京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18086号 / 理博第3964号 / 新制||理||1571(附属図書館) / 30944 / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 平田 岳史, 教授 田上 高広, 准教授 三宅 亮 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The current driven electrothermal instability (ETI) forms when the material resistivity is temperature dependent, occurring in nearly all Z-pinch-like high energy density platforms. ETI growth for high-mass density materials is predominantly striation form which corresponds to magnetically perpendicular mode growth. The striation form is caused by a resistivity that increases with temperature, which is often the case for high-mass density materials. In contrast, low-density ETI growth is mainly filamentation form, magnetically aligned modes, because the resistivity tends to decrease with temperature. Simulating ETI is challenging due to the coupling of magnetic field transport to equation of state over a large region of state space spanning solids to plasmas. This dissertation presents a code-code verification study to effectively model the ETI. Specifically, this study provides verification cases which ensure the unit physics components essential to modeling ETI are accurate. This provides a way for fluid-based codes to simulate linear and nonlinear ETI. Additionally, the study provides a sensitivity analysis of nonlinear ETI to equation of state, vacuum resistivity, and vacuum density. Simulations of ETI typically use a collisional form of the resistivity as provided, e.g., in a Lee-More Desjarlais conductivity table. In regions of low-mass density, collision-less transport needs to be incorporated to properly simulate the filamentation form of ETI growth. Anomalous resistivity (AR) is an avenue by which these collision-less micro-turbulent effects can be incorporated into a collisional resistivity. AR directly changes the resistivity which will directly modify the linear growth rate of ETI, so a new linear growth rate is derived which includes AR's added dependency on current density. This linear growth rate is verified through a filamentation ETI simulation using an ion acoustic based AR model. Kinetically based simulations of vacuum contaminant plasmas provide a physical platform to study the use of AR models in pulsed-power platforms. Using parameters from the Z-machine pulsed-power device, the incorporation of AR can increase a collisional-based resistivity by upwards of four orders of magnitude. The presence of current-carrying vacuum contaminant plasmas can indirectly affect nonlinear ETI growth through modification of the magnetic diffusion wave. The impact of AR on nonlinear ETI is explored through pulsed-power simulations of a dielectrically coated solid metallic liner surrounded by a low-density vacuum contaminant plasma. / Doctor of Philosophy / High-energy-density physics (HEDP) is the study of materials with pressures that exceed 1Mbar, and is difficult to reach here on Earth. Inertial confinement fusion concepts and experiments are the primary source for achieving these pressures in the laboratory. Inertial confinement fusion (ICF) is a nuclear fusion concept that relies on the inertia of imploding materials to compress a light fuel (often deuterium and tritium) to high densities and temperatures to achieve fusion reactions. The imploding materials in ICF are driven in many ways, but this dissertation focuses on ICF implosions driven by pulsed-power devices. Pulsed-power involves delivering large amounts of capacitive energy in the form of electrical current over very short time scales (nanosecond timescale). The largest pulsed-power driver is the Z-machine at Sandia National Laboratory (SNL) which is capable of delivering upwards of 30 MA in 130 ns approximately. During an ICF implosion there exists instabilities that disrupt the integrity of the implosion causing non-ideal lower density and temperature yields. One such instability is the Rayleigh-Taylor instability where a light fluid supports a heavy fluid under the influence of gravity. The Rayleigh-Taylor is one of the most detrimental instabilities toward achieving ignition and was one of the main research topics in the early stages of this Ph.D. The study of this instability provided a nice intro for modeling in the HEDP regime, specifically, in the uses of tabulated equations-of-state and tabulated transport coefficients (e.g., resistivity and thermal conductivity). The magneto Rayleigh-Taylor instability occurs in pulsed-power fusion platforms where the heavy fluid is now supported by a magnetic field instead of a light fluid. The magneto Rayleigh-Taylor instability is the most destructive instability in many pulsed-power fusion platforms, so understanding seeding mechanisms is critical in mitigating its impact. Magnetized liner inertial fusion (MagLIF) is a pulsed-power fusion concept that involves imploding a solid cylindrical metal annulus on laser-induced pre-magnetized fuel. The solid metal liners have imperfections and defects littered throughout the surface. The imperfections on the surface create a perturbation during the initial phases of the implosion when the solid metal liner is undergoing ohmic heating. Because a solid metal has a resistivity that increases with temperature, as the metal heats the resistivity increases causing more heating which creates a positive feedback loop. This positive feedback loop is similar to the heating process in a nichrome wire in a toaster, and is the fundamental bases of the main instability studied in this dissertation, the electrothermal instability (ETI). ETI is present in all pulsed-power fusion platforms where a current-carrying material has a resistivity that changes with temperature. In MagLIF, ETI is dominant in the early stages of a current pulse where the resistivity of the metal increases with temperature. An increasing resistivity with temperature is connected to the axially growing modes of ETI which is denoted as the striation form of ETI. Contrary to the striation form of ETI, the filamentation form of ETI occurs when resistivity decreases with temperature and is associated with the azimuthally growing modes of ETI. Chapter 2 in this dissertation details a study of how to simulate striaiton ETI for a MagLIF-like configuration across different resistive magnetohydrodynamics (MHD) codes. Resistivity that decreases with temperature typically occurs in low-density materials which are often in a gaseous or plasma state. Low density plasmas are nearly collision-less and have resistivity definitions that often overestimate the conductivity of a plasma in certain experiments. Anomalous resistivity (AR) addresses this overestimation by increasing a collisional resistivity through micro-turbulence driven plasma phenomenon that mimic collisional behavior. The creation of AR involves reduced-modeling of micro-turbulence driven plasma phenomenon, such as the lower hybrid drift instability, to construct an effective collision frequency based on drift speeds. Because AR directly modifies a collisional resistivity for certain conditions, it will directly alter the growth of ETI which is the topic of Chapter 3. The current on the Z-machine is driven by the capacitor bank through the post-hole convolute, the magnetically insulated transmission lines, and then into the chamber. Magnetically insulated transmission lines have been shown to create low-density plasma through desorption processes in the vacuum leading to a load surrounded by a low-density plasma referred to as a vacuum contaminant plasmas (VCP). VCP can divert current from the load by causing a short between the vacuum anode and cathode gap. In simulations, this plasma would be highly conducting when represented by a collisionally-based resistivity model resulting in non-physical vacuum heating that is not observed in experiments. VCP are current-carrying low-density and high-temperature plasmas which make them ideal candidates to study the role of AR as described in Chapter 4. Chapter 4 investigates the role AR in a VCP would have on striation ETI for a MagLIF-like load.

La capture du CO2 en sortie d’une centrale thermique constitue un réel défi technologique. Les procédés d’adsorption peuvent être utilisés pour traiter de telles fumées caractérisées principalement par leurs grands débits et leurs faibles teneurs en CO2 (2x106 à 3x106 m3.h-1 pour une centrale de 750 MW, % Vol de CO2 = 12-15 %). Certains procédés d’adsorption existants comme les procédés PSA et TSA ont été utilisés pour le traitement des COV. Dans le cas de l’adsorption modulée en pression (PSA) l’effluent à traiter passe à travers d’un lit fixe d’adsorbant à haute pression. L’adsorbant est régénéré en baissant la pression. Pour l’adsorption modulée en température (TSA), l’adsorbant est régénéré en augmentant sa température. C’est souvent de l’air chaud qui est utilisé pour chauffer le lit. Ces deux procédés ne semblent pas bien adaptés pour la capture du CO2. Alors que le premier nécessite l’augmentation de la pression de grands débits de gaz, le deuxième procédé, basé sur le chauffage avec de l’air chaud, n’est pas énergétiquement efficace. De plus le CO2 récupéré est dilué par de l’air. L’objectif de ce travail est d’étudier un nouveau procédé d’adsorption qui permet de : 1- Traiter de grands débits de gaz à faible pression et capturer la majeure partie du dioxyde de carbone qu’ils contiennent ; 2- Récupérer le CO2 avec une haute pureté ; 3- Réduire le coût énergétique de la régénération. Pour réaliser ce travail, trois procédés d’adsorption ont été examinés expérimentalement et théoriquement : Adsorption avec régénération électrothermique (ESA), Adsorption avec régénération sous vide (VSA) et ESA-VSA couplés. La première étape du travail a consisté à choisir un adsorbant performant. Pour cela, plusieurs solides ont été considérés (charbons actifs, tamis moléculaires carbonés, matériaux polymères, zéolites ...) et deux adsorbants ont été choisis (zéolite 5A et matériau composite PDMS-charbon actif). Dans le cas de la régénération électrothermique, l'adsorbant a été chauffé de façon indirecte, par l'effet de Joule. Après avoir étudié les trois méthodes de régénération expérimentalement, un module de calcul a été développé au moyen de COMSOL la Multiphysics permettant d'ajuster les paramètres de cinétique de transfert de masse pour les étapes d'adsorption et de régénération / The recovery of CO2 from the fossil fuel power plant flue gas is a very important technical challenge. Adsorption processes can be applied to recover CO2 from such dilute and voluminous flue gas (2x106 to 3x106 m3.h-1 for a 750 MW power plant, CO2 Vol % = 12-15 %). Some existing processes like PSA and TSA have been used for VOCs separation. In pressure Swing Adsorption (PSA) the gas mixture flows through a packed bed of adsorbent at elevated pressure. The bed is regenerated by reducing the pressure. In Temperature Swing Adsorption (TSA), the bed is regenerated by raising its temperature. It is generally based on air heating. These two processes do not seem adapted for CO2 recovery. The first one needs an increase of a very voluminous flue gas pressure. TSA based on air heating is not energitically efficient and it produces diluted CO2. In this work, we aim to study a new adsorption process that permitts to: 1- treat voluminous flue gas at low pressure to recover most of the carbon dioxide that it contains 2- recover CO2 with a high purity 3- reduce the energitic cost of the regeneration To do this work, three adsorption processes were examined experimentally and theoretically: Electrothermal Swing Adsorption (ESA), Vaccum Swing Adsorption (VSA) and coupled ESA-VSA. The first step of the work consisted in the choice of a performent adsorbent. Thus different solids were tested (active carbon, carbon molecular sieves, polymer adsorbents, zeolites...) and two adsorbents which were chosen (zeolite 5A and mixed matrix PDMS-active carbon). For the electrothermal regeneration, the adsorbents were heated indirectly by Joule effect. After having tested the three different ways of regeneration experimentally, different calculation modules were created using COMSOL Multiphysics, permitting adjust the kinetic and mass transfer parameters for both adsorption and regeneration

Este trabalho teve como objetivo avaliar o filamento de tungstênio de 150 W (OSRAM) como atomizador eletrotérmico para determinação de alumínio em amostras de águas, incluindo um estudo sistemático sobre o seu comportamento eletrotérmico na presença de até 1000 mg l-1 de sódio, potássio, cálcio, magnésio e/ou da mistura destes elementos. Alguns parâmetros, como comprimento de onda, corrente da lâmpada de catodo oco, altura de observação e temperatura de atomização do alumínio foram avaliados visando à melhoria da qualidade dos resultados e do limite de detecção. Após uma primeira avaliação, fixaram-se o comprimento de onda em 309,3 nm e a corrente da lâmpada de catodo oco em 10 mA, elegendo-se altura de observação de 1,5 mm e temperatura de atomização de 2860 oC (13,0 V). No programa de aquecimento usado no desenvolvimento deste trabalho adotou-se rampa invertida de voltagem variando entre 0,65 a 0,30 V durante 50 s para secagem de 10 µl, 2,8 V durante 10 s para pirólise e 13,0 V durante 1 s para atomização. As soluções usadas no desenvolvimento deste trabalho formam preparadas, em sua maioria, em meio 0,1 % v/v HNO3. A avaliação dos potenciais interferentes Na, K, Ca, Mg e a mistura desses elementos foi realizada nas alturas de observação de 0,0 a 2,0 mm e nas composições do gás de proteção de 90% Ar/10% H2, 80% Ar/20% H2, 65% Ar/35% H2. Pode-se inferir que o aumento do hidrogênio na composição do gás de proteção não acarretou melhora significativa na ação dos interferentes na atomização do alumínio. Não foram observadas interferências significativas em até 1000 mg l-1 Na e K na atomização de 100 µg l-1 Al na altura de observação de 0,0 mm. Na mesma condição de altura de observação, a mistura dos interferentes não afetou significativamente a atomização do alumínio. Observaram-se interferências em torno de 40 % na atomização de 100 µg l-1 Al em 0,1 % v/v HNO3 na altura de observação de 0,0 mm na presença de até 100 mg l-1 de Ca e Mg. Nessa mesma condição, mas com a mistura 65 % Ar/35 % H2, a supressão do sinal de absorbância de alumínio foi da ordem 90%. Os resultados obtidos na determinação de alumínio em amostras de água foram obtidos nas condições anteriormente citadas, utilizando gás de proteção 90% Ar/ 10% H2. Nestas condições, o limite de detecção foi de 2,3 µg l-1 Al e a massa característica de 69 pg Al. Os resultados encontrados foram satisfatórios e concordantes com aqueles encontrados quando se utilizou o forno de grafite como método de comparação. Aproximadamente 500 queimas foram feitas com um único filamento de tungstênio. / The aim of this paper was to evaluate the 150 W (OSRAM) tungsten coil as electrothermal atomizer in order to determine aluminum in water samples as well as a systematic study of its electrothermal behavior in the presence of up to 1000 mg l-1 of sodium, potassium, calcium, magnesium and/or of mixture of these elements. Some parameters, such as wavelength, hollow cathode lamp current, observation height and atomization temperature were evaluated in order to improve the quality of results and the detection limit. After a first evaluation, measurements were always carried out at 309,3 nm as well as the hollow cathode lamp current at 10 mA, and it was adopted an observation height of 1,5 mm and atomization temperature at 2860 oC (13,0 V). In the heating program defined experimentally, the inverted voltage ramp was adopted for drying 10 μl of sample solution by varying the applied voltage from 0,65 to 0,30 V during 50 s, with further application of 2,8 V for 10 s in the pyrolysis step and 13,0 V for 1 s in the atomization step. Most solutions were prepared in 0,1% v/v HNO3. The evaluation of the potential interfering elements such as Na, K, Ca, Mg an the mixture of these elements, was carried out in observations heights from 0,0 to 2,0 mm at different gas compositions: 90% Ar/ 10% H2 , 80 % Ar/ 20% H2 and 65 % Ar/ 35% H2. It can be inferred that the hydrogen increase in the protection gas did not change the interference behavior of the studied concomitants on aluminum atomization. Significant interferences were not observed up to 1000 mg l-1 of Na and K in the atomization of 100 μg l-1 Al when the optical beam was intercepting the atomizer (0,0 mm observation height). In the same condition, the mixture of the interfering species did not significantly affect the aluminum atomization. In addition, 100 mg l-1 of Ca and Mg depressed the absorbance of 100 μg l-1 Al in 0,1 % v/v HNO3 by approximately 40 %. When the atomization was made in the presence of 65 % Ar/ 35 % H2, the suppression of the aluminum absorbance signal was about 90 %. The results obtained in the determination of aluminum in water samples were achieved in the conditions previously mentioned, using protection gas of 90 % / 10 % H. In these conditions, the detection limit was 2,3 μg l-1 Al and the characteristic mass was 69 pg Al. The results were reasonable and in agreement with those found by atomic absorption with graphite furnace as a comparative method. Approximately 500 firings were made with a single tungsten coil.

Este trabalho teve como objetivo avaliar o uso do método das médias móveis na atomização de cádmio, crômio e chumbo utilizando filamento de tungstênio de 150 W (OSRAM) como atomizador eletrotérmico. Realizou-se um estudo sistemático da influência da altura de observação, da temperatura e taxa de aquecimento na atomização dos analitos e a viabilidade do uso do método das médias móveis no tratamento dos sinais transientes gerados na atomização. O estudo da influência da altura de observação foi realizado posicionado-se o filamento no centro (0 mm), 1 e 2 mm abaixo do feixe de radiação. A influência da temperatura e da taxa de aquecimento foi estudada utilizando temperaturas na etapa de atomização entre 1890 e 2780 °C. O método das médias móveis foi aplicado aos sinais transientes gerados na atomização, com o filamento posicionado no centro (0 mm), 1 e 2 mm e com temperatura de atomização entre 2060 e 2780 °C, utilizando fatores 0, 3, 5, 7 e 9. No estudo da temperatura e da taxa de aquecimento foram aplicadas ddps no software de controle na etapa de atomização entre 4 e 12 V. As soluções usadas no desenvolvimento deste trabalho foram preparadas em meio 0,1 % v/v HNO3. Utilizou-se como gás de proteção a mistura de 90% Ar+10 % H2. Para o cádmio, recomenda-se a utilização da altura de observação de 1 mm, para o chumbo recomenda-se 0 mm e para o crômio a altura recomendada é a de 2 mm. Os estudos comprovaram a dependência dos sinais de absorção atômica em altura de pico com a temperatura e a taxa de aquecimento. O cádmio foi o analito em que a taxa de aquecimento foi a menos crítica para a atomização, enquanto que o crômio foi o mais afetado pela variação da taxa de aquecimento. Não foi observada diferença significativa entre os sinais de cádmio com alturas de observação de 0 e 1 mm. Para o chumbo, a diferença entre os sinais com altura de observação de 0 e 1 mm foi constante em todas as taxas de aquecimento estudadas. A 2 mm a diferença entre os sinais aumentou com o aumento da taxa de aquecimento. Para o crômio, não ocorreu uma diferença significativa entre os sinais nas alturas de 1 e 2 mm com atomização até 2180 °C. Nos três analitos a sensibilidade aumentou com o aumento da taxa de aquecimento. O método das médias móveis permitiu a diminuição da variação dos sinais transientes do branco e do ruído. Para o cádmio, não ocorreu uma melhora no limite de detecção do método com a aplicação das médias móveis em nenhuma condição. Para o chumbo e crômio, ocorreu uma melhora no limite de detecção do método nas alturas de observação de 0 e 1 mm. O limite de detecção instrumental apresentou uma melhora significativa para os três elementos em todas as condições estudadas. / The aim of this paper was to evaluate the use of moving averages of cadmium, chromium and lead transient atomic absorption signals generated by 150 W (OSRAM) tungsten coil electrothermal atomizer. A systematic study dealing with the influence of observation height, temperature and heating rate on atomization was carried through in order to demonstrate the viability of moving averages in the treatment of the transient signals during the atomization step. The influence of observation height was carried out with the tungsten coil in the center (0 mm), at 1 and 2 mm below the radiation beam. The influence of atomization temperature and heating rate were evaluated between 1890 °C (3.3 K.ms-1) and 2780 °C (9,3 K.ms-1). The transient moving averages were obtained by using factors 0, 3, 5, 7 and 9, with the tungsten coil in the center (0 mm), 1 and 2 mm and with atomization between 2060 and 2780 °C. For obtaining different temperatures and heating rates, an appropriate power supply was used by applying 4 to 12 V (40 to 120 W) to the atomizer during atomization and a mixture 90% Ar+10% H2 was used as purge/atomization gas. Blanks and reference solutions were prepared in 0,1% v/v HNO3. Best results for cadmium were obtained at 1 mm. For lead it is recommended 0 mm and for chromium 2 mm. The studies had proven the dependence of peak height absorbance signals with temperature and heating rate. Cadmium was the analyte where the heating rate was to less critical for the atomization, whereas chromium was affected by the variation of the heating rate. Significant differences were not observed between cadmium signals with observation heights of 0 and 1 mm. For lead, the difference between the absorbance signals with observation heights of 0 and 1 mm were constant in all tested heating rates. At 2 mm the difference between signals increased by increasing the heating rates. For chromium, a significant difference was not noticed between peak height absorbance signals at 1 and 2 mm with up to 2180 °C. As expected, sensitivity increased for all three analytes by increasing the heating rate. The moving average is a powerful mathematical treatment for minimizing unpredictable fluctuations of the base line during the chosen time interval for measuring the transient absorbance signals. With the exception of Cd, where no improvements on the method detection limit were noticed, the application of the moving average for the lead and chromium showed 3 to 4 fold improvement in the LDmet at 0 and 1 mm observation heights, respectively. The LDinstr presented a significant improvement (3 to 6 fold) for the three analytes in all studied conditions.

Ultrasonic slurry sampling electrothermal vaporization dynamic reaction cellTM inductively coupled plasma mass spectrometry (USS-ETV-DRC-ICP-MS) has been applied to determine Cr, Cu, Cd, Hg and Pb in several rice samples. The influences of instrument operating conditions and slurry preparation on the ion signals were reported. Ascorbic acid was used as the modifier to enhance the ion signals. The background ions at the chromium masses were reduced in intensity significantly by using 0.4 ml min-1 NH3 as reaction cell gas in the dynamic reaction cell (DRC) while a q value of 0.6 was used. Since the sensitivities of Cr, Cu, Cd, Hg and Pb in rice flour slurry and aqueous solution were quite different, standard addition and isotope dilution methods were used for the determination of Cr, Cu, Cd, Hg and Pb in these rice samples. This method has been applied to the determination of Cr, Cu, Cd, Hg and Pb in NIST SRM 1568a rice flour reference material and two rice samples purchased from the market. The analysis results of the reference material agreed with the certified values. The results for the rice samples for which no reference values were available were also found to be in good agreement between isotope dilution method and standard addition method. The method detection limits estimated from standard addition curves were about 0.44, 1.7, 0.4, 0.53 and 0.69 ng g-1 for Cr, Cu, Cd, Hg and Pb, respectively, in original rice flour.Ultrasonic slurry sampling electrothermal vaporization dynamic reaction cellTM inductively coupled plasma mass spectrometry (USS-ETV-DRC-ICP-MS) has been applied to the determination of Cr, Cd and Pb in several plastic samples. The influences of instrument operating conditions and slurry preparation on the ion signals were investigated. NH4NO3 was used as the modifier to enhance the ion signals. The background ions at the chromium masses were reduced in intensity significantly by using NH3 as reaction cell gas in the DRC. Standard addition method and isotope dilution method were used for the determination of Cr, Cd and Pb in these plastic samples. This method was applied to the determination of Cr, Cd and Pb in two polystyrene and a polyvinyl chloride samples. The analysis results were found to be in good agreement between isotope dilution method and standard addition method. Furthermore, we digested these samples and analyzed the digested sample solutions by ultrasonic nebulization DRC ICP-MS. The analysis results were close to the isotope dilution and standard addition results. The precision between sample replicates was better than 3% with USS-ETV-DRC-ICP-MS method. The method detection limits estimated from standard addition curves were about 6.2-9.2, 1.1-1.6 and 8.4-11 ng g-1 for Cr, Cd and Pb, respectively, in original plastic samples.

Both electrothermal vaporization (ETV) and nebulizer introduction sources offer unique advantages for inductively coupled plasma mass spectrometry (ICP-MS) analyses. A device for coupling the ETV and nebulizer was developed so that a quick switch from the nebulizer to the ETV (termed 'inline-ETV') could help gain additional information. The inline-ETV produced similar limits of detection (LODs) for most elements in both HNO₃ and HCl matrices compared to a conventional nebulizer or ETV. However, in a problematic matrix, isobaric interferences could exist that may not be accounted for in a typical nebulizer analysis. In a 1% HCl matrix, the LODs for ⁵¹V and ⁵³Cr--which are interfered with by ⁵¹ClO⁺ and ⁵³ClO⁺, respectively--improved 65- and 22-fold using the inline-ETV source compared to a typical nebulizer. In recent applications, ICP-MS has gained attention as a way of determining metal-protein associations. A novel broad-based methodology was developed to characterize metal-protein associations. The method utilized native gel electrophoresis for separation followed by electroblotting onto chemically-modified quartz membranes. The membranes were analyzed for metals using laser ablation ICP-MS. Modified membranes were shown to improve sensitivity compared to ablating a dried gel directly or using a commercially-available membrane. The coupling of separation by preparative ultracentrifugation and metal detection by ICP-MS was explored for metal-protein equilibrium determinations. This study characterizes the stoichiometry as well as apparent (K[subscript app]) and intrinsic (K[subscript int]) binding affinities for Cu-BSA, which was used as a model protein. K[subscript app] and K[subscript int] were determined at two different conditions, pH 9.53 and pH 7.93 in 100mM Tris buffer. The pH-independent K[subscript int] value at pH 9.53 agreed closely with literature values, while the value at pH 7.93 was approximately 2.5x larger. BSA undergoes a structural rearrangement between pH 7-9, and the generally accepted pH-dependency of protein tertiary structure may be responsible for the variations in the "intrinsic" binding constant. Overall, this study validates and shows the efficacy of combining preparative ultracentrifugation with ICP-MS detection for interrogating metal-protein associations while causing minimal equilibrium perturbations as a result of the separation and measurement processes. / text

Infectious diseases resulting from bacterial pathogens are the most common causes of patient morbidity and mortality worldwide. The rapid identification of the pathogens and their antibiotic resistances is crucial for proper clinical management. However, the standard culture-based diagnostic approach requires a minimum of two days from the initial specimen collection to result reporting. As a consequence, broad-spectrum antibiotics are often prescribed under the worst-case assumption without knowledge of the pathogens or their resistances. The current clinical practice results in improper treatment of the patient and causes the rapid emergence of multi-drug resistant pathogens. A rapid diagnostics system has therefore been developed which performs hybrid electrokinetic sample preparation and volume reduction, for single-cell antimicrobial susceptibility testing (AST). The system combines multiple electrokinetic forces for sample preparation, which reduces the sample volume for over 3 orders of magnitude and minimizes the matrix effects of physiological samples for enhanced sensitivity. The device is integrated with a single-cell AST system with microfluidic confinement and electrokinetic loading to phenotypically determine the bacterial antibiotic resistance at the single-cell level. The applicability of the system has been demonstrated for performing direct AST with urine and blood samples within one hour, enabling rapid infectious disease diagnostics in non-traditional healthcare settings.

Microfluidics and its applications to Lab-on-a-Chip have attracted a lot of attention. Because of the small length scale, the flow is characterized by a low Re number. The governing equations become linear. Boundary element method (BEM) is a very good option for simulating the fluid flow with high accuracy. In this thesis, we present a 2D numerical simulation of the electrothermal flow using BEM. In electrothermal flow the volumetric force is caused by electric field and temperature gradient. The physics is mathematically modeled by (i) Laplace equation for the electrical potential, (ii) Poisson equation for the heat conduction caused by Joule heating, (iii) continuity and Stokes equation for the low Reynolds number flow. We begin by solving the electrical potential and electrical field. The heat conduction is caused by the Joule heating as the heat generation term. Superposition principle is used to solve for the temperature field. The Coulomb and dielectric forces are generated by the electrical field and temperature gradient of the system. The buoyancy force is caused by the non-uniform temperature distribution inside the system. We analyze the Stokes flow problem by superposition of fundamental solution for free-space velocity caused by body force and BEM for the corresponding homogeneous Stokes equation. It is well known that a singularity integral arises when the source point approaches the field point. To overcome this problem, we solve the free-space velocity analytically. For the BEM part, we also calculate all the integrals analytically. With this effort, our solution is more accurate. In addition, we improve the robustness of the matrix system by combining the velocity integral equation with the traction integral equation when we simulate the electrothermal pump. One of our purpose is to design a pump for the microfluidics system. Since the system is a long channel, the flow is fully developed in the area far away from the electrodes. With this assumption, the velocity profile is parabolic at the inlet and outlet of the channel. So we can get appropriate boundary conditions for the BEM part of Stokes equation. Consequently, we can simulate the electrothermal flow in an open channel. In this thesis, we will present the formulation and implementation of BEM to model electrothermal flow. Results of electrical potential, temperature field, Joule heating, electrothermal force, buoyancy force and velocity field will be presented.

Established techniques for the detection of pathogens, such as bacteria and viruses, require long timeframes for culturing. State of the art biosensors rely on the diffusion of the target analyte to the sensor surface. AC electric fields can be exploited to enhance the sampling of pathogens and concentrate them at specific locations on the sensor surface, thus overcoming these bottlenecks. AC electrokinetic effects like the dielectrophoretic force and electrothermal flows apply forces on the particle and the bulk fluid, respectively. While dielectrophoresis forces pathogens towards a target location, electrothermal flows circulates the fluid, thus replenishing the local concentration. Numerical simulations and experimental proof of principle demonstrate how AC electrokinetics can be used to collect model bioparticles on an antibody functionalized selective surface from a heterogeneous solution having physiologically relevant conductivity. The presence of parallel channels in a quadrupolar microelectrode design is identified as detrimental during the negative dielectrophoretic collection of bioparticles at the centre of the design while simultaneously providing secondary concentration points. These microelectrodes were incorporated onto the surface of a novel cantilever design for the rapid positive dielectrophoretic collection of Escherichia coli bacteria and enabled the subsequent detection of the bacteria by measuring the shift in the resonance frequency of the cantilever. Finally, a proof of principle setup for a Raman coupled, AC electrokinetically enhanced sampling and detection of viruses is shown where the presence of M13 phages are identified on a selective antibody functionalized surface using Raman spectroscopy. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2012-01-30 19:23:48.958