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The capability of manipulating microparticle in small volumes is fundamental to many biological and medical applications, including separation and detection of cells. The development of microtools for effective sample handling and separation in such volumes is still a challenge. DEP (dielectrophoresis) is one of the most widely used methods in handling the microparticles. In this thesis we show that forces generated by nonuniform electric field (DEP) can be used for trapping and separating the microparticles (latex beads). This work further explores the DEP force based on different electrode geometries and medium conductivity. A micromanipulator for latex bead separation was designed, fabricated and characterized. For the development of DEP manipulator, the fabrication and packaging of microfluidic structure with the microelectrode is crucial for reliable analysis. A combination of SU-8 photoresist and polydimethylsiloxane polymer was used for this purpose. Besides, the DEP manipulator, preliminary study on a Coulter counter was conducted. The Coulter counter works on the principle of resistive pulse sensing. This counter is used for counting the beads as they pass through the microfluidic channel. Its possible integration with the manipulator was also explored.

Ziel der Arbeit war es, die Eignung des Coulter Counters für das Eutergesundheitsmonitoring zu untersuchen. Hierfür wurde, als Voraussetzung für den Einsatz des Coulter Counters in der prozessnahen Milchuntersuchung, eine Probenaufbereitungsmethode entwickelt. Diese ermöglicht es durch Überkopfzentrifugation mit hoher Geschwindigkeit (1600 × g; 4 °C; 15 Minuten) die Proben binnen weniger Minuten so aufzubereiten, dass sie im Coulter Counter gemessen werden können. Die Überkopfzentrifugation garantiert dabei die Messbarkeit der Zellen sowohl des Zellpellets auch des Überstands ohne Fettrückstände in der Probe. Es wurde festgestellt, dass sich die Partikelgrößenverteilung im Falle einer Mastitis deutlich verändert. Basierend auf den Partikelgrößenverteilungsdaten konnten mittels eines Trainingsdatensatzes Algorithmen zur Differenzierung des Gesundheitsstatus entwickelt werden. Die Zuordnung des Gesundheitsstatus konnte im Testdatensatz mit einer Spezifität von 100 % für den Status „gesund“, 96,9 % für den Status „subklinisch erkrankt“ und 91,2 % für den Status „erkrankt“ nachgewiesen werden. / The aim of this study was, to examine the suitability of the Coulter Counter for udder health monitoring. Therefore a sample preparation method was developed as precondition for using the Coulter Counter for online Monitoring. The preparation method allows to prepare the samples within a few minutes to make them measurable in the Coulter Counter. For this a high speed centrifugation in overhead position is used (1600 × g; 4 °C; 15 min). This guarantees to measure the cells of the cell pellet as well as of the supernatant, without any fat particles in the sample. It could be shown that the particle size distribution changes during a mastitis. Based on the data of the particle size distribution algorithms to differentiate the udder health status could be developed. The classification of the udder health status could be done with a specifity of 100 % for the status healthy, 96.6 % for the status subclinical infected and 91.2 % for the status clinical infected.

Microfluidics has seen an explosion in growth in the past few years, providing researchers with new and exciting lab-on-chip platforms with which to perform a wide variety of biological and biochemical experiments. In this work, a volume quantification tool is developed, demonstrating the ability to measure the volume of individual cells at high resolution and while enabling microfluidic sample manipulations. Care is taken to maximise measurement sensitivity, range and accuracy, though novel use of buoyancy and dynamically tunable microchannels. This first demonstration of a microfluidic tunable volume sensor meant volume sensing over a much wider range, enabling the detection of ̴ 1 µm3 E.coli that would otherwise go undetected. Software was written that enables pressure-driven flow control on the scale of individual cells, which is used to great success in (a) sorting cells based on size measurement and (b) monitoring the growth of cells. While there are a number of macroscopic techniques capable of sorting cells, microscopic lab-on-chip equivalents have only recently started to emerge. In this work, a label-free, volume sensor operating at high resolution is used in conjunction with pressure-driven flow control to actively extract particle/cell subpopulations. Next, a microfluidic growth monitoring device is demonstrated, whereby a cell is flowed back and forth through a volume sensor. The integration of sieve valves allows cell media to be quickly exchanged. The combination of dynamic trapping and rapid media exchange is an important technological contribution to the field, one that opens the door to studies focusing on cell volumetric response to drugs and environmental stimuli. This technology was designed and fabricated in-house using soft lithography techniques readily available in most biotechnology labs. The main thesis body contains four scientific articles that detail this work (Chapters 2-5), all published in peer-reviewed scientific journals. These are preceded by an introductory chapter which provides an overview to the theory underlying this work, in particular the non-intuitive physics at the microscale and the Coulter principle.

Microfluidics has seen an explosion in growth in the past few years, providing researchers with new and exciting lab-on-chip platforms with which to perform a wide variety of biological and biochemical experiments. In this work, a volume quantification tool is developed, demonstrating the ability to measure the volume of individual cells at high resolution and while enabling microfluidic sample manipulations. Care is taken to maximise measurement sensitivity, range and accuracy, though novel use of buoyancy and dynamically tunable microchannels. This first demonstration of a microfluidic tunable volume sensor meant volume sensing over a much wider range, enabling the detection of ̴ 1 µm3 E.coli that would otherwise go undetected. Software was written that enables pressure-driven flow control on the scale of individual cells, which is used to great success in (a) sorting cells based on size measurement and (b) monitoring the growth of cells. While there are a number of macroscopic techniques capable of sorting cells, microscopic lab-on-chip equivalents have only recently started to emerge. In this work, a label-free, volume sensor operating at high resolution is used in conjunction with pressure-driven flow control to actively extract particle/cell subpopulations. Next, a microfluidic growth monitoring device is demonstrated, whereby a cell is flowed back and forth through a volume sensor. The integration of sieve valves allows cell media to be quickly exchanged. The combination of dynamic trapping and rapid media exchange is an important technological contribution to the field, one that opens the door to studies focusing on cell volumetric response to drugs and environmental stimuli. This technology was designed and fabricated in-house using soft lithography techniques readily available in most biotechnology labs. The main thesis body contains four scientific articles that detail this work (Chapters 2-5), all published in peer-reviewed scientific journals. These are preceded by an introductory chapter which provides an overview to the theory underlying this work, in particular the non-intuitive physics at the microscale and the Coulter principle.

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In this diploma thesis, there are described different types of soil tillage and options of their use. The thesis focuses on comparision selected plow in comparable conditions. Plows were compared by efficiency, possibilities of the type of rotation on headlands, fuel consumption and durability of wearing parts. For measuring were chosen lands with a slope as small as possible and with furrow that should be as long as possible to minimize distortion of the results.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The objective was to determine the effect of longitudinal distance between coulters and furrow openers about the operational performance of these associations working in different forward speeds, with regard to the energy requeriment and the amount of furrow, with the purpose of identifying the integration mechanism/regulation that presents the lowest energy consumption without compromising the quality of the furrow. This was carried out in an agricultural area located in the municipality of Santa Maria (Rio Grande do Sul), belonging to Universidade Federal de Santa Maria. The soil of the experimental area was classified as Ultisol and sandy. The experiment was composed of 24 combinations of treatments, in a factorial scheme of 2x3x4. These were composed by the interaction of the factors groove opening mechanisms (hoe furrow opener and mismatched double discs), longitudinal distance from center to center of coulter and furrowers (0,50,1,0 e 1,50 m) and forward speeds (1,11, 1,67, 2,22 e 2,78 m s-1). The variables responses of the performance of the mechanisms associations were obtained directly or indirectly, through the application of different methods by different tools. After the acquisition of the data, they were submitted to statistical analysis of variance and verified the significance of the factors through the F test. In addition, a mathematical analysis of the instantaneous rate of change, with the use of the differential calculus. The furrow, distance and velocity factors had a statistically significant influence on the primary performance variables resulting from instrumentation, except the distance factor on the slipping of the driving wheels. For the variables of soil mobilization, the furrow factor provided a significant change in all, while the distance factor significantly modified only the raised area and the maximum furrow depth. Already the velocity, interfered significantly in the latter and in the area of mobilized soil. In addition, in the secondary variables, the modification of the furrow and speed factors did not provide significant change only in the variable soil swelling, while the distance did not change the specific fuel consumption. The traction, the hourly consumption and the skating were higher for the configurations that employ the hoe furrow opener, present greater distance and work at higher speeds. The distance did not modify the mobilized area, the width and the depth of the furrow, and the reduction of this reduced the elevated area. The use of lower speeds and distances provides greater efficiency in the use of traction per unit of depth and of soil mobilized for both furrowers. / O objetivo foi determinar o efeito da distância longitudinal entre disco de corte e sulcador de fertilizante sobre o desempenho operacional destas associações trabalhando em diferentes velocidades de deslocamento, no que diz respeito ao requerimento energético e a qualidade de sulco, com o propósito de identificar a integração mecanismo/regulagem que apresente o menor consumo energético sem comprometer a qualidade do sulco. Este foi realizado em área agrícola situada no município de Santa Maria (Rio Grande do Sul), pertencente à Universidade Federal de Santa Maria. O solo da área experimental foi classificado como Argissolo e textura franca. O experimento foi composto por 24 combinações de tratamentos, em um esquema fatorial de 2x3x4. Estes foram compostos pela interação dos fatores mecanismos de abertura de sulco (haste sulcadora e discos duplos desencontrados), distância longitudinal de centro a centro do mecanismo de corte e dos sulcadores (0,50, 1,0 e 1,50 m) e velocidades de deslocamento (1,11, 1,67, 2,22 e 2,78 m s-1). As variáveis respostas do desempenho das associações de mecanismos foram obtidas de forma direta ou indireta, através da aplicação de diferentes métodos por distintas ferramentas. Após a aquisição dos dados, os mesmos foram submetidos à análise estatística de variância e verificado a significância dos fatores através do teste F. Além disso, foi realizada uma análise matemática da taxa de variação instantânea, com o uso do cálculo diferencial. Os fatores sulcador, distância e velocidade apresentaram influência estatisticamente significativa sobre as variáveis de desempenho primárias oriundas da instrumentação, exceto o fator distância sobre o patinamento dos rodados motrizes. Para as variáveis de mobilização do solo, o fator sulcador proporcionou alteração significativa em todas, enquanto que o fator distância modificou significativamente apenas a área elevada e a profundidade máxima do sulco. Já a velocidade, interferiu significativamente nesta última e na área de solo mobilizada. Ademais, nas variáveis secundárias, a modificação dos fatores sulcador e velocidade não proporcionaram alteração significativa apenas na variável empolamento, enquanto que a distância não modificou o consumo específico de combustível. O esforço tratório, o consumo horário e o patinamento, foram mais elevados para as configurações que empregam a haste sulcadora, apresentam maior distância e trabalham em maiores velocidades. A distância não modificou a área mobilizada, a largura e a profundidade do sulco, sendo que a redução desta diminuiu a área elevada. O emprego de velocidades e distâncias menores propiciou maior eficiência no uso da tração por unidade de profundidade e de solo mobilizada para ambos os sulcadores.