Development of flow focusing device for the visualization of leukocyte rolling adhesion

La microfluídica es un área de la microtecnología basada en chips de PDMS que está siendo utilizada cada vez más en multitud de aplicaciones. Una de estas aplicaciones es la investigación biomédica. La microfluídica o “Lab on a Chip” se ha convertido en una manera de realizar experimentos biomédicos y diagnósticos de una manera barata, rápida y eficaz. Cuando se realizan estudios sobre la extravasación leucocitaria utilizando chips microfluídicos, podemos observar la inconsistencia en la trayectoria de rodadura de los leucocitos debido a un flujo laminar. En este trabajo de fin de grado presentamos un método para centrar la interfaz de células en el centro de canal microfluídico. Cuando las células circulan por los sistemas microfluídicos, las células tienden a circular de manera aleatoria por los canales. Por tanto, con el sistema propuesto en este trabajo, dichas células serán redirigidas a la porción central del canal con el fin de recrear el fenómeno de rodadura presente en nuestro sistema circulatorio y así obtener información más detallada. Los resultados de este trabajo muestran la utilidad y la versatilidad de este dispositivo para experimentos relacionados

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

Micro/Nano Devices for Blood Analysis, Volume II

The development of micro- and nanodevices for blood analysis continues to be a growing interdisciplinary subject that demands the careful integration of different research fields. Following the success of the book “Micro/Nano Devices for Blood Analysis”, we invited more authors from the scientific community to participate in and submit their research for a second volume. Researchers from different areas and backgrounds cooperated actively and submitted high-quality research, focusing on the latest advances and challenges in micro- and nanodevices for diagnostics and blood analysis; micro- and nanofluidics; technologies for flow visualization and diagnosis; biochips, organ-on-a-chip and lab-on-a-chip devices; and their applications to research and industry

Elasto-Magnetic Pumps for Point-of-Care Diagnostics

In recent decades the development of microfluidic lab-on-a-chip devices has accelerated dramatically, revolutionising the fields of microbiology and medicine. However, these systems are not without limitations. Many of these devices are powered by comparatively large and expensive external pumping systems, which limit their widespread applications in areas such as point of care medical devices. As such there is a need to carry out research into miniaturising the pumping systems in order to be integrated directly within the device. The same is true for the reliance on macroscopic sample preparation such as particle filtration. This thesis will focus on a new class of elasto-magnetic pumps and the physical rinciples underpinning their functionality when integrated within microfluidic lab-on-a-chip devices, as well as investigating the novel use of herringbone micromixers for particle filtration.Operating Budge

Lab on chip for cell separation

Cells are the basic functional units of human life, which led researcher in molecular biology, biochemistry, and biotechnology focus their skills to obtain efficient and cost-effective methods for cell enrichment, isolation, and handling. For instance, the main problem of biochemical, pharmaceutical, and clinical studies is the requirement of homogenous cell populations, which consist of a single cell type. For these reasons, the aim of this work is to develop a microfluidic platform to study the influence of fluid, particle, and cell properties on the separation efficiency. To obtain that, we have designed, fabricated, and tested a novel microfluidic device, that exploit the effect of viscoelastic fluid properties on biophysical cell properties to separate different cell types in-flow

Real-time droplet monitoring for digital Polymerase Chain Reaction in microfluidic chip

Current cancer diagnosis techniques are often dependent on the collection of tumour tissue, involving invasive processes for the patient. Circulating Tumour DNA (ctDNA) emerges as an alternative resource for cancer detection and monitoring, that can be har vested from simple blood samples. Digital Polymerase Chain Reaction (dPCR) is a fast and sensitive technique for DNA amplification, suitable for low DNA concentrations such as ctDNA. Advances in microfluidics allow the partition of PCR samples into droplets based in water-in-oil emulsions, so that PCR amplification occurs within each droplet. In this way, the PCR reaction is a well controlled process with a low probability of contami nation and allowing a high throughput analysis. The aimed of this work was to develop droplet-based microfluidic device for application to dPCR technique coupled with real-time droplet monitoring. This work focused on the design and fabrication of a microfluidic device capable of producing a large number of uniform droplets with volumes in the nanoliter range and constant frequency. For this, a polydimethylsiloxane (PDMS) droplet generator device was developed, through photo and soft-lithography techniques, and tested with several oil/water flow rates ratios. Then, the droplets generated were characterized in terms of droplet size, velocity and frequency through the implementation of a powerful open-source software for real-time analysis. Several tests on different devices were carried out to evaluate the device reproducibility. Finally, the droplet generator was incorporated with a serpentine design, allowing the PCR cycles to occur in continuous flow. The results revealed that was possible to generate droplets with radius between 22-99 µm and a coefficient of variation bellow 10%. The correspondents volumes ranged between 90 pL-4.18 nL. Moreover, the velocities obtained situated between 0.05 mm/s-7.62 mm/s with droplet generating frequency of 2-50 Hz. Regarding to the droplet monitoring, the results of the workflows developed revealed similarity with the results obtained trough a widely used software for this purposes, with the advantage of allowing real-time analysis for a larger sample of results.As técnicas actuais usadas no diagnóstico de cancro, geralmente dependem da recolha de tecido tumoral, envolvendo processos invasivos para o paciente. O DNA tumoral circu lante (ctDNA) surge como alternativa para a detecção e monitorização do cancro, podendo ser extraído através de amostras de sangue. A reação em cadeia da polimerase de modo digital (dPCR) é uma técnica rápida e sensível para amplificação de DNA, adequado para baixas concentrações de DNA, como o ctDNA. Os avanços na microfluídica permitem a partição das amostras de PCR em gotas com base em emulsões de água em óleo, de modo que a amplificação por PCR ocorra dentro de cada gota. Deste modo, a reação de PCR é um processo bem controlado com baixa probabilidade de contaminação, permitindo uma análise de alto rendimento. Este trabalho teve como objetivo o desenho e a fabricação de um dispositivo de micro fluídica capaz de produzir um elevado número de gotas uniformes, cujos volumes se encontram na gama dos nanolitros, com frequência constante. Para tal, foi desenvolvido um dispositivo para geração de gotas em polidimetilsiloxano (PDMS), através de técnicas de fotolitografia e litografia suave, tendo sido testado com diversas taxas de fluxos entre óleo / água. Posteriormente, as gotas geradas foram caracterizadas em relação ao seu ta manho, velocidade e frequência através do software de análise de vídeo Bonsai. Diversos testes em diferentes dispositivos foram realizados de modo a avaliar a reprodutibilidade do dispositivo. Por último, o gerador de gotas foi incorporado com desenho da serpentina, permitindo que os ciclos de PCR ocorram em fluxo contínuo. Os estudos realizados revelaram que foi possível gerar gotas com raios entre 22-99 µm, e coeficiente de variação inferior a 10%. Os volumes correspondentes variaram entre 90 pL 4.18 nL. Além disso, as velocidades obtidas situaram-se entre 0.05 mm/s-7.62 mm/s com frequência de geração de gotas de 2-50 Hz. Relativamente à monitorização das gotas, os resultados dos workflows desenvolvidos revelaram similaridade com os resultados obtidos através de um software amplamente utilizado para estes fins, com a vantagem de permitir a análise em tempo real para uma amostra maior de resultados

Computational cytometer based on magnetically modulated coherent imaging and deep learning.

Detecting rare cells within blood has numerous applications in disease diagnostics. Existing rare cell detection techniques are typically hindered by their high cost and low throughput. Here, we present a computational cytometer based on magnetically modulated lensless speckle imaging, which introduces oscillatory motion to the magnetic-bead-conjugated rare cells of interest through a periodic magnetic force and uses lensless time-resolved holographic speckle imaging to rapidly detect the target cells in three dimensions (3D). In addition to using cell-specific antibodies to magnetically label target cells, detection specificity is further enhanced through a deep-learning-based classifier that is based on a densely connected pseudo-3D convolutional neural network (P3D CNN), which automatically detects rare cells of interest based on their spatio-temporal features under a controlled magnetic force. To demonstrate the performance of this technique, we built a high-throughput, compact and cost-effective prototype for detecting MCF7 cancer cells spiked in whole blood samples. Through serial dilution experiments, we quantified the limit of detection (LoD) as 10 cells per millilitre of whole blood, which could be further improved through multiplexing parallel imaging channels within the same instrument. This compact, cost-effective and high-throughput computational cytometer can potentially be used for rare cell detection and quantification in bodily fluids for a variety of biomedical applications

Shear-horizontal surface acoustic wave microfluidics for lab-on-chip applications

Surface acoustic wave (SAW) devices based on the piezoelectric principle have been used extensively in telecommunication applications over the last 20 years, but have recently shown promise in the area of biomedical applications due to their efficient micro-fluidic functions and highly sensitive and label-free detection of pathogens, bacteria, cells, DNA and proteins. There are two types of surface acoustic wave modes: i.e., Rayleigh SAW (R-SAW) and shear horizontal SAW (SH-SAW). R-SAW is widely used for microfluidics and sensing in dry conditions, whereas SH-SAW is mainly used for sensing in liquid conditions. This thesis firstly reviewed the current theoretical and research progress related to these devices and application within the biomedical fields to date, and then the SH-SAW was applied into a novel lab-on-chip combining both bio-sensing and micro-fluidic functions. Simulations of the SH-SAW propagation on 36o Y-cut LiTaO3 were undertaken. Results showed a weak vertical wave component, and at a 90° rotation cut, the crystal was able to support a vertical Rayleigh component showing mixed sensing and streaming possibilities on a single crystal. Experimental investigation of the SH-SAW identified the ability for the shear wave to support mixing, pumping, heating, nebulisation and ejection of sessile droplets on the surface of the crystal with a theoretical explanation for the behaviour presented. A comparison with a standard R-SAW devices made of 128o Y-cut LiNbO3 and sputtered ZnO films was performed. This novel behaviour of digital microfludics, i.e., using sessile droplet with the SH-SAW, demonstrated by this work offers the possibility to manufacture a fully integrated micro-fluidic bio-sensing platform using a single crystal to realise a range of micro-fluidic functions

Quantitative Macro- and Microscale Methods for Characterizing Cell Viability

The goal of this study is to combine molecular and microdevice methods to characterize and quantify viability of single mammalian cells. Fluorescent-based assays were optimized for adherent HeLa and suspension Jurkat cells and were used as a tool for validation of a microfabricated diagnostic device. Cell and substrate/surface interactions were considered for designing a microfluidic device that can be used to characterize cell viability for quantitative biomedical and cell biology applications, which require label-free, real-time monitoring of cells. Several interdisciplinary methods are employed to evaluate electrical impedance differences between live and dead Jurkat cells in a microfluidic device. Biological Micro-Electro-Mechanical Systems (BioMEMS) offer many advantages over the conventional macroscale approaches to biomedical diagnostics, such as reduced reagents, costs, and power consumption; shorter reaction time; portability; versatility; and potential for parallel, integrated operations, thus having the potential to revolutionize how many current cell-based biomolecular assays are performed. A microchip device to detect cell viability at the single-cell level in real-time has much potential for pharmacological drug screening or point-of-care diagnostics. Optimal cell media conditions such as pH and osmolarity are evaluated to ensure cell viability and adequate sensitivity for detecting cell events via electrical impedance measurements. A fluorescent cell assay using Calcein was optimized for optical validation of Jurkat cell viability studies for cells flowing through a microchannel. Fluorescence microscopy was combined with acquired electrical impedance (at 2 MHz) to validate the presence and viability of each cell at the detection electrodes. The microchip design parameters such as substrate material and geometry of microchannel and electrodes were based of the average 12 um-diameter of Jurkat cells tested. Here, we demonstrate the design of a polymer-based chip device that is able to differentiate between live and dead Jurkat cells on the basis of electrical impedance magnitude and phase signals, which could be related to inherent dielectric differences of live and dead cells. The overall outcome of this study provides groundwork for quantifying cell viability of single cells on-chip, in real-time, in a flow-through system, without the use of expensive fluorescent labels

Development of front-end pre-analytical modules for integrated blood plasma separation

Blood plasma separation is a fundamental step in numerous biomedical assays involving low abundance plasma-borne biomarkers. The interest in microscale blood plasma separation solutions has emerged with the development of microfluidic technologies in the early 2000s and has continued in recent years as few solutions have so far achieved both high yield and high purity without sample dilution, in volumes compatible with current clinical assays. Hydrodynamic or acoustic blood plasma separation microdevices have attracted considerable attention from the microfluidic community in the continuous separation of blood samples with a volume of a few mL due to their high throughput and insensitivity to clogging. However, obtaining a high yield from whole blood is challenging because the volume of red blood cells or hematocrit typically rises above physiological levels after each separation region, following plasma extraction. Some key parameters that influence the microfluidic blood plasma separation efficiency and yield of such devices have been investigated in this project. In particular, this project sought to establish experimentally, for the first time, the maximum hematocrit level and flow rate achievable in a microchannel, without hemolysis. Furthermore, the influence of flow fluctuation in syringe pumps, which are commonly employed in microfluidic setups, on the separation performance of blood plasma separation devices was investigated. These studies not only reveal the reasons behind the slow progress in the development of high-throughput microfluidic blood plasma separation devices capable of handling whole blood samples but also provides a framework for the design optimisation of future microfluidic blood plasma separation devices. While for low to mid-volume clinical sample volume (<4 mL), microscale solutions are viable, for high clinical sample volume (>4 mL) blood plasma separation traditional centrifugation approach remains the gold standard but is currently cost-prohibitive. In the third part of this thesis, a low-cost and open-source centrifugation setup for clinical blood sample volume has been developed. This centrifugation system capable of processing clinical blood tubes could be valuable to mobile laboratories or low-resource settings where centrifugation is required immediately after blood withdrawal for further testing