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1
Wilking, Connie Chang. "Viral encapsulation of emulsion and nanoemulsion droplets". Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1692370451&sid=4&Fmt=2&clientId=1564&RQT=309&VName=PQD.
Testo completo
2
Sachdev, Suchanuch. "Emulsion droplets as reactors for assembling nanoparticles". Thesis, Loughborough University, 2018. https://dspace.lboro.ac.uk/2134/36206.
Testo completoAbstract (sommario):
Materials on the nanoscale have very interesting properties. Hence, they are commonly used for a variety of applications such as drug delivery, bio-imaging and sensing devices. Moreover, coating these particles with other materials forming core@shell or Janus particles can further enhance their properties. However, for the particles to be used in medical and electronic devices, their properties such as size, shape and composition need to be precisely controlled. In this PhD., an emulsification technique was chosen to investigate the synthesis of nanoparticles; it is a simple process, does not require any harsh chemicals or temperature and is fast. Emulsification occurs when two or more immiscible liquids and surfactants are mixed. Here, emulsion droplets were produced using a microfluidic device which allowed for the creation of uniform droplets. These were employed as templates to synthesise and assemble nanomaterials. The main aim of the Ph.D. was to develop a droplet based synthesis process to generate nanoparticles and then assemble them into core@shell particles. This Ph.D., starts by synthesising Fe3O4 nanoparticles (~ 12 nm) and assembling them into microparticles (~ 1µm 2µm) using emulsion droplets as microreactors. By tuning the surfactant, droplet size and evaporation rate of the dispersed phase, microparticles of varying shapes and sizes, such as spherical or crumbled shapes, were produced. When these particles are compared with the commercially available particles, the magnetic content of the in-house particles, or sometimes referred to as Loughborough University Enterprises Ltd. (LUEL), are much higher and more uniform, hence resulting in faster separation when used for extraction of analytes. LUEL particles were supplied as part of commercial collaboration. The use of Pickering emulsions were then explored to create core@shell particles using gold nanoparticles instead of a surfactant to produce gold shells and the addition of pre-synthesised Fe3O4 nanoparticles results in Fe3O4@Au core@shell particles. This is the first time Pickering emulsions were used to produce Fe3O4@Au core@shell particles (~ 1.5 µm) within a microfluidic device. However, the shells were not uniform in thickness. In order to improve the coverage, nanoparticles were synthesised in situ at the droplet interface. By placing the gold chloride (AuCl4-) in the continuous phase and by varying the concentration of the electron donor in hexane droplet, single crystal gold nanoparticles and platelets were formed. The reaction is spontaneous at room temperature, creating gold nanoparticles at the interface of the emulsion droplet. The size and shape of the gold nanoparticles were controlled by varying the concentration of the reactants and the size of the droplets. By adding pre-synthesised particles (Fe3O4 nanoparticles) to the droplet, Au@Fe3O4 core@shell particles were formed with an approximate size of 250 nm. The same concept of forming core@shell particles using gold nanoparticles was further expanded by using other metal ions; palladium and silver. Unlike gold, palladium and silver only formed spherical nanoparticles, no platelets were observed. The addition of preformed iron oxide nanoparticles to the palladium results in core@shell particles. However, in the case of silver, no core@shell particles were formed. The study of the rate of reaction was conducted to understand the details of the mechanism. Overall, the process developed in this Ph.D. study allows for the facile synthesis of core@shell particles in a rapid, high throughput reaction. In the future, it is believed it could be scaled up for commercial purposes.
3
Patel, Vishal M. "Synthesis of calcium carbonate coated emulsion droplets for drug detoxification". [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE1001175.
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4
Pangu, Gautam D. "ACOUSTICALLY AIDED COALESCENCE OF DROPLETS IN AQUEOUS EMULSIONS". Case Western Reserve University School of Graduate Studies / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=case1138379076.
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5
Nagelberg, Sara(Sara Nicole). "Dynamic and stimuli-responsive multi-phase emulsion droplets for optical components". Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127708.
Testo completoAbstract (sommario):
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2020
Cataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages 136-143).
Dynamic micro-optical components have revolutionized imaging, sensing, and display technologies. Multi-phase emulsions are micro-scale droplets formed from multiple immiscible material components suspended in a fluid medium. An interesting aspect of these droplets is that by tailoring the chemistry of the surrounding medium it is possible to control the droplet morphology or to render the droplets responsive to stimuli in the environment, including light, heat, specific molecules, or even bacteria. This thesis explores the optical characteristics of multi-phase droplets, including their refractive, emissive, and reflective properties. This work focuses predominantly on bi-phase droplets formed from two immiscible oils in water, which form double emulsions or Janus droplets. As tunable refractive components, these droplets form dynamic compound micro-lenses with adjustable focal length that is continuously variable from converging lenses to diverging lenses.
Macroscopically these refractive droplets can appear nearly transparent or strongly scattering, depending on their configurations. When a fluorescent dye is dispersed within the higher refractive index phase, a portion of the light emitted will undergo total internal reflection. This results in a strong morphology-dependent angular emission profile, which can be used in molecular sensing for chemicals or pathogens. In reflection, the droplets produce striking iridescent colors. This is due to the interference light being totally internally reflected at the internal interface along distinct optical paths, leading to color. These optical characteristics are analyzed both experimentally and theoretically. Finite Difference Time Domain simulations were used to model wave-optical effects and phenomena that could be treated using geometrical optics were calculated using a custom-built ray tracing algorithm.
Additionally, a theoretical model was developed to explain the iridescent colors, under a geometric approximation that takes into account interference effects. Experimentally the droplets were characterized using several different custom-built microscope setups. Beyond the optical characteristics, we used these setups to investigate the effects of thermal Marangoni flows within the droplets, which cause the droplets to re-orient towards a heat source. This work sets the foundation of understanding the refractive, reflective, and emissive properties of multi-phase droplets, which could form the basis of dynamically controllable or stimuli-responsive micro-scale optical components.
by Sara Nagelberg.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering
6
Wang, Yiwei. "Coalescence and disproportionation of air bubbles stabilized by proteins and emulsion droplets". Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496337.
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Lange, Tobias. "Precipitation in confined droplets - development of microfluidic and imogolite Pickering emulsion approaches". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLV069.
Testo completoAbstract (sommario):
Dans de nombreux secteurs industriels tels que la production de pigments, de catalyseurs, de produits pharmaceutiques, de minerais ou le recyclage de combustibles nucléaire, les étapes de précipitation et de cristallisation sont cruciales. Bien que ces procédés soient utilisés à grandes échelles avec un contrôle relatif des solides formés, les mécanismes de formation ne sont pas toujours bien compris, en particulier à l’échelle microscopique. Une meilleure compréhension des différentes étapes de formation permettrait d’obtenir des leviers de contrôle adapté à chaque composé et application.Cette thèse se place dans ce cadre très général du contrôle de la précipitation et plus particulièrement de la précipitation en gouttes d’emulsion eau dans l’huile. Deux approches différentes ont été explorées pour moduler et suivre la réactivité dans une goutte d’emulsion. La première approche était basée sur le couplage d’une puce microfluidique générateur de gouttes avec la diffusion de rayons X aux petits angles (SAXS) in situ. Après une caractérisation complète de la compatibilité du polymère non stoechiometrique thiol-ene-epoxy (OSTE+) avec le SAXS, une puce en OSTE+ compatible avec le suivi in situ SAXS a été développée. Un traitement original permettant d’extraire séparément le signal des gouttes du signal de l’huile a permis de valider le montage dans le cas de la précipitation d’oxalate de cerium. La deuxième approche avait pour but l’utilisation de nanotubes d’imogolites pour stabiliser des gouttes d’émulsion et étudier le transport de réactifs entre gouttes via ces nanotubes. Cette approche nécessitait de fonctionnaliser les nanotubes pour les rendre hydrophobe. La caractérisation poussée de la fonctionnalisation des imogolites par des alkylphosphoniques a montré pour la première fois que cette réaction ne conduisait pas à une fonctionnalisation de surface mais à un matériau composite aux propriétés interfaciales remarquables. De nouvelles voies de fonctionnalisation de surface ont été développées pour rendre les imogolites hydrophobesIn the industrial production of pigments, catalysts, plant protection agents, nuclear fuel and pharmaceuticals precipitation and crystallization plays a fundamental role. Although these processes are often applied and a relative control over the formed solids can be achieved, the processes are not always well understood on a microscopic level. To identify how the solids are formed and which mechanisms govern their formation potentially gives the capabilities to better control such processes.In this thesis two different approaches are explored to study precipitation and crystallization by confining reactions into droplets. The first approach focuses on the combination of a droplet microfluidic device and in-situ small angle X-ray scattering. Off-stochiomestry thiol-ene-epoxy polymer is characterized for the use with in-situ X-ray scattering and a protocol is presented to prepare suitable microfluidic devices from this material. An original approach to isolate the scattering signal of the carrier phase and the droplets is then used to study the precipitation of cerium oxalate in droplets. The second approach aims to use imogolite nanotubes to stabilize droplets against coalescence and to study their transport properties to control reactant feeding into droplets. By fully characterizing the necessary surface modification by alkylphosphonic acids for the first time, evidence is found that the reaction does not yield surface modified tubes. Consequentially, new approaches are explored to obtain individually dispersed imogolite nanotubes with a hydrophobic surface
8
Lattin, James R. "Ultrasound-Induced Phase Change of Emulsion Droplets for Targeted Gene and Drug Delivery". BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3377.
Testo completoAbstract (sommario):
This dissertation explores the potential of using perfluorocarbon emulsion droplets to add an ultrasound-sensitive element to drug delivery systems. These emulsion droplets may be induced to vaporize with ultrasound; during the rarefactional phase of an ultrasound wave, the pressure around the droplets may fall below the vapor pressure of the liquid forming the emulsion, providing a thermodynamic potential for vaporization. This ultrasound-induced phase change of the emulsion droplet could release therapeutics attached to the droplet surface or aid in drug delivery due to mechanical effects associated with vaporization and expansion, similar to the ability of cavitating bubbles to aid in drug delivery. In contrast to bubbles, stable emulsions can be formed at nano-scale sizes, allowing them to extravasate into tissues and potentially be endocytosed into cells. Perfluorohexane and perfluoropentane were selected to form the emulsions due to their relatively high vapor pressure, low water solubility, and biocompatibility. Acoustic droplet vaporization was explored for its potential to increase ultrasound-induced drug release from liposomes. Liposomes have proven to be versatile and effective drug carriers, but are not inherently responsive to ultrasound. eLiposomes, defined as a liposome with encapsulated emulsion droplets, were developed due to the potential of the expanding vapor phase to disrupt bilayer membranes. The resulting vesicle retains the advantages of liposomes for drug delivery, while adding an ultrasound-sensitive element. eLiposomes were loaded with calcein, a fluorescent molecule, as a model drug in order to quantify ultrasound-mediated drug release compared to release from conventional liposomes. Upon exposure to ultrasound, eLiposomes typically released 3 to 5 times as much of the encapsulated load compared to conventional liposomes, with some eLiposome samples approaching 100% release. Emulsion droplets were also added to the outside of conventional liposomes, but resulted in little to no increase compared to control samples without emulsions. Lastly, in vitro experiments were performed with HeLa cells to explore the ability of emulsion droplets and eLiposomes to deliver calcein inside of cells. Calcein delivery to the cytosol was accomplished, and the emulsion-containing samples demonstrated the ability to aid in endosomal escape.
9
Hart, Helen Mary. "A study of the interaction between oil-in-water emulsion droplets and polymer particles". Thesis, University of Bristol, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296451.
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10
Lacava, Johann Verfasser], e Eduard [Akademischer Betreuer] [Arzt. "Assembly of gold nanoparticles into regular clusters inside emulsion droplets / Johann Lacava. Betreuer: Eduard Arzt". Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2015. http://d-nb.info/1064868533/34.
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Schmitt, Maximilian [Verfasser], Holger [Akademischer Betreuer] Stark e Uwe [Gutachter] Thiele. "Active emulsion droplets driven by Marangoni flow / Maximilian Schmitt ; Gutachter: Uwe Thiele ; Betreuer: Holger Stark". Berlin : Technische Universität Berlin, 2017. http://d-nb.info/1156010268/34.
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Accurso, Charity Einhaus. "Fibrinogen-Coated Droplets of Olive Oil for the Targeted Delivery of Docetaxel to Fibrin(ogen)-Rich Tumors: Evaluation of Efficacy and Mechanism". Cincinnati, Ohio : University of Cincinnati, 2004. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1078283884.
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13
Ben, M'Barek Kalthoum. "Adhésion et phagocytose de gouttes d'émulsions fonctionnalisées". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066034/document.
Testo completoAbstract (sommario):
La phagocytose par les macrophages est un processus biologique essentiel au système immunitaire et joue un rôle clé dans le maintien de l’homéostasie cellulaire. Les cibles à éliminer varient en terme de tailles, des bactéries (µm) aux cellules cancéreuses ou senescentes (10 – 20 µm). La plupart des études quantitatives sur la phagocytose reposent sur l'utilisation de microparticules de polymère rigides en tant que cibles modèles pour la compréhension des paramètres qui régissent ce processus. Cependant, ces particules ne rendent pas compte de la mobilité latérale des ligands à leur surface malgré la pertinence de ce paramètre dans le contexte immunologique. Cette étude a pour but de synthétiser un matériau biomimétique qui constitue un nouveau système modèle pour l’étude de la phagocytose. Il s’agit de gouttes d’émulsions monodisperses fonctionnalisées avec des IgGs libres de diffuser sur toute la surface. Dans le cadre de cette thèse, nous avons obtenu différentes densités contrôlées de fonctionnalisation, caractérisées de façon quantitative. Ainsi, il nous a été possible de déterminer une densité minimale d’IgGs nécessaire à induire une internalisation efficace des gouttes. Pour des densités supérieures d’IgGs, ces gouttes sont efficacement et spécifiquement internalisées par phagocytose induite par les récepteurs FcR in vitro. Nous avons plus précisément cherché à approfondir la compréhension de certains aspects mécaniques. Nous montrons que, contrairement à des billes de polymères solides, l’internalisation des gouttes est efficace même pour de faibles densités d’IgGs. La phagocytose s’accompagne, pendant la phase d’adhésion à la surface du macrophage, d’une mobilité latérale des ligands en zone de contact. Il apparaît donc que la mobilité latérale des protéines à l'interface d'une cible améliore considérablement sa phagocytose par les macrophages. Ainsi, ces gouttes permettrons d’aborder de nouvelles questions biologiques pour approfondir certaines mécanismes moléculaires et/ou mécaniquesPhagocytosis by macrophages represents a fundamental process essential for both immunity and tissue homeostasis. The size of targets to be eliminated ranges from small particles as bacteria to large objects as cancerous or senescent cells. Most of our current quantitative knowledge on phagocytosis is based on the use of solid polymer microparticles as model targets that are well adapted to the study of phagocytosis mechanisms that do not involve any lateral mobility of the ligands, despite the relevance of this parameter in the immunological context. The aim of this study is to synthesize a biomimetic material that constitutes a new model system for the study of phagocytosis. We designed monodisperse, lateraly mobile IgG-coated emulsion droplets, with different controlled densities of IgGs, that are efficiently and specifically internalized by macrophages through in-vitro FcγR-mediated phagocytosis. The excellent control of the opsonization density allowed us to measure the minimal IgGs density required to induce an efficient internalization. We also attempted to deepen the understanding of certain mechanical aspects. We show that, contrary to solid polymeric beads, droplet uptake is high even for low IgG densities and is accompagnied by the clustering of the opsonins in the zone of contact with the macrophage during the adhesion step. Beyond the sole interest in the design of the material, our results suggest that lateral mobility of proteins at the interface of a target greatly enhances the phagocytic uptake. Thus, emulsion droplets constitute a new interesting target to investigate different biological issues and understand molecular and/or mechanical mechansims
14
Zhuang, Jianqin, e Ruediger Voelkel. "Emulsion droplet size distribution by PFG NMR: high concentrations, small radii, and suspo-emulsions". Diffusion fundamentals 3 (2005) 37, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14327.
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Lignel, Sarah. "Emulsions eau-dans-huile générées par un procédé microfluidique : contribution à l'étude de la congélation de l'eau dispersée en émulsion". Thesis, Compiègne, 2014. http://www.theses.fr/2014COMP2143/document.
Testo completoAbstract (sommario):
Ces travaux entrent dans la cadre du projet européen Fundamental and Applied Studies on Emulsion Stability (FASES). L'objectif de ce projet est de comprendre les phénomènes responsables de la déstabilisation des émulsions dans le temps, en relation avec les propriétés interfaciales de ces systèmes. Les travaux de thèse décrits dans ce mémoire se divisent en deux parties : ils portent tout d'abord sur la fabrication de gouttes d'émulsions eau-dans-huile par un procédé microfluidique, puis sur l'étude de la taille et de l'état de dispersion des gouttes sur la cristallisation de l'eau dispersée. Dans un premier temps, nous avons étudié les conditions opératoires permettant de fabriquer des gouttes de taille contrôlée par microfluidique avec le système de fluides mis en œuvre dans le projet FASES. Suivant le mode d'introduction des phases liquides, soit les débits, soit les pressions appliquées, ont été modifiés pour délimiter les zones de fabrication des gouttes. Afin de mieux comprendre les différences observées entre les deux modes d'introduction des fluides, un modèle reposant sur l'analogie entre circuits électriques et circuits microfluidiques a été proposé. Dans un second temps, les émulsions obtenues avec le dispositif microfluidique ont été analysées par calorimétrie et par thermo-microscopie. Les expériences ont permis de mettre en évidence, suivant les conditions étudiées (viscosité, taille des gouttes), différents processus de cristallisation des gouttes. Ces résultats mettent en avant directement le rôle du phénomène de sédimentation, les signaux de congélation observés dépendant fortement de l'état de dispersion des gouttes d'émulsionThis thesis takes place in the framework of the European project FASES (Fundamentaland Applied Studies on Emulsion Stability). The aim of this project is to understand the phenomena responsible for emulsions destabilization, in relation with the interfacial properties of these systems. The research work described in this thesis is divided into twoparts : the first part deals with the creation of water-in-oil emulsion droplets in a microfluidic device, and in the second part, the influence of the size and the state of dispersion of the droplets on the crystallization of dispersed water is analyzed.To begin with, the operating conditions required to create emulsion droplets by microfluidic were studied. Two modes of introduction of the liquid phases, based on flow and pressure-driven techniques, were used to create the droplets. Maps of the droplet formation regions were drawn as a function of the applied flow rates and pressures. In order to compare the two processes, a model based on the analogy between electrical and microfluidic circuits was proposed.Then, emulsions obtained with the microfluidic device were analyzed by calorimetry and thermo-microscopy. The experimental results evidenced different droplet crystallization processes, depending on the system parameters (oil phase viscosity, droplet size …). The water freezing signals strongly depend on the state of dispersion of the droplets, showing themajor role of droplet sedimentation in the emulsion destabilization process
16
Meng, Kejie. "MECHANISTIC STUDIES OF PROTON-COUPLED ELECTRON TRANSFER REACTIONS INVOLVING ANTIOXIDANTS". VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5498.
Testo completoAbstract (sommario):
The objective of the research was to investigate proton-coupled electron transfer (PCET) reactions involving antioxidants to gain insight into the detailed mechanisms of glutathione (GSH), Trolox, and α-tocopherol (α-TOH). PCET reactions are complex redox reactions that transfer electrons and protons sequentially or in concert. These reactions are ubiquitous in natural or artificial processes that produce electrochemical energy that is extractable as electricity or as chemical fuels of high energy content. Examples of processes based on PCET are photosynthesis, respiration, nitrogen fixation, carbon dioxide reduction, redox fuel cells, and artificial photosynthesis. Antioxidants were selected as a PCET model to understand the coupling between proton transfer (PT) and electron transfer (ET) in order to elucidate structure-reactivity relationships under different experimental conditions. PCET reactions were studied with a set of electrochemical techniques to propose a preliminary mechanism that could be validated with digital simulations matching the electrochemical response. In some cases, other analytical techniques were used to aid in the system characterization. This thesis presents the results and discussion of the effects of oxidant-base pairs on the mediated oxidation of GSH, the -2e-/-H+ process of Trolox in aqueous and nonaqueous solvents with various pH values, and the particle collision electrolysis of α-tocopherol in oil-in-water emulsion droplets on an ultramicroelectrode. Ultimately our goal was to determine the kinetic and thermodynamic factors that control PCET reactions so that they can be applied in designing artificial systems for the production of energy using more abundant reagents with lower cost and better yields.
17
Zhuang, Jianqin, e Ruediger Voelkel. "Emulsion droplet size distribution by PFG NMR". Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-195027.
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Bauer, Wolfgang-Andreas Christian. "Complex emulsion systems via droplet-based microfluidics". Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610619.
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19
Chang, Emily P. "Controlled emulsion droplet solvent evaporation for particle production". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/81748.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
In this work, we are motivated by the need to produce particles of well-controlled size, shape and morphology for general application in catalysis, environmental remediation, nanomedicine, pharmaceuticals, the development of new materials, and other fields. Moreover, our approaches are guided by the desire for continuous and scalable production, in contrast to the batch-wise processes typically used. We employ the emulsion droplet solvent evaporation method, which is extremely versatile, to create, for example, magnetic nanoparticles, polymeric Janus beads, and crystalline particles. The emulsion droplets act as confined spaces, or templates, within which the particles can form. Upon removal of the solvent, primary magnetite nanoparticles pack into dense magnetic clusters, polymers precipitate as beads, or small molecules crystallize out of the solution to form spherical particulates. The thesis is comprised of experimental, theoretical and computational work that discusses the control of polymeric Janus bead morphology; demonstrates the potential of various operations for integration into large-scale manufacturing systems for monodisperse particle production; and offers insight into solvent and particle diffusion during the solvent evaporation process. The formation of Janus beads by solvent evaporation-induced phase separation of polymer blends is studied using a model system of polystyrene (PS), poly(propylene carbonate) (PPC) and chloroform. The phase separation of the polymer solutions in the bulk is analyzed and a phase diagram is constructed. PS/PPC Janus beads of varying composition are synthesized and we demonstrate the ability to tune the morphology by varying the type and concentration of the surfactant. Thermodynamic models that describe the particle morphologies as functions of the interfacial tensions are discussed. The remainder of the thesis focuses on the development and characterization of continuous, high-throughput synthesis methods for functional particles based on solvent evaporation techniques. We introduce membrane emulsification and pervaporation as operations that have the potential to be integrated into such a process. We develop a population balance model to describe the transport of solvent from nanocrystal- or polymer-laden droplets in an emulsion as it flows through a pervaporation unit. The solvent transport is simulated using a high-resolution finite volume algorithm, which affords a smooth solution with second-order accuracy. The simulations provide information regarding the evolution of the particle size distributions and the diffusional behavior of the droplets. Furthermore, the required fiber length to remove the solvent completely from an emulsion can be determined in terms of natural dimensionless constants that arise from the structure of the model equations, making the model useful as a design tool. For systems with a high Biot number, we show that a lumped capacitance assumption, which greatly simplifies the model and reduces the computational requirement, is valid. Finally, we investigate the evaporative crystallization of glycine and alanine, and the clustering of magnetite nanocrystals, in emulsion films flowing down an inclined plane. The temperature and the solvent evaporation configuration are shown to have a significant effect on the transport behavior of the solvent and droplets. The potential of the inclined plane system in particle production is established, and the flow of emulsion droplets of different sizes is studied, using an experimental test apparatus.
by Emily P. Chang.
Ph.D.
20
Mehrotra, Rajat. "Monodispersed polygonal water droplets in microchannel". [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2726.
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Sinker, Alastair Brenton. "An experimental study droplet stability and separation performance in dewatering hydrocyclones". Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387899.
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Chacon, Orellana Laura A. "Fluorinated pickering emulsions for droplet-based microfluidics technology". Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0121/document.
Testo completoAbstract (sommario):
Les émulsions fluorées de Pickering sont étudiées et mises au point dans la technologie demicrofluidique en gouttes pour des applications d’études sur des cellules adhérentes isolées.Les principaux résultats de ce projet sont : l’établissement d’un lien entre la couverture desurface des nanoparticules et la fluidité de l’émulsion de Pickering ; l’établissement deslignes directrices pour la stabilisation des gouttes avec un débit de production élevé et unminimum de déchets de particules ; et la mise en oeuvre d’une plateforme technologiquecomplète pour l’étude des cellules RPE, pour mesurer leur hétérogénéité phénotypique auniveau de la cellule individuelleFluorinated Pickering emulsions are studied and engineered within droplet-based microfluidicstechnology for adherent-cell studies applications. The main findings of this projectinclude: linking the nanoparticles surface coverage to the bulk flowability of the Pickeringemulsion; deriving guidelines for droplet stabilization with high production throughput andminimal particle waste; and implementing the full technological platform for the study ofRPE cells, while unraveling their phenotypic heterogeneity at the single cell level
23
Maltas, Stephen K. "Microfluidic emulsion characterization for the development of armored droplet arrays". Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35060.
Testo completoAbstract (sommario):
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.Includes bibliographical references (p. 41-42).
An experimental study was performed to determine the best method for using a flow-focusing device to produce monodisperse water droplets in a polymer flow with sufficient spacing to polymerize a protective shell around the droplets using continuous flow lithography. Contact angle measurements and surface tension measurements were used to determine how wettable the polymer is with respect to water and PDMS. Polymerization reaction kinetics tests were used to determine a suitable polymer for the system. The droplet size and spacing for different flow-focusing devices with different dimensions were characterized to determine the best dimensions. Finally, characterization tests for various polymer and water flow rates were performed to examine the droplet size, spacing, velocity and frequency of production, as well as the fluctuations and instabilities in the system. From these characterization tests it was determined that the best flow systems for armoring droplets arise when the water flow rate is greater than 0.05pL/min, the polymer flow rate is between 0.4 and 1.2pL/min and the flow-rate ration of water to polymer is less than 1:10.
by Stephen K. Maltas.
S.B.
24
Al-Mulla, Adam. "Droplet coalescence in the shear flow of model emulsions". Morgantown, W. Va. : [West Virginia University Libraries], 1998. http://etd.wvu.edu/templates/showETD.cfm?recnum=384.
Testo completoAbstract (sommario):
Thesis (M.S.)--West Virginia University, 1998.Title from document title page. Document formatted into pages; contains xxi, 153 p. : ill. Includes abstract. Includes bibliographical references (p. 68-72).
25
Manica, Rogério. "Modelling hydrodynamic interactions between deformable droplets /". Connect to thesis, 2007. http://eprints.unimelb.edu.au/archive/00003700.
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Wehking, Jonathan. "Electrohydrodynamic Manipulation of Liquid Droplet Emulsions in a Microfluidic Channel". Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6034.
Testo completoAbstract (sommario):
This work specifically aims to provide a fundamental framework, with some experimental validation, for understanding droplet emulsion dynamics in a microfluidic channel with an applied electric field. Electrification of fluids can result in several different modes of electrohydrodynamics (EHD). Several studies to date have provided theoretical, experimental, and numerical results for stationary droplet deformations and some flowing droplet configurations, but none have reported a method by which droplets of different diameters can be separated, binned and routed through the use of electric fields. It is therefore the goal of this work to fill that void and report a comprehensive understanding of how the electric field can affect flowing droplet dynamics.
This work deals with two primary models used in electrohydrodynamics: the leaky dielectric model and the perfect dielectric model. The perfect dielectric model assumes that fluids with low conductivities do not react to any effects from the small amount of free charge they contain, and can be assumed as dielectrics, or electrical insulators. The leaky dielectric model suggests that even though the free charge is minimal in fluids with low conductivities, it is still is enough to affect droplet deformations. Finite element numerical results of stationary droplet deformations, implemented using the level set method, compare well both qualitatively (prolate/oblate and vortex directions), and quantitatively with results published by other researchers. Errors of less than 7.5% are found when comparing three-dimensional (3D) numerical results of this study to results predicted by the 3D leaky dielectric model, for a stationary high conductivity drop suspended in a slightly lower conductivity suspending medium. Droplet formations in a T-junction with no applied electric field are adequately predicted numerically using the level set finite element technique, as demonstrated by other researchers and verified in this study. For 3D models, droplet size is within 6%, and droplet production frequency is within 2.4% of experimental values found in the microfluidic T-junction device. In order to reduce computational complexity, a larger scale model was solved first to obtain electrical potential distributions localized at the channel walls for the electrode placement configurations.
Droplet deceleration and pinning is demonstrated, both experimentally and numerically, by applying steep gradients of electrical potential to the microchannel walls. As droplets flow over these electrical potential ``steps," they are pinned to the channel walls if the resulting electric forces are large enough to overcome the hydrodynamic forces. A balance between four dimensionless force ratios, the electric Euler number (Eu_e - ratio of inertial to electric forces), Mason number (Ma - ratio of viscous to electric forces), electric pressure (Ps - ratio of upstream pressure forces to electric forces), and the electric capillary number (Ca_e - ratio of electric to capillary forces) are used to quantify the magnitudes of each of these forces required to pin a droplet, and is consistent with a cubic dependency on the drop diameter. For larger drop diameters, effects of hydrodynamic forces become more prominent, and for smaller droplets, a greater electric forces is required due to the proximity of the droplet boundary with reference to the electrified channel wall. Droplet deceleration and pinning can be exploited to route droplets into different branches of a microfluidic T-junction. In addition, using steep electrical potential gradients placed strategically along a microchannel, droplets can even be passively binned by size into separate branches of the microfluidic device. These characteristics have been identified and demonstrated in this work.Ph.D.
Doctorate
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering
27
Shastry, Vineet. "Identification Of The Nucleation Locus In Emulsion Polymerization Processes". [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000221.
Testo completo
28
Aubrecht, Donald Michael. "Droplet Microfluidics: Tools for Screening and Sorting Applications". Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11069.
Testo completoAbstract (sommario):
Microfluidic droplets are a powerful tool for screening large populations of cells, molecules, and biochemical reactions. Droplet systems are able to encapsulate, incubate, screen, and sort millions of samples, providing access to large number statistics that make searching for rare events feasible. Initial development of the microfluidic devices and methods has attracted applications in biology, biochemistry, and material science, but the set of tools remains incomplete. Efforts are required to develop micro-scale droplet analogs for all bulk-scale bench top procedures and instruments. The droplet analogs must be versatile, robust, and process samples rapidly.Engineering and Applied Sciences
29
Pedersen, Arne Halvor Thingstad. "Producing tubes of a droplet in an emulsion with surface particles at the interface". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26371.
Testo completoAbstract (sommario):
The aim of the work done in connection to this thesis was to find different methods with which long tubes of one liquid suspended in another can be made (an emulsion). Various liquids (silicone oil, castor oil, diethyl-phtalate, water, and a mixture of water and glycerol) as well as different types of surface particles were used in the hope of making tubes. When good results were obtained, the length l was measured and the aspect ratio a=l/d (l=the length of the tube, d=the diameter of the tube) calculated, so that it was possible to compare the results. Eight different methods were applied, through which different factors influencing the lengths and ratios of the tubes were discovered.After withdrawing some of the fluid from a droplet, which was then covered by buckles of particles, an electric field could be applied onto the system causing a deformation of the droplet or pipette tips could be moved manually alongside the droplet, allowing the surrounding fluid to deform it. At high field strengths, Quincke rotations occurred which made the process unpredictable. Nevertheless, satisfactory results were obtained. A third method was used, in which two droplets were coalesced into one and then deformed by an electric field or pipette tips, without any further success.The method yielding the best results in this thesis was the one including an object, of a known diameter and volume, sinking through a particle layer situated at the interface of two liquids which are placed directly on top of each other. Factors that were found to be crucial to obtaining the longest tubes were the diameter of the surface particles, the friction between the object and the fluids and particles, and the relationship between the horizontal cross-sectional areas of the object and the container.Four other methods were tried as well. Objects of different materials were used to pull at a particle layer situated at the interface of two liquids, yielding some interesting results. Also, a pipette was moved vertically upwards whilst releasing a liquid into another liquid, with a couple of interesting consequences. Another method included the ejection of a jet of a liquid containing particles from a pipette into another liquid, without any further success. In the last method, the idea was to pour a liquid onto another, the latter covered by a layer of particles at its surface. This gave some discouraging results. In future experiments with the last four methods, the densities of liquids in an emulsion should be matched, as long as the properties of the system do not change notably, and the surface tensions of the liquids should be paid closer attention to. Furthermore, the concentration and the type of particles are important. In the method of pulling at a particle layer, the material, and hence the friction caused, of the pulling object might matter.
30
Abramov, Serghei [Verfasser]. "Crystallization in emulsions: Influence of formulation and process parameters on solidification in droplets / Serghei Abramov". München : Verlag Dr. Hut, 2018. http://d-nb.info/1162767901/34.
Testo completo
31
Debas, Hélène. "Émulsification en systèmes microstructurés". Thesis, Vandoeuvre-les-Nancy, INPL, 2009. http://www.theses.fr/2009INPL075N/document.
Testo completoAbstract (sommario):
Cette thèse, intitulée « Emulsification en systèmes microstructurés », s’inscrit au sein de la tâche « Emulsification contrôlée » du projet européen IMPULSE. Deux micromélangeurs en acier inoxydable, un V-type et un Caterpillar, ont été testés en utilisant un pilote d’émulsification continue. Ces dispositifs conçus en acier inoxydable et fonctionnant comme des boîtes noires, des micromélangeurs transparents ont ensuite été utilisés afin de comprendre leurs mécanismes d’émulsification. Les paramètres-clés intervenant dans la formation de gouttes à un orifice à l’échelle macroscopique ont dans un premier temps été identifiés. A l’échelle microscopique, la formation des gouttelettes dans le micromélangeur V-type est issue de la mise en contact des jets des phases aqueuse et organique formés à la sortie de ce dispositif et d’un phénomène élongationnel avec des instabilités interfaciales. Dans le cas du Caterpillar, la taille des gouttelettes dépend de la géométrie interne des éléments en série de ce micromélangeur. La formation des gouttelettes est issue d’un phénomène de cisaillement au niveau de la jonction en Y. La réduction de la taille de ces gouttelettes est ensuite due à leur passage dans les éléments de mélange. L’utilisation de micromélangeurs transparents a, quant à elle, permis de caractériser davantage ces deux micromélangeurs par micro-PIV et caméra rapide. Enfin, une dépendance du diamètre des gouttelettes par rapport à l’énergie dissipée est constatée pour le Caterpillar mais par pour le V-type. L’énergie dissipée dans ces deux micromélangeurs semble être moindre et les émulsions formées de meilleure qualité par rapport aux procédés classiques d’émulsificationThis thesis, entitled “Emulsification in micromixers” was carried out within the framework of the Task “Controlled Emulsification” of the European IMPULSE project. Two micromixers in stainless steel, the V-type and the Caterpillar, were tested in an experimental setup. These microdevices working as black boxes, transparent micromixers were used after to gain insight into the fundamental mechanisms for emulsification. Firstly, the key parameters enabling the drop formation at macroscopic scale were identified. At microscopic scale, the droplet formation in the V-type micromixer results from the contact of aqueous and organic phases jets at the outlet of the microdevice and from elongational phenomena with interfacial instabilities. In the case of the Caterpillar, the droplets size depends on the internal geometry of the microdevice. The droplet formation can be mainly attributed to the shearing phenomena at the Y-junction. The decrease of the droplets’ size is then due to their passage through the mixing elements in series in the outlet channel. Moreover, the use of transparent micromixers allows to characterize these two micromixers by the micro-PIV and high speed camera. A straightforward relationship between the energy dissipation and the size of droplets was established for the Caterpillar, but not for the V-type. Moreover, the energy dissipation within these two micromixers is lower and the emulsions obtained having a more satisfactory quality than in the case of the classical emulsification processes
32
Almutairi, Saleh Haif. "Effect of droplet size on the behavior and characteristics of emulsified acid". Texas A&M University, 2008. http://hdl.handle.net/1969.1/85947.
Testo completoAbstract (sommario):
Emulsified acids have been extensively used in the oil industry since 1933. Most
of the available research and publications discussed mainly the application of emulsified
acid in the field. A fair number of the published work also discussed in depth some of
the emulsified acid properties such viscosity, stability and reactivity. However, all of the
available research discussed the emulsified acid without sufficient details of its
preparation.
Beside their chemical composition, the ways emulsified acids are prepared cause
significant differences in their physical properties. The characterization of emulsified
acid by its droplet size and size distribution complements its chemical composition and
gives the emulsified acid a unique description and thus reproducible properties. No
previous study considered the impact of the droplet size on the characteristics and
properties of emulsified acid. Therefore, the main objective of this research is to study the effects of the droplet size on various properties of emulsified acid such as viscosity,
stability and reactivity.
Results showed that the droplet size and size distribution have a strong effect on
the stability, viscosity and diffusion rate of the emulsified acid. The results of this work
are important because knowledge of the effect of the droplet size on major design
parameters will guide the way emulsified acid is prepared and applied in the field.
33
Opedal, Nils van der Tuuk, Geir Sørland e Johan Sjöblom. "Methods for droplet size distribution determination of water-inoil emulsions using low-field NMR". Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-192826.
Testo completoAbstract (sommario):
A method using Pulsed Field Gradient Nuclear Magnetic Resonance PFG-NMR for water-incrude oil emulsion droplet size determination has been optimized and compared with optical microscope for validation. The method applies a combination of Pulsed-Field Gradient
(PFG) NMR, Stimulated Echo (STE), and Carr-Purcell-Meimboom-Gill (CPMG) sequences for measuring diffusion, resolving oil and water signal and for measuring the attenuation due to a distribution in T2 values. This returns the droplet size distributions of water-in-oil emulsions within a minute. No prior assumption is made on the shape of the droplet size distribution, which enables the method to resolve for instance bimodal distributions. To validate this method, three different crude oils were used in the experiment.
The emulsions prepared had water cuts from 10 to 40 %. The correlation between PFG-NMR and optical microscopy was good for the emulsions. Any potential discrepancies between the two techniques are discussed, so are the limitations and advantages of the methods.
34
Opedal, Nils van der Tuuk, Geir Sørland e Johan Sjöblom. "Methods for droplet size distribution determination of water-inoil emulsions using low-field NMR". Diffusion fundamentals 9 (2009) 7, S. 1-29, 2009. https://ul.qucosa.de/id/qucosa%3A14145.
Testo completoAbstract (sommario):
A method using Pulsed Field Gradient Nuclear Magnetic Resonance PFG-NMR for water-incrude oil emulsion droplet size determination has been optimized and compared with optical microscope for validation. The method applies a combination of Pulsed-Field Gradient
(PFG) NMR, Stimulated Echo (STE), and Carr-Purcell-Meimboom-Gill (CPMG) sequences for measuring diffusion, resolving oil and water signal and for measuring the attenuation due to a distribution in T2 values. This returns the droplet size distributions of water-in-oil emulsions within a minute. No prior assumption is made on the shape of the droplet size distribution, which enables the method to resolve for instance bimodal distributions. To validate this method, three different crude oils were used in the experiment.
The emulsions prepared had water cuts from 10 to 40 %. The correlation between PFG-NMR and optical microscopy was good for the emulsions. Any potential discrepancies between the two techniques are discussed, so are the limitations and advantages of the methods.
35
Torbensen, Kristian. "Physico-Chemical and Microfluidic Approaches Toward Engineering Oscillating and Communicating Chemical Droplets". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066707/document.
Testo completoAbstract (sommario):
La génération, propagation et la réception d’informations (bio/chimiques) entre les organismes individuels sont la clé de voûte de nombreux systèmes communicants intelligents et sont omniprésents dans la nature. Les colonies de lucioles synchronisent leurs flashs, et la contraction et l’expansion des muscles cardiaques sont quelques exemples parmi d’autres, où les signaux bio / chimiques générés par des sources synchronisées produisent un comportement coopératif. L’objectif final de cette thèse est de développer une plateforme fiable pour générer des réseaux de communication de liposomes, en encapsulant la réaction de Belousov-Zhabotinsky (BZ) en tant que source d’information ou un signal transmis, et d’étudier la dynamique d’un tel système. Pour atteindre cet objectif, plusieurs questions ont été abordées par une approche “bottom-up” et multi-échelle. Tout d’abord, nous avons étudié l’interaction entre des liposomes de DMPC dopés et non-dopés avec le cholestérol, l’acide myristique, tétradécylsulfate, tétradécylamine, et les espèces impliquées dans la reaction BZ en utilisant la diffusion de rayons X aux petits angles et par spectrophotométrie UV-visible. Des rangées 1D de micro-gouttelettes ont été fabriquées en encapsulant la réaction BZ en microgouttelettes au moyen de la microfluidique et la communication entre les gouttelettes adjacentes a été étudiée. Plus tard, nous avons démontré un système microfluidique facile à monter / démonter avec une conception robuste et une géométrie modulable pour générer des emulsions doubles d’eau dans l’huile dans l’eau (E/ H / O). Enfin, le comportement de ces doubles emulsions générées dans système microfluidique en utilisant des phosphoplipides comme tensioactif et du chloroforme comme phase huileuse, est rapporté. Nous avons montré, avec cette composition de la phase d’huile, que le comportement dynamique des émulsions doubles sous écoulement donne lieu à des phénomènes riches incluant la déformation et du “tip-streaming”Generation, propagation and reception of (bio/chemical) information between individual organisms are the keystone of many intelligent communicating systems, and are ubiquitous in Nature. Colonies of fireflies synchronize their flashes, and contraction and expansion of heart muscles are few examples among others, where bio/chemical signals generated by synchronized sources produce a cooperative behaviour. The final objective of this thesis is to develop a reliable platform for generating communicative networks of liposomes, encapsulating the Belousov-Zhabotinsky (BZ) reaction as source of information or transmitted signals, and to study the dynamics of such a system. To reach this goal, several issues were addressed by following bottom-up and multi-scale approaches. First we investigated the interaction between both bulk DMPC liposomes, and liposomes doped with cholesterol, myristic acid, tetradecylsulfate, tetradecylamine, and the species involved in the BZ-reaction by using small angle X-ray scattering (SAXS) and UV-visible spectrophotometry. Than 1D arrays of micro-droplets were fabricated by encapsulating the BZ reaction into microdroplets by means of microfluidics, and the communication between adjacent droplets was studied. Later, we demonstrated an easy to assemble/disassemble and robust design for a microfluidic device with adjustable geometry, for generating monodisperse water-in-oil-in-water (w/o/w) double emulsions. Finally, the behavior of w/o/w double emulsions generated in a microfluidic device, using phospholipids as surfactant and chloroform as the oil phase, was reported. We showed, with this composition of the oil phase, that the dynamic behaviour of the double emulsions under flow gave rise to different phenomena, such as deformation and tip-streaming
36
Assenhaimer, Cristhiane. "Evaluation of emulsion destabilization by light scattering applied to metalworking fluids". Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-17062016-131417/.
Testo completoAbstract (sommario):
Monitoring of emulsion properties is important in many applications, like in foods and pharmaceutical products, or in emulsion polymerization processes, since aged and broken emulsions perform worse and may affect product quality. In machining processes, special types of emulsions called metalworking fluids (MWF) are widely used, because of its combined characteristics of cooling and lubrication, increasing the productivity, enabling the use of higher cutting speeds, decreasing the amount of power consumed and increasing tool life. Even though emulsion quality monitoring is a key issue in manufacturing processes, traditional methods are far from accurate and generally fail in providing the tools for determining the optimal useful life of these emulsions, with high impact in costs. The present study is dedicated to the application of a spectroscopic sensor to monitor MWF emulsion destabilization, which is related to changes in its droplet size distribution. Rapeseed oil emulsions, artificially aged MWF and MWF in machining application were evaluated, using optical measurements and multivariate calibration by neural networks, for developing a new method for emulsion destabilization monitoring. The technique has shown good accuracy in rebuilding the droplet size distribution of emulsions for monomodal and bimodal distributions and different proportions of each droplet population, from the spectroscopic measurements, indicating the viability of this method for monitoring such emulsions. This study is part of a joint project between the University of São Paulo and the University of Bremen, within the BRAGECRIM program (Brazilian German Cooperative Research Initiative in Manufacturing) and is financially supported by FAPESP, CAPES, FINEP and CNPq (Brazil), and DFG (Germany).Sem resumo em português.
37
Azzopardi, Charles-Louis. "Dispositifs microfluidiques pour l’injection de fluides à travers un réseau de gouttes : application biocapteur". Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCD020/document.
Testo completoAbstract (sommario):
La microfluidique, domaine de recherche qui a émergé il y a juste 20 ans, a permis de réduire les dimensions des dispositifs d’analyse biologique ouvrant la porte au concept de « laboratoire-sur-puce » (lab-on-chip). Les succès de cette approche sont déjà nombreux, depuis l’analyse du génome en passant par la réduction du coût des analyses médicales. L’utilisation de gouttes comme enceinte réactionnelle au sein de ces dispositifs est une évolution récente qui permet de réduire encore le volume des échantillons biologiques et d’augmenter la vitesse d’analyse en parallélisant les mesures.Notre équipe développe des capteurs acoustiques dédiés à la détection d’analytes biologiques en milieu liquide. Ce type de capteur a pour principal défaut de ne permettre qu’une mesure contraignant au remplacement de l’interface de biodétection pour une réutilisation éventuelle du capteur. Dès lors, ils utilisent majoritairement une chambre de détection tout ou partie jetable, même si quelques travaux de recherche ont pu montrer la régénération d’un capteur par traitement chimique.Nous proposons ici de s’affranchir des étapes lourdes de remplacement ou de traitement de l’interface de détection qui conduisent entre chaque mesure au démontage du dispositif de détection. Nous employons dans ce cas les gouttes non plus comme enceinte réactionnelle mais comme interface de détection mobile. Elles ont ainsi le potentiel d’être générées et fonctionnalisées directement dans le dispositif pour détecter un analyte spécifique et peuvent être simplement évacuées afin de régénérer l’interface pour effectuer une mesure différente.Les travaux présentés dans cette thèse visent plus particulièrement la capture sur gouttes fonctionnalisées dans ce type de capteur innovant. Ils exposent le développement, incluant la fabrication et la caractérisation, de ces dispositifs microfluidiques ainsi que le montage d’un banc de test expérimental dédié. Ce sujet est suivi de deux projets ancillaires de développement de dispositifs microfluidiques liés aux capteurs acoustiques et à l’utilisation de gouttes. Le premier vise à homogénéiser les vitesses d’écoulements dans une chambre réactionnelle. Le second exploite les propriétés de génération de gouttes pour réaliser un condensateur à capacité variableSince two decades the research on microfluidics systems allowed creating devices for biological detection with regular improvement in compactness, functionality integration and quantity of biological sample, leading to the concept of lab-on-chip. This approach has resulted in dramatic changes in the biomedical field, for example, opening the possibility to perform genomic analysis or improving the medical analysis cost. Using droplet as reaction chamber is a recent evolution that leads to a decrease in biological sample volume and an increase in analysis speed by multiplexing.Our team develops acoustical sensors dedicated to detect biomarker of interest in liquids. The principal weakness of theses sensors lies in their need for replacement of the biodetection interface for performing a new measurement. Accordingly, they use a detection chamber partially or totally disposable. However, few research works showed reusability of sensor by regenerating the bioreceptor layer on the detection interface by chemical treatment.We are proposing to avoid the replacement or the chemical treatment of the detection interface that requires dismounting the device between measurements. We are using here droplets, not as reaction chambers but as movable detection interface. They can be generated and configured directly inside the device to detect a specific biomarker. Then, droplets can be easily evacuated and replaced through the device, which allows to chain measurement of various configurations without dismounting it.The research work conducted in this thesis focuses on the fluidic aspects of this innovative sensor. They show development, including realization and characterization, of theses microfluidic devices and its dedicated characterization setup. This project is followed by two ancillary works about development of microfluidic devices for acoustical sensors and droplets systems. The first one is aiming at the homogenization of the flow velocity inside a reaction chamber. The second one is exploiting property of droplet generation for the realization of a variable capacitance capacitor
38
Xia, You. "Experiments on EHD injection, interaction and electrocoalescence of water droplet pairs in oil". Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI039/document.
Testo completoAbstract (sommario):
Lorsque des champs électriques sont appliqués à des mélanges eau-huile, les petites gouttelettes d'eau sont attirées entre elles et se regroupent en gouttes plus grosses. Ce processus d’électrocoalescence rend plus efficace la séparation huile-eau par sédimentation.Des données expérimentales sur l’électrocoalescence de très petites gouttelettes sont nécessaires pour améliorer la compréhension de la dynamique de l'interface eau-huile et pour valider les modèles numériques. La configuration simple étudiée dans ce travail de thèse concerne une petite paire de gouttelettes tombant dans une cuve d'huile modèle et soumise à un champ électrique aligné avec l’axe de symétrie des gouttes et la gravité.La première partie du travail a consisté à générer de façon contrôlée d’une paire de très petites gouttelettes (dans la gamme de diamètres 20-200 microns) alignée avec le champ électrique. La génération de goutte à la demande, par méthode éléctrohydrodynamique (EHD) a été améliorée pour un meilleur contrôle du diamètre et de la charge électrique des gouttelettes injectées à partir d'une aiguille métallique unique. Ceci a été obtenu en appliquant à un ménisque d'eau pendant à l’extrémité de l’aiguille des impulsions électriques de forme optimisée.La caractérisation électrique et hydrodynamique des paires de gouttelettes et leur coalescence sont alors principalement déduites de l'analyse des vitesses de chute, avec et sans application d’un champ électrique à courant continu. Des données complètes de positions des gouttelettes et de leur vitesse en fonction du temps sont déduites de prises de vues vidéo. Une attention particulière a été accordée aux visualisations de très petites gouttelettes tombant à petites vitesses, associant des angles multiples de prise de vue, de forts zooms et des vidéos à grande vitesse.La modélisation des différents termes d'interactions hydrodynamiques et électrostatiques entre les gouttelettes permet de déduire des vitesses enregistrées leur masse charge électrique respectives. Quand se produit une coalescence des deux gouttelettes, un enregistrement de la vitesse de la gouttelette résultante, avec et sans tension électrique appliquée, permet de contrôler la conservation de la masse et de la charge électrique, et la validation du procédé.Un premier ensemble de données est constitué d'environ 70 cas différents, avec différentes paire des gouttelettes (dans une plage de diamètre limitée de façon à ce que les vitesses de chute soient comprises entre 0,1 et 0,3 mm/s) et en faisant varier la tension appliquée à courant continu ou alternatif. L'analyse des résultats et des incertitudes expérimentales et un exemple de comparaison possible avec des simulations numériques utilisant le logiciel Comsol Multiphysics ™, permettent d'effectuer des recommandations pour les travaux futurs.Ce travail a été financé par le projet “Fundamental understanding of electrocoalescence in heavy crude oils”; coordonné par SINTEF Energy Research. Le projet a été soutenu par The Research Council of Norway, dans le cadre du contrat n °: 206976 / E30, et par les partenaires industriels suivants: Wärtsilä Oil & Gas Systems AS, Petrobras et Statoil ASAWhen electric fields are applied in oil-water mixtures small water droplets are attracted to others and merge in larger drops. This electrocoalescence process makes more efficient the oil-water separation by sedimentation.Experimental data on the electrocoalescence of very small droplets will be useful to improve the understanding of the dynamics of water-oil interface and to validate numerical models. The simple configuration studied consists in a small droplet pair falling in stagnant model oil, under electric field aligned with the symmetry axis of the droplet pair and the direction of gravity.First part of the work consisted in the well-controlled generation of very small droplet pair (range 20-200 microns) aligned with electric field. Droplet-on-Demand generation by EHD method was improved for a better control of the diameter and electric charge of droplets injected from a single metallic needle. This was obtained by applying to a pendant water meniscus optimized multistage high voltage electric pulses.Electrical and hydrodynamic characterization of the droplet pairs and their coalescence are then mainly deduced from the analysis of falling velocities, with and without applied DC electric field. A complete data set of droplet position and velocity is deduced from video. A special attention was paid to the visualizations of very small droplet and small falling velocities, involving multiple angle of view, strong zooming and high speed video.Modelling the different terms of hydrodynamic and electrostatic interactions between droplets allows deducing from the recorded velocities their respective mass and electric charge. When coalescence occurs, a record of the resulting single droplet velocity, with and without applied voltage, allows controlling the mass and charge conservations and validating the method.A first data set was constituted of about 70 different cases, with varying droplets pair (with a limited diameter range to remain with falling velocities between 0.1 and 0.3 mm/s) and varying applied DC or AC voltage. Analyses of the results and experimental uncertainties, and example of possible comparison with numerical simulations using Comsol Multiphysics™ software, allow performing some recommendations for future work.This work was funded by the project “Fundamental understanding of electrocoalescence in heavy crude oils”; co-ordinated by SINTEF Energy Research. The project was supported by The Research Council of Norway, under the contract no: 206976/E30, and by the following industrial partners: Wärtsilä Oil & Gas Systems AS, Petrobras and Statoil ASA
39
Fanzar, Abdelaziz. "Développement d’un code numérique pour la simulation et l’étude de l’hydrodynamique et de la physico-chimie de milieux diphasiques incompressibles. Cas d’une goutte d’eau dans l’huile de paraffine". Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4339.
Testo completoAbstract (sommario):
Depuis plusieurs décennies, une importante activité scientifique se concentre sur la description numérique, théorique ou expérimentale de l'hydrodynamique des écoulements multiphasiques. Ces écoulements sont caractérisés par l'existence d'interfaces, et d'une force à l'interface, la tension superficielle, séparant généralement deux fluides non miscibles. Un cas d'étude dans ce contexte est le problème du drainage d'une unique goutte dans une phase continue, l'ensemble étant soumis à la gravité. Ce système fait apparaître des écoulements récemment décrits pour une goutte d'eau dans l'huile de paraffine. Ce système constitue également un modèle simple pour l'étude des propriétés aux interfaces, Mais d'un point de vue numérique, se pose alors le problème de la stabilité des algorithmes pouvant être utilisés. Les effets aux interfaces impliquent en effet des domaines spatiaux très limités dans lesquels les grandeurs physiques entre les deux fluides sont discontinues. D'importants artéfacts numériques peuvent alors être générés dans les simulations et faire perdre la richesse de la physico-chimie du système considéré. Le problème de la simulation d'écoulements multiphasiques intéresse aussi bien le monde académique que le monde industriel. L'objectif de ce travail de thèse est donc d'implémenter les techniques numériques les plus récentes et de développer un code pour permettre la simulation de l'hydrodynamique de systèmes dispersés. Pour parvenir à ce but, il reste encore des problèmes algorithmiques importants à résoudre comme la prise en compte des effets thermocapillaires et thermosolutaux. Ces deux derniers points sont l'objet de cette thèseFor several decades, an important scientific activity has focused on the numerical, theoretical and experimental hydrodynamics of drops. This work presents numerical results of a single droplet in the gravity field and in non-isothermal conditions. The simulation such a multiphase system is important in both academic and industrial world. This is particularly the case in the field of emulsions, wetting problems and evaporation. To achieve this goal, there are still important algorithmic problems due to the free moving interfaces and the description of capillary effects. Here, a Volume of Fluid technique has been implemented with high order temporal and spatial schemes to preserve the sharpness of the drop interface. The system under consideration is a simplified model consisting in a single water droplet in a continuous paraffin oil phase. These liquids are immiscible and non-compressible and the overall evolution is unsteady. Capillary contributions such as temperature and surfactant dependent surface tension are fully accounted for. This presentation is aimed to show the capabilities of VOF techniques for the simulations of unsteady multiphase systems in non-isothermal configurations. The role of the droplet initial position and temperature field is described with good numerical stability. There are still important problems remaining in the simulation of free interface systems with such a technique. Spurious currents induced by the description of capillarity can in particular come into play. But these latter can be controlled once the droplet average velocity due to drainage becomes large enough
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Loizou, Katerina. "An experimental investigation on droplet generation in microfluidic T-junctions and characterisation of the resulting nanoparticle stabilsed emulsions". Thesis, University of Nottingham, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.716483.
Testo completoAbstract (sommario):
The utilisation of microfluidic devices and methods at a submillimeter scale to manipulate and control fluid flows has been spreading fast over fields such as chemistry, physics or biology. Microfluidics have been used as a platform in an attempt to miniaturise processes and techniques in handheld Lab-on-Chip devices. Specifically, droplet microfluidics have found several applications in a wide range of industries such as pharmaceutical, food or cosmetic industry. The generation of monodispersed, nanoliter droplets using such networks is beneficial in terms of the intrinsic control over different parameters that these devices offer. These emulsions can be considered as building blocks for particles, encapsulating carriers for chemicals or even microreactors. The stabilisation of such droplets to generate Pickering emulsions is another promising aspect, as these have found applications in the industries mentioned above or as precursors for shell or particle generation. Incorporating particles in emulsion systems to stabilise the system against coalescence is not a new concept. As emulsions are inherently unstable due to the increased surface to volume ratios, formation of stabilised emulsions using particles or surfactants has received significant attention over the years. Particle stabilised emulsions are also used as drug delivery precursors. The backbone of this study is the investigation of droplet generation in microfluidic T-junctions, in an attempt to revisit fundamental mechanisms governing droplet generation. Experimental tests examining the effect of flow and fluid properties as well as geometrical characteristics on the droplet generation mechanism are presented. A scaling law to predict droplet volume is constructed from conclusions drawn for the parametric space tested. The proposed scaling law is evaluated using several different fluids and it is compared with existing scaling laws. In another context, the transition between droplet generation regimes is investigated. Transition between regimes at constant Capillary numbers is reported and an intermediate regime observed between squeezing and dripping 1 has been identified. The intermediate or transitional regime identified is reproducible, stable over time and reoccurring. It is customary that the transition between regimes to be characterised using Capillary number. However in this work it is demonstrated that regime transition occurs at constant Capillary numbers when the flowrate ratio is the parameter being altered. The second part of this study focuses on the utilisation of T-shaped microfluidic junctions to generate Pickering emulsions. Nanoparticles of different geometries and contact angles are employed to generate nanofluids of different physical properties in order to assess their ability to stabilise nanoliter droplets generated in microfluidic T-junctions. The effect of nanofluids on the droplet generation mechanism is described, as it is suggested that two different modes of droplet generation are observed. The effect of nanoparticle concentration on droplet size and stability is also assessed. Nanoparticle stabilised droplets are observed to collapse after 7 days in storage. It is postulated that as the encapsulated liquid diffuses through the particle laden interface, the decrease of the encapsulated volume together with the transition of the liquid film to a solid film are causing the collapse. The behaviour of droplets that are stable against coalescence in different environments is also summarised. It was found that nanoparticle stabilised droplets collapse when heated. Additionally, the effect of varying pH of the encapsulated liquid is also investigated. It is concluded that weak acidic solutions can be encapsulated. In this thesis, it is demonstrated that nearly monodisperse microdroplets generated using a microfluidic T-Junction are successfully stabilised using a type of bioactive and biodegradable nanoparticles.
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Villar, Gabriel. "Aqueous droplet networks for functional tissue-like materials". Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:602f9161-368c-48c0-9619-7974f743f2f2.
Testo completoAbstract (sommario):
An aqueous droplet in a solution of lipids in oil acquires a lipid monolayer coat, and two such droplets adhere to form a bilayer at their interface. Networks of droplets have been constructed in this way that function as light sensors, batteries and electrical circuits by using membrane proteins incorporated into the bilayers. However, the droplets have been confined to a bulk oil phase, which precludes direct communication with physiological environments. Further, the networks typically have been assembled manually, which limits their scale and complexity. This thesis addresses these limitations, and thereby enables prospective medical and technological applications for droplet networks. In the first part of the work, defined droplet networks are encapsulated within mm-scale drops of oil in water to form structures called multisomes. The encapsulated droplets adhere to one another and to the surface of the oil drop to form interface bilayers that allow them to communicate with each other and with the surrounding aqueous environment through membrane pores. The contents of the droplets can be released by changing the pH or temperature of the surrounding solution. Multisomes have potential applications in synthetic biology and medicine. In the second part of the work, a three-dimensional printing technique is developed that allows the construction of complex networks of tens of thousands of heterologous droplets ~50 µm in diameter. The droplets form a self-supporting material in bulk oil or water analogous to biological tissue. The mechanical properties of the material are calculated to be similar to those of soft tissues. Membrane proteins can be printed in specific droplets, for example to establish a conductive pathway through an otherwise insulating network. Further, the networks can be programmed by osmolarity gradients to fold into designed shapes. Printed droplet networks can serve as platforms for soft devices, and might be interfaced with living tissues for medical applications.
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Falahati, Hamid. "The Characterization of Bimodal Droplet Size Distributions in the Ultrafiltration of Highly Concentrated Emulsions Applied to the Production of Biodiesel". Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/19585.
Testo completoAbstract (sommario):
A non-reactive model system comprising a highly concentrated and unstable oil-in-water emulsion was used to investigate the retention of oil by the membrane in producing biodiesel with a membrane reactor. Critical flux was identified using the relationship between the permeate flux and transmembrane pressure along with the separation efficiency of the membrane. It was shown that separation efficiencies above 99.5% could be obtained at all operating conditions up to the critical flux. It was observed that the concentration of oil in all collected permeate samples using the oil-water system was below 0.2 wt% when operating at a flux below the critical flux. Studies to date have been limited to the characterization of low concentrated emulsions below 15 vol.%. The average oil droplet size in highly concentrated emulsions was measured as 3200 nm employing direct light scattering (DLS) measurement methods. It was observed that the estimated cake layer thickness of 20 to 80 mm was larger than external diameter of the membrane tube i.e. 6 mm based on a large particle size. Settling of the concentrated emulsion permitted the detection of a smaller particle size distribution (30-100 nm) within the larger particles averaging 3200 nm. It was identified that DLS methods could not efficiently give the droplet size distribution of the oil in the emulsion since large particles interfered with the detection of smaller particles. The content of the smaller particles represented 1% of the total weight of oil at 30°C and 5% at 70°C. This was too low to be detected using DLS measurements but was sufficient to affect ultrafiltration. In order to study the critical flux in the presence of transesterification reaction and the effect of cross flow velocity on separation, various oils were transesterified in another membrane reactor providing higher cross flow velocity. higher cross flow velocity provides better separation by reducing materials deposition on the surface of the membrane due to higher shearing. The oils tested were canola, corn, sunflower and unrefined soy oils (Free Fatty Acids (FFA< 1%)), and waste cooking oil (FFA= 9%). The quality of all biodiesel samples was studied in terms of glycerine, mono-glyceride, di-glyceride and tri-glyceride concentrations. The composition of all biodiesel samples were in the range required by ASTM D6751 and EN 14214 standards. A critical flux based on operating pressure in the reactor was reached for waste cooking and pre-treated corn oils. It was identified that the reaction residence time in the reactor was an extremely important design parameter affecting the operating pressure in the reactor.Natural Sciences and Engineering Research Council of Canada (NSERC)
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Guillaument, Romain. "Modélisation globale de l'alimentation d'une emprise lubrifiée par émulsion : simulation numérique directe et analyse physique des phénomènes". Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14166/document.
Testo completoAbstract (sommario):
L'objet de cette thèse est de modéliser et simuler des écoulements diphasique/triphasique à phase non miscibles. L'impact de plusieurs gouttes d' émulsion (eau/huile) sur une plaque mouillante l'huile est simulée. Ainsi, une méthode pour lisser l'interface (SVOF), afin d'obtenir une courbure précise, basée sur une méthode eulérienne de type "Volume Of Fluid" (VOF) spécifique au caractère multiphasique de l' écoulement est développée. Un modèle de ligne triple et un modèle de mouillabilité sont développés pour calculer les forces capillaires. Ces modèles et ces méthodes sont validées partir de données expérimentales puis utilisées pour simuler le Plate-Outet les écoulements macroscopiques au voisinage du cylindre de laminageThe scope of this dissertation is to model and simulate non-miscible multiphase °ows. Theimpact of several emulsion droplet on the wetting steel strip is simulated. So, the method ofsmooth VOF based on Eulerian "Volume Of Fluid" approach which is particulary adapted tointerfacial °ows is developed. The new method SVOF allows to calculate the curvature with abetter precison than other method. A wettability model and a triple line model are developedto calculate the capillary forces. This models and this methods validated on the experimentaldata and used to simulate the Plate-Out and the macroscopic °ows in neighbourhood of coldrolling system
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Schmit, Alexandre. "Quelques opérations élémentaires en microfluidique digitale : encapsulation, fragmentation et trafic de gouttes". Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S050/document.
Testo completoAbstract (sommario):
Les écoulements de trains périodiques de gouttes monodisperses confinées dans des microcanaux sont largement utilisés pour diverses applications haut-débits en microfluidique digitale. Pour cela, il est nécessaire de réaliser différentes opérations sur ces gouttes comme les fragmenter, les fusionner ou les trier. Dans ce manuscrit, nous discutons de trois de ces opérations expérimentalement et théoriquement. La première concerne l’encapsulation d’un train de gouttelettes dans des gouttes. Nous étudions la dynamique d’encapsulation et nous présentons une nouvelle méthode d’encapsulation. Par suite, nous investiguons deux modes de fragmentation de gouttes, tous deux influencés par des interactions hydrodynamiques entre gouttes consécutives dans un train. Enfin, nous cherchons à comprendre la sélection du chemin suivi par des gouttes à des bifurcations successivesFlows of periodic trains of monodisperse drops confined in microchannels are widely used for numerous high-throughput applications in digital microfluidics. The development of such applications requires performing and combining various operations on these drops like breakup, fusion or sorting. In this manuscript, we study experimentally and theoretically three of these operations. We first discuss the encapsulation of a train of droplets inside drops, focusing on the encapsulation dynamics. Also, we present a new way to encapsulate drops to produce double emulsions. We then investigate two ways to break drops against micro-obstacles, both being influenced by hydrodynamics interactions between two consecutives drops in a train. Lastly, we report the investigation of the path selection of drops at successive bifurcations
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Keiser, Ludovic. "Formation et déplacement de gouttes confinées : Instabilités et dynamiques". Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC080/document.
Testo completoAbstract (sommario):
Les écoulements biphasiques en milieux poreux sont généralement accompagnés par des phénomènes d'émulsification d'une phase dans l'autre. Les causes peuvent être nombreuses, de la digitation visqueuse aux instabilités purement capillaires. Cette thèse expérimentale a pour objet l'étude d'un mécanisme particulier d'émulsification de l'huile en milieu poreux, ainsi que le transport des gouttes produites dans des milieux confinés. Dans la première partie de cette thèse, l'instabilité gravito-capillaire de Rayleigh-Taylor est revisitée dans un coin formé entre deux plaques de verre centimétriques. La présence d'un gradient de confinement introduit une force capillaire supplémentaire à cette instabilité canonique, susceptible de stabiliser une couche de liquide suspendue au-dessus du vide. Le seuil de stabilité, les longueurs d'onde caractéristiques et les taux de croissance sont bien modélisés par une analyse de stabilité linéaire de l'interface. La caractérisation de cette force capillaire induite par le gradient de confinement nous amène par la suite à l'étude d'une instabilité purement capillaire se produisant lorsqu'un fluide en mouillage très favorable migre vers les régions les plus confinées d'un coin, occupées initialement par un fluide en mouillage moins favorable. Le gradient de confinement introduit alors une force déstabilisante, aboutissant à l'inversion de la position respective des deux phases. Le liquide le moins mouillant est complètement émulsifié et transporté vers les régions les moins confinées sous la forme de gouttelettes. Une analyse de stabilité linéaire de l'interface permet, là encore, de prédire cette sélection de taille. Les taux de croissance mesurés ne sont en revanche pas en accord avec la modélisation, basée sur la loi de Darcy. Leur valeur suggère une localisation de la dissipation visqueuse dans les lignes de contact déplacées durant le développement de l'instabilité, ainsi que dans les films de lubrification également déposés. Ces dynamiques "non-darciennes" nous ont amenés dans une seconde partie de la thèse à l'étude du transport de gouttes d'huile très visqueuses confinées dans de l'eau en mouillage total. Dans cette configuration, la présence de films de lubrification d'eau entre la goutte et le substrat assure la localisation de la dissipation dans les films peu visqueux, favorisant ainsi la mobilité des gouttes. Nous montrons également que la présence de rugosités sur les parois du confinement induit un ralentissement significatif de la vitesse des gouttes, lié à l'amincissement du film de lubrification par ces rugosités. L'interdépendance subtile entre friction visqueuse à l'avant de la goutte et dans son volume est notamment mise en lumière. Dans une dernière partie, nous étudions l'instabilité capillaire se produisant lorsqu'une goutte binaire d'eau et d'alcool est déposée à la surface d'un bain d'huile. L'évaporation majoritaire de l'alcool à la surface de la goutte induit des variations locales de la tension de surface. Des écoulements interfaciaux de Marangoni se produisent, et aboutissent à la déstabilisation spectaculaire de la goutte en étalementBiphasic flows in porous media generally lead to the emulsification of one phase into the other. This may be due to several phenomena, such as viscous fingering or pure capillary instabilities. In this experimental thesis, we study a particular emulsifying phenomenon of oil in a model porous medium, as well as the transport of the produced droplets in confined regions. In the first part of the manuscript, the Rayleigh-Taylor instability is revisited in a wedge formed between two centimetric glass plates. The gradient of confinement leads to a capillary force not present in the canonical Rayleigh-Taylor instability. This new force can stabilize liquid layer above air submitted to gravity. The threshold of the instability, the characteristic wavelength and the growth rate are captured by a linear stability analysis of the interface. This characterization of the confinement-induced capillary force drove us to the study of a pure capillary instability occurring when a wetting liquid migrates toward the most confined regions of a wedge, initially filled with a less wetting liquid. The gradient of confinement generates a destabilizing force, leading to the complete inversion of the position of both phases. The less wetting liquid is fully emulsified and the produced droplets are convected towards the less confined regions. A linear stability analysis of the interface here again predicts the characteristic size of the droplets. However, the measured growth rates are not in agreement with the model, based on the Darcy law. This suggests a localization of viscous dissipation in the contact lines displaced during the development of the instability. Another source of viscous dissipation can be in the deposited lubrication films. Those "non-Darcian" dynamics motivated the second part of this thesis, which focuses on the motion of very viscous and non-wetting droplets confined in water. In this configuration, the lubrication film of water between the drop and the substrate ensures the localization of viscous dissipation in those films of low viscosity. This favors the extremely high mobility of the droplets. We also show that wall roughness may induce a thinning of these lubrication films. We shed light on the intricate coupling between viscous friction at the front of the drop and in its bulk. In a last part of this work, we study the capillary instability occurring when a binary droplet of water and alcohol is deposited at the surface of a vegetable oil bath. The dominant evaporation of alcohol at the surface of the drop induces local variations of surface tension. Interfacial Marangoni flows are thus observed, leading to the spectacular destabilization of the spreading droplet
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Prestes, Paula Souza. "Tomografia por coerência óptica (OCT), reologia, análise térmica e tamanho de partículas aplicados na caracterização de sistemas emulsionados de orientação de uso cosmético". Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/9/9139/tde-08032013-163451/.
Testo completoAbstract (sommario):
Os atributos físicos, físico-químicos e químicos dos sistemas emulsionados são influenciados pelas características das gotículas da fase interna destes, como: concentração, tamanho e morfologia. Dessa forma, os objetivos envolveram a caracterização física e físico-química de sistemas emulsionados obtidos a partir dos tensoativos álcool estearílico 21 OE (óxidos de etileno) (steareth-21) e álcool oleílico 20 OE (oleth-20), bem como, a introdução da tomografia por coerência óptica (OCT) como técnica analítica para determinação do tamanho de partículas e caracterização morfológica das emulsões. Prepararam-se três formulações, diferindo-se no tensoativo utilizado, sendo o sistema emulsionado SE-1 composto por 8,0% (p/p) de oleth-20; o SE-2 por 4,0% (p/p) de oleth-20 e 4,0% (p/p) steareth-21; e o SE-3 por 8,0% (p/p) steareth-21. Avaliaram-se a estabilidade preliminar, o valor de pH, os perfis reológico e termogravimétrico. A presença de fase gel cristalina foi determinada por meio da microscopia com luz polarizada e, o tamanho das gotículas, por meio da microscopia óptica comum, difração a laser e OCT. As amostras não apresentaram sinais de instabilidade por meio dos testes da centrifugação e do estresse térmico. O valor de pH foi considerado compatível com o da pele humana (4,6 a 5,8). Os sistemas apresentaram comportamento reológico não-Newtoniano pseudoplástico. SE-1 apresentou viscosidade aparente inferior (223,53 mPa.s) e área de histerese (2238,38 Pa/s) estatisticamente igual ao SE-2 (2911,19 Pa/s); SE-2 apresentou valor intermediário de viscosidade aparente (332,20 mPa.s) e, SE-3, valores superiores para ambos os parâmetros (636,40 mPa.s e 4248,97 Pa/s). Os testes oscilatórios constataram a predominância do caráter elástico para os três sistemas. Por meio da termogravimetria, o perfil das três amostras foi semelhante, independentemente do tipo e concentração do tensoativo não-iônico. Observou-se a presença de fase gel cristalina para os três sistemas, sendo aparentemente mais pronunciado para o SE-2. Tanto na análise microscópica quanto na difração a laser foram obtidos tamanho médio de partículas menor que 6,0 µm. De acordo com os resultados da OCT, as partículas menores que 6,0 µm não foram possíveis de serem conclusivamente observadas e aquelas maiores sugeriram ser a fase interna dos sistemas.The physical, physicochemical and chemical attributes of the emulsified systems are influenced by the characteristics of their internal phase droplets, such as: concentration, size and morphology. Thus, the aims involved the physical and physicochemical characterization of emulsions obtained from the stearyl alcohol condensed with 21 mols ethylene oxide (EO) (steareth-21) and oleyl alcohol with 20 mols EO (oleth-20), as well as, the introduction of the optical coherence tomography (OCT) as the analytical technique tool to the determination of the particle size and morphological characterization of the emulsified systems. Three formulations were prepared, differing at the surfactant used, being the emulsified system SE-1 composed by 8.0% (p/p) of oleth-20, the SE-2 by 4.0% (p/p) of oleth-20 and 4.0% (p/p) steareth-21; and the SE-3 by 8.0% (p/p) steareth-21. The preliminary stability was evaluated, such as the ph value and the rheological and thermogravimetric profiles. The presence of the crystalline gel phase was determined from microscopy with polarized light and the droplet size through regular optical microscopy, laser diffraction and OCT. The samples did not present signs of instability throughout the centrifugation and thermal stress tests. The ph value was considered compatible to human skin (4.6 to 5.8). Systems represent the non-Newtonian pseudoplastic rheological behaviour. The SE-1 presented inferior apparent viscosity (223.53 mPa.s) and the hysteresis area (2238.38 Pa/s) statistically equal to SE-2 (2911.19 Pa/s); the SE-2 presented an average value of apparent viscosity (332.20 mPa.s) and, the SE-3, superior values to both parameters (636.40 mPa.s and 4248.97 Pa/s). The oscillating tests verified the elastic character predomination to the three systems. Throughout the thermogravimetry, the profile of the three samples was similar, independent from the kind and concentration of the non-ionic surfactant. The presence of the crystalline gel phase was identified at the three systems, being apparently more pronounced to the SE-2. Either at the microscopic analysis as well as at the laser diffraction were obtained an average size of the particles minor than 6.0 µm. According to OCT results, the particles below 6.0 µm were not possible to be identified and the major particles were suggested be the internal phase of the systems, however new studies should be performed.
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Truman, Sutanto Pagra. "Multifunktionsfeldeffekttransistoren zur Strömungs-, Chemo- und Biosensorik in Lab on a Chip-Systemen". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1199907096113-76856.
Testo completoAbstract (sommario):
In dieser Arbeit wird eine neue Methode und ein neuartiges FET -Sensorelement zum Nachweis von Flüssigkeitsbewegungen vorgestellt, das zudem bei Bedarf auch als Chemo- oder Biosensor fungieren kann. Das Einsatzspektrum von FET-basierten Sensoren in Lab on a Chip-Systemen wird dadurch entscheidend erweitert. Bei dem entwickelten FET-Sensor Bauelement handelt es sich um einen normally-on n-leitenden Dünnschichtfeldeffekttransistor mit Ti-Au-Kontakten, basierend auf Silicon-on-Insulator- Substraten, wobei das natürliche Oxid des Siliziumfilms als Schnittstelle zum Elektrolyten bzw. zur Flüssigkeit verwendet wird. Der mit 10exp16 Bor Atomen pro cm³ p-dotierte Siliziumdünnfilm hat eine Dicke von nur 55 nm und ist durch eine 95 nm dicke Siliziumdioxidschicht vom darunterliegenden Siliziumsubstrat von 600 µm Dicke elektrisch isoliert. Aufgrund der geringen Schichtdicke durchdringt die feldempfindliche Raumladungs- bzw. Verarmungszone die gesamte Dünnschicht, so dass durch Anlegen einer Backgatespannung am Substrat der spezifische Widerstand und die Empfindlichkeit des Bauelements eingestellt werden können. Grundlegende ISFET-Funktionalitäten wie die Empfindlichkeit auf Änderungen der Ionenstärke und des pH-Wertes werden nachgewiesen und ein ENFET-Glukosesensor realisiert. Zudem wird im Hinblick auf die Separation von Emulsionen der Nachweis erbracht, dass die Benetzung mit Hexan und Toluol eine Änderung der spezifischen Leitfähigkeit bewirkt, und die Empfindlichkeit des Bauelements nach Beschichtung mit einem hydrophoben Methacrylatcopolymerfilm erhalten bleibt. Hinsichtlich der Verwendung des FET-Sensor Bauelements zum Nachweis von Flüssigkeitsbewegungen wird zunächst ein theoretisches Modell entwickelt, dessen Kernaussage ist, dass sich in einem rechteckigen Kanal der relative Bedeckungsgrad mit Flüssigkeit direkt proportional zum Drainstrom des FET-Sensors verhält. Basierend auf diesem theoretischen Modell, welches experimentell belegt wird, können mittels eines einzelnen FET-Sensors Füllstand und Füllgeschwindigkeit bzw. bei bekannter Füllgeschwindigkeit Kapillarvolumen und Kapillargeometrie bestimmt werden. Abweichungen von der direkten Proportionalität erlauben zudem, Rückschlüsse auf die Benetzungseigenschaften der Kapillaren und die Dynamik an der Halbleitergrenzfläche zu ziehen. Ist ein Sensorelement vollständig mit Flüssigkeit bedeckt, wird mittels Lösungsmitteltropfen als Markerobjekten die Strömungsgeschwindigkeit bestimmt. Ändert sich die Ionenkonzentration im Elektrolyten als Funktion der Strömungsgeschwindigkeit, so kann die Strömungsgeschwindigkeit durch Messung der Ionenkonzentration mittels FET-Sensor ebenfalls ermittelt werden. Als wichtigster Demonstrator für die Verwendung des FET-Sensors wird ein komplexes Lab on a Chip-System zur Separation von Emulsionen auf chemisch strukturierten Oberflächen entwickelt, bei dem der Separationsvorgang mittels FET-Sensorarray verfolgt werden kann. Zur einfachen Herstellung chemisch modifizierter Oberflächen für die Separationsexperimente werden die Abscheidung von nanoskaligen hydrophoben Methacrylatcopolymerfilmen und die selektive Fluorsilanisierung von Oberflächen sowie deren Lösungsmittelbeständigkeit in Wasser, Toluol und Aceton untersucht. Dabei zeigt sich, dass die Hydrophobie nach Lösungsmittelbehandlung weitestgehend erhalten bleibt, Wasserrückstände im Methacrylatfilm aber zu einer reversiblen Schichtdegradation führen können. Als Modellsystem werden Hexan-Wasser- bzw. Toluol-Wasser-Emulsionen verwendet, die auf Oberflächen getrennt werden, deren eine Seite hydrophil, und deren andere Seite hydrophob ist (Stufengradient). Der Separationsprozess beruht auf der großen Affinität des Wassers hin zu polaren Oberflächen, wobei das wenig selektive Lösungsmittel zur unpolaren Seite gedrängt wird. Zur Erlangung eines tieferen Verständnisses des Prozesses werden die Tropfenkoaleszenz und der Einfluss geometrischer Beschränkungen untersucht. Die Versuche werden sowohl auf offenen Oberflächen als auch im Spalt, unter Verwendung von hydrophilen und hydrophoben Oberflächen, durchgeführt. Es zeigt sich, dass sich die Dynamik der Tropfenkoaleszenz im Spalt umgekehrt zur Dynamik auf offenen Oberflächen verhält. Dies wird mittels eines hierzu entwickelten theoretischen Modells erklärt, welches die Minimierung der Oberflächenenergie und Hystereseeffekte einbezieht. Das Lab on a Chip-System schließlich besteht aus einem mit Siliziumnitrid beschichteten FET-Sensorchip, auf den eine Separationszelle aufgeklebt ist. Neben dem Einlass für die Emulsion ist ein weiterer Einlass vorhanden, durch den Salzsäure für eine pH-Reaktion zugegeben werden kann. Der gesamte Separationsprozess sowie die anschließende pH-Reaktion, lassen sich bequem am PC anhand der Änderung der Stromstärke der einzelnen Sensoren verfolgen und analysieren. Wichtige Ergebnisse hier sind: 1) Mittels eines quasi 1-dimensionalen Sensorarrays kann der Verlauf einer Flüssigkeitsfront in einem 2-dimensionalen Areal überwacht bzw. dargestellt werden. 2) Anhand der Signatur des Signalverlaufs bei pH-Änderung und Flüssigkeitsbewegung, können beide Prozesse unterschieden werden. Der Sensor kann also zum Nachweis von Flüssigkeitsbewegungen und zugleich als Chemosensor eingesetzt werden. Es wurde also nicht nur ein neuartiges, äußerst robustes, chemikalienbeständiges und biokompatibles Multifunktionssensorelement mit Abmessungen im Mikrometer- bis Millimeterbereich entwickelt, sondern auch eine neue Methode entwickelt, mit der es möglich ist, sowohl (bio-)chemische Reaktionen als auch die Bewegung von Flüssigkeiten in Lab on a Chip-Systemen nachzuweisen.
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Silva, Carlos Felipe Bueno da. "Estudo comparativo de técnicas numéricas de inversão para obtenção de distribuição de tamanho de gotas em emulsões". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-04072016-152253/.
Testo completoAbstract (sommario):
O desenvolvimento de algoritmos computacionais para a obtenção de distribuições de tamanho de partícula em dispersões e que utilizam dados espectroscópicos em tempo real e in-line a partir de sensores permitirá uma variedade de aplicações, como o monitoramento de propriedades em fluidos de corte industriais, acompanhamento de processos de polimerização, tratamento de efluentes e sensoriamento atmosférico. O presente estudo tem como objetivo a implementação e comparação de técnicas para resolução de problemas de inversão, desenvolvendo algoritmos que forneçam distribuição de tamanho de partículas em dispersões a partir de dados de espectroscopia UV-Vis-Nir (Ultravioleta, Visível e Infravermelho próximo). Foram implementadas quatro técnicas, sendo uma delas um método alternativo sem a presença de etapas de inversão. Os métodos que utilizaram alguma técnica de inversão evidenciaram a dificuldade em se obter distribuições de tamanho de gotas (DTG) de boa qualidade, enquanto o método alternativo foi aquele que se mostrou mais eficiente e confiável. Este estudo é parte de um programa cooperativo entre a Universidade de São Paulo e a Universidade de Bremen chamado programa BRAGECRIM (Brazilian German Cooperative Research Initiative in Manufacturing) e é financiado pela FAPESP, CAPES, FINEP e CNPq (Brasil) e DFG (Alemanha).The development of computer algorithms to obtain the particle size distributions in dispersions using spectroscopic data in real time and in-line from sensors enable a variety of applications such as monitoring properties in industrial cutting fluids, monitoring of polymerization processes, wastewater, atmospheric sensing and other applications. The aim of this study is to implement techniques for inversion problem solving, by testing algorithms that provide particle size distribution in dispersions from UV-Vis-Nir (Ultraviolet, Visible and Near-Infrared) spectroscopic data. Four techniques have been implemented, one of them being an alternative method without the inversion step. The methods using inversion techniques showed difficulties to obtain droplet size distributions (DSD) with good quality, while the alternative method was the one that was more efficient and reliable. This study is part of a cooperative program between the University of São Paulo and the University of Bremen, within the BRAGECRIM program (Brazilian German Cooperative Research Initiative in Manufacturing) and is financially supported by FAPESP, CAPES, FINEP and CNPq (Brazil) and DFG (Germany).
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Truman, Sutanto Pagra. "Multifunktionsfeldeffekttransistoren zur Strömungs-, Chemo- und Biosensorik in Lab on a Chip-Systemen". Doctoral thesis, Technische Universität Dresden, 2007. https://tud.qucosa.de/id/qucosa%3A25010.
Testo completoAbstract (sommario):
In dieser Arbeit wird eine neue Methode und ein neuartiges FET -Sensorelement zum Nachweis von Flüssigkeitsbewegungen vorgestellt, das zudem bei Bedarf auch als Chemo- oder Biosensor fungieren kann. Das Einsatzspektrum von FET-basierten Sensoren in Lab on a Chip-Systemen wird dadurch entscheidend erweitert. Bei dem entwickelten FET-Sensor Bauelement handelt es sich um einen normally-on n-leitenden Dünnschichtfeldeffekttransistor mit Ti-Au-Kontakten, basierend auf Silicon-on-Insulator- Substraten, wobei das natürliche Oxid des Siliziumfilms als Schnittstelle zum Elektrolyten bzw. zur Flüssigkeit verwendet wird. Der mit 10exp16 Bor Atomen pro cm³ p-dotierte Siliziumdünnfilm hat eine Dicke von nur 55 nm und ist durch eine 95 nm dicke Siliziumdioxidschicht vom darunterliegenden Siliziumsubstrat von 600 µm Dicke elektrisch isoliert. Aufgrund der geringen Schichtdicke durchdringt die feldempfindliche Raumladungs- bzw. Verarmungszone die gesamte Dünnschicht, so dass durch Anlegen einer Backgatespannung am Substrat der spezifische Widerstand und die Empfindlichkeit des Bauelements eingestellt werden können. Grundlegende ISFET-Funktionalitäten wie die Empfindlichkeit auf Änderungen der Ionenstärke und des pH-Wertes werden nachgewiesen und ein ENFET-Glukosesensor realisiert. Zudem wird im Hinblick auf die Separation von Emulsionen der Nachweis erbracht, dass die Benetzung mit Hexan und Toluol eine Änderung der spezifischen Leitfähigkeit bewirkt, und die Empfindlichkeit des Bauelements nach Beschichtung mit einem hydrophoben Methacrylatcopolymerfilm erhalten bleibt. Hinsichtlich der Verwendung des FET-Sensor Bauelements zum Nachweis von Flüssigkeitsbewegungen wird zunächst ein theoretisches Modell entwickelt, dessen Kernaussage ist, dass sich in einem rechteckigen Kanal der relative Bedeckungsgrad mit Flüssigkeit direkt proportional zum Drainstrom des FET-Sensors verhält. Basierend auf diesem theoretischen Modell, welches experimentell belegt wird, können mittels eines einzelnen FET-Sensors Füllstand und Füllgeschwindigkeit bzw. bei bekannter Füllgeschwindigkeit Kapillarvolumen und Kapillargeometrie bestimmt werden. Abweichungen von der direkten Proportionalität erlauben zudem, Rückschlüsse auf die Benetzungseigenschaften der Kapillaren und die Dynamik an der Halbleitergrenzfläche zu ziehen. Ist ein Sensorelement vollständig mit Flüssigkeit bedeckt, wird mittels Lösungsmitteltropfen als Markerobjekten die Strömungsgeschwindigkeit bestimmt. Ändert sich die Ionenkonzentration im Elektrolyten als Funktion der Strömungsgeschwindigkeit, so kann die Strömungsgeschwindigkeit durch Messung der Ionenkonzentration mittels FET-Sensor ebenfalls ermittelt werden. Als wichtigster Demonstrator für die Verwendung des FET-Sensors wird ein komplexes Lab on a Chip-System zur Separation von Emulsionen auf chemisch strukturierten Oberflächen entwickelt, bei dem der Separationsvorgang mittels FET-Sensorarray verfolgt werden kann. Zur einfachen Herstellung chemisch modifizierter Oberflächen für die Separationsexperimente werden die Abscheidung von nanoskaligen hydrophoben Methacrylatcopolymerfilmen und die selektive Fluorsilanisierung von Oberflächen sowie deren Lösungsmittelbeständigkeit in Wasser, Toluol und Aceton untersucht. Dabei zeigt sich, dass die Hydrophobie nach Lösungsmittelbehandlung weitestgehend erhalten bleibt, Wasserrückstände im Methacrylatfilm aber zu einer reversiblen Schichtdegradation führen können. Als Modellsystem werden Hexan-Wasser- bzw. Toluol-Wasser-Emulsionen verwendet, die auf Oberflächen getrennt werden, deren eine Seite hydrophil, und deren andere Seite hydrophob ist (Stufengradient). Der Separationsprozess beruht auf der großen Affinität des Wassers hin zu polaren Oberflächen, wobei das wenig selektive Lösungsmittel zur unpolaren Seite gedrängt wird. Zur Erlangung eines tieferen Verständnisses des Prozesses werden die Tropfenkoaleszenz und der Einfluss geometrischer Beschränkungen untersucht. Die Versuche werden sowohl auf offenen Oberflächen als auch im Spalt, unter Verwendung von hydrophilen und hydrophoben Oberflächen, durchgeführt. Es zeigt sich, dass sich die Dynamik der Tropfenkoaleszenz im Spalt umgekehrt zur Dynamik auf offenen Oberflächen verhält. Dies wird mittels eines hierzu entwickelten theoretischen Modells erklärt, welches die Minimierung der Oberflächenenergie und Hystereseeffekte einbezieht. Das Lab on a Chip-System schließlich besteht aus einem mit Siliziumnitrid beschichteten FET-Sensorchip, auf den eine Separationszelle aufgeklebt ist. Neben dem Einlass für die Emulsion ist ein weiterer Einlass vorhanden, durch den Salzsäure für eine pH-Reaktion zugegeben werden kann. Der gesamte Separationsprozess sowie die anschließende pH-Reaktion, lassen sich bequem am PC anhand der Änderung der Stromstärke der einzelnen Sensoren verfolgen und analysieren. Wichtige Ergebnisse hier sind: 1) Mittels eines quasi 1-dimensionalen Sensorarrays kann der Verlauf einer Flüssigkeitsfront in einem 2-dimensionalen Areal überwacht bzw. dargestellt werden. 2) Anhand der Signatur des Signalverlaufs bei pH-Änderung und Flüssigkeitsbewegung, können beide Prozesse unterschieden werden. Der Sensor kann also zum Nachweis von Flüssigkeitsbewegungen und zugleich als Chemosensor eingesetzt werden. Es wurde also nicht nur ein neuartiges, äußerst robustes, chemikalienbeständiges und biokompatibles Multifunktionssensorelement mit Abmessungen im Mikrometer- bis Millimeterbereich entwickelt, sondern auch eine neue Methode entwickelt, mit der es möglich ist, sowohl (bio-)chemische Reaktionen als auch die Bewegung von Flüssigkeiten in Lab on a Chip-Systemen nachzuweisen.
50
Postal, Victor. "Estudo da degradação térmica de emulsões via espectroscopia UV-Vis aplicado a fluidos de corte". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-23012017-113619/.
Testo completoAbstract (sommario):
O monitoramento de emulsões utilizadas na indústria metalmecânica compõe uma importante atividade para o controle da qualidade das peças trabalhadas, proporcionando também o aumento da vida útil de ferramentas e maquinários utilizados neste setor através da lubrificação e refrigeração da região de corte. Em grande parte dos casos, estas emulsões são preparadas pela diluição de um fluido de corte em meio aquoso, constituindo assim um conjunto de gotículas estabilizadas em um meio contínuo devido à presença de compostos emulsificantes, estando constantemente sujeitas a ciclos de aquecimento e resfriamento durante os processos de usinagem. Apesar do acompanhamento deste material ser realizado através de análises periódicas usuais, não há um método eficiente estabelecido para verificar sua qualidade em tempo real e em linha de processo. Neste contexto, torna-se possível aplicar técnicas relacionadas à espectroscopia UV-Vis para se obterem informações sobre a estabilidade destes sistemas, correlacionando intensidades de espalhamento de luz com as dimensões das gotas presentes no meio. Dessa forma, tornou-se possível o estudo da desestabilização térmica de emulsões de um fluido de corte comercial, a qual mostrou-se, através do acompanhamento do cálculo do expoente do comprimento de onda, dependente do tempo de exposição ao aquecimento e de sua temperatura média temporal, não sendo influenciada pela perda de meio contínuo por processos evaporativos ou sua posterior reposição. Também se verificou que parâmetros típicos do processo de preparo de emulsões, como a temperatura do meio dispersante e o tempo de repouso do fluido de corte sobre a superfície do mesmo, apresentam fundamental importância para a definição do tamanho médio de gota inicial destes sistemas, o que forneceu evidência da possibilidade de se relacionar a área sob espectros de extinção de luz com tamanhos médios de gota.The monitoring of emulsions used in the metal-mechanical industry comprise an important activity to the quality control of the products manufectured, also providing an increase in the working life of the tools and machinery employed in this sector through the lubrication and refrigeration of the cutting zone. In the majority of cases, these emulsions are prepared diluting a metalworking fluid in an aqueous media, constituting a collection of particles stabilized by emulsifiers and undergoing heating and cooling cycles during metalworking processes. Currently, monitoring routines are based on regular analyses of samples taken from the process fluid, and an effective in-line method is not available to monitor emulsion quality in real time. In this context, it is possible to apply techniques related to UV-Vis spectrocopy in order to obtain information concerning the stability of those systems, correlating light scattering intensities to the droplet dimensions. In this study, it was possible to investigate the thermal destabilisation of a commercial metalworking fluid emulsion, which showed, through the evaluation of the wavelength exponent, to be dependant on the exposure time to heating and its time-averaged temperature. It was also noted that the loss of continuous phase by evaporation and its reposition do not affect the emulsion stability. Moreover, it was observed that important emulsion preparation parameters, such as continuous phase temperature and the time span between the addition of the metalworking fluid on the water surface and the stirring, have fundamental roles in defining the initial average droplet size, which made possible to correlate the area under the light extinction spectra with average droplet sizes.