Esta dissertação teve como objetivo o desenvolvimento de um dispositivo microfluídico para a determinação de nutrientes em solo. A motivação para o desenvolvimento de uma plataforma microfluídica dedicada à agricultura vem do crescimento populacional, que chegará em 2030 a 8,5 bilhões de pessoas, ante 7,3 bilhões atuais. Com um crescimento tão expressivo da população mundial o fornecimento de alimentos torna-se vital. A agricultura desempenha um papel notável no fornecimento de alimentos e na economia brasileira. O monitoramento de nutrientes no solo para uma boa produção é indispensável. O desenvolvimento de dispositivos microfluídicos vêm tomando destaque na área industrial, alimentar, ambiental e criminal, devido a sua portabilidade, baixo peso, custo de fabricação e consumo de reagentes. Com uma aplicação de amostra de 50 µL no centro do dispositivo microfluídico, o líquido percola o interior do dispositivo por capilaridade até as zonas reacionais, onde estão depositados pequenos volumes de reagente. Após a amostra reagir na zona reacional, uma alteração visual da cor é observada e esta pode ser utilizada para quantificar a espécie de interesse. Dentre os extratores utilizados, a água não é um bom extrator para os analitos aqui trabalhados. A curva analítica de borato e cobalto apresentaram resultados promissores tanto em solução aquosa quanto em ácido cítrico 2%. O emprego de solução de ácido cítrico 2% para construção da curva analítica e extração de ferro e cobre do solo é um reagente eficiente se comparado a água e citrato neutro de amônio. Para o fosfato, o emprego de soluções de água ou citrato neutro de amônio podem ser empregados. A construção de testes para quantificação de nitrito, nitrato e zinco apresentaram problemas de reprodutibilidade. As reações colorimétricas apresentaram resultados promissores para aplicação em dispositivos microfluídicos a base papel. A associação entre reações colorimétricas simples e dispositivos microfluídicos possibilitou o desenvolvimento de testes químicos para serem empregados na agricultura. Os dados gerados podem ser utilizados na modelação da distribuição de nutrientes no terreno em estudo e posterior correção visando benefícios à agricultura. / This dissertation aimed at the development of a microfluidic device for the determination of nutrients in soil. The motivation for the development of a microfluidic platform dedicated to agriculture comes from population growth, which in 2030 will reach 8.5 billion people, compared to 7.3 billion today. With such a significant growth of the world population, food supply becomes vital. Agriculture plays a notable role in food supply and in the Brazilian economy. The monitoring of nutrients in the soil for good production is indispensable. The development of microfluidic devices has been highlighted in the industrial, food, environmental and criminal areas, due to their portability, low weight, manufacturing cost and reagent consumption. With a 50 ?L sample application in the center of the microfluidic device, the liquid percolates the interior of the device by capillarity to the reaction zones where small volumes of reagent are deposited. After the sample reacts in the reaction zone, a visual color change is observed and this can be used to quantify the species of interest. Among the extractors used, water is not a good extractor for the analytes used here. The analytical curve of borate and cobalt presented promising results in both aqueous solution and 2% citric acid. The use of 2% citric acid solution for the construction of the analytical curve and extraction of iron and copper from the soil is an efficient reagent when compared to water and neutral ammonium citrate. For phosphate, the use of water solutions or neutral ammonium citrate may be employed. The construction of tests for quantification of nitrite, nitrate and zinc presented problems of reproducibility. The colorimetric reactions presented promising results for application in paper - based microfluidic devices. The association between simple colorimetric reactions and microfluidic devices allowed the development of chemical tests to be used in agriculture. The data generated can be used in the modeling of nutrient distribution in the field under study and later correction aiming at benefits to agriculture.

O uso de antibióticos em animais de produção pode ser ministrado de diferentes formas: i) como método de prevenção de doenças, ii) como tratamento e combate de doenças como mastite, infecções respiratórias, genitais e oftálmicas, e iii) aplicados às rações, a fim de aumentar o ganho de peso, promovendo também a eficiência de aproveitamento dos alimentos e tornando menores os índices de morbidez e mortalidade. No entanto, alguns produtores utilizam os antibióticos de forma inadequada, ministrando o mesmo em dosagens superiores às recomendadas ou até mesmo adicionando os antibióticos diretamente no leite, a fim de inibir o crescimento indesejável de bactérias, o que pode causar graves riscos à saúde humana. Uma das maneiras de se detectar resíduos de antibióticos (sulfonamidas) em leite é a partir da reação enzimática entre a anidrase carbônica e um éster (4-nitrofenil acetato), que gera uma coloração amarelo brilhante. As sulfonamidas inibem tal reação, impedindo o surgimento de cor. Dispositivos microfluídicos fabricados em papel (μAD) foram desenvolvidos como um novo método simples, rápido, portátil e de baixo custo, a fim de se detectar a presença ou ausência das três principais sulfonamidas (sulfametazina, sulfadimetoxina e sulfatiazol), como exigido pela Agência Nacional de Vigilância Sanitária (ANVISA). A imobilização de uma fina camada uniforme de pasta de metil celulose, nos spots dos microdispositivos, permitiu maior estabilidade na superfície reacional do papel, de forma a alcançar limites de detecção (LOD) menores, equivalentes à 2,80 μmol L-1 (7,79x10-7 g mL-1) para a sulfametazina, 2,70 μmol L-1(8,37x10-7 g mL-1) para a sulfadimetoxina e 2,50 μmol L-1 (6,38x10-7 g mL-1) para o sulfatiazol. O método apresentou, como principal vantagem, a análise das amostras de leite bovino sem qualquer tratamento prévio. Além disso, o método apresentou boa linearidade e repetitividade nos ensaios realizados intra-dia e inter-dia, além de se mostrar seletivo para compostos da classe das sulfonamidas, mostrou-se também robusto com relação a alterações na temperatura do leite bovino. Dessa forma, o teste pode ser transportado para a área rural, sem a necessidade de um profissional especializado, a fim de se obter um diagnóstico local rápido, simples e de baixo custo, para a qualidade do leite. / The use of antibiotics in animal production can be delivered in diferent ways: i) as a method of preventing disease in animals, ii) as treatment and combat diseases such as mastitis, respiratory infections, genital infections and ophthalmic infections, and iii) applied to the feed in order to increase the weight gain of the animals, promoting the efficiency of food utilization, and making lower the morbidity and mortality. However, some producers use antibiotics improperly, administering it in doses higher than those recommended or even directly adding antibiotics to the milk, in order to inhibit the unwanted growth of bacteria. This fact alone can cause serious risks to human health. One way of detecting antibiotic residues (sulfonamides) in milk, is using the enzymatic reaction between an ester (4-nitrophenyl acetate) and carbonic anhydrase, which gives a bright yellow color. The sulfonamides inhibit this reaction, preventing color appearance. Paper-based microfluidic devices (μPAD) have been developed as a new simple, fast, portable and inexpensive, in order to detect the presence or absence of the three most common sulfonamides (sulfamethazine, sulfadimethoxine and sulfathiazole), as required by the National Agency of Sanitary Surveillance (ANVISA). The immobilization of a uniform thin layer of methyl cellulose pulp on the spots of microdevices, allowed greater stability in the reaction surface of the paper, and achieved lower limits of detection (LOD) than without the additive, equivalent to 2.80 5mol L-1 (7.79x10-7 g mL-1)for sulfamethazine, 2.70 5mol L-1 (8.37x10-7 g mL-1) for sulfadimethoxine and 2.50 5mol L-1 (6.38x10-7 g mL-1) for sulfathiazole. The principal advantage of this method is that allows the analysis of bovine milk samples without any prior treatment. Furthermore, the method i) has good linearity and repeatability in tests performed intra-day and inter-day, ii) shows selectivity for compounds of the sulfonamide class, and iii) is robust to changes in bovine milk temperature. Thus, the test can be transported to the rural area, without a specialized professional, providing locally a fast, simple and low cost diagnostic for the presence of sulfonamide antibiotics in milk.

Neste trabalho são apresentados resultados relativos ao desenvolvimento de um processo de fabricação para a produção de sistemas de microcanais em vidro tipo borosilicato, 7059 Corning Glass. O objetivo do trabalho é implementar um processo básico, mas completo, de fabricação de sistemas microfluídicos em vidro, que possam futuramente ser aprimorados com a introdução de dispositivos ópticos e eletrônicos e de elementos microfluídicos ativos, como válvulas e microbombas, para sensoreamento e controle de fluxo. O processo de fabricação foi dividido em três grandes etapas, sendo a primeira delas, a produção dos microcanais, envolvendo processos como litografia e corrosão úmida. Nos estudos de corrosão procurou-se uma solução que permitisse a obtenção de canais com superfície uniforme e lisa, sem a produção de resíduos durante a corrosão do vidro. Os melhores resultados foram obtidos com a solução HF + HCl + H2O (1:2:3), com a possibilidade de produzir canais com até 150 µm de profundidade. A segunda etapa do processo de produção dos sistemas microfluídicos envolveu o encapsulamento dos microcanais, o que foi feito através de um processo de soldagem direta (vidro com vidro) à temperatura ambiente, com aplicação de pressão entre 0,1 a 1,0 MPa. Os melhores resultados nesta etapa envolveram pressões acima de 0,5 MPa, podendo-se obter cerca de 95 - 100% da área das lâminas soldadas. A terceira etapa do processo de fabricação engloba a interconexão com o meio externo, envolvendo a produção dos furos no vidro para entrada e saída de líquidos e a introdução dos tubos de acesso para o meio externo. Para a produção dos furos foi desenvolvido um sistema posicionador computarizado que movimenta o substrato de vidro nas direções x, y e z com precisão de alguns micrometros, garantindo o alinhamento necessário entre as duas lâminas de vidro que devem ser soldadas para encapsular os microcanais. Os furos foram feitos com broca diamantada de uso odontológico fixa em uma furadeira comum. Cateteres e scalps de uso médico foram empregados como tubos de acesso, sendo selados com resina epóxi. Os sistemas microfluídicos fabricados foram testados monitorando o fluxo de soluções aquosas de anilina, o qual foi mantido através de bomba peristáltica. Os resultados se mostraram reprodutíveis, tendo se obtido microcanais lisos e sem resíduos, sem apresentar vazamentos e exibindo regime de fluxo tipicamente laminar. Em conjunto, estes resultados mostraram-se muito promissores para desenvolvimento futuro de aplicações em áreas como Biotecnologia e Análises Químicas. / In this work, a process for the fabrication of microchannels over borlosilicate 7059 Corning Glass is presented. The main objective is to develop a simple and complete process for the fabrication of microfluidic systems over glass, that can be further improved in the future, with the integration of optical, electronic and active microfluidic devices such as valves and micropumps, for sensing and flow control. The fabrication process has three main parts. The first part is the microchannel production, which is achieved through contact-lithography and wet etching. In the etching studies, a solution that led to the fabrication of channels with uniform and smooth surfaces, without residue formation was sought. The best results were attained with a HF + HCl + H2O (1:2:3), which allow for the production of channels with depths of up to 150 µm. The second part of the fabrication process is the microchannels encapsulation, which is achieved through direct (glass-glass) bonding at room temperature, with applied pressure ranging from 0.1 to 1.0 MPa. The best results were obtained with pressure values above 0.5 MPa, which allowed for the bonding of up to 95 -100% of the glass sufaces. The third part of the fabrication process concerns the interconnection with the outside environment, which involves hole production and the introduction of tubes, to allow external access of liquids. For the hole production, a computer controlled positioning system was developed, for accurate positioning of the glass substrate in the x, y and z directions, with a precision of a few micrometers. This system guaranteed the necessary alignment of the upper and lower glass substrates, which were bonded for the encapsulation of the microchannels. The holes were made with diamond burs with a common drill. Medical catheters and scalps were used as access tubes, with epoxy resin. The characterization of the fabricated microfluidic systems was achieved by monitoring the flow of aniline aqueous solutions, which was maintained through a peristaltic pump. Reproducible results were obtained, with the production smooth and residue free microchannels, which did not present leakage and exhibited a laminar flow behavior. These results are very promising for the future application of this process in the fabrication of devices for areas such as biotechnology and chemical analysis, among others.

Neste trabalho são apresentados resultados relativos ao desenvolvimento de um processo de fabricação para a produção de sistemas de microcanais em vidro tipo borosilicato, 7059 Corning Glass. O objetivo do trabalho é implementar um processo básico, mas completo, de fabricação de sistemas microfluídicos em vidro, que possam futuramente ser aprimorados com a introdução de dispositivos ópticos e eletrônicos e de elementos microfluídicos ativos, como válvulas e microbombas, para sensoreamento e controle de fluxo. O processo de fabricação foi dividido em três grandes etapas, sendo a primeira delas, a produção dos microcanais, envolvendo processos como litografia e corrosão úmida. Nos estudos de corrosão procurou-se uma solução que permitisse a obtenção de canais com superfície uniforme e lisa, sem a produção de resíduos durante a corrosão do vidro. Os melhores resultados foram obtidos com a solução HF + HCl + H2O (1:2:3), com a possibilidade de produzir canais com até 150 µm de profundidade. A segunda etapa do processo de produção dos sistemas microfluídicos envolveu o encapsulamento dos microcanais, o que foi feito através de um processo de soldagem direta (vidro com vidro) à temperatura ambiente, com aplicação de pressão entre 0,1 a 1,0 MPa. Os melhores resultados nesta etapa envolveram pressões acima de 0,5 MPa, podendo-se obter cerca de 95 - 100% da área das lâminas soldadas. A terceira etapa do processo de fabricação engloba a interconexão com o meio externo, envolvendo a produção dos furos no vidro para entrada e saída de líquidos e a introdução dos tubos de acesso para o meio externo. Para a produção dos furos foi desenvolvido um sistema posicionador computarizado que movimenta o substrato de vidro nas direções x, y e z com precisão de alguns micrometros, garantindo o alinhamento necessário entre as duas lâminas de vidro que devem ser soldadas para encapsular os microcanais. Os furos foram feitos com broca diamantada de uso odontológico fixa em uma furadeira comum. Cateteres e scalps de uso médico foram empregados como tubos de acesso, sendo selados com resina epóxi. Os sistemas microfluídicos fabricados foram testados monitorando o fluxo de soluções aquosas de anilina, o qual foi mantido através de bomba peristáltica. Os resultados se mostraram reprodutíveis, tendo se obtido microcanais lisos e sem resíduos, sem apresentar vazamentos e exibindo regime de fluxo tipicamente laminar. Em conjunto, estes resultados mostraram-se muito promissores para desenvolvimento futuro de aplicações em áreas como Biotecnologia e Análises Químicas. / In this work, a process for the fabrication of microchannels over borlosilicate 7059 Corning Glass is presented. The main objective is to develop a simple and complete process for the fabrication of microfluidic systems over glass, that can be further improved in the future, with the integration of optical, electronic and active microfluidic devices such as valves and micropumps, for sensing and flow control. The fabrication process has three main parts. The first part is the microchannel production, which is achieved through contact-lithography and wet etching. In the etching studies, a solution that led to the fabrication of channels with uniform and smooth surfaces, without residue formation was sought. The best results were attained with a HF + HCl + H2O (1:2:3), which allow for the production of channels with depths of up to 150 µm. The second part of the fabrication process is the microchannels encapsulation, which is achieved through direct (glass-glass) bonding at room temperature, with applied pressure ranging from 0.1 to 1.0 MPa. The best results were obtained with pressure values above 0.5 MPa, which allowed for the bonding of up to 95 -100% of the glass sufaces. The third part of the fabrication process concerns the interconnection with the outside environment, which involves hole production and the introduction of tubes, to allow external access of liquids. For the hole production, a computer controlled positioning system was developed, for accurate positioning of the glass substrate in the x, y and z directions, with a precision of a few micrometers. This system guaranteed the necessary alignment of the upper and lower glass substrates, which were bonded for the encapsulation of the microchannels. The holes were made with diamond burs with a common drill. Medical catheters and scalps were used as access tubes, with epoxy resin. The characterization of the fabricated microfluidic systems was achieved by monitoring the flow of aniline aqueous solutions, which was maintained through a peristaltic pump. Reproducible results were obtained, with the production smooth and residue free microchannels, which did not present leakage and exhibited a laminar flow behavior. These results are very promising for the future application of this process in the fabrication of devices for areas such as biotechnology and chemical analysis, among others.

在不均勻電場下產生的交流電動力是一種非常重要的物理現象，並且非常適合對微流體系統中的微粒子和溶液進行直接操控。微流體中主導的力會根據所加交流電場的參數，如電壓和頻率；以及溶液和微粒子的特性，如導電率和介電常數而改變。 / 這篇論文將會討論在微流體芯片中利用交流電動力的三個生物醫學領域應用範例。第一個例子中，介電電泳被用來擔任集中器的作用，將溶液中DNA附著的碳納米顆粒排列在微電極之間。這種納米材料的性質以及作為傳感器應用的可能性也將被研究。第二個應用著重在微通道中對細胞的操控。試驗過程中觀察到黑色素細胞在正介電電泳力作用下的自旋現象，而不含黑色素的細胞在相同條件下鮮少發生。研究的重點包括產生這種現象的條件和可能原因，以及對細胞旋轉速度的量化和比較。在這基礎上，實驗證實了對原本不含黑色素的細胞實現人為引發自旋現象的可能性。在第三個應用中，交流電熱流被用來輔助電化學生物傳感器的RNA雜交過程從而克服封閉系統生物傳感器的一些缺點，進而實現快速病原檢測。優化后的生物傳感器序列陣列性能非常有競爭力。具體來說，傳感器特異性良好，信噪比提高，檢測限提升。另外，初步臨床樣本檢測證實這種交流電動力輔助下的生物傳感器陣列具有在將來被整合成便攜式醫療檢測儀器從而實現分子生物診斷的潛質。 / AC Electrokinetics is a very important phenomenon in the presence of non-uniform electric fields that is suited for direct manipulation of both particles and bulk fluid in the microfluidic system. Based on the parameters of the applied AC electric field such as voltage and frequency, as well as the properties of solution and the particles, for example, conductivity and permittivity, dominant forces in the microfluidic system may vary. / In this thesis, three examples of utilizing AC Electrokinetics in the microfluidic system for biomedical applications will be discussed. The first application was to use dielectrophoresis as a concentrator to form DNA attached carbon nanoparticles alignment between microelectrodes. The properties of this type of nanomaterial were investigated for further sensing applications. Then, the second example focused on cell manipulation in the microchannel, as self-rotation phenomenon of the pigment cells under positive dielectrophoretic force was observed, while there was no movement for non-pigment cells applied with the same dielectrophoresis parameters. The conditions and possible reasons for this phenomenon were investigated, the cell rotation speed was quantified and compared, based on which, manually induced rotation using non-pigment cells was proved successful. Last but not least, AC Electrothermal effect was utilized to facilitate the hybridization process of electrochemical biosensor arrays to overcome the disadvantages of enclosed sensor system and to further realize rapid pathogen identification. Optimized biosensor arrays showed promising performance including good specificity for a panel of target species, enhanced signal-to-noise ratio and improved limit-of-detection. Furthermore, preliminary clinical sample validation was conducted to confirm the feasibility of using this type of AC Electrokinetically facilitated biosensor arrays for future integration into a point-of-care device for molecular diagnostics. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Ouyang, Mengxing. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 103-110). / Abstract also in Chinese. / List of Figures --- p.ix / List of Tables --- p.xiii / List of Abbreviation --- p.xiv / Chapter I. --- Introduction to AC Electrokinetics --- p.15 / Chapter 1.1. --- AC Electrokinetics --- p.15 / Chapter 1.2. --- Dielectrophoresis --- p.16 / Chapter 1.3. --- AC Electrothermal Flow --- p.17 / Chapter 1.4. --- Advantage of Miniaturized Microfluidic Device --- p.18 / Chapter II. --- DEP Manipulation of CNPs and DNA-CNPs --- p.20 / Chapter 2.1. --- Introduction --- p.20 / Chapter 2.1.1. --- Carbon Nanoparticles and Their Applications --- p.20 / Chapter 2.1.2. --- Fluorescent CNPs and Bio-imaging --- p.21 / Chapter 2.1.3. --- DNA Attached Nanomaterials --- p.23 / Chapter 2.2. --- Preparation of CNPs --- p.24 / Chapter 2.2.1 --- Fabrication Process --- p.24 / Chapter 2.2.2 --- Fluorescence Property --- p.24 / Chapter 2.3. --- DEP Manipulation of CNPs --- p.27 / Chapter 2.3.1. --- CNPs Linkage Formation --- p.27 / Chapter 2.3.2. --- DEP Parameters --- p.28 / Chapter 2.3.3. --- Electrical Stability --- p.30 / Chapter 2.4. --- DEP Manipulation of DNA-attached CNPs --- p.32 / Chapter 2.4.1. --- Preparation of Sensor Chips --- p.32 / Chapter 2.4.2. --- Current-Voltage Characterization --- p.34 / Chapter 2.4.3. --- Stability --- p.35 / Chapter 2.4.4. --- Temperature Dependency --- p.39 / Chapter 2.4.5. --- Humidity Dependency --- p.40 / Chapter 2.5. --- Summary --- p.44 / Chapter III. --- Self-Rotation of Cells in the DEP Field --- p.45 / Chapter 3.1 --- Introduction --- p.45 / Chapter 3.2 --- Preparation of Microfluidic Chips --- p.46 / Chapter 3.2.1 --- Electrode Design --- p.46 / Chapter 3.2.2 --- Fabrication of Microfluidic Chips --- p.47 / Chapter 3.3 --- Cell Rotation Experiments --- p.49 / Chapter 3.3.1 --- Cell Behavior in the Dielectrophoretic Field --- p.49 / Chapter 3.3.2 --- Conditions to Induce Self-Rotation Phenomenon --- p.50 / Chapter 3.3.3 --- Pigment Cells Versus Non-Pigment Cells --- p.54 / Chapter 3.3.4 --- Investigation of Self-Rotation Speed of Pigment Cells --- p.55 / Chapter 3.3.5 --- Self-Rotation of Pigment Cells from Different Passages --- p.60 / Chapter 3.3.6 --- Cell Rotation Speed Calculation Using Algorithm --- p.62 / Chapter 3.3.7 --- Manually Induced Cell Rotation --- p.64 / Chapter 3.4 --- Summary --- p.67 / Chapter IV. --- AC Electrothermal Flow Facilitated Biosensors --- p.68 / Chapter 4.1 --- Introduction --- p.68 / Chapter 4.2 --- Probes and Biosensor Arrays --- p.71 / Chapter 4.2.1 --- Probe Design --- p.71 / Chapter 4.2.2 --- Specificity and Sensitivity of The Enclosed System --- p.71 / Chapter 4.2.3 --- Clinical Urine Sample --- p.73 / Chapter 4.2.4 --- Electrochemical Biosensor Arrays and Their Functionalization --- p.74 / Chapter 4.3 --- Mechanism and Experimental Methods --- p.76 / Chapter 4.3.1 --- Detection Mechanism of 16S rRNA --- p.76 / Chapter 4.3.2 --- Two-Color Fluorescence Thermometry --- p.78 / Chapter 4.3.3 --- Fluorescent Sphere Velocity Measurement --- p.79 / Chapter 4.4 --- Microscale Characterization of the Enclosed System --- p.80 / Chapter 4.4.1 --- Improvement of Washing Process --- p.80 / Chapter 4.4.2 --- Temperature Measurement --- p.80 / Chapter 4.4.3 --- Quantification of ACEK facilitated Mixing --- p.82 / Chapter 4.5 --- Optimization of ACEK Parameters --- p.84 / Chapter 4.5.1 --- Hybridization Duration --- p.84 / Chapter 4.5.2 --- Voltage --- p.85 / Chapter 4.6 --- Performance of a Panel of Target Species --- p.89 / Chapter 4.6.1 --- Limit of Detection --- p.89 / Chapter 4.6.2 --- Specificity --- p.90 / Chapter 4.7 --- Clinical Sample Validation --- p.92 / Chapter 4.8 --- Discussion --- p.94 / Chapter 4.8.1 --- Hybridization Efficiency --- p.94 / Chapter 4.8.2 --- Background Signal --- p.96 / Chapter 4.9 --- Summary --- p.97 / Chapter V. --- Conclusion --- p.98 / Chapter 5.1 --- Nanoparticles Concentration Using DEP --- p.98 / Chapter 5.2 --- Cell Manipulation in the DEP field --- p.100 / Chapter 5.3 --- AC Electrothermal Flow Facilitated Enclosed Biosensors --- p.101 / Bibliography --- p.103

Micro-electro-mechanical Systems (MEMS) technology has revolutionized the micro/nano world by making micro/nano devices feasible. These devices allow more exploration and understanding of the micro/nano world. In this dissertation, we will discuss the measurement of wall shear stress in an integrated microfluidic system built by MEMS technology. Specifically, carbon nanotubes (CNTs) were used as the sensing element for gas-flow shear stress measurement in this work. CNTs have already been proven to have an excellent sensing response to temperature, pressure, and alcohol vapour. Based on the thermal sensing response of CNTs, the sensor was designed to operate using convective heat transfer principles in fluid flow. Dielectrophretic manipulation was used to batch fabricate CNTs on a PMMA substrate. The CNT sensor was then integrated into a PMMA microchannel, which was fabricated by a rapid prototyping technique using moulding/hot-embossing processes. The sensor responded to impinging flow as well as gas-flow shear stress. The sensor activation power was found to be linearly related to the 1/3 exponential power of the wall shear stress. With the measurements of an array of sensors, the flow profile of a microchannel with various types of flow could be studied. Compared with the conventional polysilicon sensor, the CNT sensor has the advantage of small dimensions, i.e. a greater spatial resolution for fluidic measurements, and low power consumption, i.e. it consumes ∼1,000 times less power than polysilicon sensors. Therefore, CNT sensors have a great potential to serve as an alternative to silicon-based sensors. / Chow, Wing Yin Winnie. / Adviser: Wen J. Li. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3743. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 105-110). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Depuis que l’optofluidique a été introduite au début des années 2000, beaucoup de dispositifs combinant à la fois l’optique et la microfluidique ont été développés. Ces travaux ont proposé de nombreuses voies originales pour l’analyse biologique et le diagnostique médical. Parmi ceux-ci, citons par exemple, les guides d’ondes liquide-liquide (également appelés guides d’ondes L2), les lentilles liquides adaptatives, les lasers multicolores à microgouttes, ou encore les microscopes optofluidiques sans lentilles.Ces systèmes offrent de nombreux avantages liés à la microfluidique comme leurs flexibilités et leurs accordabilités. Néanmoins, la plupart de ces systèmes reposent sur l’utilisation d’une source de pompage optique externe devant être couplée aux puces microfluidiques avec le plus grand soin.Le but de ces travaux de thèse est d’augmenter l’autonomie et la portabilité des systèmes optofluidiques en intégrant directement la source lumineuse sur les puces. Nous proposons donc ici d’exploiter la voie électrochimiluminescente comme méthode de pompage électrique. L’annihilation du luminophore 9,10-Diphenylanthracene permet ainsi d’obtenir une faible longueur d’onde d’émission dans le domaine du visible.Ainsi nous montrons dans ces travaux la mise en œuvre d’une nouvelle technologie de fabrication pour réaliser un circuit optofluidique d’une source lumineuse intégrée. La fabrication de cette puce a permis d’obtenir des résultats d’électrochimiluminescence sur puce montrant ainsi la compatibilité de cette approche. Les expériences effectuées pendant ces travaux ouvrent ainsi la voie au pompage électrique sur dispositifs optofluidiques. / Since optofluidics was introduced in the early 2000s, a lot of devices combining microfluidic and optic have been developed such as L2 waveguides, adaptive liquid lenses, microdroplet multicolour dye laser, or lensless optofluidics microscopes.These systems offer many advantages allowed by microfluidic like flexibility and accordability. However most of them generally need an external optical source carefully coupled to the microfluidic device.The purpose of this PhD thesis is to improve autonomy and portability of microfluidics systems integrating light source on the chip. Hence, we suggest here to use the electrochemiluminescence way to reach electrical pumping. 9,10-Diphenylanthracene annihilation allowed us to obtain a low wavelength in the visible domain.Therefore, we show here the implementation of a new fabrication technology to make an integrated on chip optical source. The chip fabrication allowed us to obtain on chip electrochemiluminescence results showing the compatibility of this approach. The experiments realised during these works open the way to electrical pumping way on optofluidic chips.

Chen, Qiulan. / "November 2010." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 140-152). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Fang, Caihong = 基於表面等離子體基元的微流芯片光熱技术和金納米棒-納米球二聚體中的表面等離子體基元共振耦合 / 房彩虹. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references. / Abstracts in English and Chinese. / Fang, Caihong = Ji yu biao mian deng li zi ti ji yuan de wei liu xin pian guang re ji shu he jin na mi bang-na mi qiu er ju ti zhong de biao mian deng li zi ti ji yuan gong zhen ou he / Fang Caihong. / Abstract --- p.i / 摘要 --- p.iv / Acknowledgement --- p.vi / Table of Contents --- p.viii / List of Figures --- p.x / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Temperature Control on Microfluidic Chips --- p.2 / Chapter 1.1.1 --- Introduction to Microfluidics --- p.2 / Chapter 1.1.2 --- Temperature Control on Microfluidic Systems and Its Applications --- p.5 / Chapter 1.1.2.1 --- Heating Applications on Microfluidic Chips --- p.5 / Chapter 1.1.2.2 --- Heating/Cooling Methods in Microfluidic Systems --- p.7 / Chapter 1.1.2.3 --- Temperature Measurements in Microfluidic Systems --- p.10 / Chapter 1.2 --- Plasmonic Properties of Noble Metal Nanocrystals --- p.14 / Chapter 1.2.1 --- Localized Surface Plasmon Resonances of Noble Metal Nanocrystals --- p.15 / Chapter 1.2.2 --- Photothermal Conversion of Gold Nanocrystals --- p.19 / Chapter 1.2.3 --- Plasmon Coupling in Gold Nanocrystals --- p.21 / Chapter 1.3 --- Motivation and Outline of the Thesis --- p.23 / References --- p.24 / Chapter 2. --- Growth of Gold Nanocrystals and Characterization Techniques --- p.33 / Chapter 2.1 --- Growth of Au Nanocrystals Samples --- p.33 / Chapter 2.2 --- Characterization Techniques --- p.36 / References --- p.40 / Chapter 3 --- Plasmonic Heating Using Gold Nanorod-Embedded poly(dimethylsiIoxane --- p.43 / Chapter 3.1 --- Embedding Gold Nanorods with Varying Plasmon Resonance Wavelengths into Poly(dimcthylsiloxanc) (PDMS) --- p.43 / Chapter 3.2 --- Plasmonic Heating using Gold Nanorod-Embedded PDMS --- p.54 / Chapter 3.2.1 --- Photothermal Conversion of the Gold Nanorod-Embedded PDMS --- p.54 / Chapter 3.2.2 --- Temperature Measurements Using Rhodaminc B --- p.56 / Chapter 3.2.3 --- Plasmonic Heating and Temperature Measurements on Microfluidic Chips --- p.60 / Chapter 3.2.4 --- Flow Switching Based on the Gold Nanorod-Embedded-PDMS Microfluidic Chips --- p.63 / Chapter 3.3 --- Summary --- p.67 / References --- p.69 / Chapter 4 --- Surface Plasmon Coupling in Gold Nanorod-Nanosphere Heterodimers --- p.73 / Chapter 4.1 --- Preparation of Gold Nanorod-Nanosphere Heterodimers --- p.74 / Chapter 4.2 --- Plasmon Coupling in Gold Nanorod-Nanosphere Heterodimers --- p.77 / Chapter 4.2.1 --- Experimental Results --- p.77 / Chapter 4.2.2 --- Electrodynamic Calculations --- p.82 / Chapter 4.3 --- Summary --- p.89 / References --- p.90 / Chapter 5 --- Summary and Conclusion --- p.93 / Chapter 6 --- Curriculum Vitae --- p.95

O uso de antibióticos em animais de produção pode ser ministrado de diferentes formas: i) como método de prevenção de doenças, ii) como tratamento e combate de doenças como mastite, infecções respiratórias, genitais e oftálmicas, e iii) aplicados às rações, a fim de aumentar o ganho de peso, promovendo também a eficiência de aproveitamento dos alimentos e tornando menores os índices de morbidez e mortalidade. No entanto, alguns produtores utilizam os antibióticos de forma inadequada, ministrando o mesmo em dosagens superiores às recomendadas ou até mesmo adicionando os antibióticos diretamente no leite, a fim de inibir o crescimento indesejável de bactérias, o que pode causar graves riscos à saúde humana. Uma das maneiras de se detectar resíduos de antibióticos (sulfonamidas) em leite é a partir da reação enzimática entre a anidrase carbônica e um éster (4-nitrofenil acetato), que gera uma coloração amarelo brilhante. As sulfonamidas inibem tal reação, impedindo o surgimento de cor. Dispositivos microfluídicos fabricados em papel (μAD) foram desenvolvidos como um novo método simples, rápido, portátil e de baixo custo, a fim de se detectar a presença ou ausência das três principais sulfonamidas (sulfametazina, sulfadimetoxina e sulfatiazol), como exigido pela Agência Nacional de Vigilância Sanitária (ANVISA). A imobilização de uma fina camada uniforme de pasta de metil celulose, nos spots dos microdispositivos, permitiu maior estabilidade na superfície reacional do papel, de forma a alcançar limites de detecção (LOD) menores, equivalentes à 2,80 μmol L-1 (7,79x10-7 g mL-1) para a sulfametazina, 2,70 μmol L-1(8,37x10-7 g mL-1) para a sulfadimetoxina e 2,50 μmol L-1 (6,38x10-7 g mL-1) para o sulfatiazol. O método apresentou, como principal vantagem, a análise das amostras de leite bovino sem qualquer tratamento prévio. Além disso, o método apresentou boa linearidade e repetitividade nos ensaios realizados intra-dia e inter-dia, além de se mostrar seletivo para compostos da classe das sulfonamidas, mostrou-se também robusto com relação a alterações na temperatura do leite bovino. Dessa forma, o teste pode ser transportado para a área rural, sem a necessidade de um profissional especializado, a fim de se obter um diagnóstico local rápido, simples e de baixo custo, para a qualidade do leite. / The use of antibiotics in animal production can be delivered in diferent ways: i) as a method of preventing disease in animals, ii) as treatment and combat diseases such as mastitis, respiratory infections, genital infections and ophthalmic infections, and iii) applied to the feed in order to increase the weight gain of the animals, promoting the efficiency of food utilization, and making lower the morbidity and mortality. However, some producers use antibiotics improperly, administering it in doses higher than those recommended or even directly adding antibiotics to the milk, in order to inhibit the unwanted growth of bacteria. This fact alone can cause serious risks to human health. One way of detecting antibiotic residues (sulfonamides) in milk, is using the enzymatic reaction between an ester (4-nitrophenyl acetate) and carbonic anhydrase, which gives a bright yellow color. The sulfonamides inhibit this reaction, preventing color appearance. Paper-based microfluidic devices (μPAD) have been developed as a new simple, fast, portable and inexpensive, in order to detect the presence or absence of the three most common sulfonamides (sulfamethazine, sulfadimethoxine and sulfathiazole), as required by the National Agency of Sanitary Surveillance (ANVISA). The immobilization of a uniform thin layer of methyl cellulose pulp on the spots of microdevices, allowed greater stability in the reaction surface of the paper, and achieved lower limits of detection (LOD) than without the additive, equivalent to 2.80 5mol L-1 (7.79x10-7 g mL-1)for sulfamethazine, 2.70 5mol L-1 (8.37x10-7 g mL-1) for sulfadimethoxine and 2.50 5mol L-1 (6.38x10-7 g mL-1) for sulfathiazole. The principal advantage of this method is that allows the analysis of bovine milk samples without any prior treatment. Furthermore, the method i) has good linearity and repeatability in tests performed intra-day and inter-day, ii) shows selectivity for compounds of the sulfonamide class, and iii) is robust to changes in bovine milk temperature. Thus, the test can be transported to the rural area, without a specialized professional, providing locally a fast, simple and low cost diagnostic for the presence of sulfonamide antibiotics in milk.