Clement De Loubens

French National Centre for Scientific Research | CNRS · Laboratoire Rhéologie et Procédés

Tuning the mechanical properties of microcapsules with cost-efficient route of fabrication is still a challenge. The traditional method of layer-by-layer assembly of microcapsules allows building a tailored composite multi-layer membrane but is technically complex as it requires numerous steps. The objective of this article is to characterize the i...

Flow and mixing in the small intestine are multi-scale processes. Flows at the scale of the villi (finger-like structures of $\approx$500 $\mu$m length) are poorly understood. We developed a three-dimensional lattice-Boltzmann model to gain insight into the effects of villous movements and the rheology of digesta on flow, mixing and absorption of n...

We investigated experimentally the deformation of soft microcapsules and the dynamics of their membrane in simple shear flows. Firstly, the tank-treading motion, i.e. the rotation of the membrane, was visualized and quantified by tracking particles included in the membrane by a new protocol. The period of membrane rotation increased quadratically w...

Soft bio-microcapsules are drops bounded by a thin elastic shell made of cross-linked proteins. Their shapes and their dynamics in flow depend on their membrane constitutive law characterized by shearing and area-dilatation resistance. The deformations of such capsules are investigated experimentally in planar elongation flows and compared with num...

The objective of this study was to develop a model to simulate salt release during eating. Salt release kinetics during eating was measured for four model dairy products with different dynamic salty perceptions. A simple in vivo model of salt release was developed to differentiate between the contribution of the individual and of the product to sal...

Many bio‐hydrogels are prepared thanks to the addition of divalent ions. These gels usually exhibit partial ionic selectivity, a feature is leveraged to instigate an osmotic flow during the gelation process across a range of bio‐hydrogels. A simple experimental setup consisting a glass capillary filled by the reactant solution is taken as an advant...

Mechanistic understanding of anorectal (patho)physiology is missing to improve the medical care of patients suffering from defaecation disorders. Our objective is to show that complex fluid dynamics modelling of video defaecography may open new perspectives in the diagnosis of defaecation disorders. Based on standard X-ray video defaecographies, we...

Despite the numerous available clinical investi-gation tests, the associated alteration of quality of life and the socio-economic cost, it remains difficult for physicians to identify the pathophysiological origins of defecation disorders and therefore to provide the appropriate clinical care. Based on standardized dynamic X-ray defecography, we de...

Using fractal protein aggregates as building blocks, porous fibers were produced. The suspension of aggregates was co-injected with a solution of calcium chloride. Sol-gel transition of the suspension was induced by diffusion of calcium ions in the jet. The production of these fibers required a precise control of both hydrodynamic and physicochemic...

Physiological transport of fluid at small scales is often achieved by microscopic active finger-like structures. It is recognized that they have to move in a non-symmetric fashion in order to break the symmetry of creeping flow and to induce a net movement of the fluid. However, in the limit of low, but non-vanishing, Reynolds number, irreversible...

Controlling the assembly of polyelectrolytes and surfactant at liquid-liquid interfaces offers new ways to fabricate soft materials with specific physical properties. However, little is known of the relationships between the kinetics of interfacial assembly, structural and rheological properties of such interfaces. We studied the kinetics at water-...

Using absorbance measurements through a Couette cell containing an emulsion of buoyant droplets, volume fraction profiles are measured at various shear rates. These viscous resuspension experiments allow a direct determination of the normal stress in the vorticity direction in connection with the suspension balance model that has been developed for...

Citation: Mehdaoui, H.; Ait Abderrahmane, H.; de Loubens, C.; Nait Bouda, F.; Hamani, S. Dynamics of a Gel-Based Artificial Tear Film with an Emphasis on Dry Disease Treatment Applications. Gels 2021, 7, 215. https://doi.org/10.3390/ gels7040215 Academic Editors: Abstract: This paper discusses the spreading of gel-based ophthalmic formulation on th...

Using absorbance measurements through a Couette cell containing an emulsion of buoyant droplets, volume fraction profiles are measured at various shear rates. These viscous resuspension experiments allow a direct determination of the normal stress in connection with the suspension balance model that has been developed for suspensions of solid parti...

Controlling the assembly of colloids at liquid-liquid interfaces offers new ways to fabricate soft materials with specific physical properties. However, little is known of the relationships between the kinetics of interfacial assembly, structural and rheological properties of such interfaces. We studied the kinetics of the assembly of two oppositel...

A way forward for high throughput fabrication of microcapsules with uniform size and mechanical properties was reported irrespective of the kinetic process of shell assembly. Microcapsules were produced using lab-scale emulsification equipment with a micro-engineered membrane in the size range 10–100 μm. The shell of the microcapsules was assembled...

A way forward for high throughput fabrication of microcapsules with uniform size and mechanical properties was reported irrespective of the kinetic process of shell assembly. Microcapsules were produced using lab-scale emulsification equipment with a micro-engineered membrane in the size range 10-100 $\mu$m. The shell of the microcapsules was assem...

Whey protein isolates (WPI) can be aggregated upon heating to create new functional properties (e.g. texture), which depend on aggregate size and structural properties. In industrial conditions, aggregates are obtained in continuous processes at high temperature (≥ 75∘C) in few minutes. When studying the kinetics of WPI aggregation at high temperat...

Background Rectal evacuation involves multiple mechanisms that are not completely understood. The aim of this study was to quantify the rheologic property, i.e., yield stress, which governs the ease of deformation of a range of faeces of differing consistency and understand its influence on the pathophysiology of defaecation.Methods Yield stresses...

Particles migrate in the transverse direction of the flow due to the existence of normal stress anisotropy in weakly viscoelastic liquids. We test the ability of theoretical predictions to predict the transverse velocity migration of particles in a confined Poiseuille flow according to the viscoelastic constitutive parameters of dilute polymer solu...

Viscoelastic transverse particle migration is studied in a confined slit geometry with a great accuracy in order to test existing theoretical predictions and to achieve a quantitative description. For that purpose, we have developed a fast 3D particle tracking velocimetry method without scanning, which allows to acquire probability density function...

Flows of particles in viscoelastic liquids are involved in geological, biological or industrial applications. Recently, numerous studies have revealed that the particle motion is affected by fluid elasticity 1,2,3. In particular, transverse migration of particles, i.e. a motion across streamlines, is reported due to a gradient of shear rate around...

The development of innovative experimental approaches is necessary to gain insights in the complex biomechanics of swallowing. In particular, unraveling the mechanisms of formation of the thin film of bolus coating the pharyngeal mucosa after the ingestion of liquid or semi-liquid food products is an important challenge, with implication in dysphag...

Soft microcapsules moving in a cylindrical capillary deform from quasi-spherical shapes to elongated shapes with an inversion of curvature at the rear. We investigated the perturbation of the flow by particle tracking velocimetry around deformed microcapsules in confined flow. These experiments are completed by numerical simulations. Microcapsules...

A microfluidic technique is used to characterize the mechanical behavior of capsules that are produced in a two-step process: first, an emulsification step to form droplets, followed by a cross-linking step to encapsulate the droplets within a thin membrane composed of cross-linked proteins. The objective is to study the influence of the capsule si...

We examined the coordination between contractile events at different sites in the basal portion of the rabbit caecum and its associated structures that were identified by electrophysiological recordings with simultaneous one-dimensional, and a novel two-dimensional, spatiotemporal mapping technique. The findings of this work provide evidence that t...

The small intestine is a convoluted flexible tube of inconstant form and capacity through which chyme is propelled and mixed by varying patterns of contraction. These inconstancies have prevented quantitative comparisons of the manner in which contractile activity engenders mixing of contained chyme. Recent quantitative work based on spatiotemporal...

Background Spatiotemporal (ST) mapping has mainly been applied to ex vivo preparations of the gut. We report the results of ST mapping of the spontaneous and remifentanil-induced motility of circular and longitudinal muscles of the distal ileum in the postprandial anaesthetized pig.Methods Spatiotemporal maps of strain rate were derived from image...

We investigated the passive mechanical properties of villi in ex vivo preparations of sections of the wall of the distal ileum from the brushtail possum (Trichosurus vulpecula) by using a flow cell to impose physiological and supra-physiological levels of shear stress on the tips of villi. We directly determined the stress applied from the magnitud...

The understanding of mixing and mass transfers of nutrients and drugs in the small intestine is of prime importance in creating formulations that manipulate absorption and digestibility. We characterised mixing using a dye tracer methodology during spontaneous longitudinal contractions, i.e. pendular activity, in 10 cm segments of living proximal d...

Controlling the deformation of microcapsules and capsules is essential in numerous biomedical applications. The mechanical properties of the membrane of microcapsules made of cross-linked human serum albumin (HSA) are revealed by two complementary experiments in the linear elastic regime. The first provides the surfacic shear elastic modulus G s by...

After swallowing a liquid or a semi-liquid food product, a thin film responsible for the dynamic profile of aroma release coats the pharyngeal mucosa. A biomechanical model of swallowing and in vivo aroma release experiments showed that the product coating the mucosa is very diluted by saliva during the swallowing process. Consequently, the impact...

A mechanistic model of salt release during mastication of dairy gels was developed and fitted to experimental data. It was assumed that concentration gradients within the food did not develop because the mastication time is short compared to the characteristic time of salt release. The evolution of the contact area between the product and the saliv...

The main pattern of contractile activity in the proximal duodenum of the rat is characterized by non propagating longitudinal contractions organized into spatial domains. These contractions generate region of relative high shear strain that accelerates diffusive mass transfers between adjacent domains.

Ce numéro d'Innovations Agronomiques comprend les articles correspondant aux présentations du colloque « Comprendre et utiliser la structure des aliments pour améliorer leurs qualités nutritionnelles et sensorielles » qui s'est tenu à Rennes le 13 mai 2014.

Controlling the deformation of microcapsules and capsules is essential in numerous biomedical applications. The mechanical properties of the membrane of microcapsules made of cross-linked human serum albumin (HSA) are revealed by two complementary experiments in the linear elastic regime. The first provides the surfacic shear elastic modulus Gs by...

Recent work suggests that mixing in the small intestine takes place in central luminal and peripheral compartments. However, while movements of villi have been described, the mechanisms by which peripheral mixing are engendered remain unclear. We examined the disposition and movement of mucosa and associated villi during contractions of the everted...

We conducted numerical experiments to study the influence of non-propagating longitudinal and circular contractions, i.e. pendular activity and segmentation, respectively, on flow and mixing in the proximal duodenum. A lattice-Boltzmann numerical method was developed to simulate the fluid mechanical consequences for each of 22 randomly selected seq...

We report the results of spatiotemporal mapping of the spontaneous actions of component muscles of the gizzard and associated structures in ex vivo preparations with combined superfusion and vascular perfusion. Ongoing spontaneous contraction of cranial and caudal thin muscles occurred at a frequency of 2.2 ± 0.1 cycles per minute. Contractions of...

Little is known of the spatiotemporal organization of pendular duodenal contractions. We used longitudinal and radial spatiotemporal mapping to examine and compare pendular and segmental contractile activity in the proximal duodenum of the rat and guinea pig when the lumen was perfused with saline or micellar decanoic acid. Isolated phasic longitud...

In vivo aroma release during solid food consumption is a complex phenomenon that depends on food structure and composition, as well as on oral processing (combination of mastication and incorporation of saliva into the food product). The objective of this study was to understand and to predict the physico-chemical properties of aroma compounds thro...

We used high definition radial, strain rate and intensity spatiotemporal mapping to quantify contractile movements of the body and associated structures of the rabbit caecum when the terminal ileum was being perfused with saline at a constant rate. This perfusion caused gradual distension of the caecum as a result of relative restriction of outflow...

The objective of this study was to analyse the viscosity effect of liquid Newtonian products on aroma release, taking human physiological characteristics into account. In vivo release of diacetyl from glucose syrup solutions varying widely in viscosity (from 0.7 to 405mPas) was assessed by five panelists using Proton Transfer Reaction Mass Spectrom...

The aim of this study was to better understand salt release and perception in model dairy products, having different composition, structure and/or texture. Sensory and instrumental methods were used to quantify and relate texture to salt mobility and perception. A high dry matter content (protein and fat jamming) and a gel structure with a protein...

After eating a liquid or a semi-liquid food product, a thin film responsible for the dynamic profile of aroma release coats the pharyngeal mucosa. The aim of this article was to analyse the fluid mechanics of pharyngeal peristalsis and to develop a simple biomechanical model in order to understand the role of saliva and food bolus viscosity on the...

Understanding and modeling phenomena governing stimuli release during food consumption make it possible to respect both nutritional and sensorial criteria during its for- mulation. 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 betw...

L’objectif des substituts lacrymaux est tri- ple : protection de la surface oculaire par la formation d’un film isolant ; hydratation, avec allongement du temps de rupture et rémanence ; soulagement des irritations, amélioration du confort visuel par lubrifi- cation. L’efficacité et la rémanence des produits disponibles diffèrent selon les caractér...

Tear substitutes are used to treat dry eye syndrome. Shear-thinning should help to delay the appearance of dry spots and improve comfort. This article discusses a numerical model study of the spreading of shear-thinning tear substitutes during blinking. The Ellis model, which takes account of the Newtonian plateau at low shear rate, was chosen. Flo...

The measurement of physicochemical properties, such as partition or diffusion coefficients of small molecules like salt and aroma compounds, represents an important challenge to better understanding stimuli release and perception. Owing to the lack of simple and fast methods, we developed three methods for practical and rapid determination of parti...

La libération des arômes lors de la déglutition dépend de la quantité du bol enduisant les muqueuses pharyngées. Un modèle assimilant la déglutition à un phénomène d’enduction réalisé par des cylindres rotatifs et lubrifiés par un film de salive est développé. Les résultats de ce modèle étudiés dans le cas newtonien montre que l’enduction des paroi...

Dans la perspective de mieux comprendre les mécanismes de libération en bouche des molécules responsables des stimuli sensoriels, nous nous sommes intéressés à la prédiction de l'étalement du bol alimentaire entre la langue et le palais. Les bols alimentaires considérés dans cette étude sont deux gels laitiers dont la représentation physique est un...