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Gong, Xiuqing. "PDMS based microfluidic chips and their application in material synthesis /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?NSNT%202009%20GONG.
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Lamperti, Emanuele. "PDMS based microfluidics membrane contactors for CO2 removal applications." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/15261/.
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This work proposes a gas-liquid contactor study in microfluidics field, using dense membrane working with a concentration gradient; a microfluidic gas-liquid contactor was developed for CO2 removal and the general idea is to transport CO2 through a polymer dense membrane, followed by its capture by a liquid solvent with chemical absorption. Like recent studies demonstrate, this kind of devices could solve problems related to extracorporeal lung oxygenation (Garofalo, C. Quintavalle, G. Romano, C.M. Croce, 2013) for critical surgical support and critical care medicine, it can work like a real lung because can mimic the architecture of the human vasculature better than the existing technologies. Applications in this fields are related for example to the separation of Xenon from CO2 in anaesthesia. Xe is a very expensive element perfect for anaesthesia, is hemodynamically stable, low soluble in liquid and produces high regional blood flow reducing the risk of hypoxia (Malankowska et al., 2018). The major advantage of using microfluidics devices is that they could be reach a high surface to volume ratio and thanks to miniaturization can be tested reducing the time as well as the production of waste, thus increasing the number of experimental tests can be achieved.
In the present thesis in particular one alveolar design channel based of literature results (Malankowska et al., 2018) was realized with soft lithography and tested in different experimental conditions. In particular, for the present geometry the transport of CO2 through the membrane was monitored, calculating the overall mass transfer coefficient and the molar flow of the gas through the membrane in different operating conditions.
In additions, the production of other two microfluidics device with different channels configurations was attempted by using a 3-D printing technique that allows the generations of complex structures with high surface to volume ratio.
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Thorslund, Sara. "Microfluidics in Surface Modified PDMS : Towards Miniaturized Diagnostic Tools." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7270.
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JOTHIMUTHU, PREETHA. "Photodefinable Polydimethylsiloxane (PDMS) Thin Films." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1212181335.
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Cartin, Charles. "DESIGN, FABRICATION, AND TESTING OF A PDMS MICROPUMP WITH MOVING MEMBRANES." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/2742.
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This paper will discuss the design, fabrication, and testing of a Poly(dimethylsiloxane) (PDMS) microfluidic pump. PDMS is commonly described as a soft polymer with very appealing chemical and physical properties such as optical transparency, low permeability to water, elasticity, low electrical conductivity, and flexible surface chemistry. PDMS microfluidic device fabrication is done easily with the use of soft lithography and rapid prototyping. PDMS microfluidic devices make it easier to integrate components and interface devices with particular users, than using typically harder materials such as glass and silicon. Fabrication and design of single and multilayer PDMS microfluidic devices is much easier and straightforward than traditional methods. A novel design of a PDMS micropump with multiple vibrating membranes has been developed for application in drug delivery and molecule sorting. The PDMS micropump consists of three nozzle/diffuser elements with vibrating membranes, which are used to create pressure difference in the pump chamber. Preliminary analysis of the fluidic characteristics of the micropump was analyzed with ANSYS to investigate the transient responses of fluid velocity, pressure distributions, and flow rate during the operating cycle of the micropump. The design simulation results showed that the movement of the wall membranes combined with rectification behavior of three nozzle/diffuser elements can minimize back flow and improve net flow in one direction. To prove that the theoretical design is valid, the fabrication and testing process of the micropump has been carried out and completed. This paper will discuss in depth the design, fabrication, and testing of the PDMS micropump.
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Redington, Cecile D. "AN ANALYSIS OF ELIMINATING ELECTROOSMOTIC FLOW IN A MICROFLUIDIC PDMS CHIP." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/1079.
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The goal of this project is to eliminate electroosmotic flow (EOF) in a microfluidic chip. EOF is a naturally occurring phenomenon at the fluid-surface interface in microfluidic chips when an electric field is applied across the fluid. When isoelectric focusing (IEF) is carried out to separate proteins based on their surface charge, the analytes must remain in the separation chamber, and not migrate to adjacent features in the microfluidic chip, which happens with EOF.
For this project, a microfluidic chip was designed and commissioned to be photolithographically transferred onto a Si wafer. A PDMS component was then casted on the Si wafer and plasma bonded to a glass substrate. This chip was initially designed to carry out continuous IEF, and the focus of the project was shifted to the analysis of eliminating EOF in a microfluidic chamber.
Per previous research test methods, methylcellulose will be used to analyze the phenomenon of electroosmotic flow in the chamber. A COMSOL model is used a theoretical basis of comparison when analyzing the flow velocities of the treated versus untreated microfluidic chips.
The purpose of this project is to use the research performed in on this chip as a precursor to future analyses of continuous IEF on microfluidic chips in the Cal Poly Microfluidics group.
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Bell, Laurence Livingstone. "Optically interrogated biosensors in microfluidics." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610215.
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NARASIMHAN, JAGANNATHAN. "POLYMER EMBOSSING TOOLS FOR RAPID PROTOTYPING OF PLASTIC MICROFLUIDIC DEVICES." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1061298554.
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Samel, Björn. "Novel Microfluidic Devices Based on a Thermally Responsive PDMS Composite." Doctoral thesis, KTH, Mikrosystemteknik, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4470.
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The field of micro total analysis systems (μTAS) aims at developments toward miniaturized and fully integrated lab-on-a-chip systems for applications, such as drug screening, drug delivery, cellular assays, protein analysis, genomic analysis and handheld point-of-care diagnostics. Such systems offer to dramatically reduce liquid sample and reagent quantities, increase sensitivity as well as speed of analysis and facilitate portable systems via the integration of components such as pumps, valves, mixers, separation units, reactors and detectors. Precise microfluidic control for such systems has long been considered one of the most difficult technical barriers due to integration of on-chip fluidic handling components and complicated off-chip liquid control as well as fluidic interconnections. Actuation principles and materials with the advantages of low cost, easy fabrication, easy integration, high reliability, and compact size are required to promote the development of such systems. Within this thesis, liquid displacement in microfluidic applications, by means of expandable microspheres, is presented as an innovative approach addressing some of the previously mentioned issues. Furthermore, these expandable microspheres are embedded into a PDMS matrix, which composes a novel thermally responsive silicone elastomer composite actuator for liquid handling. Due to the merits of PDMS and expandable microspheres, the composite actuator's main characteristic to expand irreversibly upon generated heat makes it possible to locally alter its surface topography. The composite actuator concept, along with a novel adhesive PDMS bonding technique, is used to design and fabricate liquid handling components such as pumps and valves, which operate at work-ranges from nanoliters to microliters. The integration of several such microfluidic components promotes the development of disposable lab-on-a-chip platforms for precise sample volume control addressing, e.g. active dosing, transportation, merging and mixing of nanoliter liquid volumes. Moreover, microfluidic pumps based on the composite actuator have been incorporated with sharp and hollow microneedles to realize a microneedle-based transdermal patch which exhibits on-board liquid storage and active dispensing functionality. Such a system represents a first step toward painless, minimally invasive and transdermal administration of macromolecular drugs such as insulin or vaccines. The presented on-chip liquid handling concept does not require external actuators for pumping and valving, uses low-cost materials and wafer-level processes only, is highly integrable and potentially enables controlled and cost-effective transdermal microfluidic applications, as well as large-scale integrated fluidic networks for point-of care diagnostics, disposable biochips or lab-on-a-chip applications. This thesis discusses several design concepts for a large variety of microfluidic components, which are promoted by the use of the novel composite actuator. Results on the successful fabrication and evaluation of prototype devices are reported herein along with comprehensive process parameters on a novel full-wafer adhesive bonding technique for the fabrication of PDMS based microfluidic devices.QC 20100817
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Graham, Brennan P. "Application of Argon Plasma Technology to Hydrophobic and Hydrophilic Microdroplet Generation in PDMS Microfluidic Devices." DigitalCommons@CalPoly, 2017. https://digitalcommons.calpoly.edu/theses/1728.
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Abstract Application of Argon Plasma Technology to Hydrophobic and Hydrophilic Microdroplet Generation in PDMS Microfluidic Devices Brennan Graham Microfluidics has gained popularity over the last decade due to the ability to replace many large, expensive laboratory processes with small handheld chips with a higher throughput due to the small channel dimensions [1]. Droplet microfluidics is the field of fluid manipulation that takes advantage of two immiscible fluids to create droplets from the geometry of the microchannels. This project includes the design of a microfluidic device that applies the results of an argon plasma surface treatment to polydimethylsiloxane (PDMS) to successfully produce both hydrophobic and hydrophilic surfaces to create oil in water (O/W) and water in oil (W/O) microdroplets. If an argon plasma surface treatment renders the surface of PDMS hydrophilic, then O/W microdroplets can be created and integrated into a larger microdroplet emulsion device. The major aims of this project include: (1) validating previously established Cal Poly lab protocols to produce W/O droplets in hydrophobic PDMS microdroplet generators (2) creating hydrophilic PDMS microdroplet generators (3) making oil in water droplets in hydrophilic PDMS microdroplet generators (4) designing a multilayer microfluidic device to transfer W/O droplets to a second hydrophilic PDMS microdroplet generator v W/O droplets were successfully created and transferred to a second hydrophilic PDMS device. The hydrophilic PDMS device also produced O/W droplets in separate testing from the multilayered microfluidic PDMS device. The ultimate purpose of this project is to create a multilayer microdroplet generator that produces water in oil in water (W/O/W) microdroplet emulsions through a stacked device design that can be used in diagnostic microdroplet applications. Thesis Supervisor: Dave Clague Title: Professor of Biomedical Engineering
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BHAGAT, ALI ASGAR SALEEM. "DESIGN AND CHARACTERIZATION OF PLANAR LOW REYNOLDS NUMBER MICROFLUIDIC MIXERS FOR LAB-ON-A-CHIP APPLICATIONS." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1154956875.
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Tsai, Long-Fang. "Microfluidic Devices and Biosensors." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/5821.
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My research broadly covers various important aspects of microfluidic devices and biosensors. Specifically, this dissertation reports: (1) a new and effective room temperature method of bonding polydimethylsiloxane (PDMS) microfluidics to substrates such as silicon and glass, (2) a new microfluidic pump concept and implementation specifically designed to repeatedly drive a small sample volume (<1 µL) very rapidly (~500 µL/min) through a sensor-containing flow channel to significantly decrease sensor response time through advection-driven rather than diffusion-driven mass transport, (3) use of a new microfluidic material based on polyethylene glycol diacrylate (PEGDA) to implement impedance-based dynamic nanochannel sensors for protein sensing, and (4) an investigation of galvanoluminescence and how to avoid it for conditions important to fluorescence-based dielectrophoresis (DEP) microfluidic biosensors. Over the last decade, the Nordin research group has developed a lab-on-a-chip (LOC) biosensor based on silicon photonic microcantilever arrays integrated with polydimethylsiloxane (PDMS) microfluidics for protein biomarker detection. Integration requires reliable bonding at room temperature with adequate bond strength between the PDMS element and microcantilever sensor substrate. The requirement for a room temperature process is particularly critical because microcantilevers must be individually functionalized with antibody-based receptor molecules prior to bonding and cannot withstand significant heating after functionalization. I developed a new room temperature bonding method using PDMS curing agent as an intermediate adhesive layer. Two curing agents (Sylgard 184 and 182) were compared, as well as an alternate UV curable adhesive (NOA 75). The bond strength of Sylgard 184 was found to be stronger than Sylgard 182 under the same curing conditions. Overnight room temperature curing with Sylgard 184 yields an average burst pressure of 433 kPa, which is more than adequate for many PDMS sensor devices. In contrast, UV curable epoxy required a 12 hour bake at 50 °C to achieve maximum bond strength, which resulted in a burst pressure of only 124 kPa. In many biosensing scenarios it is desirable to use a small sample volume (<1 µL) to detect small analyte concentrations in as short a time as possible. I report a new microfluidic pump to address this need, which we call a reflow pump. It is designed to rapidly pump a small sample volume back and forth in a flow channel. Ultimately, the flow channel would contain functionalized sensor surfaces. The rapid flow permits use of advection-driven mass transport to the sensor surfaces to dramatically reduce sensor response times compared to diffusion-based mass transport. Normally such rapid flow would have the effect of decreasing the fraction of analyte molecules in the volume that would see the sensor surfaces. By configuring the pump to reflow fluid back and forth in the flow channel, the analyte molecules in the small sample volume are used efficiently in that they have many opportunities to make it to the sensor surfaces. I describe a 3-layer PDMS reflow pump that pumps 300 nL of fluid at 500 µL/min for 15 psi actuation pressure, and demonstrate a new two-layer configuration that significantly simplifies pump fabrication. Impedance-based nanochannel sensors operate on the basis of capturing target molecules in nanochannels such that impedance through the nanochannels is increased. While simple in concept, the response time can be quite long (8~12 hours) because the achievable flow rate through a nanochannel is very limited. An approach to dramatically increase the flow rate is to form nanochannels only during impedance measurements, and otherwise have an array of nanotrenches on the surface of a conventional microfluidic flow channel where they are exposed to normal microfluidic flow rates. I have implemented such a dynamic nanochannel approach with a recently-developed microfluidic material based polyethylene glycol diacrylate (PEGDA). I present the design, fabrication, and testing of PEGDA dynamic nanochannel array sensors, and demonstrate an 11.2 % increase in nanochannel impedance when exposed to 7.2 µM bovine serum albumin (BSA) in phosphate buffered saline (PBS). Recently, LOC biosensors for cancer cell detection have been demonstrated based on a combination of dielectrophoresis (DEP) and fluorescence detection. For fluorescence detection it is critical to minimize other sources of light in the system. However, reported devices use a non-noble metal electrode, indium tin oxide (ITO), to take advantage of its optical transparency. Unfortunately, use of non-noble metal electrodes can result in galvanoluminescence (GL) in which the AC voltage applied to the electrodes to achieve DEP causes light emission, which can potentially confound the fluorescence measurement. I designed and fabricated two types of devices to examine and identify conditions that lead to GL. Based on my observations, I have developed a method to avoid GL that involves measuring the impedance spectrum of a DEP device and choosing an operating frequency in the resistive portion of the spectrum. I also measure the emission spectrum of twelve salt solutions, all of which exhibited broadband GL. Finally, I show that in addition to Au, Cr and Ni do not exhibit GL, are therefore potentially attractive as low cost DEP electrode materials.
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Mier, Alexandro Castellanos. "Poly(N-Isopropylacrylamide) based BioMEMS/NEMS for cell manipulation." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001814.
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DiBartolomeo, Franklin. "HIGH SPEED CONTINUOUS THERMAL CURING MICROFABRICATION SYSTEM." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_theses/105.
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Rapid creation of devices with microscale features is a vital step in the commercialization of a wide variety of technologies, such as microfluidics, fuel cells and self-healing materials. The current standard for creating many of these microstructured devices utilizes the inexpensive, flexible material poly-dimethylsiloxane (PDMS) to replicate microstructured molds. This process is inexpensive and fast for small batches of devices, but lacks scalability and the ability to produce large surface-area materials. The novel fabrication process presented in this paper uses a cylindrical mold with microscale surface patterns to cure liquid PDMS prepolymer into continuous microstructured films. Results show that this process can create continuous sheets of micropatterned devices at a rate of 1.9 in2/sec (~1200 mm2/sec), almost an order of magnitude faster than soft lithography, while still retaining submicron patterning accuracy.
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Hansson, Jonas. "Microfluidic blood sample preparation for rapid sepsis diagnostics." Licentiate thesis, KTH, Cellens fysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-96313.
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Sepsis, commonly referred to as blood poisoning, is a serious medical condition characterized by a whole-body inflammatory state caused by microbial infection. Rapid treatment is crucial, however, traditional culture-based diagnostics usually takes 2-5 days. The overall aim of the thesis is to develop microfluidic based sample preparation strategies, capable of isolating bacteria from whole blood for rapid sepsis diagnostics. Although emerging technologies, such as microfluidics and “lab-on-a-chip” (LOC) devices have the potential to spur the development of protocols and affordable instruments, most often sample preparation is performed manually with procedures that involve handling steps prone to introducing artifacts, require skilled technicians and well-equipped, expensive laboratories. Here, we propose the development of methods for fast and efficient sample preparation that can isolate bacteria from whole blood by using microfluidic techniques with potential to be incorporated in LOC systems. We have developed two means for high throughput bacteria isolation: size based sorting and selective lysis of blood cells. To process the large blood samples needed in sepsis diagnostics, we introduce novel manufacturing techniques that enable scalable parallelization for increased throughput in miniaturized devices. The novel manufacturing technique uses a flexible transfer carrier sheet, water-dissolvable release material, poly(vinyl alcohol), and a controlled polymerization inhibitor to enable highly complex polydimethylsiloxane (PDMS) structures containing thin membranes and 3D fluidic networks. The size based sorting utilizes inertial microfluidics, a novel particles focusing method that operates at extremely high flow rates. Inertial focusing in flow through a single inlet and two outlet, scalable parallel channel devices, was demonstrated with filtration efficiency of >95% and a flowrate of 3.2 mL/min. Finally, we have developed a novel microfluidic based sample preparation strategy to continuously isolate bacteria from whole blood for downstream analysis. The method takes advantage of the fact that bacteria cells have a rigid cell wall protecting the cell, while blood cells are much more susceptible to chemical lysis. Whole blood is continuously mixed with saponin for primary lysis, followed by osmotic shock in water. We obtained complete lysis of all blood cells, while more than 80% of the bacteria were readily recovered for downstream processing. Altogether, we have provided new bacteria isolation methods, and improved the manufacturing techniques and microfluidic components that, combined offer the potential for affordable and effective sample preparation for subsequent pathogen identification, all in an automated LOC format.QC 20120611
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Grove, Fraser Traves Smith. "Impedance Sensing of N2A and Astrocytes as Grounds for a Central Nervous System Cancer Diagnostic Device." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/782.
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This thesis utilizes previously described manufacturing and design techniques for the creation of a PDMS-glass bonded microfluidic device, capable of electrochemical impedance spectroscopy (EIS). EIS has been used across various fields of research for different diagnostic needs. The major aim of this thesis was to capture cancerous and non-cancerous cells between micron sized electrodes within a microfluidic path, and to complete analysis on the measured impedances recorded from the two differing cell types. Two distinct ranges of impedance frequency were analyzed – the α dispersion range, which quantifies the impedance of the membranes of the cells of interest, and the β dispersion range, which quantifies the impedance of the cytosol of the cells of interest. This thesis is unique in the fact that it looks at the cellular impedances of two types of neural cells, which has not been documented previously in literature. The type of cancerous cells analyzed were Neuro-2-A cells, an immortalized line of murine glio/neuroblastoma. The type of non-cancerous cells analyzed were murine primary astrocytes, a mortal line of neurological support cells found throughout the nervous system, and with great abundance in the brain.
By using a LabView program coded by a previous Cal Poly student, a sweep scan across a wide frequency range was completed on both cell types, and statistical analysis was completed on target frequencies of interest. A significant difference was found between the two cell lines’ membrane impedances, however no difference was found between the cytoplasm impedances.
In total, this thesis aimed to fabricate a reusable microfluidic device capable of EIS for future Cal Poly students, create a protocol suitable for cell culturing and device operation, and to lay a foundation of knowledge for impedance comparisons regarding neural cancerous and non-cancerous cells.
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Aristizábal, Sergio Lopera. "Desenvolvimento de sistemas Lab-on-a-Chip para análises em biofísica celular." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-10052012-113950/.
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Este estudo tem por objetivo o desenvolvimento de uma metodologia de fabricação de sistemas Lab On Chip, úteis no estudo de processos celulares, a partir da adaptação de tecnologias próprias da microeletrônica. Foram exploradas todas as etapas envolvidas na fabricação de sistemas Lab On Chip em Poli-Di-Metil-Siloxano e desenvolvidos protocolos de fabricação de moldes, técnicas de moldagem e processos de ativação de PDMS com plasma de oxigênio para sua solda química sobre diferentes materiais, obtendo uniões irreversíveis que permitem a integração com outras tecnologias como a microeletrônica em silício e o encapsulamento com cerâmica verde, completando uma metodologia que permite a prototipagem de dispositivos micro-fluídicos de multicamadas com um nível de sofisticação comparável ao estado da arte. Foi desenvolvido o protótipo de um equipamento ótico para litografia por projeção que permite a fabricação de máscaras óticas com resolução de 5 m e oferece a possibilidade de litografia em escala de cinzas para gerar canais e estruturas com relevos arbitrários. Foram adicionalmente abordados três problemas de biofísica celular, para os quais foram propostos novos dispositivos para separação de células móveis de acordo às suas velocidades lineares, dispositivos para crescimento confinado de bactérias e dispositivos para manipulação da curvatura de membranas celulares.The objective of this study is the development of a methodology for the fabrication of Lab On Chip systems, useful for the analysis of cellular processes, through the adaptation of technologies from microelectronics. All the steps involved with the fabrication of Lab on Chip system in Poly-Di-Methil-Siloxane (PDMS) were explored, developing protocols for mold fabrication, molding techniques and processes for oxygen plasma activation of PDMS for its bonding to different materials, achieving irreversible bonds that enable the integration with other technologies such as silicon microelectronics and green tape packaging. All this techniques constitute a methodology that allows the prototyping of multilayer microfluidic devices comparable with state of the art devices. It was developed the prototype of optical equipment for projection lithography capable of mask fabrication with 5 m resolution, and which offers also the capability of gray scale lithography for the generation of free form microchannels. Additionally three different problems in cellular biophysics where boarded, proposing new devices for the separation of motile cells according to their linear speeds in liquids, new devices for constrained bacterial growth and for curvature manipulation of cell membranes.
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Pussadee, Nirut. "Poly(dimethylsiloxane) Based Micro- and Nanofluidic Device Fabrication for Electrophoresis Applications." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1268179904.
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Bodin, Noémi. "Formation d'émulsions multiples stables, stimulables et biocompatibles; application à l'encapsulation et au relargage contrôlé de principes actifs." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX060/document.
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Dans ce travail, nous nous sommes intéressés aux émulsions stabilisées par une famille de copolymères diblocs biocompatibles polydiméthylsiloxane-b-poly(méthacrylate de diméthylaminoéthyle) (PDMS-b-PDMAEMA). Le bloc PDMAEMA, porteur de fonctions amines, est sensible au pH et à la force ionique. En faisant varier ces deux paramètres, des émulsions directes, inverses et multiples E/H/E ont pu être obtenues en une seule étape d’émulsification, par cisaillement d’une phase aqueuse et d’une phase huile biocompatible (Miglyol® 812 ou myristate d’isopropyle). Pour un copolymère présentant des longueurs de blocs hydrophile et hydrophobe similaires, le PDMS60-b-PDMAEMA50, des émulsions multiples stables sur plus de deux ans sont obtenues avec les deux huiles, pour des pH proches du pKa du PDMAEMA et dans une vaste gamme de sel ajouté. Il a en outre été établi sur des cellules intestinales humaines que les émulsions formées à partir de ces copolymères ne présentent pas de cytotoxicité et peuvent être utilisées pour développer des applications pour l’homme.La diminution du pH de la phase aqueuse conduit à la déstabilisation des émulsions doubles en émulsions directes, permettant d’obtenir la libération contrôlée des espèces encapsulées dans les gouttelettes d’eau internes. Des essais d’encapsulation ont été réalisés avec une molécule modèle, le saccharose, et un antioxydant naturellement présent dans le thé vert, la catéchine, molécule fragile facilement dégradée. Ces molécules peuvent être libérées à loisir par diminution du pH et déstabilisation de l’émulsion multiple, la formation de liaisons hydrogènes entre les molécules encapsulées et le copolymère limitant cependant le relargage. Il a également été démontré que les émulsions ont un effet protecteur sur la catéchine lors du stockage et permettent d’exalter son pouvoir antioxydant.Enfin, nous avons étudié la formation d’émulsions stabilisées par le PDMS-b-PDMAEMA par voie microfluidique. Une méthode originale a été développée pour permettre de former de façon simple des émulsions doubles sur des puces en PDMS. Des émulsions E/H/E ont été obtenues dans des conditions de pH et de force ionique bien précises, et la catéchine a pu également être encapsulée au cœur des gouttelettes internes par cette méthodeIn this work, we studied different kinds of emulsions stabilized by biocompatible diblock copolymers polydimethylsiloxane-b-poly(dimethylaminoethyle methacrylate) (PDMS-b-PDMAEMA). PDMAEMA is sensitive to pH and ionic strength thanks to the amine groups carried by the chain. Varying the latter parameters, we obtained direct, inverse and W/O/W double emulsions in only one emulsification step, by shearing an aqueous phase and a biocompatible oil (Miglyol® 812 or isopropyle myristate). For a copolymer having hydrophilic and hydrophobic blocks of similar lengths, PDMS60-b-PDMAEMA50, very stable multiple emulsions (more than two years) were obtained, for pH close to pKa of PDMAMEA and in a large range of salt concentrations. Cytotoxicity measurements were performed on intestinal human cells, proving the possibility of using the emulsions stabilized with these copolymers to develop applications for health care.pH lowering allows to turn direct emulsions to multiple ones, leading to the controlled release of encapsulated species in the inner water drops. Encapsulation tests have been carried out with a model molecule, sucrose, and with an antioxidant extracted from green tea, catechin. Both molecules could be released from our emulsions by reducing the pH, despite the formation of hydrogen bonds between the encapsulated compounds and the copolymer which prevented complete deliverance. We demonstrated the ability of our multiple emulsions to protect the fragile catechin molecule during storage and preserve its antioxidant capacity.Additionally, we achieved the formation of PDMS-b-PDMAEMA stabilized emulsions by microfluidics. An innovative method was developed to allow the formation of double emulsions on PDMS microchips in an easy way. W/O/W emulsions were obtained for precise pH and salt concentrations, and catechin could also be successfully encapsulated in the internal water droplets by this method
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Jo, Myeong Chan. "An Acoustic-based Microfluidic Platform for Active Separation and Mixing." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4697.
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Particle separation is of great interest to many biological and biomedical applications. Flow-based methods have been used to sort particles and cells. However, the main challenge with flow based particle separation systems is the need for a sheath flow for successful operation. Existence of the sheath liquid dilutes the analyte, necessitates precise flow control between sample and sheath flow, requires a complicated design to create sheath flow and separation efficiency depends on the sheath liquid composition. In addition, current gold standard active separation techniques are only capable of separation based on particle size; hence, separation cannot be achieved for same-size particles with different densities. In this dissertation, a sheathless acoustic-based microfluidic platform using surface acoustic wave for not only size-dependent but also density-dependent particle separation has been investigated. In this platform, two different functions were incorporated within a single microfluidic channel with varying the number of pressure node and position. The first function was to align particles on the center of the microfluidic channel without adding any external sheath flow. The second function was to separate particles according to their size or density. Two different size-pairs of polystyrene particles with different diameters (3 µm and 10 µm for general size-resolution, 3 µm and 5 µm for higher size-resolution) were successfully separated. Also, the separation of two 10 µm diameter, different-density particle streams (polystyrene: 1.05 g/cm3, melamine: 1.71 g/cm3) was successfully demonstrated. The effects of the input power, the flow rate, and particle concentration on the separation efficiency were investigated. A range of high separation efficiencies with 94.8-100 % for size-based separation and 87.2 - 98.9 % for density-based separation were accomplished.
In this dissertation, an acoustic-based microfluidic platform using dual acoustic streaming for active mixing has also been investigated. The rapid and high efficiency mixing of a fluorescent dye solution and deionized water in a microfluidic channel was demonstrated with single acoustic excitation by one interdigital transducer (IDT) as well as dual excitation by two IDTs. The mixing efficiencies were investigated as a function of applied voltage and flow rates. The results indicate that with the same operation parameters, the mixing efficiency with dual-IDT design increased to 96.7 % from 69.8 % achievable with the traditional single-IDT design. The effect of aperture length of the IDT on mixing efficiency was also investigated.
Additionally, the effects of the polydimethylsiloxane (PDMS) channel wall thickness on the insertion loss and the particle migration to the pressure node due to acoustic radiation forces induced by SAW have been investigated. The results indicate that as the PDMS channel wall thickness decreased, the SAW insertion loss is reduced as well as the velocity of the particle migration due to acoustic forces increased significantly. As an example, reducing the side wall thickness of the PDMS channel from 8 mm to 2 mm in the design results in 31.2 % decrease in the insertion loss at the resonant frequency of 13.3 MHz and 186 % increase the particle migration velocity at the resonant frequency of 13.3 MHz with input power of 27 dBm.
Lastly, a novel acoustic-based method of manipulating the particles using phase-shift has been proposed and demonstrated. The location of the pressure node was adjusted simply by modulating the relative phase difference (phase-shift) between two IDTs. As a result, polystyrene particles of 5 µm diameter trapped in the pressure node were manipulated laterally across the microfluidic channel. The lateral displacements of the particles from -72.5 µm to 73.1 µm along the x-direction were accomplished by varying the phase-shift with a range of -180° to 180°. The relationship between the particle displacement and the phase-shift of SAW was obtained experimentally and shown to agree with theoretical prediction of the particle position.
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Klepáčová, Ivana. "Detekce biomarkerů pomocí elektrochemických metod mikrofluidickým čipem." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-317012.
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The thesis is focused on the development of the electrochemical system with microfluidic platform for the detection of multiple biomarkers. It analyses the use of biomarkers for the early diagnosis of cancer. The theoretical part contains basic information about voltammetric methods and microfluidic systems. The practical part provides solutions to the microfluidic chips, including the description of the used materials, designs, methodologies of preparation and conclusions from the testing of the manufactured microfluidic systems. The thesis describes the lock-in electrochemical system which measures the response of 4 electrochemical cells simultaneously. For the electrochemical system measurements, an electrochemical chip consisting of 64 electrochemical cells was used. The results of the analysis include the processing of the system tests and detected voltammetric curves of the Fe2+/Fe3+ solution and cysteine.
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Cottet, Jonathan. "Development of microsystems for the controlled formation of cell aggregates by dielectrophoresis." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEC033/document.
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Les agrégats cellulaires constituent un modèle intermédiaire entre les cellules uniques et les tissues cellulaires et sont utilisés dans de nombreux domaines tels que l’ingénierie tissulaire et le criblage de médicaments in vitro. La création de tels agrégats cellulaires dont les propriétés et la taille seraient contrôlées nécessite cependant le développement de nouvelles approches ascendantes. Le travail présenté dans ce manuscrit vise à développer des microsystèmes pour la formation contrôlée d’agrégats de cellules sous flux via des champs électriques. Cette approche se base sur la diélectrophorèse (DEP), un phénomène induisant le déplacement des particules diélectriques lorsqu’elles sont placées dans un champ électrique non-uniforme. Un outil de calcul, MyDEP, a tout d’abord été développé afin d’être en mesure de prédire le comportement des cellules en suspension dans un certain milieu. Cet outil permet d’étudier la réponse diélectrique des particules et des cellules en fonction de la fréquence du champ. Il contient une base de données regroupant les propriétés diélectriques des cellules publiées dans la littérature afin d’aider tant les spécialistes que les utilisateurs néophytes à comprendre le comportement diélectrophorétique des particules et des cellules ainsi qu’à choisir les paramètres expérimentaux tels que la conductivité électrique du milieu et la fréquence du champ préalablement aux manipulations expérimentales en laboratoire. Différents designs pour le piégeage de cellules sont proposés avec les simulations, par la méthode des éléments finis en utilisant COMSOL Multiphysics, associées. Leur fabrication a nécessité le développement d’une méthode d’alignement reproductible, précise au micromètre, des microcanaux d’un polymère appelé le polydiméthylsiloxane (PDMS) avec des électrodes coplanaires en titane/platine déposées sur du verre via l’utilisation d’une aligneuse de masques conventionnelle. La méthode est basée sur l’utilisation d’un moule en silicium associé à un sarcophage en Poly(methyl methacrylate) (PMMA) afin de garantir le contrôle du parallélisme entre les parties supérieure et inférieure du PDMS moulé. Les puces contenant les différents designs de piégeage ainsi fabriquées ont été testées avec succès sur des cellules rénales embryonnaires humaines (HEK) à l’aide d’une installation expérimentale démontrant par la même la capacité des puces à créer des agrégats constitués d’un nombre contrôlé de cellules par diélectrophorèse. Les agrégats ainsi formés se sont avérés stables après 5 minutes de contact cellule à cellule sans qu’une séparation des cellules n’ait été observée. Le design d’un capteur par impédance a par ailleurs été proposé pour caractériser tant les cellules uniques que les agrégats cellulaires avant et après la chambre de piégeage. Celui-ci, associé au design de piégeage par DEP, a été testé expérimentalement avec succès pour détecter leur passageCell aggregates are an intermediary model between single cells and cell tissues used in many applications such as tissue engineering and in vitro drug screening. The creation of cells aggregates of controlled size and properties requires the development of new bottom-up strategies. The work developed in this manuscript aims at presenting the development of microsystems for the electric force-driven controlled formation of cell aggregates under flow conditions. This approach is based on dielectrophoresis, a phenomenon that causes induced motion on dielectric particles placed in a non-uniform electric field. A computational tool, MyDEP, was first developed in order to predict the behavior of cells in a specific medium. It allows to study the dielectric response of particles and cells as a function of frequency. The software also includes a database gathering cell dielectric models available in the literature to help experienced users as well as neophytes to understand the dielectrophoretic behavior of particles and cells and to choose parameters such as electric conductivity of the medium and frequency before performing laboratory experiments. Different designs for cell trapping are proposed and simulated in 2D with FEM using COMSOL Multiphysics. Their fabrication implied the development of a reproducible method for μm precision alignment of microchannels in a polymer called polydimethylsiloxane (PDMS) with coplanar titanium/platinum electrodes deposited on glass, using a conventional mask aligner. It is based on the use of a silicon mold in combination with a Poly(methyl methacrylate) (PMMA) sarcophagus for precise control of the parallelism between top and bottom surfaces of molded PDMS. The trapping design based on coplanar electrodes was successfully tested experimentally on human embryonic kidney cells (HEK) with an automated setup. It proves its capability to create aggregates of a controlled number of cells with DEP. The cell aggregates proved to be stable (no disruption) after only 5 minutes of cell-cell contact. An impedance-based sensor design was proposed for characterizing single cells and cells aggregates before and after the trapping chamber. This sensor was successfully tested experimentally to detect particle passage in combination with the dielectrophoretic trapping design
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Liu, Miao. "A CUSTOMER PROGRAMMABLE MICROFLUIDIC SYSTEM." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2330.
Full textAbstract:
Microfluidics is both a science and a technology offering great and perhaps even revolutionary capabilities to impact the society in the future. However, due to the scaling effects there are unknown phenomena and technology barriers about fluidics in microchannel, material properties in microscale and interactions with fluids are still missing. A systematic investigation has been performed aiming to develop "A Customer Programmable Microfluidic System". This innovative Polydimethylsiloxane (PDMS)-based microfluidic system provides a bio-compatible platform for bio-analysis systems such as Lab-on-a-chip, micro-total-analysis system and biosensors as well as the applications such as micromirrors. The system consists of an array of microfluidic devices and each device containing a multilayer microvalve. The microvalve uses a thermal pneumatic actuation method to switch and/or control the fluid flow in the integrated microchannels. It provides a means to isolate samples of interest and channel them from one location of the system to another based on needs of realizing the customers' desired functions. Along with the fluid flow control properties, the system was developed and tested as an array of micromirrors. An aluminum layer is embedded into the PDMS membrane. The metal was patterned as a network to increase the reflectivity of the membrane, which inherits the deformation of the membrane as a mirror. The deformable mirror is a key element in the adaptive optics. The proposed system utilizes the extraordinary flexibility of PDMS and the addressable control to manipulate the phase of a propagating optical wave front, which in turn can increase the performance of the adaptive optics. Polydimethylsiloxane (PDMS) has been widely used in microfabrication for microfluidic systems. However, few attentions were paid in the past to mechanical properties of PDMS. Importantly there is no report on influences of microfabrication processes which normally involve chemical reactors and biologically reaction processes. A comprehensive study was made in this work to study fundamental issues such as scaling law effects on PDMS properties, chemical emersion and temperature effects on mechanical properties of PDMS, PDMS compositions and resultant properties, as well as bonding strength, etc. Results achieved from this work will provide foundation of future developments of microfluidics utilizing PDMS.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering PhD
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Marchington, Robert F. "Applications of microfluidic chips in optical manipulation & photoporation." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/1633.
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Integration and miniaturisation in electronics has undoubtedly revolutionised the modern world. In biotechnology, emerging lab-on-a-chip (LOC) methodologies promise all-integrated laboratory processes, to perform complete biochemical or medical synthesis and analysis encapsulated on small microchips. The integration of electrical, optical and physical sensors, and control devices, with fluid handling, is creating a new class of functional chip-based systems. Scaled down onto a chip, reagent and sample consumption is reduced, point-of-care or in-the-field usage is enabled through portability, costs are reduced, automation increases the ease of use, and favourable scaling laws can be exploited, such as improved fluid control. The capacity to manipulate single cells on-chip has applications across the life sciences, in biotechnology, pharmacology, medical diagnostics and drug discovery. This thesis explores multiple applications of optical manipulation within microfluidic chips. Used in combination with microfluidic systems, optics adds powerful functionalities to emerging LOC technologies. These include particle management such as immobilising, sorting, concentrating, and transportation of cell-sized objects, along with sensing, spectroscopic interrogation, and cell treatment. The work in this thesis brings several key applications of optical techniques for manipulating and porating cell-sized microscopic particles to within microfluidic chips. The fields of optical trapping, optical tweezers and optical sorting are reviewed in the context of lab-on-a-chip application, and the physics of the laminar fluid flow exhibited at this size scale is detailed. Microfluidic chip fabrication methods are presented, including a robust method for the introduction of optical fibres for laser beam delivery, which is demonstrated in a dual-beam optical trap chip and in optical chromatography using photonic crystal fibre. The use of a total internal reflection microscope objective lens is utilised in a novel demonstration of propelling particles within fluid flow. The size and refractive index dependency is modelled and experimentally characterised, before presenting continuous passive optical sorting of microparticles based on these intrinsic optical properties, in a microfluidic chip. Finally, a microfluidic system is utilised in the delivery of mammalian cells to a focused femtosecond laser beam for continuous, high throughput photoporation. The optical injection efficiency of inserting a fluorescent dye is determined and the cell viability is evaluated. This could form the basis for ultra-high throughput, efficient transfection of cells, with the advantages of single cell treatment and unrivalled viability using this optical technique.
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González, Domenzain Walter. "Design and fabrication of microfluidic systems in PDMS." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612009.
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Stanton, John W. "DESIGN AND FABRICATION OF A MICROFLUIDIC ELECTROCHEMICAL PH-STAT." Cleveland, Ohio : Case Western Reserve University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1270498159.
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Thesis (Master of Sciences (Engineering))--Case Western Reserve University, 2010Department of EECS - Electrical Engineering Title from PDF (viewed on 2010-05-25) Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center
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Samel, Björn. "Novel microfluidic devices based on a thermally responsive PDMS composite /." Stockholm : Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4470.
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Hum, Philip W. (Philip Wing-Jung). "Exploration of large scale manufacturing of polydimethylsiloxane (PDMS) microfluidic devices." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36748.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (leaves 54-56).
Discussion of the current manufacturing process of polydimethylsiloxane (PDMS) parts and the emergence of PDMS use in biomedical microfluidic devices addresses the need to develop large scale manufacturing processes for the fabrication of said devices. Casting PDMS parts is found to be the best mass production process after evaluating several different production methods. Automation of the manufacturing process is introduced as a solution to the need for mass production. Changing variables within the production process and its effects are also discussed with the recommendation being made for using low viscosity pre-cured PDMS, high temperature curing and high vacuum degassing techniques to produce high quality parts at high production rates. The further development of producing two-sided PDMS parts is recommended by investigating the usage of a non-closed aspect limited casting process.
by Philip W. Hum.
S.B.
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Hu, Jenny (Jenny Ezu). "Characterization and optimization of PDMS microfluidic devices for rapid DNA hybridization." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32936.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (p. 51-53).
Two elastomeric microfluidic devices were designed for the purpose of conducting rapid, flow-based, multiplexed DNA hybridization. Experimental results showed that flowing hybridization assays could detect similar concentrations of labeled probe as standard stationary microarrays, but in 1/100h of the time, using 2% of the sample volume. An 8-channel device was used to spot glass slides with 64 hybridization assays and generate data supporting a theoretical model of DNA hybridization in both traditional stationary microarrays and flowing sample arrays. Larger devices were also used to create rrays of 96x96 spots on a single slide, demonstrating the scalability of the technology. Protocols were written and optimized for the use of both chips, allowing the technology to be distributed to collaborating labs for further development.
by Jenny Hu.
S.B.
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Lobo, Júnior Eulício de Oliveira. "Plataformas alternativas para sistemas eletroforéticos integrados com detecção condutométrica sem contato." Universidade Federal de Goiás, 2016. http://repositorio.bc.ufg.br/tede/handle/tede/6332.
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Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq
This report describes the development of two alternative platforms for electrophoretic runs in microsystems. Firstly, the development of a hybrid capillary system that dispenses microfabrication steps is presented using fused silica capillaries interconnected by a commercial crossed shape interface. This hybrid system was coupled with contactless conductivity detector (C4D) to allow the determination of inorganic cations in biological samples. Electrokinetic sample injection was performed through gated mode approach for the first time in this arrangement. Operational parameters such as: (i) wave frequency and amplitude applied in C4D system, (ii) electrical potential applied in injection, (iii) injection time, (iv) detection point, (v) effect of capillary conditioning as well as and (vi) recovery percentage were extensively investigated and optimized. Better separations of cationic mixture containing NH4+, K+, Na+, Ca2+ and Mg2+ were achieved using a buffer system composed of 50 mM Lactic Acid, 20 mM Histidine and 3 mM 18-crown-6 on a capillary with effective length of 14.5 cm. . Addition of internal standard was used to ensure analytical reproducibility and allow the recording of merit figures. Linear behaviors were observed in concentration ranges between 10 and 100 M for NH4+, K+, Ca2+ e Mg2+, and 20-200 M for Na+. The limit of detection values calculated were 3.75 μM (NH4+), 3.70 μM (K+), 7.50 μM (Na+), 5.00 μM (Ca2+) and 5.35 μM (Mg2+). The concentration levels achieved for cations in biological samples ranged from 4,1 μM to 200 μM. Besides the hybrid system, this report also describes the development of an alternative methodology for the fabrication of high-relief masters for soft-lithography in poly(dimethylsiloxane) (PDMS) substrate. One of the innovative features makes reference to the use of low cost commercial photoresist from textile industry - poly(vinyl acetate) (PVAc) - which exhibits low toxicity. PVAc films were deposited on printed cirtuitry boards through the use of a homemade spincoater developed by desktop cooler, with rotation time control. This methodology allowed the production of high relief masters and PDMS channels with width and depth of 50 μm and 40 μm, respectively. Channels and masters profiles They were characterized with the following techniques: scan electron microscopy, perfilometry, optical and electrical. PDMS electrophoresis devices were successfully used for the separation of major inorganic cations.
Esta dissertação descreve o desenvolvimento de duas plataformas alternativas para a realização de eletroforese em microssistemas. Inicialmente é descrita um sistema eletroforético híbrido que dispensa etapas de microfabricação utilizando capilares de sílica fundida, conectados por uma interface comercial com formato em cruz. Este sistema capilar híbrido foi acoplado com detecção condutométrica sem contato (C4D) e aplicado na determinação de cátions inorgânicos (NH4+, K+, Na+, Ca2+, Mg2+) em amostras biológicas. A injeção de amostras foi realizada eletrocineticamente no modo gated, sendo o primeiro estudo em capilares utilizando esta modalidade de injeção. Foram avaliados os parâmetros operacionais de funcionamento do sistema incluindo (i) frequência e amplitude da onda senoidal aplicada ao sistema de detecção, (ii) potencial elétrico aplicado na injeção, (iii) tempo de injeção, (iv) composição do tampão, (v) ponto de detecção, (vi) efeito do condicionamento do capilar e (vii) recuperação. As melhores separações para uma mistura contendo os cátions inorgânicos foram obtidas usando-se um sistema tamponante composto de ácido lático 50 mM, histidina 20 mM e éter coroa (18-crown-6) 3 mM em um capilar com comprimento efetivo de 14,5 cm. As figuras de mérito analítico foram obtidas a partir da adição do íon Li+ como padrão interno, o qual assegurou confiabilidade nas análises quantitativas. A partir da otimização dos parâmetros analíticos, as curvas analíticas para os íons NH4+, K+, Ca2+ e Mg2+ exibiram comportamento linear (R2>0,99) na faixa de 10-100 M enquanto a curva analítica para o íon Na+ proporcionou resposta linear na faixa de 20-200 M. Os limites de detecção encontrados para os cinco cátions foram entre 3,75 μM (NH4+), 3,75 μM (K+), 7,50 μM (Na+), 5,00 μM (Ca2+) e 5,35 μM (Mg2+). O sistema desenvolvido foi explorado para a determinação dos cátions inorgânicos em amostras de urina, saliva e lágrimas. As concentrações encontradas nas amostras biológicas variaram de 4,1 μM a 200 μM. Além do sistema híbrido, a dissertação também apresenta uma metodologia de baixo custo para produção de moldes em alto relevo para litografia suave em poli(dimetilsiloxano) (PDMS). A principal inovação é o uso de fotoresiste de baixo custo, que se trata de uma emulsão fotossensível de poli(acetato de vinila) (PVAc) utilizada na indústria têxtil e que apresenta baixa toxicidade. Outra inovação é o controle da altura dos moldes utilizando um spincoater de produção própria, com controle de tempo de rotação. Com esta metodologia foram produzidos moldes em alto relevo, e microchips em PDMS com 50 μm de largura e 40 μm de altura. Foram realizadas separações eletroforéticas dos cátions NH4+,K+,Na+,Ca2+,Mg2+e Li+. As eficiências de separação variaram entre 73.000 e 120.000 pratos/m. O que comprova que a metodologia alternativa apresenta aplicabilidade microfluídica
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Ness, Stanley J. "Functionalization of In-plane Photonic Microcantilever Arrays for Biosensing Applications." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3281.
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Microcantilevers have been investigated as high sensitivity, label free biosensors for approximately 15 years. In nearly all cases, a thin gold film deposited on the microcantilevers is used as an intermediate attachment layer because of the convenience of thiol-gold chemistry. Unfortunately, this attachment chemistry can be unstable when used with complex sample media such as blood plasma. The Nordin group at BYU has recently developed an all-silicon in-plane photonic microcantilever (PMCL) technology to serve as a platform for label-free biosensing. It has the advantage of being readily scalable to simultaneous readout of many PMCLs in array format, and allows integration with polymer microfluidics to facilitate the introduction of biological samples and reagents. An essential processing step for the transformation of the PMCL into a practical biosensor is the ability to effectively immobilize active biological receptors directly on silicon PMCL surfaces such that ligand binding generates sufficient surface stress to cause measureable PMCL deflection. This dissertation presents the development of a method to functionalize the sensor surface of all-silicon in-plane photonic microcantilever (PMCL) arrays. This method employs a materials inkjet printer for non-contact jetting and a fluid that is custom designed for ink-jetting and biological applications with approximately 1 pL droplet size. The method facilitates the application of different receptors on select PMCLs with drop placement accuracy in the +/- 7.5 μm range. The functionalization fluid facilitates further processing using humidity control to achieve full coverage of only the PMCL's top surface and removal of dissolved salts to improve uniformity of receptor coverage and to prevent fouling of the sensor surface. Once a functionalization method was successfully developed, a series of experiments were performed to investigate the amount of surface stress that can be generated when receptors are immobilized directly to the silicon surface. In one series of experiments, a 4.8 μM streptavidin solution was used with biotin immobilized on multiple PMCLs to demonstrate adsorption-induced surface stress and concomitant deflection of the PMCL. The group observed ~ 15 nm PMCL deflection on average, with a corresponding surface stress of approximately 4 mN/m. These experiments yield the sensor response in real-time and employ a combination of multiple PMCLs functionalized as either sensors or unfunctionalized to serve as references. Investigation of various attachment chemistries is included, as well as a comparison with and without passivation of non-sensor surfaces. Investigated passivation strategies prevented ligand binding from generating a differential surface stress. Failure modes and physical mechanisms for adsorption-induced surface stress are discussed. Immobilization and passivation strategies for antibody-based biosensing are demonstrated with fluorescence microscopy and a corresponding PMCL sensing experiment using rabbit anti-goat F(ab') fragments as the receptors and Alex Fluor 488 labeled goat anti-rabbit IgGs as the ligand. While the results of these experiments remain inconclusive, suggestions for future research involving the PMCL sensor array are recommended.
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Carroll, Andrew W. "Photodefinable and Conductive Polydimethylsiloxane (PDMS) for Low-Cost Prototyping of Microfluidic Systems." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1250719648.
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Forster, Simon. "Surface modification of PDMS-based microfluidic devices through plasma polymerisation : production and application." Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531221.
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Wong, Eehern J. "Modeling and control of rapid cure in polydimethylsiloxane (PDMS) for microfluidic device applications." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61615.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 147-151).
Polydimethylsiloxane (PDMS) is an important thermosetting elastomer for microfluidic devices because it can replicate nano-scale features and form flexible membranes useful for microactuation. PDMS is used extensively in research environments because it is readily available and biocompatible. However, the prototyping process is too slow for volume manufacturing. The dominant rate limiting step is curing, and high temperature cures used to speed the curing process have adverse effects on the shape of the parts produced. This thesis examines the PDMS cure process and presents a methodology to intelligently design faster cure processes without compromising the quality of parts produced. The first part of this thesis applies statistical mechanics to relate the time evolution of cure with the modulus of elasticity. This enables mechanical testing strategies to be used in situ to monitor the extent of cure, which is important to determine the critical gel point and quantify when the cure process is complete. The gel point describes when PDMS first transitions from a liquid to a solid, and is important for modeling shrinkage and warpage. A novel heated microindentation setup is designed to monitor curing of thin PDMS films, and experimentally validate the theory. The second part of this thesis presents a model for final PDMS shrinkage and warpage using the gel point. Gelation is spatially and temporally distributed, and temperature at the gel point has a direct impact on the shrinkage and warpage observed. The model is validated with experimental data. Since gel temperature is the only parameter to affect shrinkage and curvature, the cure process is accelerated after the gel point without affecting dimensional quality. Increasing the process temperature immediately following gelation is indeed shown to decrease the current cure process time by a factor of five, while maintaining comparable quality. Tolerances on shrinkage and curvature can be used with these models to determine the gel temperatures required, and design multi-temperature processes that speed the cure process.
by Eehern J. Wong.
Ph.D.
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Santos, Diógenes Meneses dos. "Microssistemas eletroforéticos em materiais poliméricos de duplo canal com detecção amperométrica." Universidade Federal de Alagoas, 2014. http://www.repositorio.ufal.br/handle/riufal/1919.
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Electrophoretic microsystems (EM) are powerful tools for the separation of species of microsystems analyzes which can easily be combined with electrochemical detection (ECD) and therefore making it ideal for a method of detection. However, the influence of high voltage at the working electrode used for the separation is a problem to be overcome due to the increased signal/noise ratio and possible damage of the electrode and/or the potentiostat. Thus, it was proposed in this thesis one EM hybrid PDMS / glass configuration with dual-channel potentiostat coupled to an electrically isolated in order to minimize the influence of high potential in the separation channel and improve the separation efficiency of the species and subsequently, improve detection limits. The EM contains two separate parallel channels 200 microns and a channel separation and another reference, and each containing a platinum electrode 15 or 50 μm placed about 1 to 4 μm in the channel. An electrode served as the working electrode, positioned in the separation channel, and another electrode as reference electrode, placed in the reference channel. This configuration associated with the electrically isolated potentiostat allowed the amperometric signals were measured without any change or potential interference arising from the high voltage applied separation. Aiming to evaluate the effectiveness of the methodology proposed in this thesis, samples nitrite, tyrosine and peroxynitrite (reactive nitrogen species – RNS), hydrogen peroxide (reactive oxygen species – ROS), ascorbic acid, glutathione and cysteine were injected into the channel containing the working electrode, while simultaneously boric acid buffer pH 11 containing TTAB was injected into the reference channel containing the reference electrode. From this configuration, we obtained a significant reduction in noise level (about 0.94 pA) and a relative improvement in the resolution ratified by electropherograms, compared with using single channel configuration. The limits of detection (LOD) for the chemical species mentioned above were 0.58 μM, 0.14 μM, 0.75 μM, 0.21 μM, 0.82 μM, was not obtained for cysteine and 1.63 μM, respectively. The efficiency can also be seen by analyzing nitrite performed on samples of perfusate blood of sheeps and rats, where have been detected a concentration of 68.05 μM and 22.04 μM, respectively, by the proposed method. It was also proposed in this thesis, microfabrication and evaluation of a PMMA electrophoretic microsystem with single channel configuration coupled to a base made of the same material to fix the microchip with electrochemical detection using a carbon paste electrode. The purpose of the construction of the base was to obtain, by fixing, reproducibility of events. And the microfabrication of PMMA EM aimed the viability of its use in analysis perspective as having the lowest cost per unit made due to the use of CO2 laser for microfabrication, which has a value considerably lower, compared with photolithographic processes. The evaluation of this system was performed through the analysis standards of serotonin and acetaminophen, which proved that the microfabrication of this system showed good reproducibility and repeatability of events, making it viable processing.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Os microssistemas eletroforéticos (MSE) são ferramentas poderosas para a separação de espécies em microssistemas de análises, onde pode ser facilmente combinada com detecção eletroquímica (DEQ) e tornando-se, portanto, um método de detecção ideal. No entanto, a influência da alta tensão no eletrodo de trabalho utilizada para a separação é um problema a ser contornado devido o aumento da relação sinal/ruído e possíveis danificações do eletrodo e/ou do potenciostato. Assim, foi proposto nesta tese um MSE híbrido de PDMS/vidro com configuração de duplo-canal acoplado a um potenciostato eletricamente isolado com objetivo de minimizar a influência do elevado potencial no canal de separação e melhorar a eficiência de separação das espécies e, subsequentemente, melhorar os limites de detecção. O MSE contém dois canais paralelos separados 200 μm, sendo um canal de separação e outro de referência, e cada um deles contendo um eletrodo de platina de 15 ou 50 μm colocados cerca de 1 a 4 μm dentro do canal. Um eletrodo serviu como eletrodo de trabalho, posicionado no canal de separação, e o outro eletrodo como eletrodo de referência, posicionado no canal de referência. Essa configuração associado ao potenciostato eletricamente isolado permitiu que os sinais amperométricos fossem medidos sem qualquer mudança de potencial ou de interferência oriunda da alta tensão de separação aplicada. Objetivando avaliar a eficiência da metodologia proposta nessa tese, amostras de nitrito e peroxinitrito (espécies reativas de nitrogênio – ERN), tirosina, peróxido de hidrogênio (espécie reativa de oxigênio – ERO), ácido ascórbico, glutationa e cisteína foram injetadas no canal contendo o eletrodo de trabalho, enquanto que simultaneamente o tampão de ácido bórico contendo TTAB pH 11 foi injetado no canal de referência contendo o eletrodo de referência. A partir desta configuração, obteve-se uma significativa diminuição no nível de ruído (cerca de 0,94 pA) e uma relativa melhora na resolução ratificadas pelos eletroferogramas, se comparado com a configuração que utiliza canal único. Os limites de detecção (LOD) para as espécies químicas supracitados foram de 0,58 μM, 0,14 μM, 0,75 μM, 0,21 μM, 0,82 μM, não foi obtida para a cisteína, e 1,63 μM, respectivamente. A eficiência também pode ser vista através das análises de nitrito realizadas em amostras de perfusato de sangue de ovelhas e ratos, onde foram detectados uma concentração de 68,05 μM e 22,04 μM, respectivamente, através da metodologia proposta. Foi proposto também nessa tese, a microfabricação e avaliação de um microssistema eletroforético de PMMA com configuração de canal único acoplado a uma base feita do mesmo material para fixar o microchip, com detecção eletroquímica usando eletrodo de pasta de carbono. O objetivo da construção da base foi obter, através da fixação, reprodutibilidade de eventos. E a microfabricação do MSE de PMMA objetivou a viabilidade do seu uso em análises tendo como perspectiva o baixo custo por unidade confeccionada devido ao uso de laser de CO2 para a microfabricação, o qual possui um valor agregado consideravelmente menor, se comparado com os processos fotolitográficos. A avaliação desse sistema foi feita através das análises de padrões de serotonina e acetaminofeno, onde comprovou-se que a microfabricação desse sistema apresentou boa reprodutibilidade e repetitividade de eventos, tornando-se viável o seu processamento.
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Nordh, Nicki. "Development of a cell cultureplatform in PDMS : Microfluidic systems for in vitro productionof platelets." Thesis, Uppsala universitet, Mikrosystemteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-261711.
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To be able to effectively study blood platelets in different environments adevelopment of an in vitro model of a microfluidic system for plateletproduction was started. The purpose of this thesis was to fabricate systemsand then characterize them and visualize the flow. The system consists of twochannels, one in the middle and the other one enclosing it. They are connectedthrough pores where Megakaryocytes can protrude through and produce platelets.The designs were produced in PDMS. This was done by first transfer the designsas structures onto a silicon wafer through UV lithography. The wafer served asa mould for casting PDMS that later was bonded to glass. The systems were thenstudied with three different methods. Computer simulations, flow tests andultimately tests with cells. From the results new designs were made andfabricated. The new designs were then tested the same ways as the first ones.The systems can most probably produce platelets with some optimisation of thetest parameters. No definite results were gathered to prove plateletproduction. Different flow speeds were tested and the flow profile atdifferent flow rates was visualised. The full capability of the new designscould not be fully studied due to unforeseen debris of PDMS clogging thechannels. A few things need to be done to achieve better results and establishfor sure if this method of producing platelets is possible. This thesis is agood ground for future work to stand on.
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Padilla, Scott T. "Novel Transducer Calibration and Simulation Verification of Polydimethylsiloxane (PDMS) Channels on Acoustic Microfluidic Devices." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6922.
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The work and results presented in this dissertation concern two complimentary studies that are rooted in surface acoustic waves and transducer study.
Surface acoustic wave devices are utilized in a variety of fields that span biomedical applications to radio wave transmitters and receivers. Of interest in this dissertation is the study of surface acoustic wave interaction with polydimethylsiloxane. This material, commonly known as PDMS, is widely used in the microfluidic field applications in order to create channels for fluid flow on the surface of a piezoelectric substrate. The size, and type of PDMS that is created and ultimately etched on the surface of the substrate, plays a significant role in its operation, chiefly in the insertion loss levels experienced. Here, through finite element analysis, via ANSYS® 15 Finite Element Modeling software, the insertion loss levels of varying PDMS sidewall channel dimensions, from two to eight millimeters is investigated. The simulation is modeled after previously published experimental data, and the results demonstrate a clear increase in insertion loss levels with an increase in channel sidewall dimensions. Analysis of the results further show that due to the viscoelastic nature of PDMS, there is a non -linear increase of insertion loss as the sidewall dimensions thicken. There is a calculated variation of 8.31 decibels between the insertion loss created in a microfluidic device with a PDMS channel sidewall thickness of eight millimeters verse a thickness of two millimeters. Finally, examination of the results show that insertion loss levels in a device are optimized when the PDMS sidewall channels are between two and four millimeters.
The second portion of this dissertation concerns the calibration of an ultrasonic transducer. This work is inspired by the need to properly quantify the signal generated by an ultrasonic transducer, placed under a static loading condition, that will be used in measuring ultrasonic bone conducted frequency perception of human subjects. Ultrasonic perception, classified as perception beyond the typical hearing limit of approximately 20 kHz, is a subject of great interest in audiology. Among other reasons, ultrasonic signal perception in humans is of interest because the mechanism by which either the brain or the ear interprets these signals is not entirely understood. Previous studies have utilized ultrasonic transducers in order to study this ultrasonic perception; however, the calibration methods taken, were either incomplete or did not properly account for the operation conditions of the transducers. A novel transducer calibration method is detailed in this dissertation that resolves this issue and provides a reliable means by which the signal that is being created can be compared to the perception of human subjects.
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To, Josiah. "Developing a novel heterogeneous three electrode system for a PDMS-based microfluidic electrochemical sensor." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/56174.
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Biosensors have seen an increased use in recent years as an in situ testing device for various industries such as agriculture, environmental sustainability, food, health, etc. On-site testing devices have an advantage over traditional testing system because they can be used for real-time monitoring and improving the accuracy of time-sensitive detection results. Out of all the industries, the health industry benefits most from in situ devices as point-of-care diagnostic devices. Point-of-care devices are useful tools to quickly diagnose diseases and direct patients’ course of treatment in low-income countries with few resources.
In 2014 there were approximately 9.6 million global cases of tuberculosis (TB) and 1.5 million deaths due to TB (caused by the infection of Mycobacterium Tuberculosis [MTB]). Globally, this made TB the second most common cause of death by an infection disease in 2014. With a rising incidence of multi drug-resistant and extensive drug-resistant TB, TB is again becoming a global issue that wealthy countries will likely be unable to ignore. Since transmission is commonly through airborne particulates, early diagnosis and correct treatment of TB are fundamental to not only preventing the spread of the disease, but also eradicating it.
Currently, the screening and detection tools that lower resource countries have are limited. Although the MTB genome has been sequenced since 1998, cost-effective, point-of-care, gene-based detection technology has had limited development. Since the integration of MEMS technology to biologically relevant needs in the late 90s there has been much development in creating small, portable detection systems for point-of-care use. Furthermore, this work details the development of a novel heterogeneous 3-material 3-electrode electrochemical sensor in a PDMS based bonded device. This sensor was developed with the intention of integration into a biosensor system.
The final 3-electrode system was composed of 3 different materials: Au counter electrode, carbon working electrode, and Ag/AgCl reference electrode. The 3 material 3-electrode system was tested as an electrochemical system by detection of aqueous 5 μM carminic acid in room temperature and post 65◦C heating conditions. Parallel work was done to develop a robust, leak-free bonding method that survived 65◦C heating conditions and preserved electrochemical functionality.Applied Science, Faculty of
Graduate
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Azizi, Farouk. "Microfluidic Chemical Signal Generation." Cleveland, Ohio : Case Western Reserve University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1244664596.
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Thesis(Ph.D.)--Case Western Reserve University, 2009Title from PDF (viewed on 2009-11-23) Department of Electrical Engineering Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center
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Herrera, Cristhiano da Costa. "Desenvolvimento e controle de circuitos microfluídicos." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-29012019-084425/.
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A primeira etapa do projeto foi realizar testes para usinagem controlada e otimizada de vidro ótico de borosilicato (BK7) por laser de femtossegundos. Parâmetros como energia, pulsos sobrepostos e a variação da posição focal foram investigados para controle da taxa de remoção do material e extensão da cratera ablacionada. Especial atenção foi dada à condição física e topográfica da superfície resultante da usinagem para torná-la menos rugosa e evitar a retenção de reagentes que possam contaminar e alterar as reações pretendidas. Microcanais, microválvulas, microbombas, misturadores, microrreatores, aquecedores e outros componentes foram desenvolvidos para compor sistemas microfluídicos. Os microcanais construídos sobre a superfície de vidro BK7 vedados por uma lâmina de polidimetilsiloxano (PDMS) são a base dos sistemas microfluídicos. O controle de fluxo de reagentes é feito por miniválvulas pneumáticas controladas por um microcontrolador Arduino através de uma plataforma Labview. Este trabalho mostra os componentes desenvolvidos e dois sistemas microfluídicos criados. O primeiro contém um circuito capaz de replicar ensaios imunoenzimáticos (ELISA) com um custo muito menor de insumos. O segundo é um sistema para a produção de nanocristais fluorescentes de NaYF4 especialmente utilizados como marcadores em imagens de sistemas biológicos.The first stage of the project was to perform tests for controlled and optimized machining of borosilicate optical glass (BK7) by femtosecond laser. Parameters such as energy, number of overlapped pulses, and the focal position variation were investigated for a better extraction of material. Microchannels, microvalves, micropumps, mixers, reactors, heaters and other components were developed to compose applied microfluidic systems. Microchannels built on the surface of BK7 glass sealed by a polydimethylsiloxane (PDMS) sheet form the basis of the microfluidic circuits. The reagents flow control is done by pneumatic mini-valves controlled by an Arduino microcontroller through a Labview platform. This work shows the components developed and two microfluidic systems created. The first contains a microfluidic circuit capable of replicating enzyme-linked immunosorbent assays (ELISA) with a much lower cost of materials. The second has a microfluidic circuit for the production of NaYF4 fluorescent nanocrystals specially used as markers in images of biologic systems.
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Cao, Hong Ha. "The fabrication process of microfluidic devices integrating microcoils for trapping magnetic nano particles for biological applications." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112150/document.
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Le but de cette étude est de concevoir, fabriquer et caractériser une puce microfluidique afin de mettre en oeuve la capture de nanoparticules magnétiques fonctionnalisées en vue de la reconnaissance d’anticorps spécifiques (couplage d’une très grande spécificité et sensibilité). Après avoir modélisé et simulé les performances de la microbobine intégrée dans le canal de la puce microfluidique en prenant soin de limiter la température du fluide à 37°C, la capture devant être effective, le microsystème est fabriqué en salle blanche en utilisant des procédés de fabrication collective. La fabrication du microdispositif en PDMS a aussi donné lieu à l’optimisation de procédés de modification de surface afin d’assurer la ré-utilisation du microdispositif (packaging réversible) et la limitation de l’adsorption non spécifique. L’immobilisation des anticorps su les billes (300 nm) a été menée à l’intérieur du canal en utilisant un protocole de type ELISA éprouvé. Le procédé a montré qu’il était également efficient pour cet environnement puisque nous avons pu mettre ne évidence la capture de nanoparticulesIn this study, a concept of microfluidic chip with embedded planar coils is designed and fabricated for the aim of trapping effectively functionalized magnetic nanobeads and immobilizing antibody (IgG type). The planar coils as a heart of microfluidic chip is designed with criterion parameters which are optimized from simulation parameters of the maximum magnetic field, low power consumption and high power efficiency by FE method. The characterization of microcoils such as effectively nanobeads (300 nm) at low temperature (<37oC) is performed and confirmed. The channel network in PDMS material is designed for matching with entire process (including mixing and trapping beads) in microfluidic chip. A process of PDMS’s surface modification is also carried out in the assemble step of chip in order to limit the non-specific adsorption of many bio substances on PDMS surface. The microfluidic chip assemble is performed by using some developed techniques of reversible packaging PDMS microfluidic chip (such as stamping technique, using non-adhesive layer, oxygen plasma combining with solvent treatment). These packaging methods are important to reused microchip (specially the bottom substrate) in many times. The immobilization of antibody IgG-type is performed inside microfluidic chip following the standard protocol of bead-based ELISA in micro test tube. The result showed that IgG antibodies are well grafted on the surface of carboxyl-beads (comparing to result of standard protocol); these grafted antibodies are confirmed by coupling them with labeled second antibody (Fab-FITC conjugation)
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Abram, Timothy J. "A PDMS Sample Pretreatment Device for the Optimization of Electrokinetic Manipulations of Blood Serum." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/172.
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This project encompasses the design of a pretreatment protocol for blood serum and adaption of that protocol to a microfluidic environment in order to optimize key sample characteristics, namely pH, conductivity, and viscosity, to enable on-chip electrokinetic separations. The two major parts of this project include (1) designing a pretreatment protocol to optimize key parameters of the sample solution within a target range and (2) designing /fabricating a microchip that will effectively combine the sample solution with the appropriate buffers to replicate the same bench-scale protocol on the micro-scale.
Biomarker detection in complex samples such as blood necessitates appropriate sample “pretreatment” in order for specific markers to be isolated through subsequent separations. This project, though using conventional mixing techniques and buffer solutions, is one of the first to observe the effects of the combination of micro-mixing and sample pretreatment in order to create an all-in-one “pretreatment chip”.
Using previous literature related to capillary electrophoresis, a bench-scale pretreatment protocol was developed to tune these parameters to an optimal range. A PDMS device was fabricated and used to combine raw sample with specific buffer solutions. Off-chip electrodes were used to induce electrokinetic micro-mixing in the mixing chamber, where homogeneous analyte mixing was achieved in less than one second using an 800V DC pulse wave. Ultimately, we wish to incorporate this device with pre-fabricated electrokinetic devices to optimize certain bioseparations.
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Viberg, Pernilla. "Development of non-adherent single cell culturing and analysis techniques on microfluidic devices." Diss., Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1441.
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Qin, Yubo. "Developing a Poly(Dimethylsiloxane) (PDMS)/SU-8 (Negative Photoresist) Hybrid Microfluidic System for Sensitive Detection of Circulating Tumour Cells." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37892.
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Cancer is the second leading cause of death in the world. It is therefore critically important to detect cancer in its early stage to significantly increase the survival rate of cancer patients. Circulating tumour cells (CTCs) are cancer cells that peel off from primary tumour and enter bloodstream in early stage of a cancer, and thus it has been established that these CTCs are reliable targets for early cancer diagnosis. However, background signal reduction and optimization of CTC capturing mechanisms are still significant challenges in CTC detections with high sensitivities and accuracies. To this end, we have developed an aptamers and dendrimers based ultra non-fouling microfluidic detection system for sensitive detections of circulating tumour cells.
More specifically, we demonstrate a simple strategy to bind PDMS and SU-8 surfaces in order to prepare a hybrid microfluidic device and subsequently modify both surfaces simultaneously using poly(amidoamine) (PAMAM), a highly hydrophilic dendrimer to improve non-fouling properties of the hybrid microfluidic channel. The resulting hybrid microfluidic system shows a remarkable non-specific adsorption suppression of 99.7% when tested with hydrophobic microbead suspension, an ultra non-fouling performance that has not been reported before. This is significantly important for detections with high sensitivities. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and water contact angle are used to characterize and confirm surface modifications. In addition, we investigate the combined effects of surface properties on surface non-fouling performance to both live and dead cells. (3-aminopropyl)-trimethoxysilane (APTMS), carboxyl functionalized PAMAM dendrimer (PAMAM-COOH) and amino functionalized PAMAM dendrimer (PAMAM-NH2) are used to provide different surfaces with various surface hydrophilicity, electric charge and roughness. We show that electric charge of a surface is the most important factor influencing non- specific adsorption of live cells to the surface while hydrophilicity/hydrophobicity of a surface is the most important factor for dead cells. Atomic force microscopy, water contact angle and microscopy are used to characterize and confirm surface modifications. To further exploit and improve capturing efficiency of target cancer cells, we investigate the effect of the length of spacers that tether capturing aptamer to the microfluidic surfaces on capturing performance of CCRF-CEM circulating tumour cells. Aptamers with different lengths of thymine base spacers are immobilized onto PAMAM dendrimer modified surfaces in microfluidic channels. We demonstrate that ten thymine bases spacer has the best length for sgc8 aptamer to form its secondary structure for CCRF-CEM cell capture. Water contact angle, and microscopy are used to characterize and confirm surface modifications. Taken together, the results of this study significantly highlight the importance of different considerations on surface modification and its optimizations when designing a microfluidic system for high sensitivity detection and biosensing applications.
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Slavík, Jan. "Analytické metody na mikrofluidním čipu." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220229.
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Riordon, Jason A. "Developing Microfluidic Volume Sensors for Cell Sorting and Cell Growth Monitoring." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30955.
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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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Tiller, Ben. "Surface acoustic wave streaming in a PDMS microfluidic system : effect of frequency and fluid geometry, &, A remote ultrasonic glucose sensor." Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7670/.
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This thesis describes two separate projects. The first is a theoretical and experimental investigation of surface acoustic wave streaming in microfluidics. The second is the development of a novel acoustic glucose sensor. A separate abstract is given for each here. Optimization of acoustic streaming in microfluidic channels by SAWs Surface Acoustic Waves, (SAWs) actuated on flat piezoelectric substrates constitute a convenient and versatile tool for microfluidic manipulation due to the easy and versatile interfacing with microfluidic droplets and channels. The acoustic streaming effect can be exploited to drive fast streaming and pumping of fluids in microchannels and droplets (Shilton et al. 2014; Schmid et al. 2011), as well as size dependant sorting of particles in centrifugal flows and vortices (Franke et al. 2009; Rogers et al. 2010). Although the theory describing acoustic streaming by SAWs is well understood, very little attention has been paid to the optimisation of SAW streaming by the correct selection of frequency. In this thesis a finite element simulation of the fluid streaming in a microfluidic chamber due to a SAW beam was constructed and verified against micro-PIV measurements of the fluid flow in a fabricated device. It was found that there is an optimum frequency that generates the fastest streaming dependent on the height and width of the chamber. It is hoped this will serve as a design tool for those who want to optimally match SAW frequency with a particular microfluidic design. An acoustic glucose sensor Diabetes mellitus is a disease characterised by an inability to properly regulate blood glucose levels. In order to keep glucose levels under control some diabetics require regular injections of insulin. Continuous monitoring of glucose has been demonstrated to improve the management of diabetes (Zick et al. 2007; Heinemann & DeVries 2014), however there is a low patient uptake of continuous glucose monitoring systems due to the invasive nature of the current technology (Ramchandani et al. 2011). In this thesis a novel way of monitoring glucose levels is proposed which would use ultrasonic waves to ‘read’ a subcutaneous glucose sensitive-implant, which is only minimally invasive. The implant is an acoustic analogy of a Bragg stack with a ‘defect’ layer that acts as the sensing layer. A numerical study was performed on how the physical changes in the sensing layer can be deduced by monitoring the reflection amplitude spectrum of ultrasonic waves reflected from the implant. Coupled modes between the skin and the sensing layer were found to be a potential source of error and drift in the measurement. It was found that by increasing the number of layers in the stack that this could be minimized. A laboratory proof of concept system was developed using a glucose sensitive hydrogel as the sensing layer. It was possible to monitor the changing thickness and speed of sound of the hydrogel due to physiological relevant changes in glucose concentration.
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Jeong, Seung Hee. "Soft Intelligence : Liquids Matter in Compliant Microsystems." Doctoral thesis, Uppsala universitet, Mikrosystemteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-281281.
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Soft matter, here, liquids and polymers, have adaptability to a surrounding geometry. They intrinsically have advantageous characteristics from a mechanical perspective, such as flowing and wetting on surrounding surfaces, giving compliant, conformal and deformable behavior. From the behavior of soft matter for heterogeneous surfaces, compliant structures can be engineered as embedded liquid microstructures or patterned liquid microsystems for emerging compliant microsystems. Recently, skin electronics and soft robotics have been initiated as potential applications that can provide soft interfaces and interactions for a human-machine interface. To meet the design parameters, developing soft material engineering aimed at tuning material properties and smart processing techniques proper to them are to be highly encouraged. As promising candidates, Ga-based liquid alloys and silicone-based elastomers have been widely applied to proof-of-concept compliant structures. In this thesis, the liquid alloy was employed as a soft and stretchable electrical and thermal conductor (resistor), interconnect and filler in an elastomer structure. Printing-based liquid alloy patterning techniques have been developed with a batch-type, parallel processing scheme. As a simple solution, tape transfer masking was combined with a liquid alloy spraying technique, which provides robust processability. Silicone elastomers could be tunable for multi-functional building blocks by liquid or liquid-like soft solid inclusions. The liquid alloy and a polymer additive were introduced to the silicone elastomer by a simple mixing process. Heterogeneous material microstructures in elastomer networks successfully changed mechanical, thermal and surface properties. To realize a compliant microsystem, these ideas have in practice been useful in designing and fabricating soft and stretchable systems. Many different designs of the microsystems have been fabricated with the developed techniques and materials, and successfully evaluated under dynamic conditions. The compliant microsystems work as basic components to build up a whole system with soft materials and a processing technology for our emerging society.
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Epshteyn, Alla. "Design and Fabrication of a Membrane Integrated Microfluidic Cell Culture Device Suitable for High-Resolution Imaging." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3517.
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Malaria remains a serious concern for people living and traveling to warm climates in Africa, Asia, and some parts of America. Understanding the mechanism of the malaria parasite in the liver phase could lead to important discoveries for preventative and treatment therapeutics before the disease develops into the blood stage. While in vitro liver cell culture models have been explored, a device that mimics the liver cell architecture with the capability of high-resolution imaging has never been created. In this research, a cell culture microfluidic device was designed and fabricated with a membrane integrated design to mimic the architecture of a liver, cell chamber dimensions affable for high-resolution imaging, and fluidic port design for optical access to both sides of the membrane for the study of malaria parasite invasion.
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Vargová, Alžběta. "Pokročilé membránové systémy." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2017. http://www.nusl.cz/ntk/nusl-316229.
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The diploma thesis deals with cellular membrane model preparation on microfluidic devices. It summarizes means of microfluidic device fabrication, phospholipid bilayer formation mechanisms, optimization techniques and characterization methods of those systems. It focuses on free-standing planar lipid bilayers which are easily accessible by a number of different characterization methods and at the same time exhibit good stability and variability. The aim of this work is to design and prepare a microfluidic chip on which a planar lipid bilayer can be prepared. It therefore presents microfluidic device prepared by soft lithography of PDMS adapted for model membrane formation by self-assembly of phospholipids at the interface of aqueous and organic phases created by the architecture of the microfluidic device. Formation of the model membrane was visualized by optical microscopy and fluorescence-lifetime imaging microscopy.