WorldWideScience

Sample records for volatile liquid droplets

  1. Droplet impacts upon liquid surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ching, B.; Golay, M.W.; Johnson, T.J.

    1984-11-02

    The absorption and rebounding of single droplets and streams of droplets (of diameter less than 1200 micrometers) impacting upon the surface of a deep liquid were examined experimentally. Conservation of mechanical energy and momentum were used to explain rebounding droplet interactions, and impaction criteria have been established regarding the absorption of droplet streams. Surface tension is the dominant mechanism governing the observed behavior. Single droplets were never observed to rebound.

  2. Mechanical vibrations of pendant liquid droplets

    OpenAIRE

    Temperton, Robert H.; Smith, Michael I.; Sharp, James S.

    2015-01-01

    A simple optical deflection technique was used to monitor the vibrations of microlitre pendant droplets of deuterium oxide, formamide, and 1,1,2,2-tetrabromoethane. Droplets of different volumes of each liquid were suspended from the end of a microlitre pipette and vibrated using a small puff of nitrogen gas. A laser was passed through the droplets and the scattered light was collected using a photodiode. Vibration of the droplets resulted in the motion of the scattered beam and time-dependen...

  3. Self-propelled chemotactic ionic liquid droplets

    OpenAIRE

    Francis, Wayne; Fay, Cormac; Florea, Larisa; Diamond, Dermot

    2015-01-01

    Herein we report the chemotactic behaviour of self-propelled droplets composed solely of the ionic liquid trihexyl(tetradecyl)phosphonium chloride ([P6,6,6,14][Cl]). These droplets spontaneously move along an aqueous-air boundary in the direction of chloride gradients to specific destinations due to asymmetric release of [P6,6,6,14]+ cationic surfactant from the droplet into the aqueous phase.

  4. Kinetics of Evaporation of Pinned Nanofluid Volatile Droplets at Subatmospheric Pressures.

    Science.gov (United States)

    Orejon, Daniel; Shanahan, Martin E R; Takata, Yasuyuki; Sefiane, Khellil

    2016-06-14

    We examine the effects of nanoparticle addition at low concentration on the evaporation kinetics of droplets in the constant radius mode. The evaporative behavior of deionized water and Al2O3 nanoparticle laden water on an aluminum substrate was observed at atmospheric and at different subatmospheric pressures. The two fluids exhibit the same evaporative behavior, independent of the droplet volume or the subatmospheric pressure. Moreover, the linear relationship between evaporation rate and droplet radius, initially proposed by Picknett and Bexon nearly four decades ago for droplets evaporating in the constant radius mode, is satisfied for both liquids. In addition, we have established a unified correlation solely function of fluid properties that extends this relationship to any subatmospheric pressure and fluid tested. We conclude that the addition of a small quantity of nanoparticles to the base fluid does not modify the kinetics of evaporation for pinned volatile droplets.

  5. Liquid Droplets on a Highly Deformable Membrane

    Science.gov (United States)

    Schulman, Rafael; Dalnoki-Veress, Kari

    2015-11-01

    We present measurements of the deformation produced by micro-droplets atop thin elastomeric and glassy free-standing films. Due to the Laplace pressure, the droplets deform the elastic membrane thereby forming a bulge. Thus, there are two angles that define the droplet/membrane geometry: the angle the liquid surface makes with the film and the angle the deformed bulge makes with the film. The contact line geometry is well captured by a Neumann construction which includes contributions from interfacial and mechanical tensions. Finally, we show that a droplet atop a film with biaxial tension assumes an equilibrium shape which is elongated along the axis of high tension.

  6. Bouncing of polymeric droplets on liquid interfaces

    Science.gov (United States)

    Gier, S.; Dorbolo, S.; Terwagne, D.; Vandewalle, N.; Wagner, C.

    2012-12-01

    The effect of polymers on the bouncing behavior of droplets in a highly viscous, vertically shaken silicone oil bath was investigated in this study. Droplets of a sample liquid were carefully placed on a vibrating bath that was maintained well below the threshold of Faraday waves. The bouncing threshold of the plate acceleration depended on the acceleration frequency. For pure water droplets and droplets of aqueous polymer solutions, a minimum acceleration amplitude was observed in the acceleration threshold curves as a function of frequency. The bouncing acceleration amplitude for a droplet of a dilute aqueous polymer solution was higher than the acceleration amplitude for a pure water droplet. Measurements of the center of mass trajectory and the droplet deformations showed that the controlling parameter in the bouncing process was the oscillating elongational rate of the droplet. This parameter can be directly related to the elongational viscosity of the polymeric samples. The large elongational viscosity of the polymer solution droplets suppressed large droplet deformations, resulting in less chaotic bouncing.

  7. The effect of liquid film on liquid droplet impingement erosion

    Energy Technology Data Exchange (ETDEWEB)

    Fujisawa, Nobuyuki, E-mail: fujisawa@eng.niigata-u.ac.jp [Visualization Research Center, Niigata University, 8050, Ikarashi 2-Nocho, Nishi-ku, Niigata 950-2181 (Japan); Yamagata, Takayuki, E-mail: yamagata@eng.niigata-u.ac.jp [Visualization Research Center, Niigata University, 8050, Ikarashi 2-Nocho, Nishi-ku, Niigata 950-2181 (Japan); Saito, Kengo; Hayashi, Kanto [Graduate School of Science and Technology, Niigata University, 8050, Ikarashi 2-Nocho, Nishi-ku, Niigata 950-2181 (Japan)

    2013-12-15

    Highlights: • Liquid droplet impingement erosion is studied experimentally using high-speed conical spray. • Erosion rate is increased with decreasing the liquid film thickness. • Erosion model is proposed considering the influence of liquid film thickness. -- Abstract: In the present paper, the pipe-wall thinning due to liquid droplet impingement erosion is studied experimentally by using a high-speed conical spray under the influences of liquid film on the target specimen. The size of the droplets considered is an order of tens of micrometers in diameter, which is the same order as those expected in the pipeline of nuclear/fossil power plants. In order to evaluate the erosion rate by the liquid droplet impingement under the influence of liquid film, the experiments are conducted by various combinations of the specimen diameters and the standoff distances of the spray from the nozzle. The experimental results show that the erosion depth increases linearly with the local flow volume, indicating the presence of terminal stage of erosion. The present results indicate that the erosion rate increases with decreasing the specimen diameter and increases slightly with increasing the standoff distance. This result combined with the theoretical consideration of the liquid film on the specimen leads to the conclusion that the erosion rate increases with decreasing the liquid film thickness, which supports the numerical result of liquid droplet impingement erosion in literature. Then, the erosion model for predicting the erosion rate by the liquid droplet impingement is proposed considering the influence of the liquid film.

  8. Stability of thin liquid films and sessile droplets under confinement.

    Science.gov (United States)

    Dörfler, Fabian; Rauscher, Markus; Dietrich, S

    2013-07-01

    The stability of nonvolatile thin liquid films and of sessile droplets is strongly affected by finite size effects. We analyze their stability within the framework of density functional theory using the sharp kink approximation, i.e., on the basis of an effective interface Hamiltonian. We show that finite size effects suppress spinodal dewetting of films because it is driven by a long-wavelength instability. Therefore nonvolatile films are stable if the substrate area is too small. Similarly, nonvolatile droplets connected to a wetting film become unstable if the substrate area is too large. This instability of a nonvolatile sessile droplet turns out to be equivalent to the instability of a volatile drop which can attain chemical equilibrium with its vapor.

  9. Mechanical vibrations of pendant liquid droplets.

    Science.gov (United States)

    Temperton, Robert H; Smith, Michael I; Sharp, James S

    2015-07-01

    A simple optical deflection technique was used to monitor the vibrations of microlitre pendant droplets of deuterium oxide, formamide, and 1,1,2,2-tetrabromoethane. Droplets of different volumes of each liquid were suspended from the end of a microlitre pipette and vibrated using a small puff of nitrogen gas. A laser was passed through the droplets and the scattered light was collected using a photodiode. Vibration of the droplets resulted in the motion of the scattered beam and time-dependent intensity variations were recorded using the photodiode. These time-dependent variations were Fourier transformed and the frequencies and widths of the mechanical droplet resonances were extracted. A simple model of vibrations in pendant/sessile drops was used to relate these parameters to the surface tension, density and viscosity of the liquid droplets. The surface tension values obtained from this method were found to be in good agreement with results obtained using the standard pendant drop technique. Damping of capillary waves on pendant drops was shown to be similar to that observed for deep liquid baths and the kinematic viscosities obtained were in agreement with literature values for all three liquids studied.

  10. Acoustophoresis in Variously Shaped Liquid Droplets

    CERN Document Server

    Yu, Gan; Xu, Jie; 10.1039/c1sm05871a

    2012-01-01

    The ability to precisely trap, transport and manipulate micrometer-sized objects, including biological cells, DNA-coated microspheres and microorganisms, is very important in life science studies and biomedical applications. In this study, acoustic radiation force in an ultrasonic standing wave field is used for micro-objects manipulation, a technique termed as acoustophoresis. Free surfaces of liquid droplets are used as sound reflectors to confine sound waves inside the droplets. Two techniques were developed for precise control of droplet shapes: edge pinning and hydrophilic/hydrophobic interface pinning. For all tested droplet shapes, including circular, annular and rectangular, our experiments show that polymer micro particles can be manipulated by ultrasound and form into a variety of patterns, for example, concentric rings and radial lines in an annular droplet. The complexity of the pattern increases with increasing frequency, and the observations are in line with simulation results. The acoustic mani...

  11. Burning Behavior of Liquid Fuel Droplets

    Directory of Open Access Journals (Sweden)

    Shah Shahood Alam

    2015-06-01

    Full Text Available Ignition of flammable liquids by hot surfaces is well known to automotive and aviation industries. However, only a limited data regarding hot surface ignition (HSI of pure and commercial fuels is available in literature. Further, relatively few studies have determined the ignition delay and to our knowledge the combustion lifetime. In the present work, we have generated results from an efficient, reproducible, yet simple experimental setup involving a liquid fuel droplet, a horizontal heated stainless steel plate and quiescent environment. Tests were conducted for diesel, biodiesel and its blends as well as vegetable oils, applied/used as single droplets under variety of conditions to the heated surface. The droplet size range was approximately between 1500 micron to 2000 micron. The objective of this experiment was to determine the minimum temperatures for HSI and also the temperatures where 100% probability of ignition was expected. Further, from this experiment, we were also able to obtain the ignition delay and droplet lifetime. As an extension to this study, a separate droplet combustion model was developed to closely study the general burning behavior of these droplets by generating temperature and species concentration profiles. The droplet mass burning rate was also determined. The results obtained in the present work were in a general agreement with the experimental and modeling observations of other studies.

  12. Liquid Droplets on a Highly Deformable Membrane

    Science.gov (United States)

    Schulman, Rafael D.; Dalnoki-Veress, Kari

    2015-11-01

    We examine the deformation produced by microdroplets atop thin elastomeric and glassy free-standing films. Because of the Laplace pressure, the droplets deform the elastic membrane thereby forming a bulge. Thus, two angles define the droplet or membrane geometry: the angles the deformed bulge and the liquid surface make with the film. These angles are measured as a function of the film tension, and are in excellent agreement with a force balance at the contact line. Finally, we find that if the membrane has an anisotropic tension, the droplets are no longer spherical but become elongated along the direction of high tension.

  13. Vitrification and levitation of a liquid droplet on liquid nitrogen

    Science.gov (United States)

    Song, Young S.; Adler, Douglas; Xu, Feng; Kayaalp, Emre; Nureddin, Aida; Anchan, Raymond M.; Maas, Richard L.; Demirci, Utkan

    2010-01-01

    The vitrification of a liquid occurs when ice crystal formation is prevented in the cryogenic environment through ultrarapid cooling. In general, vitrification entails a large temperature difference between the liquid and its surrounding medium. In our droplet vitrification experiments, we observed that such vitrification events are accompanied by a Leidenfrost phenomenon, which impedes the heat transfer to cool the liquid, when the liquid droplet comes into direct contact with liquid nitrogen. This is distinct from the more generally observed Leidenfrost phenomenon that occurs when a liquid droplet is self-vaporized on a hot plate. In the case of rapid cooling, the phase transition from liquid to vitrified solid (i.e., vitrification) and the levitation of droplets on liquid nitrogen (i.e., Leidenfrost phenomenon) take place simultaneously. Here, we investigate these two simultaneous physical events by using a theoretical model containing three dimensionless parameters (i.e., Stefan, Biot, and Fourier numbers). We explain theoretically and observe experimentally a threshold droplet radius during the vitrification of a cryoprotectant droplet in the presence of the Leidenfrost effect. PMID:20176969

  14. Catching proteins in liquid helium droplets

    CERN Document Server

    Kupser, Peter; Meijer, Gerard; von Helden, Gert

    2010-01-01

    An experimental approach is presented that allows for the incorporation of large mass/charge selected ions in liquid helium droplets. It is demonstrated that droplets can be efficiently doped with a mass/charge selected amino acid as well as with the much bigger m$\\approx$12 000 amu protein Cytochrome C in selected charge states. The sizes of the ion-doped droplets are determined via electrostatic deflection. Under the experimental conditions employed, the observed droplet sizes are very large and range, dependent on the incorporated ion, from 10$^{10}$ helium atoms for protonated Phenylalanine to 10$^{12}$ helium atoms for Cytochrome C. As a possible explanation, a simple model based on the size- and internal energy-dependence of the pickup efficiency is given.

  15. MODEL OF LASER INTERACTION WITH LIQUID DROPLET

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    K. N. Volkov,

    2016-09-01

    Full Text Available Subject of Research. A mathematical model of optical breakdown in the dielectric liquid droplets when exposed to pulsed laser radiation was developed. The process is considered in several stages: heating, evaporation of the particle, forming a steam halo, ionization of the steam halo. Numerical study was carried out on the basis of the mathematical model to determine the threshold characteristics of the laser pulse. Main Results.Distributions of pressure, density and temperature of the particle steam halo were obtained by means of a calculation. The temperature field around the liquid droplet was determined. It has been found that at high energies in the gas bubble, the conditions are provided for thermal gas ionization and start of the electron avalanche, leading to plasma formation. Due to the volumetric heat generation, the droplet is overheated and is in a metastable state. The plasma cloud is almost opaque to radiation that causes an abrupt increase of temperature. As a result, an explosion occurs inside the droplet with the formation of a shock wave that is propagating outward. Practical Relevance.The results can be used to assess the performance of high-power laser scanning (LIDAR under the presence of liquid droplets in the atmosphere and other suspensions. Lasers can be used in fire and explosion aerospace systems. Obtained findings can be applied also in the systems of laser ignition and detonation initiation.

  16. High Velocity Droplet Rebound On Liquid Pools

    Science.gov (United States)

    Doak, William; Laiacona, Danielle; Chiarot, Paul; German, Guy

    2015-11-01

    Rebound of high velocity, periodic droplet streams off viscous liquid pools is studied experimentally. Droplets, approximately 60 micrometers in diameter, impact the oil surface at velocities up to 13 m/s and at angles between 2-25 degrees. The oil surface does not degrade or lose its ability to provide rebound even after millions of droplet impacts. The oil was varied to examine the effect that surface tension and viscosity had on droplet rebound. Stable rebound is achievable on oils varying in dynamic viscosity in the range 13-970 Pa.s and surface tensions in the range 19-28 mN/m. When rebound occurs, a consistent 29% loss of droplet kinetic energy is observed. This is a surprising relationship due to the fact that it holds true for all cases of stable rebound regardless of the oil used. We further observe an upper inertial limit where droplets no longer provide stable rebound and instead become fully entrained in the oil pool. This limit is governed by the Rayleigh-Plateau instability and can be characterized and predicted using a modified version of the Weber number. The droplet rebound presented in this study is unique due to the size, velocity, and frequency of the droplets used. Another unique feature is that the rebound manifests itself as an effectively static phenomenon. No motion of the interface - oscillations, waves, or otherwise - was observed during rebound. The quasi-static nature of rebound enabled distinctions to be made regarding energy dissipation and the transition from droplet rebound to entrainment.

  17. Structural Transitions in Cholesteric Liquid Crystal Droplets

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Ye; Bukusoglu, Emre; Martinez-Gonzalez, Jose A.; Rahimi, Mohammad; Roberts, Tyler F.; Zhang, Rui; Wang, Xiaoguang; Abbott, Nicholas L.; de Pablo, Juan J.

    2016-07-01

    Confinement of cholesteric liquid crystals (ChLC) into droplets leads to a delicate interplay between elasticity, chirality, and surface energy. In this work, we rely on a combination of theory and experiments to understand the rich morphological behavior that arises from that balance. More specifically, a systematic study of micrometer-sized ChLC droplets is presented as a function of chirality and surface energy (or anchoring). With increasing chirality, a continuous transition is observed from a twisted bipolar structure to a radial spherical structure, all within a narrow range of chirality. During such a transition, a bent structure is predicted by simulations and confirmed by experimental observations. Simulations are also able to capture the dynamics of the quenching process observed in experiments. Consistent with published work, it is found that nanoparticles are attracted to defect regions on the surface of the droplets. For weak anchoring conditions at the nanoparticle surface, ChLC droplets adopt a morphology similar to that of the equilibrium helical phase observed for ChLCs in the bulk. As the anchoring strength increases, a planar bipolar structure arises, followed by a morphological transition to a bent structure. The influence of chirality and surface interactions are discussed in the context of the potential use of ChLC droplets as stimuli-responsive materials for reporting molecular adsorbates.

  18. Simulation of sliding of liquid droplets

    Science.gov (United States)

    Alen, Saif Khan; Farhat, Nazia; Rahman, Md. Ashiqur

    2016-07-01

    Numerical simulations of sliding behavior of liquid droplets on flat and periodic microgrooved surfaces with a range of groove geometry are conducted. A numerical model is developed which is capable of predicting the critical sliding angle of the drop by comparing the advancing and the receding angles obtained from numerical and experimental findings. The effect of microgroove topography, droplet size and inclination angle on the droplet sliding characteristics is analysed. Using an open-source platform (Surface Evolver), a 3D drop-shape model is developed to numerically determine the drop stability and contact angle hysteresis on tilted surfaces. In this numerical model, the three phase contact line of the drop is obtained by numerically calculating the vertex force and local contact angle at each vertex of the base contour. Several numerical models are developed based on various assumptions of base contour shape (circular or elliptical) and implementation of gravitational force to the droplet. Droplet shapes and critical sliding angles, obtained from these numerical models, are compared with those of experimental results and are found to be in very good agreement.

  19. Adaptive Liquid Lens Actuated by Droplet Movement

    Directory of Open Access Journals (Sweden)

    Chao Liu

    2014-08-01

    Full Text Available In this paper we report an adaptive liquid lens actuated by droplet movement. Four rectangular PMMA (Polymethyl Methacrylate substrates are stacked to form the device structure. Two ITO (Indium Tin Oxide sheets stick on the bottom substrate. One PMMA sheet with a light hole is inserted in the middle of the device. A conductive droplet is placed on the substrate and touches the PMMA sheet to form a small closed reservoir. The reservoir is filled with another immiscible non-conductive liquid. The non-conductive liquid can form a smooth concave interface with the light hole. When the device is applied with voltage, the droplet stretches towards the reservoir. The volume of the reservoir reduces, changing the curvature of the interface. The device can thus achieve the function of an adaptive lens. Our experiments show that the focal length can be varied from −10 to −159 mm as the applied voltage changes from 0 to 65 V. The response time of the liquid lens is ~75 ms. The proposed device has potential applications in many fields such as information displays, imaging systems, and laser scanning systems.

  20. A frictional sliding algorithm for liquid droplets

    Science.gov (United States)

    Sauer, Roger A.

    2016-12-01

    This work presents a new frictional sliding algorithm for liquid menisci in contact with solid substrates. In contrast to solid-solid contact, the liquid-solid contact behavior is governed by the contact line, where a contact angle forms and undergoes hysteresis. The new algorithm admits arbitrary meniscus shapes and arbitrary substrate roughness, heterogeneity and compliance. It is discussed and analyzed in the context of droplet contact, but it also applies to liquid films and solids with surface tension. The droplet is modeled as a stabilized membrane enclosing an incompressible medium. The contact formulation is considered rate-independent such that hydrostatic conditions apply. Three distinct contact algorithms are needed to describe the cases of frictionless surface contact, frictionless line contact and frictional line contact. For the latter, a predictor-corrector algorithm is proposed in order to enforce the contact conditions at the contact line and thus distinguish between the cases of advancing, pinning and receding. The algorithms are discretized within a monolithic finite element formulation. Several numerical examples are presented to illustrate the numerical and physical behavior of sliding droplets.

  1. Vapor Transport of a Volatile Solvent for a Multicomponent Aerosol Droplet

    CERN Document Server

    Feng, James Q

    2015-01-01

    This work presents analytical formulas derived for evaluating vapor transport of a volatile solvent for an isolated multicomponent droplet in a quiescent environment, based on quasi-steady-state approximation. Among multiple solvent components, only one component is considered to be much more volatile than the rest such that other components are assumed to be nonvolatile remaining unchanged in the droplet during the process of (single-component) volatile solvent evaporation or condensation. For evaporating droplet, the droplet size often initially decreases following the familiar "d^2 law" at an accelerated rate. But toward the end, the rate of droplet size change diminishes due to the presence of nonvolatile cosolvent. Such an acceleration-deceleration reversal behavior is unique for evaporating multicomponent droplet, while the droplet of pure solvent has an accelerated rate of size change all the way through the end. This reversal behavior is also reflected in the droplet surface temperature evolution as "...

  2. Vaporization dynamics of volatile perfluorocarbon droplets: A theoretical model and in vitro validation

    Energy Technology Data Exchange (ETDEWEB)

    Doinikov, Alexander A., E-mail: doinikov@bsu.by; Bouakaz, Ayache [Inserm U930, Université François Rabelais, Tours 37044 (France); Sheeran, Paul S.; Dayton, Paul A. [Joint Department of Biomedical Engineering, The University of North Carolina and North Carolina State University, Chapel Hill, North Carolina 27599 (United States)

    2014-10-15

    Purpose: Perfluorocarbon (PFC) microdroplets, called phase-change contrast agents (PCCAs), are a promising tool in ultrasound imaging and therapy. Interest in PCCAs is motivated by the fact that they can be triggered to transition from the liquid state to the gas state by an externally applied acoustic pulse. This property opens up new approaches to applications in ultrasound medicine. Insight into the physics of vaporization of PFC droplets is vital for effective use of PCCAs and for anticipating bioeffects. PCCAs composed of volatile PFCs (with low boiling point) exhibit complex dynamic behavior: after vaporization by a short acoustic pulse, a PFC droplet turns into a vapor bubble which undergoes overexpansion and damped radial oscillation until settling to a final diameter. This behavior has not been well described theoretically so far. The purpose of our study is to develop an improved theoretical model that describes the vaporization dynamics of volatile PFC droplets and to validate this model by comparison with in vitro experimental data. Methods: The derivation of the model is based on applying the mathematical methods of fluid dynamics and thermodynamics to the process of the acoustic vaporization of PFC droplets. The used approach corrects shortcomings of the existing models. The validation of the model is carried out by comparing simulated results with in vitro experimental data acquired by ultrahigh speed video microscopy for octafluoropropane (OFP) and decafluorobutane (DFB) microdroplets of different sizes. Results: The developed theory allows one to simulate the growth of a vapor bubble inside a PFC droplet until the liquid PFC is completely converted into vapor, and the subsequent overexpansion and damped oscillations of the vapor bubble, including the influence of an externally applied acoustic pulse. To evaluate quantitatively the difference between simulated and experimental results, the L2-norm errors were calculated for all cases where the

  3. Vaporization dynamics of volatile perfluorocarbon droplets: a theoretical model and in vitro validation.

    Science.gov (United States)

    Doinikov, Alexander A; Sheeran, Paul S; Bouakaz, Ayache; Dayton, Paul A

    2014-10-01

    Perfluorocarbon (PFC) microdroplets, called phase-change contrast agents (PCCAs), are a promising tool in ultrasound imaging and therapy. Interest in PCCAs is motivated by the fact that they can be triggered to transition from the liquid state to the gas state by an externally applied acoustic pulse. This property opens up new approaches to applications in ultrasound medicine. Insight into the physics of vaporization of PFC droplets is vital for effective use of PCCAs and for anticipating bioeffects. PCCAs composed of volatile PFCs (with low boiling point) exhibit complex dynamic behavior: after vaporization by a short acoustic pulse, a PFC droplet turns into a vapor bubble which undergoes overexpansion and damped radial oscillation until settling to a final diameter. This behavior has not been well described theoretically so far. The purpose of our study is to develop an improved theoretical model that describes the vaporization dynamics of volatile PFC droplets and to validate this model by comparison with in vitro experimental data. The derivation of the model is based on applying the mathematical methods of fluid dynamics and thermodynamics to the process of the acoustic vaporization of PFC droplets. The used approach corrects shortcomings of the existing models. The validation of the model is carried out by comparing simulated results with in vitro experimental data acquired by ultrahigh speed video microscopy for octafluoropropane (OFP) and decafluorobutane (DFB) microdroplets of different sizes. The developed theory allows one to simulate the growth of a vapor bubble inside a PFC droplet until the liquid PFC is completely converted into vapor, and the subsequent overexpansion and damped oscillations of the vapor bubble, including the influence of an externally applied acoustic pulse. To evaluate quantitatively the difference between simulated and experimental results, the L2-norm errors were calculated for all cases where the simulated and experimental

  4. Relaxation of liquid bridge after droplets coalescence

    Directory of Open Access Journals (Sweden)

    Jiangen Zheng

    2016-11-01

    Full Text Available We investigate the relaxation of liquid bridge after the coalescence of two sessile droplets resting on an organic glass substrate both experimentally and theoretically. The liquid bridge is found to relax to its equilibrium shape via two distinct approaches: damped oscillation relaxation and underdamped relaxation. When the viscosity is low, damped oscillation shows up, in this approach, the liquid bridge undergoes a damped oscillation process until it reaches its stable shape. However, if the viscous effects become significant, underdamped relaxation occurs. In this case, the liquid bridge relaxes to its equilibrium state in a non-periodic decay mode. In depth analysis indicates that the damping rate and oscillation period of damped oscillation are related to an inertial-capillary time scale τc. These experimental results are also testified by our numerical simulations with COMSOL Multiphysics.

  5. Compartmentalized Droplets for Continuous Flow Liquid-Liquid Interface Catalysis.

    Science.gov (United States)

    Zhang, Ming; Wei, Lijuan; Chen, Huan; Du, Zhiping; Binks, Bernard P; Yang, Hengquan

    2016-08-17

    To address the limitations of batch organic-aqueous biphasic catalysis, we develop a conceptually novel method termed Flow Pickering Emulsion, or FPE, to process biphasic reactions in a continuous flow fashion. This method involves the compartmentalization of bulk water into micron-sized droplets based on a water-in-oil Pickering emulsion, which are packed into a column reactor. The compartmentalized water droplets can confine water-soluble catalysts, thus "immobilizing" the catalyst in the column reactor, while the interstices between the droplets allow the organic (oil) phase to flow. Key fundamental principles underpinning this method such as the oil phase flow behavior, the stability of compartmentalized droplets and the confinement capability of these droplets toward water-soluble catalysts are experimentally and theoretically investigated. As a proof of this concept, case studies including a sulfuric acid-catalyzed addition reaction, a heteropolyacid-catalyzed ring opening reaction and an enzyme-catalyzed chiral reaction demonstrate the generality and versatility of the FPE method. Impressively, in addition to the excellent durability, the developed FPE reactions exhibit up to 10-fold reaction efficiency enhancement in comparison to the existing batch reactions, indicating a unique flow interface catalysis effect. This study opens up a new avenue to allow conventional biphasic catalysis reactions to access more sustainable and efficient flow chemistry using an innovative liquid-liquid interface protocol.

  6. Open-atmosphere sustenance of highly volatile attoliter-size droplets on surfaces.

    Science.gov (United States)

    Galliker, Patrick; Schneider, Julian; Rüthemann, Lukas; Poulikakos, Dimos

    2013-08-13

    The controlled formation and handling of minute liquid volumes on surfaces is essential to the success of microfluidics in biology, chemistry, and materials applications. Even though current methods have demonstrated their potential in a variety of experimental assays, there remain significant difficulties concerning breadth of applicability, standardization, throughput, and economics. Here we introduce a unique microfluidic paradigm in which microscopic volatile droplets are formed, sustained, and manipulated in size and content at any desired spot on unpatterned substrates. Their sustainability is warranted by continuous replacement of the rapidly vaporizing sessile fluid through controlled equivalent volume deposition of smaller discrete liquid entities by an electrohydrodynamic nanodripping process. Using nanoparticle inks we show that the concentration of solutes in so-stabilized droplets can be linearly increased at isochoric conditions and user-defined rates. An intriguing insensitivity of the droplet shape toward surface heterogeneities ensures robustness and experimental reproducibility, even when handling attoliter quantities. The unique capabilities and technical simplicity of the presented method introduce a high degree of flexibility and make it pertinent to a diverse range of applications.

  7. Superhydrophobic-like tunable droplet bouncing on slippery liquid interfaces

    Science.gov (United States)

    Hao, Chonglei; Li, Jing; Liu, Yuan; Zhou, Xiaofeng; Liu, Yahua; Liu, Rong; Che, Lufeng; Zhou, Wenzhong; Sun, Dong; Li, Lawrence; Xu, Lei; Wang, Zuankai

    2015-01-01

    Droplet impacting on solid or liquid interfaces is a ubiquitous phenomenon in nature. Although complete rebound of droplets is widely observed on superhydrophobic surfaces, the bouncing of droplets on liquid is usually vulnerable due to easy collapse of entrapped air pocket underneath the impinging droplet. Here, we report a superhydrophobic-like bouncing regime on thin liquid film, characterized by the contact time, the spreading dynamics, and the restitution coefficient independent of underlying liquid film. Through experimental exploration and theoretical analysis, we demonstrate that the manifestation of such a superhydrophobic-like bouncing necessitates an intricate interplay between the Weber number, the thickness and viscosity of liquid film. Such insights allow us to tune the droplet behaviours in a well-controlled fashion. We anticipate that the combination of superhydrophobic-like bouncing with inherent advantages of emerging slippery liquid interfaces will find a wide range of applications. PMID:26250403

  8. Impact of Droplets on Inclined Flowing Liquid Films

    CERN Document Server

    Che, Zhizhao; Matar, Omar K

    2015-01-01

    The impact of droplets on an inclined falling liquid film is studied experimentally using high-speed imaging. The falling film is created on a flat substrate with controllable thicknesses and flow rates. Droplets with different sizes and speeds are used to study the impact process under various Ohnesorge and Weber numbers, and film Reynolds numbers. A number of phenomena associated with droplet impact are identified and analysed, such as bouncing, partial coalescence, total coalescence, and splashing. The effects of droplet size, speed, as well the film flow rate are studied culminating in the generation of an impact regime map. The analysis of the lubrication force acted on the droplet via the gas layer shows that a higher flow rate in the liquid film produces a larger lubrication force, slows down the drainage process, and increases the probability of droplet bouncing. Our results demonstrate that the flowing film has a profound effect on the droplet impact process and associated phenomena, which are marked...

  9. Experimental Investigation Evaporation of Liquid Mixture Droplets during Depressurization into Air Stream

    Science.gov (United States)

    Liu, L.; Bi, Q. C.; Terekhov, Victor I.; Shishkin, Nikolay E.

    2010-03-01

    The objective of this study is to develop experimental method to study the evaporation process of liquid mixture droplets during depressurization and into air stream. During the experiment, a droplet was suspended on a thermocouple; an infrared thermal imager was used to measure the droplet surface temperature transition. Saltwater droplets were used to investigate the evaporation process during depressurization, and volatile liquid mixtures of ethanol, methanol and acetone in water were applied to experimentally research the evaporation into air stream. According to the results, the composition and concentration has a complex influence on the evaporation rate and the temperature transition. With an increase in the share of more volatile component, the evaporation rate increases. While, a higher salt concentration in water results in a lower evaporation rate. The shape variation of saltwater droplet also depends on the mass concentration in solution, whether it is higher or lower than the eutectic point (22.4%). The results provide important insight into the complex heat and mass transfer of liquid mixture during evaporation.

  10. A Microfluidic Chip for Liquid Metal Droplet Generation and Sorting

    Directory of Open Access Journals (Sweden)

    Lu Tian

    2017-01-01

    Full Text Available A liquid metal based microfluidic system was proposed and demonstrated for the generation and sorting of liquid metal droplets. This micro system utilized silicon oil as the continuous phase and Ga66In20.5Sn13.5 (66.0 wt % Ga, 20.5 wt % In, 13.5 wt % Sn, melting point: 10.6 °C as the dispersed phase to generate liquid metal droplets on a three-channel F-junction generator. The F-junction is an updated design similar to the classical T-junction, which has a special branch channel added to a T-junction for the supplement of 30 wt % aqueous NaOH solution. To perform active sorting of liquid metal droplets by dielectrophoresis (DEP, the micro system utilized liquid-metal-filled microchannels as noncontact electrodes to induce electrical fields through the droplet channel. The electrode channels were symmetrically located on both sides of the droplet channel in the same horizontal level. According to the results, the micro system can generate uniformly spherical liquid metal droplets, and control the flow direction of the liquid metal droplets. To better understand the control mechanism, a numerical simulation of the electrical field was performed in detail in this work.

  11. Marangoni Effect on the Shape of Freely Receding Evaporating Sessile Droplets of Perfectly Wetting Liquids

    Science.gov (United States)

    Tsoumpas, Yannis; Dehaeck, Sam; Rednikov, Alexey; Colinet, Pierre

    2014-11-01

    Freely receding evaporating sessile droplets of perfectly wetting liquids (HFE-7100, 7200 and 7500), with small finite contact angles induced by evaporation, are studied with a Mach-Zehnder interferometer. Surprisingly, the experimentally obtained profiles turn out to deviate from the classical macroscopic static shape of a sessile droplet (as determined by gravity and capillarity), often used when modeling evaporating droplets. These deviations can be seen in two ways. Namely, either the droplet appears to be inflated as compared to the classical static shape assuming the same contact angle and contact radius, or the apparent contact angle appears lower than the classical static one assuming the same volume and contact radius. In reality, the experimental profiles exhibit a local decrease of the slope near the contact line, which we attribute to the Marangoni effect in an evaporating sessile droplet. In this case, the radially inward (along the liquid-air interface) direction of the flow delivers more liquid to the center of the droplet making it appear inflated. When the Marangoni effect is weak, as in the case of the poorly volatile HFE-7500, no significant influence is noticed on the drop shape. The experimental results are compared with the predictions of a lubrication-type theoretical model that incorporates the evaporation-induced Marangoni flow. Financial support of FP7 Marie Curie MULTIFLOW Network (PITN-GA-2008-214919), ESA/BELSPO-PRODEX, BELSPO- μMAST (IAP 7/38) & FRS-FNRS is gratefully acknowledged.

  12. Precursors to splashing of liquid droplets on a solid surface.

    Science.gov (United States)

    Mandre, Shreyas; Mani, Madhav; Brenner, Michael P

    2009-04-03

    A high velocity impact between a liquid droplet and a solid surface produces a splash. Classical work traced the origin of the splash to a thin sheet of fluid ejected near the impact point. Mechanisms of sheet formation have heretofore relied on initial contact of the droplet and the surface. We demonstrate that, neglecting intermolecular forces between the liquid and the solid, the liquid does not contact the solid, and instead spreads on a very thin air film. The interface of the droplet develops a high curvature and emits capillary waves.

  13. Drying of liquid food droplets. Enzyme inactivation and multicomponent diffusion.

    NARCIS (Netherlands)

    Meerdink, G.

    1993-01-01

    In this thesis the drying of liquid food droplets is studied from three different points of view: drying kinetics, enzyme inactivation and multicomponent diffusion. Mathematical models are developed and validated experimentally.Drying experiments are performed with suspended droplets and with free f

  14. The influence of material hardness on liquid droplet impingement erosion

    Energy Technology Data Exchange (ETDEWEB)

    Fujisawa, Nobuyuki, E-mail: fujisawa@eng.niigata-u.ac.jp [Visualization Research Center, Niigata University, 8050, Ikarashi 2-Nocho, Nishi-ku, Niigata 950-2181 (Japan); Yamagata, Takayuki, E-mail: yamagata@eng.niigata-u.ac.jp [Visualization Research Center, Niigata University, 8050, Ikarashi 2-Nocho, Nishi-ku, Niigata 950-2181 (Japan); Takano, Shotaro; Saito, Kengo [Graduate School of Science and Technology, Niigata University, 8050, Ikarashi 2-Nocho, Nishi-ku, Niigata 950-2181 (Japan); Morita, Ryo; Fujiwara, Kazutoshi; Inada, Fumio [Central Research Institute of Electric Power Industry, 2-11-1, Iwatokita, Komae, Tokyo 201-8511 (Japan)

    2015-07-15

    Highlights: • Liquid droplet impingement erosion is studied for various metal materials. • Average power dependency on droplet velocity is found as 7. • Power dependency on Vickers hardness is found as −4.5. • An empirical formula is constructed for erosion rates of metal materials. • Predicted erosion rate is well correlated with experiment within a factor of 1.5. - Abstract: This paper describes the experimental study on the liquid droplet impingement erosion of metal materials to understand the influence of material hardness on the erosion rate. The experiment is carried out using a water spray jet apparatus with a condition of relatively thin liquid film thickness. The metal materials tested are pure aluminum, aluminum alloy, brass, mild steel, carbon steel and stainless steel. The liquid droplets considered are 30 ± 5 μm in volume average diameter of water, which is the same order of droplet diameter in the actual pipeline in nuclear/fossil power plants. In order to understand the influence of material hardness on the liquid droplet impingement erosion, the scanning electron microscope (SEM) observation on the eroded surface and the measurement of erosion rate are carried out in the terminal stage of erosion. The experimental results indicate that the erosion rates are expressed by the droplet velocity, volume flux, Vickers hardness and the liquid film thickness, which are fundamentals of the liquid droplet impingement erosion. The empirical formula shows that the power index for droplet velocity dependency is found to be 7 with a scattering from 5 to 9 depending on the materials, while the power index for Vickers hardness dependency is found as −4.5.

  15. Liquid Droplet Dynamics in Gravity Compensating High Magnetic Field

    Science.gov (United States)

    Bojarevics, V.; Easter, S.; Pericleous, K.

    2012-01-01

    Numerical models are used to investigate behavior of liquid droplets suspended in high DC magnetic fields of various configurations providing microgravity-like conditions. Using a DC field it is possible to create conditions with laminar viscosity and heat transfer to measure viscosity, surface tension, electrical and thermal conductivities, and heat capacity of a liquid sample. The oscillations in a high DC magnetic field are quite different for an electrically conducting droplet, like liquid silicon or metal. The droplet behavior in a high magnetic field is the subject of investigation in this paper. At the high values of magnetic field some oscillation modes are damped quickly, while others are modified with a considerable shift of the oscillating droplet frequencies and the damping constants from the non-magnetic case.

  16. Mechanical vibration of viscoelastic liquid droplets

    Science.gov (United States)

    Sharp, James; Harrold, Victoria

    2014-03-01

    The resonant vibrations of viscoelastic sessile droplets supported on different substrates were monitored using a simple laser light scattering technique. In these experiments, laser light was reflected from the surfaces of droplets of high Mw poly acrylamide-co-acrylic acid (PAA) dissolved in water. The scattered light was allowed to fall on the surface of a photodiode detector and a mechanical impulse was applied to the drops using a vibration motor mounted beneath the substrates. The mechanical impulse caused the droplets to vibrate and the scattered light moved across the surface of the photodiode. The resulting time dependent photodiode signal was then Fourier transformed to obtain the mechanical vibrational spectra of the droplets. The frequencies and widths of the resonant peaks were extracted for droplets containing different concentrations of PAA and with a range of sizes. This was repeated for PAA loaded water drops on surfaces which displayed different values of the three phase contact angle. The results were compared to a simple model of droplet vibration which considers the formation of standing wave states on the surface of a viscoelastic droplet. We gratefully acknowledge the support of the Leverhulme trust under grant number RPG-2012-702.

  17. Dynamics of Non-Newtonian Liquid Droplet Collision

    Science.gov (United States)

    Chen, Xiaodong; Yang, Vigor

    2012-11-01

    Collision of Newtonian liquid droplets has been extensively investigated both experimentally and numerically for decades. Limited information, however, is available about non-Newtonian droplet collision dynamics. In the present work, high-fidelity numerical simulations were performed to study the situation associated with shear-thinning non-Newtonian liquids. The formulation is based on a complete set of conservation equations for the liquid and the surrounding gas phases. An improved volume-of-fluid (VOF) method, combined with an innovative topology-oriented adaptive mesh refinement (TOAMR) technique, was developed and implemented to track the interfacial dynamics. The complex evolution of the droplet surface over a broad range of length scales was treated accurately and efficiently. In particular, the thin gas film between two approaching droplets and subsequent breakup of liquid threads were well-resolved. Various types of droplet collision were obtained, including coalescence, bouncing, and reflexive and stretching separations. A regime diagram was developed and compared with that for Newtonian liquids. Fundamental mechanisms and key parameters that dictate droplet behaviors were identified. In addition, collision-induced atomization was addressed. This work was sponsored by the U.S. Army Research Office under the Multi-University Research Initiative under contract No. W911NF-08-1-0124. The support and encouragement provided by Dr. Ralph Anthenien are gratefully acknowledged.

  18. Retreating behavior of a charged ionic liquid droplet in a dielectric liquid under electric field

    Science.gov (United States)

    Ahn, Myung Mo; Im, Do Jin; Kang, In Seok

    2013-11-01

    Ionic liquids show great promise as excellent solvents or catalysts in energy and biological fields due to their unique chemical and physical properties. The ionic liquid droplets in microfluidic systems can also be used as a potential platform for chemical biological reactions. In order to control electrically the ionic liquid droplets in a microfluidic device, the charging characteristics of ionic liquid droplets need to be understood. In this work, the charging characteristics of various ionic liquids are investigated by using the parallel plate electrodes system. Under normal situation, a charged droplet shows bouncing motion between electrodes continuously. However, for some special ionic liquids, interesting retreating behavior of charged ionic liquid droplet has been observed. This retreating behavior of ionic liquid droplet has been analyzed experimentally by the image analysis and the electrometer signal analysis. Based on the hypothesis of charge leakage of the retreating ionic liquid droplets, FT-IR spectroscopy analysis has also been performed. The retreating behavior of ionic liquid droplet is discussed from the intermolecular point of view according to the species of ionic liquids. This research was supported by grant No. 2013R1A1A2011956 funded by the Ministry of Science, ICT and Future Planning (MSIP) and by grant No. 2013R1A1A2010483 funded by the Ministry of Education, Science and Technology (MEST) through the NRF.

  19. Prediction on Droplet Sauter Mean Diameter in Gas-Liquid Mist Flow Based on Droplet Fractal Theory

    OpenAIRE

    Jian-Yi Liu; Xiao-Hua Tan; Zhou Fan; Xu-Tao You; Zhou Li; Jia-Hui Zhao

    2015-01-01

    We present a fractal model for droplet Sauter mean diameter in gas-liquid mist flow, based on the droplet fractal theory and the balance relationship between total droplet surface energy and total gas turbulent kinetic energy. The present model is expressed as functions of the droplet fractal dimension, gas superficial velocity, liquid superficial velocity, and other fluid characteristics. Agreement between the present model predictions and experimental measurements is obtained. Results verif...

  20. Prediction on Droplet Sauter Mean Diameter in Gas-Liquid Mist Flow Based on Droplet Fractal Theory

    Directory of Open Access Journals (Sweden)

    Jian-Yi Liu

    2015-01-01

    Full Text Available We present a fractal model for droplet Sauter mean diameter in gas-liquid mist flow, based on the droplet fractal theory and the balance relationship between total droplet surface energy and total gas turbulent kinetic energy. The present model is expressed as functions of the droplet fractal dimension, gas superficial velocity, liquid superficial velocity, and other fluid characteristics. Agreement between the present model predictions and experimental measurements is obtained. Results verify the reliability of the present model.

  1. Movement of liquid droplets containing polymers on substrate

    Science.gov (United States)

    Hu, Guohui; Wang, Heng

    2016-11-01

    It is of both fundamental and practical interests to study the flow physics in the manipulation of droplets. As a microreactor, the macromolecules or particles inside the droplets might have significant influences on their movement. In the present study, the many-body dissipative particle dynamics (MDPD) is utilized to investigate the translocation of droplets containing polymer on a substrate driven by the wettability gradient, where the polymer is modelled as worm-like chain (WLC). The internal flows of the droplets are analyzed, as well as the comparison to the polymer-free moving droplets. The effects of physical parameters, such as the interaction potential between liquid particle and polymer beads, the mass of the beads, on the translocation speed are also addressed in the present study. These results might be helpful to the optimization in design of the microfluidic systems.

  2. Thermophoretic transport of ionic liquid droplets in carbon nanotubes

    Science.gov (United States)

    Rajegowda, Rakesh; Kannam, Sridhar Kumar; Hartkamp, Remco; Sathian, Sarith P.

    2017-04-01

    Thermal-gradient induced transport of ionic liquid (IL) and water droplets through a carbon nanotube (CNT) is investigated in this study using molecular dynamics simulations. Energetic analysis indicates that IL transport through a CNT is driven primarily by the fluid–solid interaction, while fluid–fluid interactions dominate in water–CNT systems. Droplet diffusion analysis via the moment scaling spectrum reveals sub-diffusive motion of the IL droplet, in contrast to the self-diffusive motion of the water droplet. The Soret coefficient and energetic analysis of the systems suggest that the CNT shows more affinity for interaction with IL than with the water droplet. Thermophoretic transport of IL is shown to be feasible, which can create new opportunities in nanofluidic applications.

  3. Vapor condensation onto a non-volatile liquid drop

    Energy Technology Data Exchange (ETDEWEB)

    Inci, Levent; Bowles, Richard K., E-mail: richard.bowles@usask.ca [Department of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5C9 (Canada)

    2013-12-07

    Molecular dynamics simulations of miscible and partially miscible binary Lennard–Jones mixtures are used to study the dynamics and thermodynamics of vapor condensation onto a non-volatile liquid drop in the canonical ensemble. When the system volume is large, the driving force for condensation is low and only a submonolayer of the solvent is adsorbed onto the liquid drop. A small degree of mixing of the solvent phase into the core of the particles occurs for the miscible system. At smaller volumes, complete film formation is observed and the dynamics of film growth are dominated by cluster-cluster coalescence. Mixing into the core of the droplet is also observed for partially miscible systems below an onset volume suggesting the presence of a solubility transition. We also develop a non-volatile liquid drop model, based on the capillarity approximations, that exhibits a solubility transition between small and large drops for partially miscible mixtures and has a hysteresis loop similar to the one observed in the deliquescence of small soluble salt particles. The properties of the model are compared to our simulation results and the model is used to study the formulation of classical nucleation theory for systems with low free energy barriers.

  4. Mechano-regulated surface for manipulating liquid droplets

    Science.gov (United States)

    Tang, Xin; Zhu, Pingan; Tian, Ye; Zhou, Xuechang; Kong, Tiantian; Wang, Liqiu

    2017-04-01

    The effective transfer of tiny liquid droplets is vital for a number of processes such as chemical and biological microassays. Inspired by the tarsi of meniscus-climbing insects, which can climb menisci by deforming the water/air interface, we developed a mechano-regulated surface consisting of a background mesh and a movable microfibre array with contrastive wettability. The adhesion of this mechano-regulated surface to liquid droplets can be reversibly switched through mechanical reconfiguration of the microfibre array. The adhesive force can be tuned by varying the number and surface chemistry of the microfibres. The in situ adhesion of the mechano-regulated surface can be used to manoeuvre micro-/nanolitre liquid droplets in a nearly loss-free manner. The mechano-regulated surface can be scaled up to handle multiple droplets in parallel. Our approach offers a miniaturized mechano-device with switchable adhesion for handling micro-/nanolitre droplets, either in air or in a fluid that is immiscible with the droplets.

  5. High-Genus nematic liquid crystal droplets

    Science.gov (United States)

    Jayalakshmi, V.; Ekapop, P.; Fernandez-Nieves, Alberto

    2017-05-01

    We will discuss the defect structures that originate in nematic droplets with two or more handles. In these cases, the topology of the bounding surface requires the presence of defects. Our experiments elucidate where do these defects locate and how many of them populated the ground state of the system.

  6. a Theoretical Model of a Superheated Liquid Droplet Neutron Detector.

    Science.gov (United States)

    Harper, Mark Joseph

    Neutrons can interact with the atoms in superheated liquid droplets which are suspended in a viscous matrix material, resulting in the formation of charged recoil ions. These ions transfer energy to the liquid, sometimes resulting in the droplets vaporizing and producing observable bubbles. Devices employing this mechanism are known as superheated liquid droplet detectors, or bubble detectors. The basis of bubble detector operation is identical to that of bubble chambers, which have been well characterized by researchers such as Wilson, Glaser, Seitz, and others since the 1950's. Each of the microscopic superheated liquid droplets behaves like an independent bubble chamber. This dissertation presents a theoretical model which considers the three principal aspects of detector operation: nuclear reactions, charged particle energy deposition, and thermodynamic bubble formation. All possible nuclear reactions were examined and those which could reasonably result in recoil ions sufficiently energetic to vaporize a droplet were analyzed in detail. Feasible interactions having adequate cross sections include elastic and inelastic scattering, n-proton, and n-alpha reactions. Ziegler's TRansport of Ions in Matter (TRIM) code was used to calculate the ions' stopping powers in various compounds based on the ionic energies predicted by standard scattering distributions. If the ions deposit enough energy in a small enough volume then the entire droplet will vaporize without further energy input. Various theories as to the vaporization of droplets by ionizing radiation were studied and a novel method of predicting the critical (minimum) energy was developed. This method can be used to calculate the minimum required stopping power for the ion, from which the threshold neutron energy is obtainable. Experimental verification of the model was accomplished by measuring the response of two different types of bubble detectors to monoenergetic thermal neutrons, as well as to neutrons

  7. The recoiling of liquid droplets upon collision with solid surfaces

    Science.gov (United States)

    Kim, H.-Y.; Chun, J.-H.

    2001-03-01

    Although the spreading behavior of liquid droplets impacting on solid surfaces has been extensively studied, the mechanism of recoiling which takes place after the droplet reaches its maximum spread diameter has not yet been fully understood. This paper reports the study of the recoiling behavior of different liquid droplets (water, ink, and silicone oil) on different solid surfaces (polycarbonate and silicon oxide). The droplet dynamics are experimentally studied using a high speed video system. Analytical methods using the variational principle, which were originated by Kendall and Rohsenow (MIT Technical Report 85694-100, 1978) and Bechtel et al. [IBM J. Res. Dev. 25, 963 (1981)], are modified to account for wetting and viscous effects. In our model, an empirically determined dissipation factor is used to estimate the viscous friction. It is shown that the model closely predicts the experimental results obtained for the varying dynamic impact conditions and wetting characteristics. This study shows that droplets recoil fast and vigorously when the Ohnesorge number decreases or the Weber number increases. Droplets with a large equilibrium contact angle are also found to recoil faster. Here the Ohnesorge number scales the resisting force to the recoiling motion, and is shown to play the most important role in characterizing the recoiling motion.

  8. Liquid droplet movement on horizontal surface with gradient surface energy

    Institute of Scientific and Technical Information of China (English)

    LIAO Qiang; WANG Hong; ZHU Xun; LI Mingwei

    2006-01-01

    A surface with gradient surface energy was fabricated on a silicon wafer by using the chemical vapor deposition (CVD) technology with the dodecyltrichlorosilane (C12H25Cl3Si) vapor which was adsorbed chemically on the surface of the silicon wafer to form a self-assemble monolayer (ASM) and thus a gradient profile of wettability. The microscopic contours of the gradient surface were measured with Seiko SPA400 atom force microscope (AFM). And the surface wettability profile was characterized by the sessile drop method, measuring the contact angle of fine water droplets that lay on the gradient surface, to represent the distribution of the surface energy on the surface. Using a high-speed video imaging system, the motion of water droplet on the horizontal gradient surface was visualized and the transient velocity was measured under ambient condition. The experimental results show that the liquid droplets can be driven to move from hydrophobic side to hydrophilic side on the horizontal gradient surface and the velocity of droplet can reach up to 40 mm/s. In addition, the motion of the water droplet can be generally divided into two stages: an acceleration stage and a deceleration stage. The droplet presents a squirming movement on the surface with a lower peak velocity and a larger extent of deceleration motion. And the static advancing contact angle of the droplet is obviously larger than the dynamic advancing contact angle on the gradient energy surface.

  9. Equilibrium contact angles of liquid droplets on ideal rough solids.

    Science.gov (United States)

    Kang, Hie Chan; Jacobi, Anthony M

    2011-12-20

    This work proposes a theoretical model for predicting the apparent equilibrium contact angle of a liquid on an ideal rough surface that is homogeneous and has a negligible body force, line tension, or contact angle hysteresis between solid and liquid. The model is derived from the conservation equations and the free-energy minimization theory for the changes of state of liquid droplets. The work of adhesion is expressed as the contact angles in the wetting process of the liquid droplets. Equilibrium contact angles of liquid droplets for rough surfaces are expressed as functions of the area ratios for the solid, liquid, and surrounding gas and the roughness ratio and wetting ratio of the liquid on the solid for the partially and fully wet states. It is found that the ideal critical angle for accentuating the contact angles by the surface roughness is 48°. The present model is compared with existing experimental data and the classical Wenzel and Cassie-Baxter models and agrees with most of the experimental data for various surfaces and liquids better than does the Wenzel model and accounts for trends that the Wenzel model cannot explain.

  10. Moving liquid droplets with inertia: Experiment, simulation, and theory

    NARCIS (Netherlands)

    Kim, H.

    2013-01-01

    This thesis is a work on a contact line instability at a finite Reynolds number, 0 < Re < O(100). This problem corresponds to an immersion droplet applied in a liquid- immersion lithography machine. We perform extensive works to understand this instability problem by means of experimental,

  11. Evaporation of Sessile Droplets of Liquid on Solid Substrates

    Science.gov (United States)

    Semenov, S.; Starov, V. M.; Velarde, M. G.; Rubio, R. G.

    Evaporation of sessile droplets of liquid on solid substrates is considered here. Different parameters and processes influencing the evaporation rate are discussed. Cases of complete wetting and partial wetting with contact angle hysteresis are described mathematically. The influence of Kelvin's and kinetic effects and subsequent deviation from diffusion-limited evaporation is shown by means of computer simulations.

  12. Moving liquid droplets with inertia: Experiment, simulation, and theory

    NARCIS (Netherlands)

    Kim, H.

    2013-01-01

    This thesis is a work on a contact line instability at a finite Reynolds number, 0 < Re < O(100). This problem corresponds to an immersion droplet applied in a liquid- immersion lithography machine. We perform extensive works to understand this instability problem by means of experimental, numerical

  13. Shape and stability in liquid threads and jets : a link to droplet formation

    NARCIS (Netherlands)

    Heugten, van W.G.N.

    2015-01-01

    This thesis explores relevant fluid dynamic processes for the formation of uniformly sized droplets in microfluidic systems. Growing droplets made from a bulk source have often liquid threads or jets in between to supply liquid to the droplet. Liquid threads and jets are however known to be instable

  14. Liquid quantum droplets of ultracold magnetic atoms

    Science.gov (United States)

    Ferrier-Barbut, Igor; Schmitt, Matthias; Wenzel, Matthias; Kadau, Holger; Pfau, Tilman

    2016-11-01

    The simultaneous presence of two competing inter-particle interactions can lead to the emergence of new phenomena in a many-body system. Among others, such effects are expected in dipolar Bose-Einstein condensates, subject to dipole-dipole interaction and short-range repulsion. Magnetic quantum gases and in particular Dysprosium gases, offering a comparable short-range contact and a long-range dipolar interaction energy, remarkably exhibit such emergent phenomena. In addition an effective cancellation of mean-field effects of the two interactions results in a pronounced importance of quantum-mechanical beyond mean-field effects. For a weakly dominant dipolar interaction the striking consequence is the existence of a new state of matter equilibrated by the balance between weak mean-field attraction and beyond mean-field repulsion. Though exemplified here in the case of dipolar Bose gases, this state of matter should appear also with other microscopic interactions types, provided a competition results in an effective cancellation of the total mean-field. The macroscopic state takes the form of so-called quantum droplets. We present the effects of a long-range dipolar interaction between these droplets.

  15. Multiscale Simulation of Gas Film Lubrication During Liquid Droplet Collision

    Science.gov (United States)

    Chen, Xiaodong; Khare, Prashant; Ma, Dongjun; Yang, Vigor

    2012-02-01

    Droplet collision plays an elementary role in dense spray combustion process. When two droplets approach each other, a gas film forms in between. The pressure generated within the film prevents motion of approaching droplets. This fluid mechanics is fluid film lubrication that occurs when opposing bearing surfaces are completely separated by fluid film. The lubrication flow in gas film decides the collision outcome, coalescence or bouncing. Present study focuses on gas film drainage process over a wide range of Weber numbers during equal- and unequal-sized droplet collision. The formulation is based on complete set of conservation equations for both liquid and surrounding gas phases. An improved volume-of-fluid technique, augmented by an adaptive mesh refinement algorithm, is used to track liquid/gas interfaces. A unique thickness-based refinement algorithm based on topology of interfacial flow is developed and implemented to efficiently resolve the multiscale problem. The grid size on interface is up O(10-4) of droplet size with a max resolution of 0.015 μm. An advanced visualization technique using the Ray-tracing methodology is used to gain direct insights to detailed physics. Theories are established by analyzing the characteristics of shape changing and flow evolution.

  16. Relating CCN activity, volatility, and droplet growth kinetics of β-caryophyllene secondary organic aerosol

    Directory of Open Access Journals (Sweden)

    A. Asa-Awuku

    2009-02-01

    Full Text Available This study investigates the droplet formation characteristics of secondary organic aerosol (SOA formed during the ozonolysis of sesquiterpene β-caryophyllene (with and without hydroxyl radicals present. Emphasis is placed on understanding the role of semi-volatile material on Cloud Condensation Nucleus (CCN activity and droplet growth kinetics. Aging of β-caryophyllene SOA significantly affects all CCN-relevant properties measured throughout the experiments. Using a thermodenuder and two CCN instruments, we find that CCN activity is a strong function of temperature (activation diameter at ~0.6% supersaturation: 100±10 nm at 20°C and 130±10 nm at 35°C, suggesting that the hygroscopic fraction of the SOA is volatile. The water-soluble organic carbon (WSOC is extracted from the SOA and characterized with Köhler Theory Analysis (KTA; the results suggest that the WSOC is composed of low molecular weight (<200 g mol−1 slightly surface-active material that constitute 5–15% of the SOA mass. These properties are similar to the water-soluble fraction of monoterpene SOA, suggesting that predictive understanding of SOA CCN activity requires knowledge of the WSOC fraction but not its exact speciation. Droplet growth kinetics of the CCN are found to be strongly anticorrelated with WSOC fraction, suggesting that the insoluble material in the SOA forms a kinetic barrier that delays droplet growth. Overall, volatilization effects can increase activation diameters by 30%, and depress droplet growth rate by a factor of two; these results may have important implications for the droplet formation characteristics of SOA, and the atmospheric relevance of CCN measurements carried out at temperatures different from ambient.

  17. Glucose sensor using liquid-crystal droplets made by microfluidics.

    Science.gov (United States)

    Kim, Jiyeon; Khan, Mashooq; Park, Soo-Young

    2013-12-26

    Micrometer-sized, 4-cyno-4-pentylbiphenyl (5CB) droplets were developed for glucose detection in an aqueous medium by coating with poly(acrylicacid-b-4-cynobiphenyl-4-oxyundecylacrylate) (PAA-b-LCP) at the 5CB/water interface and covalently immobilizing glucose oxidase (GOx) to the PAA chains. This functionalized liquid-crystal (LC) droplet detected glucose from a radial to bipolar configurational change by polarized optical microscopy under crossed polarizers at concentrations as low as 0.03 mM and response times of ~3 min and showed the selective detection of glucose against galactose. This new and sensitive LC-droplet-based glucose biosensor has the merits of low production cost and easy detection by the naked eye and might be useful for prescreening the glucose level in the human body.

  18. Endotoxin-Induced Structural Transformations in Liquid Crystalline Droplets

    Science.gov (United States)

    Lin, I.-Hsin; Miller, Daniel S.; Bertics, Paul J.; Murphy, Christopher J.; de Pablo, Juan J.; Abbott, Nicholas L.

    2011-06-01

    The ordering of liquid crystals (LCs) is known to be influenced by surfaces and contaminants. Here, we report that picogram per milliliter concentrations of endotoxin in water trigger ordering transitions in micrometer-size LC droplets. The ordering transitions, which occur at surface concentrations of endotoxin that are less than 10-5 Langmuir, are not due to adsorbate-induced changes in the interfacial energy of the LC. The sensitivity of the LC to endotoxin was measured to change by six orders of magnitude with the geometry of the LC (droplet versus slab), supporting the hypothesis that interactions of endotoxin with topological defects in the LC mediate the response of the droplets. The LC ordering transitions depend strongly on glycophospholipid structure and provide new designs for responsive soft matter.

  19. Transient heating and evaporation of moving mono-component liquid fuel droplets

    DEFF Research Database (Denmark)

    Yin, Chungen

    2016-01-01

    This paper presents a complete description of a model for transient heating and evaporation of moving mono-component liquid fuel droplets. The model mainly consists of gas phase heat and mass transfer analysis, liquid phase analysis, and droplet dynamics analysis, which address the interaction...... between the moving droplets and free-stream flow, the flow and heat and mass transfer within the droplets, and the droplet dynamics and size, respectively. For the liquid phase analysis, the droplets are discretized into a number of control volumes along the radial, polar and azimuthal directions, on each...

  20. Liquid Droplet Detachment and Entrainment in Microscale Flows

    Science.gov (United States)

    Hidrovo, Carlos

    2005-11-01

    In this talk we will present a first order study of liquid water detachment and entrainment into air flows in hydrophobic microchannels. Silicon based microstructures consisting of 23 mm long U-shaped channels of different geometry were used for this purpose. The structures are treated with a Molecular Vapor Deposition (MVD) process that renders them hydrophobic. Liquid water is injected through a side slot located 2/3 of the way downstream from the air channel inlet. The water entering the air channel beads up into slugs or droplets that grow in size at this injection location until they fill and flood the channel or are carried away by the air flow. The slugs/droplets dimensions at detachment are correlated against superficial gas velocity and proper dimensionless parameters are postulated and examined to compare hydrodynamic forces against surface tension. It is found that slug/droplet detachment is dominated by two main forces: pressure gradient drag, arising from confinement of a viscous flow in the channel, and inertial drag, arising from the stagnation of the air due to obstruction by the slugs/droplets. A detachment regime map is postulated based on the relative importance of these forces under different flow conditions.

  1. Modeling texture transitions in cholesteric liquid crystal droplets

    Science.gov (United States)

    Selinger, Robin; Gimenez-Pinto, Vianney; Lu, Shin-Ying; Selinger, Jonathan; Konya, Andrew

    2012-02-01

    Cholesteric liquid crystals can be switched reversibly between planar and focal-conic textures, a property enabling their application in bistable displays, liquid crystal writing tablets, e-books, and color switching ``e-skins.'' To explore voltage-pulse induced switching in cholesteric droplets, we perform simulation studies of director dynamics in three dimensions. Electrostatics calculations are solved at each time step using an iterative relaxation method. We demonstrate that as expected, a low amplitude pulse drives the transition from planar to focal conic, while a high amplitude pulse drives the transition from focal conic back to the planar state. We use the model to explore the effects of droplet shape, aspect ratio, and anchoring conditions, with the goal of minimizing both response time and energy consumption.

  2. Volatility of methylglyoxal cloud SOA formed through OH radical oxidation and droplet evaporation

    Science.gov (United States)

    Ortiz-Montalvo, Diana L.; Schwier, Allison N.; Lim, Yong B.; McNeill, V. Faye; Turpin, Barbara J.

    2016-04-01

    The volatility of secondary organic aerosol (SOA) formed through cloud processing (aqueous hydroxyl radical (radOH) oxidation and droplet evaporation) of methylglyoxal (MGly) was studied. Effective vapor pressure and effective enthalpy of vaporization (ΔHvap,eff) were determined using 1) droplets containing MGly and its oxidation products, 2) a Vibrating Orifice Aerosol Generator (VOAG) system, and 3) Temperature Programmed Desorption Aerosol-Chemical Ionization Mass Spectrometry (TPD Aerosol-CIMS). Simulated in-cloud MGly oxidation (for 10-30 min) produces an organic mixture of higher and lower volatility components with an overall effective vapor pressure of (4 ± 7) × 10-7 atm at pH 3. The effective vapor pressure decreases by a factor of 2 with addition of ammonium hydroxide (pH 7). The fraction of organic material remaining in the particle-phase after drying was smaller than for similar experiments with glycolaldehyde and glyoxal SOA. The ΔHvap,eff of pyruvic acid and oxalic acid + methylglyoxal in the mixture (from TPD Aerosol-CIMS) were smaller than the theoretical enthalpies of the pure compounds and smaller than that estimated for the entire precursor/product mix after droplet evaporation. After 10-30 min of aqueous oxidation (one cloud cycle) the majority of the MGly + radOH precursor/product mix (even neutralized) will volatilize during droplet evaporation; neutralization and at least 80 min of oxidation at 10-12 M radOH (or >12 h at 10-14 M) is needed before low volatility ammonium oxalate exceeds pyruvate.

  3. The Study of a Liquid Droplet Falling Through Two Immiscible Layers of Liquids

    Science.gov (United States)

    Mesa, Bianca

    2013-11-01

    In an exploratory experiment, we noticed the unusual behaviors of liquid droplets falling through layers of oil and water. A rectangular container was filled with an aqueous solution and a layer of oil. A dropper was used to control the size of the droplet. Water was mixed with Bromothymol Blue dye, a chemical indicator, to visualize the flow processes. Surface tension and the buoyancy of the oil layer between the liquid droplet and the water below caused the liquid droplet to be stopped at the interface. Over time, the support weakened and the droplet would fall quickly through the water. The first of two cases was a salt water solution with NaOH, and the second consisted of balsamic vinegar and NaOH. Once the salt water droplet touched the aqueous solution, it collapsed, sank and spread rapidly at the interface. The sinking motion dragged the spreading fluid back to its center and then down. For the second case, a trace amount of the droplet spread rapidly at the interface while the main portion of the droplet sank and then spontaneously exploded. The difference in behavior is mainly due to the surface tension of the droplet in water. The underlying mechanisms of the droplet's flow instability are from the effects of diffusion weakening the surface tension. Bianca Mesa is an undergraduate student in the Ocean and Mechanical Engineering Department at Florida Atlantic University. She is pursuing a B.S. degree in Ocean Engineering. In addition to her academic interests, she is also an avid sailor.

  4. Electro-driven interfacial phenomena of droplets, emulsions and liquid marbles

    OpenAIRE

    Liu, Zhou; 刘洲

    2015-01-01

    The interplay of electric stress and surface tension enriches the interfacial phenomena of droplets, emulsions and liquid marbles. In this thesis, we mainly focus on how the electric stress affects the generation, coalescence/non-coalescence and mixing of liquid droplets as well as liquid droplets with stabilizers. By exploring the science behind these phenomena, we have also extended some approaches to characterize the robustness/ stability of the emulsions and liquid marbles. Chapter 2 f...

  5. Droplet entrainment rate in gas-liquid annular flow

    Energy Technology Data Exchange (ETDEWEB)

    Sawant, P. [Energy Research Inc., Rockville, Maryland (United States); Liu, Y.; Ishii, M. [Purdue Univ., West Lafayette, Indiana (United States); Mori, M. [Tokyo Electric Power Co., Inc., Yokohama (Japan); Chen, S. [Purdue Univ., West Lafayette, Indiana (United States)

    2011-07-01

    Droplet entrainment and deposition are the two most important physical phenomena in the gas-liquid annular two-phase flow. Modeling of these phenomena is essential for the estimation of dryout margins in the Light Water Reactors (LWRs) and the boilers. In this study, gas-liquid annular two-phase flow experiments are performed in a vertical round tube test section under adiabatic conditions. Air-water and organic fluid Freon-113 are used as the test fluids. The experiments covered a wide range of pressure and flow conditions. Liquid film extraction technique was used for the measurement of droplet entrainment and deposition rates. Additionally, the thickness of liquid film was measured in the air-water experiments using the ring type conductance probes. In this paper, the experimental data on entrainment rate is used to analyze the currently available correlations in the literature. The analysis showed that the existing correlations failed to predict the data at high gas velocity conditions. At high gas velocity, the experimental entrainment rate approaches a maximum limiting value; however, the correlations predicted continuously increasing entrainment rate as the gas velocity increases. (author)

  6. Turbulent Phenomena in the Aerobreakup of Liquid Droplets

    Directory of Open Access Journals (Sweden)

    Andras Horvath

    2012-09-01

    Full Text Available This work presents the computational simulation results of turbulent phenomena in a high velocity multiphase flow, where the predominantly turbulent phase is the gaseous phase. For reliable simulation results the code is validated by comparing results of a single phase supersonic turbulent flow to other simulation and experimental results and good agreement is found. This is a precondition for the simulation of the initial stages of the breakup of a liquid droplet in a high Weber number flow. The role of the subgrid-scale turbulence is investigated and two distinct regions are identified. In the second region turbulence phenomena seem to be the predominant factors for the characteristic shape. Simulation results are compared to experiments of the droplet breakup at high Weber number.

  7. Droplet Breakup of the Nematic Liquid Crystal MBBA

    CERN Document Server

    Nachman, Benjamin

    2012-01-01

    Droplet breakup is a well studied phenomena in Newtonian fluids. One property of this behavior is that, independent of initial conditions, the minimum radius exhibits power law scaling with the time left to breakup tau. Because they have additional structure and shear dependent viscosity, liquid crystals pose an interesting complication to such studies. Here, we investigate the breakup of a synthetic nematic liquid crystal known as MBBA. We determine the phase of the solution by using a cross polarizer setup in situ with the liquid bridge breakup apparatus. Consistent with previous studies of scaling behavior in viscous-inertial fluid breakup, when MBBA is in the isotropic phase, the minimum radius decreases as tau^{1.03 \\pm 0.04}. In the nematic phase however, we observe very different thinning behavior. Our measurements of the thinning profile are consistent with two interpretations. In the first interpretation, the breakup is universal and consists of two different regimes. The first regime is characterize...

  8. Evaporation of liquid droplets on solid substrates. I. Flat substrate with pinned or moving contact line

    Science.gov (United States)

    Amini, Amirhossein; Homsy, G. M.

    2017-04-01

    We study the evolution of the profile of a two-dimensional volatile liquid droplet that is evaporating on a flat heated substrate. We adopt a one-sided model with thermal control that, together with the lubrication approximation, results in an evolution equation for the local height of the droplet. Without requiring any presumption for the shape of the drop, the problem is formulated for the two modes of evaporation: a pinned contact line and a moving contact line with fixed contact angle. Numerical solutions are provided for each case. For the pinned contact line case, we observe that after a time interval the contact angle dynamics become nonlinear and, interestingly, the local contact angle goes to zero in advance of total evaporation of the drop. For the case of a moving contact line, in which the singularity at the contact line is treated by a numerical slip model, we find that the droplet nearly keeps its initial circular shape and that the contact line recedes with constant speed.

  9. Self-bound droplets of a dilute magnetic quantum liquid

    OpenAIRE

    Schmitt, Matthias; Wenzel, Matthias; Böttcher, Fabian; Ferrier-Barbut, Igor; Pfau, Tilman

    2016-01-01

    Self-bound many-body systems occur in different scenarios all across the fields of physics. For example in the astrophysical context the stellar classification is based on a detailed balance of attractive self-gravitating forces and repulsive terms e.g. due to Fermi pressure. Also liquid droplets are formed by mutual attractive forces due to covalent or van der Waals attraction and repulsive parts of the inter-particle potential due to the electronic Pauli exclusion principle. Self-bound ense...

  10. Liquid crystals in micron-scale droplets, shells and fibers

    Science.gov (United States)

    Urbanski, Martin; Reyes, Catherine G.; Noh, JungHyun; Sharma, Anshul; Geng, Yong; Subba Rao Jampani, Venkata; Lagerwall, Jan P. F.

    2017-04-01

    The extraordinary responsiveness and large diversity of self-assembled structures of liquid crystals are well documented and they have been extensively used in devices like displays. For long, this application route strongly influenced academic research, which frequently focused on the performance of liquid crystals in display-like geometries, typically between flat, rigid substrates of glass or similar solids. Today a new trend is clearly visible, where liquid crystals confined within curved, often soft and flexible, interfaces are in focus. Innovation in microfluidic technology has opened for high-throughput production of liquid crystal droplets or shells with exquisite monodispersity, and modern characterization methods allow detailed analysis of complex director arrangements. The introduction of electrospinning in liquid crystal research has enabled encapsulation in optically transparent polymeric cylinders with very small radius, allowing studies of confinement effects that were not easily accessible before. It also opened the prospect of functionalizing textile fibers with liquid crystals in the core, triggering activities that target wearable devices with true textile form factor for seamless integration in clothing. Together, these developments have brought issues center stage that might previously have been considered esoteric, like the interaction of topological defects on spherical surfaces, saddle-splay curvature-induced spontaneous chiral symmetry breaking, or the non-trivial shape changes of curved liquid crystal elastomers with non-uniform director fields that undergo a phase transition to an isotropic state. The new research thrusts are motivated equally by the intriguing soft matter physics showcased by liquid crystals in these unconventional geometries, and by the many novel application opportunities that arise when we can reproducibly manufacture these systems on a commercial scale. This review attempts to summarize the current understanding of

  11. Self-bound droplets of a dilute magnetic quantum liquid

    CERN Document Server

    Schmitt, Matthias; Böttcher, Fabian; Ferrier-Barbut, Igor; Pfau, Tilman

    2016-01-01

    Self-bound many-body systems occur in different scenarios all across the fields of physics. For example in the astrophysical context the stellar classification is based on a detailed balance of attractive self-gravitating forces and repulsive terms e.g. due to Fermi pressure. Also liquid droplets are formed by mutual attractive forces due to covalent or van der Waals attraction and repulsive parts of the inter-particle potential due to the electronic Pauli exclusion principle. Self-bound ensembles of ultracold atoms at densities 100 million times lower than in a helium droplet, the only other quantum liquid known so far, have been suggested. However, they have been elusive up to now as they require more than the usual contact interaction, which is either attractive or repulsive but never both. Based on the recent finding that an unstable bosonic dipolar gas can be stabilized by a repulsive many-body term, which is due to quantum depletion and a corresponding exclusion volume at small distances, it was predict...

  12. Liquid droplet coalescence and fragmentation at the aqueous-air surface.

    Science.gov (United States)

    Paneru, Govind; Law, Bruce M; Ibi, Koki; Ushijima, Baku; Flanders, Bret N; Aratono, Makoto; Matsubara, Hiroki

    2015-01-13

    For hexadecane oil droplets at an aqueous-air surface, the surface film in coexistence with the droplets exhibits two-dimensional gaseous (G), liquid (L), or solid (S) behavior depending upon the temperature and concentration of the cationic surfactant dodecyltrimethylammonium bromide. In the G (L) phase, oil droplets are observed to coalesce (fragment) as a function of time. In the coalescence region, droplets coalesce on all length scales, and the final state is a single oil droplet at the aqueous-air surface. The fragmentation regime is complex. Large oil droplets spread as oil films; hole nucleation breaks up this film into much smaller fluctuating and fragmenting or metastable droplets. Metastable droplets are small contact angle spherical caps and do not fluctuate in time; however, they are unstable over long time periods and eventually sink into the bulk water phase. Buoyancy forces provide a counterbalancing force where the net result is that small oil droplets (radius r droplets at liquid surfaces indicates that droplet coalesce is primarily driven by surface tension effects. This theory, which only considers spherical cap shaped surface droplets, qualitatively suggests that in the L phase the sinking of metastable surface droplets into the bulk aqueous medium is driven by a negative line tension and a very small spreading coefficient.

  13. Manipulation of Spherical Droplets on a Liquid Platform Using Thermal Gradients

    CERN Document Server

    Yakhshi-Tafti, Ehsan; Kumar, Ranganathan; 10.1063/1.3456391

    2010-01-01

    In the recent years, there has been a growing interest in droplet-based (digital) microfluidics for which, reliable means of droplet manipulation are required. In this study we demonstrate thermal actuation of droplets on liquid platforms, which is ideal for biochemical microsystems and lab-on-chip applications because droplets can be transported with high speed, good control and minimal thermal loading as compared to using conventional solid substrates. In addition, other disadvantages of using solid surfaces such as evaporation, contamination, pinning, hysteresis and irreversibility of droplet motion are avoided. Based on the theoretical development and measurements, a silicon-based droplet transportation platform was developed with embedded Titanium micro heaters. A shallow liquid pool of inert liquid (FC-43) served as the carrier liquid. Heaters were interfaced with control electronics and driven through a computer graphical user interface. By creating appropriate spatio-temporal thermal gradient maps, tr...

  14. Optical biosensor based on liquid crystal droplets for detection of cholic acid

    Science.gov (United States)

    Niu, Xiaofang; Luo, Dan; Chen, Rui; Wang, Fei; Sun, Xiaowei; Dai, Haitao

    2016-12-01

    A highly sensitive cholic acid biosensor based on 4-cyano-4‧-penthlbiphenyl (5CB) Liquid crystal droplets in phosphate buffer saline solution was reported. A radial-to-bipolar transition of 5CB droplet would be triggered during competitive reaction of CA at the sodium dodecyl sulfate surfactant-laden 5CB droplet surface. Our liquid crystal droplet sensor is a low-cost, simple and fast method for CA detection. The detection limit (5 μM) of our method is 2.4 times lower than previously report by using liquid crystal film to detection of CA.

  15. Single fiber optical trapping of a liquid droplet and its application in microresonator

    Science.gov (United States)

    Liu, Zhihai; Chen, Yunhao; Zhao, Li; Zhang, Yu; Wei, Yong; Zhu, Zongda; Yang, Jun; Yuan, Libo

    2016-12-01

    We propose and demonstrate an optical trapping of a liquid droplet and its application based on an annular core microstructured optical fiber. We grind and polish the annular core fiber tip to be a special frustum cone shape to make sure the optical force large enough to trap the liquid droplet non-intrusively. The axial and transverse optical trapping forces are simulated. In addition, we investigate the whispering gallery modes resonance characteristic of the trapped liquid droplet as the example of applications. The whispering gallery modes spectrum is sensitive to the size of the micro liquid droplet. Due to the simple construction and flexible manipulation, the fiber-based optical trapping technology for micro liquid droplets trapping, manipulating, and controlling has great application penitential in many fields, such as physics, biology, and interdisciplinary studies.

  16. Trace Material Capture by Controlled Liquid Droplets on a Superhydrophobic/Hydrophilic Surface.

    Science.gov (United States)

    Fukada, Kenta; Kawamura, Naoya; Shiratori, Seimei

    2017-09-15

    A liquid droplet in contact with a superhydrophobic surface can be used to collect dissolved trace materials after evaporating the solvent. This process effect enhances detection limits, but a liquid droplet easily rolls off a superhydrophobic surface. Keeping it at a specific collecting spot area is challenging. Here the means for controlling and capturing a liquid droplet on a superhydrophobic surface is demonstrated. To induce a liquid droplet to a collecting spot, its rolling direction was controlled by two superhydrophobic fabric guides. The liquid droplet was then captured by hydrophilic polymer and hydrophilic nanoparticles at the measuring spot. After removing the solvent, the trace compounds were evaluated with a colorimetric analysis visible to the naked eye.

  17. Slippery Liquid-Infused Porous Surfaces and Droplet Transportation by Surface Acoustic Waves

    Science.gov (United States)

    Luo, J. T.; Geraldi, N. R.; Guan, J. H.; McHale, G.; Wells, G. G.; Fu, Y. Q.

    2017-01-01

    On a solid surface, a droplet of liquid will stick due to the capillary adhesion, and this causes low droplet mobility. To reduce contact line pinning, surface chemistry can be coupled to micro- and/or nanostructures to create superhydrophobic surfaces on which a droplet balls up into an almost spherical shape, thus, minimizing the contact area. Recent progress in soft matter has now led to alternative lubricant-impregnated surfaces capable of almost zero contact line pinning and high droplet mobility without causing droplets to ball up and minimize the contact area. Here we report an approach to surface-acoustic-wave- (SAW) actuated droplet transportation enabled using such a surface. These surfaces maintain the contact area required for efficient energy and momentum transfer of the wave energy into the droplet while achieving high droplet mobility and a large footprint, therefore, reducing the threshold power required to induce droplet motion. In our approach, we use a slippery layer of lubricating oil infused into a self-assembled porous hydrophobic layer, which is significantly thinner than the SAW wavelength, and avoid damping of the wave. We find a significant reduction (up to 85%) in the threshold power for droplet transportation compared to that using a conventional surface-treatment method. Moreover, unlike droplets on superhydrophobic surfaces, where interaction with the SAW induces a transition from a Cassie-Baxter state to a Wenzel state, the droplets on our liquid-impregnated surfaces remain in a mobile state after interaction with the SAW.

  18. Rebound of continuous droplet streams from an immiscible liquid pool

    Science.gov (United States)

    Doak, William J.; Laiacona, Danielle M.; German, Guy K.; Chiarot, Paul R.

    2016-05-01

    We report on the rebound of high velocity continuous water droplet streams from the surface of an immiscible oil pool. The droplets have diameters and velocities of less than 90 μm and 15 m/s, respectively, and were created at frequencies up to 60 kHz. The impact and rebound of continuous droplet streams at this scale and velocity have been largely unexplored. This regime bridges the gap between single drop and jet impacts. The impinging droplets create a divot at the surface of the oil pool that had a common characteristic shape across a wide-range of droplet and oil properties. After impact, the reflected droplets maintain the same uniformity and periodicity of the incoming droplets but have significantly lower velocity and kinetic energy. This was solely attributed to the generation of a flow induced in the viscous oil pool by the impacting droplets. Unlike normally directed impact of millimeter-scale droplets with a solid surface, our results show that an air film does not appear to be maintained beneath the droplets during impact. This suggests direct contact between the droplets and the surface of the oil pool. A ballistic failure limit, correlated with the Weber number, was identified where the rebound was suppressed and the droplets were driven through the oil surface. A secondary failure mode was identified for aperiodic incoming streams. Startup effects and early time dynamics of the rebounding droplet stream were also investigated.

  19. Experimental Measurements of Spreading of Volatile Liquid Droplets

    Science.gov (United States)

    Zhang, Neng-Li; Chao, David F.

    2001-01-01

    Based on the laser shadowgraphic system used by the first author of the present paper, a simple optical system, which combined the laser shadowgraphy and the direct magnified-photography, has been developed to measure the contact angle, the spreading speed, and the evaporation rate. Additionally, the system can also visualize thermocapillary convection inside of a sessile drop simultaneously. The experimental results show that evaporation/condensation and thermocapillary convection in the sessile drop induced by the evaporation strongly affects the wetting and spreading of the drop. Condensation always promotes the wetting and spreading of the drop. Evaporation may increase or decrease the contact angle of the evaporating sessile drops, depending on the evaporation rate. The thermocapillary convection in the drop induced by the evaporation enhances the effects of evaporation to suppress the spreading.

  20. Three-Dimensional Smoothed Particle Hydrodynamics Simulation for Liquid Droplet with Surface Tension

    OpenAIRE

    Terissa, Hanifa; Barecasco, Agra; Naa, Christian Fredy

    2013-01-01

    We provide a basic method of Smoothed Particle Hydrodynamics (SPH) to simulate liquid droplet with surface tension in three dimensions. Liquid droplet is a simple case for surface tension modeling. Surface tension works only on fluid surface. In SPH method, we simply apply the surface tension on the boundary particles of liquid. The particle on the 3D boundary was detected dynamically using Free-Surface Detection algorithm. The normal vector and curvature of the boundary surface were calculat...

  1. Influence of Liquid Viscosity on Droplet Impingement on Superhydrophobic Surfaces

    CERN Document Server

    Pearson, John T; Webb, Brent W

    2010-01-01

    This fluid dynamics video describes droplet impingement experiments performed on superhydrophobic surfaces. When droplets of pure water are impinged upon superhydrophobic surfaces, a region of thin coherent jets are observed for Weber numbers between 5 and 15. Also, peripheral splashing is observed for Weber numbers above about 200. When the viscosity of the droplet is increased by mixing glycerol with the water, the thin jets are not observed and peripheral splashing is delayed somewhat. In the Weber number range where pure water droplets are observed to splash peripherally, the water/glycerol droplets are observed to have two-pronged jets.

  2. RESEARCH ON STABILITY OF LIQUID FILM ON HOT SOLID SURFACE IMPINGED BY SMALL DROPLETS

    Institute of Scientific and Technical Information of China (English)

    GUO Jia-hong; DAI Shi-qiang

    2007-01-01

    A heat and mass transfer model was proposed for the thin liquid film on the hot solid surface cooled by the impinging small droplets, with consideration of the effect of the droplet impact, surface tension, thermocapillary, evaporation/condensation, and van der Waals attraction. The nondimensional equation for predicting the evolution of the interface of the thin liquid film was derived in the presented model with the relevant boundary conditions. The stability of the thin liquid film impacted by cool small droplets is discussed.

  3. Droplet condensation and growth on nanotextured surfaces impregnated with an immiscible liquid

    Science.gov (United States)

    Anand, Sushant; Paxson, Adam; Smith, Jonathan; Dhiman, Rajeev; Varanasi, Kripa

    2012-02-01

    For effective dropwise condensation, a surface that sheds droplets easily is desirable due to the enhancement in accompanying heat transfer. Incorporating nano-textures on the surface can enhance the droplet shedding or spreading. We demonstrate that droplet shedding can be further influenced by impregnating the nano-textured surface with a liquid which is immiscible with respect to the droplet. In this study, the dynamics of dropwise condensation on such immiscible liquid impregnated nano-textured surfaces have been investigated in pure quiescent water vapor conditions. Condensation experiments were conducted using an Environmental Scanning Electron Microscope by controlling the chamber water vapor pressure and substrate temperature. We show preferential sites for condensation and different modes under which droplets grow, depending upon the surface chemistry, surface texture, and the impregnating liquid properties. Concurrently, we show an evolution of apparent contact angles during the condensation process on the impregnated surfaces.

  4. Investigation on Shock Induced Stripping Breakup Process of A Liquid Droplet

    KAUST Repository

    Liu, Yao

    2017-03-02

    Stripping breakup process of a single liquid droplet under the impact of a planar shock wave is investigated both experimentally and numerically. The droplet breakup experiment is conducted in a horizontal shock tube and the evolution of the droplet is recorded by direct high-speed photography. The experimental images clearly illustrate the droplet interface evolution features from its early to relatively late stage. Compressible Euler equations are solved using an in-house inviscid upwind characteristic space-time conservation element and solution element (CE/SE) method coupled with the HLLC approximate Riemann solver. A reduced five-equation model is employed to demonstrate the air/liquid interface. Numerical results accurately reproduce the water column and axi-symmetric water droplet breakup processes in experiments. The present study confirms the validity of the present numerical method in solving the shock wave induced droplet breakup problem and elaborates the stripping breakup process numerically in a long period. Droplet inner flow pattern is depicted, based on which the drives of protrusions emerged on the droplet surface are clearly seen. The droplet deformation is proved to be determined by not only the outer air flow, but also the inner liquid flow.

  5. Finite-difference time-domain analysis of light propagation in cholesteric liquid crystalline droplet array

    Science.gov (United States)

    Yamamoto, Kaho; Iwai, Yosuke; Uchida, Yoshiaki; Nishiyama, Norikazu

    2016-08-01

    We numerically analyzed the light propagation in cholesteric liquid crystalline (CLC) droplet array by the finite-difference time-domain (FDTD) method. The FDTD method successfully reproduced the experimental light path observed in the complicated photonic structure of the CLC droplet array more accurately than the analysis of CLC droplets by geometric optics with Bragg condition, and this method help us understand the polarization of the propagating light waves. The FDTD method holds great promise for the design of various photonic devices composed of curved photonic materials like CLC droplets and microcapsules.

  6. Communication: Orientational structure manipulation in nematic liquid crystal droplets induced by light excitation of azodendrimer dopant

    Science.gov (United States)

    Shvetsov, Sergey A.; Emelyanenko, Alexander V.; Boiko, Natalia I.; Liu, Jui-Hsiang; Khokhlov, Alexei R.

    2017-06-01

    Reversible orientational transitions in the droplets of a nematic liquid crystal (NLC) caused by the change of boundary conditions under the low intensity diode illumination are investigated. Photosensitivity of NLC is achieved by the addition of the dendrimer compound with azobenzene terminal groups. Two types of NLC droplets in glycerol are considered: the spherical droplets in the bulk of glycerol and the droplets laid-down onto the solid substrate. In the second case, the first order phase transition is revealed. The effects described can be useful for the development of highly sensitive chemical detectors and microsized photo-tunable optical devices.

  7. Marangoni Convection in Evaporating Organic Liquid Droplets on a Nonwetting Substrate.

    Science.gov (United States)

    Chandramohan, Aditya; Dash, Susmita; Weibel, Justin A; Chen, Xuemei; Garimella, Suresh V

    2016-05-17

    We quantitatively characterize the flow field inside organic liquid droplets evaporating on a nonwetting substrate. A mushroom-structured surface yields the desired nonwetting behavior with methanol droplets, while use of a cooled substrate (5-15 °C) slows the rate of evaporation to allow quasi-static particle image velocimetry. Visualization reveals a toroidal vortex within the droplet that is characteristic of surface tension-driven flow; we demonstrate by means of a scaling analysis that this recirculating flow is Marangoni convection. The velocities in the droplet are on the order of 10-45 mm/s. Thus, unlike in the case of evaporation on wetting substrates where Marangoni convection can be ignored for the purpose of estimating the evaporation rate, advection due to the surface tension-driven flow plays a dominant role in the heat transfer within an evaporating droplet on a nonwetting substrate because of the large height-to-radius aspect ratio of the droplet. We formulate a reduced-order model that includes advective transport within the droplet for prediction of organic liquid droplet evaporation on a nonwetting substrate and confirm that the predicted temperature differential across the height of the droplet matches experiments.

  8. Liquid-Liquid Phase Equilibria and Interactions between Droplets in Water-in-Oil Microemulsions.

    Science.gov (United States)

    Yin, Tianxiang; Wang, Mingjie; Tao, Xiaoyi; Shen, Weiguo

    2016-12-20

    The liquid-liquid phase equilibria of [water/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/n-decane] with the molar ratio w0 of water to AOT being 37.9 and [water/AOT/ethoxylated-2,5,8,11-tetramethyl-6-dodecyne-5,8-diol(Dynol-604)/n-decane] with w0 = 37.9 and the mole fraction α of Dynol-604 in the total surfactants being 0.158 were measured in this study. From the data collected in the critical region, the critical exponent β corresponding to the width of the coexistence curve was determined, which showed good agreement with the 3D-Ising value. A thermodynamic approach based on the Carnahan-Starling-van der Waals type equation was proposed to describe the coexistence curves and to deduce the interaction properties between droplets in the microemulsions. The interaction enthalpies were found to be positive for the studied systems, which evidenced that the entropy effect dominated the phase separations as the temperature increased. The addition of Dynol-604 into the (water/AOT/n-decane) microemulsion resulted in the decrease in the critical temperature and the interaction enthalpy. Combining the liquid-liquid equilibrium data for (water/AOT/n-decane) microemulsions with various w0 values determined previously, it was shown that the interaction enthalpy decreased with w0 and tended to change its sign at low w0, which coincided with the results from the isothermal titration calorimetry investigation. All of these behaviors were interpreted by the effects of entropy and enthalpy and their competition, which resulted from the release of solvent molecules entrapped in the interface of microemulsion droplets and were dependent on the rigidity of the surfactant layers and the size of the droplet.

  9. The Explosive Ejection of Small Droplets From a Liquid-Gas Interface.

    Science.gov (United States)

    James, Ashley; Smith, Marc K.; Glezer, Ari

    1996-11-01

    Vibration-induced liquid atomization is a process that occurs when a liquid droplet is placed on a vibrating membrane. When the proper operating conditions are attained, the droplet resonates with the motion of the membrane and explosively bursts into a spray of very small droplets. The process occurs through an instability of the surface wave motion on the free surface of the large droplet set up by the vibration of the underlying surface. We present experimental data on this process that shows how the droplet ejection event depends on the frequency and amplitude of the vibrating surface and on the initial volume of the large liquid droplet. Video images are also presented that show the basic process and some interesting transient behaviors leading to the ejection event. Our current and future experimental and analytical work on this process is directed towards an understanding of the mechanism behind the atomization process, a full characterization of the free surface instability leading to the droplet ejection event, and a knowledge of the size and velocity distributions in the resulting spray. In addition, vibration-induced droplet atomization is the basis of a new design for an evaporative heat transfer cell that is currently under development for micro-gravity applications. Supported by NASA and Georgia Tech.

  10. Investigation on the liquid water droplet instability in a simulated flow channel of PEM fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Tae Hun; Kim, Bok Yung; Kim, Han Sang; Min, Kyoung Doug [Seoul National University, Seoul (Korea, Republic of)

    2008-05-15

    To investigate the characteristics of water droplets on the gas diffusion layer from both top-view and side-view of the flow channel, a rig test apparatus was designed and fabricated with prism attached plate. This experimental device was used to simulate the growth of a single liquid water droplet and its transport process with various air flow velocity and channel height. Not only dry condition but also fully humidified condition was also simulated by using a water absorbing sponge. The detachment height of the water droplet with dry and wet conditions was measured and analyzed. It was found that the droplet tends towards becoming unstable by decreased channel height, increased flow velocity or making a gas diffusion layer (GDL) dryer. Also, peculiar behavior of the water droplet in the channel was presented like attachment to hydrophilic wall or sudden breaking of droplet in case of fully hydrated condition. The simplified force balance model matches with experimental data as well

  11. Experimental investigation on effects of liquid subcooling on droplet collision heat transfer above Leidenfrost temperature

    Energy Technology Data Exchange (ETDEWEB)

    Park, Junseok; Kim, Hyungdae [Kyung Hee University, Yongin (Korea, Republic of)

    2016-10-15

    In this study, the droplet-wall collision heat transfer experiments above the Leidenfrost point temperature were conducted to experimentally investigate the effects of droplet subcooling. Dynamic behavior of a droplet impinging on the heated wall and the temperature distribution were simultaneously measured using synchronized HSV camera (Phantom v7.3) and infrared camera (FLIR SC6000, 3-5 μm). Heat transfer experiments during collision of a subcooled droplet with a heated surface above the Leidenfrost temperature were conducted by varying temperature of droplet from 40 to 100 °C under the conditions that the collision velocity and wall temperature were maintained constant at 0.7 m/s at 500 °C, respectively. When increasing subcooling of a liquid droplet colliding on a surface heated above Leidenfrost temperature, vapor film thickness decreases while residence time increases. Those effects significantly increase heat transfer amount beyond values predicted by existing correlations.

  12. Cloud liquid water, mean droplet radius, and number density measurements using a Raman lidar

    Energy Technology Data Exchange (ETDEWEB)

    Whiteman, David N. [Laser Remote Sensing Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland (United States); Melfi, S. Harvey [Department of Physics, University of Maryland, Baltimore County, Baltimore (United States)

    1999-12-27

    A new technique for measuring cloud liquid water, mean droplet radius, and droplet number density is outlined. The technique is based on simultaneously measuring Raman and Mie scattering from cloud liquid droplets using a Raman lidar. Laboratory experiments on liquid microspheres have shown that the intensity of Raman scattering is proportional to the amount of liquid present in the spheres. This fact is used as a constraint on calculated Mie intensity assuming a gamma function particle size distribution. The resulting retrieval technique is shown to give stable solutions with no false minima. It is tested using Raman lidar data where the liquid water signal was seen as an enhancement to the water vapor signal. The general relationship of retrieved average radius and number density is consistent with traditional cloud physics models. Sensitivity to the assumed maximum cloud liquid water amount and the water vapor mixing ratio calibration are tested. Improvements to the technique are suggested. (c) 1999 American Geophysical Union.

  13. Cloud Liquid Water, Mean Droplet Radius and Number Density Measurements Using a Raman Lidar

    Science.gov (United States)

    Whiteman, David N.; Melfi, S. Harvey

    1999-01-01

    A new technique for measuring cloud liquid water, mean droplet radius and droplet number density is outlined. The technique is based on simultaneously measuring Raman and Mie scattering from cloud liquid droplets using a Raman lidar. Laboratory experiments on liquid micro-spheres have shown that the intensity of Raman scattering is proportional to the amount of liquid present in the spheres. This fact is used as a constraint on calculated Mie intensity assuming a gamma function particle size distribution. The resulting retrieval technique is shown to give stable solutions with no false minima. It is tested using Raman lidar data where the liquid water signal was seen as an enhancement to the water vapor signal. The general relationship of retrieved average radius and number density is consistent with traditional cloud physics models. Sensitivity to the assumed maximum cloud liquid water amount and the water vapor mixing ratio calibration are tested. Improvements to the technique are suggested.

  14. On the effects of isotropic turbulence on the evaporation rate of a liquid droplet

    Science.gov (United States)

    Dodd, Michael; Ferrante, Antonino

    2016-11-01

    Our objective is to explain the effects of isotropic turbulence on the vaporization rate of a liquid droplet in conditions that are relevant to spray combustion applications. To this end, we have performed direct numerical simulation (DNS) of a single droplet in homogeneous isotropic turbulence using the volume-of-fluid method for resolving fully the process of momentum, heat, and mass transfer between the liquid droplet and the gas. The simulations were performed using 10243 grid points. The effect of turbulence on the droplet vaporization rate is investigated by varying the gas-phase Reynolds number based on the Taylor microscale, Reλ. Reλ is increased from 0 to 75 by increasing the r.m.s. velocity of the gas phase while keeping all other physical properties constant. We will present the droplet evaporation rate as a function of turbulence Reynolds number and investigate the physical mechanisms.

  15. Microfluidic droplet trapping array as nanoliter reactors for gas-liquid chemical reaction.

    Science.gov (United States)

    Zhang, Qingquan; Zeng, Shaojiang; Qin, Jianhua; Lin, Bingcheng

    2009-09-01

    This article presents a simple method for trapping arrays of droplets relying on the designed microstructures of the microfluidic device, and this has been successfully used for parallel gas-liquid chemical reaction. In this approach, the trapping structure is composed of main channel, lateral channel and trapping region. Under a negative pressure, array droplets can be generated and trapped in the microstructure simultaneously, without the use of surfactant and the precise control of the flow velocity. By using a multi-layer microdevice containing the microstructures, single (pH gradient) and multiple gas-liquid reactions (metal ion-NH3 complex reaction) can be performed in array droplets through the transmembrane diffusion of the gas. The droplets with quantitative concentration gradient can be formed by only replacing the specific membrane. The established method is simple, robust and easy to operate, demonstrating the potential of this device for droplet-based high-throughput screening.

  16. A numerical study of thermocapillary migration of a small liquid droplet on a horizontal solid surface

    Science.gov (United States)

    Nguyen, Huy-Bich; Chen, Jyh-Chen

    2010-06-01

    In the present study, the transient thermocapillary migration of a small liquid droplet on a horizontal solid surface is numerically investigated. The droplet has a large static contact angle and a high aspect ratio of the maximum height of the droplet to its footprint. The Navier-Stokes and energy equations for both the droplet and surrounding air are solved through the finite element method. The evolution of the isotherms, the flow fields and the contact angle hysteresis are presented. Two asymmetric thermocapillary vortices appear inside the droplet. The variation of the size of the thermocapillary vortex during the migration process causes the speed of the droplet to first increase significantly, and then decrease gradually to approach a constant value. The higher imposed temperature gradient causes the droplet velocity to reach its maximal value earlier and have a higher final speed. If the static contact angle of the droplet is less than (or higher) than 90°, the droplet speed is lower (or higher) since the net thermocapillary momentum in the horizontal direction is diminished (or enhanced) by the presence of capillary force. The present results for the migration velocity and the contact angle hysteresis for a squalane droplet are also in good agreement with the previous experimental results.

  17. Reduction in the Vapor Pressure in Condensation on Cold Droplets of a Liquid

    Science.gov (United States)

    Bochkareva, E. M.; Nemtsev, V. A.; Sorokin, V. V.; Terekhov, V. V.; Terekhov, V. I.

    2016-05-01

    A physicomathematical model of the process of depressurization in a pure saturated and superheated vapor due to the injection of monodisperse cold droplets of a liquid has been developed. A cellular model has been developed that is based on solving the equation of heat conduction in a liquid phase and on the integral method for a gas phase in a spherically symmetric one-dimensional formulation. Numerical investigation has been carried out of the influence of the size and concentration of the droplets and of the initial parameters of the steam on the dynamics of depressurization during the vapor condensation on the droplets.

  18. Investigation of Critical Burning of Fuel Droplets. [of liquid rocket propellant

    Science.gov (United States)

    Chanin, S. P.; Shearer, A. J.; Faeth, G. M.

    1976-01-01

    An earlier analysis for the combustion response of a liquid monopropellant strand (hydrazine) was extended to consider individual droplets and sprays. While small drops gave low or negative response, large droplets provided response near unity at low frequencies, with the response declining at frequencies greater than the characteristic liquid phase frequency. Temperature gradients in the liquid phase resulted in response peaks greater than unity. A second response peak was found for large drops which corresponded to gas phase transient effects. Spray response was generally reduced from the response of the largest injected droplet, however, even a small percentage of large droplets can yield appreciable response. An apparatus was designed and fabricated to allow observation of bipropellant fuel spray combustion at elevated pressures. A locally homogeneous model was developed to describe this combustion process which allows for high pressure phenomena associated with the thermodynamic critical point.

  19. Modeling of the deformation of a liquid droplet impinging upon a flat surface

    Science.gov (United States)

    Fukai, J.; Zhao, Z.; Poulikakos, D.; Megaridis, C. M.; Miyatake, O.

    1993-11-01

    This article presents a theoretical study of the deformation of a spherical liquid droplet impinging upon a flat surface. The study accounts for the presence of surface tension during the spreading process. The theoretical model is solved numerically utilizing deforming finite elements and grid generation to simulate accurately the large deformations, as well as the domain nonuniformities characteristic of the spreading process. The results document the effects of impact velocity, droplet diameter, surface tension, and material properties on the fluid dynamics of the deforming droplet. Two liquids with markedly different thermophysical properties, water and liquid tin, are utilized in the numerical simulations because of their relevance in the industrial processes of spray cooling and spray deposition, respectively. The occurrence of droplet recoiling and mass accumulation around the splat periphery are standout features of the numerical simulations and yield a nonmonotonic dependence of the maximum splat radius on time.

  20. Three-Dimensional Smoothed Particle Hydrodynamics Simulation for Liquid Droplet with Surface Tension

    CERN Document Server

    Terissa, Hanifa; Naa, Christian Fredy

    2013-01-01

    We provide a basic method of Smoothed Particle Hydrodynamics (SPH) to simulate liquid droplet with surface tension in three dimensions. Liquid droplet is a simple case for surface tension modeling. Surface tension works only on fluid surface. In SPH method, we simply apply the surface tension on the boundary particles of liquid. The particle on the 3D boundary was detected dynamically using Free-Surface Detection algorithm. The normal vector and curvature of the boundary surface were calculated simultaneously with 3D boundary surface reconstruction using Moving Least-Squares (MLS) method. Before the reconstruction, the coordinate system was transformed into a local coordinate system. Afterwards, the surface tension force which depends on curvature of the surface, was calculated and applied on the boundary particles of the droplet. We present the simulation result of droplet motion with gravity force. By using the basic method of SPH for fluid modeling, and a combination of 3D Free-Surface Detection algorithm ...

  1. Excitation and dynamics of liquid tin micrometer droplet generation

    Science.gov (United States)

    Rollinger, B.; Abhari, R. S.

    2016-07-01

    The dynamics of capillary breakup-based droplet generation are studied for an excitation system based on a tunable piezoelectrically actuated oscillating piston, which generates acoustic pressure waves at the dispenser nozzle. First, the non-ideal pressure boundary conditions of droplet breakup are measured using a fast response pressure probe. A structural analysis shows that the axial modes of the excitation system are the main reasons for the resonance peaks in the pressure response. Second, a correlation between the nozzle inlet pressure and the droplet timing jitter is established with the help of experiments and a droplet formation model. With decreasing wave number, the growth rate of the main excitation decreases, while noise contributions with wave numbers with higher growth rates lead to a non-deterministic structure of the droplet train. A highly coherent and monodisperse droplet stream is obtained when the excitation system is tuned to generate high acoustic pressures at the desired operation frequency and when the noise level on the jet is limited. The jet velocity, hence droplet spacing for a set frequency is then adjusted by varying the reservoir pressure, according to the trade-off between lowest wave number and acceptable timing jitter.

  2. Dispensing picoliter droplets on insulating substrates using liquid dielectrophoretic (DEP) microactuation

    Science.gov (United States)

    Ahmed, Rajib U.

    Liquid Dielectrophoretic (DEP) microactuation uses simple co-planar electrodes patterned on an insulating substrate to manipulate small volumes of liquid, including aqueous solutions. One important capability of DEP microfluidics is the dispensing of multiple droplets down to ˜10 picoliters starting directly from microliter-sized, sessile parent drops deposited manually on the substrate with a micropipette. The dispensing process occurs in two subsequent stages. First, the electrodes are energized with AC, causing a narrow finger of liquid to flow from the parent droplet along the electrodes. The motion of the leading edge of this finger seems to obey a square root law, that is, Z( t) ∝ t and when it gets to the end of the electrode structure, it stops. The finger (or rivulet) then remains in a hydrostatically stable configuration as long as the non-uniform field is present. Second, when the voltage is removed, capillary instability breaks up the rivulet into small droplets. Periodic circular bumps patterned on the structure, when spaced according to the most unstable wavelength based on Rayleigh's inviscid theory for the cylindrical liquid jet, lead to the uniformly spaced and sized droplets. The effect of viscosity on droplet formation has been successfully accounted for with the modified Weber number. Experiments are also conducted to demonstrate a robust and reliable droplet dispensing mechanism with a trapped liquid design. Finally, some exploratory work has also been included with ionic salt solution.

  3. Evaporation of Liquid Droplet in Nano and Micro Scales from Statistical Rate Theory.

    Science.gov (United States)

    Duan, Fei; He, Bin; Wei, Tao

    2015-04-01

    The statistical rate theory (SRT) is applied to predict the average evaporation flux of liquid droplet after the approach is validated in the sessile droplet experiments of the water and heavy water. The steady-state experiments show a temperature discontinuity at the evaporating interface. The average evaporation flux is evaluated by individually changing the measurement at a liquid-vapor interface, including the interfacial liquid temperature, the interfacial vapor temperature, the vapor-phase pressure, and the droplet size. The parameter study shows that a higher temperature jump would reduce the average evaporation flux. The average evaporation flux can significantly be influenced by the interfacial liquid temperature and the vapor-phase pressure. The variation can switch the evaporation into condensation. The evaporation flux is found to remain relative constant if the droplet is larger than a micro scale, while the smaller diameters in nano scale can produce a much higher evaporation flux. In addition, a smaller diameter of droplets with the same liquid volume has a larger surface area. It is suggested that the evaporation rate increases dramatically as the droplet shrinks into nano size.

  4. Application of maximum entropy method for droplet size distribution prediction using instability analysis of liquid sheet

    Science.gov (United States)

    Movahednejad, E.; Ommi, F.; Hosseinalipour, S. M.; Chen, C. P.; Mahdavi, S. A.

    2011-12-01

    This paper describes the implementation of the instability analysis of wave growth on liquid jet surface, and maximum entropy principle (MEP) for prediction of droplet diameter distribution in primary breakup region. The early stage of the primary breakup, which contains the growth of wave on liquid-gas interface, is deterministic; whereas the droplet formation stage at the end of primary breakup is random and stochastic. The stage of droplet formation after the liquid bulk breakup can be modeled by statistical means based on the maximum entropy principle. The MEP provides a formulation that predicts the atomization process while satisfying constraint equations based on conservations of mass, momentum and energy. The deterministic aspect considers the instability of wave motion on jet surface before the liquid bulk breakup using the linear instability analysis, which provides information of the maximum growth rate and corresponding wavelength of instabilities in breakup zone. The two sub-models are coupled together using momentum source term and mean diameter of droplets. This model is also capable of considering drag force on droplets through gas-liquid interaction. The predicted results compared favorably with the experimentally measured droplet size distributions for hollow-cone sprays.

  5. Molecular Beam Studies of Volatile Liquids and Fuel Surrogates Using Liquid Microjets

    Science.gov (United States)

    2014-12-18

    Molecular Beam Studies of Volatile Liquids and Fuel Surrogates Using Liquid Microjets Gilbert Nathanson, Department of Chemistry University of...alter the dynamics of evaporation from the commercial jet fuel Jet A. These results are outlined below. Exploring Fuels in Vacuum using Liquid ...hydrocarbon liquids inside a vacuum chamber. These jets, narrower than a human hair, are typically 10 – 40 µm in diameter. Their small surface area and

  6. Experimental study on the effect of surface conditions on evaporation of sprayed liquid droplet

    Energy Technology Data Exchange (ETDEWEB)

    El-Sayed R, Negeed [Reactors Department, Nuclear Research Center, Atomic Energy Authority, Cairo (Egypt); El-Sayed R, Negeed; Ishihara, N.; Tagashira, K.; Hidaka, S.; Kohno, M.; Takata, Y. [Department of Mechanical Engineering Science, Faculty of Engineering, Kyushu University, Fukuoka (Japan)

    2010-12-15

    The present study investigates experimentally the effects of thermal properties of the hot surface and droplet characteristics on the droplet evaporation. Cylindrical blocks made of Stainless Steel, Aluminum and Brass with different degrees of surface roughness were used. The droplet diameter and velocity were controlled independently. The behavior of droplet during the collision with hot surface was observed with a high-speed camera. The results presented the effect of the thermal properties of the hot surface, droplet Weber number, droplet velocity, droplet size, hot surface conditions; surface superheat and degree of surface roughness on the solid-liquid contact time and the maximum spread of droplet over the surface. Empirical correlations have been deduced describing the relationship between the hydrodynamic characteristics of an individual droplet impinging on a heated surface and concealing the affecting parameters in such process. Also, the comparison between the current results and the results due to others investigators shows good agreement in which the difference between them ranged from 5% to 25%. (authors)

  7. Turbulence effects on volatilization rates of liquids and solutes

    Science.gov (United States)

    Lee, J.-F.; Chao, H.-P.; Chiou, C.T.; Manes, M.

    2004-01-01

    Volatilization rates of neat liquids (benzene, toluene, fluorobenzene, bromobenzene, ethylbenzene, m-xylene, o-xylene, o-dichlorobenzene, and 1-methylnaphthalene) and of solutes (phenol, m-cresol, benzene, toluene, ethylbenzene, o-xylene, and ethylene dibromide) from dilute water solutions have been measured in the laboratory over a wide range of air speeds and water-stirring rates. The overall transfer coefficients (KL) for individual solutes are independent of whether they are in single- or multi-solute solutions. The gas-film transfer coefficients (kG) for solutes in the two-film model, which have hitherto been estimated by extrapolation from reference coefficients, can now be determined directly from the volatilization rates of neatliquids through anew algorithm. The associated liquid-film transfer coefficients (KL) can then be obtained from measured KL and kG values and solute Henry law constants (H). This approach provides a novel means for checking the precision of any kL and kG estimation methods for ultimate prediction of KL. The improved kG estimation enables accurate K L predictions for low-volatility (i.e., low-H) solutes where K L and kGH are essentially equal. In addition, the prediction of KL values for high-volatility (i.e., high-H) solutes, where KL ??? kL, is also improved by using appropriate reference kL values.

  8. Experiments and Direct Numerical Simulations of binary collisions of miscible liquid droplets with different viscosities

    CERN Document Server

    Focke, C; Kuschel, M; Sommerfeld, M

    2012-01-01

    Binary droplet collisions are of importance in a variety of practical applications comprising dispersed two-phase flows. The background of our research is the prediction of properties of particulate products formed in spray processes. To gain a more thorough understanding of the elementary sub-processes inside a spray, experiments and direct numerical simulations of binary droplet collisions are used. The aim of these investigations is to develop semi-analytical descriptions for the outcome of droplet collisions. Such collision models can then be employed as closure terms for scale-reduced simulations. In the present work we focus on the collision of droplets of different liquids. These kinds of collisions take place in every spray drying process when droplets with different solids contents collide in recirculation zones. A new experimental method has been developed allowing for high spatial and time resolved recordings via Laser-induced fluorescence. The results obtained with the proposed method will be comp...

  9. Hydrodynamic directional control of liquid metal droplets within a microfluidic flow focusing system

    Science.gov (United States)

    Gol, Berrak; Kurdzinski, Michael E.; Tovar-Lopez, Francisco J.; Petersen, Phred; Mitchell, Arnan; Khoshmanesh, Khashayar

    2016-04-01

    Here, we investigate the directional control of Galinstan liquid metal droplets when transferring from the high-viscosity glycerol core into the parallel low-viscosity NaOH sheath streams within a flow focusing microfluidic system. In the presence of sufficient flow mismatch between the sheath streams, the droplets are driven toward the higher velocity interface and cross the interface under the influence of surface tension gradient. A minimum flow mismatch of 125 μl/min is required to enable the continuous transfer of droplets toward the desired sheath stream. The response time of droplets, the time required to change the direction of droplet transfer, is governed by the response time of the syringe pump driven microfluidic system and is found to be 3.3 and 8.8 s when increasing and decreasing the flow rate of sheath stream, respectively.

  10. Bouncing, Helical and Buckling Instabilities During Droplet Collision: Newtonian and Non-Newtonian Liquids

    CERN Document Server

    Chen, Xiaodong

    2012-01-01

    In this video, Ray-tracing data visualization technique was used to obtain realistic and detailed flow motions during droplet collision. The differences of collision outcome between Newtonian and non-Newtonian were compared. Various types of droplet collision were presented, including bouncing, coalescence, and stretching separation. Because of the reducing of equivalent viscosity caused by shear stress, the gas film between shear-thinning droplet is thinner than Newtonian liquid. Since thinner gas film promotes coalescence, shear thinning liquid has smaller area of bouncing regime in the diagram of Weber number and impact parameter. During the ligament/thread breakup process of stretching separation, two kinds of instabilities are identified, helical and buckling instabilities. Helical instability is analogous to a viscous rotating liquid jet, while the buckling instability is analogous to electrically charged liquid jets of polymer solutions.

  11. Fragmentation dynamics of liquid-metal droplets under ultra-short laser pulses

    Science.gov (United States)

    Basko, M. M.; Krivokorytov, M. S.; Vinokhodov, A. Yu; Sidelnikov, Yu V.; Krivtsun, V. M.; Medvedev, V. V.; Kim, D. A.; Kompanets, V. O.; Lash, A. A.; Koshelev, K. N.

    2017-03-01

    We present the measurements and theoretical analysis of the deformation and fragmentation of spherical liquid-metal drops by picosecond and subpicosecond laser pulses. In the experiments, 60 μm droplets of Sn-In alloy were irradiated by Ti:Sa laser pulses with a peak energy fluence of  ˜100 J cm-2. The observed evolution of the droplet shape dramatically differs from that previously reported for nanosecond pulses. Invoking 2D hydrodynamic simulations, we explain how, due to the specifics of matter dynamics in the liquid-vapor phase coexistence region, a liquid droplet is transformed into a characteristic acorn-like expanding shell with two inner cavities. High sensitivity of the measured shell parameters to the details of the equation of state and metastable dynamics suggests that such experiments offer new possibilities in exploration of thermophysical properties of metals in the region of liquid-vapor phase transition.

  12. High effectiveness liquid droplet/gas heat exchanger for space power applications

    Science.gov (United States)

    Bruckner, A. P.; Mattick, A. T.

    A high-effectiveness liquid droplet/gas heat exchanger (LDHX) concept for thermal management in space is described. Heat is transferred by direct contact between fine droplets (≈ 100-300 μm dia.) of a suitable low vapor pressure liquid and an inert working gas. Complete separation of the droplet and gas media in the zero-g environment is accomplished by configuring the LDHX as a vortex chamber. The large heat transfer area presented by the small droplets permits heat exchanger effectiveness of 0.9-0.95 in a compact, lightweight geometry which avoids many of the limitations of conventional plate and fin or tube and shell heat exchangers, such as their tendency toward single point failure. The application of the LDHX in a high temperature Brayton cycle is discussed to illustrate the performance and operational characteristics of this new heat exchanger concept.

  13. High effectiveness liquid droplet/gas heat exchanger for space power applications

    Science.gov (United States)

    Bruckner, A. P.; Mattick, A. T.

    1983-01-01

    A high-effectiveness liquid droplet/gas heat exchanger (LDHX) concept for thermal management in space is described. Heat is transferred by direct contact between fine droplets (approximately 100-300 microns in diameter) of a suitable low vapor pressure liquid and an inert working gas. Complete separation of the droplet and gas media in the zero-g environment is accomplished by configuring the LDHX as a vortex chamber.The large heat transfer area presented by the small droplets permits heat exchanger effectiveness of 0.9-0.95 in a compact, lightweight geometry which avoids many of the limitations of conventional plate and fin or tube and shell heat exchangers, such as their tendency toward single point failure. The application of the LDHX in a high temperature Brayton cycle is discussed to illustrate the performance and operational characteristics of this new heat exchanger concept.

  14. Non-Equilibrium Gibbs' Criterion for Completely Wetting Volatile Liquids

    CERN Document Server

    Tsoumpas, Yannis; Galvagno, Mariano; Rednikov, Alexey; Ottevaere, Heidi; Thiele, Uwe; Colinet, Pierre

    2014-01-01

    During the spreading of a liquid over a solid substrate, the contact line can stay pinned at sharp edges until the contact angle exceeds a critical value. At (or sufficiently near) equilibrium, this is known as Gibbs' criterion. Here, we show both experimentally and theoretically that for completely wetting volatile liquids there also exists a dynamically-produced critical angle for depinning, which increases with the evaporation rate. This suggests that one may introduce a simple modification of the Gibbs' criterion for (de)pinning, that accounts for the non-equilibrium effect of evaporation.

  15. Liquid Droplet Impact Dynamics on Micro-Patterned Superhydrophobic Surfaces

    CERN Document Server

    Clavijo, Cristian; Crockett, Julie

    2013-01-01

    The video exhibits experimental qualitative and quantitative results of water/glycerol (50%/50% by mass) droplet impact on two types of micro-patterned superhydrophobic surfaces. The two types of surfaces used were 80% cavity fraction ribs and posts with a periodic spacing of 40 {\\mu}m and 32 {\\mu}m, respectively. All surfaces were manufactured through photolithography. The impact Weber number is used as the dynamic parameter to compare splash and rebound behaviors between the two types of surfaces. While droplets exhibit similar dynamics at low Weber numbers, rebound jet speed (normalized by droplet impact speed) is notably higher on posts than ribs for all Weber numbers tested here (5 265. On posts, satellite droplets also follow a specific path but in a different orientation. Satellite droplets form in locations aligned with the post lattice structure. This behavior is observed for 600 < We < 750. Jet rebound exhibits an interesting phenomenon on ribs under certain conditions. Due to the uneven shear...

  16. Continuously rotating chiral liquid crystal droplets in a linearly polarized laser trap.

    Science.gov (United States)

    Yang, Y; Brimicombe, P D; Roberts, N W; Dickinson, M R; Osipov, M; Gleeson, H F

    2008-05-12

    The transfer of optical angular momentum to birefringent particles via circularly polarized light is common. We report here on the unexpected, continuous rotation of chiral nematic liquid crystal droplets in a linearly polarized optical trap. The rotation is non-uniform, occurs over a timescale of seconds, and is observed only for very specific droplet sizes. Synchronized vertical motion of the droplet occurs during the rotation. The motion is the result of photo-induced molecular reorganization, providing a micron sized opto-mechanical transducer that twists and translates.

  17. Liquid droplets on a free-standing glassy membrane: Deformation through the glass transition.

    Science.gov (United States)

    Fortais, Adam; Schulman, Rafael D; Dalnoki-Veress, Kari

    2017-07-01

    In this study, micro-droplets are placed on thin, glassy, free-standing films where the Laplace pressure of the droplet deforms the free-standing film, creating a bulge. The film's tension is modulated by changing temperature continuously from well below the glass transition into the melt state of the film. The contact angle of the liquid droplet with the planar film as well as the angle of the bulge with the film are measured and found to be consistent with the contact angles predicted by a force balance at the contact line.

  18. Liquid crystal droplets as a hosting and sensing platform for developing immunoassays.

    Science.gov (United States)

    Aliño, Vera Joanne; Pang, Jasmine; Yang, Kun-Lin

    2011-10-04

    In this paper, we report an immunoassay in which probe proteins are immobilized on the surface of liquid crystal (LC) droplets rather than on solid surfaces. The advantage of this immunoassay is that the binding of antibodies to the probe proteins can be transduced by the LC droplets directly without the need for additional steps. For example, when we incubate the LC droplets decorated with immunoglobulin G (IgG) in a solution containing anti-IgG (AIgG), these droplets change their orientations from radial to bipolar configuration. In contrast, when we incubate the IgG-LC droplets in a solution containing anti-human serum albumin (AHSA), no changes are observed. The change of orientational configuration indicates the formation of the antigen-antibody immunocomplex on the surface of the LC droplets. Using LC droplet immunoassays, we successfully detect antibody concentrations as low as 0.01 μg/mL for AIgG and 0.02 μg/mL for AHSA. Because the immunoassay using LC droplets is label-free and gives a unique optical response, it has the potential to be further developed as a portable and low-cost immunoassay.

  19. Development and analysis of a capacitive touch sensor using a liquid metal droplet

    Science.gov (United States)

    Baek, Seungbum; Won, Dong-Joon; Gil Kim, Joong; Kim, Joonwon

    2015-09-01

    In this paper, we introduce a small-sized capacitive touch sensor with large variations in its capacitance. This sensor uses the changes in capacitance caused by the variation of the overlap area between a liquid metal (LM) droplet and a flat electrode while keeping the gap between the droplet and the bottom electrode at a small constant value (i.e. thickness of dielectric layer). Initially, the droplet is placed inside a polydimethylsiloxane (PDMS) chamber, and a thin silicon dioxide film separates the droplet and the electrode. Owing to the high surface tension of the LM, the droplet retains its spherical shape and the overlap area remains small, which means that the capacitance between the droplet and the electrode also remains small. When normal force is applied, the pressure on the membrane pushes the droplet downward, thus spreading the droplet to the bottom of the chamber and increasing the capacitance. To verify our concept, we performed theoretical analyses and experiments using a 2 mm  ×  2 mm  ×  2 mm 1-cell touch sensor. Finally, we obtained a capacitance variation of ~30 pF by applying forces between 0 N and 1 N.

  20. Liquid droplet radiator development status. [waste heat rejection devices for future space vehicles

    Science.gov (United States)

    White, K. Alan, III

    1987-01-01

    Development of the Liquid Droplet Radiator (LDR) is described. Significant published results of previous investigators are presented, and work currently in progress is discussed. Several proposed LDR configurations are described, and the rectangular and triangular configurations currently of most interest are examined. Development of the droplet generator, collector, and auxiliary components are discussed. Radiative performance of a droplet sheet is considered, and experimental results are seen to be in very good agreement with analytical predictions. The collision of droplets in the droplet sheet, the charging of droplets by the space plasma, and the effect of atmospheric drag on the droplet sheet are shown to be of little consequence, or can be minimized by proper design. The LDR is seen to be less susceptible than conventional technology to the effects of micrometeoroids or hostile threats. The identification of working fluids which are stable in the orbital environments of interest is also made. Methods for reducing spacecraft contamination from an LDR to an acceptable level are discussed. Preliminary results of microgravity testing of the droplet generator are presented. Possible future NASA and Air Force missions enhanced or enabled by a LDR are also discussed. System studies indicate that the LDR is potentially less massive than heat pipe radiators. Planned microgravity testing aboard the Shuttle or space station is seen to be a logical next step in LDR development.

  1. Droplet charging regimes for ultrasonic atomization of a liquid electrolyte in an external electric field

    Science.gov (United States)

    Forbes, Thomas P.; Degertekin, F. Levent; Fedorov, Andrei G.

    2011-01-01

    Distinct regimes of droplet charging, determined by the dominant charge transport process, are identified for an ultrasonic droplet ejector using electrohydrodynamic computational simulations, a fundamental scale analysis, and experimental measurements. The regimes of droplet charging are determined by the relative magnitudes of the dimensionless Strouhal and electric Reynolds numbers, which are a function of the process (pressure forcing), advection, and charge relaxation time scales for charge transport. Optimal (net maximum) droplet charging has been identified to exist for conditions in which the electric Reynolds number is of the order of the inverse Strouhal number, i.e., the charge relaxation time is on the order of the pressure forcing (droplet formation) time scale. The conditions necessary for optimal droplet charging have been identified as a function of the dimensionless Debye number (i.e., liquid conductivity), external electric field (magnitude and duration), and atomization drive signal (frequency and amplitude). The specific regime of droplet charging also determines the functional relationship between droplet charge and charging electric field strength. The commonly expected linear relationship between droplet charge and external electric field strength is only found when either the inverse of the Strouhal number is less than the electric Reynolds number, i.e., the charge relaxation is slower than both the advection and external pressure forcing, or in the electrostatic limit, i.e., when charge relaxation is much faster than all other processes. The analysis provides a basic understanding of the dominant physics of droplet charging with implications to many important applications, such as electrospray mass spectrometry, ink jet printing, and drop-on-demand manufacturing.

  2. Droplet charging regimes for ultrasonic atomization of a liquid electrolyte in an external electric field

    Science.gov (United States)

    Forbes, Thomas P.; Degertekin, F. Levent; Fedorov, Andrei G.

    2011-01-01

    Distinct regimes of droplet charging, determined by the dominant charge transport process, are identified for an ultrasonic droplet ejector using electrohydrodynamic computational simulations, a fundamental scale analysis, and experimental measurements. The regimes of droplet charging are determined by the relative magnitudes of the dimensionless Strouhal and electric Reynolds numbers, which are a function of the process (pressure forcing), advection, and charge relaxation time scales for charge transport. Optimal (net maximum) droplet charging has been identified to exist for conditions in which the electric Reynolds number is of the order of the inverse Strouhal number, i.e., the charge relaxation time is on the order of the pressure forcing (droplet formation) time scale. The conditions necessary for optimal droplet charging have been identified as a function of the dimensionless Debye number (i.e., liquid conductivity), external electric field (magnitude and duration), and atomization drive signal (frequency and amplitude). The specific regime of droplet charging also determines the functional relationship between droplet charge and charging electric field strength. The commonly expected linear relationship between droplet charge and external electric field strength is only found when either the inverse of the Strouhal number is less than the electric Reynolds number, i.e., the charge relaxation is slower than both the advection and external pressure forcing, or in the electrostatic limit, i.e., when charge relaxation is much faster than all other processes. The analysis provides a basic understanding of the dominant physics of droplet charging with implications to many important applications, such as electrospray mass spectrometry, ink jet printing, and drop-on-demand manufacturing. PMID:21301636

  3. Droplet charging regimes for ultrasonic atomization of a liquid electrolyte in an external electric field.

    Science.gov (United States)

    Forbes, Thomas P; Degertekin, F Levent; Fedorov, Andrei G

    2011-01-01

    Distinct regimes of droplet charging, determined by the dominant charge transport process, are identified for an ultrasonic droplet ejector using electrohydrodynamic computational simulations, a fundamental scale analysis, and experimental measurements. The regimes of droplet charging are determined by the relative magnitudes of the dimensionless Strouhal and electric Reynolds numbers, which are a function of the process (pressure forcing), advection, and charge relaxation time scales for charge transport. Optimal (net maximum) droplet charging has been identified to exist for conditions in which the electric Reynolds number is of the order of the inverse Strouhal number, i.e., the charge relaxation time is on the order of the pressure forcing (droplet formation) time scale. The conditions necessary for optimal droplet charging have been identified as a function of the dimensionless Debye number (i.e., liquid conductivity), external electric field (magnitude and duration), and atomization drive signal (frequency and amplitude). The specific regime of droplet charging also determines the functional relationship between droplet charge and charging electric field strength. The commonly expected linear relationship between droplet charge and external electric field strength is only found when either the inverse of the Strouhal number is less than the electric Reynolds number, i.e., the charge relaxation is slower than both the advection and external pressure forcing, or in the electrostatic limit, i.e., when charge relaxation is much faster than all other processes. The analysis provides a basic understanding of the dominant physics of droplet charging with implications to many important applications, such as electrospray mass spectrometry, ink jet printing, and drop-on-demand manufacturing.

  4. Evaporation of Sessile Droplets on Slippery Liquid-Infused Porous Surfaces (SLIPS).

    Science.gov (United States)

    Guan, Jian H; Wells, Gary G; Xu, Ben; McHale, Glen; Wood, David; Martin, James; Stuart-Cole, Simone

    2015-11-03

    Over the past decade, the most common approach to creating liquid shedding surfaces has been to amplify the effects of nonwetting surface chemistry, using micro/nanotexturing to create superhydrophobic and superoleophobic surfaces. Recently, an alternative approach using impregnation of micro/nanotextured surfaces with immiscible lubricating liquids to create slippery liquid-infused porous surfaces (SLIPS) has been developed. These types of surfaces open up new opportunities to study the mechanism of evaporation of sessile droplets in zero contact angle hysteresis situations where the contact line is completely mobile. In this study, we fabricated surfaces consisting of square pillars (10-90 μm) of SU-8 photoresist arranged in square lattice patterns with the center-to-center separation between pillars of 100 μm, on which a hydrophobic coating was deposited and the textures impregnated by a lubricating silicone oil. These surfaces showed generally low sliding angles of 1° or less for small droplets of water. Droplet profiles were more complicated than on nonimpregnated surfaces and displayed a spherical cap shape modified by a wetting ridge close to the contact line due to balancing the interfacial forces at the line of contact between the droplet, the lubricant liquid and air (represented by a Neumann triangle). The wetting ridge leads to the concept of a wetting "skirt" of lubricant around the base of the droplet. For the SLIP surfaces, we found that the evaporation of small sessile droplets (∼2 mm in diameter) followed an ideal constant contact angle mode where the apparent contact angle was defined from the intersection of the substrate profile with the droplet spherical cap profile. A theoretical model based on diffusion controlled evaporation was able to predict a linear dependence in time for the square of the apparent contact radius. The experimental data was in excellent quantitative agreement with the theory and enabled estimates of the diffusion

  5. An Integrated microfluidic platform for liquid droplet in gas flow generation with in liquid flow collection and manipulation

    Science.gov (United States)

    Tirandazi, Pooyan; Hidrovo, Carlos H.

    2016-11-01

    Discretization of biological samples and chemical reactions within digital droplets is a powerful technique which has rapidly emerged in many biochemical syntheses. The ability to generate, manipulate, and monitor millions of microdroplets in a short time provides great potential for high throughput screening and detection in microbiology. Here we report a microfluidic device for the formation of uniform microdroplets (50 μm-100 μm) using a high speed gas as the continuous phase. Gas-borne droplets are generated in a chip-based flow-focusing device fabricated in PDMS, and travel along the gaseous microchannel and are subsequently captured within a second liquid phase. The droplets are then transferred and collected in a minichamber and move into the manipulation section for further processing operations on the drops. All these steps are performed automatically in a single multilayer chip. This integrated microfluidic platform for generation, collection, and manipulation of the droplets provides great opportunities for monitoring and detection of gas-analytes. Utilizing the generated picoliter airborne droplets feature lower reaction times and higher transfer rates as compared to conventional air sampling techniques. Thus, it can greatly facilitate the investigation of airborne analytes by interrogation of the digital droplets using different analytical techniques. Furthermore, the presented liquid-in-gas generation method can be utilized for production of oil-free microparticles and microcapsules used in the food industry and for drug delivery.

  6. Phase change events of volatile liquid perfluorocarbon contrast agents produce unique acoustic signatures

    Science.gov (United States)

    Sheeran, Paul S.; Matsunaga, Terry O.; Dayton, Paul A.

    2014-01-01

    Phase-change contrast agents (PCCAs) provide a dynamic platform to approach problems in medical ultrasound (US). Upon US-mediated activation, the liquid core vaporizes and expands to produce a gas bubble ideal for US imaging and therapy. In this study, we demonstrate through high-speed video microscopy and US interrogation that PCCAs composed of highly volatile perfluorocarbons (PFCs) exhibit unique acoustic behavior that can be detected and differentiated from standard microbubble contrast agents. Experimental results show that when activated with short pulses PCCAs will over-expand and undergo unforced radial oscillation while settling to a final bubble diameter. The size-dependent oscillation phenomenon generates a unique acoustic signal that can be passively detected in both time and frequency domain using confocal piston transducers with an ‘activate high’ (8 MHz, 2 cycles), ‘listen low’ (1 MHz) scheme. Results show that the magnitude of the acoustic ‘signature’ increases as PFC boiling point decreases. By using a band-limited spectral processing technique, the droplet signals can be isolated from controls and used to build experimental relationships between concentration and vaporization pressure. The techniques shown here may be useful for physical studies as well as development of droplet-specific imaging techniques.

  7. To grate a liquid into tiny droplets by its impact on a hydrophobic micro-grid

    CERN Document Server

    Brunet, P; Zoueshtiagh, F; Thomy, V; Merlen, A

    2009-01-01

    We report on experiments of drop impacting a hydrophobic micro-grid, of typical spacing a few tens of $\\mu$m. Above a threshold in impact speed, liquid emerges to the other side, forming micro-droplets of size about that of the grid holes. We propose a method to produce either a mono-disperse spray or a single tiny droplet of volume as small as a few picoliters corresponding to a volume division of the liquid drop by a factor of up to 10$^5$. We also discuss the discrepancy of the measured thresholds with that predicted by a balance between inertia and capillarity.

  8. Dispensing nano-pico droplets and liquid patterning by pyroelectrodynamic shooting.

    Science.gov (United States)

    Ferraro, P; Coppola, S; Grilli, S; Paturzo, M; Vespini, V

    2010-06-01

    Manipulating and dispensing liquids on the micrometre- and nanoscale is important in biotechnology and combinatorial chemistry, and also for patterning inorganic, organic and biological inks. Several methods for dispensing liquids exist, but many require complicated electrodes and high-voltage circuits. Here, we show a simple way to draw attolitre liquid droplets from one or multiple sessile drops or liquid film reservoirs using a pyroelectrohydrodynamic dispenser. Local pyroelectric forces, which are activated by scanning a hot tip or an infrared laser beam over a lithium niobate substrate, draw liquid droplets from the reservoir below the substrate, and deposit them on the underside of the lithium niobate substrate. The shooting direction is altered by moving the hot tip or laser to form various patterns at different angles and locations. Our system does not require electrodes, nozzles or circuits, and is expected to have many applications in biochemical assays and various transport and mixing processes.

  9. New method to quantify volatile organic compounds (VOCs) in cloud droplets sampled at the puy de Dôme research station.

    Science.gov (United States)

    Colomb, A.; Fleuret, J.; Gaimoz, C.; Deguillaume, L.

    2012-04-01

    In recent years several studies have focused on the health and environmental effects of atmospheric pollution, and especially on the emissions of volatile organic compounds (VOCs). In cloud droplets, chemical reactions in the liquid phase modify the amount of radicals which drive the oxidizing power of the atmosphere. The objective of this project was to identify and quantify VOCs in cloud water samples at the puy de Dôme research site using a combination of stir bar sorptive extraction (SBSE)-thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS). Experimental studies were carried out at the puy de Dôme (PDD) Station (48°N, 2°E; 1465 m a.s.l.), in the Massif Central Region (France). It is a strategic point from which to observe warm and mixed clouds that are present 30% of the time on an annual basis. Clouds are frequently formed at the top of the site either during advection of frontal systems or by orographic rise of moist air. The station is in the free troposphere a large fraction of the time and air masses are usually exempt from the influence of local pollution. Non-precipitating cloud droplets are sampled using a single-stage cloud collector. Cloud droplets larger than 7 µm (cut-off diameter) are collected by impaction onto a rectangular plate at a flow rate of approximately 86 m3 h-1. This work has established a functional procedure to allow the quantitative extraction of 80 VOCs in cloud water. The method has been optimized to determine the best repeatability and detection limit for most of the compounds (hydrophobic and hydrophilic). According to SBSE theory, at equilibrium the distribution coefficients of the analytes between the aqueous matrix and coated film of the stir bar (PDMS) are correlated with the corresponding octanol-water partitioning coefficients (Kpdms/w vs Ko/w). Hydrophobic compounds, characterized by a high octanol-water distribution coefficient (Kow), are extracted from water by SBSE with a high recovery. However

  10. Continuous rotation of a cholesteric liquid crystalline droplet by a circularly polarized optical tweezers

    Science.gov (United States)

    Tamura, Yuta; Kimura, Yasuyuki

    2017-04-01

    We studied the opto-mechanical response of droplets composed of cholesteric liquid crystal (ChLC) to a circularly polarized optical tweezers. Although the alignment of LC molecular within a droplet depends on the relative ratio of the droplet diameter d to the helical pitch p, the optically induced rotation was found to be asymmetric to the direction of circularly polarized light irrespective to the inner molecular alignment. We studied the rotation of the droplets with various sizes, helical pitch (strength of chirality) and different chirality. In the case of d/p 1, the direction of the rotation was simply determined by chirality of ChLC and the rotation was also observed for linearly polarized light, which has already been reported by Yang et al.

  11. Liquid-in-gas droplet microfluidics; experimental characterization of droplet morphology, generation frequency, and monodispersity in a flow-focusing microfluidic device

    Science.gov (United States)

    Tirandazi, Pooyan; Hidrovo, Carlos H.

    2017-07-01

    Microfluidic techniques for production of uniform droplets usually rely on the use of two immiscible liquids (e.g. water-in-oil emulsions). It has been shown recently that a continuous gas flow instead of a second liquid carrier can be used as an alternative approach in droplet microfluidics. In this work we experimentally investigate the generation of liquid water droplets within air in flow-focusing configurations. Over a wide range of flow conditions we identify six distinct flow regimes inside the microchannel: Co-flowing, Threading, Plugging, Dripping, Multi-Satellite Formation, and Jetting. Flow regimes and their transitions are plotted and characterized based on the Weber number (We) of the system. We further investigate the impact of liquid microchannel size on the flow maps. Generation frequency, morphology, and monodispersity of the droplets are characterized in more detail in the Dripping regime. Generation frequency can be related to the product of the liquid and gas flow rates. However, droplet morphology (length and width) is more dependent on the gas flow rate. We demonstrate the production of monodisperse droplets (d lab-on-a-chip systems for a variety of applications in biochemical research and material synthesis.

  12. Nanoparticle self-assembly at the interface of liquid crystal droplets.

    Science.gov (United States)

    Rahimi, Mohammad; Roberts, Tyler F; Armas-Pérez, Julio C; Wang, Xiaoguang; Bukusoglu, Emre; Abbott, Nicholas L; de Pablo, Juan J

    2015-04-28

    Nanoparticles adsorbed at the interface of nematic liquid crystals are known to form ordered structures whose morphology depends on the orientation of the underlying nematic field. The origin of such structures is believed to result from an interplay between the liquid crystal orientation at the particles' surface, the orientation at the liquid crystal's air interface, and the bulk elasticity of the underlying liquid crystal. In this work, we consider nanoparticle assembly at the interface of nematic droplets. We present a systematic study of the free energy of nanoparticle-laden droplets in terms of experiments and a Landau-de Gennes formalism. The results of that study indicate that, even for conditions under which particles interact only weakly at flat interfaces, particles aggregate at the poles of bipolar droplets and assemble into robust, quantized arrangements that can be mapped onto hexagonal lattices. The contributions of elasticity and interfacial energy corresponding to different arrangements are used to explain the resulting morphologies, and the predictions of the model are shown to be consistent with experimental observations. The findings presented here suggest that particle-laden liquid crystal droplets could provide a unique and versatile route toward building blocks for hierarchical materials assembly.

  13. Dynamics of liquid metal droplets and jets influenced by a strong axial magnetic field

    Science.gov (United States)

    Hernández, D.; Karcher, Ch

    2017-07-01

    Non-contact electromagnetic control and shaping of liquid metal free surfaces is crucial in a number of high-temperature metallurgical processes like levitation melting and electromagnetic sealing, among others. Other examples are the electromagnetic bending or stabilization of liquid metal jets that frequently occur in casting or fusion applications. Within this context, we experimentally study the influence of strong axial magnetic fields on the dynamics of falling metal droplets and liquid metal jets. GaInSn in eutectic composition is used as test melt being liquid at room temperature. In the experiments, we use a cryogen-free superconducting magnet (CFM) providing steady homogeneous fields of up to 5 T and allowing a tilt angle between the falling melt and the magnet axis. We vary the magnetic flux density, the tilt angle, the liquid metal flow rate, and the diameter and material of the nozzle (electrically conducting/insulating). Hence, the experiments cover a parameter range of Hartmann numbers Ha, Reynolds numbers Re, and Weber numbers We within 0 magnetic field, droplet rotation ceases and the droplets are stretched in the field direction. Moreover, we observe that the jet breakup into droplets (spheroidization) is suppressed, and in the case of electrically conducting nozzles and tilt, the jets are bent towards the field axis.

  14. Nanoparticle self-assembly at the interface of liquid crystal droplets

    Science.gov (United States)

    Rahimi, Mohammad; Roberts, Tyler F.; Armas-Pérez, Julio C.; Wang, Xiaoguang; Bukusoglu, Emre; Abbott, Nicholas L.; de Pablo, Juan J.

    2015-01-01

    Nanoparticles adsorbed at the interface of nematic liquid crystals are known to form ordered structures whose morphology depends on the orientation of the underlying nematic field. The origin of such structures is believed to result from an interplay between the liquid crystal orientation at the particles’ surface, the orientation at the liquid crystal’s air interface, and the bulk elasticity of the underlying liquid crystal. In this work, we consider nanoparticle assembly at the interface of nematic droplets. We present a systematic study of the free energy of nanoparticle-laden droplets in terms of experiments and a Landau–de Gennes formalism. The results of that study indicate that, even for conditions under which particles interact only weakly at flat interfaces, particles aggregate at the poles of bipolar droplets and assemble into robust, quantized arrangements that can be mapped onto hexagonal lattices. The contributions of elasticity and interfacial energy corresponding to different arrangements are used to explain the resulting morphologies, and the predictions of the model are shown to be consistent with experimental observations. The findings presented here suggest that particle-laden liquid crystal droplets could provide a unique and versatile route toward building blocks for hierarchical materials assembly. PMID:25870304

  15. Gas phase microreaction: nanomaterials synthesis via plasma exposure of liquid droplets

    Science.gov (United States)

    Maguire, Paul; Mahony, Charles; Kelsey, Colin; Hamilton, Neil; Askari, Sadegh; Macias-Montero, Manuel; Diver, Declan; Mariotti, Davide

    2015-09-01

    Plasma-liquid interactions are complex but offer considerable scope for use in nanomaterials synthesis. The introduction of individual picolitre micro-droplets into a steady-state low temperature plasma at atmospheric pressure, offers opportunities for enhanced scope and control of plasma-liquid chemistry and material properties. The gas-phase micro-reactor is similar in concept to liquid bubble microfluidics currently under intense research but with enhanced opportunities for scale-up. For nanomaterials and quantum dot synthesis, the addition of a liquid phase within the plasma expands considerably the scope for core-shell and alloy formation. The synthesis and encapsulation within a liquid droplet allows continuous delivery of nanoparticles to remote sites for plasma medicine, device fabrication or surface coating. We have synthesized Au nanoparticles in flight using AuHCl4 droplets with plasma flight times <0.1 ms. Also, Ag nanoparticles have been synthesized downstream via the delivery of plasma exposed water droplets onto AgNO3 laden substrates. Funding from EPSRC acknowledged (Grants EP/K006088/1 and EP/K006142/1).

  16. Pinning of a perfectly wetting volatile liquid at a sharp edge - experiment and theory

    Science.gov (United States)

    Tsoumpas, Yannis; Dehaeck, Sam; Rednikov, Alexey; Galvagno, Mariano; Thiele, Uwe; Colinet, Pierre

    2012-11-01

    It is well known that contact lines of drops, even those of wetting liquids, stay pinned at sharp edges of the substrate until the apparent contact angle exceeds a critical value. In the present study, we show that evaporation influences this effect. The edge of a circular groove is used as an example. Experiments with wetting liquids of different evaporation rate show indeed that not only the spreading of the liquid is adequately halted, but also that the pinning is enhanced for the more volatile cases. The experimental results are qualitatively compared with predictions of a thin film model in two dimensions. The approach employs an evolution equation for the height profile of an evaporating thin film (small contact angle droplet) on a substrate with a rounded edge, and enables one to predict the dependence of the apparent contact angle on the position of the contact line. The calculations confirm our experimental observations, namely that there exists a dynamically produced critical angle for depinning that increases with the evaporation rate. This suggests that one may introduce a simple modification of the Gibbs criterion for pinning that accounts for the non-equilibrium effect of evaporation. Supported by the Marie Curie MULTIFLOW Network, by ESA & BELSPO, and by FRS-FNRS.

  17. Evolution of temperature of a droplet of liquid composite fuel interacting with heated airflow

    Science.gov (United States)

    Glushkov, D. O.; Zakharevich, A. V.; Strizhak, P. A.; Syrodoy, S. V.

    2016-11-01

    The macroscopic patterns of a temperature change at the center of a droplet of three-component (coal, water, petroleum) composite liquid fuel (CLF) were studied using a low-inertia thermoelectric converter and system of high-speed (up to 105 frames per second) video recording during the induction period at different heating intensity by the air flow with variable parameters: temperature of 670-870 K and motion velocity of 1-4 m/s. The studies were carried out for two groups of CLF compositions: fuel based on brown coal and coal cleaning rejects (filter cake). To assess the effect of liquid combustible component of CLF on characteristics of the ignition process, the corresponding composition of two-component coal-water fuel (CWF) was studied. The stages of inert heating of CLF and CWF droplets with characteristic size corresponding to radius of 0.75-1.5 mm, evaporation of moisture and liquid oil (for CLF), thermal decomposition of the organic part of coal, gas mixture ignition, and carbon burnout were identified. Regularities of changes in the temperature of CLF and CWF droplets at each of identified stages were identified for the cooccurrence of phase transitions and chemical reactions. Comparative analysis of the times of ignition delay and complete combustion of the droplets of examined fuel compositions was performed with varying droplet dimensions, temperatures, and oxidant flow velocity.

  18. Splashing phenomena of room temperature liquid metal droplet striking on the pool of the same liquid under ambient air environment

    CERN Document Server

    Li, Haiyan; Wang, Lei; Gao, Yunxia; Liu, Jing

    2013-01-01

    In this article, the fluid dynamics of room temperature liquid metal (RTLM) droplet impacting onto a pool of the same liquid in ambient air was investigated. A series of experiments were conducted in order to disclose the influence of the oxidation effect on the impact dynamics. The droplet shape and impact phenomenology were recorded with the aid of a high-speed digital camera. The impact energy stored in the splash structures was estimated via a theoretical model and several morphological parameters obtained from instantaneous images of the splash. It was observed that the droplet shape and the splashing morphology of RTLM were drastically different from those of water, so was the impact dynamics between room temperature LM pool and high temperature LM pool. The energy analysis disclosed that the height of the jet is highly sensitive to the viscosity of the fluid, which is subjected to the oxidation effect and temperature effect simultaneously, and thus perfectly explained the phenomena. These basic finding...

  19. Continuous transfer of liquid metal droplets across a fluid-fluid interface within an integrated microfluidic chip.

    Science.gov (United States)

    Gol, Berrak; Tovar-Lopez, Francisco J; Kurdzinski, Michael E; Tang, Shi-Yang; Petersen, Phred; Mitchell, Arnan; Khoshmanesh, Khashayar

    2015-06-07

    Micro scale liquid metal droplets have been hailed as the potential key building blocks of future micro-electro-mechanical systems (MEMS). However, most of the current liquid metal enabled systems involve millimeter scale droplets, which are manually injected onto the desired locations of the microchip. Despite its simplicity, this method is impractical for patterning large arrays or complex systems based on micro scale droplets. Here, we present a microfluidic chip, which integrates continuous generation of micro scale galinstan droplets in glycerol, and the hydrodynamic transfer of these droplets into sodium hydroxide (NaOH) solution. Observation via high-speed imaging along with computational fluid dynamics (CFD) analysis are utilised to comprehend the lateral migration of droplets from the glycerol to NaOH fluid. This platform is simple, can be readily integrated into other microfluidic systems, and creates flexibility by separating the continuous phase for droplet generation from the eventual target carrier fluid within a monolithic chip.

  20. Study of deformation of droplet in external force field by using liquid-gas model of lattice-gas

    Energy Technology Data Exchange (ETDEWEB)

    Ebihara, Ken-ichi; Watanabe, Tadashi [Japan Atomic Energy Research Inst., Center for Promotion of Computational Science and Engineering, Tokai, Ibaraki (Japan)

    2000-10-01

    The deformation of the droplet by the external force which is assumed to be gravity is studied by using the liquid-gas model of lattice-gas. Two types of liquid-gas models, one is the minimal model and the other is the maximal model, which are distinguished from each other by the added long-range interactions are used for the simulation of the droplet deformation. The difference of the droplet deformation between the maximal model and the minimal model was observed. While the droplet of the minimal model elongates in the direction of the external force, the droplet of the maximal model elongates in the perpendicular direction to the external force. Therefore the droplet deformation in the external force field of the maximal model is more similar to the droplet deformation which is observed in experiments than that of the minimal model. (author)

  1. SIMULATION OF THE TWO PHASE FLOW OF DROPLET IMPINGEMENT ON LIQUID FILM BY THE LATTICE BOLTZMANN METHOD

    Institute of Scientific and Technical Information of China (English)

    GUO Jia-hong; WANG Xiao-yong

    2012-01-01

    A Lattice Boltzmann Method (LBM) with two-distribution functions is employed for simulating the two-phase flow induced by a liquid droplet impinging onto the film of the same liquid on solid surface.The model is suitable for solution of twophase flow problem at high density and viscosity ratios of liquid to vapor and phase transition between liquid and its vapor.The roles of the vapor flow,the density ratio of liquid to vapor and the surface tension of the droplet in the splashing formation are discussed.It is concluded that the vapour flow induced by the droplet fall and splash in the whole impinging process may affect remarkably the splash behaviour.For the case of large density ratio of liquid to vapor a crown may engender after the droplet collides with the film.However,for the case of small density ratio of liquid to vapor a “bell” like splash may be observed.

  2. Capillary torque caused by a liquid droplet sandwiched between two plates.

    Science.gov (United States)

    Takei, Atsushi; Matsumoto, Kiyoshi; Shimoyama, Isao

    2010-02-16

    Capillary force makes a liquid droplet's surface have the minimum area. If the droplet is sandwiched between two plates, it exerts capillary force on the plates. The magnitude of the force depends on the shape of the sandwiched droplet, which is in turn determined by the shape of the plates and the volume of the liquid. The liquid's shape, however, is hard to determine analytically. In this paper, the torque caused by a droplet sandwiched between two noncircular plates is experimentally and theoretically analyzed. We patterned a magnetic material on the surface of the plates and used it to apply a magnetic force to the plates. The torque on the plates was measured. The torque caused by capillary force was calculated by observing the equilibrium between the capillary force and magnetic force. We obtained approximate theoretical solutions for the liquid's shape and torque and verified that they were in accordance with the experimental results. The experimental and theoretical results presented in this paper are useful for designing microdevices or self-assemblies actuated by capillary force.

  3. Impact of Line Tension on the Equilibrium Shape of Liquid Droplets on Patterned Substrates

    NARCIS (Netherlands)

    Buehrle, Juergen; Herminghaus, Stephan; Mugele, Frieder

    2002-01-01

    We studied the morphology of liquid droplets on substrates with a lateral wettability pattern using numerical calculations. We analyzed the influence of the wettability contrast, the sharpness of the transitions between adjacent hydrophilic and hydrophobic stripes, and the line tension of the three-

  4. Impact of Line Tension on the Equilibrium Shape of Liquid Droplets on Patterned Substrates

    NARCIS (Netherlands)

    Buehrle, Juergen; Herminghaus, Stephan; Mugele, Friedrich Gunther

    2002-01-01

    We studied the morphology of liquid droplets on substrates with a lateral wettability pattern using numerical calculations. We analyzed the influence of the wettability contrast, the sharpness of the transitions between adjacent hydrophilic and hydrophobic stripes, and the line tension of the

  5. The effect of the interaction between the minority phase droplets on the nucleation behavior during the liquid-liquid phase transformation

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The microstructure evolution during the liquid-liquid phase transformation of Al-Pb alloy was calculated. The numerical results indicate that the interaction between the minority phase droplets has effect on the nucleation process of the droplets, and the effect increases with the cooling rate and the content of Pb.

  6. Terminal Liquid Mass Fractions and Terminal Mean Droplet Sizes in He Free-Jet Expansions

    Science.gov (United States)

    Knuth, E. L.; Kornilov, O.; Toennies, J. P.

    2011-05-01

    The terminal liquid mass fraction in He free-jet expansions is deduced from time-of-flight measurements using conservation of energy. Both the present results and results from prior measurements are correlated using a scaling parameter which was used previously for correlating droplet size as a function of source conditions. Deduced values of the mass fraction range from 0.047 to 0.42. The terminal mean droplet size is determined using a novel technique based on a size-dependent attenuation of the beam droplets when impacted by electrons. The determined sizes are in agreement with sizes obtained previously by crossing the droplet beam with an atomic beam, confirming the suitability of the present technique, which is relatively simple in comparison with crossing the droplet beam with an atomic beam. Measured values of the terminal velocity of the droplets are compared with values calculated for a model in which real-fluid properties are used for the enthalpy in the source but conversion of heat of condensation into energy of directed motion is neglected. The deviations from perfect-gas behavior in free-jet expansions are shown to be due to real-fluid properties and condensation.

  7. Specific detection of avidin-biotin binding using liquid crystal droplets.

    Science.gov (United States)

    Khan, Mashooq; Park, Soo-Young

    2015-03-01

    Poly(acrylicacid-b-4-cynobiphenyl-4'-undecylacrylate) (PAA-b-LCP)-functionalized 4-cyano-4'-pentylbiphenyl (5CB) droplets were made by using microfluidic technique. The PAA chains on the 5CB droplets, were biotinylated, and used to specifically detect avidin-biotin binding at the 5CB/aqueous interface. The avidin-biotin binding was characterized by the configurational change (from radial to bipolar) of the 5CB droplets, as observed through a polarized optical microscope. The maximum biotinylation was obtained by injecting a >100 μg/mL biotin aqueous solution, which enabled a limit of detection of 0.5 μg/mL avidin. This droplet biosensor could specifically detect avidin against other proteins such as bovine serum albumin, lysozyme, hemoglobin, and chymotrypsinogen solutions. Avidin detection with 5CBPAA-biotin droplets having high sensitivity, specificity, and stability demonstrates new applications of the functionalized liquid crystal droplets that can detect specific proteins or other analytes through a ligand/receptor model.

  8. Droplet-Sizing Liquid Water Content Sensor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Icing is one of the most significant hazards to aircraft. A sizing supercooled liquid water content (SSLWC) sonde is being developed to meet a directly related need...

  9. Dispersiveness of Liquid Droplets Sprayed with Cocurrent Gas Flow

    Directory of Open Access Journals (Sweden)

    Arkhipov Vladimir

    2016-01-01

    Full Text Available Pneumohydraulic stand, equipped with a set of aerosol systems laser diagnostics devices, are presented. The results of experimental measurements of the aerosol liquid-drop size distribution in the ejection nozzle spray pattern are provided.

  10. Microfluidic room temperature ionic liquid droplet generation depending on the hydrophobicity and interfacial tension

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Jung Wook; Chang, Woo-Jin [University of Wisconsin-Milwaukee, Milwaukee (United States); Choi, Joo Hyung; Koo, Yoon Mo [Department of Biological Engineering, Incheon (Korea, Republic of); Choi, Bum Joon; Lee, Gyu Do; Lee, Sang Woo [Yonsei University, Wonju (Korea, Republic of)

    2016-01-15

    We have characterized micro-droplet generation using water immiscible hexafluorophosphate ([PF{sub 6}])- and bis(trifluoro methylsulfonyl)imide ([Tf{sub 2}N])-based room temperature ionic liquids (RTILs). The interfacial tension between total 7 RTILs and phosphate buffered saline (PBS) was measured using a tensiometer for the first time. PBS is one of the most commonly used buffer solutions in cell-related researches. The measured interfacial tension ranges from 8.51 to 11.62 and from 9.56 to 13.19 for [Tf{sub 2}N]- and [PF{sub 6}]-based RTILs, respectively. The RTILs micro-droplets were generated in a microfluidic device. The micro-droplet size and generation frequency were determined based on continuous monitoring of light transmittance at the interface in microchannel. The size of RTIL micro-droplets was inversely proportional to the increase of PBS solution flow rate and RTILs hydrophobicity, while droplet generation frequency was proportional to those changes. The measured size of RTILs droplets ranged from 0.6 to 10.5 nl, and from 1.0 to 17.1 nl for [Tf{sub 2}N]- and [PF{sub 6}]-based RTILs, respectively. The measured frequency of generated RTILs droplets ranged from 2.3 to 37.2 droplet/min, and from 2.7 to 17.1 droplet/min for [Tf{sub 2}N]- and [PF{sub 6}]-based RTILs, respectively. The capillary numbers were calculated depending on the RTILs, and ranged from 0.51x10{sup -3} to 1.06x10{sup -3} and from 5.00x10{sup -3} to 8.65x10{sup -3}, for [Tf{sub 2}N]- and [PF{sub 6}]-based RTILs, respectively. The interfacial tension between RTILs and PBS will contribute to developing bioprocesses using immiscible RTILs. Also, the RTILs micro-droplets will enable the high-throughput monitoring of various biological and chemical reactions using RTILs as new reaction media.

  11. Light transmission of polymer-dispersed liquid crystal layer composed of droplets with inhomogeneous surface anchoring

    Science.gov (United States)

    Loiko, V. A.; Zyryanov, V. Ya.; Konkolovich, A. V.; Miskevich, A. A.

    2016-01-01

    We have developed a model and realized an algorithm for the calculation of the coefficient of coherent (direct) transmission of light through a layer of liquid crystal (LC) droplets in a polymer matrix. The model is based on the Hulst anomalous diffraction approximation for describing the scattering by an individual particle and the Foldy-Twersky approximation for a coherent field. It allows one to investigate polymer dispersed LC (PDLC) materials with homogeneous and inhomogeneous interphase surface anchoring on the droplet surface. In order to calculate the configuration of the field of the local director in the droplet, the relaxation method of solving the problem of minimization of the free energy volume density has been used. We have verified the model by comparison with experiment under the inverse regime of the ionic modification of the LC-polymer interphase boundary. The model makes it possible to solve problems of optimization of the optical response of PDLC films in relation to their thickness and optical characteristics of the polymer matrix, sizes, polydispersity, concentration, and anisometry parameters of droplets. Based on this model, we have proposed a technique for estimating the size of LC droplets from the data on the dependence of the transmission coefficient on the applied voltage.

  12. Controlling micro-sized droplet generation using electrical pulses for studying liquid-liquid systems

    Science.gov (United States)

    Fernandino, M.; La Forgia, N.; Vera, A. J.; Bjerknes, J.; Dorao, C. A.

    2014-04-01

    Water droplets removal from oil is a critical process in several industries, in particular in the oil and gas industry. Water/oil separation is commonly done in large gravitational sedimentation tanks, which are over dimensioned due to the lack of accurate models to allow for optimization. This can become challenging for off-shore and subsea processing installations. One of the bottlenecks to study droplet dynamics in the micron range, is the generation of droplets with less than 100μm in diameter. In this regard, one of the most promising techniques for controlling the generated droplet size is based on the use of a high voltage electrical signal or electro-hydrodynamic technique (EHD). Although much work on EHD and droplet generation can been found in the literature, many challenges still remain. One of this is the generation of droplets smaller than 100μm in diameter in a controllable, on-demand manner. In this work, the effect of the meniscus shape and the electric pulse characteristics on the size of the generated droplet is investigated. Both the meniscus height and width help to determine the droplet size, with the latter having a stronger effect. No significant influence of the pulse amplitude and pulse width was observed for the tested conditions.

  13. Using liquid droplet penetration experiments to determine wetting properties of powders

    Science.gov (United States)

    Callegari, Gerardo; Liu, Zhanjie; Wang, Yifan; Muzzio, Fernando; Drazer, German

    2016-11-01

    We show that the spontaneous penetration of droplets on a powder bed provides a simple way to characterize the wetting properties of a test liquid. Specifically, we demonstrate that calculating the appropriate dimensionless penetrating volume and time, and performing supplementary experiments with a reference liquid, it is possible to obtain the contact angle between the test liquid and the powder. Interestingly, the proposed analysis lets us calculate the contact angle without having to compute the solution to the 3D penetration problem. This approach is valid when the contact area between the droplet and the powder bed remains constant, which is a good approximation in many powder systems. We first test the validity of our approach by studying droplets of different sizes and show that the non-dimensional penetration curves are independent of the initial volume and contact radius of the drops, as predicted. We then use a reference liquid (silicone oil) to measure the contact angle of water on three powder systems with increasing number of pharmaceutical components and different processing conditions known to affect blend wettability. We show that the proposed method is able to capture the overlubrication of the blend, a well-known effect in pharmaceutical manufacturing.

  14. Shape evolution of a single liquid-crystal droplet immersed in an isotropic matrix under transient and steady flow

    Science.gov (United States)

    Wu, Youjun; Yu, Wei; Zhou, Chixing; Xu, Yuanze

    2007-04-01

    The morphology evolution of immiscible polymer-liquid crystal systems is quite different from flexible polymer-polymer mixtures due to the anisotropic properties of liquid crystals. The deformation and retraction of a single low molar mass liquid crystal 4' -pentyl-4-biphenylcarbonitrile (5CB) droplet and 4' -octyl-4-biphenylcarbonitrile (8CB) dispersed in polydimethyl-siloxane under two-dimensional linear flow was investigated by a computer-controlled four-roll mill, which is equipped with an optical microscope and a digital camera. The deformation parameter and orientation angle during deformation versus capillary number was obtained and compared with calculations using the Maffettone-Minale (MM) model and the Yu-Zhou liquid-crystal (YZ-LC) model. The MM model can describe the behavior of a Newtonian droplet in another Newtonian matrix whereas the YZ-LC model can describe the behavior of a LC droplet in a Newtonian matrix. The results showed that the deformation and rotation of a LC droplet is more difficult than viscoelastic droplets, possibly because of the resistance of the nematic elastic energy induced by the nematic mesogens deformation and orientation under flow field. Furthermore, the different behavior between flow-aligning 5CB and flow-tumbling 8CB droplets and the influence of droplet size of LC on deformation and retraction were discussed by experiment and calculation; the results reveal that the different size LC droplets show different evolution curves.

  15. Plasma charging and electron-based reactions at the plasma-liquid interface of an isolated liquid droplet

    Science.gov (United States)

    Maguire, Paul; Mahony, Charles; Kelsey, Colin; Rutherford, David; Mariotti, Davide; Diver, Declan

    2016-09-01

    The study of plasma-liquid interactions opens up exciting new opportunities for applications but numerous investigative challenges remain. The use of isolated and stable spherical liquid microdroplets in a non-thermal equilibrium atmospheric pressure plasma offers a new platform for experimental and theoretical investigations. Since the droplet assumes floating potential, a high flux of electrons with low net energy ( thermal) becomes fixed and solvated within the first monolayers of the liquid leading to highly reactive and rapid chemical reactions. We observe such reactions, e.g. H2 O2 and metal nanoparticle formation, at rates that are much higher than reported elsewhere. Since the isolated droplet radius is greater than Debye lengths and mean free paths, we have an opportunity to directly compare, for the first time, long-standing collisional probe theories in this important regime. We measure a lower bound average charge of >1E5 electrons on a 13um droplet. Simulations of unipolar corona charging for this size predict 1E3 electrons. A Comsol-based drift-diffusion model is currently under development and so far experiment and theory match within 1 order of magnitude but improvements in measurement technique are in progress. Funding from EPSRC acknowledged (Grants EP/K006088/1 and EP/K006142/1).

  16. Modeling of Coalescence and Separation of Liquid Droplets During Solidification of Immiscible Alloys

    Institute of Scientific and Technical Information of China (English)

    Lirong; Tong; Nagy; El-Kaddah

    2002-01-01

    Directional solidification methods are being used f or in-situ production of metallic immiscible composites. A quantitative understa nding of the dynamic behavior and growth kinetics of the nucleated second phase during solidification is necessary to produce homogeneous dispersion in solidifi ed composites. This paper presents a mathematical model for describing the grow th of nucleated dispersed phase in the two-liquid phase region ahead of the sol idification front and the entrapment of these droplets...

  17. Two-frequency forcing of droplet rebounds on a liquid bath

    Science.gov (United States)

    Sampara, Naresh; Gilet, Tristan

    2016-11-01

    Droplets can bounce indefinitely on a liquid bath vertically vibrated in a sinusoidal fashion. We here present experimental results that extend this observation to forcing signals composed of a combination of two commensurable frequencies. The Faraday and Goodridge thresholds are characterized. Then a number of vertical bouncing modes are reported, including walkers. The vertical motion can become chaotic, in which case the horizontal motion is an alternation of walk and stop.

  18. Characteristics of a non-volatile liquid propellant in liquid-fed ablative pulsed plasma thrusters

    Science.gov (United States)

    Ling, William Yeong Liang; Schönherr, Tony; Koizumi, Hiroyuki

    2017-02-01

    In the past several decades, the use of electric propulsion in spacecraft has experienced tremendous growth. With the increasing adoption of small satellites in the kilogram range, suitable propulsion systems will be necessary in the near future. Pulsed plasma thrusters (PPTs) were the first form of electric propulsion to be deployed in orbit, and are highly suitable for small satellites due to their inherent simplicity. However, their lifetime is limited by disadvantages such as carbon deposition leading to thruster failure, and complicated feeding systems required due to the conventional use of solid propellants (usually polytetrafluoroethylene (PTFE)). A promising alternative to solid propellants has recently emerged in the form of non-volatile liquids that are stable in vacuum. This study presents a broad comparison of the non-volatile liquid perfluoropolyether (PFPE) and solid PTFE as propellants on a PPT with a common design base. We show that liquid PFPE can be successfully used as a propellant, and exhibits similar plasma discharge properties to conventional solid PTFE, but with a mass bit that is an order of magnitude higher for an identical ablation area. We also demonstrate that the liquid PFPE propellant has exceptional resistance to carbon deposition, completely negating one of the major causes of thruster failure, while solid PTFE exhibited considerable carbon build-up. Energy dispersive X-ray spectroscopy was used to examine the elemental compositions of the surface deposition on the electrodes and the ablation area of the propellant (or PFPE encapsulator). The results show that based on its physical characteristics and behavior, non-volatile liquid PFPE is an extremely promising propellant for use in PPTs, with an extensive scope available for future research and development.

  19. Organized Assemblies of Colloids Formed at the Poles of Micrometer-Sized Droplets of Liquid Crystal

    Science.gov (United States)

    Wang, Xiaoguang; Miller, Daniel S.; de Pablo, Juan J.

    2014-01-01

    We report on the formation of organized assemblies of 1 μm-in-diameter colloids (polystyrene (PS)) at the poles of water-dispersed droplets (diameters 7 - 20 μm) of nematic liquid crystal (LC). For 4-cyano-4′-pentylbiphenyl droplets decorated with two to five PS colloids, we found 32 distinct arrangements of the colloids to form at the boojums of bipolar droplet configurations. Significantly, all but one of these configurations (a ring comprised of five PS colloids) could be mapped onto a local (non-close packed) hexagonal lattice. To provide insight into the origin of the hexagonal lattice, we investigated planar aqueous—LC interfaces, and found that organized assemblies of PS colloids did not form at these interfaces. Experiments involving the addition of salts revealed that a repulsive interaction of electrostatic origin prevented formation of assemblies at planar interfaces, and that regions of high splay near the poles of the LC droplets generated cohesive interactions between colloids that could overcome the repulsion. Support for this interpretation was obtained from a model that included (i) a long-range attraction between adsorbed colloids and the boojum due to the increasing rate of strain (splay) of LC near the boojum (splay attraction), (ii) an attractive inter-colloid interaction that reflects the quadrupolar symmetry of the strain in the LC around the colloids, and (iii) electrostatic repulsion between colloids. The model predicts that electrostatic repulsion between colloids can lead to a ∼1,000 kBT energy barrier at planar interfaces of LC films, and that the repulsive interaction can be overcome by splay attraction of the colloids to the boojums of the LC droplets. Overall, the results reported in this paper advance our understanding of the directed assembly of colloids at interfaces of LC droplets. PMID:25284139

  20. Dynamic analysis of a liquid droplet and optimization of helical angles for vortex drainage gas recovery

    Directory of Open Access Journals (Sweden)

    Xiaodong Wu

    2016-10-01

    Full Text Available Downhole vortex drainage gas recovery is a new gas production technology. So far, however, the forces and motions of liquid phase in the swirling flow field of wellbores during its field application have not been figured out. In this paper, the forces of liquid droplets in the swirling flow field of wellbores were analyzed on the basis of two-phase fluid dynamics theories. Then, the motion equations of fluid droplets along axial and radical directions were established. Magnitude comparison was performed on several typical acting forces, including Basset force, virtual mass force, Magnus force, Saffman force and Stokes force. Besides, the formula for calculating the optimal helical angle of vortex tools was established according to the principle that the vertical resultant force on fluid droplets should be the maximum. And afterwards, each acting force was comprehensively analyzed in terms of its origin, characteristics and direction based on the established force analysis model. Magnitude comparison indicates that the forces with less effect can be neglected, including virtual mass force, Basset force and convection volume force. Moreover, the vertically upward centrifugal force component occurs on the fluid droplets in swirling flow field instead of those in the conventional flow field of wellbores, which is favorable for the fluid droplets to move upward. The reliability of optimal helical angle calculation formula was verified by means of case analysis. It is demonstrated that with the decrease of well depth, the fluid-carrying capability of gas and the optimal helical angle increase. The research results in this paper have a guiding significance to the optimization design of downhole vortex tools and the field application of downhole vortex drainage gas recovery technology.

  1. Self-Assembly of Silver Nanowire Ring Structures Driven by the Compressive Force of a Liquid Droplet.

    Science.gov (United States)

    Seong, Baekhoon; Park, Hyun Sung; Chae, Ilkyeong; Lee, Hyungdong; Wang, Xiaofeng; Jang, Hyung-Seok; Jung, Jaehyuck; Lee, Changgu; Lin, Liwei; Byun, Doyoung

    2017-04-11

    In a nanowire dispersed in liquid droplets, the interplay between the surface tension of the liquid and the elasticity of the nanowire determines the final morphology of the bent or buckled nanowire. Here, we investigate the fabrication of a silver nanowire ring generated as the nanowire encapsulated inside of fine droplets. We used a hybrid aerodynamic and electrostatic atomization method to ensure the generation of droplets with scalable size in the necessary regime for ring formation. We analytically calculate the compressive force of the droplet driven by surface tension as the key mechanism for the self-assembly of ring structures. Thus, for potential large-scale manufacturing, the droplet size provides a convenient parameter to control the realization of ring structures from nanowires.

  2. Packaging a liquid metal ESD with micro-scale Mercury droplet.

    Energy Technology Data Exchange (ETDEWEB)

    Barnard, Casey Anderson

    2011-08-01

    A liquid metal ESD is being developed to provide electrical switching at different acceleration levels. The metal will act as both proof mass and electric contact. Mercury is chosen to comply with operation parameters. There are many challenges surrounding the deposition and containment of micro scale mercury droplets. Novel methods of micro liquid transfer are developed to deliver controllable amounts of mercury to the appropriate channels in volumes under 1 uL. Issues of hermetic sealing and avoidance of mercury contamination are also addressed.

  3. Liquid-grain mixing suppresses droplet spreading and splashing during impact

    CERN Document Server

    Zhao, Song-Chuan; van der Meer, Devaraj

    2016-01-01

    Would a raindrop impacting on a coarse beach behave differently from that impacting on a desert of fine sand? We study this question by a series of model experiments, where the packing density of the granular target, the wettability of individual grains, the grain size, the impacting liquid, and the impact speed are varied. We find that by increasing the grain size and/or the wettability of individual grains the maximum droplet spreading undergoes a transition from a capillary regime towards a viscous regime, and splashing is suppressed. The liquid-grain mixing is discovered to be the underlying mechanism. An effective viscosity is defined accordingly to quantitatively explain the observations.

  4. Liquid-Grain Mixing Suppresses Droplet Spreading and Splashing during Impact

    Science.gov (United States)

    Zhao, Song-Chuan; de Jong, Rianne; van der Meer, Devaraj

    2017-02-01

    Would a raindrop impacting on a coarse beach behave differently from that impacting on a desert of fine sand? We study this question by a series of model experiments, where the packing density of the granular target, the wettability of individual grains, the grain size, the impacting liquid, and the impact speed are varied. We find that by increasing the grain size and/or the wettability of individual grains the maximum droplet spreading undergoes a transition from a capillary regime towards a viscous regime, and splashing is suppressed. The liquid-grain mixing is discovered to be the underlying mechanism. An effective viscosity is defined accordingly to quantitatively explain the observations.

  5. IR spectra of water droplets in no man's land and the location of the liquid-liquid critical point.

    Science.gov (United States)

    Ni, Yicun; Skinner, J L

    2016-09-28

    No man's land is the region in the metastable phase diagram of water where it is very difficult to do experiments on liquid water because of homogeneous nucleation to the crystal. There are a number of estimates of the location in no man's land of the liquid-liquid critical point, if it exists. We suggest that published IR absorption experiments on water droplets in no man's land can provide information about the correct location. To this end, we calculate theoretical IR spectra for liquid water over a wide range of temperatures and pressures, using our E3B3 model, and use the results to argue that the temperature dependence of the experimental spectra is inconsistent with several of the estimated critical point locations, but consistent with others.

  6. IR spectra of water droplets in no man's land and the location of the liquid-liquid critical point

    Science.gov (United States)

    Ni, Yicun; Skinner, J. L.

    2016-09-01

    No man's land is the region in the metastable phase diagram of water where it is very difficult to do experiments on liquid water because of homogeneous nucleation to the crystal. There are a number of estimates of the location in no man's land of the liquid-liquid critical point, if it exists. We suggest that published IR absorption experiments on water droplets in no man's land can provide information about the correct location. To this end, we calculate theoretical IR spectra for liquid water over a wide range of temperatures and pressures, using our E3B3 model, and use the results to argue that the temperature dependence of the experimental spectra is inconsistent with several of the estimated critical point locations, but consistent with others.

  7. Use of levitating liquid micro-droplets as tracers to study the evaporation in the vicinity of the contact line

    Directory of Open Access Journals (Sweden)

    Zaitsev Dmitry

    2017-01-01

    Full Text Available Self-organization of a cloud of liquid micro-droplets into an ordered two-dimensional array, levitating over a heated layer of liquid due to upward vapor flow, has been observed in several recent experimental works. In the present paper, the levitating micro-droplet array is studied under the condition when the liquid layer ruptures and a dry spot form on the heater. It has been found, that when the levitating micro-droplets are moving from wetted heater area to dry heater area and passing over the contact line, the micro-droplets levitation height is drastically increased, which is indicative of the intensive evaporation occurring in the region of the contact line.

  8. Nucleation of liquid droplets and voids in a stretched Lennard-Jones fcc crystal.

    Science.gov (United States)

    Baidakov, Vladimir G; Tipeev, Azat O

    2015-09-28

    The method of molecular dynamics simulation has been used to investigate the phase decay of a metastable Lennard-Jones face-centered cubic crystal at positive and negative pressures. It is shown that at high degrees of metastability, crystal decay proceeds through the spontaneous formation and growth of new-phase nuclei. It has been found that there exists a certain boundary temperature. Below this temperature, the crystal phase disintegrates as the result of formation of voids, and above, as a result of formation of liquid droplets. The boundary temperature corresponds to the temperature of cessation of a crystal-liquid phase equilibrium when the melting line comes in contact with the spinodal of the stretched liquid. The results of the simulations are interpreted in the framework of classical nucleation theory. The thermodynamics of phase transitions in solids has been examined with allowance for the elastic energy of stresses arising owing to the difference in the densities of the initial and the forming phases. As a result of the action of elastic forces, at negative pressures, the boundary of the limiting superheating (stretching) of a crystal approaches the spinodal, on which the isothermal bulk modulus of dilatation becomes equal to zero. At the boundary of the limiting superheating (stretching), the shape of liquid droplets and voids is close to the spherical one.

  9. Size prediction of κ-carrageenan droplets formed in co-flowing immiscible liquid

    Institute of Scientific and Technical Information of China (English)

    Jun-Yee Leong; Tek-Kaun Lim; Ravindra Pogaku; Eng-Seng Chan

    2011-01-01

    The formation of κ-carrageenan droplets in channel emulsification was experimentally investigated.The dispersed phase was vertically injected into co-flowing immiscible palm oil in the direction of gravity.This study focused on predicting κ-carrageenan drop size using force balance analysis.The force balance model considers the interfacial tension to be the solitary attaching force,while a combination of the drag force from the co-flowing palm oil and the body force of the extruding κ-carrageenan liquid act as the detaching forces.The conventional model gave poor predictions for droplet size,with an average relative deviation of 23%.This large deviation could be attributed to necking phenomena and an underestimation of the drag force generated on the shear-thinning κ-carrageenan solution.By incorporating correction factors,the average relative deviation of the force balance model dropped to 4%.

  10. Injectable Spontaneous Generation of Tremendous Self-Fueled Liquid Metal Droplet Motors in a Moment

    CERN Document Server

    Yao, You-You; Liu, Jing

    2015-01-01

    Micro motors that could run in liquid environment is very important for a variety of practices such as serving as pipeline robot, soft machine, drug delivery, or microfluidics system etc. However, fabrication of such tiny motors is generally rather time and cost consumptive and has been a tough issue due to involve too many complicated procedures and tools. Here, we show a straightforward injectable way for spontaneously generating autonomously running soft motors in large quantity. A basic fabrication strategy thus enabled is established and illustrated. It was found that, injecting the GaIn alloy pre-fueled with aluminum into electrolyte would automatically split in seconds into tremendous droplet motors swiftly running here and there. The driving force originated from the galvanic cell reaction among alloy, aluminum and surrounding electrolyte which offers interior electricity and hydrogen gas as motion power. This finding opens the possibility to develop injectable tiny-robots, droplet machines or microfl...

  11. Modeling the Maximum Spreading of Liquid Droplets Impacting Wetting and Nonwetting Surfaces.

    Science.gov (United States)

    Lee, Jae Bong; Derome, Dominique; Guyer, Robert; Carmeliet, Jan

    2016-02-09

    Droplet impact has been imaged on different rigid, smooth, and rough substrates for three liquids with different viscosity and surface tension, with special attention to the lower impact velocity range. Of all studied parameters, only surface tension and viscosity, thus the liquid properties, clearly play a role in terms of the attained maximum spreading ratio of the impacting droplet. Surface roughness and type of surface (steel, aluminum, and parafilm) slightly affect the dynamic wettability and maximum spreading at low impact velocity. The dynamic contact angle at maximum spreading has been identified to properly characterize this dynamic spreading process, especially at low impact velocity where dynamic wetting plays an important role. The dynamic contact angle is found to be generally higher than the equilibrium contact angle, showing that statically wetting surfaces can become less wetting or even nonwetting under dynamic droplet impact. An improved energy balance model for maximum spreading ratio is proposed based on a correct analytical modeling of the time at maximum spreading, which determines the viscous dissipation. Experiments show that the time at maximum spreading decreases with impact velocity depending on the surface tension of the liquid, and a scaling with maximum spreading diameter and surface tension is proposed. A second improvement is based on the use of the dynamic contact angle at maximum spreading, instead of quasi-static contact angles, to describe the dynamic wetting process at low impact velocity. This improved model showed good agreement compared to experiments for the maximum spreading ratio versus impact velocity for different liquids, and a better prediction compared to other models in literature. In particular, scaling according to We(1/2) is found invalid for low velocities, since the curves bend over to higher maximum spreading ratios due to the dynamic wetting process.

  12. Generation of droplets via oscillations of a tapered capillary tube filled with low-viscosity liquids

    Science.gov (United States)

    Mao, Xinyu; Zhang, Lei; Zhao, Zhenhao; Lin, Feng

    2017-06-01

    Droplet formation via the oscillations of a tapered capillary tube is experimentally and numerically investigated using incompressible, low-viscosity Newtonian liquids. As in many other common methods of droplet generation, this technique features a transient flow that is directed out of a nozzle. However, due to the interactions of the oscillations, the tube, and the fluids, the flow rate upstream of the nozzle cannot be directly obtained. In this study, the motion of the tube is measured under the activation of a specific waveform, and the flow inside the tube and drop formation are further numerically studied using a non-inertial reference system in which the tube is stationary. The mechanism of ejection is quantitatively explained by analyzing the temporal variation in the velocity and pressure distributions inside the tube. The dynamics of drop formation, the drop velocity, and the drop radius are studied as functions of the dimensionless groups that govern the problem, including the Ohnesorge number Oh, the Weber number We, the gravitational Bond number G, and various length scale ratios. The results show that droplets are generated due to the inertia of the liquid and velocity amplification in the tapered section. By influencing the balance between the viscous effect and inertial effect of the liquid along the entire tube, the length scale ratios affect the evolution of the transient flow at the nozzle and eventually influence the drop radius and velocity. For liquids with viscosities close to that of pure water, the critical Reynolds number, at which a drop can be generated, linearly depends on the Z number (the reciprocal of Oh) at the nozzle.

  13. Liquidity, Volatility and Stock Price Adjustment: Evidence from Seasoned Equity Offerings in an Emerging Market

    OpenAIRE

    Chia-Cheng Ho; Chin-Chuan Lee; Chien-Ting Lin; C. Edward Wang

    2005-01-01

    Using data from the Taiwanese stock market, an emerging market, this paper documents positive changes in liquidity and volatility around seasoned equity offerings (SEOs). These findings are consistent with the uncertain signal hypothesis that investors with diverse views on the information content of SEOs are likely to induce larger trading activity and subsequent higher stock return volatility. We also provide direct evidence that changes in liquidity is positively associated with stock pric...

  14. Sequential operation droplet array: an automated microfluidic platform for picoliter-scale liquid handling, analysis, and screening.

    Science.gov (United States)

    Zhu, Ying; Zhang, Yun-Xia; Cai, Long-Fei; Fang, Qun

    2013-07-16

    This contribution describes a sequential operation droplet array (SODA) system, a fully automated droplet-based microfluidic system capable of performing picoliter-scale liquid manipulation, analysis, and screening. The SODA system was built using a tapered capillary-syringe pump module and a two-dimensional (2D) oil-covered droplet array installed on an x-y-z translation stage. With the system, we developed a novel picoliter-scale droplet depositing technique for forming a 2D picoliter-droplet array. On this basis, an automated droplet manipulation method with picoliter precision was established using the programmable combination of the capillary-based liquid aspirating-depositing and the moving of the oil-covered droplet array, the so-called "aspirating-depositing-moving" (ADM) method. Differing from the previously reported droplet systems based on microchips, microcapillaries, or digital microfluidics, this method can achieve complete and flexible droplet manipulations, including droplet assembling, generation, indexing, transferring, splitting, and fusion in the picoliter range, endowing the present system with ultralow sample/reagent consumptions and substantial versatility in analysis and screening for multiple different samples. To demonstrate its feasibility and versatility, we applied the SODA system in multiple experiments required in drug screening, including the screening of inhibitors for capases-1 from a chemical library, the measurement of IC50 values for the identified inhibitors, and the screening of the synergistic effect of multiple inhibitors. In the experiments, the consumptions of samples and reagents are only 60-180 pL for each droplet microreactor, which are commonly 3-5 orders of magnitude lower than those of conventional multiwell plate systems, and 1-2 orders of magnitude lower than other droplet-based microfluidic systems for multiple sample screening. The ability of the SODA system in performing complicated and multistep droplet

  15. Milking liquid nano-droplets by an IR laser: a new modality for the visualization of electric field lines

    Science.gov (United States)

    Vespini, Veronica; Coppola, Sara; Grilli, Simonetta; Paturzo, Melania; Ferraro, Pietro

    2013-04-01

    Liquid handling at micron- and nano-scale is of paramount importance in many fields of application such as biotechnology and biochemistry. In fact, the microfluidics technologies play an important role in lab-on-a-chip devices and, in particular, the dispensing of liquid droplets is a required functionality. Different approaches have been developed for manipulating, dispensing and controlling nano-droplets under a wide variety of configurations. Here we demonstrate that nano-droplets can be drawn from liquid drop or film reservoirs through a sort of milking effect achieved by the absorption of IR laser radiation into a pyroelectric crystal. The generation of the pyroelectric field induced by the IR laser is calculated numerically and a specific experiment has been designed to visualize the electric field stream lines that are responsible for the liquid milking effect. The experiments performed are expected to open a new route for the visualization, measure and characterization procedures in the case of electrohydrodynamic applications.

  16. Wicking/absorption of a liquid droplet into nano-porous fibers

    Science.gov (United States)

    Callegari, Gerardo; Qi, Jia; Ribaudo, Anthony

    2010-11-01

    Contrary to what happens on a planar wetting substrate, a droplet sitting on a wetting solid smooth fiber can stay without spreading. In a fiber with parallel grooves, the liquid wicks into the channels. Here, we are interested in characterizing nano-porous fibers where the wicking front propagates through longitudinal micron size grooves and the liquid also penetrates inside the nano-porous fiber with tuned pore size in the range of tens of nm. The difference in groove to pore sizes produces a faster longitudinal than transversal liquid movement, allowing for model simplifications and leading to analytical solutions for the model proposed, that couples absorption with wicking dynamics. Experimental data on the droplet shape/volume together with front propagation are compared with the solution of the model to extract information of the fiber's structure which is compared with SEM images of the cross-sections of the fibers. The nano-porous composite fibers produced by coagulation wet spinning, were proposed to be used as bio-sensing device, drug delivery systems and neuron-implantable electrodes.

  17. Large scale molecular dynamics simulations of a liquid crystalline droplet with fast multipole implementations

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Z.; Lupo, J.; Patnaik, S.S.; McKenney, A.; Pachter, R.

    1999-07-01

    The Fast Multipole Method (FMM) offers an efficient way (order O(N)) to handle long range electrostatic interactions, thus enabling more realistic molecular dynamics simulations of large molecular systems. The performance of the fast molecular dynamics (FMD) code, a parallel MD code being developed in the group, using the three-dimensional fast multipole method, shows a good speedup. The application to the full atomic-scale molecular dynamics simulation of a liquid crystalline droplet of 4-n-pentyl-4{prime}-cyanobiphenyl (5CB) molecules, of size 35,872 atoms, shows strong surface effects on various orientational order parameters.

  18. Mean droplet size and local velocity in horizontal isothermal free jets of air and water, respectively, viscous liquid in quiescent ambient air

    Energy Technology Data Exchange (ETDEWEB)

    Al Rabadi, S.; Friedel, L. [Fluid Mechanics Institute, Technical University of Hamburg-Harburg (Germany); Al Salaymeh, A. [Mechanical Engineering Department, University of Jordan (Jordan)

    2007-01-15

    Measurements using two-dimensional Phase Doppler Anemometry as well as high speed cinematography in free jets at several nozzle exit pressures and mass flow rates, show that the Sauter mean droplet diameter decreases with increasing air and liquid-phase mass flow ratio due to the increase of the air stream impact on the liquid phase. This leads to substantial liquid fragmentation, respectively primary droplet breakup, and hence, satellite droplet formation with small sizes. This trend is also significant in the case of a liquid viscosity higher than that of water. The increased liquid viscosity stabilizes the droplet formation and breakup by reducing the rate of surface perturbations and consequently droplet distortions, ultimately also leading, in total, to the formation of smaller droplets. The droplet velocity decreases with the nozzle downstream distance, basically due to the continual air entrainment and due to the collisions between the droplets. The droplet collisions may induce further liquid fragmentation and, hence, formation of a number of relatively smaller droplets respectively secondary breakup, or may induce agglomeration to comparatively larger liquid fragments that may rain out of the free jet. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  19. Dynamics and heat and mass transfer under spreading of liquid-droplet aviation fuel in the atmosphere

    Science.gov (United States)

    Arkhipov, Vladimir; Zharova, Irina; Kozlov, Eugene; Tkachenko, Aleksey

    2014-08-01

    A physical-mathematical model of dynamics and heat and mass transfer during spreading of liquid-droplet aviation fuel in the atmosphere is presented. The optimal emergency discharge height of kerosene for different Russian regions was evaluated based on the proposed mathematical model. The developed model can be used to select the height limit of reset kerosene, guaranteeing complete evaporation of the droplets in the atmosphere to the different aircraft velocities.

  20. Swimming Droplets

    Science.gov (United States)

    Maass, Corinna C.; Krüger, Carsten; Herminghaus, Stephan; Bahr, Christian

    2016-03-01

    Swimming droplets are artificial microswimmers based on liquid droplets that show self-propelled motion when immersed in a second liquid. These systems are of tremendous interest as experimental models for the study of collective dynamics far from thermal equilibrium. For biological systems, such as bacterial colonies, plankton, or fish swarms, swimming droplets can provide a vital link between simulations and real life. We review the experimental systems and discuss the mechanisms of self-propulsion. Most systems are based on surfactant-stabilized droplets, the surfactant layer of which is modified in a way that leads to a steady Marangoni stress resulting in an autonomous motion of the droplet. The modification of the surfactant layer is caused either by the advection of a chemical reactant or by a solubilization process. Some types of swimming droplets possess a very simple design and long active periods, rendering them promising model systems for future studies of collective behavior.

  1. Nanofocusing, shadowing, and electron mean free path in the photoemission from aerosol droplets

    CERN Document Server

    Signorell, Ruth; Yoder, Bruce L; Bodi, Andras; Chasovskikh, Egor; Lang, Lukas; Luckhaus, David

    2016-01-01

    Angle-resolved photoelectron spectroscopy of aerosol droplets is a promising method for the determination of electron mean free paths in liquids. It is particularly attractive for volatile liquids, such as water. Here we report the first angle-resolved photoelectron images of droplets with defined sizes, viz. of water, glycerol, and dioctyl phthalate droplets. We present an approach that allows one to gradually vary the conditions from dominant shadowing to dominant nanofocusing to optimize the information content contained in the photoelectron images. Example simulations of water droplet photoelectron images and preliminary data for electron mean free paths for liquid water at low kinetic energy (<3eV) are provided.

  2. Determination of the solubility of low volatility liquid organic compounds in water using volatile-tracer assisted headspace gas chromatography.

    Science.gov (United States)

    Zhang, Shu-Xin; Chai, Xin-Sheng; Barnes, Donald G

    2016-02-26

    This study reports a new headspace gas chromatographic method (HS-GC) for the determination of water solubility of low volatility liquid organic compounds (LVLOs). The HS-GC analysis was performed on a set of aqueous solutions containing a range of concentrations of toluene-spiked (as a tracer) LVLOs, from under-saturation to over-saturation. A plot of the toluene tracer GC signal vs. the concentration of the LVLO results in two lines of different slopes that intersect at the concentration corresponding to the compound's solubility in water. The results showed that the HS-GC method has good precision (RSD solubility of LVLOs at elevated temperatures. This approach should be of special interest to those concerned about the impact of the presence of low-volatility organic liquids in waters of environmental and biological systems.

  3. Modeling of movement of liquid metal droplets driven by an electric field.

    Science.gov (United States)

    Wang, M F; Jin, M J; Jin, X J; Zuo, S G

    2017-07-19

    The motion of liquid metal has potential applications ranging from micro-pumps and self-fueled motors to rapid cooling and drug delivery. In this study, we systematically investigate the effects of the radius of LMDs (liquid metal droplets), the concentration of electrolyte solution and the applied electric field on the movement behavior of LMDs experimentally. The research also explains the experimental phenomenon with an innovative modeling analysis, which combines pertinent forces (i.e., the driving force induced by the gradient of surface tension, the viscous friction between the droplet and its surrounding electrolyte, and the friction between the droplet and the substrate). The model is highly consistent with the rule that LMDs with a larger radius need smaller actuation voltage, and we can predict the critical voltages of LMDs with r = 2-4 mm through Velectrode = 30.62/r(2) - 0.998, which is obtained by fitting the parameters. We also obtain the model V = [-66.2Vr(2)/(259.7-17.7) + 1.253]r(2), which can predict the average velocity-voltage lines of LMDs with r = 3, 3.5 mm and V = 1-13 V. In addition, the velocity increases upon increasing the concentration of the electrolyte solution from 0.1 mol L(-1) to 0.3 mol L(-1), and tends to be stable at more than 0.3 mol L(-1) owing to the saturation of the EDL (electrical double layer) charge density. Additionally, we discuss the phenomenon of elongation during movement that occurs upon increasing the size of the LMDs. If the size of the LMDs continues to increase, the reverse movement from the anode to the cathode can occur, and the phenomenon can also be explained by the model.

  4. Surface-tension-driven convection in pure liquid layers evaporating into ambient air: influence of liquid volatility

    Science.gov (United States)

    Chauvet, Fabien; Dehaeck, Sam; Colinet, Pierre

    2011-11-01

    The spontaneous surface-tension-driven convective patterns induced by evaporation of a pure liquid layer are studied experimentally. A volatile liquid layer placed in a cylindrical container is left free to evaporate into air at rest under ambient conditions. The thermal dynamics of the evaporating liquid layer is visualized using an infrared camera. Evaporation rate and liquid thickness are measured by weighting. We focus on the transition between the convective state and the conductive state appearing at a certain instant during the drying of the liquid layer. The critical Marangoni number Mac associated to this transition is estimated from evaporation rate and layer thickness measurements at this instant. The effect of the evaporation rate on Mac and kc (the critical wavenumber) has been investigated by changing the container height and, separately, the effect of the liquid volatility has been studied by using different liquids. Interestingly, it appears that Mac does not depend on the evaporation rate while it depends strongly on the liquid volatility. Given the typical uncertainties associated with liquid properties, a quite reasonable agreement is found with a ``one-sided'' linear stability analysis of this problem. Supported by ESA & BELSPO, by the EU, by ULB, and by FRS - FNRS.

  5. Intensive evaporation and boiling of a heterogeneous liquid droplet with an explosive disintegration in high-temperature gas area

    Directory of Open Access Journals (Sweden)

    Piskunov Maxim V.

    2016-01-01

    Full Text Available The using of the high-speed (not less than 105 frames per second video recording tools (“Phantom” and the software package ("TEMA Automotive" allowed carrying out an experimental research of laws of intensive vaporization with an explosive disintegration of heterogeneous (with a single solid nontransparent inclusion liquid droplet (by the example of water in high-temperature (500-800 K gases (combustion products. Times of the processes under consideration and stages (liquid heat-up, evaporation from an external surface, bubble boiling at internal interfaces, growth of bubble sizes, explosive droplet breakup were established. Necessary conditions of an explosive vaporization of a heterogeneous droplet were found out. Mechanisms of this process and an influence of properties of liquid and inclusion material on them were determined.

  6. On the Dynamic Behavior of a Liquid Droplet Impacting upon a Wall Having Obstacles

    Directory of Open Access Journals (Sweden)

    Boseon Kang

    2015-01-01

    Full Text Available In this paper, the effects of a step edge and a stationary droplet on the dynamic behavior of a droplet impacting upon a wall are experimentally studied. The main parameters were the distance from the step edge to the center of the impacting droplet and the center-to-center distance between the stationary and impacting droplets. Photographic images showed the coalescence dynamics, shape evolution and contact line movement of the impacting droplet. The spread length is presented for the step edge and two coalescing droplets. The droplets exhibited much different dynamic behavior depending on the location of the step edge. The momentum of the impacting droplet was better transferred to the stationary droplet as the center-to-center distance between the two droplets was reduced, resulting in more spreading of the coalescing droplet.

  7. Application of linear polarized light for the discrimination of frozen and liquid droplets in ice nucleation experiments

    Directory of Open Access Journals (Sweden)

    T. Clauss

    2012-08-01

    Full Text Available We report on the development and test results of the new optical particle counter TOPS-Ice (Thermostabilized Optical Particle Spectrometer for the detection of Ice particles. The instrument uses measurements of the depolarized component of light scattered by single particles into the near-forward direction (42.5° ± 12.7° to distinguish between spherical and non-spherical particles. This approach allows the differentiation between liquid water droplets (spherical and ice particles (non-spherical having similar volume equivalent sizes and therefore can be used to determine the fraction of frozen droplets in a typical immersion freezing experiment. We show that the numerical simulation of the light scattering on non-spherical particles (ellipsoids in random orientation with account for the actual scattering geometry used in the instrument supports the validity of the approach, even though the cross polarized component of the light scattered by spherical droplets is not vanishing in this scattering angle. For the separation of the ice particle mode from the liquid droplet mode, we use the width of the pulse detected in the depolarization channel instead of the pulse height. Exploiting the intrinsic relationship between pulse height and pulse width for Gaussian pulses allows us to calculate the fraction of frozen droplets even if the liquid droplet mode dominates the particle ensemble. We present test results obtained with TOPS-Ice in the immersion freezing experiments at the laminar diffusion chamber LACIS (Leipzig Aerosol Cloud Interaction Simulator and demonstrate the excellent agreement with the data obtained in the same experiment with a different optical instrument. Finally, the advantages of using the cross-polarized light measurements for the differentiation of liquid and frozen droplets in the realistic immersion freezing experiments are discussed.

  8. Application of linear polarized light for the discrimination of frozen and liquid droplets in ice nucleation experiments

    Directory of Open Access Journals (Sweden)

    T. Clauss

    2013-04-01

    Full Text Available We report on the development and test results of the new optical particle counter TOPS-Ice (Thermo-stabilized Optical Particle Spectrometer for the detection of Ice. The instrument uses measurements of the cross-polarized scattered light by single particles into the near-forward direction (42.5° ± 12.7° to distinguish between spherical and non-spherical particles. This approach allows the differentiation between liquid water droplets (spherical and ice particles (non-spherical having similar volume-equivalent sizes and therefore can be used to determine the fraction of frozen droplets in a typical immersion freezing experiment. We show that the numerical simulation of the light scattered on non-spherical particles (spheroids in random orientation considering the actual scattering geometry used in the instrument supports the validity of the approach, even though the cross-polarized component of the light scattered by spherical droplets does not vanish in this scattering angle. For the separation of the ice particle mode from the liquid droplet mode, we use the width of the pulse detected in the depolarization channel instead of the pulse height. Exploiting the intrinsic relationship between pulse height and pulse width for Gaussian pulses allows us to calculate the fraction of frozen droplets even if the liquid droplet mode dominates the particle ensemble. We present test results obtained with TOPS-Ice in the immersion freezing experiments at the laminar diffusion chamber LACIS (Leipzig Aerosol Cloud Interaction Simulator and demonstrate the excellent agreement with the data obtained in similar experiments with a different optical instrument. Finally, the advantages of using the cross-polarized light measurements for the differentiation of liquid and frozen droplets in the realistic immersion freezing experiments are discussed.

  9. Electronic absorption spectroscopy of PAHs in supersonic jets and ultracold liquid helium droplets

    Science.gov (United States)

    Huisken, Friedrich; Staicu, Angela; Krasnokutski, Serge; Henning, Thomas

    Neutral and cationic polycyclic aromatic hydrocarbons (PAHs) are discussed as possible carriers of the diffuse interstellar bands (DIBs), still unassigned astrophysical absorption features observed in the spectra of reddened stars (Salama et al. 1999). Despite the importance of this class of molecules for astrophysics and nanophysics (PAHs can be regarded as nanoscale fragments of a sheet of graphite), the spectroscopic characterization of PAHs under well-defined conditions (low temperature and collision-free environment) has remained a challenge. Recently we have set up a cavity ring-down spectrometer combined with a pulsed supersonic jet expansion to study neutral and cationic PAHs under astrophysical conditions. PAHs studied so far include the neutral molecules anthracene (Staicu et al. 2004) and pyrene (Rouillé et al. 2004) as well as the cationic species naphthalene+ and anthracene+ (Sukhorukov et al. 2004). Employing another molecular beam apparatus, the same molecules (except of the cationic species) were also studied in liquid helium droplets (Krasnokutski et al. 2005, Rouillé et al. 2004). This novel technique combines several advantages of conventional matrix spectroscopy with those of gas phase spectroscopy. Notable advantages are the possibility to study molecules with low vapor pressure and to use a mass spectrometer facilitating spectral assignments. The most recent studies were devoted to phenanthrene and the more complicated (2,3)-benzofluorene. These molecules were investigated in the gas phase by cavity ring-down spectroscopy and in liquid helium droplets using depletion spectroscopy. For benzofluorene the present studies constitute the first reported measurements both in the gas phase and in helium droplets. The origin of the S1 ← S0 gas phase transition could be located at 29 894.3 cm-1, and a series of vibronic bands was recorded below 31 500 cm-1. In contrast to previously studied PAHs, the shift induced by the helium droplets was very

  10. Coupling liquid chromatography/mass spectrometry detection with microfluidic droplet array for label-free enzyme inhibition assay.

    Science.gov (United States)

    Wang, Xiu-Li; Zhu, Ying; Fang, Qun

    2014-01-07

    In this work, the combination of droplet-based microfluidics with liquid chromatography/mass spectrometry (LC/MS) was achieved, for providing a fast separation and high-information-content detection method for the analysis of nanoliter-scale droplets with complex compositions. A novel interface method was developed using an oil-covered droplet array chip to couple with an LC/MS system via a capillary sampling probe and a 4 nL injection valve without the need of a droplet extraction device. The present system can perform multistep operations including parallel enzyme inhibition reactions in nanoliter droplets, 4 nL sample injection, fast separation with capillary LC, and label-free detection with ESI-MS, and has significant flexibility in the accurate addressing and sampling of droplets of interest on demand. The system performance was evaluated using angiotensin I and angiotensin II as model samples, and the repeatabilities of peak area for angiotensin I and angiotensin II were 2.7% and 7.5% (RSD, n = 4), respectively. The present system was further applied to the screening for inhibitors of cytochrome P450 (CYP1A2) and measurement of the IC50 value of the inhibitor. The sample consumption for each droplet assay was 100 nL, which is reduced 10-100 times compared with conventional 384-multi-well plate systems usually used in high-throughput drug screening.

  11. [Development of a droplet-interfaced high performance liquid chromatography-capillary electrophoresis two dimensional separation platform].

    Science.gov (United States)

    Ye, Linquan; Wu, Qingshi; Dai, Simin; Xiao, Zhiliang; Zhang, Bo

    2011-09-01

    Proteomics demands high resolution multidimensional separation techniques due to its extremely high complexity. Droplet microfluidics provides a series of unique advantages in manipulating micro and nanolitre samples, such as micro-volume operation, limited diffusion and none cross-contaminating, therefore has the potential to be an ideal interface strategy for multidimensional separation. Using the microchips of different structures, functions such as "droplet generation" and "oil depletion" can be realized. Based on these functions, samples can be transferred from continuous flow to segmented flow and then back to continuous flow. In this way, different separation modes can be combined. In this study, droplet technology was utilized as a novel interface strategy in combining high performance liquid chromatography (HPLC) and capillary electrophoresis (CE). Using tryptic peptides mixture as a sample, this two dimensional HPLC-CE system provided high resolution separation with a peak capacity over 3000. This proof-of-principle study has demonstrated the usefulness of droplet interface technology in multidimensional separation.

  12. Droplet phase characteristics in liquid-dominated steam--water nozzle flow

    Energy Technology Data Exchange (ETDEWEB)

    Alger, T.W.

    1978-08-09

    An experimental study was undertaken to determine the droplet size distribution, the droplet spatial distribution and the mean droplet velocity in low-quality, steam-water flow from a rectangular cross-section, converging-diverging nozzle. A unique forward light scattering technique was developed for droplet size distribution measurements. Droplet spatial variations were investigated using light transmission measurements, and droplet velocities were measured with a laser-Doppler velocimeter (LDV) system incorporating a confocal Fabry-Perot interferometer. Nozzle throat radius of curvature and height were varied to investigte their effects on droplet size. Droplet size distribution measurements yielded a nominal Sauter mean droplet diameter of 1.7 ..mu..m and a nominal mass-mean droplet diameter of 2.4 ..mu..m. Neither the throat radius of curvature nor the throat height were found to have a significant effect upon the nozzle exit droplet size. The light transmission and LDV measurement results confirmed both the droplet size measurements and demonstrated high spatial uniformity of the droplet phase within the nozzle jet flow. One-dimensional numerical calculations indicated that both the dynamic breakup (thermal equilibrium based on a critical Weber number of 6.0) and the boiling breakup (thermal nonequilibrium based on average droplet temperature) models predicted droplet diameters on the order of 7.5 ..mu..m, which are approximately equal to the maximum stable droplet diameters within the nozzle jet flow.

  13. Modeling Droplet Motion on Liquid-Infused Surface Using Lattice Boltzmann Method

    Science.gov (United States)

    Zhao, Mingfei; Yong, Xin

    2015-11-01

    Understanding self-assembly of nanoparticles driven by the evaporation of the particle-covered sacrificial liquid mass dispensed on a solid substrate is of technological important for various printing and deposition techniques. Although the convective deposition of suspended nanoparticles (known as the coffee ring effect) has been studied extensively, the self-assembly of nanoparticles directly delivered to the liquid-gas interface remains unexplored. In this work, we develop a hybrid model that combines free-energy multiphase LBM with Lagrangian particle tracking method to reveal the complex interplay between nanoparticles, convective flow in liquid, and the dynamics of three-phase contact line on the substrate. We first verify our computational model using existing computational and experimental results. We then investigate the evaporation phenomena of a particle-covered droplet with specified nanoparticle distributions and wetting properties. By controlling the boundary conditions, we can implement desired contact angle hysteresis on the substrate that matches experiment observations. This study provides a theoretical framework to explore the dynamics of nanoparticle self-assembly at evaporating liquid-vapor interfaces.

  14. Dispersive liquid-liquid microextraction based on solidification of floating organic droplets followed by high performance liquid chromatography for the determination of duloxetine in human plasma.

    Science.gov (United States)

    Suh, Joon Hyuk; Lee, Yun Young; Lee, Hee Joo; Kang, Myunghee; Hur, Yeoun; Lee, Sun Neo; Yang, Dong-Hyug; Han, Sang Beom

    2013-03-05

    A novel dispersive liquid-liquid microextraction method based on solidification of floating organic droplets (DLLME-SFO) technique was developed for the determination of duloxetine in human plasma samples by high performance liquid chromatography with fluorescence detection (HPLC-FLD). During the extraction procedure, plasma protein was precipitated by using a mixture of zinc sulfate solution and acetonitrile. After the protein precipitation step, duloxetine in an alkaline sample solution was quickly extracted by DLLME-SFO with 50 μL of 1-undecanol (extractant). Disperser was unnecessary because the small amount of remaining acetonitrile, which acts as a protein precipitating reagent, was also employed as a disperser; therefore, organic solvent consumption was reduced as much as possible. The emulsion was centrifuged and then fine droplets were floated to the top of the sample solution. The floated droplets were solidified in an ice bath and easily transferred. Various DLLME-SFO parameters such as extractant type, extractant amount, ionic strength, pH and extraction time were optimized. The chromatographic separation of duloxetine was carried out using ethanol as mobile phase. Validation of the method was performed with respect to linearity, intra- and inter-day accuracy and precision, limit of quantification (LOQ), and recovery. Calibration curves for duloxetine showed good linearity with correlation coefficients (r²) higher than 0.99. The method showed good precision and accuracy, with intra- and inter-assay coefficients of variation less than 15% (LOQ: less than 20%) at all concentrations. The recovery was carried out following the standard addition procedure with yields ranging from 59.6 to 65.5%. A newly developed environmentally friendly method was successfully applied to the pharmacokinetic study of duloxetine in human plasma and was shown to be an alternative green approach compared with the conventional solid-phase microextraction (SPME) and dispersive

  15. Three-dimensional simulation of impingement of a liquid droplet on a flat surface in the Leidenfrost regime

    Science.gov (United States)

    Ge, Yang; Fan, L.-S.

    2005-02-01

    The hydrodynamics and heat transfer phenomena of a liquid droplet impacting upon a hot flat surface are analyzed based on three-dimensional (3D) numerical simulation considering film-boiling behavior. The 3D level-set method is employed to portray the droplet surface variation during its deformation. The governing equations for the droplet and the surrounding gas phase are solved utilizing the finite-volume method with the arbitrary Lagrangian Eulerian technique. To account for the lubrication resistant effects of the vapor cushion formed by the film-boiling evaporation, a separate vapor flow model is developed to simulate the pressure and velocity distribution along the vapor layer between the droplet and the surface. The temperature fields in all phases and the local evaporation rate on the droplet surface are determined by using a full field heat transfer model. Both the water and n-heptane droplets impacting on the solid wall with different Weber numbers are investigated. The comparisons of the simulation results with the experimental results reported in the literatures are made to substantiate the model presented in this study. Specially, the spreading and recoiling motions of the impacting droplets are reproduced accurately for a wide range of the Weber number. The oscillation of the thickness of the vapor layer and the temperature distribution across the interface are also calculated and compared favorably with the experimental results. As the Weber number increases, the extent of the droplet spreading increases, but the residence time of the droplet on the surface is almost unchanged. Compared to the saturated impacts, the subcooled impact yields a thinner vapor layer and a higher heat transfer rate.

  16. Drying, phase separation, and deposition in droplets of sunset yellow chromonic liquid crystal

    Science.gov (United States)

    Gross, Adam; Davidson, Zoey S.; Huang, Yongyang; Still, Tim; Zhou, Chao; Yodh, A. G.

    We investigate the drying process and the final deposition patterns of multi-phase sessile droplets containing aqueous lyotropic chromonic liquid crystal (LC). The experiments employ a variety of optical techniques including profilometry, polarization optical microscopy and optical coherence microscopy. An unusual hierarchical LC assembly is observed during drying; in particular, LC mesogens are first formed at the start of drying and then compartments of isotropic, nematic and columnar phases arise. Nonuniform evaporation creates concentration gradients in droplets such that LC phases emerge from the outer edge of the drop and advance to the center over the course of drying. Distinct outward flows associated with the ``coffee-ring effect'' are seen initially, but the assembly of the mesogens creates viscosity, density, and surface tension gradients that effectively introduce new convective flows and complex LC phase boundaries within the drop. Finally, we show that the final deposit shape of chromonic materials changes with rate of evaporation. We gratefully acknowledge financial support through NSF DMR12-05463, MRSEC DMR11-20901, NASA NNX08AO0G, and NSF DBI-1455613.

  17. Generation of Oil Droplets in a Non-Newtonian Liquid Using a Microfluidic T-Junction

    Directory of Open Access Journals (Sweden)

    Enrico Chiarello

    2015-11-01

    Full Text Available We have compared the formation of oil drops in Newtonian and non-Newtonian fluids in a T-junction microfluidic device. As Newtonian fluids, we used aqueous solutions of glycerol, while as non-Newtonian fluids we prepared aqueous solutions of xanthan, a stiff rod-like polysaccharide, which exhibit strong shear-thinning effects. In the squeezing regime, the formation of oil droplets in glycerol solutions is found to scale with the ratio of the dispersed flow rate to the continuous one and with the capillary number associated to the continuous phase. Switching to xanthan solutions does not seem to significantly alter the droplet formation process. Any quantitative difference with respect to the Newtonian liquid can be accounted for by a suitable choice of the capillary number, corresponding to an effective xanthan viscosity that depends on the flow rates. We have deduced ample variations in the viscosity, on the order of 10 and more, during normal operation conditions of the T-junction. This allowed estimating the actual shear rates experienced by the xanthan solutions, which go from tens to hundreds of s−1.

  18. Simulation of a liquid droplet ejection device using multi-actuator

    Science.gov (United States)

    Ono, Yoshihiro; Yoshino, Michitaka; Yasuda, Akira; Tanuma, Chiaki

    2016-07-01

    An equivalent circuit model for a liquid droplet ejection device using a multiactuator has been developed. The equivalent circuit was simplified using a gyrator in the synthesis of the outputs of many elements. The simulation was performed for an inkjet head having three piezoelectric elements using MATLAB/Simulink. In this model, the pressure chamber is filled with a Newtonian fluid. For this reason, the model assumed only the resistance component of the pressure chamber and the nozzle as a load. Furthermore, since the resistance component of the inlet is much larger than that of the nozzle, it is not considered in this model. As a result, by providing a time difference between the driving signals of the piezoelectric elements, we found that the pressure of the ink chamber could be arbitrarily controlled. By this model, it becomes possible to control the pressure in the ink chamber of the inkjet head required for the ejection of various inks.

  19. Rising and boiling of a drop of volatile liquid in a heavier one: application to the LMFBR severe accidents

    Energy Technology Data Exchange (ETDEWEB)

    Pigny, Sylvain L.; Coste, Pierre F. [DEN/DER/SSTH, CEA/Grenoble, 38054 Grenoble Cedex 9 (France)

    2005-07-01

    Full text of publication follows: The rising and, simultaneously the boiling, of a droplet of volatile liquid in a heavier one is computation-ally investigated. Our calculations are performed with the help of the SIMMER code, in which a specific DNS algorithm is developed, to represent surface tension between the different media in an explicit way. This is required to represent the physical contact that occurs between two liquids and the vapor from the lighter one, since interfacial heat transfers, and therefore boiling kinetics, merely depend on it. The behavior of the three fluids system is of interest as a key phenomenon related to the transition phase of LMFBR severe accidents, before the formation of a fully developed bubble column. The driven force due to the boiling of steel drops can play a major role in the relocation, and, consequently, the recriticality of UO{sub 2} fuel. The problem is investigated focusing first on analytical experiments, built-up with simulating materials, and for which accurate experimental results are provided. The dependence of results with regard to thermodynamical and physical properties is underlined. This point is of interest in view of some uncertainties in the knowledge of data concerning the materials present in the reactor at high temperature. The pressure level is a key parameter in the accident scenarios: its influence is uppermost on the volumic mass of the gas. It is also outlined. (authors)

  20. The features of heterogeneous water droplet evaporation in high-temperature combustion products of typical flammable liquids

    Directory of Open Access Journals (Sweden)

    Piskunov Maxim V.

    2017-01-01

    Full Text Available This paper presents the experimental results on heating and evaporation features of heterogeneous (with opaque solid particles – the size of 0.05-0.5 mm, relative mass concentration 0-1% water droplets (the initial size – radius 1-3 mm during their motion through high-temperature (500-1800 K gases. A significant increase in the integral characteristics of evaporation by introducing opaque inclusions into droplets was observed. The influence of energy accumulation on the conditions of droplet evaporation at the internal solid/liquid interfaces was established. For proportioned inclusions, the conditions of intensive vaporization (leading to the explosive disintegration of droplets at internal inclusion/liquid interfaces was set. To summarize research results, experiments were conducted with the combustion products of kerosene, gasoline, industrial alcohol, acetone, and oil. The particles of graphite, carbon, and aluminum as solid inclusions were used. The investigation compared integral characteristics of heterogeneous droplet evaporation under the conditions of non-stationary (gas temperature varied from 1800 K to 500 K over the length of channel and nearly stationary (gas temperature was maintained at about 1100 K heating.

  1. Experimental Study of the Influence of Operating Position on the Behavior of an Electromechanical Actuator with Volatile Liquid

    Directory of Open Access Journals (Sweden)

    NITAN Ilie

    2013-05-01

    Full Text Available This paper presents an experimental study of the influence of operating position on the behavior of an electrochemical actuator with volatile liquid. In the introduction, the operating principle of electromechanical actuators with volatile liquid is described. Are then presented experimental stand used, the study results and conclusions drawn from the studies.

  2. Interaction phenomena between liquid droplets and hot particles-Captured via high-speed camera

    Institute of Scientific and Technical Information of China (English)

    Sebastian Gehrke; Karl-Ernst Wirth

    2009-01-01

    bed surface were captured via a high-speed camera. While the ethanol droplet developed a stable steam cushion due to Leidenfrost phenomena, water showed intense interaction and steam explosions which induced repulsion and atomisation of the droplet.

  3. Experimental Investigation of Droplet Evaporation of Water with Ground Admixtures while Motion in a Flame of Liquid Fuel

    Directory of Open Access Journals (Sweden)

    Dmitriyenko Margarita A.

    2016-01-01

    Full Text Available The evaporation features for the atomized flow of suspension on the base of water with ground admixtures in an area of high-temperature combustion products of liquid flammable substance (acetone were investigated experimentally by the optical methods of gas flow diagnostic and the high-speed video recording. The scales of influence of clay and silt concentration in droplets of atomized flow on the intensity of its evaporation were determined. The approximation dependences describing a decrease in typical size of suspension droplets at various values of ground admixtures were obtained.

  4. Numerical Simulation of Unsteady Flows and Shape Oscillations in Liquid Droplets Induced by Deployment Needle Retraction

    Science.gov (United States)

    Yan, Jin; Shaw, Benjamin D.

    2010-02-01

    Retractable opposed needles are often used in reduced-gravity droplet combustion experiments to deploy droplets prior to ignition. Needle retraction induces droplet shape oscillations and internal flows that can have important effects on subsequent droplet behaviors. In the present paper, the unsteady flows and droplet shape oscillations associated with deployment needle retraction are investigated using the commercial CFD software package Fluent. A volume-of-fluid method with a second-order upwind scheme and a dual time stepping solver is employed to solve the conservation equations in 2-d and 3-d simulations of droplets prior to ignition. A moving-mesh method is employed to model needle movements. Calculations indicate that rapid needle retraction causes ligament formation between a droplet and a needle, with ligament breakage sometimes resulting in the formation of satellite droplets. Needle retraction also induces droplet shape oscillations that rapidly decay, though significant internal flows are predicted to remain within droplets even after droplet shape oscillations have damped to low levels. The calculations indicate that the initial needle spacing can have important effects on droplet shape oscillations and internal flow characteristics. Comparison of model predictions and experimental data is favorable.

  5. Determination of parabens in beverage samples by dispersive liquid-liquid microextraction based on solidification of floating organic droplet.

    Science.gov (United States)

    Hou, Fang; Deng, Xiaoying; Jiang, Xinyu; Yu, Jingang

    2014-01-01

    A simple and efficient method for dispersive liquid-liquid microextraction of methylparaben, ethylparaben, propylparaben and butylparaben in real beverage samples was developed. It is making use of solidified floating organic droplets of 1-dodecanol which has low density and a proper melting point. Parameters influencing the extraction efficiency, such as the type of extraction and dispersive solvent, the volume of extraction and dispersive solvent, salt effect, pH, extraction time, were optimized and resulted in enrichment factors (EFs) of 84 for methylparaben, 103 for ethylparaben, 115 for propylparaben and 126 for butylparaben. The limits of detection for parabens were 1.52, 1.06, 0.32 and 0.17 ng/mL, respectively. Excellent linearity with coefficients of correlation from 0.9970 to 0.9997 was observed in the concentration range of 5-1,000 ng/mL. The repeatability of the proposed method expressed as relative standard deviations (RSDs) ranged from 2.54 to 3.89% (n = 5). The relative recoveries for parabens in beverage samples were good and in the ranges of 89.8-109.9, 90.2-107.3, 90.9-101.7 and 92.3-118.1%, respectively. Thus, the proposed method has excellent potential for the determination of parabens in beverage samples. © The Author [2013]. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  6. A microfluidic platform for the rapid determination of distribution coefficients by gravity assisted droplet-based liquid-liquid extraction

    DEFF Research Database (Denmark)

    Poulsen, Carl Esben; Wootton, Robert C. R.; Wolff, Anders

    2015-01-01

    for the testing of valuable and scarce drug candidates. Herein we present a simple micro fluidic platform for the determination of distribution coefficients using droplet-based liquid-liquid extraction. For simplicity, this platform makes use of gravity to enable phase separation for analysis and is 48 times...... faster and uses 99 % less reagents than performing an equivalent measurement using the shake-flask method. Furthermore, the D measurements achieved in our platform are in good agreement with literature values measured using traditional shake-flask techniques. Since D is affected by volume ratios, we use...... the apparent acid dissociation constant, pK', as a proxy for inter-system comparison. Our platform determines a pK' value of 7.24 ± 0.15, compared to 7.25 ± 0.58 for the shake-flask method in our hands and 7.21 for the shake-flask method in literature. Devices are fabricated using injection moulding, the batch...

  7. The wall shear force on a liquid droplet adhering to a solid surface under an imposed shear

    Science.gov (United States)

    Shabtay, Royi; Frankel, Itzchak

    2011-11-01

    We focus on large droplet viscosities typical of those appearing in the upper respiratory tract of CF or chronically ventilated patients. To further simplify the problem we assume vanishingly small capillary numbers and consider (non-deformable) hemispherical droplets. Under these assumptions the problem decouples into (i) the external problem of imposed shear flow over a planar solid wall with a hemispherical protuberance which is simulated by means of a commercially available finite - volume code and (ii) the inner Stokes flow animated by the now prescribed shear stress distribution over the liquid surface. The latter problem is addressed through use of series expansions in spherical harmonics. The interaction between the caterpillar inner - fluid motion and the solid substrate results in a shear force adding to the external - flow drag force acting in the downstream direction. Throughout the range of outer - flow Reynolds numbers considered (0.05-50) this interaction contributes over 35% of the total hydrodynamic force acting to dislodge the droplet.

  8. Discrete electrostatic charge transfer by the electrophoresis of a charged droplet in a dielectric liquid.

    Science.gov (United States)

    Im, Do Jin; Ahn, Myung Mo; Yoo, Byeong Sun; Moon, Dustin; Lee, Dong Woog; Kang, In Seok

    2012-08-14

    We have experimentally investigated the electrostatic charging of a water droplet on an electrified electrode surface to explain the detailed inductive charging processes and use them for the detection of droplet position in a lab-on-a-chip system. The periodic bouncing motion of a droplet between two planar electrodes has been examined by using a high-resolution electrometer and an image analysis method. We have found that this charging process consists of three steps. The first step is inductive charge accumulation on the opposite electrode by the charge of a droplet. This induction process occurs while the droplet approaches the electrode, and it produces an induction current signal at the electrometer. The second step is the discharging of the droplet by the accumulated induced charge at the moment of contact. For this second step, there is no charge-transfer detection at the electrometer. The third step is the charging of the neutralized droplet to a certain charged state while the droplet is in contact with the electrode. The charge transfer of the third step is detected as the pulse-type signal of an electrometer. The second and third steps occur simultaneously and rapidly. We have found that the induction current by the movement of a charged droplet can be accurately used to measure the charge of the droplet and can also be used to monitor the position of a droplet under actuation. The implications of the current findings for understanding and measuring the charging process are discussed.

  9. Wetting effects on the spreading of a liquid droplet colliding with a flat surface: Experiment and modeling

    Science.gov (United States)

    Fukai, J.; Shiiba, Y.; Yamamoto, T.; Miyatake, O.; Poulikakos, D.; Megaridis, C. M.; Zhao, Z.

    1995-02-01

    In this paper an experimental and theoretical study of the deformation of a spherical liquid droplet colliding with a flat surface is presented. The theoretical model accounts for the presence of inertia, viscous, gravitation, surface tension, and wetting effects, including the phenomenon of contact-angle hysteresis. Experiments with impingement surfaces of different wettability were performed. The study showed that the maximum splat radius decreased as the value of the advancing contact angle increased. The effect of impact velocity on droplet spreading was more pronounced when the wetting was limited. The experimental results were compared to the numerical predictions in terms of droplet deformation, splat radius, and splat height. The theoretical model predicted well the deformation of the impacting droplet, not only in the spreading phase, but also during recoiling and oscillation. The wettability of the substrate upon which the droplet impinges was found to affect significantly all phases of the spreading process, including the formation and development of a ring structure around the splat.

  10. Liquid Metal Droplet and Micro Corrugated Diaphragm RF-MEMS for reconfigurable RF filters

    Science.gov (United States)

    Irshad, Wasim

    detail and have proved pivotal to this work. The second part of the dissertation focuses on the Liquid Metal Droplet RF-MEMS. A novel tunable RF MEMS resonator that is based upon electrostatic control over the morphology of a liquid metal droplet (LMD) is conceived. We demonstrate an LMD evanescent-mode cavity resonator that simultaneously achieves wide analog tuning from 12 to 18 GHz with a measured quality factor of 1400-1840. A droplet of 250-mum diameter is utilized and the applied bias is limited to 100 V. This device operates on a principle called Electro-Wetting On Dielectric (EWOD). The liquid metal employed is a non-toxic eutectic alloy of Gallium, Indium and Tin known as Galinstan. This device also exploits interfacial surface energy and viscous body forces that dominate at nanoliter scale. We then apply our Liquid Metal Droplet (LMD) RF-MEMS architecture to demonstrate a continuously tunable electrostatic Ku-Band Filter. A 2-pole bandpass filter with measured insertion loss of less than 0.4dB and 3dB FBW of 3.4% is achieved using a Galinstan droplet of 250mum diameter and bias limited to 100V. We demonstrate that the LMD is insensitive to gravity by performing inversion and tilt experiments. In addition, we study its thermal tolerance by subjecting the LMD up to 150° C. The third part of the dissertation is dedicated to the Micro-Corrugated Diaphragm (MCD) RF-MEMS. We present an evanescent-mode cavity bandpass filter with state-of-the-art RF performance metrics like 4:1 tuning ratio from 5 to 20 GHz with less than 2dB insertion loss and 2-6% 3dB bandwidth. Micro-Corrugated Diaphragm (MCD) is a novel electrostatic MEMS design specifically engineered to provide large-scale analog deflections necessary for such continuous and wide tunable filtering with very high quality factor. We demonstrate a 1.25mm radius and 2mum thick Gold MCD which provides 30mum total deflection with nearly 60% analog range. We also present a detailed and systematic MCD design

  11. Moving Liquids with Sound: The Physics of Acoustic Droplet Ejection for Robust Laboratory Automation in Life Sciences.

    Science.gov (United States)

    Hadimioglu, Babur; Stearns, Richard; Ellson, Richard

    2016-02-01

    Liquid handling instruments for life science applications based on droplet formation with focused acoustic energy or acoustic droplet ejection (ADE) were introduced commercially more than a decade ago. While the idea of "moving liquids with sound" was known in the 20th century, the development of precise methods for acoustic dispensing to aliquot life science materials in the laboratory began in earnest in the 21st century with the adaptation of the controlled "drop on demand" acoustic transfer of droplets from high-density microplates for high-throughput screening (HTS) applications. Robust ADE implementations for life science applications achieve excellent accuracy and precision by using acoustics first to sense the liquid characteristics relevant for its transfer, and then to actuate transfer of the liquid with customized application of sound energy to the given well and well fluid in the microplate. This article provides an overview of the physics behind ADE and its central role in both acoustical and rheological aspects of robust implementation of ADE in the life science laboratory and its broad range of ejectable materials.

  12. Emulsion of aqueous-based nonspherical droplets in aqueous solutions by single-chain surfactants: templated assembly by nonamphiphilic lyotropic liquid crystals in water.

    Science.gov (United States)

    Varghese, Nisha; Shetye, Gauri S; Bandyopadhyay, Debjyoti; Gobalasingham, Nemal; Seo, JinAm; Wang, Jo-Han; Theiler, Barbara; Luk, Yan-Yeung

    2012-07-24

    Single-chain surfactants usually emulsify and stabilize oily substances into droplets in an aqueous solution. Here, we report a coassembly system, in which single types of anionic or non-ionic surfactants emulsify a class of water-soluble nonamphiphilic organic salts with fused aromatic rings in aqueous solutions. The nonamphiphilic organic salts are in turn promoted to form droplets of water-based liquid crystals (chromonic liquid crystals) encapsulated by single-chain surfactants. The droplets, stabilized against coalescence by encapsulated in a layer (or layers) of single chain surfactants, are of both nonspherical tactoid (elongated ellipsoid with pointy ends) and spherical shapes. The tactoids have an average long axis of ∼9 μm and a short axis of ∼3.5 μm with the liquid crystal aligning parallel to the droplet surface. The spherical droplets are 5-10 μm in diameter and have the liquid crystal aligning perpendicular to the droplet surface and a point defect in the center. Cationic and zwitterionic surfactants studied in this work did not promote the organic salt to form droplets. These results illustrate the complex interplay of self-association and thermodynamic incompatibility of molecules in water, which can cause new assembly behavior, including potential formation of vesicles or other assemblies, from surfactants that usually form only micelles. These unprecedented tactoidal shaped droplets also provide potential for the fabrication of new soft organic microcapsules.

  13. Displacement of liquid droplets on a surface by a shearing air flow.

    Science.gov (United States)

    Fan, J; Wilson, M C T; Kapur, N

    2011-04-01

    The motion of droplets on surfaces is crucial to the performance of a wide range of processes; this study examines the initiation of droplet motion through a shearing mechanism generated here by a controlled air flow. Systematic experiments are carried out for a range of fluids and well defined surfaces. A model is postulated that balances surface tension forces at the contact line and the drag force due to the air motion. Experiments reveal that the critical velocity at which droplet motion is initiated depends on the contact angle and the droplet size. Visualizations highlight three modes of motion: (I) the droplet retains a footprint similar to that at the point of motion; (II) a tail exists at the rear of the droplet; (III) a trail remains behind the droplet (that can shed smaller droplets). The predictions of droplet initiation velocity are good for type I motion, in accordance with the assumptions inherent within the model. This model confirms the dominant physics associated with the initiation of droplet motion and provides a useful predictive expression. Copyright © 2011 Elsevier Inc. All rights reserved.

  14. High Frequency Acoustic Reflectometry for Solid/Liquid Interface Characterization: Application to Droplet Evaporation

    Science.gov (United States)

    Carlier, Julien; Toubal, Malika; Li, Sizhe; Campistron, Pierre; Callens, Dorothée; Thomy, Vincent; Senez, Vincent; Nongaillard, Bertrand

    Evolution of the local concentration in a 1 μL droplet of ethanol/water mixture during an evaporation process has been followed using high frequency acoustic reflectometry. This method has been developed for wetting characterization on micro/nanostructures and makes it possible to follow concentration evolution in a droplet deposited on a solid surface. This information gives the opportunity to predict wetting depending on surface tension linked to alcohol concentration evolution. The calibration of the method and concentration evolution in 50% and 30% ethanol droplets are presented. The evolution of a pure ethanol droplet composition is tracked so as to follow hydration process.

  15. Liquid Droplets Act as "Compass Needles" for the Stresses in a Deformable Membrane

    Science.gov (United States)

    Schulman, Rafael D.; Ledesma-Alonso, René; Salez, Thomas; Raphaël, Elie; Dalnoki-Veress, Kari

    2017-05-01

    We examine the shape of droplets atop deformable thin elastomeric films prepared with an anisotropic tension. As the droplets generate a deformation in the taut film through capillary forces, they assume a shape that is elongated along the high tension direction. By measuring the contact line profile, the tension in the membrane can be completely determined. Minimal theoretical arguments lead to predictions for the droplet shape and membrane deformation that are in excellent agreement with the data. On the whole, the results demonstrate that droplets can be used as probes to map out the stress field in a membrane.

  16. Analysis of liquid samples using dried-droplet laser ablation inductively coupled plasma mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Do, Trong-Mui; Hsieh, Hui-Fang; Chang, Wei-Ciang [Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, 30013 Taiwan (China); Chang, E.-E. [Department of Biochemistry, Taipei Medical University, Taipei City, 11031 Taiwan (China); Wang, Chu-Fang, E-mail: cfwang@mx.nthu.edu.tw [Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, 30013 Taiwan (China); Institute of Nuclear Engineering and Science, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

    2011-08-15

    In this study we developed a dried-droplet method for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The proposed method provides accurate and precise results when building calibration curves and determining elements of interest in real liquid samples. After placing just 1 {mu}L of a liquid standard solution or a real sample onto the filter surface and then converting the solution into a very small, thin dry spot, the sample could be applied as an analytical subject for LA. To demonstrate the feasibility of this proposed method, we used LA-ICP-MS and conventional ICP-MS to determine the levels of 13 elements (Li, V, Mn, Co, Ni, Cu, Zn, As, Mo, Cd, Sb, Tl, and Pb) in five water samples. The correlation coefficients obtained from the various calibration curves ranged from 0.9920 ({sup 205}Tl) to 0.9998 ({sup 51}V), sufficient to allow the determination of a wide range of elements in the samples. We also investigated the effects of Methylene Blue (MB) and the NaCl concentration on the elemental analyses. MB could be used as an indicator during the ablation process; its presence in the samples only negligibly influenced the intensities of the signals of most of the tested elements. Notably, high NaCl contents led to signal suppression for some of the elements. In comparison with the established sample introduction by nebulization, our developed technique abrogates the need for time-consuming sample preparation and reduces the possibility of sample contamination.

  17. Superhydrophobic photosensitizers. Mechanistic studies of (1)O2 generation in the plastron and solid/liquid droplet interface.

    Science.gov (United States)

    Aebisher, David; Bartusik, Dorota; Liu, Yang; Zhao, Yuanyuan; Barahman, Mark; Xu, QianFeng; Lyons, Alan M; Greer, Alexander

    2013-12-18

    We describe here a physical-organic study of the first triphasic superhydrophobic sensitizer for photooxidations in water droplets. Control of synthetic parameters enables the mechanistic study of "borderline" two- and three-phase superhydrophobic sensitizer surfaces where (1)O2 is generated in compartments that are wetted, partially wetted, or remain dry in the plastron (i.e., air layer beneath the droplet). The superhydrophobic surface is synthesized by partially embedding silicon phthalocyanine (Pc) sensitizing particles to specific locations on polydimethylsiloxane (PDMS) posts printed in a square array (1 mm tall posts on 0.5 mm pitch). In the presence of red light and oxygen, singlet oxygen is formed on the superhydrophobic surface and reacts with 9,10-anthracene dipropionate dianion (1) within a freestanding water droplet to produce an endoperoxide in 54-72% yields. Control of the (1)O2 chemistry was achieved by the synthesis of superhydrophobic surfaces enriched with Pc particles either at the PDMS end-tips or at PDMS post bases. Much of the (1)O2 that reacts with anthracene 1 in the droplets was generated by the sensitizer "wetted" at the Pc particle/water droplet interface and gave the highest endoperoxide yields. About 20% of the (1)O2 can be introduced into the droplet from the plastron. The results indicate that the superhydrophobic sensitizer surface offers a unique system to study (1)O2 transfer routes where a balance of gas and liquid contributions of (1)O2 is tunable within the same superhydrophobic surface.

  18. Classification of the ejection mechanisms of charged macromolecules from liquid droplets

    Science.gov (United States)

    Consta, Styliani; Malevanets, Anatoly

    2013-01-01

    The relation between the charge state of a macromolecule and its ejection mechanism from droplets is one of the important questions in electrospray ionization methods. In this article, effects of solvent-solute interaction on the manifestation of the charge induced instability in a droplet are examined. We studied the instabilities in a prototype system of a droplet comprised of charged poly(ethylene glycol) and methanol, acetonitrile, and water solvents. We observed instances of three, previously only conjectured, [S. Consta, J. Phys. Chem. B 114, 5263 (2010), 10.1021/jp912119v] mechanisms of macroion ejection. The mechanism of ejection of charged macroion in methanol is reminiscent of "pearl" model in polymer physics. In acetonitrile droplets, the instability manifests through formation of solvent spines around the solvated macroion. In water, we find that the macroion is ejected from the droplet through contiguous extrusion of a part of the chain. The difference in the morphology of the instabilities is attributed to the interplay between forces arising from the macroion solvation energy and the surface energy of the droplet interface. For the contiguous extrusion of a charged macromolecule from a droplet, we demonstrate that the proposed mechanism leads to ejection of the macromolecule from droplets with sizes well below the Rayleigh limit. The ejected macromolecule may hold charge significantly higher than that suggested by prevailing theories. The simulations reveal new mechanisms of macroion evaporation that differ from conventional charge residue model and ion evaporation mechanisms.

  19. Numerical Study on Deformation and Interior Flow of a Droplet Suspended in Viscous Liquid under Steady Electric Fields

    Directory of Open Access Journals (Sweden)

    Zhentao Wang

    2014-07-01

    Full Text Available A model based on the volume of fluid (VOF method and leaky dielectric theory is established to predict the deformation and internal flow of the droplet suspended in another vicious fluid under the influence of the electric field. Through coupling with hydrodynamics and electrostatics, the rate of deformation and internal flow of the single droplet are simulated and obtained under the different operating parameters. The calculated results show that the direction of deformation and internal flow depends on the physical properties of fluids. The numerical results are compared with Taylor's theory and experimental results by Torza et al. When the rate of deformation is small, the numerical results are consistent with theory and experimental results, and when the rate is large the numerical results are consistent with experimental results but are different from Taylor's theory. In addition, fluid viscosity hardly affects the deformation rate and mainly dominates the deformation velocity. For high viscosity droplet spends more time to attain the steady state. The conductivity ratio and permittivity ratio of two different liquids affect the direction of deformation. When fluid electric properties change, the charge distribution at the interface is various, which leads to the droplet different deformation shapes.

  20. Pre-concentration and determination of amitriptyline residues in waste water by ionic liquid based immersed droplet microextraction and HPLC

    Institute of Scientific and Technical Information of China (English)

    M.T. Hamed Mosavian; Z. Es'haghi; N. Razavi; S. Banihashemi

    2012-01-01

    This paper describes a new approach for the determination of amitriptyline in wastewater by ionic liquid based immersed droplet microextraction (IL-IDME) prior to highperformance liquid chromatography with ultraviolet detection. 1-Hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]) was used as an ionic liquid. Various factors that affect extraction, such as volume of ionic liquid, stirring rate, extraction time, pH of the aqueous solution and salting effect, were optimized. The optimal conditions were as follows: microextraction time, 10 min; stirring rate, 720 rpm; pH, 11; ionic drop volume, 100 uL; and no sodium chloride addition. In quantitative experiments the method showed linearity in a range from 0.01 to 10 ug/mL, a limit of detection of 0.004 ug/mL and an excellent pre-concentration factor (PF) of 1100. Finally, the method was successfully applied to the determination of amitriptyline in the hospital wastewater samples.

  1. Contact line pinning of a perfectly wetting and volatile liquid at a sharp edge

    Science.gov (United States)

    Tsoumpas, Yannis; Dehaeck, Sam; Rednikov, Alexey; Colinet, Pierre

    2011-11-01

    According to the Gibbs' criterion, a sharp edge can act as an energy barrier during the spreading of a liquid drop on a rigid substrate. In this study, however, we are trying to determine experimentally whether Gibbs' criterion is also valid for the case of a perfectly wetting and volatile liquid. To this purpose, we constructed a groove of triangular cross section on a Plexiglas substrate. During the experiments liquid was injected in the region surrounded by the groove, which had a square shape with rounded corners. The results indicated that a microgroove edge can indeed prevent the spreading of the liquid drop up to a certain extent, with the maximum apparent contact angle being in close agreement with the one given by Gibbs' criterion. Nevertheless, the apparent contact angle at breakup was found to be significantly lower in the corner of our region. To study this further we developed a static model, which takes into account surface tension and gravity but not the evaporation. Both the simulations and the experiments have confirmed a remarkable behaviour of the contact line at the corner. Finally, to grasp the effect of evaporation, experiments have also been conducted with drops of equally wetting but less volatile liquids. Supported by ESA & BELSPO, by the EU, and by FRS-FNRS.

  2. Silver halide fiber-based evanescent-wave liquid droplet sensing with room temperature mid-infrared quantum cascade lasers

    Science.gov (United States)

    Chen, J. Z.; Liu, Z.; Gmachl, C. F.; Sivco, D. L.

    2005-08-01

    Quantum cascade lasers and unclad silver halide fibers were used to assemble mid-infrared fiber-optics evanescent-wave sensors suitable to measure the chemical composition of liquid droplets. The laser wavelengths were chosen to be in the regions which offer the largest absorption contrast between constituents inside the mixture droplets. A pseudo-Beer-Lambert law fits well with the experimental data. Using a 300μm diameter fiber with a 25 mm immersion length, the signal to noise ratios correspond to 1 vol.% for α-tocophenol in squalane and 2 vol.% for acetone in aqueous solution for laser wavenumbers of 1208 cm-1 and 1363 cm-1, respectively.

  3. Nematic-Field Driven Positioning of Particles in Liquid Crystal Droplets

    Science.gov (United States)

    Whitmer, Jonathan K.; Wang, Xiaoguang; Mondiot, Frederic; Miller, Daniel S.; Abbott, Nicholas L.; de Pablo, Juan J.

    2015-01-01

    Common nematic oils, such as 5CB, experience planar anchoring at aqueous interfaces. When these oils are emulsified, this anchoring preference and the resulting topological constraints lead to formation of droplets that exhibit one or two point defects within the nematic phase. Here, we explore the interactions of adsorbed particles at the aqueous interface through a combination of experiments and coarse-grained modeling, and demonstrate that surface-active particles, driven by elastic forces in the droplet, readily localize to these defect regions in a programmable manner. When droplets include two nanoparticles, these preferentially segregate to the two poles, thereby forming highly regular dipolar structures that could serve for hierarchical assembly of functional structures. Addition of sufficient concentrations of surfactant changes the interior morphology of the droplet, but pins defects to the interface, resulting in aggregation of the two particles. PMID:24329470

  4. Breathing, crawling, budding, and splitting of a liquid droplet under laser heating.

    Science.gov (United States)

    Song, Chaeyeon; Moon, Jong Kyun; Lee, Kyuyong; Kim, Kipom; Pak, Hyuk Kyu

    2014-04-21

    The manipulation of droplets with sizes on the millimetre scale and below has attracted considerable attention over the past few decades for applications in microfluidics, biology, and chemistry. In this paper, we report the response of an oil droplet floating in an aqueous solution to local laser heating. Depending on the laser power, distinct dynamic transitions of the shape and motion of the droplet are observed, namely, breathing, crawling, budding, and splitting. We found that the selection of the dynamic modes is determined by dynamic instabilities due to the interplay between the convection flows and capillary effects. Our findings can be useful for constructing microfluidic devices to control the motion and shape of a small droplet by simply altering the laser power, and for understanding thermal convective systems with fully soft boundaries.

  5. Nematic-field-driven positioning of particles in liquid crystal droplets.

    Science.gov (United States)

    Whitmer, Jonathan K; Wang, Xiaoguang; Mondiot, Frederic; Miller, Daniel S; Abbott, Nicholas L; de Pablo, Juan J

    2013-11-27

    Common nematic oils, such as 5CB, experience planar anchoring at aqueous interfaces. When these oils are emulsified, this anchoring preference and the resulting topological constraints lead to the formation of droplets that exhibit one or two point defects within the nematic phase. Here, we explore the interactions of adsorbed particles at the aqueous interface through a combination of experiments and coarse-grained modeling, and demonstrate that surface-active particles, driven by elastic forces in the droplet, readily localize to these defect regions in a programmable manner. When droplets include two nanoparticles, these preferentially segregate to the two poles, thereby forming highly regular dipolar structures that could serve for hierarchical assembly of functional structures. Addition of sufficient concentrations of surfactant changes the interior morphology of the droplet, but pins defects to the interface, resulting in aggregation of the two particles.

  6. A tunable microflow focusing device utilizing controllable moving walls and its applications for formation of micro-droplets in liquids

    Science.gov (United States)

    Lee, Chun-Hong; Hsiung, Suz-Kai; Lee, Gwo-Bin

    2007-06-01

    This study reports a new microfluidic device capable of fine-tuned sample-flow focusing and generation of micro-droplets in liquids by controlling moving wall structures. Two microfluidic components including an 'active microchannel width controller' and a 'micro chopper' can be used to fine-tune the width of the hydrodynamically pre-focused stream and subsequently generate micro-droplets. In this study, a basic concept of a 'controllable moving wall' structure was addressed and applied as the active microchannel width controller and the micro chopper to generate the proposed function. Pneumatic side chambers were placed next to a main flow channel to construct the controllable moving wall structures. The deformation of the controllable moving wall structure can be generated by the pressurized air injected into the pneumatic side chambers. The proposed chip device was fabricated utilizing polymer material such as PDMS (polydimethylsiloxane) to provide the flexibility of the controllable moving wall deformation. The microfluidic chip device with dimensions of 2.5 cm in width and 3.0 cm in length can be fabricated using a simple fabrication process. Experimental data showed that the deformation of the controllable moving wall structure can be adjusted by applying different air pressures, so that the width of the main flow channel can be controlled accordingly. By utilizing the proposed mechanism, the pre-focused dispersed phase stream could be actively focused into a narrower stream, and well-controlled micro-droplets with smaller diameters could be generated. The stream width can be reduced from 30 µm to 9 µm and micro-droplets with a diameter of 76 µm could be generated by utilizing the proposed device. In addition, to generate micro-droplets within smaller diameters, uniform size distribution of the micro-droplets can be obtained. According to the experimental results, development of the microfluidic device could be promising for a variety of applications such

  7. Electric-field triggered controlled release of bioactive volatiles from imine-based liquid crystalline phases.

    Science.gov (United States)

    Herrmann, Andreas; Giuseppone, Nicolas; Lehn, Jean-Marie

    2009-01-01

    Application of an electric field to liquid crystalline film forming imines with negative dielectric anisotropy, such as N-(4-methoxybenzylidene)-4-butylaniline (MBBA, 1), results in the expulsion of compounds that do not participate in the formation of the liquid crystalline phase. Furthermore, amines and aromatic aldehydes undergo component exchange with the imine by generating constitutional dynamic libraries. The strength of the electric field and the duration of its application to the liquid crystalline film influence the release rate of the expelled compounds and, at the same time, modulate the equilibration of the dynamic libraries. The controlled release of volatile organic molecules with different chemical functionalities from the film was quantified by dynamic headspace analysis. In all cases, higher headspace concentrations were detected in the presence of an electric field. These results point to the possibility of using imine-based liquid crystalline films to build devices for the controlled release of a broad variety of bioactive volatiles as a direct response to an external electric signal.

  8. A reexamination of the relationship between volatility, liquidity and trading activity

    Directory of Open Access Journals (Sweden)

    Khine Kyaw

    2013-03-01

    Full Text Available Este trabajo investiga si la relación entre actividad negociadora en el mercado de acciones, la liquidez del mercado y la volatilidad a nivel de cartera, es similar a dicha relación a nivel deacciones individuales. Para las carteras de empresas de mayor tamaño, la mayor actividad negociadora está relacionada con mayor liquidez y más volatilidad. Sin embargo, a pesar de quela relación volatilidad-liquidez es la misma para las carteras de acciones pequeñas, encontramos que la mayor actividad negociadora está negativamente asociada con la liquidez para estaagrupación. Este contraste en las relaciones está causado por las interrelaciones dinámicas entre las tres variables y una vez que se controla por esas interrelaciones, dicho contraste en losresultados desparece. Estos hallazgos contribuyen al debate sobre el comportamiento del mercado, que ha adquirido un renovado interés en los últimos años.We investigate whether the relationship between equity trading activity, market liquidity and return volatility at the portfolio level is similar to the relationship at the individual security level. For the very largest firm-size portfolio, higher trading activity is positively associated with greater liquidity and more volatile returns. However, despite the volatility-liquidity relationship being the same for smaller equity portfolios, we find that higher trading activity is negatively associated with liquidity for this grouping. These contrasting relationships are shown to be caused by the interdynamics between all three variables and once we control for these interrelationships, the contrasting results disappear. The findings contribute to the debate on market behaviour that has taken on renewed vigour in recent years.

  9. Simultaneous monitoring of protein adsorption at the solid-liquid interface from sessile solution droplets by ellipsometry and axisymmetric drop shape analysis by profile

    NARCIS (Netherlands)

    Wormeester, H; Busscher, HK

    1999-01-01

    In this paper two in situ techniques are combined to simultaneously examine protein adsorption at the solid-liquid interface from sessile solution droplets. With axisymmetric drop shape analysis by profile (ADSA-P) the change in solid-liquid interfacial tension is determined, while ellipsometry is e

  10. Simultaneous monitoring of protein adsorption at the solid–liquid interface from sessile solution droplets by ellipsometry and axisymmetric drop shape analysis by profile

    NARCIS (Netherlands)

    Noordmans, Jaap; Wormeester, Herbert; Busscher, Henk J.

    1999-01-01

    In this paper two in situ techniques are combined to simultaneously examine protein adsorption at the solid–liquid interface from sessile solution droplets. With axisymmetric drop shape analysis by profile (ADSA-P) the change in solid–liquid interfacial tension is determined, while ellipsometry is e

  11. Development of a three-dimensional correction method for optical distortion of flow field inside a liquid droplet.

    Science.gov (United States)

    Gim, Yeonghyeon; Ko, Han Seo

    2016-04-15

    In this Letter, a three-dimensional (3D) optical correction method, which was verified by simulation, was developed to reconstruct droplet-based flow fields. In the simulation, a synthetic phantom was reconstructed using a simultaneous multiplicative algebraic reconstruction technique with three detectors positioned at the synthetic object (represented by the phantom), with offset angles of 30° relative to each other. Additionally, a projection matrix was developed using the ray tracing method. If the phantom is in liquid, the image of the phantom can be distorted since the light passes through a convex liquid-vapor interface. Because of the optical distortion effect, the projection matrix used to reconstruct a 3D field should be supplemented by the revision ray, instead of the original projection ray. The revision ray can be obtained from the refraction ray occurring on the surface of the liquid. As a result, the error on the reconstruction field of the phantom could be reduced using the developed optical correction method. In addition, the developed optical method was applied to a Taylor cone which was caused by the high voltage between the droplet and the substrate.

  12. Long-term investigation of erosion behaviors on metal surfaces by impingement of liquid droplet with high-speed

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Duk Hyun; Kim, Kyung Hoon [Kyunghee University, Yongin (Korea, Republic of); Kim, Hyung Joon [Seoul National University, Seoul (Korea, Republic of)

    2015-03-15

    Understanding wall-thinning erosion of pipelines in nuclear or steam power plants is critically important for predicting and preventing human and material accidents. Wall thinning of pipelines in power plants occurs mainly by flow acceleration corrosion (FAC), cavitation erosion (C/E), and liquid droplet impingement erosion (LIE). Wall thinning by FAC and C/E has been well-investigated; however, LIE in plant industries has rarely been studied due to the experimental difficulty of setting up a long injection of highly pressurized air. We designed a long-term experimental system for LIE and investigated the behavior of LIE for three kinds of materials (A106B, SS400, A6061). The main control parameter was the air-water ratio (α), which was defined as the volumetric ratio of water to air (0.79, 1.00, 1.72). To clearly understand LIE, the spraying velocity (v) of liquid droplets was controlled larger than 160 m/s and the experiments were performed for 15 days. The surface morphology and hardness of the materials were examined every five days. Since the spraying velocity of liquid droplets and their contact area (A{sub c}) on specimens were changed according to the air-water ratio, we analyzed the behavior of LIE for the materials using the impulse (I), which was defined as I = (α × v) / A{sub c} . Finally, the prediction equations (the erosion rate) for the LIE of the materials were determined for the air-water ratios.

  13. Predictive Model of Supercooled Water Droplet Pinning/Repulsion Impacting a Superhydrophobic Surface: The Role of the Gas-Liquid Interface Temperature.

    Science.gov (United States)

    Mohammadi, Morteza; Tembely, Moussa; Dolatabadi, Ali

    2017-02-28

    Dynamical analysis of an impacting liquid drop on superhydrophobic surfaces is mostly carried out by evaluating the droplet contact time and maximum spreading diameter. In this study, we present a general transient model of the droplet spreading diameter developed from the previously defined mass-spring model for bouncing drops. The effect of viscosity was also considered in the model by definition of a dash-pot term extracted from experiments on various viscous liquid droplets on a superhydrophobic surface. Furthermore, the resultant shear force of the stagnation air flow was also considered with the help of the classical Homann flow approach. It was clearly shown that the proposed model predicts the maximum spreading diameter and droplet contact time very well. On the other hand, where stagnation air flow is present in contradiction to the theoretical model, the droplet contact time was reduced as a function of both droplet Weber numbers and incoming air velocities. Indeed, the reduction in the droplet contact time (e.g., 35% at a droplet Weber number of up to 140) was justified by the presence of a formed thin air layer underneath the impacting drop on the superhydrophobic surface (i.e., full slip condition). Finally, the droplet wetting model was also further developed to account for low temperature through the incorporation of classical nucleation theory. Homogeneous ice nucleation was integrated into the model through the concept of the reduction of the supercooled water drop surface tension as a function of the gas-liquid interface temperature, which was directly correlated with the Nusselt number of incoming air flow. It was shown that the experimental results was qualitatively predicted by the proposed model under all supercooling conditions (i.e., from -10 to -30 °C).

  14. Impact of plasma induced liquid chemistry and charge on bacteria loaded aerosol droplets

    Science.gov (United States)

    Rutherford, David; McDowell, David; Mariotti, Davide; Mahony, Charles; Diver, Declan; Potts, Hugh; Bennet, Euan; Maguire, Paul

    2014-10-01

    The introduction of living organisms, such as bacteria, into atmospheric pressure microplasmas offers a unique opportunity to study the local chemical and electrical effects on cell structure and viability. Individual bacteria, each encapsulated in an aerosol droplet, were successfully transmitted through a non-thermal equilibrium RF coaxial plasma, using a custom-design concentric double gas shroud interface and via adjustment of transit times and plasma parameters, we can control cell viability. Plasma electrical characteristics (ne ~ 1013 cm-3), droplet velocity profiles and aspects of plasma-induced droplet chemistry were determined in order to establish the nature of the bacteria in droplet environment. Plasma-exposed viable E coli cells were subsequently cultured and the growth rate curves (lag and exponential phase gradient) used to explore the effect of radical chemistry and electron bombardment on cell stress. The extent and nature of membrane disruption in viable and non-viable cells were investigated through genomic and protein/membrane lipid content estimation. We will also compare our results with simulations of the effect of bacterial presence on plasma induced droplet charging and evaporation. Funding from EPSRC acknowledged (Grants EP/K006088/1 and EP/K006142/1).

  15. Droplet collisions in turbulence

    NARCIS (Netherlands)

    Oldenziel, G.

    2014-01-01

    Liquid droplets occur in many natural phenomena and play an important role in a large number of industrial applications. One of the distinct properties of droplets as opposed to solid particles is their ability to merge, or coalesce upon collision. Coalescence of liquid drops is of importance in for

  16. Droplet collisions in turbulence

    NARCIS (Netherlands)

    Oldenziel, G.

    2014-01-01

    Liquid droplets occur in many natural phenomena and play an important role in a large number of industrial applications. One of the distinct properties of droplets as opposed to solid particles is their ability to merge, or coalesce upon collision. Coalescence of liquid drops is of importance in for

  17. Detachment of liquid droplets from fibres--experimental and theoretical evaluation of detachment force due to interfacial tension effects.

    Science.gov (United States)

    Mullins, Benjamin J; Pfrang, Andreas; Braddock, Roger D; Schimmel, Thomas; Kasper, Gerhard

    2007-08-15

    The detachment of barrel-shaped oil droplets from metal, glass and polymer fibres was examined using an atomic force microscope (AFM). The AFM was used to detach the droplets from the fibres while measuring the force-distance relationship. A novel fibre-droplet interfacial tension model was applied to predict the force required to draw the droplet away from its preferential axisymmetric position on the fibre, and also to predict the maximal force required to detach the droplet. The model assumes that the droplet retains a spherical shape during detachment, i.e., that droplet distortion is negligible. This assumption was found to be reasonably accurate for small radius oil droplets (droplets (>25 microm). However, it was found that the model produced a good agreement with the maximal detachment force measured experimentally--regardless of droplet size and degree of deformation--even though the model could not predict droplet extension beyond a length of one droplet radius.

  18. Modeling contact angle hysteresis of a liquid droplet sitting on a cosine wave-like pattern surface.

    Science.gov (United States)

    Promraksa, Arwut; Chen, Li-Jen

    2012-10-15

    A liquid droplet sitting on a hydrophobic surface with a cosine wave-like square-array pattern in the Wenzel state is simulated by using the Surface Evolver to determine the contact angle. For a fixed drop volume, multiple metastable states are obtained at two different surface roughnesses. Unusual and non-circular shape of the three-phase contact line of a liquid droplet sitting on the model surface is observed due to corrugation and distortion of the contact line by structure of the roughness. The contact angle varies along the contact line for each metastable state. The maximum and minimum contact angles among the multiple metastable states at a fixed viewing angle correspond to the advancing and the receding contact angles, respectively. It is interesting to observe that the advancing/receding contact angles (and contact angle hysteresis) are a function of viewing angle. In addition, the receding (or advancing) contact angles at different viewing angles are determined at different metastable states. The contact angle of minimum energy among the multiple metastable states is defined as the most stable (equilibrium) contact angle. The Wenzel model is not able to describe the contact angle along the three-phase contact line. The contact angle hysteresis at different drop volumes is determined. The number of the metastable states increases with increasing drop volume. Drop volume effect on the contact angles is also discussed.

  19. TRACKING METHODS FOR FREE SURFACE AND SIMULATION OF A LIQUID DROPLET IMPACTING ON A SOLID SURFACE BASED ON SPH

    Institute of Scientific and Technical Information of China (English)

    LI Da-ming; XU Ya-nan; LI Ling-ling; LU Hui-jiao; BAI Ling

    2011-01-01

    With some popular tracking methods for free surface,simulations of several typical examples are carried out under various flow field conditions.The results show that the Smoothed Particle Hydrodynamics(SPH)method is very suitable in simulating the flow problems with a free surface.A viscous liquid droplet with an initial velocity impacting on a solid surface is simulated based on the SPH method,and the surface tension is considered by searching the free surface particles,the initial impact effect is considered by using the artificial viscosity method,boundary virtual particles and image virtual particles are introduced to deal with the boundary problem,and the boundary defect can be identified quite well.The comparisons of simulated results and experimental photographs show that the SPH method can not only exactly simulate the spreading process and the rebound process of a liquid droplet impacting on a solid surface but also accurately track the free surface particles,simulate the free-surface flow and determine the shape of the free surface due to its particle nature.

  20. Onset of liquid droplet entrainment on a direct vessel injection system for APR1400

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Han-sol; Lee, Jae-Young [Handong Global University, Pohang (Korea, Republic of); Kim, Jong-Rok; Euh, Dong-Jin [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    In this research, a series of visualization works was conducted to understand droplet entrainment of the flow pattern generated in direct vessel injection system(DVI) of Korea nuclear power plant, APR 1400. In the emergency situation of a nuclear power plant, reliability of DVI cooling can be an important issue. It is known that, the amount and the rate of entrainment during the DVI cooling process can significantly affect the total heat removal. To visualize the film Reynolds number closely related with onset of droplet entrainment induced by falling film flow and lateral air flow in a small gap, confocal chromatic sensing method for measuring accurately film thickness and depth averaging particle image velocimetry for film velocity were used. The results have been post processed 4G Insight software. By measuring two dimensional film Reynolds number, we can predict the onset of droplet entrainment and obtain visible breakup region intuitively. To visualize the droplet entrainment induced by falling film flow and lateral air flow in a small gap, shadowgraph method with CCD camera (2200fps, 1280 pixel X 800 pixel, ) on coated plate with super water-repellent agent was used. The results have been post processed using 4G Insight software. By measuring two dimensional film Reynolds number, we can predict the onset of droplet entrainment and obtain visible breakup region intuitively. By adopting both super hydrophobic coating method and shadowgraph method, entrainment in a narrow gap was successfully visualized that has rarely performed before and meaningful results for DVI system research fields have been made.

  1. Droplet organelles?

    Science.gov (United States)

    Courchaine, Edward M; Lu, Alice; Neugebauer, Karla M

    2016-08-01

    Cells contain numerous, molecularly distinct cellular compartments that are not enclosed by lipid bilayers. These compartments are implicated in a wide range of cellular activities, and they have been variously described as bodies, granules, or organelles. Recent evidence suggests that a liquid-liquid phase separation (LLPS) process may drive their formation, possibly justifying the unifying term "droplet organelle". A veritable deluge of recent publications points to the importance of low-complexity proteins and RNA in determining the physical properties of phase-separated structures. Many of the proteins linked to such structures are implicated in human diseases, such as amyotrophic lateral sclerosis (ALS). We provide an overview of the organizational principles that characterize putative "droplet organelles" in healthy and diseased cells, connecting protein biochemistry with cell physiology.

  2. On the slip number choice in computations of liquid droplet impinging on a hydrophilic surface

    CERN Document Server

    Ganesan, Sashikumaar

    2015-01-01

    A mesh-dependent relation for the slip number in the Navier-slip with friction boundary condition for computations of impinging droplets is proposed. The relation is obtained as a function of the Reynolds number, the Weber number and the mesh size. The proposed relation is validated for several test cases by comparing the numerically obtained wetting diameter with the experimental results. Further, the computationally obtained maximum wetting diameter using the proposed slip relation is verified with the theoretical predictions. The relative error between the computationally obtained maximum wetting diameter and the theoretical predictions is less than 10\\% for impinging droplet on a hydrophilic surface, and the error increases in the case of hydrophobic surface.

  3. Effects of Liquid Superheat on Droplet Disruption and Vaporization in Supersonic Conditions

    Science.gov (United States)

    2007-11-02

    studies.’ .- 3 Model Structure The limiting approximation of model is that the droplets are modeled as non - evaporating , rigid spheres. The reason for...of the test fluids vary only slightly, and ethanol has the median density of the three fluids . The Newtonian equation for change in velocity due to... Evaporation at the Superheat Limit," International Journal of Heat and Mass Transfer, Vol. 31, No. 8, 1988, pp. 1687-1988. 14Ried, Robert C

  4. Precision charging of microparticles in plasma via the Rayleigh instability for evaporating charged liquid droplets

    Science.gov (United States)

    Bennet, Euan; Mahony, Charles M. O.; Potts, Hugh E.; Everest, Paul; Rutherford, David; Askari, Sadegh; Kelsey, Colin; Perez-Martin, Fatima; Hamilton, Neil; McDowell, David A.; Mariotti, Davide; Maguire, Paul; Diver, Declan A.

    2015-09-01

    In this paper we describe a novel method for delivering a precise, known amount of electric charge to a micron-sized solid target. Aerosolised microparticles passed through a plasma discharge will acquire significant electric charge. The fluid stability under evaporative stress is a key aspect that is core to the research. Initially stable charged aerosols subject to evaporation (i.e. a continually changing radius) may encounter the Rayleigh stability limit. This limit arises from the electrostatic and surface tension forces and determines the maximum charge a stable droplet can retain, as a function of radius. We demonstrate that even if the droplet charge is initially much less than the Rayleigh limit, the stability limit will be encountered as the droplet evaporates. The instability emission mechanism is strongly linked to the final charge deposited on the target, providing a mechanism that can be used to ensure a predictable charge deposit on a known encapsulated microparticle. The authors gratefully acknowledge support from EPSRC via Grant Numbers EP/K006142/1 and EP/K006088/1.

  5. Puddle jumping: Spontaneous ejection of large liquid droplets from hydrophobic surfaces during drop tower tests

    Science.gov (United States)

    Attari, B.; Weislogel, M.; Wollman, A.; Chen, Y.; Snyder, T.

    2016-10-01

    Large droplets and puddles jump spontaneously from sufficiently hydrophobic surfaces during routine drop tower tests. The simple low-cost passive mechanism can in turn be used as an experimental device to investigate dynamic droplet phenomena for drops up to 104 times larger than their normal terrestrial counterparts. We provide and/or confirm quick and qualitative design guides for such "drop shooters" as employed in drop tower tests including relationships to predict droplet ejection durations and velocities as functions of drop volume, surface texture, surface contour, wettability pattern, and fluid properties including contact angle. The latter is determined via profile image comparisons with numerical equilibrium interface computations. Water drop volumes of 0.04-400 ml at ejection speeds of -0.007-0.12 m/s are demonstrated herein. A sample application of the drop jump method is made to the classic problem of low-gravity phase change heat transfer for large impinging drops. Many other candidate problems might be identified by the reader.

  6. Expressions for the evaporation of sessile liquid droplets incorporating the evaporative cooling effect.

    Science.gov (United States)

    Wang, Yilin; Ma, Liran; Xu, Xuefeng; Luo, Jianbin

    2016-12-15

    The evaporation along the surface of pinned, sessile droplets is investigated numerically by using the combined field approach. In the present model, the evaporative cooling at the droplet surface which leads to a reduction in the evaporation is taken into account. Simple, yet accurate analytical expressions for the local evaporation flux and for the total evaporation rate of sessile droplets are obtained. The theoretical analyses indicate that the reduction in the evaporation becomes more pronounced as the evaporative cooling number Ec increases. The results also reveal that the variation of total evaporation rate with contact angle will change its trend as the intensity of the evaporative cooling changes. For small values of Ec, the total evaporation rate increases with the contact angle, the same as predicted by Deegan et al. and by Hu and Larson in their isothermal models in which the evaporative cooling is neglected. Contrarily, when the evaporative cooling effect is strong enough, the total evaporation rate will decrease as the contact angle increases. The present theory is corroborated experimentally, and found in good agreement with the expressions proposed by Hu and Larson in the limiting isothermal case.

  7. Ultrasound-air-assisted demulsified liquid-liquid microextraction by solidification of a floating organic droplet for determination of three antifungal drugs in water and biological samples.

    Science.gov (United States)

    Ezoddin, Maryam; Shojaie, Mehran; Abdi, Khosrou; Karimi, Mohammad Ali

    2017-03-01

    A novel ultrasound-air-assisted demulsified liquid-liquid microextraction by solidification of a floating organic droplet (UAAD-LLM-SFO) followed by HPLC-UV detection was developed for the analysis of three antifungal drugs in water and biological samples. In this method, 1-dodecanol was used as the extraction solvent. The emulsion was rapidly formed by pulling in and pushing out the mixture of sample solution and extraction solvent for 5 times repeatedly using a 10-mL glass syringe while sonication was performed. Therefore, an organic dispersive solvent required in common microextraction methods was not used in the proposed method. After dispersing, an aliquot of acetonitrile was introduced as a demulsifier solvent into the sample solution to separate two phases. Therefore, some additional steps, such as the centrifugation, ultrasonication, or agitation of the sample solution, are not needed. Parameters influencing the extraction recovery were investigated. The proposed method showed a good linearity for the three antifungal drugs studied with the correlation coefficients (R (2) > 0.9995). The limits of detection (LODs) and the limits of the quantification (LOQs) were between 0.01-0.03 μg L(-1) and 0.03-0.08 μg L(-1), respectively. The preconcentration factors (PFs) were in the range of 107-116, respectively. The precisions, as the relative standard deviations (RSDs) (n = 5), for inter-day and intra-day analysis were in the range of 2.1-4.5% and 6.5-8.5%, respectively. This method was successfully applied to determine the three antifungal drugs in tap water and biological samples. The recoveries of antifungal drugs in these samples were 92.4-98.5%. Graphical abstract Ultrasound-air-assisted demulsified liquid-liquid microextraction by solidification of a floating organic droplet for the analysis of three antifungal drugs prior HPLC-UV.

  8. Electro-optical response of polymer-dispersed liquid crystal single layers of large nematic droplets oriented by rubbed teflon nanolayers

    Science.gov (United States)

    Marinov, Y. G.; Hadjichristov, G. B.; Petrov, A. G.; Marino, S.; Versace, C.; Scaramuzza, N.

    2013-02-01

    The surface orienting effect of rubbed teflon nanolayers on the morphology and electro-optical (EO) response of polymer-dispersed liquid crystal (PDLC) single layers of large nematic droplets was studied experimentally. In PDLC composites of the nematic liquid crystal (LC) E7 and NOA65 polymer, single droplets of LC with diameters as larger as 10 μm were confined in layers with a thickness of 10 μm, and the nematic director field was efficiently modified by nanostructuring teflon rubbing of the glass plates of the PDLC cell. For layered PDLCs arranged and oriented in this way, the modulated EO response by the dielectric oscillations of the nematic director exhibits a selective amplitude-frequency modulation controllable by both temperature and voltage applied, and is simply related to the LC droplet size. That may be of practical interest for PDLC-based modulators operating in the infrasound frequency range.

  9. An impulse-driven liquid-droplet deposition interface for combining LC with MALDI MS and MS/MS.

    Science.gov (United States)

    Young, J Bryce; Li, Liang

    2006-03-01

    A simple and robust impulse-driven droplet deposition system was developed for off-line liquid chromatography matrix-assisted laser desorption ionization mass spectrometry (LC-MALDI MS). The system uses a solenoid operated with a pulsed voltage power supply to generate impulses that dislodge the hanging droplets from the LC outlet directly to a MALDI plate via a momentum transfer process. There is no contact between the LC outlet and the collection surface. The system is compatible with solvents of varying polarity and viscosity, and accommodates the use of hydrophobic and hydrophilic MALDI matrices. MALDI spots are produced on-line with the separation, and do not require further processing before MS analysis. It is shown that high quality MALDI spectra from 5 fmol of pyro-Glu-fibrinopeptide deposition after LC separation could be obtained using the device, indicating that there was no sample loss in the interface. To demonstrate the analytical performance of the system as a proteome analysis tool, a range of BSA digest concentrations covering about 3 orders of magnitude, from 5 fmol to 1 pmol, were analyzed by LC-MALDI quadrupole time-of-flight MS, yielding 6 and 57% amino acid sequence coverage, respectively. In addition, a complex protein mixture of an E. coli cell extract was tryptically digested and analyzed by LC-MALDI MS, resulting in the detection of a total of 409 unique peptides from 100 fractions of 15-s intervals.

  10. Computational and experimental study of the interactions between ionic liquids and volatile organic compounds.

    Science.gov (United States)

    Gao, Tingting; Andino, Jean M; Alvarez-Idaboy, J Raul

    2010-09-07

    Computational chemistry calculations were performed to investigate the interactions of ionic liquids with different classes of volatile organic compounds (VOCs), including alcohols, aldehydes, ketones, alkanes, alkenes, alkynes and aromatic compounds. At least one VOC was studied to represent each class. Initially, 1-butyl-3-methylimindazolium chloride (abbreviated as C(4)mimCl) was used as the test ionic liquid compound. Calculated interaction lengths between atoms in the ionic liquid and the VOC tested as well as thermodynamic data suggest that C(4)mimCl preferentially interacts with alcohols as compared to other classes of volatile organic compounds. The interactions of methanol with different kinds of ionic liquids, specifically 1-butyl-3-methylimidazolium bromine (C(4)mimBr) and 1-butyl-3-methylimidazolium tetrafluoroborate (C(4)mimBF(4)) were also studied. In comparing C(4)mimCl, C(4)mimBr, and C(4)mimBF(4), the computational results suggest that C(4)mimCl is more likely to interact with methanol. Laboratory experiments were performed to provide further evidence for the interaction between C(4)mimCl and different classes of VOCs. Fourier transform infrared spectroscopy was used to probe the ionic liquid surface before and after exposure to the VOCs that were tested. New spectral features were detected after exposure of C(4)mimCl to various alcohols. The new features are characteristic of the alcohols tested. No new IR features were detected after exposure of the C(4)mimCl to the aldehyde, ketone, alkane, alkene, alkyne or aromatic compounds studied. In addition, after exposing the C(4)mimCl to a multi-component mixture of various classes of compounds (including an alcohol), the only new peaks that were detected were characteristic of the alcohol that was tested. These experimental results demonstrated that C(4)mimCl is selective to alcohols, even in complex mixtures. The findings in this work provide information for future gas-phase alcohol sensor design.

  11. A volatile fluid assisted thermo-pneumatic liquid metal energy harvester

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Jianbo, E-mail: zhouyuan@mail.ipc.ac.cn, E-mail: jianbotang@mail.ipc.ac.cn [Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Wang, Junjie; Liu, Jing; Zhou, Yuan, E-mail: zhouyuan@mail.ipc.ac.cn, E-mail: jianbotang@mail.ipc.ac.cn [Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

    2016-01-11

    A close-cycle self-driving thermal energy harvester using liquid metal as energy carrier fluid has been proposed. The driving force that pushes the liquid metal against flow resistance and gravity is provided by a resistively heated volatile fluid based on thermo-pneumatic principle. The tested harvester prototype demonstrated its capability to extract thermal energy between small temperature gradient, at a scale of 10 °C. During a 5-h operation, it further demonstrated robust liquid metal recirculating performance at a time-average volume flow rate of 14 ml/min with a 12.25 W heating load. The prototype also managed to self-adjust to variable working conditions which indicated the reliability of this method. Advantages of this method include simple-structural design, rigid-motion free operation, and low-temperature actuation. These advantages make it uniquely suited for solar energy and low-grade heat harvesting, high heat flux electronics cooling, as well as autonomous machines actuating.

  12. Nuclear magnetic resonance study of epoxy- based polymer-dispersed liquid crystal droplets

    CERN Document Server

    Han, J W

    1998-01-01

    In this work, polymer-dispersed liquid crystals (PDLC) samples were prepared and studied by nuclear magnetic resonance. Proton NMR spectra and spin-lattice relaxations of 4-cyano-4'-pentylbiphenyl(5CB) and p-methoxybenzylidene-p-n-butylaniline (MBBA) liquid crystals confined in microdroplets were measured. The experimental results were compared with those of the liquid crystals in the pores of silica-gels and with those of the mixing components. The experimental results indicated that the nematic ordering in the microdroplets differed markedly from that observed in bulk nematic crystals. In addition, we examined spin-lattice relaxation mechanisms. The proton spin-lattice relaxation mechanisms in bulk nematic liquid crystals are well established. However, when nematic liquid crystals are confined in microdroplets, the relaxation mechanisms are expected to be affected. We examined possible relaxation mechanisms to explain the observed increase in the spin-lattice relaxation rate of liquid crystals confined in m...

  13. SELFIES, EMOJIS, LIKES: VOLATILE REPRESENTATIONS AND LIQUID READINGS IN THE DIGITAL AGE

    Directory of Open Access Journals (Sweden)

    Josiane da Cruz Lima Ribeiro

    2016-12-01

    Full Text Available This work aims at discussing the roles that hypermedia codes, such as selfies, emoji and likes, have played as representations and readings of self and other in the digital age, and how the school has behaved on this new outlook in dealing with volatile information and communication. The roads previously experienced by unilineal paths give way to the establishment of misshapen interconnective roads surrounding cyberspace and become unstable records of us and the reading we make of another person, constantly re-enacted by new records and, consequently, for new readings. Ubiquity, mediated mainly by mobile devices – mobile phones, smartphones and tablets –, provides this constant updating and metamorphoses, uninterruptedly, our representation in cyberspace. In this framework, the school is challenged to think about how to deal with these new perspectives of reading, since this is a reality brought by the student to the field of formal education. Therefore, we use the literature and took as a basis some theorists such as Santaella (2004; 2007; 2013, Hall (2006, Lévy (1994, Malini & Antoun (2013, among others, to bring to the discussion concepts of liquid identities, volatile representations, information and communication technologies and education.

  14. Surfactant-Induced Ordering and Wetting Transitions of Droplets of Thermotropic Liquid Crystals “Caged” Inside Partially Filled Polymeric Capsules

    Science.gov (United States)

    2015-01-01

    We report a study of the wetting and ordering of thermotropic liquid crystal (LC) droplets that are trapped (or “caged”) within micrometer-sized cationic polymeric microcapsules dispersed in aqueous solutions of surfactants. When they were initially dispersed in water, we observed caged, nearly spherical droplets of E7, a nematic LC mixture, to occupy ∼40% of the interior volume of the polymeric capsules [diameter of 6.7 ± 0.3 μm, formed via covalent layer-by-layer assembly of branched polyethylenimine and poly(2-vinyl-4,4-dimethylazlactone)] and to contact the interior surface of the capsule wall at an angle of ∼157 ± 11°. The internal ordering of LC within the droplets corresponded to the so-called bipolar configuration (distorted by contact with the capsule walls). While the effects of dodecyltrimethylammonium bromide (DTAB) and sodium dodecyl sulfate (SDS) on the internal ordering of “free” LC droplets are similar, we observed the two surfactants to trigger strikingly different wetting and configurational transitions when LC droplets were caged within polymeric capsules. Specifically, upon addition of SDS to the aqueous phase, we observed the contact angles (θ) of caged LC on the interior surface of the capsule to decrease, resulting in a progression of complex droplet shapes, including lenses (θ ≈ 130 ± 10°), hemispheres (θ ≈ 89 ± 5°), and concave hemispheres (θ < 85°). The wetting transitions induced by SDS also resulted in changes in the internal ordering of the LC to yield states topologically equivalent to axial and radial configurations. Although topologically equivalent to free droplets, the contributions that surface anchoring, LC elasticity, and topological defects make to the free energy of caged LC droplets differ from those of free droplets. Overall, these results and others reported herein lead us to conclude that caged LC droplets offer a platform for new designs of LC-droplet-based responsive soft matter that cannot

  15. Atomized spraying of liquid metal droplets on desired substrate surfaces as a generalized way for ubiquitous printed electronics

    Science.gov (United States)

    Zhang, Qin; Gao, Yunxia; Liu, Jing

    2014-09-01

    A direct electronics printing technique through atomized spraying for patterning room-temperature liquid metal droplets on desired substrate surfaces is proposed and experimentally demonstrated for the first time. This method is highly flexible and capable of fabricating electronic components on various target objects, with either flat or rough surfaces, made of different materials, or having different orientations from 2D to 3D geometrical configurations. With a pre-designed mask, the liquid metal ink can be directly deposited on the substrate to form various specific patterns which lead to the rapid prototyping of electronic devices. Further, extended printing strategies were also suggested to illustrate the adaptability of the method. For example, it can be used for making transparent conductive film with an optical transmittance of 47 % and a sheet resistance of 5.167Ω/□ due to natural porous structure. Different from the former direct writing technology where large surface tension and poor adhesion between the liquid metal and the substrate often impede the flexible printing process, the liquid metal here no longer needs to be pre-oxidized to guarantee its applicability on target substrates. One critical mechanism was that the atomized liquid metal microdroplets can be quickly oxidized in the air due to its large specific surface area, resulting in a significant increase of the adhesion capacity and thus firm deposition of the ink to the substrate. This study paved a generalized way for pervasively and directly printing electronics on various substrates which are expected to be significant in a wide spectrum of electrical engineering areas.

  16. Volatile Compounds Detected in Coconut Shell Liquid Smoke through Pyrolysis at a Fractioning Temperature of 350-420 C

    Directory of Open Access Journals (Sweden)

    Ruslin Hadanu

    2016-09-01

    Full Text Available This study evaluated the volatile components of liquid smoke from coconut shells obtained through the pyrolysis process at fraction 350-420 °C. The volatile compounds of liquid smoke from a coconut shell were analyzed using gas chromatography and mass spectrometry (GC-MS. Nineteen peaks were detected by GC-MS in the coconut shell liquid smoke, and 19 compounds also were identified. The volatile compounds were identified as follows based on their function group’s composition percentage: phenol (90.75%, carbonyl (3.71%, alcohol (1.81%, and benzene (3.73%, respectively. The liquid smoke contains a high ratio of phenol derivatives (90.75% in volatile profile. The phenol derivatives were the major volatile compounds found in the coconut shell liquid smoke.

  17. Measurements of liquid film thickness for a droplet at a two-fluid interface

    CERN Document Server

    Miessner, U; Delfos, R; Lindken, R; Westerweel, J

    2011-01-01

    The impact of a buoyancy driven oil droplet with an oil-water interface is investigated using time-resolved Particle Image Velocimetry (PIV) along with a phase discrimination by means of high-speed Laser Induced Fluorescence (LIF). In this paper we focus on the investigation of strategies to optimize the performance of high-speed PIV algorithms. Furthermore this data will be used for validation of numerical simulations of two phase flows. To simultaneously measure the flow velocities inside and around the oil droplet by PIV the refractive indices of both phases need to be matched. The aqueous phase consists of a mixture of corn syrup and water, which defines the viscosity as well as the refractive index. The disperse phase consists of a mixture of two mineral oils. The latter are mixed to match the refractive index of the continuous phase. Both phases are seeded with tracer particles required for PIV. A fluorescent dye is added to the dispersed phase to allow discrimination of the PIV signals originating from...

  18. Influence of radiative heat and mass transfer mechanism in system “water droplet-high-temperature gases” on integral characteristics of liquid evaporation

    Directory of Open Access Journals (Sweden)

    Glushkov Dmitrii O.

    2015-01-01

    Full Text Available Physical and mathematical (system of differential equations in private derivatives models of heat and mass transfer were developed to investigate the evaporation processes of water droplets and emulsions on its base moving in high-temperature (more than 1000 K gas flow. The model takes into account a conductive and radiative heat transfer in water droplet and also a convective, conductive and radiative heat exchange with high-temperature gas area. Water vapors characteristic temperature and concentration in small wall-adjacent area and trace of the droplet, numerical values of evaporation velocities at different surface temperature, the characteristic time of complete droplet evaporation were determined. Experiments for confidence estimation of calculated integral characteristics of processes under investigation - mass liquid evaporation velocities were conducted with use of cross-correlation recording video equipment. Their satisfactory fit (deviations of experimental and theoretical velocities were less than 15% was obtained. The influence of radiative heat and mass transfer mechanism on characteristics of endothermal phase transformations in a wide temperature variation range was established by comparison of obtained results of numerical simulation with known theoretical data for “diffusion” mechanisms of water droplets and other liquids evaporation in gas.

  19. Electrostatic charging of jumping droplets

    Science.gov (United States)

    Miljkovic, Nenad; Preston, Daniel J.; Enright, Ryan; Wang, Evelyn N.

    2013-09-01

    With the broad interest in and development of superhydrophobic surfaces for self-cleaning, condensation heat transfer enhancement and anti-icing applications, more detailed insights on droplet interactions on these surfaces have emerged. Specifically, when two droplets coalesce, they can spontaneously jump away from a superhydrophobic surface due to the release of excess surface energy. Here we show that jumping droplets gain a net positive charge that causes them to repel each other mid-flight. We used electric fields to quantify the charge on the droplets and identified the mechanism for the charge accumulation, which is associated with the formation of the electric double layer at the droplet-surface interface. The observation of droplet charge accumulation provides insight into jumping droplet physics as well as processes involving charged liquid droplets. Furthermore, this work is a starting point for more advanced approaches for enhancing jumping droplet surface performance by using external electric fields to control droplet jumping.

  20. OPTIMIZED DETERMINATION OF TRACE JET FUEL VOLATILE ORGANIC COMPOUNDS IN HUMAN BLOOD USING IN-FIELD LIQUID-LIQUID EXTRACTION WITH SUBSEQUENT LABORATORY GAS CHROMATOGRAPHIC-MASS SPECTROMETRIC ANALYSIS AND ON-COLUMN LARGE VOLUME INJECTION

    Science.gov (United States)

    A practical and sensitive method to assess volatile organic compounds (VOCs) from JP-8 jet fuel in human whole blood was developed by modifying previously established liquid-liquid extraction procedures, optimizing extraction times, solvent volume, specific sample processing te...

  1. Silver halide fiber-based evanescent-wave liquid droplet sensing with thermoelectrically cooled room temperature mid-infrared quantum cascade lasers

    Science.gov (United States)

    Chen, Jian Z.; Liu, Zhijun; Gmachl, Claire F.; Sivco, Deborah L.

    2005-11-01

    Quantum cascade lasers coupled directly to unclad silver halide fibers were used to assemble mid-infrared fiber-optics evanescent-wave sensors suitable to measure the chemical composition of simple liquid droplets. Quantum cascade lasers can be designed to emit across a wide range of mid-infrared wavelengths by tailoring the quantum-well structure, and the wavelength can be fine tuned by a thermoelectric cooler. Here, laser wavelengths were chosen which offer the largest absorption contrast between two constituents of a droplet. The laser was coupled to an unclad silver halide fiber, which penetrates through the droplet resting on a hydrophobic surface. For the same liquid composition and droplet size, the transmitted intensity is weaker for a droplet on a 1H,1H,2H,2H-perfluoro-octyltrichlorosilane coated glass slide than for one on a hexadecanethiol (HDT) coated Au-covered glass slide because of the high reflectivity of the HDT/Au surface at mid-infrared wavelengths. The absorption coefficients of water, glycerol, α-tocophenol acetate, and squalane were measured by varying the immersion length of the fiber; i.e. the droplet size. A pseudo-Beer-Lambert law fits well with the experimental data. We tested both aqueous liquid mixtures (acetone/water and ethanol/water) and oil-base solutions (n-dodecane/squalane and α-tocophenol acetate/squalane); α-tocophenol acetate and squalane are common ingredients of cosmetics, either as active ingredients or for chemical stabilization. Using a 300μm diameter silver halide fiber with a 25mm immersion length, the detection limits are 1 vol.% for α-tocophenol in squalane and 2 vol.% for acetone in water for laser wavenumbers of 1208 cm -1 and 1363 cm -1, respectively. This work was previously been reported in J. Z. Chen et al. Optics Express 13, 5953 (2005).

  2. Experimental evaluation and modeling of liquid jet penetration to estimate droplet size in a three-phase riser reactor

    Institute of Scientific and Technical Information of China (English)

    Ali Akbar Jamali; Shahrokh Shahhosseini; Yaghoub Behjat

    2016-01-01

    In this work, the effects of injecting an evaporating liquid jet into solid–gas flow are experimentally investigated. A new model (SHED model) and a supplementary model (spray model) have also been proposed to investigate some flow-field characteristics in three-phase fluidized bed with the mean relative error 4.3%between model and measured results. Some experiments were conducted to study the influences of flow-field parameters such as liquid volumetric flow rate, injection velocity, jet angle and gas superficial velocity as well as solid mass flux on the jet penetration depth (JPD). In addition, independent variables were experimentally employed to propose two empirical correlations for JPD by using multiple regression method and spray cone angle (SCA) by using dimensional analysis technique. The mean relative errors between the JPD and SCA correlations versus ex-perimental data were 7.5%and 3.9%, respectively. In addition, in order to identify the variable effect, a parametric study was carried out. Applying the proposed model can avoid direct use of expensive devices to measure JPD and to predict droplet size.

  3. Droplet impact on a thin liquid film: anatomy of the splash

    CERN Document Server

    Josserand, Christophe; Zaleski, Stéphane

    2015-01-01

    We investigate the dynamics of drop impact on a thin liquid film at short times in order to identify the mechanisms of splashing formation. Using numerical simulations and scaling analysis, we show that the splashing formation depends both on the inertial dynamics of the liquid and the cushioning of the gas. Two asymptotic regimes are identified, characterized by a new dimensionless number $J$: when the gas cushioning is weak, the jet is formed after a sequence of bubbles are entrapped and the jet speed is mostly selected by the Reynolds number of the impact. On the other hand, when the air cushioning is important, the lubrication of the gas beneath the drop and the liquid film controls the dynamics, leading to a single bubble entrapment and a weaker jet velocity.

  4. Droplet impact on a thin liquid film: anatomy of the splash

    Science.gov (United States)

    Josserand, Christophe; Ray, Pascal; Zaleski, Stéphane

    2016-09-01

    We investigate the dynamics of drop impact on a thin liquid film at short times in order to identify the mechanisms of splashing formation. Using numerical simulations and scaling analysis, we show that the splashing formation depends both on the inertial dynamics of the liquid and the cushioning of the gas. Two asymptotic regimes are identified, characterized by a new dimensionless number $J$: when the gas cushioning is weak, the jet is formed after a sequence of bubbles are entrapped and the jet speed is mostly selected by the Reynolds number of the impact. On the other hand, when the air cushioning is important, the lubrication of the gas beneath the drop and the liquid film controls the dynamics, leading to a single bubble entrapment and a weaker jet velocity.

  5. Transient behaviour of deposition of liquid metal droplets on a solid substrate

    Science.gov (United States)

    Chapuis, J.; Romero, E.; Soulié, F.; Bordreuil, C.; Fras, G.

    2016-10-01

    This paper investigates the mechanisms that contribute to the spreading of liquid metal macro-drop deposited during Stationary Pulsed Gas Metal Arc Welding on an initially cold solid workpiece. Surface tension and inertial effects take an important part in the behaviour of the liquid metal macro-drop, but in this configuration the influence of energetic effects can also be significant. The experimental results are discussed in the light of dimensional analysis in order to appreciate the influence of the process parameters and the physical mechanisms involved on the spreading of a macro-drop. A law is established to model forced non-isothermal spreading.

  6. Self-propelled droplets

    Science.gov (United States)

    Seemann, Ralf; Fleury, Jean-Baptiste; Maass, Corinna C.

    2016-11-01

    Self-propelled droplets are a special kind of self-propelled matter that are easily fabricated by standard microfluidic tools and locomote for a certain time without external sources of energy. The typical driving mechanism is a Marangoni flow due to gradients in the interfacial energy on the droplet interface. In this article we review the hydrodynamic prerequisites for self-sustained locomotion and present two examples to realize those conditions for emulsion droplets, i.e. droplets stabilized by a surfactant layer in a surrounding immiscible liquid. One possibility to achieve self-propelled motion relies on chemical reactions affecting the surface active properties of the surfactant molecules. The other relies on micellar solubilization of the droplet phase into the surrounding liquid phase. Remarkable cruising ranges can be achieved in both cases and the relative insensitivity to their own `exhausts' allows to additionally study collective phenomena.

  7. Droplets in annular-dispersed gas-liquid pipe-flows

    NARCIS (Netherlands)

    Van 't Westende, J.M.C.

    2008-01-01

    Annular-dispersed gas-liquid pipe-flows are commonly encountered in many industrial applications, and have already been studied for many decades. However, due to the great complexity of this type of flow, there are still many phenomena that are poorly understood. The aim of this thesis is to shed mo

  8. Characterization of the evaporation of interacting droplets using combined optical techniques

    Science.gov (United States)

    Perrin, Lionel; Castanet, Guillaume; Lemoine, Fabrice

    2015-02-01

    A monodisperse droplet stream is injected into a high-temperature enclosure supplied with air heated up to 540 °C. The two-color laser-induced fluorescence (2cLIF) is used for measuring the droplet temperature. The liquid fuel is seeded by pyrromethene 597-C8, which is a temperature-sensitive fluorescent dye. Calibration tests are performed for different types of fuels including ethanol and several alkanes and some of their mixtures. Morphology-dependent resonances (MDRs) are identified as a possible adverse effect for temperature measurements. Due to MDRs, lasing of pyrromethene 597-C8 may occur within fluorescent droplets and affect drastically the fluorescence signal upon which temperature measurement relies. The determination of the droplet size and velocity is achieved by means of quantitative shadow imaging. A double cavity PIV laser is focused on a piece of PMMA doped with a fluorescent dye to produce the background illumination of the droplets. A PIV camera is used to capture the drop motion between the pulses of the laser cavities. A large range of initial distance parameters (the ratio between the inter-droplet distance and the droplet diameter) is explored for different liquid fuels (ethanol, isohexane, n-heptane, n-decane, n-dodecane) and their mixtures. To put forward the effects of the interactions between the droplets, size and temperature measurements are compared to the isolated droplet whose evolution can be predicted with the use of classical models. Comparisons reveal that the inter-droplet spacing and also the fuel volatility play an important role in the reduction of the heat and mass transfers for these interacting droplets. Finally, the ability of the 2cLIF techniques to address the case of multicomponent droplet is also demonstrated.

  9. Dispersive liquid-liquid microextraction method based on solidification of floating organic droplet for the determination of triazine herbicides in water and sugarcane samples.

    Science.gov (United States)

    Sanagi, Mohd Marsin; Abbas, Hana Hassan; Ibrahim, Wan Aini Wan; Aboul-Enien, Hassan Y

    2012-07-15

    Dispersive liquid-liquid microextraction method based on solidification of floating organic droplet (DLLME-SFO) was developed for the analysis of triazines. As model compounds four selected triazine herbicides namely, simazine, atrazine, secbumeton and cyanazine were employed to estimate the extraction efficiency. The experimental conditions were comprehensively studied for the DLLME-SFO method. Under the use of 10 μL of 1-undecanol as extraction solvent, 100 μL of acetonitrile as disperser solvent and 5% (w/v) NaCl for 3 min the results demonstrated that the repeatability (RSD%) of the optimised DLLME-SFO method ranged from 0.03% to 5.1% and the linearity in the range of 0.01-100 ppb. Low limits of detection (0.037-0.008 ppb), and good enrichment factors (195-322) were obtained. The DLLME-SFO method applied in water and sugarcane samples showed excellent relative recoveries (95.7-116.9%) with RSDs <8.6% (n=3) for all samples.

  10. Dynamics of a Water Droplet over a Sessile Oil Droplet: Compound Droplets Satisfying a Neumann Condition.

    Science.gov (United States)

    Iqbal, R; Dhiman, S; Sen, A K; Shen, Amy Q

    2017-06-13

    We report the dynamics of compound droplets with a denser liquid (water) droplet over a less dense sessile droplet (mineral oil) that satisfies the Neumann condition. For a fixed size of an oil droplet, depending on the size of the water droplet, either it attains the axisymmetric position or tends to migrate toward the edge of the oil droplet. For a water droplet-to-oil droplet at volume ratio Vw/Vo ≥ 0.05, stable axisymmetric configuration is achieved; for Vw/Vo droplet is observed. The stability and migration of water droplets of size above and below critical size, respectively, are explained using the force balance at the three-phase contact line and film tension. The larger and smaller droplets that initially attain the axisymmetric position or some radial position, respectively, evaporate continuously and thus migrate toward the edge of the oil droplet. The radial location and migration of the water droplets of different initial sizes with respect to time are studied. Experiments with water droplets on a flat oil-air interface did not show migration, which signified the role of the curved oil-air interface for droplet migration. Finally, coalescence of water droplets of size above the critical size at the axisymmetric position is demonstrated. Our compound droplet studies could be beneficial for applications involving droplet transport where contamination due to direct contact and pinning of droplets on solid surfaces is of concern. Migration and coalescence of water droplets on curved oil-air interfaces could open new frontiers in chemical and biological applications including multiphase processing and biological interaction of cells and atmospheric chemistry.

  11. Role of Aerosol Liquid Water in Secondary Organic Aerosol Formation from Volatile Organic Compounds.

    Science.gov (United States)

    Faust, Jennifer A; Wong, Jenny P S; Lee, Alex K Y; Abbatt, Jonathan P D

    2017-02-07

    A key mechanism for atmospheric secondary organic aerosol (SOA) formation occurs when oxidation products of volatile organic compounds condense onto pre-existing particles. Here, we examine effects of aerosol liquid water (ALW) on relative SOA yield and composition from α-pinene ozonolysis and the photooxidation of toluene and acetylene by OH. Reactions were conducted in a room-temperature flow tube under low-NOx conditions in the presence of equivalent loadings of deliquesced (∼20 μg m(-3) ALW) or effloresced (∼0.2 μg m(-3) ALW) ammonium sulfate seeds at exactly the same relative humidity (RH = 70%) and state of wall conditioning. We found 13% and 19% enhancements in relative SOA yield for the α-pinene and toluene systems, respectively, when seeds were deliquesced rather than effloresced. The relative yield doubled in the acetylene system, and this enhancement was partially reversible upon drying the prepared SOA, which reduced the yield by 40% within a time scale of seconds. We attribute the high relative yield of acetylene SOA on deliquesced seeds to aqueous partitioning and particle-phase reactions of the photooxidation product glyoxal. The observed range of relative yields for α-pinene, toluene, and acetylene SOA on deliquesced and effloresced seeds suggests that ALW plays a complicated, system-dependent role in SOA formation.

  12. Evaporation release behavior of volatile fission products from liquid sodium pool to the inert cover gas

    Energy Technology Data Exchange (ETDEWEB)

    Nakagiri, T.; Miyahara, S. [Oarai Engineering Center, Power Reactor and Nuclear Fuel Development Corp., Oaraimachi, Ibaraki (Japan)

    1996-12-01

    In fuel failure of sodium cooled fast breeder reactors, released volatile fission products (VFPs) such as iodine and cesium from the fuel will be dissolved into the liquid sodium coolant and transferred to the cover vaporization. In the cover gas system of the reactor, natural convection occurs due to temperature differences between the sodium pool and the gas phase. The release rates of VFPs together with sodium vaporization are considered to be controlled by the convection. In this study, three analytical models are developed and examined to calculate the transient release rates using the equilibrium partition coefficients of VFPs. The calculated release rates are compared with experimental results for sodium and sodium iodide. The release rate of sodium is closest to the calculation by the heterogeneous nucleation theory. The release rate of sodium iodide obtained from the experiment is between the release rates calculated by the model based on heat-and-mass transfer analogy and the Hill`s theory. From this study, it is confirmed that the realistic release rate of sodium is able to be calculated by the model based on the heterogeneous nucleation theory. The conservative release rate of sodium iodide is able to be calculated by the model based on the Hill`s theory using the equilibrium partition coefficient of sodium iodide. (author) 7 figs., 1 tab., 3 refs.

  13. Discharge characteristics of an ablative pulsed plasma thruster with non-volatile liquid propellant

    Science.gov (United States)

    Ling, William Yeong Liang; Schönherr, Tony; Koizumi, Hiroyuki

    2017-07-01

    Pulsed plasma thrusters (PPTs) are a form of electric spacecraft propulsion. They have an extremely simple structure and are highly suitable for nano/micro-spacecraft with weights in the kilogram range. Such small spacecraft have recently experienced increased growth but still lack suitable efficient propulsion systems. PPTs operate in a pulsed mode (one discharge = one shot) and typically use solid polytetrafluoroethylene (PTFE) as a propellant. However, new non-volatile liquids in the perfluoropolyether (PFPE) family have recently been found to be promising alternatives. A recent study presented results on the physical characteristics of PFPE vs. PTFE, showing that PFPE is superior in terms of physical characteristics such as its resistance to carbon deposition. This letter will examine the electrical discharge characteristics of PFPE vs. PTFE. The results demonstrate that PFPE has excellent shot-to-shot repeatability and a lower discharge resistance when compared with PTFE. Taken together with its physical characteristics, PFPE appears to be a strong contender to PTFE as a PPT propellant.

  14. Selection of ionic liquids for enhancing the gas solubility of volatile organic compounds.

    Science.gov (United States)

    Gonzalez-Miquel, Maria; Palomar, Jose; Rodriguez, Francisco

    2013-01-10

    A systematic thermodynamic analysis has been carried out for selecting cations and anions to enhance the absorption of volatile organic compounds (VOCs) at low concentration in gaseous streams by ionic liquids (ILs), using COSMO-RS methodology. The predictability of computational procedure was validated by comparing experimental and COSMO-RS calculated Henry's law constant data over a sample of 125 gaseous solute-IL systems. For more than 2400 solute-IL mixtures evaluated, including 9 solutes and 270 ILs, it was found that the lower the activity coefficient at infinite dilution (γ(∞)) of solutes in the ILs, the more the exothermic excess enthalpy (H(E)) of the equimolar IL-solute mixtures. Then, the solubility of a representative sample of VOC solutes, with very different chemical nature, was screened in a wide number of ILs using COSMO-RS methodology by means of γ(∞) and H(E) parameters, establishing criteria to select the IL structures that promote favorable solute-solvent intermolecular interactions. As a result of this analysis, an attempt of classification of VOCs respect to their potential solubility in ILs was proposed, providing insights to rationally select the cationic and anionic species for a possible development of absorption treatments of VOC pollutants based on IL systems.

  15. Stability of a volatile liquid film spreading along a heterogeneously-heated substrate.

    Science.gov (United States)

    Tiwari, Naveen; Davis, Jeffrey M

    2011-03-01

    The dynamics and stability of a thin, viscous film of volatile liquid flowing under the influence of gravity over a non-uniformly heated substrate are investigated using lubrication theory. Attention is focused on the regime in which evaporation balances the flow due to gravity. The film terminates above the heater at an apparent contact line, with a microscopically thin precursor film adsorbed due to the disjoining pressure. The film develops a weak thermocapillary ridge due to the Marangoni stress at the upstream edge of the heated region. As for spreading films, a more significant ridge is formed near the apparent contact line. For weak Marangoni effects, the film evolves to a steady profile. For stronger Marangoni effects, the film evolves to a time-periodic state. Results of a linear stability analysis reveal that the steady film is unstable to transverse perturbations above a critical value of the Marangoni parameter, leading to finger formation at the contact line. The streamwise extent of the fingers is limited by evaporation. The time-periodic profiles are always unstable, leading to the formation of periodically-oscillating fingers. For rectangular heaters, the film profiles after instability onset are consistent with images from published experimental studies.

  16. Demonstration of Four Fundamental Operations of Liquid Droplets for Digital Microfluidic Systems Based on an Electrowetting-on-Dielectric Actuator

    Institute of Scientific and Technical Information of China (English)

    YUE Rui-Feng; WU Jian-Gang; ZENG Xue-Feng; KANG Ming; LIU Li-Tian

    2006-01-01

    @@ An electrowetting-on-dielectric actuator is developed, in which the liquid is sandwiched between top and bottom plates. For the bottom plate, silicon wafer is used as the substrate, the heavily phosphorus-doped polysilicon film is deposited by low pressure chemical vapour deposition as the microelectrode array, and thermally grown SiO2 film as the dielectric layer. The top plate is a glass plate covered with transparent and conductive indium tin oxide as the ground electrode. In addition, a Teflon(R) AFl600 film is spun on the surface of both the platee as the hydrophobic layer. The experimental results show that when the gap height between two plates is 133μm,a prototype of the device is capable of creating, transporting, merging and dividing droplets of deionized water in an air environment with a 70 V at 10Hz voltage pulse. This is also established by simulations using the computational fluidic software of CFD-ACE+.

  17. Comparison of ultrasound-induced bioeffects in glass catfish after injection with optison and liquid perflourocarbon droplets

    Science.gov (United States)

    Maruvada, Subha; Hynynen, Kullervo

    2003-04-01

    This work is an investigation of ultrasound-induced bioeffects in vivo. Glass catfish were used for these experiments because they are optically transparent. Anaesthetized fish were injected with either optison (OPT) or liquid perflourocarbon droplets (LPD), using microinjection techniques. Shortly after injection, the fish were insonified with one of two single element focused transducers (1.091 MHz and 0.747 MHz). An inverted microscope combined with a digital camera was used to optically monitor ultrasound interaction with the blood vessels in the tail of the fish at 200x magnification. The entire interaction was videotaped and digitized. The fish were insonified at power levels between 1-80 W, which translated into acoustic pressures from 0.45-15 MPa. Sonications were pulsed with burst lengths of 10 ms and 100 ms and a repetition frequency of 1 Hz. The entire length of one sonication at a specific pressure was 20 seconds. The effects of the sonication were analyzed at each pressure level. The ultrasound-induced bioeffects due to OPT and LPD were compared. Threshold values for damage were lower after OPT injection than after LPD injection, especially at lower frequencies.

  18. The Effects of Resistance to Shift of the Equilibrium State of a Liquid Droplet in Contact with a Solid.

    Science.gov (United States)

    Iliev

    1999-05-01

    The effect of blocking the shift of the contact surface between a liquid drop and a solid body is discussed. The model proposed in (S. D. Iliev, 1997, J. Colloid Interface Sci., 194, 287) is discussed. This equilibrium model considers the resistance to shift by adding an energy to the classical capillary equilibrium model. It is shown that the set of equilibrium shapes of static droplets is effectively modeled. Studying the set of equilibrium axisymmetric drops, located on a horizontal surface, the analysis proves that the contact angle hysteresis is described without introducing a dependence between the resistance-to-shift coefficients and the drop volume and Bond's number. A possibility of realizing a stick-slip motion and division of the equilibrium drops is studied, too. It is shown that the equilibrium model describes also the set of equilibrium nonaxisymmetric static drops. The everyday experience to obtain the various nonaxisymmetric drop shapes by the deforming of contact line with a thin rod is numerically modeled. Copyright 1999 Academic Press.

  19. Effect of an oxygen plasma on the physical and chemical properties of several fluids for the Liquid Droplet Radiator

    Science.gov (United States)

    Gulino, Daniel A.; Coles, Carolyn E.

    1987-01-01

    The Liquid Droplet Radiator is one of several radiator systems currently under investigation by NASA Lewis Research Center. It involves the direct exposure of the radiator working fluid to the space environment. An area of concern is the potential harmful effects of the low-Earth-orbit atomic oxygen environment on the radiator working fluid. To address this issue, seven candidate fluids were exposed to an oxygen plasma environment in a laboratory plasma asher. The fluids studied included Dow Corning 705 Diffusion Pump Fluid, polymethylphenylsiloxane and polydimethylsiloxane, both of which are experimental fluids made by Dow Corning, Fomblin Z25, made by Montedison, and three fluids from the Krytox family of fluids, Krytox 143AB, 1502, and 16256, which are made by DuPont. The fluids were characterized by noting changes in visual appearance, physical state, mass, and infrared spectra. Of the fluids tested, the Fomblin and the three Krytoxes were the least affected by the oxygen plasma. The only effect noted was a change in mass, which was most likely due to an oxygen-catalyzed depolymerization of the fluid molecule.

  20. INFLUENCE OF INVESTORS’ ATTENTION ON STOCK RETURN, LIQUIDITY, AND RETURN VOLATILITY COMPARISON BETWEEN MANUFACTURE COMPANIES IN INDONESIA AND INDIA

    OpenAIRE

    Puspita Sari, Noviana Icha

    2014-01-01

    This research aims to examine the influence of investors’ attention of company stock on stock return, liquidity, and return volatility comparison between manufacture companies in Indonesia and India in the year of 2011-2013. Investors’ attention is measured by a direct proxy which is Google Search Volume Index from Google trends. This research uses secondary data and processed by regression analysis. The samples are gathered from Indonesia stock exchange and India stock exchange. The result o...

  1. Fragment structure from vapor explosions during the impact of molten metal droplets into a liquid pool

    Science.gov (United States)

    Kouraytem, Nadia; Li, Er Qiang; Vakarelski, Ivan Uriev; Thoroddsen, Sigurdur

    2015-11-01

    High-speed video imaging is used in order to look at the impact of a molten metal drop falling into a liquid pool. The interaction regimes are three: film boiling, nucleate boiling or vapor explosion. Following the vapor explosion, the metal fragments and different textures are observed. It was seen that, using a tin alloy, a porous structure results whereas using a distinctive eutectic metal, Field's metal, micro beads are formed. Different parameters such as the metal type, molten metal temperature, pool surface tension and pool boiling temperature have been altered in order to assess the role they play on the explosion dynamics and the molten metal's by product.

  2. HIGH-SPEED, CLINICAL-SCALE MICROFLUIDIC GENERATION OF STABLE PHASE-CHANGE DROPLETS FOR GAS EMBOLOTHERAPY

    Science.gov (United States)

    Bardin, David; Martz, Thomas D.; Sheeran, Paul S.; Shih, Roger; Dayton, Paul A.; Lee, Abraham P.

    2013-01-01

    In this study we report on a microfluidic device and droplet formation regime capable of generating clinical-scale quantities of droplet emulsions suitable in size and functionality for in vivo therapeutics. By increasing the capillary number – based on the flow rate of the continuous outer phase – in our flow-focusing device, we examine three modes of droplet breakup: geometry-controlled, dripping, and jetting. Operation of our device in the dripping regime results in the generation of highly monodisperse liquid perfluoropentane droplets in the appropriate 3–6 µm range at rates exceeding 105 droplets per second. Based on experimental results relating droplet diameter and the ratio of the continuous and dispersed phase flow rates, we derive a power series equation, valid in the dripping regime, to predict droplet size by Dd ≅ 27(QC/QD)−5/12. The volatile droplets in this study are stable for weeks at room temperature yet undergo rapid liquid-to-gas phase transition, and volume expansion, above a uniform thermal activation threshold. The opportunity exists to potentiate locoregional cancer therapies such as thermal ablation and percutaneous ethanol injection using thermal or acoustic vaporization of these monodisperse phase-change droplets to intentionally occlude the vessels of a cancer. PMID:22011845

  3. Ionic liquid-assisted liquid-phase microextraction based on the solidification of floating organic droplets combined with high performance liquid chromatography for the determination of benzoylurea insecticide in fruit juice.

    Science.gov (United States)

    Yang, Miyi; Zhang, Panjie; Hu, Lu; Lu, Runhua; Zhou, Wenfeng; Zhang, Sanbing; Gao, Haixiang

    2014-09-19

    A green, simple, and efficient method, ionic liquid-assisted liquid-liquid microextraction based on the solidification of floating organic droplets (ILSFOD-LLME) collected via a bell-shaped collection device (BSCD) coupled to high performance liquid chromatography with a variable-wavelength detector, was developed for the preconcentration and analysis of seven benzoylurea insecticides (BUs) in fruit juice. In the proposed method, the low-density solvent 1-dodecanol and the ionic liquid trihexyl(tetradecyl)phosphonium hexafluorophosphate ([P14, 6, 6, 6]PF6) were used as extractant. The extraction solvent droplet was easily collected and separated by the BSCD without centrifugation. The experimental parameters were optimized by the one-factor-at-a-time approach and were followed using an orthogonal array design. The results indicated the different effects of each parameter for extraction efficiency. Under the optimal conditions in the water model, the limits of detection for the analytes varied from 0.03 to 0.28μgL(-1). The enrichment factors ranged from 160 to 246. Linearities were achieved for hexaflumuron and flufenoxuron in the range of 0.5-500μgL(-1), for triflumuron, lufenuron and diafenthiuron in the range of 1-500μgL(-1), and for diflubenzuron and chlorfluazuron in the range of 5-500μgL(-1); the correlation coefficients for the BUs ranged from 0.9960 to 0.9990 with recoveries of 75.6-113.9%. Finally, the developed technique was successfully applied to real fruit juice with acceptable results. The relative standard deviations (RSDs) of the seven BUs at two spiked levels (50 and 200μgL(-1)) varied between 0.1% and 7.3%.

  4. Analysis of Liquid–Liquid Droplets Fission and Encapsulation in Single/Two Layer Microfluidic Devices Fabricated by Xurographic Method

    Directory of Open Access Journals (Sweden)

    Chang Nong Lim

    2017-02-01

    Full Text Available This paper demonstrates a low cost fabrication approach for microscale droplet fission and encapsulation. Using a modified xurography method, rapid yet reliable microfluidic devices with flexible designs (single layer and double layer are developed to enable spatial control of droplet manipulation. In this paper, two different designs are demonstrated, i.e., droplet fission (single layer and droplet encapsulation (double layer. In addition, the current fabrication approach reduces the overall production interval with the introduction of a custom-made polydimethylsiloxane (PDMS aligner. Apart from that, the fabricated device is able to generate daughter droplets with the coefficient of variance (CV below 5% and double emulsions with CV maintained within 10% without involvement of complex surface wettability modification.

  5. Determination of fungicides in fruit juice by ultrasound-assisted dispersive liquid-liquid microextraction based on solidification of floating organic solvent droplets followed by high performance liquid chromatography.

    Science.gov (United States)

    Fan, Run-Zhen; Liu, Congyun; Jiang, Wenqing; Wang, Xiaonan; Liu, Fengmao

    2014-01-01

    Ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) based on solidification of the floating organic solvent droplets (SFO) combined with HPLC was used for determination of five fungicides in fruit juice samples. 1-Dodecanol, which has a low density and low toxicity, was used as the extraction solvent in UA-DLLME. The solidification of floating organic droplets facilitates the transfer of analytes from the aqueous phase to the organic phase. This method was easy, quick, inexpensive, precise, and linear over a wide range. Under the optimized conditions, the enrichment factors for a 5 mL fruit juice sample were 25 to 56, and the LODs for the five fungicides ranged from 5 to 50 microg/L. The average recoveries ranged from 71.8 to 118.2% with RSDs of 0.9 to 13.9%. Application of the DLLME-SFO technique allows successful separation and preconcentration of the fungicides at a low concentration level in fruit juice samples.

  6. Sensitivity of the Grid-point Atmospheric Model of IAP LASG (GAMIL1.1.0) Climate Simulations to Cloud Droplet Effective Radius and Liquid Water Path

    Institute of Scientific and Technical Information of China (English)

    LI Lijuan; Yuqing WANG; WANG Bin; ZHOU Wianjun

    2008-01-01

    This paper documents a study to examine the sensitivity to cloud droplet effective radius and liquid water path and the alleviation the energy imbalance at the top of the atmosphere and at the surface in the latest version of the Grid-point Atmospheric Model of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics (IAP) (GAMILI.I.0). Considerable negative biases in all flux components, and thus an energy imbalance, are found in GAMIL1.1.0. In order to alleviate the energy imbalance, two modifications, namely an increase in cloud droplet effective radius and a decrease in cloud liquid water path, have been made to the cloud properties used in GAMIL. With the increased cloud droplet effective radius, the single scattering albedo of clouds is reduced, and thus the reflection of solar radiation into space by clouds is reduced and the net solar radiation flux at the top of the atmosphere is increased. With the reduced cloud optical depth, the net surface shortwave radiation flux is increased, causing a net warming over the land surface. This results in an increase in both sensible and latent heat fluxes over the land regions, which is largely balanced by the increased terrestrial radiation fluxes. Consequently, the energy balance at the top of atmosphere and at the surface is achieved with energy flux components consistent with available satellite observations.

  7. Sensitive determination of methadone in human serum and urine by dispersive liquid-liquid microextraction based on the solidification of a floating organic droplet followed by HPLC-UV.

    Science.gov (United States)

    Taheri, Salman; Jalali, Fahimeh; Fattahi, Nazir; Jalili, Ronak; Bahrami, Gholamreza

    2015-10-01

    Dispersive liquid-liquid microextraction based on solidification of floating organic droplet was developed for the extraction of methadone and determination by high-performance liquid chromatography with UV detection. In this method, no microsyringe or fiber is required to support the organic microdrop due to the usage of an organic solvent with a low density and appropriate melting point. Furthermore, the extractant droplet can be collected easily by solidifying it at low temperature. 1-Undecanol and methanol were chosen as extraction and disperser solvents, respectively. Parameters that influence extraction efficiency, i.e. volumes of extracting and dispersing solvents, pH, and salt effect, were optimized by using response surface methodology. Under optimal conditions, enrichment factor for methadone was 134 and 160 in serum and urine samples, respectively. The limit of detection was 3.34 ng/mmL in serum and 1.67 ng/mL in urine samples. Compared with the traditional dispersive liquid-liquid microextraction, the proposed method obtained lower limit of detection. Moreover, the solidification of floating organic solvent facilitated the phase transfer. And most importantly, it avoided using high-density and toxic solvents of traditional dispersive liquid-liquid microextraction method. The proposed method was successfully applied to the determination of methadone in serum and urine samples of an addicted individual under methadone therapy.

  8. Droplet turbulence interactions under subcritical and supercritical conditions

    Science.gov (United States)

    Coy, E. B.; Greenfield, S. C.; Ondas, M. S.; Song, Y.-H.; Spegar, T. D.; Santavicca, D. A.

    1993-01-01

    The goal of this research is to experimentally characterize the behavior of droplets in vaporizing liquid sprays under conditions typical of those encountered in high pressure combustion systems such as liquid fueled rocket engines. Of particular interest are measurements of droplet drag, droplet heating, droplet vaporization, droplet distortion, and secondary droplet breakup, under both subcritical and supercritical conditions. The paper presents a brief description of the specific accomplishments which have been made over the past year.

  9. Simultaneous Distillation Extraction of Some Volatile Flavor Components from Pu-erh Tea Samples—Comparison with Steam Distillation-Liquid/Liquid Extraction and Soxhlet Extraction

    Science.gov (United States)

    Gu, Xungang; Zhang, Zhengzhu; Wan, Xiaochun; Ning, Jingming; Yao, Chengcheng; Shao, Wanfang

    2009-01-01

    A simutaneous distillation extraction (SDE) combined GC method was constructed for determination of volatile flavor components in Pu-erh tea samples. Dichloromethane and ethyl decylate was employed as organic phase in SDE and internal standard in determination, respectively. Weakly polar DB-5 column was used to separate the volatile flavor components in GC, 10 of the components were quantitatively analyzed, and further confirmed by GC-MS. The recovery covered from 66.4%–109%, and repeatability expressed as RSD was in range of 1.44%–12.6%. SDE was most suitable for the extraction of the anlytes by comparing with steam distillation-liquid/liquid extraction and Soxhlet extraction. Commercially available Pu-erh tea samples, including Pu-erh raw tea and ripe tea, were analyzed by the constructed method. the high-volatile components, such as benzyl alcohol, linalool oxide, and linalool, were greatly rich in Pu-erh raw teas, while the contents of 1,2,3-Trimethoxylbenzene and 1,2,4-Trimethoxylbenzene were much high in Pu-erh ripe teas. PMID:20169174

  10. Detection of heavy-metal ions using liquid crystal droplet patterns modulated by interaction between negatively charged carboxylate and heavy-metal cations.

    Science.gov (United States)

    Han, Gyeo-Re; Jang, Chang-Hyun

    2014-10-01

    Herein, we demonstrated a simple, sensitive, and rapid label-free detection method for heavy-metal (HM) ions using liquid crystal (LC) droplet patterns on a solid surface. Stearic-acid-doped LC droplet patterns were spontaneously generated on an n-octyltrichlorosilane (OTS)-treated glass substrate by evaporating a solution of the nematic LC, 4-cyano-4'-pentylbiphenyl (5CB), dissolved in heptane. The optical appearance of the droplet patterns was a dark crossed texture when in contact with air, which represents the homeotropic orientation of the LC. This was caused by the steric interaction between the LC molecules and the alkyl chains of the OTS-treated surface. The dark crossed appearance of the acid-doped LC patterns was maintained after the addition of phosphate buffered saline (PBS) solution (pH 8.1 at 25°C). The deprotonated stearic-acid molecules self-assembled through the LC/aqueous interface, thereby supporting the homeotropic anchoring of 5CB. However, the optical image of the acid-doped LC droplet patterns incubated with PBS containing HM ions appeared bright, indicating a planar orientation of 5CB at the aqueous/LC droplet interface. This dark to bright transition of the LC patterns was caused by HM ions attached to the deprotonated carboxylate moiety, followed by the sequential interruption of the self-assembly of the stearic acid at the LC/aqueous interface. The results showed that the acid-doped LC pattern system not only enabled the highly sensitive detection of HM ions at a sub-nanomolar concentration but it also facilitated rapid detection (<10 min) with simple procedures.

  11. Characteristics of the entrained droplets in gas-liquid two-phase annular flow%气液两相环状流中夹带液滴特性研究

    Institute of Scientific and Technical Information of China (English)

    樊文娟; 彭颖

    2016-01-01

    气液两相环状流中液体薄膜沿着管壁流动而速度较大的气核在管中心流动,通常速度较大的气核会夹带部分液滴。液滴夹带来源于沿着管壁流动的液体层的雾化速率和液滴沉积速率之间的平衡过程。目前大多数环状两相流的研究主要集中在对主要夹带现象的分析上。文中主要从夹带液滴直径、液滴速度分布和夹带分数3个方面进行夹带液滴特性研究。%The liquid film flows along the pipe wall and the gas nucleus of higher speed flows in the center of the pipe flow in the gas-liquid two-phase annular flow,usually the high speed gas nucleus entrains some droplets. The droplet entrainment is derived from a balance between the rate of atomization of the liquid layer flowing along the pipe wall and the rate of deposition of droplets. When gas flow rate is low,gravity sedimentation controls the deposition rate,and when the gas phase is at high flow velocity,droplet turbulence controls the deposition rate. At present,most of the annular two-phase flow research focuses on the analysis of the main entrainment phenomenon. This article mainly discussed the entrained droplets from the gas liquid interface,because the entrained droplets play an important role in a lot of flow parameters. Therefore, this article made the droplet entrainment characteristics research mainly from the three aspects,namely droplet diameter, droplet velocity distribution and entrainment fraction.

  12. A comparison and survey of the measured cloud liquid water content and an analysis of the bimodal droplet spectra observed during COPE-MED

    Science.gov (United States)

    Siegfried, Jeffrey Alan

    The primary objective of the COnvective Precipitation Experiment - Microphysics and Entrainment Dependencies (COPE-MED) was part of a larger field campaign undertaken during July and August 2013 with the primary goal of improving quantitative precipitation forecasts for summertime convection over SW England, with a special emphasis on understanding microphysical processes that impact hydrometeor development. Understanding the interplay between the warm rain and ice processes is necessary to lead to better parameterizations for precipitation rates in numerical simulations so, to that end, a detailed survey of the liquid water content and total cloud droplet number concentrations measured during COPE-MED is undertaken. Additionally, a probe-by-probe comparison of the liquid water content was performed in order to ascertain their relative performance and consistency during COPE-MED and under certain conditions. These comparisons reveal generally good agreement between the in situ probes used during COPE-MED, but also reveals that there may be potential issues with certain probes under certain conditions. Secondly, observations from the University of Wyoming King Air research aircraft show occurrences of bimodal cloud droplet spectra, where there exist two distinct droplet diameter populations. An analysis of several COPE-MED cases, based on observations from in situ cloud microphysical probes, is presented. Several environmental factors are examined to look for evidence of entrainment events within regions containing bimodal spectra. Correlations between the adiabaticity and concentration in each mode are examined. While some of these analyses indicate evidence of entrainment, others are less clear. The theoretical super-saturation a parcel would experience when neglecting the small mode and the updraft speed required to achieve various levels of super-saturation are also calculated. Initial results show evidence that secondary activation could potentially explain the

  13. A universal bubble-growth equation for pure liquids and binary solutions with a non-volatile solute

    Energy Technology Data Exchange (ETDEWEB)

    Miyatake, Osamu [Kyushu Univ., Fukuoka (Japan). Dept. of Chemical Engineering; Tanaka, Itsuo [Gifu Univ. (Japan). Dept. of Biological Production System; Lior, N. [Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Mechanical Engineering and Applied Mechanics

    1996-12-31

    A simple equation suitable for predicting the growth rate of a vapor bubble in uniformly-superheated pure liquids and in binary solutions with a non-volatile solute was developed. The equation also improves on the popular pure-liquid bubble growth expression of Mikie et al. (1970) in that it is valid throughout the bubble growth history, i.e., in the surface-tension-, inertia-, and heat-transfer-controlled regimes, it accounts for bubble growth acceleration effects, and uses correctly-related and variable fluid properties. It was found to agree very well with experimental data for pure water and for aqueous NaCl solutions. As the bubble growth in superheated solutions with a non-volatile solute was found to be quite insensitive to diffusion and non-equilibrium effects in a broad range of common solution properties, this equation is likely to be universally valid for many liquids and solutions. Bubble growth in superheated fluids is of key interest in boiling phenomena in general and in flash evaporation in particular. Applications include a wide variety of separation processes such as water desalination, and energy conversion processes such as ocean-thermal energy conversion, geothermal power generation, and nuclear reactor safety.

  14. Significance of droplet-droplet interactions in droplet streams: Atmospheric to supercritical conditions

    Science.gov (United States)

    Connon, Corinne Shirley

    In an effort to optimize liquid fuel combustion a considerable amount of research has been directed towards the atomization of large liquid masses into small droplets to increase the surface area available for vaporization. The current work uses a single linear array of moving droplets of uniform size and spacing to investigate the behavior of interacting droplets. A series of experiments, over a range of ambient conditions, demonstrate how a lead droplet alters the environment experienced by its trailing neighbor. This behavior is of particular interest for droplet groups under high pressure and temperature, where experimental data has been limited. Gas phase velocity and vapor concentration measurements show that as the space between adjacent droplets decreases entrainment of fluid towards the axis of motion is reduced. Trapped gases create a gaseous cylinder, composed of ambient gas and fuel vapor, which surrounds and moves with the droplet stream. As ambient pressure increase, the oscillatory behavior of the lead droplet wake begins to interfere with its trailing neighbor. Loss of stream stability and enhanced droplet stripping in part result from these oscillating wakes. However, acceleration of droplet stripping is mainly produced by liquid and gas density similarity, which increases the centrifugal stress and the growth rate of capillary waves. Further, injection of subcritical droplets into an ambient environment at temperatures and pressures above the liquid droplet critical point shows behavior not greatly different from the results obtained at high ambient pressures. The similarity results from thermal heatup times exceeding the breakup times generated from the severe aerodynamics encountered at high ambient density and high liquid-gas relative velocities.

  15. Quantitative Analysis of Volatile Impurities in Diallyldimethylammonium Chloride Monomer Solution by Gas Chromatography Coupled with Liquid-Liquid Extraction

    Directory of Open Access Journals (Sweden)

    Cheng Liu

    2017-01-01

    Full Text Available The quantitative analysis method for volatile impurities in diallyldimethylammonium chloride (DADMAC monomer solution was established in this paper. The volatile impurities were quantitatively analyzed with trichloromethane as extraction solvent and n-hexane as internal standard by using gas chromatography (GC coupled with solvent extraction, and the chromatographic conditions, quantitative methods, and extraction conditions were systematically investigated in detail. The results showed that excellent linear relationships of 5 volatile impurities (dimethylamine, allyldimethylamine, allyl chloride, allyl alcohol, and allyl aldehyde were obtained in the range of 1–100 mg·L−1. The method also showed good specificity, recovery (95.0%–107.5%, and relative standard deviation (RSD, 1.40%–7.67%. This method could accurately detect the whole volatile impurities in DADMAC monomer solution quantitatively in one time with a low detection limit. Furthermore, this method is conducive to the preparation of highly pure DADMAC monomer and the development of national and international standards of the DADMAC monomer product quality, and the results could provide a strong foundation for the regulation and mechanism research of impurities on monomer reactivity in polymerization.

  16. Control of initiation, rate, and routing of spontaneous capillary-driven flow of liquid droplets through microfluidic channels on SlipChip.

    Science.gov (United States)

    Pompano, Rebecca R; Platt, Carol E; Karymov, Mikhail A; Ismagilov, Rustem F

    2012-01-24

    This Article describes the use of capillary pressure to initiate and control the rate of spontaneous liquid-liquid flow through microfluidic channels. In contrast to flow driven by external pressure, flow driven by capillary pressure is dominated by interfacial phenomena and is exquisitely sensitive to the chemical composition and geometry of the fluids and channels. A stepwise change in capillary force was initiated on a hydrophobic SlipChip by slipping a shallow channel containing an aqueous droplet into contact with a slightly deeper channel filled with immiscible oil. This action induced spontaneous flow of the droplet into the deeper channel. A model predicting the rate of spontaneous flow was developed on the basis of the balance of net capillary force with viscous flow resistance, using as inputs the liquid-liquid surface tension, the advancing and receding contact angles at the three-phase aqueous-oil-surface contact line, and the geometry of the devices. The impact of contact angle hysteresis, the presence or absence of a lubricating oil layer, and adsorption of surface-active compounds at liquid-liquid or liquid-solid interfaces were quantified. Two regimes of flow spanning a 10(4)-fold range of flow rates were obtained and modeled quantitatively, with faster (mm/s) flow obtained when oil could escape through connected channels as it was displaced by flowing aqueous solution, and slower (micrometer/s) flow obtained when oil escape was mostly restricted to a micrometer-scale gap between the plates of the SlipChip ("dead-end flow"). Rupture of the lubricating oil layer (reminiscent of a Cassie-Wenzel transition) was proposed as a cause of discrepancy between the model and the experiment. Both dilute salt solutions and complex biological solutions such as human blood plasma could be flowed using this approach. We anticipate that flow driven by capillary pressure will be useful for the design and operation of flow in microfluidic applications that do not

  17. Buckling instability of squeezed droplets

    CERN Document Server

    Elfring, Gwynn J

    2015-01-01

    Motivated by recent experiments, we consider theoretically the compression of droplets pinned at the bottom on a surface of finite area. We show that if the droplet is sufficiently compressed at the top by a surface, it will always develop a shape instability at a critical compression. When the top surface is flat, the shape instability occurs precisely when the apparent contact angle of the droplet at the pinned surface is pi, regardless of the contact angle of the upper surface, reminiscent of past work on liquid bridges and sessile droplets as first observed by Plateau. After the critical compression, the droplet transitions from a symmetric to an asymmetric shape. The force required to deform the droplet peaks at the critical point then progressively decreases indicative of catastrophic buckling. We characterize the transition in droplet shape using illustrative examples in two dimensions followed by perturbative analysis as well as numerical simulation in three dimensions. When the upper surface is not f...

  18. Molecular dynamics analysis of multiphase interfaces based on in situ extraction of the pressure distribution of a liquid droplet on a solid surface.

    Science.gov (United States)

    Nishida, S; Surblys, D; Yamaguchi, Y; Kuroda, K; Kagawa, M; Nakajima, T; Fujimura, H

    2014-02-21

    Molecular dynamics simulations of a nanoscale liquid droplet on a solid surface are carried out in order to examine the pressure tensor field around the multiphase interfaces, and to explore the validity of Young's equation. By applying the virial theorem to a hemicylindrical droplet consisting of argon molecules on a solid surface, two-dimensional distribution of the pressure tensor is obtained. Tensile principal pressure tangential to the interface is observed around the liquid-vapor transition layer, while both tensile and compressive principal pressure tangential to the interface exists around the solid-liquid transition layer due to the inhomogeneous density distribution. The two features intermix inside the overlap region between the transition layers at the contact line. The contact angle is evaluated by using a contour line of the maximum principal pressure difference. The interfacial tensions are calculated by using Bakker's equation and Young-Laplace equation to the pressure tensor distribution. The relation between measured contact angle and calculated interfacial tensions turns out to be consistent with Young's equation, which is known as the description of the force balance at the three-phase interface.

  19. Cloud Droplet Size and Liquid Water Path Retrievals From Zenith Radiance Measurements: Examples From the Atmospheric Radiation Measurement Program and the Aerosol Robotic Network

    Science.gov (United States)

    Chiu, J. C.; Marshak, A.; Huang, C.-H.; Varnai, T.; Hogan, R. J.; Giles, D. M.; Holben, B. N.; Knyazikhin, Y.; O'Connor, E. J.; Wiscombe, W. J.

    2012-01-01

    The ground-based Atmospheric Radiation Measurement Program (ARM) and NASA Aerosol Robotic Network (AERONET) routinely monitor clouds using zenith radiances at visible and near-infrared wavelengths. Using the transmittance calculated from such measurements, we have developed a new retrieval method for cloud effective droplet size and conducted extensive tests for non-precipitating liquid water clouds. The underlying principle is to combine a water-absorbing wavelength (i.e. 1640 nm) with a nonwater-absorbing wavelength for acquiring information on cloud droplet size and optical depth. For simulated stratocumulus clouds with liquid water path less than 300 g/sq m and horizontal resolution of 201m, the retrieval method underestimates the mean effective radius by 0.8 m, with a root-mean-squared error of 1.7 m and a relative deviation of 13 %. For actual observations with a liquid water path less than 450 gm.2 at the ARM Oklahoma site during 2007-2008, our 1.5 min-averaged retrievals are generally larger by around 1 m than those from combined ground-based cloud radar and microwave radiometer at a 5min temporal resolution. We also compared our retrievals to those from combined shortwave flux and microwave observations for relatively homogeneous clouds, showing that the bias between these two retrieval sets is negligible, but the error of 2.6 m and the relative deviation of 22% are larger than those found in our simulation case. Finally, the transmittance-based cloud effective droplet radii agree to better than 11% with satellite observations and have a negative bias of 1 m. Overall, the retrieval method provides reasonable cloud effective radius estimates, which can enhance the cloud products of both ARM and AERONET.

  20. Extraction and Esterification of Low-Titer Short-Chain Volatile Fatty Acids from Anaerobic Fermentation with Ionic Liquids.

    Science.gov (United States)

    Andersen, Stephen J; Berton, Jan K E T; Naert, Pieter; Gildemyn, Sylvia; Rabaey, Korneel; Stevens, Christian V

    2016-08-23

    Ionic liquids can both act as a solvent and mediate esterification to valorize low-titer volatile fatty acids and generate organic solvents from renewable carbon sources including biowaste and CO2 . In this study, four phosphonium ionic liquids were tested for single-stage extraction of acetic acid from a dilute stream and esterification to ethyl acetate with added ethanol and heat. The esterification proceeded with a maximum conversion of 85.9±1.3 % after 30 min at 75 °C at a 1:1 stoichiometric ratio of reactants. Extraction and esterification can be tailored using mixed-anion ionic liquids; this is demonstrated herein using a common trihexyl(tetradecyl)phosphonium cation and a mixed chloride and bis(trifluoromethylsulfonyl)imide anion ionic liquid. As a further proof-of-concept, ethyl acetate was generated from an ionic liquid-driven esterification of an acetic acid extractant generated using CO2 as the only carbon source by microbial electrosynthesis.

  1. Dispersive solid-phase extraction followed by vortex-assisted dispersive liquid-liquid microextraction based on the solidification of a floating organic droplet for the determination of benzoylurea insecticides in soil and sewage sludge.

    Science.gov (United States)

    Peng, Guilong; He, Qiang; Mmereki, Daniel; Lu, Ying; Zhong, Zhihui; Liu, Hanyang; Pan, Weiliang; Zhou, Guangming; Chen, Junhua

    2016-04-01

    A novel dispersive solid-phase extraction combined with vortex-assisted dispersive liquid-liquid microextraction based on solidification of floating organic droplet was developed for the determination of eight benzoylurea insecticides in soil and sewage sludge samples before high-performance liquid chromatography with ultraviolet detection. The analytes were first extracted from the soil and sludge samples into acetone under optimized pretreatment conditions. Clean-up of the extract was conducted by dispersive solid-phase extraction using activated carbon as the sorbent. The vortex-assisted dispersive liquid-liquid microextraction based on solidification of floating organic droplet procedure was performed by using 1-undecanol with lower density than water as the extraction solvent, and the acetone contained in the solution also acted as dispersive solvent. Under the optimum conditions, the linearity of the method was in the range 2-500 ng/g with correlation coefficients (r) of 0.9993-0.9999. The limits of detection were in the range of 0.08-0.56 ng/g. The relative standard deviations varied from 2.16 to 6.26% (n = 5). The enrichment factors ranged from 104 to 118. The extraction recoveries ranged from 81.05 to 97.82% for all of the analytes. The good performance has demonstrated that the proposed methodology has a strong potential for application in the multiresidue analysis of complex matrices.

  2. Effect of Marangoni Flows on the Shape of Thin Sessile Droplets Evaporating into Air

    Science.gov (United States)

    Tsoumpas, Yannis; Dehaeck, Sam; Rednikov, Alexey; Colinet, Pierre

    2015-11-01

    With the help of Mach-Zehnder interferometry, we study the (largely) axisymmetric shapes of freely receding evaporating sessile droplets of various HFE liquids. The droplets evaporate into ambient air and, although the liquids are perfectly wetting, possess small finite contact angles reckoned to be evaporation-induced. The experimentally determined droplet profiles are shown here to deviate, under some conditions, from the classical macroscopic static profile of a sessile droplet, as this is determined by gravity and capillarity. These deviations are attributed to a Marangoni flow, due to evaporation-induced thermal gradients along the liquid-air interface, and are mostly observed in conditions of high evaporation. Unlike the classical static shapes, the distorted experimental profiles exhibit an inflection point at the contact line area. When a poorly volatile liquid is considered, however, the temperature differences and the Marangoni stresses are weak, and the measurements are found to be in a good agreement with the classical static shape. Overall, the experimental findings are quantitatively confirmed by the predictions of a lubrication model accounting for the impact of the Marangoni effect on the droplet shape. Financial support of FP7 Marie Curie MULTIFLOW Network (PITNGA-2008-214919), ESA/BELSPO-PRODEX, BELSPO- μMAST (IAP 7/38) & FRS-FNRS is gratefully acknowledged.

  3. Lattice Boltzmann simulation of the droplet impact onto liquid film%液滴撞击液膜过程的格子Boltzmann方法模拟∗

    Institute of Scientific and Technical Information of China (English)

    黄虎; 洪宁; 梁宏; 施保昌; 柴振华

    2016-01-01

    本文采用格子Boltzmann方法对液滴撞击液膜过程进行了研究,主要考察了雷诺数(Re)、韦伯数(W e)、相对液膜厚度(h)以及表面张力(σ)等物理参数对界面运动过程的影响。首先,随着Re数和W e数的增加,可以明显观察到液滴撞击液膜过程中形成的皇冠状水花以及卷吸现象;当Re数较大时,液体会发生飞溅,由液体飞溅形成的小液滴则会继续下落,并与液膜再次发生碰撞。其次,当相对液膜厚度较小时,液滴撞击液膜并最终导致液膜断裂;然而随着相对液膜厚度的增大,尽管撞击过程溅起的液体会越来越多,但是液膜并不会发生断裂。再次,随着表面张力的增大,界面变形阻力增大,撞击过程中产生的界面形变也逐渐减弱。最后还发现皇冠(由液滴溅起形成)半径r 随时间满足r/(2R)≈α√U t/(2R),这一结果与已有结论是一致的。%The process of the droplet impact onto the liquid film, as one of the basic multiphase problems, is very important in many fields of science and engineering. On the other hand, the problem is also very complicated since there are many parameters that may influence the process of the droplet impact on the liquid film. To clearly understand the physical phenomena appearing in the process droplet impact on the liquid film, a parametric study on this problem is conduced based on a recently developed lattice Boltzmann method in which a lattice Boltzmann model is used to solve the Navier-Stokes equations, and the other is adopted to solve the Cahn-Hilliard equation that is used to depict the interface between different phases. In this paper, we mainly focus on the effects of the Reynolds number (Re), the Weber number (W e), the relative thickness of film (h) and the surface tension (σ) on the dynamic behavior of interface between different phases, and the velocity and pressure fields are also presented. It is found that with the

  4. Air-assisted liquid–liquid microextraction by solidifying the floating organic droplets for the rapid determination of seven fungicide residues in juice samples

    Energy Technology Data Exchange (ETDEWEB)

    You, Xiangwei [Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao 266101 (China); College of Science, China Agricultural University, Beijing 100193 (China); Xing, Zhuokan [College of Science, China Agricultural University, Beijing 100193 (China); Liu, Fengmao, E-mail: liufengmao@cau.edu.cn [College of Science, China Agricultural University, Beijing 100193 (China); Zhang, Xu [College of Science, China Agricultural University, Beijing 100193 (China)

    2015-05-22

    Highlights: • A novel AALLME-SFO method was firstly reported for pesticide residue analysis. • Solvent with low density and proper melting point was used as extraction solvent. • The formation of “cloudy solvent” with a syringe only. • The new method avoided the use of organic dispersive solvent. - Abstract: A novel air assisted liquid–liquid microextraction using the solidification of a floating organic droplet method (AALLME-SFO) was developed for the rapid and simple determination of seven fungicide residues in juice samples, using the gas chromatography with electron capture detector (GC-ECD). This method combines the advantages of AALLME and dispersive liquid–liquid microextraction based on the solidification of floating organic droplets (DLLME-SFO) for the first time. In this method, a low-density solvent with a melting point near room temperature was used as the extraction solvent, and the emulsion was rapidly formed by pulling in and pushing out the mixture of aqueous sample solution and extraction solvent for ten times repeatedly using a 10-mL glass syringe. After centrifugation, the extractant droplet could be easily collected from the top of the aqueous samples by solidifying it at a temperature lower than the melting point. Under the optimized conditions, good linearities with the correlation coefficients (γ) higher than 0.9959 were obtained and the limits of detection (LOD) varied between 0.02 and 0.25 μg L{sup −1}. The proposed method was applied to determine the target fungicides in juice samples and acceptable recoveries ranged from 72.6% to 114.0% with the relative standard deviations (RSDs) of 2.3–13.0% were achieved. Compared with the conventional DLLME method, the newly proposed method will neither require a highly toxic chlorinated solvent for extraction nor an organic dispersive solvent in the application process; hence, it is more environmentally friendly.

  5. On the Contribution of Drag and Turbulent Stresses in the Fragmentation of Liquid Droplets: A Computational Study

    Directory of Open Access Journals (Sweden)

    Tholudin M. Lazim

    2010-08-01

    model takes into account both the drag and turbulence induced fragmentation stresses. In the present paper, the authors investigate the relative contribution of the two different stresses in the break-up process using the new model for a case of a co-axial air-blast atomizer. The results show that turbulent stresses play the dominant role in the fragmentation of liquid droplets.

  6. Dancing Droplets

    Science.gov (United States)

    Cira, Nate; Prakash, Manu

    2013-11-01

    Inspired by the observation of intricate and beautifully dynamic patterns generated by food coloring on corona treated glass slides, we have investigated the behavior of propylene glycol and water droplets on clean glass surfaces. These droplets exhibit a range of interesting behaviors including long distance attraction or repulsion, and chasing/fleeing upon contact. We present explanations for each of these behaviors, and propose a detailed model for the long distance interactions based on vapor facilitated coupling. Finally we use our understanding to create several novel devices which: passively sort droplets by surface tension, spontaneously align droplets, drive droplets in circles, and cause droplets to bounce on a vertical surface. The simplicity of this system lends it particularly well to application as a toy model for physical systems with force fields and biological systems such as chemotaxis and motility.

  7. Black Droplets

    CERN Document Server

    Santos, Jorge E

    2014-01-01

    Black droplets and black funnels are gravitational duals to states of a large N, strongly coupled CFT on a fixed black hole background. We numerically construct black droplets corresponding to a CFT on a Schwarzchild background with finite asymptotic temperature. We find two branches of such droplet solutions which meet at a turning point. Our results suggest that the equilibrium black droplet solution does not exist, which would imply that the Hartle-Hawking state in this system is dual to the black funnel constructed in \\cite{Santos:2012he}. We also compute the holographic stress energy tensor and match its asymptotic behaviour to perturbation theory.

  8. Simultaneous determination of volatile and non-volatile nitrosamines in processed meat products by liquid chromatography tandem mass spectrometry using atmospheric pressure chemical ionisation and electrospray ionisation

    DEFF Research Database (Denmark)

    Herrmann, Susan Strange; Duedahl-Olesen, Lene; Granby, Kit

    2014-01-01

    A sensitive, selective and generic method has been developed for the simultaneous determination of the contents (μgkg−1 range) of both volatile nitrosamines (VNA) and non-volatile nitrosamines (NVNA) in processed meat products. The extraction procedure only requires basic laboratory equipment and...

  9. Dancing Droplets

    CERN Document Server

    Cira, Nate J

    2013-01-01

    Inspired by the observation of intricate and beautifully dynamic patterns generated by food coloring on clean glass slides, we have investigated the behavior of propylene glycol and water droplets on high energy surfaces. In this fluid dynamics video we show a range of interesting behaviors including long distance attraction, and chasing/fleeing upon contact. We present explanations for each of these behaviors including a mechanism for the long distance interactions based on vapor facilitated coupling. Finally we use our understanding to create several novel devices which: spontaneously align droplets, drive droplets in circles, cause droplets to bounce on a vertical surface, and passively sort droplets by surface tension. The simplicity of this system lends it particularly well to application as a toy model for physical systems with force fields and biological systems such as chemotaxis and motility.

  10. An Experimental Investigation of Vibration-Induced Single Droplet Ejection.

    Science.gov (United States)

    Range, Kai; Smith, Marc K.; Glezer, Ari

    1998-11-01

    Vibration-induced droplet atomization occurs when small secondary droplets are ejected from the free surface of a larger droplet placed on a vibrating membrane. To model a single ejection event, a liquid droplet is placed on a small piston and vibrated using an electromagnetic driver. The droplet oscillates in a characteristic mode shape that depends on the driving frequency and amplitude, the properties of the liquid, and the size of the droplet. When the excitation amplitude is large enough, a small secondary droplet is ejected from the primary droplet. Observations of this process using high-speed digital video imaging show that droplet ejection occurs when a small liquid column or jet appears on the primary droplet and a secondary droplet forms on the column by a capillary-pinching mechanism. The liquid column or jet emanates from a crater in the primary droplet. As the driving frequency increases, this crater becomes smaller and the diameter of the ejected droplet decreases. We shall present results showing how the ejected droplet diameter and speed depends on the driving frequency and amplitude, the liquid properties, and the primary droplet volume.

  11. A simple technique to reduce evaporation of crystallization droplets by using plate lids with apertures for adding liquids

    Energy Technology Data Exchange (ETDEWEB)

    Zipper, Lauren E. [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Binghamton University, 4400 Vestal Parkway East, Vestal, NY 13902 (United States); Aristide, Xavier [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); North Babylon High School, 1 Phelps Lane North, Babylon, NY 11703 (United States); Bishop, Dylan P. [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Northport High School, 154 Laurel Hill Road, Northport, NY 11768 (United States); Joshi, Ishita [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); St Augustine Catholic High School, 2188 Rodick Road, Markham, ON L6C 1S3 (Canada); Kharzeev, Julia [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Earl L. Vandermeulen High School, 350 Old Post Road, Port Jefferson, NY 11777 (United States); Patel, Krishna B. [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); John P. Stevens High School, 855 Grove Avenue, Edison, NJ 08820 (United States); Santiago, Brianna M. [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Connetquot High School, 190 7th Street, Bohemia, NY 11716 (United States); Joshi, Karan [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Department of Electronics and Electrical Communication Engineering, PEC University of Technology, Chandigarh (India); Dorsinvil, Kahille [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Sweet, Robert M. [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Soares, Alexei S., E-mail: soares@bnl.gov [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States)

    2014-11-28

    This article describes the use of evaporation control lids that are fitted to crystallization plates to improve the reproducibility of trials using as little as 5 nl. The plate lids contain apertures which are large enough for the transfer of protein containing droplets, but small enough to greatly reduce the rate of evaporation during the time needed to prepare the plate. A method is described for using plate lids to reduce evaporation in low-volume vapor-diffusion crystallization experiments. The plate lids contain apertures through which the protein and precipitants were added to different crystallization microplates (the reservoir was filled before fitting the lids). Plate lids were designed for each of these commonly used crystallization microplates. This system minimizes the dehydration of crystallization droplets containing just a few nanolitres of protein and precipitant, and results in more reproducible diffraction from the crystals. For each lid design, changes in the weight of the plates were used to deduce the rate of evaporation under different conditions of temperature, air movement, droplet size and precipitant. For comparison, the state of dehydration was also visually assessed throughout the experiment. Finally, X-ray diffraction methods were used to compare the diffraction of protein crystals that were conventionally prepared against those that were prepared on plates with plate lids. The measurements revealed that the plate lids reduced the rate of evaporation by 63–82%. Crystals grown in 5 nl drops that were set up with plate lids diffracted to higher resolution than similar crystals from drops that were set up without plate lids. The results demonstrate that plate lids can be instrumental for improving few-nanolitre crystallizations.

  12. Experimental evidence supporting the insensitivity of cloud droplet formation to the mass accommodation coefficient for condensation of water vapor to liquid water

    Science.gov (United States)

    Langridge, Justin M.; Richardson, Mathews S.; Lack, Daniel A.; Murphy, Daniel M.

    2016-06-01

    The mass accommodation coefficient for uptake of water vapor to liquid water, αM, has been constrained using photoacoustic measurements of aqueous absorbing aerosol. Measurements performed over a range of relative humidities and pressures were compared to detailed model calculations treating coupled heat and mass transfer occurring during photoacoustic laser heating cycles. The strengths and weaknesses of this technique are very different to those for droplet growth/evaporation experiments that have typically been applied to these measurements, making this a useful complement to existing studies. Our measurements provide robust evidence that αM is greater than 0.1 for all humidities tested and greater than 0.3 for data obtained at relative humidities greater than 88% where the aerosol surface was most like pure water. These values of αM are above the threshold at which kinetic limitations are expected to impact the activation and growth of aerosol particles in warm cloud formation.

  13. Droplets bouncing over a vibrating fluid layer

    CERN Document Server

    Cabrera-Garcia, Pablo

    2012-01-01

    This is an entry for the Gallery of Fluid Motion of the 65st Annual Meeting of the APS-DFD (fluid dynamics video). This video shows the motion of levitated liquid droplets. The levitation is produced by the vertical vibration of a liquid container. We made visualizations of the motion of many droplets to study the formation of clusters and their stability.

  14. Small droplets on superhydrophobic substrates.

    Science.gov (United States)

    Gross, Markus; Varnik, Fathollah; Raabe, Dierk; Steinbach, Ingo

    2010-05-01

    We investigate the wetting behavior of liquid droplets on rough hydrophobic substrates for the case of droplets that are of comparable size to the surface asperities. Using a simple three-dimensional analytical free-energy model, we have shown in a recent letter [M. Gross, F. Varnik, and D. Raabe, EPL 88, 26002 (2009)] that, in addition to the well-known Cassie-Baxter and Wenzel states, there exists a further metastable wetting state where the droplet is immersed into the texture to a finite depth, yet not touching the bottom of the substrate. Due to this new state, a quasistatically evaporating droplet can be saved from going over to the Wenzel state and instead remains close to the top of the surface. In the present paper, we give an in-depth account of the droplet behavior based on the results of extensive computer simulations and an improved theoretical model. In particular, we show that releasing the assumption that the droplet is pinned at the outer edges of the pillars improves the analytical results for larger droplets. Interestingly, all qualitative aspects, such as the existence of an intermediate minimum and the "reentrant transition," remain unchanged. We also give a detailed description of the evaporation process for droplets of varying sizes. Our results point out the role of droplet size for superhydrophobicity and give hints for achieving the desired wetting properties of technically produced materials.

  15. Analysis of beer volatiles by polymeric imidazolium-solid phase microextraction coatings: Synthesis and characterization of polymeric imidazolium ionic liquids.

    Science.gov (United States)

    González-Álvarez, Jaime; Blanco-Gomis, Domingo; Arias-Abrodo, Pilar; Pello-Palma, Jairo; Ríos-Lombardía, Nicolás; Busto, Eduardo; Gotor-Fernández, Vicente; Gutiérrez-Álvarez, María Dolores

    2013-08-30

    Two polymeric ionic liquids, 3-(but-3″-en-1″-yl)-1-[2'-hydroxycyclohexyl]-1H-imidazol-3-ium bis(trifluoromethanesulfonyl)imide (IL-1) and 1-(2'-hydroxycyclohexyl)-3-(4″-vinylbenzyl)-1H-imidazol-3-ium bis(trifluoromethylsulfonyl)imide (IL-2), have been synthesized by a free radical polymerization reaction and used as coatings for solid-phase microextraction (SPME). These new fibers exhibit good film stability, high thermal stability (270-290°C) and long lifetimes, and are used for the extraction of volatile compounds in lemon beer using gas chromatography separation and flame ionization detection. The scanning electron micrographs of the fiber surface revealed a polymeric ionic liquid (PIL) film, which is distributed homogeneously on the fiber. The developed PIL fiber showed good linearity between 50 and 2000μg/L with regression coefficients in the range of 0.996-0.999. The relative standard deviations (RSD) obtained in the peak area were found to vary between 1% and 12%, which assured that adequate repeatability was achieved. The spiked recoveries for three beer samples ranged from 78.4% to 123.6%. Experimental design has been employed in the optimization of extraction factors and robustness assessment. The polymeric IL-1 butenyl fiber showed a greater efficiency compared to the PDMS-DVB (65μm) and CAR-PDMS (75μm) for the extraction of all of the analytes studied.

  16. Controlling the volatility of the written optical state in electrochromic DNA liquid crystals

    NARCIS (Netherlands)

    Liu, Kai; Varghese, Justin; Gerasimov, Jennifer Y.; Polyakov, Alexey O.; Shuai, Min; Su, Juanjuan; Chen, Dong; Zajaczkowski, Wojciech; Marcozzi, Alessio; Pisula, Wojciech; Noheda, Beatriz; Palstra, Thomas T. M.; Clark, Noel A.; Herrmann, Andreas

    Liquid crystals are widely used in displays for portable electronic information display. To broaden their scope for other applications like smart windows and tags, new material properties such as polarizer-free operation and tunable memory of a written state become important. Here, we describe an

  17. Prediction of the vapor-liquid distribution constants for volatile nonelectrolytes in water up to its critical temperature

    Science.gov (United States)

    Plyasunov, Andrey V.; Shock, Everett L.

    2003-12-01

    The distribution of solutes between coexisting liquid and vapor phases of water can be expressed by the distribution constant, K D, defined as K D= limitlim x→0y/x, where y and x stand for the mole fraction concentrations of a solute in vapor and liquid phases, respectively. Research reported here is concerned with the prediction of this property, K D, for volatile nonelectrolytes, over the whole temperature range of existence of the vapor-liquid equilibrium for water, i.e. from 273 K to the critical temperature at 647.1 K. A simple empirical method is proposed to extrapolate the values of K D from 298 K to 500-550 K. Calculations at higher temperatures are based on the theoretical relation that establishes the proportionality between RTlnK D and the Krichevskii parameter, A Kr, which is the single most important property of a solute at near-critical conditions, and can be evaluated using the method proposed here. The comparison of predicted and experimental values of K D and A Kr for a few well-studied solutes reveals the satisfactory performance of the proposed method. It appears that the accuracy of predictions in the framework of this method is limited mainly by the accuracy of the values of the thermodynamic functions of hydration of solutes at 298 K, and that the best way to improve the quality of predictions of K D and A Kr is to increase the inventory of accurate calorimetric enthalpy and heat capacity data for aqueous solutes at 298 K. We stress that the values of the Krichevskii parameter, such as those generated in this study, are of crucial importance for reliable predictions of the chemical potential and its derivatives (V 2o, Cp 2o) for aqueous solutes at near-critical and supercritical conditions. Values of K D and A Kr are predicted for many inorganic volatile nonelectrolytes and some halogenated derivatives of methane and ethene. We show that both ln K D and A Kr for aqueous organic solutes follow group additivity systematics, and we derive a set

  18. Ultrasound-assisted dispersive liquid-liquid microextraction based on the solidification of a floating organic droplet followed by gas chromatography for the determination of eight pyrethroid pesticides in tea samples.

    Science.gov (United States)

    Hou, Xiaohong; Zheng, Xin; Zhang, Conglu; Ma, Xiaowei; Ling, Qiyuan; Zhao, Longshan

    2014-10-15

    A novel ultrasound-assisted dispersive liquid-liquid microextraction based on solidification of floating organic droplet method (UA-DLLME-SFO) combined with gas chromatography (GC) was developed for the determination of eight pyrethroid pesticides in tea for the first time. After ultrasound and centrifugation, 1-dodecanol and ethanol was used as the extraction and dispersive solvent, respectively. A series of parameters, including extraction solvent and volume, dispersive solvent and volume, extraction time, pH, and ultrasonic time influencing the microextraction efficiency were systematically investigated. Under the optimal conditions, the enrichment factors (EFs) were from 292 to 883 for the eight analytes. The linear ranges for the analytes were from 5 to 100μg/kg. The method recoveries ranged from 92.1% to 99.6%, with the corresponding RSDs less than 6.0%. The developed method was considered to be simple, fast, and precise to satisfy the requirements of the residual analysis of pyrethroid pesticides.

  19. A simple technique to reduce evaporation of crystallization droplets by using plate lids with apertures for adding liquids.

    Science.gov (United States)

    Zipper, Lauren E; Aristide, Xavier; Bishop, Dylan P; Joshi, Ishita; Kharzeev, Julia; Patel, Krishna B; Santiago, Brianna M; Joshi, Karan; Dorsinvil, Kahille; Sweet, Robert M; Soares, Alexei S

    2014-12-01

    A method is described for using plate lids to reduce evaporation in low-volume vapor-diffusion crystallization experiments. The plate lids contain apertures through which the protein and precipitants were added to different crystallization microplates (the reservoir was filled before fitting the lids). Plate lids were designed for each of these commonly used crystallization microplates. This system minimizes the dehydration of crystallization droplets containing just a few nanolitres of protein and precipitant, and results in more reproducible diffraction from the crystals. For each lid design, changes in the weight of the plates were used to deduce the rate of evaporation under different conditions of temperature, air movement, droplet size and precipitant. For comparison, the state of dehydration was also visually assessed throughout the experiment. Finally, X-ray diffraction methods were used to compare the diffraction of protein crystals that were conventionally prepared against those that were prepared on plates with plate lids. The measurements revealed that the plate lids reduced the rate of evaporation by 63-82%. Crystals grown in 5 nl drops that were set up with plate lids diffracted to higher resolution than similar crystals from drops that were set up without plate lids. The results demonstrate that plate lids can be instrumental for improving few-nanolitre crystallizations.

  20. Determination of volatile components of saffron by optimised ultrasound-assisted extraction in tandem with dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometry.

    Science.gov (United States)

    Sereshti, Hassan; Heidari, Reza; Samadi, Soheila

    2014-01-15

    In the present research, a combined extraction method of ultrasound-assisted extraction (UAE) in conjunction with dispersive liquid-liquid microextraction (DLLME) was applied to isolation and enrichment of saffron volatiles. The extracted components of the saffron were separated and determined by gas chromatography-mass spectrometry (GC-MS) technique. The mixture of methanol/acetonitrile was chosen for the extraction of the compounds and chloroform was used at the preconcentration stage. The important parameters, such as composition of extraction solvent, volume of preconcentration solvent, ultrasonic applying time, and salt concentration were optimised by using a half-fraction factorial central composite design (CCD). Under the optimal conditions, the linear dynamic ranges (LDRs) were 10-10,000mgL(-)(1). The determination coefficients (R(2)) were from 0.9990 to 0.9997. The limits of detection (LODs) and limits of quantification (LOQs) for the extracted compounds were 6-123mgL(-)(1) and 20-406mgL(-)(1), respectively. The relative standard deviations (RSDs) were 2.48-9.82% (n=3). The enhancement factors (EFs) were 3.6-41.3.

  1. Droplets Acoustics

    CERN Document Server

    Dahan, Raphael; Carmon, Tal

    2015-01-01

    Contrary to their capillary resonances (Rayleigh, 1879) and their optical resonances (Ashkin, 1977), droplets acoustical resonances were rarely considered. Here we experimentally excite, for the first time, the acoustical resonances of a droplet that relies on sound instead of capillary waves. Droplets vibrations at 37 MHz rates and 100 quality factor are optically excited and interrogated at an optical threshold of 68 microWatt. Our vibrations span a spectral band that is 1000 times higher when compared with drops previously-studied capillary vibration.

  2. Synthesis and toxicity evaluation of hydrophobic ionic liquids for volatile organic compounds biodegradation in a two-phase partitioning bioreactor

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez Castillo, Alfredo Santiago [Ecole Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, 11 Allée de Beaulieu, CS 50837, 35708 Rennes Cedex 7 (France); Université européenne de Bretagne (France); Guihéneuf, Solène, E-mail: solene.guiheneuf@wanadoo.fr [Université européenne de Bretagne, Université de Rennes 1, Sciences Chimiques de Rennes, UMR, CNRS 6226, Groupe Ingénierie Chimique & Molécules Pour le Vivant (ICMV), Bât. 10A, Campus de Beaulieu, Avenue du Général Leclerc, CS 74205, 35042 Rennes cedex (France); Le Guével, Rémy [Plate-forme ImPACcell Structure Fédérative de Recherche BIOSIT Université de Rennes 1, Bat. 8, Campus de Villejean, 2 Avenue du Pr. Leon Bernard, CS 34317, 35043 Rennes Cedex (France); Biard, Pierre-François [Ecole Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, 11 Allée de Beaulieu, CS 50837, 35708 Rennes Cedex 7 (France); Université européenne de Bretagne (France); and others

    2016-04-15

    Highlights: • Description of a VOC depollution system suitable with industrial processes, TPPB. • Novel association of TPPB and hydrophobic ionic liquids. • Synthesis of several hydrophobic ionic liquids designed to fit desired properties. • Toxicity evaluation of these ILs towards cells, animals and bacteria. - Abstract: Synthesis of several hydrophobic ionic liquids (ILs), which might be selected as good candidates for degradation of hydrophobic volatile organic compounds in a two-phase partitioning bioreactor (TPPB), were carried out. Several bioassays were also realized, such as toxicity evaluation on activated sludge and zebrafish, cytotoxicity, fluoride release in aqueous phase and biodegradability in order to verify their possible effects in case of discharge in the aquatic environment and/or human contact during industrial manipulation. The synthesized compounds consist of alkylimidazoliums, functionalized imidazoliums, isoqinoliniums, triazoliums, sulfoniums, pyrrolidiniums and morpholiniums and various counter-ions such as: PF{sub 6}{sup −}, NTf{sub 2}{sup −} and NfO{sup −}. Toxicity evaluation on activated sludge of each compound (5% v/v of IL) was assessed by using a glucose uptake inhibition test. Toxicity against zebrafish and cytotoxicity were evaluated by the ImPACCell platform of Rennes (France). Fluoride release in water was estimated by regular measurements using ion chromatography equipment. IL biodegradability was determined by measuring BOD{sub 28} of aqueous samples (compound concentration,1 mM). All ILs tested were not biodegradable; while some of them were toxic toward activated sludge. Isoquinolinium ILs were toxic to human cancerous cell lines. Nevertheless no toxicity was found against zebrafish Danio rerio. Only one IL released fluoride after long-time agitation.

  3. Volatile heavy metal mobility in silicate liquids: Implications for volcanic degassing and eruption prediction

    Science.gov (United States)

    MacKenzie, Jason M.; Canil, Dante

    2008-05-01

    The volatilization of Cd, Re, Tl, Pb, Sb and Te from melts in the system CaO-MgO-Al 2O 3-SiO 2 (CMAS) and Na 2O-MgO-Al 2O 3-SiO 2 (NMAS) has been investigated at 0.1 MPa and 1200-1350 °C. Experiments were conducted in air using metal-doped melts in Pt crucibles. Analysis of quenched glasses by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) normal to the melt/gas interface produced concentration profiles for Cd, Re, Tl, Pb, Sb and Te to which a semi-infinite one-dimensional diffusion model could be applied to extract diffusion coefficients ( D). The melt was also doped with Cu, Zn, In, Mo, Sn and W but concentration profiles for these metals did not develop. In the CMAS composition at 1300 °C, the fastest diffusing element was Cd having a log DCd = - 6.5 ± 0.2. The slowest element was Re with log DRe = - 7.5 ± 0.3. Diffusivities of Sb, Te, Pb and Tl have intermediate values where log DSb = - 7.1 ± 0.1, log DTe = - 7.2 ± 0.3, log DPb = - 7.1 ± 0.2, log DTl = - 7.0 ± 0.2 cm 2/s. In the NMAS composition, log DRe = - 6.5 ± 0.2, log DSb = - 6.0 ± 0.2, log DPb = - 6.1 ± 0.1, log DTl = - 5.8 ± 0.2 cm 2/s (values for Cd and Te were not determined). Differences in diffusivity of volatile heavy metal ions to a melt-gas interface lead to significant fractionation between these metals in magmas during degassing. Given the observed differences in Cd and Re diffusivities in the CMAS composition, we predict an increase in the normalized Cd/Re ratio in the gas phase with increasing bubble growth rate. Monitoring of the Cd/Re ratios in aerosols from degassing volcanoes may provide a tool for predicting volcanic eruption.

  4. Untargeted metabolomic analysis using liquid chromatography quadrupole time-of-flight mass spectrometry for non-volatile profiling of wines

    Energy Technology Data Exchange (ETDEWEB)

    Arbulu, M. [Department of Analytical Chemistry, Faculty of Pharmacy, University of the Basque Country, 01006 Vitoria-Gasteiz (Spain); Sampedro, M.C. [Central Service of Analysis, SGIker, University of the Basque Country, 01006 Vitoria-Gasteiz (Spain); Gómez-Caballero, A.; Goicolea, M.A. [Department of Analytical Chemistry, Faculty of Pharmacy, University of the Basque Country, 01006 Vitoria-Gasteiz (Spain); Barrio, R.J., E-mail: r.barrio@ehu.es [Department of Analytical Chemistry, Faculty of Pharmacy, University of the Basque Country, 01006 Vitoria-Gasteiz (Spain)

    2015-02-09

    Highlights: • An untargeted metabolomic method for the non-volatile profile of the Graciano wine was developed. • 411 different metabolites in Graciano Vitis vinifera red wine were identified. • 15 compounds could serve to differentiate Graciano and Tempranillo wines. • An enological database (WinMet) with 2080 compounds was constructed. - Abstract: The current study presents a method for comprehensive untargeted metabolomic fingerprinting of the non-volatile profile of the Graciano Vitis vinifera wine variety, using liquid chromatography/electrospray ionization time of flight mass spectrometry (LC–ESI-QTOF). Pre-treatment of samples, chromatographic columns, mobile phases, elution gradients and ionization sources, were evaluated for the extraction of the maximum number of metabolites in red wine. Putative compounds were extracted from the raw data using the extraction algorithm, molecular feature extractor (MFE). For the metabolite identification the WinMet database was designed based on electronic databases and literature research and includes only the putative metabolites reported to be present in oenological matrices. The results from WinMet were compared with those in the METLIN database to evaluate how much the databases overlap for performing identifications. The reproducibility of the analysis was assessed using manual processing following replicate injections of Vitis vinifera cv. Graciano wine spiked with external standards. In the present work, 411 different metabolites in Graciano Vitis vinifera red wine were identified, including primary wine metabolites such as sugars (4%), amino acids (23%), biogenic amines (4%), fatty acids (2%), and organic acids (32%) and secondary metabolites such as phenols (27%) and esters (8%). Significant differences between varieties Tempranillo and Graciano were related to the presence of fifteen specific compounds.

  5. Electrostatic charging and control of droplets in microfluidic devices.

    Science.gov (United States)

    Zhou, Hongbo; Yao, Shuhuai

    2013-03-07

    Precharged droplets can facilitate manipulation and control of low-volume liquids in droplet-based microfluidics. In this paper, we demonstrate non-contact electrostatic charging of droplets by polarizing a neutral droplet and splitting it into two oppositely charged daughter droplets in a T-junction microchannel. We performed numerical simulation to analyze the non-contact charging process and proposed a new design with a notch at the T-junction in aid of droplet splitting for more efficient charging. We experimentally characterized the induced charge in droplets in microfabricated devices. The experimental results agreed well with the simulation. Finally, we demonstrated highly effective droplet manipulation in a path selection unit appending to the droplet charging. We expect our work could enable precision manipulation of droplets for more complex liquid handling in microfluidics and promote electric-force based manipulation in 'lab-on-a-chip' systems.

  6. Coalescence-induced droplet actuation

    Science.gov (United States)

    Sellier, Mathieu; Verdier, Claude; Nock, Volker

    2011-11-01

    This work investigates a little explored driving mechanism to actuate droplets: the surface tension gradient which arises during the coalescence of two droplets of liquid having different compositions and therefore surface tensions. The resulting surface tension gradient gives rise to a Marangoni flow which, if sufficiently large, can displace the droplet. In order to understand, the flow dynamics arising during the coalescence of droplets of different fluids, a model has been developed in the lubrication framework. The numerical results confirm the existence of a self-propulsion window which depends on two dimensionless groups representing competing effects during the coalescence: the surface tension contrast between the droplets which promotes actuation and species diffusion which tends to make the mixture uniform thereby anihilating Marangoni flow and droplet motion. In parallel, experiments have been conducted to confirm this self-propulsion behaviour. The experiment consists in depositing a droplet of distilled water on a ``hydrophilic highway.'' This stripe was obtained by plasma-treating a piece of PDMS shielded in some parts by glass coverslips. This surface functionalization was found to be the most convenient way to control the coalescence. When a droplet of ethanol is deposited near the ``water slug,'' coalescence occurs and a rapid motion of the resulting mixture is observed. The support of the Dumont d'Urville NZ-France Science & Technology program is gratefully acknowledged.

  7. Can clouds enhance long-range transport of low volatile, ionizable and surface-active chemicals?

    DEFF Research Database (Denmark)

    Franco, Antonio; Trapp, Stefan

    2011-01-01

    were run for a constant emission to the atmospheric boundary layer to identify key model inputs. The degradation rate, the duration of dry and wet periods and the parameters describing air-water bulk partitioning (KAW and T) and ionization (pKa and pH) determine the residence time in the ABL....... The longer residence time predicted for some compounds in the LMT is due to the capacity of clouds to sorb non-volatile molecules in the liquid water and at the interface of cloud droplets. The efficiency of wet deposition to remove low volatile organic pollutants from the atmosphere is limited primarily...

  8. Application of dispersive liquid-liquid microextraction and gas chromatography with mass spectrometry for the determination of oxygenated volatile organic compounds in effluents from the production of petroleum bitumen.

    Science.gov (United States)

    Boczkaj, Grzegorz; Makoś, Patrycja; Przyjazny, Andrzej

    2016-07-01

    We present a new procedure for the determination of oxygenated volatile organic compounds in samples of postoxidative effluents from the production of petroleum bitumens using dispersive liquid-liquid microextraction and gas chromatography with mass spectrometry. The eight extraction parameters were optimized for 43 oxygenated volatile organic compounds. The detection limits obtained ranged from 0.07 to 0.82 μg/mL for most of the analytes, the precision was good (relative standard deviation below 2.91% at the 5 μg/mL level and 4.75% at the limit of quantification), the recoveries for the majority of compounds varied from 70.6 to 118.9%, and the linear range was wide, which demonstrates the usefulness of the procedure. The developed procedure was used for the determination of oxygenated volatile organic compounds in samples of raw postoxidative effluents and in effluents after chemical treatment. In total, 23 compounds at concentration levels from 0.37 to 32.95 μg/mL were identified in real samples. The same samples were also analyzed in the SCAN mode, which resulted in four more phenol derivatives being identified and tentatively determined. The studies demonstrated the need for monitoring volatile organic compounds content in effluents following various treatments due to the formation of secondary oxygenated volatile organic compounds.

  9. Exposure to volatile organic compounds and kidney dysfunction in thin film transistor liquid crystal display (TFT-LCD) workers.

    Science.gov (United States)

    Chang, Ta-Yuan; Huang, Kuei-Hung; Liu, Chiu-Shong; Shie, Ruei-Hao; Chao, Keh-Ping; Hsu, Wen-Hsin; Bao, Bo-Ying

    2010-06-15

    Many volatile organic compounds (VOCs) are emitted during the manufacturing of thin film transistor liquid crystal displays (TFT-LCDs), exposure to some of which has been reported to be associated with kidney dysfunction, but whether such an effect exists in TFT-LCD industry workers is unknown. This cross-sectional study aimed to investigate the association between exposure to VOCs and kidney dysfunction among TFT-LCD workers. The results showed that ethanol (1811.0+/-1740.4 ppb), acetone (669.0+/-561.0 ppb), isopropyl alcohol (187.0+/-205.3 ppb) and propylene glycol monomethyl ether acetate (PGMEA) (102.9+/-102.0 ppb) were the four dominant VOCs present in the workplace. The 63 array workers studied had a risk of kidney dysfunction 3.21-fold and 3.84-fold that of 61 cell workers and 18 module workers, respectively. Workers cumulatively exposed to a total level of isopropyl alcohol, PGMEA and propylene glycol monomethyl ether> or =324 ppb-year had a significantly higher risk of kidney dysfunction (adjusted OR=3.41, 95% CI=1.14-10.17) compared with those exposed to LCD industry, and cumulative exposure to specific VOCs might be associated with kidney dysfunction.

  10. Effect of Mono-and Di-ethanolammonium Formate Ionic Liquids on the Volatility of Water, Ethanol, and Methanol

    Institute of Scientific and Technical Information of China (English)

    李雪梅; 沈冲; 李春喜

    2013-01-01

    Vapor pressures were measured for six binary systems containing water, ethanol, or methanol with one of the two ionic liquids (ILs) at different component concentrations and temperatures using a quasi-static ebulliometer, with the ILs mono-ethanolammonium formate ([HMEA][HCOO]) and di-ethanolammonium formate ([HDEA][HCOO]). The vapor pressures of the IL-containing binary systems are well correlated using the NRTL model with an overall average absolute relative deviation (AARD) of 0.0062. The effect of ILs on the vapor pressure depression of sol-vents at 0.050 mole fraction of IL is that [HDEA][HCOO]>[HMEA][HCOO], and the vapor pressure lowering de-gree follows the order of water>methanol>ethanol. Further, the activity coefficients of three solvents (viz. water, ethanol, and methanol) for the binary systems{solvent (1)+IL (2)}predicted based on the fitted NRTL parameters at T=333.15 K indicate that the two ILs generate a negative deviation from Raoult’s law for water and methanol and a positive deviation for ethanol to a varying degree, change the relative volatility of a solvent. [HMEA][HCOO] may be a promising entrainer to efficiently separate ethanol aqueous solutions by special rectification.

  11. Synthesis and toxicity evaluation of hydrophobic ionic liquids for volatile organic compounds biodegradation in a two-phase partitioning bioreactor.

    Science.gov (United States)

    Rodriguez Castillo, Alfredo Santiago; Guihéneuf, Solène; Le Guével, Rémy; Biard, Pierre-François; Paquin, Ludovic; Amrane, Abdeltif; Couvert, Annabelle

    2016-04-15

    Synthesis of several hydrophobic ionic liquids (ILs), which might be selected as good candidates for degradation of hydrophobic volatile organic compounds in a two-phase partitioning bioreactor (TPPB), were carried out. Several bioassays were also realized, such as toxicity evaluation on activated sludge and zebrafish, cytotoxicity, fluoride release in aqueous phase and biodegradability in order to verify their possible effects in case of discharge in the aquatic environment and/or human contact during industrial manipulation. The synthesized compounds consist of alkylimidazoliums, functionalized imidazoliums, isoqinoliniums, triazoliums, sulfoniums, pyrrolidiniums and morpholiniums and various counter-ions such as: PF6(-), NTf2(-) and NfO(-). Toxicity evaluation on activated sludge of each compound (5% v/v of IL) was assessed by using a glucose uptake inhibition test. Toxicity against zebrafish and cytotoxicity were evaluated by the ImPACCell platform of Rennes (France). Fluoride release in water was estimated by regular measurements using ion chromatography equipment. IL biodegradability was determined by measuring BOD28 of aqueous samples (compound concentration,1mM). All ILs tested were not biodegradable; while some of them were toxic toward activated sludge. Isoquinolinium ILs were toxic to human cancerous cell lines. Nevertheless no toxicity was found against zebrafish Danio rerio. Only one IL released fluoride after long-time agitation. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Quantification approach for assessment of sparkling wine volatiles from different soils, ripening stages, and varieties by stir bar sorptive extraction with liquid desorption.

    Science.gov (United States)

    Coelho, Elisabete; Coimbra, Manuel A; Nogueira, J M F; Rocha, Sílvia M

    2009-03-01

    Stir bar sorptive extraction with liquid desorption followed by large volume injection coupled to gas chromatography-quadrupole mass spectrometry (SBSE-LD/LVI-GC-qMS) was applied for the quantification of varietal and fermentative volatiles in sparkling wines. The analytical data were performed by using suitable standards of monoterpene hydrocarbons (alpha-pinene), monoterpenols (linalool), sesquiterpenoids (E,E-farnesol, Z-nerolidol, and guaiazulene), C(13) norisoprenoids (beta-ionone), aliphatic and aromatic alcohols (hexanol and 2-phenylethanol), and esters (hexyl acetate and ethyl decanoate) as model compounds. The wine volatiles were quantified using the structurally related standards. The methodology showed good linearity over the concentration range tested, with correlation coefficients ranging from 0.950 to 0.997, and a reproducibility of 9-18%. The SBSE-LD/LVI-GC-qMS methodology allowed, in a single run, the quantification of 71 wine volatiles that can be quantified accurately at levels lower than their respective olfactory thresholds. This methodology was used for assessment of sparkling wine volatiles from different soils, ripening stages, and varieties. The variety and soil influenced significantly the volatile composition of sparkling wines; lower effect was observed for the ripening stage of grapes picked up one week before or after the maturity state.

  13. Experimental determination of the nucleation rates of undercooled micron-sized liquid droplets based on fast chip calorimetry

    Energy Technology Data Exchange (ETDEWEB)

    Simon, Christian, E-mail: ch.simon@uni-muenster.de; Peterlechner, Martin; Wilde, Gerhard

    2015-03-10

    Highlights: • Fast scanning calorimeter calibration with position dependence. • Calibration of fast scanning calorimeter during cooling. • Quantitative determination of nucleation rates by treating the undercooling as stochastic parameter - Abstract: Accurate thermal analyzes and calorimetry measurements depend on careful calibration measurements. For conventional differential scanning calorimeters (DSC) the calibration procedure is well known. The melting point of different pure metals is measured and compared with literature data to adjust the temperature reading of the calorimeter. Likewise, the measured melting enthalpies of standard reference substances serve for enthalpy calibration. Yet for fast chip calorimetry, new procedures need to be established. For the medium-area and large-area calorimeter chips, this procedure needs to be modified, because the calibration behavior depends on the position of the sample on the measurement area. Additionally, a way to calibrate the calorimeter for measurements performed during cooling will also be shown. For this second aspect, the athermal and diffusionless martensitic phase transformation of Ni{sub 49.9}–Ti{sub 50.1} at% was used. The well-calibrated sensor chips are ideally suited to perform nucleation rate density analyzes based on a statistical approach. Here, the nucleation rate densities of micron-sized pure Sn droplets that had been coated with a non-catalytic coating have been determined by experimental analysis of the statistical variance of the undercooling response.

  14. Liquid droplet-like behaviour of whole casein aggregates adsorbed on graphite studied by nanoindentation with AFM

    NARCIS (Netherlands)

    Helstad, K.; Rayner, M.; Vliet, van T.; Paulsson, M.; Dejmek, P.

    2007-01-01

    AFM measurements in the force volume mode were performed over the total penetration depth for different positions on casein aggregates adsorbed to a graphite surface in a liquid cell. The stiffness of the force curves was correlated to indentation depths, layer depth and lateral position within the

  15. Robust and versatile ionic liquid microarrays achieved by microcontact printing

    Science.gov (United States)

    Gunawan, Christian A.; Ge, Mengchen; Zhao, Chuan

    2014-04-01

    Lab-on-a-chip and miniaturized systems have gained significant popularity motivated by marked differences in material performance at the micro-to-nano-scale realm. However, to fully exploit micro-to-nano-scale chemistry, solvent volatility and lack of reproducibility need to be overcome. Here, we combine the non-volatile and versatile nature of ionic liquids with microcontact printing in an attempt to establish a facile protocol for high throughput fabrication of open microreactors and microfluidics. The micropatterned ionic liquid droplets have been demonstrated as electrochemical cells and reactors for microfabrication of metals and charge transfer complexes, substrates for immobilization of proteins and as membrane-free high-performance amperometric gas sensor arrays. The results suggest that miniaturized ionic liquid systems can be used to solve the problems of solvent volatility and slow mass transport in viscous ionic liquids in lab-on-a-chip devices, thus providing a versatile platform for a diverse number of applications.

  16. A method to determine true air temperature fluctuations in clouds with liquid water fraction and estimate water droplet effect on the calculations of the spectral structure of turbulent heat fluxes in cumulus clouds based on aircraft data

    Science.gov (United States)

    Strunin, Alexander M.; Zhivoglotov, Dmitriy N.

    2014-03-01

    Liquid water droplets could distort aircraft temperature measurements in clouds, leading to errors in calculated heat fluxes and incorrect flux distribution pattern. The estimation of cloud droplet effect on the readings of the high-frequency aircraft thermometer employed at the Central Aerological Observatory (CAO) was based on an experimental study of the sensor in a wind tunnel, using an air flow containing liquid water droplets. Simultaneously, calculations of the distribution of speed and temperature in a flow through the sensitive element of the sensor were fulfilled. This permitted estimating the coefficient of water content effect on temperature readings. Another way of estimating cloud droplet effect was based on the analysis of data obtained during aircraft observations of cumulus clouds in a tropical zone (Cuba Island). As a result, a method of correcting air temperature and recovering true air temperature fluctuations inside clouds was developed. This method has provided consistent patterns of heat flux distribution in a cumulus area. Analysis of the results of aircraft observations of cumulus clouds with temperature correction fulfilled has permitted investigation of the spectral structure of the fields of air temperature and heat fluxes to be performed in cumulus zones based on wavelet transformation. It is shown that mesoscale eddies (over 500 m in length) were the main factor of heat exchange between a cloud and the ambient space. The role of turbulence only consisted in mixing inside the cloud.

  17. Supercritical droplet combustion and related transport phenomena

    Science.gov (United States)

    Yang, Vigor; Hsieh, K. C.; Shuen, J. S.

    1993-01-01

    An overview of recent advances in theoretical analyses of supercritical droplet vaporization and combustion is conducted. Both hydrocarbon and cryogenic liquid droplets over a wide range of thermodynamic states are considered. Various important high-pressure effects on droplet behavior, such as thermodynamic non-ideality, transport anomaly, and property variation, are reviewed. Results indicate that the ambient gas pressure exerts significant control of droplet gasification and burning processes through its influence on fluid transport, gas-liquid interfacial thermodynamics, and chemical reactions. The droplet gasification rate increases progressively with pressure. However, the data for the overall burnout time exhibit a considerable change in the combustion mechanism at the criticl pressure, mainly as a result of reduced mass diffusivity and latent heat of vaporization with increased pressure. The influence of droplet size on the burning characteristics is also noted.

  18. Droplet lasers: a review of current progress

    Science.gov (United States)

    McGloin, D.

    2017-05-01

    It is perhaps surprising that something as fragile as a microscopic droplet could possibly form a laser. In this article we will review some of the underpinning physics as to how this might be possible, and then examine the state of the art in the field. The technology to create and manipulate droplets will be examined, as will the different classes of droplet lasers. We discuss the rapidly developing fields of droplet biolasers, liquid crystal laser droplets and explore how droplet lasers could give rise to new bio and chemical sensing and analysis. The challenges that droplet lasers face in becoming robust devices, either as sensors or as photonic components in the lab on chip devices, is assessed.

  19. Dancing droplets: Contact angle, drag, and confinement

    Science.gov (United States)

    Benusiglio, Adrien; Cira, Nate; Prakash, Manu

    2015-11-01

    When deposited on a clean glass slide, a mixture of water and propylene glycol forms a droplet of given contact angle, when both pure liquids spread. (Cira, Benusiglio, Prakash: Nature, 2015). The droplet is stabilized by a gradient of surface tension due to evaporation that induces a Marangoni flow from the border to the apex of the droplets. The apparent contact angle of the droplets depends on both their composition and the external humidity as captured by simple models. These droplets present remarkable properties such as lack of a large pinning force. We discuss the drag on these droplets as a function of various parameters. We show theoretical and experimental results of how various confinement geometries change the vapor gradient and the dynamics of droplet attraction.

  20. Curvature Gradient Driving Droplets in Fast Motion

    CERN Document Server

    Lv, Cunjing; Yin, Yajun; Tseng, Fan-gang; Zheng, Quanshui

    2011-01-01

    Earlier works found out spontaneous directional motion of liquid droplets on hydrophilic conical surfaces, however, not hydrophobic case. Here we show that droplets on any surface may take place spontaneous directional motion without considering contact angle property. The driving force is found to be proportional to the curvature gradient of the surface. Fast motion can be lead at surfaces with small curvature radii. The above discovery can help to create more effective transportation technology of droplets, and better understand some observed natural phenomena.

  1. Single Mobile Micro Droplet-Particle Pairs Spatially Captured by Macro Host Droplets on a Superhydrophobic Surface

    Directory of Open Access Journals (Sweden)

    Gregory S. Watson

    2015-01-01

    Full Text Available In this preliminary study, we demonstrate how small single water droplets can be spatially captured on the surface of individual micron sized hydrophobic coated particles (C18 which adhere to the surface of a nonmobile larger host water droplet resting on a superhydrophobic surface. The formation of the larger droplet, particle adhesion to that droplet, and smaller droplet formation on the particle all take place spontaneously from condensation conditions. These micro droplet-particle pairs are confined to the surface (liquid-air interface of the larger host droplet; however, they are free to engage with external forces to promote mobility. This response may find applications for particle pair transport on liquid surfaces. We also demonstrate that droplets can be captured or removed from the larger droplet surface via a self-propulsion mechanism.

  2. Droplets, Bubbles and Ultrasound Interactions.

    Science.gov (United States)

    Shpak, Oleksandr; Verweij, Martin; de Jong, Nico; Versluis, Michel

    2016-01-01

    The interaction of droplets and bubbles with ultrasound has been studied extensively in the last 25 years. Microbubbles are broadly used in diagnostic and therapeutic medical applications, for instance, as ultrasound contrast agents. They have a similar size as red blood cells, and thus are able to circulate within blood vessels. Perfluorocarbon liquid droplets can be a potential new generation of microbubble agents as ultrasound can trigger their conversion into gas bubbles. Prior to activation, they are at least five times smaller in diameter than the resulting bubbles. Together with the violent nature of the phase-transition, the droplets can be used for local drug delivery, embolotherapy, HIFU enhancement and tumor imaging. Here we explain the basics of bubble dynamics, described by the Rayleigh-Plesset equation, bubble resonance frequency, damping and quality factor. We show the elegant calculation of the above characteristics for the case of small amplitude oscillations by linearizing the equations. The effect and importance of a bubble coating and effective surface tension are also discussed. We give the main characteristics of the power spectrum of bubble oscillations. Preceding bubble dynamics, ultrasound propagation is introduced. We explain the speed of sound, nonlinearity and attenuation terms. We examine bubble ultrasound scattering and how it depends on the wave-shape of the incident wave. Finally, we introduce droplet interaction with ultrasound. We elucidate the ultrasound-focusing concept within a droplets sphere, droplet shaking due to media compressibility and droplet phase-conversion dynamics.

  3. Polymeric ionic liquid coatings versus commercial solid-phase microextraction coatings for the determination of volatile compounds in cheeses.

    Science.gov (United States)

    Trujillo-Rodríguez, María J; Yu, Honglian; Cole, William T S; Ho, Tien D; Pino, Verónica; Anderson, Jared L; Afonso, Ana M

    2014-04-01

    The extraction performance of four polymeric ionic liquid (PIL)-based solid-phase microextraction (SPME) coatings has been studied and compared to that of commercial SPME coatings for the extraction of 16 volatile compounds in cheeses. The analytes include 2 free fatty acids, 2 aldehydes, 2 ketones and 10 phenols and were determined by headspace (HS)-SPME coupled to gas chromatography (GC) with flame-ionization detection (FID). The PIL-based coatings produced by UV co-polymerization were more efficient than PIL-based coatings produced by thermal AIBN polymerization. Partition coefficients of analytes between the sample and the coating (Kfs) were estimated for all PIL-based coatings and the commercial SPME fiber showing the best performance among the commercial fibers tested: carboxen-polydimethylsyloxane (CAR-PDMS). For the PIL-based fibers, the highest K(fs) value (1.96 ± 0.03) was obtained for eugenol. The normalized calibration slope, which takes into account the SPME coating thickness, was also used as a simpler approximate tool to compare the nature of the coating within the determinations, with results entirely comparable to those obtained with estimated K(fs) values. The PIL-based materials obtained by UV co-polymerization containing the 1-vinyl-3-hexylimidazolium chloride IL monomer and 1,12-di(3-vinylimiazolium)dodecane dibromide IL crosslinker exhibited the best performance in the extraction of the select analytes from cheeses. Despite a coating thickness of only 7 µm, this copolymeric sorbent coating was capable of quantitating analytes in HS-SPME in a 30 to 2000 µg L(-1) concentration range, with correlation coefficient (R) values higher than 0.9938, inter-day precision values (as relative standard deviation in %) varying from 6.1 to 20%, and detection limits down to 1.6 µg L(-1).

  4. Optimization of dynamic headspace extraction system for measurement of halogenated volatile organic compounds in liquid or viscous samples

    Science.gov (United States)

    Taniai, G.; Oda, H.; Kurihara, M.; Hashimoto, S.

    2010-12-01

    Halogenated volatile organic compounds (HVOCs) produced in the marine environment are thought to play a key role in atmospheric reactions, particularly those involved in the global radiation budget and the depression of tropospheric and stratospheric ozone. To evaluate HVOCs concentrations in the various natural samples, we developed an automated dynamic headspace extraction method for the determination of 15 HVOCs, such as chloromethane, bromomethane, bromoethane, iodomethane, iodoethane, bromochloromethane, 1-iodopropane, 2-iodopropane, dibromomethane, bromodichloromethane, chloroiodomethane, chlorodibromomethane, bromoiodomethane, tribromomethane, and diiodomethane. Dynamic headspace system (GERSTEL DHS) was used to purge the gas phase above samples and to trap HVOCs on the adsorbent column from the purge gas. We measured the HVOCs concentrations in the adsorbent column with gas chromatograph (Agilent 6890N)- mass spectrometer (Agilent 5975C). In dynamic headspace system, an glass tube containing Tenax TA or Tenax GR was used as adsorbent column for the collection of 15 HVOCs. The parameters for purge and trap extraction, such as purge flow rate (ml/min), purge volume (ml), incubation time (min), and agitator speed (rpm), were optimized. The detection limits of HVOCs in water samples were 1270 pM (chloromethane), 103 pM (bromomethane), 42.1 pM (iodomethane), and 1.4 to 10.2 pM (other HVOCs). The repeatability (relative standard deviation) for 15 HVOCs were < 9 % except chloromethane (16.2 %) and bromomethane (11.0 %). On the basis of the measurements for various samples, we concluded that this analytical method is useful for the determination of wide range of HVOCs with boiling points between - 24°C (chloromethane) and 181°C (diiodomethane) for the liquid or viscous samples.

  5. On-demand droplet loading for automated organic chemistry on digital microfluidics.

    Science.gov (United States)

    Shah, Gaurav J; Ding, Huijiang; Sadeghi, Saman; Chen, Supin; Kim, Chang-Jin C J; van Dam, R Michael

    2013-07-21

    Organic chemistry applications on digital microfluidic devices often involve reagents that are volatile or sensitive and must be introduced to the chip immediately before use. We present a new technique for automated, on-demand loading of ~1 μL droplets from large (~1 mL), sealed, off-chip reservoirs to a digital microfluidic chip in order to address this challenge. Unlike aqueous liquids which generally are non-wetting to the hydrophobic surface and must be actively drawn into the electrowetting-on-dielectric (EWOD) chip by electrode activation, organic liquids tend to be wetting and can spontaneously flood the chip, and hence require a retracting force for controlled liquid delivery. Using a combination of compressed inert gas and gravity to exert driving and retracting forces on the liquid, the simple loading technique enables precise loading of droplets of both wetting and non-wetting liquids in a reliable manner. A key feature from a practical point of view is that all of the wetted parts are inexpensive and potentially disposable, thus avoiding cross-contamination in chemical and biochemical applications. We provide a theoretical treatment of the underlying physics, discuss the effect of geometry and liquid properties on its performance, and show repeatable reagent loading using the technique. Its versatility is demonstrated with the loading of several aqueous and non-aqueous liquids on an EWOD digital microfluidic device.

  6. Droplets and sprays

    CERN Document Server

    Sazhin, Sergei

    2014-01-01

    Providing a clear and systematic description of droplets and spray dynamic models, this book maximises reader insight into the underlying physics of the processes involved, outlines the development of new physical and mathematical models, and broadens understanding of interactions between the complex physical processes which take place in sprays. Complementing approaches based on the direct application of computational fluid dynamics (CFD), Droplets and Sprays treats both theoretical and practical aspects of internal combustion engine process such as the direct injection of liquid fuel, subcritical heating and evaporation. Includes case studies that illustrate the approaches relevance to automotive applications,  it is also anticipated that the described models can find use in other areas such as in medicine and environmental science.

  7. Dynamic behavior of the water droplet impact on a textured hydrophobic/superhydrophobic surface: the effect of the remaining liquid film arising on the pillars' tops on the contact time.

    Science.gov (United States)

    Li, Xiying; Ma, Xuehu; Lan, Zhong

    2010-04-06

    We have fabricated a series of textured silicon surfaces decorated by square arrays of pillars whose radius and pitch can be adjusted independently. These surfaces possessed a hydrophobic/superhydrophobic property after silanization. The dynamic behavior of water droplets impacting these structured surfaces was examined using a high-speed camera. Experimental results validated that the remaining liquid film on the pillars' tops gave rise to a wet surface instead of a dry surface as the water droplet began to recede away from the textured surfaces. Also, experimental results demonstrated that the difference in the contact time was subjected to the solid fraction referred to as the ratio of the actual area contacting with the liquid to its projected area on the textured surface. Because the mechanism by which the residual liquid film emerges on the pillars' tops can essentially be ascribed to the pinch-off of the liquid threads, we further addressed the changes in the contact time in terms of the characteristic time of pinch-off of an imaginary liquid cylinder whose radius is related to the solid fraction and the maximum contact area. The match of the theoretical analysis and the experimental results substantiates the assumption aforementioned.

  8. Vortex-assisted surfactant-enhanced-emulsification liquid-liquid microextraction with solidification of floating organic droplet combined with flame atomic absorption spectrometry for the fast determination of cadmium in water samples.

    Science.gov (United States)

    Peng, Guilong; Lu, Ying; He, Qiang; Mmereki, Daniel; Tang, Xiaohui; Zhong, Zhihui; Zhao, Xiaolong

    2016-01-01

    A novel vortex-assisted surfactant-enhanced-emulsification liquid-liquid microextraction with solidification of floating organic droplet (VSLLME-SFO) was developed for the fast, simple and efficient determination of cadmium (Cd) in water samples followed by flame atomic absorption spectrometry (FAAS). In the VSLLME-SFO process, the addition of surfactant (as an emulsifier), could enhance the mass transfer from the aqueous solution into the extraction solvent. The extraction solvent could be dispersed into the aqueous phase under vigorous shaking with the vortex. In this paper, we investigated the influences of analytical parameters, including pH, extraction solvent type and its volume, surfactant type and its volume, concentration of chelating agent, salt effect and vortex time, on the extraction efficiency of Cd. Under the optimized conditions, the limit of detection was 0.16 μg/L. The analyte enrichment factor was 37.68. The relative standard deviation was 3.2% (10 μg/L, n = 10) and the calibration graph was linear, ranging from 0.5 to 30 μg/L. The proposed method was successfully applied for the analysis of ultra-trace Cd in river water and wastewater samples.

  9. Application of dispersive Liquid-Liquid microextraction based on solidification of floating organic droplet multi-residue method for the simultaneous determination of polychlorinated biphenyls, organochlorine, and pyrethroid pesticides in aqueous sample

    Energy Technology Data Exchange (ETDEWEB)

    Zuo, Mei; Li, Man-Liang [Enshi Prefecture Tobacco Company, Enshi, Hubei (China); Cheng, Jing; Matsadiq, Guzalnur; Liu, Lu; Zhang, Miao [Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan (China)

    2012-12-15

    Dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) technique was successfully applied for simultaneous assay of eight polychlorinated biphenyls, two organochlorine, and four pyrethroid pesticides multi-residue in aqueous samples by using GC-electron capture detection. The effects of various parameters such as kind of extractant and dispersant and volume of them, extraction time, effect of salt addition, and pH were optimized. As a result, 5.0 {mu}L 1-dodecanol was chosen as extraction solvent, 600 {mu}L methanol were used as dispersive solvent without salt addition, pH was adjusted to 7. Under the optimized conditions, the limits of detection (LOD) were ranged from 1.4 to 8.3 ng L{sup -1}. Satisfactory linear range was observed from 5.0 to 2000 ng L{sup -1} with correlation coefficient better than 0.9909. Good precisions were also acquired with RSD better than 13.6% for all target analytes. The enrichment factors of the method were ranged from 786 to 1427. The method can be successfully applied to simultaneous separation and determination of three class residues in real water samples and good recoveries were obtained ranging from 76 to 130, 73 to 129, and 78 to 130% for tap water, lake water, and industrial waste water, respectively. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. A novel extraction method for β-carotene and other carotenoids in fruit juices using air-assisted, low-density solvent-based liquid-liquid microextraction and solidified floating organic droplets.

    Science.gov (United States)

    Sricharoen, Phitchan; Limchoowong, Nunticha; Techawongstien, Suchila; Chanthai, Saksit

    2016-07-15

    Green extraction using air-assisted, low-density solvent-based liquid-liquid microextraction and solidified floating organic droplets (AA-LDS-LLME-SFOD) prior to spectrophotometry was successfully applied for quantitation of carotenoids in fruit juices. Under optimal conditions, β-carotene could be quantified with a linear response up to a concentration of 60 μg mL(-1). The procedure was performed in a microcentrifuge tube with 40 μL of 1-dodecanol as the extraction solvent and a 1.0 mL juice sample containing 8% NaCl under seven extraction cycles of air pumping by syringe. This method was validated based on linearity (0.2-30 μg mL(-1), R(2) 0.998), limit of detection (0.04 μg mL(-1)) and limit of quantification (0.13 μg mL(-1)). The precision, expressed as the relative standard deviation (RSD) of the calibration curve slope (n=12), for inter-day and intra-day analysis was 4.85% and 7.92%, respectively. Recovery of β-carotene was in the range of 93.6-101.5%. The newly proposed method is simple, rapid and environmentally friendly, particularly as a useful screening test for food analysis.

  11. Vortices catapult droplets in atomization

    Science.gov (United States)

    Jerome, J. John Soundar; Marty, Sylvain; Matas, Jean-Philippe; Zaleski, Stéphane; Hoepffner, Jérôme

    2013-11-01

    A droplet ejection mechanism in planar two-phase mixing layers is examined. Any disturbance on the gas-liquid interface grows into a Kelvin-Helmholtz wave, and the wave crest forms a thin liquid film that flaps as the wave grows downstream. Increasing the gas speed, it is observed that the film breaks up into droplets which are eventually thrown into the gas stream at large angles. In a flow where most of the momentum is in the horizontal direction, it is surprising to observe these large ejection angles. Our experiments and simulations show that a recirculation region grows downstream of the wave and leads to vortex shedding similar to the wake of a backward-facing step. The ejection mechanism results from the interaction between the liquid film and the vortex shedding sequence: a recirculation zone appears in the wake of the wave and a liquid film emerges from the wave crest; the recirculation region detaches into a vortex and the gas flow over the wave momentarily reattaches due to the departure of the vortex; this reattached flow pushes the liquid film down; by now, a new recirculation vortex is being created in the wake of the wave—just where the liquid film is now located; the liquid film is blown up from below by the newly formed recirculation vortex in a manner similar to a bag-breakup event; the resulting droplets are catapulted by the recirculation vortex.

  12. Vortices catapult droplets in atomization

    Energy Technology Data Exchange (ETDEWEB)

    Jerome, J. John Soundar, E-mail: soundar@dalembert.upmc.fr; Zaleski, Stéphane; Hoepffner, Jérôme [Institut Jean Le Rond d' Alembert, UPMC Univ. Paris 06 and CNRS-UMR 7190, F-75005 Paris (France); Marty, Sylvain; Matas, Jean-Philippe [Laboratoire des Écoulements Géophysiques et Industriels (LEGI), Univ. Grenoble Alpes and CNRS - UMR 5519, F-38000 Grenoble (France)

    2013-11-15

    A droplet ejection mechanism in planar two-phase mixing layers is examined. Any disturbance on the gas-liquid interface grows into a Kelvin-Helmholtz wave, and the wave crest forms a thin liquid film that flaps as the wave grows downstream. Increasing the gas speed, it is observed that the film breaks up into droplets which are eventually thrown into the gas stream at large angles. In a flow where most of the momentum is in the horizontal direction, it is surprising to observe these large ejection angles. Our experiments and simulations show that a recirculation region grows downstream of the wave and leads to vortex shedding similar to the wake of a backward-facing step. The ejection mechanism results from the interaction between the liquid film and the vortex shedding sequence: a recirculation zone appears in the wake of the wave and a liquid film emerges from the wave crest; the recirculation region detaches into a vortex and the gas flow over the wave momentarily reattaches due to the departure of the vortex; this reattached flow pushes the liquid film down; by now, a new recirculation vortex is being created in the wake of the wave—just where the liquid film is now located; the liquid film is blown up from below by the newly formed recirculation vortex in a manner similar to a bag-breakup event; the resulting droplets are catapulted by the recirculation vortex.

  13. Thermocapillary migration of an isolated droplet and interaction of two droplets in zero gravity

    Science.gov (United States)

    Alhendal, Yousuf; Turan, Ali; Kalendar, Abdulrahim

    2016-09-01

    Fluid transfer within a stagnant liquid presents a significant challenge in zero-gravity conditions due to the lack of buoyancy effects. This challenge can be overcome by the utilisation of the Marangoni effect, or more specifically thermocapillary migration. The thermocapillary migration of droplets is driven by temperature gradients within the multiphase system which bring about a surface tension gradient driving the flow from the cold to the hot region. The migration speed of the droplet is significantly impacted by the heat transfer both inside the droplet and in its surroundings. This paper presents the analysis of drop movement in a stagnant liquid using computational fluid dynamics (CFD). The commercial software package Ansys-Fluent v.13 [1] is used to solve the governing continuum conservation equations for two-phase flow using the Volume of Fluid (VOF) method to track the liquid/liquid interface in 2D domain. This approach has been shown to be a valuable tool for studying the phenomena of liquid-liquid interaction. A strong agreement has been found with experimental observations conducted in microgravity. The inherent velocity of drops has been found to decrease with increasing Marangoni number. This finding is in line with the previous space experiments of Xie et al. (2005) [2] and in contrast to the numerical results of Ma (1999) [3] using the same liquid for the droplet and the host liquid. Data obtained in the present numerical study has been used to derive an expression predicting the scaled droplet velocity as a function of Marangoni number. A numerical study of the interaction of two spherical droplets undergoing thermocapillary migration in microgravity is also presented. The temperature thrust from the leading droplet towards the trailing droplet was found to disturb its migration velocity, but the trailing droplet was found to have no influence on the migration of the leading droplet.

  14. Compound droplet manipulations on fiber arrays

    CERN Document Server

    Weyer, Floriane; Dreesen, Laurent; Vandewalle, Nicolas

    2015-01-01

    Recent works demonstrated that fiber arrays may constitue the basis of an open digital microfluidics. Various processes, such as droplet motion, fragmentation, trapping, release, mixing and encapsulation, may be achieved on fiber arrays. However, handling a large number of tiny droplets resulting from the mixing of several liquid components is still a challenge for developing microreactors, smart sensors or microemulsifying drugs. Here, we show that the manipulation of tiny droplets onto fiber networks allows for creating compound droplets with a high complexity level. Moreover, this cost-effective and flexible method may also be implemented with optical fibers in order to develop fluorescence-based biosensor.

  15. A Theory of Shape-Shifting Droplets

    Science.gov (United States)

    Haas, Pierre; Goldstein, Raymond; Smoukov, Stoyan; Denkov, Nikolai

    2016-11-01

    Recent observations of cooled oil emulsion droplets uncovered a remarkable array of shape transformations: the initially spherical droplets flatten into polygonal shapes, first hexagons, then triangles or quadrilaterals that ultimately grow thin protrusions from their corners. These transformations are driven by a partial phase transition of the bulk liquid phase. In this talk, we explore theoretically the simplest geometric competition between this phase transition and surface tension in planar polygons. We recover the experimental sequence of shapes and predict shape statistics in qualitative agreement with experiments. Extending the model to capture some of the three-dimensional structure of the droplets, we analyse the topological transition of droplet puncture observed in experiments.

  16. CO2激光诱导液滴射流等离子体的实验研究%Experimental research of CO2 laser-induced liquid droplet jet flow plasma

    Institute of Scientific and Technical Information of China (English)

    陈子琪; 王新兵; 左都罗

    2016-01-01

    In order to study the characteristics and the evolution of laser-induced liquid droplet jet flow plasma, the behaviors of laser-induced liquid droplet plasma were investigated by the shadow method based on laser-droplet interaction system. Time-series images of CO2 laser-induced plasma with liquid droplet were captured. The evolution of air shock wave was obtained and the energy of shockwaves was estimated by theoretical model. The results show that air shock wave occurrs with laser-induced plasma and the radial expansion of shockwaves increases linearly under current time range. In addition, laser energy dissipated in the droplet was estimated to 32% for generating air shockwaves. The characteristics and the evolution of shockwaves generated by laser-induced droplet could provide a reference for laser induced fuel spray ignition.%为了研究激光诱导射流等离子体特性,了解激光诱导液滴等离子体的发展过程,基于脉冲激光-液滴同步作用系统,采用阴影法,观测了激光作用液滴的阴影图像,取得了液滴在CO2脉冲激光作用下的演化过程数据。对图像进行处理获得了激光诱导液滴等离子体冲击波膨胀范围随时间的变化,并估算出了产生冲击波的激光能量。结果表明,空气冲击波的膨胀半径在当前观测时间范围内线性膨胀,约32%的激光能量用于产生冲击波。空气冲击波的变化规律对激光诱导液态燃料点火的研究提供了一定的参考依据。

  17. Response of two-phase droplets to intense electromagnetic radiation

    Science.gov (United States)

    Spann, James F.; Maloney, Daniel J.; Lawson, William F.; Casleton, Kent H.

    1993-04-01

    The behavior of two-phase droplets subjected to high intensity radiation pulses is studied. Droplets are highly absorbing solids in weakly absorbing liquid medium. The objective of the study was to define heating thresholds required for causing explosive boiling and secondary atomization of the fuel droplet. The results point to mechanisms for energy storage and transport in two-phase systems.

  18. An extension of dynamic droplet deformation models to secondary atomization

    NARCIS (Netherlands)

    Bartz, F.O.; Schmehl, R.; Koch, R.; Bauer, H.J.

    2010-01-01

    A detailed model for secondary atomization of liquid droplets by aerodynamic forces is presented. As an empirical extension of dynamic droplet deformation models, it accounts for temporal variations of the relative velocity between droplet and gas phase during the deformation and breakup process and

  19. Simultaneous determination of volatile and non-volatile nitrosamines in processed meat products by liquid chromatography tandem mass spectrometry using atmospheric pressure chemical ionisation and electrospray ionisation.

    Science.gov (United States)

    Herrmann, S S; Duedahl-Olesen, L; Granby, K

    2014-02-21

    A sensitive, selective and generic method has been developed for the simultaneous determination of the contents (μgkg(-1) range) of both volatile nitrosamines (VNA) and non-volatile nitrosamines (NVNA) in processed meat products. The extraction procedure only requires basic laboratory equipment and a small volume of organic solvent. Separation and quantification were performed by the developed LC-(APCI/ESI)MS/MS method. The method was validated using spiked samples of three different processed meat products. Satisfactory recoveries (50-130%) and precisions (2-23%) were obtained for eight VNA and six NVNAs with LODs generally between 0.2 and 1μgkg(-1), though for a few analyte/matrix combinations higher LODs were obtained (3 to 18μgkg(-1)). The validation results show that results obtained for one meat product is not always valid for other meat products. We were not able to obtain satisfactory results for N-nitrosohydroxyproline (NHPRO), N-nitrosodibenzylamine (NDBzA) and N-nitrosodiphenylamine (NDPhA). Application of the APCI interface improved the sensitivity of the method, because of less matrix interference, and gave the method a wider scope, as some NAs were ionisable only by APCI. However, it was only possible to ionize N-nitroso-thiazolidine-4-carboxylic acid (NTCA) and N-nitroso-2-methyl-thiazolidine-4-carboxylic acid (NMTCA) by ESI. The validated method was applied for the analysis of processed meat products and contents of N-nitrosodimethylamine (NDMA), N-nitrosopyrrolidine (NPYR), N-nitrosomethylaniline (NMA), N-nitrosoproline (NPRO), NTCA, and NMTCA were found in one or several nitrite cured meat products, whereas none were detected in non-nitrite cured bacon.

  20. Droplet based cavities and lasers

    DEFF Research Database (Denmark)

    Mølhave, Kristian; Kristensen, Anders; Mortensen, Asger

    2009-01-01

    The self-organized and molecularly smooth surface on liquid microdroplets makes them attractive as optical cavities with very high quality factors. This chapter describes the basic theory of optical modes in spherical droplets. The mechanical properties including vibrational excitation are also d...

  1. Simultaneous flame ionization and absorbance detection of volatile and nonvolatile compounds by reversed-phase liquid chromatography with a water mobile phase.

    Science.gov (United States)

    Bruckner, C A; Ecker, S T; Synovec, R E

    1997-09-01

    A flame ionization detector (FID) is used to detect volatile organic compounds that have been separated by water-only reversed-phase liquid chromatography (WRP-LC). The mobile phase is 100% water at room temperature, without use of organic solvent modifiers. An interface between the LC and detector is presented, whereby a helium stream samples the vapor of volatile components from individual drops of the LC eluent, and the vapor-enriched gas stream is sent to the FID. The design of the drop headspace cell is simple because the water-only nature of the LC separation obviates the need to do any organic solvent removal prior to gas phase detection. Despite the absence of organic modifier, hydrophobic compounds can be separated in a reasonable time due to the low phase volume ratio of the WRP-LC columns. The drop headspace interface easily handles LC flows of 1 mL/min, and, in fact, compound detection limits are improved at faster liquid flow rates. The transfer efficiency of the headspace interface was estimated at 10% for toluene in water at 1 mL/min but varies depending on the volatility of each analyte. The detection system is linear over more than 5 orders of 1-butanol concentration in water and is able to detect sub-ppb amounts of o-xylene and other aromatic compounds in water. In order to analyze volatile and nonvolatile analytes simultaneously, the FID is coupled in series to a WRP-LC system with UV absorbance detection. WRP-LC improves UV absorbance detection limits because the absence of organic modifier allows the detector to be operated in the short-wavelength UV region, where analytes generally have significantly larger molar absorptivities. The selectivity the headspace interface provides for flame ionization detection of volatiles is demonstrated with a separation of 1-butanol, 1,1,2-trichloroethane (TCE), and chlorobenzene in a mixture of benzoic acid in water. Despite coelution of butanol and TCE with the benzoate anion, the nonvolatile benzoate anion

  2. Velocity and rotation measurements in acoustically levitated droplets

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Abhishek [University of Central Florida, Orlando, FL 32816 (United States); Basu, Saptarshi [Indian Institute of Science, Bangalore 560012 (India); Kumar, Ranganathan, E-mail: ranganathan.kumar@ucf.edu [University of Central Florida, Orlando, FL 32816 (United States)

    2012-10-01

    The velocity scale inside an acoustically levitated droplet depends on the levitator and liquid properties. Using Particle Imaging Velocimetry (PIV), detailed velocity measurements have been made in a levitated droplet of different diameters and viscosity. The maximum velocity and rotation are normalized using frequency and amplitude of acoustic levitator, and droplet viscosity. The non-dimensional data are fitted for micrometer- and millimeter-sized droplets levitated in different levitators for different viscosity fluids. It is also shown that the rotational speed of nanosilica droplets at an advanced stage of vaporization compares well with that predicted by exponentially fitted parameters. -- Highlights: ► Demonstrates the importance of rotation in a levitated droplet that leads to controlled morphology. ► Provides detailed measurements of Particle Image Velocimetry inside levitated droplets. ► Shows variation of vortex strength with the droplet diameter and viscosity of the liquid.

  3. Heat transfer and phase change in an impinging droplet

    Science.gov (United States)

    Rangchian, Aysan; Shirazi, Nikki L.; Kavehpour, H. Pirouz

    2016-11-01

    Non isothermal droplet impact on solid surfaces has several industrial applications such as spray cooling and 3D printing. Impinging of a droplet on a surface involves an initial phase of spreading followed by a subsequent return to the equilibrium shape. Thermal energy exchanged within the droplet fluid as well as between liquid/solid during the impact has been studied using an ultra high speed infrared camera. Variable parameters in the experiment include droplet temperature and kinetic energy of the droplet during the impact. The evolution of droplet shape viewed by IR camera is similar to what previously observed by high speed photography. The thermal map of droplet over time in these experiments agrees with previously reported numerical simulation. In addition, spacial and temporal temperature variations of liquid droplets on a surface as they solidify are presented. IR camera provides an accurate temperature diagram as the phase change occurs, which is essential for understanding the physics of 3D printing.

  4. Analysis of coalescence behavior for compressed droplets

    Science.gov (United States)

    Choi, Sung Woong; Lee, Dong Eon; Lee, Woo Il; Kim, Han Sang

    2017-03-01

    Coalescence of droplets is a significant phenomenon, and it has been adapted to many applications such as raindrop formation, emulsion polymerization, ink-jet printing, coating, and multiphase flows. In this study, the morphological characteristics of two compressed adjacent droplets between two parallel plates were investigated to study the phenomenon of coalescence of droplets. By controlling the distance of the dispensed droplets, various results for coalescence of droplets were evaluated, especially, from the view of the minor axis, major axis, and meniscus liquid bridge of the coalesced droplet. Experimental results show that the length of the meniscus liquid bridge rapidly increases and then the rate of increase slows with time. The increase rate of the major and minor axes is largely influenced by the meniscus liquid bridge, which is mainly due to the curvature between the droplets. The numerical modeling of the coalescence of the two compressed droplets between two parallel plates was presented and simulation was conducted to realize the coalescence behavior. Comparison with numerical simulation showed that there was a good agreement with the experimental results.

  5. Liquid Swine Manure Can Kill Verticillium dahliae Microsclerotia in Soil by Volatile Fatty Acid, Nitrous Acid, and Ammonia Toxicity.

    Science.gov (United States)

    Conn, Kenneth L; Tenuta, Mario; Lazarovits, George

    2005-01-01

    ABSTRACT In previous studies, liquid swine manure (LSM) was sometimes shown to reduce Verticillium wilt of potato caused by Verticillium dahliae. We also observed that microsclerotia of this fungus died within 1 day, or between 3 and 6 weeks, after addition of LSM to some acid soils and within 1 week in some alkaline soils. In this study, we demonstrated that a volatile fatty acid (VFA) mixture with an identical concentration of VFAs as that found in an effective LSM reduced germination in an acid soil (pH 5.1) to the same extent as the LSM after 1 day of exposure. Germination was reduced by 45, 75, and 90% in the 10, 20, and 40% ([wt/wt] soil moisture) treatments, respectively, with the latter being equivalent to an application of 80 hl/ha. Addition to this acid soil of 19 LSMs (30% [wt/wt] soil moisture) collected from different producers resulted in complete kill of microsclerotia with 12 manures. Effective manures had a total concentration of nonionized forms of VFAs in soil solution of 2.7 mM or higher. In some acid soils (pH 5.8), addition of LSM (40% [wt/wt] soil moisture) did not kill microsclerotia until 3 to 6 weeks later. Here, a reduction in viability of microsclerotia was attributed to the accumulation of 0.06 mM nitrous acid in the soil solution at 4 weeks. When an LSM was added (40% [wt/wt] soil moisture) to an alkaline soil (pH 7.9) where VFAs are not toxic, microsclerotia germination was reduced by 80% after 1 week. Here the pH increased to 8.9 and the concentration of ammonia reached 30 mM in the soil solution. An ammonium chloride solution having an equivalent concentration of ammonium as the manure was shown to have the same spectrum of toxicity as the manure in assays ranging from pH 7 to 9, both in solutions and above the solutions. At pH 9, the concentration of ammonia reached 18 mM and 100% mortality of microsclerotia occurred. Thus, in acid soils, LSM can kill microsclerotia of V. dahliae by VFA and/or nitrous acid toxicity and in alkaline

  6. Photophoretic trampoline - Interaction of single airborne absorbing droplets with light

    CERN Document Server

    Esseling, Michael; Alpmann, Christina; Denz, Cornelia

    2012-01-01

    We present the light-induced manipulation of absorbing liquid droplets in air. Ink droplets from a printer cartridge are used to demonstrate that absorbing liquids - just like their solid counterparts - can interact with regions of high light intensity due to the photophoretic force. It is shown that droplets follow a quasi-ballistic trajectory after bouncing off a high intensity light sheet. We estimate the intensities necessary for this rebound of airborne droplets and change the droplet trajectories through a variation of the manipulating light field.

  7. Impact of Viscous Droplets on Superamphiphobic Surfaces

    Science.gov (United States)

    Zhao, Binyu; Chen, Longquan; Deng, Xu

    2016-11-01

    Superamphiphobic coating is promising for various applications in industry, e.g. self-cleaning windows, where the impingement of droplets on surfaces is commonly encountered. In this work, we experimentally investigated the impact of droplets with similar surface tension (63-72 mN/m) but much different viscosity (1-150 mPa s) on superamphiphobic surfaces. We found that droplets can rebound from the superamphiphobic surfaces when the impact velocity is larger than a critical value, which linearly increases with the liquid viscosity. Droplet with higher viscosity spreads, retracts slower, and eventually rebounds lower and fewer times than that of low viscous droplet. These findings have important implications for surface engineers to use superamphiphobic coatings. Furthermore, we measured the maximum spreading factors for droplet impact on superamphiphobic surfaces and proposed a simple model based on energy conversation to describe its relationship to the Weber number and Reynolds number.

  8. Dynamics of Electrically Modulated Colloidal Droplet Transport.

    Science.gov (United States)

    Dey, Ranabir; Ghosh, Udita Uday; Chakraborty, Suman; DasGupta, Sunando

    2015-10-20

    Electrically actuated transport dynamics of colloidal droplets, on a hydrophobic dielectric film covering an array of electrodes, is studied here. Specifically, the effects of the size and electrical properties (zeta-potential) of the colloidal particles on such transport characteristics are investigated. For the colloidal droplets, the application of an electrical voltage leads to additional attenuation of the local dielectric-droplet interfacial tension. This is due to the electrically triggered enhanced colloidal particle adsorption at the dielectric-droplet interface, in the immediate vicinity of the droplet three-phase contact line (TPCL). The extent of such interfacial particle adsorption, and hence, the extent of the consequential reduction in the interfacial tension, is dictated by the combined effects of the three-phase contact line spreading, particle size, the interfacial electrostatic interaction between the colloidal particles (if charged) and the charged dielectric surface above the activated electrode, and the interparticle electrostatic repulsion. The electrical driving force of varying magnitude, stemming from this altered solid-liquid interfacial tension gradient in the presence of the colloidal particles, culminates in different droplet transport velocity and droplet transfer frequency for different colloidal droplets. We substantiate the inferences from our experimental results by a quasi-steady state force balance model for colloidal droplet transport. We believe that the present work will provide an accurate framework for determining the optimal design and operational parameters for digital microfluidic chips handling colloidal droplets, as encountered in a plethora of applications.

  9. Compound droplet manipulations on fiber arrays

    Science.gov (United States)

    Weyer, Floriane; Lismont, Marjorie; Dreesen, Laurent; Vandewalle, Nicolas

    2014-11-01

    Recent works demonstrated that fibers are the basis of an open digital microfluidics. Indeed, various processes such as droplet motion, fragmentation, trapping, releasing, mixing and encapsulation can be constructed on fiber arrays. However, addressing a large number of tiny droplets resulting from the mixing of several liquid components is still a challenge. Here we show that it is possible to manipulate tiny droplets reaching a high level of complexity. Wetting droplets are known to glide along vertical fibers. When a droplet reaches an horizontal fiber, it sticks at the crossing if capillary overcomes gravity. Otherwise, the droplet continues its way, crosses the node and leaves a tiny residue. Therefore, a vertical fiber decorated with a series of horizontal fibers will retain residual droplets at the successive nodes. An oil droplet, sliding on the vertical fiber, is able to collect the residues. Thus a multicompound droplet is created. The volume of the residual droplets has been studied and seems to be related to the diameters of both vertical and horizontal fibers. Moreover, the conditions under which the residues are released have been investigated in order to understand the formation of such a fluidic object. F. Weyer is financially supported by an FNRS grant. This work is also supported by the FRFC 2.4504.12.

  10. Enhancement of evaporation of droplet using EHD effect. 2nd Report. ; Onset of instability of gas-liquid interface under electric field. EHD koka wo mochiita ekiteki no johatsu sokushin. 2. ; Denba no moto deno kieki kaimen no fuantei gensho ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Takano, K.; Tanasawa, I.; Nishio, S. (tokyo University, Tokyo (Japan). Institute of Industrial Science)

    1991-12-25

    Evaporation is accelerated when an electric field is applied to droplets evaporating in a spheroid condition. To identify the correlation with an liquid column generated at the bottom of the droplet in the accelerated evaporation, experiments and analyses were carried out by applying electric fields onto horizontal free surfaces of several kinds of liquid. The minimum voltage (critical voltage) at which a turbulence occurs on the free liquid surface can be analyzed as a stability problem on the interface turbulence when pressure, gravitational force, surface tension and electrical power act upon the two-dimensional horizontal free liquid surfaces. From the fact that the critical voltage analytic values on the unstable generation agree well with the experimental results, this analytic method was expanded and calculated to predict the upper limit of the evaporation accelerating temperature (the heat transfer face temperature at which the unstable turbulence wavelength becomes equal to the droplet's bottom diameter) when an electric field is applied to droplets generating in the spheroid condition. The analysis agreed with the experimental result qualitatively. Therefore, the solid-liquid contact in a liquid column that is generated when an electric field is applied to droplets evaporating in a spheroid condition suggests a close correlation with the interface instability. 15 refs., 13 figs., 1 tab.

  11. Shock wave-droplet interaction

    Science.gov (United States)

    Habibi Khoshmehr, Hamed; Krechetnikov, Rouslan

    2016-11-01

    Disintegration of a liquid droplet under the action of a shock wave is experimentally investigated. The shock wave-pulse is electromagnetically generated by discharging a high voltage capacitor into a flat spiral coil, above which an isolated circular metal membrane is placed in a close proximity. The Lorentz force arising due to the eddy current induced in the membrane abruptly accelerates it away from the spiral coil thus generating a shock wave. The liquid droplet placed at the center of the membrane, where the maximum deflection occurs, is disintegrated in the process of interaction with the shock wave. The effects of droplet viscosity and surface tension on the droplet destruction are studied with high-speed photography. Water-glycerol solution at different concentrations is used for investigating the effect of viscosity and various concentrations of water-sugar and water-ethanol solution are used for studying the effect of surface tension. Here we report on how the metamorphoses, which a liquid drop undergoes in the process of interaction with a shock wave, are affected by varied viscosity and surface tension.

  12. Plasma Propulsion of a Metallic Micro-droplet and its Deformation upon Laser Impact

    CERN Document Server

    Kurilovich, Dmitry; Torretti, Francesco; Lassise, Adam; Hoekstra, Ronnie; Ubachs, Wim; Gelderblom, Hanneke; Versolato, Oscar O

    2016-01-01

    The propulsion of a liquid indium-tin micro-droplet by nanosecond-pulse laser impact is experimentally investigated. We capture the physics of the droplet propulsion in a scaling law that accurately describes the plasma-imparted momentum transfer, enabling the optimization of the laser-droplet coupling. The subsequent deformation of the droplet is described by an analytical model that accounts for the droplet's propulsion velocity and the liquid properties. Comparing our findings to those from vaporization-accelerated mm-sized water droplets, we demonstrate that the hydrodynamic response of laser-impacted droplets is scalable and independent of the propulsion mechanism.

  13. Ultrasound leaching-dispersive liquid-liquid microextraction based on solidification of floating organic droplet for determination of polybrominated diphenyl ethers in sediment samples by gas chromatography-tandem mass spectrometry.

    Science.gov (United States)

    Lana, Nerina B; Berton, Paula; Covaci, Adrian; Atencio, Adrián G; Ciocco, Néstor F; Altamirano, Jorgelina C

    2013-04-12

    Ultrasound leaching-dispersive liquid-liquid microextraction using solidification of floating organic droplet (USL-DLLME-SFO) technique is proposed for extraction and isolation of polybrominated diphenyl ethers (PBDEs) from sediment and further determination by gas chromatography-tandem mass spectrometry (GC-MS/MS). Parameters that affect the efficiency of the procedure were investigated by a full factorial (2(k)) screening design. Variables showing significant effects on the analytical responses were considered within a further central composite design (CCD). The optimization assays have led to following protocol: ultrasound assisted lixiviation of 1g sediment was carried out by using 1.2 mL MeOH. Further, the analytes were isolated from 0.4 mL of the extract using the DLLME-SFO technique. The microextraction was performed using 0.1 mL MeOH, 22 mg 1-dodecanol, 1 mL NaCl solution 6.15M and 4.4 mL ultrapure water as dispersive and extracting solvents, medium ionic strength and dispersant bulk, respectively. Under optimum conditions, the method exhibits good performance in terms of linearity and precision (RSD<9.2%), with recoveries above 71% and limits of detection (LODs) within the range 0.5-1.8 pgg(-1) dry weight (d.w.). Method validation was demonstrated through the analysis of environmental sediment samples in which PBDEs were detected and quantified. The presence of BDE-47, -100, -99 and -153 was reported within the concentration range of

  14. Determination of volatile compounds in cider apple juices using a covalently bonded ionic liquid coating as the stationary phase in gas chromatography.

    Science.gov (United States)

    Pello-Palma, Jairo; González-Álvarez, Jaime; Gutiérrez-Álvarez, María Dolores; Dapena de la Fuente, Enrique; Mangas-Alonso, Juan José; Méndez-Sánchez, Daniel; Gotor-Fernández, Vicente; Arias-Abrodo, Pilar

    2017-04-01

    A chromatographic method for the separation of volatile compounds in Asturian cider apple juices has been developed. For this separation purpose, a monocationic imidazolium-based ionic liquid bearing a reactive terminal iodine atom was synthesized by a quaternization-anion exchange chemical sequence. Next, the gas chromatography (GC) stationary phase was prepared by covalently linking the imidazolium monolith to the reactive silanol groups of the inner capillary wall at 70 °C. This coated GC column exhibited good thermal stability (290 °C), as well as good efficiency (2000 plates/m) in the separation of volatile compounds from Asturian apple cider juices, and was characterized using the Abraham solvation parameter model. The intra-day and inter-day precision of the chromatographic method was evaluated, obtaining relative standard deviations from 3.7 to 12.9% and from 7.4 to 18.0%, respectively. Furthermore, recoveries from 82.5 to 122% were achieved. Graphical Abstract Covalent bonding of an ionic liquid to inner column wall led to a great improvement of the separation efficiencies of stationary phases in gas chromatography.

  15. Grooved organogel surfaces towards anisotropic sliding of water droplets.

    Science.gov (United States)

    Zhang, Pengchao; Liu, Hongliang; Meng, Jingxin; Yang, Gao; Liu, Xueli; Wang, Shutao; Jiang, Lei

    2014-05-21

    Periodic micro-grooved organogel surfaces can easily realize the anisotropic sliding of water droplets attributing to the formed slippery water/oil/solid interface. Different from the existing anisotropic surfaces, this novel surface provides a versatile candidate for the anisotropic sliding of water droplets and might present a promising way for the easy manipulation of liquid droplets for water collection, liquid-directional transportation, and microfluidics.

  16. Binary droplet collision at high Weber number.

    Science.gov (United States)

    Pan, Kuo-Long; Chou, Ping-Chung; Tseng, Yu-Jen

    2009-09-01

    By using the techniques developed for generating high-speed droplets, we have systematically investigated binary droplet collision when the Weber number (We) was increased from the range usually tested in previous studies on the order of 10 to a much larger value of about 5100 for water (a droplet at 23 m/s with a diameter of 0.7 mm). Various liquids were also used to explore the effects of viscosity and surface tension. Specifically, beyond the well-known regimes at moderate We's, which exhibited coalescence, separation, and separation followed by satellite droplets, we found different behaviors showing a fingering lamella, separation after fingering, breakup of outer fingers, and prompt splattering into multiple secondary droplets as We was increased. The critical Weber numbers that mark the boundaries between these impact regimes are identified. The specific impact behaviors, such as fingering and prompt splattering or splashing, share essential similarity with those also observed in droplet-surface impacts, whereas substantial variations in the transition boundaries may result from the disparity of the boundary conditions at impacts. To compare the outcomes of both types of collisions, a simple model based on energy conservation was carried out to predict the maximum diameter of an expanding liquid disk for a binary droplet collision. The results oppose the dominance of viscous drag, as proposed by previous studies, as the main deceleration force to effect a Rayleigh-Taylor instability and ensuing periphery fingers, which may further lead to the formations of satellite droplets.

  17. Vibration-Induced Droplet Atomization --- A Theoretical Investigation.

    Science.gov (United States)

    James, Ashley; Smith, Marc K.; Glezer, Ari

    1997-11-01

    The atomization of a liquid droplet placed on a vibrating membrane starts with the development of Faraday free surface waves. As the excitation amplitude increases, the waves grow in amplitude and ultimately begin to eject smaller secondary droplets from the wave crests. The rate of droplet ejection can be large enough to completely drain the primary droplet, an event we call bursting. The evolution of the droplet ejection process depends on a coupled system dynamic between the droplet and the membrane. When droplets are ejected the resonant frequency of the system increases. This changes the acceleration felt by the droplet and, in turn, the rate of droplet ejection. Depending on the excitation frequency and amplitude, various types of bursting or droplet ejection processes may occur. A simple, single degree-of-freedom model of this coupled system is presented. The model is used to illustrate the effect of the excitation frequency and amplitude and the initial droplet size on the acceleration of the membrane and the droplet ejection rate. The results of the model will be compared to our experimental data on droplet ejection. Additional work is directed towards an understanding of the mechanism behind the droplet ejection process.

  18. Uniform-droplet spray forming

    Energy Technology Data Exchange (ETDEWEB)

    Blue, C.A.; Sikka, V.K. [Oak Ridge National Lab., TN (United States); Chun, Jung-Hoon [Massachusetts Institute of Technology, Cambridge, MA (United States); Ando, T. [Tufts Univ., Medford, MA (United States)

    1997-04-01

    The uniform-droplet process is a new method of liquid-metal atomization that results in single droplets that can be used to produce mono-size powders or sprayed-on to substrates to produce near-net shapes with tailored microstructure. The mono-sized powder-production capability of the uniform-droplet process also has the potential of permitting engineered powder blends to produce components of controlled porosity. Metal and alloy powders are commercially produced by at least three different methods: gas atomization, water atomization, and rotating disk. All three methods produce powders of a broad range in size with a very small yield of fine powders with single-sized droplets that can be used to produce mono-size powders or sprayed-on substrates to produce near-net shapes with tailored microstructures. The economical analysis has shown the process to have the potential of reducing capital cost by 50% and operating cost by 37.5% when applied to powder making. For the spray-forming process, a 25% savings is expected in both the capital and operating costs. The project is jointly carried out at Massachusetts Institute of Technology (MIT), Tuffs University, and Oak Ridge National Laboratory (ORNL). Preliminary interactions with both finished parts and powder producers have shown a strong interest in the uniform-droplet process. Systematic studies are being conducted to optimize the process parameters, understand the solidification of droplets and spray deposits, and develop a uniform-droplet-system (UDS) apparatus appropriate for processing engineering alloys.

  19. Use of volatile organic solvents in headspace liquid-phase microextraction by direct cooling of the organic drop using a simple cooling capsule.

    Science.gov (United States)

    Ghiasvand, Ali Reza; Yazdankhah, Fatemeh; Hajipour, Somayeh

    2016-08-01

    A low-cost and simple cooling-assisted headspace liquid-phase microextraction device for the extraction and determination of 2,6,6-trimethyl-1,3 cyclohexadiene-1-carboxaldehyde (safranal) in Saffron samples, using volatile organic solvents, was fabricated and evaluated. The main part of the cooling-assisted headspace liquid-phase microextraction system was a cooling capsule, with a Teflon microcup to hold the extracting organic solvent, which is able to directly cool down the extraction phase while the sample matrix is simultaneously heated. Different experimental factors such as type of organic extraction solvent, sample temperature, extraction solvent temperature, and extraction time were optimized. The optimal conditions were obtained as: extraction solvent, methanol (10 μL); extraction temperature, 60°C; extraction solvent temperature, 0°C; and extraction time, 20 min. Good linearity of the calibration curve (R(2) = 0.995) was obtained in the concentration range of 0.01-50.0 μg/mL. The limit of detection was 0.001 μg/mL. The relative standard deviation for 1.0 μg/mL of safranal was 10.7% (n = 6). The proposed cooling-assisted headspace liquid-phase microextraction device was coupled (off-line) to high-performance liquid chromatography and used for the determination of safranal in Saffron samples. Reasonable agreement was observed between the results of the cooling-assisted headspace liquid-phase microextraction high-performance liquid chromatography method and those obtained by a validated ultrasound-assisted solvent extraction procedure.

  20. Structure formation by nanosilica particles suspended in levitated droplet

    CERN Document Server

    Saha, Abhishek; Kumar, Ranganathan; Basu, Saptarshi

    2010-01-01

    Vaporization of liquid droplets containing particles has been studied extensively for its applications in combustion, thermal coating, ink-jet printing, spray cooling, drug delivery, and surface patterning. Droplets containing solid particles show a preferential solute-migration during drying process. Recently we carried out experiments with vaporizing droplet suspended in an acoustic levitator. In this work, we present detailed study of a laser irradiated droplet containing nanosilica particles. Infrared and High speed imaging of the heating process for different concentrations of nanosilica revealed an interesting solute migration pattern. Further investigation with Particle Image Velocimetry shows presence of strong recirculation within the levitated droplet. It also reveals that with increasing viscosity of the liquid the strength of this recirculation decreases. Due to the droplets rotation about the levitator axis, a centrifugal force also dominated the flow field within the droplet. High speed imaging ...

  1. The role of the droplet deformations in the bouncing droplet dynamics

    Science.gov (United States)

    Terwagne, D.; Ludewig, F.; Vandewalle, N.; Dorbolo, S.

    2013-12-01

    Droplets bouncing on a vibrated liquid bath open ways to methods of manipulating droplets, creating double emulsion, and performing pilot wave model experiments. In this work, we focus on the role of the droplet deformations in the vertical bouncing dynamics by neglecting the deformation of the surface of the bath. To be under this favorable condition, low viscous oil droplets are dropped over a highly viscous oil bath that is vibrated. These droplets bounce vertically on the surface of the bath and exhibit many periodic trajectories and resonant modes when tuning the forcing parameters, i.e., the oscillation of the bath. This complex dynamics emphasizes the interplay between elastic energy storage and energy dissipation in droplets at each bounce. We propose to model droplets using a bouncing mass-spring-damper system that mimics a deformable droplet bouncing on a non-deformable liquid bath. From the experimental measurements, we constructed bifurcation diagrams of the bouncing trajectories and challenged our bouncing spring model. The agreement between experiment and the spring model reveals that this model can be used to rationalize and predict a variety of bouncing droplets behaviors involving multi-periodicities.

  2. Droplet motion driven by electro-elasto-capillary effects

    Science.gov (United States)

    Shah, Jaymeen; Yang, Xin; Sun, Ying

    2013-11-01

    The motion of droplets on natural and synthetic fibers underlines many technological applications including flexible displays, insulation, and smart filters. However, there is a lack of fundamental understanding of the coupled electrical, elastic, and capillary forces on droplets in fiber networks. In the present study, the motion of a water droplet suspended between two electrically insulated fibers of different Young's modulus, lengths and diameters are examined under electric fields. The results on rigid fibers reveal a critical voltage, under which the droplet remain stationary. Above this critical voltage, droplet self-propulsion is observed as a result of the interplay of electro, elasto and capillary forces on the droplet. The effects of the inter-fiber distance and Young's modulus on droplet motion are also discussed. The controllable motion of droplets can be used to manipulate or transport liquid at small scales.

  3. A novel coarsening mechanism of droplets in immiscible fluid mixtures.

    Science.gov (United States)

    Shimizu, Ryotaro; Tanaka, Hajime

    2015-06-16

    In our daily lives, after shaking a salad dressing, we see the coarsening of oil droplets suspended in vinegar. Such a demixing process is observed everywhere in nature and also of technological importance. For a case of high droplet density, domain coarsening proceeds with inter-droplet collisions and the resulting coalescence. This phenomenon has been explained primarily by the so-called Brownian-coagulation mechanism: stochastic thermal forces exerted by molecules induce random motion of individual droplets, causing accidental collisions and subsequent interface-tension-driven coalescence. Contrary to this, here we demonstrate that the droplet motion is not random, but hydrodynamically driven by the composition Marangoni force due to an interfacial tension gradient produced in each droplet as a consequence of composition correlation among droplets. This alters our physical understanding of droplet coarsening in immiscible liquid mixtures on a fundamental level.

  4. Droplet sorting in a loop of flat microfluidic channels

    Science.gov (United States)

    Kadivar, Erfan; Herminghaus, Stephan; Brinkmann, Martin

    2013-07-01

    Motivated by recent experiments, we numerically study the droplet traffic in microfluidic channels forming an asymmetric loop with a long and a short arm. The loop is connected to an inlet and an outlet channel by two right angled T-junctions. Assuming flat channels, we employ the boundary element method (BEM) to numerically solve the two-dimensional Darcy equation that governs two phase flow in the Hele-Shaw limit. The occurrence of different sorting regimes is summarized in sorting diagrams in terms of droplet size, distance between consecutive droplets in the inlet channel, and loop asymmetry for mobility ratios of the liquid phases larger and smaller than one. For large droplet distances, the traffic is regulated by the ratio of the total hydraulic resistances of the long and short arms. At high droplet densities and below a critical droplet size, droplet-droplet collisions are observed for both mobility ratios.

  5. Numerical Modeling of Thermocapillary Deformation and Film Breakdown in a Locally Heated Thin Horizontal Volatile Liquid Layer

    Directory of Open Access Journals (Sweden)

    Barakhovskaya Ella

    2016-01-01

    Full Text Available The problem of thermocapillary deformation and film breakdown in a thin horizontal layer of viscous incompressible liquid with a free surface is considered. The deformable liquid layer is locally heated. The problem of thermocapillary deformation of the locally heated horizontal liquid layer has been solved numerically for two-dimensional unsteady case. The lubrication approximation theory is used. Capillary pressure, viscosity and gravity are taken into account. Evaporating rate is supposed to be proportional to the temperature difference between the liquid and ambient. Heat transfer in the substrate is also simulated. The numerical algorithm for the joint solution of the energy equation and the evolution equation for the thickness of liquid layer has been developed. The model predicts the thermocapillary deformation of the liquid surface and the formation of dry spots. The dynamics of liquid surface, the dry spots formation and the velocity of the contact line have been calculated. The deformation of the free surface has been calculated for different values of the heating power and thickness of the liquid layer. The effect of surface tension coefficient and wetting contact angle on the velocity of the contact line motion has been analyzed. It has been obtained that the velocity of the contact line increases with the increase of the wetting contact angle value and of the surface tension coefficient.

  6. A study of the effect of binary oxide materials in a single droplet vapor explosion

    Energy Technology Data Exchange (ETDEWEB)

    Hansson, R.C., E-mail: rch@kth.se [Royal Institute of Technology, Stockholm (Sweden); Dinh, T.N.; Manickam, L.T. [Royal Institute of Technology, Stockholm (Sweden)

    2013-11-15

    In an effort to explore fundamental mechanisms that may govern the effect of melt material on vapor explosion's triggering, fine fragmentation and energetics, a series of experiments using a binary-oxide mixture with eutectic and non-eutectic compositions were performed. Interactions of a hot liquid (WO{sub 3}–CaO) droplet and a volatile liquid (water) were investigated in well-controlled, externally triggered, single-droplet experiments conducted in the Micro-interactions in steam explosion experiments (MISTEE) facility. The tests were visualized by means of a synchronized digital cinematography and continuous X-ray radiography system, called simultaneous high-speed acquisition of X-ray radiography and photography (SHARP). The acquired images followed by further analysis indicate milder interactions for the droplet with non-eutectic melt composition in the tests with low melt superheat, whereas no evident differences between eutectic and non-eutectic melt compositions regarding bubble dynamics, energetics and melt preconditioning was observed in the tests with higher melt superheat.

  7. Laser-induced motion in nanoparticle suspension droplets on a surface

    Science.gov (United States)

    Dietzel, Mathias; Poulikakos, Dimos

    2005-10-01

    The fluid and particle motion in a volatile colloidal nanoparticle suspension droplet ("nano-ink") spreading on a flat surface upon local heating through a laser beam is investigated numerically. The laser diameter, laser intensity, and the absorption coefficient of the nano-ink as well as the substrate thermal diffusivity were varied. The simulations are conducted with a finite-element method discretization of the extended axisymmetric Navier-Stokes equations in Lagrangian coordinates, accounting for evaporation, thermocapillarity, and Young-force-driven wetting for the fluid phase as well as for inertia-controlled particle motion for the solid phase. An additional continuous particle coagulation model with a locally monodispersed particle distribution is solved on the locations of the discrete computational particles for example cases. The localized heating leads, through the action of thermocapillarity, to a displacement of the liquid in the radial (outward) direction. A dimple in the droplet center region is formed as a consequence, which becomes flattened for larger laser beam diameters due to a significant enlargement in spreading. Substrates with high thermal diffusivity or large thermal contact resistance to the liquid can inhibit the Marangoni-induced enlargement of the droplet footprint. The coagulation model predicts for large absorption coefficients particle clustering primarily at the free surface, which prevents the formation of structures (built by the coagulated nanoparticles) with a uniform thickness.

  8. Optimized determination of trace jet fuel volatile organic compounds in human blood using in-field liquid-liquid extraction with subsequent laboratory gas chromatographic-mass spectrometric analysis and on-column large-volume injection.

    Science.gov (United States)

    Liu, S; Pleil, J D

    2001-03-05

    A practical and sensitive method to assess volatile organic compounds (VOCs) from JP-8 jet fuel in human whole blood was developed by modifying previously established liquid-liquid extraction procedures, optimizing extraction times, solvent volume, specific sample processing techniques, and a new on-column large-volume injection method for GC-MS analysis. With the optimized methods, the extraction efficiency was improved by 4.3 to 20.1 times and the detection sensitivity increased up to 660 times over the standard method. Typical detection limits in the parts-per-trillion (ppt) level range were achieved for all monitored JP-8 constituents; this is sufficient for assessing human fuels exposures at trace environmental levels as well as occupational exposure levels. The sample extractions are performed in the field and only solvent extracts need to be shipped to the laboratory. The method is implemented with standard biological laboratory equipment and a modest bench-top GC-MS system.

  9. Determination of effective droplet radius and optical depth of liquid water clouds over a tropical site in northern Thailand using passive microwave soundings, aircraft measurements and spectral irradiance data

    Science.gov (United States)

    Nimnuan, P.; Janjai, S.; Nunez, M.; Pratummasoot, N.; Buntoung, S.; Charuchittipan, D.; Chanyatham, T.; Chantraket, P.; Tantiplubthong, N.

    2017-08-01

    This paper presents an algorithm for deriving the effective droplet radius and optical depth of liquid water clouds using ground-based measurements, aircraft observations and an adiabatic model of cloud liquid water. The algorithm derives cloud effective radius and cloud optical depth over a tropical site at Omkoi (17.80°N, 98.43°E), Thailand. Monthly averages of cloud optical depth are highest in April (54.5), which is the month with the lowest average cloud effective radius (4.2 μm), both occurring before the start of the rainy season and at the end of the high contamination period. By contrast, the monsoon period extending from May to October brings higher cloud effective radius and lower cloud optical depth to the region on average. At the diurnal scale there is a gradual increase in average cloud optical depth and decrease in cloud effective radius as the day progresses.

  10. Nonaxisymmetric shapes of a magnetically levitated and spinning water droplet.

    Science.gov (United States)

    Hill, R J A; Eaves, L

    2008-12-05

    The shape of a weightless spinning liquid droplet is governed by the balance between the surface tension and centrifugal forces. The axisymmetric shape for slow rotation becomes unstable to a nonaxisymmetric distortion above a critical angular velocity, beyond which the droplet progresses through a series of 2-lobed shapes. Theory predicts the existence of a family of 3- and 4-lobed equilibrium shapes at higher angular velocity. We investigate the formation of a triangular-shaped magnetically levitated water droplet, driven to rotate by the Lorentz force on an ionic current within the droplet. We also study equatorial traveling waves which give the droplet threefold, fourfold, and fivefold symmetry.

  11. THE INFLUENCE OF DROPLET VOLUME AND CONTACT-ANGLE ON LIQUID SURFACE-TENSION MEASUREMENTS BY AXISYMMETRICAL DROP SHAPE ANALYSIS-PROFILE (ADSA-P)

    NARCIS (Netherlands)

    BUSSCHER, HJ

    1991-01-01

    The axisymmetric drop shape analysis-profile (ADSA-P) technique was evaluated with respect to the influence of contact angle and droplet volume. The system was implemented on our standard contact angle measuring apparatus employing a Vidicon video camera and a 512 x 256 pixels framegrabber. For cali

  12. Hydroxypropyl Cellulose Based Non-Volatile Gel Polymer Electrolytes for Dye-Sensitized Solar Cell Applications using 1-methyl-3-propylimidazolium iodide ionic liquid

    Science.gov (United States)

    Khanmirzaei, Mohammad Hassan; Ramesh, S.; Ramesh, K.

    2015-12-01

    Gel polymer electrolytes using imidazolium based ionic liquids have attracted much attention in dye-sensitized solar cell applications. Hydroxypropyl cellulose (HPC), sodium iodide (NaI), 1-methyl-3-propylimidazolium iodide (MPII) as ionic liquid (IL), ethylene carbonate (EC) and propylene carbonate (PC) are used for preparation of non-volatile gel polymer electrolyte (GPE) system (HPC:EC:PC:NaI:MPII) for dye-sensitized solar cell (DSSC) applications. The highest ionic conductivity of 7.37 × 10-3 S cm-1 is achieved after introducing 100% of MPII with respect to the weight of HPC. Temperature-dependent ionic conductivity of gel polymer electrolytes is studied in this work. XRD patterns of gel polymer electrolytes are studied to confirm complexation between HPC polymer, NaI and MPII. Thermal behavior of the GPEs is studied using simultaneous thermal analyzer (STA) and differential scanning calorimetry (DSC). DSSCs are fabricated using gel polymer electrolytes and J-V centeracteristics of fabricated dye sensitized solar cells were analyzed. The gel polymer electrolyte with 100 wt.% of MPII ionic liquid shows the best performance and energy conversion efficiency of 5.79%, with short-circuit current density, open-circuit voltage and fill factor of 13.73 mA cm-2, 610 mV and 69.1%, respectively.

  13. Hydroxypropyl Cellulose Based Non-Volatile Gel Polymer Electrolytes for Dye-Sensitized Solar Cell Applications using 1-methyl-3-propylimidazolium iodide ionic liquid.

    Science.gov (United States)

    Khanmirzaei, Mohammad Hassan; Ramesh, S; Ramesh, K

    2015-12-11

    Gel polymer electrolytes using imidazolium based ionic liquids have attracted much attention in dye-sensitized solar cell applications. Hydroxypropyl cellulose (HPC), sodium iodide (NaI), 1-methyl-3-propylimidazolium iodide (MPII) as ionic liquid (IL), ethylene carbonate (EC) and propylene carbonate (PC) are used for preparation of non-volatile gel polymer electrolyte (GPE) system (HPC:EC:PC:NaI:MPII) for dye-sensitized solar cell (DSSC) applications. The highest ionic conductivity of 7.37 × 10(-3) S cm(-1) is achieved after introducing 100% of MPII with respect to the weight of HPC. Temperature-dependent ionic conductivity of gel polymer electrolytes is studied in this work. XRD patterns of gel polymer electrolytes are studied to confirm complexation between HPC polymer, NaI and MPII. Thermal behavior of the GPEs is studied using simultaneous thermal analyzer (STA) and differential scanning calorimetry (DSC). DSSCs are fabricated using gel polymer electrolytes and J-V centeracteristics of fabricated dye sensitized solar cells were analyzed. The gel polymer electrolyte with 100 wt.% of MPII ionic liquid shows the best performance and energy conversion efficiency of 5.79%, with short-circuit current density, open-circuit voltage and fill factor of 13.73 mA cm(-2), 610 mV and 69.1%, respectively.

  14. Droplet actuation induced by coalescence: experimental evidences and phenomenological modeling

    CERN Document Server

    Sellier, Mathieu; Gaubert, Cécile; Verdier, Claude

    2012-01-01

    This paper considers the interaction between two droplets placed on a substrate in immediate vicinity. We show here that when the two droplets are of different fluids and especially when one of the droplet is highly volatile, a wealth of fascinating phenomena can be observed. In particular, the interaction may result in the actuation of the droplet system, i.e. its displacement over a finite length. In order to control this displacement, we consider droplets confined on a hydrophilic stripe created by plasma-treating a PDMS substrate. This controlled actuation opens up unexplored opportunities in the field of microfluidics. In order to explain the observed actuation phenomenon, we propose a simple phenomenological model based on Newton's second law and a simple balance between the driving force arising from surface energy gradients and the viscous resistive force. This simple model is able to reproduce qualitatively and quantitatively the observed droplet dynamics.

  15. Droplets climbing a rotating helical fiber

    CERN Document Server

    Texier, Baptiste Darbois

    2015-01-01

    A liquid droplet is placed on a rotating helical fiber. We find that the droplet may slide down, attach or climb up the fiber. We inspect experimentally the domain of existence of these three behaviors as a function of the geometrical characteristics of the fiber, its angle relatively to the horizontal, the wetting properties of the fluid and the rotating speed of the helix. A theoretical model is proposed in order to capture the boundaries of the experimental phase diagram.

  16. Orbiting droplets on a vibrated bath

    Science.gov (United States)

    Sampara, Naresh; Burger, Loic; Gilet, Tristan; Microfluidics, university of liege Team

    2015-11-01

    A millimeter-sized oil droplet can bounce on a vertically vibrated liquid bath for unlimited time. It may couple to the surface wave it emits; leading to horizontal self-propulsion called walking. When several walkers coexist close to one another, they either repel or attract each other, in response to the superposition of the waves they generate. Attraction leads to various bound states, including droplets that orbit around each other. We have experimentally investigated the variety of quantized orbital motions exhibited by two, three and more identical walkers, as a function of forcing acceleration. Each motion is quantified in terms of droplet and wave energy.

  17. Bitcoin Piyasalarının Etkinliği, Likiditesi ve Oynaklığı - Efficiency, Liquidity and Volatility of Bitcoin Markets

    Directory of Open Access Journals (Sweden)

    Şahnaz KOÇOĞLU

    2016-06-01

    Full Text Available Bitcoin is a virtual money and a new payment system which is not regulated by a central authority. Bitcoin became popular quickly and gained the ability of affecting the real economy. Being used extensively and seen as an investment tool, Bitcoin created its own market, users and investors. This study aims to shed light on Bitcoin market. To understand what Bitcoin is, the history of Bitcoin was summarized firstly and the Bitcoin system and how the protocol works was explained. Then Efficiency, Liquidity and Volatility of the Bitcoin Markets were analyzed. We concluded that the pricing of Bitcoin is too complicated; and the Bitcoin market is still vulnerable to many risks and speculation.

  18. Driving Droplets by Curvi-Propulsion

    CERN Document Server

    Lv, Cunjing; Chuang, Yin-Chuan; Tseng, Fan-Gang; Yin, Yajun; Grey, Francois; Zheng, Quanshui

    2012-01-01

    How to make small liquid droplets move spontaneously and directionally on solid surfaces is a challenge in lab-on-chip technologies, DNA analysis, and heat exchangers. The best-known mechanism, a wettability gradient, does not move droplets rapidly enough for most purposes and cannot move droplets smaller than a critical size defined by the contact angle hysteresis. Here we report on a mechanism using curvature gradients, which we show is particularly effective at accelerating small droplets, and works for both hydrophilic and hydrophobic surfaces. Experiments for water droplets on glass cones in the sub-millimeter range show a maximum speed of 0.28 m/s, two orders of magnitude higher than obtained by wettability gradient. From simple considerations of droplet surface area change, we show that the force exerted on a droplet on a conical surface scales as the curvature gradient. This force therefore diverges for small droplets near the tip of a cone. We illustrate this using molecular dynamics simulations, and...

  19. Study of airborne particles during the impact of droplets on a dry surface or on a liquid film; Etude de la mise en suspension de micro-gouttelettes lors de l'impact d'une goutte sur une surface seche ou sur un film liquide

    Energy Technology Data Exchange (ETDEWEB)

    Motzkus, C.; Gensdarmes, F. [Institut de Radioprotection et de Surete Nucleaire (IRSN), Service d' Etudes et de Recherches en Aerodispersion des polluants et en Confinement, 91 - Gif sur Yvette (France); Motzkus, C.; Gehin, E. [Paris-12 Univ., Centre d' Etudes et de Recherches en Thermique, Environnement et Systeme, 94 - Creteil (France)

    2007-07-01

    The safety analyses of the nuclear facilities require extensive knowledge on the airborne micro-droplet, in order to assess the potential sources of contamination in the case of hypothetical scenarios of accidental falls of liquids caused by leakage or discharge from a container. There are very few data in the literature in the case of the impaction of millimeter-size droplets on the airborne particles. The objective of our work is to study experimentally the emission of the particles during the impaction on a dry or wet plane surface, in order to understand the mechanisms leading to the airborne icles. First experiments are carried out in order to study the airborne particles produced by the free falls of droplet according to the fall height. These results are faced with a semi empirical correlation, which describes the transition between deposition and splash. In the case of a dripping of 3.84 mm-diameter droplets, our results show that the splash occurs for a fall height above 30 cm, which leads to resuspension fractions between 1,9 10{sup -6} at 46 cm and 7,5 10{sup -6} at 80 cm. (authors)

  20. Scaling Laws for Inter-droplet Ice Bridging

    Science.gov (United States)

    Nath, Saurabh; Ahmadi, Farzad; Boreyko, Jonathan

    2016-11-01

    In this work, we study the dynamics of an ice bridge growing from a frozen droplet towards its neighboring supercooled liquid droplet. Experiments were done on a Peltier stage inside a humidity chamber with deposited or condensed droplets where the substrate temperature and ambient humidity could be controlled. Following a quasi-steady diffusion-driven model, we develop scaling laws to show how the growth rate depends on the substrate temperature, droplet sizes and inter-droplet distances over and above other environmental parameters such as air temperature and humidity. The growth rate as well as the success or failure of an ice bridge to connect to its neighboring liquid droplet depend on a nondimensional number called the separation parameter S*, defined as the ratio of the initial inter-droplet spacing to the diameter of the evaporating liquid droplet. It is shown that the maximum value of S* for connection scales as 1 as long as frozen drop is larger than the liquid droplet. For the converse case of a larger water drop, there are at least three separate regimes of critical S*, depending on whether the water drop is a puddle, a spherical cap or if the frozen drop is a puddle.

  1. Vibration-induced droplet atomization

    Science.gov (United States)

    Vukasinovic, Bojan

    The atomization of liquid drops is investigated experimentally using laser vibrometry, high-speed imaging, and particle tracking techniques. The spray is generated by a novel vibration-induced droplet atomization (VIDA) process in which a sessile drop is atomized by an underlying vibrating thin metal diaphragm, resulting in rapid ejection of small secondary droplets from the free surface of the primary drop. Under some conditions, the primary drop can be atomized extremely rapidly by a bursting-like mechanism (e.g., a 0.1 ml water drop can be atomized in 0.4 seconds). The present research has focused on four major areas: global characteristics of VIDA process, instability modes and free surface dynamics of the forced drop, mechanisms of the interface breakup, and parametric characterization of the ensuing spray. Prior to atomization, the drop free surface undergoes three transitions: from axisymmetric standing waves to azimuthal waves, to a newly-observed lattice mode, and to a disordered pre-ejection state. The droplet ejection results from localized collapse of surface troughs and initiation and ultimate breakup of momentary liquid spikes. Breakup begins with capillary pinch-off from spike tips and can be followed by additional pinching of liquid droplets. For a relatively low-viscosity liquid, e.g., water, a capillary-wave instability of the spike is observed in some cases, while for a very viscous liquid, e.g., a glycerin/water solution, the first breakup occurs near the stem of the spike, with or without subsequent breakup of the detached, elongated thread. Different mechanisms dominating the primary breakup of the spike are operative in the low- and high-viscosity ejection regimes. When ejection of the secondary droplets is triggered, the evolution and rate of atomization depend on the coupled dynamics of the primary drop and the vibrating diaphragm. Due to these dynamics, the process can be either self-intensifying or self-decaying. The resulting VIDA spray

  2. 液滴在梯度微结构表面上的铺展动力学分析∗%Spreading dynamics of liquid droplet on gradient micro-structured surfaces

    Institute of Scientific and Technical Information of China (English)

    林林; 袁儒强; 张欣欣; 王晓东

    2015-01-01

    Designed microtextured surfaces have shown promising applications in tuning the wettability of a liquid droplet on the surfaces and attracted great attention over the past decade;unfortunately, the effect of surface geometry on wetting properties is still poorly understood. In this work, two- and multi-stage pillar microtextures are designed to construct gradient surfaces by altering pillar width and spacing. Then, the multi-phase lattice-Boltzmann method (LBM) is used to investigate the wetting dynamics of a liquid droplet on the gradient surface. Results show that for the two-stage gradient surface with variable pillar spacing, the contact angle hysteresis is found to be proportional to the roughness gradient when droplet/surface system is in the Cassie-Baxter state. However, this proportional relation is no longer correct when the system is in the transition state between the Wenzel and Cassie-Baxter states. For the two-stage gradient surface with variable pillar spacing, the contact angle hysteresis always increases linearly with increasing roughness gradient. Results also show that when a larger droplet is placed on the multi-stage gradient surface, stronger droplet motion is observed due to the smaller contact angle hysteresis. The present LBM simulations provide a guideline for the design and manufacture of the microtextured surfaces to tune the droplet wettability and motion.%本文通过改变肋柱宽度和间距,构造了二级和多级梯度微结构表面,采用格子-Boltzmann方法对液滴在两种梯度表面上的铺展过程进行了研究,探析液滴运动的机理和调控方法。结果表明,在改变肋柱间距的二级梯度表面上,当液滴处于Cassie态时,接触角滞后大小与粗糙度梯度成正比关系;当液滴从Cassie态转换为Wenzel态或介于两者之间的不稳定态时,这一正比关系不再遵循。在改变肋柱宽度的二级梯度表面上,接触角滞后大小与粗糙度梯度始终成

  3. Hydrolysis-acidogenesis of food waste in solid-liquid-separating continuous stirred tank reactor (SLS-CSTR) for volatile organic acid production.

    Science.gov (United States)

    Karthikeyan, Obulisamy Parthiba; Selvam, Ammaiyappan; Wong, Jonathan W C

    2016-01-01

    The use of conventional continuous stirred tank reactor (CSTR) can affect the methane (CH4) recovery in a two-stage anaerobic digestion of food waste (FW) due to carbon short circuiting in the hydrolysis-acidogenesis (Hy-Aci) stage. In this research, we have designed and tested a solid-liquid-separating CSTR (SLS-CSTR) for effective Hy-Aci of FW. The working conditions were pH 6 and 9 (SLS-CSTR-1 and -2, respectively); temperature-37°C; agitation-300rpm; and organic loading rate (OLR)-2gVSL(-1)day(-1). The volatile fatty acids (VFA), enzyme activities and bacterial population (by qPCR) were determined as test parameters. Results showed that the Hy-Aci of FW at pH 9 produced ∼35% excess VFA as compared to that at pH 6, with acetic and butyric acids as major precursors, which correlated with the high enzyme activities and low lactic acid bacteria. The design provided efficient solid-liquid separation there by improved the organic acid yields from FW.

  4. Relaxation of contact-line singularities solely by the Kelvin effect and apparent contact angles for isothermal volatile liquids in contact with air

    Science.gov (United States)

    Rednikov, Alexey; Colinet, Pierre

    2013-11-01

    The contact (triple) line of a volatile liquid on a flat solid is studied theoretically. Like with a pure-vapor atmosphere [Phys. Rev. E 87, 010401, 2013], but here for isothermal diffusion-limited evaporation/condensation in the presence of an inert gas, we rigorously show that the notorious contact-line singularities (related to motion or phase change itself) can be regularized solely on account of the Kelvin effect (curvature dependence of the saturation conditions). No disjoining pressure, precursor films or Navier slip are in fact needed to this purpose, and nor are they taken into consideration here (``minimalist'' approach). The model applies to both perfect (zero Young's angle) and partial wetting, and is in particular used to study the related issue of evaporation-induced contact angles. Their modification by the contact-line motion (either advancing or receding) is assessed. The formulation is posed for a distinguished immediate vicinity of the contact line (the ``microregion''), the corresponding problem decoupling to leading order, here up to one unknown coefficient, from what actually happens at the macroscale. The lubrication approximation (implying sufficiently small contact angles) is used in the liquid, coupled with the diffusion equation in the gaz phase. Supported by ESA and BELSPO PRODEX and F.R.S.-FNRS.

  5. Non-equilibrium solidification of undercooled droplets during atomization process

    Indian Academy of Sciences (India)

    Prashant Shukla; R K Mandal; S N Ojha

    2001-10-01

    Thermal history of droplets associated with gas atomization of melt has been investigated. A mathematical model, based on classical theory of heterogeneous nucleation and volume separation of nucleants among droplets size distribution, is described to predict undercooling of droplets. Newtonian heat flow condition coupled with velocity dependent heat transfer coefficient is used to obtain cooling rate before and after nucleation of droplets. The results indicate that temperature profile of droplets in the spray during recalescence, segregated and eutectic solidification regimes is dependent on their size and related undercooling. The interface temperature during solidification of undercooled droplets rapidly approaches the liquidus temperature of the alloy with a subsequent decrease in solid–liquid interface velocity. A comparison in cooling rates of atomized powder particles estimated from secondary dendrite arm spacing measurements are observed to be closer to those predicted from the model during segregated solidification regime of large size droplets.

  6. Electromagnetic emission of a strongly charged oscillating droplet

    Science.gov (United States)

    Grigor'ev, A. I.; Kolbneva, N. Yu.; Shiryaeva, S. O.

    2016-08-01

    Analytical expressions for electric field in the vicinity of an oscillating strongly charged droplet of nonviscous conducting liquid and intensity of electromagnetic radiation are derived in the linear approximation with respect to perturbation amplitude of the droplet surface. Order-of-magnitude estimations of the radiation intensity are presented. The intensity of electromagnetic radiation of a ball lightning that can be simulated using a charged droplet is not related to the surface oscillations.

  7. Volatility Discovery

    DEFF Research Database (Denmark)

    Dias, Gustavo Fruet; Scherrer, Cristina; Papailias, Fotis

    The price discovery literature investigates how homogenous securities traded on different markets incorporate information into prices. We take this literature one step further and investigate how these markets contribute to stochastic volatility (volatility discovery). We formally show...... that the realized measures from homogenous securities share a fractional stochastic trend, which is a combination of the price and volatility discovery measures. Furthermore, we show that volatility discovery is associated with the way that market participants process information arrival (market sensitivity...

  8. Volatile Metabolites

    Directory of Open Access Journals (Sweden)

    Daryl D. Rowan

    2011-11-01

    Full Text Available Volatile organic compounds (volatiles comprise a chemically diverse class of low molecular weight organic compounds having an appreciable vapor pressure under ambient conditions. Volatiles produced by plants attract pollinators and seed dispersers, and provide defense against pests and pathogens. For insects, volatiles may act as pheromones directing social behavior or as cues for finding hosts or prey. For humans, volatiles are important as flavorants and as possible disease biomarkers. The marine environment is also a major source of halogenated and sulfur-containing volatiles which participate in the global cycling of these elements. While volatile analysis commonly measures a rather restricted set of analytes, the diverse and extreme physical properties of volatiles provide unique analytical challenges. Volatiles constitute only a small proportion of the total number of metabolites produced by living organisms, however, because of their roles as signaling molecules (semiochemicals both within and between organisms, accurately measuring and determining the roles of these compounds is crucial to an integrated understanding of living systems. This review summarizes recent developments in volatile research from a metabolomics perspective with a focus on the role of recent technical innovation in developing new areas of volatile research and expanding the range of ecological interactions which may be mediated by volatile organic metabolites.

  9. Response of two-phase droplets to intense electromagnetic radiation

    Energy Technology Data Exchange (ETDEWEB)

    Spann, J.F. (Morgantown Energy Technology Center, U.S. Department of Energy, P.O. Box 880, Morgantown, West Virginia 26507-0880 (United States)); Maloney, D.J.; Lawson, W.F.; Casleton, K.H. (Morgantown Energy Technology Center, U.S. Department of Energy, P.O. Box 880, Morgantown, West Virginia 26507-0880 (United States))

    1993-04-20

    The response of two-phase droplets to intense radiant heating is studied to determine the incident power that is required for causing explosive boiling in the liquid phase. The droplets studied consist of strongly absorbing coal particles dispersed in a weakly absorbing water medium. Experiments are performed by confining droplets (radii = 37, 55, and 80 [mu]m) electrodynamically and irradiating them from two sides with pulsed laser beams. Emphasis is placed on the transition region from accelerated droplet vaporization to droplet superheating and explosive boiling. The time scale observed for explosive boiling is more than 2 orders of magnitude longer than published values for pure liquids. The delayed response is the result of energy transfer limitations between the absorbing solid phase and the surrounding liquid.

  10. Francois Frenkiel Award Lecture: Thermocapillary migration of interfacial droplets

    Science.gov (United States)

    Greco, Edwin F.

    2010-11-01

    Thermocapillary migration of bubbles through the bulk liquid--a process in which tangential surface stresses arising from the variation of surface tension with temperature create a propulsive force on the bubble--has been extensively studied in the past. In contrast, the motion of droplets confined to the free surface of a liquid substrate has received much less attention. Recent developments in microfluidics provided new motivation to understand how applied thermal gradients can affect the motion of, and mixing inside, small aqueous droplets. In particular, the quality and speed of mixing depend rather sensitively on the flow structure inside the droplet. In this talk we describe different approaches that allow one to compute both the flow inside interfacial droplets and the flow in the layer of liquid substrate supporting the droplet and the lessons which can be learned by analyzing these flows.

  11. Response of two-phase droplets to intense electromagnetic radiation

    Science.gov (United States)

    Spann, James F.; Maloney, Daniel J.; Lawson, William F.; Casleton, Kent H.

    1993-01-01

    The response of two-phase droplets to intense radiant heating is studied to determine the incident power that is required for causing explosive boiling in the liquid phase. The droplets studied consist of strongly absorbing coal particles dispersed in a weakly absorbing water medium. Experiments are performed by confining droplets (radii of 37, 55, and 80 microns) electrodynamically and irradiating them from two sides with pulsed laser beams. Emphasis is placed on the transition region from accelerated droplet vaporization to droplet superheating and explosive boiling. The time scale observed for explosive boiling is more than 2 orders of magnitude longer than published values for pure liquids. The delayed response is the result of energy transfer limitations between the absorbing solid phase and the surrounding liquid.

  12. An Experimental Study on the Dynamics of a Single Droplet Vapor Explosion

    Energy Technology Data Exchange (ETDEWEB)

    Concilio Hansson, Roberta

    2010-07-01

    The present study aims to develop a mechanistic understanding of the thermal-hydraulic processes in a vapor explosion, which may occur in nuclear power plants during a hypothetical severe accident involving interactions of high-temperature corium melt and volatile coolant. Over the past several decades, a large body of literature has been accumulated on vapor explosion phenomenology and methods for assessment of the related risk. Vapor explosion is driven by a rapid fragmentation of high temperature melt droplets, leading to a substantial increase of heat transfer areas and subsequent explosive evaporation of the volatile coolant. Constrained by the liquid-phase coolant, the rapid vapor production in the interaction zone causes pressurization and dynamic loading on surrounding structures. While such a general understanding has been established, the triggering mechanism and subsequent dynamic fine fragmentation have yet not been clearly understood. A few mechanistic fragmentation models have been proposed, however, computational efforts to simulate the phenomena generated a large scatter of results. Dynamics of the hot liquid (melt) droplet and the volatile liquid (coolant) are investigated in the MISTEE (Micro-Interactions in Steam Explosion Experiments) facility by performing well-controlled, externally triggered, single-droplet experiments, using a high-speed visualization system with synchronized digital cinematography and continuous X-ray radiography, called SHARP (Simultaneous High-speed Acquisition of X-ray Radiography and Photography). After an elaborate image processing, the SHARP images depict the evolution of both melt material (dispersal) and coolant (bubble dynamics), and their microscale interactions, i.e. the triggering phenomenology. The images point to coolant entrainment into the droplet surface as the mechanism for direct contact/mixing ultimately responsible for energetic interactions. Most importantly, the MISTEE data reveals an inverse

  13. Lattice Boltzmann Simulations of Evaporating Droplets with Nanoparticles

    Science.gov (United States)

    Zhao, Mingfei; Yong, Xin

    2016-11-01

    Elucidating the nanoparticle dynamics in drying droplets provides fundamental hydrodynamic insight into the evaporation-induced self-assembly, which is of great importance to materials printing and thin film processing. We develop a free-energy-based multiphase lattice Boltzmann model coupled with Lagrangian particle tracking to simulate evaporating particle-laden droplets on a solid substrate with specified wetting behavior. This work focuses on the interplay between the evaporation-driven advection and the self-organization of nanoparticles inside the droplet and at the droplet surface. For static droplets, the different parameters, fluid-particle interaction strength and particle number, governing the nanoparticle-droplet dynamics are systematically investigated, such as particle radial and circumferential distribution. We clarify the effect of nanoparticle presence on the droplet surface tension and wetting behavior. For evaporating droplets, we observe how droplet evaporation modulates the self-assembly of nanoparticles when the droplet has different static contact angles and hysteresis windows. We also confirm that the number of nanoparticles at the liquid-vapor interface influences the evaporation flux at the liquid-vapor interface.

  14. Electrowetting Actuation of Polydisperse Nanofluid Droplets

    Directory of Open Access Journals (Sweden)

    Crismar Patacsil

    2017-01-01

    Full Text Available We present results of electrowetting experiments employing droplets formed from aqueous suspensions of Au nanoparticles. A planar electrowetting system, consisting of a Pt wire electrode and a bottom Cu electrode with an insulating silicone layer, is used to observe changes in droplet contact angle when an external electric field is applied. The equilibrium contact angle at 0 V decreases with increasing nanoparticle concentration, dropping from 100.4° for pure deionized water to 94.7° for a 0.5 μM nanofluid. Increasing the nanoparticle content also lowers the required voltage for effective actuation. With actuation at 15 V, contact angle decreases by 9% and 35% for droplets formed from pure water and a 0.5 μM nanoparticle suspension, respectively. Contact angle saturation is observed with nanofluid droplets, with the threshold voltage decreasing as nanoparticle concentration rises. Maximum droplet actuation before contact angle saturation is achieved at only 10 V for a concentration of 0.5 μM. A proposed mechanism for the enhanced electrowetting response of a nanofluid droplet involves a reduction in surface tension of the droplet as nanoparticles accumulate at the liquid-vapor interface.

  15. Three dimensional force balance of asymmetric droplets

    Science.gov (United States)

    Kim, Yeseul; Lim, Su Jin; Cho, Kun; Weon, Byung Mook

    2016-11-01

    An equilibrium contact angle of a droplet is determined by a horizontal force balance among vapor, liquid, and solid, which is known as Young's law. Conventional wetting law is valid only for axis-symmetric droplets, whereas real droplets are often asymmetric. Here we show that three-dimensional geometry must be considered for a force balance for asymmetric droplets. By visualizing asymmetric droplets placed on a free-standing membrane in air with X-ray microscopy, we are able to identify that force balances in one side and in other side control pinning behaviors during evaporation of droplets. We find that X-ray microscopy is powerful for realizing the three-dimensional force balance, which would be essential in interpretation and manipulation of wetting, spreading, and drying dynamics for asymmetric droplets. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2016R1D1A1B01007133).

  16. Vortices catapult droplets in atomization

    CERN Document Server

    Jerome, J John Soundar; Matas, Jean-Philippe; Zaleski, Stéphane; Hoepffner, Jérôme

    2016-01-01

    A droplet ejection mechanism in planar two-phase mixing layers is examined. Any disturbance on the gas-liquid interface grows into a Kelvin-Helmholtz wave, and the wave crest forms a thin liquid film that flaps as the wave grows downstream. Increasing the gas speed, it is observed that the film breaks up into droplets which are eventually thrown into the gas stream at large angles. In a flow where most of the momentum is in the horizontal direction, it is surprising to observe these large ejection angles. Our experiments and simulations show that a recirculation region grows downstream of the wave and leads to vortex shedding similar to the wake of a backward-facing step. The ejection mechanism results from the interaction between the liquid film and the vortex shedding sequence: a recirculation zone appears in the wake of the wave and a liquid film emerges from the wave crest; the recirculation region detaches into a vortex and the gas flow over the wave momentarily reattaches due to the departure of the vor...

  17. Capillary droplets on Leidenfrost micro-ratchets

    CERN Document Server

    Marin, Alvaro G; Römer, Gertwillem R B E; Pathiraj, B; Veld, Albertus Huis in 't; Lohse, Detlef

    2012-01-01

    Leidenfrost ratchets are structures with the ability of transporting liquid droplets when heated over the critical Leidenfrost temperature. Once this temperature is reached, the droplet levitates over the surface and moves in the direction marked by the slope of the ratchet at terminal velocities around 10 cm/s. Here we provide new experiments with micron-sized ratchets, which have been produced with picosecond pulse laser ablation. In the following work, we use a simple method to measure the thrust driving droplets of capillary size over the micro-ratchets. The mechanism responsible for the force acting on the drop on superheated ratchets has been recently under debate. We extend the recently proposed 'viscous mechanism' proposed by Dupeaux et al. [Europhys. Lett., 96, 58001 (2011)] to capillary droplets and find good agreement with our measurements.

  18. Profiling of adrenocorticotropic hormone and arginine vasopressin in human pituitary gland and tumor thin tissue sections using droplet-based liquid-microjunction surface-sampling-HPLC-ESI-MS-MS.

    Science.gov (United States)

    Kertesz, Vilmos; Calligaris, David; Feldman, Daniel R; Changelian, Armen; Laws, Edward R; Santagata, Sandro; Agar, Nathalie Y R; Van Berkel, Gary J

    2015-08-01

    Described here are the results from the profiling of the proteins arginine vasopressin (AVP) and adrenocorticotropic hormone (ACTH) from normal human pituitary gland and pituitary adenoma tissue sections, using a fully automated droplet-based liquid-microjunction surface-sampling-HPLC-ESI-MS-MS system for spatially resolved sampling, HPLC separation, and mass spectrometric detection. Excellent correlation was found between the protein distribution data obtained with this method and data obtained with matrix-assisted laser desorption/ionization (MALDI) chemical imaging analyses of serial sections of the same tissue. The protein distributions correlated with the visible anatomic pattern of the pituitary gland. AVP was most abundant in the posterior pituitary gland region (neurohypophysis), and ATCH was dominant in the anterior pituitary gland region (adenohypophysis). The relative amounts of AVP and ACTH sampled from a series of ACTH-secreting and non-secreting pituitary adenomas correlated with histopathological evaluation. ACTH was readily detected at significantly higher levels in regions of ACTH-secreting adenomas and in normal anterior adenohypophysis compared with non-secreting adenoma and neurohypophysis. AVP was mostly detected in normal neurohypophysis, as expected. This work reveals that a fully automated droplet-based liquid-microjunction surface-sampling system coupled to HPLC-ESI-MS-MS can be readily used for spatially resolved sampling, separation, detection, and semi-quantitation of physiologically-relevant peptide and protein hormones, including AVP and ACTH, directly from human tissue. In addition, the relative simplicity, rapidity, and specificity of this method support the potential of this basic technology, with further advancement, for assisting surgical decision-making. Graphical Abstract Mass spectrometry based profiling of hormones in human pituitary gland and tumor thin tissue sections.

  19. Droplet impact on superheated micro-structured surfaces

    NARCIS (Netherlands)

    Tran, A.T.; Staat, H.J.J.; Susarrey-Arce, A.; Foertsch, T.C.; Houselt, van A.; Gardeniers, J.G.E.; Prosperetti, A.; Lohse, D.; Sun, C.

    2013-01-01

    When a droplet impacts upon a surface heated above the liquid's boiling point, the droplet either comes into contact with the surface and boils immediately (contact boiling), or is supported by a developing vapor layer and bounces back (film boiling, or Leidenfrost state). We study the transition be

  20. Simple technique for scattering experiments of submillimeter droplets

    OpenAIRE

    1995-01-01

    A simple technique is presented of allowing the generation of submillimeter-sized single droplets for scattering experiments. Multiorder Raman spectra (including Stokes, anti-Stokes, and combination emission) from a liquid CCl4 spherical droplet formed by a hollow glass fiber is also obtained by this technique, with a frequency-doubled Nd:YAG pulsed pumping (532 nm).

  1. Vibration-Induced Droplet Atomization --- An Experimental Investigation.

    Science.gov (United States)

    Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari

    1997-11-01

    The atomization of a liquid droplet placed on a vibrating membrane starts with the development of Faraday free surface waves. As the excitation amplitude increases, the waves grow in amplitude and ultimately begin to eject smaller secondary droplets from the wave crests. The rate of droplet ejection can be large enough to completely drain the primary droplet, an event we call bursting. The evolution of the droplet ejection process depends on a coupled system dynamic between the droplet and the membrane. When droplets are ejected the resonant frequency of the system increases. This changes the acceleration felt by the droplet and, in turn, the rate of droplet ejection. Depending on the excitation frequency and amplitude, various types of bursting or droplet ejection processes may occur. In the present experiments, the high acceleration needed to attain ejection (typically 300g) is achieved by driving a light-weight membrane near its resonant frequency (nominally 1000 Hz). The resonant characteristics and the acceleration during the ejection process for various droplet sizes and excitation amplitudes are investigated using a surface-mounted microfabricated accelerometer and a laboratory computer system.

  2. Pore-scale visualization of the mobilization of a partially wetting droplet

    Science.gov (United States)

    Hsu, Shao-Yiu; Hilpert, Markus

    2016-09-01

    We experimentally investigated the mobilization process of a partially wetting droplet in a pore doublet model. The process, involving contact line movement, liquid film generation, and interface deformation, has not been fully understood and modeled. In equilibrium, the droplet sat in one of the capillary tubes of the pore doublet, and the contact lines of the droplet were pinned with nonzero contact angles. The droplet was subject to pressure differences that were generated by pumping the continuous liquid into the pore doublet at different flow rates. At low flow rates, the droplet moved with sliding contact lines, and the shapes of the droplet's menisci roughly resembled spherical caps. When the flow rate increased, the velocity of the droplet increased, and the shapes of the liquid-liquid interfaces changed dramatically forming finger-like structures and films. Once films form, the classical Young-Laplace equation, which assumes a spherical interface, is not sufficient to describe droplet mobilization and the corresponding pressure drops. The films ruptured as the droplet moved forward, and a certain amount of droplet liquid was left behind. When the flow rates reached a certain level, the droplet snapped off from the tube wall and rolled while being surrounded by thin films formed by the continuous liquid.

  3. Enhanced resolution of Mentha piperita volatile fraction using a novel medium-polarity ionic liquid gas chromatography stationary phase.

    Science.gov (United States)

    Ragonese, Carla; Sciarrone, Danilo; Grasso, Elisa; Dugo, Paola; Mondello, Luigi

    2016-02-01

    The evaluation of a novel medium-polarity ionic-liquid-based gas chromatography column, SLB-IL60, towards the analysis of a complex essential oil, namely, a peppermint essential oil sample, is reported. The SLB-IL60 30 m column was subjected to bleeding measurements, by means of conventional gas chromatography with mass spectrometry. The SLB-IL60 column was then evaluated in the analysis of pure standard compounds, chosen as typical constituents of peppermint essential oil. Resolution and peak symmetry (expressed as tailing factors at 10% of peak height) were measured and the results were compared to those obtained on the most widely used columns in such an application, namely a medium-polarity [100% poly(ethyleneglycol)] stationary phase, and an apolar 5% diphenyl/95% dimethyl siloxane. The final part of the evaluation was dedicated to the gas chromatography with mass spectrometry analysis of a peppermint essential oil sample and again the data were compared to those obtained on the 100% poly(ethyleneglycol) and the 5% diphenyl/95% dimethyl siloxane phase. Linear retention indices were determined for all the identified components on the ionic liquid capillary. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Capillary effects during droplet impact on a solid surface

    Science.gov (United States)

    Pasandideh-Fard, M.; Qiao, Y. M.; Chandra, S.; Mostaghimi, J.

    1996-03-01

    Impact of water droplets on a flat, solid surface was studied using both experiments and numerical simulation. Liquid-solid contact angle was varied in experiments by adding traces of a surfactant to water. Impacting droplets were photographed and liquid-solid contact diameters and contact angles were measured from photographs. A numerical solution of the Navier-Stokes equation using a modified SOLA-VOF method was used to model droplet deformation. Measured values of dynamic contact angles were used as a boundary condition for the numerical model. Impacting droplets spread on the surface until liquid surface tension and viscosity overcame inertial forces, after which they recoiled off the surface. Adding a surfactant did not affect droplet shape during the initial stages of impact, but did increase maximum spread diameter and reduce recoil height. Comparison of computer generated images of impacting droplets with photographs showed that the numerical model modeled droplet shape evolution correctly. Accurate predictions were obtained for droplet contact diameter during spreading and at equilibrium. The model overpredicted droplet contact diameters during recoil. Assuming that dynamic surface tension of surfactant solutions is constant, equaling that of pure water, gave predicted droplet shapes that best agreed with experimental observations. When the contact angle was assumed constant in the model, equal to the measured equilibrium value, predictions were less accurate. A simple analytical model was developed to predict maximum droplet diameter after impact. Model predictions agreed well with experimental measurements reported in the literature. Capillary effects were shown to be negligible during droplet impact when We≫Re1/2.

  5. Photoacoustic spectral characterization of perfluorocarbon droplets

    Science.gov (United States)

    Strohm, Eric; Gorelikov, Ivan; Matsuura, Naomi; Kolios, Michael

    2012-02-01

    Perfluorocarbon droplets containing optical absorbing nanoparticles have been developed for use as theranostic agents (for both imaging and therapy) and as dual-mode contrast agents. Droplets can be used as photoacoustic contrast agents, vaporized via optical irradiation, then the resulting bubbles can be used as ultrasound imaging and therapeutic agents. The photoacoustic signals from micron-sized droplets containing silica coated gold nanospheres were measured using ultra-high frequencies (100-1000 MHz). The spectra of droplets embedded in a gelatin phantom were compared to a theoretical model which calculates the pressure wave from a spherical homogenous liquid undergoing thermoelastic expansion resulting from laser absorption. The location of the spectral features of the theoretical model and experimental spectra were in agreement after accounting for increases in the droplet sound speed with frequency. The agreement between experiment and model indicate that droplets (which have negligible optical absorption in the visible and infrared spectra by themselves) emitted pressure waves related to the droplet composition and size, and was independent of the physical characteristics of the optical absorbing nanoparticles. The diameter of individual droplets was calculated using three independent methods: the time domain photoacoustic signal, the time domain pulse echo ultrasound signal, and a fit to the photoacoustic model, then compared to the diameter as measured by optical microscopy. It was found the photoacoustic and ultrasound methods calculated diameters an average of 2.6% of each other, and 8.8% lower than that measured using optical microscopy. The discrepancy between the calculated diameters and the optical measurements may be due to the difficulty in resolving the droplet edges after being embedded in the translucent gelatin medium.

  6. Stabilization and enhanced reactivity of actinorhodin polyketide synthase minimal complex in polymer-nucleotide coacervate droplets.

    Science.gov (United States)

    Crosby, John; Treadwell, Tom; Hammerton, Michelle; Vasilakis, Konstantinos; Crump, Matthew P; Williams, David S; Mann, Stephen

    2012-12-18

    Compartmentalization of the minimal complex of actinorhodin polyketide synthase in coacervate liquid droplets produces enhanced yields of shunt polyketides under conditions of low and high ionic strength.

  7. Reversible Shape Transformation of Ultrathin Polydopamine-Stabilized Droplet.

    Science.gov (United States)

    Abe, Hiroya; Matsue, Tomokazu; Yabu, Hiroshi

    2017-06-27

    Here we report on the flattening of water droplets using an ultrathin membrane of autopolymerized polydopamine at the air/water interface. This has only been previously reported with the use of synthetic or extracted peptides, two-dimensional designed synthetic peptide thin films with thicknesses of several tens of nanometers. However, in the previous study, the shape of the water droplet was changed irreversibly and the phenomenon was observed only at the air/water interface. In the present study, an ultrathin polydopamine membrane-stabilized droplet induced the flattening of a water droplet at the air/liquid and liquid/liquid interfaces because a polydopamine membrane was spontaneously formed at these interfaces. Furthermore, a reversible transformation of the droplet to flat and dome shape droplets were discovered at the liquid/liquid interface. These are a completely new system because the polydopamine membrane is dynamically synthesized at the interface and the formation speed of the polydopamine membrane overcomes the flattening time scale. These results will provide new insight into physical control of the interfacial shapes of droplets.

  8. Liquid Crystalline Compositions as Gas Sensors

    Science.gov (United States)

    Shibaev, Petr; Murray, John; Tantillo, Anthony; Wenzlick, Madison; Howard-Jennings, Jordan

    2015-03-01

    Droplets and films of nematic and cholesteric liquid crystalline mixtures were studied as promising detectors of volatile organic compounds (VOCs) in the air. Under increasing concentration of VOC in the air the detection may rely on each of the following effects sequentially observed one after the other due to the diffusion of VOC inside liquid crystalline matrix: i. slight changes in orientation and order parameter of liquid crystal, ii. formation of bubbles on the top of the liquid crystalline droplet due to the mass transfer between the areas with different order parameter, iii. complete isotropisation of the liquid crystal. All three stages can be easily monitored by optical microscopy and photo camera. Detection limits corresponding to the first stage are typically lower by a factor of 3-6 than detection limits corresponding to the beginning of mass transfer and isotropisation. The prototype of a compact sensor sensitive to the presence of organic solvents in the air is described in detail. The detection limits of the sensor is significantly lower than VOC exposure standards. The qualitative model is presented to account for the observed changes related to the diffusion, changes of order parameter and isotropisation.

  9. Differences in liquid cloud droplet effective radius and number concentration estimates between MODIS collections 5.1 and 6 over global oceans

    Directory of Open Access Journals (Sweden)

    J. Rausch

    2017-06-01

    Full Text Available Differences in cloud droplet effective radius and cloud droplet number concentration (CDNC estimates inferred from the Aqua–MODIS (Moderate Resolution Imaging Spectroradiometer collections 5.1 (C5.1 and 6 (C6 cloud products (MYD06 are examined for warm clouds over global oceans for the year 2008. Individual pixel level retrievals for both collections are aggregated to 1°  ×  1° and compared globally and regionally for the three main spectral channel pairs used for MODIS cloud optical property retrievals. Comparisons between both collections are performed for cases in which all three effective radii retrievals are classified by the MODIS cloud product as valid. The contribution to the observed differences of several key MYD06 Collection 6 algorithm updates are also explored, with a focus on changes to the surface reflectance model, assumed solar irradiance, above-cloud emission, cloud-top pressure (CTP, and pixel registration. Global results show a neutral to positive (> 50 cm−3 change for C6-derived CDNC relative to C5.1 for the 1.6 and 2.1 µm channel retrievals, corresponding to a neutral to −2 µm difference in droplet effective radius (re. For 3.7 µm retrievals, CDNC results show a negative change in the tropics, with differences transitioning toward positive values with increasing latitude spanning −25 to +50 cm−3 related to a +2.5 to −1 µm transition in effective radius. Cloud optical thickness (τ differences were small relative to effective radius and found to not significantly impact CDNC estimates. Regionally, the magnitude and behavior of the annual CDNC cycle are compared for each effective radius retrieval. Results from this study indicate significant inter-collection differences in aggregated values of effective radius due to changes to the precomputed retrieval lookup tables (LUTs for ocean scenes, changes to retrieved cloud-top pressure, solar irradiance, or above-cloud thermal emission

  10. Numerical simulation of droplet evaporation between two circular plates

    Energy Technology Data Exchange (ETDEWEB)

    Bam, Hang Jin; Son, Gi Hun [Sogang University, Seoul (Korea, Republic of)

    2015-06-15

    Numerical simulation is performed for droplet evaporation between two circular plates. The flow and thermal characteristics of the droplet evaporation are numerically investigated by solving the conservation equations of mass, momentum, energy and mass fraction in the liquid and gas phases. The liquid-gas interface is tracked by a sharp-interface level-set method which is modified to include the effects of evaporation at the liquid-gas interface and contact angle hysteresis at the liquid-gas-solid contact line. An analytical model to predict the droplet evaporation is also developed by simplifying the mass and vapor fraction equations in the gas phase. The numerical results demonstrate that the 1-D analytical prediction is not applicable to the high rate evaporation process. The effects of plate gap and receding contact angle on the droplet evaporation are also quantified.

  11. Liquid Crystal Research Shows Deformation By Drying

    Science.gov (United States)

    2003-01-01

    These images, from David Weitz's liquid crystal research, show ordered uniform sized droplets (upper left) before they are dried from their solution. After the droplets are dried (upper right), they are viewed with crossed polarizers that show the deformation caused by drying, a process that orients the bipolar structure of the liquid crystal within the droplets. When an electric field is applied to the dried droplets (lower left), and then increased (lower right), the liquid crystal within the droplets switches its alignment, thereby reducing the amount of light that can be scattered by the droplets when a beam is shone through them.

  12. Türkiye Hisse Senedi Piyasasında Likidite Ölçülerinin Karşılaştırılması ve Likidite Volatilitesi Hisse Senedi Getirisi Arasındaki İlişki (Comparison of Liquidity Measures and The Relationship Between Volatility of Liquidity and Stock Returns in Turkish Stock Market

    Directory of Open Access Journals (Sweden)

    Cüneyt AKAR

    2015-06-01

    Full Text Available This paper aims to determine the relationship between stock returns and volatility of liquidity in Turkish Stock Market. It is also investigated whether various liquidity measures sort the stocks in the same way according to their liquidities. The data used in the study contains the closing prices, trading volumes and free floating of the stocks that are included in Borsa Istanbul 100 Index (BIST100 and covers the period from 28.02.2011 to 18.11.2014. Generalized Autoregressive Conditional Heteroscedasticity (GARCH and Autoregressive Moving Average models (ARMA are used to perform empirical analysis. According to the results, it can not be determined the clear significant relationship between stock returns and volatility of liquidity. Results also show that while stock size and Amihud illiquidity criteria sort the stocks in the same way, stock return standard deviation criterion produces different ranking.

  13. Moving droplets: The measurement of contact lines

    NARCIS (Netherlands)

    Poelma, C.; Franken, M.J.Z.; Kim, H.; Westerweel, J.

    2014-01-01

    Contact lines are the locations where a gas, liquid and a solid meet. From everyday experience we know that such contact lines can be mobile, for example in the case of a water droplet sliding over a glass surface. However, the continuum description of the flow towards or away from a contact line im

  14. Virtual volatility

    Science.gov (United States)

    Silva, A. Christian; Prange, Richard E.

    2007-03-01

    We introduce the concept of virtual volatility. This simple but new measure shows how to quantify the uncertainty in the forecast of the drift component of a random walk. The virtual volatility also is a useful tool in understanding the stochastic process for a given portfolio. In particular, and as an example, we were able to identify mean reversion effect in our portfolio. Finally, we briefly discuss the potential practical effect of the virtual volatility on an investor asset allocation strategy.

  15. Virtual volatility

    OpenAIRE

    A. Christian Silva; Prange, Richard E.

    2006-01-01

    We introduce the concept of virtual volatility. This simple but new measure shows how to quantify the uncertainty in the forecast of the drift component of a random walk. The virtual volatility also is a useful tool in understanding the stochastic process for a given portfolio. In particular, and as an example, we were able to identify mean reversion effect in our portfolio. Finally, we briefly discuss the potential practical effect of the virtual volatility on an investor asset allocation st...

  16. Droplet Mobility Manipulation on Porous Media Using Backpressure.

    Science.gov (United States)

    Vourdas, N; Pashos, G; Kokkoris, G; Boudouvis, A G; Stathopoulos, V N

    2016-05-31

    Wetting phenomena on hydrophobic surfaces are strongly related to the volume and pressure of gas pockets residing at the solid-liquid interface. In this study, we explore the underlying mechanisms of droplet actuation and mobility manipulation when backpressure is applied through a porous medium under a sessile pinned droplet. Reversible transitions between the initially sticky state and the slippery states are thus incited by modulating the backpressure. The sliding angles of deionized (DI) water and ethanol in DI water droplets of various volumes are presented to quantify the effect of the backpressure on the droplet mobility. For a 50 μL water droplet, the sliding angle decreases from 45 to 0° when the backpressure increases to ca. 0.60 bar. Significantly smaller backpressure levels are required for lower surface energy liquids. We shed light on the droplet actuation and movement mechanisms by means of simulations encompassing the momentum conservation and the continuity equations along with the Cahn-Hilliard phase-field equations in a 2D computational domain. The droplet actuation mechanism entails depinning of the receding contact line and movement by means of forward wave propagation reaching the front of the droplet. Eventually, the droplet skips forward. The contact line depinning is also corroborated by analytical calculations based on the governing vertical force balance, properly modified to incorporate the effect of the backpressure.

  17. Efficient transport of droplet sandwiched between saw-tooth plates.

    Science.gov (United States)

    Wang, Liya; Wu, Hengan; Wang, Fengchao

    2016-01-15

    The transport of droplet sandwiched between smooth and saw-tooth plates was investigated using molecular dynamics method. The repeated opening and closing of the plates result in sequential stretching and squeezing of the droplet, which provide the driving force. The asymmetrical saw tooth obstructs the backward motion of the droplet, and gives rise to a net forward displacement of the droplet in every opening and closing cycle. This unidirectional motion facilitates the efficient droplet transport, which is referred to as the ratchet-like effect in this work. Our simulations also reveal that the influence of the surface wettability on the droplet transport is different for saw-tooth and smooth plates. Droplet transport efficiency exhibits monotonic decrease with the increase of the solid-liquid interactions for saw-tooth plates. While for smooth plates, unidirectional droplet movement was only observed for certain solid-liquid interactions. Taken together these simulation results and theoretical analysis, we demonstrate that hydrophobic saw-tooth plates can improve the transport efficiency significantly. These findings not only enhance our understanding of the droplet transport from atomistic scale, but also are beneficial to practical applications in designing of micro- and nano-fluidic systems.

  18. Plant volatiles.

    Science.gov (United States)

    Baldwin, Ian T

    2010-05-11

    Plant volatiles are the metabolites that plants release into the air. The quantities released are not trivial. Almost one-fifth of the atmospheric CO2 fixed by land plants is released back into the air each day as volatiles. Plants are champion synthetic chemists; they take advantage of their anabolic prowess to produce volatiles, which they use to protect themselves against biotic and abiotic stresses and to provide information - and potentially disinformation - to mutualists and competitors alike. As transferors of information, volatiles have provided plants with solutions to the challenges associated with being rooted in the ground and immobile.

  19. Dynamics of droplets

    Energy Technology Data Exchange (ETDEWEB)

    Frohn, A.; Roth, N. [Stuttgart Univ. (Germany). Inst. fuer Thermodynamik der Luft- und Raumfahrt

    2000-07-01

    Intended to privide an up-to-date overview of the field, this book is also likely to become a standard work of reference on the science of droplets. Beginning with the theoretical background important for droplet dynamics, it continues with a presentation of the various methods for generating single droplets and regular droplet systems. Also included is a detailed description of the experimental methods employed in droplet research. A special chapter is devoted to the various types of droplet interactions without phase transition. A separate chapter then treats many examples of the possible phase transition processes. The final part of the book gives a summary of important applications. With its comprehensive content, this book will be of interest to all scientists and lecturers concerned with two-phase flow, spray technology, heterogeneous combustion, and aerosol science. (orig.)

  20. 电子烟雾化液挥发性成分分析及开发思路探讨%Analysis and Discussion on Volatile Components in Electronic Cigarette Liquids

    Institute of Scientific and Technical Information of China (English)

    温光和; 杨雪燕; 潘红成; 马涛; 肯生叶; 姜正灯; 汤小民

    2016-01-01

    为了深入探索电子烟雾化液的挥发性成分,采用气相色谱-质谱联用(GC-MS)分析技术检测了4家公司生产的6种烟草口味电子烟雾化液产品,对样品中的挥发性成分进行了定性和半定量分析。在所有电子烟雾化液样品中,共检测出45种挥发性成分,并根据挥发性成分绘制了香味轮廓图。在此基础上,对比了电子烟雾化液与传统卷烟烟气的差异,提出了电子烟雾化液的开发思路,使其更接近传统卷烟的抽吸品质。%In order to further explore the volatile components in the electronic cigarette liquid, six kinds of tobacco flavor electronic cigarette liquids from four companies were detected by gas chromatography-mass spectrometry(GC-MS), the volatile components in the samples were qualitatively and semi-quantitatively analyzed. Forty-five volatile components were detected, and according to the main volatile constituents, their aroma profiles were mapped. On the basis of the analytical results, the difference between the e-cigarette liquid and the traditional cigarette smoke was compared. Furthermore, some ideas that how to formulate e-cigarette liquids were discussed, so as to make the product with the quality of suction closer to that of traditional cigarettes.

  1. Tunable Superomniphobic Surfaces for Sorting Droplets by Surface Tension

    Science.gov (United States)

    Movafaghi, Sanli; Wang, Wei; Metzger, Ari; Williams, Desiree; Williams, John; Kota, Arun

    2016-11-01

    Manipulation of liquid droplets on super-repellent surfaces (i.e., surfaces that are extremely repellent to liquids) has been widely studied because droplets exhibit high mobility on these surfaces due to the ultra-low adhesion, which leads to minimal sample loss and contamination. Although droplet manipulation has been demonstrated using electric fields, magnetic fields, guiding tracks and wettability gradients, to the best of our knowledge, there are no reports of droplet manipulation methods that can sort droplets by surface tension on super-repellent surfaces. In this work, we utilized tunable superomniphobic surfaces (i.e., surfaces that are extremely repellent to virtually all liquids) to develop a simple device with precisely tailored solid surface energy domains that, for the first time, can sort droplets by surface tension. Droplet sorting occurs on our device entirely due to a balance between the work done by gravity and the work expended due to adhesion, without the need for any external energy input. Our device can be fabricated easily in a short time and is particularly useful for in-the-field and on-the-go operations, where complex analysis equipment is unavailable. We envision that our methodology for droplet sorting will enable inexpensive and energy-efficient analytical devices for personalized point-of-care diagnostic platforms and lab-on-a-chip systems.

  2. Ejection of small droplet from microplate using focused ultrasound

    Science.gov (United States)

    Tanaka, Hiroki; Mizuno, Yosuke; Nakamura, Kentaro

    2017-08-01

    We discussed an ultrasonic system for single-droplet ejection from a microplate, which is one of the basic and important procedures in the noncontact handling of droplets in air. In this system, a 1.5 MHz concave transducer located below the microplate is used for chasing the liquid surface through a pulse echo method, and also for the ejection of a 1 µL single droplet by the burst of focused ultrasound. We investigated the relationship between the droplet ejection characteristics, the distance from the transducer to the surface of liquid, the material property, and the excitation condition of the focused ultrasonic transducer. It was verified that the optimal position of the transducer was off the focal point of sound pressure by ±1 mm, because the sound intensity had to be controlled to eject a single droplet. Subsequently, we confirmed experimentally that the ejected droplet volume linearly depended on the surface tension of the liquid, and that the droplet volume and ejection velocity were determined by the Webber number, Reynolds number, and Ohnesolge number. In addition, by optimizing the duration of the burst ultrasound, the droplet volume and ejection velocity were controlled.

  3. An Experimental Investigation of Vibration Induced Droplet Atomization*

    Science.gov (United States)

    Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari

    1999-11-01

    The atomization of a millimeter-scale liquid droplet placed on a vibrating diaphragm is investigated experimentally using high-speed imaging and particle-tracking techniques. Atomization is the result of the rapid ejection of small secondary droplets from the wave crests of a hierarchy of forced surface waves on the primary droplet. The evolution and rate of ejection depend on the coupled dynamics of the primary droplet and the vibrating diaphragm. The present data indicate that secondary droplet ejection results from the collapse of surface craters formed during the evolution of capillary surface waves on the primary droplet. The collapse of the crater and the ensuing ejection of a momentary liquid jet are similar to ejection processes at free surfaces that are induced by the bursting of gas bubbles or the impingement of liquid droplets. The spray characteristics of the ejected droplets are investigated over a broad range of vibrating frequencies (up to 14 kHz) using particle-tracking velocimetry. * Supported by NASA Microgravity Res. Div., Grant NAG3-1949.

  4. Dynamic effects induced transition of droplets on biomimetic superhydrophobic surfaces.

    Science.gov (United States)

    Jung, Yong Chae; Bhushan, Bharat

    2009-08-18

    Superhydrophobic surfaces have considerable technological potential for various applications because of their extreme water-repellent properties. Dynamic effects, such as the bouncing and vibration of a droplet, can destroy the composite solid-air-liquid interface. The impact pressure of a bouncing droplet and the inertia force of a vibrating droplet affect the transition from a solid-air-liquid interface to a solid-liquid interface. Therefore, it is necessary to study the dynamic effect of droplets under various system parameters (impact velocity and frequency and amplitude of vibration). A new model for the prediction of the wetting and dewetting process during droplet vibration based on the relationship between the adhesion force and the inertia force of a droplet is proposed. To investigate whether micro-, nano-, and hierarchical structures can resist the destabilizing factors responsible for the transition, a study of bouncing and vibration of a water droplet is systematically conducted on various surfaces. The physics of wetting phenomena for water droplet studies is of fundamental importance in the geometrical design of superhydrophobic surfaces.

  5. Non-volatile polymer electrolyte based on poly(propylene carbonate), ionic liquid, and lithium perchlorate for electrochromic devices.

    Science.gov (United States)

    Zhou, Dan; Zhou, Rui; Chen, Chuanxiang; Yee, Wu-Aik; Kong, Junhua; Ding, Guoqiang; Lu, Xuehong

    2013-06-27

    A series of solvent-free ionic liquid (IL)-based polymer electrolytes composed of amorphous and biodegradable poly(propylene carbonate) (PPC) host, LiClO4, and 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM(+)BF4(-)) were prepared and characterized for the first time. FTIR studies reveal that the interaction between PPC chains and imidazolium cations weakens the complexation between PPC chains and Li(+) ions. Thermal analysis (DSC and TGA) results show that the incorporation of BMIM(+)BF4(-) into PPC/LiClO4 remarkably decreases the glass transition temperature and improves the thermal stability of the electrolytes. AC impedance results show that the ionic conductivities of the electrolytes are significantly increased with the increase of BMIM(+)BF4(-) amount, the ambient ionic conductivity of the electrolyte at a PPC/LiClO4/BMIM(+)BF4(-) weight ratio of 1/0.2/3 is 1.5 mS/cm, and the ionic transport behavior follows the Arrhenius equation. Both PPC/LiClO4/BMIM(+)BF4(-) and PPC/BMIM(+)BF4(-) electrolytes were applied in electrochromic devices with polyaniline as the electrochromic layer. The PPC/LiClO4/BMIM(+)BF4(-)-based device exhibits much better electrochromic performance in terms of optical contrast and switching time due to the presence of much smaller cations.

  6. Droplet microfluidics--a tool for single-cell analysis.

    Science.gov (United States)

    Joensson, Haakan N; Andersson Svahn, Helene

    2012-12-03

    Droplet microfluidics allows the isolation of single cells and reagents in monodisperse picoliter liquid capsules and manipulations at a throughput of thousands of droplets per second. These qualities allow many of the challenges in single-cell analysis to be overcome. Monodispersity enables quantitative control of solute concentrations, while encapsulation in droplets provides an isolated compartment for the single cell and its immediate environment. The high throughput allows the processing and analysis of the tens of thousands to millions of cells that must be analyzed to accurately describe a heterogeneous cell population so as to find rare cell types or access sufficient biological space to find hits in a directed evolution experiment. The low volumes of the droplets make very large screens economically viable. This Review gives an overview of the current state of single-cell analysis involving droplet microfluidics and offers examples where droplet microfluidics can further biological understanding.

  7. Direct contact droplet heat exchangers for thermal management in space

    Science.gov (United States)

    Bruckner, A. P.; Hertzberg, A.

    1982-01-01

    A liquid droplet heat exchanger for space applications is described which transfers heat between a gas and a liquid metal dispersed into droplets. The ability of the droplet heat exchanger to transfer heat between two media in direct contact over a wide temperature range circumvents many of the material limitations of conventional tube-type heat exchangers and does away with complicated plumbing systems and their tendency toward single point failure. Droplet heat exchangers offer large surface to volume ratios in a compact geometry, very low gas pressure drop, and high effectiveness. The application of the droplet heat exchanger in a high temperature Brayton cycle is discussed to illustrate its performance and operational characteristics.

  8. Evaporation of an inkjet droplet on a flat substrate

    Science.gov (United States)

    Masuda, Takashi; Shimoda, Tatsuya

    2017-01-01

    Understanding the evaporation behavior of inkjet droplets has become increasingly important as printed electronic technology develops. In this study, the evaporation phenomena of a 5-6-pL droplet were studied. Four types of non-polar liquid droplets were prepared via the inkjet method and placed on substrates with small contact-angle hystereses. The observed contact radius and contact angle during evaporation were in good agreement with the theoretical model. This model, that of diffusion-controlled evaporation, was obtained based on a microliter droplet or bulk liquid wherein the evaporation was considered to be a quasi-steady state. The square of contact radius R decreased linearly with the evaporation time t, and the gradient of the R 2 vs t plot provided the diffusivity of vapor in the air. The experimentally obtained diffusivity values were helpful for estimating the evaporation speeds and times of droplets at any contact angle.

  9. Grating droplets with a mesh

    Science.gov (United States)

    Soto, Dan; Le Helloco, Antoine; Clanet, Cristophe; Quere, David; Varanasi, Kripa

    2016-11-01

    A drop thrown against a mesh can pass through its holes if impacting with enough inertia. As a result, although part of the droplet may remain on one side of the sieve, the rest will end up grated through the other side. This inexpensive method to break up millimetric droplets into micrometric ones may be of particular interest in a wide variety of applications: enhancing evaporation of droplets launched from the top of an evaporative cooling tower or preventing drift of pesticides sprayed above crops by increasing their initial size and atomizing them at the very last moment with a mesh. In order to understand how much liquid will be grated we propose in this presentation to start first by studying a simpler situation: a drop impacting a plate pierced with a single off centered hole. The study of the role of natural parameters such as the radius drop and speed or the hole position, size and thickness allows us to discuss then the more general situation of a plate pierced with multiple holes: the mesh.

  10. Combustion of Interacting Droplet Arrays Being Studied

    Science.gov (United States)

    Dietrich, Daniel L.

    2002-01-01

    The combustion of liquid fuels is a major source of energy in the world today, and the majority of these fuels are burned in the form of a spray. This droplet combustion project at the NASA Glenn Research Center has the overall goal of providing a better understanding of spray combustion by extending existing studies of single droplets to a regime where droplet interactions are important (as occurs in a practical spray). The Combustion of Interacting Droplet Arrays is a collaborative effort between Glenn and the National Center for Microgravity Research. The group at Glenn also collaborates with scientists at the National Institute of Advanced Industrial Science and Technology in Hokkaido, Japan. The project is studying the combustion of a small number of droplets suspended on small quartz fibers in a 0.1-atm combustion chamber. Data consist primarily of video images of the flames and droplets. The tests are being conducted in Glenn's reduced-gravity facilities (2.2-sec and 5.2-sec drop towers) and in the Japan Microgravity Center's 10-sec drop tower (JAMIC).

  11. Whole Teflon valves for handling droplets.

    Science.gov (United States)

    Cybulski, Olgierd; Jakiela, Slawomir; Garstecki, Piotr

    2016-06-21

    We propose and test a new whole-Teflon gate valve for handling droplets. The valve allows droplet plugs to pass through without disturbing them. This is possible due to the geometric design, the choice of material and lack of any pulses of flow generated by closing or opening the valve. The duct through the valve resembles a simple segment of tubing, without constrictions, change in lumen or side pockets. There are no extra sealing materials with different wettability or chemical resistance. The only material exposed to liquids is FEP Teflon, which is resistant to aggressive chemicals and fully biocompatible. The valve can be integrated into microfluidic systems: we demonstrate a complex system for culturing bacteria in hundreds of microliter droplet chemostats. The valve effectively isolates modules of the system to increase precision of operations on droplets. We verified that the valve allowed millions of droplet plugs to safely pass through, without any cross-contamination with bacteria between the droplets. The valve can be used in automating complex microfluidic systems for experiments in biochemistry, biology and organic chemistry.

  12. The effect of binary oxide materials on a single droplet vapor explosion triggering

    Energy Technology Data Exchange (ETDEWEB)

    Hansson, R.C.; Manickam, L.T.; Dinh, T.N. [Royal Inst. of Tech., Stockholm (Sweden)

    2011-07-01

    In order to explore the fundamental mechanism dictated by the material influence on triggering, fine fragmentation and subsequent vapor explosion energetics, a series of experiments using a mixture of eutectic and non-eutectic binary oxide were initiated. Dynamics of the hot liquid (WO{sub 3}-CaO) droplet and the volatile liquid (water) were investigated in the MISTEE (Micro-Interactions in Steam Explosion Experiments) facility by performing well-controlled, externally triggered, single-droplet experiments, using a high-speed visualization system with synchronized digital cinematography and continuous X-ray radiography, called SHARP (Simultaneous High-speed Acquisition of X-ray Radiography and Photography). The acquired images followed by further analysis showed a milder interaction for the non-eutectic melt composition for the tests with low melt superheat, whether no evident differences between eutectic and non-eutectic melt compositions regarding bubble dynamics, energetics and melt preconditioning was perceived for the high melt superheat tests. (author)

  13. A validated high performance liquid chromatography method for the analysis of thymol and carvacrol in Thymus vulgaris L. volatile oil

    Directory of Open Access Journals (Sweden)

    H Hajimehdipoor

    2010-01-01

    Full Text Available Thymus vulgaris L. (Lamiaceae is a well-known medicinal plant that contains important compounds such as thymol and carvacrol and it has been used in many pharmaceutical dosage forms. Thymol and carvacrol in essential oils are often quantified by gas chromatography (GC technique but in this work, a validated and reliable high performance liquid chromatography (HPLC method has been developed for the analysis of these two components in T. vulgaris essential oil. The essential oil of the plant was analyzed by HPLC and GC techniques. The HPLC system consisted of ACE C 18 column and an isocratic acetonitrile:water (50:50 as the mobile phase which was kept at a flow rate of 1 ml/min. The method was validated for selectivity, linearity (r2 > 0.997 for both thymol and carvacrol, precision (intra-day 0.8-1.9, 1.7-2.6; and inter-day 3.5-4.5, 3.6-4.7 and recovery (97.7%, 97.6% for thymol and carvacrol, respectively. The limits of detection (LODs and limits of quantization (LOQs were calculated to be 2.8, 0.6 μg/ml and 8.6, 1.8 μg/ml for thymol and carvacrol, respectively. The GC system consisted of flame ionization detector (FID and CP-SIL 8 column. The concentrations of thymol and carvacrol in essential oil obtained by HPLC (41.2%, 4.3% and GC (40.7%, 4.2% were compared by statistical methods and they showed good agreement.

  14. A validated high performance liquid chromatography method for the analysis of thymol and carvacrol in Thymus vulgaris L. volatile oil.

    Science.gov (United States)

    Hajimehdipoor, H; Shekarchi, M; Khanavi, M; Adib, N; Amri, M

    2010-07-01

    Thymus vulgaris L. (Lamiaceae) is a well-known medicinal plant that contains important compounds such as thymol and carvacrol and it has been used in many pharmaceutical dosage forms. Thymol and carvacrol in essential oils are often quantified by gas chromatography (GC) technique but in this work, a validated and reliable high performance liquid chromatography (HPLC) method has been developed for the analysis of these two components in T. vulgaris essential oil. The essential oil of the plant was analyzed by HPLC and GC techniques. The HPLC system consisted of ACE C(18) column and an isocratic acetonitrile:water (50:50) as the mobile phase which was kept at a flow rate of 1 ml/min. The method was validated for selectivity, linearity (r(2) > 0.997 for both thymol and carvacrol), precision (intra-day 0.8-1.9, 1.7-2.6; and inter-day 3.5-4.5, 3.6-4.7) and recovery (97.7%, 97.6%) for thymol and carvacrol, respectively. The limits of detection (LODs) and limits of quantization (LOQs) were calculated to be 2.8, 0.6 µg/ml and 8.6, 1.8 µg/ml for thymol and carvacrol, respectively. The GC system consisted of flame ionization detector (FID) and CP-SIL 8 column. The concentrations of thymol and carvacrol in essential oil obtained by HPLC (41.2%, 4.3%) and GC (40.7%, 4.2%) were compared by statistical methods and they showed good agreement.

  15. A reconfigurable optofluidic Michelson interferometer using tunable droplet grating.

    Science.gov (United States)

    Chin, L K; Liu, A Q; Soh, Y C; Lim, C S; Lin, C L

    2010-04-21

    This paper presents a novel optofluidic Michelson interferometer based on droplet microfluidics used to create a droplet grating. The droplet grating is formed by a stream of plugs in the microchannel with constant refractive index variation. It has a real-time tunability in the grating period through varying the flow rates of the liquids and index variation via different combinations of liquids. The optofluidic Michelson interferometer is highly sensitive and is suitable for the measurement of biomedical and biochemical buffer solutions. The experimental results show that it has a sensitivity of 66.7 nm per refractive index unit (RIU) and a detection range of 0.086 RIU.

  16. Nanoscale footprints of self-running gallium droplets on GaAs surface.

    Directory of Open Access Journals (Sweden)

    Jiang Wu

    Full Text Available In this work, the nanoscale footprints of self-driven liquid gallium droplet movement on a GaAs (001 surface will be presented and analyzed. The nanoscale footprints of a primary droplet trail and ordered secondary droplets along primary droplet trails are observed on the GaAs surface. A well ordered nanoterrace from the trail is left behind by a running droplet. In addition, collision events between two running droplets are investigated. The exposed fresh surface after a collision demonstrates a superior evaporation property. Based on the observation of droplet evolution at different stages as well as nanoscale footprints, a schematic diagram of droplet evolution is outlined in an attempt to understand the phenomenon of stick-slip droplet motion on the GaAs surface. The present study adds another piece of work to obtain the physical picture of a stick-slip self-driven mechanism in nanoscale, bridging nano and micro systems.

  17. Proteolysis in microfluidic droplets: an approach to interface protein separation and peptide mass spectrometry

    OpenAIRE

    Ji, Ji; Nie, Lei; Qiao, Liang; Li, Yixin; Guo, Liping; Liu, Baohong; Yang, Pengyuan; Girault, Hubert H.

    2012-01-01

    A versatile microreactor protocol based on microfluidic droplets has been developed for on-line protein digestion. Proteins separated by liquid chromatography are fractionated in water-in-oil droplets and digested in sequence. The microfluidic reactor acts also as an electrospray ionization emitter for mass spectrometry analysis of the peptides produced in the individual droplets. Each droplet is an enzymatic micro-reaction unit with efficient proteolysis due to rapid mixing, enhanced mass tr...

  18. Difference Of Evaporation and Boiling for Heterogeneous Water Droplets in a High-Temperature Gas

    Directory of Open Access Journals (Sweden)

    Legros Jean Claude

    2015-01-01

    Full Text Available Experimental investigation of vapor formation was carried out on water droplets on fixed graphite substrate and heterogeneous droplets (containing solid single inclusions when heating in high-temperature gas. High-speed video shooting (up to 105 frames per second, optical method (Particle Image Velocimetry and TEMA Automotive software were used. We revealed two phase change mechanisms of heterogeneous liquid droplets. Effect of evaporation and boiling on evaporation times of water droplets was determined.

  19. Unstable volatility

    DEFF Research Database (Denmark)

    Casas, Isabel; Gijbels, Irène

    2012-01-01

    The objective of this paper is to introduce the break-preserving local linear (BPLL) estimator for the estimation of unstable volatility functions for independent and asymptotically independent processes. Breaks in the structure of the conditional mean and/or the volatility functions are common i...

  20. Unstable volatility

    DEFF Research Database (Denmark)

    Casas, Isabel; Gijbels, Irène

    2012-01-01

    The objective of this paper is to introduce the break-preserving local linear (BPLL) estimator for the estimation of unstable volatility functions for independent and asymptotically independent processes. Breaks in the structure of the conditional mean and/or the volatility functions are common i...

  1. Microfluidic separation of satellite droplets as the basis of a monodispersed micron and submicron emulsification system.

    Science.gov (United States)

    Tan, Yung-Chieh; Lee, Abraham Phillip

    2005-10-01

    Emulsions are widely used to produce sol-gel, drugs, synthetic materials, and food products. Recent advancements in microfluidic droplet emulsion technology has enabled the precise sampling and processing of small volumes of fluids (picoliter to femtoliter) by the controlled viscous shearing in microchannels. However the generation of monodispersed droplets smaller than 1 microm without surfactants has been difficult to achieve. Normally, the generation of satellite droplets along with parent droplets is undesirable and makes it difficult to control volume and purity of samples in droplets. In this paper, however, several methods are presented to passively filter out satellite droplets from the generation of parent droplets and use these satellite droplets as the source for monodispersed production of submicron emulsions. A passive satellite droplet filtration system and a dynamic satellite droplet separation system are demonstrated. Satellite droplets are filtered from parent droplets with a two-layer channel geometry. This design allows the creation and collection of droplets that are less than 100 nm in diameter. In the dynamic separation system, satellite droplets of defined sizes can be selectively separated into different collecting zones. The separation of the satellite droplets into different collecting zones correlates with the cross channel position of the satellite droplets during the breakup of the liquid thread. The delay time for droplets to switch between the different alternating collecting zones is nominally 1 min and is proportional to the ratio of the oil shear flows. With our droplet generation system, monodispersed satellite droplets with an average radius of 2.23 +/- 0.11 microm, and bidispersed secondary and tertiary satellite droplets with radii of 1.55 +/- 0.07 microm and 372 +/- 46 nm respectively, have been dynamically separated and collected.

  2. Erosion Effects of Liquid Water and Volatiles in a Former Lacustrine Environment - From Gale Crater to Death Valley

    Science.gov (United States)

    Iacob, R. H.; Bonaccorsi, R.; Iacob, C. E.

    2014-12-01

    During its first two years of exploration, Curiosity rover provided strong evidence of water activity at Gale Crater on Mars. While liquid water is not commonly present on the surface of Mars, large depressions such as Gale Crater hold evidence that water was collected in impact craters on Mars in the distant past. Specific features such as alluvial fans, inverted riverbeds, moat areas, and sedimentary formations, demonstrate strong water activity on low elevation regions of Mars. While surface water (gradually) disappeared as the climate and atmosphere of Mars changed, important water deposits formed underground, either as sub-surface ice shelves, or in the form of hydrated minerals, as demonstrated by MER and MSL. Although the presence of water ice under the ancient lake bed at the foothills of Mount Sharp is still to be determined, the area explored so far by Curiosity exhibits erosion features that can help describe the history of water activity along billions of years, e.g., river streams, lacustrine sedimentation, and later cycles of evaporation, frosting and sublimation. This presentation features a comparative study of water erosion processes at Gale Crater on Mars and Death Valley (DV) on Earth, from ancient water flows and lacustrine environments, through evaporation, dryness, and cyclic frosting and sublimation. Groundwater deposits in Death Valley offer best opportunities to study the process of minerals hydration, as well as landforms related to underground water percolation and evaporation, similar to those discovered by Curiosity at Yellowknife Bay. Furthermore, sedimentary processes in lacustrine proximal settings similar to those argued for Mount Sharp, or seen at Gale Crater's floor, have been studied in several locations of DV. These include, but are not limited to, younger dry lake beds of former lakes Manly and Panamint, carved badland formations of Furnace Creek Lake (Zabriskie Point) and older Tertiary lacustrine and fanglomeratic deposits

  3. Optical droplet vaporization of micron-sized perfluorocarbon droplets and their photoacoustic detection

    Science.gov (United States)

    Strohm, Eric; Rui, Min; Gorelikov, Ivan; Matsuura, Naomi; Kolios, Michael

    2011-03-01

    An acoustic and photoacoustic characterization of micron-sized perfluorocarbon (PFC) droplets is presented. PFC droplets are currently being investigated as acoustic and photoacoustic contrast agents and as cancer therapy agents. Pulse echo measurements at 375 MHz were used to determine the diameter, ranging from 3.2 to 6.5 μm, and the sound velocity, ranging from 311 to 406 m/s of nine droplets. An average sound velocity of 379 +/- 18 m/s was calculated for droplets larger than the ultrasound beam width of 4.0 μm. Optical droplet vaporization, where vaporization of a single droplet occurred upon laser irradiation of sufficient intensity, was verified using pulse echo acoustic methods. The ultrasonic backscatter amplitude, acoustic impedance and attenuation increased after vaporization, consistent with a phase change from a liquid to gas core. Photoacoustic measurements were used to compare the spectra of three droplets ranging in diameter from 3.0 to 6.2 μm to a theoretical model. Good agreement in the spectral features was observed over the bandwidth of the 375 MHz transducer.

  4. Nano-liter droplet libraries from a pipette: step emulsificator that stabilizes droplet volume against variation in flow rate.

    Science.gov (United States)

    Dutka, Filip; Opalski, Adam S; Garstecki, Piotr

    2016-05-24

    Many modern analytical assays, for example, droplet digital PCR, or screening of the properties of single cells or single mutated genes require splitting a liquid sample into a number of small (typically ca. nano-liter in volume) independent compartments or droplets. This calls for a method that would allow splitting small (microliter) samples of liquid into libraries of nano-liter droplets without any dead volume or waste. Step emulsification allows for facile protocols that require delivery of only the sample liquid, yet they typically exhibit dependence of the droplet size on the rate at which the sample is injected. Here, we report a novel microfluidic junction that reduces the dependence of the volume of droplets on the rate of injection. We also demonstrate generation of tightly monodisperse nanoliter droplets by introduction of solely the dispersed phase into the system from an automatic pipette. The method presented here can readily be used and can replace the sophisticated devices typically used to generate libraries of nano-liter droplets from liquid samples.

  5. On The Validity of the Assumed PDF Method for Modeling Binary Mixing/Reaction of Evaporated Vapor in GAS/Liquid-Droplet Turbulent Shear Flow

    Science.gov (United States)

    Miller, R. S.; Bellan, J.

    1997-01-01

    An Investigation of the statistical description of binary mixing and/or reaction between a carrier gas and an evaporated vapor species in two-phase gas-liquid turbulent flows is perfomed through both theroetical analysis and comparisons with results from direct numerical simulations (DNS) of a two-phase mixing layer.

  6. On The Validity of the Assumed PDF Method for Modeling Binary Mixing/Reaction of Evaporated Vapor in GAS/Liquid-Droplet Turbulent Shear Flow

    Science.gov (United States)

    Miller, R. S.; Bellan, J.

    1997-01-01

    An Investigation of the statistical description of binary mixing and/or reaction between a carrier gas and an evaporated vapor species in two-phase gas-liquid turbulent flows is perfomed through both theroetical analysis and comparisons with results from direct numerical simulations (DNS) of a two-phase mixing layer.

  7. In vitro characterization of perfluorocarbon droplets for focused ultrasound therapy

    Science.gov (United States)

    Schad, Kelly C.; Hynynen, Kullervo

    2010-09-01

    Focused ultrasound therapy can be enhanced with microbubbles by thermal and cavitation effects. However, localization of treatment is difficult as bioeffects can occur outside of the target region. Spatial control of bubbles can be achieved by ultrasound-induced conversion of liquid perfluorocarbon droplets to gas bubbles. This study was undertaken to determine the acoustic parameters for bubble production by droplet conversion and how it depends on the acoustic conditions and droplet physical parameters. Lipid-encapsulated droplets containing dodecafluoropentane were manufactured with sizes ranging from 1.9 to 7.2 µm in diameter and diluted to a concentration of 8 × 106 droplets mL-1. The droplets were sonicated in vitro with a focused ultrasound transducer and varying frequency and exposure under flow conditions through an acoustically transparent vessel. The sonications were 10 ms in duration at frequencies of 0.578, 1.736 and 2.855 MHz. The pressure threshold for droplet conversion was measured with an active transducer operating in pulse-echo mode and simultaneous measurements of broadband acoustic emissions were performed with passive acoustic detection. The results show that droplets cannot be converted at low frequency without broadband emissions occurring. However, the pressure threshold for droplet conversion decreased with increasing frequency, exposure and droplet size. The pressure threshold for broadband emissions was independent of the droplet size and was 2.9, 4.4 and 5.3 MPa for 0.578, 1736 and 2.855 MHz, respectively. In summary, we have demonstrated that droplet conversion is feasible for clinically relevant sized droplets and acoustic exposures.

  8. In vitro characterization of perfluorocarbon droplets for focused ultrasound therapy

    Energy Technology Data Exchange (ETDEWEB)

    Schad, Kelly C; Hynynen, Kullervo, E-mail: khynynen@sri.utoronto.c [Imaging Research, Sunnybrook Health Sciences Centre, 2075 Bayview Ave, Toronto, Ontario M4N 3M5 (Canada); Department of Medical Biophysics, University of Toronto (Canada)

    2010-09-07

    Focused ultrasound therapy can be enhanced with microbubbles by thermal and cavitation effects. However, localization of treatment is difficult as bioeffects can occur outside of the target region. Spatial control of bubbles can be achieved by ultrasound-induced conversion of liquid perfluorocarbon droplets to gas bubbles. This study was undertaken to determine the acoustic parameters for bubble production by droplet conversion and how it depends on the acoustic conditions and droplet physical parameters. Lipid-encapsulated droplets containing dodecafluoropentane were manufactured with sizes ranging from 1.9 to 7.2 {mu}m in diameter and diluted to a concentration of 8 x 10{sup 6} droplets mL{sup -1}. The droplets were sonicated in vitro with a focused ultrasound transducer and varying frequency and exposure under flow conditions through an acoustically transparent vessel. The sonications were 10 ms in duration at frequencies of 0.578, 1.736 and 2.855 MHz. The pressure threshold for droplet conversion was measured with an active transducer operating in pulse-echo mode and simultaneous measurements of broadband acoustic emissions were performed with passive acoustic detection. The results show that droplets cannot be converted at low frequency without broadband emissions occurring. However, the pressure threshold for droplet conversion decreased with increasing frequency, exposure and droplet size. The pressure threshold for broadband emissions was independent of the droplet size and was 2.9, 4.4 and 5.3 MPa for 0.578, 1736 and 2.855 MHz, respectively. In summary, we have demonstrated that droplet conversion is feasible for clinically relevant sized droplets and acoustic exposures.

  9. Liquid acrobatics

    CERN Document Server

    Bird, James C

    2008-01-01

    We experiment with injecting a continuous stream of gas into a shallow liquid, similar to how one might blow into a straw placed at the bottom of a near-empty drink. By varying the angle of the straw (here a metal needle), we observe a variety of dynamics, which we film using a high-speed camera. Most noteworthy is an intermediate regime in which cyclical jets erupt from the air-liquid interface and breakup into air-born droplets. These droplets trace out a parabolic trajectory and bounce on the air-liquid interface before eventually coalescing. The shape of each jet, as well as the time between jets, is remarkably similar and leads to droplets with nearly identical trajectories. The following article accompanies the linked fluid dynamics video submitted to the Gallery of Fluid Motion in 2008.

  10. Free running droplets on packed powder beds

    Science.gov (United States)

    Whitby, Catherine P.; Bian, Xun; Sedev, Rossen

    2013-06-01

    We observed that water drops placed on horizontal beds of fine molybdenite particles move freely over the bed surface for about 1 second. The drops collect an irregular coating of unevenly distributed particles as they bounce and roll. We manipulated the distance that the drops travel, and hence the area of the droplet surface coated with particles, by varying the water surface tension and the kinetic energy of the initial droplet impact on the bed surface. Our results highlight the role of contact angle hysteresis in particle encapsulation of liquid drops.

  11. Vitrification and devitrification of micro-droplets

    Science.gov (United States)

    Ryoun Youn, Jae; Song, Young Seok

    2012-11-01

    Vitrification can be achieved by flash freezing and thawing (i.e. quenching) when ice crystal formation is inhibited in a cryogenic environment. Such ultra-rapid cooling and rewarming occurs due to the large temperature difference between the liquid and its surrounding medium. Here, we analyze the crystallization behavior of a droplet (i.e. vitrification and devitrification) by using a numerical model. The numerical results were found to explain the experimental observations successfully. The findings showed that for successful cryopreservation not only sufficiently fast cooling, but also rewarming processes should be designed and controlled to avoid devitrification of a droplet.

  12. Levitated droplet dye laser

    DEFF Research Database (Denmark)

    Azzouz, H.; Alkafadiji, L.; Balslev, Søren

    2006-01-01

    a high quality optical resonator. Our 750 nL lasing droplets consist of Rhodamine 6G dissolved in ethylene glycol, at a concentration of 0.02 M. The droplets are optically pumped at 532 nm light from a pulsed, frequency doubled Nd:YAG laser, and the dye laser emission is analyzed by a fixed grating...

  13. Critical parameters for the partial coalescence of a droplet

    CERN Document Server

    Gilet, T; Lecomte, J P; Mulleners, K; Vandewalle, N

    2006-01-01

    The partial coalescence of a droplet onto a planar liquid/liquid interface is investigated theoretically by using a dimensional analysis. It mainly depends on the Bond number (gravity vs. surface tension), the Ohnesorge numbers (viscosity in both fluids in contact vs. surface tension) and the density relative difference. An experimental work on 2000 coalescence events is made in order to study the impact of viscosities and gravity on the coalescence process. Global quantities such as the available surface energy of the droplet has been measured during the coalescence. The surface energy is converted into kinetic energy at a constant rate that is independent of the coalescence outcome. The ratio between the daughter droplet size and the mother droplet size is investigated as a function of the dimensionless numbers. Theoretical models are proposed to fit experimental data. The asymmetrical behavior when liquids are inverted indicates that the viscous dissipation is different in both fluids. In the surrounding f...

  14. Monodisperse droplet generation for microscale mass transfer studies

    Science.gov (United States)

    Roberts, Christine; Rao, Rekha; Grillet, Anne; Jove-Colon, Carlos; Brooks, Carlton; Nemer, Martin

    2011-11-01

    Understanding interfacial mass transport on a droplet scale is essential for modeling liquid-liquid extraction processes. A thin flow-focusing microfluidic channel is evaluated for generating monodisperse liquid droplets for microscale mass transport studies. Surface treatment of the microfluidic device allows creation of both oil in water and water in oil emulsions, facilitating a large parameter study of viscosity and flow rate ratios. The unusually thin channel height promotes a flow regime where no droplets form. Through confocal microscopy, this regime is shown to be highly influenced by the contact angle of the liquids with the channel. Drop sizes are found to scale with a modified capillary number. Liquid streamlines within the droplets are inferred by high speed imagery of microparticles dispersed in the droplet phase. Finally, species mass transfer to the droplet fluid is quantitatively measured using high speed imaging. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85.

  15. Determination of hydrogen sulfide and volatile thiols in air samples by mercury probe derivatization coupled with liquid chromatography-atomic fluorescence spectrometry.

    Science.gov (United States)

    Bramanti, Emilia; D'Ulivo, Lucia; Lomonte, Cristina; Onor, Massimo; Zamboni, Roberto; Raspi, Giorgio; D'Ulivo, Alessandro

    2006-10-02

    A new procedure is proposed for the sampling and storage of hydrogen sulphide (H2S) and volatile thiols (methanethiol or methyl mercaptan, ethanethiol and propanethiol) for their determination by liquid chromatography. The sampling procedure is based on the trapping/pre-concentration of the analytes in alkaline aqueous solution containing an organic mercurial probe p-hydroxymercurybenzoate, HO-Hg-C6H4-COO- (PHMB), where they are derivatized to stable PHMB complexes based on mercury-sulfur covalent bonds. PHMB complexes are separated on a C18 reverse phase column, allowing their determination by liquid chromatography coupled with sequential non-selective UV-vis (DAD) and mercury specific (chemical vapor generation atomic fluorescence spectrometry, CVGAFS) on-line detectors. PHMB complexes, S(PHMB)2CH3S-PHMB, C2H5S-PHMB and C3H7S-PHMB, are stable alt least for 12 h at room temperature and for 3 months if stored frozen (-20 degrees C). The best analytical figures of merits in the optimized conditions were obtained by CVGAFS detection, with detection limits (LODc) of 9.7 microg L(-1) for H2S, 13.7 microg L(-1) for CH(3)SH, 17.7 microg L(-1) for C2H5SH and 21.7 microg L(-1) for C3H7SH in the trapping solution in form of RS-PHMB complexes, the relative standard deviation (R.S.D.) ranging between 1.0 and 1.5%, and a linear dynamic range (LDR) between 10 and 9700 microg L(-1). Conventional UV absorbance detectors tuned at 254 nm can be employed as well with comparable R.S.D. and LDR, but with LODc one order of magnitude higher than AFS detector and lower specificity. The sampling procedure followed by LC-DAD-CVGAFS analysis has been validated, as example, for H2S determination by a certified gas permeation tube as a source of 3.071+/-0.154 microg min(-1) of H2S, giving a recovery of 99.8+/-7% and it has been applied to the determination of sulfur compounds in real gas samples (biogas and the air of a plant for fractional distillation of crude oil).

  16. Determination of hydrogen sulfide and volatile thiols in air samples by mercury probe derivatization coupled with liquid chromatography-atomic fluorescence spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Bramanti, Emilia [Italian National Research Council, CNR-Istituto per i Processi Chimico-Fisici, Laboratory of Instrumental Analytical Chemistry, Via G. Moruzzi 1, 56124 Pisa (Italy)]. E-mail: emilia@ipcf.cnr.it; D' Ulivo, Lucia [Italian National Research Council, CNR-Istituto per i Processi Chimico-Fisici, Laboratory of Instrumental Analytical Chemistry, Via G. Moruzzi 1, 56124 Pisa (Italy); Lomonte, Cristina [Italian National Research Council, CNR-Istituto per i Processi Chimico-Fisici, Laboratory of Instrumental Analytical Chemistry, Via G. Moruzzi 1, 56124 Pisa (Italy); Ambiente s.c.r.l., Via Frassina 21, 54033, Carrrara, Massa (Italy); Onor, Massimo [Italian National Research Council, CNR-Istituto per i Processi Chimico-Fisici, Laboratory of Instrumental Analytical Chemistry, Via G. Moruzzi 1, 56124 Pisa (Italy); Zamboni, Roberto [Department of Chemistry and Industrial Chemistry, University of Pisa, Via Risorgimento 35, 56126 Pisa (Italy); Raspi, Giorgio [Italian National Research Council, CNR-Istituto per i Processi Chimico-Fisici, Laboratory of Instrumental Analytical Chemistry, Via G. Moruzzi 1, 56124 Pisa (Italy); D' Ulivo, Alessandro [Italian National Research Council, CNR-Istituto per i Processi Chimico-Fisici, Laboratory of Instrumental Analytical Chemistry, Via G. Moruzzi 1, 56124 Pisa (Italy)

    2006-10-02

    A new procedure is proposed for the sampling and storage of hydrogen sulphide (H{sub 2}S) and volatile thiols (methanethiol or methyl mercaptan, ethanethiol and propanethiol) for their determination by liquid chromatography. The sampling procedure is based on the trapping/pre-concentration of the analytes in alkaline aqueous solution containing an organic mercurial probe p-hydroxymercurybenzoate, HO-Hg-C{sub 6}H{sub 4}-COO{sup -} (PHMB), where they are derivatized to stable PHMB complexes based on mercury-sulfur covalent bonds. PHMB complexes are separated on a C{sub 18} reverse phase column, allowing their determination by liquid chromatography coupled with sequential non-selective UV-vis (DAD) and mercury specific (chemical vapor generation atomic fluorescence spectrometry, CVGAFS) on-line detectors. PHMB complexes, S(PHMB){sub 2}CH{sub 3}S-PHMB, C{sub 2}H{sub 5}S-PHMB and C{sub 3}H{sub 7}S-PHMB, are stable alt least for 12 h at room temperature and for 3 months if stored frozen (-20 deg. C). The best analytical figures of merits in the optimized conditions were obtained by CVGAFS detection, with detection limits (LODc) of 9.7 {mu}g L{sup -1} for H{sub 2}S, 13.7 {mu}g L{sup -1} for CH{sub 3}SH, 17.7 {mu}g L{sup -1} for C{sub 2}H{sub 5}SH and 21.7 {mu}g L{sup -1} for C{sub 3}H{sub 7}SH in the trapping solution in form of RS-PHMB complexes, the relative standard deviation (R.S.D.) ranging between 1.0 and 1.5%, and a linear dynamic range (LDR) between 10 and 9700 {mu}g L{sup -1}. Conventional UV absorbance detectors tuned at 254 nm can be employed as well with comparable R.S.D. and LDR, but with LODc one order of magnitude higher than AFS detector and lower specificity. The sampling procedure followed by LC-DAD-CVGAFS analysis has been validated, as example, for H{sub 2}S determination by a certified gas permeation tube as a source of 3.071 {+-} 0.154 {mu}g min{sup -1} of H{sub 2}S, giving a recovery of 99.8 {+-} 7% and it has been applied to the determination of

  17. An Experimental Investigation of Vibration-Induced Droplet Atomization.

    Science.gov (United States)

    Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari

    1998-11-01

    The atomization process in a mm-scale liquid droplet placed on a vibrating membrane is investigated experimentally. When the wavelength of the Faraday surface waves is smaller than the characteristic dimension of the droplet, the waves grow in amplitude as the excitation amplitude increases and ultimately begin to eject small secondary droplets from the wave crests. The high membrane acceleration needed to attain ejection (typically 300g) is achieved by driving a light-weight membrane near its resonant frequencies (nominally 1000-6000 Hz). The evolution and rate of the droplet-ejection process depend on a coupled system dynamic between the liquid droplet and the vibrating membrane. Depending on the excitation frequency and amplitude, various types of droplet-ejection processes can occur. For example, when step forcing (with prescribed frequency and amplitude) is applied, rapid atomization occurs. This event is triggered along the circumference of the droplet near the contact line by a strong azimuthal instability. In the present experiments, the droplet-ejection process and the resulting spray characteristics are investigated using high-speed video and two-frame particle tracking velocimetry.

  18. Detailed finite element method modeling of evaporating multi-component droplets

    Energy Technology Data Exchange (ETDEWEB)

    Diddens, Christian, E-mail: C.Diddens@tue.nl

    2017-07-01

    The evaporation of sessile multi-component droplets is modeled with an axisymmetic finite element method. The model comprises the coupled processes of mixture evaporation, multi-component flow with composition-dependent fluid properties and thermal effects. Based on representative examples of water–glycerol and water–ethanol droplets, regular and chaotic examples of solutal Marangoni flows are discussed. Furthermore, the relevance of the substrate thickness for the evaporative cooling of volatile binary mixture droplets is pointed out. It is shown how the evaporation of the more volatile component can drastically decrease the interface temperature, so that ambient vapor of the less volatile component condenses on the droplet. Finally, results of this model are compared with corresponding results of a lubrication theory model, showing that the application of lubrication theory can cause considerable errors even for moderate contact angles of 40°. - Graphical abstract:.

  19. Bouncing droplets : A classroom experiment to visualize wave-particle duality on the macroscopic level

    NARCIS (Netherlands)

    Sleutel, Pascal; Dietrich, Erik; Van Der Veen, Jan T.; Van Joolingen, Wouter R.

    2016-01-01

    This study brings a recently discovered macroscopic phenomenon with wave-particle characteristics into the classroom. The system consists of a liquid droplet levitating over a vertically shaken liquid pool. The droplets allow visualization of a wave-particle system in a directly observable way. We

  20. Versatile microfluidic droplets array for bioanalysis.

    Science.gov (United States)

    Hu, Shan-Wen; Xu, Bi-Yi; Ye, Wei-Ke; Xia, Xing-Hua; Chen, Hong-Yuan; Xu, Jing-Juan

    2015-01-14

    We propose a novel method to obtain versatile droplets arrays on a regional hydrophilic chip that is fabricated by PDMS soft lithography and regional plasma treatment. It enables rapid liquid dispensation and droplets array formation just making the chip surface in contact with solution. By combining this chip with a special Christmas Tree structure, the droplets array with concentrations in gradient is generated. It possesses the greatly improved performance of convenience and versatility in bioscreening and biosensing. For example, high throughput condition screening of toxic tests of CdSe quantum dots on HL-60 cells are conducted and cell death rates are successfully counted quickly and efficiently. Furthermore, a rapid biosensing approach for cancer biomarkers carcinoma embryonic antigen (CEA) is developed via magnetic beads (MBs)-based sandwich immunoassay methods.

  1. Dynamic response of vaporizing droplet to pressure oscillation

    Science.gov (United States)

    Yuan, Lei; Shen, Chibing; Zhang, Xinqiao

    2017-02-01

    Combustion instability is a major challenge in the development of the liquid propellant engines, and droplet vaporization is viewed as a potential mechanism for driving instabilities. Based on the previous work, an unsteady droplet heating and vaporization model was developed. The model and numerical method are validated by experimental data available in literature, and then the oscillatory vaporization of n-Heptane droplet exposed to unsteady harmonic nitrogen atmosphere was numerically investigated over a wide range of amplitudes and frequencies. Also, temperature variations inside the droplet were demonstrated under oscillation environments. It was found that the thermal wave is attenuated with significantly reduced wave intensities as it penetrates deep into droplet from the ambient gas. Droplet surface temperature exhibits smaller fluctuation than that of the ambient gas, and it exhibits a time lag with regard to the pressure variation. Furthermore, the mechanism leading to phase lag of vaporization rate with respect to pressure oscillation was unraveled. Results show that this phase lag varies during the droplet lifetime and it is strongly influenced by oscillation frequency, indicating droplet vaporization is only capable of driving combustion instability in some certain frequency domains. Instead, the amplitude of the oscillation does not have very significant effects. It is noteworthy that thermal inertia of the droplet also plays a considerable role in determining the phase lag.

  2. Chasing volatility

    DEFF Research Database (Denmark)

    Caporin, Massimiliano; Rossi, Eduardo; Santucci de Magistris, Paolo

    The realized volatility of financial returns is characterized by persistence and occurrence of unpreditable large increments. To capture those features, we introduce the Multiplicative Error Model with jumps (MEM-J). When a jump component is included in the multiplicative specification, the condi...... models, the introduction of the jump component provides a sensible improvement in the fit, as well as for in-sample and out-of-sample volatility tail forecasts....

  3. Volatility Risk

    OpenAIRE

    Zhiguang Wang

    2009-01-01

    Classical capital asset pricing theory tells us that riskaverse investors would require higher returns to compensate for higher risk on an investment. One type of risk is price (return) risk, which reflects uncertainty in the price level and is measured by the volatility (standard deviation) of asset returns. Volatility itself is also known to be random and hence is perceived as another type of risk. Investors can bear price risk in exchange for a higher return. But are investors willing to p...

  4. Burning of droplets and particles of explosives

    Energy Technology Data Exchange (ETDEWEB)

    Kondrikov, B.N. [Mendeleev University of Chemical Technology, Moscow (Russian Federation)

    1996-12-31

    Small droplets of organic diazides investigated by C.K. Law and coworkers burn in hot gas at 1 atm with rates inversely proportional to the droplet diameter presumably owing to leading chemical reaction proceeds in gas phase. These burning rates are obviously much lower than those obtained by extrapolation of the results measured for the some substances in glass tubes (at pressure of about 10{sup -2}-10{sup -1} atm, and temperature 0-100 deg C) on the burning conditions of the droplets. Kinetic constants estimated using Zel`dovich equation for the burning rate in gas phase and Semenov relation for delay time of the droplets micro-explosion in liquid phase are about the same: E {approx_equal} 0.17 MJ/mol, log{sub 10}k{sub o} {approx_equal} 15(S{sup -1}). In both of the cases the leading chemical reaction is supposed to be of the first order. Landau instability is assumed to be reflected in distortion of the droplets at burning but, as opposed to the liquids pools or columns burning, it is not followed by the burning rate augmentation or (as it is observed sometimes) by the combustion extinguishment. Simple dependence of burning rate of droplets of diazides of the row of normal alkanes on their enthalpy of formation is obtained. Burning rate of ball-shaped particles of polyvinyl-nitrate estimated by A. Merzhanov and collaborators is about the same as measured by the data E.I. Maximov, the member of the same team, for PVN strands, at extrapolation of his results on the suggested preheating temperature of the particle. Probably it is a result of the leading chemical reaction proceeding in condensed phase. (author) 10 refs.

  5. Application of Ultrasound-Assisted Surfactant-Enhanced Emulsification Microextraction Based on Solidification of Floating Organic Droplets and High Performance Liquid Chromatography for Preconcentration and Determination of Alprazolam and Chlordiazepoxide in Human Serum Samples.

    Science.gov (United States)

    Goudarzi, Nasser; Amirnavaee, Monavar; Arab Chamjangali, Mansour; Farsimadan, Sahar

    2017-03-03

    An improved microextraction method is proposed on the basis of ultrasound-assisted surfactant-enhanced emulsification and solidification of a floating organic droplet procedure combined with high performance liquid chromatography for the preconcentration and quantification of alprazolam (ALP) and chlordiazepoxide (CHL) present in a number of human serum samples. Several parameters affecting the extraction efficiency were investigated by the Plackett -Burman factorial design as the screening design. Then the response surface methodology based on the Box-Behnken design was used to optimize the effective parameters in the proposed procedure. The limits of detection for the proposed method were found to be 3.0 and 3.1 ng mL-1 for CHL and ALP, respectively. The calibration curves obtained for the method were linear in the ranges of 10.0-3,500.0 and 10.0-3,000.0 ng mL-1 for CHL and ALP, respectively, with a good determination coefficient. The recoveries of the drugs in the spiked human serum samples were above 93.0%. The developed method was successfully applied to the analysis of these studied drugs in human serum samples. The pre-treatment of the serum samples was performed using acetonitrile to remove the proteins. The proposed procedure was an accurate and reliable one for the determination and preconcentration of these drugs in blood samples.

  6. Speciation of Tl(III and Tl(I in hair samples by dispersive liquid–liquid microextraction based on solidification of floating organic droplet prior to flame atomic absorption spectrometry determination

    Directory of Open Access Journals (Sweden)

    S.Z. Mohammadi

    2016-11-01

    Full Text Available Dispersive liquid–liquid microextraction based on solidification of floating organic droplet was successfully used as a sample preparation method prior to flame atomic absorption determination of trace amounts of Tl(III and Tl(I in hair samples. In the proposed method, 1-(2-pyridylazo-2-naphthol, 1-dodecanol and ethanol were used as chelating agent, extraction and dispersive solvent, respectively. Several factors that may be affected in the extraction process, such as type and volume of extraction and disperser solvents, pH, salting out effect, ionic strength and extraction time were studied. Under the optimal conditions, linearity was maintained between 6.0 and 900.0 ng mL−1 for Tl(III. The relative standard deviation for seven replicate determinations of 0.2 μg mL−1 Tl(III was 2.5%. The detection limit based on 3Sb for Tl(III in the original solution was 2.1 ng mL−1. The proposed method has been applied for the determination of trace amounts of thallium in hair samples and satisfactory results were obtained.

  7. Radial line-scans as representative sampling strategy in dried-droplet laser ablation of liquid samples deposited on pre-cut filter paper disks

    Science.gov (United States)

    Nischkauer, Winfried; Vanhaecke, Frank; Bernacchi, Sébastien; Herwig, Christoph; Limbeck, Andreas

    2014-11-01

    Nebulising liquid samples and using the aerosol thus obtained for further analysis is the standard method in many current analytical techniques, also with inductively coupled plasma (ICP)-based devices. With such a set-up, quantification via external calibration is usually straightforward for samples with aqueous or close-to-aqueous matrix composition. However, there is a variety of more complex samples. Such samples can be found in medical, biological, technological and industrial contexts and can range from body fluids, like blood or urine, to fuel additives or fermentation broths. Specialized nebulizer systems or careful digestion and dilution are required to tackle such demanding sample matrices. One alternative approach is to convert the liquid into a dried solid and to use laser ablation for sample introduction. Up to now, this approach required the application of internal standards or matrix-adjusted calibration due to matrix effects. In this contribution, we show a way to circumvent these matrix effects while using simple external calibration for quantification. The principle of representative sampling that we propose uses radial line-scans across the dried residue. This compensates for centro-symmetric inhomogeneities typically observed in dried spots. The effectiveness of the proposed sampling strategy is exemplified via the determination of phosphorus in biochemical fermentation media. However, the universal viability of the presented measurement protocol is postulated. Detection limits using laser ablation-ICP-optical emission spectrometry were in the order of 40 μg mL- 1 with a reproducibility of 10 % relative standard deviation (n = 4, concentration = 10 times the quantification limit). The reported sensitivity is fit-for-purpose in the biochemical context described here, but could be improved using ICP-mass spectrometry, if future analytical tasks would require it. Trueness of the proposed method was investigated by cross-validation with

  8. Radial line-scans as representative sampling strategy in dried-droplet laser ablation of liquid samples deposited on pre-cut filter paper disks

    Energy Technology Data Exchange (ETDEWEB)

    Nischkauer, Winfried [Institute of Chemical Technologies and Analytics, Vienna University of Technology, Vienna (Austria); Department of Analytical Chemistry, Ghent University, Ghent (Belgium); Vanhaecke, Frank [Department of Analytical Chemistry, Ghent University, Ghent (Belgium); Bernacchi, Sébastien; Herwig, Christoph [Institute of Chemical Engineering, Vienna University of Technology, Vienna (Austria); Limbeck, Andreas, E-mail: Andreas.Limbeck@tuwien.ac.at [Institute of Chemical Technologies and Analytics, Vienna University of Technology, Vienna (Austria)

    2014-11-01

    Nebulising liquid samples and using the aerosol thus obtained for further analysis is the standard method in many current analytical techniques, also with inductively coupled plasma (ICP)-based devices. With such a set-up, quantification via external calibration is usually straightforward for samples with aqueous or close-to-aqueous matrix composition. However, there is a variety of more complex samples. Such samples can be found in medical, biological, technological and industrial contexts and can range from body fluids, like blood or urine, to fuel additives or fermentation broths. Specialized nebulizer systems or careful digestion and dilution are required to tackle such demanding sample matrices. One alternative approach is to convert the liquid into a dried solid and to use laser ablation for sample introduction. Up to now, this approach required the application of internal standards or matrix-adjusted calibration due to matrix effects. In this contribution, we show a way to circumvent these matrix effects while using simple external calibration for quantification. The principle of representative sampling that we propose uses radial line-scans across the dried residue. This compensates for centro-symmetric inhomogeneities typically observed in dried spots. The effectiveness of the proposed sampling strategy is exemplified via the determination of phosphorus in biochemical fermentation media. However, the universal viability of the presented measurement protocol is postulated. Detection limits using laser ablation-ICP-optical emission spectrometry were in the order of 40 μg mL{sup −1} with a reproducibility of 10 % relative standard deviation (n = 4, concentration = 10 times the quantification limit). The reported sensitivity is fit-for-purpose in the biochemical context described here, but could be improved using ICP-mass spectrometry, if future analytical tasks would require it. Trueness of the proposed method was investigated by cross-validation with

  9. 烟草味电子烟油中挥发性成分分析%Analysis of the Volatile Components in Tobacco Flavor Electronic Cigarette Liquids

    Institute of Scientific and Technical Information of China (English)

    王萍娟; 冯守爱; 吴彦; 黄天辉; 刘绍华; 黄东业; 黄世杰; 李小兰; 田兆福

    2014-01-01

    采用二氯甲烷对3家公司的5种电子烟油样品进行萃取,并用气-质联用(GC-MS)法鉴定。通过对 NIST 11谱库的检索,对5种样品中挥发性成分进行了比较分析。结果表明5种样品中的挥发性成分差别较大,共鉴定出40种挥发性成分,依据作用或来源分为雾化剂、烟叶提取物和薄荷提取物三类。其中相对含量水平较高且在5种样品中都检出的成分是丙二醇、烟碱和甘油。3家公司的5种烟草味电子烟油在抽吸品质上有所差异,C 公司样品在抽吸感官感受上相较其他两家公司样品具有明显优势,其中样品 C1又略好于 C2。比较发现,C 公司电子烟油的挥发性成分中含特有的8种多甘醇类化合物,可能是这些物质的协同作用而改善了抽吸品质。%Five kinds of tobacco flavor electronic cigarette liquids origin from three companies were extracted by dichlorometh-ane,40 volatile components were identified by GC-MS.Results indicated that the differences were significant among five kinds of tobacco flavor electronic cigarette liquids.All components were sorted to three groups according their function and origin:fogging agent,tobacco extracts and mint extracts.There were three common compounds with higher content in five samples, including propylene glycol,nicotine and glycerin.There were significant differences in smoking quality of samples from three companies,company C′s showed a notable advantage over the other two companies,sample C1 was slightly better than sample C2.Meanwhile,there were 8 kinds of distinctive multiethylene glycol compound that only existed in samples from company C, but not found in samples from companies A or B.It was probably the combined effect of these substances that improved the sensory quality of tobacco flavor electronic cigarette liquids.

  10. Organic liquids storage tanks volatile organic compounds (VOCS) emissions dispersion and risk assessment in developing countries: the case of Dar-es-Salaam City, Tanzania.

    Science.gov (United States)

    Jackson, Msafiri M

    2006-05-01

    The emission estimation of nine volatile organic compounds (VOCs) from eight organic liquids storage tanks companies in Dar-es-Salaam City Tanzania has been done by using US EPA standard regulatory storage tanks emission model (TANKS 4.9b). Total VOCs atmospheric emission has been established to be 853.20 metric tones/yr. It has been established further that petrol storage tanks contribute about 87% of total VOCs emitted, while tanks for other refined products and crude oil were emitting 10% and 3% of VOCs respectively. Of the eight sources (companies), the highest emission value from a single source was 233,222.94 kg/yr and the lowest single source emission value was 6881.87 kg/yr. The total VOCs emissions estimated for each of the eight sources were found to be higher than the standard level of 40,000 kg/yr per source for minor source according to US EPA except for two sources, which were emitting VOCs below the standard level. The annual emissions per single source for each of the VOCs were found to be below the US EPA emissions standard which is 2,000 kg/yr in all companies except the emission of hexane from company F1 which was slightly higher than the standard. The type of tanks used seems to significantly influence the emission rate. Vertical fixed roof tanks (VFRT) emit a lot more than externally floating roof tanks (EFRT) and internally floating roof tanks (IFRT). The use of IFRT and EFRT should be encouraged especially for storage of petrol which had highest atmospheric emission contribution. Model predicted atmospheric emissions are less than annual losses measured by companies in all the eight sources. It is possible that there are other routes for losses beside atmospheric emissions. It is therefore important that waste reduction efforts in these companies are directed not only to reducing atmospheric emissions, but also prevention of the spillage and leakage of stored liquid and curbing of the frequently reported illegal siphoning of stored products

  11. Waveguides for walking droplets

    CERN Document Server

    Filoux, Boris; Schlagheck, Peter; Vandewalle, Nicolas

    2015-01-01

    When gently placing a droplet onto a vertically vibrated bath, a drop can bounce permanently. Upon increasing the forcing acceleration, the droplet is propelled by the wave it generates and becomes a walker with a well defined speed. We investigate the confinement of a walker in different rectangular cavities, used as waveguides for the Faraday waves emitted by successive droplet bounces. By studying the walker velocities, we discover that 1d confinement is optimal for narrow channels. We also propose an analogy with waveguide models based on the observation of the Faraday instability within the channels.

  12. Precision stacking of nanoparticle laden sessile droplets to control solute deposit morphology

    Science.gov (United States)

    Kabi, Prasenjit; Basu, Saptarshi; Sanyal, Apratim; Chaudhuri, Swetaprovo

    2015-02-01

    Stacking pure solvent droplets on a solid substrate is apparently impossible in the absence of an external force as the second droplet will invariably spill over the first leading to a large wetted area. However, the unique feature that emerges during the drying of a nanoparticle laden droplet is the progressively enlarging thin solid film along the evaporating sessile droplet liquid periphery. This solid interface: the edge of which we shall refer to as the agglomeration front comprises of a thin layer of nanoparticle assembly and can support a carefully dispensed second droplet thereby allowing droplet stacking. It will be shown that the growth of this agglomeration front can also be effectively controlled by the dispensing time difference and the nanoparticle concentration in the two droplets. So far, we are commonly aware of material stacking in solid phase. This letter demonstrates stacking in the liquid phase and control over the thin solid interface growth.

  13. Droplet impact on soft viscoelastic surfaces

    Science.gov (United States)

    Chen, Longquan; Bonaccurso, Elmar; Deng, Peigang; Zhang, Haibo

    2016-12-01

    In this work, we experimentally investigate the impact of water droplets onto soft viscoelastic surfaces with a wide range of impact velocities. Several impact phenomena, which depend on the dynamic interaction between the droplets and viscoelastic surfaces, have been identified and analyzed. At low We , complete rebound is observed when the impact velocity is between a lower and an upper threshold, beyond which droplets are deposited on the surface after impact. At intermediate We , entrapment of an air bubble inside the impinging droplets is found on soft surfaces, while a bubble entrapment on the surface is observed on rigid surfaces. At high We , partial rebound is only identified on the most rigid surface at We ≳92 . Rebounding droplets behave similarly to elastic drops rebounding on superhydrophobic surfaces and the impact process is independent of surface viscoelasticity. Further, surface viscoelasticity does not influence drop spreading after impact—as the surfaces behave like rigid surfaces—but it does affect drop recoiling. Also, the postimpact drop oscillation on soft viscoelastic surfaces is influenced by dynamic wettability of these surfaces. Comparing sessile drop oscillation with a damped harmonic oscillator allows us to conclude that surface viscoelasticity affects the damping coefficient and liquid surface tension sets the spring constant of the system.

  14. Evaluating the capabilities and uncertainties of droplet measurements for the fog droplet spectrometer (FM-100

    Directory of Open Access Journals (Sweden)

    J. K. Spiegel

    2012-05-01

    Full Text Available Droplet size spectra measurements are crucial to obtain a quantitative microphysical description of clouds and fog. However, cloud droplet size measurements are subject to various uncertainties. This work focuses on the evaluation of two key measurement uncertainties arising during cloud droplet size measurements with a conventional droplet size spectrometer (FM-100: first, we addressed the precision with which droplets can be sized with the FM-100 on the basis of Mie theory. We deduced error assumptions and proposed how to correct measured size distributions for these errors by redistributing the measured droplet size distribution using a stochastic approach. Second, based on a literature study, we derived corrections for particle losses during sampling with the FM-100. We applied both corrections to cloud droplet size spectra measured at the high alpine site Jungfraujoch for a temperature range from 0 °C to 11 °C. We show that Mie scattering led to spikes in the droplet size distributions using the default sizing procedure, while the stochastic approach reproduced the ambient size distribution adequately. A detailed analysis of the FM-100 sampling efficiency revealed that particle losses were typically below 10% for droplet diameters up to 10 μm. For larger droplets, particle losses can increase up to 90% for the largest droplets of 50 μm at ambient windspeeds below 4.4 m s−1 and even to >90% for larger angles between the instrument orientation and the wind vector (sampling angle at higher wind speeds. Comparisons of the FM-100 to other reference instruments revealed that the total liquid water content (LWC measured by the FM-100 was more sensitive to particle losses than to re-sizing based on Mie scattering, while the total number concentration was only marginally influenced by particle losses. As a consequence, for further LWC measurements with the FM-100 we strongly recommend to consider (1 the error arising due to Mie

  15. Evaluating the capabilities and uncertainties of droplet measurements for the fog droplet spectrometer (FM-100

    Directory of Open Access Journals (Sweden)

    J. K. Spiegel

    2012-09-01

    Full Text Available Droplet size spectra measurements are crucial to obtain a quantitative microphysical description of clouds and fog. However, cloud droplet size measurements are subject to various uncertainties. This work focuses on the error analysis of two key measurement uncertainties arising during cloud droplet size measurements with a conventional droplet size spectrometer (FM-100: first, we addressed the precision with which droplets can be sized with the FM-100 on the basis of the Mie theory. We deduced error assumptions and proposed a new method on how to correct measured size distributions for these errors by redistributing the measured droplet size distribution using a stochastic approach. Second, based on a literature study, we summarized corrections for particle losses during sampling with the FM-100. We applied both corrections to cloud droplet size spectra measured at the high alpine site Jungfraujoch for a temperature range from 0 °C to 11 °C. We showed that Mie scattering led to spikes in the droplet size distributions using the default sizing procedure, while the new stochastic approach reproduced the ambient size distribution adequately. A detailed analysis of the FM-100 sampling efficiency revealed that particle losses were typically below 10% for droplet diameters up to 10 μm. For larger droplets, particle losses can increase up to 90% for the largest droplets of 50 μm at ambient wind speeds below 4.4 m s−1 and even to >90% for larger angles between the instrument orientation and the wind vector (sampling angle at higher wind speeds. Comparisons of the FM-100 to other reference instruments revealed that the total liquid water content (LWC measured by the FM-100 was more sensitive to particle losses than to re-sizing based on Mie scattering, while the total number concentration was only marginally influenced by particle losses. Consequently, for further LWC measurements with the FM-100 we strongly recommend to consider (1 the

  16. Oil droplet self-transportation on oleophobic surfaces

    Science.gov (United States)

    Li, Juan; Qin, Qi Hang; Shah, Ali; Ras, Robin H. A.; Tian, Xuelin; Jokinen, Ville

    2016-01-01

    Directional liquid transportation is important for a variety of biological processes and technical applications. Although surface engineering through asymmetric chemical modification or geometrical patterning facilitates effective liquid manipulation and enables water droplet self-transportation on synthetic surfaces, self-transportation of oil droplets poses a major challenge because of their low surface tension. We report oil droplet self-transportation on oleophobic surfaces that are microtextured with radial arrays of undercut stripes. More significantly, we observe three modes of oil motion on various sample surfaces, namely, inward transportation, pinned, and outward spreading, which can be switched by the structure parameters, including stripe intersection angle and width. Accompanying theoretical modeling provides an in-depth mechanistic understanding of the structure–droplet motion relationship. Finally, we reveal how to optimize the texture parameters to maximize oil droplet self-transportation capability and demonstrate spontaneous droplet movement for liquids down to a surface tension of 22.4 mN/m. The surfaces presented here open up new avenues for power-free liquid transportation and oil contamination self-removal applications in various analytical and fluidic devices. PMID:27386574

  17. On the pH of Aqueous Attoliter-Volume Droplets

    Science.gov (United States)

    Ramos, Kieran P.; Velpula, Samson S.; Demille, Trevor B.; Pajela, Ryan; Goldner, Lori S.

    Droplets of water dispersed in perfluorinated liquids have widespread use including microfluidics, drug delivery and single-molecule measurements. Perfluorinated liquids are distinctly biocompatible due to their stability, low surface tension, lipophobicity, and hydrophobicity. For this reason, the effect of the perfluorinated surface on droplet contents is usually ignored. However, as the droplet diameter is reduced, we expect that any effect of the water/oil interface on droplet contents will become more obvious. We studied the pH of attoliter-volume aqueous droplets in perfluorinated liquids using pH-sensing fluorescent dyes. Droplets were prepared either by sonication or extrusion from buffer and perfluorinated liquids (FC40 or FC77). A non-ionic surfactant was used to stabilize the droplets. Buffer strength, ionic strength, and pH of the aqueous phase were varied and resulting droplet pH compared to the pH of the buffer from which they were formed. Preliminary data are consistent with a pH in droplets that depends on the concentration of non-ionic surfactant. At low surfactant concentrations, the pH in droplets is distinctly lower than the stock buffer. However, as the concentration of non-ionic surfactant is increased the change in pH decreases. This work was funded by NSF/DBI-1152386.

  18. Determination of hydroxycinnamic acids and volatile phenols in wort and beer by isocratic high-performance liquid chromatography using electrochemical detection.

    Science.gov (United States)

    Vanbeneden, Nele; Delvaux, Filip; Delvaux, Freddy R

    2006-12-15

    The suitability of a simple and rapid isocratic RP-HPLC method with amperometric electrochemical detection for the simultaneous detection and quantification of hydroxycinnamic acids and their corresponding aroma-active volatile phenols in wort and beer is reported. The technique gives good specificity and sensitivity, and can therefore be used for routine monitoring of hydroxycinnamic acids in wort and the development of volatile phenolic flavour compounds during the beer production process and subsequent conservation.

  19. Bioprinting: Functional droplet networks

    Science.gov (United States)

    Durmus, Naside Gozde; Tasoglu, Savas; Demirci, Utkan

    2013-06-01

    Tissue-mimicking printed networks of droplets separated by lipid bilayers that can be functionalized with membrane proteins are able to spontaneously fold and transmit electrical currents along predefined paths.

  20. Butschli Dynamic Droplet System

    DEFF Research Database (Denmark)

    Armstrong, R.; Hanczyc, M.

    2013-01-01

    of a technology with living properties. Otto Butschli first described the system in 1898, when he used alkaline water droplets in olive oil to initiate a saponification reaction. This simple recipe produced structures that moved and exhibited characteristics that resembled, at least superficially, the amoeba. We......Dynamical oil-water systems such as droplets display lifelike properties and may lend themselves to chemical programming to perform useful work, specifically with respect to the built environment. We present Butschli water-in-oil droplets as a model for further investigation into the development...... to the oil phase), qualify this system as an example of living technology. The analysis of the Butschli droplets suggests that a set of conditions may precede the emergence of lifelike characteristics and exemplifies the richness of this rudimentary chemical system, not only for artificial life...