Tesis sobre el tema "Contact angle"
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Lam, C. N. Catherine. "A study of advancing & receding contact angles and contact angle hysteresis". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ58840.pdf.
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He, Ying Bin. "Contact angle measurements on fine coal particles". Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27882.
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This study investigates the techniques of contact angle measurement on fine coal particles. Two techniques, one direct and one indirect, have been investigated and modified.
In the direct contact angle measurement technique, high pressure is employed to compress the coal powder into a pellet and the artificial surface of the pellet is employed in the contact angle measurements. The contact angle versus time and versus drop size on the pellet surface are examined. In addition, the pellet properties and factors affecting the pellet properties are also studied. A pellet surface model and a method for contact angle correction are proposed.
In the indirect measurement, the contact angle is calculated from the penetration rate. The method is modified to employ high pressures to produce highly compact columns. The holding glass tube traditionally used for the column of powder is, therefore, no longer needed. The change in penetration behaviour of the liquid within such columns is investigated. The properties of the columns and the impact of the pressure applied in their formation on the rate of liquid penetration as well as other phenomena are studied. A contact angle calculation procedure is also proposed.Applied Science, Faculty of
Mining Engineering, Keevil Institute of
Graduate
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Hatipogullari, Metin. "Modelling of contact lines on heterogeneous substrates :stick-slip and contact angle hysteresis". Doctoral thesis, Universite Libre de Bruxelles, 2020. https://dipot.ulb.ac.be/dspace/bitstream/2013/304847/5/contratMH.pdf.
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This thesis highlights generic aspects of contact angle hysteresis and stick-slip motion,encountered in most practical wetting situations.First, we study the scaling relation between the heterogeneity strength and the amplitudeof the contact angle hysteresis it induces in the model configuration of a chemicallyheterogeneous microchannel. A key parameter which determines the qualitativefeatures is the heterogeneity wavelength. In particular, we identify a near-thresholdbehavior where the quadratic scaling between the heterogeneity amplitude and the resultinghysteresis, already known for a dilute system of wetting defects, is explainedby the closeness to the threshold, and a macroscopic limit without observable stick-slipwhere this scaling is linear.In the second part, we adapt the description to the configuration of a meniscusaround a wavy fibre. This adaptation brings the generic results of the first part in thereach of experiments. A comparison with experiments is achieved at the level of theindividual topography-induced jumps.In the third part, we expand the formulation to treat the quasi-steady interface shapecontact line dynamics and study how the the presence of stick-slip motion at the observableor unobservable scale modifies the scaling relation between the contact linevelocity and contact angle. We recover the known result that the scaling exponent dependson the nature of the externally controlled parameter, identify the causes of thisdependency in the corresponding static limits, and predict the disappearance of this dependencyabove a critical velocity which decreases with the heterogeneity wavelength.Finally, we show trough examples how the modelling framework which permitscapturing contact angle hysteresis and stick-slip motion in a minimalistic way can beadopted to treat configurations with a finite amount of contact points, or the 3D problemof a drop with a deformed contact line. We discuss the arising configuration-specificeffects, also in configurations of biomimetic interest.Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
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Burel, Thomas. "Investigation of smooth contact angle treatment in porous media". Thesis, University of Strathclyde, 2018. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=30826.
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Some of the key challenges faced in the oil/gas extraction and carbon dioxide injection/storage processes are the presence of complex geometries and the significant effect of the capillary forces which arise at low capillary numbers. Therefore, the contact angle needs to be carefully treated. Mesoscopic techniques such as lattice Boltzmann methods are capable of dealing with lower capillary numbers as compared to the Navier-Stokes solvers, which can also implicitly capture the interface between two fluids. To investigate immiscible two-phase ows at low Reynolds and capillary numbers (Re < 1 and Ca < 1), the colour-fluid model is used i.e. the Rothman-Keller model [1]. This model includes two steps: a perturbation operator from Lishchuk et al [2] (the continuum surface force [3]) or Gunstensen et al [4] approaches and a recolouring operator [5]. However, the lattice Boltzmann implementation employs a Cartesian grid for domain discretisation that is unable to conform with curved surfaces. It misinterprets those curved surfaces as a series of stair-like patterns. On those surfaces, a non-physical contact angle could be defined which may lead to a numerically flooding of the wetting fluid inside the droplet for a non-spreading drop or outside for a spreading droplet. To remove this unphysical behaviour and take into account the flow field effect on the contact angle, interpolation techniques are employed to estimate the real contact angle on the 'stairs' boundaries. We also employ extrapolations to obtain more accurate density on concave corners, thus the grid resolution can be reduced. After the code is numerically validated on static droplets, on droplets deformed under a simple shear, and on simple geometries. Finally, we perform simulations on a Berea sandstone sample [6] to understand dynamics behaviour of immiscible fluids in porous media.
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Vijayan, Ria. "Wheel-terrain contact angle estimation for planetary exploration rovers". Thesis, Luleå tekniska universitet, Rymdteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-70676.
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During space missions, real time tele-operation of a rover is not practical because of significant signal latencies associated with inter planetary distances, making some degree of autonomy in rover control desirable. One of the challenges to achieving autonomy is the determination of terrain traversability. As part of this field, the determination of motion state of a rover on rough terrain via the estimation of wheel-terrain contact angles is proposed. This thesis investigates the feasibility of estimating the contact angles from the kinematics of the rover system and measurements from the onboard inertial measurement unit (IMU), joint angle sensors and wheel encoders. This approach does not rely on any knowledge of the terrain geometry or terrain mechanical properties. An existing framework of rover velocity and wheel slip estimation for flat terrain has been extended to additionally estimate the wheel-terrain contact angle along with a side slip angle for each individual wheel, for rough terrain drive. A random walk and a damped model are used to describe the evolution of the contact angle and side slip angle over an unknown terrain. A standard strapdown algorithm for the estimation of attitude and velocity from IMU measurements, is modified to incorporate the 3D kinematics of the rover in the implementation of a nonlinear Kalman filter to estimate the motion states. The estimation results from the filter are verified using tests performed on the ExoMars BB2. The obtained contact angle estimates are found to be consistent with the reference values.
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Gujjula, Sushrutha Reddy. "Numerical Investigation of Droplet Spread: Effect of Contact Angle Models". University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1460447092.
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Ritchie, John. "Contact Angle Of A Nano-Drop On A Heterogeneous Surface". VCU Scholars Compass, 2010. http://scholarscompass.vcu.edu/etd/174.
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CONTACT ANGLE OF A NANO-DROP ON A HETEROGENEOUS SURFACE By John Andre Ritchie, Master of Science A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science at Virginia Commonwealth University Virginia Commonwealth University, 2010 Major Director: Dr. Alenka Luzar, Professor of Chemistry
We examine the relation between contact angle of a nanodrop of water and the location of surface-water interaction energy at the perimeter and beneath the drop. Young’s equations gives the relationship between surface tension, at the three phase solid liquid vapor interface, and contact angle on a homogeneous surface. Cassie and Baxter generalized this equation to heterogeneous surfaces implying that contact angle corresponds to the average properties of the surface under the drop. McCarthy and coworkers pointed out it is the nature of the substrate at droplet perimeter that controls contact angle. And more recently, McHale in his theoretical derivation applies the Cassie-Baxter equation to the area at the drop’s perimeter. For a nanodrop, the situation is further complicated by the finite range of water-substrate interactions making the definition of the perimeter region somewhat arbitrary. We simulate nanodroplets of water on graphene-like surfaces having hydrophobic and hydrophilic interaction energy at the perimeter and beneath the drop using molecular dynamics. The microscopic analogue of the contact angle was extracted from simulation trajectory data. We confirm the contact angle is exclusively related to the surface interaction energy in the region of the drop’s perimeter. We test the role of finite range of substrate-water interaction when the area of a circular hydrophilic patch beneath the drop’s core is incrementally expanded until the contact angle is equivalent to that on the pure hydrophilic surface. We identify a range of interaction corresponding to a considerable drop in θ when plotting contact angle as a function of patch size. We show the observed contact angle dependence on the size of the patch can be predicted by the Cassie-Baxter mixing relation when limited to the area within the interaction range from the drop’s perimeter.
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Sasges, Michael R. "The effect of gravity on fluid configuration and contact angle hysteresis". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ27716.pdf.
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Moon, Jungun. "Effect of contact-release angle on hand-handrim for peak velocity". Virtual Press, 1992. http://liblink.bsu.edu/uhtbin/catkey/834622.
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The purpose of this study was to investigate the relationships between the arm joint angle at contact-release with peak velocity in experienced cerebral palsied athletes during wheelchair propulsion. The subjects (n = 5) exercised for a few minutes to familiarize themselves with the roller set up. After practice, each subject was asked to push the wheelchair as fast as possible up to 10 seconds. A tach-generator was attached to the core of the roller and interfaced to a computer via an eight bit A/D converter. The sampling rate of the roller speed was 200Hz. One video camera operating at 30 frames per second, and posisioned 7 m from the roller side was used. The data were analyzed for shoulder, elbow, and wrist angles with the Peak Performance program in I.B.M. compatible computer. Subjects' peak velocities were 8.85, 4.49, 4.19, 3.66, and 4.09 m/s, and the mean percent of contact and release times were 32.8% vs 67.2%. Shoulder, elbow, and wrist contact angles were not statisticaly in this study. Results indicate that contact-release angle on hand-handrim was effected for peak velocity. Also there was no significantrelationship between speed and cycle time.Key WordsRacing wheelchair, cerebral palsy, Peak velocity, Propulsion, Joint angle.School of Physical Education
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Dakpanon, Yaï Laurent. "Contributions expérimentale et théorique à l'identification de paramètres adéquats pour la modélisation de la mouillabilité en ingénierie". Vandoeuvre-les-Nancy, INPL, 2002. http://www.theses.fr/2002INPL103N.
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Ce travail, essentiellement expérimental, s'inscrit dans le cadre des travaux de modélisation mathématique de l'équipe; ceux ci cherchent à identifier des paramètres susceptibles de caractériser les propriétés de mouillabilité d'un support solide par un liquide, lesquelles dépendent du fluide environnant. Le premier résultat de cette étude est la validation de deux corrélations admissibles entre le volume d'une goutte sessile axisymétrique (contrôlé de façon incrémentale et quasi- statique), et l'aire (mesurée) de la surface mouillée associée; ceci tout au long d'un cycle manifestant un phénomène d'hystérésis. Le deuxième apport de ce travail est l'élaboration d'une loi implicite de corrélation entre le volurne de la goutte et l'angle de contact. Enfin la réduction dimensionnelle du modèle de base et des lois de corrélation précédentes, par la longueur caractéristique "Volume/ Aire Mouillée", permet de mettre en évidence une courbe remarquable; Celle ci est monotone très régulière et représente à elle seule tous les états possibles (avancée, palier, retrait) du cycle d'hystérésis. Cette courbe, qualifiée de "Maîtresse" pour le comportement "Mouillabilité", reste à interpréterThe purpose of this work consists in identifying parameters able to characterize wetting properties of a solid sample by a liquid, in the presence of an other fluid. The first result of our study is the validation of two admissible correlation laws between the controlled volume of a sessile, axisymmetrical drop; and the corresponding measured wetted area. The second contribution of this research is the working out of an implicit correlation law between the drop volume and the contact angle. Finally, the dimensional reduction (of the basic model and the previous correlation laws) by the characteristic length "Volume/Wetting Area" allows to point out a remarkable curve; this last one, very regular, is monotone; it represents alone all the possible, states of the hysteresis cycle. This curve, qualified of "Master Curve" in order to explicit the wetting behaviour, has still to be interpreted
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Epstein, Lindsay(Lindsay M. ). "Bi-modal hemispherical sensors for three axis force and contact angle measurement". Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127161.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 139-143).
Humans and animals demonstrate a unique ability to interact with the physical environment around them with coordination and control, including moving quickly across rugged terrain or deftly handling small objects. Much of this success is related to our ability to accurately perceive the world around us through a sense of touch. In order to better perform dynamic, physical interactions, such as locomotion or manipulation, robots need to be able to accurately measure contact locations and forces. However, many existing sensors do not satisfy the stringent requirements or do not supply sufficient information for robotic locomotion and manipulation. This thesis builds on work by a previous PhD student, Meng Yee (Michael) Chuah, of the MIT Biomimetic Robotics Laboratory to develop stress field based force sensors for use in robotic applications. The concept of stress field based force sensing consists of pressure sensors embedded within a rubber hemisphere.
The pressure sensors sample the stress distribution within the rubber, and use these signals to reconstruct the applied force. This type of sensor is inherently robust, low cost, and insensitive to inertial noise. This work focuses on the development of bi-modal hemishperical sensing technology for two novel sensor designs --
one footpad sensor intended for use in a high force range corresponding to legged locomotion, and one fingertip sensor intended for use in a lower force, higher sensitivity range, corresponding to robotic manipulation applications. Both sensors have the ability to simultaneously measure applied force in three axes (Fx, Fy, Fz) and the contact location of quasi-point contact, as described by two angles ([theta], [phi]) in real time (1kHz and 200Hz, respectively). The sensors each contain eight embedded pressure sensors, and can accurately reconstruct the five desired outputs from the eight input signals using either a Gaussian process regression (GPR) estimator, or an artificial neural net (ANN). The performance of both sensors using each estimator is quantified through testing on multiple data types. The properties of the sensor, including sensitivity, repeatability, and drift over time are also characterized.
The performance of the footpad sensor is further validated through two applications on a robotic arm. In the first, normal force and contact angle information from the footpad sensor is used to accurately sense and track a moving surface. In the second, normal and shear force information from the sensor is used to detect and prevent slip. Overall, these sensors demonstrate the ability to quickly and accurately measure forces in three axes and contact surface normal, while being robust and low cost. These sensors have the potential to greatly improve the capability of robots to perform dynamic, physical interactions with the world around them.
by Lindsay Epstein.
S.M.
S.M. Massachusetts Institute of Technology, Department of Mechanical Engineering
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Diawara, Jules. "Mouillabilité de surfaces hétérogènes (fer/oxyde) par un alliage de zinc liquide". Phd thesis, Ecole Centrale Paris, 2011. http://tel.archives-ouvertes.fr/tel-00658768.
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Le phénomène de mouillage intervient dans de nombreux procédés, parmi lesquels la galvanisation en continu de tôles d'acier pour carrosserie automobile. Dans ce procédé, la tôle est immergée dans un bain de zinc liquide afin de la recouvrir d'une couche protectrice de zinc. Mais avant cela, cette tôle, laminée à froid, est soumise à un recuit sous atmosphère réductrice dans le but d'éliminer l'écrouissage et les oxydes de fer superficiels et favoriser ainsi les réactions de galvanisation. Des nouveaux aciers, dits à haute limite d'élasticité, ont été élaborés afin d'améliorer la sécurité passive des véhicules sans trop augmenter leur masse et leur consommation de carburant. Ces aciers contiennent des teneurs élevées en éléments d'addition oxydables qui, lors du recuit, diffusent de la masse de l'acier vers la surface où ils forment des particules d'oxydes qui ne sont pas mouillées par le zinc liquide. Il parait donc important de comprendre le mouillage par le zinc liquide de surfaces hétérogènes, composées de fer métallique et d'oxydes. Pour cela, nous avons étudié l'étalement d'une goutte de zinc liquide, à des temps très courts, à l'aide d'une caméra rapide dans un dispositif de chute de goutte. Nous avons mené nos expériences sur des alliages fer - silicium et un acier industriel, recuits à haute température avant le dépôt de la goute, ce qui a permis d'obtenir un taux de couverture par les oxydes variant de 0 à 100%. Le mouillage est décrit à l'aide de deux paramètres : le diamètre d'étalement et l'angle de contact. Nous nous sommes attachés à la compréhension et à la modélisation de l'évolution de ces deux paramètres aux cours des premiers instants de contact et en fin d'étalement. Nous avons, en particulier, mis en évidence l'influence du taux de couverture par les oxydes et de l'énergie cinétique initiale de la goutte. Le manuscrit se termine par une extrapolation des résultats de mouillage obtenus pour les surfaces hétérogènes modèles à des substrats recuits dans des conditions voisines du recuit continu industriel
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Klier, Jurgen. "Liquid helium on weak binding substrates". Thesis, University of Exeter, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337745.
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Zhang, Ning. "SURFACE MODIFICATION OF MICRON-SIZE POWDERS BY PLASMA POLYMERIZATION". University of Cincinnati / OhioLINK, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=ucin971280515.
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Janeček, Valdislav. "Evaporation à l'échelle microscopique et à haut flux thermique". Paris 6, 2012. http://www.theses.fr/2012PA066512.
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Cette thèse étudie théoriquement les processus de transport au voisinage de la ligne triple de contact liquide-gaz-solide et leur impact sur l'évaporation macroscopique. Dans la première partie de la thèse, l'hydrodynamique au voisinage de la ligne de contact est étudiée sous les conditions de mouillage partiel. L'évaporation induite par le chauffage du substrat dans l'atmosphère de vapeur du même fluide est considérée. La relaxation de la singularité hydrodynamique de la ligne triple est considérée. La principale conclusion de la thèse est que l'effet Kelvin (dépendance de la température de saturation de la pression) est suffisant en soi, pour faire disparaitre la singularité des variables hydrodynamiques. La microrégion (le voisinage de la ligne de contact) est résolue numériquement et analytiquement pour de faibles pentes de l'interface liquide-vapeur. Les échelles de longueur caractéristiques du problème sont identifiées et la nature multi-échelle du phénomène est prise en compte. Les études paramétriques effectuées révèlent le rôle de la résistance thermique de l'interface vapeur-liquide, de la longueur de glissement, du terme thermocapillaire, du recul de vapeur et ainsi que des forces de surface. Une extension de l'approximation de lubrification pour de pentes élevées de l'interface gaz-liquide à l'évaporation est discutée. Dans la seconde partie de la thèse, le modèle précédemment établi pour la microrégion est couplé à des simulations numériques de la croissance d'une bulle de vapeur. Le départ de la bulle de vapeur de la paroi chauffante pendant l'ébullition a également été étudiée. Il a été proposé dans la thèse, que sous des charges thermiques élevées, l'augmentation de l'angle de contact apparent provoque l'étalement de la bulle de vapeur sur la paroi chauffante. Ce phénomène peut conduire, au séchage de la paroi observé pendant la crise d'ébullitionThis thesis theoretically investigates the transport processes in the vicinity of the triple gas-liquid-solid contact line and its impact on macroscopic evaporation. In the first part of the thesis, the hydrodynamics close to the contact line at partial wetting is studied. Specifically, evaporation into the atmosphere of pure vapor driven by heating of the substrate is considered. The question of singularity relaxation is addressed. The main finding of the thesis is that the Kelvin effect (dependence of saturation temperature on pressure) is sufficient by itself to relax the hydrodynamic contact line singularity. The proposed microregion (the contact line vicinity) model for small interface slopes is solved numerically. Asymptotic solutions are found for some specific cases. The governing length scales of the problem are identified and the multiscale nature of the phenomenon is addressed. Parametric studies revealing the role of the thermal resistance of vapor-liquid interface, slip length, thermocapillary term, the vapor recoil and surface forces are also performed. An extension of the lubrication approximation for high slopes of the gas-liquid interface at evaporation is discussed. In the second part of the thesis, the previously established microregion model is coupled to a simplified single vapor bubble growth numerical simulation. The bubble departure from the heater at boiling is also studied. It was proposed in the thesis, that under high heat loads, the increase of the apparent contact angle causes the vapor bubble to spread over the heated substrate. Such a behavior may cause the heater dry-out that occurs during the boiling crisis
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Jakubowicz, Agnieszka. "Investigation of growth kinetics of self-assembling monolayers by means of contact angle, optical ellipsometry, angle-resolved XPS and IR spectroscopy". Thesis, University of North Texas, 2004. https://digital.library.unt.edu/ark:/67531/metadc4602/.
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Absorption of octadecanethiol and p-nitrobenzenethiol onto gold surfaces from ethanol solutions has been studied by means of contact angle, optical ellipsometry, angle-resolved XPS (ARXPS), and with grazing angle total reflection FTIR. Growth of the monolayers from dilute solutions has been monitored and Langmuir isotherm adsorption curves were fitted to experimental data. A saturated film is formed within approximately 5h after immersion in solutions of concentrations ranging from 0.0005mM to 0.01mM. We found, that the final density of monolayer depends on the concentration of the solution.
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Butz, Julia [Verfasser] y Helmut [Akademischer Betreuer] Abels. "The Curve Diffusion Flow with a Contact Angle / Julia Butz ; Betreuer: Helmut Abels". Regensburg : Universitätsbibliothek Regensburg, 2018. http://d-nb.info/1168009448/34.
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Osborne, III Kenneth L. "Temperature-Dependence of the Contact Angle of Water on Graphite, Silicon, and Gold". Digital WPI, 2009. https://digitalcommons.wpi.edu/etd-theses/900.
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"The temperature dependence of the contact angle of water on graphite, silicon and gold was investigated under various conditions to test the Sharp-Kink Approximation. Despite correctly predicting the contact angle at room temperature, the ideal Sharp-Kink Approximation was not found to accurately describe the contact angle's temperature dependence. The discrepancies from the predicted contact angle were characterized in terms of a correction H(T) to the liquid-solid surface tension. H(T) was found to be linear in temperature and decreasing, and is consistent with electrostatic charge effects."
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Jalalahmadi, Golnaz. "Development of A New Methodology for Contact Angle Measurment on Monolayer of Cells". University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1374765701.
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Baird, Russell A. "Novel techniques for interfacial tension and contact angle measurements in polymer/CO2 systems". Connect to this title online, 2005. http://hdl.handle.net/1811/306.
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Senior Honors Thesis (Chemical Engineering)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains 27 p.; also includes graphics Includes bibliographical references (p. 24-25). Available online via Ohio State University's Knowledge Bank.
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Trapuzzano, Matthew A. "Controlled Wetting Using Ultrasonic Vibration". Scholar Commons, 2019. https://scholarcommons.usf.edu/etd/7974.
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Many industrial processes such as printing and cleaning, as well as products like adhesives, coatings, and biological testing devices, rely on the wetting of liquids on a surfaces. Wetting is commonly controlled through material selection, coatings, and/or surface texture, but these means are sensitive to environmental conditions. Wetting is influenced by variables like surface tension, density, the surface chemistry, local energy barriers like surface roughness, and how the droplet is placed on the surface. Wetting of droplets can also be influenced externally in many ways such as introducing surfactants, applying electrical fields, or by dynamically excitation. Low-frequency, high amplitude vibration can initiate wetting changes prompted by droplet contact line oscillations that exceed the range of stable contact angles inherent of a droplet on a solid surface.
The study of ultrasonic vibration wetting and spreading effects is sparse [1, 2], and is usually only qualitatively analyzed. Therefore, the specific goal of this thesis is somewhat unique, but also has potential as a means to controllably reverse surface adhesion.
High frequency vibration effects and the governing mechanisms are relatively uncharacterized due to difficulties posed by the spatial and temporal scales. To investigate, droplets of 10, 20, and 30 µL are imaged as they vibrate on a hydrophobic surface forced via a piezoelectric transducer over different high frequencies (>10 kHz). Wetting transitions occur abruptly over a range of parameters, but coincide with transducer resonance modes. The magnitude of contact angle change is dependent on droplet volume and surface acceleration, and remains after cessation of vibration, however new droplets wet with the original contact angle.
A more detailed investigation of this phenomenon was necessary to obtain a better understanding. This required repeatable testing conditions, which relies heavily on surface integrity. However, some “hydrophobic” coatings are sensitive to extended water exposure. To determine which hydrophobic coatings may be appropriate for investigating dynamic wetting phenomena, samples of glass slides coated with a series of fluoropolymer coatings were tested by measuring water contact angle before, during, and after extended submersion in deionized water and compared to the same coatings subjected to ultrasonic vibration while covered in deionized water. Both methods caused changes in advancing and receding contact angle, but degradation rates of vibrated coatings, when apparent, were significantly increased. Prolonged soaking caused significant decreases in the contact angle of most coatings, but experienced significant recovery of hydrophobicity when later heat-treated at 160 C. Dissimilar trends apparent in receding contact angles suggests a unique degradation cause in each case. Roughening and smoothing of coatings was noted for coatings that were submerged and heat-treated respectively, but this did not correlate well with the changing water contact angle. Degradation did not correspond to surface acceleration levels, but may be related to how well coatings adhere to the substrate, indicative of a dissolved coating. Most coatings suffered from contact angle degradation between 20-70% when exposed to water over a long period of time, however the hydrophobic fluoropolymer coating FluoroSyl was found to remain unchanged. For this reason it was found to be the most robust coating for providing long term wetting repeatability of vibrated droplets.
Droplets (10 to 70 µL) were imaged on hydrophobic surfaces as they were vibrated with ultrasonic piezoelectric transducers. Droplets were vibrated at a constant frequency with ramped amplitude. Spreading of droplets occurs abruptly when a threshold surface acceleration is exceeded of approximately 20,000 m/s2. Droplet contact area (diameter) can be controlled by varying acceleration levels above the threshold. The threshold acceleration was relatively independent of droplet volume, while initial contact angle impacts the extent of spreading. Wetting changes remain after cessation of vibration as long as the vibrated droplet remained within the equilibrium contact angle range for the surface (> the receding contact angle), however new droplets wet with the original contact angle except for some cases where vibration of liquid can affect the integrity of the coating. Reversible wettability of textured surfaces is a desired effect that has various industry applications where droplet manipulation is used, like biomedical devices, coating technologies, and agriculture [3-5].
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Bukiet, Frédéric. "Influence de la modification de l'hypochlorite de sodium par adjonction de tensioactifs sur l'énergie interfaciale et la viscosité dynamique de la solution d'irrigation". Thesis, Montpellier 1, 2014. http://www.theses.fr/2014MON12201/document.
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La complexité anatomique de l'endodonte implique un protocole d'irrigation efficace. L'hypochlorite de sodium doit donc pouvoir pénétrer dans l'ensemble du réseau endodontique afin d'exercer son activité antiseptique et protéolytique. Dans cet objectif, l'utilisation d'un tensioactif mélangé à l'hypochlorite de sodium constitue une approche potentiellement intéressante pour optimiser la pénétration et l'étalement de l'hypochlorite de sodium au sein du système canalaire. Cette thèse sur publications a donc pour objectif d'étudier l'influence de la modification de l'hypochlorite de sodium par adjonction de tensioactifs sur l'énergie interfaciale et la viscosité dynamique de la solution d'irrigation. Le premier chapitre décrit les enjeux, les différentes problématiques liées à l'irrigation ainsi qu'une revue de littérature critique des différentes techniques d'irrigation disponibles. Le second chapitre se focalise sur les propriétés physico-chimiques des solutions d'irrigation et sur des aspects plus spécifiquement liés à l'hydrodynamique et au mouillage des liquides et en particulier les notions d'énergie interfaciale, de concentration micellaire critique, de viscosité dynamique et de régime d'écoulement. Après une synthèse des aspects théoriques et des implications potentielles en endodontie, l'ensemble des matériels et méthodes expérimentales est détaillé dans le troisième chapitre. Le quatrième chapitre décrit l'influence de l'adjonction d'un tensioactif sur le mouillage de la solution d'irrigation sur la base d'une étude préliminaire et d'études complémentaires ayant abouti à une première publication internationale. Le cinquième chapitre décrit l'influence de l'adjonction d'un tensioactif sur l'écoulement de la solution d'irrigation, cette étude ayant débouché sur une seconde publication internationale. Enfin, le sixième chapitre constitue la conclusion de ce travail et les perspectives de recherche sur la thématiqueThe complexity of the root canal anatomy requires an efficient irrigation protocol. Sodium hypochlorite must penetrate in the whole of the endodontic system in order to be strongly active in terms of antiseptic and solvant properties. Therefore, the use of surfactants mixed to sodium hypochlorite is a promising approach to enhance the penetration depth and the spreading of endodontic irrigant within the root canal. The purpose of this thesis based on two international publications is to study the influence of surfactant addition to sodium hypochlorite on its surface tension and dynamic viscosity. The first chapter describes the different stakes, issues and irrigation techniques thanks to a critical review of the literature. The second chapter focuses on hydrodynamics and wetting properties especially surface energy, critical micellar concentration, dynamic viscosity and flow regimen. After a description of the theoretical aspects and the potential applications in root canal therapy, all the materials and methods used in this thesis are detailed in the third chapter. The fourth chapter describes the influence of surfactant addition on the wettability of endodontic irrigant on the basis of a preliminary study and several additional studies that led to a first international publication. The fifth chapter describes the influence of surfactant addition on the dynamic viscosity of endodontic irrigant and its flow regimen on the basis of a study which led to a second international publication.The final chapter of this thesis constitues the conclusion of this work and the associated prospects regarding this topic
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Alvarellos, Jose. "Fundamental Studies of Capillary Forces in Porous Media". Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5314.
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The contact angle defined by Young's equation depends on the ratio between solid and liquid surface energies. Young's contact angle is constant for a given system, and cannot explain the stability of fluid droplets in capillary tubes. Within this framework, large variations in contact angle and explained aassuming surface roughness, heterogeneity or contamination. This research explores the static and dynamic behavior of fluid droplets within capillary tubes and the variations in contact angle among interacting menisci. Various cases are considered including wetting and non-wetting gluids, droplets in inclined capillary tubes or subjected to a pressure difference, within one-dimensional and three-dimensional capillary systems, and under static or dynamic conditions (either harmonic fluid pressure or tube oscillation). The research approach is based on complementary analytical modeling (total energy formulation) and experimental techniques (microscopic observations). The evolution of meniscus curvatures and droplet displacements are studied in all cases. Analytical and experimental results show that droplets can be stable within capillary tubes even under the influence of an external force, the resulting contact angles are not constant, and bariations from Young's contact angle aare extensively justified as menisci interaction. Menisci introduce stiffness, therefore two immiscible Newtonian fluids behave as a Maxwellian fluid, and droplets can exhibit resonance or relaxation spectral features.
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Al-Siyabi, Zaid Khamis Sarbookh. "The contact angle, interfacial tension and viscosity of reservoir fluids : experimental data and modelling". Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/10399/1198.
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Fedeli, Livio. "Numerical techniques for the study of wetting on rough surfaces and contact angle hysteresis". Doctoral thesis, SISSA, 2011. http://hdl.handle.net/20.500.11767/4256.
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Martinez, Nelson. "Wettability of Silicon, Silicon Dioxide, and Organosilicate Glass". Thesis, University of North Texas, 2009. https://digital.library.unt.edu/ark:/67531/metadc12161/.
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Wetting of a substance has been widely investigated since it has many applications to many different fields. Wetting principles can be applied to better select cleans for front end of line (FEOL) and back end of line (BEOL) cleaning processes. These principles can also be used to help determine processes that best repel water from a semiconductor device. It is known that the value of the dielectric constant in an insulator increases when water is absorbed. These contact angle experiments will determine which processes can eliminate water absorption. Wetting is measured by the contact angle between a solid and a liquid. It is known that roughness plays a crucial role on the wetting of a substance. Different surface groups also affect the wetting of a surface. In this work, it was investigated how wetting was affected by different solid surfaces with different chemistries and different roughness. Four different materials were used: silicon; thermally grown silicon dioxide on silicon; chemically vapor deposited (CVD) silicon dioxide on silicon made from tetraethyl orthosilicate (TEOS); and organosilicate glass (OSG) on silicon. The contact angle of each of the samples was measured using a goniometer. The roughness of the samples was measured by atomic force microscopy (AFM). The chemistry of each of the samples were characterized by using X-ray photoelectron spectroscopy (XPS) and grazing angle total attenuated total reflection Fourier transform infrared spectroscopy (FTIR/GATR). Also, the contact angle was measured at the micro scale by using an environmental scanning electron microscope (ESEM).
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Griffiths, Peter Robert. "Static and Dynamic Components of Droplet Friction". Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4897.
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As digital microfluidics has continued to mature since its advent in the early 1980's, an increase in new and novel applications of this technology have been developed. However, even as this technology has become more common place, a consensus on the physics and force models of the motion of the contact line between the fluid, substrate, and ambient has not been reached. This uncertainty along with the dependence of the droplet geometry on the force to cause its motion has directed much of the research at specific geometries and droplet actuation methods.
The goal of this thesis is to help characterize the components of the friction force which opposes droplet motion as a one dimensional system model based upon simple system parameters independent from the actuation method. To this end, the force opposing the motion of a droplet under a thin rectangular glass cover slip was measured for varying cover slip dimensions (widths, length), gap height between the cover slip and substrate, and bulk droplet velocity. The stiffness of the droplet before droplet motion began, the force at which the motion initiated, and the steady-state force opposing the droplet motion were measured. The data was then correlated to hypothesized equations and compared to simple models accounting for the forces due to the contact angle hysteresis, contact line friction, and viscous losses.
It was found that the stiffness, breakaway force, and steady-state force of the droplet could be correlated to with an error standard deviation of 8 %, 14%, and 10 % respectively. Much of the error was due to an unexpected height dependence for the breakaway and steady-state forces and testing error associated with the velocity. The models for the stiffness and breakaway force over predicted the results by 36% and 16% respectively. During testing,
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stability issues with the cover slip were observed and simple dye testing was conducted to visualize the droplet flow field.
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Hayoun, Pascaline. "Partial wetting of thin liquid films in polymer tubes". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066202/document.
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Les tubes polymères, de PDMS ou de PVC, sont des matériaux hydrophobes polyvalents et peu couteux. Ils sont très largement utilisés dans l'industrie pour transférer des fluides plus ou moins complexes tels que de l'eau potable, des émulsions (e.g lait), des suspensions (e.g café), ou encore des solutions de molécules actives (e.g médicament). La plupart de ces applications mettent en jeux des écoulements intermittents répétés de liquide qui peuvent contaminer le matériau. Cette étude a pour but de mieux comprendre comment ces écoulements de fluides complexes entraînent la contamination des tubes. Nous étudions expérimentalement et théoriquement les régimes d'un segment de liquide de faible viscosité s'écoulant dans un tube en conditions de mouillage partiel. Deux processus sont en compétition : à cause de la vitesse élevée du segment de liquide, un film de liquide se forme à l'arrière du segment, alors qu'à cause de des conditions de mouillage partiel le film de liquide démouille. Nous montrons qu'au-delà de la limite en vitesse correspondant à la transition de mouillage dynamique qui est bien inférieure à la prédiction de Cox-Voinov, un régime précédemment inconnu avec un film épais, dont l'épaisseur dépend de la vitesse, est obtenu bien avant la formation classique d'un film de Landau-Levich-Derjaguin. Nos simulations numériques sont en partie en accord avec nos observationsPolymer tubes, made of PDMS or PVC, are versatile, low cost, hydrophobic materials. They are heavily used in industry for transferring more or less complex fluids such as drinkable water, emulsions (e.g milk), suspensions (e.g coffee), or solution of active molecules (e.g pharmaceutics). Most of these applications involve repeated, intermittent flow of liquids which can lead to unwanted contamination. This study aims at better understanding the mechanisms of contamination for intermittent flow. We experimentally and theoretically investigate the flow regimes of low viscosity liquid slugs flowing down a vertical tube under partial wetting condition. Two processes are in competition: because of the large slug velocity, a liquid film tends to be created at the back of the slug whereas because of the partial wetting condition, the liquid film dewets. We investigate how this competition controls film deposition in hydrophobic tubes. We show that above the threshold velocity for dynamic wetting which is much lower than predicted by Cox-Voinov, a previously unknown regime is found where we observe a velocity dependent thick film well before the classical Landau-Levich-Derjaguin regime
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Bushnell, Tyler D. "A Biomechanical Analysis of Sprinters vs. Distance Runners at Equal and Maximal Speeds". BYU ScholarsArchive, 2004. https://scholarsarchive.byu.edu/etd/217.
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In the sport of track and field, sprinting and distance running represent two major categories of athletes. Sprinting is associated with power and speed, whereas distance running focuses on the economy of movement. With distance running there are elements of sprint technique that overlap. With distance events, there comes a time near the end of the race where economy gives way to speed. If the distance runners knew how to alter their technique in a way to become more sprint-like, this process could possibly be more successful. PURPOSE: This study compared the differences in technique between sprinters and distance runners while running at equal and maximal speeds. METHODS: Subjects for the study consisted of 10 Division I collegiate distance runners, 10 Division I collegiate sprinters, and 10 healthy non-runners. The subjects performed two tests, with each consisting of a 60 meter run completed on the track. Test 1 was run at a pace of 5.81 m/s (4:37 min/mile), while Test 2 was completed at maximal speed. Video footage of each trial was collected at 180 Hz, monitoring hip, knee, thigh, and shank positions, as well as stride length, and contact time. RESULTS: Significant differences (p < .05) between the sprint and distance groups at maximal speed were found in the following areas: speed, minimum hip angle, knee extension at toe-off, stride length, contact time, and the position of the recovery knee at touchdown. Sprinters and distance runners exhibited a significantly lower minimum knee angle than those in the control group. Significant differences between the sprint and control group existed at the minimum hip angle, speed, stride length, contact time, and the position of the recovery knee at touchdown. Regarding the paced trial, the sprinters and distance runners showed significant difference concerning the minimum hip angle, center of mass at touchdown, and recovery knee at touchdown. Sprinters differed significantly from the control group in contact time, the center of mass at touchdown and the position of the recovery knee at touchdown. CONCLUSION: As distance runners attempt to sprint, the desired adaptations do not necessarily occur. The development of economical distance form is a fairly natural process that occurs with the miles of training. Sprinting, however, is a separate, learned technique that often requires specific feedback. When attempting maximal speed, distance runners may benefit by focusing on one characteristic of technique. If knee extension at toe-off could be trained to become more sprint-like, the other characteristics unique to sprinters may follow.
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Nguyen, Sébastien Thanh-Lâm. "Dynamique d'une interface en présence d'une singularité de contact solide/fluide". Paris 11, 2005. https://tel.archives-ouvertes.fr/tel-01390365.
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La solution d'un grande nombre de problèmes académiques, embrassant une grande variété de configurations : la cavité entrainée, la ligne de contact mobile, les écoulements thermocapillaires confinés, possède une singularité (discontinuité d'un champ ou d'une de ses dérivées). Il est bien connu que les méthodes spectrales sont très sensibles aux singularités, ce qui se traduit par la présence d'oscillations non-physiques (phénomène de Gibbs) au voisinage de la discontinuité. Pour cette raison, il est nécessaire de remplacer les conditions aux limites singulières par des conditions régulières filtrant explicitement la singularité pour employer ce type d'approximation numérique. Il est moins connu que les méthodes de précision finie (différences finies, volumes finis, éléments finis. . . ), qui permettent l'emploi direct des conditions singulières, introduisent un filtrage passif de la singularité lié à la finesse de résolution spatiale imposée. Des travaux précédents (thèse d'Eric Chénier) ont montré que l'échelle de filtrage pouvait influencer la structure de l'écoulement à l'échelle globale. En partant du principe que la physique est régulière, il devrait exister un mécanisme modifiant le comportement du fluide dans la région où le modèle classique est mis en défaut. On est alors amené à formuler deux questions fondamentales. D'une part, quel est l'ordre de grandeur de la petite échelle à laquelle la physique change ? D'autre part, existe-t'il un modèle macroscopique à même de rendre compte de ces effets locaux dans une simulation numérique du milieu continu ?Cette thèse est une tentative de répondre à ces deux questionsThe research objective of this work is to achieve a physically relevant modeling removing velocity or vorticitysingularities which occur at solid/fluid junctions. These singularities are very common in a number of fluid flows(e. G. Lid-driven cavity corners, laterally heated liquid bridges, moving contact lines). It is well known that spectralmethods are very sensitive to singularities, and exhibit non physical oscillations (Gibbs Phenomenon) in the vicinityof a discontinuity. For this reason, when using such methods, singular boundary conditions have to be replaced by someregular condition obtained by explicitly filtering the discontinuity. It is less known that finite precision methods(e. G. Finite differences, finite volumes, finite elements), though allowing to keep the original conditions, introducesome implicit filter depending on the scale of discretization. In previous work, evidence was brought up that the localscale of filtering can play a determinant role on the global flow structure. It can, for instance, be responsible forsymmetry breaking of the solution in full zone liquid bridges simulations. Assuming that physics is regular, there must exist some mechanism that modifies the fluid's behavior in the region where the classical model fails. Two fundamental questions show up. First, what is the length of the small scale at which physics differs. Second, does there exist somemacroscopic model which can incorporate these local effects in numerical simulations of continuum. This thesis is devoted to address these two questions
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Hayoun, Pascaline. "Partial wetting of thin liquid films in polymer tubes". Electronic Thesis or Diss., Paris 6, 2016. http://www.theses.fr/2016PA066202.
Texto completoResumen
Les tubes polymères, de PDMS ou de PVC, sont des matériaux hydrophobes polyvalents et peu couteux. Ils sont très largement utilisés dans l'industrie pour transférer des fluides plus ou moins complexes tels que de l'eau potable, des émulsions (e.g lait), des suspensions (e.g café), ou encore des solutions de molécules actives (e.g médicament). La plupart de ces applications mettent en jeux des écoulements intermittents répétés de liquide qui peuvent contaminer le matériau. Cette étude a pour but de mieux comprendre comment ces écoulements de fluides complexes entraînent la contamination des tubes. Nous étudions expérimentalement et théoriquement les régimes d'un segment de liquide de faible viscosité s'écoulant dans un tube en conditions de mouillage partiel. Deux processus sont en compétition : à cause de la vitesse élevée du segment de liquide, un film de liquide se forme à l'arrière du segment, alors qu'à cause de des conditions de mouillage partiel le film de liquide démouille. Nous montrons qu'au-delà de la limite en vitesse correspondant à la transition de mouillage dynamique qui est bien inférieure à la prédiction de Cox-Voinov, un régime précédemment inconnu avec un film épais, dont l'épaisseur dépend de la vitesse, est obtenu bien avant la formation classique d'un film de Landau-Levich-Derjaguin. Nos simulations numériques sont en partie en accord avec nos observationsPolymer tubes, made of PDMS or PVC, are versatile, low cost, hydrophobic materials. They are heavily used in industry for transferring more or less complex fluids such as drinkable water, emulsions (e.g milk), suspensions (e.g coffee), or solution of active molecules (e.g pharmaceutics). Most of these applications involve repeated, intermittent flow of liquids which can lead to unwanted contamination. This study aims at better understanding the mechanisms of contamination for intermittent flow. We experimentally and theoretically investigate the flow regimes of low viscosity liquid slugs flowing down a vertical tube under partial wetting condition. Two processes are in competition: because of the large slug velocity, a liquid film tends to be created at the back of the slug whereas because of the partial wetting condition, the liquid film dewets. We investigate how this competition controls film deposition in hydrophobic tubes. We show that above the threshold velocity for dynamic wetting which is much lower than predicted by Cox-Voinov, a previously unknown regime is found where we observe a velocity dependent thick film well before the classical Landau-Levich-Derjaguin regime
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Koran, Karen M. "Surface interactions of surface washing agents an examination of detergency, interfacial tension and contact angle /". Cincinnati, Ohio : University of Cincinnati, 2007. http://www.ohiolink.edu/etd/view.cgi?ucin1186105489.
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SANTOS, SAMANTHA FONSECA DOS. "DSC, DMA, XPS, CONTACT ANGLE E AFM ANALYSIS OF DE ACC/PHAMCL THICK FILMS SURFACES". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2005. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=7887@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICONeste trabalho, foram estudadas filmes poliméricos densos formadas por acetato de celulose (AcC) e polihidroxialkanoato de cadeia média PHAmcl, com diferentes concentrações relativas de cada polímero. Os filmes de PHAmcl/DAC foram preparadas a partir de soluções poliméricas, diluídas em dimetil cetona, na qual se realiza uma mistura com agitação contínua. Foram preparadas as amostras: AcC puro, PHAmcl puro e seis misturas com concentrações variando de 2 porcento a 12 porcento (m/v) de PHAmcl em AcC. Medidas de calorimetria diferencial exploratória e análise dinâmica mecânica foram realizadas a fim de se conhecer a miscibilidade das blendas formadas A composição química das superfícies desses filmes foi caracterizada utilizando a técnica de espectroscopia de fotoelétrons induzida por raios-X (XPS). A morfologia e as propriedades mecânicas das amostras foram estudadas com o auxílio da microscopia de força atômica (AFM). Observou-se nas misturas um enriquecimento na superfície de PHAmcl e uma alteração da morfologia para toda a superfície com a incorporação de PHAmcl. Foi observada uma diminuição na dureza com o aumento a concentração de PHAmcl no filmes. Os filmes apresentaram miscibilidade até 10 porcento PHAmcl/90porcentoAcC em volume.
In this work, the study of thick films formed by cellulose acetate and medium chain length polyhydroxyalkanotes with different molar concentration of PHB is presented. The films were prepared by polymeric solutions diluted in dimethil ketone with continued agitation. The solvent evaporation occurs on a glass plate in controlled atmosphere of 300 C. Eight samples were prepared: pure AcC and PHAmcl and mixtures with PHAmcl bulk concentrations in the range of 2 to 12 percent (w/v). Differential scanning calorimetry and dynamic mechanical analysis measurements were performed in order to know the samples miscibility. The surface chemical composition of the samples was characterized by X- ray photoelectron spectroscopy (XPS). The morphology and mechanical properties were studied by atomic force microscopy (AFM). PHAmcl surface enrichment and morphology modification of the films were observed on the whole surface with the increasing of PHAmcl. A decrease in the films hardness was observed for increasing PHAmcl bulk concentration. The films were found to be miscible until 10percentPHAmcl/90percentAcC bulk concentration.
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Vaskov, Sean K. (Sean Kikeri). "Characterizing the spreading behavior of radius, contact angle, and spreading velocity of trisiloxane "superspreader" surfactants:/". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74913.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 35).
The ability of surfactants to lower surface tension makes them a key element in many products in a variety of industries. Trisiloxane surfactants have shown extraordinary wetting on hydrophobic surfaces, and are known as "superspreaders". Studies in the past have had inconsistent results characterizing the spreading of these surfactants. In this study, the radius and contact angle during spreading of different concentrations of trisiloxane ethoxylate are measured in a humidity-controlled box. Consistent with other studies, concentrations above the critical aggregation concentration spread more, resulting in lower contact angles and larger radii. The spreading behavior for radius and contact angle can be modeled using an exponential fit. Using the exponential models, a relationship between spreading velocity and contact angle can be found. For concentrations above the critical aggregation concentration, a linear relationship between contact angle and spreading velocity was found.
by Sean K. Vaskov.
S.B.
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Chandra, Santanu. "A NUMERICAL STUDY FOR LIQUID BRIDGE BASED MICROGRIPPING AND CONTACT ANGLE MANIPULATION BY ELECTROWETTING METHOD". University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1197299987.
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KORAN, KAREN M. "SURFACE INTERACTIONS OF SURFACE WASHING AGENTS: AN EXAMINATION OF DETERGENCY, INTERFACIAL TENSION AND CONTACT ANGLE". University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1186105489.
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Cunha, Alex Pereira da. "A method for measuring contact angle and influence of surface fluid parameters on the boiling heat transfer performance /". Ilha Solteira, 2019. http://hdl.handle.net/11449/183048.
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Orientador: Elaine Maria CardosoResumo: O avanço de novas tecnologias, associado à minimização dos custos de fabricação e instala-ção, constitui um grande desafio para a área de refrigeração, uma vez que a geração de calor tem aumentado gradativamente nos últimos anos. Assim, a busca de novos fluidos com pro-priedades térmicas superiores aos comumente usados tornou-se indispensável para melhorar a eficiência energética. Nas últimas décadas os nanofluidos - dispersões de partículas de escala nanométrica (1 a 100nm) em um fluido-base - têm atraído especial interesse não somente da comunidade acadêmica, mas também da indústria em áreas como: a microeletrônica, microflu-ídica, transporte, manufatura, assistência médica, entre outras. O melhor desempenho térmico e a vasta gama de aplicações fazem dos nanofluidos potenciais substitutos dos refrigerantes utilizados em diversos segmentos da engenharia. Dentro desse contexto, o presente trabalho teve como objetivos: o estudo teórico e experimental da influência das propriedades termofísi-cas e concentração de nanofluidos, bem como, das características geométricas da superfície aquecedora sobre o ângulo de contato e a molhabilidade. Também, atenção foi dada à prepa-ração e caracterização dos nanofluidos (Al2O3-água e Fe2O3-água), por meio da análise expe-rimental da condutividade térmica e da viscosidade dinâmica para diferentes concentrações; uma bancada experimental, para aquisição de imagens de gota séssil, foi construída a fim de viabilizar as análises de ângulo de conta... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The advance of new technologies, associated to the minimization of manufacturing and installation costs, presents a great challenge for the refrigeration area, since the heat generation has increased in recent years. Thus, the search for new fluids with thermal properties higher than those commonly used has become indispensable to improve energy efficiency. In recent decades, nanofluids-dispersions of nanometer-scale particles (1 to 100 nm) in a base fluid - have attracted special interest not only from the academic community but also from industry in areas such as microelectronics, microfluidics, transport, manufacturing, medical assistance, among others. In this context, the present work had the following goals: the theoretical and experimental study of the influence of thermophysical properties and nanofluid concentration, as well as the geometric characteristics of the heating surface on the contact angle and wetta-bility. Attention was also given to the preparation and characterization of nanofluids (Al2O3-water and Fe2O3-water) by the experimental analysis of thermal conductivity and dynamic viscosity for different concentrations; an experimental apparatus for the acquisition of sessile droplet images was designed in order to analyze the contact angle and wettability; and a computational routine was developed to obtain the drop profile and the surface-fluid interaction for the different nanofluids and surfaces used. Based on database, it was possible to evaluate the pre... (Complete abstract click electronic access below)
Doutor
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Emonot, Jérôme. "Contribution à l'étude du contact dynamique entre une nappe de liquide et un substrat solide". Lyon 1, 1994. http://www.theses.fr/1994LYO10232.
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Une operation d'enduction concerne le revetement en continu d'une surface solide par un liquide et se retrouve dans de nombreux secteurs de l'industrie (papier, plastique, textile non tisse, emballage, magnetique, photographie). L'interet porte par les scientifiques sur le sujet n'est pas nouveau mais force est de constater que le savoir faire technologique a jusqu'a present devance la comprehension physique pour le developpement des nombreux outils d'enduction existants. Celle-ci se heurte a deux problemes majeurs: la presence de surfaces libres et le contact du liquide avec la surface du substrat solide. Le probleme des surfaces libres a ete resolu recemment dans la plupart des configurations a l'aide de methodes numeriques evoluees. L'intersection de l'interface liquide-air par la surface solide, au moment du contact avec le substrat, demeure, quant a elle, un probleme incompletement resolu. Il releve a la fois de la physique microscopique de l'etalement de goutte et de la mecanique des fluides macroscopique. D'un point de vue de mecanicien, l'analyse de l'ecoulement du liquide au voisinage du contact avec le substrat se heurte a deux difficultes: la singularite de la ligne triple (valeur infinie du taux de cisaillement au contact) et l'indetermination sur la valeur reelle de l'angle de contact dynamique. L'enduction a haute vitesse a revele un nouveau phenomene qui perturbe la phase de contact: l'entrainement d'air. En se placant resolument dans une situation ou une lame d'air est entrainee sous le film liquide, le contact n'est alors qu'apparent et un modele complet d'ecoulement d'air est propose. Ce modele conduit a la prediction de l'epaisseur de la lame d'air susceptible d'etre entrainee, en fonction des differents parametres du procede. Nous montrons alors comment la prise en compte de cette lame d'air permet de s'affranchir du probleme de la ligne triple et de l'angle de contact dynamique. Nous appliquons ensuite le modele au cas de la fabrication de films plastique. Un prototype d'aide au contact, concu sur la base des calculs, permet de verifier experimentalement la validite des simulations. Enfin, l'influence sur le refroidissement du film par la surface solide, de la lame d'air piegee au contact, est evaluee dans le cas particulier du cast-film
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Giljean, Sylvain. "Caractérisation Multi-Échelles de la Rugosité de Matériaux Métalliques à Usage Biomédical : Effet sur la Mouillabilité et l'Adhésion de Cellules Osseuses". Mulhouse, 2007. http://www.theses.fr/2007MULH0888.
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Ce travail a pour but de caractériser, à différentes échelles, par profilométrie tactile et par des méthodes de calcul rigoureuses, la topographie de biomatériaux métalliques (acier inoxydable, titane et alliage de titane) obtenue par polissage à différents grades de papier abrasif et par électroérosion. L'effet de la rugosité sur la mouillabilité. Quantifiée par gonion et l'effet de la rugosité sur le comportement de cellules osseuses humaines, quantifie iac r- analyse d'images est statistiquement déterminé par le calcul de la pertinence de 101 paramètres de rugosité à toutes les échelles allant de 0,2 µm à 5 mm. Il apparaît que la seule connaissance du paramètre de rugosité Ra calculé à une longueur d'évaluation arbitrairement choisie est insuffisante pour étudier l'effet de la rugosité. La rugosité doit être définie par des paramètres d'amplitude, de fréquence, hybrides et fractals et la longueur d'évaluation doit être adaptée à la taille de l'élément étudiéeThis work aims to characterize the topography of metallic biomaterials (stainless steel, pure titanium and titanium alloy) by using a tactile profilometer and powerful mathematical treatments. The samples topography is obtained either by grinding with different paper grades or by electroerosion. The roughness effect on wettability, evaluated by goniometry, and the roughness effect on human bone cell behaviour, determined by image analyses, is statistically evaluated by calculating the relevance of 101 roughness parameters at different scales from 0. 2 m to 5 mm. The major conclusion is that the evaluation of the rouglmess by the Ra parameter at only one scale, arbitrarily chosen, is insufficient to understand the roughness effect. Roughness must be defined by amplitude, frequency, hybrid and fractal parameters and the evaluation length must be adapted to the size of the studied element
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Manzo, Gabriel M. "Drop Motion on Superhydrophobic Fiber Mats". University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1323465810.
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Eratak, Deniz Ozlem. "Determination Of Contact Angles Of Powders By Capillaric Dewatering Of Filter Cakes". Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12605901/index.pdf.
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Solid-liquid contact angle is an important parameter in many particulate processes of the mineral, ceramic and chemical industries. In particular, modification of the contact angle through surface active agents plays a crucial role in froth flotation of minerals. In the case of flat solid surfaces, direct measurement of the contact angle is possible. However, such flat surfaces can not be obtained with finely divided solids typically encountered in flotation applications. Then, indirect methods based on powder beds as thin layers of powders deposited on glass plates or packed columns are used for the determination of apparent contact angles.
This thesis presents an alternative novel method based on the capillaric dewatering of filter cakes for the measurement of the receding contact angle and correlates the contact angles measured as such with column wicking and micro-flotation test results of zircon and rutile mineral particles. The experimental procedure is simple and fast. The results have proven that the proposed method is reliable and give a good measure of the contact angle in the absence and presence of surface active non-wetting agents.
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Munzer, Charlotte. "Etude de l'action d'un bioadjuvant aux substances extracellulaires sur la microstructure et les caractéristiques de surface de pâtes cimentaires pour des bétons plus éco-respectueux". Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAD028/document.
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L’influence de l’incorporation d’un produit bio sourcé comme adjuvant dans les matériaux cimentaires tant à l’état frais qu’à l’état durci a été étudiée. La présence du bioproduit ne provoque pas de modifications sur les résistances mécaniques et sur la microstructure des pâtes de ciment (ATG/ATD et DRX). Des essais de caractérisation du réseau poreux de mortiers et pâtes cimentaires ont montré un effet du bioproduit sur la qualité de la peau des échantillons. Un protocole de réalisation et de conservation d’échantillons de pâte cimentaire a été mis au point afin de permettre différents essais sur des surfaces identiques dans le cas du projet « substances extracellulaires pour les bétons » impliquant des partenaires microbiologistes. L’étude de l’évolution de l’angle de contact dynamique d’une goutte d’eau posée sur des pâtes de ciment a montré que la présence du bioproduit favorise l’étalement au détriment de la pénétration de celle-ci au sein du matériau, en modifiant la tortuosité des capillaires de la matrice cimentaire. Une méthode d’analyse d’évolution de l’angle de contact en fonction du diamètre de la goutte a été développée et validée avec des données de la littérature. Cette technique originale a permis une détermination précise des angles d’avancée et de recul sur des substrats poreuxThe influence of the incorporation of a product organically sourced in cementitious materials (at fresh and hardened state) was studied. The presence of the bioproduct does not cause changes on mechanical strength and on cement past microstructure (TGA / DTA and XRD). Porous network characterization tests on mortar and cement paste showed an effect of bioproduct on the quality of skin samples. A protocol of realization and conservation of cement paste samples was developed in order to allow various tests on same surfaces for the microbiologists partners of the « extra cellular substances for concrete » project. The study of the evolution of the dynamic contact angle of a drop of water placed on cement pastes showed that the presence of the bioproduct favored at the expense of spreading the penetration of water within the material, modifying the tortuosity of the capillaries of the cementitious matrix. An analytical method of drop behaviour (contact angle versus diameter) was developed and validated with literature data. This original technique allowed an accurate determination of the angles of advance and retreat on porous substrates
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Liu, Jie. "Chemical composition of coal surface as derived from micro-FTIR and its effects on contact angle". Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58636.
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In this study, in-situ image analysis, contact angle measurements, micro-FTIR spectroscopy and SEM are used to obtain information on the surface composition of coal. The heterogeneous coal surface is investigated with regard to the distribution of the chemical functional groups and its effect on hydrophobicity as derived from contact angle measurements. Contact angles obtained from sessile drop and captive bubble techniques are correlated with the semi-quantitative ratios from micro-FTIR spectroscopy. As part of the new methodology, image analysis and SEM are also applied in order to characterize and analyze for the petrographic composition of areas that are subjected to these measurements. An opposite trend between high rank coal and low rank coal is found in relation to the micro-FTIR semi-quantitative ratios versus contact angle. For lower rank coal, the increase in Aromaticity 1 and 2 led to an increase in the contact angle, while the increased quantity of aliphatic groups decreased the contact angle values. For high rank coal, the rising aliphatic groups increased the contact angle values and the increase in Aromaticity 1 and 2 led to smaller contact angle values. The newly introduced CHal/C=O was used to assess the abundance of aliphatic groups and oxygenated groups. The increased content of oxygenated groups in the high rank coal samples led to a decrease in the contact angle, which is consistent with the findings of previous studies. For low rank coal samples, although the correlation was less distinct, an opposite trend was observed.Applied Science, Faculty of
Mining Engineering, Keevil Institute of
Graduate
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Zhang, Yi. "Static and Dynamic Behaviour of Inter-granular Liquid Bridges: Hysteresis of Contact Angle and Capillary Forces". Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/16151.
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The wet granular material, a mixture of solid grains, liquid and air, has been studied in many industrial applications. Understanding the mechanical properties of wet granular materials is extremely important in geotechnical engineering. The cohesion in these materials arising from a liquid bridge between a pair of grains is produced by the capillary force and the viscous force. Thus, investigating the behaviour of liquid bridges between grains helps people obtain a better understanding of the factors influencing the cohesion, including the geometry and topological distribution of liquid bridges, the size of grains, or the liquid flow rate. This thesis focuses on the static and dynamic behaviour of liquid bridges connecting two solid substrates. The aims of our study are to (1) explore the quasi-static and dynamic force arising from liquid bridges when two substrates move at various speeds and (2) established an analytical model to describe and predict the behaviour of liquid bridge when it moves at different speeds. Our work can be divided into three parts: parallel plates experiments, analytical modelling and extended experiments. The working content and the main results are presented in the below. 1. A series of parallel plates experiments are conducted to systematically investigate the capillary force and the contact angle hysteresis of a liquid bridge which forms between two moveable parallel plates under the quasi-static and dynamic conditions. The experimental results show that the contact angle hysteresis can be divided into pinning and slipping stages in both of the extension and compression processes. With the increase of plate moving speeds, it is observed that in the slipping stage, the receding angle becomes smaller and the advancing angle becomes larger. The capillary force hysteresis also changes correspondently. The liquid bridge hysteresis can be used to predict the cohesion behaviour of wet granular material during the wetting and drying processes. Moreover, in some geotechnical events such as the seepage in soil or the shear movement of the grains, the rate effect on the contact angle and the force between grains can provide a potential direction to investigate the failure criterion of soils and their dynamic behaviour. 2. In the quasi-static regime, an analytical model has been first established based on the geometrical shape of liquid bridges. According to the pinning and slipping stages of liquid bridge hysteresis, the proposed model describes the geometrical characteristics of a liquid bridge being extended and compressed under the quasi-static condition. The models have been compared to the experimental results and the analytical model can particularly predict the quasi-static contact angle and contact radius hysteresis. In the dynamic regime, an empirical rate-dependent contact angle fitting function has been established to capture the change of dynamic contact angle with respect to the loading rate. Furthermore, the dynamic analytical model has been established to predict the variation of viscous force and dynamic contact angle hysteresis with the increase of plate moving speeds. The model predictions are in a good agreement with the experiments. 3. Moreover, to consider the effects of surface curvature and roughness, we extended the experiments forming liquid bridges between various substrates: (1) two plates with different surface roughness; (2) two spheres; (3) a sphere and a plate. The influence of surface properties and curvatures on the behaviour of liquid bridges has been discussed and possible future research directions are provided. As the cohesion between gains is influence by many factors such as the volume, size, contact angle of a liquid bridge, as well as the flow speeds and the grain movement, this study provides a good start to investigate the capillary force and the contact angle hysteresis under the quasi-static and dynamic conditions. In this work, the experimental observation of liquid bridge hysteresis is presented and the analytical models are established to predict the force and contact angle hysteresis at a given moving speed. This study demonstrates potential to use this microscopic information towards the macro scale properties of wet granular materials, such as the soil-water retention hysteresis under different wetting and drainage rates.
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Stefin-Tyree, Amanda Joy. "Investigating Interfacial Behaviors of Silicon Dioxide in Contact with Liquids and Polymers in Contact with Water". University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1627404674037109.
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Frost, Daniel Wayne. "Study of adsorption of biological and nanoparticle solutions at the solid-liquid interface". Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/411.
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Lomax, Deborah. "Electrowetting and electrodeposition on graphitic surfaces". Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/electrowetting-and-electrodeposition-on-graphitic-surfaces(0ecee720-fb95-48cb-bfb2-75e7adc305f3).html.
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Graphite and graphene electrodes are used to study two electrochemical processes: the decoration of these electrodes with Au metallic nanoparticles through the use of electrodeposition, and electrowetting, the potential-dependent change in hydrophobicity of a surface. Electrodeposition provides a useful route to electrode functionalisation, in particular to combine the enhanced properties of metallic nanoparticles with the advantageous features of carbon materials. A combination of cyclic voltammetry, chronoamperometry, and both ex situ and in situ atomic force microscopy are used to deduce the mechanism of Au electrodeposition on graphite and graphene. Notably, the mechanism of Au nanoparticle formation cannot be deduced from simple voltammetry alone, and the spontaneous formation of Au within the timescale of the electrodeposition experiment is confirmed. Electrowetting is a uniquely responsive method to manipulate the wetting properties of an electrode. However, a dielectric coating is commonly required to protect the surface from electrolysis, which in turn further increases the potentials needed to perform electrowetting. In contrast to this, here it is shown that bare graphite and graphene electrodes support electrowetting without the disadvantages of a dielectric coating, allowing an unprecedented combination of performance and efficiency. Furthermore, the ideal behaviour this system demonstrates is implemented as a platform to study electrowetting itself. The influence of electrolyte composition, surface defects and electrode-blocking dielectric-like films are investigated to determine the factors that impede electrowetting, a key step to understanding the phenomenon that is normally hindered by the use of the dielectric.
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KIM, BONGSU. "LONG-TERM STABILITY OF PLASMA OXIDIZED POLYDIMETHYLSILOXANE SURFACES". University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1100893247.
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Viswanadam, Goutham. "Water-Diesel Secondary Dispersion Separation Using Superhydrophobic Tubes of Nanofibers". University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1373984491.
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Dugáček, Ján. "Automatizované optické měření kontaktního úhlu kapky". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-377330.
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Measurement of surface tension of solids usually requires manual processing of photographs of droplets of liquids with known properties on the measured material's surface, during which the contact angle is manually determined. The objective of this work is to implement an algorithm that can determine these contact angles from photographs and does not require the photographs to be made under specific light conditions. The implementation cannot depend on paid libraries and must be simple to incorporate into existing software.