Computational Fluid Dynamics Modeling of Two-Dimensional and Three-Dimensional Segmented Flow in Microfluidic Chips

Microfluidics is a rapidly growing topic of interest for scientists, engineers, and medical researchers. The micrometer length scale constrains flow to a laminar behavior, allowing for a more predictable system. High-throughput experimentation is possible with laminar multiphase flow, specifically microdroplets. Manipulating microdroplets by generating, splitting, separating, and fusing provides a versatile environment for analysis in a variety of biological and chemical systems. The process of design, fabrication, and testing of microfluidic systems is an iterative and tedious procedure. The purpose of this research was to utilize computational fluid dynamics software to expedite the fabrication and design process by simulating time-dependent data as droplets flow through a channel. The two-dimensional segmented flow investigated the effect of droplet generation by inspecting three different nozzle widths combined with four different post nozzle designs. Droplets were successfully generated in all nozzle widths and all post nozzle geometries, but certain nozzle and post nozzle geometries were found to be a more efficient combination. The three-dimensional project analyzes droplet generation and merging in a pillar induced merging chamber. Multiple droplets successfully merged in the three-dimensional analysis

Design and implementation of microfluidic chip to study chemotactic migration of cancer cells

Chemotactic movement in response to drug candidates is one of the leading tangible indicators of cell's state, which has widely spread in biomedical fields ranging from normal wound healing to metastatic migration of cancer cells. To facilitate its development, a microfluidic chemotaxis chip has been designed and implemented on top of dynamic cell culture. Different from static chip confining itself to inadequate cellular functions, the microfluidic chemotaxis chip provides a more versatile alternative to enable a better compatible experimental condition forming. A soft lithography-based method is used to prepare chips from polydimethylsiloxane (PDMS), which is a favourable material for manufacturing microfluidic devices. The competitive features of the chemotactic chip include a wide range of controllable flow rates, higher levels of automation, economic feasibility based on the small usage amount of material in microscale, to name but a few. In the chemotactic chip, the mixing efficiency between two inflowing liquids is finely controlled by a syringe or pressure-based pump, resulting in a chemotactic gradient that can be manipulated by adjusting the flow rate. The chip model that applied in the experiments is simulated by COMSOL Multiphysics®, which is a dominated fluidic simulation software. The final selections, such as flow rate, design, and dimension of the chip are contingent on the simulation results and empirical considerations. Finally, the chip with fluorescein isothiocyanate (FITC) is validated under the microscope. And the experimental data is analysed in comparison to the theoretical data computed from the simulation

Computational methods and software for the design of inertial microfluidic flow sculpting devices

The ability to sculpt inertially flowing fluid via bluff body obstacles has enormous promise for applications in bioengineering, chemistry, and manufacturing within microfluidic devices. However, the computational difficulty inherent to full scale 3-dimensional fluid flow simulations makes designing and optimizing such systems tedious, costly, and generally tasked to computational experts with access to high performance resources. The goal of this work is to construct efficient models for the design of inertial microfluidic flow sculpting devices, and implement these models in freely available, user-friendly software for the broader microfluidics community. Two software packages were developed to accomplish this: uFlow and FlowSculpt . uFlow solves the forward problem in flow sculpting, that of predicting the net deformation from an arbitrary sequence of obstacles (pillars), and includes estimations of transverse mass diffusion and particles formed by optical lithography. FlowSculpt solves the more difficult inverse problem in flow sculpting, which is to design a flow sculpting device which produces a target flow shape. Each piece of software uses efficient, experimentally validated forward models developed within this work, which are applied to deep learning techniques to explore other routes to solving the inverse problem. The models are also highly modular, capable of incorporating new microfluidic components and flow physics to the design process. It is anticipated that the microfluidics community will integrate the tools developed here into their own research, and bring new designs, components, and applications to the inertial flow sculpting platform

Numerical and experimental analysis on microbubble generation and multiphase mixing in novel microfluidic devices

In this study, a novel K-junction microfluidic junction and a conventional cross-junction were investigated numerically and experimentally for microbubble generation and multiple fluids mixing. In the K-junction, liquid solutions were injected into the junction via three liquid inlet channels, along with inert nitrogen gas supplied via the gas inlet channel, to periodically generate microbubbles in a controlled manner at the outlet channel. Numerical simulations based on Finite Volume method and Volume of Fluid (VOF) technique and experiments of both the K-junction and the cross-junction were conducted. The effect of parameters such as contact angle, surface tension, viscosity, gas pressure and gas-liquid flow ratios on the microbubble size distribution was investigated. The process of microbubble generation, obtained through high speed camera imaging and the numerical simulation, has shown good agreement in both junctions as well as the influence of viscosity and gas-liquid flow ratios for the K-junction and cross-junction. It was indicated that parameters like solution viscosities, gas-to-liquid flow ratios, gas inlet pressure, and their combination have a significant influence on the microbubble diameter, which was found to be in the range of 70-240 µm when using micro capillaries of 100 µm inner diameter. The multiple fluids mixing study was investigated by using two or three different polymer solutions for the cross-junction and the K-junction respectively in simulations and experiments. It can be seen that the mixing process obtained from simulations agrees well with experimental results and chaotic mixing was found in the mixing area of the K-junction, with higher mixing efficiency than the cross junction. Fluorescent images of microbubbles generated by using polymer solutions with dyes inside have shown the devices’ potential of encapsulating fluorescent dyes and polymers on the shell of bubbles and could be adopted as a method to encapsulate active pharmaceutical ingredients for potential applications in drug delivery

Glioma on Chips Analysis of glioma cell guidance and interaction in microfluidic-controlled microenvironment enabled by machine learning

In biosystems, chemical and physical fields established by gradients guide cell migration, which is a fundamental phenomenon underlying physiological and pathophysiological processes such as development, morphogenesis, wound healing, and cancer metastasis. Cells in the supportive tissue of the brain, glia, are electrically stimulated by the local field potentials from neuronal activities. How the electric field may influence glial cells is yet fully understood. Furthermore, the cancer of glia, glioma, is not only the most common type of brain cancer, but the high-grade form of it (glioblastoma) is particularly aggressive with cells migrating into the surrounding tissues (infiltration) and contribute to poor prognosis. In this thesis, I investigate how electric fields in the microenvironment can affect the migration of glioblastoma cells using a versatile microsystem I have developed. I employ a hybrid microfluidic design to combine poly(methylmethacrylate) (PMMA) and poly(dimethylsiloxane) (PDMS), two of the most common materials for microfluidic fabrication. The advantages of the two materials can be complemented while disadvantages can be mitigated. The hybrid microfluidics have advantages such as versatile 3D layouts in PMMA, high dimensional accuracy in PDMS, and rapid prototype turnaround by facile bonding between PMMA and PDMS using a dual-energy double sided tape. To accurately analyze label-free cell migration, a machine learning software, Usiigaci, is developed to automatically segment, track, and analyze single cell movement and morphological changes under phase contrast microscopy. The hybrid microfluidic chip is then used to study the migration of glioblastoma cell models, T98G and U-251MG, in electric field (electrotaxis). The influence of extracellular matrix and chemical ligands on glioblastoma electrotaxis are investigated. I further test if voltage-gated calcium channels are involved in glioblastoma electrotaxis. The electrotaxes of glioblastoma cells are found to require optimal laminin extracellular matrices and depend on different types of voltage-gated calcium channels, voltage-gated potassium channels, and sodium transporters. A reversiblysealed hybrid microfluidic chip is developed to study how electric field and laminar shear can condition confluent endothelial cells and if the biomimetic conditions affect glioma cell adhesion to them. It is found that glioma/endothelial adhesion is mediated by the Ang1/Tie2 signaling axis and adhesion of glioma is slightly increased to endothelial cells conditioned with shear flow and moderate electric field. In conclusion, robust and versatile hybrid microsystems are employed for studying glioma biology with emphasis on cell migration. The hybrid microfluidic tools can enable us to elucidate fundamental mechanisms in the field of the tumor biology and regenerative medicine.Okinawa Institute of Science and Technology Graduate Universit

Establishment of a fully automatized microfluidic platform for the screening and characterization of novel Hepatitis B virus capsid assembly modulators

El procés de descobriment de fàrmacs s'enfronta a importants desafiaments a causa de la constant disminució dels guanys per medicament atesa la disminució en les noves aprovacions de la FDA combinada amb el constant augment dels costos i el temps de desenvolupament. Les plataformes integrades de detecció usant microfluídica van sorgir com a possibles solucions per accelerar el desenvolupament de molècules actives i reduir els requisits de temps i costos. El projecte VIRO-FLOW té com a objectiu identificar nous agents curatius per al virus de l'hepatitis B (VHB), integrant els avantatges de la química de flux continu amb tecnologies de bioassaigs in vitro en microfluídica. Durant aquesta tesi es va construir un sistema microfluídic aplicant dispositius modulars automatitzats. Es van redactar protocols d'avaluació per a les dades de fluorescència i reflexió, permetent el càlcul del factor Z, les desviacions estàndard, les corbes de dilució i els valors de concentracions efectives mitjanes màximes (EC50). La proteïna central del VHB (HBc) es va seleccionar com a objectiu principalEl proceso de descubrimiento de fármacos se enfrenta a importantes desafíos debido a la constante disminución de las ganancias por medicamento dada la disminución en las nuevas aprobaciones de la FDA combinada con el constante aumento de los costes y el tiempo de desarrollo. Las plataformas integradas de detección usando microfluídica surgieron como posibles soluciones para acelerar el desarrollo de moléculas activas y reducir los requisitos de tiempo y costes. El proyecto VIRO-FLOW tiene como objetivo la identificación de nuevos agentes curativos para el virus de la hepatitis B (VHB), integrando las ventajas de la química de flujo continuo con tecnologías de bioensayos in vitro en microfluídica. Durante la presente tesis se construyó un sistema microfluídico aplicando dispositivos modulares automatizados. Se redactaron protocolos de evaluación para los datos de fluorescencia y reflexión, permitiendo el cálculo del factor Z, desviaciones estándar, curvas de dilución y valores de concentraciones efectivas medias máximas (EC50). La proteína central del VHB (HBc) se seleccionó como objetivo principal.Drug Discovery as known today faces major challenges due to the constant decrease of earnings per drug given the decrease in new FDA approvements combined with the steadily rising development costs and time. Integrated microfluidic screening platforms emerged as possible solutions by accelerating the hit-to-lead development cycle and reducing time and cost requirements. The VIRO-FLOW project aims at the fast and efficient identification of novel curative agents for the Hepatitis B Virus (HBV), integrating the advantages of continuous flow chemistry with in vitro microfluidic bioassay technologies. During the present thesis a microfluidic system was built, applying automatized modular devices. Evaluation protocols were written for the fluorescence and reflection data, allowing the Z´-factor calculation, standard deviations, dilution curves, and half‐maximal effective concentrations (EC50) values. HBV core protein (HBc) was selected as primary target due to the ongoing demand for a functional cure to reduce the economic and social challenges imposed by the chronic diseas

Analysis, Design and Fabrication of Micromixers

This book includes an editorial and 12 research papers on micromixers collected from the Special Issue published in Micromachines. The topics of the papers are focused on the design of micromixers, their fabrication, and their analysis. Some of them proposed novel micromixer designs. Most of them deal with passive micromixers, but two papers report studies on electrokinetic micromixers. Fully three-dimensional (3D) micromixers were investigated in some cases. One of the papers applied optimization techniques to the design of a 3D micromixer. A review paper is also included and reports a review of recently developed passive micromixers and a comparative analysis of 10 typical micromixers

Microparticle image processing and field profile optimisation for automated Lab-On-Chip magnetophoretic analytical systems

The work described in this thesis, concerns developments to analytical microfluidic Lab-On-Chip platform originally developed by Prof Pamme's research group at the University of Hull. This work aims to move away from traditional laboratory analysis system towards a more effective system design which is fully automated and therefore potentially deployable in applications such as point of care medical diagnosis. The microfluidic chip platform comprises an external permanent magnet and chip with multiple parallel reagent streams through which magnetic micro-particles pass in sequence. These streams may include particles, analyte, fluorescent labels and wash solutions; together they facilitate an on-chip multi-step analytical procedure. Analyte concentration is measured via florescent intensity of the exiting micro-particles. This has previously been experimentally proven for more than one analytical procedure. The work described here has addressed a couple of issues which needed improvement, specifically optimizing the magnetic field and automating the measurement process. These topics are related by the fact that an optimal field will reduce anomalies such as aggregated particles which may degrade automated measurements.For this system, the optimal magnetic field is homogeneous gradient of sufficient strength to pull the particles across the width of the device during fluid transit of its length. To optimise the magnetic field, COMSOL (a Multiphysics simulation program) was used to evaluate a number of multiple magnet configurations and demonstrate an improved field profile. The simulation approach was validated against experimental data for the original single-magnet design.To analyse the results automatically, a software tool has been developed using C++ which takes image files generated during an experiment and outputs a calibration curve or specific measurement result. The process involves detection of the particles (using image segmentation) and object tracking. The intensity measurement follows the same procedure as the original manual approach, facilitating comparison, but also includes analysis of particle motion behaviour to allow automatic rejection of data from anomalous particles (e.g. stuck particles). For image segmentation a novel texture based technique called Temporal- Adaptive Median Binary Pattern (T-AMBP) combining with Three Frame Difference method to model the background for representing the foreground was proposed. This proposed approached is based on previously developed Adaptive Median Binary Pattern (AMBP) and Gaussian Mixture Model (GMM) approach for image segmentation. The proposed method successfully detects micro-particles even when they have very low fluorescent intensity, while most of the previous approaches failed and is more robust to noise and artefacts. For tracking the micro-particles, we proposed a novel algorithm called "Hybrid Meanshift", which combines Meanshift, Histogram of oriented gradients (HOG) matching and optical flow techniques. Kalman filter was also combined with it to make the tracking robust.The processing of an experimental data set for generating a calibration curve, getting effectively the same results in less than 5 minutes was demonstrated, without needing experimental experience, compared with at least 2 hours work by an experienced experimenter using the manual approach