Neste trabalho são apresentados processos de microfabricação de estruturas contendo microcanais e sistemas de manipulação hidrodinâmica e eletroosmótica de fluídos. Foram desenvolvidos processos de microfabricação utilizando toner sobre poliéster, toner sobre vidro, toner como resiste, além de métodos alternativos de perfuração de lâminas e selagem de microestruturas em vidro, desenvolvimento de microestruturas para eletroforese capilar e espectrometria de massas com ionização por eletronebulização. A caracterização dos materiais e processos permitiu uma ampla visão das potencialidades e alternativas dos processos de microfabricação, tendo sido demonstrado que os dispositivos produzidos em toner-poliéster são quimicamente resistentes às substâncias tipicamente utilizadas em eletroforese capilar. Neste trabalho, um detector condutométrico sem contato foi implementado em microestruturas de toner-poliéster e a separação eletroforética de alguns metais alcalinos é demonstrada. A microestrutura foi projetada no formato padrão em cruz, tendo o canal de separação 22 mm de comprimento, 12 µm de profundidade e largura típica. A cela condutométrica foi construída sobre o canal de separação utilizando-se fita adesiva de cobre (1 mm de largura) como eletrodos. O sinal aplicado na cela foi de 530 kHz e 10 Vpp . A separação de K+, Na+ e Li+ na concentração de 100 µmol L-1 foi efetuada em torno de 0,8 min, utilizando-se 1 kV como potencial de separação. Foram desenvolvidos microchips para análise por espectrometria de massas com introdução de amostra por eletronebulização, sendo determinado cluster do íon cloreto em concentração de 1 mmol L+. Também solução com 1 mmol/L de glucosamina em água/metanol 1: 1 (v/v), sob corrente de 100 nA gerou sinal estável e livre de descarga corona. Utilizando detecção amperométrica, obteve-se eletroferogramas mostrando a separação de iodeto (10 mmol L-1) e ascorbato (40 mmol L-1) em potencial de separação de 4,0 kV (800 V cm-1 potencial de detecção de 0,9 V (vs. Ag/AgCI), injeção com 1,0 kV/1°s, tampão borato de sódio 10 mmol L+ com CTAH 0,2 mmol L-1, pH 9,2. Obteve-se eficiência de 1,6.104 pratos/m e foi possível obter limites de detecção de 500 nmol L-1 (135 amol) e 1,8 µmol L-1 (486 amol) para iodeto e ascorbato, respectivamente. O processo de fabricação utilizando toner como material estrutural para microchips em vidro foi bem estabelecido, assim como os modos de detecção fotométrico e condutométrico foram demonstrados. Foram obtidos eletroferogramas par detecção condutométrica sem contato de solução 200 µmol L-1 de K+, Na+ e U+, em tampão histidina/ácido lático 30 mmol L-1 9:1 (v/v) água:metanol, injeção eletrocinética de 2,0 kV/5,0 s, potencial de separação de 1 kV, 530 kHz de frequência e tensão de 2,0 Vpp. Também foi implementado um sistema de detecção fotométrico para microchip operando em 660 nm, tendo sido utilizado para a detecção de azul de metileno 1,0 mmol L-1 em tampão de corrida de barato de sódio 20 mmol L-1 (pH 9,2), com o detector posicionado a 40 mm do ponto de injeção e com injeção eletrocinética a 2,0 kV por 12 s com picos bem resolvidos em menos de 1 min. / Microfabrication processes and devices for hydrodynamic and electroosmotic manipulation were developed based on toner-polyester, toner-glass and toner-as-resist techniques. Additionally, techniques to perforate glass slides and sealing of glass devices were introduced. Microdevices for capillary electrophoresis and electrospray for mass spectrometry were developed using these techniques. The characterization of the materiais and the processes demonstrated that the devices obtained by the toner-polyester process are compatible with the media used for capillary electrophoresis. The detection of alkaline ions with capillary electrophoresis with contactless conductivity detection was demonstrated. The typical cross shape microstructure was designed with a 22-mm long and 12-µm deep separation channel. The conductivity cell was implemented with 1-mm wide adhesive copper stripes. The applied signal was 530kHz and 10Vpp . The separation of 100µmo1L-1 K+, Na+, and Li+ was accomplished in 0.8 min under a voltage of 1 kV. Another toner-polyester microchip was developed to demonstrate its usefulness for electrospray/mass spectrometry. Solutions of 1 mmol L-1 potassium chloride and 1 mmol L-1 glucosamine in water/methanol 1:1 (v/v) were introduced with stable current of 100 nA without corona discharge. Capillary electrophoresis with amperometric detection was also demonstrated. The separation of iodide (10 mmol L-1) and ascorbate (40 mmol L-1) was carried out at 4.0 kV (800 V cm-1) with detection potential of 0.9 V (vs. Ag/AgCl), electrokinetic injection at 1.0 kV/10 s, running buffer of sodium borate 10 mmol L-1 with CTAH 0.2 mmol L-1 , pH 9.2. The efficiency was 1.6.104 plates/m and the limits of detection were 500 nmol L-1 (135 9mol) and 1.8 µmol L-1 (486 amol) for iodide and ascorbate, respectively. The toner-glass process was proposed and conductivity and photometric detections were demonstrated for the devices generated by this new technique. The separation of 200 pmol L-1 K+, Na+, and Li+ was achieved in buffer histidine/lactic acid 30 mmol L-1 water/methanol 9: 1 (v/v), electrokinetic injection at 2.0 kV/5.0 s, separation potential of 1 kV, and contactless conductivity detection at 530 kHz and 2.0 Vpp. The photometric detection of methylene blue at 660 nm was carried out in sodium borate 20 mmol L-1 (pH 9.2).

Philosophiae Doctor - PhD / The need for clean, non-toxic drinking water supplies, free of pollutants and metal contamination is vital in impoverished areas and the developing world alike. With this in mind, the development of accurate, inexpensive, portable and simple devices for remote sensing applications is therefore pivotal for early detection and the prevention of illnesses. Over the last two decades, adsorptive stripping voltammetry (AdSV) has emerged as a superior detection method over common analytical techniques due to its low-cost instrumentation, unskilled labour and ability to detect a wide range of analytes. / 2020-08-31

Dans cette thèse, on a étudié l’évolution de l’interface par électro-osmose entre deux couches de fluides dans un canal microfluidique. Les applications de ce problème concernent le mélange et le transport, sans contact avec des actionneurs, de fluides en micro-canal. De nombreuses questions restent toutefois posées lorsque le champ est oscillant en temps, notamment vis à vis de la stabilité de l'interface entre les deux fluides. Une analyse de stabilité linéaire basée sur une perturbation à l’interface a été réalisée pour un film mince d'électrolyte sous des champs électriques continus (constants) et alternatifs (dépendant du temps). Une analyse asymptotique avec une hypothèse de grande longueur d’onde des équations d'Orr-Sommerfeld a été appliquée afin de déterminer les seuils de stabilité paramétriques d'un film mince aqueux. L’accent a été mis sur les effets de la tension de surface, de la pression de disjonction pour l'interaction gaz-liquide-substrat, de l'amplitude et de la fréquence du champ électrique appliqué, ainsi que du potentiel zêta du substrat et de la surface libre. Une analyse comparative des profils de vitesse de l’état de base avec et sans contraintes de Maxwell à l’interface, a montré que les gradients de vitesse étaient importants à l'interface liquide-liquide avec les contraintes de Maxwell. De tels gradients sont essentiels à l'instabilité interfaciale sous l’action d’un champ électrique périodique car ils peuvent atténuer ou amplifier les ondes à l’interface. Parallèlement, un dispositif expérimental a été conçu et monté afin de caractériser l’écoulement électroosmotique dans un micro-canal rectangulaire. Avec l'aide d'une analyse PTV (« Particle Tracking Velocimetry »), les distributions de vitesse ont été obtenues et comparées aux prédictions théoriques. Cette comparaison a permis d’estimer le potentiel zêta du PDMS utilisé, valeur conforme à la valeur indiquée dans la littérature. / Since the past decade, use of electro-osmotic flow (EOF) as an alternative flow mechanism in microdevices is becoming more popular due to its less bulky and low maintenance system design. However, one of the biggest shortcomings for its usage in mainstream applications is that it requires the concerned liquid to be electrically conductive. One idea can be to use the flow of conductive fluids to transport non-conductive liquids passively via interfacial shear transfer. Such an idea can has numerous applications in a wide range of fields like bio-chemical processing (e.g. lab-on-a-chip reactors, mixers, etc.), to oil extraction from porous rock formations. One of the significant characteristics of micro-scale flows is high surface to volume ratio, which significantly highlights the role of multi-phase interfaces in such dynamics. The presence of a fluid-fluid interface in an EOF necessitates the characterization of the parameters responsible for hydrodynamic instability of such systems. The present work focuses on the role of steady and time-dependent electric stress (Maxwell stress), capillary force and disjoining pressure on fluid-fluid interfacial instability. A linear stability analysis of interfacial perturbation was performed for a thin film of electrolyte under DC and AC electric fields. Through long wave asymptotic analysis of the Orr-Sommerfeld equations, parametric stability thresholds of a thin aqueous film explored. Further, a set of experiments were performed in order to characterize the EOF in a rectangular microchannel. With the help of a Particle Tracking Velocimetry analysis, velocity distributions were obtained which agreed well to the theoretical values. This was further used to estimate PDMS zeta potential, which was found to be within the reported values in the existing literature. Liquid-liquid interfacial deformation was also explored under a time-periodic EOF and a wide range of the magnitudes of capillary force, and diffusive and convective transport.

This thesis aims to investigate the use of additive manufacturing (AM) as a novel manufacturing process for the production of milli-scale chemical reaction systems. Five well developed additive manufacturing techniques; stereolithography (SL), selective laser melting (SLM), fused deposition modelling (FDM), ultrasonic additive manufacture (UAM) and selective laser sintering (SLS) were used to manufacture a number of miniaturised flow devices which were tested using a range of organic and inorganic reactions. SL was used to manufacture a range of functioning milli-scale flow devices from Accura 60 photoresin, with both simple and complex internal channel networks. These devices were used to perform a range of organic and inorganic reactions, including aldehyde and ketone functional group interconversions. Conversion of products within these reactors, were shown to be comparable to commercially available milli-scale coil reactors. More complex designs, which allowed SL parts to be integrated to existing flow and analytical instrumentation, allowed us to develop an automated reaction analysis and optimisation platform. This platform allowed precise control over the reaction conditions, including flow rate, temperature and reagent composition. We also designed a simplex type reaction optimisation software package that could input data in the form of reaction conversions, peak intensities, and thermocouple data, and generate a new set of optimal reaction conditions. SL parts which incorporated embedded analytical components were also manufactured, which allowed us to perform inline reaction analysis as a feedback method for input into the optimisation platform. Stereolithography was shown to be a highly versatile manufacturing method for designing and producing these flow devices, however the process was shown to be still limited by the range of processable materials currently commercially available. SLM was also used to manufacture a number of functioning milli-scale flow devices from stainless steel and titanium, which had simplistic internal channel designs of diameters ranging from 1 to 3 mm. Again, SLM parts were manufactured which incorporated embedded analytical components, which could be integrated into an automated reaction platform. These devices, unlike parts produced via SL, could be attached to heating platforms to allow us to perform high temperature reactions. This control over the reaction temperature formed an essential part of the reaction optimisation platform. These parts were again used to perform a ketone functional group interconversion. Internal structures of these SLM parts were also visualised via micro computed tomography (μCT or microCT) scanning as well as optical microscopy. FDM was used throughout the project as an inexpensive method of prototyping parts which were to be manufactured via more expensive manufacturing processes. This prototyping allowed the optimisation of intricate design features, such as the manufacture of an inline spectroscopic flow cell for integration with a commercially available LC system. FDM was also proposed as a customisable approach to designing and manufacturing flow devices with embedded components, however the current limitations in build resolution and materials choices severely limited the use of FDM for this application. UAM was also proposed as a novel manufacturing process whereby the build process would allow discrete components to be embedded directly into a flow channel. This was demonstrated by embedding a type-k thermocouple across a 2 mm channel. The data from this thermocouple was monitored during a heated reaction, and used as a method of determining the exact reaction conditions the reaction medium was being exposed to. SLS was also proposed as a possible manufacturing method for milli-scale flow devices, however it proved difficult to remove un-sintered powder from parts with internal channel diameters as high as 5 mm. It was shown that this powder was forming a dense semi solid, due to the large degree of shrinkage upon cooling of the SLS parts, which was compressing the powder. More research into optimum processing conditions is required before SLS could be used for the production of intricate channel networks.

In 21 century finned surfaces are used in almost all condensers to enhance their heat transfer capabilities. A lot of different models are presented in the literature: on horizontal and vertical finned tubes, inside finned tubes. The validation method of the theoretical models is based on comparison between measurement of average heat transfer coefficient and one calculated by the model. But in this case it is impossible to validate all approaches made in the theory.<p>\ / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

L’objectif de ce travail fut de développer et d’étudier les performances d’un microprocédé basse pression à écoulement élongationnel pour la production de nanoémulsions polymérisables de tailles contrôlées et de distributions de taille étroites. Le diamètre des nanogouttelettes a pu être précisément ajusté dans la gamme 50-300 nm en modifiant simplement les paramètres de procédé : le débit réciproque au travers du micromélangeur, le nombre de cycles et la dimension caractéristique du microcanal. Les nanoémulsions produites furent, dans une seconde étape, polymérisées par voie thermique ou par irradiation UV afin de générer des suspensions colloïdales de nanoparticules de polymère de tailles également contrôlées (87-360 nm). Un monomère, un agent de réticulation ainsi qu’un amorceur thermique ou photochimique appropriés furent par la suite ajoutés au milieu continu de ces nanosuspensions. Les solutions résultantes servirent comme phases dispersées dans des générateurs microfluidiques de gouttelettes à capillaires. Les microgouttelettes de taille contrôlée ainsi produites furent polymérisées en ligne par irradiation UV pour donner lieu à des microsphères ou à des microparticules coeur-écorce composites de polymère toutes deux dopées avec des nanoparticules de polymère. Des microparticles composites et hydrides comportant des nanoparticules d’or dans le coeur et d’argent dans l’écorce furent également obtenues grâce à la réduction photochimique in situ des sels précurseurs lors de la photopolymérisation des microgouttelettes. Ce travail a démontré l’efficacité d’un nouveau dispositif microfluidique basse énergie pour la production de nanoémulsions et leur emploi pour la synthèse de matériaux polymères morphologiquement complexes. / The aim of this work was to develop and to study the performances of a low pressure elongational-flow microprocess for the production of size-controlled polymerizable nanoemulsions with narrow size distributions. Nanodroplets diameter was easily tuned in the size range 50-300 nm by varying the process parameters, namely the reciprocating flow rate through the micromixer, the number of cycles and the characteristic dimension of the microchannel. Obtained nanoemulsions were in a second step thermally or UV-assisted polymerized to give colloidal suspensions of size-tunable polymer nanoparticles (87-360 nm). Then, a proper monomer, crosslinker and thermal- or photo-initiator were added to the continuous phase of these nanosupensions. The resulting mixtures were used as the dispersed phases of two different capillaries-based microfluidic droplet generators. The produced sizecontrolled microdroplets were finally UV polymerized online and plain as well as core-shell composite polymeric microparticles doped with lower scale polymer nanoparticles were obtained. Composite/hybrid polymeric core-shell microparticles were also synthesized for which gold nanoparticles in the core and silver nanoparticles in the shell were synthesized in situ from their salt precursors during microdroplets polymerization. This work has demonstrated the high efficiency of a novel low energy microfluidic emulsification device for the production of nanoemulsions which were used for the synthesis of morphologically complex polymeric materials.

Significant technological advances of the last years have been possible by developments in Optofluidics, which is a field that deals with the integration of optics and microfluidics into single devices. The work described in this thesis is based on five scientific publications related to the use of fiber optic technology to build integrated optofluidic devices. The first three publications are within the field of life-science and point towards in-vivo and point-of-care applications, whereas the last two publications cover the study and the use of plasmonic nanoparticles for electrical modulation of light. Aiming at developing useful tools for in-vivo biological applications, the first publication consists of designing and testing a functional optical fiber for real-time monitoring and selective collection of fluorescent microparticles. This probe relies on a microstructured optical fiber with a hole along its cladding, which is used to selectively aspirate individual particles of interest once their fluorescence signal is detected. On the same line of research, the second publication contemplates the fabrication of a fiber probe that traps single microparticles and allows for remote detection of their optical properties. This probe is also based on a microstructured fiber that enables particle trapping by fluidic forces. The third publication addresses the development of an all-fiber miniaturized flow cytometer for point-of-care applications. This system can analyze, with excellent accuracy and sensitivity, up to 2500 cells per second by measuring their fluorescence and scattering signal. A novel microfluidic technique, called Elasto-inertial microfluidics, is employed for aligning the cells into a single-stream to optimize detection and throughput. The fourth publication involves the experimental and theoretical study of the electrical-induced alignment of plasmonic gold nanorods in suspension and its applicability to control light transmission. This study is done by using an all-fiber optofluidic device, based on a liquid-core fiber, which facilitates the interaction of light, electric fields, and liquid suspensions. Results show that nanorods can be aligned in microseconds, providing a much better performance than liquid-crystal devices. Finally, the fifth publication consists of an upgrade of the previous device by integrating four electrodes in the cladding of the liquid-core fiber. This improvement enables nanosecond response time and the possibility of digitally switching nanorods between two orthogonal aligned states, overcoming the limitation of slow thermal relaxation. The work presented here shows that optofluidics based on optical fibers is a robust and convenient platform, as well as a promising direction for the developing of novel instruments in fields such as life-science, non-linear optics, plasmonic, and sensing. / <p>QC 20171018</p>

Miniaturization of biological analysis is a trend in the field of biotechnology aiming to increase resolution and sensitivity in biological assays. Decreasing the reaction volumes to analyze fewer analytes in each reaction vessel enables the detection of rare analytes in a vast background of more common variants. Droplet microfluidics is a high throughput technology for the generation, manipulation and analysis of picoliter scale water droplets an in immiscible oil. The capacity for high throughput processing of discrete reaction vessels makes droplet microfluidics a valuable tool for miniaturization of biological analysis. In the first paper, detection methods compatible with droplet microfluidics was expanded to include SiNR FET sensors. An integrated droplet microfluidics SiNR FET sensor device capable of extracting droplet contents, transferring a train of droplets to the SiNR to measure pH was implemented and tested. In paper II, a workflow was developed for scalable and target flexible multiplex droplet PCR using fluorescently color-coded beads for target detection. The workflow was verified for concurrent detection of two microorganisms infecting poultry. The detection panel was increased to multiple targets in one assay by the use of target specific capture probes on color-coded detection beads.   In paper III, droplet microfluidics has been successfully applied to single cell processing, demonstrated in paper III, where reverse transcription was performed on 65000 individually encapsulated mammalian cells. cDNA yield was approximately equivalent for reactions performed in droplets and in microliter scale. This workflow was further developed in paper IV to perform reverse transcription PCR in microfluidic droplets for detection of exosomes based on 18S RNA content. The identification of single exosomes based on RNA content can be further developed to detect specific RNA biomarkers for disease diagnostics. Droplet microfluidics has great potential for increasing resolution in biological analysis and to become a standard tool in disease diagnostics and clinical research. / <p>QC 20171024</p>

L’objectif de cette thèse est d’étudier expérimentalement les deformations de microcapsules dans un écoulement confiné. Les microcapsules sont composées d’albumine du sérum humain avec des concentrations de 5 à 20 [g/100mL]. Leur taille varie de 50 à 1000 [μm]. Les capsules sont injectées dans des écoulements de Poiseuille produits dans des canaux microfluidiques présentant deux sections différentes : circulaire ou carrée.La mesure des caractéristiques géométriques de microcapsules déformées couplée à des simulations numériques mène à la détermination du module de cisaillement surfacique. Cette caractéristique mécanique augmente fortement tant avec la taille qu’avec la concentration en protéine de la capsule, et plus précisément avec le produit de ces deux paramètres.Le fluide est ensemencé avec des microparticules pour mesurer l’écoulement induit par une capsule dans un capillaire cylindrique par la méthode de la vélocimétrie par suivi de particules. Les zones de recirculation et de perturbation sont alors déduites et comparées avec la simulation numérique d’un objet rigide dans un capillaire et présentant le profil donné par les expériences. Finalement un système original de visualisation optique est consacré à l’observation simultanée de la vue de côté et de la vue de face des capsules pour obtenir sa forme entière. Ceux-ci révèlent l’existence des plis tout autour de la membrane des capsules. Le seuil de formation et l’évolution de ces plis sont étudiés en fonction de la vitesse, de la taille et du confinement, dans des canaux de section circulaire ou carrée. / The objective of this thesis is to study experimentally microcapsule deformations in confined flows. The microcapsules are made of cross-linked proteins, the human serum albumin (HSA) with concentrations from 5 to 20 [g/100mL]. Their size vary from 50 to 1000 [μm]. Capsules are injected in Poiseuille flows generated within microfluidics channels with two different cross sections geometries : circular or square.The measurement of geometrical characteristics of deformed microcapsules coupled with numerical simulations leads to the determination of the surface shear modulus. This mechanical characteristic increases strongly with both the size and the protein concentration of the capsule, and more precisely with the product of these two parameters.The flow is seeded with microparticles to measure the induced flow of a capsule in a cylindrical capillary by particle tracking velocimetry. The recirculation and perturbation zones are then deduced and compared with numerical simulation of a rigid body flowing in a capillary. Finally an original system of optical visualization is dedicated to the simultaneous observation of the side and the front view of the capsules to get its whole shape. These reveal radial wrinkles all around capsules membrane. The formation threshold and the evolution of these wrinkles are studied as function of the capsule velocity and size and the confinement within capillaries with circular or square cross–section.

Cette thèse présente une étude numérique et expérimentale d’écoulements gazeux raréfiés confinés, induits par gradients thermiques. L’écoulement d’un gaz raréfié peut en effet être généré en appliquant uniquement un gradient tangentiel de température le long d'une paroi. Ainsi, sans gradient initial de pression, le gaz peut se déplacer de la région froide vers la région chaude. Ce phénomène, appelé transpiration thermique, est à la base du fonctionnement des pompes dites de Knudsen, capables de générer un pompage du gaz sans utiliser de pièces mécaniques mobiles. L’apport principal de ce travail est relatif à l’investigation numérique de l’écoulement de transpiration thermique dans trois nouvelles configurations de pompe Knudsen. Dans ce but, une méthode numérique de simulation d’écoulements dans le régime de glissement a été développée ; elle implémente des conditions aux limites de saut de vitesse et de température spécifiques dans un code CFD commercial. Parallèlement, un code DSMC a été mis en œuvre pour étudier des écoulements plus fortement raréfiés dans les géométries les plus complexes. Des écoulements de transpiration thermique générés dans des canaux courbés, dans des canaux convergents/divergents ou entre deux surfaces spécialement micro-texturées ont ainsi été étudiés. D’autre part, l’analyse expérimentale d’un écoulement de transpiration thermique dans un microtube de section circulaire a été réalisée sur un nouveau banc d’essais conçu pour être adaptable à diverses géométries de canaux ou de pompes Knudsen. / This thesis presents a numerical and experimental analysis of internal rarefied gas flows induced by temperature fields. In rarefied gases, a flow can be generated by solely applying a tangential temperature gradient along a wall: without any initial pressure gradient, the gas macroscopically moves from the cold toward the hot region. This phenomenon is the so-called thermal creep or thermal transpiration effect. It is the main operating principle of the Knudsen pump, which can generate gas pumping without the need of any moving parts. The main aspect of this work is centered on numerical investigations of thermal transpiration flows in three new possible configurations of Knudsen pumps. For that goal, a numerical model for slip flows has been developed in which the appropriate slip boundary conditions are implemented in a commercial CFD code and a DSMC code has been adapted for studying transition flows in complex geometries. The pumping effect of curved-channel Knudsen pumps, the thermal transpiration flows through tapered channels and between two ratchets surfaces at different uniform temperatures have been investigated. In addition, an experimental study of thermal transpiration flow through a single micro-tube has been carried out on a new experimental set-up designed to be adaptable for testing thermally driven flows through various kinds of microchannels or generated by autonomous Knudsen compressors