Microfluidics refers to devices and methods for controlling and manipulating fluid flows at length scales less than a millimeter. Miniaturization of a laboratory to a small device, usually termed as lab-on-a-chip, is an advanced technology that integrates a microfluidic system including channels, mixers, reservoirs, pumps and valves on a micro scale chip and can manipulate very small sample volumes of fluids. While several flow control concepts for microfluidic devices have been developed to date, here flow control concepts based on thermally responsive polymer solutions are presented. In particular, flow control concepts base on the thermally triggered reversible phase change of aqueous solutions of the polymer Pluronic will be discussed. Selective heating of small regions of microfluidic channels, which leads to localized gel formation in these channels and reversible channel blockage, will be used to control a membrane valve that controls flow in a separate channel. This new technology will allow generating inexpensive portable bioanalysis tools where microvalve actuation occurs simply through heaters at a constant pressure source without a need for large external pressure control systems as is currently the case. Furthermore, a concept for controlled cross-channel transport of particles and potentially cells is presented that relies on the continuous regeneration of a gel wall at the diffusive interface of two co-streaming fluids in a microfluidic channel.

Microfluidics refers to devices and methods for controlling and manipulating fluid flows at length scales less than a millimeter. Miniaturization of a laboratory to a small device, usually termed as lab-on-a-chip, is an advanced technology that integrates a microfluidic system including channels, mixers, reservoirs, pumps and valves on a micro scale chip and can manipulate very small sample volumes of fluids. While several flow control concepts for microfluidic devices have been developed to date, here flow control concepts based on thermally responsive polymer solutions are presented. In particular, flow control concepts base on the thermally triggered reversible phase change of aqueous solutions of the polymer Pluronic will be discussed. Selective heating of small regions of microfluidic channels, which leads to localized gel formation in these channels and reversible channel blockage, will be used to control a membrane valve that controls flow in a separate channel. This new technology will allow generating inexpensive portable bioanalysis tools where microvalve actuation occurs simply through heaters at a constant pressure source without a need for large external pressure control systems as is currently the case. Furthermore, a concept for controlled cross-channel transport of particles and potentially cells is presented that relies on the continuous regeneration of a gel wall at the diffusive interface of two co-streaming fluids in a microfluidic channel.

Microfluidics refers to devices and methods for controlling and manipulating fluid flows at length scales less than a millimeter. Miniaturization of a laboratory to a small device, usually termed as lab-on-a-chip, is an advanced technology that integrates a microfluidic system including channels, mixers, reservoirs, pumps and valves on a micro scale chip and can manipulate very small sample volumes of fluids. While several flow control concepts for microfluidic devices have been developed to date, here flow control concepts based on thermally responsive polymer solutions are presented. In particular, flow control concepts base on the thermally triggered reversible phase change of aqueous solutions of the polymer Pluronic will be discussed. Selective heating of small regions of microfluidic channels, which leads to localized gel formation in these channels and reversible channel blockage, will be used to control a membrane valve that controls flow in a separate channel. This new technology will allow generating inexpensive portable bioanalysis tools where microvalve actuation occurs simply through heaters at a constant pressure source without a need for large external pressure control systems as is currently the case. Furthermore, a concept for controlled cross-channel transport of particles and potentially cells is presented that relies on the continuous regeneration of a gel wall at the diffusive interface of two co-streaming fluids in a microfluidic channel. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Ignition and combustion characteristics of n-butanol/air, 2-butanol.air and isobutanol/air mixtures at stoichiometric (ϕ = 1) and lean (ϕ = 0.5) conditions were investigated in a micro flow reactor with a controlled temperature profile from 323 K to 1313 K, under atmospheric pressure. Sole distinctive weak flame was observed for each mixture, with inlet fuel/air mixture velocity set low at 2 cm/s. One-dimensional computation with comprehensive chemistry and transport was conducted. At low mixture velocities, one-stage oxidation was confirmed from heat release rate profiles, which was broadly in agreement with the experimental results. The weak flame positions were congruent with literature describing reactivity of the butanol isomers. These weak flame responses were also found to mirror the trend in Anti-Knock Indexes of the butanol isomers. Flux and sensitivity analyses were performed to investigate the fuel oxidation pathways at low and high temperatures. Further computational investigations on oxidation of butanol isomers at higher pressure of 5 atm indicated two-stage oxidation through the heat release rate profiles. Low temperature chemistry is accentuated in the region near the first weak cool flame for oxidation under higher pressure, and its impact on key species – such as hydroxyl radical, hydrogen peroxide and carbon monoxide – were considered. Both experimental and computational findings demonstrate the advantage of employing the micro flow reactor in investigating oxidation processes in the temperature region of interest along the reactor channel. By varying physical conditions such as pressure, the micro flow reactor system is proven to be highly beneficial in elucidating oxidation behavior of butanol isomers in conditions in engines such as those that mirror HCCI operations.

The prevention of waterborne diseases requires rapid detection of pathogens in drinking water, with an ultimate goal of in-line monitoring in real time. Standard cultivation-based methods are too time-consuming and thus not suitable for this purpose. Many technologies were proposed to achieve this goal, such as ELISA, PCR, FISH, FTIR and flow cytometry. However, they still have limitations of non-specificity, complexity and high cost. Therefore, an optical system is proposed and developed towards the in-line monitoring of bacteria, which combines the advantages of FTIR and micro-flow cytometer for bacterial identification and precise quantification. The in-line use requires obtaining IR spectra of bacterial cells directly in water, which is achieved using a CaF2 liquid cell. The spectra of a series of bacterial samples are collected and analyzed using principal component analysis for their differentiation. A preliminary study on fabricating a CaF2 concentrator is conducted, in which a novel phenomenon on stress release of silicon nitride film on CaF2 substrate is discovered and studied. To determine the concentration of bacteria in drinking water, a micro-flow cytometer is built based on a micro-fabricated device that integrates on-chip beam-shaping optics and microfluidic channels. With this micro-flow cytometer and optimized data analysis for counting particles in real time, linearity with correlation coefficient of over 0.99 is achieved for the dependences of throughput on both volumetric flow rate and concentration of sample. With a one-dimensional hydrodynamic focusing, no degradation of the counting efficiency is demonstrated when the focused sample stream expands. The high accuracy of counting makes this micro-flow cytometer a promising candidate for low concentration applications. Counting of E. coli DH5α cell suspensions in phosphate buffered saline is performed using the micro-flow cytometer. Side-scattered light signals are used to count the E. coli cells. A detection efficiency of 92% is achieved when compared with the expected count from a haemocytometer. It is demonstrated that E. coli can be easily distinguished from beads of similar sizes (2-4µm) as their scattering intensities are different. / Thesis / Doctor of Philosophy (PhD)

Made available in DSpace on 2015-05-14T13:21:51Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 3041446 bytes, checksum: ababcafc4806728e34bf8d0bd8ea021e (MD5) Previous issue date: 2010-09-10 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This study proposed a miniaturized flow-batch system for chemical analysis. The technique used microfabricated urethane-acrylate, a commercial polymer. The microsystem was evaluated and optimized by analysis of synthetic dye samples. Afterwards, it was employed for the determination of tannins in tea samples. The tannins are a group of polyphenols of significant relevance in the food industry and pharmaceuticals. The samples used were green and black tea, obtained from the local market. The determinations were performed by turbidimetric methods using copper (II) in an acetate medium, with photometric methods and ferrous tartrate as a reference. Miniaturization in urethane-acrylate implies low cost and low maintenance, rapid prototyping and includes the satisfactory physicochemical properties of polymer. These characteristics combined with the general advantages of miniaturization in analytical devices, such as high frequency analysis and low waste generation, make the system a great source in academic research. For analysis of tannins in tea samples, the system had precise and accurate results, and high speeds. This flow-batch microsystem was able to perform up to 300 tests per hour, for the photometric method of reference and up to 200 tests per hour for the turbidimetric method. Each analysis performed generated waste volumes lower than 70 μL. Data validation of statistical models obtained have proved very satisfactory and promising for new optical applications. / Neste trabalho de pesquisa foi proposto o uso da técnica de microfabricação em polímero comercial uretana-acrilato para a miniaturização de um sistema automático de análises químicas em fluxobatelada, o flow-batch. O microssistema desenvolvido foi avaliado e otimizado pela análise de amostras sintéticas de corantes. Posteriormente, o microssistema, foi empregado para a determinação de taninos, grupo de polifenóis de expressiva relevância industrial, em amostras de chá verde e preto, por dois métodos ópticos distintos, fotométrico e turbidimétrico. A técnica de microfabricação em uretana-acrilato se caracteriza pelos baixos custos de implementação e manutenção, satisfatórias propriedades físicoquímicas do polímero e a rápida prototipagem de sistemas microfluídicos. Tais características aliadas às vantagens inerentes da miniaturização de dispositivos analíticos, como a elevada frequência de análise e a baixa geração de resíduos, conferem a esse sistema de análise uma ótima fonte de pesquisa acadêmica. Para análise dos taninos em amostras de chá, o sistema apresentou resultados precisos e exatos, além de uma alta velocidade analítica para ambos os métodos ópticos, sendo capaz de executar até 300 análises por hora, no método fotométrico e 200 análises por hora pelo método turbidimétrico. Cada análise efetuada gerou resíduos cujos volumes foram inferiores a 70 μL. Os dados de validação estatística dos modelos obtidos se mostraram bastante satisfatórios e promissores para novas aplicações ópticas.

This research mainly develops a new z-position measurement based on the chromatic aberration effect. An objective-type dark-field illumination scheme is built to produce diascopic chromatic aberration light, and aimed to enhance the signal-to-noise ratio. The xenon lamp is adapted to create white light with continuous spectrum, besides, lens with low Abbe number is needed to extend the degree of chromatic aberration, so lens made of PMMA is as a chromatic aberration component. In the proposed system, the depths of samples in micro-channel is illuminated by the dispersed light and scatter the optical signals, which are captured by a low numerical aperture (N.A.) objective lens. After the simple normalization, the intensity ratio of two selected wavelengths 450 nm (blue light) and 670 nm (red light) from the scattered spectrum becomes a reliable index for the depth information of the detecting objects. By means of establishing the relationship between depth and intensity ratio, every object flowing through diagnosed spot is able to be determined the depth level by cross-referencing the database. By using spectrometer as detector, delicate moving components for light filtering or electrical stage for light scanning can be excluded for high-speed z-position detection. Furthermore, in order to identify the depth level of sample with high flowing rate, avalanche photodiodes are adapted to achieve rapid detection. The experimental results show that the relationship between depth and intensity ratio is a parabola curve, but in this research, the region which tends to behavior linearly is adapted. The proposed system provides a linear detection range of ¡Ó15 £gm for particles with a diameter of 20 £gm. The lens with high Abbe number only obtains ¡Ó10 £gm with linear detection range though, the resolution for size is better than PMMA. The BK7 lens is capable to discriminate the depth change of 2 £gm micro-beads, note that there is no limitation of depth discrimination in this system, because of the measurement is achieved by cross-referencing the linear line. The use of UV-Vis-NIR spectrometer enable this system to analyze the depths of the samples in flow rate 0.5 mm/s. To gain the higher performance, the two avalanche photodiodes are utilized, and the short(CWL=450 nm, ¡Ó20 nm) and long(CWL=650 nm, ¡Ó20 nm) band pass filter are also equipped to represent enhancements of blue and red ray. The effective detection range extends to ¡Ó25 £gm and has high linearity(R square=0.99285) after the optimization of light stop. In high flowing rate detection, this system is able to identify the depth of sample when the flow velocity is 4.167 mm/s, the calculated throughput is 126 particles/s. It also successfully analyzes the depth of flowing human erythrocytes under the flow velocity is 2.778 mm/s, the velocity which the developed system is capable to analyze is about 5-8 folds to the conventional micro-PIV system. With this novel and simple approach, there will be the quantified information from z-direction of flowing body for bio-analysis, and also benefits estimating the performance of micro structure or device in the microfluidic chip, also the analysis of flow field. Except for dynamical detection, this system also be capable to apply in a open and static situation, such as cell or tissue proliferation assay.

Made available in DSpace on 2015-05-14T13:21:29Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 3046844 bytes, checksum: 9fc0abd4ac9137e94ab4a27445373f2f (MD5) Previous issue date: 2013-08-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this study, a micro-flow-batch analyzer (μFBA) using an in-line cadmium reduction microcolumn for the photometric determination of nitrate and nitrite in dairy samples was developed. The method is based on the Griess-Llosvay reaction and measuring of the absorbance at 540 nm using a green LED integrated into the μFBA built in the urethane-acrylate resin. Initially, the natural nitrite ion content of natural dairy sample product is determined in the micro-mixing chamber, while the nitrate is reduced to nitrite in the micro-column coupled to the micro cadmium sponge and then determined as in the micro-chamber nitrite. content of nitrate ions was estimated from the difference between the first and second determination. The analytical curve for nitrate and nitrite was linear in the work range of 10.0 100.0 μg L 1 with a correlation coefficient of 0.992 and 0.998, respectively. The limit of detection and relative standard deviation were estimated at 0.39 μg L 1 and < 1.7 % (n = 5) for nitrite and, 0.41 μg L 1 and < 1.3 % (n = 5) for nitrate. Comparing with the reference methods, no statistically significant differences were observed when applying the paired t-test at a 95% confidence level. The accuracy was assessed through recovery test (97.7 to 102.9 %). The proposed microsystem employed in-line cadmium sponge microcolumn presented satisfactory portability, robustness, flexibility, low-cost device and reduced chemicals consumption compared to recent methods. / Neste estudo, um analisador micro-flow-batch (μFBA) utilizando uma micro-coluna redutora de cádmio em linha foi desenvolvido para a determinação fotométrica de íons nitrato e nitrito em amostras de laticínios. O método empregado baseia-se na reação de Griess-Llosvay e a medição da absorbância foi realizada a 540 nm, utilizando um LED verde integrado na micro-câmara construída em resina fotopolimerizável uretano-acrilato. Inicialmente, o teor de íons nitritos natural da amostra de lacticínio é determinado na micro-câmara de mistura, enquanto que o nitrato é reduzido a nitrito na micro-coluna de cádmio esponjoso acoplada ao microssistema e posteriormente determinado na micro-câmara como nitrito. O teor de íons nitrato foi estimado a partir da diferença entre a segunda e a primeira determinação. A curva analítica para nitrato e para nitrito foi linear na faixa de trabalho de 10,0 a 100,0 μg L-1, com um coeficiente de correlação (r2) de 0,992 e 0,998, respectivamente. O limite de detecção e o desvio padrão relativo foi calculado em 0,39 μg L-1 e <1,7% (n = 5) para o nitrito, e 0,41 μg L-1 e <1,3% (n = 5) para o nitrato. Comparando-se com os métodos de referência, não foram observadas diferenças estatisticamente significativas quando se aplica o teste t pareado com nível de confiança de 95%. A exatidão do método foi avaliada através do teste de recuperação (97,7 a 102,9%). O microssistema proposto empregando a micro-coluna de cádmio esponjoso em linha apresentou portabilidade satisfatória, robustez, flexibilidade, aparelhagem simples e consumo reduzido de produtos químicos em relação aos métodos automáticos mais recentes.

La microcirculation sanguine est un système constitué de réseaux complexesde vaisseaux sanguins de diamètres micrométriques. C’est le lieu privilégié deséchanges de gaz et de nutriments entre le sang et les tissus.Les écoulements dans ces réseaux sont gouvernés par les propriétés des constituantsdu sang c’est-à-dire des cellules en suspension dans du plasma et plus particulièrementdes globules rouges qui sont les cellules majoritaires dans le sang.Selon les conditions de l’écoulement, les globules rouges, qui sont des particulesdéformables, peuvent présenter différents types de formes et de dynamiques quiinfluencent la rhéologie de la suspension. Les interactions hydrodynamiques entreglobules rouges et avec les parois dans les vaisseaux confinés influencent égalementles écoulements à travers des phénomènes de diffusion mais aussi de structurationdes globules au sein de la suspension. Il a notamment été montré que des couchesde plasma dépourvues de globules rouges près des parois des vaisseaux sanguins induisentune diminution de la viscosité effective de la suspension lorsqu’on diminuele diamètre du vaisseau. Par ailleurs, des structurations en file ont également étéobservées dans la microcirculation sanguine avec des conséquences probables surla rhéologie. Au cours de ces travaux de thèse, nous avons investigué les propriétésrhéologiques de suspensions de globules rouges en micro-écoulement grâce à uneméthode de rhéométrie microfluidique. Nous avons focalisé notre attention sur larelation entre la rhéologie et la structuration de la suspension dans un canal, liéeau confinement ainsi qu’aux régimes dynamiques des globules en écoulement.Dans certains cas pathologiques comme la drépanocytose où les propriétés desglobules rouges peuvent être modifiées, les écoulements dans la microcirculationpeuvent être perturbés et conduire à des crises vaso-occlusives dont les mécanismesphysiques restent mal compris. Nous avons exploré la dynamique de formationd’occlusions et leurs évolutions dans des réseaux de canaux micrométriques modèlesavec des suspensions de globules rouges dont les propriétés ont été modifiées,révélant ainsi une dynamique complexe où l’adhésion et des effets d’obstructionsinterviennent. / Blood microcirculation consists in blood flowing in complex microvessel networks.Gas and nutrient exchanges between blood and tissues occur in these networks.Microcirculatory blood flows are governed by the properties of blood components,mainly red blood cells suspended in plasma. Red blood cells are deformableparticles which can exibit different shapes and motion dynamics that influence therheology. Hydrodynamic interactions between red blood cells and with walls of theconfined channels lead to diffusion and structuration in the suspension that alsoaffects the rheology. Plasma cell-free layers near walls observed in the microcirculationinduce a decrease of the effective viscosity with decreasing vessel diameter.Other types of structuration like layering of red blood cells have been observed inthe microcirculation with possible rheological consequences. In the present work,we investigated the rheology of confined red blood cell suspensions and focusedon the link between rheology and structuration of the suspension thanks to amicrofluidic viscosimeter.The sickle cell disease which modifies the properties of red blood cells leadsto flow disorders with the formation of occlusions in the narrow capillaries ofthe microcirculation. We explored the formation and the evolution of occlusionsin simplified networks of microchannels when properties of red blood cells aremodified, revealing complex dynamics where adhesion and jamming effect occur.

Made available in DSpace on 2015-05-14T13:21:42Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2308276 bytes, checksum: 30fe5bd9f0346db5777a9c5983218c0f (MD5) Previous issue date: 2014-08-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Sulfites are chemical additives major role in the beverage industry, however, the excessive use of these additives can cause disease and its limit is a maximum of 0,7 mg/kg of body weight per day SO2. This study proposes a micro-batch-flow analyser (μFBA) for photometric determination of sulphites in beverages. The μFBA was built from the commercial urethane-acrylate resin and polymerized exhibiting photo of ultra-violet radiation. The photometric method for the determination of sulfites in beverages based on the reaction of salts of sulfites in an acid medium with formaldehyde solution subsequently reacted with pararosaniline hydrochloride solution giving finally, a complex of violet color with maximum absorption at 565 nm. The linear model of the calibration curve was validated by ANOVA, residual plot and left by the F test model. The detection limit was 0,08 mg L-1 and the relative standard deviation less than 1,5% (n = 3). A test precision assessed by recovery test (96,8% to 102,6%) was performed. The μFBA is potentially useful as an alternative to sulfites photometric determinations as parameters of quality of beverage and yield of 240 samples per hour, producing low consumption of sample and reagents. The results obtained by the proposed μFBA compared to the conventional method, no statistically significant differences in applying paired with a confidence level of 95% t-test / Os sulfitos são aditivos químicos com grande atuação na indústria de bebidas, entretanto o uso desses aditivos em excesso podem causar patologias e seu limite encontra-se no máximo de 0,7 mg/kg de SO2 peso corpóreo por dia. Esse estudo propõe um microanalisador em fluxo batelada (μFBA) para determinação fotométrica de sulfitos em bebidas. A microcâmara do μFBA foi construído a partir da resina comercial uretana-acrilato e polimerizado em fotoexpositora de radiação ultra-violeta. O método fotométrico para determinação de sulfitos em bebidas baseou-se na reação dos sais de sulfitos, em meio ácido, com solução de formaldeído que posteriormente reagiu com a solução de cloridrato de pararosanilina originando, por fim, um complexo de cor violeta com absorção máxima em 565 nm. O modelo linear da curva analítica foi validada através da ANOVA, gráfico dos resíduos e teste F deixados pelo modelo. O limite de detecção foi de 0.08 mg L-1 e o desvio padrão relativo inferior a 1,5% (n = 3). Foi realizado um teste de precisão avaliada através do teste de recuperação (96,8% a 102,6%). O μFBA é potencialmente útil como uma alternativa para determinações fotométricas de sulfitos como parâmetros de qualidade de bebidas e rendimento de 240 amostras por hora, gerando baixo consumo de amostra e reagentes. Os resultados obtidos pelo μFBA proposto comparado ao método convencional, não apresentou diferenças estatisticamente significativas na aplicação do teste t pareado com nível de confiança de 95%