Дисертації з теми "Microfluidic fuell cell"

The microfluidic fuel cell or laminar flow-based fuel cell is a membraneless fuel cell which typically consists of two electrodes mounted within a T- or Y-shaped microchannel. Aqueous fuel and oxidant are introduced from the two inlets of the channel and flow together side-by-side toward the end of the channel. The Reynolds number in the microchannel is low, and hence viscous forces are dominant over the inertial forces. This causes the anolyte and catholyte form a co-laminar flow inside the microchannel which is required to maintain the separation of the fuel and oxidant and limit the reactions to the appropriate electrodes. In this work, a comprehensive numerical model of the microfluidic fuel cell is developed using COMSOL Multiphysics. This model accounts for the mass and momentum transport phenomena inside the device as well as the electrochemical reaction kinetics which are described by the Butler-Volmer equations. Potential equations are used to model both the ionic conduction in the electrolyte and the electrical conduction in the solid electrodes. The validity of the developed model is first checked by verifying it against the numerical and experimental results previously reported in the literature. The model is then used to assess the effect of different modifications, which have been applied on the microfluidic fuel cell since its advent, by calculating the polarization curves associated with each modification. In this thesis, a novel design of microfluidic fuel cell with a tapered channel is also proposed. Using the numerical model, it is shown that the tapered geometry improves the fuel utilization by up to four times in addition to a substantial improvement in the power density. A similar numerical model is developed to study the performance of a microfluidic fuel cell with flow-through porous electrodes. Using this model, the effect of porosity on the net power output of the fuel cell is investigated and an optimum value for porosity is calculated. The model presented is a valuable tool, as it can be used to study the effect of any modifications on the cell performance before fabricating and testing the new design in an extensive experimental study.

The demand for novel renewable energy sources, together with the new findings on bacterial electron transport mechanisms and the progress in microbial fuel cell design, have raised a noticeable interest in microbial power generation. Microbial fuel cell (MFC) is an electrochemical device that converts organic substrates into electricity via catalytic conversion by microorganism. It has represented a continuously growing research field during the past few years. The great advantage of this device is the direct conversion of the substrate into electricity and in the future, MFC may be linked to municipal waste streams or sources of agricultural and animal waste, providing a sustainable system for waste treatment and energy production. However, these novel green technologies have not yet been used for practical applications due to their low power outputs and challenges associated with scale-up, so in-depth studies are highly necessary to significantly improve and optimize the device working conditions. For the time being, the micro-scale MFCs show great potential in the rapid screening of electrochemically active microbes. This thesis presents how it will be possible to optimize the properties and design of the micro-size microbial fuel cell for maximum efficiency by understanding the MFC system. So it will involve designing, building and testing a miniature microbial fuel cell using a new species of microorganisms that promises high efficiency and long lifetime. The new device offer unique advantages of fast start-up, high sensitivity and superior microfluidic control over the measured microenvironment, which makes them good candidates for rapid screening of electrode materials, bacterial strains and growth media. It will be made in the Centre of Hybrid Biodevices (Faculty of Physical Sciences and Engineering, University of Southampton) from polymer materials like PDMS. The eventual aim is to develop a system with the optimum combination of microorganism, ion exchange membrane and growth medium. After fabricating the cell, different bacteria and plankton species will be grown in the device and the microbial fuel cell characterized for open circuit voltage and power. It will also use photo-sensitive organisms and characterize the power produced by the device in response to optical illumination.

Esta tesis presenta el desarrollo y la fabricación de pilas de combustibles microfluídicas para aplicaciones portátiles de baja potencia. En concreto, pilas biológicas que utilizan las enzimas en la degradación de la glucosa. El trabajo está dividido en dos secciones dependiendo de si los dispositivos fabricados son activos, es decir, los reactivos son suministrados a la micropila por bombeo (Capítulo 2 y 3). O si por el contrario los reactivos fluyen sin necesidad de mecanismos externos los dispositivos serán pasivos (Capítulo 4 y 5). En el primer capítulo de la tesis se ha llevado a cabo la primera aproximación en el desarrollo de micro pilas de combustible glucosa/O2 con el objetivo de hacer posible las primeras medidas electroquímicas con enzimas. La pila microfluídica fue construida sobre un sustrato de vidrio en el cual se grabaron electrodos de oro mediante técnicas de microfabricación. Por otro lado, se utilizó fotolitografía suave para la fabricación de los canales (con forma de Y) en PDMS. Esta forma de canal permitió fluir dos soluciones en paralelo usando una bomba de jeringa. Como primera aproximación, las enzimas se encontraban fluyendo de manera continua a través del canal. Eso provocaba experimentos caros y dificultaba su posible aplicación portátil. De este modo, el siguiente aspecto en abordarse fue la inmovilización de los biocatalizadores sobre los electrodos de la micro pila. El Capítulo 2 presenta la fabricación de una pila de combustible que posee los biocatalizadores inmovilizados en la superficie de los electrodos lo cual hace que los biocatalizores sean aprovechados más eficientemente que en la anterior pila. Los electrodos se han fabricado utilizando resina pirolizada y se han usado por primera vez con éxito en pilas microfluídicas enzimáticas de este tipo. La pila está compuesta por diferentes capas de material plástico laminado que han sido cortadas usando un plotter de corte. Esto hace que la fabricación del dispositivo sea rápida, barata y compatible con la manufacturación a gran escala. El canal microfluídico se ha definido también sobre este tipo de material plástico, evitando el largo proceso litográfico relacionado con el PDMS. Por otro lado, el canal (en forma de Y) permite optimizar la potencia que obtenemos de la pila cuando bombeamos dos soluciones diferentes. Por otro lado, el dispositivo necesita ser simplificado para finalmente obtener una fuente de energía portátil. Con este objetivo se abordó la siguiente fase de la tesis. El Capítulo 4 describe la fabricación de una pila microfluídica implementada utilizando sustratos de papel a través de los cuales fluyen los reactivos (de manera pasiva) por efecto capilar. Los componentes de la pila se cortaron utilizando un plotter de corte, lo que permitía fabricar dispositivos con mucha rapidez. Se probó el buen funcionamiento de una pila de combustible de papel y enzimática obteniendo valores de potencia similares a los presentados en el Capítulo 3 (donde las soluciones eran bombeadas). A partir de aquí el trabajo se centró en aproximar la pila de papel a la simplicidad de los test de flujo lateral. Así que la micro pila fue adaptada y operada con éxito usando una única solución, generando energía de una bebida comercial. El Capítulo 5 presenta una micropila de combustible fabricada en papel mucho más sofisticada y pequeña que la del capítulo anterior. Se probó satisfactoriamente una nueva combinación de biocatalizadores que permitió trabajar utilizando muestras a pH neutro. Además, el tamaño compacto del sistema abrió la posibilidad de operar la pila de combustible con fluidos fisiológicos como por ejemplo la sangre. Finalmente, se ha demostrado que es posible tener una pila preparada para alimentar dispositivos que requieran poca demanda de energía. Sin embargo, todavía se deben hacer esfuerzos para acercar esta pila a un mundo real, debido principalmente a que el tiempo de vida de las enzimas es todavía limitado.
This thesis presents the development and fabrication of microfluidic fuel cells for low power and portable applications. Specifically, biological fuel cells that use enzymes for glucose degradation. This work is divided in two sections depending on whether the fabricated devices are active, i. e. the reagents are supplied into the micro fuel cell by pumping (Chapters 2 and 3). If, on the contrary, the reagents flow without needing external mechanisms they are passive devices (Chapters 4 and 5). In the first chapter of the thesis the first approach in the development of glucose/O2 micro fuel cells was conducted in order to allow for the initial electrochemical measurements with enzymes. The microfluidic fuel cell was fabricated using a glass substrate in which gold electrodes were impressed using microfabrication techniques. On the other hand, soft lithography was used to fabricate the Y-shaped PDMS channels. This channel shape enabled to flow two solutions in parallel using a syringe pump. The enzymes were continuously flowing through the channel causing expensive experiments in addition to hindering its possible portable application. Thereby, the biocatalysts immobilization on the electrodes was next addressed in this thesis. Chapter 2 presents the fabrication of a micro fuel cell with enzymes trapped on the electrode surfaces which lead to an effective use of the biocatalysts. The electrodes were fabricated using pyrolyzed resists and were successfully used for the first time in enzymatic microfluidic fuel cells of this kind. The fuel cell was formed by different layers of plastic laminated materials cut using a cutter plotter. This promotes a fast and inexpensive device fabrication which is compatible with large scale manufacturing. The microfluidic channel was also defined on this type of plastic materials, thus avoiding the long lithographic process related to the PDMS. Moreover, this Y-shaped channel allows to optimize the power obtained from the fuel cell when two different solution are pumped into the system. Therefore, the following aspect to be addressed was the biocatalyst immobilization over the electrodes of the micro fuel cell Chapter 4 describes the construction of a microfluidic fuel cell fabricated using paper substrates. The reagents flow through this paper (in a passive way) by capillary action. The fuel cell components were cut using a cutting plotter which allows fabricating devices much faster. The proper functioning of this paper-based microfluidic fuel cell was verified obtaining similar power values to those presented in Chapter 3 (were solution were pumped). From here, the work focused on bringing the paper fuel cell closer to the simplicity of lateral flow tests. The fuel cell was then adapted and successfully operated using a single solution, generating energy from a commercial drink. Chapter 5 presents a microfluidic paper-based fuel cell smaller and more sophisticated than the one presented in previous chapter. A new combination of enzyme was tested which allowed to work with samples at neutral pH. Additionally, the compact size of the system opened the possibility to operate the paper fuel cell with physiological fluids, such as blood. Finally, it was demonstrated that was possible to have a fuel cell ready to fed devices demanding low energy. However, more efforts have to be done in the field to approach this fuel cell to a real world mainly due to the still limited lifetime of the enzymes.

Les piles à combustible sont des dispositifs qui transforment l'énergie stockée dans un oxydant et un réducteur en électricité grâce à des réactions électrochimiques. La technologie la plus mature pour réaliser cette conversion est la pile à hydrogène à membrane échangeuse de protons (PEMFC), mais d'autres systèmes alternatifs émergent. En particulier, les piles à combustible microfluidiques (PCM) ont permis de s’affranchir des problématiques liées à l’utilisation d’une membrane et du stockage gazeux grâce à l’utilisation de réactifs liquides à température et pression ambiante. Les dimensions du canal (1-5 mm de large et 20-100 µm de haut) permettent un écoulement co-laminaire des deux réactifs et de l’électrolyte liquides dans un micro-canal contenant les électrodes. Les PCMs n'ont donc pas de membrane et leurs performances sont dirigées par le transport de charges et de masse.À ce jour, il est difficile de caractériser expérimentalement tous les phénomènes physiques qui ont lieu dans la PCM car les méthodes existantes sont plutôt basées sur la caractérisation électrochimique. Ces méthodes permettent d'avoir une caractérisation globale du système mais ne fournissent pas d'informations précises sur les phénomènes de transport de masse dans le canal. Pour étudier le transport de masse, la modélisation numérique est généralement utilisée et permet de simuler le champ de concentration et les performances de la PCM pour différentes architectures et conditions opératoires. Toutefois, l'utilisation de ces modèles repose sur la connaissance de paramètres in-situ tels que le coefficient de diffusion D et le coefficient de réaction k0. Dans les travaux numériques, ces paramètres sont généralement approximés, ce qui permet une appréhension plutôt qualitative des phénomènes de transport. De plus, ces études numériques n'ont à ce jour pas été vérifiées avec des études expérimentales.Ainsi, le principal verrou scientifique de cette thèse repose sur le développement de méthodes d'imagerie quantitatives pour la caractérisation du champ de concentration dans une PCM en fonctionnement.Pour répondre à ce besoin, une plateforme d'imagerie basée sur la spectroscopie ainsi que trois méthodes de caractérisation ont été développées dans cette thèse. Dans un premier temps, les travaux se sont concentrés sur le développement d'un banc de spectroscopie pour étudier le phénomène d'interdiffusion. Cette étude a permis d'estimer le coefficient de diffusion du permanganate de potassium dans l'acide formique. Ces solutions ont été spécifiquement choisies car ceux sont celle utilisées dans la PCM développées pour la suite de l’étude.Le banc de spectroscopie a ensuite été adapté pour étudier le champ de concentration 2D en régime permanent d'une PCM en fonctionnement. Un modèle analytique du transfert de masse (advection/réaction/diffusion) couplé au champ de concentration 2D a ainsi permis de déterminer le taux de réaction. Les variations de concentration mises en jeu étant parfois très faibles (quelques micro-moles), une autre technique de caractérisation a été mis en place pour diminuer le bruit de mesure.Afin d'améliorer le rapport signal sur bruit, une méthode basée sur la modulation du champ de concentration a été développée. La démodulation du signal a permis de réduire significativement le bruit et des concentrations de 20 µM ont ainsi été estimées. Un modèle analytique décrivant le champ modulé a été établi afin d'implémenter une méthode inverse. La méthode proposée a permis de retrouver le taux de réaction associé à la variation de concentration.En conclusion, les méthodes de caractérisation proposées dans cette thèse permettent d'estimer quantitativement le transfert de masse et la cinétique de réaction à partir du champ de concentration 2D d'une PCM en fonctionnement. Cette technique a été appliquée au PCM, mais elle peut être transférée à un système micrométrique dans lequel les phénomènes de diffusion-advection-réaction ont lieu
Fuel cells are devices that convert the energy stored in an oxidant and a reductant into electricity through electrochemical reactions. The most mature technology for this conversion is the proton exchange membrane fuel cell (PEMFC), but other alternative systems are emerging. In particular, microfluidic fuel cells (MFCs) have overcome the problems associated with the use of a membrane and gas storage by using liquid reagents at ambient temperature and pressure. The dimensions of the channel (1-5 mm wide and 20-100 µm high) allow co-laminar flow of the two liquid reagents and the electrolyte in a microchannel containing the electrodes. Therefore, PCMs do not need membrane to separate reactants and performances are driven by charge and mass transport.Experimental characterization of all the physical phenomena involved in PCMs is difficult because actuals methods are more based on electrochemical characterisation. These methods provide an overall characterisation of the system but they do not give precise information on the mass transport phenomena occurring in the channel. To investigate concentration field, numerical modelling is generally used. Numerical methods evaluate the impact of the geometry or the operating conditions on MFC performances. However, the use of these models relies on the knowledge of in-situ parameters such as the diffusion coefficient D and the reaction rate k0. In numerical studies, these parameters are generally approximated leading to a qualitative understanding of the transport phenomena. Furthermore, these numerical studies have not yet been verified by experimental studies.Thus, the main scientific challenge of this thesis is to develop quantitative imaging methods for characterising the concentration field in an operating PCM.To meet this need, an imaging platform based on spectroscopy and three characterisation methods were developed in this thesis. First of all, the work focused on developing an experimental setup based on spectroscopy to study the interdiffusion phenomenon. This study reports the estimation of the diffusion coefficient of potassium permanganate in formic acid. These solutions were specifically chosen because they are used in the PCM developed for the rest of the study.The imaging plateform was then adapted to study the in operando MFC 2D concentration field in steady-state. An analytical mass transfer model (advection/reaction/diffusion) coupled to the 2D concentration field was used to determine the reaction rate. As the concentration variations involved can be very small (few micro-moles), another characterisation technique was implemented to reduce the measurement noise.To improve the signal-to-noise ratio, a method based on modulation of the concentration field was developed. Demodulation of the signal significantly reduced the noise and concentrations of 20 µM were estimated. An analytical model describing the modulated field was established in order to implement an inverse method. The proposed method made it possible to recover the reaction rate associated with the concentration variation.To conclude, the proposed characterisation methods enable the estimation of the mass transfer and the reaction kinetics using the 2D concentration field from an in operando MFC. This technique has been applied to the MFC, but it can be transferred to a micrometric system in which diffusion-advection-reaction phenomena take place

3D cell cultures replicate the in-vivo physiology much more accurately than 2D cell cultures; but it remains challenging to recreate the 3D in-vivo tissue architecture of soft tissues in-vitro. Different methods have been developed to print cell scaffolds in 3 dimensions, the two most popular being inkjet printing and direct extrusion. Extrusion is promising because 3D structures can be written directly; however, they incur a high shear stress, which was shown to damage or even kill cells. We have designed and fabricated a novel microfluidic probe (MFP) and developed a direct write method to dispense alginate fibers seeded with cells and to construct a 3D cell scaffold. This system allows for low shear stress deposition of cells inside of a fiber onto the surface because a liquid is used, which gelates only after extrusion while still being surrounded by an ensheathing liquid. The MFP comprises two main intersecting microchannels, one for the alginate precursor solution and one for the sheath flow of calcium chloride, which triggers the gelation of the alginate. The main branching point is designed so as to ensheath the alginate solution, which solidifies into a fiber that can be varied in diameter of around 100 μm before exiting through the nozzle of the MFP. We further incorporated a declogging microchannel, which proved to be of great practical importance and through which we flow a chelating agent that binds the calcium and leads to the dissolution of alginate that may have gelated inside of the device. Throughout this project, i) different probe designs were considered and tested, ii) different fabrication methods were examined and used to fabricate the different probes, iii) the fiber dimensions were measured and characterized as a function of the liquid flow rates, iv) different parameter of the probe, and v) liquid were examined to reduce curl formation during direct writing, , vi) glass substrate was surface coated to optimize the binding of the fibers onto the surface, vii) and multiple layers of fiber were deposited onto the glass substrate. Finally cell viability was optimized and cells were loaded directly within 3D scaffolds and shown to grow.
Les cultures cellulaires tridimensionnelles (3D) reproduisent de manière plus fidèle la physiologie in vivo que les cultures bi-dimentionnelles (2D) faites enboîtes de Pétri, mais cet architecture 3D reste difficile à recréer in vitro. Différentes méthodes ont été développées pour imprimer des échafaudages cellulaires 3D. Des Bio-imprimeurs qui extrudent des matières biologiques contenant des cellules se sont, entre autres, montrés très prometteurs. Cependant, lors de l'extrusion, les forces de cisaillement appliquées sur les cellules sont telles qu'elles peuvent endommager ou même tuer les cellules. Nous avons conçu et fabriqué une nouvelle sonde microfluidique (Microfluidic Probe) et avons développé une méthode pour imprimer des fibres d'alginate contenant des cellules et ainsi construire un échafaudage cellulaire 3D. Ce système permet de produire et déposer des fibres d'alginate contenant des cellules avec moins de contrainte de cisaillement sur des cellules. La MFP est composée de deux principaux microcanaux qui se croisent, l'un apportant le précurseur d'alginate et l'autre l'agent gélifiant (chlorure de calcium). Le point debranchement est conçu de manière à entourer la solution d'alginate qui se solidifie en une fibre de diamètre variable d'environ 100 μm avant de sortir àl'embouchure de la MFP. Nous avons également incorporé un troisième microcanal qui sert au décolmatage, par lequel nous circulons de l'EDTA3 (éthylènediaminetétraacétate), un chélateur de calcium qui dissout l'alginate bloqué à l'intérieur de l'appareil. Au cours de ce projet de recherche, nous avons i) considéré et testé différents designs pour notre sonde, ii) examiné et utilisé différentes méthodes de fabrication, iii) mesuré et caractérisé la dimension des fibres en fonction du débit des liquides, iv) testé différents paramètres de la sonde, et v) testé des liquides pour réduire la formation d'ondulations pendant l'impression, vi) modifié la surface du verre pour optimiser l'adhésion des fibres d'alginate et vii) y avons déposé plusieurs couches de fibres. Finalement, nous avons démontré que des cellules ensemencées directement dans l'échafaudage 3D avec notre sonde pouvaient survivre et proliférer.

Microfluidic systems open up new possibilities for in vitro cell biology research, mainly due to their ability to control the cellular microenvironment at physiologically relevant spatiotemporal scales. As such, several microfluidic systems have been introduced for the generation of concentration gradients and have been used for cell chemotaxis studies. However, these methods typically involve a trade-off between temporal control of the gradient and minimizing the applied shear stresses on the cells, and often require culturing cells in micro-channels. In this dissertation, we develop microfluidic quadrupoles (MQs) and demonstrate their first use in a laboratory setting. Two MQs with different configurations are presented; a lateral MQ that is associated with a stagnation point at its center, and a linear MQ with a stagnation zone bounded by two hydrodynamically confined streams. We also introduce "floating" concentration gradients of biochemicals that can be produced using MQs by injecting a solute through one of the poles. Floating gradients are controllable, associated with minimal shear stresses, can be applied to any flat substrate in a channel-less microfluidic system, and can be rapidly adjusted and moved. We used the lateral MQ to apply floating gradients of Interleukin-8 to cultured human neutrophils in a culture dish, and developed novel chemotaxis assays with stationary and moving gradients. Furthermore, we observed the real-time dynamics of neutrophils during adhesion, polarization, and migration, and showed that neutrophils migrate longer distances when following moving gradients in comparison to stationary gradients.The work presented in this dissertation introduces a new area of research in the field of fluidic multipoles and floating gradients, as well as their applications in the biomedical sciences. Furthermore, this work sets the foundation for developing novel biological and cell chemotaxis assays using moving concentration gradients. These assays can then be combined with pharmacological studies and help to further understand the mechanisms of cellular polarization, migration, and desensitization.
Les systèmes microfluidiques ouvrent de nouvelles possibilités pour la recherche in vitro en biologie cellulaire, notamment par leur capacité à contrôler le microenvironnement cellulaire à des échelles spatiotemporelles physiologiquement pertinentes. En ce sens, plusieurs systèmes microfluidiques ont été introduits pour la génération de gradients de concentration et ont été utilisés pour des études sur la chimiotaxie cellulaire. Cependant, ces méthodes font face à un compromis entre le contrôle temporel du gradient et la minimisation de la contrainte de cisaillement appliqué sur les cellules. De plus, elles requièrent souvent de mettre les cellules en culture dans des microcanaux. Dans cette dissertation, nous démontrons la première utilisation des quadripôles microfluidiques (QM) dans un contexte expérimental. Nous présentons deux QM avec des configurations différentes : un QM latéral associé à un point de stagnation en son centre, et un QM linéaire avec une zone de stagnation reliée par deux flux hydrodynamiquement confinés. Nous présentons aussi des gradients de concentration « flottants » de produits biochimiques réalisés à l'aide de QM en injectant un soluté à travers un des pôles. Les gradients mobiles sont réglables, associés à une contrainte de cisaillement minimale, peuvent être appliqués à n'importe quel substrat plat dans un système microfluidique sans canal, et peuvent être rapidement ajustés et déplacés. Nous avons utilisé le QM latéral pour appliquer des gradients de concentration mobiles de l'Interleukin-8 à des neutrophiles humains dans une plaque de culture, et avons développé de nouveaux tests pour mesurer la chimiotaxie avec des gradients fixes et mobiles. De plus, nous avons observé la dynamique des neutrophiles en temps réel durant l'adhésion, la polarisation, et la migration, et avons démontré que les neutrophiles migrent sur de plus longues distances lorsqu'ils suivent des gradients mobiles plutôt que des gradients fixes.Les travaux présentés dans cette dissertation ouvrent un nouveau champ de recherche dans le domaine des multipôles fluidiques et des gradients mobiles, ainsi que leur application dans les sciences biomédicales. De plus, ces travaux sont une base pour le développement de nouveaux tests biologiques et mesurant la chiomiotaxie utilisant des gradients de concentration mobiles. Ces tests peuvent ensuite être combinés à des études pharmacologiques pour aider à mieux comprendre les mécanismes de polarisation, migration, et désensibilisation cellulaire.

Biotechnology is defined as the use of biological techniques to engineer or manufacture a product. Development and optimization of systems in biotechnology have witnessed extraordinary advances over the last few decades. It can be further enhanced through combination with micro/nanotechnology, enabling de vices miniaturization to the microscale that leads to a rapid and cost effective analysis using microfluidic systems. Microfluidic systems offer high parallelization and high throughput screening assays. This thesis aims to expand biotechnology in two main areas: (i) preparation of a suitable expression system for production of human Interleukin-7 (hIL-7) in insect cells, and (ii) fabrication of microfluidic systems for integration with biotechnology for high throughput cell screening assays using insect and yeast cells. Human IL-7 has multiple immune-enhancing properties, which make it an ideal candidate for immunotherapy in a variety of clinical situations. Currently, there is no convenient and cost effective method for producing hIL-7. We present the production of hIL-7 in insect cells for the first time. We used a baculovirus expression vector system (BEVS) and a non-lytic system to produce hIL-7 in insect cells. In addition, we investigated large scale production of hIL-7 using various bioreactors. The resulting insect cells produce hIL-7 at different rates. To select highly productive single cells, the presently existing methods are time consuming, labor intensive and have low throughput capacity. In addition, these methods need special equipment for operation, as well as large amounts of chemicals. In order to rapidly select cells that produce high amounts of hIL-7, we designed and fabricated a new microfluidic system based on a polyethylene glycol (PEG) microwell array and a track etched membrane. Using this system, single cells can be selected on the basis of their protein secretion rate after a few hours only wit
La biotechnologie est définie comme l'utilisation de techniques biologiques pour développer ou fabriquer un produit. Le développement et l'optimisation de systèmes dans la biotechnologie ont été témoins d'avances extraordinaires pendant les dernières dix années. Ils peuvent être davantage améliorés par la combinaison avec la micro/nanotechnology, qui nous permet de miniaturiser des artifices à la microéchelle qui cause une analyse rapide, efficace et à un bon prix en utilisant les systèmes microfluidiques. Les systèmes microfluidiques offrent une haute parallélisassion et un haut débit de criblage. Cette thèse a pour but de développer la biotechnologie dans deux régions principales : (i) la préparation d'un système d'expression convenable pour la production d'Interleukine-7 humaine (hIL-7) dans les cellules d'insectes et (ii) la fabrication de systèmes microfluidiques, intégrant la biotechnologie, pour le criblage à haut débit de cellules en utilisant des cellules de levure et d'insecte.L'IL-7 humaine a des propriétés activatrices du système immunitaire, qui le font un candidat idéal à l'immunothérapie dans une variété de cas cliniques. Actuellement, il n'y a aucune méthode convenable et peu coûteuse pour produire hIL-7Nous présentons la production de hIL-7 dans les cellules d'insectes pour la première fois. Nous avons utilisé un système de vecteurs d'expression baculovirus (BEVS) et un système non-lytique pour produire hIL-7 dans des cellules d'insectes. En plus nous avons enquêté la production grande échelle de hIL-7 en utilisant différents bioréacteurs.Les cellules d'insectes produites génèrent l'hIL-7 à différents taux. Les méthodes existantes pour choisir les cellules extrêmement productives sont très lentes avec une faible capacité de traitement en plus d'exiger de l'équipement spécifique pour l'opération, aussi bien que de grandes quantités de produits c

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
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 (pages 83-90).
This thesis presents design, manufacturing, testing, and modeling of a laminar-flow microbial fuel cell. Novel means were developed to use graphite and other bulk-scale materials in a microscale device without loosing any properties of the bulk material. Micro-milling techniques were optimized for use on acrylic to achieve surface roughness averages as low as Ra = 100nm for a 55 [mu]m deep cut. Power densities as high as 0.4mW · m⁻², (28mV at open circuit) in the first ever polarization curve for a laminar-flow microbial fuel cell. A model was developed for biofilm behavior incorporating shear and pore pressure as mechanisms for biofilm loss. The model agrees with experimental observations on fluid flow through biofilms, biofilm structure, and other biofilm loss events.
by A-Andrew D. Jones, III.
S.M.

Nanomaterials are increasingly being developed for applications in biotechnology, including the delivery of therapeutic drugs and vaccine antigens. However, there is a lack of screening systems that can rapidly assess nanoparticle uptake and their consequential effects on cells. Established analytical in vitro approaches are often carried out on single time points, rely on time-consuming bulk measurements and are based primarily on populations of immortalised cell lines. As such, these procedures provide averaged results, do not guarantee precise control over the delivery of nanoparticles to cells and cannot easily generate information about the dynamic nature of nanoparticle-cell interactions and/or nanoparticle-mediated compound delivery. The present work addresses these issues by combining microfluidics, nanotechnology and imaging techniques into a high-throughput microfluidic platform to monitor nanoparticle uptake and intracellular processing in real-time and at the single-cell level. For this, a microfluidic device and protocols for cell trapping and live-cell monitoring were developed. In parallel, specific formulations of gold nanorods were produced, tested and optimised for intracellular multimodal imaging. Subsequently, controlled nanorod delivery to cells trapped in the microfluidic array was achieved across a range of concentrations, with intracellular nanorod signal detected using both fluorescence microscopy and surface-enhanced Raman scattering spectroscopy. Furthermore, on-chip measurement of specific cellular responses to nanorod delivery was also demonstrated. As a proof-of-concept application, the potential of the developed platform for understanding nanovaccine delivery and processing was investigated. Controlled delivery of ovalbumin-conjugated gold nanorods to primary dendritic cells was demonstrated, followed by real-time monitoring of nanoparticle uptake and antigen processing across a range of concentrations over several hours on hundreds of single-cells. This system represents a novel application of single-cell microfluidics for nanomaterial screening, providing a general platform for studying the dynamics of cell-nanomaterial interactions and representing a cost-saving and time-effective screening tool for many nanomaterial formulations and cell types.

Les piles à combustible sans membrane polymérique comme les piles à combustible microfluidique ont des perspectives très intéressantes pour des applications énergétiques à basse puissance. L'étude menée consistait donc à poursuivre le développement de catalyseurs cathodiques nanométriques pouvant être utilisés en tant que cathode dans une pile à combustible microfluidique directe. Au cours de ce travail de thèse, une modification du comportement catalytique du platine a été réalisée grâce à un effet de support, d'alliage avec un métal de transition 3d (titane), ou bien encore par coordination de la surface de nanoparticules de platine avec un élément chalcogène (sélénium). Les effets induits par ces modifications sur les propriétés électroniques du matériau catalytique, et leurs implications sur son activité catalytique ont été étudiés au même titre que sa stabilité et sa tolérance vis-à-vis de petites molécules organiques. Les études ont été menées dans le but de présenter un nouveau paradigme des relations structure-activité, structure-stabilité et structure-tolérance gouvernant le comportement catalytique d'une surface de platine. Les expériences ont par voie de conséquence été conduites de façon à pouvoir séparer les effets catalytiques induits par le support, de ceux induits par un effet d'alliage ou bien encore par coordination des atomes de surface avec un élément chalcogène. En conclusion, ces études ont démontrés l'effet de l'interaction du métal avec le support (oxyde ou matériau carboné présentant divers degrés de graphitisation) sur l'activité et la stabilité des catalyseurs. Un autre point important, qui a été développé dans ce travail de thèse, est la modif
Fuel cells without polymeric membrane such as the microfluidic fuel cells (MFFC) possess very interesting perspectives for low-power energy applications. The study aimed at pursuing the development of nanometric cathodic catalysts and to study their activity, stability and tolerance in a microfluidic system. In the present thesis, the activity, stability and tolerance of Pt-based nanoparticle electrocatalysts were investigated. The effect of the support materials and the influence of surface modification by a second element including 3d transition metal (titanium) and chalcogenide (selenium) were studied. The separation and reduction of the complexity of the interaction between nanoparticles-support and nanoparticles modification by a second element enables to achieve a clear relationship of the structure-activity-stability-tolerance of the supported fuel-cell electrocatalysts. The present experimental results from the effects of the support materials and of the modification of Pt by a second element led to improve activity, stability and tolerance. The developed approach and acquired knowledge about surface property correlation can be further generalized and used in the design of advanced selective electrocatalysts. Furthermore, the synthesized electrocatalysts were used as cathode in an organic microfluidic fuel cell

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

Microfluidic fuel cell architectures are presented in this thesis. This work represents the mechanical and microfluidic portion of a microfluidic biofuel cell project. While the microfluidic fuel cells developed here are targeted to eventual integration with biocatalysts, the contributions of this thesis have more general applicability. The cell architectures are developed and evaluated based on conventional non-biological electrocatalysts. The fuel cells employ co-laminar flow of fuel and oxidant streams that do not require a membrane for physical separation, and comprise carbon or gold electrodes compatible with most enzyme immobilization schemes developed to date. The demonstrated microfluidic fuel cell architectures include the following: a single cell with planar gold electrodes and a grooved channel architecture that accommodates gaseous product evolution while preventing crossover effects; a single cell with planar carbon electrodes based on graphite rods; a three-dimensional hexagonal array cell based on multiple graphite rod electrodes with unique scale-up opportunities; a single cell with porous carbon electrodes that provides enhanced power output mainly attributed to the increased active area; a single cell with flow-through porous carbon electrodes that provides improved performance and overall energy conversion efficiency; and a single cell with flow-through porous gold electrodes with similar capabilities and reduced ohmic resistance. As compared to previous results, the microfluidic fuel cells developed in this work show improved fuel cell performance (both in terms of power density and efficiency). In addition, this dissertation includes the development of an integrated electrochemical velocimetry approach for microfluidic devices, and a computational modeling study of strategic enzyme patterning for microfluidic biofuel cells with consecutive reactions.

abstract: Portable devices rely on battery systems that contribute largely to the overall device form factor and delay portability due to recharging. Membraneless microfluidic fuel cells are considered as the next generation of portable power sources for their compatibility with higher energy density reactants. Microfluidic fuel cells are potentially cost effective and robust because they use low Reynolds number flow to maintain fuel and oxidant separation instead of ion exchange membranes. However, membraneless fuel cells suffer from poor efficiency due to poor mass transport and Ohmic losses. Current microfluidic fuel cell designs suffer from reactant cross-diffusion and thick boundary layers at the electrode surfaces, which result in a compromise between the cell's power output and fuel utilization. This dissertation presents novel flow field architectures aimed at alleviating the mass transport limitations. The first architecture provides a reactant interface where the reactant diffusive concentration gradients are aligned with the bulk flow, mitigating reactant mixing through diffusion and thus crossover. This cell also uses porous electro-catalysts to improve electrode mass transport which results in higher extraction of reactant energy. The second architecture uses porous electrodes and an inert conductive electrolyte stream between the reactants to enhance the interfacial electrical conductivity and maintain complete reactant separation. This design is stacked hydrodynamically and electrically, analogous to membrane based systems, providing increased reactant utilization and power. These fuel cell architectures decouple the fuel cell's power output from its fuel utilization. The fuel cells are tested over a wide range of conditions including variation of the loads, reactant concentrations, background electrolytes, flow rates, and fuel cell geometries. These experiments show that increasing the fuel cell power output is accomplished by increasing reactant flow rates, electrolyte conductivity, and ionic exchange areas, and by decreasing the spacing between the electrodes. The experimental and theoretical observations presented in this dissertation will aid in the future design and commercialization of a new portable power source, which has the desired attributes of high power output per weight and volume and instant rechargeability.
Dissertation/Thesis
Ph.D. Mechanical Engineering 2010

In this work, a microfluidics approach is applied to two fuel cell related projects; the study of deformation and contact angle hysteresis on water invasion in porous media and the introduction of bubble fuel cells. This work was carried out as collaboration between the microfluidics and CFCE groups in the Department of Mechanical Engineering at the University of Victoria. Understanding water transport in the porous media of Polymer Electrolyte Membrane fuel cells is crucial to improve performance. One popular technique for both numeric simulations and experimental micromodels is pore network modeling, which predicts flow behavior as a function of capillary number and relative viscosity. An open question is the validity of pore network modeling for the small highly non-wetting pores in fuel cell porous media. In particular, current pore network models do not account for deformable media or contact angle hysteresis. We developed and tested a deformable microfluidic network with an average hydraulic diameter of 5 μm, the smallest sizes to date. At a capillary number and relative viscosity for which conventional theory would predict strong capillary fingering behavior, we report almost complete saturation. This work represents the first experimental pore network model to demonstrate the combined effects of material deformation and contact angle hysteresis. Microfluidic fuel cells are small scale energy conversion devices that take advantage of microscale transport phenomena to reduce size, complexity and cost. They are particularly attractive for portable electronic devices, due to their potentially high energy density. The current state of the art microfluidic fuel cell uses the laminar flow of liquid fuel and oxidant as a membrane. Their performance is plagued by a number of factors including mixing, concentration polarization, ohmic polarization and low fuel utilization. In this work, a new type of microfluidic fuel cell is conceptualized and developed that uses bubbles to transport fuel and oxidant within an electrolyte. Bubbles offer a phase boundary to prevent mixing, higher rates of diffusion, and independent electrolyte selection. One particular bubble fuel cell design produces alternating current. This work presents, to our knowledge, the first microfluidic chip to produce bubbles of alternating composition in a single channel, class of fuel cells that use bubbles to transport fuel and oxidant and fuel cell capable of generating alternating current.
Graduate

碩士
國立成功大學
化學工程學系
102
In this study, the vertical streaming of two fluid flows and diffusion inside the microchannel with micropillar array were investigated. Moreover, the effect of the micropillar electrodes on the performance of microfluidic fuel cell (MFC) was discussed. It was found that the interface between two fluid flows moved away from the center line and toward the plane surface as the height of the micropillars increased. In addition, the diffusion zone increased after the fluid flowing through the micropillar array. As to the performance of MFC, the uniformity of the platinum provided better MFC efficiency. The maximum current and power density increased as the height of micropillars increased up to 20 micron and, in this study, were measured 9.8 mA/cm2 and 2.6 mW/cm2, respectively using 120 micron micropillar array.

碩士
國立臺灣大學
環境工程學研究所
106
Microbial fuel cells (MFCs) are a promising technology simultaneously for treating wastewater and generating electricity, which is powered by microorganisms utilizing substrates on the anode to release reducing power and generate electricity. In recent years, micro-MFCs have received increasing attention due to its many advantages, such as short start-up time, high surface-to-volume ratio in the structure, and the potential of biosensors for water quality detection. Microfluidic MFCs (MMFCs), first reported in 2011, is a particularly novel structure that is also a kind of micro-MFCs. These cells use laminar flow to distinguish anolytes and catholytes without the membrane separation, and thus the internal resistance can be reduced to enhance the power density. We use the MMFCs as a tool to quickly examine the performance of catalysts on electrodes. Because of its small volume, the reaction time is short and the microbial is easy to be disturbed by the surrounding changed. This study is to compare the performances of microorganism-coated electrodes (bio-anode) cultivated with different resistors in the H-type MFC. The max power density of MMFC is measured to be calculated 2150 mW m-2, which is obtained under the condition of 1000 ohms cultivated. The internal resistance can be evaluated by reading the power-density-curve. We also operate the MMFC for 100 hours and the results show a stable power density output about 2360 mW m-2 and assess the performance of MMFCs in series and parallel. The results indicate that cultivated using lower resistors (e.g., 550 ohms) can generate stronger power density. The MMFCs also has potential for applications in many aspects such as identifying exoelectrogens and toxicity testing.

碩士
國立成功大學
化學工程學系
102
SUMMARY This study demonstrates the screening of carbon sources for electricity generation by the membraneless microfluidic microbial fuel cell (μMFC) and the corresponding validation in lab-scale H-type MFC. Two kinds of microorganisms are utilized in this study, one is a mixed culture microorganisms obtained from the seacoast of Taiwan and the other is Proteus hauseri (ZMd44). When the mixed culture microorganism was investigated in the μMFC, sucrose resulted in the highest ΔOCV, which was about 120 mV and other carbon sources (acetate, glucose, and glycerol) brought out 50-70 mV. However, glycerol resulted in the highest ΔOCV with ZMd44, which was about 80 mV and the other carbon sources generated ΔOCV around 20-40 mV. After testing these carbon sources in the μMFC, they were further examined in the lab-scale MFC to validate the results from microfluidic detections. The extracted electron amounts from lab-scale MFC when the mixed culture microorganisms were fed with the above carbon sources were highly correlated (R2=0.99) with the ΔOCV from μMFC. This shows that μMFC can predict the electricity generation in a larger scale setup and has great potential in screening operating conditions for microbial fuel cells. Keywords：membraneless, microfluidic, microbial fuel cell, carbon sources

This thesis is part of an ongoing collaborative research project focused on the development of microstructured enzymatic fuel cells. Both enzymatic fuel cells and co-laminar fuel cells are, more generally, varieties of microfluidic membraneless fuel cells. A primary goal of this particular work is the establishment of microfabrication capabilities to develop these technologies. Rapid prototyping soft lithography capabilities are established in-house and protocols specific to the lab equipment are developed. These prototyping methods are then adapted for the fabrication of microfluidic membraneless fuel cells. Fabrication techniques using polymeric stencils and photoresist-based channel structures are developed to enable electrode patterning and current collection in the enzymatic and co-laminar fuel cells of interest. A variety of electrode patterning methods are developed. Gold electrode patterning by etching and lift-off techniques are investigated for the patterning of base electrode layers. An in-situ gold electrode patterning methodology is designed and tested, eliminating the need for precision alignment during device assembly. Carbon electrode patterning methods are developed for use in a vanadium-based colaminar fuel cell. Thin-film carbon electrodes are fabricated using a mixture of carbon microparticles and a polymeric binder. Alternatively, graphite rods are investigated for use as electrodes due to their high conductivity and chemical stability. The integration of channel structure and electrode fabrication methods is investigated to establish compatibilities and facilitate the assembly of functional devices. In addition to the development of these methods, the application of co-laminar streaming to microfabrication is explored through the development of a dynamic microfluidic photomasking device.

碩士
國立高雄應用科技大學
機械與精密工程研究所
103
The performance of air-breathing direct formate microfluidic fuel cells using the mixture of Potassium hydroxide and Potassium formate solution as fuel under various operating conditions, including the flow rates of fuel, operating temperature, catalyst loading, reactant concentration and Nafion content, was tested and investigated. Also, the performance comparison of the direct formate microfluidic fuel cells was also made between the fuel cells with 0.5-M H2SO4 and the fuel cells with 1.0-M or 2.0-M KOH as liquid electrolyte. Besides, flow visualization was also performed during the experiment. The Nafion content in the anode was 3.73 mg/cm2, 5.6 mg/cm2, and 7.46 mg/cm2 and the concentration of Potassium formate was 1.0 M and 2.0 M. The microfluidic fuel cells were operated with flow rate of fuel ranging from 0.1 to 0.6 mL/min at temperature of 300C, 400C and 500C. The result suggests that the cell performance becomes higher as the operating temperature of the fuel cell gets higher. Because no gas bubble could be observed in the microchannel as the KOH solution was used as electrolyte, the cell output of the fuel cell using alkaline electrolyte would not significant increased with the increase of flow rate. Besides, the Nafion was used as binder in the anode which affected both the electrode reliability and cell performance. Although direct formate microfluidic fuel cells using 0.5-M H2SO4 as electrolyte had much higher open circuit potential, the electricity generation was so unstable because the numerous gas bubbles occupied the microchannel before electrochemical reaction. As the Pd loading loading was 2.0 mg/cm2 with Pd/C ratio of 30% and Nafion content was 5.6 mg/cm2 in the anode, concentration of Potassium formate was2.0M, concentration of Potassium hydroxide electrolyte was 2.0M, and the volume flow rate was 0.1 mL/min, the maximum current density and power density of the air-breathing direct formate microfluidic fuel cells reached 469 mA/cm2 and 111 mW/cm2, respectively, at operating temperature of 500C with [KOH] = 2.0 M and [HCOOK] = 2.0 M as fuel and electrolyte.

In this work, a MFC fabrication procedure including two non-conventional techniques (partial baking and cap-sealing) were employed for the development of an up-scaled microfluidic fuel cell (MFC). Novel carbon-based electrode materials were employed, including carbon foam, fibre, and cloth, the results from which were compared with traditionally-employed carbon paper. The utilization of carbon cloth led to 15% of the maximum power that resulted from carbon paper; however, carbon fibre led to a 24.6% higher power density than carbon paper (normalized by electrode volume). When normalized by projected electrode area, the utilization of carbon foams resulted in power densities up to 42.5% higher than that from carbon paper. The impact of catalyst loading on MFC performance was also investigated, with an increase from 10.9 to 48.3 mgPt cm-2 resulting in a 195% increase in power density.

Indiana University-Purdue University Indianapolis (IUPUI)
An integrated micro PEM fuel cell system with self-regulated hydrogen generation from ammonia borane is reported to power portable electronics. Hydrogen is generated via catalytic hydrolysis reaction of ammonia borane solution in microchannels with nanoporous platinum catalyst electroplated inside the microchannels. The self-regulation of the ammonia borane solution is achieved by using directional growth and selective venting of hydrogen bubbles in microchannels, which leads to agitation and addition of fresh solution without power consumption. The device is fabricated on combination of polystyrene sheets cut by graphic cutter, a stainless steel layer cut using wire electrical discharge machining and bonding layers with double-sided polyimide tape. Due to the seamless bonding between the hydrogen generator and the micro fuel cell, the dead volume in the gas connection loops can be significantly reduced and the response time of self-regulation is reduced.

博士
國立高雄應用科技大學
機械工程系
105
This study numerically investigated the effects of various factors on the performance of air-breathing direct formic acid microfluidic fuel cells (DFAMFCs). An air-breathing microfluidic fuel cells with a microchannel width of 1.5 mm, depth of 0.05 mm, and electrode spacing of 0.3 mm was used in the simulation. Formic acid at concentrations of 0.3, 0.5, and 1.0 M was mixed with 0.5 M sulfuric acid in an aqueous solution, and the mixture served as the fuel; moreover, a 0.5 M sulfuric acid stream served as the electrolyte introduced at inlet flow rates of 0.05, 0.1, and 0.5 mL/min. First, a three-dimensional MFC model was built using COMSOL Multiphysics 5.1 to simulate the fuel cell performance. Subsequently, I–V curves obtained from simulations and from published experimental data under similar operating conditions were compared to ensure the validity of the simulation. Transport phenomena were formulated with a continuity equation, momentum equation, species transport equation, and ion charge equation. Additionally, the flow through porous media in the gas diffusion layer was described using the Brinkman equation, whereas the Butler–Volmer equations was applied to obtain I–V and P–I curves. The current density distribution resulting from fuel crossover and reactant concentration on both electrodes, the effects of bubble formation included bubble blockage, transverse dimension and the distance bubble growth between two in-line bubbles on the anode surfaces was also determined in this study.

碩士
國立成功大學
化學工程學系碩博士班
100
In recent years, research and development of microfluidic fuel cell (MFC) have been greatly pursued by many researchers owing to its attractive characteristics such as small size, high power density and membraneless feature, which is suitable to become a new electricity-supplied device for portable electric product. In MFC, the diffusion zone between the oxidant and fuel streams is regarded as the ion-exchange membrane, and the electrodes can be located at either the channel side walls, or two sides at the bottom (or top) plate or the top and bottom plates. In order to investigate the effect of the electrode surface on the efficiency of laminar flow-based MFC, we divide the oxidant and fuel to form the top and bottom streams, i.e. vertical streaming, which allows us to easily construct the 3D electrodes. The deionized water and fluorescein solution were used for flow visualization and distribution of the fluorescein was measured by confocal laser scanning microscopy. The flow behavior of top and bottom streams under different inlet flow rates was also simulated by commercial software package CFD-ACE+. The results showed that the mixing zone between the top and bottom streams is closely related to the flow rates and the length of channel. The higher the flow rates, the smaller the mixing zone. In addition, the position of mixing zone in the z-direction can be controlled by the ratio of the flow rates of the top and bottom streams. The fluorescence intensity profile measured by the confocal microscopy and the simulated concentration profile are in relatively good agreement. For the test of MFC, the maximum output power density of 0.75 mW/cm2 was achieved when the flow rate of both fuel (formic acid) and oxidant (acidic hydrogen peroxide) was 8 ml/hr. The power density further increased up to 0.92 mW/cm2 when the micropillar electrode was used as cathode.

碩士
國立臺灣大學
環境工程學研究所
107
Microbial fuel cell (MFC) is one kind of green energy harvesting techniques. Although many exoelectrogens as essential anode-respiring bacteria have been proved to be able to produce electricity and treat pollutants simultaneously, there are still many potential exoelectrogens unclear and warrant the need for further research. In this study, mixed-culture exoelectrogens were steadily cultivated under constant potential in the dual-chamber microbial fuel cells with microbial community analyses and electrochemical performance of biofilms being evaluated by utilizing 16S rRNA gene high throughput sequencing and power density curve, polarization curve, electrochemical impedance spectroscopy and cyclic voltammetry. After isolating diverse pure bacterial strains from the anode biofilms, we established a fast-screening system using the microfluidic laminar flow MFC (MLFMFC). By inoculating the isolated strains in the anode of MLFMFC and measuring its open circuit and closed circuit voltages, we can rapidly and efficiently identify the electroactive bacteria among these isolates. Results showed the bioanode domesticated under a constant potential of −200 mV had the better performance with maximum power density of 187.3 mW m-2. Acinetobacter brisouii, Arcobacter lacus, Chryseobacterium cucumeris, Pseudomonas citronellolis, and Pseudomonas delhiensis were isolated and first proved to be capable of producing electricity in this study by our fast-screening systems. In conclusion, this fast-screening system was successfully established and verified and it is expected to be widely utilized in the future to better isolate effective exoelectrogens.

碩士
國立高雄應用科技大學
機械與精密工程研究所
101
In this study, air-breathing direct formic acid microfluidic fuel cells were fabricated by assembly of a PDMS Y-shaped microchannel, which was formed based on soft-lithography process, together with a PMMA sheet having rectangular slots and through holes fabricated by using CO2 laser machining. Various anode parameters, including Pd/C or Pd/MWCNT ratio (75%, 85%, 95%) and Nafion contents (6 mg/cm2, 10 mg/cm2) on a Toray carbon paper, were tested at various operating conditions to investigate the cell performance. Both fuel of concentration ranging from 0.3 M to 1.0 M and 0.5-M-sulfric-acid electrolyte were simultaneously supplied to the microchannel with identical volumetric flow rate ranging from 0.1 mL/min to 1.0 mL/min. Besides cell performance measurement, flow visualization was also synchronously performed to observe the bubble formation process under different anode parameters and operating conditions. Results showed that both higher volumetric flow rate and concentration caused a better cell output. In order to possess both better carbon nanoparticle arrangement and linkage and better electrode morphology, an optimal Nafion content depended on the Pd/C ratio. In general, the optimal Nafion content has to increase with a lower Pd/C ratio. The present study showed an inferior cell performance as the Pd catalyst was supported by multiwall carbon nanotube because of the unfavorable distribution of the catalyst and support based on the diagnosis of the TEM pictures and CV results. In this study, a maximum power density as high as 37.83 mW/cm2 was observed when the 1.0-M HCOOH was operated at 0.6 mL/min with Pd/C and Nafion content of 85% and 6 mg/cm2, respectively.

Chau, Long Ho.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2009.
Includes bibliographical references (leaves 73-82).
Abstract also in Chinese.
ABSTRACT --- p.III
摘要 --- p.IV
PUBLICATIONS CORRESPOND TO THIS THESIS --- p.V
ACKNOWLEDGEMENTS --- p.VI
TABLE OF CONTENTS --- p.VII
LIST OF FIGURES --- p.IX
LIST OF TABLES --- p.XI
ABBREVIATIONS AND NOTATIONS --- p.XII
Chapter CHAPTER 1 --- INTRODUCTION --- p.1
Chapter 1.1 --- Background --- p.1
Chapter 1.1.1 --- Types of Biofuel Cells --- p.1
Chapter 1.1.2 --- Properties of Using Enzymes in Bio-energy Generation Systems --- p.2
Chapter 1.1.3 --- Application of Bio-energy Generation Systems --- p.3
Chapter 1.2 --- Objectives of the Project --- p.4
Chapter 1.3 --- Organization of the Thesis --- p.5
Chapter CHAPTER 2 --- LITERATURE REVIEW --- p.7
Chapter 2.1 --- Working Principle of a Typical Fuel Cell --- p.7
Chapter 2.2 --- Introduction of Enzymes and Co-enzymes --- p.9
Chapter 2.3 --- Functions and Activities of Glucose Dehydrogenase (GDH) --- p.10
Chapter 2.4 --- Functions and Activities of Laccase --- p.11
Chapter 2.5 --- Introduction of Carbon Nanotubes (CNTs) --- p.12
Chapter 2.6 --- Introduction of Gold Nanoparticles (AuNPs) --- p.13
Chapter 2.7 --- Introduction of PdNPs --- p.14
Chapter 2.8 --- Summary of Literature Review --- p.15
Chapter CHAPTER 3 --- WORKING PRINCIPLE OF AN ENZYMATIC BIOFUEL CELL --- p.16
Chapter 3.1 --- Enzymatic Biofuel Cell Using Glucose as a Fuel --- p.16
Chapter 3.2 --- Deterministic Factors of the Fuel Cell´ةs Performance --- p.19
Chapter 3.3 --- Energy --- p.22
Chapter 3.3 --- Chapter Conclusion --- p.23
Chapter CHAPTER 4 --- ENZYMATIC BIOFUEL CELL DESIGN --- p.24
Chapter 4.1 --- Engineering Structure of the EBFC --- p.24
Chapter 4.2 --- Chemical Structures of the EBFCs --- p.25
Chapter 4.2.1 --- 1st Structure of EBFC - Au-Ll-CNTs-Ll-AuNPs-L2-{(GDH-NAD)/Laccase} --- p.26
Chapter 4.2.2 --- 2nd Structure of EBFC - Au-Ll-CNTs-Ll-AuNPs-L2-{GDH/Laccase} --- p.28
Chapter 4.2.3 --- 3rd Structure of EBFC- Pd-Ll-CNTs-Ll-AuNPs-L2-{(GDH-NAD)/Laccase} --- p.28
Chapter 4.2.4 --- 4th Structure of EBFC - Pd-Ll -A uNPs-L2-{(GDH~NAD)/Laccase} --- p.29
Chapter 4.2.5 --- 5th Structure of EBFC- Au-Ll-CNTs~L4'{(GDH-NAD)/Laccase} --- p.30
Chapter 4.2.6 --- 6th Structure ofEBFC 一 Au-Ll-CNTs-{L3- NAD-GDH/L4-Laccase} --- p.31
Chapter 4.3 --- Chapter Conclusion --- p.33
Chapter CHAPTER 5 --- FABRICATION AND CHARACTERIZATION OF EBFCS --- p.34
Chapter 5.1 --- Materials Preparation --- p.34
Chapter 5.1.1 --- Preparation of Linker 1 --- p.34
Chapter 5.1.2 --- Preparation of Linker 2 --- p.35
Chapter 5.1.3 --- Preparation of Linker 4 --- p.35
Chapter 5.1.4 --- Purification of Linkers --- p.35
Chapter 5.1.5 --- Verification of Linkers --- p.36
Chapter 5.2 --- 3-D Micro Electrode Fabrication --- p.37
Chapter 5.3 --- Electrode Modification --- p.40
Chapter 5.3.1 --- 1st Structure of EBFC --- p.40
Chapter 5.3.2 --- 2nd Structure of EBFC --- p.41
Chapter 5.3.3 --- 3rd Structure of EBFC --- p.41
Chapter 5.3.4 --- 4th Structure of EBFC --- p.42
Chapter 5.3.5 --- 5th Structure of EBFC --- p.42
Chapter 5.3.6 --- 6th Structure of EBFC --- p.42
Chapter 5.4 --- Characterization --- p.43
Chapter 5.4.1 --- Atomic Force Microscopy (AFM) --- p.43
Chapter 5.4.2 --- Scanning Electron Microscopy (SEM) & Energy-Disperse X-ray Spectroscopy (EDX) --- p.46
Chapter 5.4.3 --- Cyclic Voltammetry (CV) --- p.47
Chapter 5.5 --- Chapter Conclusion --- p.52
Chapter CHAPTER 6 --- RESULTS OF EBFCS --- p.53
Chapter 6.1 --- Experimental Setup --- p.53
Chapter 6.2 --- Results --- p.55
Chapter 6.2.1 --- Results of 1st EBFC --- p.55
Chapter 6.2.2 --- Results of 2nd EBFC --- p.57
Chapter 6.2.3 --- Results of 3rd EBFC --- p.58
Chapter 6.2.4 --- Results of 4th EBFC --- p.60
Chapter 6.2.5 --- Results of 5th EBFC --- p.60
Chapter 6.2.6 --- Results of 6th EBFC --- p.65
Chapter 6.3 --- Chapter Conclusion --- p.67
Chapter CHAPTER 7 --- CONCLUSION --- p.69
Chapter 7.1 --- Conclusion --- p.69
Chapter 7.2 --- Future Work for the Biofuel Cell Project --- p.70
Chapter 7.2.1 --- Study the Effect of Temperature Change --- p.70
Chapter 7.2.2 --- Study the Effect of the Change of pH in Substrates --- p.70
Chapter 7.2.3 --- Further Modified the Electrodes to Enhance the Output Power --- p.70
APPENDIX --- p.71
BIBLIOGRAPHY --- p.73

碩士
國立高雄應用科技大學
機械與精密工程研究所
99
This study investigated the performance of direct H2O2 microfluidic fuel cells with two different microchannel designs under various operating conditions. Besides performance measurement, flow visualization was also synchronously performed to observe the bubble generation, growth and movement under different operating conditions. Those cells were carried out by bonding a PDMS microchannel and a Pt-patterned glass slide after oxygen plasma treatment. The 50-m-deep PDMS T-shaped microchannel of the microfluidic fuel cells was fabricated by soft lithography process and the Pt-patterned glass slide was obtained via lift-off process. There are two microchannel designs, including rectangular and stairstepped-bulged microchannel, and three different microchannel widths, 0.5 mm, 1 mm and 1.5 mm, were tested under three different reactan concentrations of 0.1 M, 0.3 M,0.6 M, and various volumetric flow rates of the fuel and oxidant ranged from 0.01 mL/min to 1.0 mL/min to measure the cells performance. The experimental results showed that cells of narrower microchannel or larger electrode distance yielded higher cell performance at a given volumetric flow rate. The rectangular microchannel design revealed better cell performance than bulged microchannel. Besides, the cell output increased with the increase of either reactant concentration or volumetric flow rate. The results demonstrated that the cell output was 160.88 mA/cm2 at 0.26 V and the maximum power density reached 41.67 mW/cm2 at volumetric flow rate of 1 mL/min.