WorldCat Identities

Leng, Jacques (19..-....).

Overview
Works: 16 works in 17 publications in 2 languages and 18 library holdings
Roles: Thesis advisor, Opponent, Other, Author
Publication Timeline
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Most widely held works by Jacques Leng
Structure et dynamique de la texture ognon des phases lamellaires lyotropes by Jacques Leng( Book )

2 editions published in 1999 in French and held by 2 WorldCat member libraries worldwide

LES PHASES LAMELLAIRES LYOTROPES SONT CONSTITUEES D'UN EMPILEMENT PERIODIQUE DE MEMBRANES DE MOLECULES TENSIOACTIVES. SOUMISE A UN ECOULEMENT DE CISAILLEMENT, CES PHASES PRESENTENT DIVERS ETATS D'ORIENTATION DES MEMBRANES, AVEC EN PARTICULIER, UN ETAT DE VESICULES MULTILAMELLAIRES MONODISPERSES EN PHASE COMPACTE. LA TAILLE ET L'ORGANISATION DE CES VESICULES ETANT FIXEES PAR LES PARAMETRES EXPERIMENTAUX, CET ETAT OFFRE UNE TEXTURE PARFAITEMENT CONTROLEE DE LA PHASE LAMELLAIRE. DANS UNE PREMIERE PARTIE, L'ORGANISATION SPATIALE DES VESICULES A ETE DETERMINEE PAR DIFFUSION DU RAYONNEMENT A DES ECHELLES FORT DIFFERENTES. NOUS OPPOSONS UNE ORGANISATION AMORPHE A UNE ORGANISATION ORDONNEE DU POSITIONNEMENT SPATIAL DES VESICULES. NOUS AVONS ENSUITE CARACTERISE, PAR DES MESURES MECANIQUES, L'ELASTICITE DE CES DEUX ORGANISATIONS. SI L'ELASTICITE DE LA TEXTURE AMORPHE PEUT ETRE DECRITE COMME CELLE D'UNE MOUSSE, CELLE DE LA TEXTURE ORDONNEE EST SENSIBLEMENT INDEPENDANTE DE LA TAILLE DES VESICULES, REMETTANT EN CAUSE LA DESCRIPTION DE LA CONTRIBUTION DU DESORDRE A L'ELASTICITE DE CE MATERIAU. NOUS AVONS ENSUITE CARACTERISE LA DYNAMIQUE DE LA TEXTURE AMORPHE D'OGNON. SONDEE PAR DIFFUSION QUASI-ELASTIQUE DE LA LUMIERE, CETTE TEXTURE PRESENTE DEUX DYNAMIQUES. LA PLUS RAPIDE CORRESPOND A LA DYNAMIQUE DE FLUCTUATION DES MEMBRANES ET SON ANALYSE PERMET LA MESURE DES PROPRIETES ELASTIQUES DE LA PHASE LAMELLAIRE. LA DYNAMIQUE LENTE CORRESPOND PROBABLEMENT A UNE DYNAMIQUE DE REORGANISATION DE CE MATERIAU DESORDONNE. ENFIN, DANS UNE DERNIERE ETUDE, NOUS AVONS ETUDIE LA CINETIQUE DE REGONFLEMENT DE VESICULES COMPRESSEES PAR L'ECOULEMENT. L'IDENTIFICATION DES MECANISMES DE REGONFLEMENT A ETE RENDUE POSSIBLE PAR LE COUPLAGE DE DIFFERENTES TECHNIQUES EXPERIMENTALES. LE MECANISME LE PLUS LENT CONSISTE EN LA PERMEATION DU SOLVANT AU TRAVERS DE CANAUX CONNECTANT LES MEMBRANES. UN MODELE SIMPLE NOUS A PERMIS D'ESTIMER L'EVOLUTION DE LA DENSITE DE CES DEFAUTS AVEC LA TEMPERATURE
Fluidic Patterning of Transparent Polymer Heaters by Laura J Romasanta( )

1 edition published in 2018 in English and held by 2 WorldCat member libraries worldwide

Structuration périodique de la surface par séchage modulé dans le temps d'une suspension colloïdale by Essa Shawail( )

1 edition published in 2021 in English and held by 1 WorldCat member library worldwide

Fabricating ordered morphologies via evaporation of colloidal suspensions is a challenge for numerous emerging technologies. These structures can be achieved via directed convective assembly leading to controlled particle deposition at the drying front. In this work we propose a user-friendly method based on convective assembly for generating periodic surface morphologies through time-modulating the evaporation rate. We show that the advancing and arrest of the drying front can be tuned by the variation of the evaporation rate in certain colloidal suspensions, and we demonstrate that this mechanism can be used to govern particles deposition on demand. Periodic surface structures are made by time-modulated drying rate in polystyrene and polybutylacrylates suspensions and their blends. These structures were predicted via a model which takes into consideration the dynamics of the particle deposition and the drying front. The roles of surfactant, ionic strength and particle size on surface periodicity were also investigated. We show that adding aliquots of SDS surfactant drastically affects the drying front dynamic under a modulated drying rate as well as the resulting surface morphologies
Réalisation de revêtements composites par voie liquide pour la gestion des infrarouges solaires by Moncef Lehtihet( )

1 edition published in 2020 in French and held by 1 WorldCat member library worldwide

This PhD project focuses on the designing, realization and characterization of coatings deposited by liquid means, for the management of infrared solar light, regarding applications towards building efficency and solar energy harvesting. We aim to produce composite thin films, composed of polymeric matrix in which solid inclusions are added. An engineering of these inclusions permits one to reach the desired functionality. A complete modelling of composite thin film on a substrate is proposed. An optimal transport regime of light is found where the absorption is enhanced by the addition of scattering. A bench for thin film production is realized and experimental methods of characerization of the various physical phenomena occuring during material deposition is studied. A theoretical and experimental study of the influence of the optical properties of thin film on its thermal performances is proposed. Polymeric thin films containing gold nanoparticles are used as proof-of-concept of the enhanced heat generation by light scattering. Also, PEDOT:PSS/Silicon thin films are realized to control independently the absorption and scattering in films and explore such optimal regime in the near-infrared part of the spectrum
Étude de la formation de fibres en microfluidique : compétition entre mise en forme et gélification de fluides complexes sous écoulement by Oriane Bonhomme( )

1 edition published in 2011 in French and held by 1 WorldCat member library worldwide

Cette thèse est consacrée à l'étude en microfluidique de la fabrication de fibres. Les deux étapes critiques sont : - la mise en forme du matériau : nous avons étudié des instabilités qui peuvent se déclencher dans des coécoulements coeur/écorce faisant intervenir des fluides complexes (polymères, suspensions concentrées), celles-ci peuvent empêcher un contrôle de cette étape ; - le figeage de cette forme : nous avons étudié la gélification de l'alginate (un biopolymère formant un gel par l'ajout d'ions calcium) sous écoulement. Nous avons étudié des phénomènes de diffusion-réaction sous écoulement pour comprendre les points de fonctionnement de nos dispositifs. Une fois ces étapes contrôlées, nous nous sommes intéressés à la fabrication des fibres d'alginates fortement chargées en cellules pour l'ingénierie tissulaire
Séchage de fluides complexes en géométrie confinée by Laure Sylvie Véronique Daubersies( )

1 edition published in 2012 in French and held by 1 WorldCat member library worldwide

In this work, we developed two methods in order to access rapidly and easily physico-chemical, thermodynamic and kinetic properties of complex fluids. We focused on the role of the concentration on these properties. The two methods that we developed are based on the continuous concentration of an aqueous solution thanks to the evaporation of the solvent. The first tool is a microliter droplet confined between two circular plates with a cell height of about 100 µm. Within this two dimensional cylindrical geometry, the evaporation of the droplet is totally described by a model that we developed. The observation of the droplet evaporation combined to local Raman spectroscopy measurements permits us to build a quantitative phase diagram, to measure the activity of the solution and to estimate its mutual diffusion coefficient. The second tool is a microfluidic chip in which water is removed through a thin membrane. This device permits us to build with a few micrograms of solutes a stationary concentration gradient along a microchannel. Raman confocal spectroscopy and small angle X-ray scattering give access to the quantitative phase diagram and also permit to evidence that the mutual diffusion coefficient is discontinuous at some of the phase boundaries
Microfluidic fabrication of metamaterials out of colloidal dispersions by Sara De Cicco( )

1 edition published in 2020 in English and held by 1 WorldCat member library worldwide

Synthèse de polymères poreux à base de PEG-DA par voie microfluidique et pour une application en tant qu'isolant acoustique by Alexandre Turani-I-Belloto( )

1 edition published in 2018 in French and held by 1 WorldCat member library worldwide

The fabrication of thin, solid and insulating coatings containing small porous particles is the major challenge of these works. Several key points need to be raised to succeed. First, a good material for the particles has to be found, we chose a soft polymer, PEG-DA. Then, the choice of the synthesis routine to make porous polymers is crucial. A technique using UV photopolymerization and dissolution of sacrificial porogen (CaCO3) will be used. Next, we will decide to make porous particles by microfluidics to obtain well controlled sizes and good monodispersity. The last step will be about the dispersion of those particles in a matrix to create coatings. Acoustics measurements will show the acoustic response of PEG-DA in ultrasounds. Moreover, this work will also permit us to study the frontal photopolymerization of transparent and scattering media and to present a method with Monte-Carlo simulations to describe conversion profiles of polymer as a function of intensity and path length. Other studies will present drying of PEG-DA hydrogels and dissolution of CaCO3 through those hydrogels. A physical model will be proposed to describe the competition between kinetics and acid diffusion
Outils microfluidiques pour l'exploration de diagrammes de phase : de la pervaporation à la microdialyse by Nadia Ziane( )

1 edition published in 2015 in French and held by 1 WorldCat member library worldwide

This work deals with the technological development of miniaturized tools for theexploration of the phase diagram of complex fluids (colloidal dispersions, solutions ofpolymers or surfactants, etc). The microfluidic tools we elaborated make it possibleto determine phase diagrams of a series of formulations of complex fluids by consumingonly minute amounts of samples. These devices exploit two types of membraneprocesses to concentrate the chemical species : pervaporation (solvent evaporationthrough a dense membrane) and dialysis (osmotic exchanges through a membrane).Concerning the case of pervaporation, we demonstrated theoretically and experimentallythat a specific microfluidic design exists for which concentration fields of chemicalspecies remain spatially homogeneous along the kinetic path followed withinthe phase diagram. Then, it enables to obtain phase diagrams of multi-componentsmixtures from molecular compounds up to colloids, at the nanolitre scale. We reporta study concerning the understanding of the drying process of commercial silica nanoparticlesusing a dedicated microfluidic experiment involving pervaporation. Wepresent the kinetics of the concentration of the particles within the channel up to theformation of a dense colloidal packed bed which invades the channel at a controlledrate. We developed an original microfluidic tool integrating a dialysis membranewhich makes it possible to control osmotic exchanges at the nanoliter scale. We reportthe protocol of microfabrication of this chip and its specific geometry.We presentpreliminary results showing that this tool can be used to measure osmotic pressures ofcolloidal suspensions
Calibration Procedure for Attenuation Coefficient Measurements in Highly Opaque Media Using Infrared Focal Plane Array (IRFPA) Spectroscopy( )

in English and held by 1 WorldCat member library worldwide

The purpose of this article is to present a new calibration procedure for spectroscopic measurements using an infrared focal plane array (IRFPA) spectrometer on highly opaque middle-wave infrared (MWIR) media. The procedure is based on the properties of the IRFPA camera and especially the integration time (IT), which is the main parameter that can be adjusted to control the sensitivity of the measurements. The goal of the paper is to experimentally validate this dependence with the direct reference intensity light coming out of the IR monochromator in order to predict the spectrum shape and intensity level in a range out of the camera saturation. This method allows determining spectrum used as background for transmittance calculation. It has been applied in the case of measurement of water transmittance, which is a highly opaque medium and whose measurement requires high ITs. The main result is the ability to take an IR spectroscopic imaging measurement through 300 µm of water and the determination of its transmittance with sufficient sensitivity due to the proposed calibration procedure. This procedure allows the possibility of transitory studies in heterogeneous aqueous media
Understanding in vivo degradation of mesoporous silica therapeutic vectors through in situ ellipsometry by Elisa Bindini( )

1 edition published in 2018 in English and held by 1 WorldCat member library worldwide

Dans les dernières 15 ans, la recherche biomédicale a exploré en profondeur l'utilisation de nanoparticules pour la délivrance ciblée de médicaments. Parmi plusieurs matériaux étudiés, la silice mésoporeuse représente une plateforme exceptionnelle pour ce type d'applications puisque elle est biocompatible et capable d'être chargé avec une quantité élevée de médicament, tout en étant facile à synthétiser et à fonctionnaliser. La connaissance des interactions entre nanoparticules de silice et environnement biologique est nécessaire pour concevoir des vecteurs thérapeutiques efficaces et pas toxiques. Cet étude a développé une nouvelle méthode d'analyse in situ pour suivre les interactions entre silice mésoporeuse et fluides biologiques réels (sérum et sang), employant une cellule d'analyse microfluidique et l'ellipsométrie en réflexion totale interne. Nous avons ainsi réalisé le suivi dynamique de la dégradation de vecteurs models à base de silice poreuse structuré dans une solution tampon à pH physiologique et une solution concentré de protéines. Ces analyses ont permis d'évaluer l'influence de la structure poreuse, de l'adsorption de protéines sur la surface et de la vitesse du flux sur la dissolution de la silice mésoporeuse
Engineering three-dimensional extended arrays of densely packed nano particles for optical metamaterials using microfluidIque evaporation by Antonio Iazzolino( )

1 edition published in 2013 in English and held by 1 WorldCat member library worldwide

Les métamatériaux sont définis comme étant des matériaux artificiels présentant des propriétés exotiques qui modifient la propagation des ondes électromagnétiques. À la fin des années 90, Pendry et al. démontrèrent théoriquement qu'il est possible de générer de tels métamatériaux, grâce à des structures particulières au sein du matériau (le fameux "splitring resonator"). Les métamatériaux sont donc structurés à une échelle inférieure à la longueur d'onde incidente, et décrits par une permittivité et une perméabilité effective. En 2000, Smith et al. fabriquèrent le premier métamatériau mais dans la gamme micro-onde. Les perspectives dans le domaine de l'optique (300800 nm) sont très prometteuses, mais le transfert des technologies utilisées en micro-ondes rencontre des obstacles. Un des défis dans le domaine émergent des métamatériaux est d'assembler à grande échelle des nanoparticules NPs (10-50 nm) en des super-réseaux présentant des propriétés collectives. Des nanostructures tridimensionnelles de matériaux nobles, ayant de fortes réponses plasmoniques, peuvent en effet générer des matériaux aux nouvelles propriétés optiques. Cette thèse fait partie du projet européen METACHEM, dont le but est de fabriquer des métamatériaux dans le domaine de l'infrarouge et du visible, en se basant sur l'utilisation de la nanochimie et de l'assemblage de matériaux. Plus précisément, ce travail de thèse se situe à l'interface entre les groupes de chimie qui synthétisent des nanoparticules en dispersion, et les groupes de caractérisation optique des matériaux. Dans ce travail de thèse, nous utilisons une technique originale la microévaporation basée sur les outils microfluidiques, afin de générer de façon contrôlée des assemblées 3D de nanoparticules (dimensions typiques 1 mm10 m 50 m)
Pickering Foams : Particle Design and Catalysis by Andong Feng( )

1 edition published in 2021 in English and held by 1 WorldCat member library worldwide

The versatility of colloidal particles endows Pickering foams with unique features, which can potentially be used for engineering gas-liquid-solid (G-L-S) catalytic microreactors for multiphase reactions. G-L-S microreactors based on Pickering foams can promote the G-L-S contact and enhance the catalytic activity, showing promising credentials for oxidation and hydrogenation reactions with broad industrial impact. This thesis aims to boost the understanding of particle behavior at gas-liquid interfaces, and develop novel foaming systems for efficient multiphase reactions. First, we investigated the foaming behavior of Aquivion® PFSA, a perfluorinated acid resin, in different solvents, and constructed an original foaming system for a one-pot cascade reaction combining Aquivion® PFSA with a homemade Pd/SiO2 catalyst. The catalytic performance of the foam system was found to be superior to that of a conventional non-foam multiphase system. Afterwards, a variety of organosilica particles was prepared by sol-gel synthesis using different organic precursors. The foaming properties of the resulting particles were studied after handshaking, high-speed homogenization, and using a homemade microfluidic device. The key parameters controlling foam formation were systematically investigated. It was demonstrated that stable organic foams could be obtained with biphenyl-bridged particles and fluorinated organosilica particles
Spontaneous curvature of polydimethylsiloxane thin films : Mechanisms and applications : A new route for the low cost fabrication of new functionalities for microfluidics by Rémy Brossard( )

1 edition published in 2017 in English and held by 1 WorldCat member library worldwide

The guideline of this work is the spontaneous rolling of oxidized polydimethylsiloxane (PDMS) thin films in organic solvant vapors. Briefly, thin films of PDMS are produced by spin coating. Those films are then exposed to oxygen plasma which oxidizes and hardens their surfaces. When those systems are immersed in appropriate solvent vapors, non oxidized PDMS selectively swells. This leads to the spontaneous rolling of the films and thus to the formation of capillaries. This mechanism is of great interest for the fabrication of microfluidic channels because what is to become the inner surface of those channels can be characterized and functionalized prior to rolling.In a first chapter, different aspects of spontaneous rolling are reviewed theoretically and numerically.A second chapter is dedicated to the investigation of the oxide layer by AFM nanoindentation. The mechanical properties of the composite system (hard layer on a soft substrate) are measured and interpreted with a new model in order to extract in particular the thickness of the oxide layer.A third chapter dwells on engineering of the rolled-up tubes. The inner diameter of the capillaries as a function of experimental parameters is measured and confronted to theory. We present tubes with various inner surface functionalizations as a proof of concept of the method.Finally, in order to solve the issue of the integration of the system in a wider structure, an innovative method is proposed in a final fourth chapter. Based on the fabrication of a sacrificial mold by inkjet printing, the method is first established and implemented. Several proof-of-concept systems are then displayed in order to demonstrate the great potential of that idea
Cinétiques de concentration de suspensions colloïdales par évaporation microfluidique : de la solution diluée aux cristaux colloïdaux by Aurore Merlin( )

1 edition published in 2010 in French and held by 1 WorldCat member library worldwide

This work is devoted to studying processes of colloidal solutions concentration by microfluidic way to shape dense and organized states. Using a tool based on the water permeation through the PDMS: the microevaporator, we propose to control drying of solution for controlling solute concentration to form dense states as one chooses, alternating crystals and amorphous states of colloids.By adapting microevaporation tool at different observation techniques, nucleation and growth are particularly studied and correlated to a simple microevaporation model. This experimental work demonstrates the good control on kinetics of chemical species concentration offered by microevaporation, in order to shape dense states of particles.Further studies also reveal existence of a dynamic construction of colloidal crystal with some reorganization in the front growth and a compaction effect of the dense state during the growth
Développement d'un système de culture perfusé pour l'élaboration de modèles de tissus osseux by Mikhael Hadida( )

1 edition published in 2019 in French and held by 1 WorldCat member library worldwide

L'utilisation des modèles animaux reste la norme en biologie pour la recherche fondamentale comme pour les tests de nouveaux médicaments, mais présente de lourds désavantages éthiques, scientifiques et financiers. Pour ces raisons, certaines procédures biologiques s'orientent vers un changement de paradigme des modèles animaux vers les modèles in vitro de tissus et/ou d'organes miniaturisés générés à partir de cellules humaines. Pour l'heure, les modèles de tissus osseux restent rudimentaires, et l'influence des paramètres de culture sur le comportement cellulaire est globalement inconnue.Cette thèse a pour objectif de développer un système innovant de culture en trois dimensions perfuse permettant la culture maitrisée, standardisée et simplifiée de tissus osseux modèles fabriqués in vitro sur des supports de culture; exploitable notamment dans le cadre de la biologie exploratoire, de la recherché pharmaceutique ou des études précliniques. Le manuscrit s'articule autour d'une analyse critique de la littérature, de la conception du dispositif de culture et des stratégies de valorisation (brevet, projet européen) mises en place pour assurer la pérennité du projet
 
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Audience level: 0.95 (from 0.88 for Spontaneou ... to 1.00 for Structure ...)

Alternative Names
Jacques Leng wetenschapper

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