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A microfluidic device for partial cell separation and deformability assessment

Pinho, D.; Yaginuma, Tomoko; Lima, R.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.92%
Blood flow in microcirculation shows several interesting phenomena that can be used to develop microfluidic devices for blood separation and analysis in continuous flow. In this study we present a novel continuous microfluidic device for partial extraction of red blood cells (RBCs) and subsequent measurement of RBC deformability. For this purpose, we use polydimethylsiloxane (PDMS) microchannels having different constrictions (25%, 50% and 75%) to investigate their effect on the cell-free layer (CFL) thickness and separation efficiency. By using a combination of image analysis techniques we are able to automatically measure the CFL width before and after an artificial constriction. The results suggest that the CFL width increases with enhancement of the constriction and contributes to partial cell separation. The subsequent measurements of RBCs deformation index reveal that the degree of deformation depends on the constriction geometries and hematocrit after the cell separation module. The proposed microfluidic device can be easily transformed into a simple, inexpensive and convenient clinical tool able to perform both RBC separation and deformability analysis in one single device. This would eliminate the need for external sample handling and thus reducing associated labor costs and potential human errors.

Visualization and measurement of red blood cells flowing in microfluidic devices

Rodrigues, Raquel; Pinho, Diana; Faustino, Vera; Yaginuma, T.; Bento, David; Fernandes, Carla S.; Garcia, Valdemar; Lima, R.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
36.92%
Several experimental techniques were performed in the past years using in vitro environments, in an attempt to not only understand the blood flow behaviour in microcirculation but also develop microfluidic devices as an alternative clinical methodology to detect blood diseases. Hence, the visualization and measurement of red blood cells (RBCs) flowing in a microfluidic device are important to provide not only essential information about hydrodynamic characteristics of the blood but also vital information to diagnose the initial symptoms of diseases during clinical investigations. For instance, RBC rigidity has been correlated with myocardial infarction, diabetes mellitus, hypertension, and also other haematological disorders and diseases that affect RBC deformation more directly, such as, hereditary spherocytosis, sickle cell anaemia and malaria. Regarding a better understanding of the RBCs deformation and motion, we present in this paper a compilation of studies made in our research group, using several microfluidic devices with different microchannel geometries and fabrication techniques (i.e., soft-lithography, xurography and hybrids) that focus in the shear and extensional flow behaviour, either in healthy or chemically stiffed RBCs.

Sistemas de microcanais em vidro para aplicações em microfluidica.; Glass microchannels systems for microfluidic applications.

Schianti, Juliana de Novais
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 27/05/2008 PT
Relevância na Pesquisa
36.92%
Neste trabalho são apresentados resultados relativos ao desenvolvimento de um processo de fabricação para a produção de sistemas de microcanais em vidro tipo borosilicato, 7059 Corning Glass. O objetivo do trabalho é implementar um processo básico, mas completo, de fabricação de sistemas microfluídicos em vidro, que possam futuramente ser aprimorados com a introdução de dispositivos ópticos e eletrônicos e de elementos microfluídicos ativos, como válvulas e microbombas, para sensoreamento e controle de fluxo. O processo de fabricação foi dividido em três grandes etapas, sendo a primeira delas, a produção dos microcanais, envolvendo processos como litografia e corrosão úmida. Nos estudos de corrosão procurou-se uma solução que permitisse a obtenção de canais com superfície uniforme e lisa, sem a produção de resíduos durante a corrosão do vidro. Os melhores resultados foram obtidos com a solução HF + HCl + H2O (1:2:3), com a possibilidade de produzir canais com até 150 µm de profundidade. A segunda etapa do processo de produção dos sistemas microfluídicos envolveu o encapsulamento dos microcanais, o que foi feito através de um processo de soldagem direta (vidro com vidro) à temperatura ambiente...

Desenvolvimento de um sistema voltametrico microfluidico; Development of a microfluidic voltammetric system

Mario Henrique Montazzolli Killner
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 25/10/2007 PT
Relevância na Pesquisa
36.83%
O presente trabalho descreve o desenvolvimento de um sistema voltametrico microfluidico, de um potenciostato de baixo custo e de um programa computacional para controle do potenciostato e aquisição de dados. O sistema voltamétrico microfluídico foi confeccionado empregando dois fotopolímeros, sendo um sólido e outro líquido. Foi também avaliado o uso de uma resina acrílica. Técnica de litografia utilizando radiação UVA foi empregada para a confecção dos protótipos. O fotopolímero líquido, a base de uretano-acrilato, apresentou as melhores características como flexibilidade, fácil manuseio e boa selagem dos canais analíticos. Estes canais foram confeccionados com largura de 600 mm e profundidade de 100 mm. O eletrodo de trabalho foi construido empregando um fio de platina de 75 mm de diâmetro e 1,5 mm de comprimento. Uma agulha de aço inox de 13 mm de comprimento e 0,45 mm de diametro foi empregada como eletrodo auxiliar e um fio de prata de 600 mm de diâmetro e 2,0 mm de comprimento recoberto com cloreto de prata foi utilizado na construção do eletrodo de referência. Os resultados de voltametria cíclica para soluções de diferentes concentrações de FeK4(CN)6 obtidos utilizando o sistema desenvolvido foram semelhantes aqueles obtidos empregando um potenciostato comercial. A determinação de Pb(II) em uma amostra certificada (452...

Produção de emulsões em dispositivos microfluídicos; Emulsion production in microfluidic devices

Davi Rocha Bernardes de Oliveira
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 07/04/2014 PT
Relevância na Pesquisa
36.83%
A emulsificação em dispositivos microfluídicos destaca-se pela sua capacidade em gerar gotas de maneira individual em um processo totalmente controlado. Através dele, é possível a obtenção de emulsões com coeficientes de variação de tamanho de gotas inferiores a 5%. Soluções de glicerol (fluidos Newtonianos) com concentrações variando entre 10 e 75% (m/m) foram utilizadas como fase dispersa para obtenção de emulsões água em óleo em microcanais planares com junções do tipo T e Y. Como fase contínua foi utilizado óleo de soja contendo 5% (m/m) de emulsificante PGPR. Como condições de processo, quatro diferentes razões entre as vazões das fases contínua e dispersa foram avaliadas. Paralelamente, quatro soluções de goma xantana (fluidos não-Newtonianos) com concentrações variando de 0,05 a 0,50% (m/m) foram avaliadas como fase dispersa num microcanal com junção em Y, e submetidas às mesmas condições das soluções de glicerol. Em todos os sistemas avaliados, a razão entre as fases foi o fator de maior influência no tamanho das gotas formadas. Em relação aos fluidos Newtonianos, a emulsificação no canal em T se mostrou menos sensível às propriedades físicas dos fluidos, enquanto na geometria em Y...

Produção de microgéis de goma gelana em dispositivos de microfluídica; Production of gellan gum microgels in microfluidic devices

Ana Letícia Rodrigues Costa
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 22/04/2015 PT
Relevância na Pesquisa
36.98%
A técnica de emulsificação em dispositivos de microfluídica é utilizada para a produção de gotas de diâmetro reduzido e distribuição de tamanho monodispersa. A gelificação da fase dispersa de emulsões água em óleo pode levar à formação de microgéis com elevado potencial para encapsulação de compostos ativos. Do ponto de vista tecnológico, a utilização de partículas de tamanho reduzido permite entrega mais fácil e liberação do bioativo de forma mais eficiente no local alvo. Este trabalho teve como objetivo estudar o processo de formação de microgéis de goma gelana em dispositivos de microfluídica utilizando a técnica de focalização hidrodinâmica. Foram avaliadas as concentrações da goma gelana de 0,5 a 0,7% (m/m) e do agente gelificante acetato de cálcio nas concentrações de 0,5 e 2,0% (m/m) para formação dos microgéis. Na primeira etapa, emulsões simples água em óleo, sendo a fase dispersa constituída de água ou dispersões aquosas de goma gelana e fase contínua constituída por uma mistura composta por óleo de soja e o emulsificante polirricinoleato de poliglicerol (PGPR), foram avaliadas quanto ao regime de formação de gotas em diferentes vazões das fases e razões entre as vazões das fases dispersa e contínua. Também foram determinadas as velocidades reais das fases dentro dos dispositivos de microfluídica e os números adimensionais de Reynolds...

Electrochemical detection of Pb and Cd in paper-based microfluidic devices

Shi,Jianjun; Tang,Fan; Xing,Honglong; Zheng,Huxiang; Lianhua,Bi; Wei,Wang
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
Relevância na Pesquisa
36.83%
Filter paper strips combined with screen-printed carbon electrodes (SPCE) were used in the assembly of a microfluidic device for detecting Pb(II) and Cd(II) in aqueous samples. The portable microfluidic device (with direct electrochemical detection) was tested for direct quantification of multiple analytes (Pb(II) and Cd(II)) in contaminated aqueous samples without pretreatment. Square wave anodic stripping voltammetric (SWASV) signal was greatly enhanced and displayed excellent analytical performance for Pb(II) and Cd(II) detection (from 0 to 100 ppb) with low limit of detection of 2.0 and 2.3 ppb, respectively. The proposed electrochemical devices also exhibited good selectivity and stability for analyses of real samples of gas dissolved salty soda water and ground water with physical contamination. The device is simple, low-cost, easy-to-fabricate and portable. This analytical device has the possibility of being useful for point-of-care applications in environmental monitoring, public health and food safety.

Environmentally responsive polymeric "intelligent" materials: the ideal components of non-mechanical valves that control flow in microfluidic systems

Ruben Morones-Ramirez,J.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2010 EN
Relevância na Pesquisa
37.07%
Miniaturization and commercialization of integrated microfluidic systems has had great success with the development of a wide variety of techniques in microfabrication, since they allowed their construction at a low cost and by following simple step-series procedures. However, one of the major challenges in the design of microfluidic systems is to achieve control of flow and delivery of different chemical reagents. This feature is especially important when using microfluidic systems in the development of cell culture systems, the construction of labs on a chip and the fabrication and design of chemical microreactors. Spatiotemporal control of the microenvironment in microfluidic devices has been only partially achieved by incorporating actuator parts (mechanical and non-mechanical) within these devices; nevertheless, recently there has been enormous progress due to advances in the materials sciences, and the development of novel polymeric "intelligent" materials. These materials have proved to be excellent candidates in the construction of non-mechanical actuators in the form of environmentally responsive valves. These valves can more efficiently control flows because these "intelligent" materials are capable of undergoing conformational changes and phase transitions in response to different local or external environmental stimuli; allowing them to turn the valves from "on" to "off". In addition...

An Analytical Solution on Convective and Diffusive Transport of Analyte in Laminar Flow of Microfluidic Slit

Chen, X.; Lam, Yee Cheong
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Artigo de Revista Científica Formato: 260412 bytes; application/pdf
EN_US
Relevância na Pesquisa
36.92%
Microfluidic devices could find applications in many areas, such as BioMEMs, miniature fuel cells and microfluidic cooling of electronic circuitry. One of the important considerations of microfluidic device in analytical and bioanalytical chemistry is the dispersion of solute. In this study, we have developed an analytical solution, which considers the axial dispersion of a solute along the flow direction, to simulate convection and diffusion transport in a pressure driven creeping flow for a rectangular shape slit. During flow, the balance of competing effects of diffusion (especially cross-section diffusion) and convective diffusion in the flow direction are investigated.; Singapore-MIT Alliance (SMA)

Non-linear mechanical behavior of polydimethylsiloxane (PDMS): application to the manufacture of microfluidic devices

Huang, Regina; Lele, Suvrat P.; Anand, Lallit
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Artigo de Revista Científica Formato: 49625 bytes; application/pdf
EN_US
Relevância na Pesquisa
37.12%
Soft-lithography is a low-cost and convenient microfabrication technique that is becoming increasingly popular in the manufacture of microfluidic devices. A typical elastomer used in soft-lithography is polydimethylsiloxane (PDMS), an organic polymer that is commercially available, inexpensive, optically transparent, permeable to gases, and nontoxic. For soft-lithography to become a viable microfabrication technique for the commercial manufacture of microfluidic devices, several issues concerning the mechanical behavior of this material must be considered and addressed. We are currently working on the following materials-related issues that are critical to the development of this process for mass production:
•Multilayer microfluidic devices are made by layering thin films having alternating ratios of monomer to curing agent, in order to facilitate bonding between the layers. Common mixing ratios of monomer to curing agent are 5:1, 10:1, and 20:1. Characterization of the mechanical behavior of these materials with different compositions is necessary in the design of these devices. We have conducted uniaxial tension tests at the macroscale and found that the monomer-to-curing agent ratio contributes significantly to the non-linear stress-strain behavior of PDMS (see adjoining figure). We are working on uniaxial tension tests on microscale specimens which are approximately 10 µm thick and have a gauge width of 1 mm; this smaller scale is representative of actual dimensions in microfluidic devices.
•The fabrication of microfluidic devices involves curing the mixture of PDMS monomer and curing agent on a mold. Currently...

Desenvolvimento de dispositivos microfluídicos de papel com superfície quimicamente modificada para ensaios clínicos utilizando detecção colorimétrica; Development of microfluidic paper-based devices with chemically modified surface for clinical assays using colorimetric detection

Garcia, Paulo de Tarso
Fonte: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Química (IQ); Instituto de Química - IQ (RG) Publicador: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Química (IQ); Instituto de Química - IQ (RG)
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
36.83%
This report describes the development of microfluidic paper-based analytical devices (μPADs) with chemically modified surface for clinical assays with colorimetric detection. The μPADs were fabricated by a stamping-based method with a heated metal stamp for obtain hydrophobic barriers of paraffin in paper. Before of the stamp step, the paper was oxidized to promote the conversion of hydroxyl groups in aldehyde groups for further chemical activation for the immobilization of enzymes. The μPADs were used for complexometric assays of nitrite and bovine serum albumin (BSA) and enzymatic assays of glucose and uric acid (UA). The chemical modification did provide better color uniformity inside of the detection zones of the enzymatic bioassays. After the chemical modification, the relative standard deviation (RSD) values for glucose and UA assays decreased from 40 to 10% and from 20 to 8%, respectively. Clinical assays for glucose, UA, nitrite and BSA were performed in levels which included the clinical range for each bioassay. We performed quantitative analysis of all analytes in artificial urine sample with error values ranged from 2,5 to 4,0%. The robustness tests proved the stability of the chemical modification process and the thermal stability of the μPADs when stored at different temperatures...

Integration of enzyme immobilised single-walled carbon nanotube arrays into microfluidic devices for glucose detection

Yu, J.; Le Roux, R.; Gu, Y.; Yunus, K.; Matthews, S.; Shapter, J.; Fisher, A.
Fonte: IEEE; Online Publicador: IEEE; Online
Tipo: Conference paper
Publicado em //2008 EN
Relevância na Pesquisa
36.92%
Microfluidic devices for glucose detection have been constructed and developed by integration of glucose oxidase covalently immobilised single-walled carbon nanotube arrays into a poly (dimethylsiloxane)-based microfluidic channel. This microfluidic device was tested for electrochemical glucose detection, and the results showed that the glucose can be detected with a linear response up to a concentration of 5times10-3 mol L-1. Because of the small amounts of fluids and enzyme used in microchannels, this approach offers a number of technical advantages, such as portability, shorter analysis time and lower consumption of expensive analytes.; Jingxian Yu, Rudolph Le Roux, Yunfeng Gu, Kamran Yunus, Sinéad Matthews, Joe G. Shapter and Adrian C. Fisher

High-sensitivity metamaterial-inspired sensor for microfluidic dielectric characterization

Ebrahimi, A.; Withayachumnankul, W.; Al-Sarawi, S.; Abbott, D.
Fonte: The Institute of Electrical and Electronic Engineers Inc. Publicador: The Institute of Electrical and Electronic Engineers Inc.
Tipo: Artigo de Revista Científica
Publicado em //2014 EN
Relevância na Pesquisa
36.98%
A new metamaterial-inspired microwave microfluidic sensor is proposed in this paper. The main part of the device is a microstrip coupled complementary split-ring resonator (CSRR). At resonance, a strong electric field will be established along the sides of CSRR producing a very sensitive area to a change in the nearby dielectric material. A micro-channel is positioned over this area for microfluidic sensing. The liquid sample flowing inside the channel modifies the resonance frequency and peak attenuation of the CSRR resonance. The dielectric properties of the liquid sample can be estimated by establishing an empirical relation between the resonance characteristics and the sample complex permittivity. The designed microfluidic sensor requires a very small amount of sample for testing since the cross-sectional area of the sensing channel is over five orders of magnitude smaller than the square of the wavelength. The proposed microfluidic sensing concept is compatible with lab-on-a-chip platforms owing to its compactness.; Amir Ebrahimi, Withawat Withayachumnankul, Said Al-Sarawi and Derek Abbott

Microfluidic Plastic Devices for Single-use Applications in High-Throughput Screening and DNA-Analysis

Gerlach, Andreas; Knebel, Günther; Guber, A. E.; Heckele, M.; Herrmann, D.; Muslija, A.; Schaller, T.
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Sonstiges
EN
Relevância na Pesquisa
37.03%
Microfluidic devices fabricated by mass production offer an immense potential of applications such as high-throughput drug screening, clinical diagnostics and gene analysis [1]. The low unit production costs of plastic substrates make it possible to produce single-use devices, eliminating the need for cleaning and reuse [2]. Fabrication of microfluidic devices can be applied by microtechnical fabrication processes in combination with plastic molding techniques [3]. Basically, replication in plastics requires a hot embossing or injection molding tool. Various microfabrication technologies for the masterfabrication are established, such as the LIGA technique, mechanical micromachining and the micro electrical discharge machining technique (µEDM). Depending on the specific requirements, the most suitable process can be selected. The availability of these technologies allows to generate robust metal molding tools which exhibit the inverse shapes of the intended microstructures. In close collaboration, Greiner Labortechnik and Forschungszentrum Karlsruhe have fabricated prototype single-use plastic microfluidic devices in a standard microplate format by hot embossing with a mechanical micromachined molding tool and subsequent sealing of the microchannels. The microfluidic lab-on-chip structures are compatible with existing plate and liquid handling robotics. Sub-microliter sample volumes can be applied in the 96-channel multiplexed microstructures. Additionally...

ELECTROKINETIC SEPARATIONS ON MICROFLUIDIC DEVICES FOR N-GLYCAN PROFILING

Zhuang, Zexi
Fonte: [Bloomington, Ind.] : Indiana University Publicador: [Bloomington, Ind.] : Indiana University
Tipo: Doctoral Dissertation
EN
Relevância na Pesquisa
36.98%
Thesis (Ph.D.) - Indiana University, Chemistry, 2010; Microfluidic devices have been employed for various chromatographic and electrophoretic separations of biomolecules. However, the inherent complexity of analyzing real biological samples requires faster and more efficient separation techniques. N-glycans are essential molecules in many living systems and may become important biomarkers for cancer and other diseases in humans. In this work, we developed several microfluidic platforms for separation and analysis of N-glycans. On microfluidic devices, channels with high separation efficiencies can be incorporated while maintaining a small footprint. However, incorporating turns with small radii of curvature can cause significant band broadening. We explored two options to minimize the turn-induced band broadening: a spiral channel with a large radius of curvature and serpentine channels with asymetrically tapered turns. The latter serpentine design offers a more compact footprint than the spiral design. Using separation lengths of ~20 cm and electric field strengths up to 1500 V/cm, analysis times were less than 1.2 min, and separation efficiencies were between 500,000 and 655,000 plates for the N-glycans. These high efficiencies are necessary to separate structural isomers that exist in these samples. A direct comparison between microchip and capillary electrophoresis demonstrated the separation performance on microchips was as good as or better than on capillaries. Statistical analysis of the glycan profiles derived from blood serum samples revealed differences between healthy individuals and cancer patients...

Low cost microfluidic device for partial cell separation: micromilling approach

Lopes, Raquel; Rodrigues, Raquel O.; Pinho, Diana; Valdemar, Garcia; Schutte, Helmut; Lima, Rui; Gassmann, Stefan
Fonte: IEEE Publicador: IEEE
Tipo: Conferência ou Objeto de Conferência
POR
Relevância na Pesquisa
36.92%
Several studies have already demonstrated that it is possible to perform blood flow studies in microfluidic systems fabricated by using low-cost techniques. However, most of these techniques do not produce microchannels smaller than 100 microns and as a result they have several limitations related to blood cell separation. Recently, manufacturers have been able to produce milling tools smaller than 100 microns, which consequently have promoted the ability of micromilling machines to fabricate microfluidic devices able to perform separation of red blood cells (RBCs) from plasma. In this work, we show the ability of a micromilling machine to manufacture microchannels with dimensions down to 30 microns. Additionally, we show for the first time the ability of the proposed microfluidic device to enhance the cell-free layer close to the walls, leading to perform partial separation of RBCs from plasma.

Effects of surfactants on the formation of microdroplets in the flow focusing microfluidic device

Wu, Nan; Zhu, Yonghau; Leech, P W; Sexton, B A; Brown, Sue; Easton, Christopher
Fonte: SPIE Publicador: SPIE
Tipo: Conference paper
Relevância na Pesquisa
36.83%
Droplet-based in vitro compartmentalization (IVC) platform is a powerful tool in protein analysis. Reliable formation of microdroplets is important for the development of the microfluidic chip. In this study, we will examine the effect of surfactants on t

Optimization, Testing and Design-for-Testability of Flow-Based Microfluidic Biochips

Hu, Kai
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Relevância na Pesquisa
37.14%

Flow-based microfluidic biochips constitute an emerging technology for the automation of biochemical procedures. Recent advances in fabrication techniques have enabled the development of these devices. Increasing integration levels provide biochips with tremendous potential; a large number of bioassays, i.e., protocols for biochemistry, can be processed independently, simultaneously, and automatically on a coin-sized microfluidic platform. However, the increases in integration level introduce new challenges in the design optimization and the testing of these devices, which impede their further adoption and deployment.

This thesis is focused on enhancing the automated design and use of flow-based microfluidic biochips and on developing a set of solutions to facilitate the full exploitation of design complexities that are possible with current fabrication techniques. Four key research challenges are addressed in the thesis; these include design automation, wash optimization, testing, and defect diagnosis.

Despite the increase in the number of on-chip valves, designers are still using full-custom methodologies involving many manual steps to implement these chips. Since these chips can easily have thousands of valves, manual design procedure can be time-consuming and error-prone...

Analysis of Tandem Bubble Interaction and Jet Formation in a Microfluidic Channel

Yang, Chen
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Tese de Doutorado
Publicado em //2013
Relevância na Pesquisa
36.83%

Tandem bubble interactions have been shown to produce jets that can be used to create membrane poration on single cells, and jet speed has been implicated as a critical parameter for tandem bubble-induced bioeffects. In this thesis, the dynamics of single and tandem bubbles in a microfluidic channel (25 × 800 μm in height and width) are investigated to access the effects of bubble size on tandem bubble interaction and resultant jet. Experimentally, the dynamics of bubble oscillation produced by laser irradiation of a gold dot (15 nm thick and 6 μm in diameter) coated on the glass substrate of the microfluidic channel are captured by a high-speed camera, from which the time history of bubble size and jet speed are determined. Numerically, the bubble dynamics are simulated using 3DynaFS-BEM (DYNAFLOW, INC.) based on a potential flow model solved by boundary element method (BEM). By adjusting the initial conditions in the BEM code, the dynamics of laser-generated single bubbles of different sizes were matched with experimental results. The model was subsequently used to simulate the tandem bubble interactions in anti-phase oscillation. The results show that jet shape and volume are predominately controlled by the maximum diameter of the first bubble (D1) while jet speed is linearly correlated with the maximum diameter of the second bubble (D2). In comparison...

Optimization of Conditions for Endothelial Seeding of Microfluidic Devices with Long Branching Networks and Small Channel Dimensions

Zhao, Kevin
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Tese de Doutorado
Publicado em //2013
Relevância na Pesquisa
36.98%

Many hematologic diseases may have interactions with proteins and endothelium within small microvascular environments that are currently hard to understand. These effects are hard to produce in vitro, and relevant studies performed in vivo are difficult to image and evaluate at high resolutions. In order to better understand these phenomena, in vitro models with optically clear material should be developed that act as platforms for higher power imaging and analysis. Microfluidic devices made out of polydimethylsiloxane (PDMS) bonded to glass provide this platform and are capable of generating channels of long length (>2.5 cm from inlet to outlet) and of microvascular size (<30 microns). However, current methods of seeding endothelial cells into devices of such dimensions have proven to be very difficult to perform.

One goal of this thesis is to develop a new and reproducible method of seeding endothelial cells into microfluidic devices of many branching networks and small channel dimensions. To examine conditions that lead to optimal seeding, we fabricated a microfluidic device that contains five sets of binary diverging junctions; starting from an inlet of 1000x30 micron dimensions, the flow path splits into a total of 32 small channels of 20x30 micron dimensions. The total distance from inlet to outlet is 3 cm and each channel length is 0.4 cm. We found that traditional flow-in seeding methods are not very effective for long channel networks in which the smallest size is 20x30 microns or less...