Dissertations / Theses on the topic 'Microfluidics and nanofluidics'
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Wang, Shengnian. "Micro-/nanofluidics and single DNA dynamics in non-uniform electrokinetic flows." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1149002340.
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Laohakunakorn, Nadanai. "Electrokinetic phenomena in nanopore transport." Thesis, University of Cambridge, 2015. https://www.repository.cam.ac.uk/handle/1810/252690.
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Nanopores are apertures of nanometric dimensions in an insulating matrix. They are routinely used to sense and measure properties of single molecules such as DNA. This sensing technique relies on the process of translocation, whereby a molecule in aqueous solution moves through the pore under an applied electric field. The presence of the molecule modulates the ionic current through the pore, from which information can be obtained regarding the molecule's properties. Whereas the electrical properties of the nanopore are relatively well known, much less work has been done regarding their fluidic properties. In this thesis I investigate the effects of fluid flow within the nanopore system. In particular, the charged nature of the DNA and pore walls results in electrically-driven flows called electroosmosis. Using a setup which combines the nanopore with an optical trap to measure forces with piconewton sensitivity, we elucidate the electroosmotic coupling between multiple DNA molecules inside the confined environment of the pore. Outside the pore, these flows produce a nanofluidic jet, since the pore behaves like a small electroosmotic pump. We show that this jet is well-described by the low Reynolds number limit of the classical Landau-Squire solution of the Navier-Stokes equations. The properties of this jet vary in a complex way with changing conditions: the jet reverses direction as a function of salt concentration, and exhibits asymmetry with respect to voltage reversal. Using a combination of simulations and analytic modelling, we are able to account for all of these effects. The result of this work is a more complete understanding of the fluidic properties of the nanopore. These effects govern the translocation process, and thus have consequences for better control of single molecule sensing. Additionally, the phenomena we have uncovered could potentially be harnessed in novel microfluidic applications, whose technological implications range from lab-on-a-chip devices to personalised medicine.
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Pussadee, Nirut. "Poly(dimethylsiloxane) Based Micro- and Nanofluidic Device Fabrication for Electrophoresis Applications." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1268179904.
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Misiunas, Karolis. "Hydrodynamic interactions in narrow channels." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/286289.
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Particle-particle interactions are of paramount importance in every multi-body system as they determine the collective behaviour and coupling strength. Many well-known interactions like electro-static, van der Waals or screened Coulomb, decay exponentially or with negative powers of the particle spacing r. Similarly, hydrodynamic interactions between particles undergoing Brownian motion decay as 1/r in bulk, and are assumed to decay in small channels. Such interactions are ubiquitous in biological and technological systems. Here I confine multiple particles undergoing Brownian motion in narrow, microfluidic channels and study their coupling through hydrodynamic interactions. Our experiments show that the hydrodynamic particle-particle interactions are distance-independent in these channels. We also show that these interactions affect actively propelled particles via electrophoresis or gravity, resulting in non-linear transport phenomena. These findings are of fundamental importance for understanding transport of dense mixtures of particles or molecules through finite length, water-filled channels or pore networks.
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Kumar, Suresh. "Design, Fabrication, and Optimization of Miniaturized Devices for Bioanalytical Applications." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5979.
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My dissertation work integrates the techniques of microfabrication, micro/nanofluidics, and bioanalytical chemistry to develop miniaturized devices for healthcare applications. Semiconductor processing techniques including photolithography, physical and chemical vapor deposition, and wet etching are used to build these devices in silicon and polymeric materials. On-chip micro-/nanochannels, pumps, and valves are used to manipulate the flow of fluid in these devices. Analytical techniques such as size-based filtration, solid-phase extraction (SPE), sample enrichment, on-chip labeling, microchip electrophoresis (µCE), and laser induced fluorescence (LIF) are utilized to analyze biomolecules. Such miniaturized devices offer the advantages of rapid analysis, low cost, and lab-on-a-chip scale integration that can potentially be used for point-of-care applications.The first project involves construction of sieving devices on a silicon substrate, which can separate sub-100-nm biostructures based on their size. Devices consist of an array of 200 parallel nanochannels with a height step in each channel, an injection reservoir, and a waste reservoir. Height steps are used to sieve the protein mixture based on size as the protein solution flows through channels via capillary action. Proteins smaller than the height step reach the end of the channels while larger proteins stop at the height step, resulting in separation. A process is optimized to fabricate 10-100 nm tall channels with improved reliability and shorter fabrication time. Furthermore, a protocol is developed to reduce the electrostatic interaction between proteins and channel walls, which allows the study of size-selective trapping of five proteins in this system. The effects of protein size and concentration on protein trapping behavior are evaluated. A model is also developed to predict the trapping behavior of different size proteins in these devices. Additionally, the influence of buffer ionic strength, which can change the effective cross-sectional area of nanochannels and trapping of proteins at height steps, is explored in nanochannels. The ionic strength inversely correlates with electric double layer thickness. Overall, this work lays a foundation for developing nanofluidic-based sieving systems with potential applications in lipoprotein fractionation, protein aggregate studies in biopharmaceuticals, and protein preconcentration. The second project focuses on designing and developing a microfluidic-based platform for preterm birth (PTB) diagnosis. PTB is a pregnancy complication that involves delivery before 37 weeks of gestation, and causes many newborn deaths and illnesses worldwide. Several serum PTB biomarkers have recently been identified, including three peptides and six proteins. To provide rapid analysis of these PTB biomarkers, an integrated SPE and µCE device is assembled that provides sample enrichment, on-chip labeling, and separation. The integrated device is a multi-layer structure consisting of polydimethylsiloxane valves with a peristaltic pump, and a porous polymer monolith in a thermoplastic layer. The valves and pump are fabricated using soft lithography to enable pressure-based sample actuation, as an alternative to electrokinetic operation. Porous monolithic columns are synthesized in the SPE unit using UV photopolymerization of a mixture consisting of monomer, cross-linker, photoinitiator, and various porogens. The hydrophobic surface and porous structure of the monolith allow both protein retention and easy flow. I have optimized the conditions for ferritin retention, on-chip labelling, elution, and µCE in a pressure-actuated device. Overall functionality of the integrated device in terms of pressure-controlled flow, protein retention/elution, and on-chip labelling and separation is demonstrated using a PTB biomarker (ferritin). Moreover, I have developed a µCE protocol to separate four PTB biomarkers, including three peptides and one protein. In the future, an immunoaffinity extraction unit will be integrated with SPE and µCE to enable rapid, on-chip analysis of PTB biomarkers. This integrated system can be used to analyze other disease biomarkers as well.
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Chen, Lei. "Electroosmotic Flow and DNA Electrophoretic Transport in Micro/Nano Channels." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1252612019.
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Smith, Ross Andrew. "Biomedical Applications Employing Microfabricated Silicon Nanoporous Membranes." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1278705155.
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Yuan, Xichen. "Charges à l’interface liquide/solide : caractérisation par courants d’écoulement et application à la préconcentration de molécules biologiques dans un système micro/nanofluidique." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1214/document.
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Les charges à l'interface liquide/solide sont un élément originel majeur des phénomènes électrocinétiques observés en micro/nanofluidique. Elles sont donc la colonne vertébrale de mon manuscrit de thèse, qui se décompose en trois parties : Dans la première partie, un rappel des concepts de base sur les interfaces liquides/solides est proposé au lecteur. Il est suivi d'une description des différentes méthodes expérimentales permettant de mesurer le potentiel zeta de couples solide/électrolyte, puis d'une présentation des travaux de la littérature exploitant les charges aux interfaces pour la préconcentration de molécules biologiques dans des systèmes Micro-Nano-Micro (MNM) fluidiques. Ensuite, une deuxième partie est consacrée à la mesure du potentiel zeta par la méthode des courants d'écoulement. Nous y présentons l'amélioration du banc expérimental issu des travaux antérieurs à ma thèse, ainsi que le développement de nouveaux protocoles de préparation des surfaces permettant de rationaliser et de stabiliser les mesures. Une application à un détecteur original de molécules biologiques clos cette deuxième partie. Enfin, la troisième et dernière partie s'intéresse à la préconcentration de molécules biologiques. Une méthode originale de fabrication des dispositifs MNM et les résultats de préconcentration obtenus, très encourageants, sont décrits. Des premiers modèles numériques et phénoménologiques sont proposés, qui mettent en avant l'originalité de notre travailThe charges at liquid/solid interfaces are a key element for both understanding and exploiting the electrokinetic phenomena in micro/nanofluidics. The manuscript of my Ph.D thesis is dedicated to these phenomena, which is divided into three main parts: Above all, a simple overview of charges at the liquid/solid interface is proposed. Then, several common methods for measuring the zeta potential at the liquid/solid interface are described. Next, various effective methods to preconcentrate the biological molecules is presented with the help of the surface charges. Secondly, the streaming current, which is a standard method to measure the zeta potential in our laboratory, is detailed. It contains the upgrade of the experimental setup from the previous version and the development of new protocols, which improve dramatically the stabilization and the reproducibility of the measurements. In addition, an original biological sensor is briefly presented based on these advancements. Lastly, in the final part, we describe a method which is primitively utilised in the fabrication of Micro-Nano-Micro fluidic system. Based on this system, some favorable preconcentration results is obtained. Moreover, numerical simulations are presented to prove the originality of our work
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Hamblin, Mark Noble. "Thin Film Microfluidic and Nanofluidic Devices." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2281.
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Lab-on-a-chip devices, also known as micro total analysis systems (μTAS), are implementations of chemical analysis systems on microchips. These systems can be fabricated using standard thin film processing techniques. Microfluidic and nanofluidic channels are fabricated in this work through sacrificial etching. Microchannels are fabricated utilizing cores made from AZ3330 and SU8 photoresist. Multi-channel electroosmotic (EO) pumps are evaluated and the accompanying channel zeta potentials are calculated. Capillary flow is studied as an effective filling mechanism for nanochannels. Experimental departure from the Washburn model is considered, where capillary flow rates lie within 10% to 70% of theoretical values. Nanochannels are fabricated utilizing cores made from aluminum, germanium, and chromium. Nanochannels are made with 5 μm thick top layers of oxide to prevent dynamic channel deformation. Nanochannel separation schemes are considered, including Ogston sieving, entropic trapping, reptation, electrostatic sieving, and immutable trapping. Immutable trapping is studied through dual-segment nanochannels that capture analytes that are too large to pass from one channel into a second, smaller channel. Polymer nanoparticles, Herpes simplex virus type 1 capsids, and hepatitis B virus capsids are trapped and detected. The signal-to-noise ratio of the fluorescently-detected signal is shown to be greater than 3 for all analyte concentrations considered.
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Zhang, Yuxiang, and 张玉相. "Microfluidics: fabrication, droplets, bubblesand nanofluids synthesis." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B44903935.
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Pardon, Gaspard. "From Macro to Nano : Electrokinetic Transport and Surface Control." Doctoral thesis, KTH, Mikro- och nanosystemteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-144994.
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Today, the growing and aging population, and the rise of new global threats on human health puts an increasing demand on the healthcare system and calls for preventive actions. To make existing medical treatments more efficient and widely accessible and to prevent the emergence of new threats such as drug-resistant bacteria, improved diagnostic technologies are needed. Potential solutions to address these medical challenges could come from the development of novel lab-on-chip (LoC) for point-of-care (PoC) diagnostics. At the same time, the increasing demand for sustainable energy calls for the development of novel approaches for energy conversion and storage systems (ECS), to which micro- and nanotechnologies could also contribute. This thesis has for objective to contribute to these developments and presents the results of interdisciplinary research at the crossing of three disciplines of physics and engineering: electrokinetic transport in fluids, manufacturing of micro- and nanofluidic systems, and surface control and modification. By combining knowledge from each of these disciplines, novel solutions and functionalities were developed at the macro-, micro- and nanoscale, towards applications in PoC diagnostics and ECS systems. At the macroscale, electrokinetic transport was applied to the development of a novel PoC sampler for the efficient capture of exhaled breath aerosol onto a microfluidic platform. At the microscale, several methods for polymer micromanufacturing and surface modification were developed. Using direct photolithography in off-stoichiometry thiol-ene (OSTE) polymers, a novel manufacturing method for mold-free rapid prototyping of microfluidic devices was developed. An investigation of the photolithography of OSTE polymers revealed that a novel photopatterning mechanism arises from the off-stoichiometric polymer formulation. Using photografting on OSTE surfaces, a novel surface modification method was developed for the photopatterning of the surface energy. Finally, a novel method was developed for single-step microstructuring and micropatterning of surface energy, using a molecular self-alignment process resulting in spontaneous mimicking, in the replica, of the surface energy of the mold. At the nanoscale, several solutions for the study of electrokinetic transport toward selective biofiltration and energy conversion were developed. A novel, comprehensive model was developed for electrostatic gating of the electrokinetic transport in nanofluidics. A novel method for the manufacturing of electrostatically-gated nanofluidic membranes was developed, using atomic layer deposition (ALD) in deep anodic alumina oxide (AAO) nanopores. Finally, a preliminary investigation of the nanopatterning of OSTE polymers was performed for the manufacturing of polymer nanofluidic devices.QC 20140509
Rappid
NanoGate
Norosensor
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Reschke, Kathleen C. "Development of nanofluidic/microfluidic interfaces as analyte concentrators for proteomic samples." Morgantown, W. Va. : [West Virginia University Libraries], 2010. http://hdl.handle.net/10450/11161.
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Thesis (Ph. D.)--West Virginia University, 2010.Title from document title page. Document formatted into pages; contains xii, 124 p. : ill. (some col.). Includes abstract. Includes bibliographical references.
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Twine, Nicholas B. "Open Nanofluidic Films with Rapid Transport and No Analyte Loss for Ultra-Low Sample Volumes." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535633706613122.
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Sepúlveda, Palma Francisco Hernán. "Déformation de champs thermiques et traitement d’images infrarouges. Application à la caractérisation de systèmes dynamiques." Thesis, Toulouse, INPT, 2009. http://www.theses.fr/2009INPT036G/document.
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Les caméras infrarouges modernes permettent d’accéder à la mesure de champs thermiques et de leur évolution temporelle. Le traitement d’images obtenues permet d’analyser la signature thermique d’objets mobiles ou de fluides en écoulement. Dans ce contexte nous avons fait l’étude de trois expériences différentes. La première consiste à suivre des billes mobiles et à évaluer leurs coefficients d’échanges thermiques avec l’environnement par l’estimation de temps caractéristiques. Dans le deuxième cas, nous faisons une comparaison entre deux fluides qui s’écoulent dans un microcanal, afin de déterminer les variations relatives des propriétés thermiques. La dernière application consiste à réaliser une cartographie de diffusivité thermique avec une source de chaleur mobileThe modern infrared cameras allow the measurement of thermal fields and their temporal evolution. Infrared images processing is suitable to analyze the thermal signature of moving objects or fluid flows. In this context, we made the study of three different experiments. The first one is relative to infrared tracking of randomly moving balls and then estimate their thermal exchanges with the environment by the estimation of some characteristic time. In the second case we made a comparison between two fluids which flow inside a microchannel in order to determine the relative changes of thermal properties. The last application was to estimate a thermal diffusivity field with a mobile heat source
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Jardinier, Elsa. "Co-intégration de fonctions optiques et microfluidiques sur substrat de verre pour l'analyse en milieu hostile." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENT107/document.
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La volonté actuelle de réduire les risques environnementaux et humains amène les chercheurs à trouver de nouvelles solutions de traitement-recyclage poussé des combustibles usés. Dans le but de réduire les volumes d’effluents qu’elle génère, ses temps de réponse et son coût, la miniaturisation de l’analyse chimique en ligne constitue l’un des principaux enjeux de ces recherches. Dans ce contexte, le présent manuscrit traite de la conception, du dimensionnement, de la fabrication et de la caractérisation d’un capteur spectrophotométrique intégré sur verre borosilicate, pour l’analyse des cations radioactifs. Le dispositif, nommé « guide à nanocanal », est réalisé à l’aide des techniques de gravure sèche par plasma et d’échange d’ions. Il contient un coeur ruban surmonté d’un canal de (100 ± 10) nm de profondeur et d’un coeur plan, et permet la propagation d’un mode hybride optimisant ainsi l’interaction fluide/onde guidée sur un large domaine de longueurs d’ondes. Des mesures spectrales d’une solution de nitrate de néodyme en milieu nitrique peu acide (pH 2) et un traitement statistique ont permis de démontrer une limite de détection minimale en terme de coefficient d’absorption de (3,7 ± 0,9) x 10-3 cm-1 sur une longueur de (3,70 ± 0,05) cm et un volume de seulement (7 ± 3) nL. Une structure permettant d’augmenter la longueur d’interaction et donc de diminuer la limite de détection est proposée en perspectives de ce travail, de même qu’une étude préliminaire pour l’utilisation du dispositif en milieu actifThe current will of reducing environment and human hazards has led the scientists to imagine new solutions for nuclear waste reprocessing. Miniaturized online chemical analysis of industrial processes has in particular an important role to play to reduce effluent volumes, response times and costs. In this context, we present the design, fabrication and characterization of an integrated spectrophotometric sensor on glass for chemical analysis of radioactive cations. The device is called a ―nanochannel waveguide‖ and is fabricated by reactive ion etching and ion exchange on glass. It is made of two borosilicate glass wafers bonded together. The first one contains a strip core and the second one a (100 ±10) nm deep nanochannel and a slab core. It allows the propagation of a hybrid mode, optimizing the fluid/guide wave interaction on a large wavelength range. Spectrometric measurements of a neodymium nitrate in nitric acid (pH 2) followed by statistical treatment have led to a limit of detection in terms of absorption coefficient of (3.7 ± 0.9) x 10-3 cm-1 for a device length of (3.70 ± 0.05) cm and fluid volume as low as (7 ± 3) nL. A structure allowing to increase the interaction length and therefore further decrease the detection limit has been proposed as an outlook of this work, and a preliminary study for use in a nuclear environment has been performed
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Pascual, Marc. "Etude hydrodynamique des mélanges binaires thermosensibles." Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLS009.
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La nanofluidique marque l'émergence de nouvelles technologies prometteuses pour la production d'énergies bleues. Ces énergies renouvelables à faible impact environnemental exploitent l'entropie de mélange de l'eau douce et l'eau salée, par exemple à l'estuaire d'un fleuve, pour générer de l'électricité. La diffusio-osmose (écoulement associé au déplacement diffusiophorétique) est un candidat sérieux pour la génération de courants électriques. Ce phénomène prend naissance à l'intérieur même des nanopores d’une membrane, et son intensité est directement liée à la charge de surface du matériau. Les mélanges binaires thermosensibles eau-liquide ionique sont une alternative aux fleuves et océans pour générer un gradient salin. L'état monophasique ou biphasique du mélange est contrôlé par la température; dans le cas présent la nature LCST du fluide induit une démixtion par chauffage.Nos travaux se concentrent sur la séparation de phase du mélange en cavité microfluidique, où nous montrons qu'un gradient de confinement ou de température sont une aide précieuse pour isoler sélectivement les deux phases. Nous mesurons également l'intensité des courants diffusio-osmotiques avec ces solutions de liquides ioniques dans des nanopores uniques et des membranes multiporesNanofluidics marks the emergence of promising new technologies for the production of blue energies. These renewable energies with low environmental impact harness the entropy of mixing of fresh and salt water, for example at the estuary of a river, to generate electricity. Diffusio-osmosis (which flow is associated with diffusiophoretic displacement) is a serious candidate for the generation of electric currents. This phenomenon stems from osmotic effects inside the nanopores of the membrane and its intensity is directly linked to the surface charge of the material. Waterionic liquid thermoresponsive binary mixtures are an alternative to rivers and oceans to generate a salt gradient. The monophasic or biphasic state of the mixture is controlled by temperature; in the present case the LCST nature of the fluid induces a demixing by heating. Our work focuses on the phase separation of the mixture in a microfluidic cavity, where we show that a confinement or temperature gradient is a precious help to selectively isolate the two phases. We also measure the intensity of diffusio-osmotic currents with these solutions of ionic liquids in single nanopores and multi-pore membranes
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Teulon, Lauryanne. "Nouvelles approches pour l'assemblage électrostatique de particules colloïdales par nanoxérographie : du procédé aux applications." Thesis, Toulouse, INSA, 2018. http://www.theses.fr/2018ISAT0044.
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Grâce à leurs propriétés physiques/chimiques uniques, les nanoparticules colloïdales sont au cœur de nombreuses applications innovantes. Afin de faciliter leur caractérisation ou de les intégrer dans des dispositifs fonctionnels, il est nécessaire de les assembler de manière dirigée sur des surfaces solides. Dans ce contexte, l’objectif de cette thèse est de mieux comprendre et d’optimiser la technique de nanoxérographie, méthode d’assemblage dirigé où des nanoparticules sont piégées sur des motifs de charges électrostatiques. Après un premier travail consistant à améliorer le procédé de nanoxérographie, trois problématiques spécifiques ont été adressées : (i) l’assemblage de particules micrométriques. Le couplage de simulations numériques et de manipulations expérimentales a permis d’identifier les paramètres clés de l’assemblage de telles particules colloïdales et d’élargir (facteur 100) la gamme de tailles de particules assemblables par nanoxérographie. (ii) l’analyse de l’assemblage multicouche. Par le biais de nanoparticules modèles luminescentes et par la mise en place d’un nouveau protocole d’assemblage, les critères clés génériques pour l’assemblage 3D de colloïdes par nanoxérographie ont été dégagés. (ii) l’assemblage dirigé de nanogels sensibles à un stimulus environnemental extérieur. L’utilisation d’un protocole d’assemblage optimisé a permis d’élaborer des assemblages de nanogels interactifs avec leur environnement et du faire du tri sélectif de ces nanoparticules sur une même surfaceOwing to their unique physico-chemical properties, colloidal nanoparticles are building blocks for the creation of plentiful innovative devices. In order to make easier their characterization and to incorporate them into functional nano-devices, it is necessary to perfectly control their directed assemblies onto solid surfaces. In this context, this thesis’ purpose is to simultaneously better understand and optimize the nanoxerography method, which allows electrostatic and selective directing assemblies of nanoparticles onto charged patterns. After an optimization of the nanoxerography process, three specific problematics have been addressed: (1) micron-sized particles assembly. The combined use of numerical simulations and experiments enabled to unveil the key parameters involved in micron-sized particles assembly and to expend the particle size range foreseeable for an assembly by nanoxerography (factor 100). (2) the 3D assembly analysis. The influence of diverse parameters on the 3D assembly of luminescent model nanoparticles was quantified by using a new assembly protocol. The results gave the generic key criterions for the 3D assembly of colloids by nanoxerography. (3) directed assembly of nanogels sensitive to an external environmental stimulus. The use of an optimized protocol allowed elaborating nanogels assemblies interactive with their environment and to sort these nanoparticles onto the same surface
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Iazzolino, Antonio. "Engineering three-dimensional extended arrays of densely packed nano particles for optical metamaterials using microfluidIque evaporation." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-01059235.
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1-Microevaporation - Microfluidics is the branch of fluid mechanics dedicated to the study of flows in the channel withdimensions between 1 micron and 100 micron. The object of this chapter is to illustrate the basicprinciples and possible applications of microfluidic chip, called microevaporator. In the first part ofthe chapter, we present a detailed description of the physics of microevaporators using analyticalarguments, and describe some applications. In the second part of the chapter, we present theexperimental protocol of engineering of micro evaporator and different type of microfluidics device.2- On-chip microspectroscopy - The object of this chapter is to illustrate a method to measure absorption spectra during theprocess of growth of our materials in our microfluidic tools. The aim is to make an opticalcharacterization of our micro materials and to carry-out a spatio-temporal study of kineticproperties of our dispersion under study. This instrumental chapter presents the theoretical basis !of the method we used.3-Role of colloidal stability in the growth of micromaterials - We used combined microspectroscopy and videomicroscopy to follow the nucleation and growth ofmaterials made of core-shell Ag@SiO2 NPs in micro evaporators.!We evidence that the growth is actually not always possible, and instead precipitation may occurduring the concentration process. This event is governed by the concentration of dispersion in thereservoir and we assume that its origin come from ionic species that are concentrated all togetherwith the NPs and may alter the colloidal stability en route towards high concentration. 4-Microfluidic-induced growth and shape-up of three-dimensional extended arrays of denselypacked nano particles - In this chapter I present in details microfluidic evaporation experiments to engineer various denselypacked 3D arrays of NPs.5-Bulk metamaterials assembled by microfluidic evaporation - In this chapter I introduced the technique we used (microspot ellipsometry) in close collaborationswith V.Kravets and A.Grigorenko(University of Manchester) and with A.Aradian, P.Barois, A.Baron,K.Ehrhardt(CRPP, Pessac) to characterized the solids made of densely packed NPs. I describe theconstraints that emerge from the coupling between the small size of our materials and the opticalrequirements, the analysis and interpretation of the ellipsometry experiments show that for thematerial with high volume fraction of metal exists the strong electrical coupling between the NPsand the materials display an extremely high refraction index in the near infra-red regime.
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Scarff, Brent. "Radial analyte concentration in microfluidics with an integrated planar nanoporous film." Thesis, 2010. http://hdl.handle.net/1828/2978.
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This work revolves around the development of microfluidic technology for use in biomedical diagnostics with a specific focus on analyte concentration. At the reduced scale inherent with microfluidic technologies the sensing of target species can be difficult since the sample volume is reduced to nanolitres leading to low amounts of target species. This necessitates the need to preconcentrate samples prior to the sensing step. The exclusion-enrichment phenomenon associated with concentration polarization has been used within microfluidic platforms for the purpose of analyte concentration though methods have all been inherently 1-D, axial configurations.
Within this work a novel radial concentration strategy based on a single microfluidic layer on a uniform nanoporous film is presented. The active nanostructured region is defined by the microfluidics, providing flexibility and opening opportunities beyond the single-channel axial configurations to date. Radial geometries have not been previously shown operating as CP based concentration devices, though the unique geometry offers enhanced flux at the perimeter and the capability to focus samples down to small central regions. This focusing ability allows the concentration to take place on a separate layer and does not compete for space with other analysis fluidics. This radial configuration is numerically modeled and experimentally demonstrated.
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Raghu, Riyad. "Polymer Conformational Changes under Pressure Driven Compressible Flow in Nanofluidic Channels." Thesis, 2011. http://hdl.handle.net/1807/29843.
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A hybrid molecular dynamics/multiparticle collision dynamics algorithm was constructed to model the pressure-driven flow of a compressible fluid through a nanoscopic channel of square cross-sectional area, as well as the effect of this flow on the configuration of a polymer chain that was tethered to the surface of this nanochannel. In the process of simulating channel flow, a new adiabatic partial slip boundary condition was created as well as a modified source/sink inlet and outlet boundary condition that could maintain a specified pressure gradient across the channel without the large entrance effects typically associated with these algorithms. The results of the flow simulations were contrasted with the results from a series solution to the Navier-Stokes equation for isothermal compressible flow, and showed excellent agreement with the results from the series solution when slip-boundary conditions were applied. A finitely extendible non-linear elastic spring and bead polymer chain was used to simulate the effect of flow on the polymer chain configuration under poor solvent and θ solvent conditions. Under θ solvent conditions, the cyclical dynamics that have been previousy observed for tethered polymer chains in pure shear flows were noted, however they were restricted to the end of the polymer chain. Under poor solvent conditions, the polymer adopted a metastable helix configuration as it collapsed to a globule state. The study also examined interchain and intrachain entanglements in polymers using the granny knot and overhand knot. The mechanisms by which these tangles untied themselves were determined. At low flow rates, the tangles unravelled by the end of the chain migrating through the loops of the tangle. At high flow rates, the tangles behaved like an entrained object as they reptated towards the end of the chain.
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Zangle, Thomas Andrew Santiago Juan G. Eaton John Howe Roger. "Concentration polarization at microfluidic-nanofluidic interfaces." 2010. http://purl.stanford.edu/rz014nz6164.
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Wood, Paul G. "Measurement and manipulation in microchannels using AC electric fields." Thesis, 2009. http://hdl.handle.net/1828/1694.
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In this work, alternating current (AC) electric fields are used in combination with microfluidics to manipulate micro- and nano-sized particles and to probe the electrical characteristics of microchannels with potential application in portable diagnostics. This work was carried out as contribution to a collaborative research project involving researchers from chemistry, electrical engineering and mechanical engineering at the University of Victoria, in addition to researchers from the BC Cancer Deeley Research Centre.
The manipulation of particles or cells within a microchannel flow is central to many microfluidic applications. In the context of diagnostics that utilize antibodies in serum, for example, the removal of cells from the sample is often required. Continuous removal of particles and cells is particularly critical in the case of flow-through nanohole array based sensing, as these serve as fine filters and thus are very susceptible to clogging. In this work, chevron shaped, interdigitated electrodes are used to produce dielectrophoretic forces in combination with hydrodynamic drag to displace particles from their corresponding streamlines to the center of a microchannel. Analytical and finite element modeling are used to provide insight into the focusing mechanism.
Dielectrophoresis (DEP) also offers opportunities for particle manipulation in combination with porous media. In this preliminary work, the viability of dielectrophoresis tuned nano-particle transport in a nanohole array is investigated through analytical and numerical modeling. The effects of hydrodynamic drag and Brownian motion are considered in the context of applied voltage, flow rate and particle size. Preliminary flow-through tests are performed experimentally as proof of concept.
The final contribution focuses primarily on external infrastructure that enables AC microfluidic diagnostics, with particular relevance to portable device applications and so-called point-of-care devices. Cell phones, and mp3 players are examples of consumer electronics that are easily operated and are ubiquitous in both developed and developing regions. Audio output (play) and input (record) signals are voltage-based and contain frequency and amplitude information. Audio signal based concentration, conductivity, flow rate, and particle detection measurements are demonstrated in a microfluidic platform.
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Ozturk, Serdar 1979. "Microfluidic Investigation of Tracer Dye Diffusion in Alumina Nanofluids." Thesis, 2012. http://hdl.handle.net/1969.1/148127.
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Nanofluids, a new class of fluids engineered by suspending nanometer-sized particles in a host liquid, are offered as a new strategy in order to improve heat and mass transfer efficiency. My research was motivated by previous exciting studies on enhanced mass diffusion and the possibility of tailoring mass transport by direct manipulation of molecular diffusion. Therefore, a microfluidic approach capable of directly probing tracer diffusion between nanoparticle-laden fluid streams was developed. Under conditions matching previously reported studies, strong complexation interactions between the dye and nanoparticles at the interface between fluid streams was observed. When the tracer dye and surfactant were carefully chosen to minimize the collective effects of the interactions, no significant change in tracer dye diffusivity was observed in the presence of nanoparticles.
Next, adapting tracer dyes for studies involving colloidal nanomaterials was explored. Addition of these charged tracers poses a myriad of challenges because of their propensity to disrupt the delicate balance among physicochemical interactions governing suspension stability. Here it was shown how important it is to select the compatible combinations of dye, nanoparticle, and stabilizing surfactant to overcome these limitations in low volume fraction (< 1 vol%) aqueous suspensions of Al2O3 nanoparticles. A microfluidic system was applied as a stability probe that unexpectedly revealed how rapid aggregation could be readily triggered in the presence of local chemical gradients. Suspension stability was also assessed in conjunction with coordinated measurements of zeta potential, steady shear viscosity and bulk thermal conductivity.
These studies also guided our efforts to prepare new refrigerant formulations containing dispersed nanomaterials, including graphene nanosheets, carbon nanotubes and metal oxide and nitride. The influence of key parameters such as particle type, size and volume fraction on the suspension's thermal conductivity was investigated using a standard protocol. Our findings showed that thermal conductivity values of carbon nanotube and graphene nanosheet suspensions were higher than TiO2 nanoparticles, despite some nanoparticles with large particle sizes provided noticeable thermal conductivity enhancements. Significantly, the graphene containing suspensions uniquely matched the thermal conductivity enhancements attained in nanotube suspensions without accompanying viscosity, thus making them an attractive new coolant for demanding applications such as electronics and reactor cooling.
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De, Leebeeck Angela. "Nanofluidic species transport and nanostructure based detection on-chip." Thesis, 2006. http://hdl.handle.net/1828/2142.
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Transport in nanostructures and on-chip detection using nanohole arrays are investigated using a combination of analytical, numerical and experimental techniques. The first half of the thesis describes a fundamental theoretical contribution to the study of nanofluidic species transport. The second half of the thesis describes an applied experimental application of nanostructure-based species detection in a microfluidic framework.
A continuum based analytical solution and numerical model are developed to quantify ionic dispersion of charged and neutral species in nanochannels and identify fundamental dispersion mechanisms unique to nanoscale flows. Ionic dispersion for circular cross-section nanochannels is quantified as a function of a valance parameter. the relative electrical double layer thickness. and the form of the velocity profile. Two unique mechanisms governing ionic dispersion in both pressure- and electrokinetically driven flows are identified. The results of the analytical solution are supported and extended by the results of the numerical model. Collectively, these results indicate that dispersion of ionic species in nanoscale channels is markedly charge dependent and substantially deviates from that of neutral solutes in the same flow.
A microfluidic device with a set of embedded nanohole array surface plasmon resonance sensors is developed and successfully demonstrated experimentally as a chemical/biological sensor. The device takes advantage of the unique optical properties. the surface-based sensitivity, the transmission mode operation. relatively small footprint, and repeatability characteristic of nanohole arrays. Proof-of-concept measurements are performed on-chip to detect changes in liquid refractive index at the array surface. proportional to change in near wall concentration or indicative of a surface binding event. Employing a cross-stream array of nanohole arrays. the device is applied to detect microfluidic concentration gradients as well as to detect surface binding in the assembly process of a cysteamine monolayer-biotin-streptavidin system.
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Tsung-ChenTsai and 蔡宗承. "Power Generation by Reverse Electrodialysis in Nanopore Membranes from a Microfluidic and Nanofluidic System." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/02664774512989023119.
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Kim, Bo Young. "Biofunctionalization of submicrometer pores and mass limited sample manipulations in three-dimensional hybrid microfluidic/nanofluidic devices /." 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3337818.
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Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2008.Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 6759. Adviser: Jonathan V. Sweedler. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.