Dissertations / Theses on the topic 'Droplet'
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Umapathi, Udayan. "Droplet IO : programmable droplets for human-material interaction." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/114062.
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Thesis: S.M., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 87-93).
In this thesis, I propose aqueous droplets as a form of programmable material that can computationally transform its physical properties. Liquid matter can undergo physical transformation through interfacial forces and surface tension. I introduce a system called DropletIO to regulate interfacial forces through a programmable electric field. The system can actuate and sense macro-scale (micro-liter to milli-liter) droplets on arbitrary planar and curved surfaces. The system can precisely move, merge, split, and change shape of droplets and thus enables a range of applications with human interactivity, information displays, parallelized programmable chemistry and dynamically tunable optics. DropletIO system uses electrowetting on dielectric (EWOD) to manipulate droplets. EWOD is a physical phenomenon where a polar droplet on a dielectric surface is attracted to a charged electrode. I constructed EWOD arrays with integrated actuation and sensing on inexpensive printed circuit boards that can scale to arbitrarily large areas and different form factors. Additionally, in this thesis I discuss how semiconductor device scaling applies to electrowetting for smaller volume droplets and hence miniaturized programmable lab-on-a-chip. Droplet based microfluidics is extensively used in biology and chemistry. In this thesis I describe two novel fluid manipulation mechanism for microfluidics. First, I show an approach for splitting aqueous droplets on an open digital microfluidic platform and thus a system capable of performing a complete set of microfluidic operations on an open surface. Second, I demonstrate how electrowetting platforms can handle large volume fluids, and hence enable a new direction in programmable fluid handling called digital millifluidics.
by Udayan Umapathi.
S.M.
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Sahu, Sucharita. "Thermal state of Sn-Pb droplets in the droplet-based manufacturing process." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/34081.
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Caën, Ouriel. "Droplet microfluidics for cancer cell evolution Parallelized ultra-high throughput microfluidic emulsifier for multiplex kinetic assays Counting single cells in droplets Multiplexed droplet sorting." Thesis, Sorbonne Paris Cité, 2016. https://wo.app.u-paris.fr/cgi-bin/WebObjects/TheseWeb.woa/wa/show?t=1888&f=11697.
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Cette thèse porte sur une problématique moderne: la prise en charge de patients cancéreux par thérapie ciblée. De tels traitements sont efficaces et représentent une récente avancée thérapeutique majeure pour des patients multi-traités en cas d'échec thérapeutique. Cependant, les réponses des patients sont souvent transitoires puisqu'ils rechutent plusieurs mois après le traitement. Il a été récemment démontré que pour les cancers du poumon, ces rechutes sont associées à l'émergence de nouvelles altérations génétiques au sein des tumeurs. Il est donc important de discriminer avant traitement le processus de résistance qui pourrait se produire et proposer ainsi la combinaison de traitements qui empêcheraient l'apparition d'une résistance. Une telle évaluation précoce pourrait être facilitée grâce à l'utilisation de la microfluidique de goutte qui permet un criblage à haut débit à l’échelle de la cellule unique. Cette technologie pourrait ainsi devenir un outil générique pour identifier la résistance à un traitement à un stade précoce de son développement. Dans le cadre de cette thèse, nous avons utilisé comme modèle in vitro des lignées cellulaires NSCLC (Non-Small Cell Lung Cancer) respectivement sensibles et résistantes au traitement. Nous avons développé de nouveaux outils de microfluidique de goutte qui ont permis de discriminer entre le phénotype et le génotype de cellules uniques sensibles au traitement et résistantes au traitement. Une telle preuve de principe constitue une première étape vers la compréhension de l'hétérogénéité de populations de cellules tumorales, dont il a été montré qu’elle est corrélée avec la résistance aux thérapiesThis thesis deals with a modern problematic: the management of cancer patients using targeted therapy. Such treatments are efficient and represent a recent major therapeutic advance for multi-treated patients in therapeutic failure. However patients responses are often transitory as they relapse several months following the treatment. It has been recently demonstrated that for lung cancers these escapes are associated with the emergence of new genetic alterations within tumors. It is thus important to discriminate before treatment the resistance process that could occur and thus propose the therapeutic combination of treatments that would prevent the appearing of a resistance. Such early assessment could be eased-up thanks to the use of droplet microfluidics which allows high-throughput screening at a single-cell level resolution. This technology could hence become a generic tool to identify resistance to a treatment in an early stage of its development. In the framework of this thesis we used as an in vitro model treatment-sensitive and treatment-resistant NSCLC (Non-Small Cell Lung Cancer) cell lines. We developed novel droplet microfluidics tools which allowed to discriminate between the phenotype and genotype of single treatment-sensitive and treatment-resistant single cells. Such a proof of principle constitutes a first step towards the understanding of tumor cell population heterogeneity, which has been shown to be correlated with resistance to therapies
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Ciobanescu, Husanu Irina N. Choi Mun Young Ruff Gary A. "Droplet interactions during combustion of unsupported droplet clusters in microgravity : numerical study of droplet interactions at low reynolds number /." Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/729.
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You, David, and Jeong-Yeol Yoon. "Droplet centrifugation, droplet DNA extraction, and rapid droplet thermocycling for simpler and faster PCR assay using wire-guided manipulations." BioMed Central, 2012. http://hdl.handle.net/10150/610171.
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A computer numerical control (CNC) apparatus was used to perform droplet centrifugation, droplet DNA extraction, and rapid droplet thermocycling on a single superhydrophobic surface and a multi-chambered PCB heater. Droplets were manipulated using "wire-guided" method (a pipette tip was used in this study). This methodology can be easily adapted to existing commercial robotic pipetting system, while demonstrated added capabilities such as vibrational mixing, high-speed centrifuging of droplets, simple DNA extraction utilizing the hydrophobicity difference between the tip and the superhydrophobic surface, and rapid thermocycling with a moving droplet, all with wire-guided droplet manipulations on a superhydrophobic surface and a multi-chambered PCB heater (i.e., not on a 96-well plate). Serial dilutions were demonstrated for diluting sample matrix. Centrifuging was demonstrated by rotating a 10 muL droplet at 2300 round per minute, concentrating E. coli by more than 3-fold within 3min. DNA extraction was demonstrated from E. coli sample utilizing the disposable pipette tip to cleverly attract the extracted DNA from the droplet residing on a superhydrophobic surface, which took less than 10min. Following extraction, the 1500bp sequence of Peptidase D from E. coli was amplified using rapid droplet thermocycling, which took 10min for 30cycles. The total assay time was 23min, including droplet centrifugation, droplet DNA extraction and rapid droplet thermocycling. Evaporation from of 10 muL droplets was not significant during these procedures, since the longest time exposure to air and the vibrations was less than 5min (during DNA extraction). The results of these sequentially executed processes were analyzed using gel electrophoresis. Thus, this work demonstrates the adaptability of the system to replace many common laboratory tasks on a single platform (through re-programmability), in rapid succession (using droplets), and with a high level of accuracy and automation.
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Abel, Godard Karl. "Characterization of droplet flight path and mass flux in droplet-based manufacturing." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/12047.
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Vukasinovic, Bojan. "Vibration-induced droplet atomization." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17237.
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James, Ashley Jean. "Vibration induced droplet ejection." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/17337.
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Pacitti, Antony Gerard. "Droplet motion in flames." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421855.
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Wilkins, Jonathan Hugh. "Droplet impingement onto surfaces." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298261.
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Gilani, Mohammad Nejad Hamzeei. "CFD of droplet entrainment." Thesis, Imperial College London, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542939.
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Wollman, Andrew Paul. "Capillarity-Driven Droplet Ejection." PDXScholar, 2012. http://pdxscholar.library.pdx.edu/open_access_etds/563.
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Drop Towers provide brief terrestrial access to microgravity environments. When used for capillary fluidics research, a drop tower allows for unique control over an experiment's initial conditions, which enables, enhances, or otherwise improves the study of capillary phenomena at significantly larger length scales than can normally be achieved on the ground. This thesis provides a historical context for the introduction of a new, highly accessible, 2.1s tower design used for capillary research and presents a variety of demonstrative experimental results for purely capillarity-driven flows leading to bubble ingestion, sinking flows, multiphase flows, and droplet ejections. The focus of this thesis is paid to capillarity-driven droplet ejection including historical significance, mathematical models, criteria for ejection and experimental validation. A scale analysis provides a single parameter Su+ which is used to predict the flow velocity at the base of the nozzle. By simplifying the flow in the nozzle we identify two criteria for auto-ejection, the nozzle must be `short' and the velocity of the flow must be sufficient to invert the liquid meniscus and overpower surface tension at the nozzle tip such that We⁺ > 12. Drop tower experiments are conducted and compared to analytical predictions using a regimemap. This thesis also includes results from experiments experiments conducted in a stationary ground-based laboratory and aboard the International Space Station which clearly demonstrate droplet ejection in regimes from transient liquid jets to large isolated drops. Droplets generated in a microgravity environment are 106 times larger than 1g₀ counter-parts.
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Cherng, Jean-Pei Jeanie. "Solidification and cooling analysis of aluminum alloy droplets with the uniform droplet spray process." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/36325.
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Chen, Chen-An. "Droplet solidification and its effects on deposit microstructure in the uniform droplet spray process." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10947.
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Roberts, Ian David. "Droplet evaporation from porous surfaces." Thesis, University of Manchester, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294978.
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England, Pinar. "Droplet behaviour in microfluidic devices." Thesis, University of Strathclyde, 2018. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=30138.
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This work is a study to understand the various aspects of a microfluidic device. In the first half we take the role of an end user, experimenting to learn how best to use the device efficiently. In the second half we are the manufacturer, trying to fabricate a user friendly, and fully functioning microfluidic device. As the end user, we have three different T-junction droplet generator devices, with similar geometries. We start investigating by generating water droplets in an oil medium. They self-organise into various flow patterns: single-profile, double-helix profile and triple-helix profile. We document how, with increasing flow rate ratio and capillary number, we observe more densely packed droplet flow patterns. The device with the deeper expansion channel provides more space for the droplets and they self-organise the triple-helix pattern in 3-dimension. We then use the same devices to generate droplets for which we can calculate the volume. The fluid flow in a microchannel happens in four different regimes: ballooning, squeezing, dripping and jetting regimes. In single-cell and single-molecule analysis devices, the ability to create droplets on demand and of a certain volume is a desired capability. This can be achieved by understanding and learning how to use the fluid flow characteristics accurately. We experiment with the three different sized microfluidic devices, to measure the droplet volume throughout the squeezing to dripping regimes. This is achieved by manipulating the capillary number and the flow rate ratio. We observe a similar result as with the flow patterns: that the capillary number has an impact on the droplet volume. As the capillary number increases the droplet diameter decreases. Further, for a set capillary number we can fine tune the droplet diameter by changing the flow rate ratio. As the flow rate ratio increases the volume of water droplets increases, despite the fact the capillary number is set. These coincide with our flow pattern results. Our results fit to the scaling law to predict the droplet size introduced by Tanet al. in 2008 [51]. Unlike some other authors in the literature, we did not observe a critical capillary number where the droplet volume changes suddenly. However, we did observe a transition area where we cannot define the regime of the fluid flow. As the manufacturer we designed and fabricated our own planar free standing microfluidic devices using a polymer called SU-8. After looking into the weaknesses and the strengths of using SU-8, we describe how we successfully fabricated working devices and developeda new procedure in adhesive low temperature bonding. We finish by considering the challenges of connecting micro sized structures to a macro sized syringe pump, and fabricated a chip-holder inspired by applications in industry.
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Zhang, Jing. "Microfluidic droplet-enabled supramolecular microcapsules." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607842.
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Fry, H. M. "A study of droplet deformation." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1306708/.
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In both engineering and medical applications it is often useful to use the knowledge of the conditions under which adhering liquid droplets appear, deform and interact with surrounding fluids, in order to either remove or create them. Examples include the de-wetting of aircraft surfaces and the process of injecting glue into the bloodstream in the treatment of aneurysms. The particular types of models discussed here theoretically are based on droplets with a large density compared to that of the surrounding fluid. Using this ratio as a small parameter, the Navier-Stokes equations may be simplified, and in view of the nature of the interfacial bound- ary conditions the droplet may be considered as solid to leading order at any given time step for a certain time scale. In the first part of the thesis, we study an example of an initially semicircular droplet adhering to a wall for low-to-medium Reynolds numbers (along with simpler test problems). We numerically determine unsteady solutions in both the surrounding fluid and the droplet, coupling them together to obtain a model of the droplet deformation. Analysis within the droplet leads to the identification of two temporal stages, and the effect on large-time velocities is discussed. The second part of the thesis sees a similar approach applied to a surface mounted droplet completely contained within the boundary layer of an external fluid for high Reynolds numbers. The two-fluid interface for such a regime is analysed using a lubrication approximation within the viscous sublayer of a triple-deck structure. Finally, the lubrication is abandoned and we present a fully non-linear solution in air over any obstacle shape, as well as a two-way interacting model of droplet deformation, capable of simulating the free surface of the droplet as it becomes severely distorted.
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Moevius, Lisa. "Droplet dynamics on superhydrophobic surfaces." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:52737169-86fa-41ef-abae-0883a67ecaad.
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Millions of years of evolution have led to a wealth of highly adapted functional surfaces in nature. Among the most fascinating are superhydrophobic surfaces which are highly water-repellent and shed drops very easily owing to their chemical hydrophobicity combined with micropatterning. Superhydrophobic materials have attracted a lot of attention due to their practical applications as ultra-low friction surfaces for ships and pipes, water harvesters, de-humidifiers and cooling systems. At small length scales, where surface tension dominates over gravity, these surfaces show a wealth of phenomena interesting to physicists, such as directional flow, rolling, and drop bouncing. This thesis focuses on two examples of dynamic drop interactions with micropatterned surfaces and studies them by means of a lattice Boltzmann simulation approach. Inspired by recent experiments, we investigate the phenomenon of the self-propelled bouncing of coalescing droplets. On highly hydrophobic patterned surfaces drop coalescence can lead to an out-of-plane jump of the composite drop. We discuss the importance of energy dissipation to the jumping process and identify an anisotropy of the jumping ability with respect to surface features. We show that Gibbs' pinning is the source of this anisotropy and explain how it leads to the inhibition of coalescence-induced jumping. The second example we study is the novel phenomenon of pancake bouncing. Conventionally, a drop falling onto a superhydrophobic surface spreads due to its inertia, retracts due to its surface tension, and bounces off the surface. Here we explain a different pathway to bouncing that has been observed in recent experiments: A drop may spread upon impact, but leave the surface whilst still in an elongated shape. This new behaviour, which occurs transiently for certain impact and surface parameters, is due to reversible liquid imbibition into the superhydrophobic substrate. We develop a theoretical model and test it on data from experiments and simulations. The theoretical model is used to explain pancake bouncing in detail.
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Mujahid, Raqibul I. "Evaporation of liquid fuel droplet." abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1460767.
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Clavijo, Angeles Cristian Esteban. "Droplet Impingement on Superhydrophobic Surfaces." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6306.
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This dissertation explores the physics of droplet impingement on superhydrophobic surfaces. The research is divided in three categories. First, the effect of a slip boundary condition on droplet spreading/retracting is considered. A model is developed based on energy conservation to evaluate spreading rates on surfaces exhibiting isotropic and anisotropic slip. The results show that larger slip causes the droplet to spread out farther owing to reduced friction at the interface for both slip scenarios. Furthermore, effects of slip become magnified for large Weber numbers due to the larger solid-liquid contact area during the process. On surfaces with anisotropic slip, droplets adopt an elliptical shape following the azimuthal contour of the slip on the surface. It is common for liquid to penetrate into the cavities at the superhydrophobic interface following droplet impact. Once penetrated, the flow is said to be in the Wenzel state and many superhydrophobic advantages, such as self-cleaning and drag-reduction, become negated. Transition from the Wenzel to the Cassie state (liquid resides above the texture) is referred to as dewetting and is the focus of the second piece of this dissertation. Micro-pillar pitch, height and temperature play a role on dewetting dynamics. The results show that dewetting rates increase with increasing pillar height and increasing surface temperature. A scaling model is constructed to obtain an explanation for the experimental observations and suggests that increasing pillar height increasing the driving dewetting force, while increasing surface temperature decreases dissipation. The last piece of work of this dissertation entails droplet impingement on superheated surfaces (100°C - 400°C). We find that the Leidenfrost point (LFP) occurs at a lower temperature on a hydrophobic surface than a hydrophilic one, where the LFP refers to the lowest temperature at which secondary atomization ceases to occur. This behavior is attributed to the manner in which vapor bubbles grow at the solid-liquid interface. Also in this work, high-speed photographs reveal that secondary atomization can be significantly suppressed on a superhydrophobic surface owing to the micro-pillar forest which allows vapor to escape hence minimizing bubble formation within the droplet. However, a more in-depth study into different superhydrophobic texture patterns later reveals that atomization intensity can significantly increase for small pitch values given the obstruction to vapor flow presented by the increased frequency of the pillars.
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Lupo, Giandomenico. "Detailed simulations of droplet evaporation." Licentiate thesis, KTH, Mekanik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-217614.
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Droplet evaporation (and condensation) is one of the most common instancesof multiphase flow with phase change, encountered in nature as well as intechnical and industrial applications. Examples include falling rain drops, fogsand mists, aerosol applications like electronic cigarettes and inhalation drugdelivery, engineering applications like spray combustion, spray wet scrubbing orgas absorption, spray drying, flame spray pyrolysis.Multiphase flow with phase change is a challenging topic due to the inter-twined physical phenomena that govern its dynamics. Numerical simulation isan outstanding tool that enables us to gain insight in the details of the physics,often in cases when experimental studies would be too expensive, impracticalor limited.In the present work we focus on simulation of the evaporation of smalldroplets. We perform simulation of evaporation of a pure and two−componentdroplet, that includes detailed thermodynamics and variable physical andtransport properties. Some of the conclusions drawn include the importance ofenthalpy transport by species diffusion in the thermal budget of the system, andthe identification and characterization of evaporating regimes for an azeotropicdroplet.In the second part we develop a method based on the immersed boundaryconcept for interface resolved numerical simulation of laminar and turbulentflows with a large number of spherical droplets that undergo evaporation orcondensation.Droppförångning (och kondensation) är en av de vanligaste fallen av flerfasflöde med fasförändring, både i naturen och i tekniska och industriella tillämpningar. Exempel är fallande regndroppar, dimma, aerosol-tillämpningar som elektroniskacigaretter och läkemedelsleverans via inandning, tekniska tillämpningar som sprayförbränning, våtskrubbning med sprayning, gasabsorption, spraytorkning samt flammsprayspyrolys. Flerfasflöde med fasförändring är ett utmanande ämne på grund av de sammanflätade fysikaliska fenomen som styr dess dynamik. Numerisk simulering är ett utmärkt verktyg som gör det möjligt för oss att få insikt i detaljerna i fysiken, ofta i fall då experimentella studier skulle vara för dyra, opraktiska eller begränsade. I det nuvarande arbetet fokuserar vi på simulering av förångning av små droppar. Vi utför simulering av förångning av en ren och två−komponentdroppe, som inkluderar detaljerad termodynamik samt varierande fysikaliska och transportegenskaper. Några av de slutsatser som dras inbegriper betydelsen av entalpitransport genom diffusion av olika ämnen i systemets termiska budget samt identifieringen och karakterisering av förångningsregimer för en azeotropiskdroppe. I den andra delen utvecklar vi en metod baserad på det nedsänkta rand konceptet för gränssnittskompletterad numerisk simulering av laminära och turbulenta flöden med ett stort antal sfäriska droppar som genomgår förångning eller kondensering.
QC 20171117
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Krahmer, Natalie. "Analysis of Lipid Droplet Proteins and their Contribution to Phospholipid Homeostasis during Lipid Droplet Expansion." Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-133305.
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Amin, Lekhraj Purushotham. "An investigation of droplet stability and droplet size distribution in a continuous oscillatory baffled tube." Thesis, Heriot-Watt University, 2005. http://hdl.handle.net/10399/226.
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Harshman, Dustin Karl. "Droplet Manipulation and Droplet Microfluidics for Rapid Amplification and Real-Time Detection of Nucleic Acids." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/556818.
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Molecular diagnostics offer quick access to information for healthcare decision-making towards personalized therapeutics, but complicated procedures requiring extensive labor and infrastructure restrict their use. Droplet-based technologies can expand the accessibility of molecular diagnostics by miniaturizing devices, shortening sample-to-answer times, decreasing costs and increasing throughput. Methods for droplet manipulation are central to the automation of molecular diagnostics protocols. The innovative method, wire-guided droplet manipulation (WDM), is the actuation of liquid droplets in a hydrophobic milieu with a wire, or needle, guide. In this work, WDM is demonstrated for the automation of the polymerase chain reaction (PCR) on reprogrammable platforms for the diagnosis of cardiovascular infections. WDM is used to minimize thermal resistance by convective heat transfer for PCR amplification at a maximum speed of 8.67 s/cycle. The oil-water interfacial boundary is shown to passively partition molecular contaminants from sample matrices, including blood and heart valve tissue. Molecular self-assembly at the oil-water interface is used to increase PCR efficiency with blood in situ and is used as an innovative sensing modality for real-time monitoring of PCR amplification. Temperature feedback controlled droplet actuation is achieved by using a thermocouple loop as a functionalized wire-guide. Our novel methodology for real-time PCR, droplet-on-thermocouple silhouette real-time PCR (DOTS qPCR), utilizes interfacial effects to achieve droplet actuation, relief from PCR inhibitors and amplification sensing, for a sample-to-answer time as short as 3 min 30 s. DOTS qPCR addresses three major issues for rapid PCR—sample preparation, rapid thermocycling and sensitive real-time detection—on an inexpensive, disposable device with smartphone-based detection. In contrast, commercially available real-time PCR systems rely on fluorescence detection, have substantially higher threshold cycles, and require expensive optical components and extensive sample preparation. Due to the advantages of low threshold cycle detection we anticipate extending this technology towards trending biological research applications such as single cell, single nucleus, and single DNA molecule analyses, especially in droplet microfluidic platforms.
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Teo, Adrian J. "Active Droplet Control and Manipulation in Microfluidics." Thesis, Griffith University, 2020. http://hdl.handle.net/10072/392033.
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Droplet microfluidics involves the use of small volumes of fluids dispersed in an immiscible phase to perform multiple functions. Droplet microfluidics brings advantages such as the miniaturization of experiments, portability of devices, efficient use of resources and capabilities for scaling up production. These tools have been finding their use in a broad range of applications, from chemical and biological analysis to optics and information technology. Various types of controls have been developed to enable the manipulation of droplets. These techniques are categorized into passive and active methods. Passive methods only involve the device geometries and the fluid flow. Active techniques on the other hand provide another level of controllability for adjusting droplet parameters, allowing rapid change of droplet parameters within a single experiment. This flexibility enables user to select parameters and subsequent actions on the same device. Particularly, droplet-on-demand systems benefit from these techniques.
The aim of this thesis is the development of different active methods for droplet manipulation. The thesis first focuses on three active control methods, pneumatic, acoustic and electric. Firstly, negative pressure is applied for the controlling droplet generation in a device. The novel application of negative pressure directly affects the flow in the microchannel to generate droplets on demand. This control approach, unlike other active approaches eliminates space constraints within the device with no need for external equipment. Next, a new fabrication approach for interdigitated transducers for generating acoustic waves was developed. This approach eliminates the use of expensive fabrication equipment and simplifies fabrication procedures. Acoustic streaming in a droplet was successfully demonstrated with these transducers. Finally, electric methods are used for controls in droplet generation and coalescence. Non-Newtonian droplets are generated through application of the electric field. On-demand coalescence of droplets is also observed using a combination of AC electric field and a micropillar.
The new approaches reported in this thesis provide a greater versatility in microfluidics applications. The simpler alternatives suggested here would overcome current limitations of fabrication complexity and large device footprint, allowing microfluidics to be more accessible and easily implemented. The outcome of this thesis contributes to enhancing the uptake of microfluidics in multidisciplinary research and to broadening the user base of this technology.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
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De, Souza Lima Roger Williams. "Drying droplets as a template for multi-component solid particles : experimental study and modeling at the droplet scale Drying droplet as a template for solid formation: a review In situ Raman composition profiling in drying droplets." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2020. http://www.theses.fr/2020EMAC0003.
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Les gouttes liquides se sont avérées l’un des principaux vecteurs pour la génération de particules solides à propriétés contrôlées. Ce type de vecteur est utilisé dans plusieurs domaines industriels, y compris le séchage par atomisation. Le développement de ces particules structurées est poussé par la demande pour des particules à propriétés contrôlées, comme la cinétique de dissolution, le relargage contrôlé ou la réactivité. Le principal verrou scientifique est la description détaillée de la distribution des constituants au sein de la goutte pendant le séchage, en plus de la prédiction de la morphologie de la particule finale. L'objectif de cette thèse est de comprendre, par une approche couplée modélisation/expérimentation, comment les conditions de séchage et les formulations liquides impactent la structure de la poudre. L'étude expérimentale a d'abord été réalisée dans un sécheur par atomisation à l'échelle laboratoire pour la création d'une cartographie représentant les morphologies obtenues pour les deux systèmes de séchage. Un dispositif expérimental a été conçu de manière à étudier la formation d'une particule solide à partir d'une goutte suspendue par un filament, ce qui permet d'appréhender des éléments fondamentaux relatifs au séchage de la goutte ainsi que des aspects sur la modification de la structure solide. Une nouveauté explorée à l'échelle de la goutte avec un lévitateur acoustique consistait à appliquer la spectroscopie Raman in situ afin d'évaluer l'évolution de la distribution spatiale de deux composants lors du séchage de la goutte. Enfin, un modèle de séchage de goutte en 2-D avec la Dynamique des Fluides Numérique est conçu, ce qui permet de quantifier la distribution spatiale des composants de la goutte sous un séchage convectif, jusqu’à la formation de la croûte. Une analyse de sensibilité est réalisée de manière à montrer l'influence des conditions expérimentales sur la cinétique de séchage et la distribution spatiale des solutésLiquid droplets are one of the major means of generation of solid particles with controlled. These templates are encountered with a variety of industrial processes, among them, spray drying. These tailored structures would meet the demand for particles with controlled properties, like improved kinetics, sustained release or controlled reactivity. The major scientific obstacle is the detailed description of the components distribution inside the droplet during drying, besides prediction of the final particle morphology. An experimental/modeling approach is undertaken in this thesis to understand how the drying conditions and the liquid formulation impact the final structure of the powders. The drying systems studied were sucrose-dextran and lactose-whey protein isolate aqueous solutions. The experimental work was firstly carried out at the lab-scale spray-dryer giving a reference picture of the possible particle morphologies for the drying systems. An experimental set-up was designed and developed to suspend a liquid droplet by a filament, from which the droplet mass variation over time could be accurately measured, giving fundamental insight into the drying process and allowing the analysis of the modification of the solid structures. A novelty explored at the droplet scale with an acoustic levitator was to apply an in situ Raman spectroscopy to assess the evolution of the spatial distribution of two components in drying droplets. Finally, a 2-D droplet drying model using Computational Fluid Dynamics was developed for allowing the assessment of the spatial distribution of the droplet components under a convective drying, until the formation of a crust. A sensitivity analysis was performed in order to show the influence of the experimental conditions on the drying kinetics and the component spatial distribution
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Towell, Samuel Thurston 1977. "Evaluation of an adaptive control algorithm for use in uniform droplet spray in droplet based manufacturing." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/26884.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000.Includes bibliographical references (leaf 32).
This thesis presents the results of a simulation study comparing the current integral control system with an adaptive control system for potential use in a Uniform Droplet Spray Process. First, an adaptive control algorithm was derived. Then, this algorithm and the existing integral control algorithm were coded for use in MATLAB simulations. The simulations were performed against each other over various sampling periods and noise classes to compare the performance of both droplet diameter mean and standard deviation. Results showed that for the target diameter of 760 [mu]m, the adaptive controller could produce droplets with the mean diameter of 759.9 [mu]m and a standard deviation of 0.0066 [mu]m, while the integral controller produced droplets having the mean diameter and standard deviation of 759.7 [mu]m and 0.0084 [mu]m, respectively. Over the sampling periods experimented with, the adaptive controller could produce droplets with the mean diameter of 759.9 [mu]m and a standard deviation of 0.0061 [mu]m, while the integral controller produced droplets having the mean diameter and standard deviation of 759.9 [mu]m and 0.0074 [mu]m, respectively.
by Samuel Thurston Towell.
S.B.
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Musehane, Ndivhuwo M. "Direct numerical simulation of bubble-bubble and droplet-droplet interaction using a Surface Thin Film model." Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/22963.
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This dissertation deals with the simulation of dispersed multiphase flow. The particle-particle and particle-fluid interactions in this class of flows play an important role on the hydrodynamics and fluid transport phenomena that govern the overall flow behaviour. Accurate computational modelling of the particle-particle and particle- fluid interactions is thus required to correctly model the flow. The aim of this study is to use a Direct Numerical Simulation approach based on a smoothed Volume Of Fluid method to model particle-particle interactions in a dispersed multiphase flow at a fundamental level, and employing a surface thin film model, to drastically reduce the computational effort required. A multiscale modelling approach is followed with the smoothed Volume Of Fluid simulation on the particle scale and the surface thin film model simulation on the thin- film scale. The resulting governing equations are the Navier-Stokes equations for an incompressible viscous multiphase Newtonian fluid undergoing laminar and isothermal three-dimensional flow, the interface advection equation and the reduced order surface thin film equation. The model equations are discretized using the Finite Volume Method and implemented into the open source software OpenFOAM®. The numerical solution is obtained by solving the resulting non-linear system of equations implicitly on a structured computational grid on parallel processors using a pressure correction algorithm to converge the pressure at each time step. The study is restricted to gas-liquid systems where particles could either be bubbles or droplets; rigid particles are not considered. The model is tested against experimental results from binary collision of hydrocarbon droplets. Good qualitative numerical results are obtained at a practical computational cost.
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Hessling, Oscar. "Influence of Oxygen Partial Pressure on the Droplet Shape of Stainless Steel Using Levitated Droplet Method." Thesis, KTH, Materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-199668.
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An induction setup for levitation studies of molten metals was built. The setup was used to levitate and heat stainless steel samples of 2.00 g to 1600 °C and subject them to different atmospheres. Changes in shape and temperature were recorded by video and infrared thermocouple. Oxide films forming on the droplets during levitation were observed. It was possible to notice an immediate surface reaction when the reaction gas was introduced. This reaction is concluded to influence the surface and bulk composition, and therefore have an effect on the shape evolution of the droplet. A more oxidizing atmosphere resulted in a more conical droplet shape; this is thought to be an effect of lowered surface tension and the conically shaped volumetric force caused by the magnetic field. Changes in temperature after the sample is molten are thought to be an effect of changes in emissivity, caused by surface oxidization. Post mortem analysis show a difference in surface morphology for samples subjected to different gases, as well as a difference in amount of oxidization.
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Ip, Leong-Teng. "Comprehensive Black Liquor Droplet Combustion Studies." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd677.pdf.
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Maimaiti, Abdula. "Multi Exposure Droplet Imaging System – MEDIS." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-52745.
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A new fast flash photography fast imaging system is devised to develop for studying the evolution of micron sized droplets travelling from the ink jet nozzle to substrate at 5 - 20 m/s. using flash illumination of 10 short pulses from different angles consecutively, sharp images of evolving droplets are expected to be captured. The electrical and optical characterization of the laser driver and photodetector is presented along with corresponding measurements. Detailed schematics of the whole optical system design are presented.
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Mohammadi, Kimia. "Synthetic biology in droplet-based microfluidics." Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7596/.
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Droplet microfluidics is an active multidisciplinary area of research that evolved out of the larger field of microfluidics. It enables the user to handle, process and manipulate micrometer-sized emulsion droplets on a micro- fabricated platform. The capability to carry out a large number of individual experiments per unit time makes the droplet microfluidic technology an ideal high-throughput platform for analysis of biological and biochemical samples. The objective of this thesis was to use such a technology for designing systems with novel implications in the newly emerging field of synthetic biology. Chapter 4, the first results chapter, introduces a novel method of droplet coalescence using a flow-focusing capillary device. In Chapter 5, the development of a microfluidic platform for the fabrication of a cell-free micro-environment for site-specific gene manipulation and protein expression is described. Furthermore, a novel fluorescent reporter system which functions both in vivo and in vitro is introduced in this chapter. Chapter 6 covers the microfluidic fabrication of polymeric vesicles from poly(2-methyloxazoline-b-dimethylsiloxane-b-2-methyloxazoline) tri-block copolymer. The polymersome made from this polymer was used in the next Chapter for the study of a chimeric membrane protein called mRFP1-EstA∗. In Chapter 7, the application of microfluidics for the fabrication of synthetic biological membranes to recreate artificial cell- like chassis structures for reconstitution of a membrane-anchored protein is described.
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Syeda, Ruhma. "Potassium channels in droplet interface bilayers." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.669989.
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Roberts, Warren B. "Black liquor droplet combustion and modeling /." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1339.pdf.
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Rennie, Allan E. W. "Droplet deposition of liquid metal microdrops." Thesis, Brunel University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366644.
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Seidel, Susanne. "Nanoliter-droplet thermophoresis for biomedical applications." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-173039.
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Specific interactions of biomolecules are central to cellular processes, drug discovery and immunodiagnostics. Such biological binding events are quantifiable via thermophoresis, the directed molecule movement driven by a temperature gradient. Biomolecule thermophoresis can be induced by infrared laser heating and analyzed using fluorescence. The objective of this thesis was to enhance and optimize these all-optical measurements, regarding instrumentation, assay design and biomedical applications.
In the first part, a novel measurement device and approach are presented, which cut down sample consumption 50-fold compared to established capillary thermophoresis. Instead of capillaries, analysis was performed in 10 nl-sample droplets transferred into standard 1536-well plates with a non-contact liquid handler (Labcyte). To prevent evaporation, the aqueous sample droplets were stabilized in an oil-surfactant mix. Temperature induced effects in this water-in-oil system were experimentally characterized and the results agreed with numerical simulation. The system’s applicability for biomolecular interaction analysis was confirmed with a DNA aptamer. The achieved miniaturization and the easy-to-handle multi-well plate format promote automated high-throughput screens. Besides aptamers, proteins should also be measurable very well when judging from the application depth of capillary measurements.
This versatility of protein investigation via capillary thermophoresis is demonstrated in the second part. Successful experiments were not only conducted in diverse liquids including crude cell lysate, but also for binding partners with a broad range of molecular weight ratios. Affinities between protein and protein, protein and peptide, as well as protein and small molecule were determined with high accuracy. Further flexibility arises from the herein presented label free approach which utilizes protein intrinsic UV fluorescence. It is caused by aromatic amino acids with tryptophan being the major intrinsic fluorophore. This approach exempts from the need to attach a dye, which saves time and excludes labeling artifacts.
The wide variety of proteins that can be analyzed with thermophoresis also includes anti-bodies.
Two applications of such thermophoretic immunoassays are introduced in the third part. Firstly, the therapeutically interesting antibody MCPR3-7 was assessed. MCPR3-7 binds proteinase 3 (PR3), the major autoimmune target in granulomatosis with polyangiitis. Thermophoresis allowed to quantified MCPR3-7’s affinity and selectivity for different PR3 forms. In addition, it revealed that the antibody interferes with the complexation of PR3 and alpha-1-proteinase inhibitor (alpha-1PI). Secondly, a diagnostic autocompetition assay is described, which directly determines affinity and concentration of disease related biomarkers. It was applied for autoantibodies against the cardiac β1-adrenoceptor found in patients suffering from dilated cardiomyopathy. To detect these autoantibodies, the small peptide COR1 mimicking the adrenoceptor’s dominant epitope served as an artificial antigen. This tracer was labeled with a red-fluorescent dye, which ensured selectivity for measurements directly in untreated human blood serum. The results prove that thermophoresis is a valuable tool to characterize antibodies including those of diagnostic value and those with a therapeutic potential.
Taken together, the presented innovations in assay design and the novel nl-droplet approach can be expected to considerably widen the application spectrum of thermophoresis in fundamental research, industrial drug discovery and clinical laboratory diagnostics.Spezifische Interaktionen von Biomolekülen sind von zentraler Bedeutung für zelluläre Prozesse, die Entwicklung neuer Medikamente und die Immundiagnostik. Solche biologischen Bindungsvorgänge lassen sich mittels Thermophorese, der gerichteten Molekülbewegung entlang eines Temperaturgradienten, quantifizieren. Die Thermophorese von Biomolekülen kann durch Infrarotlaser-Heizen induziert und mittels Fluoreszenz analysiert werden. Die Weiterentwicklung dieses optischen Verfahrens bezüglich des Messinstruments, des Versuchsdesigns und der biomedizinischen Anwendungen war das Ziel der vorliegenden Dissertation. Im ersten Teil wird eine neuartige Technik vorgestellt, die den Probenverbrauch verglichen mit etablierten Kapillarmessungen um den Faktor 50 verkleinert. Statt in Kapillaren wurde in 10 nl-großen Probentropfen gemessen, die mit einem kontaktfreien Liquid-Handler (Labcyte) in eine 1536-Well-Platte übertragen wurden. Zum Schutz vor Verdunstung wurden die Tropfen in eine Öl-Tensid-Schicht transferiert. Temperaturinduzierte Effekte in diesem Wasser-in-Öl-System wurden experimentell charakterisiert, wobei die Ergebnisse durch numerischen Simulationen bestätigt wurden. Dass sich die Methode für biomolekulare Interaktionstests eignet, wurde anhand eines DNA-Aptamers belegt. Die Miniaturisierung und die einfache Handhabung der Multi-Well-Platten ermöglichen automatisierte Hochdurchsatz-Screens. Neben Aptameren sollten sich auch Proteine sehr gut untersuchen lassen, wenn man von einer ähnlichen Anwendungsbreite wie bei Kapillarmessungen ausgeht. Auf derartige Proteinuntersuchungen mittels Kapillarthermophorese wird im zweiten Teil eingegangen. Analysen wurden nicht nur in diversen Puffern und sogar in rohem Zelllysat durchgeführt, sondern auch mit unterschiedlichsten Bindungspartnern. So wurden Affinitäten zwischen Protein und Protein, Protein und Peptid, sowie Protein und niedermolekularer Verbindung mit hoher Genauigkeit bestimmt. Thermophoresetests gewinnen durch das in dieser Arbeit präsentierte, markierungsfreie Verfahren zusätzlich an Flexibilität. Es basiert auf der intrinsischen UV-Fluoreszenz von Proteinen, die auf aromatische Aminosäuren, hauptsächlich Tryptophan, zurückzuführen ist. Somit müssen Proteine nicht mehr mit Fluoreszenzfarbstoffen markiert werden, was Zeit spart und Artefakte ausschließt. Der dritte Teil behandelt die Quantifizierung von Antikörpern. Thermophoretische Immunassays wurden für zwei biomedizinische Fragestellungen eingesetzt. Zunächst wurde der aus therapeutischer Sicht interessante Antikörper MCPR3-7 untersucht. Er ist gegen Proteinase 3 (PR3) gerichtet, das Hauptepitop autoimmuner Antikörper bei der granulomatösen Polyangiitis. Mithilfe der Thermophorese wurde sowohl die Affinität von MCPR3-7 für verschiedene PR3-Formen quantifiziert, als auch gezeigt, dass der Antikörper die Komplexierung von PR3 und alpha-1-Proteinaseinhibitor (alpha-1PI) stört. Ferner wird ein diagnostisches Autokompetitionsverfahren vorgestellt, das gleichzeitig die Affinität und die Konzentration von Biomarkern in humanem Blutserum quantifiziert. Autoantikörper gegen den kardialen β1-Adrenozeptor, die mit der dilatativen Kardiomyopathie assoziiert sind, wurden mithilfe des kurzen Peptides COR1 analysiert, das das dominante Epitop nachstellt. Die Ergebnisse belegen, dass die Thermophorese ein wertvolles Werkzeug für die Antikörpercharakterisierung ist. Zusammengefasst lassen die vorgestellten Neuerungen eine umfangreiche Erweiterung des Anwendungssprektrums der Biomolekülthermophorese in der Grundlagenforschung, der industriellen Wirkstoffsuche und der klinischen Labordiagnostik erwarten.
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Brown, Philip Simon. "Water droplet impact on functional surfaces." Thesis, Durham University, 2013. http://etheses.dur.ac.uk/9446/.
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The impact and spreading of picolitre-sized water droplets on a substrate is of importance in many applications such as rapid cooling, delayed freezing, crop spraying, and inkjet printing. In this thesis, the effects of substrate chemistry, roughness, hardness, charge, and porosity on such droplet impact are studied. The effect of roughness was investigated through the use of superhydrophobic CF4 plasma fluorinated polybutadiene. Comparison of the maximum spreading ratio and droplet oscillation frequencies with literature models shows that both are found to be lower than theoretically predicted. Further study of the effect of multiple types of surface topography was carried out via the CF4 plasma texturing of honeycomb surfaces, leading to hierarchical surfaces with roughness on two length scales. This led to the discovery that surfaces with similar static contact angles can give rise to different droplet impact dynamics, governed by the underlying surface topography. The effect of the mechanical properties of the substrate upon picolitre droplets can be important in microfluidics. The oscillatory dynamics of picolitre droplets following impact were found to depend upon the thickness and elasticity of the substrate. Higher oscillation frequencies are measured for softer and thicker films, which are correlated to larger surface deformations around the contact line. Static buildup during inkjet printing is known to affect print quality. The role of surface charge on picolitre droplet impact onto polymer substrates is found to give rise to increased droplet impact velocities. Higher surface potentials can result in unexpected behaviour such as droplet bouncing or increased contact area diameters leading to a decrease in print resolution. Printing on porous materials is important as porosity can aid ink adhesion and durability. CF4 plasma fluorination of porous membranes can inhibit droplet spreading laterally over a surface, with little change in the imbibition behaviour in the material, leading to printing that is more highly defined. These hydrophobic membranes remain oleophilic and could also find use in oil–water separation. Similarly, a hydrophilic–oleophobic switching surface can be beneficial in a range of applications such as anti-fogging, self-cleaning, and oil– water separation. Polelectroyle–fluorosurfactant complexes were found to exhibit excellent switching, resulting in a surface that quickly becomes hydrophilic whilst remaining oleophobic.
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Lin, Gungun. "Multifunctional Droplet-based Micro-magnetofluidic Devices." Doctoral thesis, Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-208797.
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Confronted with the global demographic changes and the increasing pressure on modern healthcare system, there has been a surge of developing new technology platforms in the past decades. Droplet microfluidics is a prominent example of such technology platforms, which offers an efficient format for massively parallelized screening of a large number of samples and holds great promise to boost the throughput and reduce the costs of modern biomedical activities. Despite recent achievements, the realization of a compact and generic screening system which is suited for resource-limited settings and point-of-care applications remains elusive.
To address the above challenges, the dissertation focuses on the development of a compact multifunctional droplet micro-magnetofluidic system by exploring the advantages of magnetic in-flow detection principles. The methodologies behind a novel technique for biomedical applications, namely, magnetic in-flow cytometry have been put forth, which encompass magnetic indexing schemes, quantitative multiparametric analytics and magnetically-activated sorting. A magnetic indexing scheme is introduced and intrinsic to the magnetofluidic system. Two parameters characteristic of the magnetic signal when detecting magnetically functionalized objects, i.e. signal amplitude and peak width, providing information which is necessary to perform quantitative analysis in the spirit of optical cytometry has been proposed and realized. Magnetically-activated sorting is demonstrated to actively select individual droplets or to purify a population of droplets of interest. Together with the magnetic indexing scheme and multiparametric analytic technique, this functionality synergistically enables controlled synthesis, quality administration and screening of encoded magnetic microcarriers, which is crucial for the practical realization of magnetic suspension arrays technologies. Furthermore, to satisfy the needs of cost-efficient fabrication and high-volume delivery, an approach to fabricate magnetofluidic devices on flexible foils is demonstrated. The resultant device retains high performance of its rigid counterpart and exhibits excellent mechanical properties, which promises long-term stability in practical applications.
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Jones, Dominic. "Spray Modelling without Droplet Size Segregation." Thesis, University of Manchester, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521565.
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Donini, Mariovane Sabino. "Numerical solution for the droplet combustion." Universidade Federal do Pampa, 2017. http://dspace.unipampa.edu.br:8080/jspui/handle/riu/1955.
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In the present work, vaporization and combustion of an isolated fuel droplet at diferente ambient temperatures are examined numerically in order to analyze the effect of buoyancy force on the flame. Generally, fuel droplets in combustion devices are so small that the influence of buoyancy force on vaporization and combustion of droplets is negligible. On the other hand, fuel droplets in experimental devices are affected by the buoyancy force due to their diameters being around or more than 1 mm. To reduce the buoyancy effects, expensive experimental studies are performed in microgravity ambient (drop-tower or out of space). In normal-gravity conditions, the buoyancy force is induced by temperature gradient on ambient atmosphere. The buoyancy is positive in regions of hot gases and negative in regions of cold gases compared with the ambient atmosphere gas. Hot gases move upward and cold gases downward. Playing with the positive buoyancy force of hot gases around the flame and with the negative (cold) buoyancy force of cold gases around the droplet via ambient atmosphere temperature, it is possible to modify the flame shape. In the numerical simulations, incompressible Navier–Stokes equations along with mixture fraction and excess enthalpy conservation equations are solved using a finite volume technique with a uniform structured grid. An artificial compressibility method was applied to reach steady state solutions. The numerical predictions have been compared with analytical results for a zero gravity condition, showing good agreement. For normal gravity condition the numerical results showed that when the ambient temperature increases, the velocity gradient and buoyancy source term decreases. Despite that, the flame increased in all directions. The results have also shown that increasing the ambient temperature, decreases the temperature gradient in the flame, which ends up affecting the flame position.
No presente trabalho, a vaporização e a combustão de uma gota de combustível isolada a diferentes temperaturas ambiente são examinadas numericamente para analisar o efeito da força de flutuação na chama. Geralmente, as gotículas de combustível em dispositivos de combustão são tão pequenas que a influência da força de flutuação na vaporização e na combustão de gotículas é insignificante. Por outro lado, as gotículas de combustível em dispositivos experimentais são afetadas pela força de flutuabilidade devido ao seu diâmetro em torno de ou mais de 1 mm. Para reduzir os efeitos de flutuabilidade, estudos experimentais caros são realizados em ambiente de microgravidade (drop-tower ou fora do espaço). Em condições de gravidade normal, a força de flutuação é induzida por gradiente de temperatura na atmosfera ambiente. A flutuabilidade é positiva em regiões de gases quentes e negativas em regiões de gases frios em comparação com o gás atmosférico ambiente. Os gases quentes movem-se para cima e os gases frios para baixo. Jogando com a força de flutuação positiva dos gases quentes ao redor da chama e com a força de flutuação negativa (fria) dos gases frios ao redor da gota através da temperatura da atmosfera ambiente, é possível modificar a forma da chama. Nas simulações numéricas, as equações de Navier-Stokes incompressíveis juntamente com a fração de mistura e as equações de conservação de entalpia em excesso são resolvidas usando uma técnica de volume finito com uma grade estruturada uniforme. Foi aplicado um método de compressibilidade artificial para alcançar soluções de estado estacionário. As previsões numéricas foram comparadas com resultados analíticos para uma condição de gravidade zero, mostrando boa concordância. Para a condição de gravidade normal, os resultados numéricos mostraram que, quando a temperatura ambiente aumenta, o gradiente de velocidade e o termo da fonte de flutuação diminuem. Apesar disso, a chama aumentou em todas as direções. Os resultados também mostraram que aumentar a temperatura ambiente, diminui o gradiente de temperatura na chama, o que acaba afetando a posição da chama.
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Perima, Angga. "Combinatorial antibiotic screening using droplet microfluidics." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066741.
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De nos jours, nous vivons à l'époque où la résistance aux antibiotiques est devenue une grave menace mondiale. L'une des solutions pour découvrir de nouveaux antibiotiques est de combiner des médicaments existants qui ont été approuvés par la FDA. Cependant, cette via les méthodes conventionnelles est très coûteuse et lente. Le but de ce projet est de combiner les antibiotiques à l'aide de la microfluidique en gouttelettes pour surmonter ces limites. Tout d'abord, nous avons caractérisé la croissance bactérienne dans les gouttelettes et calibrons un dosage de croissance de fluorescence à haut débit en utilisant Syto-9. Ensuite, nous avons sélectionné un ensemble de 11 antibiotiques qui ne fuient pas des gouttelettes aux gouttelettes. Nous présentons une technique pour émulsifier en parallèle jusqu'à 96 puits contenant des antibiotiques à différentes doses. Nous avons montré ensuite comment le couplage et la fusion microfluidiques permettent de combiner différentes bibliothèques de médicaments. Enfin, nous avons présenté une preuve de concept d'une mesure des interactions médicamenteuses dans les gouttelettes. Dans la dernière partie de ce travail, nous avons élaboré une stratégie de codage par l'ADN pour identifier les interactions médicamenteuses par séquençage après une étape de tri basée sur le test de croissance. Pour conclure, nous avons conçu et optimisé les différents modules microfluidiques au niveau suffisant pour pouvoir être combinés de manière robuste. Ils peuvent fournir une plate-forme technologique capable de réduire les coûts et le temps de dosage pour les combinaisons de médicaments à l'échelle du laboratoire avant l'essai cliniqueNowadays, we are living in the era where antibiotic resistance has become a serious worldwide threat. One of the solution to discover novel antibiotics is to combine existing drugs that have been approved by FDA. However, drug combination using conventional method is highly expensive and has low throughput. The aim of this project is to combine antibiotics using droplet microfluidics to overcome these limitations. First, we show how to control the encapsulation of bacteria E. coli MG1655 by correlating Poisson distribution and OD (Optical Density) for different volume of droplets. We then characterize bacterial growth inside droplets and calibrate a high-throughput fluorescence growth assay using Syto-9. Then, we select a set of 11 antibiotics that do not leak from droplets to droplets and represent major classes of mechanisms. We present a technique to emulsify in parallel up to 96 wells containing antibiotics at different doses. We then show how microfluidic pairing and fusion allow to combine different drug-dose libraries. Finally, we present a proof of concept of a measurement of drug interactions in droplets. In the last part of this work, we elaborate a DNA barcoding strategy to identify drug interactions by sequencing after a sorting step based on the growth assay. To conclude, we have designed and optimized the different microfluidic modules to level sufficient so that they can be combined robustly. It can provide a technological platform that is able to reduce cost and assay time for drug combinations at a laboratory scale, before clinical trial
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Mazutis, Linas. "Droplet-based microfluidics for protein evolution." Strasbourg, 2009. http://www.theses.fr/2009STRA6178.
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La compartimentalisation de la "soupe primordiale" dans des vésicules est considérée comme l'un des principaux facteurs ayant permis l'émergence de la vie. Ces gouttelettes de quelques micromètres créent un lien entre génotype et phénotype, et grâce à la division, un mécanisme pour l’hérédité et l’évolution, qui a conduit à l'émergence des cellules actuelles. De tels microcompartiments, peuvent être créés au laboratoire sous la forme d’une émulsion composée de millions de gouttelettes contenant des gènes et tous les ingrédients nécessaires pour leur expression in vitro. Ces émulsions miment ainsi des populations de cellules artificielles qui peuvent être sélectionnées pour un phénotype donné sous des conditions strictement contrôlées non réalisables dans des systèmes in vivo. Cette thèse de doctorat présente le développement de systèmes microfluidiques pour l’évolution dirigée. Les résultats obtenus montrent qu’il est possible de produire des gouttelettes hautement monodisperses pouvant être manipulées de manière précise et contrôlable, ce qui était jusqu’à présent impossible pour des émulsions réalisées par des méthodes classiques. En utilisant un ensemble de nouveaux dispositifs microfluidiques et une composition adéquate d’huile porteuse, des gènes uniques ont été amplifiés et leur expression in vitro mesurée en microgouttelettes. Ces dispositifs ont ensuite été utilisés pour réaliser et analyser des réactions biologiques complexes et multi-étapes. Une technique originale de fusion passive de paires de gouttelettes a également été développée. Ces travaux constituent les premiers pas vers la création de plate-formes microfluidiques intégrées et totalement in vitroThe compartmentalization of the primordial soup into vesicles is thought to be one of the key features in the early emergence of life. These tiny micrometer-sized droplets provided a linkage between phenotype and genotype, and through division, a mechanism for heredity and evolution, which gave rise to modern cells. Man-made compartments, in the form of an emulsion, can also provide a tool of linking genotype to phenotype. Composed of millions of droplets containing genes with all ingredients necessary for in vitro expression, emulsions mimic populations of artificial cells that can be selected for a particular phenotype under strictly controlled conditions not feasible in living systems. The research described in this doctoral thesis focuses on the development of droplet-based microfluidics for protein evolution and presents the first steps toward an integrated and completely in vitro microfluidics platform. The results obtained in this work show that it is possible to produce highly monodisperse picoliter volume droplets (CV<1%) that can be manipulated in a precise and controllable manner, previously impossible in bulk emulsions. Using a set of novel microfluidic devices and an adequate composition of carrier oil single genes in droplets were amplified and their in vitro expression measured. The same microfluidic system was also used to perform multiple operations in order to analyze complex and sequential biological reactions in droplets. Moreover, a new passive droplet fusion technique has been developed, which can be used for preparation of monodisperse emulsions composed of pairwise fused droplets
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Davoudi, Masoume. "Aerosol Droplet Migration in Fibrous Media." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1509120181801687.
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Torkkeli, Altti. "Droplet microfluidics on a planar surface /." Espoo : Technical Research Centre of Finland, 2003. http://www.vtt.fi/inf/pdf/publications/2003/P504.pdf.
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Roberts, Warren Benjamin. "Black Liquor Droplet Combustion and Modeling." BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/745.
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Black liquor is an intermediate product of pulp production. Recovery boilers process black liquor to recover the inorganic material for recycling in the mill and to generate electricity and steam for the paper mill. Black liquor droplet combustion rates and mechanisms dictate many aspects of recovery boiler performance. This investigation documents new experimental data on single droplet pyrolysis and combustion in a laboratory furnace that mimics many of the essential features of commercial boilers (temperature, composition, droplet size, etc.). These experiments monitored single droplets placed on a thermocouple wire and suspended from a mass balance. Simultaneous video images and pyrometry data provide mass loss and internal temperature data. These investigations provide an extensive data set from which to validate a model and insight into the mechanisms of combustion. Particles burning in air expelled ejecta from the particle during the entire combustion process, though ejection rates during the late stages of char combustion were observed to be higher than during other stages. In addition, char burning began almost the instant the particle entered the reactor; showing significant overlap in the combustion processes. A transient, 1-dimensional, single-droplet model describes droplet combustion. This model solves the momentum, energy, species continuity, and overall continuity equations using the control volume method. The model uses the power-law scheme for combined advection diffusion, and the fully-implicit scheme for the time step. It predicts internal velocities, gas and solid temperatures (assumed equal), pressure, and composition. Pressure and velocity equations use Darcy's Law for flow through a porous medium. Modeling results show the large effect of swelling on all particle properties. This model describes the flame region by extending the control volume into the gas phase.
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Farhan, Noor M. "Multiphase Droplet Interactions with a Single Fiber." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/5937.
Full textAbstract:
Abstract
Multiphase Droplet Interactions with a Single Fiber
By: Noor M. Farhan
A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Virginia Commonwealth University.
Virginia Commonwealth University, 2019
Director: Hooman V. Tafreshi,
Professor, Department of Mechanical and Nuclear Engineering
Formulating the physics of droplet adhesion to a fiber is interesting intellectually and important industrially. A typical example of a droplet–fiber system in nature is the dew droplets on spider webs, where droplets first precipitate and grow on the fibers, but they eventually fall when they become too heavy. Obviously, quantifying the force of adhesion between a droplet and a fiber is crucial in designing fog harvesting devices or manufacturing filtration media for liquid–gas or liquid–liquid separation, among many other industrial applications. This study is aimed at developing a mathematical framework for the mechanical forces between a droplet and a fiber in terms of their physical and wetting properties. To this end, a series of experiments were conducted to detach ferrofluid droplets of varying volumes from fibers with different diameters and Young–Laplace contact angles (YLCAs) in a controlled magnetic field. The force of detachment was measured using a sensitive scale and used along with the results of numerical simulations to develop a semi-analytical expression for the force required to detach a droplet from a fiber. This universally-applicable expression allows one to predict the force detachment without the need to run an experiment or a computer simulation.
This work also reports on the use of magnetic force to measure the force of detachment for nonmagnetic droplets for the first time. This is accomplished by adding a small amount of a ferrofluid to the original nonmagnetic droplet to create a compound droplet with the ferrofluid nesting inside or cloaking the nonmagnetic droplet. The ferrofluid is then used to induce a body force to the resulting compound droplet and thereby detach it from the fiber. The recorded detachment force is used directly (the case of nesting ferrofluid) or after scaling (the case of cloaking ferrofluid) to obtain the force of detachment for the original nonmagnetic droplet. The accuracy of these measurements was examined through comparison with numerical simulations as well as available experimental data in the literature. In addition, a simple method is developed to directly measure the intrinsic contact angle of a fiber (i.e., Young–Laplace Contact angle of the fiber material) with any arbitrary liquid. It is shown that the intrinsic contact angle of a fiber can be obtained by simply measuring the angle between the tangent to the fiber surface and the tangent to the droplet at the contact line, if the droplet possesses a clamshell conformation and is viewed from the longitudinal direction. The novelty of the proposed method is that its predictions are not affected by the volume of the droplet used for the experiment, the wettability of the fiber, the surface tension of the liquid, or the magnitude of the body force acting on the droplet during the experiment.
Also, a liquid droplet interaction with granular coatings is simulated and the droplet apparent contact angle (ACA) and the transition from Cassie (fully dry) to Wenzel (fully wet) state as a function to the roughness wavelength have been studied. For a fixed droplet volume, two different granular coatings have been used, spherical and hemispherical bumps. It is demonstrated that the chemistry (YLCA) and geometrical parameters for the granular microtexture play an important effect on the droplet ACA and its transition from Cassie to Wenzel state.
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Deepu, P. "Dynamics of Droplets Under Support, Acoustic And/Or Ambient Flow Excitation." Thesis, 2013. http://etd.iisc.ac.in/handle/2005/3459.
Full textAbstract:
The first step on the way to understanding the complicated dynamics of spray is to study the behavior of isolated droplets. In many industrial and natural processes such as turbulent combustion, agricultural sprays, spray cooler, falling raindrops and cloud evolution the droplet is subjected to a chaotic unsteady external flow field. The interaction between the liquid and gaseous phases results in very intricate droplet dynamics like capillary instabilities, atomization, droplet collision and coalescence and vaporization, to name a few.
In this dissertation, the focus is on shape oscillations, atomization and vaporization dynamics of pendant and sessile droplets. A droplet residing on a substrate which vibrates vertically at ultrasonic frequency will exhibit different modes of shape oscillation. The competition between capillary forces and inertia forces is basically responsible for these oscillations. However, when an acoustic force field is introduced asymmetrically around the droplet, we discover with the help of ultra high-speed imaging, a new droplet spreading phase. This new method of droplet manipulation could nd application in micro fluidics and lab-on-a-chip systems. By lading the droplet with nanoparticles, the spreading rate can be easily controlled. The spreading phase is followed by an atomization phase where surface ligaments grow to disintegrate into daughter droplets; the intensity of atomization is found to decrease with increase in fluid viscosity. The ability to control atomization characteristics of droplets by lading them with nanoparticles is a powerful technique that may be implemented in spray coolers and combustors to control the spray characteristics or combustion efficiency. Both the spreading and ligament dynamics have been theoretically simulated and the physics behind the observed trends is explained. The growth rate of the ligaments is found to be governed by Weber number modified to include the acoustic pressure level of the standing wave. The frequency of ligament breakup is found to decrease with fluid viscosity and this observation is adequately supported by a theory developed based on the evolution crater on the droplet surface.
Turning now to the pendant droplets, by decomposing the droplet shape into Legendre modes, the shape oscillations exhibited by a droplet hanging from the junction of cross-wire placed at the center of an air jet is studied. Both high-speed imaging and hot-wire anemometry are employed. The driving force of oscillation of droplets subjected to the air jet is proved to be the inherent pressure fluctuations in the jet. The effect of surface tension, viscosity and Reynolds number on the shape oscillation level has been examined. The first experimental evidence of viscous attenuation of lower frequencies in a particular mode in glycerol/water mixture is reported. A theoretical model was developed to simulate the droplet shape oscillations induced by different ambient flow fields like pulsatile flow, vortical flow and flow with broadband energy spectrum. The time of interaction of the droplet with an eddy in the flow is found to be very crucial in determining the amplitude of oscillation of the droplet. The shorter the interaction time, the higher are the chances of the droplet oscillation being pushed into resonance.
Finally, the heat transfer and droplet regression dynamics of pendant droplets in a hot air stream of various chemical compositions (like conventional fuels, alternative fuels and nanosuspensions) have been experimentally analyzed using high speed imaging. The droplet is deployed at the junction of cross-wire at the centre of a vertical air jet. A hybrid timescale has been proposed which incorporates the effects of latent heat of vaporization, saturation vapor pressure and thermal diffusivity. This timescale in essence encapsulates the different parameters that influence the droplet vaporization rate. The analysis further permitted the evaluation of the effect of various parameters such as surrounding temperature, Reynolds number, far-field vapor presence, impurity content and agglomeration dynamics (nanosuspensions) in the droplet.
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Deepu, P. "Dynamics of Droplets Under Support, Acoustic And/Or Ambient Flow Excitation." Thesis, 2013. http://etd.iisc.ernet.in/2005/3459.
Full textAbstract:
The first step on the way to understanding the complicated dynamics of spray is to study the behavior of isolated droplets. In many industrial and natural processes such as turbulent combustion, agricultural sprays, spray cooler, falling raindrops and cloud evolution the droplet is subjected to a chaotic unsteady external flow field. The interaction between the liquid and gaseous phases results in very intricate droplet dynamics like capillary instabilities, atomization, droplet collision and coalescence and vaporization, to name a few.
In this dissertation, the focus is on shape oscillations, atomization and vaporization dynamics of pendant and sessile droplets. A droplet residing on a substrate which vibrates vertically at ultrasonic frequency will exhibit different modes of shape oscillation. The competition between capillary forces and inertia forces is basically responsible for these oscillations. However, when an acoustic force field is introduced asymmetrically around the droplet, we discover with the help of ultra high-speed imaging, a new droplet spreading phase. This new method of droplet manipulation could nd application in micro fluidics and lab-on-a-chip systems. By lading the droplet with nanoparticles, the spreading rate can be easily controlled. The spreading phase is followed by an atomization phase where surface ligaments grow to disintegrate into daughter droplets; the intensity of atomization is found to decrease with increase in fluid viscosity. The ability to control atomization characteristics of droplets by lading them with nanoparticles is a powerful technique that may be implemented in spray coolers and combustors to control the spray characteristics or combustion efficiency. Both the spreading and ligament dynamics have been theoretically simulated and the physics behind the observed trends is explained. The growth rate of the ligaments is found to be governed by Weber number modified to include the acoustic pressure level of the standing wave. The frequency of ligament breakup is found to decrease with fluid viscosity and this observation is adequately supported by a theory developed based on the evolution crater on the droplet surface.
Turning now to the pendant droplets, by decomposing the droplet shape into Legendre modes, the shape oscillations exhibited by a droplet hanging from the junction of cross-wire placed at the center of an air jet is studied. Both high-speed imaging and hot-wire anemometry are employed. The driving force of oscillation of droplets subjected to the air jet is proved to be the inherent pressure fluctuations in the jet. The effect of surface tension, viscosity and Reynolds number on the shape oscillation level has been examined. The first experimental evidence of viscous attenuation of lower frequencies in a particular mode in glycerol/water mixture is reported. A theoretical model was developed to simulate the droplet shape oscillations induced by different ambient flow fields like pulsatile flow, vortical flow and flow with broadband energy spectrum. The time of interaction of the droplet with an eddy in the flow is found to be very crucial in determining the amplitude of oscillation of the droplet. The shorter the interaction time, the higher are the chances of the droplet oscillation being pushed into resonance.
Finally, the heat transfer and droplet regression dynamics of pendant droplets in a hot air stream of various chemical compositions (like conventional fuels, alternative fuels and nanosuspensions) have been experimentally analyzed using high speed imaging. The droplet is deployed at the junction of cross-wire at the centre of a vertical air jet. A hybrid timescale has been proposed which incorporates the effects of latent heat of vaporization, saturation vapor pressure and thermal diffusivity. This timescale in essence encapsulates the different parameters that influence the droplet vaporization rate. The analysis further permitted the evaluation of the effect of various parameters such as surrounding temperature, Reynolds number, far-field vapor presence, impurity content and agglomeration dynamics (nanosuspensions) in the droplet.
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高天冀. "Droplets-Collision Analysis and Droplet-Generator Development." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/64196574472669709072.
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