Engineering Commons^™

Numerical Study Of Droplet Evaporation, Ritul Gandhi

Mechanical and Aerospace Engineering Theses

Droplet evaporation plays a vital role in various engineering fields such as air/fuel premixing, inkjet printing and many more. The high rate of power dissipation from the integrated circuits and chips of electronic devices creates a need for cooling it to achieve their optimal functionality. The high rate of cooling can be achieved by thin film evaporation of water by phase change as compared to the air cooling methods. Therefore, the study of droplet evaporation is necessary to understand the underlying physics and effects of different parameters on cooling performance. Numerical study of droplet evaporation has been done by using …

Manufacturing Microfluidic Flow Focusing Devices For Stimuli Responsive Alginate Microsphere Generation And Cell Encapsulation, Michael A. Karasinski

Graduate College Dissertations and Theses

In this paper a novel stimuli responsive hydrogel material, methacrylated sodium alginate beta-cyclodextrin (Alg-MA-β-CD), was used in combination with a microfluidic device to create microspheres. Currently there is no reliable method for fabricating homogeneous stimuli-responsive microspheres, in-house microfluidic devices are not reliable in manufacture quality or long-term use. Alginate hydrogels have many attractive characteristics for bioengineering applications and are commonly used to mimic the features and properties of the extracellular matrix (ECM). Human mesenchymal stem cells (hMSCs) are of top interest to tissue engineers. hMSCs are widely available and can be harvested and cultured directly out of human bone marrow. …

Concurrent Detection And Isolation Of Cellular And Molecular Biomarkers, Wanfeng Huang

Open Access Dissertations

Detection of cancer markers such as protein biomolecules and cancer cells in bodily fluids is of great importance in early diagnosis, prognosis as well as evaluation of therapy efficacy. Numerous devices have been developed for detecting either cellular or molecular targets, however there has not yet been a system that can simultaneously detect both cellular and molecular targets effectively. Molecule and cell-based assays are important because each type of target can tell a different story about the state of the disease and the two types of information can potentially be combined and/or compared for more accurate biological or clinical assessments. …

Fundamental Studies Of Electrochemical Reactions And Microfluidics In Proton Exchange Membrane Electrolyzer Cells, Jingke Mo

Doctoral Dissertations

In electrochemical energy devices, including fuel cells, electrolyzers and batteries, the electrochemical reactions occur only on triple phase boundaries (TPBs). The boundaries provide the conductors for electros and protons, the catalysts for electrochemical reactions and the effective pathways for transport of reactants and products. The interfaces have a critical impact on the overall performance and cost of the devices in which they are incorporated, and therefore could be a key feature to optimize in order to turn a prototype into a commercially viable product. For electrolysis of water, proton exchange membrane electrolyzer cells (PEMECs) have several advantages compared to other …

Analysis Of Shock-Plugs In Quasi-One-Dimensional Compressible Flow, Matthew Alexander Thompson

Graduate Theses - Mechanical Engineering

At small length scales, such as in micro-nozzles, the assumption that a shock wave is infinitesimally thin breaks-down due to the thickness of the shock being non-negligible compared to the dimensions of the nozzle. In this thesis, shock waves of finite thickness, or “shock-plugs,” are modeled using the same methods and assumptions as a standard shock wave analysis. Due to the finite thickness of shock-plugs, however, two additional parameters are required in order to account for the differing inlet and exit areas, as well as the pressure on the side walls of the channel. A “typical” micro-nozzle with appropriate dimensions …

Analysis Of Capillary Flow In Interior Corners : Perturbed Power Law Similarity Solutions, Joshua Thomas Mccraney

Dissertations and Theses

The design of fluid management systems requires accurate models for fluid transport. In the low gravity environment of space, gravity no longer dominates fluid displacement; instead capillary forces often govern flow. This thesis considers the redistribution of fluid along an interior corner. Following a rapid reduction of gravity, fluid advances along the corner measured by the column length z = L(t), which is governed by a nonlinear partial differential equation with dynamical boundary conditions. Three flow types are examined: capillary rise, spreading drop, and tapered corner. The spreading drop regime is shown to exhibit column length growth L ~ …

Design, Fabrication, And Testing Of A 3d Printer Based Microfluidic System, Carlton A. Mcmullen

Graduate Theses and Dissertations

A pneumatically actuated PDMS based microfluidic devices were designed and fabricated by soft-lithography. Two types of molds were fabricated out of different material for this experiment. The first mold, (device 1), was fabricated from a sheet of Polymethyl methacrylate (PMMA) material, similar to Plexiglas. The device features were micro-engraved onto the face of the material. The second mold, (device 2), was fabricated from the use of fused deposition modeling (FDM) 3D printing. The pumping efficiency of the PDMS devices was analyzed through the characterization of the micro-pumps flowrate with respect to the pumps driving pressure and the actuation frequency. Tested …

Numerical Studies Of Liquid-Liquid Segmented Flows In Square Microchannels Using A Front-Tracking Algorithm, Eamonn Daire Walker

LSU Doctoral Dissertations

Liquid-liquid segmented flows in a square microchannel are investigated numerically using a hybrid front-tracking/front-capturing method. The code is found to be well-adapted to a large range of flow parameters, but droplet flows are limited by poor accuracy at Laplace number above 100 – 1000 and plug flows are limited by the code’s current inability to adequately model the flow in thin films at low capillary numbers. A Schwarz-Aitken acceleration technique is investigated as a means to reduce computation time, but is found not to be advantageous compared to the parallel multigrid formulation of the code. Numerical simulations are divided into …

Effect Of Junction Geometry On Monodispersed Microdroplet Generation In Microfluidic Aqueous Two-Phase Systems, Young Gyu Nam

Theses and Dissertations

Aqueous two-phase system (ATPS) consists of two immiscible water-based solutions of polymers, which can form phase partitioning. Dextran and polyethylene glycol I used in this thesis is the one of common components of aqueous two-phase system give a reliable and incompatible environment for purification of biomedical products and cellular macromolecules. Recently, ATPS have received increasing attention as a separation method in microfluidic device due to the advantages of biocompatibility, unlimited combination, and low interfacial tension. Hence, it became an important to discover researches related to ATPS microfluidic device.

Microdroplets produced in microfluidic device are a largely interesting phenomenon for various …

Electrokinetic Particle Manipulations In Spiral Microchannels, John Dubose

All Theses

Recent developments in the field of microfluidics have created a multitude of new useful techniques for practical particle and cellular assays. Among them is the use of dielectrophoretic forces in 'lab-on-a-chip' devices. This sub-domain of electrokinetic flow is particularly popular due to its advantages in simplicity and versatility. This thesis makes use of dielectrophoretic particle manipulations in three distinct spiral microchannels. In the first of these experiments, we demonstrate the utility of a novel single-spiral curved microchannel with a single inlet reservoir and a single outlet reservoir for the continuous focusing and filtration of particles. The insulator-based negative-dielectrophoretic (repulsive) force …

Development Of Confocal Imaging Techniques For Probing Interfacial Dynamics In Microscale, Gas-Liquid, Two-Phase Flow, Joseph E. Hernandez

Dissertations, Master's Theses and Master's Reports - Open

Micro-scale, two-phase flow is found in a variety of devices such as Lab-on-a-chip, bio-chips, micro-heat exchangers, and fuel cells. Knowledge of the fluid behavior near the dynamic gas-liquid interface is required for developing accurate predictive models. Light is distorted near a curved gas-liquid interface preventing accurate measurement of interfacial shape and internal liquid velocities. This research focused on the development of experimental methods designed to isolate and probe dynamic liquid films and measure velocity fields near a moving gas-liquid interface. A high-speed, reflectance, swept-field confocal (RSFC) imaging system was developed for imaging near curved surfaces.

Experimental studies of dynamic gas-liquid …

A Parametric Investigation Of A Novel, Modular, Gasketless, Microfluidic Interconnect Using Parallel Superhydrophobic Surfaces, Christopher Ramsey Brown

LSU Master's Theses

The gasketless microfluidic interconnect has the potential to offer a standardized approach to interconnects between modular microfluidic components. This strategy uses parallel superhydrophobic surfaces (contact angle ≥ 150ᴼ) to passively seal adjacent, concentric, microfluidic ports separated by an air gap using a liquid bridge created between the chips. The parallel superhydrophobic surfaces do not require the addition of a gasket or other additional components so that the assembly process scales favorably with an increasing number of fluidic interconnects. The gasketless seal does not contribute to geometric constraint between the component chips which allows alignment between chips to scale favorably with …

Magnetic Manipulation Of Particles And Cells In Ferrofluid Flow Through Straight Microchannels Using Two Magnets, Jian Zeng

All Theses

Microfluidic devices have been increasingly used in the past two decades for particle and cell manipulations in many chemical and biomedical applications. A variety of force fields have been demonstrated to control particle and cell transport in these devices including electric, magnetic, acoustic, and optical forces etc. Among these particle handling techniques, the magnetic approach provides clear advantages over others such as low cost, noninvasive, and free of fluid heating issues. However, the current knowledge of magnetic control of particle transport is still very limited, especially lacking is the handling of diamagnetic particle. This thesis is focused on the magnetic …

Development Of A Pdms Based Micro Total Analysis System For Rapid Biomolecule Detection, Balaji Srinivasan Venkatesh

Graduate Theses and Dissertations

The emerging field of micro total analysis system powered by microfluidics is expected to revolutionize miniaturization and automation for point-of-care-testing systems which require quick, efficient and reproducible results. In the present study, a PDMS based micro total analysis system has been developed for rapid, multi-purpose, impedance based detection of biomolecules. The major components of the micro total analysis system include a micropump, micromixer, magnetic separator and interdigitated electrodes for impedance detection. Three designs of pneumatically actuated PDMS based micropumps were fabricated and tested. Based on the performance test results, one of the micropumps was selected for integration. The experimental results …

An Acoustic-Based Microfluidic Platform For Active Separation And Mixing, Myeong Chan Jo

USF Tampa Graduate Theses and Dissertations

Particle separation is of great interest to many biological and biomedical applications. Flow-based methods have been used to sort particles and cells. However, the main challenge with flow based particle separation systems is the need for a sheath flow for successful operation. Existence of the sheath liquid dilutes the analyte, necessitates precise flow control between sample and sheath flow, requires a complicated design to create sheath flow and separation efficiency depends on the sheath liquid composition. In addition, current gold standard active separation techniques are only capable of separation based on particle size; hence, separation cannot be achieved for same-size …

Electrohydrodynamic Manipulation Of Liquid Droplet Emulsions In A Microfluidic Channel, Jonathan Wehking

Electronic Theses and Dissertations

This work specifically aims to provide a fundamental framework, with some experimental validation, for understanding droplet emulsion dynamics in a microfluidic channel with an applied electric field. Electrification of fluids can result in several different modes of electrohydrodynamics (EHD). Several studies to date have provided theoretical, experimental, and numerical results for stationary droplet deformations and some flowing droplet configurations, but none have reported a method by which droplets of different diameters can be separated, binned and routed through the use of electric fields. It is therefore the goal of this work to fill that void and report a comprehensive understanding …

Electrokinetic Mixing And Separation In Microfluidic Systems, Fang Yang

Theses and Dissertations

Electrokinetics involves the study of liquid or particle motion under the action of an electric field; it includes electroosmosis, electrophoresis, dielectrophoresis, and electrowetting, etc. The applications of electrokinetics in the development of microfluidic devices have been widely attractive in the past decade. Electrokinetic devices generally require no external mechanical moving parts and can be made portable by replacing the power supply by small battery. Therefore, electrokinetic based microfluidic systems can serve as a viable tool in creating a lab-on-a-chip (LOC) for use in biological and chemical assays. Here we present our works of electrokenitic based mixing and separation in microfluidics …

Adsorption Of Particles On Fluid-Liquid Interfaces, Bhavin Dalal

Dissertations

Particles floating on fluid-liquid interfaces are of considerable interest because of their importance in a range of physical applications and biological processes, e.g., self-- assembly of particles at fluid-fluid interfaces resulting in novel nano structured materials, stabilization of emulsions, formation of pollen and insect egg rafts, etc. The aim of this dissertation is to explore the mechanism by which particles are adsorbed at fluid-liquid interfaces. It is shown that the inertia of a particle plays an important role in its motion in the direction normal to a fluid-liquid interface, and in determining the particles adsorption trajectory and orientation in …

The Design And Fabrication Of A Microfluidic Reactor For Synthesis Of Cadmium Selenide Quantum Dots Using Silicon And Glass Substrates, Peter Robert Gonsalves

Master's Theses

A microfluidic reactor for synthesizing cadmium selenide (CdSe) quantum dots (QDs) was synthesized out of a silicon wafer and Pyrex glass. Microfabrication techniques were used to etch channels into the silicon wafer. Holes were wet-drilled into the Pyrex glass using a diamond-tip drill bit. The Pyrex wafer was anodically bonded to the etched silicon wafer to enclose the microfluidic reactor. Conditions for anodic bonding were created by exposing the stacked substrates to 300V at ~350oC under 5.46N of force. A syringe containing a room temperature CdSe solution was interfaced to the microfluidic reactor by using Poly (dimethylsiloxane) (PDMS) as an …

Pdms Based Waveguides For Microfluidics And Eocb, Weiping Qiu

LSU Master's Theses

Due to the low cost, fast and ease of molding, PDMS has become one of the most popular materials for microfluidics devices, bioMEMS applications. Meanwhile, the integration of different functional components on to one single chip (or Lab on a Chip) is the dream for many scientists and engineers in the related area. In addition to the necessary mechanical components for accommodating the reactions, such as pumps, valves, mixers and so on, optical components such as waveguides, lens, interferers are all desired to be lumped into such a system.

The waveguide for such a system requires the material to have …

Silk Cryogels For Microfluidics, Christopher David Hinojosa

Dissertations and Theses

Silk fibroin from silkworm cocoons is found in numerous applications ranging from textiles to medical implants. Its recent adoption as a biomaterial is due to the material's strength, biocompatibility, self-assembling behavior, programmable degradability, optical clarity, and its ability to be functionalized with antibodies and proteins. In the field of bioengineering it has been utilized as a tissue scaffolding, drug delivery system, biosensor, and implantable electrode. This work suggests a new application for porous silk in a microscale chromatography column. We demonstrate in situ cryotropic polymerization of highly porous structures in microscale geometries by freezing aqueous silk with a solvent. The …

In Situ Preconcentration By Ac Electrokinetics For Rapid And Sensitive Nanoparticle Detection, Kai Yang

Doctoral Dissertations

Reducing cost and time is a major concern in clinical diagnostics. Current molecular diagnostics are multi-step processes that usually take at least several hours or even days to complete multiple reagents delivery, incubations and several washing processes. This highly labor-intensive work and lack of automation could result in reduced reliability and low efficiency. The Laboratory-on-a-chip (LOC), taking advantage of the merger and development of microfluidics and biosensor technology, has shown promise towards a solution for performing analytical tests in a self-contained and compact unit, enabling earlier and decentralized testing. However, challenges are to integrate the fluid regulatory elements on a …

Direct Current Electrokinetic Particle Transport In Micro/Nano-Fluidics, Ye Ai

Mechanical & Aerospace Engineering Theses & Dissertations

Electrokinetics has been widely used to propel and manipulate particles in micro/nano-fluidics. The first part of this dissertation focuses on numerical and experimental studies of direct current (DC) electrokinetic particle transport in microfluidics, with emphasis on dielectrophoretic (DEP) effect. Especially, the electrokinetic transports of spherical particles in a converging-diverging microchannel and an L-shaped microchannel, and cylindrical algal cells in a straight microchannel have been numerically and experimentally studied. The numerical predictions are in quantitative agreement with our own and other researchers' experimental results. It has been demonstrated that the DC DEP effect, neglected in existing numerical models, plays an important …

High Speed Continuous Thermal Curing Microfabrication System, Franklin Dibartolomeo

University of Kentucky Master's Theses

Rapid creation of devices with microscale features is a vital step in the commercialization of a wide variety of technologies, such as microfluidics, fuel cells and self-healing materials. The current standard for creating many of these microstructured devices utilizes the inexpensive, flexible material poly-dimethylsiloxane (PDMS) to replicate microstructured molds. This process is inexpensive and fast for small batches of devices, but lacks scalability and the ability to produce large surface-area materials. The novel fabrication process presented in this paper uses a cylindrical mold with microscale surface patterns to cure liquid PDMS prepolymer into continuous microstructured films. Results show that this …

A Cfd Model Of Mixing In A Microfludic Device For Space Medicine Technology, Terri Lynn Mckay

ETD Archive

The DNA Medicine Institute (DMI) is currently developing a device to be used for blood analysis to satisfy the unique requirements of space medicine applications. A key component of that device is the micromixer, which will ensure mixing and dilution of reagents utilized for detection assays. As part of the device design process, the micromixer was modeled, and the mixing characteristics were analyzed and compared to experimental data. The experimental data was based on a top-view of the system and, lacking data throughout the fluid domain, could not provide the insight into the mixing process that modeling could readily provide. …

A Microfluidic Device For Impedance Spectroscopy, Ahmet Can Sabuncu

Mechanical & Aerospace Engineering Theses & Dissertations

Recently, microfluidics has become a versatile tool to investigate cellular biology and to build novel biomedical devices. Dielectric spectroscopy, on the other hand, allows non-invasive probing of biological cells. Information on the cell membrane, cytoplasm, and nucleus can be obtained by dielectric spectroscopy provided that appropriate tools are used in specific frequency ranges. This dissertation includes fabrication, characterization, and testing of a simple microfluidic device to measure cell dielectric properties. The dielectric measurements are performed on human T-cell leukemia (Jurkat), mouse melanoma (B16), mouse hepatoma (Hepa), and human costal chondrocyte cells. Dielectric measurements consist of measuring the complex impedance of …

Experimental Investigation Of Flow And Heat Transfer Characteristics Of R -134a In Microchannels, Abdullahel Bari

Doctoral Dissertations

The purpose of this study was to investigate the flow and heat transfer characteristics of liquid refrigerant R-134a in rectangular microchannels. The research concentrated mostly upon single-phase experiments with limited investigation of boiling phenomenon in microchannels. Tests were performed using rectangular microchannels with hydraulic diameters ranging from 112 μm to 210 μm and aspect ratios varying approximately from 1.0 to 1.5. The Reynolds number in the experiments ranged from 1,200 to 13,000 although most data were collected in the transition and turbulent flow regimes.

The experimental data for friction factor measurement had a similar trend as predicted by macroscale theory …

Development Of A Low Cost Handheld Microfluidic Phosphate Colorimeter For Water Quality Analysis, Sean C. Kaylor

Master's Theses

This thesis describes the design, fabrication, and testing process for a microfluidic phosphate colorimeter utilized for water quality analysis. The device can be powered by, and interfaced for data collection with, a common cell phone or laptop to dramatically reduce costs. Unlike commercially available colorimeters, this device does not require the user to measure or mix sample and reagent. A disposable poly(dimethylsiloxane) (PDMS) microfluid chip, powered by an absorption pumping mechanism, was used to draw water samples, mix the sample at a specific ratio with a molybdovanadate reagent, and load both fluids into an onboard cuvette for colorimetric analysis. A …

Factors Affecting Redox Magnetohydrodynamics For Flow In Small Volumes, Matthew D. Gerner

Graduate Theses and Dissertations

Lab-on-a-chip technologies offer the possibility of developing analytical devices that are low-cost, portable, disposable, fast, and operable by non-technical personnel. Such devices require automated methods to manipulate ultra-small volumes (picoliters) of samples and solution, including pumping, stirring, and positioning. Current methods for ultra-small volume microfluidics have limitations that restrict their use including high voltage requirements, disadvantageous flow profiles or rates, and relatively complicated fabrication due to mechanical parts. Redox magnetohydrodyanmics (RMHD) that utilizes permanent magnets for portability shows promise as a micropump with ease of switching flow direction, no moving parts, compatibility with both aqueous and non-aqueous solutions, low voltages …

Laminar And Turbulent Flow Of A Liquid Through Channels With Superhydrophobic Walls Exhibiting Alternating Ribs And Cavities, Brady L. Woolford

Theses and Dissertations

There is significant interest in reducing the frictional resistance that occurs along a surface in contact with a liquid. A novel approach to reducing the frictional resistance across a liquid-solid interface is the use of superhydrophobic surfaces. superhydrophobic surfaces are created in this work by the use of micro-fabrication techniques where systematic roughness is fabricated on a substrate surface which is subsequently treated with a hydrophobic coating. This work reports an experimental study of superhydrophobic surfaces used to reduce drag in both laminar and turbulent channel flows. In the laminar flow regime reductions in frictional resistance greater than 55% were …