This study proposes a navel method for continuously particle sorting utilizing cascade squeeze jumping effect under microfluidic configuration. Microparticles with different sizes can be successfully separated at different stages of squeezing sheath flow. The method is based on that particles can not flow stably within a flow stream with the smaller stream width than their sizes. Big particles will jump from their original flow stream into the wider neighboring sheath flow. In this study, we have successfully designed and fabricated two kinds of particles/cells sorters using MEMS (Micro-electro-mechanical Systems) technology. The proposed microchip device includes a multi-stage sheath flow particles/cells sorter and an improved design of a cascade squeezed flow scheme. In the study, theoretical formulations, computer simulations and experimental operations are used to analyze the flow field in the microchip and evaluate the sorting performance of the devices. Results show the good sorting performance with cell recovery rate of 87.7% and yield rate of 94.1% can be obtained using the proposed micro particles/cells sorter. Furthermore, it is also important to continiously prepare reagents for in-column bio-chemical reactions. Therefore, this study presents a sheath-flow based microfluidic device for concentration fraction delivery of liquid samples. The simple and novel structure proposed in this study is able to prepare reagent with different concentration and is also easy to be integrated with other multifunctional microfluidic device. In order to demonstrate the feasibility and performance of the proposed concentration fraction delivery device, this study designs an integrated microchip device for in-line preparation of lysin reagent for cell lysis and an integrated T-form microfluidic mixer for demonstration of RBC lysis in the same microchip. Reagents for cell lysis are firstly prepared by the concentration faction delivery part of the chip. The prepared reagent is mixed with RBC sample downstream in the reaction channel using the T-form mixer. Results show a high RBC lysing rate of upto 100% in 10 mm downstream the T-junction can be achieved utilizing the proposed chip. In this study, we have successfully demonstrated three kinds of microfluidic device including a micro particles/cells sorter, a concentration fraction delivery device and a cell lysis reactor. Numerical analysis and experimental investigation confirm the proposed concepts and performance of the microfluidic devices. The contributions of the study are highly potential for developing a low-cost bioreactor system in the

The development of techniques targeting the manipulation of particles of different<p>sizes - mostly in the nano to millimeter scale - when dispersed in a carrier medium, is an increasingly important topic in many fields such as biotechnology,nanotechnology, medicine, biophysics and environmental monitoring and remediation. The underlying rationale for using such techniques stands in the sometimes compelling requirements of avoiding clogging as in micro/nano channel flows, of limiting sedimentation and wall interactions in particle/cell counting, of enhancing particle-surface interaction as in bio-sensing or of facilitating characterization and sorting as in bio-physical applications. Being developed in the frame of a Belgian national project devoted to the characterization and counting of pollutant in water media by digital holographic microscopy, this thesis tackles a peculiar class of particle manipulation techniques, commonly known as Focusing. The main goal of focusing is to avoid at best wall particle interactions and sedimentation, prevalent issues for dispersions owing in micro/mini-channels especially for applications such as optical characterization and counting.<p><p>The main attention was given to two flow focusing techniques - Hydrodynamic and Acoustic Focusing - for their wide range applicability and cost effectiveness. Hydrodynamic Focusing consists in controlling the position and spreading of the sample under investigation by means of a so-called sheath flow. A low-cost, nevertheless effective, prototype has been conceived, designed, manufactured and tested. It allowed for controlling the spreading of the sample stream and achieving a focusing ratio accounting for only 4% of the original stream width.<p><p>Acoustic Focusing takes advantage of the time-averaged pressure fields induced by the creation of standing waves in channels to manipulate and focus the dispersed particles. In the frame of this thesis, several devices have been developed using square cross section glass mini-channels. Aside from the cost-effectiveness, particles where focused in a somehow unexpected but high reproducible 3D matrix-like structure. A novel numerical model has also been implemented in order to study the conditions leading to the 3D structure formation. A good agreement between experimental and numerical results was found./Ce projet de thèse portant sur la manipulation de micro-particules dans des minicanaux s'inscrit dans le développement de cellules de flux pour des applications biologiques, qui est l'une des problématiques du projet HOLOFLOW, soutenu par<p>la région de Bruxelles Capitale. Les cellules de flux doivent permettre l'observation et la reconnaissance des micro-organismes vivants dans une large gamme de dimensions (de quelques microns à 1mm) avec la microscopie holographie digitale.<p>La problématique d'observation et de manipulation des microorganismes en flux est liée au clogging (bouchage) et à la sédimentation qui limitent la durée de vie des cellules d'observation. Ce projet de thèse s'inscrit dans cette problématique et propose deux axes d'étude pour limiter l'interaction entre organismes et canaux, la focalisation hydrodynamique, basée sur le guidage de flux, et la focalisation acoustique, basée sur la manipulation des particules.<p><p>La focalisation hydrodynamique est une technique basée sur l'injection différentiée de l'échantillon à observer et d'un fluide support. La différence des vitesses d'injection des flux permet de contrôler la dispersion des particules afin d'optimiser leur observation. Dans le cadre de cette thèse, un prototype à bas-coût a été développé et construit, permettant de focaliser les particules dans un faisceau jusqu'à 4% de leur faisceau incident.<p><p>La focalisation acoustique utilise la création d'une onde acoustique stationnaire afin de regrouper les particules en suspension au centre du canal. Au cours de cette thèse, plusieurs prototypes ont été réalisés, mettant en évidence la formation de motifs tridimensionnaux. Un model numérique a été spécialement développé afin d'étudier les conditions de génération de ces motifs, et de nombreuses expériences ont été menées afin de s'assurer de leur reproductibilité. Une bonne adéquation entre la position des particules mesurée et calculée numériquement a été démontrée. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished