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1
Castro, Angelica. "Manipulation of biomimetic objects in acoustic levitation." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2013. http://pastel.archives-ouvertes.fr/pastel-00938546.
Abstract:
La lévitation acoustique par des ondes stationnaires ultrasonores (USW), permettent la manipulation des objets micrométriques. L'objectif principal de cette thèse est d'explorer les possibilités offertes par la lévitation acoustique pour manipuler des particules, des cellules et même des bactéries. Nous avons conçu et construit tous les résonateurs et nous avons développé les méthodologies que nous allons montrer dans ce travail expérimental. Selon la nature des particules, leur déplacement est donné par son interaction avec la force acoustique primaire. La position où les particules se déplacent est le point dont les forces acoustique et gravitationnel sont équilibrées. Dans le plan de lévitation, les interactions connues comme force secondaire de Bjerknes est la première étape du processus d'agrégation. Nous présentons une méthodologie pour mesurer cette force. Nous avons mesuré cette force en conditions de micropesanteur. Dans nous résonateurs, nous travaillons avec un grand nombre des particules dont les agrégats sont 3D. Nous introduisons le mode acoustique pulsé que nous permet générer des agrégats 2D. Lorsque les particules deviennent plus petites de 1µm, sa manipulation est difficile en raison de l'influence de l'acoustic streaming qui modifie le comportement des particules. Le mode acoustique pulsé permet de réduire ou de contrôler l'acoustic streaming que nous permet manipuler des particules de taille submicronique, des bactéries et des micro-cylindres catalytiques. Une séparation a été faite par un mélange des particules de 7-12µm dans le dispositif s-SPLITT. Néanmoins la combinaison de forces hydrodynamique et acoustique (HACS) a permis améliorer la séparation.
2
Castro, Camacho Luz Angelica. "Manipulation of biomimetic objects in acoustic levitation." Paris 6, 2013. http://www.theses.fr/2013PA066673.
Abstract:
La lévitation acoustique par des ondes stationnaires ultrasonores (USW), permettent la manipulation des objets micrométriques. L'objectif principal de cette thèse est d'explorer les possibilités offertes par la lévitation acoustique pour manipuler des particules, des cellules et même des bactéries. Nous avons conçu et construit tous les résonateurs et nous avons développé les méthodologies que nous allons montrer dans ce travail expérimental. Selon la nature des particules, leur déplacement est donné par son interaction avec la force acoustique primaire. La position où les particules se déplacent est le point dont les forces acoustique et gravitationnel sont équilibrées. Dans le plan de lévitation, les interactions connues comme force secondaire de Bjerknes est la première étape du processus d'agrégation. Nous présentons une méthodologie pour mesurer cette force. Nous avons mesuré cette force en conditions de micropesanteur. Dans nous résonateurs, nous travaillons avec un grand nombre des particules dont les agrégats sont 3D. Nous introduisons le mode acoustique pulsé que nous permet générer des agrégats 2D. Lorsque les particules deviennent plus petites de 1µm, sa manipulation est difficile en raison de l'influence de l’acoustic streaming qui modifie le comportement des particules. Le mode acoustique pulsé permet de réduire ou de contrôler l’acoustic streaming que nous permet manipuler des particules de taille submicronique, des bactéries et des micro-cylindres catalytiques. Une séparation a été faite par un mélange des particules de 7-12µm dans le dispositif s-SPLITT. Néanmoins la combinaison de forces hydrodynamique et acoustique (HACS) a permis améliorer la séparationLevitation is a promising tool for contactless guiding and non-toxic manipulation. Acoustic levitation by ultrasonic standing waves (USW) allows micron-scale particle manipulation in acoustic resonators. The main goal of this thesis is to explore the possibilities given by the acoustic levitation for manipulating rigid and elastic particles, cells and even bacteria. Therefore we designed and built all the resonators we used and developed new methodologies we shall show in this experimental work. According to the particles nature, their displacement towards the node or the antinode is given by the interaction with the primary force. The position where particles move is a point where the acoustic and the gravitational forces are balanced. At the levitation plane, the first stage of the aggregation process is given by inter particles interactions known as the secondary Bjerknes force. We introduced a methodology for measuring this short range force. In addition, we measured this force in microgravity conditions. Usually, we dealt with hundreds or thousands of micron-size particles leading 3D aggregates. We introduce pulse mode acoustics, where we can generate homogeneous structures, 2D aggregates. However, when species smaller than 1µm particle manipulation is challenging due the complex influence of the acoustic streaming. Pulse mode acoustics can reduce or control the acoustic streaming leading applications to sub-micron size particles, bacteria and catalytic micro rods. A mixture of 7-12µm particles was separated in the s-SPLITT device. However the combination of hydrodynamic and the programmed acoustic of HACS device, improved the purity of the separation
3
Ramachandran, Narayanan. "MODELING AND CONTROL OF ACOUSTIC LEVITATION FOR DUST CONTROL APPLICATION." OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/364.
Abstract:
The objective is to study and model acoustic levitation by treating it as a control system problem rather than visualizing it as a physical system problem. The specific agenda is to model the acoustic levitation system and design a controller using the obtained model; this model can be used in for "Active dust control" in a closed chamber. A test-bed needs to be developed and constructed for experimental investigation and proof of concept of particle manipulation using sonic/ultrasonic waves. Acoustic standing waves are well established physical concepts, but controlling and modeling the same is a difficult control system problem because of various non-linearity that creeps in an acoustic system at high frequency. Future work would involve in designing a robust controller using the model obtained. The same needs to be extended to the 3-d acoustic dust control system.
4
Thomas, Gilles Pierre Loïc. "Modeling, design and manufacturing of an acoustic levitation linear transportation system." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-28112016-083848/.
Abstract:
Acoustic levitation is a method which uses sound radiation to suspend matter in a medium. The main use of this phenomenon is for the contactless processing of matter, allowing to manipulate small objects without any solid contact. Contactless processing of matter presents many advantages in, for example, the fabrication of MEMS (microelectromechanical systems) where handling the components is challenging because of their fragile and surface-sensitive characteristics or in the chemical/biological industry when handling high-purity or hazardous materials. Thus, a new device for noncontact linear transportation of small solid objects is presented here. In this device, ultrasonic flexural vibrations are generated along the ring shaped vibrator using two Langevin transducers and by using a reflector parallel to the vibrator, small particles are trapped at the nodal points of the resulting acoustic standing wave. The particles are then moved by generating a traveling wave along the vibrator, which can be done by modulating the vibration amplitude of the transducers. The working principle of the traveling wave along the vibrator has been modeled by the superposition of two orthogonal standing waves, and the position of the particles can be predicted by using finite element analysis of the vibrator and the resulting acoustic field. A prototype consisting of a 3 mm thick, 220 mm long, 50 mm wide and 52 mm radius aluminum ring-type vibrator and a reflector of the same length and width was built and small polystyrene spheres have been successfully transported along the straight parts of the vibrator.Levitação acústica é um método para suspender matéria em um meio através de pressão de radiação acústica gerada por intensas ondas de som. O principal uso desse fenômeno é na manipulação de partículas sem contato solido. Esse fenômeno tem várias aplicações para pesquisas onde deve ser evitado todo o contato como, por exemplo, na área de biologia, química, e na fabricação de MEMS. Assim, um novo sistema de transporte linear de partículas por levitação acústica está apresentado aqui. Nesse sistema, vibrações flexurais estão geradas em uma placa tipo anel com dois transdutores tipo Langevin, e colocando um refletor paralelo ao oscilador, partículas estão presas no pontos nodais da onda acústica gerada. As partículas estão deslocadas modulando a amplitude dos transdutores. Assim, este trabalho tem como objetivos a modelagem do fenômeno de levitação acústica, o dimensionamento de um protótipo de sistema de transporte linear de partículas por levitação acústica, bem como a fabricação e o controle desse protótipo. Um protótipo consistindo de uma estrutura tipo anel de alumínio de 3 mm de espessura, 220 mm de comprimento e um raio de 52 mm foi fabricado e o transporte de pequenas esferas de isopor foi realizado com êxito nas parte retas do vibrador.
5
Lupi, Victor D. (Victor Dominick). "The development of an acoustic levitation test facility for cloud physics research." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/27969.
6
Warschat, Carsten. "Implementierung der akustischen Levitation in ein Totalanalysesystem." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19417.
Abstract:
Als Totalanalysesysteme (TAS) werden Geräte bezeichnet, welche komplette chemische Analysen eigenständig ausführen. Die Einführung solcher Systeme ermöglicht einen effizienteren Arbeitsablauf in Analyselaboren, da beispielsweise die Probenmanipulation, Aufreinigung und die physikalisch-/chemische Analyse automatisiert in einem Arbeitsgang durchgeführt werden können. Die speziellen Mikrototalanalysesysteme benötigen geringere Probemengen im $\mu$L- Bereich. Durch Kontamination, Agglomeration oder einem Verschluss etwaiger Kanäle in mikrofluidischen Totalanalysesystemen kann es zu einem kompletten Systemausfall kommen. Eine Alternative bildet die akustische Levitation, um derartige Störfälle durch gänzlichen Verzicht auf Gefäße und Wandkontakte gezielt zu reduzieren. Damit die akustische Levitation erfolgreich in Mikrototalanalysesystemen Anwendung finden kann, bedarf es der technischen Weiterentwicklung von Analysemethoden und Kopplungstechniken.
In der vorliegenden Arbeit wird das Hauptaugenmerk auf die Kopplung von Levitationstechnik und Massenspektrometrie gelegt. Darüber hinaus wurden spektroskopische Experimente durchgeführt, welche auf Totalreflektionen innerhalb der Tropfen beruhen. Die besonders gute Reflektion hängt damit zusammen, dass sich die Phasengrenze zwischen Luft und Flüssigkeit im Schwebezustand durch molekulare Wechselwirkungen ständig erneuert und keine produktionsbedingte raue Oberfläche aufweist. Die Kombination aus automatischer Tropfengenerierung, Spektroskopie sowie der entwickelten Methode zur Ionenerzeugung aus dem Probevolumen und der massenspektrometrischen Analyse bilden die Grundlage eines neuartigen Mikrototalanalysesystems für geringe Probemengen.As a total analysis system (TAS) an instrument is called which carries out complete chemical analysis procedures independently. The introduction of such systems offers a more efficient workflow in analytical laboratories because the sample manipulation, purification and the actual automated analysis can be carried out in one single operation. Specialized and already existing micro total analysis systems require currently a small amount of sample in the $\mu$L range. Owing to contamination, agglomeration and thus cross-secion reduction of incorporated channels in micro fluidics total analysis systems it can lead to a complete system interruption. Hence, the implementation of acoustic levitation in these systems is interessting alternative in order to avoid such kind of problems by abandoning vessels and wall contacts completely. To ensure acoustic levitation in micro total analysis systems can be successfully applied, technical development of analytical methods and coupling techniques is required. In the present work, the coupling of levitation technology and mass spectrometry is the prioritized topic but, in addition, spectroscopic experiments based on total reflections within the levitated droplet are as well realized in order to gain process insights. The particularly good reflection at the freely levitated droplet's circumference is due to the fact that the phase boundary between air and liquid is renewed by molecular interactions constantly and has no production-related rough surface. The combination of automated droplet generation, spectroscopy as well as the developed method for ion generation from the sample volume and mass spectrometry forms the basis of a novel micro total analysis system for small sample quantities.
7
Yin, Yanbo. "NON-CONTACT OBJECT TRANSPORTATION USING NEAR-FIELD ACOUSTIC LEVITATION INDUCED BY ULTRASONIC FLEXURAL WAVES." NCSU, 2007. http://www.lib.ncsu.edu/theses/available/etd-09282007-091302/.
Abstract:
Handling and processing precision products, such as Compact Discs, LCDs, LSIs and silicon wafers requires strict conditions to keep the products from acquiring tiny defects, scratches and stains. A non-contact transportation system using Near-Field Acoustic Levitation (NFAL) will satisfy these conditions. An initial experiment was firstly set up to check the validation of NFAL Phenomenon. A system consisting of an aluminum beam, two piezoelectric actuators and a mechanical horn was experimentally and theoretically analyzed. With an input of 300 Vp-p, a flat object weighing 4g could be levitated and transported with the speed up to 17 cm/s. The transportation direction can be reversed by adjusting the phase angle difference between the two actuators. Computational fluid dynamics simulation was performed to obtain the time average speed in acoustic streaming. Sliding Film Theory was then utilized to investigate the mechanism of transportation, where the shear force induced by the acoustic streaming was found to be the main source of driving the floating object. To extend the transportation, transportation over a curved path and Module-to-Module connection were experimentally performed. A beam with a shape of 90 degrees of arc was found to have uniform mode shapes and experiment results confirmed its feasibility to change transportation direction. For Module-to-Module connection, a speed threshold was discovered beyond which the transportation would be smooth without any problems. Cylinder rolling induced by the acoustic streaming was also performed to find out the dynamics of the cylinder. To optimize the system performance, the mechanical parts were analyzed in frequency domain. A close-loop system, which consists of the transportation module, vision module, and instrumentation module, was proposed. PID, Single Neuron Method and Sliding Mode Control were adopted to investigate the control effects and the performance results were mixed.
8
Schiffter, Heiko A. [Verfasser]. "Single Droplet Drying of Proteins and Protein Formulations via Acoustic Levitation / Heiko A Schiffter." Aachen : Shaker, 2006. http://d-nb.info/117053404X/34.
9
Schiffter, Heiko Alexander [Verfasser]. "Single Droplet Drying of Proteins and Protein Formulations via Acoustic Levitation / Heiko A Schiffter." Aachen : Shaker, 2006. http://nbn-resolving.de/urn:nbn:de:101:1-2018110406334581120604.
10
Qasem, Amal ali. "Design and Development of an Acoustic Levitation System for Use in CVD Growth of Carbon Nanotubes." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479809526489146.
11
Andrade, Marco Aurélio Brizzotti. "Estudo da força de radiação acústica em partículas produzida por ondas progressivas e estacionárias." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-11082010-164959/.
Abstract:
O objetivo deste trabalho é estudar o fenômeno da força de radiação acústica produzida por ondas progressivas e estacionárias. Neste trabalho o estudo da força produzida por ondas estacionárias é aplicado na análise de um levitador acústico e o estudo da força de radiação acústica por ondas progressivas é feito visando a futura construção de um separador acústico. Neste trabalho é utilizado o método dos elementos finitos para simular o comportamento de um levitador acústico. Primeiramente, é feita a simulação de um levitador acústico que consiste de um transdutor de Langevin com uma face de emissão plana que opera na freqüência de aproximadamente 20 kHz e um refletor plano. O método dos elementos finitos é utilizado para determinar o deslocamento da face do transdutor e o potencial acústico que atua numa esfera pequena. O deslocamento da face do transdutor obtido numericamente é comparado com o medido experimentalmente por um vibrômetro de fibra ótica e o potencial acústico determinado pelo método dos elementos é verificado experimentalmente colocando pequenas esferas de isopor no levitador. Depois de verificar o modelo numérico, o método dos elementos finitos é utilizado na otimização de um levitador acústico composto de um refletor côncavo e um transdutor com face de emissão côncava. Os resultados numéricos mostram que a força de radiação acústica no novo levitador é aumentada em 604 vezes quando comparada com o levitador composto de um transdutor com face plana e refletor plano. Este trabalho também apresenta um modelo numérico para determinar a trajetória de partículas esféricas na presença de uma onda de ultra-som progressiva. O modelo assume que as seguintes forças atuam na partícula: gravidade, empuxo, forças viscosas e força de radiação acústica devido a uma onda progressiva. Com o objetivo de não restringir o tamanho das partículas que podem ser utilizadas no modelo é empregada uma equação empírica do coeficiente de arrasto, válida para uma grande faixa de número de Reynolds. O modelo proposto requer a distribuição de pressão gerada pelo transdutor de ultra-som. A distribuição de pressão é medida experimentalmente utilizando um hidrofone calibrado. A verificação do modelo é feita soltando-se pequenas esferas de vidro (com diâmetros da ordem de 500 m) em frente a um transdutor de ultra-som de 1 MHz e 35 mm de diâmetro.The objective of this work is to study the acoustic radiation force produced by progressive and standing waves. In this work, the studies related to the acoustic radiation force generated by ultrasonic standing waves are applied in the analysis of an acoustic levitator and the studies involving the acoustic radiation force generated by progressive waves are conducted aiming the design of acoustic separators. In this work, the finite element method is used to simulate an acoustic levitator. First, an acoustic levitator consisting of a 20 kHz Langevin ultrasonic transducer with a plane radiating surface and a plane reflector is simulated by the finite element method. The finite element method is used to determine the transducer face displacement and the acoustic radiation potential that acts on a small sphere. The numerical displacement is compared with that obtained by a fiber-optic vibration sensor and the acoustic radiation potential determined by the finite element method is verified experimentally by placing small Styrofoam spheres in the levitator. After verifying the numerical method, the finite element method was used to optimize an acoustic levitator consisting of a concave-faced transducer and a curved reflector. The numerical results show that the acoustic radiation force in the new levitator is enhanced 604 times compared with the levitator consisting of a plane transducer and a plane reflector. This work also presents a numerical model to determine the trajectory of sphere particles when submitted to ultrasonic progressive waves. This model assumes that the following forces act on the particle: gravity, buoyancy, viscous forces and acoustic radiation force due to the progressive wave. In order not to restrict the model to a small particle size range, the viscous forces that act on the sphere are modeled by an empirical relationship of drag coefficient that is valid for a wide range of Reynolds numbers. The numerical model requires the pressure field radiated by the ultrasonic transducer. The pressure field is obtained experimentally by using a calibrated needle hydrophone. The numerical model validation is done by dropping small glass spheres (on the order of 500 m diameter) in front of a 1-MHz 35-mm diameter ultrasonic transducer.
12
Omirou, Themis. "Levitataed interfaces - with sound : exploring the use of acoustic levitation for the creation of dynamic and physical visualizations." Thesis, University of Bristol, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.738242.
13
Gutierrez, Ramos Salomé. "Acoustic confinement of Escherichia coli : the impact on biofilm formation." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS599.
Abstract:
Les particules browniennes ou auto-propulsées dans des suspensions aqueuses peuvent être piégées par des champs acoustiques générés par des transducteurs piézoélectriques, généralement à des fréquences dans le mégahertz. Le confinement obtenu permet d’étudier des comportements collectifs riches tels que la dynamique de regroupement ou d’étalement dans des conditions de type microgravité. Le champ acoustique induit la lévitation des particules autopropulsées et fournit des forces latérales secondaires pour les capturer dans les plans nodaux. Dans cette thèse, nous allons plus loin dans le champ de la matière active confinée, en rapportant des expériences de lévitation de suspensions bactériennes d’Escherichia coli. La formation de grappes de bactéries vivantes s’effectue en fonction du temps, où différents comportements sont clairement distingués. Lors de la suppression du signal acoustique, les bactéries se propagent rapidement, entraînées par leur propre nage. Le piégeage de divers phénotypes bactériens entraîne des enchevêtrements irréversibles et la formation de biofilms flottant librementBrownian or self-propelled particles in aqueous suspensions can be trapped by acoustic fields generated by piezoelectric transducers usually at frequencies in the Megahertz.The obtained confinement allows the study of rich collective behaviours like clustering or spreading dynamics in microgravity-like conditions. The acoustic field induces the levitation of self- propelled particles and provides secondary lateral forces to capture them at nodal planes. Here, we give a step forward in the field of confined active matter, reporting levitation experiments of bacterial suspensions of Escherichia coli. Clustering of living bacteria ismonitored as a function of time, where different behaviours are clearly distinguished. Upon the removal of the acoustic signal, bacteria rapidly spread, impelled by their own swimming. Trapping of diverse bacteria phenotypes result in irreversible bacteria entanglements and inthe formation of free-floating biofilms
14
Stindt, Arne. "Probing levitated droplets with mass spectrometry." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17538.
Abstract:
Ultraschalllevitation kombiniert die Vorteile von Mikrofluidik, wie beispielsweise die sehr geringe benötigte Probenmenge, mit einer wandlosen Probenhandhabung. Obwohl die Kopplung zwischen le- vitierten Tröpchen und verschiedenster analytischer Methoden wie optischer Spektroskopie und Röntgenbeugung sehr genau untersucht ist, fehlt es immer noch an einer etablierten Kopplung mit einer massenspektrometrischen Methode für die Analyse auf molekularer Ebene. Die vorliegende Arbeit beschreibt die Prinzipien, auf denen eine kontaktlose massenspektrometrische Analyse von levitierten flüssi- gen Proben beruht. Zuerst wurde der neu entworfene akustische Levitator bezüglich des Einflusses seiner Geometrie auf die Levi- tationseigenschaften experimentell und mittels numerischer Simul- tationen untersucht. Die anschließend durch geführten Experimen- te demonstrieren das Potential von Infrarot-Lasern als kombinierte Desorptions- und Ionisationsquelle für organische Substanzen aus einer Mischung aus Wasser und Glycerin als Cromophor. Um einen tieferen Einblick in die hierbei ablaufenden Ionisationsmechanismen zu erhalten, wurde als Modell ein “Sonic-Spray” Konus räumlich per Massenspektrometrie und Laser-induzierter Fluoreszenz untersucht. Levitator-Geometrie auf die Levitationseigenschaften stimmen sehr gut mit numerischen Simulationen überein. Als komplementäre Ionisationsmethode wurde eine Niedertemperatur-Plasmaquelle ein- gesetzt. Nach einer zeitaufgelösten Untersuchung der grundlegenden Ionisationsmechanismen wurde diese Quelle für die Untersuchung flüchtiger Spezies aus der levitierten Probe in deren direkten Umgebung ohne störende Interferenzen ge- nutzt.Ultrasonic levitation combines advantages of microfluidics like the required small sample volumes with a wall-less sample handling. While the coupling of analytical methods like optical spectroscopy as well as x-ray scattering are very well elaborated, an established mass spectrometric method to obtain molecular analytical information is still lacking. The herein presented work describes the fundamental processes for a contactless mass spectrometric analysis of levitated droplets. First, the influences of the specially designed levitator geometry on the levitation capabilities is described. During further experiments, the use of infrared lasers has proven useful as a combined desorption and ionization source for organic molecules from a mixture of water and glycerol as chromophore. Subsequently, sonic-spray ionization was used to gain a deeper understanding of the ionization processes occurring within the spray plume. Mass spectrometric mapping as well as laser-induced fluorescence were performed to investigate the ionization during an aerodynamic breakup of the micro droplets in the spray process. As a complementary sampling method, the ionization with a low- temperature plasma source is described. First, a time-resolved mass spectrometric investigation of the ionization process is shown. Sub- sequent to this fundamental study, the application of such a plasma source for the direct analysis of volatile compounds from within the droplets in the surrounding environment without interferences from the droplets bulk phase is described.
15
Tijerino, Campollo Erick. "Agglomeration, Evaporation and Morphological Changes in Droplets with Nanosilica and Nanoalumina Suspensions in an Acoustic Field." Master's thesis, University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5531.
Abstract:
Acoustic levitation permits the study of droplet dynamics without the effects of surface interactions present in other techniques such as pendant droplet methods. Despite the complexities of the interactions of the acoustic field with the suspended droplet, acoustic levitation provides distinct advantages of controlling morphology of droplets with nanosuspensions post precipitation. Droplet morphology is controlled by vaporization, deformation and agglomeration of nanoparticles, and therefore their respective timescales are important to control the final shape. The balance of forces acting on the droplet, such as the acoustic pressure and surface tension, determine the geometry of the levitated droplet. Thus, the morphology of the resultant structure can be controlled by manipulating the amplitude of the levitator and the fluid properties of the precursor nanosuspensions. The interface area in colloidal nanosuspensions is very large even at low particle concentrations. The effects of the presence of this interface have large influence in the properties of the solution even at low concentrations. This thesis focuses on the dynamics of particle agglomeration in acoustically levitated evaporating nanofluid droplets leading to shell structure formation. These experiments were performed by suspending 500&"181;m droplets in a pressure node of a standing acoustic wave in a levitator and heating them using a carbon dioxide laser. These radiatively heated functional droplets exhibit three distinct stages, namely, pure evaporation, agglomeration and structure formation. The temporal history of the droplet surface temperature shows two inflection points. Morphology and final precipitation structures of levitated droplets are due to competing mechanisms of particle agglomeration, evaporation and shape deformation. This thesis provides a detailed analysis for each process and proposes two important timescales for evaporation and agglomeration that determine the final diameter of the structure formed. It is seen that both agglomeration and evaporation timescales are similar functions of acoustic amplitude (sound pressure level), droplet size, viscosity and density. However it is shown that while the agglomeration timescale decreases with initial particle concentration, the evaporation timescale shows the opposite trend. The final normalized diameter hence can be shown to be dependent solely on the ratio of agglomeration to evaporation timescales for all concentrations and acoustic amplitudes. The experiments were conducted with 10nm silica, 20nm silica, 20nm alumina and 50nm alumina solutions. The structures exhibit various aspect ratios (bowls, rings, spheroids) which depend on the ratio of the deformation timescale (tdef) and the agglomeration timescale (tg).M.S.A.E.
Masters
Mechanical and Aerospace Engineering
Engineering and Computer Science
Aerospace Engineering; Thermofluid Aerodynamic Systems
16
Saha, Abhishek. "Evaporation, Precipitation Dynamics and Instability of Acoustically Levitated Functional Droplets." Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5477.
Abstract:
Evaporation of pure and binary liquid droplets is of interest in thermal sprays and spray drying of food, ceramics and pharmaceutical products. Understanding the rate of heat and mass transfer in any drying process is important not only to enhance evaporation rate or vapor-gas mixing, but also to predict and control the final morphology and microstructure of the precipitates. Acoustic levitation is an alternative method to study micron-sized droplets without wall effects, which eliminates chemical and thermal contamination with surfaces. This work uses an ultrasonic levitation technique to investigate the vaporization dynamics under radiative heating, with focus on evaporation characteristics, precipitation kinetics, particle agglomeration, structure formation and droplet stability. Timescale and temperature scales are developed to compare convective heating in actual sprays and radiative heating in the current experiments. These relationships show that simple experiments can be conducted in a levitator to extrapolate information in realistic convective environments in spray drying. The effect of acoustic streaming, droplet size and liquid properties on internal flow is important to understand as the heat and mass transfer and particle motion within the droplet is significantly controlled by internal motion. Therefore, the droplet internal flow is characterized by Particle Image Velocimetry for different dropsize and viscosity. Nanosuspension droplets suspended under levitation show preferential accumulation and agglomeration kinetics. Under certain conditions, they form bowl shaped structures upon complete evaporation. At higher concentrations, this initial bowl shaped structure morphs into a ring structure. Nanoparticle migration due to internal recirculation forms a density stratification, the location of which depends on initial particle concentration. The time scale of density stratification is similar to that of perikinetic-driven agglomeration of particle flocculation. The density stratification ultimately leads to force imbalance leading to a unique bowl-shaped structure. Chemically active precursor droplet under acoustic levitation shows events such as vaporization, precipitation and chemical reaction leading to nanoceria formation with a porous morphology. The cerium nitrate droplet undergoes phase and shape changes throughout the vaporization process followed by formation of precipitate. Ex-situ analyses using TEM and SEM reveal highly porous morphology with trapped gas pockets and nanoceria crystalline structures at 70 degree C. Inhomogeneity in acoustic pressure around the heated droplet can induce thermal instability. Short wavelength (Kelvin-Helmholtz) instability for diesel and bio-diesel droplets triggers this secondary atomization, which occurs due to relative velocity between liquid and gas phase at the droplet equator. On the other hand, liquids such as Kerosene and FC43 show uncontrollable stretching followed by a catastrophic break-up due to reduction in surface tension and viscosity coupled with inhomogeneity of pressure around the droplet. Finally, a scaling analysis has been established between vaporizing droplets in a convective and radiative environment. The transient temperature normalized by the respective scales exhibits a unified profile for both modes of heating. The analysis allows for the prediction of required laser flux in the levitator experiments to show its equivalence in a corresponding heated gas stream. The theoretical equivalence shows good agreement with experiments for a range of droplet sizes.ID: 031001564; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Adviser: Ranganathan Kumar.; Co-adviser: Saptarshi Basu.; Title from PDF title page (viewed August 26, 2013).; Thesis (Ph.D.)--University of Central Florida, 2012.; Includes bibliographical references (p. 234-250).
Ph.D.
Doctorate
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering
17
Schenk, Jonas. "Optische Spektroskopie in der Ultraschallfalle." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2014. http://dx.doi.org/10.18452/17043.
Abstract:
Die Kopplung von akustischer Levitation mit optischer Spektroskopie ermöglicht die Untersuchung von Reaktionen und intermolekularen Wechselwirkungen unter besonderen Bedingungen. Mit akustischer Levitation können Proben im µL-Bereich kontaktfrei gehaltert und Verunreinigungen durch Oberflächenkontaminationen ausgeschlossen werden. Durch die Verwendung verschiedener Methoden der optischen Spektroskopie wie Raman-Streuung, UV/Vis-Absorptions- und Fluoreszenz-Spektroskopie konnten die levitierten Proben untersucht werden. Die durchgeführten Untersuchungen zeigen, dass die Ultraschallfalle aufgrund der Wandlosigkeit sowie des Kontakts der levitierten Probe mit der Atmosphäre und der daraus resultierenden möglichen Aufkonzentrierung eine interessante Möglichkeit zur Probenhandhabung in der Mikrofluidik darstellt. Anhand zweier sonochemischer Reaktionen wurde mit Absorptionsspektroskopie gezeigt, dass das Ultraschallfeld des Levitators nur einen sehr geringen Einfluss auf die levitierte Probe ausübt. Mittels Absorptions- und Fluoreszenzspektroskopie wurde die durch die Verdampfung induzierte Aggregation eines Farbstoffes untersucht. Zudem wurde die relative Quantenausbeute des Farbstoffes im levitierten Tropfen bestimmt. Der Kontakt des levitierten Tropfens mit der umgebenden Atmosphäre kann auch zur Aufnahme von Substanzen aus der Atmosphäre führen. Dieser Effekt wurde anhand von levitierten ionischen Flüssigkeiten volumetrisch und schwingungsspektroskopisch bei verschiedenen Luftfeuchten untersucht und die Wechselwirkungen mit dem absorbierten Wasser detailliert charakterisiert. Die Kopplung und simultane Messung von Raman-Streuung und UV/Vis-Spektroskopie ermöglichte die Untersuchung der Bildung und Aggregation von Silber-Nanopartikeln und deren Auswirkungen auf die oberflächenverstärkte Raman-Streuung. Zudem wurde die Stabilisierung von Silber-Nanopartikeln in ionischen Flüssigkeiten und die Wechselwirkungen der Partikel mit den ionischen Flüssigkeiten untersucht.Acoustic levitation in combination with optical spectroscopy allows for investigations of reactions and intermolecular interactions under specific conditions. Samples with microliter volumes can be handled without contact to solid surfaces resulting in the absence of impurities from surface contamination. Using different optical spectroscopy methods such as Raman, UV/vis, and fluorescence spectroscopy, different levitated samples were characterized in detail within this work. The investigations show that the acoustic levitator is an interesting tool for sample handling due to the wall-less fixture and because of the interaction of the levitated sample with the surrounding atmosphere. This interaction leads to an increase of a solved analyte upon the evaporation of the solvent. The ultrasonic field inside the trap was characterized by investigations of sonochemical reactions, which show a negligible influence of the ultrasonic field on the levitated sample. Absorption as well as fluorescence spectroscopy was used to study the aggregation of a dye due to an increasing concentration upon evaporation of the solvent. Furthermore, the relative quantum efficiency of the dye was determined from levitated droplet experiments. The interaction of the levitated droplet with the surrounding atmosphere can also lead to absorption of airborne substances. This effect was investigated for different levitated ionic liquids. Volumetric and vibrational studies were performed on levitated ionic liquids under different atmospheric humidity conditions to characterize the interaction of ionic liquids with water. Hyphenation of Raman scattering and UV/vis absorption spectroscopy enabled the investigation of the formation and aggregation of silver nanoparticles and the correlation of this information with the recorded surface-enhanced Raman spectra. In addition, the stability of silver nanoparticles in ionic liquids and the interactions of the particles with the ionic liquids were examined.
18
Silva, Cláudio José Ribeiro da. "Estudo de sistema de levitação acústica /." Bauru, 2019. http://hdl.handle.net/11449/191333.
Abstract:
Orientador: Átila Madureira BuenoResumo: O som é uma onda mecânica e como tal transporta energia que age sobre partículas devido às forças de radiação acústica. O princípio para suspender corpos é aplicar uma força de tal forma a equilibrar seu peso. Na técnica de levitação acústica (AcLev) uma pequena esfera pode ser suspensa pela força de radiação acústica gerada por uma onda estacionária, sendo que o ponto de levitação está localizado na região em que o potencial acústico é mínimo, que é condição necessária para levitar uma esfera com raio muito menor que o comprimento de onda. Levitação acústica (AcLev) é uma ferramenta importante para manusear objetos sem contêineres. Nos anos recentes muitos dispositivos foram desenvolvidos com sucesso devido ao comportamento estável dos dispositivos AcLev. Como resultado, a maioria dos trabalhos sobre Aclev se concentram sobre simulações numéricas ou testes experimentais para estudar a geometria e arranjos dos emissores acústicos, ou a influência de vários tipos de perturbações, e a maioria desses modelos matemáticos considera somente o potencial acústico. Neste trabalho, a equação não linear de movimento para uma partícula levitada imersa em campo acústico de eixo único foi desenvolvida, considerando também forças dissipativas. O espaço parâmetro foi examinado buscando a existência de bifurcações, e faixas de projeto para os ganhos do dispositivo AcLev foram determinadas a partir da condição de existência de pontos de equilíbrio. Em adição, o comportamento dinâmico do dispos... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Sound is a mechanical wave and aims to carry energy that acts on particles due to acoustic radiation forces, while the principle to suspend bodies is to apply a force in such a way as to balance their weight. In the acoustic levitation technique (Aclev) a small sphere can be suspended by the acoustic radiation force generated by a stationary wave and the levitation point is located in the region where the acoustic potential is minimal, which is a necessary condition for levitating a sphere with radius much smaller than the wavelength. AcLev is an important tool for handling objects without the use of containers. In recent years many devices have been successfully developed due to the stable behavior of AcLev. As a result, most works on Aclev focuses on numerical simulations and experimental tests to study the geometry and arrangement of acoustic emitters, or the influence of various kinds of perturbations, and most mathematical models consider only acoustic potential. In this work, the nonlinear equation of motion for a levitated particle immersed in an acoustic field with single axis was developed considering also dissipative forces. The parameter space was searched for the existence of bifurcations and the design range for AcLev device gains were determined from the condition of equilibrium points. In addition, the dynamic behavior of the AcLev device regarding gains has been studied, also considering the microgravity situation. Numerical simulations corroborated the analyt... (Complete abstract click electronic access below)
Mestre
19
Gaubert, Quentin. "Caractérisation et modélisation des phénomènes gouvernant le séchage par atomisation de suspensions colloïdales." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0300/document.
Abstract:
Ces travaux s’inscrivent dans le cadre des recherches sur l’optimisation du séchage par atomisation de suspensions colloïdales employées pour la production de supports de catalyseurs. Pour mieux appréhender les phénomènes fondamentaux qui régissent ce procédé, le problème a été ramené à celui de l’étude expérimentale et la modélisation du séchage d’une goutte unique en lévitation dans un champ acoustique sous flux gazeux. L’expérience permet de contrôler les différents paramètres de séchage dans la chambre d’évaporation. Le suivi du séchage a été réalisé à l’aide de techniques optiques (vélocimétrie laser, imagerie en transmission et diffractométrie à l’angle d’arc-en-ciel) et des analyses post-mortem complémentaires. L’emploi de la diffractométrie arc-en-ciel a nécessité le développement d’un modèle d’optique géométrique avancé capable de décrire la diffusion de gouttes ellipsoïdales et les effets des suspensions nanoparticulaires sur le phénomène d’arc-en-ciel. Le modèle de séchage est un modèle à symétrie radiale. Il permet de prédire les taux d’évaporation, les profils internes de concentration et la déformation finale du grain. Les comparaisons expérimentales ont montré qu’il prédit très correctement le taux de séchage des gouttes colloïdales pour des nombres de Reynolds compris entre 100 et 230, des températures comprises entre 25°C et 55°C et des taux d’hygrométrie compris entre 2.5% et 70%. Il ressort également que le seuil de croûtage, identifié ici à partir du changement de régime du taux d’évaporation, semble intervenir pour des concentrations volumiques locales en nanoparticules de l’ordre de 12.3% bien inférieures aux concentrations de blocage des pâtesThis PhD work takes place in the framework of researches on the optimization of the spray drying of colloidal suspensions used for catalyst support production. To better understand fundamental phenomena governing this process, the problem is reduced to the experimental study and modelling of the drying of a single droplet levitated in an acoustic field with an external gas flow. The experiment allows also controlling parameters such as composition of the suspension, temperature or humidity inside evaporation chamber. The drying is monitored using in situ optical diagnostics (particle image velocimetry, shadowgraphy and rainbow diffractometry) as well as post-mortem analyzes. The use of rainbow diffractometry has required the development of advanced light scattering models accounting for the droplet non-sphericity and heterogeneity. The drying model is a model with radial symmetry. It predicts various quantities such as the droplet evaporation rate, internal concentration profile or the deformation of the final grain. Experimental comparisons show that this model can accurately predicts the drying rate of colloidal droplet for Reynolds numbers ranging from 100 to 230, temperatures between 25°C and 55°C and relative humidity between 2.5% and 70%. It is also shown that the crust compactness factor, about 12% when identified from the change in the rate of evaporation, is much lower than that reported classically for the jamming of dense suspensions
20
Jhan, Bo-Chen, and 詹博丞. "Parameters of levitated objects in acoustic levitation system." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/7qjpjz.
Abstract:
碩士國立臺灣大學
機械工程學研究所
107
In this research, we established a non-resonant acoustic levitation system. We also discussed the effects of thicknesses, areas, densities, and shapes of planar objects on the difficulty of levitation. The experimental results show that sound pressure required to levitate the objects increases as their thicknesses or densities increase. As for the objects’ areas, the difficulty of levitation decreases with the increasing areas of the objects when the areas are lower than a critical value. Otherwise, the larger the areas of the objects are, the harder they are to be levitated. We defined a shape factor by results of sound field measurement. This factor can describe the extent of acoustic radiation forces that the objects received in the same sound field. Then we got the area formula and the shape formula by curve fitting. However, the prediction of the shape formula is contrary to the experimental data for the objects of low areas. We thought it is because the sound field inside the levitator was not axisymmetric and the centroids of the levitated objects were not located on the central axis of the levitator. Finally, by the area formula and the shape formula, we predicted the sound pressure required to levitate a sphere or an ellipsoid of arbitrary density.
21
CANNULI, ANTONIO. "ACOUSTIC LEVITATION SAMPLE-ENVIRONMENT DEVICE FOR BIOPHYSICAL APPLICATIONS." Doctoral thesis, 2018. http://hdl.handle.net/11570/3131324.
Abstract:
The thesis work is mainly focused on issues concerning an acoustic levitation sample-environment device for biophysical applications and the employment of a portable neutron source for biophysical and electronic applications.
Sample preparation and sample-container interaction are critical components for many research investigations. In fact, on the one hand, the reactions between the sample and its container can limit accessibility conditions; on the other hand, heterogeneous container nucleation limits the capacities of “supercooled” liquids or to make over-saturated solutions. In this context, acoustic levitation can be employed for sample preparation as in the case of high concentrated mixtures, starting from solutions.
The aim is to characterize and clarify the physical-chemical mechanisms involved in the formulation processes, the vectorization processes, the stability of the formulations against the stress factors, the associated effects in the presence of bio-protector matrices, characterized by different values of kinematic and thermodynamic fragility, without neglecting the theoretical processes that underlie the acoustic levitation. In this regard, a physical-mathematical model was implemented to study the drying process of a single droplet of solution placed inside a levitator. The aim was to investigate the physical phenomena involved in this process and thus contribute to the general understanding of the drying process in an ultrasonic levitator.
The second thesis section deals with the employ of a portable neutron source, for neutrons activation and detection, is mainly addressed to biophysical and electronic applications. More in detail, the MP320 neutron generator of Thermo Scientific was employed in conjunction with a PINS-GMX
Ortec solid-state photon detector, made with high purity n-type germanium, which allows the entire external contact from implanted ions, for INAA (Instrumental Neutron Activation Analysis) investigations. Various simulations have been made with MCNP (Montecarlo N-Particles software) and a special shield has been designed to perform indoor measurements. Main applications of the source, in addition to the aforementioned, are closely related to the other research topics covered such as the field of biomedical, biology, anthropology, nutritional sciences, environmental, history and archaeology, ecology, environmental sciences, materials sciences and as a reference for materials.
22
Fuentes, Arturo Alejandro. "Dynamics of deformed droplets: Thermophysical property measurement using acoustic levitation." Thesis, 2000. http://hdl.handle.net/1911/19493.
Abstract:
A general theory for the dynamics of aspherical droplets useful to interpret frequency spectra more accurately for thermophysical property measurements was developed. The oscillations of a non-spherical droplet oscillating about an oblate spheroid subjected to external forces are considered. The effect of the static deformation and the interaction between the drop oscillation and the external field on the resonance are investigated. The analysis developed can be extended to consider different static shape deformation shapes. In order to validate the analytical predictions and to conduct further investigations, an experimental apparatus and a novel experimental procedure were developed. Experimental data and observations on the frequency splitting and surface tension, and the dynamics of the droplet in the experimental apparatus are presented. Finally, the effect of fullerenes on some dynamic features of levitated droplets is investigated.
23
Mitchell, Garrick F. "Experiments in acoustic levitation: Surface tension and viscosity of deformed droplets." Thesis, 1995. http://hdl.handle.net/1911/17043.
Abstract:
Acoustic levitation permits the observation of individual oscillating liquid droplets. Droplet shape oscillation data lead to thermophysical property measurements without the contaminating effects of a solid container. For spherical droplets, analysis has shown natural frequencies are a function of droplet size, mode number, and the surface tension and density of the liquid; the damping rate of oscillations has been correlated with the viscosity of the liquid. In terrestrial levitation, however, gravity serves to deform the droplet and split the frequency spectrum. In addition, droplet evaporation causes natural frequencies to change over time. This work compares experimental data on the frequency splitting of water and ethyl alcohol with theoretical predictions. With slight refinements to the theory, good agreement is found. Surface tension and viscosity were also measured; surface tension for distilled water came within 5% of the published value, and a new approach to the measurement of viscosity via levitation is described and tested.
24
Chen, Kuan-Hsun, and 陳冠勳. "The Research of Establishment and Innovative Applications of Acoustic Levitation System." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/2teg2b.
Abstract:
碩士國立中正大學
機電光工程研究所
103
Acoustic levitation technology has been widely used in recent years. It can be used to levitate small objects, including solids and liquids, without any physical connection. The physical characteristics of the levitated objects are unrestricted. Hence, the potential applications of acoustic levitation technology are quite extensive. In this research, an acoustic levitation system is constructed using ultrasound. Standing waves for levitating objects are produced between an ultrasonic transducer and a reflector. In order to produce standing waves that can levitate the objects, the distance between the ultrasonic transducer and the reflector must equal half the wavelength of the acoustic waves. In this research, we use different reflectors (flat and concave surfaces) to provide a stronger levitation force and design an acoustic levitation system that can levitate objects through several movement modes, such as transportation and rotation.
25
TSAI, MING-CHANG, and 蔡明倡. "The Research of Establishment and Fulfillment Applications of Two Dimensional Acoustic Levitation System." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/f9549r.
Abstract:
碩士國立中正大學
光機電整合工程研究所
105
In recent years, acoustic levitation technology has been widely applied in various fields. Acoustic levitation technology can be a non-contact way of hold and levitating tiny objects, including liquid and solid. It has no restrictions on the material and shape characteristics of the suspended objects, thus the application of acoustic levitation is quite extensive. In this research, two sets of the same ultrasonic transducer and movable reflector plane are used to construct a two-dimensional acoustic levitation system. A standing wave was used to suspend the object between the ultrasonic transducer and the reflector. Among them, the distance between the ultrasonic transducer and the reflector must be the half wavelength of the acoustic wave in order to produce the standing wave to suspend the object. In this research, the distance between the two pairs of ultrasonic transducers and the reflector is varied. The varioation of the distance results in the change of the position of the standing wave node, thus the two-dimensional plane movement of the suspended matter is achieved.
26
Ansari, Hosseinzadeh Vahideh. "Development of a non-contact blood rheometer using acoustic levitation and laser scattering techniques." Thesis, 2019. https://hdl.handle.net/2144/36142.
Abstract:
Coagulopathy, a condition in which blood coagulation is impaired, can be inherited or result from a variety of conditions including severe trauma, illness or surgery. Perioperative monitoring of a patient’s coagulation status is important to identify coagulopathic patients. Thromboelastography or TEG remains the gold standard for whole blood coagulation monitoring. However, TEG suffers from certain well-documented drawbacks such as contact containment and manipulation of the blood sample, large and uncontrolled strain, and the inability to distinguish the contribution of elasticity and viscosity during blood coagulation. We developed a non-contact blood rheometer which uses a single drop of blood to measure its viscoelastic properties. Small sample size (typically 5-15 μL), low shear strain (linear viscoelasticity), and non-contact manipulation and containment of samples make this technique unique for real-time monitoring of blood coagulation.
In the first part of this work, we addressed the development of the technique, benchmarking the results against known material properties standards. We observed large amplitude oscillations of the levitated drop results in multiple resonance modes and excessive dissipation. We suggested upper bound limits for drop oscillation amplitudes required to satisfy the Lamb theoretical expressions for drop frequency and damping. In the second part, we applied our technique to study sickle-cell disease. Our technique showed that the shape oscillation of blood drops was able to assess an abnormally increased viscosity in sickle cell patients when compared with normal controls over a range of hematocrit. Furthermore, the technique was sensitive enough to detect viscosity changes induced by hydroxyurea treatment. The third part of this work focused on blood coagulation monitoring. The technique showed sensitivity to coagulation parameters, such as platelet count, calcium ion concentration, and hematocrit. A comparison of the results with TEG showed coagulation started sooner in the levitation technique, but with a lower rate and lower maximum stiffness. Thus, the technique developed can be used as a monitoring tool to assess blood mechanical properties sensitively enough to be of use in clinical diagnostic settings.2020-06-04T00:00:00Z