High Performance Fuel Breathing Microfluidic Fuel Cells

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High Performance Fuel-Breathing Microfluidic Fuel Cells

Author : Yifei Wang
Publisher : Open Dissertation Press
ISBN 13 : 9781361041932
Total Pages : 255 pages
Book Rating : 4.0/5 (419 download)

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Book Synopsis High Performance Fuel-Breathing Microfluidic Fuel Cells by : Yifei Wang

Download or read book High Performance Fuel-Breathing Microfluidic Fuel Cells written by Yifei Wang and published by Open Dissertation Press. This book was released on 2017-01-26 with total page 255 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "High Performance Fuel-breathing Microfluidic Fuel Cells" by Yifei, Wang, 王夷飞, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of the thesis entitled "HIGH PERFORMANCE FUEL-BREATHING MICROFLUIDIC FUEL CELLS" Submitted by Yifei, Wang for the degree of Doctor of Philosophy at The University of Hong Kong in September 2016 Fuel cells are broadly regarded as one of the most promising power sources. A fuel cell is generally composed of a thin membrane electrolyte sandwiched by two porous electrodes, which has a similar structure with batteries. Fuel cells are very advantageous considering their high energy density, uninterrupted operation and environmental friendliness. To date, the application of this technology is vigorously promoted by the government and industry especially for large-power applications. As for applications with small rated power, the progress is, however, impeded by their high cost, leading to less competitiveness against the mature battery technology. To lower down the cost, microfluidic fuel cell (MFC), also known as the membraneless fuel cell or laminar flow fuel cell, has been proposed recently. A MFC generally utilizes two laminar flows in parallel as electrolyte instead of any solid membrane, therefore, lowering the fabrication cost. To prevent the flows from violent mixing, micro-channel, normally with characteristic length less than 1mm, is requisite. In this manner, the mixing process is dominated by slow diffusion, forming a flow interface in the middle of the channel as a virtual membrane. Despite of its cost advantage, there are still many unsolved problems in MFCs such as poor energy density, trade-off between cell performance and fuel utilization, complex fluidic management, etc. In this thesis, research works on MFC development have been done to improve their cell performance, energy efficiency, energy density, long-term stability, etc. In addition, a novel MFC stacking strategy has been proposed, which was proved to be competent for practical applications.  First, conventional liquid-feed MFCs with either co-flow or counter-flow configuration were studied. Their cell performance and fuel utilization were optimized, which were used as benchmarks in subsequent studies.  To solve the intractable restrictions in liquid-feed MFCs, vapor-feed MFCs were proposed which breathed fuel vapor from outside the cell instead of acquiring dissolved fuel from the inside electrolyte, therefore, -2 achieving both high power density (55.4mWcm ) and high energy efficiency (9.4%) at the same time.  To better understand the mechanism behind its performance, numerical (R) simulation on vapor-feed MFCs was also conducted using COMSOL 4.2.  To achieve practical power output, a circular stacking strategy was proposed, which was especially suitable for fuel-breathing MFCs. A six- cell stack was designed and tested, proving that such a stacking strategy was not only highly efficient but also potentially robust to external flow disturbance.  The same stacking strategy was also applied to H -fueled MFCs to further improve the power output. By utilizing Al-H O reaction for H generation, 2 2 the proposed Al-feed MFC stack achieved a peak power output of 530mW. Meanwhile, difficulties in hydrogen storage and waste electrolyte management were eliminated.  In MFCs with enlarged electrode areas, cathode flooding was inevitably aggravated and cell performance dropped significantly. By cracking the cathode catalyst layer, this problem was greatly alleviated, leading to a m

High Performance Fuel-Breathing Microfluidic Fuel Cells

Author : Yifei Wang
Publisher :
ISBN 13 : 9781361041956
Total Pages : pages
Book Rating : 4.0/5 (419 download)

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Book Synopsis High Performance Fuel-Breathing Microfluidic Fuel Cells by : Yifei Wang

Download or read book High Performance Fuel-Breathing Microfluidic Fuel Cells written by Yifei Wang and published by . This book was released on 2017-01-26 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "High Performance Fuel-breathing Microfluidic Fuel Cells" by Yifei, Wang, 王夷飞, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of the thesis entitled "HIGH PERFORMANCE FUEL-BREATHING MICROFLUIDIC FUEL CELLS" Submitted by Yifei, Wang for the degree of Doctor of Philosophy at The University of Hong Kong in September 2016 Fuel cells are broadly regarded as one of the most promising power sources. A fuel cell is generally composed of a thin membrane electrolyte sandwiched by two porous electrodes, which has a similar structure with batteries. Fuel cells are very advantageous considering their high energy density, uninterrupted operation and environmental friendliness. To date, the application of this technology is vigorously promoted by the government and industry especially for large-power applications. As for applications with small rated power, the progress is, however, impeded by their high cost, leading to less competitiveness against the mature battery technology. To lower down the cost, microfluidic fuel cell (MFC), also known as the membraneless fuel cell or laminar flow fuel cell, has been proposed recently. A MFC generally utilizes two laminar flows in parallel as electrolyte instead of any solid membrane, therefore, lowering the fabrication cost. To prevent the flows from violent mixing, micro-channel, normally with characteristic length less than 1mm, is requisite. In this manner, the mixing process is dominated by slow diffusion, forming a flow interface in the middle of the channel as a virtual membrane. Despite of its cost advantage, there are still many unsolved problems in MFCs such as poor energy density, trade-off between cell performance and fuel utilization, complex fluidic management, etc. In this thesis, research works on MFC development have been done to improve their cell performance, energy efficiency, energy density, long-term stability, etc. In addition, a novel MFC stacking strategy has been proposed, which was proved to be competent for practical applications.  First, conventional liquid-feed MFCs with either co-flow or counter-flow configuration were studied. Their cell performance and fuel utilization were optimized, which were used as benchmarks in subsequent studies.  To solve the intractable restrictions in liquid-feed MFCs, vapor-feed MFCs were proposed which breathed fuel vapor from outside the cell instead of acquiring dissolved fuel from the inside electrolyte, therefore, -2 achieving both high power density (55.4mWcm ) and high energy efficiency (9.4%) at the same time.  To better understand the mechanism behind its performance, numerical (R) simulation on vapor-feed MFCs was also conducted using COMSOL 4.2.  To achieve practical power output, a circular stacking strategy was proposed, which was especially suitable for fuel-breathing MFCs. A six- cell stack was designed and tested, proving that such a stacking strategy was not only highly efficient but also potentially robust to external flow disturbance.  The same stacking strategy was also applied to H -fueled MFCs to further improve the power output. By utilizing Al-H O reaction for H generation, 2 2 the proposed Al-feed MFC stack achieved a peak power output of 530mW. Meanwhile, difficulties in hydrogen storage and waste electrolyte management were eliminated.  In MFCs with enlarged electrode areas, cathode flooding was inevitably aggravated and cell performance dropped significantly. By cracking the cathode catalyst layer, this problem was greatly alleviated, leading to a m

Microfluidic Fuel Cells and Batteries

Author : Erik Kjeang
Publisher : Springer
ISBN 13 : 3319063464
Total Pages : 81 pages
Book Rating : 4.3/5 (19 download)

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Book Synopsis Microfluidic Fuel Cells and Batteries by : Erik Kjeang

Download or read book Microfluidic Fuel Cells and Batteries written by Erik Kjeang and published by Springer. This book was released on 2014-06-14 with total page 81 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microfluidic fuel cells and batteries represent a special type of electrochemical power generators that can be miniaturized and integrated in a microfluidic chip. Summarizing the initial ten years of research and development in this emerging field, this SpringerBrief is the first book dedicated to microfluidic fuel cell and battery technology for electrochemical energy conversion and storage. Written at a critical juncture, where strategically applied research is urgently required to seize impending technology opportunities for commercial, analytical, and educational utility, the intention is for this book to be a ‘one-stop shop’ for current and prospective researchers in the general area of membraneless, microfluidic electrochemical energy conversion. As the overall goal of the book is to provide a comprehensive resource for both research and technology development, it features extensive descriptions of the underlying fundamental theory, fabrication methods, and cell design principles, as well as a thorough review of previous contributions in this field and a future outlook with recommendations for further work. It is hoped that the content will entice and enable new research groups and engineers to rapidly gain traction in their own laboratories towards the development of next generation microfluidic electrochemical cells.

Boosting Performance of Membraneless Microfluidic Fuel Cells Via Cell Architecture Optimization and Flow Management

Author : 羅詩靜
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (143 download)

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Book Synopsis Boosting Performance of Membraneless Microfluidic Fuel Cells Via Cell Architecture Optimization and Flow Management by : 羅詩靜

Download or read book Boosting Performance of Membraneless Microfluidic Fuel Cells Via Cell Architecture Optimization and Flow Management written by 羅詩靜 and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Micro Fuel Cells

Author : Tim Zhao
Publisher : Academic Press
ISBN 13 : 0080878873
Total Pages : 312 pages
Book Rating : 4.0/5 (88 download)

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Book Synopsis Micro Fuel Cells by : Tim Zhao

Download or read book Micro Fuel Cells written by Tim Zhao and published by Academic Press. This book was released on 2009-07-07 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: Today's consumers of portable electronics consumers are demanding devices not only deliver more power but also work healthy for the environment. This fact alone has lead major corporations like Intel, BIC, Duracell and Microsoft to believe that Microfuel Cells could be the next-generation power source for electronic products. Compact and readable, Microfuels Principles and Applications, offers engineers and product designers a reference unsurpassed by any other in the market. The book starts with a clear and rigorous exposition of the fundamentals engineering principles governing energy conversion for small electronic devices, followed by self-contained chapters concerning applications. The authors provide original points of view on all types of commercially available micro fuel cells types, including micro proton exchange membrane fuel cells, micro direct methanol fuel cells, micro solid oxide fuel cells and micro bio-fuel cells. The book also contains a detailed introduction to the fabrication of the components and the assembly of the system, making it a valuable reference both in terms of its application to product design and understanding micro engineering principles. An overview of the micro fuel cell systems and applications A detailed introduction to the fabrication of the components and the assembly of the system Original points of view on prospects of micro fuel cells

Microfluidic Fuel Cells

Author :
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (654 download)

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Book Synopsis Microfluidic Fuel Cells by :

Download or read book Microfluidic Fuel Cells written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Performance Enhancements of Microfluidic Fuel Cells with Flow-through Porous Electrodes

Author : Jin Wook Lee
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (95 download)

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Book Synopsis Performance Enhancements of Microfluidic Fuel Cells with Flow-through Porous Electrodes by : Jin Wook Lee

Download or read book Performance Enhancements of Microfluidic Fuel Cells with Flow-through Porous Electrodes written by Jin Wook Lee and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents performance improvements of microfluidic fuel cells with flow-through porous electrodes. The baseline cell is a laminar flow-based, membraneless, microfluidic fuel cell employing vanadium redox species (as electrolytes). The main objective of the current work is to establish a design guideline for microfluidic fuel cells and to propose new design strategies that lead to better performing cells. The fundamental physics including fluid flow, electrochemical reactions in porous media, and convective/diffusive mass transport is closely investigated. Various loss elements during the baseline cell operation such as activation, ohmic, and mass transport losses are identified and compared. Some feasible and practical remedies to reduce the overall losses are proposed and successfully demonstrated: thin film current collector for the overall ohmic loss; nanofoam material as electrodes to reduce the activation loss; and novel concept to overcome mass transport limited performances. Further improvements would be anticipated if both ohmic and fluidic resistances of the nanofoam material are reduced. Uniform distribution of the pore sizes is also important to maximize the utilization of active electrode areas. When combined, the demonstrated technologies and design improvements are anticipated to bring this unique membraneless and catalyst-free fuel cell closer to commercialization as a low-cost power source.

Microfluidic H2/O2 Fuel Cells for Contaminant and Electrode Analysis

Author : Matt Naughton
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (774 download)

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Book Synopsis Microfluidic H2/O2 Fuel Cells for Contaminant and Electrode Analysis by : Matt Naughton

Download or read book Microfluidic H2/O2 Fuel Cells for Contaminant and Electrode Analysis written by Matt Naughton and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Alkaline fuel cells (AFCs) are promising power sources due to superior cathode kinetics as compared to acidic media and the ability to use inexpensive non-noble metal catalysts. However, carbonate formation from carbon dioxide in air has long been considered a significant hurdle for liquid electrolyte-based AFC technologies. Carbonate formation consumes hydroxyl anions, which leads to (i) reduced electrode performance if formed salts precipitate from solution and (ii) lowered electrolyte conductivity, which reduces cell performance and operating lifetime. We have used a microfluidic H2/O2 fuel cell as an analytical platform to determine the effects of the carbonate formation problem in alkaline fuel cells. The microfluidic fuel cell has modular components that can easily be swapped to test electrodes, electrolyte, or other aspects of the fuel cell. A reference electrode placed at the outlet allows for individual electrode analysis, which is not normally possible in conventional membrane-based fuel cells. In this thesis, it is demonstrated that AFC performance can be resilient to a broad range of carbonate concentrations. Furthermore, the effects of carbonate formation rates on projected AFC operational lifetime are determined. A quantitative method to analyze individual electrode performance using single electrode plots and the two parameters Rohmic and Vkinetic is also developed. Results demonstrated that losses from both electrodes are substantial in an alkaline fuel cell, and that ohmic and mass transport losses are shown to only significantly affect Rohmic. IR-corrections were used to isolate individual kinetic and mass transport losses at each electrode within the operating fuel cell. These findings demonstrate great potential to broaden the scope of fuel cell research.

Enzymatic Microfluidic Fuel Cells

Author : Ma José González Guerrero
Publisher :
ISBN 13 : 9788449057472
Total Pages : 144 pages
Book Rating : 4.0/5 (574 download)

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Book Synopsis Enzymatic Microfluidic Fuel Cells by : Ma José González Guerrero

Download or read book Enzymatic Microfluidic Fuel Cells written by Ma José González Guerrero and published by . This book was released on 2015 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Microfluidics in Membraneless Fuel Cells

Author : Jesus A. Diaz-Real
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (115 download)

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Book Synopsis Microfluidics in Membraneless Fuel Cells by : Jesus A. Diaz-Real

Download or read book Microfluidics in Membraneless Fuel Cells written by Jesus A. Diaz-Real and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In the 1990s, the idea of developing miniaturized devices that integrate functions other than what normally are carried out at the laboratory level was conceived, and the so-called "lab-on-a-chip" (LOC) devices emerged as one of the most important research areas. LOC devices exhibit advantages related to the use of microfluidic channels such as small sample and reagent consumption, portability, low-power consumption, laminar flow, and higher surface area/volume ratio that enhances both thermal dissipation and electrochemical kinetics. Fuel cells are electrochemical devices that convert chemical energy to electrical energy. These are considered as one of the greener ways to generate electricity because typical fuel cells produce water and heat as the main reaction byproducts. The technical challenges to develop systems at the microscale and the advantages of microfluidics exhibited an important impact on fuel cells for several reasons, mainly related to avoid inherent problems of gaseous-based fuel cells. As a result, the birth of a new type of fuel cells as microfluidic fuel cells (MFCs) took place. The first microfluidic fuel cell was reported in 2002. This MFC was operated with liquid fuel/oxidant and had the advantage of the low laminar flow generated using a "Y" microfluidic channel to separate the anodic and cathodic streams, resulting in an energy conversion device that did not require a physical barrier to separate both streams. This electrochemical system originated a specific type of MFCs categorized as membraneless also called colaminar microfluidic fuel cells. Since that year, numerous works focused on the nature of fuels, oxidants and anodic/cathodic electrocatalysts, and cell designs have been reported. The limiting parameters of this kind of devices toward their use in portable applications are related to their low cell performances, small mass activity, and partial selectivity/durability of electrocatalysts. On the other hand, it has been observed that the cell design has a high effect on the cell performance due to internal cell resistances and the crossover effect. Furthermore, current technology is growing faster than last centuries and new microfabrication technologies are always emerging, allowing the development of smaller and more powerful microfluidic energy devices. In this chapter, the application of microfluidics in membraneless fuel cells is addressed in terms of evolution of cell designs of miniaturized microfluidic fuel cells as a result of new discoveries in microfabrication technology and the use of several fuels and electrocatalysts for specific and selective applications.

Advances in Microfluidics

Author : Xiao-Ying Yu
Publisher : BoD – Books on Demand
ISBN 13 : 9535127853
Total Pages : 424 pages
Book Rating : 4.5/5 (351 download)

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Book Synopsis Advances in Microfluidics by : Xiao-Ying Yu

Download or read book Advances in Microfluidics written by Xiao-Ying Yu and published by BoD – Books on Demand. This book was released on 2016-11-23 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt: Increasing innovations and applications make microfluidics a versatile choice for researchers in many disciplines. This book consists of multiple review chapters that aim to cover recent advances and new applications of microfluidics in biology, electronics, energy, and materials sciences. It provides comprehensive views of various aspects of microfluidics ranging from fundamentals of fabrication, flow control, and droplet manipulation to the most recent exploration in emerging areas such as material synthesis, imaging and novel spectroscopy, and marriage with electronics. The chapters have many illustrations showcasing exciting results. This book should be useful for those who are eager to learn more about microfluidics as well as researchers who want to pick up new concepts and developments in this fast-growing field.

Two-phase Flow Phenomena in Fuel Cell Microchannels

Author : Julie Elizabeth Steinbrenner
Publisher : Stanford University
ISBN 13 :
Total Pages : 149 pages
Book Rating : 4.F/5 ( download)

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Book Synopsis Two-phase Flow Phenomena in Fuel Cell Microchannels by : Julie Elizabeth Steinbrenner

Download or read book Two-phase Flow Phenomena in Fuel Cell Microchannels written by Julie Elizabeth Steinbrenner and published by Stanford University. This book was released on 2011 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proton exchange membrane (PEM) fuel cells show promise as CO2-free energy-conversion devices. Predictions show that reducing the size of the gas delivery channels could improve the efficiency and power density of PEM fuel cells, however the expected benefits of reduced channel sizes have not been realized due to flooding by water generated at the cathode. Channels with small dimensions exhibit an increased propensity toward flooding as surface tension forces become significant when compared with viscous, inertial, and pressure forces. This study characterizes the distinct two-phase flow profiles that result from the interplay of these forces. We investigate fundamental water-gas interactions in silicon channels of various hydraulic diameters and cross-sectional aspect ratios using a high-contrast fluorescent imaging technique. Then, we develop a test structure to study the evolution of two-phase flow structures in a microchannel geometry designed to mimic conditions in a fuel cell channel -- a 60-cm long channel with distributed water introduction through a porous gas diffusion layer (GDL) on one wall. Finally, we present considerations for the implementation of spinning-disk confocal microscopy to provide three-dimensional (3D) visualization of two-phase flow structures which may provide insight into key flow transitions that were observed during high-speed fluorescent flow visualization. By characterizing and modeling two-phase flow in various microchannel geometries and under a large range of flow conditions, these studies provide insight that enables the improved design of microchannels for two-phase flow in fuel cells and other practical devices.

Materials and Methods for Microfluidic Fuel Cells

Author : Ben Nearingburg
Publisher :
ISBN 13 :
Total Pages : 207 pages
Book Rating : 4.:/5 (92 download)

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Book Synopsis Materials and Methods for Microfluidic Fuel Cells by : Ben Nearingburg

Download or read book Materials and Methods for Microfluidic Fuel Cells written by Ben Nearingburg and published by . This book was released on 2014 with total page 207 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microfluidic fuel cell (MFC) devices are a promising route towards on-chip power generation for microfluidic and lab-on-a-chip systems. Current MFCs leverage fabrication techniques and materials that have been inherited from micromachining technology and macro-scale fuel cell devices. Both, these methods and materials can be costly and difficult to integrate into larger microfluidic networks or lab-on-a-chip devices. In order to fully explore the utility of MFCs, device should be composed of common microfluidic materials (i.e. formed from the same materials as the rest of the device) and amendable to fabrication alongside other components of microfluidic devices (i.e. not require specialized equipment/techniques for patterning). This thesis set out to improve the applicability of MFC devices by enhancing fabrication methods and describing new functional materials to better align MFCs with microfluidic device architectures. To achieve this goal, I focused my efforts on improving individual sub-components of the MFC device architecture to yield more effective devices. Throughout this thesis, emphasis was placed upon leveraging techniques amenable to low-cost bench-top processing (i.e. those that do not require expensive capital equipment) to broaden the applicability of MFC devices. My work was applied to three components of planar MFC devices (where a device consists of a single sided microchannel and a flat capping layer). First, proton exchange membranes capable of in situ patterning were developed and characterized. Second, oxygen transport through air breathing polymer layers was assessed through finite element modelling to better understand factors governing air breathing MFC devices. Finally, a new technique, multi-layer in situ laminar flow lithography, was introduced and characterized. This technique was shown to allow for patterning of multi-layer metal films to yield independent catalytic electrodes. Functional alkaline direct methanol fuel cell devices were then fabricated and characterized using the technique. The utility and applicability of each of these techniques to both MFCs and the wider field of microfluidics was assessed and possible applications discussed.

Microfluidic Fuel Cells

Author : Boming Zhu
Publisher :
ISBN 13 :
Total Pages : 84 pages
Book Rating : 4.:/5 (896 download)

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Book Synopsis Microfluidic Fuel Cells by : Boming Zhu

Download or read book Microfluidic Fuel Cells written by Boming Zhu and published by . This book was released on 2010 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Microfluidics for Fuel Cell Applications

Author : Ian Stewart
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (858 download)

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Book Synopsis Microfluidics for Fuel Cell Applications by : Ian Stewart

Download or read book Microfluidics for Fuel Cell Applications written by Ian Stewart and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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?m, 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.

Microfluidic Fuel Cells as Analytical Platforms

Author : Fikile R. Brushett
Publisher :
ISBN 13 :
Total Pages : 148 pages
Book Rating : 4.:/5 (612 download)

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Book Synopsis Microfluidic Fuel Cells as Analytical Platforms by : Fikile R. Brushett

Download or read book Microfluidic Fuel Cells as Analytical Platforms written by Fikile R. Brushett and published by . This book was released on 2009 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Microfluidic Platforms for the Investigation of Fuel Cell Catalysts and Electrodes

Author : Fikile R. Brushett
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (776 download)

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Book Synopsis Microfluidic Platforms for the Investigation of Fuel Cell Catalysts and Electrodes by : Fikile R. Brushett

Download or read book Microfluidic Platforms for the Investigation of Fuel Cell Catalysts and Electrodes written by Fikile R. Brushett and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A clear need exists for novel approaches to producing and utilizing energy in more efficient ways, in light of society0́9s ever increasing demand as well as growing concerns with respect to climate change related to CO2 emissions. The development of low temperature fuel cell technologies will continue to play an important role in many alternative energy conversion strategies, especially for portable electronics and automotive applications. However, widespread commercialization of fuel cell technologies has yet to be achieved due to a combination of high costs, poor durability and, system performance limitations (Chapter 1). Developing a better understanding of the complex interplay of electrochemical, transport, and degradation processes that govern the performance and durability of novel fuel cell components, particularly catalysts and electrodes, within operating fuel cells is critical to designing robust, inexpensive configurations that are required for commercial introduction. Such detailed in-situ investigations of individual electrode processes are complicated by other factors such as water management, uneven performance across electrodes, and temperature gradients. Indeed, too many processes are interdependent on the same few variable parameters, necessitating the development of novel analytical platforms with more degrees of freedom. Previously, membraneless microfluidic fuel cells have been developed to address some of the aforementioned fuel cell challenges (Chapter 2). At the microscale, the laminar nature of fluid flow eliminates the need for a physical barrier, such as a stationary membrane, while still allowing ionic transport between electrodes. This enables the development of many unique and innovative fuel cell designs. In addition to addressing water management and fuel crossover issues, these laminar flow-based systems allow for the independent specification of individual stream compositions (e.g., pH). Furthermore, the use of a liquid electrolyte enables the simple in-situ analysis of individual electrode performance using an off-the-shelf reference electrode. These advantages can be leveraged to develop microfluidic fuel cells as versatile electro-analytical platforms for the characterization and optimization of catalysts and electrodes for both membrane- and membraneless fuel cells applications. To this end, a microfluidic hydrogen-oxygen (H2/O2) fuel cell has been developed which utilizes a flowing liquid electrolyte instead of a stationary polymeric membrane. For analytical investigations, the flowing stream (i) enables autonomous control over electrolyte parameters (i.e., pH, composition) and consequently the local electrode environments, as well as (ii) allows for the independent in-situ analyses of catalyst and/or electrode performance and degradation characteristics via an external reference electrode (e.g., Ag/AgCl). Thus, this microfluidic analytical platform enables a high number of experimental degrees of freedom, previously limited to a three-electrode electrochemical cell, to be employed in the construct of working fuel cell. Using this microfluidic H2/O2 fuel cell as a versatile analytical platform, the focus of this work is to provide critical insight into the following research areas: 0́Ø Identify the key processes that govern the electrode performance and durability in alkaline fuel cells as a function of preparation methods and operating parameters (Chapter 3). 0́Ø Determine the suitability of a novel Pt-free oxygen reduction reaction catalyst embedded in gas diffusion electrodes for acidic and alkaline fuel cell applications (Chapter 4). 0́Ø Establish electrode structure-activity relationships by aligning in-situ electrochemical analyses with ex-situ microtomographic (MicroCT) structural analyses (Chapter 5). 0́Ø Investigate the feasibility and utility of a microfluidic-based vapor feed direct methanol fuel cell (VF-DMFC) configuration as a power source for portable applications (Chapter 6). In all these areas, the information garnered from these in-situ analytical platforms will advance the development of more robust and cost-effective electrode configurations and thus more durable and commercially-viable fuel cell systems (both membrane-based and membraneless).