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Numerical and experimental study of flow and wall mass transfer rates in capillary driven flows in microfluidic channelsCito, Salvatore 15 December 2009 (has links)
Micro-channels are believed to open up the prospect of precise control of fluid flow and chemical reactions. The capillary effect can be used to pump fluids in micro-channels and the flow generated can dissolve chemicals previously deposited on the walls of the channel. In this work, numerical and experimental approaches have been developed to investigate the wall mass transfer rate generated by capillary driven flows (CD-Flow). The purpose of this work is to analyze the wall mass transfer rates generated by a CD-Flow in a micro-channel. The results have implications in the optimization and design of devices for biological assays. The correlation for Sherwood number, Reynolds number, contact angle and time is reported. This correlation can be a useful tool for design purposes of microfluidic devices that work with fast heterogeneous reaction and have capillary driven flow as passive pumping system. The numerical results have been confirmed by the experimental results. / La perspectiva del uso de micro-canales para el control preciso del flujo y de las reacciones químicas está ampliamente aceptada. Considerando que el efecto de las tensiones superficiales en la micro-escala es significativo, el bombeo pasivo basado en el uso de la tensión superficial para los Lab-on-a-chip resulta ser el método más eficaz.El propósito de este trabajo es analizar la transferencia de masa en la pared en un campo dinámico de un flujo impulsado por capilaridad. Los resultados permitirán mejorar el diseño y optimizar los dispositivos para ensayos biológicos. Se presenta una correlación entre el número de Sherwood, el número de Reynolds, el ángulo de contacto y el tiempo. La correlación puede ser una herramienta útil en el diseño de dispositivos microfluídicos que trabajen con una reacción rápida y heterogénea y usen el bombeo pasivo impulsado por el flujo capilar. Los resultados numéricos han sido confirmados por los resultados experimentales.
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Micro-chamber filling experiments for validation of macro models with applications in capillary driven microfluidicsGauntt, Stephen Byron 15 May 2009 (has links)
Prediction of bubble formation during filling of microchambers is often critical
for determining the efficacy of microfluidic devices in various applications. In this study
experimental validation is performed to verify the predictions from a previously
developed numerical model using lumped analyses for simulating bubble formation
during the filling of microchambers. The lumped model is used to predict bubble
formation in a micro-chamber as a function of the chamber geometry, fluid properties
(i.e. viscosity and surface tension), surface condition (contact angle, surface roughness)
and operational parameters (e.g., flow rate) as user defined inputs. Several
microchambers with different geometries and surface properties were microfabricated.
Experiments were performed to fill the microchambers with different liquids (e.g., water
and alcohol) at various flow rates to study the conditions for bubble formation inside the
microchambers. The experimental data are compared with numerical predictions to
identify the limitations of the numerical model. Also, the comparison of the
experimental data with the numerical results provides additional insight into the physics
of the micro/nano-scale flow phenomena. The results indicate that contact angle plays a significant role on properties of fluids confined within small geometries, such as in
microfluidic devices.
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Platforms and Molecular Mechanisms for Improving Signal Transduction and Signal Enhancement in Multi-step Point-Of-Care DiagnosticsKaleb M. Byers (11192533) 28 July 2021 (has links)
<p>Swift recognition of
disease-causing pathogens at the point-of-care enables life-saving treatment
and infection control. However, current rapid diagnostic devices often fail to
detect the low concentrations of pathogens present in the early stages of
infection, causing delayed and even incorrect treatments. Rapid diagnostics
that require multiple steps and/or elevated temperatures to perform have a
number of barriers to use at the point-of-care and in the field, and despite
efforts to simplify these platforms for ease of use, many still require
diagnostic-specific training for the healthcare professionals who use them.
Most nucleic acid amplification assays require hours to perform in a sterile
laboratory setting that may be still more hours from a patient’s bedside or not
at all feasible for transport in remote or low-resourced areas. The cold-chain
storage of reagents, multistep sample preparation, and costly instrumentation
required to analyze samples has prohibited many nucleic acid detection and
antibody-based assays from reaching the point-of-care. There remains a critical
need to bring rapid and accessible pathogen identification technologies that
determine disease status and ensure effective treatment out of the laboratory.</p>
<p>Paper-based diagnostics have emerged as a portable platform for antigen
and nucleic acid detection of pathogens but are often limited by their
imperfect control of reagent incubation, multiple complex steps, and
inconsistent false positive results. Here, I have developed mechanisms to
economically improve thermal incubations, automate dried reagent flow for
multistep assays, and specifically detect pathogenic antigens while improving
final output sensitivity on paper-based devices. First, I characterize
miniaturized inkjet printed joule-heaters (microheaters) that enable thermal
control for pathogen lysis and nucleic acid amplification incubation on a
low-cost paper-based device. Next, I explore 2-Dimensional Paper Networks as a
means to automate multistep visual enhancement reactions with dried reagents to
increase the sensitivity and readability of nucleic acid detection with
paper-based devices. Lastly, I aim to create a novel Reverse-Transcription
Recombinase Polymerase Reaction mechanism to amplify and detect a specific
region of the Spike protein domain of SARS-CoV-2. This will allow the rapid
detection of SARS-CoV-2 infections to aid in managing the current COVID-19 pandemic.
In the future, these tools could be integrated into a rapid diagnostic test for
SARS-CoV-2 and other pathogens, ultimately improving the accessibility and
sensitivity of rapid diagnostics on multiple fronts.</p>
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