Literatura científica selecionada sobre o tema "Processus microfluidiques"
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Artigos de revistas sobre o assunto "Processus microfluidiques"
Destremaut, Fanny, C. Masselon, P. Laval, G. Cristobal, A. Dodge, J. B. Salmon e R. Barrett. "Microfluidique et diffusion de rayons X aux petits angles : des outils pour étudier les processus sol-gel". La Houille Blanche, n.º 6 (dezembro de 2007): 26–33. http://dx.doi.org/10.1051/lhb:2007078.
Texto completo da fonteTeses / dissertações sobre o assunto "Processus microfluidiques"
Laval, Philippe. "Outils microfluidiques pour l'étude des processus de cristallisation : solubilité, polymorphisme et cinétique de nucléation". Bordeaux 1, 2007. http://www.theses.fr/2007BOR13420.
Texto completo da fonteThis work deals with the development of microfluidic devices for studying crystallization processes. The goal is to simplify and to increase the speed of experimental data acquisition on crystallization, which is important for chemical and pharmaceutical industries. The devices are based on a precise temperature control and on the production and manipulation of hundreds of nanoliter-sized droplets in specific microfluidic systems. The droplets are used as independent microreactors in which we can induce crystal formation in a controlled way. Besides, since the different systems offer the possibility to observe directly a large number of droplets, they enable us to perform high-throughput screening of experimental conditions and to carry out statistical measurements of stochastic phenomenon such as nucleation. The first device was developed for the rapid screening of solubility diagrams. The second one enables us to detect polymorphic forms of a compound appearing during a crystallization step, and the two last systems are used to measure nucleation kinetics. The small droplet volume is crucial for these applications. Indeed, in such a small volume, it is possible to reach very high supersaturations, to induce mononuclear nucleation and as a consequence, to separate all nucleation events. Thanks to these microfluidic tools, for the first time we measured the solubility limit of a metastable form of potassium nitrate, and show the importance of impurities in crystal nucleation process
Zollo, Margaux. "Solvants à hydrophilie commutable au CO2 : applications en microfluidique pour les processus chimiques". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0193.
Texto completo da fonteOne of the main challenges in developing greener chemical processes is finding lowvolatility solvents that are easily separable, energy-efficient, and recyclable. A promising solution is the use of reversible CO2-Switchable Hydrophilicity Solvents (CO2-SHS), which offer an energy-efficient alternative to solvents with fixed properties. In this study, we propose a novel approach to rapidly investigate SHS performance using 2-2-Dibutylaminoethanol (DBAE), a known CO2-SHS, within a continuous microfluidic device made of poly(dimethylsiloxane) (PDMS). This method provides a highly adaptable alternative to traditional batch reactors and millifluidic platforms. First, the DBAE/water/CO2 system was characterized using spectroscopic techniques (ATR-IR and Raman) to identify the species involved in the phase change mechanism. Then, the hydrophilicity switch was tested, initially in a millifluidic assembly inspired by existing platforms, and subsequently in the designed PDMS device
Lounaci, Malika. "Systèmes microfluidiques pour la cristallisation des protéines : apports technologiques à la compréhension du processus et influence de la hauteur des canaux". Paris 6, 2009. http://www.theses.fr/2009PA066193.
Texto completo da fonteThe objective of this thesis was to perfect Microfluidic devices for the crystallization of proteins, to offer solutions for the screening of the conditions of crystallization and finally to contribute to understanding the physicochemical process of crystallization in a Microfluidic device. We detailed the techniques of microfabrication, the realization of microvalves as well as the multi-layered chips. A platform allowing the observation of the process of crystallization and the control of microvalves were accomplished. We brought solutions in met problems such as the box divided in two compartments for a better conservation of crystals, the method of aspiration with a minimum of sample without dead volume as well as three-layered chips. Finally, we studied the influence of the height of the microchannel on the crystallization of the lysozyme. We showed that the number of centers of nucleation, the size of crystals as well as the kinetic process of crystallization depends on the height of the channel. We offered, finally, a method of crystallization allowing decoupling the nucleation and crystals growth
Ravi, Anusuyadevi Prasaanth. "Synthèse de nouveaux nanophotocatalyseurs en microfluidique supercritique". Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0345/document.
Texto completo da fonteThis PhD thesis is part of a larger European ITN project (Photo4Future) dealing with improvement of the use of sun light for making valuable products through new heterogeneous catalytic photochemical processes. In this context, the synthesis of nanophotocatalysts is essential since their characteristics must be controlled to optimize the process efficiency towards the desired products. Supercritical fluids synthesis approaches (high pressure / high temperature) have proven to be promising for such developments. Combined to microreactors, it is then possible to reach a precise control of material properties, including surfaces. The objectives of this project are (i) to develop synthetic methods for designing new nanophotocatalysts based on titania and nitrides quantum dots, in particular GaN/TiO2 and GaxIn1-xN/TiO2, (ii) to test their photocatalytics efficiency on several model photochemical reactions (oxidation of thiols, trifluoromethylation and amine to imine conversion), both in batch mode and using continuous flow photochemical reactors and (iii) to investigate the scale-up options for increasing the production rates of such nanophotocatalysts
Sendekie, Zenamarkos Bantie. "Clogging dynamics of particles and bacteria in microfluidic systems mimicking microfiltration processes". Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30355/document.
Texto completo da fonteThe aim of the PhD is to progress in the understanding of the fouling phenomena during filtration of soft matter (colloidal particles and bacteria) and to examine the efficiency and feasibility of microfluidic separators. These studies are realized with microfluidic devices constituted of micrometric channels having the same size range as the materials being filtered. These devices, which mimic membrane dead-end and cross-flow microfiltration processes, allow in-situ and direct microscopic observations of the fouling mechanisms. The microfluidic system is equipped with flow rate and pressure measurement devices allowing a dynamic cross analysis of the observations with the variations of permeability. Experiments have been realized for different hydrodynamic conditions (flow rate, filtration mode) and for different colloidal interactions (by varying the ionic strength) in order to analyse their interplay in the clogging mechanism by soft matter (interacting particles). The results evidenced the importance of clogs formation, fragility and sweeping out dynamics during the fouling process. These dynamic events at bottlenecks induce important permeability fluctuations. The particle-particle and particle-wall interactions also play important roles on the clogging dynamics. Three different scenarios are discussed by analogy to crowd swarming: panic scenario (0.01 mM) where repulsion between particles induce pushing effects leading to the creation of robust arches at pore entrances; herding instinct scenario (10 mM) where the attraction (in secondary minima) between particles enhances the transport in pores and delays clogging; sacrifice scenario (100 mM) where the capture efficiency is high but the aggregates formed at the wall are fragile. These analyses illustrate the importance of collective behaviour exhibited by interacting particles during fouling. The fouling phenomena by biological particles (bacteria) are analysed in terms of the streamer formation conditions and mechanisms. The streamer formation phenomena are in turn analysed by playing with the cultivation conditions (the carbon to nitrogen ratio in the substrate) in order to study the effect of extracellular polymeric substances (EPS) on the process. The results show that EPS (and hence the bacterial cultivation conditions) play crucial role in streamer formation by microorganisms under flow in constrictions. Furthermore, the presence of non-EPS producing bacterial species along with EPS producing species in a mixed culture enhances the streamer formation. On the other hand, filtration of mixed particles and bacteria suspensions show that the presence of bacteria substantially modifies the clogging dynamics. Microfluidic devices with specific configurations have also been developed for fractionation in order to maximize performances of these processes. The preliminary results with these chips in cross-flow conditions show that it is possible to limit the clogging impact by working below a critical flux; their use for continuous microparticles fractionation could be then considered
Delhaye, Caroline. "Spectroscopie Raman et microfluidique : application à la diffusion Raman exaltée de surface". Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13927/document.
Texto completo da fonteThis thesis focuses on the development of a microfluidic platform coupled with confocal Raman microscopy, used in excitation conditions of Raman scattering (Surface enhanced Raman scattering, SERS) in order to gain in the detection sensitivity of molecular species flowing in channels of micrometer dimensions. This work aims to demonstrate the feasibility of coupling Raman microscopy / microfluidics for the in situ and local characterization of species and reactions taking place in the fluid flowing in microchannels. We used a T-shaped microchannel, made by soft lithography, in which gold or silver nanoparticles injected at constant speed, in one of the two branches of the channel and a solution of pyridine or pefloxacin in the other one. The laminar flow and the stationarity of the process allowed us to map the mixing zone and highlight the enhancement of the Raman signal of pyridine and pefloxacin, due to the metallic nanoparticles, in the interdiffusion zone. The recording of the both absorption band of the silver nanoparticles (plasmon band) and the Raman signal of pefloxacin, flowing in microchannel, allowed us to establish a link between the shape of the metallic nanostructure, and more precisely the silver nanoparticle aggregation state, and the enhancement of the Raman signal of pefloxacin observed. We then changed the channel geometry to introduce an electrolyte solution (NaCl and NaNO3) and locally modify the surface charge of the colloids. We have put in evidence that the change of the silver nanoparticle aggregation state, induced by the controlled addition of electrolyte solutions, could amplify the SERS signal of pefloxacin and thus optimizing the detection in microfluidics. At last, we established second a approach that consists in the metallic structuring of microchannel walls. This has shown that the surface chemical functionalization through organosilanes (APTES) allowed the pasting of the channel with silver nanoparticles, thus amplifying the Raman signal of the species flowing within the same microchannel
Ziane, Nadia. "Outils microfluidiques pour l’exploration de diagrammes de phase : de la pervaporation à la microdialyse". Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0147/document.
Texto completo da fonteThis 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
Vaur, Pauline Magda Marie. "Caractérisation des effets protecteurs du NAD+ et du Nicotinamide Riboside lors de la dégénérescence axonale dans le système nerveux central : Implications dans les processus neurodégénératifs". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066594/document.
Texto completo da fonteSynaptic and axonal degeneration (AxD) are major events in neurodegenerative diseases. Levels of NAD+, an important coenzyme for axonal integrity, are strongly reduced in different degeneration models so enhancing cellular NAD+ is one of the numerous therapeutic strategies against neuronal pathologies. Nicotinamide riboside (NR) is a good NAD+ precursor as it has already been shown to delay AxD in peripheral nervous system (PNS) and extracellular NAD+ conversion to NR was previously described in cell lines and in PNS. During my thesis project, we analyzed the role of NR metabolism to prevent degeneration processes in cortical neurons. Using an excitotoxicity model developed in microfluidic devices, we showed for the first time that both NAD+ and NR delay AxD in cortical neurons, with a more potent effect for NR. We confirm this differential effect in an in vivo ischemic model. Moreover, NR effect is mainly restricted to the axonal compartment and intracellular NAD+ depletion is reverted after NR application, suggesting that axonal integrity is totally dependent on NAD+ local metabolism. Furthermore, in a complete NAD+ depletion paradigm, NAD+ and NR have surprisingly the same strong effect, protecting equally neuronal death and AxD. Examination of the extracellular pathway suggest that NAD+ conversion to NR is limited in excitotoxicity but effective in the NAD+ depletion model. These results reveal that NR and NAD+ metabolism depend on the neurotoxic paradigm. Our results demonstrate that NR has a strong and local neuroprotective effect on AxD in several neurotoxic processes. These findings open new therapeutic strategies to prevent neurodegenerative diseases
Wu, Chang. "Dispositif microfluidique utilisant la technologie d’électromouillage sur isolant dédié à la préparation d’échantillons pour des analyses biologiques : application au suivi en ligne de bioprocédés". Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10173/document.
Texto completo da fonteThis work presents the concept, fabrication technology and characterization of a sample preparation unit using an original approach coupling channel-based continuous and electrowetting-on-dielectric (EWOD)-based digital microfluidics. The major advantage of ‘digital’ is the accurate control of multiple reagents without the need of a complex network of microvalves, while unprocessed and reprocessed ‘continuous’ format is ideal for coupling with upstream and downstream microfluidic devices. We have developed two generations. In our first work, a three layers PSP (Pyrex-Silicon-Pyrex) configuration with hydrophobic liquid-solid interfaces was employed. An original adhesive wafer bonding technique has been optimized that is sufficiently generic to be used in diverse MEMS processes. However, the preliminary characterization results have shown that most real samples used in bioprocessing could not be handled by this first prototype. To address this issue, we have developed a bilayer PS (Pyrex-Silicon) configuration with superhydrophobic liquid-solid interfaces made by chemical nanotexturation of silicon. Thanks to the low contact angle hysteresis of this superhydrophobic surface, the friction resistance and bio-adsorption on the surface were largely reduced allowing transport of real complex liquids. Finally, this prototype has been successfully used for preconditioning samples taken from a yeast bio-reactor and then delivered to analytical modules either an enzyme-linked immunosorbent assay (ELISA) or a capillary electrophoresis (CE) device coupled with a mass spectrometry (MS)
Zhang, Fan. "Intensification du procédé antisolvant supercritique (SAS) par l'usage de microréacteur sous pression". Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0269.
Texto completo da fonteIn the context of this thesis, we propose to study the thermo-hydrodynamic behavior of a mixture, a solvent and a supercritical antisolvent (CO2) in a microfluidic chip, for conditions used in the Supercritical Antisolvent (SAS) process. This work is based on a complementary approach of both experiments and simulations through the use of advanced research techniques, such as the in situ characterization inside the microfluidic reactor (Micro-Particle Image Velocimetry) and the High Performance Computing. The objective of the thesis is to determine the favorable conditions for a "very good" mixture (total and fast) of species in terms of velocity, temperature, pressure and injector "design". The simulations are performed with the massively parallel code Notus. After the first chapter detailing the state of the art on the supercritical antisolvent processes, then the second concerning the applied methodologies (numerical model, microfluidic tools), we first compare the results of the numerical simulations to the experimental data obtained by micro-PIV in laminar flow conditions. The simulation results are in good agreement with the experiments. After the validation of the numerical code, we propose to use the numerical tool to determine the optimal operating conditions of mixing. For this, simulations of the mixture of two fluids (typically CO2 and ethanol) are performed for different operating conditions (velocity, temperature, pressure) for laminar conditions but also for turbulent conditions, a regime rarely reached in microreactors. Indeed, we have shown experimentally that the turbulent mixing could be reached in the microchannel thanks to the "high pressure microfluidic" technology developed in the laboratory. The study of the mixing quality is based on two criteria commonly used in the literature. The first is the segregation intensity based on the variance of the ethanol concentration. This can be estimated for all simulation cases, from laminar to turbulent mixing. The second criterion is the micromixing time related to the turbulent kinetic energy dissipation rate directly estimated from the local velocity fluctuations in turbulent flow conditions. One of the major interests of the use of microfluidic reactors lies especially in its small scales of time and space. From a numerical point of view, such scales allow, within reasonable CPU time, to perform direct numerical simulations (DNS), i.e., in which the grid size is smaller or very close to the Kolmogorov scale. This is of primary interest because we are able to capture the smallest scales of the mixture including the micromixing. Thus, the simulation results allow us to propose a reliable analysis of the mixture from both qualitative and quantitative point of view, proving that the mixing conditions in this type of device are particularly favorable for the material synthesis by supercritical antisolvent. After determining the optimal mixing conditions, we propose in a final part to simulate the synthesis of organic nanoparticles in such devices. The numerical approach is based on the coupling between the CFD code and a population balance equation to take into account the nucleation and growth of particles. The simulation results are also in a good agreement with the experimental measurements performed in the laboratory