CO2 injection is an effective method for performing enhanced oil recovery (EOR). There are several factors that make CO2 useful for EOR, including promoting swelling, reducing oil viscosity, decreasing oil density, and vaporizing and extracting portions of crude oil. Moreover, the ease with which CO2 becomes soluble in oil makes it an ideal gas for EOR operations. However, there are several problems associated with CO2 flooding, especially when reservoir heterogeneity exists. The efficiency of CO2 is hindered by mobility problems, which result from the unfavorable mobility ratio. In such cases, the injected CO2 leads to an early breakthrough, which means fingering through the target zone occurs while leaving most of the residual and/or trapped oil untouched. Furthermore, an increase in the CO2 to oil ratio makes the EOR project uneconomical. However, if there are techniques available to control the injected CO2 volume, the problems just mentioned can be resolved. Nowadays, several methods are applied to control the CO2 flooding in heterogeneous porous media. In the present study, the CO2 coreflood system was integrated with a computed tomography (CT) scanner and obtained real-time coreflood images of the CO2 saturation distribution in the core sample. Throughout this study, two polymers, Polydimethylsiloxane (PDMS) and Poly (vinyl ethyl ether) (PVEE), were tested to assess their ability to increase the CO2 viscosity and therefore improve sweep efficiency. A drop-in pressure test was first conducted to evaluate the viscosifier's ability to increase CO2 viscosity; therefore, reduce its mobility. The results showed that the PDMS polymer has the greatest influence on increasing the CO2 viscosity and reducing its mobility. Also, the PVEE polymer has lower mobility than that of neat CO2. Based on the coreflood experiments, injection of viscosified CO2 using the PDMS polymer resulted in the highest oil recovery among the other injection tests have been conducted. Also, the laboratory tests show that injecting the viscosified CO2 using the PVEE polymer led to higher oil recovery than from the neat CO2 injection. This research serves as a preliminary study in understanding advanced CO2 mobility control using the thickening agents technique and will provide an insight into the future studies on the topic.

No description available.

Neuromodulation plays a crucial role in facilitating research into brain function and enabling treatments for neurological and psychiatric disorders. In brain research, current non-invasive tools face challenges when studying brain sub-regions due to their limited spatial resolution, which can barely reach a scale of 100 μm. Moreover, precise control over the volume of tissue activated (VTA) is needed to effectively target diverse-shaped brain regions, such as ocular dominance columns. Similarly, in disease treatment, the lack of sufficient spatial resolution poses obstacles in restoring normal vision using existing FDA-approved retina prostheses for retinitis pigmentosa. To address these challenges, my thesis work focuses on the development of optically-generated ultrasound devices for non-invasive brain stimulation and implantable retina prostheses. Firstly, to meet the need for non-invasive neuromodulation with ultrahigh precision, we have developed an optically-generated focused ultrasound device. By embedding candle soot nanoparticles in a curved polydimethylsiloxane pad, this device generates a transcranial ultrasound focus at 15 MHz with an ultrahigh lateral resolution of 83 μm. This resolution is two orders of magnitude smaller than conventional transcranial-focused ultrasound, enabling successful submillimeter transcranial stimulation in vivo targeting the mouse motor cortex. Addressing the requirement for a customized VTA in specific brain sub-regions, we have developed an optically-generated Bessel beam ultrasound device. This device was specifically designed to target brain columns with an elongated acoustic focus, and it successfully achieved a VTA with a lateral resolution of 152 μm and an axial resolution of 1.93 mm. The stimulation capability of the device has been confirmed through immunofluorescence imaging, which showed that the stimulation depth in mouse brains reached up to 2.2 mm. Furthermore, in order to address the need for an ultrahigh spatial resolution in retina prosthesis, we have developed an optically-generated ultrasound film as a subretinal prosthesis. In proof-of-concept experiments using blind rat retina, this film has successfully achieved retina stimulation ex vivo. In conclusion, optically-generated ultrasound devices offer promising opportunities for brain science research and disease treatments. They revolutionize non-invasive brain stimulation with ultrahigh precision and customized VTA for studying brain sub-regions. Additionally, they hold the potential for enhancing spatial resolution in retina prostheses, bringing hope to individuals with retinal disorders. / 2024-09-08T00:00:00Z

No description available.

Studying animal mechanics is crucial in order to understand how signals in the neuromuscular system contribute to an organism’s behaviour and how force-sensing organs and sensory neurons interact. In particular, the connection between the nerves and the muscles responsible for the force generation in the neuromuscular system needs to be established. Knowledge of the locomotion forces can be beneficial for the development of therapies for muscle disorders, neurodegenerative and human genetic diseases, such as muscular dystrophy. The simplicity of the nematode Caenorhabditis elegans’ (C. elegans) nervous system, which is limited to 302 neurons, has made it an excellent model organism for studying animal mechanics which include mechanosensation and locomotion at the neuronal level. The advent of miniaturized force sensing devices has led to the proposal of various approaches for measuring C. elegans locomotion forces. However, these existing devices are relatively complex, involving complicated microfabrication procedures and are incapable of measuring forces exerted by C. elegans in motion. This thesis addresses these shortcomings by introducing a force sensor capable of continuously measuring the forces generated by C. elegans in motion. The system consists of a micropillar-based device made of polydimethylsiloxane (PDMS) only and a vision-based algorithm for resolving the worm force from the deflection of the cantilever-like pillars. The measured force is horizontal and equivalent to a point force acting at half of the pillar height. The microdevice, sub-pixel resolution for visual tracking of the deflection, and experimental technique form an integrated system for measuring dynamic forces of moving C. elegans with force resolution of 3.13 uN for worm body width of 100 um. A simple device fabrication process based on soft-lithography and a basic experimental setup, which only requires a stereo microscope with off-the-shelf digital camera mean that this method is accessible to most biological science laboratories. The results demonstrate that the proposed device is capable of quantifying multipoint forces of moving C. elegans rather than single-point forces for a worm sample. This allows one to simultaneously collect force data from up to eight measurements points on different worm body parts. This is a significant step forward as it enables researchers to explicitly quantify the relative difference in forces exerted by the worm’s different body segments during the worms’ movements. The device’s capability to determine multipoint forces during nematode motion can also generate meaningful data to compare forces associated with different worm body muscles, gaining new understanding on how these muscles function. The forces measured during locomotion in the micropillars could also be used to differentiate mutant phenotypes. Apart from locomotion forces, the device is also capable of conducting concurrent measurement of other locomotion parameters such as speed, body amplitude and wavelength, as well as undulation frequency. This additional information can be useful to further quantify phenotypic behaviour of C. elegans and deepen the understanding of the theory behind worm locomotion forces. The relationship between C. elegans locomotion forces and their environment has also been analyzed by variation of the pillar arrangement and spacing. The results indicate that the microstructured environment significantly affects the worm’s contraction force, locomotion speed and the undulation frequency. In addition, an alternative measurement technique was provided to measure worm forces on other substrates, such that worm locomotion behaviour in varying environments can be investigated further. The combination of the conventional measurement technique with the findings of worm locomotion on a glass substrate reported show promise for biological measurements and other sensing application such as tactile force. Additional functions of on-chip worm selection, sorting, and imaging have also been integrated with the device, rendering its potential to accommodate for high-throughput application of C. elegans force measurement and locomotion studies in the future. The primary contributions of this thesis are centered around four topics: the development of the PDMS micropillar array and its application to study C. elegans locomotion forces, the analysis of C. elegans muscular forces and locomotion patterns in microstructured environments, the investigation of the worm locomotion forces using different substrates and finally the integration of the PDMS micropillar with PDMS microvalve for on-chip worm selection and imaging. Although the results presented in this thesis focus on wild type C. elegans, the method can be easily applied to its mutants and other organisms.

Este trabalho apresenta a modelagem comportamental desenvolvida para diferentes componentes necessários para a construção de uma microválvula eletromagneticamente atuável, associada ao uso de uma membrana flexível. Foram desenvolvidos modelos teóricos para a descrição do fluxo de fluidos em microcanais, especialmente canais com secções transversais retangulares, utilizadas na construção da maioria dos microcanais usados em microfluídica. O modelo para descrição da deformação experimentada por uma microponte de PDMS foi desenvolvido, permitindo estimar a rigidez elástica para diversas membranas desenvolvidas neste trabalho. Além disso um modelo teórico foi desenvolvido com o intuito de estudar as forças produzidas por uma microbobina com enrolamentos em formato espiral quadrado, sobre um imã permanente de NdFeB localizado em posições genéricas em relação à bobina. Utilizando o primeiro modelamento, estudo de microcanais, foi possível estimar a resistência hidráulica oferecida por microcanais com dimensões sub-milimétricas, permitindo avaliar a relação entre pressão de entrada e vazão de saída correspondente. Foi possível verificar analiticamente que para a faixa de trabalho especificada (vazões na faixa de 0,2 a 6 mL/min utilizando pressões na faixa de 0 a 30 kPa), canais com 1 cm de comprimento e 200 ?m de altura, devem possuir a largura variando na faixa de 300 µm a 500 µm de modo a operar na faixa de interesse estabelecida neste trabalho. Utilizando um canal com 2 cm de comprimento e 300 µm, o valor da altura pode estar entre 200 µm a 400 µm, permitindo miniaturizar o dispositivo final, garantindo a faixa de operação desejada. A partir da modelagem realizada com a finalidade de descrever o comportamento da membrana de PDMS, foi possível estimar teoricamente que uma membrana com 2 cm de comprimento, 2 mm de largura e a espessura variando na faixa de 1,6 a 2 mm, exige a realização de uma força na faixa de 10,5 mN a 13 mN (faixa para a força de atuação necessária), de modo a obter a deflexão de interesse neste trabalho (250 µm). Avaliando as microbobinas com base no modelo teórico desenvolvido neste trabalho, foi possível verificar que uma bobina contendo 36 enrolamentos, espaçamento de 80 µm, a uma distância de 1 mm do centro do imã, aplicando-se 10V (considerando uma resistência total de 100 Ohm), utilizando 10 camadas sobrepostas, é possível produzir uma força sobre um imã de NdFeB de até 0,18 N nas regiões de 3 mm a 10 mm afastadas em relação ao eixo x do imã, ainda a uma altura de 1 mm em relação ao plano xOy do imã. Após a fabricação dos componentes mencionados acima, foram propostos arranjos experimentais para a caracterização das respostas associadas a cada componente separadamente. As simulações apresentaram resultados similares aos obtidos experimentalmente, conforme pode ser avaliado visualizando os erros obtidos relacionando os resultados teóricos e experimentais, especialmente para os microcanais. Dispositivos microfluídicos foram fabricados obtendo canais com as seguintes dimensões: comprimento na faixa de 1 a 4 cm, largura na faixa de 100 a 400 µm e alturas na faixa de 200 a 600 µm, correspondentes à construção de 9 dispositivos com diferentes tamanhos, em que os 6 primeiros foram submetidos às análises experimentais sob as mesmas condições, repetidamente. Foi observado que tais microcanais foram capazes de fornecer até 1,41 mL/min a 0,8 kPa. O valor de vazão está dentro da faixa de desempenho do dispositivo (0,2 a 6 mL/min) com foco em sua aplicação na realização de análises químicas, onde as pressões fornecidas podem chegar até 60 kPa, fornecendo flexibilidade na produção de propulsão dos líquidos transportados através dos canais fabricados. Em relação aos resultados obtidos utilizando o modelo teórico para descrição do comportamento fluídico em microcanais, erros menores que 5% relativos aos resultados experimentais foram obtidos, indicando a validação do modelo teórico apresentado. Foram fabricados dispositivos com características comutadoras, normalmente abertas e normalmente fechadas, dependendo do método de fixação da membrana de PDMS ao substrato cerâmico. O projeto para o desenvolvimento de um chanfro na base do substrato cerâmico, na região de contato com a membrana de PDMS, foi desenvolvido com a finalidade de melhorar a selagem do canal com a válvula no estado fechado. Observou-se que para uma pressão de 5 kPa aplicada à entrada da válvula, não houve vazamento para os dispositivos normalmente fechados, e utilizando uma força em torno de 1 N é possível atingir taxas de fluxo de líquido da ordem de 0,45 mL/min, sendo esta superior às vazões necessárias para a aplicação em foco, qual seja, a automatização de microlaboratórios autônomos. Dois processos de montagem dos componentes para confecção das microválvulas foram desenvolvidos. Um deles visou a montagem da membrana de PDMS após a sinterização do sistema microfluídico junto à microbobina, e o outro visou a fixação da membrana antes da união entre o sistema e a bobina, necessitando de uma etapa de soldagem entre estes componentes após a fabricação das membranas junto ao substrato de LTCC. Microbobinas foram fabricadas com o intuito de realizar a atuação das microválvulas, a partir da atração/repulsão relacionada a um imã permanente de NdFeB (neodímio-ferro-boro) fixado à membrana flexível em contato com o canal. As bobinas foram fabricadas utilizando dimensões da ordem de 1 cm x 1 cm x 0,2 mm, apresentando de 15 a 44 enrolamentos, com gaps variando na faixa de 80 a 150 µm e as larguras dos fios condutores presente nos enrolamentos variando na faixa de 60 a 90 µm. Os resultados experimentais preliminares realizados demonstraram que uma bobina plana (uma camada, 36 enrolamentos, gap igual a 80 ?m, seção transversal de 1 cm x 1 cm), submetida a uma diferença de potencial de 1 V, é capaz de produzir uma força de 0,02 N sobre o imã permanente (localizado no centro a uma distância (no eixo z) de 1 mm da bobina). Este valor indica que para uma tensão de 10 V, devido a relação linear entre corrente e força magnética, utilizando até 10 camadas de bobinas sobrepostas, é possível obter esforços da ordem de 1 a 2 N (considerando a espessura do LTCC), permitindo que os dispositivos microfluídicos fabricados sejam acionados. / This work presents the physical modeling and implementation developed for different components necessary for the construction of electromagnetically actuating microvalves using a flexible membrane. Theoretical models were developed for describing the flow of fluids in microchannels, especially channels with rectangular transverse sections, routinely used as microchannels microfluidics. The model for the description of the deformation experienced by a PDMS microbridge was developed, allowing to estimate the elastic stiffness for various membranes developed in this work. In addition, a theoretical model was developed to study the forces produced by a microcoil with planar windings in squared spiral format, on a permanent magnet of NdFeB. Using the microchannel modeling, it was possible to estimate the hydraulic resistance offered by microchannels with micrometric dimensions, allowing to evaluate the relationship between inlet pressure and flow rate. It was possible to verify analytically that for the working range specified (flow rates of 0.2 to 6 mL/min for pressures from 0 to 30 kPa), channels with 1 cm in length and 200 ?m height should have a width varying in the range of 300 ?m to 500 µm in order to operate in the range of interest established in this study. Concerning the PDMS membrane, it was possible to estimate theoretically that a membrane with 2 cm in length, width of 2 mm and a thickness varying in the range of 1.6 to 2 mm, requires the implementation of a force in the range of 10.5 mN to 13 mN (range for the strength of action required) to obtain full deflection (250 µm). Evaluating Furthermore, using the theoretical model developed for the microcoils, it was possible to verify that a coil containing 36 windings, spacing of 80 µm, at a distance of 1 mm from the center of the magnet, and composed of 10 overlapping layers, it is possible to produce a force on a magnet of NdFeB up to 0.18 N in the regions from 3 mm to 10 mm away from the x-axis of the magnet, even at a height of 1 mm in relation to the plane xOy of magnet. The characterization of the responses associated with each component was made separately. The simulations showed similar results to those obtained experimentally, as evidenced from the errors obtained by relating the results of theoretical and experimental studies, especially for the microchannels. Microfluidic channels were manufactured with the following dimensions: length in the range of 1 to 4 cm, width in the range of 100 to 400 µm and heights in the range of 200 to 600 µm, 9 different devices were fabricated. It was observed that such microchannels were able to provide up to 1.41 mL/min to 0.8 kPa. The value of flow rate is within the expected range (0.2 to 6 mL/min) considering their application in chemical analysis, where the pressures provided can reach up to 60 kPa. Errors smaller than 5% for hydraulic resistance were obtained, indicating the validation of the theoretical model presented. Devices for fluidic switching with normally open and normally closed operation were fabricated and characterized with PDMS membranes and LTCC layers. Particularly a chamfer on the base of the ceramic substrates was proposed , in the region of contact with the membrane of PDMS, to better sealing the channel with the valve in a closed state. It has been observed that for a pressure of 5 kPa applied at the inlet of the valve, there was no leakage for the normally closed devices, and using a force around 1 N it is possible to achieve rates of liquid flow in the order of 0.45 mL/min, this being higher than the flow required for the intended application. Two assembling processes were developed for the microfluidic switching devices, one through the assembly of the PDMS membrane after LTCC sintering with the microcoil, and the other before the union between the switching device and the microcoil, requiring a step of welding between these components after the fabrication of membranes. Microcoils were manufactured and integrated with a NdFeB permanent magnet attached to a flexible membrane in contact with the channel. The coils were manufactured using dimensions of approximately 1 cm x 1 cm x 0.2 mm, containing 15 to 44 windings, with gaps ranging from 80 to 150 µm and the widths of the conductive wires in the range from 60 to 90 µm. The preliminary experimental results demonstrated that a planar coil (one layer, 36 windings, gap equal to 80 µm, cross section of 1 cm x 1 cm), subject to a potential difference of 1 Volt, is capable of producing a force of 0.02 N on the permanent magnet (located in the center at a z distance of 1 mm of the coil). This value indicates that at a voltage of 10 V it is possible to obtain a force of approximately 1 to 2 N for a coil with 10 layers, allowing for actuation of the microvalves developed.

Este trabalho apresenta a modelagem comportamental desenvolvida para diferentes componentes necessários para a construção de uma microválvula eletromagneticamente atuável, associada ao uso de uma membrana flexível. Foram desenvolvidos modelos teóricos para a descrição do fluxo de fluidos em microcanais, especialmente canais com secções transversais retangulares, utilizadas na construção da maioria dos microcanais usados em microfluídica. O modelo para descrição da deformação experimentada por uma microponte de PDMS foi desenvolvido, permitindo estimar a rigidez elástica para diversas membranas desenvolvidas neste trabalho. Além disso um modelo teórico foi desenvolvido com o intuito de estudar as forças produzidas por uma microbobina com enrolamentos em formato espiral quadrado, sobre um imã permanente de NdFeB localizado em posições genéricas em relação à bobina. Utilizando o primeiro modelamento, estudo de microcanais, foi possível estimar a resistência hidráulica oferecida por microcanais com dimensões sub-milimétricas, permitindo avaliar a relação entre pressão de entrada e vazão de saída correspondente. Foi possível verificar analiticamente que para a faixa de trabalho especificada (vazões na faixa de 0,2 a 6 mL/min utilizando pressões na faixa de 0 a 30 kPa), canais com 1 cm de comprimento e 200 ?m de altura, devem possuir a largura variando na faixa de 300 µm a 500 µm de modo a operar na faixa de interesse estabelecida neste trabalho. Utilizando um canal com 2 cm de comprimento e 300 µm, o valor da altura pode estar entre 200 µm a 400 µm, permitindo miniaturizar o dispositivo final, garantindo a faixa de operação desejada. A partir da modelagem realizada com a finalidade de descrever o comportamento da membrana de PDMS, foi possível estimar teoricamente que uma membrana com 2 cm de comprimento, 2 mm de largura e a espessura variando na faixa de 1,6 a 2 mm, exige a realização de uma força na faixa de 10,5 mN a 13 mN (faixa para a força de atuação necessária), de modo a obter a deflexão de interesse neste trabalho (250 µm). Avaliando as microbobinas com base no modelo teórico desenvolvido neste trabalho, foi possível verificar que uma bobina contendo 36 enrolamentos, espaçamento de 80 µm, a uma distância de 1 mm do centro do imã, aplicando-se 10V (considerando uma resistência total de 100 Ohm), utilizando 10 camadas sobrepostas, é possível produzir uma força sobre um imã de NdFeB de até 0,18 N nas regiões de 3 mm a 10 mm afastadas em relação ao eixo x do imã, ainda a uma altura de 1 mm em relação ao plano xOy do imã. Após a fabricação dos componentes mencionados acima, foram propostos arranjos experimentais para a caracterização das respostas associadas a cada componente separadamente. As simulações apresentaram resultados similares aos obtidos experimentalmente, conforme pode ser avaliado visualizando os erros obtidos relacionando os resultados teóricos e experimentais, especialmente para os microcanais. Dispositivos microfluídicos foram fabricados obtendo canais com as seguintes dimensões: comprimento na faixa de 1 a 4 cm, largura na faixa de 100 a 400 µm e alturas na faixa de 200 a 600 µm, correspondentes à construção de 9 dispositivos com diferentes tamanhos, em que os 6 primeiros foram submetidos às análises experimentais sob as mesmas condições, repetidamente. Foi observado que tais microcanais foram capazes de fornecer até 1,41 mL/min a 0,8 kPa. O valor de vazão está dentro da faixa de desempenho do dispositivo (0,2 a 6 mL/min) com foco em sua aplicação na realização de análises químicas, onde as pressões fornecidas podem chegar até 60 kPa, fornecendo flexibilidade na produção de propulsão dos líquidos transportados através dos canais fabricados. Em relação aos resultados obtidos utilizando o modelo teórico para descrição do comportamento fluídico em microcanais, erros menores que 5% relativos aos resultados experimentais foram obtidos, indicando a validação do modelo teórico apresentado. Foram fabricados dispositivos com características comutadoras, normalmente abertas e normalmente fechadas, dependendo do método de fixação da membrana de PDMS ao substrato cerâmico. O projeto para o desenvolvimento de um chanfro na base do substrato cerâmico, na região de contato com a membrana de PDMS, foi desenvolvido com a finalidade de melhorar a selagem do canal com a válvula no estado fechado. Observou-se que para uma pressão de 5 kPa aplicada à entrada da válvula, não houve vazamento para os dispositivos normalmente fechados, e utilizando uma força em torno de 1 N é possível atingir taxas de fluxo de líquido da ordem de 0,45 mL/min, sendo esta superior às vazões necessárias para a aplicação em foco, qual seja, a automatização de microlaboratórios autônomos. Dois processos de montagem dos componentes para confecção das microválvulas foram desenvolvidos. Um deles visou a montagem da membrana de PDMS após a sinterização do sistema microfluídico junto à microbobina, e o outro visou a fixação da membrana antes da união entre o sistema e a bobina, necessitando de uma etapa de soldagem entre estes componentes após a fabricação das membranas junto ao substrato de LTCC. Microbobinas foram fabricadas com o intuito de realizar a atuação das microválvulas, a partir da atração/repulsão relacionada a um imã permanente de NdFeB (neodímio-ferro-boro) fixado à membrana flexível em contato com o canal. As bobinas foram fabricadas utilizando dimensões da ordem de 1 cm x 1 cm x 0,2 mm, apresentando de 15 a 44 enrolamentos, com gaps variando na faixa de 80 a 150 µm e as larguras dos fios condutores presente nos enrolamentos variando na faixa de 60 a 90 µm. Os resultados experimentais preliminares realizados demonstraram que uma bobina plana (uma camada, 36 enrolamentos, gap igual a 80 ?m, seção transversal de 1 cm x 1 cm), submetida a uma diferença de potencial de 1 V, é capaz de produzir uma força de 0,02 N sobre o imã permanente (localizado no centro a uma distância (no eixo z) de 1 mm da bobina). Este valor indica que para uma tensão de 10 V, devido a relação linear entre corrente e força magnética, utilizando até 10 camadas de bobinas sobrepostas, é possível obter esforços da ordem de 1 a 2 N (considerando a espessura do LTCC), permitindo que os dispositivos microfluídicos fabricados sejam acionados. / This work presents the physical modeling and implementation developed for different components necessary for the construction of electromagnetically actuating microvalves using a flexible membrane. Theoretical models were developed for describing the flow of fluids in microchannels, especially channels with rectangular transverse sections, routinely used as microchannels microfluidics. The model for the description of the deformation experienced by a PDMS microbridge was developed, allowing to estimate the elastic stiffness for various membranes developed in this work. In addition, a theoretical model was developed to study the forces produced by a microcoil with planar windings in squared spiral format, on a permanent magnet of NdFeB. Using the microchannel modeling, it was possible to estimate the hydraulic resistance offered by microchannels with micrometric dimensions, allowing to evaluate the relationship between inlet pressure and flow rate. It was possible to verify analytically that for the working range specified (flow rates of 0.2 to 6 mL/min for pressures from 0 to 30 kPa), channels with 1 cm in length and 200 ?m height should have a width varying in the range of 300 ?m to 500 µm in order to operate in the range of interest established in this study. Concerning the PDMS membrane, it was possible to estimate theoretically that a membrane with 2 cm in length, width of 2 mm and a thickness varying in the range of 1.6 to 2 mm, requires the implementation of a force in the range of 10.5 mN to 13 mN (range for the strength of action required) to obtain full deflection (250 µm). Evaluating Furthermore, using the theoretical model developed for the microcoils, it was possible to verify that a coil containing 36 windings, spacing of 80 µm, at a distance of 1 mm from the center of the magnet, and composed of 10 overlapping layers, it is possible to produce a force on a magnet of NdFeB up to 0.18 N in the regions from 3 mm to 10 mm away from the x-axis of the magnet, even at a height of 1 mm in relation to the plane xOy of magnet. The characterization of the responses associated with each component was made separately. The simulations showed similar results to those obtained experimentally, as evidenced from the errors obtained by relating the results of theoretical and experimental studies, especially for the microchannels. Microfluidic channels were manufactured with the following dimensions: length in the range of 1 to 4 cm, width in the range of 100 to 400 µm and heights in the range of 200 to 600 µm, 9 different devices were fabricated. It was observed that such microchannels were able to provide up to 1.41 mL/min to 0.8 kPa. The value of flow rate is within the expected range (0.2 to 6 mL/min) considering their application in chemical analysis, where the pressures provided can reach up to 60 kPa. Errors smaller than 5% for hydraulic resistance were obtained, indicating the validation of the theoretical model presented. Devices for fluidic switching with normally open and normally closed operation were fabricated and characterized with PDMS membranes and LTCC layers. Particularly a chamfer on the base of the ceramic substrates was proposed , in the region of contact with the membrane of PDMS, to better sealing the channel with the valve in a closed state. It has been observed that for a pressure of 5 kPa applied at the inlet of the valve, there was no leakage for the normally closed devices, and using a force around 1 N it is possible to achieve rates of liquid flow in the order of 0.45 mL/min, this being higher than the flow required for the intended application. Two assembling processes were developed for the microfluidic switching devices, one through the assembly of the PDMS membrane after LTCC sintering with the microcoil, and the other before the union between the switching device and the microcoil, requiring a step of welding between these components after the fabrication of membranes. Microcoils were manufactured and integrated with a NdFeB permanent magnet attached to a flexible membrane in contact with the channel. The coils were manufactured using dimensions of approximately 1 cm x 1 cm x 0.2 mm, containing 15 to 44 windings, with gaps ranging from 80 to 150 µm and the widths of the conductive wires in the range from 60 to 90 µm. The preliminary experimental results demonstrated that a planar coil (one layer, 36 windings, gap equal to 80 µm, cross section of 1 cm x 1 cm), subject to a potential difference of 1 Volt, is capable of producing a force of 0.02 N on the permanent magnet (located in the center at a z distance of 1 mm of the coil). This value indicates that at a voltage of 10 V it is possible to obtain a force of approximately 1 to 2 N for a coil with 10 layers, allowing for actuation of the microvalves developed.

<p>The aim of the project was to modify polydimethylsiloxane (PDMS) surfaces in order to minimize adsorption of proteins. PDMS is used in micro-fluidic devices that control the delivery of samples to a sensor chip in Biacore instrumentation. These instruments are used to characterize interactions between biomolecules with a detection principle based on surface plasmon resonance (SPR). To minimize adsorption of proteins poly-ethylene-oxide (PEO) based surfactants, were added to the buffer. The added PEO surfactants were P20, Pluronic F-127 and Brij 35. Interaction of these surfactants with the sensor chip in Biacore instruments was also examined. Creating a more hydrophilic surface layer on PDMS by oxidation was also examined.</p><p>When surfactants were continuously added to protein samples, as in dynamically coating of PDMS surfaces, Brij 35 resulted in the strongest reduction in protein adsorption. Brij 35 was also the surfactant that was easiest to remove from both PDMS and the sensor surfaces. Pluronic bound strongest to surfaces, and is most suitable when only adding surfactant to the buffer in a pre-coating step. All surfactants did reduce protein adsorption considerably (99% or more) and addition is necessary when working with protein solutions and hydrophobic surfaces as PDMS. Another alternative is oxidation of PDMS surface, which is an easy procedure that decreased the protein adsorption to about 10% compared to adsorption to untreated surface.</p>

Clinical islet transplantation is a promising treatment for type 1 diabetes. It involves the transplantation of pancreatic islets, isolated from a donor, into the portal vein of a recipient in order to replace his/her dysfunctional islets. Though promising, islet implantation into the liver is greatly hindered by numerous problems, including mechanical stresses, inflammatory responses, exposure to high drug and toxin loads, as well as irretrievability. In order to address these concerns, investigation into alternative implant sites, such as the subcutaneous site, has intensified. Transplantation of islets within these extrahepatic sites is commonly met with three primary obstacles: 1) inadequate spatial distribution of the cells; 2) oxygen deficiency in the local environment; and 3) insufficient vascularization within and around the implant. Thus, the objective of this proposal is to engineer a superior bioartificial pancreas, a device combining novel biomaterials and insulin-secreting cells, by focusing on these critical issues, specifically how to best reduce islet aggregation, as well as increase oxygen delivery, both in the short term and long term. A highly macroporous silicone scaffold will be engineered to distribute the islets three-dimensionally, while not imparting diffusion resistances commonly encountered in microporous materials. Macroporous scaffolds will also permit vascular in-growth. In order to sustain oxygen levels at the moment of device implantation, a novel, oxygen generating disk, which relies on the decomposition of calcium peroxide, will be developed and incorporated alongside the scaffold to deliver short-term supplemental oxygen. Therefore, it is postulated that these bioactive scaffolds, which interact with islets on a spatial, chemical, and biological level, will improve the viability as well as the function of islets, both in vitro and in vivo, as compared to naked islets under extrahepatic conditions.

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