show that activity of smooth muscles are organised into domains of contractions. This activity is responsible for a process of shear dispersion of the luminal content in the longitudinal direction. At microscopic scales, villous movement during longitudinal contractions is a major radial mixing mechanism that increases dispersion and absorption around the mucosa despite adverse rheological properties of the digesta. Finally, we conclude that the intestinal mucosa can be considered as an active microfluidic mixer.
La médaille d’argent est destinée à récompenser une thèse de grande qualité, dont l’analyse, réalisée par l’Académie, est publiée sur le site de l’Académie d’agriculture de France.
"Clément de LOUBENS, pour ses travaux originaux sur la libération des composés à l’origine de stimuli orosensoriels. La thèse est assortie d’un nombre considérable de publications scientifiques décrivant les nouvelles méthodes mises au point."(Rapporteur : Hervé This).
The DSM Science & Technology Awards (North) are part of the DSM Innovation Awards Program. They are awarded for outstanding PhD research conducted by doctoral students from two European regions: the Netherlands, Belgium and Northern Germany (North) and Switzerland, Austria, Northeastern France and Southern Germany (South). See link.
Understanding and modeling phenomena governing stimuli release during food consumption make it possible to respect both nutritional and sensorial criteria during its formulation. A model of salt release during the course of mastication was developed for “solid” products. The breakdown was comprehended by the generation of the area of contact between the product and the saliva that governs the transfers of stimuli. The area of contact was written as the product of two functions. The first was related to the subject and was function of his masticatory performance. The second was related to the product and depended on its breakdown behavior that can be determined by in vitro tests. During the pharyngeal stage, the biomechanics of swallowing governs pharyngeal mucosa coating and aroma compounds present in this layer. These phenomena are due to a thin film flow, stationary in a soft elastohydrodynamic contact whose the kinematics is equivalent to a forward roll coating process lubricated by saliva. Two sets of conditions were distinguished. When the saliva film is thin, food bolus viscosity has a strong impact on mucosa coating and on flavour release. When the saliva film is thick, the food bolus coating the mucosa is very diluted by saliva during the swallowing process and the impact of product viscosity on flavour release is weak. This second set of condition allowed us to explain the physical origin of in vivo observations on flavour release.