WorldWideScience

Sample records for all-electronic droplet generation

  1. All-electronic droplet generation on-chip with real-time feedback control for EWOD digital microfluidics.

    Science.gov (United States)

    Gong, Jian; Kim, Chang-Jin C J

    2008-06-01

    Electrowetting-on-dielectric (EWOD) actuation enables digital (or droplet) microfluidics where small packets of liquids are manipulated on a two-dimensional surface. Due to its mechanical simplicity and low energy consumption, EWOD holds particular promise for portable systems. To improve volume precision of the droplets, which is desired for quantitative applications such as biochemical assays, existing practices would require near-perfect device fabrication and operation conditions unless the droplets are generated under feedback control by an extra pump setup off of the chip. In this paper, we develop an all-electronic (i.e., no ancillary pumping) real-time feedback control of on-chip droplet generation. A fast voltage modulation, capacitance sensing, and discrete-time PID feedback controller are integrated on the operating electronic board. A significant improvement is obtained in the droplet volume uniformity, compared with an open loop control as well as the previous feedback control employing an external pump. Furthermore, this new capability empowers users to prescribe the droplet volume even below the previously considered minimum, allowing, for example, 1 : x (x < 1) mixing, in comparison to the previously considered n : m mixing (i.e., n and m unit droplets).

  2. ALL-ELECTRONIC DROPLET GENERATION ON-CHIP WITH REAL-TIME FEEDBACK CONTROL FOR EWOD DIGITIAL MICROFLUIDICS

    Science.gov (United States)

    Gong, Jian; Kim, Chang-Jin “CJ”

    2009-01-01

    Electrowetting-on-dielectric (EWOD) actuation enables digital (or droplet) microfluidics where small packets of liquids are manipulated on a two-dimensional surface. Due to its mechanical simplicity and low energy consumption, EWOD holds particular promise for portable systems. To improve volume precision of the droplets, which is desired for quantitative applications such as biochemical assays, existing practices would require near-perfect device fabricaion and operation conditions unless the droplets are generated under feedback control by an extra pump setup off of the chip. In this paper, we develop an all-electronic (i.e., no ancillary pumping) real-time feedback control of on-chip droplet generation. A fast voltage modulation, capacitance sensing, and discrete-time PID feedback controller are integrated on the operating electronic board. A significant improvement is obtained in the droplet volume uniformity, compared with an open loop control as well as the previous feedback control employing an external pump. Furthermore, this new capability empowers users to prescribe the droplet volume even below the previously considered minimum, allowing, for example, 1:x (x < 1) mixing, in comparison to the previously considered n:m mixing (i.e., n and m unit droplets). PMID:18497909

  3. Droplet generation during core reflood

    International Nuclear Information System (INIS)

    Kocamustafaogullari, G.; De Jarlais, G.; Ishii, M.

    1983-01-01

    The process of entrainment and disintegration of liquid droplets by a flow of steam has considerable practical importance in calculating the effectivenes of the emergency core cooling system. Liquid entrainment is also important in determination of the critical heat flux point in general. Thus the analysis of the reflooding phase of a LOCA requires detailed knowledge of droplet size. Droplet size is mainly determined by the droplet generation mechanisms involved. To study these mechanisms, data generated in the PWR FLECHT SEASET series of experiments was analyzed. In addition, an experiment was performed in which the hydrodynamics of low quality post-CHF flow (inverted annular flow) were simulated in an adiabatic test section

  4. Electrohydrodynamic simulation of electrically controlled droplet generation

    International Nuclear Information System (INIS)

    Ouedraogo, Yun; Gjonaj, Erion; Weiland, Thomas; Gersem, Herbert De; Steinhausen, Christoph; Lamanna, Grazia; Weigand, Bernhard

    2017-01-01

    Highlights: • We develop a full electrohydrodynamic simulation approach which allows for the accurate modeling of droplet dynamics under the influence of transient electric fields. The model takes into account conductive, capacitive as well as convective electrical currents in the fluid. • Simulation results are shown for an electrically driven droplet generator using highly conductive acetone droplets and low conductivity pentane droplets, respectively. Excellent agreement with measurement is found. • We investigate the operation characteristic of the droplet generator by computing droplet sizes and detachment times with respect to the applied voltage. • The droplet charging effect is demonstrated for pentane droplets as well as for acetone droplets under long voltage pulses. We show that due to the very different relaxation times, the charging behavior of the two liquids is very different. • We demonstrate that due to this behavior, also the detachment mechanisms for acetone and pentane droplets are different. For low conductivity (pentane) droplets, droplet detachment is only possible after the electric fields are switched off. This is because the effective electric polarization force points upwards, thus, inhibiting the detachment of the droplet from the capillary tip. - Abstract: An electrohydrodynamic model for the simulation of droplet formation, detachment and motion in an electrically driven droplet generator is introduced. The numerical approach is based on the coupled solution of the multiphase flow problem with the charge continuity equation. For the latter, a modified convection-conduction model is applied, taking into account conductive, capacitive as well as convective electrical currents in the fluid. This allows for a proper description of charge relaxation phenomena in the moving fluid. In particular, the charge received by the droplet after detachment is an important parameter influencing the droplet dynamics in the test chamber

  5. Dual-nozzle microfluidic droplet generator

    Science.gov (United States)

    Choi, Ji Wook; Lee, Jong Min; Kim, Tae Hyun; Ha, Jang Ho; Ahrberg, Christian D.; Chung, Bong Geun

    2018-05-01

    The droplet-generating microfluidics has become an important technique for a variety of applications ranging from single cell analysis to nanoparticle synthesis. Although there are a large number of methods for generating and experimenting with droplets on microfluidic devices, the dispensing of droplets from these microfluidic devices is a challenge due to aggregation and merging of droplets at the interface of microfluidic devices. Here, we present a microfluidic dual-nozzle device for the generation and dispensing of uniform-sized droplets. The first nozzle of the microfluidic device is used for the generation of the droplets, while the second nozzle can accelerate the droplets and increase the spacing between them, allowing for facile dispensing of droplets. Computational fluid dynamic simulations were conducted to optimize the design parameters of the microfluidic device.

  6. Performance of droplet generator and droplet collector in liquid droplet radiator under microgravity

    Science.gov (United States)

    Totani, T.; Itami, M.; Nagata, H.; Kudo, I.; Iwasaki, A.; Hosokawa, S.

    2002-06-01

    The Liquid Droplet Radiator (LDR) has an advantage over comparable conventional radiators in terms of the rejected heat power-weight ratio. Therefore, the LDR has attracted attention as an advanced radiator for high-power space systems that will be prerequisite for large space structures. The performance of the LDR under microgravity condition has been studied from the viewpoint of operational space use of the LDR in the future. In this study, the performances of a droplet generator and a droplet collector in the LDR are investigated using drop shafts in Japan: MGLAB and JAMIC. As a result, it is considered that (1) the droplet generator can produce uniform droplet streams in the droplet diameter range from 200 to 280 [µm] and the spacing range from 400 to 950 [µm] under microgravity condition, (2) the droplet collector with the incidence angle of 35 degrees can prevent a uniform droplet stream, in which droplet diameter is 250 [µm] and the velocity is 16 [m/s], from splashing under microgravity condition, whereas splashes may occur at the surface of the droplet collector in the event that a nonuniform droplet stream collides against it.

  7. Microfluidic droplet generator with controlled break-up mechanism

    KAUST Repository

    Gonzalez, David Conchouso

    2017-04-13

    Droplet generation devices and systems that parallelize droplet generation devices are provided. The droplet generation devices can include a symmetric block-and-break system and a tapered droplet generation zone. The symmetric block-and-break system can include a pair of break channels and a pair of bypass channels symmetrically arranged with respect to the dispersed-phase input channel and the output channel. The droplet generation devices can generate monodisperse droplets with a predefined volume over a range of flow rates, pressures, and fluid properties. The droplet generation devices are therefore capable of parallelization to achieve large-capacity droplet generation, e.g. greater than 1 L/hr, with small overall coefficients of variation.

  8. Fast electric control of the droplet size in a microfluidic T-junction droplet generator

    Science.gov (United States)

    Shojaeian, Mostafa; Hardt, Steffen

    2018-05-01

    The effect of DC electric fields on the generation of droplets of water and xanthan gum solutions in sunflower oil at a microfluidic T-junction is experimentally studied. The electric field leads to a significant reduction of the droplet diameter, by about a factor of 2 in the case of water droplets. The droplet size can be tuned by varying the electric field strength, an effect that can be employed to produce a stream of droplets with a tailor-made size sequence. Compared to the case of purely hydrodynamic droplet production without electric fields, the electric control has about the same effect on the droplet size if the electric stress at the liquid/liquid interface is the same as the hydrodynamic stress.

  9. Droplet generating device for droplet-based μTAS using electro-conjugate fluid

    Science.gov (United States)

    Iijima, Y.; Takemura, K.; Edamura, K.

    2017-05-01

    Droplet-based μTAS, which carries out biochemical inspection and synthesis by handling samples as droplets on a single chip, has been attracting attentions in recent years. Although miniaturization of a chip is progressed, there are some problems in miniaturization of a whole system because of the necessity to connect syringe pumps to the chip. Thus, this study aims to realize a novel droplets generating device for droplet-based μTAS using electro-conjugate fluid (ECF). The ECF is a dielectric liquid generating a powerful flow when subjected to high DC voltage. The ECF flow generation allows us to realize a tiny hydraulic power source. Using the ECF flow, we can develop a droplet generating device for droplet-based μTAS by placing minute electrode pairs in flow channels. The device contains two channels filled with the ECF, which are dispersed and continuous phases meeting at a T-junction. When a sample in the dispersed phase is injected by the ECF flow to the continuous phase at T-junction, droplets are generated by shearing force between the two phases. We conducted droplet generating experiment and confirmed that droplets are successfully generated when the flow rate of the continuous phase is between 90 and 360 mm3 s-1, and the flow rate of the dispersed phase is between 10 and 40 mm3 s-1. We also confirmed that the droplet diameter and the droplet production rate are controllable by tuning the applied voltage to the electrode pairs.

  10. Control of the droplet generation by an infrared laser

    Directory of Open Access Journals (Sweden)

    Zhibin Wang

    2018-01-01

    Full Text Available In this work, the control of the droplet generation by a focused infrared (IR laser with a wavelength of 1550 nm was studied, in which the liquid water and the oil with the surfactant of Span 80 were employed as the disperse and continuous phases, respectively. The characteristics of the droplet generation controlled by the laser was explored under various flow rates, laser powers and spot positions and the comparison between the cases with/without the laser was also performed. The results showed that when the laser was focused on the region away from the outlet of the liquid water inflow channel, the droplet shedding was blocked due to the IR laser heating induced thermocapillary flow, leading to the increase of the droplet volume and the cycle time of the droplet generation as compared to the case without the laser. Decreasing the continuous phase flow rate led to the increase of the droplet volume, cycle time of the droplet generation and the volume increase ratio, while increasing the disperse phase flow rate led to the increase of the droplet volume and the decrease of the cycle time and volume increase ratio. For a given flow rate ratio between the continuous and disperse phases, the increase of the flow rates decreased the volume increase ratio. In addition, it is also found that the droplet volume, the cycle time and the volume increase ratio all increased with the laser power. When the laser was focused at the inlet of the downstream channel, the droplet volume, the cycle time and the volume increase ratio were the largest. Moving the laser spot to the downstream or upstream led to the decrease of them. When the laser was focused on the outlet of the liquid water inflow channel, the generated droplet volume and cycle time of the droplet generation were even lower than the case without the laser because of the lowered viscosity. This works provides a comprehensive understanding of the characteristics of the droplet generation controlled

  11. Next generation digital microfluidic technology: Electrophoresis of charged droplets

    Energy Technology Data Exchange (ETDEWEB)

    Im, Do Jin [Pukyong National University, Busan (Korea, Republic of)

    2015-06-15

    Contact charging of a conducting droplet in a dielectric medium is introduced as a novel and useful digital microfluidic technology as well as an interesting scientific phenomenon. The history of this phenomenon, starting from original observations to its interpretations and applications, is presented. The basic principle of the droplet contact charging is also presented. Several fundamental aspects of the droplet contact charging from view points of electrochemistry, surface science, electrocoalescence, and electrohydrodynamics are mentioned. Some promising results for future applications and potential features as a next generation digital microfluidic technology are discussed, especially for 3D organ printing. Finally, implications and significance of the proposed technology for chemical engineering community are discussed.

  12. Development of an imaging system for single droplet characterization using a droplet generator.

    Science.gov (United States)

    Minov, S Vulgarakis; Cointault, F; Vangeyte, J; Pieters, J G; Hijazi, B; Nuyttens, D

    2012-01-01

    The spray droplets generated by agricultural nozzles play an important role in the application accuracy and efficiency of plant protection products. The limitations of the non-imaging techniques and the recent improvements in digital image acquisition and processing increased the interest in using high speed imaging techniques in pesticide spray characterisation. The goal of this study was to develop an imaging technique to evaluate the characteristics of a single spray droplet using a piezoelectric single droplet generator and a high speed imaging technique. Tests were done with different camera settings, lenses, diffusers and light sources. The experiments have shown the necessity for having a good image acquisition and processing system. Image analysis results contributed in selecting the optimal set-up for measuring droplet size and velocity which consisted of a high speed camera with a 6 micros exposure time, a microscope lens at a working distance of 43 cm resulting in a field of view of 1.0 cm x 0.8 cm and a Xenon light source without diffuser used as a backlight. For measuring macro-spray characteristics as the droplet trajectory, the spray angle and the spray shape, a Macro Video Zoom lens at a working distance of 14.3 cm with a bigger field of view of 7.5 cm x 9.5 cm in combination with a halogen spotlight with a diffuser and the high speed camera can be used.

  13. Gas dynamic virtual nozzle for generation of microscopic droplet streams

    Energy Technology Data Exchange (ETDEWEB)

    DePonte, D P; Weierstall, U; Schmidt, K; Warner, J; Starodub, D; Spence, J C H; Doak, R B [Department of Physics, Arizona State University, Tempe, AZ 85287-1504 (United States)], E-mail: dandeponte@gmail.com

    2008-10-07

    As shown by Ganan-Calvo (1998 Phys. Rev. Lett. 80 285-8), a free liquid jet can be compressed in diameter through gas dynamic forces exerted by a coaxially co-flowing gas, obviating the need for a solid nozzle to form a microscopic liquid jet and thereby alleviating the clogging problems that plague conventional droplet sources of small diameter. We describe in this paper a novel form of droplet beam source based on this principle. The source is miniature, robust, dependable, easily fabricated, essentially immune to clogging and eminently suitable for delivery of microscopic liquid droplets, including hydrated biological samples, into vacuum for analysis using vacuum instrumentation. Monodisperse, single-file droplet streams are generated by triggering the device with a piezoelectric actuator.

  14. Micromachined ultrasonic droplet generator based on a liquid horn structure

    Science.gov (United States)

    Meacham, J. M.; Ejimofor, C.; Kumar, S.; Degertekin, F. L.; Fedorov, A. G.

    2004-05-01

    A micromachined ultrasonic droplet generator is developed and demonstrated for drop-on-demand fluid atomization. The droplet generator comprises a bulk ceramic piezoelectric transducer for ultrasound generation, a reservoir for the ejection fluid, and a silicon micromachined liquid horn structure as the nozzle. The nozzles are formed using a simple batch microfabrication process that involves wet etching of (100) silicon in potassium hydroxide solution. Device operation is demonstrated by droplet ejection of water through 30 μm orifices at 1.49 and 2.30 MHz. The finite-element simulations of the acoustic fields in the cavity and electrical impedance of the device are in agreement with the measurements and indicate that the device utilizes cavity resonances in the 1-5 MHz range in conjunction with acoustic wave focusing by the pyramidally shaped nozzles to achieve low power operation.

  15. Microfluidic generation of droplets with a high loading of nanoparticles.

    Science.gov (United States)

    Wan, Jiandi; Shi, Lei; Benson, Bryan; Bruzek, Matthew J; Anthony, John E; Sinko, Patrick J; Prudhomme, Robert K; Stone, Howard A

    2012-09-18

    Microfluidic approaches for controlled generation of colloidal clusters, for example, via encapsulation of colloidal particles in droplets, have been used for the synthesis of functional materials including drug delivery carriers. Most of the studies, however, use a low concentration of an original colloidal suspension (60 wt %) particle concentrations. Three types of microfluidic devices, PDMS flow-focusing, PDMS T-junction, and microcapillary devices, are investigated for direct encapsulation of a high concentration of polystyrene (PS) nanoparticles in droplets. In particular, it is shown that PDMS devices fabricated by soft lithography can generate droplets from a 25 wt % PS suspension, whereas microcapillary devices made from glass capillary tubes are able to produce droplets from a 67 wt % PS nanoparticle suspension. When the PS concentration is between 0.6 and 25 wt %, the size of the droplets is found to change with the oil-to-water flow rate ratio and is independent of the concentration of particles in the initial suspensions. Drop sizes from ~12 to 40 μm are made using flow rate ratios Q(oil)/Q(water) from 20 to 1, respectively, with either of the PDMS devices. However, clogging occurs in PDMS devices at high PS concentrations (>25 wt %) arising from interactions between the PS colloids and the surface of PDMS devices. Glass microcapillary devices, on the other hand, are resistant to clogging and can produce droplets continuously even when the concentration of PS nanoparticles reaches 67 wt %. We believe that our findings indicate useful approaches and guidelines for the controlled generation of emulsions filled with a high loading of nanoparticles, which are useful for drug delivery applications.

  16. Microfluidic generation of droplets with a high loading of nanoparticles

    Science.gov (United States)

    Wan, Jiandi; Shi, Lei; Benson, Bryan; Bruzek, Matthew J.; Anthony, John E.; Sinko, Patrick J.; Prudhomme, Robert K.; Stone, Howard A.

    2012-01-01

    Microfluidic approaches for controlled generation of colloidal clusters, e.g., via encapsulation of colloidal particles in droplets, have been used for the synthesis of functional materials including drug delivery carriers. Most of the studies, however, use a low concentration of an original colloidal suspension ( 60 wt%) particle concentrations. Three types of microfluidic devices, PDMS flow-focusing, PDMS T-junction, and microcapillary devices, are investigated for direct encapsulation of a high concentration of polystyrene (PS) nanoparticles in droplets. In particular, it is shown that PDMS devices fabricated by soft lithography can generate droplets from a 25 wt% PS suspension, whereas microcapillary devices made from glass capillary tubes are able to produce droplets from a 67 wt% PS nanoparticle suspension. When the PS concentration is between 0.6 and 25 wt%, the size of the droplets is found to change with the oil-to-water flow rate ratio and is independent of the concentration of particles in the initial suspensions. Drop sizes from ~12 to 40 μm are made using flow rate ratios Qoil/Qwater from 20 to 1, respectively, with either of the PDMS devices. However, clogging occurs in PDMS devices at high PS concentrations (> 25 wt%) arising from interactions between the PS colloids and the surface of PDMS devices. Glass microcapillary devices, on the other hand, are resistant to clogging and can produce droplets continuously even when the concentration of PS nanoparticles reaches 67 wt%. We believe that our findings indicate useful approaches and guidelines for the controlled generation of emulsions of microparticles that are filled with a high loading of nanoparticles and which are useful for drug delivery applications. PMID:22934976

  17. The precise and accurate production of millimetric water droplets using a superhydrophobic generating apparatus

    Science.gov (United States)

    Wood, Michael J.; Aristizabal, Felipe; Coady, Matthew; Nielson, Kent; Ragogna, Paul J.; Kietzig, Anne-Marie

    2018-02-01

    The production of millimetric liquid droplets has importance in a wide range of applications both in the laboratory and industrially. As such, much effort has been put forth to devise methods to generate these droplets on command in a manner which results in high diameter accuracy and precision, well-defined trajectories followed by successive droplets and low oscillations in droplet shape throughout their descents. None of the currently employed methods of millimetric droplet generation described in the literature adequately addresses all of these desired droplet characteristics. The reported methods invariably involve the cohesive separation of the desired volume of liquid from the bulk supply in the same step that separates the single droplet from the solid generator. We have devised a droplet generation device which separates the desired volume of liquid within a tee-apparatus in a step prior to the generation of the droplet which has yielded both high accuracy and precision of the diameters of the final droplets produced. Further, we have engineered a generating tip with extreme antiwetting properties which has resulted in reduced adhesion forces between the liquid droplet and the solid tip. This has yielded the ability to produce droplets of low mass without necessitating different diameter generating tips or the addition of surfactants to the liquid, well-defined droplet trajectories, and low oscillations in droplet volume. The trajectories and oscillations of the droplets produced have been assessed and presented quantitatively in a manner that has been lacking in the current literature.

  18. "V-junction": a novel structure for high-speed generation of bespoke droplet flows.

    Science.gov (United States)

    Ding, Yun; Casadevall i Solvas, Xavier; deMello, Andrew

    2015-01-21

    We present the use of microfluidic "V-junctions" as a droplet generation strategy that incorporates enhanced performance characteristics when compared to more traditional "T-junction" formats. This includes the ability to generate target-sized droplets from the very first one, efficient switching between multiple input samples, the production of a wide range of droplet sizes (and size gradients) and the facile generation of droplets with residence time gradients. Additionally, the use of V-junction droplet generators enables the suspension and subsequent resumption of droplet flows at times defined by the user. The high degree of operational flexibility allows a wide range of droplet sizes, payloads, spacings and generation frequencies to be obtained, which in turn provides for an enhanced design space for droplet-based experimentation. We show that the V-junction retains the simplicity of operation associated with T-junction formats, whilst offering functionalities normally associated with droplet-on-demand technologies.

  19. Spin transfer torque generated magnetic droplet solitons (invited)

    International Nuclear Information System (INIS)

    Chung, S.; Mohseni, S. M.; Sani, S. R.; Iacocca, E.; Dumas, R. K.; Pogoryelov, Ye.; Anh Nguyen, T. N.; Muduli, P. K.; Eklund, A.; Hoefer, M.; Åkerman, J.

    2014-01-01

    We present recent experimental and numerical advancements in the understanding of spin transfer torque generated magnetic droplet solitons. The experimental work focuses on nano-contact spin torque oscillators (NC-STOs) based on orthogonal (pseudo) spin valves where the Co fixed layer has an easy-plane anisotropy, and the [Co/Ni] free layer has a strong perpendicular magnetic anisotropy. The NC-STO resistance and microwave signal generation are measured simultaneously as a function of drive current and applied perpendicular magnetic field. Both exhibit dramatic transitions at a certain current dependent critical field value, where the microwave frequency drops 10 GHz, modulation sidebands appear, and the resistance exhibits a jump, while the magnetoresistance changes sign. We interpret these observations as the nucleation of a magnetic droplet soliton with a large fraction of its magnetization processing with an angle greater than 90°, i.e., around a direction opposite that of the applied field. This interpretation is corroborated by numerical simulations. When the field is further increased, we find that the droplet eventually collapses under the pressure from the Zeeman energy

  20. Generating high-quality single droplets for optical particle characterization with an easy setup

    Science.gov (United States)

    Xu, Jie; Ge, Baozhen; Meng, Rui

    2018-06-01

    The high-performance and micro-sized single droplet is significant for optical particle characterization. We develop a single-droplet generator (SDG) based on a piezoelectric inkjet technique with advantages of low cost and easy setup. By optimizing the pulse parameters, we achieve various size single droplets. Further investigations reveal that SDG generates single droplets of high quality, demonstrating good sphericity, monodispersity and a stable length of several millimeters.

  1. On-Chip generation of polymer microcapsules through droplet coalescence

    Science.gov (United States)

    Eqbal, Md Danish; Gundabala, Venkat; Gundabala lab Team

    Alginate microbeads and microcapsules have numerous applications in drug delivery, tissue engineering and other biomedical areas due to their unique properties. Microcapsules with liquid core are of particular interest in the area of cell encapsulation. Various methods such as coacervation, emulsification, micro-nozzle, etc. exist for the generation of microbeads and microcapsules. However, these methods have several drawbacks like coagulation, non-uniformity, and polydispersity. In this work we present a method for complete on chip generation of alginate microcapsules (single core as well as double core) through the use of droplet merging technique. For this purpose, a combined Coflow and T-junction configuration is implemented in a hybrid glass-PDMS (Polydimethylsiloxane) microfluidic device. Efficient generation is achieved through precise matching of the generation rates of the coalescing drops. Through this approach, microcapsules with intact single and double (liquid) cores surrounded by alginate shell have been successfully generated and characterized.

  2. Droplet Digital™ PCR Next-Generation Sequencing Library QC Assay.

    Science.gov (United States)

    Heredia, Nicholas J

    2018-01-01

    Digital PCR is a valuable tool to quantify next-generation sequencing (NGS) libraries precisely and accurately. Accurately quantifying NGS libraries enable accurate loading of the libraries on to the sequencer and thus improve sequencing performance by reducing under and overloading error. Accurate quantification also benefits users by enabling uniform loading of indexed/barcoded libraries which in turn greatly improves sequencing uniformity of the indexed/barcoded samples. The advantages gained by employing the Droplet Digital PCR (ddPCR™) library QC assay includes the precise and accurate quantification in addition to size quality assessment, enabling users to QC their sequencing libraries with confidence.

  3. Designed pneumatic valve actuators for controlled droplet breakup and generation.

    Science.gov (United States)

    Choi, Jae-Hoon; Lee, Seung-Kon; Lim, Jong-Min; Yang, Seung-Man; Yi, Gi-Ra

    2010-02-21

    The dynamic breakup of emulsion droplets was demonstrated in double-layered microfluidic devices equipped with designed pneumatic actuators. Uniform emulsion droplets, produced by shearing at a T-junction, were broken into smaller droplets when they passed downstream through constrictions formed by a pneumatically actuated valve in the upper control layer. The valve-assisted droplet breakup was significantly affected by the shape and layout of the control valves on the emulsion flow channel. Interestingly, by actuating the pneumatic valve immediately above the T-junction, the sizes of the emulsion droplets were controlled precisely in a programmatic manner that produced arrays of uniform emulsion droplets in various sizes and dynamic patterns.

  4. Faraday Waves-Based Integrated Ultrasonic Micro-Droplet Generator and Applications

    Directory of Open Access Journals (Sweden)

    Chen S. Tsai

    2017-02-01

    Full Text Available An in-depth review on a new ultrasonic micro-droplet generator which utilizes megahertz (MHz Faraday waves excited by silicon-based multiple Fourier horn ultrasonic nozzles (MFHUNs and its potential applications is presented. The new droplet generator has demonstrated capability for producing micro droplets of controllable size and size distribution and desirable throughput at very low electrical drive power. For comparison, the serious deficiencies of current commercial droplet generators (nebulizers and the other ultrasonic droplet generators explored in recent years are first discussed. The architecture, working principle, simulation, and design of the multiple Fourier horns (MFH in resonance aimed at the amplified longitudinal vibration amplitude on the end face of nozzle tip, and the fabrication and characterization of the nozzles are then described in detail. Subsequently, a linear theory on the temporal instability of Faraday waves on a liquid layer resting on the planar end face of the MFHUN and the detailed experimental verifications are presented. The linear theory serves to elucidate the dynamics of droplet ejection from the free liquid surface and predict the vibration amplitude onset threshold for droplet ejection and the droplet diameters. A battery-run pocket-size clogging-free integrated micro droplet generator realized using the MFHUN is then described. The subsequent report on the successful nebulization of a variety of commercial pulmonary medicines against common diseases and on the experimental antidote solutions to cyanide poisoning using the new droplet generator serves to support its imminent application to inhalation drug delivery.

  5. Faraday Waves-Based Integrated Ultrasonic Micro-Droplet Generator and Applications.

    Science.gov (United States)

    Tsai, Chen S; Mao, Rong W; Tsai, Shirley C; Shahverdi, Kaveh; Zhu, Yun; Lin, Shih K; Hsu, Yu-Hsiang; Boss, Gerry; Brenner, Matt; Mahon, Sari; Smaldone, Gerald C

    2017-01-01

    An in-depth review on a new ultrasonic micro-droplet generator which utilizes megahertz (MHz) Faraday waves excited by silicon-based multiple Fourier horn ultrasonic nozzles (MFHUNs) and its potential applications is presented. The new droplet generator has demonstrated capability for producing micro droplets of controllable size and size distribution and desirable throughput at very low electrical drive power. For comparison, the serious deficiencies of current commercial droplet generators (nebulizers) and the other ultrasonic droplet generators explored in recent years are first discussed. The architecture, working principle, simulation, and design of the multiple Fourier horns (MFH) in resonance aimed at the amplified longitudinal vibration amplitude on the end face of nozzle tip, and the fabrication and characterization of the nozzles are then described in detail. Subsequently, a linear theory on the temporal instability of Faraday waves on a liquid layer resting on the planar end face of the MFHUN and the detailed experimental verifications are presented. The linear theory serves to elucidate the dynamics of droplet ejection from the free liquid surface and predict the vibration amplitude onset threshold for droplet ejection and the droplet diameters. A battery-run pocket-size clogging-free integrated micro droplet generator realized using the MFHUN is then described. The subsequent report on the successful nebulization of a variety of commercial pulmonary medicines against common diseases and on the experimental antidote solutions to cyanide poisoning using the new droplet generator serves to support its imminent application to inhalation drug delivery.

  6. Evaporation and discharge dynamics of highly charged multicomponent droplets generated by electrospray ionization.

    Science.gov (United States)

    Grimm, Ronald L; Beauchamp, J L

    2010-01-28

    We investigate the Rayleigh discharge and evaporation dynamics of highly charged two-component droplets consisting principally of methanol with 2-methoxyethanol, tert-butanol, or m-nitrobenzyl alcohol. A phase Doppler anemometer (PDA) characterizes droplets generated by electrospray ionization (ESI) according to size, velocity, and charge as they move through a uniform electric field within an ion mobility spectrometer (IMS). Repeated field reversals result in droplet "ping-pong" through the PDA. This generates individual droplet histories of solvent evaporation behavior and the dynamics of charge loss to progeny droplets during Rayleigh discharge events. On average, methanol droplets discharge at 127% their Rayleigh limit of charge, q(R), and release 25% of the net charge. Charge loss from methanol/2-methoxyethanol droplets behaves similarly to pure 2-methoxyethanol droplets which release approximately 28% of their net charge. Binary methanol droplets containing up to 50% tert-butanol discharge at a lower percent q(R) than pure methanol and release a greater fraction of their net charge. Mixed 99% methanol/1% m-nitrobenzyl alcohol droplets possess discharge characteristics similar to those of methanol. However, droplets of methanol containing 2% m-nitrobenzyl evaporate down to a fixed size and charge that remains constant with no observable discharges. Quasi-steady-state evaporation models accurately describe observed evaporation phenomena in which methanol/tert-butanol droplets evaporate at a rate similar to that of pure methanol and methanol/2-methoxyethanol droplets evaporate at a rate similar to that of 2-methoxyethanol. We compare these results to previous Rayleigh discharge experiments and discuss the implications for binary solvents in electrospray mass spectrometry (ESI-MS) and field-induced droplet ionization mass spectrometry (FIDI-MS).

  7. Generation of entrained droplets from an imitated disturbance wave and their deposition on the wall

    International Nuclear Information System (INIS)

    Fukano, T.; Inatomi, T.; Matsuzawa, Y.; Yoshida, T.; Uchimichi, N.

    2003-01-01

    In the present experiment, an isokinetic sampling probe technique was used for the measurement of the local droplet flow rate generated from an imitated disturbance wave, which was constructed by injecting liquid through a slit mounted on the bottom wall of a horizontal rectangular duct. The experimental data on the distribution of entrained droplets and their deposition on the duct wall are presented. As a result, it is clarified that the droplet generation is periodic and the distribution of the droplet flow rate is not uniform in both axial and height directions. And accordingly the droplet flow is fundamentally unsteady. Furthermore, the correlation of the entrainment fraction proposed by Paleev-Filippovich is superior to that by others. (orig.)

  8. Study of airborne particles generated by the impact of droplets

    International Nuclear Information System (INIS)

    Motzkus, Ch.

    2007-12-01

    A liquid droplet impinging onto surfaces occurs in many industrial and natural processes. The study of this phenomenon is fundamental in order to determine the potential sources of contamination in the case of scenarios of liquid falls such as dripping. There are very few data in the literature in the case of the impact of millimeter-size droplets. The purpose of our work is to study experimentally the particle emission during the impact of droplets onto a liquid film. Experiments were conducted to study the influence of the velocity and the diameter of the droplets, the height of the liquid film, the surface tension and viscosity of the liquid on the airborne particles. Our results, original, have made it possible to examine the relevance of existing relations, describing the transition between deposition and splash regimes, in order to determine the presence or not of airborne particles. The micro droplets produced, with diameters less than fifty micrometers, are characterised in terms of total mass and size distribution. Our results also show the influence of a combination of several factors on the production of airborne particles. For this reason, it is interesting to use dimensionless numbers, to describe the relationship between the inertial, viscosity and surface tension forces, in order to understand physically the emission of airborne particles. (author)

  9. The suggestion of droplets generation prevention method of CNx coating by ion beam assisted deposition

    International Nuclear Information System (INIS)

    Yagi, Yuji; Tokoroyama, Takayuki; Kousaka, Hiroyuki; Umehara, Noritsugu; Fuwa, Yoshio; Manabe, Kazuyoshi

    2013-01-01

    It has been reported that the carbon nitride (CNx) coating was the super-low friction in which friction coefficient was less than 0.01, and it attracts attention as a high wear resistance and low friction material. When synthesizing a CNx coating with Ion Beam Assisted Deposition (IBAD) method, it was clear that the small asperities called droplets was generated onto the CNx coating surface with increasing thickness, and these droplets generated high friction. Therefore, it is necessary to clarify droplets generation mechanism to reduce droplets. To establish optimal coating conditions for controlling droplets were clarified by paying attention to the energy of an electron beam and the shape of a carbon target. First of all, 300 nm thickness CNx coatings were synthesized with five different filament current densities to clarify the relationship between the filament current density and droplet heights. Secondly, the effect of carbon target shape on droplets generation was confirmed with normal and processed carbon target. Finally, friction coefficient of these surfaces was measured by friction tests under PAO lubrication. (author)

  10. Generation of micro- and nano-droplets containing immiscible solutions in view of optical studies

    Science.gov (United States)

    Nastasa, V.; Karapantsios, T.; Samaras, K.; Dafnopatidou, E.; Pradines, V.; Miller, R.; Pascu, M. L.

    2010-08-01

    The multiple resistances to treatment, developed by bacteria and malignant tumors require finding alternatives to the existing medicines and treatment procedures. One of them is strengthening the effects of cytostatics by improving the delivery method. Such a method is represented by the use of medicines as micro/nano-droplets. This method can reduce the substance consumption by generating drug micro-droplets incorporated in substances that can favour a faster localization, than the classical mode of medicine administration, to the tumor tissues. This paper contains the results concerning the generation and study of micro/nano-droplets and the generation of micro-droplets with an inner core (medicine) and a thin layer covering it. We have measured the surface tension at water/air interface and water/oil interface for a medicine (Vancomycin) and we have generated and measured droplets of medicine containing a layer of Vitamin A by using a double capillary system. The micro/nano-droplets may be produced by mixing of two immiscible solutions in particular conditions (high rotating speed and/or high pressure difference). For this we have studied the generation of emulsions of vitamin A diluted in sunflower oil and a solution of a surfactant Tween 80 in distilled water. The concentration of surfactant in water was typically 4*10-5M. We have studied in a batch stirred tank system the dependence of the droplet dimensions in emulsion, function of the mixing rotation speed, agitation time and components ratio. The droplet diameters were measured using a Malvern light scattering instrument type Mastersizer Hydro 2000M. We have obtained droplets with diameters smaller than 100 nm; the diameters distribution exhibited a peak at 65 nm.

  11. Generation of a strong core-centering force in a submillimeter compound droplet system

    International Nuclear Information System (INIS)

    Lee, M.C.; Feng, I.; Elleman, D.D.; Wang, T.G.; Young, A.T.

    1981-01-01

    By amplitude-modulating the driving voltage of an acoustic levitating apparatus, a strong core-centering force can be generated in a submillimeter compound droplet system suspended by the radiation pressure in a gaseous medium. Depending on the acoustic characteristics of the droplet system, it has been found that the technique can be utilized advantageously in the multiple-layer coating of an inertial-confinement-fusion pellet

  12. Quantitative study of the production rate of droplets in a T-junction microdroplet generator

    Science.gov (United States)

    Fu, Hai; Zeng, Wen; Li, Songjing

    2017-12-01

    In a T-junction microdroplet generator, a mathematical model which can quantify the production rate of droplets is demonstrated. The experiments of droplet formation are performed for different geometries of the T-junction microchannels, and good agreements are shown between the predicted and the measured values of the droplet production rates. From both theoretical and experimental study, the production rate of droplets varies nonlinearly with the flow-rate ratio of the two phases during droplet formation, and by fixing the flow-rate ratio, the production rate of droplets is approximately a linear function of the flow rate of the fluids. In particular, the coefficients of the linear relation are only determined by the geometrical parameters of the T-junction microchannel. As a result, our model can be validated experimentally, and especially for a specific geometry of the T-junction, the production rate of droplets can be precisely predicted and controlled based on the flow rate of the fluids.

  13. Variation in polydispersity in pump- and pressure-driven micro-droplet generators

    Science.gov (United States)

    Zeng, Wen; Jacobi, Ian; Li, Songjing; Stone, Howard A.

    2015-11-01

    The polydispersity of droplets produced in a typical T-junction microfluidic channel under both syringe-pump-driven and pressure-driven flow configurations is measured quantitatively. Both flow systems exhibit high-frequency flow fluctuations that result in an intrinsic polydispersity due to the mechanism of droplet generation. In addition to this intrinsic polydispersity, the syringe-pump-driven device also exhibits low-frequency fluctuations due to mechanical oscillations of the pump, which overwhelm the high-frequency flow fluctuations and produce a signficantly heightened level of polydispersity. The quantitative difference in polydispersity between the two configurations and time-resolved measurements of individual droplet sizes are presented in order to enable the design of better flow control systems for droplet production.

  14. Investigation of Effective Parameters of Drop-on-Demand Droplet Generator

    Directory of Open Access Journals (Sweden)

    Mojtaba Ghodsi

    2017-06-01

    Full Text Available This article presents a design and development of a drop-on-demand (DOD droplets generator. This generator uses molten metal as a liquid and can be used in fabrication, prototyping and any kind of printing with solder droplets. This setup consists of a vibrator solenoid with tunable frequency to produce a semi-spherical shape of molten metal, close to the surface of fabrication. This design also has a nozzle with micro-size orifice, a rod for transmitting force and a heater to melt the metal and keep it in superheat temperature. This DOD can produce droplets in different sizes (less than 550 µm by controlling the vibration frequency of solenoid. This ability together with the accuracy of the droplets in positioning (the error is less than ±20 µm for 1.5 mm amplitude can be used in different applications.  Moreover, in this paper, the impact of initial position of the head and temperature on the average diameter of droplets and the impact of the frequency on the shape of the droplets have been tested and discussed

  15. Ultrasound-driven Megahertz Faraday Waves for Generation of Monodisperse Micro Droplets and Applications

    Science.gov (United States)

    Tsai, Chen S.; Mao, Rong W.; Lin, Shih K.; Tsai, Shirley C.; Boss, Gerry; Brenner, Matt; Smaldone, Gerry; Mahon, Sari; Shahverdi, Kaveh; Zhu, Yun

    Our theoretical findings on instability of Faraday waves at megahertz (MHz) drive frequency and realization of silicon-based MHz multiple-Fourier horn ultrasonic nozzles (MFHUNs) together have enabled generation of mono-disperse droplets of controllable diameter (2.5-6.0 μm) at very low electrical drive power (generator has imminent application to pulmonary (inhalation) drug delivery and other potential applications. Here an update of advances on analysis and design of the MHz MFHUNs and the underlying physical mechanism for generation of mono-disperse micro droplets, and the nebulizer platform for application to detoxification of cyanide poisoning are presented.

  16. 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.

  17. Droplet formation in microfluidic T-junction generators operating in the transitional regime. I. Experimental observations.

    Science.gov (United States)

    Glawdel, Tomasz; Elbuken, Caglar; Ren, Carolyn L

    2012-01-01

    This is the first part of a two-part study on the generation of droplets at a microfluidic T-junction operating in the transition regime where confinement of the droplet creates a large squeezing pressure that influences droplet formation. In this regime, the operation of the T-junction depends on the geometry of the intersection (height-to-width ratio, inlet width ratio), capillary number, flow ratio, and viscosity ratio of the two phases. Here in paper I we presented our experimental observations through the analysis of high-speed videos of the droplet formation process. Various parameters are tracked during the formation cycle such as the shape of the droplet (penetration depth and neck), interdroplet spacing, production rate, and flow of both phases across several T-junction designs and flow conditions. Generally, the formation process is defined by a two-stage model consisting of an initial filling stage followed by a necking stage. However, video evidence suggests the inclusion of a third stage, which we term the lag stage, at the beginning of the formation process that accounts for the retraction of the interface back into the injection channel after detachment. Based on the observations made in this paper, a model is developed to describe the formation process in paper II, which can be used to understand the design and operation of T-junction generators in the transition regime.

  18. Capacitive sensor for continuous monitoring of high-volume droplet microfluidic generation

    KAUST Repository

    Conchouso Gonzalez, David

    2016-12-19

    This paper presents a capacitive sensor for monitoring parallel microfluidic droplet generation. The great electric permittivity difference between common droplet microfluidic fluids such as air, oil and water (ϵoil ≈ 2–3 and ϵwater ≈ 80.4), allows for accurate detection of water in oil concentration changes. Capacitance variations as large as 10 pF between a channel filled with water or dodecane, are used to continuously monitor the output of a parallelization system producing 150 µl/min of water in dodecane emulsions. We also discuss a low cost fabrication process to manufacture these capacitive sensors, which can be integrated to different substrates.

  19. Note: A simple vibrating orifice monodisperse droplet generator using a hard drive actuator arm

    Energy Technology Data Exchange (ETDEWEB)

    Kosch, Sebastian, E-mail: skosch@mie.utoronto.ca, E-mail: ashgriz@mie.utoronto.ca; Ashgriz, Nasser, E-mail: skosch@mie.utoronto.ca, E-mail: ashgriz@mie.utoronto.ca [Department of Industrial and Mechanical Engineering, University of Toronto, Toronto, Ontario M5S 3G8 (Canada)

    2015-04-15

    We propose that the rotary voice coil actuators found in magnetic hard drives are fit to supercede loudspeakers as expedient vibration sources in the laboratory setting. A specific use case is the excitation of a liquid jet to induce controlled breakup into monodisperse droplets. Like loudspeakers, which are typically used for prototyping such devices, hard drive actuators are cheap and ubiquitous, but they are less unwieldy and supply greater amplitudes without producing noise. Frequencies between 0 and 17 kHz, and likely beyond, can be reproduced reliably. No machining tools or amplifying electronics are needed for the construction and operation of the presented droplet generator.

  20. Droplet formation in microfluidic T-junction generators operating in the transitional regime. II. Modeling.

    Science.gov (United States)

    Glawdel, Tomasz; Elbuken, Caglar; Ren, Carolyn L

    2012-01-01

    This is the second part of a two-part study on the generation of droplets at a microfluidic T-junction operating in the transition regime. In the preceding paper [Phys. Rev. E 85, 016322 (2012)], we presented our experimental observations of droplet formation and decomposed the process into three sequential stages defined as the lag, filling, and necking stages. Here we develop a model that describes the performance of microfluidic T-junction generators working in the squeezing to transition regimes where confinement of the droplet dominates the formation process. The model incorporates a detailed geometric description of the drop shape during the formation process combined with a force balance and necking criteria to define the droplet size, production rate, and spacing. The model inherently captures the influence of the intersection geometry, including the channel width ratio and height-to-width ratio, capillary number, and flow ratio, on the performance of the generator. The model is validated by comparing it to speed videos of the formation process for several T-junction geometries across a range of capillary numbers and viscosity ratios.

  1. Theoretic analysis for gravity separation of water droplets in PWR steam generator

    International Nuclear Information System (INIS)

    Liu Shixun

    1995-10-01

    Gravity separation space of water droplets in the PWR steam generator is one of three important separating mechanisms and provides a link between primary (vane) separator and chevron dryer. The design of steam generator should not only have highly efficient and compact separator and dryer, but also an adequate height of gravity separation space. Too short a gravity separation space will not sufficiently separate the moisture and adversely affect the performance of the dryer; too long a gravity separation space will add additional costs for steam generator and nuclear island installation. The droplet entrainment in the process of gravity separation space was theoretically studied and droplet trajectory was analytically modelled. A general expression for the height required by gravity separation, diameter and velocity of those droplets carried over was also obtained. In the analysis, the slip between two phases was considered and a combined term of diameter and viscosity was introduced. The modelling can provide a theoretical basis for determining the height of the gravity separation space. (2 refs., 2 figs.)

  2. Generation of emulsion droplets and micro-bubbles in microfluidic devices

    KAUST Repository

    Zhang, Jiaming

    2016-04-01

    Droplet-based microfluidic devices have become a preferred versatile platform for various fields in physics, chemistry and biology to manipulate small amounts of liquid samples. In addition to microdroplets, microbubbles are also needed for various pro- cesses in the food, healthcare and cosmetic industries. Polydimethylsiloxane (PDMS) soft lithography, the mainstay for fabricating microfluidic devices, usually requires the usage of expensive apparatus and a complex manufacturing procedure. In ad- dition, current methods have the limited capabilities for fabrication of microfluidic devices within three dimensional (3D) structures. Novel methods for fabrication of droplet-based microfluidic devices for the generation microdroplets and microbubbles are therefore of great interest in current research. In this thesis, we have developed several simple, rapid and low-cost methods for fabrication of microfluidic devices, especially for generation of microdroplets and mi- crobubbles. We first report an inexpensive full-glass microfluidic devices with as- sembly of glass capillaries, for generating monodisperse multiple emulsions. Different types of devices have been designed and tested and the experimental results demon- strated the robust capability of preparing monodisperse single, double, triple and multi-component emulsions. Second, we propose a similar full-glass device for generation of microbubbles, but with assembly of a much smaller nozzle of a glass capillary. Highly monodisperse microbubbles with diameter range from 3.5 to 60 microns have been successfully produced, at rates up to 40 kHz. A simple scaling law based on the capillary number and liquid-to-gas flow rate ratio, successfully predicts the bubble size. Recently, the emergent 3D printing technology provides an attractive fabrication technique, due to its simplicity and low cost. A handful of studies have already demonstrated droplet production through 3D-printed microfluidic devices. However, two

  3. High-speed monodisperse droplet generation by ultrasonically controlled micro-jet breakup

    Science.gov (United States)

    Frommhold, Philipp Erhard; Lippert, Alexander; Holsteyns, Frank Ludwig; Mettin, Robert

    2014-04-01

    A liquid jet that is ejected from a nozzle into air will disintegrate into drops via the well-known Plateau-Rayleigh instability within a certain range of Ohnesorge and Reynolds numbers. With the focus on the micrometer scale, we investigate the control of this process by superimposing a suitable ultrasonic signal, which causes the jet to break up into a very precise train of monodisperse droplets. The jet leaves a pressurized container of liquid via a small orifice of about 20 μm diameter. The break-up process and the emerging droplets are recorded via high-speed imaging. An extended parameter study of exit speed and ultrasonic frequency is carried out for deionized water to evaluate the jet's state and the subsequent generation of monodisperse droplets. Maximum exit velocities obtained reach almost 120 m s-1, and frequencies have been applied up to 1.8 MHz. Functionality of the method is confirmed for five additional liquids for moderate jet velocities 38 m s-1. For the uncontrolled jet disintegration, the drop size spectra revealed broad distributions and downstream drop growth by collision, while the acoustic control generated monodisperse droplets with a standard deviation less than 0.5 %. By adjustment of the acoustic excitation frequency, drop diameters could be tuned continuously from about 30 to 50 μm for all exit speeds. Good agreement to former experiments and theoretical approaches is found for the relation of overpressure and jet exit speed, and for the observed stability regions of monodisperse droplet generation in the parameter plane of jet speed and acoustic excitation frequency. Fitting of two free parameters of the general theory to the liquids and nozzles used is found to yield an even higher precision. Furthermore, the high-velocity instability limit of regular jet breakup described by von Ohnesorge has been superseded by more than a factor of two without entering the wind-induced instability regime, and monodisperse droplet generation was

  4. Experimental validation of a simple, low-cost, T-junction droplet generator fabricated through 3D printing

    International Nuclear Information System (INIS)

    Donvito, Lidia; Galluccio, Laura; Lombardo, Alfio; Morabito, Giacomo; Nicolosi, Alfio; Reno, Marco

    2015-01-01

    Three-dimensional printing has been recently proposed and assessed for continuous flow microfluidic devices. In this paper the focus is on a new application of this rapid and low cost method for microfluidic device prototyping: droplets production through a T-junction generator. The feasibility of this new methodology is assessed by means of an experimental study in which the statistical parameters which characterize the production of droplets are analyzed. Furthermore, this study assesses the validity of previous theoretical and experimental results, obtained for a PDMS T-junction droplet generator, also in the case of a 3D printed Acrylonitrile microfluidic chip. Finally, the feasibility of producing monodisperse droplets by analyzing the polydispersity index of the prepared droplets is demonstrated. (paper)

  5. Experimental validation of a simple, low-cost, T-junction droplet generator fabricated through 3D printing

    Science.gov (United States)

    Donvito, Lidia; Galluccio, Laura; Lombardo, Alfio; Morabito, Giacomo; Nicolosi, Alfio; Reno, Marco

    2015-03-01

    Three-dimensional printing has been recently proposed and assessed for continuous flow microfluidic devices. In this paper the focus is on a new application of this rapid and low cost method for microfluidic device prototyping: droplets production through a T-junction generator. The feasibility of this new methodology is assessed by means of an experimental study in which the statistical parameters which characterize the production of droplets are analyzed. Furthermore, this study assesses the validity of previous theoretical and experimental results, obtained for a PDMS T-junction droplet generator, also in the case of a 3D printed Acrylonitrile microfluidic chip. Finally, the feasibility of producing monodisperse droplets by analyzing the polydispersity index of the prepared droplets is demonstrated.

  6. Size Distribution and Dispersion of Droplets Generated by Impingement of Breaking Waves on Oil Slicks

    Science.gov (United States)

    Li, C.; Miller, J.; Wang, J.; Koley, S. S.; Katz, J.

    2017-10-01

    This laboratory experimental study investigates the temporal evolution of the size distribution of subsurface oil droplets generated as breaking waves entrain oil slicks. The measurements are performed for varying wave energy, as well as large variations in oil viscosity and oil-water interfacial tension, the latter achieved by premixing the oil with dispersant. In situ measurements using digital inline holography at two magnifications are applied for measuring the droplet sizes and Particle Image Velocimetry (PIV) for determining the temporal evolution of turbulence after wave breaking. All early (2-10 s) size distributions have two distinct size ranges with different slopes. For low dispersant to oil ratios (DOR), the transition between them could be predicted based on a turbulent Weber (We) number in the 2-4 range, suggesting that turbulence plays an important role. For smaller droplets, all the number size distributions have power of about -2.1, and for larger droplets, the power decreases well below -3. The measured steepening of the size distribution over time is predicted by a simple model involving buoyant rise and turbulence dispersion. Conversely, for DOR 1:100 and 1:25 oils, the diameter of slope transition decreases from ˜1 mm to 46 and 14 µm, respectively, much faster than the We-based prediction, and the size distribution steepens with increasing DOR. Furthermore, the concentration of micron-sized droplets of DOR 1:25 oil increases for the first 10 min after entrainment. These phenomena are presumably caused by the observed formation and breakup oil microthreads associated with tip streaming.

  7. Novel nano-cellulose excipient for generating non-Newtonian droplets for targeted nasal drug delivery.

    Science.gov (United States)

    Young, Paul M; Traini, Daniela; Ong, Hui Xin; Granieri, Angelo; Zhu, Bing; Scalia, Santo; Song, Jie; Spicer, Patrick T

    2017-10-01

    Thickening polymers have been used as excipients in nasal formulations to avoid nasal run-off (nasal drip) post-administration. However, increasing the viscosity of the formulation can have a negative impact on the quality of the aerosols generated. Therefore, the study aims to investigate the use of a novel smart nano-cellulose excipient to generate suitable droplets for nasal drug delivery that simultaneously has only marginally increased viscosity while still reducing nasal drips. Nasal sprays containing nano-cellulose at different concentrations were investigated for the additive's potential as an excipient. The formulations were characterized for their rheological and aerosol properties. This was then compared to conventional nasal spray formulation containing the single-component hydroxyl-propyl methyl cellulose (HPMC) viscosity enhancing excipient. The HPMC-containing nasal formulations behave in a Newtonian manner while the nano-cellulose formulations have a yield stress and shear-thinning properties. At higher excipient concentrations and shear rates, the nano-cellulose solutions have significantly lower viscosities compared to the HPMC solution, resulting in improved droplet formation when actuated through conventional nasal spray. Nano-cellulose materials could potentially be used as a suitable excipient for nasal drug delivery, producing consistent aerosol droplet size, and enhanced residence time within the nasal cavity with reduced run-offs compared to conventional polymer thickeners.

  8. Droplet generation in cross-flow for cost-effective 3D-printed “plug-and-play” microfluidic devices

    KAUST Repository

    Zhang, Jiaming; Aguirre-Pablo, Andres A.; Li, Erqiang; Buttner, Ulrich; Thoroddsen, Sigurdur T

    2016-01-01

    Droplet-based microfluidics is a rapidly growing field of research and involves various applications from chemistry to biology. Droplet generation techniques become the pre-requisite focus. Additive manufacturing (3D printing) technology has

  9. Droplet generation in cross-flow for cost-effective 3D-printed “plug-and-play” microfluidic devices

    KAUST Repository

    Zhang, Jiaming

    2016-08-04

    Droplet-based microfluidics is a rapidly growing field of research and involves various applications from chemistry to biology. Droplet generation techniques become the pre-requisite focus. Additive manufacturing (3D printing) technology has recently been exploited in microfluidics due to its simplicity and low cost. However, only relatively large droplets can be produced in current 3D-printed droplet generators, due to the channel dimension limitations on how fine a channel can be 3D-printed. Here we report a novel design of a 3D-printed

  10. Effects of multiple electronic shells on strong-field multiphoton ionization and high-order harmonic generation of diatomic molecules with arbitrary orientation: An all-electron time-dependent density-functional approach

    International Nuclear Information System (INIS)

    Telnov, Dmitry A.; Chu, S.-I

    2009-01-01

    We present a time-dependent density-functional theory approach with proper long-range potential for an ab initio study of the effect of correlated multielectron responses on the multiphoton ionization (MPI) and high-order harmonic generation (HHG) of diatomic molecules N 2 and F 2 in intense short laser pulse fields with arbitrary molecular orientation. We show that the contributions of inner molecular orbitals to the total MPI probability can be sufficiently large or even dominant over the highest-occupied molecular orbital, depending on detailed electronic structure and symmetry, laser field intensity, and orientation angle. The multielectron effects in HHG are also very important. They are responsible for enhanced HHG at some orientations of the molecular axis. Even strongly bound electrons may have a significant influence on the HHG process.

  11. High-throughput controllable generation of droplet arrays with low consumption

    Science.gov (United States)

    Lin, Yinyin; Wu, Zhongsheng; Gao, Yibo; Wu, Jinbo; Wen, Weijia

    2018-06-01

    We describe a controllable sliding method for fabricating millions of isolated femto- to nanoliter-sized droplets with defined volume, geometry and position and a speed of up to 375 kHz. In this work, without using a superhydrophobic or superoleophobic surface, arrays of droplets are instantly formed on the patterned substrate by sliding a strip of liquid, including water, low-surface-tension organic solvents and solution, along the substrate. To precisely control the volume of the droplets, we systemically investigate the effects of the size of the wettable pattern, the viscosity of the liquid and sliding speed, which were found to vary independently to tune the height and volume of the droplets. Through this method, we successfully fabricated an oriented single metal-organic framework crystal array with control over their XY positioning on the surface, as characterized by microscopy and X-ray diffraction (XRD) techniques.

  12. Fabrication of Glass Microchannel via Glass Imprinting using a Vitreous Carbon Stamp for Flow Focusing Droplet Generator

    Science.gov (United States)

    Refatul Haq, Muhammad; Kim, Youngkyu; Kim, Jun; Oh, Pyoung-hwa; Ju, Jonghyun; Kim, Seok-Min; Lim, Jiseok

    2017-01-01

    This study reports a cost-effective method of replicating glass microfluidic chips using a vitreous carbon (VC) stamp. A glass replica with the required microfluidic microstructures was synthesized without etching. The replication method uses a VC stamp fabricated by combining thermal replication using a furan-based, thermally-curable polymer with carbonization. To test the feasibility of this method, a flow focusing droplet generator with flow-focusing and channel widths of 50 µm and 100 µm, respectively, was successfully fabricated in a soda-lime glass substrate. Deviation between the geometries of the initial shape and the vitreous carbon mold occurred because of shrinkage during the carbonization process, however this effect could be predicted and compensated for. Finally, the monodispersity of the droplets generated by the fabricated microfluidic device was evaluated. PMID:29286341

  13. Fabrication of Glass Microchannel via Glass Imprinting using a Vitreous Carbon Stamp for Flow Focusing Droplet Generator

    Directory of Open Access Journals (Sweden)

    Hyungjun Jang

    2017-12-01

    Full Text Available This study reports a cost-effective method of replicating glass microfluidic chips using a vitreous carbon (VC stamp. A glass replica with the required microfluidic microstructures was synthesized without etching. The replication method uses a VC stamp fabricated by combining thermal replication using a furan-based, thermally-curable polymer with carbonization. To test the feasibility of this method, a flow focusing droplet generator with flow-focusing and channel widths of 50 µm and 100 µm, respectively, was successfully fabricated in a soda-lime glass substrate. Deviation between the geometries of the initial shape and the vitreous carbon mold occurred because of shrinkage during the carbonization process, however this effect could be predicted and compensated for. Finally, the monodispersity of the droplets generated by the fabricated microfluidic device was evaluated.

  14. Investigation of vortex clouds and droplet sizes in heated water spray patterns generated by axisymmetric full cone nozzles.

    Science.gov (United States)

    Naz, M Y; Sulaiman, S A; Ariwahjoedi, B; Ku Shaari, Ku Zilati

    2013-01-01

    The hot water sprays are an important part of many industrial processes, where the detailed knowledge of physical phenomena involved in jet transportation, interaction, secondary breakup, evaporation, and coalescence of droplets is important to reach more efficient processes. The objective of the work was to study the water spray jet breakup dynamics, vortex cloud formation, and droplet size distribution under varying temperature and load pressure. Using a high speed camera, the spray patterns generated by axisymmetric full cone nozzles were visualized as a function water temperature and load pressure. The image analysis confirmed that the spray cone angle and width do not vary significantly with increasing Reynolds and Weber numbers at early injection phases leading to increased macroscopic spray propagation. The formation and decay of semitorus like vortex clouds were also noticed in spray structures generated at near water boiling point temperature. For the nozzle with smallest orifice diameter (1.19 mm), these vortex clouds were very clear at 90°C heating temperature and 1 bar water load pressure. In addition, the sauter mean diameter (SMD) of the spray droplets was also measured by using Phase Doppler Anemometry (PDA) at different locations downstream of the nozzle exit. It was noticed that SMD varies slightly w.r.t. position when measured at room temperature whereas at higher temperature values, it became almost constant at distance of 55 mm downstream of the nozzle exit.

  15. Investigation of Vortex Clouds and Droplet Sizes in Heated Water Spray Patterns Generated by Axisymmetric Full Cone Nozzles

    Directory of Open Access Journals (Sweden)

    M. Y. Naz

    2013-01-01

    Full Text Available The hot water sprays are an important part of many industrial processes, where the detailed knowledge of physical phenomena involved in jet transportation, interaction, secondary breakup, evaporation, and coalescence of droplets is important to reach more efficient processes. The objective of the work was to study the water spray jet breakup dynamics, vortex cloud formation, and droplet size distribution under varying temperature and load pressure. Using a high speed camera, the spray patterns generated by axisymmetric full cone nozzles were visualized as a function water temperature and load pressure. The image analysis confirmed that the spray cone angle and width do not vary significantly with increasing Reynolds and Weber numbers at early injection phases leading to increased macroscopic spray propagation. The formation and decay of semitorus like vortex clouds were also noticed in spray structures generated at near water boiling point temperature. For the nozzle with smallest orifice diameter (1.19 mm, these vortex clouds were very clear at 90°C heating temperature and 1 bar water load pressure. In addition, the sauter mean diameter (SMD of the spray droplets was also measured by using Phase Doppler Anemometry (PDA at different locations downstream of the nozzle exit. It was noticed that SMD varies slightly w.r.t. position when measured at room temperature whereas at higher temperature values, it became almost constant at distance of 55 mm downstream of the nozzle exit.

  16. Droplet formation in microfluidic T-junction generators operating in the transitional regime. III. Dynamic surfactant effects.

    Science.gov (United States)

    Glawdel, Tomasz; Ren, Carolyn L

    2012-08-01

    This study extends our previous work on droplet generation in microfluidic T-junction generators to include dynamic interfacial tension effects created by the presence of surfactants. In Paper I [T. Glawdel, C. Elbuken, and C. L. Ren, Phys. Rev. E 85, 016322 (2012)], we presented experimental findings regarding the formation process in the squeezing-to-transition regime, and in Paper II [T. Glawdel, C. Elbuken, and C. L. Ren, Phys. Rev. E 85, 016323 (2012)] we developed a theoretical model that describes the performance of T-junction generators without surfactants. Here we study dynamic interfacial tension effects for two surfactants, one with a small molecular weight that adsorbs quickly, and the other with a large molecular weight that adsorbs slowly. Using the force balance developed in Paper II we extract the dynamic interfacial tension from high speed videos obtained during experiments. We then develop a theoretical model to predict the dynamic interfacial tension in microfluidic T-junction generators as a function of the surfactant properties, flow conditions, and generator design. This model is then incorporated into the overall model for generator performance to effectively predict the size of droplets produced when surfactants are present.

  17. Three-dimensional parallelization of microfluidic droplet generators for a litre per hour volume production of single emulsions

    KAUST Repository

    Conchouso Gonzalez, David

    2014-01-01

    This paper looks at the design, fabrication and characterization of stackable microfluidic emulsion generators, with coefficients of variation as low as ~6% and with production rates as high as ~1 L h-1. This work reports the highest throughput reported in the literature for a microfluidic device with simultaneous operation of liquid-liquid droplet generators. The device was achieved by stacking several layers of 128 flow-focusing droplet generators, organized in a circular array. These layers are interconnected via through-holes and fed with designated fractal distribution networks. The proposed layers were milled on poly(methylmethacrylate) (PMMA) sheets and the stack was thermo-compression bonded to create a three-dimensional device with a high density of generators and an integrated hydraulic manifold. The effect of stacking multiple layers was studied and the results show that fabrication accuracy has a greater impact on the dispersity of the emulsion than the addition of more layers to the stack. Particle crystallization of drugs was also demonstrated as a possible application of this technology in industry. © 2014 the Partner Organisations.

  18. Synthesis of Macroporous Silica Particles by Continuous Generation of Droplets for Insulating Materials.

    Science.gov (United States)

    Cho, Young-Sang; Lee, Dokyoung

    2018-09-01

    We report on the synthesis of porous silica particles by self-assembly routes in a continuous manner for application to thermal insulators. A continuous process was employed to produce tiny droplets containing precursor materials such as silica and organic templates for self-organization to fabricate particles with well defined pores. A rotating cylinder system or a spray drying process was adopted to form emulsions or aerosol droplets as micro-reactors for self-assembly, and the physical properties including the thermal conductivity of the resulting porous particles were compared between the two methods. The porous particles could be coated as a thick film by solution dripping, and the fluorination treatment using a silane coupling agent was performed to produce superhydrophobic surfaces of insulating layers by a lotus effect.

  19. Aerosols generated by 239PU and 233U droplets burning in air

    International Nuclear Information System (INIS)

    Nelson, L.S.; Raabe, O.G.

    1978-01-01

    The inhalation hazards of radioactive aerosols produced by the explosive disruption and subsequent combustion of metallic plutonium in air are not adequately understood. Results of a study to determine whether uranium can be substituted for plutonium in such a situation in which experiments were performed under identical conditions with laser-ignited, single, freely falling droplets of 239 Pu and 233 U are reported. The total amounts of aerosol produced were studied quantitatively as a function of time during the combustion. Also, particle size distributions of selected aerosols were studied with aerodynamic particle separation techniques. Results showed that the ultimate quantity of aerosols, their final particle size distributions, and depositions as a function of time are not identical mainly because of the different vapor pressures of the metals, and the unlike degrees of violence of the explosions of the droplets

  20. 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.

  1. Experimental characterization of a silicone oil-in-water droplet generator based on a micro T-junction

    Science.gov (United States)

    Rostami, B.; Pulvirenti, B.; Puccetti, G.; Morini, G. L.

    2017-01-01

    This paper deals with the emulsion of two immiscible fluids in a micro T-junction. An opposed-flow micro T-junction obtained by means of square microchannels (with a side of 300 µm) fabricated in a pure fused glass chip has been used for the formation of silicone oil-in-water (O/W) droplets. The experimental results have been obtained by considering both pure deionized water and a mixture of deionized water and surfactant (Tween 20) as the continuous flow. The results shown in this paper highlight that the presence of surfactant, also in very small concentrations, is able to change drastically the flow patterns of the two-phase flow generated by the T-junction. Concentration in weight of Tween 20 between 1 and 2% in the continuous flow is able to promote highly monodispersed emulsions with low polydispersity, especially for low flow rate ratios between the dispersed and continuous phase flows. On the contrary, by avoiding the use of surfactant, a stratified flow is obtained. The experimental results obtained in this work have been used in order to link the depth ratio of the stratified flow and the non-dimensional length of the plugs in droplet-based flow to the flow rate ratio between the dispersed and continuous flows.

  2. Design and characterization of a microreactor for monodisperse catalytic droplet generation at both elevated temperatures and pressures

    NARCIS (Netherlands)

    Vollenbroek, J. C.; Bomer, Johan G.; Van Den Berg, A.; Odijk, M.; Nieuwelink, A. E.; Weckhuysen, Bert M.; Geitenbeek, R. G.; Tiggelaar, R. M.

    2017-01-01

    We report the fabrication and characterization of a microfluidic droplet microreactor with potential use for single catalyst particle diagnostics. The aim is to capture Fluid Catalytic Cracking (FCC) particles in droplets and perform a probe reaction that results in a fluorescent output signal. The

  3. All-electronic suppression of mode hopping noise in diode lasers

    DEFF Research Database (Denmark)

    Bager, L.

    1990-01-01

    A simple all-electronic stabilization scheme is presented for suppression of external-cavity mode-hopping noise in diode lasers. This excess noise is generated when the laser is subjected to optical feedback and may degrade the overall performance of optical systems including sensors. Suppression...

  4. Droplet based microfluidics

    International Nuclear Information System (INIS)

    Seemann, Ralf; Brinkmann, Martin; Pfohl, Thomas; Herminghaus, Stephan

    2012-01-01

    Droplet based microfluidics is a rapidly growing interdisciplinary field of research combining soft matter physics, biochemistry and microsystems engineering. Its applications range from fast analytical systems or the synthesis of advanced materials to protein crystallization and biological assays for living cells. Precise control of droplet volumes and reliable manipulation of individual droplets such as coalescence, mixing of their contents, and sorting in combination with fast analysis tools allow us to perform chemical reactions inside the droplets under defined conditions. In this paper, we will review available drop generation and manipulation techniques. The main focus of this review is not to be comprehensive and explain all techniques in great detail but to identify and shed light on similarities and underlying physical principles. Since geometry and wetting properties of the microfluidic channels are crucial factors for droplet generation, we also briefly describe typical device fabrication methods in droplet based microfluidics. Examples of applications and reaction schemes which rely on the discussed manipulation techniques are also presented, such as the fabrication of special materials and biophysical experiments.

  5. Optical calorimetry in microfluidic droplets.

    Science.gov (United States)

    Chamoun, Jacob; Pattekar, Ashish; Afshinmanesh, Farzaneh; Martini, Joerg; Recht, Michael I

    2018-05-29

    A novel microfluidic calorimeter that measures the enthalpy change of reactions occurring in 100 μm diameter aqueous droplets in fluoropolymer oil has been developed. The aqueous reactants flow into a microfluidic droplet generation chip in separate fluidic channels, limiting contact between the streams until immediately before they form the droplet. The diffusion-driven mixing of reactants is predominantly restricted to within the droplet. The temperature change in droplets due to the heat of reaction is measured optically by recording the reflectance spectra of encapsulated thermochromic liquid crystals (TLC) that are added to one of the reactant streams. As the droplets travel through the channel, the spectral characteristics of the TLC represent the internal temperature, allowing optical measurement with a precision of ≈6 mK. The microfluidic chip and all fluids are temperature controlled, and the reaction heat within droplets raises their temperature until thermal diffusion dissipates the heat into the surrounding oil and chip walls. Position resolved optical temperature measurement of the droplets allows calculation of the heat of reaction by analyzing the droplet temperature profile over time. Channel dimensions, droplet generation rate, droplet size, reactant stream flows and oil flow rate are carefully balanced to provide rapid diffusional mixing of reactants compared to thermal diffusion, while avoiding thermal "quenching" due to contact between the droplets and the chip walls. Compared to conventional microcalorimetry, which has been used in this work to provide reference measurements, this new continuous flow droplet calorimeter has the potential to perform titrations ≈1000-fold faster while using ≈400-fold less reactants per titration.

  6. Millifluidic droplet analyser for microbiology

    NARCIS (Netherlands)

    Baraban, L.; Bertholle, F.; Salverda, M.L.M.; Bremond, N.; Panizza, P.; Baudry, J.; Visser, de J.A.G.M.; Bibette, J.

    2011-01-01

    We present a novel millifluidic droplet analyser (MDA) for precisely monitoring the dynamics of microbial populations over multiple generations in numerous (=103) aqueous emulsion droplets (100 nL). As a first application, we measure the growth rate of a bacterial strain and determine the minimal

  7. Droplet Growth

    Science.gov (United States)

    Marder, Michael Paolo

    When a mixture of two materials, such as aluminum and tin, or alcohol and water, is cooled below a certain temperature, the two components begin to separate. If one component is dilute in the other, it may separate out in the form of small spheres, and these will begin to enlarge, depleting the supersaturated material around them. If the dynamics is sufficiently slow, thermodynamics gives one considerable information about how the droplets grow. Two types of experiment have explored this behavior and given puzzling results. Nucleation experiments measure the rate at which droplets initially appear from a seemingly homogeneous mixture. Near the critical point in binary liquids, experiments conducted in the 1960's and early 1970's showed that nucleation was vastly slower than theory seemed to predict. The resolution of this problem arises by considering in detail the dynamics of growing droplets and comparing it with what experiments actually measure. Here will be presented a more detailed comparison of theory and experiment than has before been completed, obtaining satisfactory agreement with no free parameters needed. A second type of experiment measures droplet size distributions after long times. In the late stage, droplets compete with each other for material, a few growing at the expense of others. A theory first proposed by Lifshitz and Slyozov claims that this distribution, properly scaled, should be universal, and independent of properties of materials. Yet experimental measurements consistently find distributions that are more broad and squat than the theory would predict. Satisfactory agreement with experiment can be achieved by considering two points. First, one must study the complete time development of droplet size distributions, to understand when the asymptotic regime obtains. Second, droplet size distributions are spread by correlations between droplets. If one finds a small droplet, it is small because large droplets nearby are competing with it

  8. Heat transfer in the over-crisis region in a steam-generating channel with steam-droplet flow

    International Nuclear Information System (INIS)

    Nigmatulin, B.I.; Kukharenko, V.N.

    1991-01-01

    Statement and results of numerical solution of the problem on heat transfer in the over-crisis region under stationary and nonstationary conditions are studied. Two-temperature model, accounting for influence of phase slipping on heat exchange between steam and droplets and direct heat interaction with heated surface is used for describing steam-droplet flow. Comparison is made of calculational results and experimental data published in the literature on heated surface temperature within broad range of parameters: pressure - p=0.3-18.5 MPa; specific mass flow rate of the mixture - G=30-5000 kg/m 2 xs; specific heat flows - q=0.02-3 MW/m 2 and tube diameter - D=4-20 mm

  9. Liquid droplet radiator technology issues

    International Nuclear Information System (INIS)

    Mattick, A.T.; Hertzberg, A.

    1985-01-01

    The operation of the liquid droplet radiator (LDR) is analyzed to establish design constraints for the LDR components and to predict the performance of an integrated LDR system. The design constraints largely result from mass loss considerations: fluid choice is governed by evaporation loss; droplet generation techniques must be capable of precise aiming of >10 5 droplet streams; and collection losses must be less than 1 droplet in 10 7 . Concepts for droplet generation and collection components are discussed and incorporated into a mass model for an LDR system. This model predicts that LDR's using lithium, Dow 705 silicone fluid, or NaK may be several times lighter than heat pipe radiators. 13 refs

  10. Label-free all-electronic biosensing in microfluidic systems

    Science.gov (United States)

    Stanton, Michael A.

    Label-free, all-electronic detection techniques offer great promise for advancements in medical and biological analysis. Electrical sensing can be used to measure both interfacial and bulk impedance changes in conducting solutions. Electronic sensors produced using standard microfabrication processes are easily integrated into microfluidic systems. Combined with the sensitivity of radiofrequency electrical measurements, this approach offers significant advantages over competing biological sensing methods. Scalable fabrication methods also provide a means of bypassing the prohibitive costs and infrastructure associated with current technologies. We describe the design, development and use of a radiofrequency reflectometer integrated into a microfluidic system towards the specific detection of biologically relevant materials. We developed a detection protocol based on impedimetric changes caused by the binding of antibody/antigen pairs to the sensing region. Here we report the surface chemistry that forms the necessary capture mechanism. Gold-thiol binding was utilized to create an ordered alkane monolayer on the sensor surface. Exposed functional groups target the N-terminus, affixing a protein to the monolayer. The general applicability of this method lends itself to a wide variety of proteins. To demonstrate specificity, commercially available mouse anti- Streptococcus Pneumoniae monoclonal antibody was used to target the full-length recombinant pneumococcal surface protein A, type 2 strain D39 expressed by Streptococcus Pneumoniae. We demonstrate the RF response of the sensor to both the presence of the surface decoration and bound SPn cells in a 1x phosphate buffered saline solution. The combined microfluidic sensor represents a powerful platform for the analysis and detection of cells and biomolecules.

  11. [Micro-droplet characterization and its application for amino acid detection in droplet microfluidic system].

    Science.gov (United States)

    Yuan, Huiling; Dong, Libing; Tu, Ran; Du, Wenbin; Ji, Shiru; Wang, Qinhong

    2014-01-01

    Recently, the droplet microfluidic system attracts interests due to its high throughput and low cost to detect and screen. The picoliter micro-droplets from droplet microfluidics are uniform with respect to the size and shape, and could be used as monodispensed micro-reactors for encapsulation and detection of single cell or its metabolites. Therefore, it is indispensable to characterize micro-droplet and its application from droplet microfluidic system. We first constructed the custom-designed droplet microfluidic system for generating micro-droplets, and then used the micro-droplets to encapsulate important amino acids such as glutamic acid, phenylalanine, tryptophan or tyrosine to test the droplets' properties, including the stability, diffusivity and bio-compatibility for investigating its application for amino acid detection and sorting. The custom-designed droplet microfluidic system could generate the uniformed micro-droplets with a controllable size between 20 to 50 microm. The micro-droplets could be stable for more than 20 h without cross-contamination or fusion each other. The throughput of detection and sorting of the system is about 600 micro-droplets per minute. This study provides a high-throughput platform for the analysis and screening of amino acid-producing microorganisms.

  12. 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.

  13. Membrane fusion between baculovirus budded virus-enveloped particles and giant liposomes generated using a droplet-transfer method for the incorporation of recombinant membrane proteins.

    Science.gov (United States)

    Nishigami, Misako; Mori, Takaaki; Tomita, Masahiro; Takiguchi, Kingo; Tsumoto, Kanta

    2017-07-01

    Giant proteoliposomes are generally useful as artificial cell membranes in biochemical and biophysical studies, and various procedures for their preparation have been reported. We present here a novel preparation technique that involves the combination of i) cell-sized lipid vesicles (giant unilamellar vesicles, GUVs) that are generated using the droplet-transfer method, where lipid monolayer-coated water-in-oil microemulsion droplets interact with oil/water interfaces to form enclosed bilayer vesicles, and ii) budded viruses (BVs) of baculovirus (Autographa californica nucleopolyhedrovirus) that express recombinant transmembrane proteins on their envelopes. GP64, a fusogenic glycoprotein on viral envelopes, is activated by weak acids and is thought to cause membrane fusion with liposomes. Using confocal laser scanning microscopy (CLSM), we observed that the single giant liposomes fused with octadecyl rhodamine B chloride (R18)-labeled wild-type BV envelopes with moderate leakage of entrapped soluble compounds (calcein), and the fusion profile depended on the pH of the exterior solution: membrane fusion occurred at pH ∼4-5. We further demonstrated that recombinant transmembrane proteins, a red fluorescent protein (RFP)-tagged GPCR (corticotropin-releasing hormone receptor 1, CRHR1) and envelope protein GP64 could be partly incorporated into membranes of the individual giant liposomes with a reduction of the pH value, though there were also some immobile fluorescent spots observed on their circumferences. This combination may be useful for preparing giant proteoliposomes containing the desired membranes and inner phases. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. The dynamics of milk droplet-droplet collisions

    Science.gov (United States)

    Finotello, Giulia; Kooiman, Roeland F.; Padding, Johan T.; Buist, Kay A.; Jongsma, Alfred; Innings, Fredrik; Kuipers, J. A. M.

    2018-01-01

    Spray drying is an important industrial process to produce powdered milk, in which concentrated milk is atomized into small droplets and dried with hot gas. The characteristics of the produced milk powder are largely affected by agglomeration, combination of dry and partially dry particles, which in turn depends on the outcome of a collision between droplets. The high total solids (TS) content and the presence of milk proteins cause a relatively high viscosity of the fed milk concentrates, which is expected to largely influence the collision outcomes of drops inside the spray. It is therefore of paramount importance to predict and control the outcomes of binary droplet collisions. Only a few studies report on droplet collisions of high viscous liquids and no work is available on droplet collisions of milk concentrates. The current study therefore aims to obtain insight into the effect of viscosity on the outcome of binary collisions between droplets of milk concentrates. To cover a wide range of viscosity values, three milk concentrates (20, 30 and 46% TS content) are investigated. An experimental set-up is used to generate two colliding droplet streams with consistent droplet size and spacing. A high-speed camera is used to record the trajectories of the droplets. The recordings are processed by Droplet Image Analysis in MATLAB to determine the relative velocities and the impact geometries for each individual collision. The collision outcomes are presented in a regime map dependent on the dimensionless impact parameter and Weber ( We) number. The Ohnesorge ( Oh) number is introduced to describe the effect of viscosity from one liquid to another and is maintained constant for each regime map by using a constant droplet diameter ( d ˜ 700 μ m). In this work, a phenomenological model is proposed to describe the boundaries demarcating the coalescence-separation regimes. The collision dynamics and outcome of milk concentrates are compared with aqueous glycerol

  15. Janus droplet as a catalytic micromotor

    Science.gov (United States)

    Shklyaev, Sergey

    2015-06-01

    Self-propulsion of a Janus droplet in a solution of surfactant, which reacts on a half of a drop surface, is studied theoretically. The droplet acts as a catalytic motor creating a concentration gradient, which generates its surface-tension-driven motion; the self-propulsion speed is rather high, 60 μ \\text{m/s} and more. This catalytic motor has several advantages over other micromotors: simple manufacturing, easily attained neutral buoyancy. In contrast to a single-fluid droplet, which demonstrates a self-propulsion as a result of symmetry breaking instability, for the Janus one no stability threshold exists; hence, the droplet radius can be scaled down to micrometers.

  16. Water Entry by a Train of Droplets

    Science.gov (United States)

    Ohl, Claus-Dieter; Huang, Xin; Chan, Chon U.; Frommhold, Philipp Erhard; Lippert, Alexander

    2014-11-01

    The impact of single droplets on a deep pool is a well-studied phenomenon which reveals reach fluid mechanics. Lesser studied is the impact of a train of droplet and the accompanied formation of largely elongated cavities, in particular for well controlled droplets. The droplets with diameters of 20-40 μm and velocities of approx. 20 m/s are generated with a piezo-actuated nozzle at rates of 200-300 kHz. Individual droplets are selected by electric charging and deflection and the impact is visualized with stroboscopic photography and high-speed videos. We study in particular the formation and shape of the cavity as by varying the number of droplets from one to 64. The cavities reach centimetres in length with lateral diameters of the order of 100 of micrometres.

  17. A new technique for the deposition of standard solutions in total reflection X-ray fluorescence spectrometry (TXRF) using pico-droplets generated by inkjet printers and its applicability for aerosol analysis with SR-TXRF

    International Nuclear Information System (INIS)

    Fittschen, U.E.A.; Hauschild, S.; Amberger, M.A.; Lammel, G.; Streli, C.; Foerster, S.; Wobrauschek, P.; Jokubonis, C.; Pepponi, G.; Falkenberg, G.; Broekaert, J.A.C.

    2006-01-01

    A new technique for the deposition of standard solutions on particulate aerosol samples using pico-droplets for elemental determinations with total reflection X-ray fluorescence spectrometry (TXRF) is described. It enables short analysis times without influencing the sample structure and avoids time consuming scanning of the sample with the exciting beam in SR-TXRF analysis. Droplets of picoliter volume (∼ 5-130 pL) were generated with commercially available and slightly modified inkjet printers operated with popular image processing software. The size of the dried droplets on surfaces of different polarity namely silicone coated and untreated quartz reflectors, was determined for five different printer types and ten different cartridge types. The results show that droplets generated by inkjet printers are between 50 and 200 μm in diameter (corresponding to volumes of 5 to 130 pL) depending on the cartridge type, which is smaller than the width of the synchrotron beam used in the experiments (< 1 mm at an energy of 17 keV at the beamline L at HASYLAB, Hamburg). The precision of the printing of a certain amount of a single element standard solution was found to be comparable to aliquoting with micropipettes in TXRF, where for 2.5 ng of cobalt relative standard deviations of 12% are found. However, it could be shown that the printing of simple patterns is possible, which is important when structured samples have to be analysed

  18. Influence of film dimensions on film droplet formation.

    Science.gov (United States)

    Holmgren, Helene; Ljungström, Evert

    2012-02-01

    Aerosol particles may be generated from rupturing liquid films through a droplet formation mechanism. The present work was undertaken with the aim to throw some light on the influence of film dimensions on droplet formation with possible consequences for exhaled breath aerosol formation. The film droplet formation process was mimicked by using a purpose-built device, where fluid films were spanned across holes of known diameters. As the films burst, droplets were formed and the number and size distributions of the resulting droplets were determined. No general relation could be found between hole diameter and the number of droplets generated per unit surface area of fluid film. Averaged over all film sizes, a higher surface tension yielded higher concentrations of droplets. Surface tension did not influence the resulting droplet diameter, but it was found that smaller films generated smaller droplets. This study shows that small fluid films generate droplets as efficiently as large films, and that droplets may well be generated from films with diameters below 1 mm. This has implications for the formation of film droplets from reopening of closed airways because human terminal bronchioles are of similar dimensions. Thus, the results provide support for the earlier proposed mechanism where reopening of closed airways is one origin of exhaled particles.

  19. Quantitation of next generation sequencing library preparation protocol efficiencies using droplet digital PCR assays - a systematic comparison of DNA library preparation kits for Illumina sequencing.

    Science.gov (United States)

    Aigrain, Louise; Gu, Yong; Quail, Michael A

    2016-06-13

    The emergence of next-generation sequencing (NGS) technologies in the past decade has allowed the democratization of DNA sequencing both in terms of price per sequenced bases and ease to produce DNA libraries. When it comes to preparing DNA sequencing libraries for Illumina, the current market leader, a plethora of kits are available and it can be difficult for the users to determine which kit is the most appropriate and efficient for their applications; the main concerns being not only cost but also minimal bias, yield and time efficiency. We compared 9 commercially available library preparation kits in a systematic manner using the same DNA sample by probing the amount of DNA remaining after each protocol steps using a new droplet digital PCR (ddPCR) assay. This method allows the precise quantification of fragments bearing either adaptors or P5/P7 sequences on both ends just after ligation or PCR enrichment. We also investigated the potential influence of DNA input and DNA fragment size on the final library preparation efficiency. The overall library preparations efficiencies of the libraries show important variations between the different kits with the ones combining several steps into a single one exhibiting some final yields 4 to 7 times higher than the other kits. Detailed ddPCR data also reveal that the adaptor ligation yield itself varies by more than a factor of 10 between kits, certain ligation efficiencies being so low that it could impair the original library complexity and impoverish the sequencing results. When a PCR enrichment step is necessary, lower adaptor-ligated DNA inputs leads to greater amplification yields, hiding the latent disparity between kits. We describe a ddPCR assay that allows us to probe the efficiency of the most critical step in the library preparation, ligation, and to draw conclusion on which kits is more likely to preserve the sample heterogeneity and reduce the need of amplification.

  20. Printed droplet microfluidics for on demand dispensing of picoliter droplets and cells.

    Science.gov (United States)

    Cole, Russell H; Tang, Shi-Yang; Siltanen, Christian A; Shahi, Payam; Zhang, Jesse Q; Poust, Sean; Gartner, Zev J; Abate, Adam R

    2017-08-15

    Although the elementary unit of biology is the cell, high-throughput methods for the microscale manipulation of cells and reagents are limited. The existing options either are slow, lack single-cell specificity, or use fluid volumes out of scale with those of cells. Here we present printed droplet microfluidics, a technology to dispense picoliter droplets and cells with deterministic control. The core technology is a fluorescence-activated droplet sorter coupled to a specialized substrate that together act as a picoliter droplet and single-cell printer, enabling high-throughput generation of intricate arrays of droplets, cells, and microparticles. Printed droplet microfluidics provides a programmable and robust technology to construct arrays of defined cell and reagent combinations and to integrate multiple measurement modalities together in a single assay.

  1. Freezing of Water Droplet due to Evaporation

    Science.gov (United States)

    Satoh, Isao; Fushinobu, Kazuyoshi; Hashimoto, Yu

    In this study, the feasibility of cooling/freezing of phase change.. materials(PCMs) due to evaporation for cold storage systems was experimentally examined. A pure water was used as the test PCM, since the latent heat due to evaporation of water is about 7 times larger than that due to freezing. A water droplet, the diameter of which was 1-4 mm, was suspended in a test cell by a fine metal wire (O. D.= 100μm),and the cell was suddenly evacuated up to the pressure lower than the triple-point pressure of water, so as to enhance the evaporation from the water surface. Temperature of the droplet was measured by a thermocouple, and the cooling/freezing behavior and the temperature profile of the droplet surface were captured by using a video camera and an IR thermo-camera, respectively. The obtained results showed that the water droplet in the evacuated cell is effectively cooled by the evaporation of water itself, and is frozen within a few seconds through remarkable supercooling state. When the initial temperature of the droplet is slightly higher than the room temperature, boiling phenomena occur in the droplet simultaneously with the freezing due to evaporation. Under such conditions, it was shown that the degree of supercooling of the droplet is reduced by the bubbles generated in the droplet.

  2. Downstream pressure and elastic wall reflection of droplet flow in a T-junction microchannel

    Science.gov (United States)

    Pang, Yan; Liu, Zhaomiao; Zhao, Fuwang

    2016-08-01

    This paper discusses pressure variation on a wall during the process of liquid flow and droplet formation in a T-junction microchannel. Relevant pressure in the channel, deformation of the elastic wall, and responses of the droplet generation are analyzed using a numerical method. The pressure difference between the continuous and dispersed phases can indicate the droplet-generation period. The pressure along the channel of the droplet flow is affected by the position of droplets, droplet-generation period, and droplet escape from the outlet. The varying pressures along the channel cause a nonuniform deformation of the wall when they are elastic. The deformation is a vibration and has the same period as the droplet generation arising from the process of droplet formation.

  3. Formation of superhydrophobic/superhydrophilic patterns by combination of nanostructure-imprinted perfluoropolymer and nanostructured silicon oxide for biological droplet generation

    Science.gov (United States)

    Kobayashi, Taizo; Shimizu, Kazunori; Kaizuma, Yoshihiro; Konishi, Satoshi

    2011-03-01

    In this letter, we report a technology for fabricating superhydrophobic/superhydrophilic patterns using a combination of a nanostructure-imprinted perfluoropolymer and nanostructured silicon oxide. In our previous study, we used a combination of hydrophobic and superhydrophilic materials. However, it was difficult to split low-surface-tension liquids such as biological liquids into droplets solely using hydrophobic/hydrophilic patterns. In this study, the contact angle of the hydrophobic region was enhanced from 109.3° to 155.6° by performing nanostructure imprinting on a damage-reduced perfluoropolymer. The developed superhydrophobic/superhydrophilic patterns allowed the splitting of even those media that contained fetal bovine serum into droplets of a desired shape.

  4. Predicting Pt-195 NMR chemical shift using new relativistic all-electron basis set

    NARCIS (Netherlands)

    Paschoal, D.; Fonseca Guerra, C.; de Oliveira, M.A.L.; Ramalho, T.C.; Dos Santos, H.F.

    2016-01-01

    Predicting NMR properties is a valuable tool to assist the experimentalists in the characterization of molecular structure. For heavy metals, such as Pt-195, only a few computational protocols are available. In the present contribution, all-electron Gaussian basis sets, suitable to calculate the

  5. All electron ab initio investigations of the electronic states of the FeC molecule

    DEFF Research Database (Denmark)

    Shim, Irene; Gingerich, Karl A.

    1999-01-01

    The low lying electronic states of the molecule FeC have been investigated by performing all electron ab initio multi-configuration self-consistent-field (CASSCF) and multi reference configuration interaction (MRCI) calculations. The relativistic corrections for the one electron Darwin contact term...

  6. All Electron ab initio Investigations of the Electronic States of the MoN Molecule

    DEFF Research Database (Denmark)

    Shim, Irene; Gingerich, Karl A.

    1999-01-01

    The low lying electronic states of the molecule MoN have been investigated by performing all electron ab initio multi-configuration self-consistent-field (CASSCF) calculations. The relativistic corrections for the one electron Darwin contact term and the relativistic mass-velocity correction have...

  7. All-electron ab initio investigations of the electronic states of the NiC molecule

    DEFF Research Database (Denmark)

    Shim, Irene; Gingerich, Karl. A.

    1999-01-01

    The low-lying electronic states of NiC are investigated by all-electron ab initio multi-configuration self-consistent-field (CASSCF) calculations including relativistic corrections. The electronic structure of NiC is interpreted as perturbed antiferromagnetic couplings of the localized angular...

  8. Current-voltage curves for molecular junctions computed using all-electron basis sets

    International Nuclear Information System (INIS)

    Bauschlicher, Charles W.; Lawson, John W.

    2006-01-01

    We present current-voltage (I-V) curves computed using all-electron basis sets on the conducting molecule. The all-electron results are very similar to previous results obtained using effective core potentials (ECP). A hybrid integration scheme is used that keeps the all-electron calculations cost competitive with respect to the ECP calculations. By neglecting the coupling of states to the contacts below a fixed energy cutoff, the density matrix for the core electrons can be evaluated analytically. The full density matrix is formed by adding this core contribution to the valence part that is evaluated numerically. Expanding the definition of the core in the all-electron calculations significantly reduces the computational effort and, up to biases of about 2 V, the results are very similar to those obtained using more rigorous approaches. The convergence of the I-V curves and transmission coefficients with respect to basis set is discussed. The addition of diffuse functions is critical in approaching basis set completeness

  9. Mass spectrometry of acoustically levitated droplets.

    Science.gov (United States)

    Westphall, Michael S; Jorabchi, Kaveh; Smith, Lloyd M

    2008-08-01

    Containerless sample handling techniques such as acoustic levitation offer potential advantages for mass spectrometry, by eliminating surfaces where undesired adsorption/desorption processes can occur. In addition, they provide a unique opportunity to study fundamental aspects of the ionization process as well as phenomena occurring at the air-droplet interface. Realizing these advantages is contingent, however, upon being able to effectively interface levitated droplets with a mass spectrometer, a challenging task that is addressed in this report. We have employed a newly developed charge and matrix-assisted laser desorption/ionization (CALDI) technique to obtain mass spectra from a 5-microL acoustically levitated droplet containing peptides and an ionic matrix. A four-ring electrostatic lens is used in conjunction with a corona needle to produce bursts of corona ions and to direct those ions toward the droplet, resulting in droplet charging. Analyte ions are produced from the droplet by a 337-nm laser pulse and detected by an atmospheric sampling mass spectrometer. The ion generation and extraction cycle is repeated at 20 Hz, the maximum operating frequency of the laser employed. It is shown in delayed ion extraction experiments that both positive and negative ions are produced, behavior similar to that observed for atmospheric pressure matrix-assisted laser absorption/ionization. No ion signal is observed in the absence of droplet charging. It is likely, although not yet proven, that the role of the droplet charging is to increase the strength of the electric field at the surface of the droplet, reducing charge recombination after ion desorption.

  10. 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...

  11. 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

  12. Response of Superheated Droplet Detector (SDD) and Bubble Detector (BD) to interrupted irradiations

    Energy Technology Data Exchange (ETDEWEB)

    Mondal, Prasanna Kumar, E-mail: prasanna_ind_82@yahoo.com; Sarkar, Rupa, E-mail: sarkar_rupa2003@yahoo.com; Chatterjee, Barun Kumar, E-mail: barun_k_chatterjee@yahoo.com

    2017-06-11

    Superheated droplet detectors (SDD) and bubble detectors (BD) are suspensions of micron-sized superheated liquid droplets in inert medium. The metastable droplets can vaporise upon interaction with ionising radiation generating visible bubbles. In this work, we investigated the response of SDD and BD to interrupted neutron irradiations. We observed that the droplet vaporisation rates for SDD and BD are different in nature. The unusual increase in droplet vaporisation rate observed when the SDD is exposed to neutrons after few minutes of radiation-off period is absent for BD. - Highlights: • Superheated droplet detectors (SDD) and bubble detectors (BD) are suspensions of superheated liquid droplets in inert medium. • The bubble nucleation in superheated droplets can be induced by ionising radiation. • The droplet vaporisation rate for SDD is non-monotonic when it is irradiated periodically to neutrons. • For BD the droplet vaporisation rate decrease monotonically when it is irradiated periodically to neutrons.

  13. Butschli Dynamic Droplet System

    DEFF Research Database (Denmark)

    Armstrong, R.; Hanczyc, M.

    2013-01-01

    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...... reconstructed the Butschli system and observed its life span under a light microscope, observing chemical patterns and droplet behaviors in nearly three hundred replicate experiments. Self-organizing patterns were observed, and during this dynamic, embodied phase the droplets provided a means of introducing...... temporal and spatial order in the system with the potential for chemical programmability. The authors propose that the discrete formation of dynamic droplets, characterized by their lifelike behavior patterns, during a variable window of time (from 30 s to 30 min after the addition of alkaline water...

  14. Manipulation of microfluidic droplets by electrorheological fluid

    KAUST Repository

    Zhang, Menying

    2009-09-01

    Microfluidics, especially droplet microfluidics, attracts more and more researchers from diverse fields, because it requires fewer materials and less time, produces less waste and has the potential of highly integrated and computer-controlled reaction processes for chemistry and biology. Electrorheological fluid, especially giant electrorheological fluid (GERF), which is considered as a kind of smart material, has been applied to the microfluidic systems to achieve active and precise control of fluid by electrical signal. In this review article, we will introduce recent results of microfluidic droplet manipulation, GERF and some pertinent achievements by introducing GERF into microfluidic system: digital generation, manipulation of "smart droplets" and droplet manipulation by GERF. Once it is combined with real-time detection, integrated chip with multiple functions can be realized. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.

  15. Shape-Shifting Droplet Networks.

    Science.gov (United States)

    Zhang, T; Wan, Duanduan; Schwarz, J M; Bowick, M J

    2016-03-11

    We consider a three-dimensional network of aqueous droplets joined by single lipid bilayers to form a cohesive, tissuelike material. The droplets in these networks can be programed to have distinct osmolarities so that osmotic gradients generate internal stresses via local fluid flows to cause the network to change shape. We discover, using molecular dynamics simulations, a reversible folding-unfolding process by adding an osmotic interaction with the surrounding environment which necessarily evolves dynamically as the shape of the network changes. This discovery is the next important step towards osmotic robotics in this system. We also explore analytically and numerically how the networks become faceted via buckling and how quasi-one-dimensional networks become three dimensional.

  16. Control of charged droplets using electrohydrodynamic repulsion for circular droplet patterning

    International Nuclear Information System (INIS)

    Kim, Bumjoo; Sung, Jungwoo; Lim, Geunbae; Nam, Hyoryung; Kim, Sung Jae; Joo, Sang W

    2011-01-01

    We report a novel method to form a circular pattern of monodisperse microdroplets using an electrohydrodynamic repulsion (EDR) mechanism. EDR is a phenomenon of electrostatical bounced microdroplets from an accumulated droplet on a bottom substrate. In addition to a regular EDR system, by placing a ring electrode between the capillary and ground substrate, two separate regions were created. A parameter study of two regions was carried out for droplet formation and falling velocity to control the radius of the generated droplets and the circular patterns independently. Based on energy conservation theory, our experimental results showed that the free-falling region exerted crucial influences on the sizes of the circular patterns

  17. Liquid crystal droplet formation and anchoring dynamics in a microfluidic device

    Science.gov (United States)

    Steinhaus, Ben; Shen, Amy; Feng, James; Link, Darren

    2004-11-01

    Liquid crystal drops dispersed in a continuous phase of silicon oil are generated with a narrow distribution in droplet size in microfluidic devices both above and below the nematic to isotropic transition temperature. For these two cases, we observe not only the different LC droplet generation and coalescence dynamics, but also distinct droplet morphology. Our experiments show that the nematic liquid crystalline order is important for the LC droplet formation and anchoring dynamics.

  18. 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.

  19. Produção e utilização de gotas com diâmetro uniforme The generation and use of uniformly sized droplets

    Directory of Open Access Journals (Sweden)

    Hermes Geraldo Corrêa

    1982-01-01

    Full Text Available A execução da pesquisa com freqüência requer o desenvolvimento de aparelhagem específica. Para estudo dos parâmetros das populações de gotas produzidas por pulverizadores é necessário conhecer o fator de espalhamento de diversas formulações sobre superfícies de amostragem (papel kromekote, melamina (fórmica, vidro etc.. Essa determinação requer aparelhagem geradora de gotas com diâmetro uniforme. Com este objetivo principal, realizou-se o presente trabalho. Além de sua utilização para investigar o comportamento físico da pulverização, o aparelho poderá ter outras aplicações no campo da biologia, como a distribuição uniforme de esporos em dose determinada sobre superfícies vegetais, permitindo, também, observações sobre o efeito tóxico de determinadas doses de defensivos sobre vegetais e animais. O aparelho produziu gotas com diâmetro que, em média, apresentaram coeficiente de variação de 2,36%. o fator de espalhamento para solução aquosa de rodamina a 0,2% sobre papel kromekote apresentou a variação de 1,32 a 1,71 quando se usaram, respectivamente, gotas entre 98 e 325 micra. Para Malathion a 96% de principio ativo, sobre papel kromekote, as gotículas apresentaram fatores de espalhamento variando de 4,09 a 5,18 quando se utilizaram gotas entre 80 e 217 micra. A melamina branca (fórmica apresentou menores variações nesse fator quando lhe foi aplicado o Malathion.This paper deals with the construction and use of a spinning disc atomizer that produces uniformly sized droplets. The device has a special use in the determination of the spread factor on several sampling surfaces (Kromekote paper, glass, plastic etc.. Furthermore, it permits the study of spraying performance, the inoculation of known spore doses of fungi and observations about toxical effects of pesticides on vegetables and animals. The apparatus showed a narrow droplet size spectrum, with a coefficient of variation about 2.36%. The spread

  20. OCS in He droplets

    Energy Technology Data Exchange (ETDEWEB)

    Grebenev, V.

    2000-06-01

    Phenomenon of superfluidity of para-hydrogen (pH{sub 2}){sub 1-17} and helium {sup 4}He{sub 1-7000} systems doped with an OCS chromophore molecule was investigated in this work. The study of such systems became possible after the development of the depletion spectroscopy technique in helium droplets. The droplets can be easily created and doped with up to 100 particles such as OCS, para-hydrogen or ortho-hydrogen molecules and {sup 4}He atoms. The measured infrared depletion spectra give the information about the temperature of the droplets and their aggregate state. The depletion spectrum of OCS in pure {sup 4}He droplets was comprehensively studied. The rovibrational OCS spectrum shows well resolved narrow lines. The spectrum is shifted to the red relative to the corresponding gas phase spectrum and the rotational constant of OCS in {sup 4}He droplet is three times smaller than that for free molecule. Different models of OCS rotation in the helium environment were discussed. It was shown that the shapes of the rovibrational lines are defined mainly by inhomogeneous broadening due to the droplet size distribution. The sub-rotational structure of the OCS rovibrational lines was revealed in microwave-infrared double resonance experiments. This structure arises due to the interaction of the OCS with the He environment. However, the information obtained in the experiments was not enough to understand the nature of this interaction. (orig.)

  1. Numerical Simulation of Droplet Motion and Two-Phase Flow Field in an Oscillating Container

    Directory of Open Access Journals (Sweden)

    T Watanabe

    2016-09-01

    Full Text Available The dynamic motion of the droplet in the oscillating flow field is simulated numerically using the arbitrary Lagrangian-Eulerian and level set coupled method. It is shown that radiating flows are generated from the droplet surface in the oscillating direction and the droplet moves toward the pressure node. The translational motion of the droplet is caused by the density variation, while the radiating flows are by the pressure variation. The flow field around the droplet in the oscillating container is found to be similar to that around the oscillating droplet in the stationary container.

  2. Targeting the motor regulator Klar to lipid droplets

    Directory of Open Access Journals (Sweden)

    Einstein Jenifer

    2011-02-01

    Full Text Available Abstract Background In Drosophila, the transport regulator Klar displays tissue-specific localization: In photoreceptors, it is abundant on the nuclear envelope; in early embryos, it is absent from nuclei, but instead present on lipid droplets. Differential targeting of Klar appears to be due to isoform variation. Droplet targeting, in particular, has been suggested to occur via a variant C-terminal region, the LD domain. Although the LD domain is necessary and sufficient for droplet targeting in cultured cells, lack of specific reagents had made it previously impossible to analyze its role in vivo. Results Here we describe a new mutant allele of klar with a lesion specifically in the LD domain; this lesion abolishes both droplet localization of Klar and the ability of Klar to regulate droplet motion. It does not disrupt Klar's function for nuclear migration in photoreceptors. Using a GFP-LD fusion, we show that the LD domain is not only necessary but also sufficient for droplet targeting in vivo; it mediates droplet targeting in embryos, in ovaries, and in a number of somatic tissues. Conclusions Our analysis demonstrates that droplet targeting of Klar occurs via a cis-acting sequence and generates a new tool for monitoring lipid droplets in living tissues of Drosophila.

  3. Chip-based droplet sorting

    Energy Technology Data Exchange (ETDEWEB)

    Beer, Neil Reginald; Lee, Abraham; Hatch, Andrew

    2017-11-21

    A non-contact system for sorting monodisperse water-in-oil emulsion droplets in a microfluidic device based on the droplet's contents and their interaction with an applied electromagnetic field or by identification and sorting.

  4. Hydrodynamics of a quark droplet

    DEFF Research Database (Denmark)

    Bjerrum-Bohr, Johan J.; Mishustin, Igor N.; Døssing, Thomas

    2012-01-01

    We present a simple model of a multi-quark droplet evolution based on the hydrodynamical description. This model includes collective expansion of the droplet, effects of the vacuum pressure and surface tension. The hadron emission from the droplet is described following Weisskopf's statistical...

  5. Electronic structure of PPP@ZnO from all-electron quasiarticle calculations

    Science.gov (United States)

    Höffling, Benjamin; Nabok, Dimitri; Draxl, Claudia; Condensed Matter Theory Group, Humboldt University Berlin Team

    We investigate the electronic properties of poly(para-phenylene) (PPP) adsorbed on the non-polar (001) surface of rocksalt (rs) ZnO using all-electron density functional theory (DFT) as well as quasiparticle (QP) calculations within the GW approach. A particular focus is put on the electronic band discontinuities at the interface, where we investigate the impact of quantum confinement, molecular polarization, and charge rearrangement. For our prototypical system, PPP@ZnO, we find a type-I heterostructure. Comparison of the band offsets derived from a QP-treatment of the hybrid system with predictions based on mesoscopic methods, like the Shockley-Anderson model or alignment via the electrostatic potential, reveals the inadequacy of these simple approaches for the prediction of the electronic structure of such inorganic/organic heterosystems. Finally, we explore the optical excitations of the interface compared to the features of the pristine components and discuss the methodological implications for the ab-initio treatment of interface electronics.

  6. Efficient mixing scheme for self-consistent all-electron charge density

    Science.gov (United States)

    Shishidou, Tatsuya; Weinert, Michael

    2015-03-01

    In standard ab initio density-functional theory calculations, the charge density ρ is gradually updated using the ``input'' and ``output'' densities of the current and previous iteration steps. To accelerate the convergence, Pulay mixing has been widely used with great success. It expresses an ``optimal'' input density ρopt and its ``residual'' Ropt by a linear combination of the densities of the iteration sequences. In large-scale metallic systems, however, the long range nature of Coulomb interaction often causes the ``charge sloshing'' phenomenon and significantly impacts the convergence. Two treatments, represented in reciprocal space, are known to suppress the sloshing: (i) the inverse Kerker metric for Pulay optimization and (ii) Kerker-type preconditioning in mixing Ropt. In all-electron methods, where the charge density does not have a converging Fourier representation, treatments equivalent or similar to (i) and (ii) have not been described so far. In this work, we show that, by going through the calculation of Hartree potential, one can accomplish the procedures (i) and (ii) without entering the reciprocal space. Test calculations are done with a FLAPW method.

  7. Selfbound quantum droplets

    Science.gov (United States)

    Langen, Tim; Wenzel, Matthias; Schmitt, Matthias; Boettcher, Fabian; Buehner, Carl; Ferrier-Barbut, Igor; Pfau, Tilman

    2017-04-01

    Self-bound many-body systems are formed through a balance of attractive and repulsive forces and occur in many physical scenarios. Liquid droplets are an example of a self-bound system, formed by a balance of the mutual attractive and repulsive forces that derive from different components of the inter-particle potential. On the basis of the recent finding that an unstable bosonic dipolar gas can be stabilized by a repulsive many-body term, it was predicted that three-dimensional self-bound quantum droplets of magnetic atoms should exist. Here we report on the observation of such droplets using dysprosium atoms, with densities 108 times lower than a helium droplet, in a trap-free levitation field. We find that this dilute magnetic quantum liquid requires a minimum, critical number of atoms, below which the liquid evaporates into an expanding gas as a result of the quantum pressure of the individual constituents. Consequently, around this critical atom number we observe an interaction-driven phase transition between a gas and a self-bound liquid in the quantum degenerate regime with ultracold atoms.

  8. Mechanism of Water Droplet Breakup Near the Leading Edge of an Airfoil

    Science.gov (United States)

    Vargas, Mario; Sor, Suthyvann; Magarino, Adelaida, Garcia

    2012-01-01

    This work presents results of an experimental study on droplet deformation and breakup near the leading edge of an airfoil. The experiment was conducted in the rotating rig test cell at the Instituto Nacional de Tecnica Aeroespacial (INTA) in Madrid, Spain. The airfoil model was placed at the end of the rotating arm and a monosize droplet generator produced droplets that fell from above, perpendicular to the path of the airfoil. The interaction between the droplets and the airfoil was captured with high speed imaging and allowed observation of droplet deformation and breakup as the droplet approached the airfoil near the stagnation line. Image processing software was used to measure the position of the droplet centroid, equivalent diameter, perimeter, area, and the major and minor axes of an ellipse superimposed over the deforming droplet. The horizontal and vertical displacement of each droplet against time was also measured, and the velocity, acceleration, Weber number, Bond number, Reynolds number, and the drag coefficients were calculated along the path of the droplet to the beginning of breakup. Droplet deformation is defined and studied against main parameters. The high speed imaging allowed observation of the actual mechanism of breakup and identification of the sequence of configurations from the initiation of the breakup to the disintegration of the droplet. Results and comparisons are presented for droplets of diameters in the range of 500 to 1800 microns, and airfoil velocities of 70 and 90 m/sec.

  9. Distribution of droplet sizes for seed solution

    International Nuclear Information System (INIS)

    Marwah, R.K.; Dixit, N.S.; Venkataramani, N.; Rohatgi, V.K.

    In open cycle MHD power generation, power is generated by passing seeded hot combustion products of a fossil fuel through a magnetic field. Seeding is done with a salt which is readily ionizable, preferably in the form of an aqueous solution, such as potassium carbonate, potassium sulphate, etc. Methods of atomization and the theoretical drop size calculations are presented. Basic parameters necessary for droplet size determination and their measurement are also described. (K.B.)

  10. Active Mesogenic Droplets: Impact of Liquid Crystallinity and Collective Behavior

    Science.gov (United States)

    Bahr, Christian

    Droplets of common mesogenic compounds show a self-propelled motion when immersed in aqueous solutions containing ionic surfactants at concentrations well above the critical micelle concentration. After introducing some general properties of this type of artificial microswimmer, we focus on two topics: the influence of liquid crystallinity on the swimming behavior and the collective behavior of ensembles of a larger number of droplets. The mesogenic properties are not essential for the basic mechanism of self-propulsion, nevertheless they considerably influence the swimming behavior of the droplets. For instance, the shape of the trajectories strongly depends on whether the droplets are in the nematic or isotropic state. The droplet swimmers are also ideally suited for the study of collective behavior: Microfluidics enables the generation of large numbers of identical swimmers and we can tune their buoyancy. We report on the collective behavior in three-dimensional environments. Supported by the Deutsche Forschungsgemeinschaft (SPP 1726 ``Microswimmers'').

  11. Optical properties of alkali halide crystals from all-electron hybrid TD-DFT calculations

    Energy Technology Data Exchange (ETDEWEB)

    Webster, R., E-mail: ross.webster07@imperial.ac.uk; Harrison, N. M. [Thomas Young Centre, Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ (United Kingdom); Bernasconi, L. [Rutherford Appleton Laboratory, STFC, Harwell Oxford, Didcot OX11 0QX (United Kingdom)

    2015-06-07

    We present a study of the electronic and optical properties of a series of alkali halide crystals AX, with A = Li, Na, K, Rb and X = F, Cl, Br based on a recent implementation of hybrid-exchange time-dependent density functional theory (TD-DFT) (TD-B3LYP) in the all-electron Gaussian basis set code CRYSTAL. We examine, in particular, the impact of basis set size and quality on the prediction of the optical gap and exciton binding energy. The formation of bound excitons by photoexcitation is observed in all the studied systems and this is shown to be correlated to specific features of the Hartree-Fock exchange component of the TD-DFT response kernel. All computed optical gaps and exciton binding energies are however markedly below estimated experimental and, where available, 2-particle Green’s function (GW-Bethe-Salpeter equation, GW-BSE) values. We attribute this reduced exciton binding to the incorrect asymptotics of the B3LYP exchange correlation ground state functional and of the TD-B3LYP response kernel, which lead to a large underestimation of the Coulomb interaction between the excited electron and hole wavefunctions. Considering LiF as an example, we correlate the asymptotic behaviour of the TD-B3LYP kernel to the fraction of Fock exchange admixed in the ground state functional c{sub HF} and show that there exists one value of c{sub HF} (∼0.32) that reproduces at least semi-quantitatively the optical gap of this material.

  12. Electrical actuation of dielectric droplets

    International Nuclear Information System (INIS)

    Kumari, N; Bahadur, V; Garimella, S V

    2008-01-01

    Electrical actuation of liquid droplets at the microscale offers promising applications in the fields of microfluidics and lab-on-a-chip devices. Much prior research has targeted the electrical actuation of electrically conducting liquid droplets; however, the actuation of dielectric droplets has remained relatively unexplored, despite the advantages associated with the use of a dielectric droplet. This paper presents modeling and experimental results on the electrical actuation of dielectric droplets between two flat plates. A first-order analytical model, based on the energy-minimization principle, is developed to estimate the electrical actuation force on a dielectric droplet as it moves between two flat plates. Two versions of this analytical model are benchmarked for their suitability and accuracy against a detailed numerical model. The actuation force prediction is then combined with available semi-analytical expressions for predicting the forces opposing droplet motion to develop a model that predicts transient droplet motion under electrical actuation. Electrical actuation of dielectric droplets is experimentally demonstrated by moving transformer oil droplets between two flat plates under the influence of an actuation voltage. Droplet velocities and their dependence on the plate spacing and the applied voltage are experimentally measured and showed reasonable agreement with predictions from the models developed

  13. 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.

  14. New droplet model developments

    International Nuclear Information System (INIS)

    Dorso, C.O.; Myers, W.D.; Swiatecki, W.J.; Moeller, P.; Treiner, J.; Weiss, M.S.

    1985-09-01

    A brief summary is given of three recent contributions to the development of the Droplet Model. The first concerns the electric dipole moment induced in octupole deformed nuclei by the Coulomb redistribution. The second concerns a study of squeezing in nuclei and the third is a study of the improved predictive power of the model when an empirical ''exponential'' term is included. 25 refs., 3 figs

  15. Acoustic droplet vaporization of vascular droplets in gas embolotherapy

    Science.gov (United States)

    Bull, Joseph

    2016-11-01

    This work is primarily motivated by a developmental gas embolotherapy technique for cancer treatment. In this methodology, infarction of tumors is induced by selectively formed vascular gas bubbles that arise from the acoustic vaporization of vascular droplets. Additionally, micro- or nano-droplets may be used as vehicles for localized drug delivery, with or without flow occlusion. In this talk, we examine the dynamics of acoustic droplet vaporization through experiments and theoretical/computational fluid mechanics models, and investigate the bioeffects of acoustic droplet vaporization on endothelial cells and in vivo. Functionalized droplets that are targeted to tumor vasculature are examined. The influence of fluid mechanical and acoustic parameters, as well as droplet functionalization, is explored. This work was supported by NIH Grant R01EB006476.

  16. Drag Coefficient of Water Droplets Approaching the Leading Edge of an Airfoil

    Science.gov (United States)

    Vargas, Mario; Sor, Suthyvann; Magarino, Adelaida Garcia

    2013-01-01

    This work presents results of an experimental study on droplet deformation and breakup near the leading edge of an airfoil. The experiment was conducted in the rotating rig test cell at the Instituto Nacional de Tecnica Aeroespacial (INTA) in Madrid, Spain. An airfoil model was placed at the end of the rotating arm and a monosize droplet generator produced droplets that fell from above, perpendicular to the path of the airfoil. The interaction between the droplets and the airfoil was captured with high speed imaging and allowed observation of droplet deformation and breakup as the droplet approached the airfoil near the stagnation line. Image processing software was used to measure the position of the droplet centroid, equivalent diameter, perimeter, area, and the major and minor axes of an ellipse superimposed over the deforming droplet. The horizontal and vertical displacement of each droplet against time was also measured, and the velocity, acceleration, Weber number, Bond number, Reynolds number, and the drag coefficients were calculated along the path of the droplet to the beginning of breakup. Results are presented and discussed for drag coefficients of droplets with diameters in the range of 300 to 1800 micrometers, and airfoil velocities of 50, 70 and 90 meters/second. The effect of droplet oscillation on the drag coefficient is discussed.

  17. Spray Droplet Characterization from a Single Nozzle by High Speed Image Analysis Using an In-Focus Droplet Criterion.

    Science.gov (United States)

    Minov, Sofija Vulgarakis; Cointault, Frédéric; Vangeyte, Jürgen; Pieters, Jan G; Nuyttens, David

    2016-02-06

    Accurate spray characterization helps to better understand the pesticide spray application process. The goal of this research was to present the proof of principle of a droplet size and velocity measuring technique for different types of hydraulic spray nozzles using a high speed backlight image acquisition and analysis system. As only part of the drops of an agricultural spray can be in focus at any given moment, an in-focus criterion based on the gray level gradient was proposed to decide whether a given droplet is in focus or not. In a first experiment, differently sized droplets were generated with a piezoelectric generator and studied to establish the relationship between size and in-focus characteristics. In a second experiment, it was demonstrated that droplet sizes and velocities from a real sprayer could be measured reliably in a non-intrusive way using the newly developed image acquisition set-up and image processing. Measured droplet sizes ranged from 24 μm to 543 μm, depending on the nozzle type and size. Droplet velocities ranged from around 0.5 m/s to 12 m/s. The droplet size and velocity results were compared and related well with the results obtained with a Phase Doppler Particle Analyzer (PDPA).

  18. Mechanism of Supercooled Water Droplet Breakup near the Leading Edge of an Airfoil

    Science.gov (United States)

    Veras-Alba, Belen; Palacios, Jose; Vargas, Mario; Ruggeri, Charles; Bartkus, Tadas P.

    2017-01-01

    This work presents the results of an experimental study on supercooled droplet deformation and breakup near the leading edge of an airfoil. The results are compared to prior room temperature droplet deformation results to explore the effects of droplet supercooling. The experiments were conducted in the Adverse Environment Rotor Test Stand (AERTS) at The Pennsylvania State University. An airfoil model placed at the end of the rotor blades mounted onto the hub in the AERTS chamber was moved at speeds ranging between 50 and 80 m/sec. The temperature of the chamber was set at -20°C. A monotonic droplet generator was used to produce droplets that fell from above, perpendicular to the path of the airfoil. The supercooled state of the droplets was determined by measurement of the temperature of the drops at various locations below the droplet generator exit. A temperature prediction code was also used to estimate the temperature of the droplets based on vertical velocity and the distance traveled by droplets from the droplet generator to the airfoil stagnation line. High speed imaging was employed to observe the interaction between the droplets and the airfoil. The high speed imaging provided droplet deformation information as the droplet approached the airfoil near the stagnation line. A tracking software program was used to measure the horizontal and vertical displacement of the droplet against time. It was demonstrated that to compare the effects of water supercooling on droplet deformation, the ratio of the slip velocity and the initial droplet velocity must be equal. A case with equal slip velocity to initial velocity ratios was selected for room temperature and supercooled droplet conditions. The airfoil velocity was 60 m/s and the slip velocity for both sets of data was 40 m/s. In these cases, the deformation of the weakly supercooled and warm droplets did not present different trends. The similar behavior for both environmental conditions indicates that water

  19. Evaporation of inclined water droplets

    Science.gov (United States)

    Kim, Jin Young; Hwang, In Gyu; Weon, Byung Mook

    2017-01-01

    When a drop is placed on a flat substrate tilted at an inclined angle, it can be deformed by gravity and its initial contact angle divides into front and rear contact angles by inclination. Here we study on evaporation dynamics of a pure water droplet on a flat solid substrate by controlling substrate inclination and measuring mass and volume changes of an evaporating droplet with time. We find that complete evaporation time of an inclined droplet becomes longer as gravitational influence by inclination becomes stronger. The gravity itself does not change the evaporation dynamics directly, whereas the gravity-induced droplet deformation increases the difference between front and rear angles, which quickens the onset of depinning and consequently reduces the contact radius. This result makes the evaporation rate of an inclined droplet to be slow. This finding would be important to improve understanding on evaporation dynamics of inclined droplets. PMID:28205642

  20. Generation of native polythiophene/PCBM composite nanoparticles via the combination of ultrasonic micronization of droplets and thermocleaving from aqueous dispersion

    DEFF Research Database (Denmark)

    Nan, Yaxiong; Hu, Xiaolian; Larsen-Olsen, Thue Trofod

    2011-01-01

    -PT/PCBM nanoparticles were determined by atomic force microscopy (AFM), small-angle x-ray scattering (SAXS) and grazing incidence SAXS (GISAXS), giving an average size of ~ 140 nm. The GISAXS results reveal that n-PT/PCBM nanoparticles pack in an ordered structure as opposed to the P3MHOCT/PCBM nanoparticles......We report the preparation of native polythiophene (n-PT)/[6, 6]-phenyl-C61-butyric acid methyl ester (PCBM) composite nanoparticles from a poly[3-(2-methylhex-2-yl)oxy-carbonyldithiophene] (P3MHOCT)/PCBM aqueous dispersion prepared from an ultrasonically generated emulsion. The subsequent steps....... The successful vapour-phase preparation of phase-separated n-PT/PCBM nanoparticles provides a new route to all-aqueous processing of conjugated materials relevant to efficient polymer solar cells with long operational stability. The use of ultrasound was involved in both liquid and gas phases demonstrating...

  1. Droplet-model predictions of charge moments

    International Nuclear Information System (INIS)

    Myers, W.D.

    1982-04-01

    The Droplet Model expressions for calculating various moments of the nuclear charge distribution are given. There are contributions to the moments from the size and shape of the system, from the internal redistribution induced by the Coulomb repulsion, and from the diffuseness of the surface. A case is made for the use of diffuse charge distributions generated by convolution as an alternative to Fermi-functions

  2. Droplet morphometry and velocimetry (DMV): a video processing software for time-resolved, label-free tracking of droplet parameters.

    Science.gov (United States)

    Basu, Amar S

    2013-05-21

    Emerging assays in droplet microfluidics require the measurement of parameters such as drop size, velocity, trajectory, shape deformation, fluorescence intensity, and others. While micro particle image velocimetry (μPIV) and related techniques are suitable for measuring flow using tracer particles, no tool exists for tracking droplets at the granularity of a single entity. This paper presents droplet morphometry and velocimetry (DMV), a digital video processing software for time-resolved droplet analysis. Droplets are identified through a series of image processing steps which operate on transparent, translucent, fluorescent, or opaque droplets. The steps include background image generation, background subtraction, edge detection, small object removal, morphological close and fill, and shape discrimination. A frame correlation step then links droplets spanning multiple frames via a nearest neighbor search with user-defined matching criteria. Each step can be individually tuned for maximum compatibility. For each droplet found, DMV provides a time-history of 20 different parameters, including trajectory, velocity, area, dimensions, shape deformation, orientation, nearest neighbour spacing, and pixel statistics. The data can be reported via scatter plots, histograms, and tables at the granularity of individual droplets or by statistics accrued over the population. We present several case studies from industry and academic labs, including the measurement of 1) size distributions and flow perturbations in a drop generator, 2) size distributions and mixing rates in drop splitting/merging devices, 3) efficiency of single cell encapsulation devices, 4) position tracking in electrowetting operations, 5) chemical concentrations in a serial drop dilutor, 6) drop sorting efficiency of a tensiophoresis device, 7) plug length and orientation of nonspherical plugs in a serpentine channel, and 8) high throughput tracking of >250 drops in a reinjection system. Performance metrics

  3. Droplet size effects on film drainage between droplet and substrate.

    Science.gov (United States)

    Steinhaus, Benjamin; Spicer, Patrick T; Shen, Amy Q

    2006-06-06

    When a droplet approaches a solid surface, the thin liquid film between the droplet and the surface drains until an instability forms and then ruptures. In this study, we utilize microfluidics to investigate the effects of film thickness on the time to film rupture for water droplets in a flowing continuous phase of silicone oil deposited on solid poly(dimethylsiloxane) (PDMS) surfaces. The water droplets ranged in size from millimeters to micrometers, resulting in estimated values of the film thickness at rupture ranging from 600 nm down to 6 nm. The Stefan-Reynolds equation is used to model film drainage beneath both millimeter- and micrometer-scale droplets. For millimeter-scale droplets, the experimental and analytical film rupture times agree well, whereas large differences are observed for micrometer-scale droplets. We speculate that the differences in the micrometer-scale data result from the increases in the local thin film viscosity due to confinement-induced molecular structure changes in the silicone oil. A modified Stefan-Reynolds equation is used to account for the increased thin film viscosity of the micrometer-scale droplet drainage case.

  4. Capillary-based integrated digital PCR in picoliter droplets.

    Science.gov (United States)

    Chen, Jinyu; Luo, Zhaofeng; Li, Lin; He, Jinlong; Li, Luoquan; Zhu, Jianwei; Wu, Ping; He, Liqun

    2018-01-30

    The droplet digital polymerase chain reaction (ddPCR) is becoming more and more popular in diagnostic applications in academia and industry. In commercially available ddPCR systems, after they have been made by a generator, the droplets have to be transferred manually to modules for amplification and detection. In practice, some of the droplets (∼10%) are lost during manual transfer, leading to underestimation of the targets. In addition, the droplets are also at risk of cross-contamination during transfer. By contrast, in labs, some chip-based ddPCRs have been demonstrated where droplets always run in channels. However, the droplets easily coalesce to large ones in chips due to wall wetting as well as thermal oscillation. The loss of droplets becomes serious when such ddPCRs are applied to absolutely quantify rare mutations, such as in early diagnostics in clinical research or when measuring biological diversity at the cell level. Here, we propose a capillary-based integrated ddPCR system that is used for the first time to realize absolute quantification in this way. In this system, a HPLC T-junction is used to generate droplets and a long HPLC capillary connects the generator with both a capillary-based thermocycler and a capillary-based cytometer. The performance of the system is validated by absolute quantification of a gene specific to lung cancer (LunX). The results show that this system has very good linearity (0.9988) at concentrations ranging from NTC to 2.4 × 10 -4 copies per μL. As compared to qPCR, the all-in-one scheme is superior both in terms of the detection limit and the smaller fold changes measurement. The system of ddPCR might provide a powerful approach for clinical or academic applications where rare events are mostly considered.

  5. Particle Manipulation Methods in Droplet Microfluidics.

    Science.gov (United States)

    Tenje, Maria; Fornell, Anna; Ohlin, Mathias; Nilsson, Johan

    2018-02-06

    This Feature describes the different particle manipulation techniques available in the droplet microfluidics toolbox to handle particles encapsulated inside droplets and to manipulate whole droplets. We address the advantages and disadvantages of the different techniques to guide new users.

  6. Vaporization of irradiated droplets

    International Nuclear Information System (INIS)

    Armstrong, R.L.; O'Rourke, P.J.; Zardecki, A.

    1986-01-01

    The vaporization of a spherically symmetric liquid droplet subject to a high-intensity laser flux is investigated on the basis of a hydrodynamic description of the system composed of the vapor and ambient gas. In the limit of the convective vaporization, the boundary conditions at the fluid--gas interface are formulated by using the notion of a Knudsen layer in which translational equilibrium is established. This leads to approximate jump conditions at the interface. For homogeneous energy deposition, the hydrodynamic equations are solved numerically with the aid of the CON1D computer code (''CON1D: A computer program for calculating spherically symmetric droplet combustion,'' Los Alamos National Laboratory Report No. LA-10269-MS, December, 1984), based on the implict continuous--fluid Eulerian (ICE) [J. Comput. Phys. 8, 197 (1971)] and arbitrary Lagrangian--Eulerian (ALE) [J. Comput. Phys. 14, 1227 (1974)] numerical mehtods. The solutions exhibit the existence of two shock waves propagating in opposite directions with respect to the contact discontinuity surface that separates the ambient gas and vapor

  7. Explosive Leidenfrost droplets

    Science.gov (United States)

    Colinet, Pierre; Moreau, Florian; Dorbolo, Stéphane

    2017-11-01

    We show that Leidenfrost droplets made of an aqueous solution of surfactant undergo a violent explosion in a wide range of initial volumes and concentrations. This unexpected behavior turns out to be triggered by the formation of a gel-like shell, followed by a sharp temperature increase. Comparing a simple model of the radial surfactant distribution inside a spherical droplet with experiments allows highlighting the existence of a critical surface concentration for the shell to form. The temperature rise (attributed to boiling point elevation with surface concentration) is a key feature leading to the explosion, instead of the implosion (buckling) scenario reported by other authors. Indeed, under some conditions, this temperature increase is shown to be sufficient to trigger nucleation and growth of vapor bubbles in the highly superheated liquid bulk, stretching the surrounding elastic shell up to its rupture limit. The successive timescales characterizing this explosion sequence are also discussed. Funding sources: F.R.S. - FNRS (ODILE and DITRASOL projects, RD and SRA positions of P. Colinet and S. Dorbolo), BELSPO (IAP 7/38 MicroMAST project).

  8. A droplet entrainment model for horizontal segregated flows

    Energy Technology Data Exchange (ETDEWEB)

    Höhne, Thomas, E-mail: T.Hoehne@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf (HZDR) – Institute of Fluid Dynamics, P.O. Box 510119, D-01314 Dresden (Germany); Hänsch, Susann [Imperial College, Department of Mechanical Engineering, South Kensington Campus, London SW7 2AZ (United Kingdom)

    2015-05-15

    Highlights: • We further developed the flow morphology detection model AIAD. • An advanced droplet entrainment model was introduced. • The new approach is applied against HAWAC experiments. - Abstract: One limitation in simulating horizontal segregated flows is that there is no treatment of droplet formation mechanisms at wavy surfaces. For self-generating waves and slugs, the interfacial momentum exchange and the turbulence parameters have to be modeled correctly. Furthermore, understanding the mechanism of droplet entrainment for heat and mass transfer processes is of great importance in the chemical and nuclear industry. The development of general computational fluid dynamics models is an essential precondition for the application of CFD codes to the modeling of flow related phenomena. The new formulation for the interfacial drag at the free surface and turbulence parameters within the algebraic interfacial area density model (AIAD) represents one step toward a more physical description of free surface flows including less empiricism. The AIAD approach allows the use of different physical models depending on the local fluid morphology inside a macro-scale multi-fluid framework. A further step of improving the modeling of free interfaces lies within the consideration of droplet entrainment mechanisms. In this paper a new sub-grid entrainment model is proposed, which assumes that due to liquid turbulence the interface gets rough and wavy leading to the formation of droplets. Therefore, the droplet entrainment model requires the consideration of an additional droplet phase, which is described with an own set of balance equations in the spirit of the particle model. Two local key factors determine the rate of droplet entrainment: the liquid turbulent kinetic energy as well as the outward velocity gradient of the liquid relative to the interface motion. The new droplet entrainment approach is included into CFD simulations for attempting to reproduce existing

  9. Leidenfrost boiling of water droplet

    Directory of Open Access Journals (Sweden)

    Orzechowski Tadeusz

    2017-01-01

    Full Text Available The investigations concerned a large water droplet at the heating surface temperature above the Leidenfrost point. The heating cylinder was the main component of experimental stand on which investigations were performed. The measurement system was placed on the high-sensitivity scales. Data transmission was performed through RS232 interface. The author-designed program, with extended functions to control the system, was applied. The present paper examines the behaviour of a large single drop levitating over a hot surface, unsteady mass of the drop, and heat transfer. In computations, the dependence, available in the literature, for the orthogonal droplet projection on the heating surface as a function of time was employed. It was confirmed that the local value of the heat transfer coefficient is a power function of the area of the droplet surface projection. Also, a linear relationship between the flux of mass evaporated from the droplet and the droplet orthogonal projection was observed.

  10. Leidenfrost boiling of water droplet

    Science.gov (United States)

    Orzechowski, Tadeusz

    The investigations concerned a large water droplet at the heating surface temperature above the Leidenfrost point. The heating cylinder was the main component of experimental stand on which investigations were performed. The measurement system was placed on the high-sensitivity scales. Data transmission was performed through RS232 interface. The author-designed program, with extended functions to control the system, was applied. The present paper examines the behaviour of a large single drop levitating over a hot surface, unsteady mass of the drop, and heat transfer. In computations, the dependence, available in the literature, for the orthogonal droplet projection on the heating surface as a function of time was employed. It was confirmed that the local value of the heat transfer coefficient is a power function of the area of the droplet surface projection. Also, a linear relationship between the flux of mass evaporated from the droplet and the droplet orthogonal projection was observed.

  11. Measurement of airborne droplets by the magnesium oxide method

    Energy Technology Data Exchange (ETDEWEB)

    May, K R

    1950-01-01

    A complete calibration has been made for the first time of the method of detecting and measuring airborne droplets whereby the permanent impressions made when they strike a layer of magnesium oxide smoked on a glass slide are measured microscopically. A size range of 200 to 10 microns and a wide range of liquids and impact velocities were investigated, and it was found that the ratio of true drop size to impression size is constant at 0.86 for droplets greater than 20 microns of any liquid. The method fails below 10 microns. The calibration was made against an absolute method of droplet measurement, also against the so-called focal-length method. Droplets of any desired size were generated by a uniform spray apparatus.

  12. Cavitation-induced fragmentation of an acoustically-levitated droplet

    Science.gov (United States)

    Gonzalez Avila, Silvestre Roberto; Ohl, Claus-Dieter

    2015-12-01

    In this paper we investigate the initial sequence of events that lead to the fragmentation of a millimetre sized water droplets when interacting with a focused ns-laser pulse. The experimental results show complex processes that result from the reflection of an initial shock wave from plasma generation with the soft boundary of the levitating droplet; furthermore, when the reflected waves from the walls of the droplet refocus they leave behind a trail of microbubbles that later act as cavitation inception regions. Numerical simulations of a shock wave impacting and reflecting from a soft boundary are also reported; the simulated results show that the lowest pressure inside the droplet occurs at the equatorial plane. The results of the numerical model display good agreement with the experimental results both in time and in space.

  13. Cavitation-induced fragmentation of an acoustically-levitated droplet

    International Nuclear Information System (INIS)

    Avila, Silvestre Roberto Gonzalez; Ohl, Claus-Dieter

    2015-01-01

    In this paper we investigate the initial sequence of events that lead to the fragmentation of a millimetre sized water droplets when interacting with a focused ns-laser pulse. The experimental results show complex processes that result from the reflection of an initial shock wave from plasma generation with the soft boundary of the levitating droplet; furthermore, when the reflected waves from the walls of the droplet refocus they leave behind a trail of microbubbles that later act as cavitation inception regions. Numerical simulations of a shock wave impacting and reflecting from a soft boundary are also reported; the simulated results show that the lowest pressure inside the droplet occurs at the equatorial plane. The results of the numerical model display good agreement with the experimental results both in time and in space. (paper)

  14. Surface characterization of polymethylmetacrylate bombarded by charged water droplets

    International Nuclear Information System (INIS)

    Hiraoka, Kenzo; Takaishi, Riou; Asakawa, Daiki; Sakai, Yuji; Iijima, Yoshitoki

    2009-01-01

    The electrospray droplet impact (EDI), in which the charged electrospray water droplets are introduced in vacuum, accelerated, and allowed to impact the sample, is applied to polymethylmetacrylate (PMMA). The secondary ions generated were measured by an orthogonal time-of-flight mass spectrometer. In EDI mass spectra for PMMA, fragment ions originating from PMMA could not be detected. This is due to the fact that the proton affinities of fragments formed from PMMA are smaller than those from acetic acid contained in the charged droplet. The x-ray photoelectron spectroscopy spectra of PMMA irradiated by water droplets did not change with prolonged cluster irradiation, i.e., EDI is capable of shallow surface etching for PMMA with a little damage of the sample underneath the surface.

  15. Development of sodium droplet combustion analysis methodology using direct numerical simulation in 3-dimensional coordinate (COMET)

    International Nuclear Information System (INIS)

    Okano, Yasushi; Ohira, Hiroaki

    1998-08-01

    In the early stage of sodium leak event of liquid metal fast breeder reactor, LMFBR, liquid sodium flows out from a piping, and ignition and combustion of liquid sodium droplet might occur under certain environmental condition. Compressible forced air flow, diffusion of chemical species, liquid sodium droplet behavior, chemical reactions and thermodynamic properties should be evaluated with considering physical dependence and numerical connection among them for analyzing combustion of sodium liquid droplet. A direct numerical simulation code was developed for numerical analysis of sodium liquid droplet in forced convection air flow. The numerical code named COMET, 'Sodium Droplet COmbustion Analysis METhodology using Direct Numerical Simulation in 3-Dimensional Coordinate'. The extended MAC method was used to calculate compressible forced air flow. Counter diffusion among chemical species is also calculated. Transport models of mass and energy between droplet and surrounding atmospheric air were developed. Equation-solving methods were used for computing multiphase equilibrium between sodium and air. Thermodynamic properties of chemical species were evaluated using dynamic theory of gases. Combustion of single sphere liquid sodium droplet in forced convection, constant velocity, uniform air flow was numerically simulated using COMET. Change of droplet diameter with time was closely agree with d 2 -law of droplet combustion theory. Spatial distributions of combustion rate and heat generation and formation, decomposition and movement of chemical species were analyzed. Quantitative calculations of heat generation and chemical species formation in spray combustion are enabled for various kinds of environmental condition by simulating liquid sodium droplet combustion using COMET. (author)

  16. Simulation of water vapor condensation on LOX droplet surface using liquid nitrogen

    Science.gov (United States)

    Powell, Eugene A.

    1988-01-01

    The formation of ice or water layers on liquid oxygen (LOX) droplets in the Space Shuttle Main Engine (SSME) environment was investigated. Formulation of such ice/water layers is indicated by phase-equilibrium considerations under conditions of high partial pressure of water vapor (steam) and low LOX droplet temperature prevailing in the SSME preburner or main chamber. An experimental investigation was begun using liquid nitrogen as a LOX simulant. A monodisperse liquid nitrogen droplet generator was developed which uses an acoustic driver to force the stream of liquid emerging from a capillary tube to break up into a stream of regularly space uniformly sized spherical droplets. The atmospheric pressure liquid nitrogen in the droplet generator reservoir was cooled below its boiling point to prevent two phase flow from occurring in the capillary tube. An existing steam chamber was modified for injection of liquid nitrogen droplets into atmospheric pressure superheated steam. The droplets were imaged using a stroboscopic video system and a laser shadowgraphy system. Several tests were conducted in which liquid nitrogen droplets were injected into the steam chamber. Under conditions of periodic droplet formation, images of 600 micron diameter liquid nitrogen droplets were obtained with the stroboscopic video systems.

  17. Lossless droplet transfer of droplet-based microfluidic analysis

    Science.gov (United States)

    Kelly, Ryan T [West Richland, WA; Tang, Keqi [Richland, WA; Page, Jason S [Kennewick, WA; Smith, Richard D [Richland, WA

    2011-11-22

    A transfer structure for droplet-based microfluidic analysis is characterized by a first conduit containing a first stream having at least one immiscible droplet of aqueous material and a second conduit containing a second stream comprising an aqueous fluid. The interface between the first conduit and the second conduit can define a plurality of apertures, wherein the apertures are sized to prevent exchange of the first and second streams between conduits while allowing lossless transfer of droplets from the first conduit to the second conduit through contact between the first and second streams.

  18. Dynamics of magnetic modulation of ferrofluid droplets for digital microfluidic applications

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Uddalok; Chatterjee, Souvick [Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL, 60607 (United States); Sen, Swarnendu [Mechanical Engineering Department, Jadavpur University, Kolkata, 700032 India (India); Tiwari, Manish K. [Department of Mechanical Engineering, University College London, London, WC1E 7JE UK (United Kingdom); Mukhopadhyay, Achintya [Mechanical Engineering Department, Jadavpur University, Kolkata, 700032 India (India); Ganguly, Ranjan, E-mail: ranjan@pe.jusl.ac.in [Department of Power Engineering, Jadavpur University, Kolkata, 700098 India (India)

    2017-01-01

    Active control of droplet generation in a microfluidic platform attracts interest for development of digital microfluidic devices ranging from biosensors to micro-reactors to point-of-care diagnostic devices. The present paper characterizes, through an unsteady three-dimensional Volume of Fluid (VOF) simulation, the active control of ferrofluid droplet generation in a microfluidic T-junction in presence of a non-uniform magnetic field created by an external magnetic dipole. Two distinctly different positions of the dipole were considered – one upstream of the junction and one downstream. While keeping the ferrofluid flow rate fixed, a parametric variation of the continuous phase capillary number, dipole strength, and dipole position was carried out. Differences in the flow behaviour in terms of dripping or jetting and the droplet characteristics in terms of droplet formation time period and droplet size were studied. The existence of a threshold dipole strength, below which the magnetic force was not able to influence the flow behaviour, was identified. It was also observed that, for dipoles placed upstream of the junction, droplet formation was suppressed at some higher dipole strengths, and this value was found to increase with increasing capillary number. Droplet time period was also found to increase with increasing dipole strength, along with droplet size, i.e. an increase in droplet volume. - Highlights: • Active control of ferrofluid droplet generation in a microfluidic T-junction is demonstrated. • Unsteady three-dimensional Volume of Fluid (VOF) simulation is adopted. • Capillary number, dipole strength and position influence droplet shedding behaviour. • Magnetic actuation of a microfluidic droplet generator is characterised.

  19. Radio frequency feedback method for parallelized droplet microfluidics

    KAUST Repository

    Conchouso Gonzalez, David

    2016-12-19

    This paper reports on a radio frequency micro-strip T-resonator that is integrated to a parallel droplet microfluidic system. The T-resonator works as a feedback system to monitor uniform droplet production and to detect, in real-time, any malfunctions due to channel fouling or clogging. Emulsions at different W/O flow-rate ratios are generated in a microfluidic device containing 8 parallelized generators. These emulsions are then guided towards the RF sensor, which is then read using a Network Analyzer to obtain the frequency response of the system. The proposed T-resonator shows frequency shifts of 45MHz for only 5% change in the emulsion\\'s water in oil content. These shifts can then be used as a feedback system to trigger alarms and notify production and quality control engineers about problems in the droplet generation process.

  20. Radio frequency feedback method for parallelized droplet microfluidics

    KAUST Repository

    Conchouso Gonzalez, David; Carreno, Armando Arpys Arevalo; McKerricher, Garret; Castro, David; Foulds, Ian G.

    2016-01-01

    This paper reports on a radio frequency micro-strip T-resonator that is integrated to a parallel droplet microfluidic system. The T-resonator works as a feedback system to monitor uniform droplet production and to detect, in real-time, any malfunctions due to channel fouling or clogging. Emulsions at different W/O flow-rate ratios are generated in a microfluidic device containing 8 parallelized generators. These emulsions are then guided towards the RF sensor, which is then read using a Network Analyzer to obtain the frequency response of the system. The proposed T-resonator shows frequency shifts of 45MHz for only 5% change in the emulsion's water in oil content. These shifts can then be used as a feedback system to trigger alarms and notify production and quality control engineers about problems in the droplet generation process.

  1. Low-Cost Experimentation for the Study of Droplet Microfluidics

    Science.gov (United States)

    Bardin, David; Lee, Abraham P.

    2014-01-01

    The continued growth of microfluidics into industry settings in areas such as point-of-care diagnostics and targeted therapeutics necessitates a workforce trained in microfluidic technologies and experimental methods. Laboratory courses for students at the university and high school levels will require cost-effective in-class demonstrations that instruct in chip design, fabrication, and experimentation at the microscale. We present a hand-operated pressure pumping system to form monodisperse picoliter to nanoliter droplet streams at low cost, and a series of exercises aimed at instructing in the specific art of droplet formation. Using this setup, the student is able to generate and observe the modes of droplet formation in flow-focusing devices, and the effect of device dimensions on the characteristics of formed droplets. Lastly, at ultra-low cost we demonstrate large plug formation in a T-junction using coffee stirrers as a master mold substitute. Our method reduces the cost of experimentation to enable intuitive instruction in droplet formation, with additional implications for creating droplets in the field or at point-of-care. PMID:25133595

  2. Droplet Impact on a Heated Surface under a Depressurized Environment

    Science.gov (United States)

    Hatakenaka, Ryuta; Tagawa, Yoshiyuki

    2016-11-01

    Behavior of a water droplet of the diameter 1-3mm impacting on a heated surface under depressurized environment (100kPa -1kPa) has been studied. A syringe pump for droplet generation and a heated plate are set into a transparent acrylic vacuum chamber. The internal pressure of the chamber is automatically controlled at a target pressure with a rotary pump, a pressure transducer, and an electrical valve. A silicon wafer of the thickness 0.28 mm is mounted on the heater plate, whose temperature is directly measured by attaching a thermocouple on the backside. The droplet behavior is captured using a high-speed camera in a direction perpendicular to droplet velocity. Some unique behaviors of droplet are observed by decreasing the environmental pressure, which are considered to be due to two basic elements: Enhancement of evaporation due to the lowered saturation temperature, and shortage of pneumatic spring effect between the droplet and heated wall due to the lowered pressure of the air.

  3. The dynamics of droplets in moist Rayleigh-Benard turbulence

    Science.gov (United States)

    Chandrakar, Kamal Kant; van der Voort, Dennis; Kinney, Greg; Cantrell, Will; Shaw, Raymond

    2017-11-01

    Clouds are an intricate part of the climate, and strongly influence atmospheric dynamics and radiative balances. While properties such as cloud albedo and precipitation rate are large scale effects, these properties are determined by dynamics on the microscale, such droplet sizes, liquid water content, etc. The growth of droplets from condensation is dependent on a multitude of parameters, such as aerosol concentration (nucleation sites) and turbulence (scalar fluctuations and coalescence). However, the precise mechanism behind droplet growth and clustering in a cloud environment is still unclear. In this investigation we use a facility called the Pi Chamber to generate a (miniature) cloud in a laboratory setting with known boundary conditions, such as aerosol concentration, temperature, and humidity. Through the use of particle imaging velocimetry (PIV) on the droplets generated in the cloud, we can investigate the dynamics of these cloud droplets in the convective (Rayleigh-Benard) turbulence generated through an induced temperature gradient. We show the influence of the temperature gradient and Froude number (gravity forces) on the changing turbulence anisotropy, large scale circulation, and small-scale dissipation rates. This work was supported by National Science Foundation Grant AGS-1623429.

  4. In-line characterization and identification of micro-droplets on-chip

    Directory of Open Access Journals (Sweden)

    Weber Emanuel

    2014-01-01

    Full Text Available We present an integrated optofluidic sensor system for in-line characterization of micro-droplets. The device provides information about the droplet generation frequency, the droplet volume, and the content of the droplet. Due to its simplicity this principle can easily be implemented with other microfluidic components on one and the same device. The sensor is based on total internal reflection phenomena. Droplets are pushed through a microfluidic channel which is hit by slightly diverging monochromatic light. At the solid-liquid interface parts of the rays experience total internal reflection while another part is transmitted. The ratio of reflected to transmitted light depends on the refractive index of the solution. Both signals are recorded simultaneously and provide a very stable output signal for the droplet characterization. With the proposed system passing droplets were counted up to 320 droplets per second and droplets with different volumes could be discriminated. In a final experiment droplets with different amounts of dissolved CaCl2 were distinguished based on their reflected and transmitted light pattern. This principle can be applied for the detection of any molecules in microdroplets which significantly influence the refractive index of the buffer solution.

  5. Oleoplaning droplets on lubricated surfaces

    Science.gov (United States)

    Daniel, Dan; Timonen, Jaakko V. I.; Li, Ruoping; Velling, Seneca J.; Aizenberg, Joanna

    2017-10-01

    Recently, there has been much interest in using lubricated surfaces to achieve extreme liquid repellency: a foreign droplet immiscible with the underlying lubricant layer was shown to slide off at a small tilt angle behaviour was hypothesized to arise from a thin lubricant overlayer film sandwiched between the droplet and solid substrate, but this has not been observed experimentally. Here, using thin-film interference, we are able to visualize the intercalated film under both static and dynamic conditions. We further demonstrate that for a moving droplet, the film thickness follows the Landau-Levich-Derjaguin law. The droplet is therefore oleoplaning--akin to tyres hydroplaning on a wet road--with minimal dissipative force and no contact line pinning. The techniques and insights presented in this study will inform future work on the fundamentals of wetting for lubricated surfaces and enable their rational design.

  6. Droplet Translation Actuated by Photoelectrowetting.

    Science.gov (United States)

    Palma, Cesar; Deegan, Robert D

    2018-03-13

    In traditional electrowetting-on-dielectric (EWOD) devices, droplets are moved about a substrate using electric fields produced by an array of discrete electrodes. In this study, we show that a drop can be driven across a substrate with a localized light beam by exploiting the photoelectrowetting (PEW) effect, a light-activated variant of EWOD. Droplet transport actuated by PEW eliminates the need for electrode arrays and the complexities entailed in their fabrication and control, and offers a new approach for designing lab-on-a-chip applications. We report measurements of the maximum droplet speed as a function of frequency and magnitude of the applied bias, intensity of illumination, volume of the droplet, and viscosity and also introduce a model that reproduces these data.

  7. Quantum Nanostructures by Droplet Epitaxy

    OpenAIRE

    Somsak Panyakeow

    2009-01-01

    Droplet epitaxy is an alternative growth technique for several quantum nanostructures. Indium droplets are distributed randomly on GaAs substrates at low temperatures (120-350'C). Under background pressure of group V elements, Arsenic and Phosphorous, InAs and InP nanostructures are created. Quantum rings with isotropic shape are obtained at low temperature range. When the growth thickness is increased, quantum rings are transformed to quantum dot rings. At high temperature range, anisotropic...

  8. Estimation and control of droplet size and frequency in projected spray mode of a gas metal arc welding (GMAW) process.

    Science.gov (United States)

    Anzehaee, Mohammad Mousavi; Haeri, Mohammad

    2011-07-01

    New estimators are designed based on the modified force balance model to estimate the detaching droplet size, detached droplet size, and mean value of droplet detachment frequency in a gas metal arc welding process. The proper droplet size for the process to be in the projected spray transfer mode is determined based on the modified force balance model and the designed estimators. Finally, the droplet size and the melting rate are controlled using two proportional-integral (PI) controllers to achieve high weld quality by retaining the transfer mode and generating appropriate signals as inputs of the weld geometry control loop. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.

  9. Investigation of a piezoelectric droplet delivery method for fuel injection and physical property evaluation

    Science.gov (United States)

    Zhao, Wei; Menon, Shyam

    2017-11-01

    A piezoelectric droplet generator is investigated to deliver liquid hydrocarbon fuels to a micro-combustor application. Besides fuel delivery, the setup is intended to measure fuel physical properties such as viscosity and surface tension. These properties are highly relevant to spray generation in internal combustion engines. Accordingly, a drop-on-demand piezoelectric dispenser is used to generate fuel droplet trains, which are studied using imaging and Phase Doppler Particle Anemometry (PDPA). The diagnostics provide information regarding droplet size and velocity and their evolution over time. The measurements are correlated with results from one-dimensional (1D) models that incorporate sub-models for piezo-electric actuation and droplet vaporization. By validating the 1D models for fuels with known physical properties, a technique is developed that has the capability to meter low-vapor pressure liquid fuels to the microcombustor and use information from the droplet train to calculate physical properties of novel fuels.

  10. Accurate, consistent, and fast droplet splitting and dispensing in electrowetting on dielectric digital microfluidics

    Science.gov (United States)

    Nikapitiya, N. Y. Jagath B.; Nahar, Mun Mun; Moon, Hyejin

    2017-12-01

    This letter reports two novel electrode design considerations to satisfy two very important aspects of EWOD operation—(1) Highly consistent volume of generated droplets and (2) Highly improved accuracy in the generated droplet volume. Considering the design principles investigated two novel designs were proposed; L-junction electrode design to offer high throughput droplet generation and Y-junction electrode design to split a droplet very fast while maintaining equal volume of each part. Devices of novel designs were fabricated and tested, and the results are compared with those of conventional approach. It is demonstrated that inaccuracy and inconsistency of droplet volume dispensed in the device with novel electrode designs are as low as 0.17 and 0.10%, respectively, while those of conventional approach are 25 and 0.76%, respectively. The dispensing frequency is enhanced from 4 to 9 Hz by using the novel design.

  11. Dynamics of magnetic modulation of ferrofluid droplets for digital microfluidic applications

    Science.gov (United States)

    Sen, Uddalok; Chatterjee, Souvick; Sen, Swarnendu; Tiwari, Manish K.; Mukhopadhyay, Achintya; Ganguly, Ranjan

    2017-01-01

    Active control of droplet generation in a microfluidic platform attracts interest for development of digital microfluidic devices ranging from biosensors to micro-reactors to point-of-care diagnostic devices. The present paper characterizes, through an unsteady three-dimensional Volume of Fluid (VOF) simulation, the active control of ferrofluid droplet generation in a microfluidic T-junction in presence of a non-uniform magnetic field created by an external magnetic dipole. Two distinctly different positions of the dipole were considered - one upstream of the junction and one downstream. While keeping the ferrofluid flow rate fixed, a parametric variation of the continuous phase capillary number, dipole strength, and dipole position was carried out. Differences in the flow behaviour in terms of dripping or jetting and the droplet characteristics in terms of droplet formation time period and droplet size were studied. The existence of a threshold dipole strength, below which the magnetic force was not able to influence the flow behaviour, was identified. It was also observed that, for dipoles placed upstream of the junction, droplet formation was suppressed at some higher dipole strengths, and this value was found to increase with increasing capillary number. Droplet time period was also found to increase with increasing dipole strength, along with droplet size, i.e. an increase in droplet volume.

  12. Study of droplet flow in a T-shape microchannel with bottom wall fluctuation

    Science.gov (United States)

    Pang, Yan; Wang, Xiang; Liu, Zhaomiao

    2018-03-01

    Droplet generation in a T-shape microchannel, with a main channel width of 50 μm , side channel width of 25 μm, and height of 50 μm, is simulated to study the effects of the forced fluctuation of the bottom wall. The periodic fluctuations of the bottom wall are applied on the near junction part of the main channel in the T-shape microchannel. Effects of bottom wall's shape, fluctuation periods, and amplitudes on the droplet generation are covered in the research of this protocol. In the simulation, the average size is affected a little by the fluctuations, but significantly by the fixed shape of the deformed bottom wall, while the droplet size range is expanded by the fluctuations under most of the conditions. Droplet sizes are distributed in a periodic pattern with small amplitude along the relative time when the fluctuation is forced on the bottom wall near the T-junction, while the droplet emerging frequency is not varied by the fluctuation. The droplet velocity is varied by the bottom wall motion, especially under the shorter period and the larger amplitude. When the fluctuation period is similar to the droplet emerging period, the droplet size is as stable as the non-fluctuation case after a development stage at the beginning of flow, while the droplet velocity is varied by the moving wall with the scope up to 80% of the average velocity under the conditions of this investigation.

  13. Toward single enzyme analysis in a droplet-based micro and nanofluidic system

    NARCIS (Netherlands)

    Arayanarakool, Rerngchai

    2012-01-01

    In this thesis, we have demonstrated the application of micro- and nanofluidic devices to generate an array of aqueous droplets in oil phase for single-enzyme encapsulation and activity measurement. We chose droplet-based microfluidics for this purpose of monitoring single-enzyme reactions since the

  14. Micro-Droplet Detection Method for Measuring the Concentration of Alkaline Phosphatase-Labeled Nanoparticles in Fluorescence Microscopy

    Directory of Open Access Journals (Sweden)

    Rufeng Li

    2017-11-01

    Full Text Available This paper developed and evaluated a quantitative image analysis method to measure the concentration of the nanoparticles on which alkaline phosphatase (AP was immobilized. These AP-labeled nanoparticles are widely used as signal markers for tagging biomolecules at nanometer and sub-nanometer scales. The AP-labeled nanoparticle concentration measurement can then be directly used to quantitatively analyze the biomolecular concentration. Micro-droplets are mono-dispersed micro-reactors that can be used to encapsulate and detect AP-labeled nanoparticles. Micro-droplets include both empty micro-droplets and fluorescent micro-droplets, while fluorescent micro-droplets are generated from the fluorescence reaction between the APs adhering to a single nanoparticle and corresponding fluorogenic substrates within droplets. By detecting micro-droplets and calculating the proportion of fluorescent micro-droplets to the overall micro-droplets, we can calculate the AP-labeled nanoparticle concentration. The proposed micro-droplet detection method includes the following steps: (1 Gaussian filtering to remove the noise of overall fluorescent targets, (2 a contrast-limited, adaptive histogram equalization processing to enhance the contrast of weakly luminescent micro-droplets, (3 an red maximizing inter-class variance thresholding method (OTSU to segment the enhanced image for getting the binary map of the overall micro-droplets, (4 a circular Hough transform (CHT method to detect overall micro-droplets and (5 an intensity-mean-based thresholding segmentation method to extract the fluorescent micro-droplets. The experimental results of fluorescent micro-droplet images show that the average accuracy of our micro-droplet detection method is 0.9586; the average true positive rate is 0.9502; and the average false positive rate is 0.0073. The detection method can be successfully applied to measure AP-labeled nanoparticle concentration in fluorescence microscopy.

  15. Micro-Droplet Detection Method for Measuring the Concentration of Alkaline Phosphatase-Labeled Nanoparticles in Fluorescence Microscopy.

    Science.gov (United States)

    Li, Rufeng; Wang, Yibei; Xu, Hong; Fei, Baowei; Qin, Binjie

    2017-11-21

    This paper developed and evaluated a quantitative image analysis method to measure the concentration of the nanoparticles on which alkaline phosphatase (AP) was immobilized. These AP-labeled nanoparticles are widely used as signal markers for tagging biomolecules at nanometer and sub-nanometer scales. The AP-labeled nanoparticle concentration measurement can then be directly used to quantitatively analyze the biomolecular concentration. Micro-droplets are mono-dispersed micro-reactors that can be used to encapsulate and detect AP-labeled nanoparticles. Micro-droplets include both empty micro-droplets and fluorescent micro-droplets, while fluorescent micro-droplets are generated from the fluorescence reaction between the APs adhering to a single nanoparticle and corresponding fluorogenic substrates within droplets. By detecting micro-droplets and calculating the proportion of fluorescent micro-droplets to the overall micro-droplets, we can calculate the AP-labeled nanoparticle concentration. The proposed micro-droplet detection method includes the following steps: (1) Gaussian filtering to remove the noise of overall fluorescent targets, (2) a contrast-limited, adaptive histogram equalization processing to enhance the contrast of weakly luminescent micro-droplets, (3) an red maximizing inter-class variance thresholding method (OTSU) to segment the enhanced image for getting the binary map of the overall micro-droplets, (4) a circular Hough transform (CHT) method to detect overall micro-droplets and (5) an intensity-mean-based thresholding segmentation method to extract the fluorescent micro-droplets. The experimental results of fluorescent micro-droplet images show that the average accuracy of our micro-droplet detection method is 0.9586; the average true positive rate is 0.9502; and the average false positive rate is 0.0073. The detection method can be successfully applied to measure AP-labeled nanoparticle concentration in fluorescence microscopy.

  16. Frugal Droplet Microfluidics Using Consumer Opto-Electronics.

    Science.gov (United States)

    Frot, Caroline; Taccoen, Nicolas; Baroud, Charles N

    2016-01-01

    The maker movement has shown how off-the-shelf devices can be combined to perform operations that, until recently, required expensive specialized equipment. Applying this philosophy to microfluidic devices can play a fundamental role in disseminating these technologies outside specialist labs and into industrial use. Here we show how nanoliter droplets can be manipulated using a commercial DVD writer, interfaced with an Arduino electronic controller. We couple the optical setup with a droplet generation and manipulation device based on the "confinement gradients" approach. This device uses regions of different depths to generate and transport the droplets, which further simplifies the operation and reduces the need for precise flow control. The use of robust consumer electronics, combined with open source hardware, leads to a great reduction in the price of the device, as well as its footprint, without reducing its performance compared with the laboratory setup.

  17. 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.

  18. Calculation of spin-spin zero-field splitting within periodic boundary conditions: Towards all-electron accuracy

    Science.gov (United States)

    Biktagirov, Timur; Schmidt, Wolf Gero; Gerstmann, Uwe

    2018-03-01

    For high-spin centers, one of the key spectroscopic fingerprints is the zero-field splitting (ZFS) addressable by electron paramagnetic resonance. In this paper, an implementation of the spin-spin contribution to the ZFS tensor within the projector augmented-wave (PAW) formalism is reported. We use a single-determinant approach proposed by M. J. Rayson and P. R. Briddon [Phys. Rev. B 77, 035119 (2008), 10.1103/PhysRevB.77.035119], and complete it by adding a PAW reconstruction term which has not been taken into account before. We benchmark the PAW approach against a well-established all-electron method for a series of diatomic radicals and defects in diamond and cubic silicon carbide. While for some of the defect centers the PAW reconstruction is found to be almost negligible, in agreement with the common assumption, we show that in general it significantly improves the calculated ZFS towards the all-electron results.

  19. Modeling study of droplet behavior during blowdown period of large break LOCA based on experimental data

    International Nuclear Information System (INIS)

    Sakaba, Hiroshi; Umezawa, Shigemitsu; Teramae, Tetsuya; Furukawa, Yuji

    2004-01-01

    During LOCA (Loss Of Coolant Accident) in PWR, droplets behavior during blowdown period is one of the important phenomena. For example, the spattering from falling liquid film that flows from upper plenum generates those droplets in core region. The behavior of droplets in such flow has strong effect for cladding temperature behavior because these droplets are able to remove heat from a reactor core by its direct contact on fuel rods and its evaporation at the surface. For safety analysis of LOCA in PWR, it is necessary to evaluate droplet diameter precisely in order to predict fuel cladding temperature changing by the calculation code. Based on the test results, a new droplet behavior model was developed for the MCOBRA/TRC code that predicts the droplet behavior during such LOCA events. Furthermore, the verification calculations that simulated some blowdown tests were performed using by the MCOBRA/TRAC code. These results indicated the validity of this droplet model during blow down cooling period. The experiment was focused on investigating the Weber number of steady droplet in the blow down phenomenon of large break LOCA. (author)

  20. Communication: Mode bifurcation of droplet motion under stationary laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Takabatake, Fumi [Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Department of Bioengineering and Robotics, Graduate School of Engineering, Tohoku University, Sendai, Miyagi 980-8579 (Japan); Yoshikawa, Kenichi [Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe, Kyoto 610-0394 (Japan); Ichikawa, Masatoshi, E-mail: ichi@scphys.kyoto-u.ac.jp [Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)

    2014-08-07

    The self-propelled motion of a mm-sized oil droplet floating on water, induced by a local temperature gradient generated by CW laser irradiation is reported. The circular droplet exhibits two types of regular periodic motion, reciprocal and circular, around the laser spot under suitable laser power. With an increase in laser power, a mode bifurcation from rectilinear reciprocal motion to circular motion is caused. The essential aspects of this mode bifurcation are discussed in terms of spontaneous symmetry-breaking under temperature-induced interfacial instability, and are theoretically reproduced with simple coupled differential equations.

  1. Instability of expanding bacterial droplets.

    Science.gov (United States)

    Sokolov, Andrey; Rubio, Leonardo Dominguez; Brady, John F; Aranson, Igor S

    2018-04-03

    Suspensions of motile bacteria or synthetic microswimmers, termed active matter, manifest a remarkable propensity for self-organization, and formation of large-scale coherent structures. Most active matter research deals with almost homogeneous in space systems and little is known about the dynamics of strongly heterogeneous active matter. Here we report on experimental and theoretical studies on the expansion of highly concentrated bacterial droplets into an ambient bacteria-free fluid. The droplet is formed beneath a rapidly rotating solid macroscopic particle inserted in the suspension. We observe vigorous instability of the droplet reminiscent of a violent explosion. The phenomenon is explained in terms of continuum first-principle theory based on the swim pressure concept. Our findings provide insights into the dynamics of active matter with strong density gradients and significantly expand the scope of experimental and analytic tools for control and manipulation of active systems.

  2. Block-and-break generation of microdroplets with fixed volume

    NARCIS (Netherlands)

    Van Steijn, V.; Korczyk, P.M.; Derzsi, L.; Abate, A.R.; Weitz, D.A.; Garstecki, P.

    2013-01-01

    We introduce a novel type of droplet generator that produces droplets of a volume set by the geometry of the droplet generator and not by the flow rates of the liquids. The generator consists of a classic T-junction with a bypass channel. This bypass directs the continuous fluid around the forming

  3. 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.

  4. All Electron ab initio Investigations of the Three Lowest Lying Electronic States of the RuC Molecule

    DEFF Research Database (Denmark)

    Shim, Irene; Gingerich, K. A.

    2000-01-01

    The three lowest-lying electronic states of RuC, (1)Sigma(+), (3)Delta, and (1)Delta, have been investigated by performing all-electron ab initio multi-configuration self-consistent-field (CASSCF) and multi-reference configuration interaction (MRCI) calculations including relativistic corrections....... The electronic ground state is derived as (1)Sigma(+) with the spectroscopic constants r(e) = 1.616 Angstrom and omega(e) = 1085 cm(-1). The lowest-lying excited state, (3)Delta, has r(e) = 1.632 Angstrom, omega(e) = 1063 cm(-1), and T-e = 912 cm(-1). These results are consistent with recent spectroscopic values....... The chemical bonds in all three lowest-lying states are triple bonds composed of one sigma and two pi bonds. (C) 2000 Elsevier Science B.V. All rights reserved....

  5. All-electron ab initio calculations of YBa2Cu3O7 with self-consistence crystal field

    Institute of Scientific and Technical Information of China (English)

    刘洪霖; 陈念贻

    1995-01-01

    The quantum chemical calculations of cluster YBa2Cu3O7 considering all electrons have been per-formed by using the ab initio HF method with self-consistence crystal field.A Hartree-Fork surface potentialis proposed to make an asymmetric duster model possess a relatively symmetric potential field and to obtaina relatively symmetric electronic structure,electronic distributions,frontier orbitals,and bond order,etc.Thesuggestions that there exists a covalent bonding complex,[CuO2-O-CuO-O-Cu2]6,8-,in the cell unit ofthe crystal,and the cell units are connected with each other by ionic bonds along the c direction of the crys-tal lattice are offered based on the chemical bonding characteristics from the calculated results.The importantcontribution of the apical oxygen to superconductivities is emphasized as well.

  6. Ultrahigh throughput microfluidic platform for in-air production of microscale droplets

    Science.gov (United States)

    Tirandazi, Pooyan; Healy, John; Hidrovo, Carlos H.

    2017-11-01

    In-air droplet formation inside microfluidic networks is an alternative technique to the conventional in-liquid systems for creating uniform, microscale droplets. Recent works have highlighted and quantified the use of a gaseous continuous phase for controlled generation of droplets in the Dripping regime in planar structures. Here we demonstrate a new class of non-planar droplet-based systems which rely on controlled breakup of a liquid microjet within a high speed flow of air inside a confined microfluidic flow-focusing PDMS channel. We investigate the physics of confined gas-liquid flows and the effect of geometry on the behavior of a liquid water jet in a gaseous flow. Droplet breakup in the Jetting regime is studied both numerically and experimentally and the results are compared. We show droplet production capability at rates higher than 100 KHz with droplets ranging from 15-30 μm in diameter and a polydispersity index of less than 15%. This work represents an important investigation into the Jetting regime in confined microchannels. The ability to control jet behavior, generation rate, and droplet size in gas-liquid microflows will further expand the potential applications of this system for high throughput operations in material synthesis and biochemical analysis. We acknowledge funding support from NSF CAREER Award Grant CBET-1522841.

  7. A numerical study on the dynamics of droplet formation in a microfluidic double T-junction.

    Science.gov (United States)

    Ngo, Ich-Long; Dang, Trung-Dung; Byon, Chan; Joo, Sang Woo

    2015-03-01

    In this study, droplet formations in microfluidic double T-junctions (MFDTD) are investigated based on a two-dimensional numerical model with volume of fluid method. Parametric ranges for generating alternating droplet formation (ADF) are identified. A physical background responsible for the ADF is suggested by analyzing the dynamical stability of flow system. Since the phase discrepancy between dispersed flows is mainly caused by non-symmetrical breaking of merging droplet, merging regime becomes the alternating regime at appropriate conditions. In addition, the effects of channel geometries on droplet formation are studied in terms of relative channel width. The predicted results show that the ADF region is shifted toward lower capillary numbers when channel width ratio is less than unity. The alternating droplet size increases with the increase of channel width ratio. When this ratio reaches unity, alternating droplets can be formed at very high water fraction (wf = 0.8). The droplet formation in MFDTD depends significantly on the viscosity ratio, and the droplet size in ADF decreases with the increase of the viscosity ratio. The understanding of underlying physics of the ADF phenomenon is useful for many applications, including nanoparticle synthesis with different concentrations, hydrogel bead generation, and cell transplantation in biomedical therapy.

  8. Colliding droplets: A short film presentation

    Science.gov (United States)

    Hendricks, C. D.

    1981-12-01

    A series of experiments were performed in which liquid droplets were caused to collide. Impact velocities to several meters per second and droplet diameters up to 600 micrometers were used. The impact parameters in the collisions vary from zero to greater than the sum of the droplet radii. Photographs of the collisions were taken with a high speed framing camera in order to study the impacts and subsequent behavior of the droplets.

  9. Dynamics and Suppression Effectiveness of Monodisperse Water Droplets in Non-Premixed Counterflow Flames

    National Research Council Canada - National Science Library

    Zegers, E. J; Williams, B. A; Sheinson, R. S; Fleming, J. W

    2000-01-01

    ...-premixed propane/air counterflow flames are reported. Droplets were generated piezoelectrically, and the size and velocity distributions and the number density were determined by phase-Doppler particle anemometry...

  10. Droplet centrifugation, droplet DNA extraction, and rapid droplet thermocycling for simpler and faster PCR assay using wire-guided manipulations.

    Science.gov (United States)

    You, David J; Yoon, Jeong-Yeol

    2012-09-04

    A computer numerical control (CNC) apparatus was used to perform droplet centrifugation, droplet DNA extraction, and rapid droplet thermocycling on a single superhydrophobic surface and a multi-chambered PCB heater. Droplets were manipulated using "wire-guided" method (a pipette tip was used in this study). This methodology can be easily adapted to existing commercial robotic pipetting system, while demonstrated added capabilities such as vibrational mixing, high-speed centrifuging of droplets, simple DNA extraction utilizing the hydrophobicity difference between the tip and the superhydrophobic surface, and rapid thermocycling with a moving droplet, all with wire-guided droplet manipulations on a superhydrophobic surface and a multi-chambered PCB heater (i.e., not on a 96-well plate). Serial dilutions were demonstrated for diluting sample matrix. Centrifuging was demonstrated by rotating a 10 μL droplet at 2300 round per minute, concentrating E. coli by more than 3-fold within 3 min. DNA extraction was demonstrated from E. coli sample utilizing the disposable pipette tip to cleverly attract the extracted DNA from the droplet residing on a superhydrophobic surface, which took less than 10 min. Following extraction, the 1500 bp sequence of Peptidase D from E. coli was amplified using rapid droplet thermocycling, which took 10 min for 30 cycles. The total assay time was 23 min, including droplet centrifugation, droplet DNA extraction and rapid droplet thermocycling. Evaporation from of 10 μL droplets was not significant during these procedures, since the longest time exposure to air and the vibrations was less than 5 min (during DNA extraction). The results of these sequentially executed processes were analyzed using gel electrophoresis. Thus, this work demonstrates the adaptability of the system to replace many common laboratory tasks on a single platform (through re-programmability), in rapid succession (using droplets), and with a high level of

  11. Droplet centrifugation, droplet DNA extraction, and rapid droplet thermocycling for simpler and faster PCR assay using wire-guided manipulations

    Directory of Open Access Journals (Sweden)

    You David J

    2012-09-01

    Full Text Available Abstract A computer numerical control (CNC apparatus was used to perform droplet centrifugation, droplet DNA extraction, and rapid droplet thermocycling on a single superhydrophobic surface and a multi-chambered PCB heater. Droplets were manipulated using “wire-guided” method (a pipette tip was used in this study. This methodology can be easily adapted to existing commercial robotic pipetting system, while demonstrated added capabilities such as vibrational mixing, high-speed centrifuging of droplets, simple DNA extraction utilizing the hydrophobicity difference between the tip and the superhydrophobic surface, and rapid thermocycling with a moving droplet, all with wire-guided droplet manipulations on a superhydrophobic surface and a multi-chambered PCB heater (i.e., not on a 96-well plate. Serial dilutions were demonstrated for diluting sample matrix. Centrifuging was demonstrated by rotating a 10 μL droplet at 2300 round per minute, concentrating E. coli by more than 3-fold within 3 min. DNA extraction was demonstrated from E. coli sample utilizing the disposable pipette tip to cleverly attract the extracted DNA from the droplet residing on a superhydrophobic surface, which took less than 10 min. Following extraction, the 1500 bp sequence of Peptidase D from E. coli was amplified using rapid droplet thermocycling, which took 10 min for 30 cycles. The total assay time was 23 min, including droplet centrifugation, droplet DNA extraction and rapid droplet thermocycling. Evaporation from of 10 μL droplets was not significant during these procedures, since the longest time exposure to air and the vibrations was less than 5 min (during DNA extraction. The results of these sequentially executed processes were analyzed using gel electrophoresis. Thus, this work demonstrates the adaptability of the system to replace many common laboratory tasks on a single platform (through re-programmability, in rapid succession (using droplets

  12. High intensity laser interactions with sub-micron droplets

    International Nuclear Information System (INIS)

    Mountford, L.C.

    1999-01-01

    A high-density source of liquid ethanol droplets has been developed, characterised and used in laser interaction studies for the first time. Mie Scattering and attenuation measurements show that droplets with a radius of (0.5 ± 0.1) μm and atomic densities of 10 19 atoms/cm 3 can be produced, bridging the gap between clusters and macroscopic solids. Lower density (10 16 cm -3 ) sprays can also be produced and these are electrostatically split into smaller droplets with a radius of (0.3 ± 0.1) μm. This work has been accepted for publication in Review of Scientific Instruments. A range of high intensity interaction experiments have been carried out with this unique sub-micron source. The absolute yield of keV x-rays, generated using 527 nm, 2 ps pulses focused to ∼10 17 W/cm 2 , was measured for the first time. ∼7 μJ of x-rays with photon energies above 1 keV were produced, comparable to yields obtained from much higher Z Xenon clusters. At intensities ≤10 16 W/cm 2 the yield from droplets exceeds that from solid targets of similar Z. The droplet medium is debris free and self-renewing, providing a suitable x-ray source for lithographic techniques. Due to the spacing between the droplets, it was expected that the droplet plasma temperature would exceed that of a solid target plasma, which is typically limited by rapid heat conduction to <1 keV. Analysis of the x-ray data shows this to be true with a mean droplet plasma temperature of (2 ± 0.8) keV, and a number of measurements exceeding 5 keV (to appear in Applied Physics Letters). The absorption of high intensity laser pulses in the dense spray has been measured for the first time and this was found to be wavelength and polarisation independent and in excess of 60%. These first interaction measurements clearly indicate that there are significant differences between the laser heating of droplet, solid and cluster targets. (author)

  13. Some Physics Inside Drying Droplets

    Indian Academy of Sciences (India)

    IAS Admin

    trial applications in food, biochemical or soil sciences. .... Take a metal spoon (or any other surface that does ..... samples. The shape of the suspended particles inside the droplet itself can be used to eliminate the coffee ring effect. For example ...

  14. Vapor-droplet flow equations

    International Nuclear Information System (INIS)

    Crowe, C.T.

    1975-01-01

    General features of a vapor-droplet flow are discussed and the equations expressing the conservation of mass, momentum, and energy for the vapor, liquid, and mixture using the control volume approach are derived. The phenomenological laws describing the exchange of mass, momentum, and energy between phases are also reviewed. The results have application to development of water-dominated geothermal resources

  15. Droplets, Bubbles and Ultrasound Interactions

    NARCIS (Netherlands)

    Shpak, O.; Verweij, M.; de Jong, N.; Versluis, Michel; Escoffre, J.M.; Bouakaz, A.

    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

  16. Liquid droplet radiator performance studies

    Science.gov (United States)

    Mattick, A. T.; Hertzberg, A.

    By making use of droplets rather than solid surfaces to radiate waste heat in space, the liquid droplet radiator (LDR) achieves a radiating area/mass much larger than that of conventional radiators which use fins or heat pipes. The lightweight potential of the LDR is shown to be limited primarily by the radiative properties of the droplets. The requirement that the LDR heat transfer fluid have a very low vapor pressure limits the choice of fluids to relatively few—several liquid metals and Dow 705 silicone fluid are the only suitable candidates so far identified. An experimental determination of the emittance of submillimeter droplets of Dow 705 fluid indicates than an LDR using this fluid at temperatures of 275-335 K would be ⋍ 10 times lighter than the lightest solid surface radiators. Although several liquid metals appear to offer excellent performance in LDR applications at temperatures between 200 K and 975 K, experimental determination of liquid metal emissivities is needed for a conclusive assessment.

  17. 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...

  18. Spin lattices of walking droplets

    Science.gov (United States)

    Saenz, Pedro; Pucci, Giuseppe; Goujon, Alexis; Dunkel, Jorn; Bush, John

    2017-11-01

    We present the results of an experimental investigation of the spontaneous emergence of collective behavior in spin lattice of droplets walking on a vibrating fluid bath. The bottom topography consists of relatively deep circular wells that encourage the walking droplets to follow circular trajectories centered at the lattice sites, in one direction or the other. Wave-mediated interactions between neighboring drops are enabled through a thin fluid layer between the wells. The sense of rotation of the walking droplets may thus become globally coupled. When the coupling is sufficiently strong, interactions with neighboring droplets may result in switches in spin that lead to preferred global arrangements, including correlated (all drops rotating in the same direction) or anti-correlated (neighboring drops rotating in opposite directions) states. Analogies with ferromagnetism and anti-ferromagnetism are drawn. Different spatial arrangements are presented in 1D and 2D lattices to illustrate the effects of topological frustration. This work was supported by the US National Science Foundation through Grants CMMI-1333242 and DMS-1614043.

  19. Some Physics Inside Drying Droplets

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 19; Issue 2. Some Physics Inside Drying Droplets. Dileep Mampallil. General Article Volume 19 Issue 2 February 2014 pp 123-134. Fulltext. Click here to view fulltext PDF. Permanent link: https://www.ias.ac.in/article/fulltext/reso/019/02/0123-0134 ...

  20. Studies of the plasma droplet accelerator scheme

    International Nuclear Information System (INIS)

    Mori, W.B.; Joshi, C.; Dawson, J.M.; Lee, K.; Forslund, D.W.; Kindel, J.M.

    1985-01-01

    In the plasma droplet accelerator scheme, proposed by R. Palmer, a sequence of liquid micro-spheres generated by a jet printer are ionized by an incoming intense laser. The hope is that the micro-spheres now acting as conducting balls will allow efficient coupling of the incoming laser radiation into an accelerating mode. Motivated by this the authors have carried out 2D, particle simulations in order to answer some of the plasma physics questions hitherto unaddressed. In particular they find that at least for laser intensities exceeding v 0 /c=0.03 (/sup ∼/10 13 w/cm 2 for a CO 2 laser), the incident laser light is rather efficiently absorbed in a hot electron distribution. Up to 70% of the incident energy can be absorbed by these electrons which rapidly expand and fill the vacuum space between the microspheres with a low density plasma. These results indicate that it is advisable to stay clear of plasma formation and thus put on an upper limit on the maximum surface fields that can be tolerated in the droplet-accelerator scheme

  1. Studies of the plasma droplet accelerator scheme

    International Nuclear Information System (INIS)

    Mori, W.B.; Dawson, J.M.; Forslund, D.W.; Joshi, C.; Kindel, J.M.; Lee, K.

    1985-01-01

    In the plasma droplet accelerator scheme, proposed by R. Palmer, a sequence of liquid micro-spheres generated by a jet printer are ionized by an incoming intense laser. The hope is that the micro-spheres now acting as conducting balls will allow efficient coupling of the incoming laser radiation into an accelerating mode. Motivated by this we have carried out 2D, particle simulations in order to answer some of the plasma physics questions hitherto unaddressed. In particular we find that at least for laser intensities exceeding v /SUB o/ /c=0.03 ( about10 13 w/cm 2 for a CO 2 laser), the incident laser light is rather efficiently absorbed in a hot electron distribution. Up to 70% of the incident energy can be absorbed by these electrons which rapidly expand and fill the vacuum space between the microspheres with a low density plasma. These results indicate that it is advisable to stay clear of plasma formation and thus put on an upper limit on the maximum surface fields that can be tolerated in the droplet-accelerator scheme

  2. GPU-Accelerated Large-Scale Electronic Structure Theory on Titan with a First-Principles All-Electron Code

    Science.gov (United States)

    Huhn, William Paul; Lange, Björn; Yu, Victor; Blum, Volker; Lee, Seyong; Yoon, Mina

    Density-functional theory has been well established as the dominant quantum-mechanical computational method in the materials community. Large accurate simulations become very challenging on small to mid-scale computers and require high-performance compute platforms to succeed. GPU acceleration is one promising approach. In this talk, we present a first implementation of all-electron density-functional theory in the FHI-aims code for massively parallel GPU-based platforms. Special attention is paid to the update of the density and to the integration of the Hamiltonian and overlap matrices, realized in a domain decomposition scheme on non-uniform grids. The initial implementation scales well across nodes on ORNL's Titan Cray XK7 supercomputer (8 to 64 nodes, 16 MPI ranks/node) and shows an overall speed up in runtime due to utilization of the K20X Tesla GPUs on each Titan node of 1.4x, with the charge density update showing a speed up of 2x. Further acceleration opportunities will be discussed. Work supported by the LDRD Program of ORNL managed by UT-Battle, LLC, for the U.S. DOE and by the Oak Ridge Leadership Computing Facility, which is a DOE Office of Science User Facility supported under Contract DE-AC05-00OR22725.

  3. 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.

  4. Effect of droplet size on the droplet behavior on the heterogeneous surface

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Ho Yeon; Son, Sung Wan; Ha, ManYeong [Pusan National University, Busan (Korea, Republic of); Park, Yong Gap [Pusan National University, Busan (Korea, Republic of)

    2017-06-15

    The characteristics of a three-dimensional hemispherical droplet on a heterogeneous surface were studied using the Lattice Boltzmann method (LBM). The hydrophilic surface has a hydrophobic part at the center. The hemispherical droplets are located at the center of the heterogeneous surface. According to the contact angles of hydrophilic and hydrophobic bottom surfaces, the droplet either separates or reaches a new equilibrium state. The separation time varies according to the change in droplet size, and it affects the status of droplet separation. The droplet separation behavior was investigated by analyzing the velocity vector around the phase boundary line. The shape and separation time of a droplet are determined by the contact angle of each surface. The speed of droplet separation increases as the difference in contact angle increases between the hydrophobic surface and hydrophilic surface. The separation status and the separation time of a droplet are also determined by the change of the droplet size. As the size of the droplet decreases, the effect of surface tension decreases, and the separation time of the droplet also decreases. On the other hand, as the droplet becomes larger, the effect of surface tension increases and the time required for the droplet to separate also increases.

  5. Quantum Nanostructures by Droplet Epitaxy

    Directory of Open Access Journals (Sweden)

    Somsak Panyakeow

    2009-02-01

    Full Text Available Droplet epitaxy is an alternative growth technique for several quantum nanostructures. Indium droplets are distributed randomly on GaAs substrates at low temperatures (120-350'C. Under background pressure of group V elements, Arsenic and Phosphorous, InAs and InP nanostructures are created. Quantum rings with isotropic shape are obtained at low temperature range. When the growth thickness is increased, quantum rings are transformed to quantum dot rings. At high temperature range, anisotropic strain gives rise to quantum rings with square holes and non-uniform ring stripe. Regrowth of quantum dots on these anisotropic quantum rings, Quadra-Quantum Dots (QQDs could be realized. Potential applications of these quantum nanostructures are also discussed.

  6. Block-and-break generation of microdroplets with fixed volume

    Science.gov (United States)

    van Steijn, Volkert; Korczyk, Piotr M.; Derzsi, Ladislav; Abate, Adam R.; Weitz, David A.; Garstecki, Piotr

    2013-01-01

    We introduce a novel type of droplet generator that produces droplets of a volume set by the geometry of the droplet generator and not by the flow rates of the liquids. The generator consists of a classic T-junction with a bypass channel. This bypass directs the continuous fluid around the forming droplets, so that they can fill the space between the inlet of the dispersed phase and the exit of the bypass without breaking. Once filled, the dispersed phase blocks the exit of the bypass and is squeezed by the continuous fluid and broken off from the junction. We demonstrate the fixed-volume droplet generator for (i) the formation of monodisperse droplets from a source of varying flow rates, (ii) the formation of monodisperse droplets containing a gradation of solute concentration, and (iii) the parallel production of monodisperse droplets. PMID:24404013

  7. Numerical and experimental studies of droplet-gas flow

    Energy Technology Data Exchange (ETDEWEB)

    Joesang, Aage Ingebret

    2002-07-01

    This thesis considers droplet-gas flow by the use of numerical methods and experimental verification. A commercial vane separator was studied both numerical and by experiment. In addition some efforts are put into the numerical analysis of cyclones. The experimental part contains detailed measurements of the flow field between a pair of vanes in a vane separator and droplet size measurements. LDA (Laser Doppler Anemometry) was used to measure the velocity in two dimensions and corresponding turbulence quantities. The results from the LDA measurements are considered to be of high quality and are compared to numerical results obtained from a CFD (Computational Fluid Dynamics) analysis. The simulation showed good agreement between the numerical and experimental results. Combinations of different turbulence models; the standard k-epsilon model and the Reynold Stress Mode, different schemes; first order and higher order scheme and different near wall treatment of the turbulence; the Law of the wall and the Two-Layer Zonal model were used in the simulations. The Reynold Stress Model together with a higher order scheme performed rather poorly. The recirculation in parts of the separator was overpredicted in this case. For the other cases the overall predictions are satisfactory. PDA (Phase Doppler Anemometry) measurements were used to study the changes in the droplet size distribution through the vane separator. The PDA measurements show that smaller droplets are found at the outlet than present at the inlet. In the literature there exists different mechanisms for explaining the re-entrainment and generation of new droplets. The re-entrainments mechanisms are divided into four groups where droplet-droplet interaction, droplet break-up, splashing of impinging droplet and re-entrainment from the film are defined as the groups of re-entrainment mechanisms. Models for these groups are found in the literature and these models are tested for re-entrainment using the operational

  8. Can a droplet break up under flow without elongating? Fragmentation of smectic monodisperse droplets

    Science.gov (United States)

    Courbin, L.; Engl, W.; Panizza, P.

    2004-06-01

    We study the fragmentation under shear flow of smectic monodisperse droplets at high volume fraction. Using small angle light scattering and optical microscopy, we reveal the existence of a break-up mechanism for which the droplets burst into daughter droplets of the same size. Surprisingly, this fragmentation process, which is strain controlled and occurs homogeneously in the cell, does not require any transient elongation of the droplets. Systematic experiments as a function of the initial droplet size and the applied shear rate show that the rupture is triggered by an instability of the inner droplet structure.

  9. Impinging Water Droplets on Inclined Glass Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Armijo, Kenneth Miguel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lance, Blake [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ho, Clifford K. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-09-01

    Multiphase computational models and tests of falling water droplets on inclined glass surfaces were developed to investigate the physics of impingement and potential of these droplets to self-clean glass surfaces for photovoltaic modules and heliostats. A multiphase volume-of-fluid model was developed in ANSYS Fluent to simulate the impinging droplets. The simulations considered different droplet sizes (1 mm and 3 mm), tilt angles (0°, 10°, and 45°), droplet velocities (1 m/s and 3 m/s), and wetting characteristics (wetting=47° contact angle and non-wetting = 93° contact angle). Results showed that the spread factor (maximum droplet diameter during impact divided by the initial droplet diameter) decreased with increasing inclination angle due to the reduced normal force on the surface. The hydrophilic surface yielded greater spread factors than the hydrophobic surface in all cases. With regard to impact forces, the greater surface tilt angles yielded lower normal forces, but higher shear forces. Experiments showed that the experimentally observed spread factor (maximum droplet diameter during impact divided by the initial droplet diameter) was significantly larger than the simulated spread factor. Observed spread factors were on the order of 5 - 6 for droplet velocities of ~3 m/s, whereas the simulated spread factors were on the order of 2. Droplets were observed to be mobile following impact only for the cases with 45° tilt angle, which matched the simulations. An interesting phenomenon that was observed was that shortly after being released from the nozzle, the water droplet oscillated (like a trampoline) due to the "snapback" caused by the surface tension of the water droplet being released from the nozzle. This oscillation impacted the velocity immediately after the release. Future work should evaluate the impact of parameters such as tilt angle and surface wettability on the impact of particle/soiling uptake and removal to investigate ways that

  10. Effects of surface properties on droplet formation inside a microfluidic device

    Science.gov (United States)

    Steinhaus, Ben; Shen, Amy

    2004-11-01

    Micro-fluidic devices offer a unique method of creating and controlling droplets on small length scales. A microfluidic device is used to study the effects of surface properties on droplet formation of a 2-phase flow system. Four phase diagrams are generated to compare the dynamics of the 2 immiscible fluid system (silicone oil and water) inside microchannels with different surface properties. Results show that the channel surface plays an important role in determining the flow patterns and the droplet formation of the 2-phase fluid system.

  11. Measuring Spray Droplet Size from Agricultural Nozzles Using Laser Diffraction

    Science.gov (United States)

    Fritz, Bradley K.; Hoffmann, W. Clint

    2016-01-01

    When making an application of any crop protection material such as an herbicide or pesticide, the applicator uses a variety of skills and information to make an application so that the material reaches the target site (i.e., plant). Information critical in this process is the droplet size that a particular spray nozzle, spray pressure, and spray solution combination generates, as droplet size greatly influences product efficacy and how the spray moves through the environment. Researchers and product manufacturers commonly use laser diffraction equipment to measure the spray droplet size in laboratory wind tunnels. The work presented here describes methods used in making spray droplet size measurements with laser diffraction equipment for both ground and aerial application scenarios that can be used to ensure inter- and intra-laboratory precision while minimizing sampling bias associated with laser diffraction systems. Maintaining critical measurement distances and concurrent airflow throughout the testing process is key to this precision. Real time data quality analysis is also critical to preventing excess variation in the data or extraneous inclusion of erroneous data. Some limitations of this method include atypical spray nozzles, spray solutions or application conditions that result in spray streams that do not fully atomize within the measurement distances discussed. Successful adaption of this method can provide a highly efficient method for evaluation of the performance of agrochemical spray application nozzles under a variety of operational settings. Also discussed are potential experimental design considerations that can be included to enhance functionality of the data collected. PMID:27684589

  12. Film Levitation of Droplet Impact on Heated Nanotube Surfaces

    Science.gov (United States)

    Duan, Fei; Tong, Wei; Qiu, Lu

    2017-11-01

    Contact boiling of an impacting droplet impacting on a heated surface can be observed when the surface temperature is able to activate the nucleation and growth of vapor bubbles, the phenomena are related to nature and industrial application. The dynamic boiling patterns us is investigated when a single falling water droplet impacts on a heated titanium (Ti) surface covered with titanium oxide (TiO2) nanotubes. In the experiments, the droplets were generated from a flat-tipped needle connected to a syringe mounted on a syringe pump. The droplet diameter and velocity before impacting on the heated surface are measured by a high-speed camera with the Weber number is varied from 45 to 220. The dynamic wetting length, spreading diameter, levitation distance, and the associated parameter are measured. Interesting film levitation on titanium (Ti) surface has been revealed. The comparison of the phase diagrams on the nanotube surface and bare Ti surface suggests that the dynamic Leidenfrost point of the surface with the TiO2 nanotubes has been significantly delayed as compared to that on a bare Ti surface. The delay is inferred to result from the increase in the surface wettability and the capillary effect by the nanoscale tube structure. The further relation is discussed.

  13. CFD Model of Water Droplet Transport for ISS Hygiene Activity

    Science.gov (United States)

    Son, Chang H.

    2011-01-01

    The goal of the study is to assess the impacts of free water propagation in the Waste and Hygiene Compartment (WHC). Free water can be generated inside the WHC in small quantities due to crew hygiene activity. To mitigate potential impact of free water in Node 3 cabin the WHC doorway is enclosed by a waterproof bump-out, Kabin, with openings at the top and bottom. At the overhead side of the rack, there is a screen that prevents large drops of water from exiting. However, as the avionics fan in the WHC causes airflow toward the deck side of the rack, small quantities of free water may exit at the bottom of the Kabin. A Computational Fluid Dynamics (CFD) analysis of Node 3 cabin airflow made possible to identify the paths of water transport. The Node 3 airflow was computed for several ventilation scenarios. To simulate the droplet transport the Lagrangian discrete phase approach was used. Various initial droplet distributions were considered in the study. The droplet diameter was varied in the range of 2-20 mm. The results of the computations showed that most of the drops fall to the rack surface not far from the WHC curtain. The probability of the droplet transport to the adjacent rack surface with electronic equipment was predicted.

  14. Highly efficient capillary polymerase chain reaction using an oscillation droplet microreactor

    International Nuclear Information System (INIS)

    Liu Dayu; Liang Guangtie; Lei Xiuxia; Chen Bin; Wang Wei; Zhou Xiaomian

    2012-01-01

    Graphical abstract: An oscillation-flow approach using a droplet reactor was developed to fully explore the potential of continuous-flow PCR. By fully utilizing interfacial chemistry, a water-in-oil (w/o) droplet was automatically generated by allowing an oil–water plug to flow through a polytetrafluoroethylene (PTFE) capillary. Due to the movement of aqueous phase relative to the oil phase, the droplet moves further into the middle of the oil plug with increase in migration distance. The resulting droplet was transported spanning the two heating zones and was employed as the reactor of oscillating-flow PCR. Highlights: ► Droplet formation in a capillary. ► Transport the droplet using oscillation-flow. ► Oscillation droplet PCR. ► Improved reaction efficiency. - Abstract: The current work presents the development of a capillary-based oscillation droplet approach to maximize the potential of a continuous-flow polymerase chain reaction (PCR). Through the full utilization of interfacial chemistry, a water-in-oil (w/o) droplet was generated by allowing an oil–water plug to flow along a polytetrafluoroethylene (PTFE) capillary. The w/o droplet functioned as the reactor for oscillating-flow PCR to provide a stable reaction environment, accelerate reagent mixing, and eliminate surface adsorption. The capillary PCR approach proposed in the current research offers high amplification efficiency, fast reaction speed, and easy system control attributable to the oscillation droplet reactor. Experimental results show that the droplet-based micro-PCR assay requires lower reaction volume (2 μL) and shorter reaction time (12 min) compared with conventional PCR methods. Taking the amplification of the New Delhi metallo-beta-lactamase (NDM-1) gene as an example, the present work demonstrates that the oscillation droplet PCR assay is capable of achieving high efficiency up to 89.5% and a detection limit of 10 DNA copies. The miniature PCR protocol developed in the current

  15. Experimental test of liquid droplet radiator performance

    Science.gov (United States)

    Mattick, A. T.; Simon, M. A.

    The liquid droplet radiator (LDR) is a heat rejection system for space power systems wherein an array of heated liquid droplets radiates energy directly to space. The use of submillimeter droplets provides large radiating area-to-mass ratio, resulting in radiator systems which are several times lighter than conventional solid surface radiators. An experiment is described in which the power radiated by an array of 2300 streams of silicone oil droplets is measured to test a previously developed theory of the LDR radiation process. This system would be capable of rejecting several kW of heat in space. Furthermore, it would be suitable as a modular unit of an LDR designed for 100-kW power levels. The experiment provided confirmation of the theoretical dependence of droplet array emissivity on optical depth. It also demonstrated the ability to create an array of more than 1000 droplet streams having a divergence less than 1 degree.

  16. A parameterization of cloud droplet nucleation

    International Nuclear Information System (INIS)

    Ghan, S.J.; Chuang, C.; Penner, J.E.

    1993-01-01

    Droplet nucleation is a fundamental cloud process. The number of aerosols activated to form cloud droplets influences not only the number of aerosols scavenged by clouds but also the size of the cloud droplets. Cloud droplet size influences the cloud albedo and the conversion of cloud water to precipitation. Global aerosol models are presently being developed with the intention of coupling with global atmospheric circulation models to evaluate the influence of aerosols and aerosol-cloud interactions on climate. If these and other coupled models are to address issues of aerosol-cloud interactions, the droplet nucleation process must be adequately represented. Here we introduce a droplet nucleation parametrization that offers certain advantages over the popular Twomey (1959) parameterization

  17. Preventing droplet deformation during dielectrophoretic centering of a compound emulsion droplet

    Science.gov (United States)

    Randall, Greg; Blue, Brent

    2012-11-01

    Compound droplets, or droplets-within-droplets, are traditionally key components in applications ranging from drug delivery to the food industry. Presently, millimeter-sized compound droplets are precursors for shell targets in inertial fusion energy work. However, a key constraint in target fabrication is a uniform shell wall thickness, which in turn requires a centered core droplet in the compound droplet precursor. Previously, Bei et al. (2009, 2010) have shown that compound droplets could be centered in a static fluid using an electric field of 0.7 kV/cm at 20 MHz. Randall et al. (2012) developed a process to center the core of a moving compound droplet, though the ~kV/cm field induced small (fluid mechanics and interfacial rheology perspective and we discuss the effective interfacial charge from an emulsifier and its impact on centering. Work funded by General Atomics Internal R&D.

  18. Evaporation of nanofluid droplet on heated surface

    Directory of Open Access Journals (Sweden)

    Yeung Chan Kim

    2015-04-01

    Full Text Available In this study, an experiment on the evaporation of nanofluid sessile droplet on a heated surface was conducted. A nanofluid of 0.5% volumetric concentration mixed with 80-nm-sized CuO powder and pure water were used for experiment. Droplet was applied to the heated surface, and images of the evaporation process were obtained. The recorded images were analyzed to find the volume, diameter, and contact angle of the droplet. In addition, the evaporative heat transfer coefficient was calculated from experimental result. The results of this study are summarized as follows: the base diameter of the droplet was maintained stably during the evaporation. The measured temperature of the droplet was increased rapidly for a very short time, then maintained constantly. The nanofluid droplet was evaporated faster than the pure water droplet under the experimental conditions of the same initial volume and temperature, and the average evaporative heat transfer coefficient of the nanofluid droplet was higher than that of pure water. We can consider the effects of the initial contact angle and thermal conductivity of nanofluid as the reason for this experimental result. However, the effect of surface roughness on the evaporative heat transfer of nanofluid droplet appeared unclear.

  19. The collaborative work of droplet assembly.

    Science.gov (United States)

    Chen, Xiao; Goodman, Joel M

    2017-10-01

    Three proteins have been implicated in the assembly of cytoplasmic lipid droplets: seipin, FIT2, and perilipin. This review examines the current theories of seipin function as well as the evidence for the involvement of all three proteins in droplet biogenesis, and ends with a proposal of how they collaborate to regulate the formation of droplets. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Droplet size in a rectangular Venturi scrubber

    OpenAIRE

    Costa, M. A. M.; Henrique, P. R.; Gonçalves, J. A. S.; Coury, J.R.

    2004-01-01

    The Venturi scrubber is a device which uses liquid in the form of droplets to efficiently remove fine particulate matter from gaseous streams. Droplet size is of fundamental importance for the scrubber performance. In the present experimental study, a laser diffraction technique was used in order to measure droplet size in situ in a Venturi scrubber with a rectangular cross section. Droplet size distribution was measured as a function of gas velocity (58.3 to 74.9 m/s), liquid-to-gas ratio (0...

  1. Calculation and measurement of fog droplet size

    International Nuclear Information System (INIS)

    Laali, A.R.; Courant, J.J.; Kleitz, A.

    1991-01-01

    This paper outlines the elements involved in calculation and measurement of fog droplet size in steam turbines. The condensation calculations are performed for a 600 MW LP fossil fired, and for a 900 MW LP nuclear turbine. A simplified method based on classical condensation theory is used for these calculations. The fog droplet size measurement are carried out downstream of the last moving blades of these turbines in order to validate the program. The comparison between the results could lead to a better understanding of the condensation process in steam turbines. Some large droplet (re-entrained droplet) measurements are also taken using a microvideo probe

  2. Colliding droplets: a short film presentation

    International Nuclear Information System (INIS)

    Hendricks, C.D.

    1981-01-01

    A series of experiments were performed in which liquid droplets were caused to collide. Impact velocities to several meters per second and droplet diameters up to 600 micrometers were used. The impact parameters in the collisions vary from zero to greater than the sum of the droplet radii. Photographs of the collisions were taken with a high speed framing camera in order to study the impacts and subsequent behavior of the droplets. The experiments will be discussed and a short movie film presentation of some of the impacts will be shown

  3. Shock wave-induced evaporation of water droplets in a gas-droplet mixture 646

    NARCIS (Netherlands)

    Goossens, H.W.J.; Cleijne, J.W.; Smolders, H.J.; Dongen, van M.E.H.

    1988-01-01

    A model is presented for the droplet evaporation process induced by a shock wave propagating in a fog. The model is based on the existence of a quasi-steady wet bulb state of the droplets during evaporation. It is shown that for moderate shock strength, Ma = <2,=" and=" droplet=" radii=" in=" the="

  4. Numerical modeling of condensate droplet on superhydrophobic nanoarrays using the lattice Boltzmann method

    International Nuclear Information System (INIS)

    Zhang Qing-Yu; Zhang You-Fa; Zhu Ming-Fang; Sun Dong-Ke

    2016-01-01

    In the present study, the process of droplet condensation on superhydrophobic nanoarrays is simulated using a multi-component multi-phase lattice Boltzmann model. The results indicate that three typical nucleation modes of condensate droplets are produced by changing the geometrical parameters of nanoarrays. Droplets nucleated at the top (top-nucleation mode), or in the upside interpillar space of nanoarrays (side-nucleation mode), generate the non-wetting Cassie state, whereas the ones nucleated at the bottom corners between the nanoarrays (bottom-nucleation mode) present the wetting Wenzel state. Time evolutions of droplet pressures at the upside and downside of the liquid phase are analyzed to understand the wetting behaviors of the droplets condensed from different nucleation modes. The phenomena of droplet condensation on nanoarrays patterned with different hydrophilic and hydrophobic regions are simulated, indicating that the nucleation mode of condensate droplets can also be manipulated by modifying the local intrinsic wettability of nanoarray surface. The simulation results are compared well with the experimental observations reported in the literature. (paper)

  5. Microlayered flow structure around an acoustically levitated droplet under a phase-change process.

    Science.gov (United States)

    Hasegawa, Koji; Abe, Yutaka; Goda, Atsushi

    2016-01-01

    The acoustic levitation method (ALM) has found extensive applications in the fields of materials science, analytical chemistry, and biomedicine. This paper describes an experimental investigation of a levitated droplet in a 19.4-kHz single-axis acoustic levitator. We used water, ethanol, water/ethanol mixture, and hexane as test samples to investigate the effect of saturated vapor pressure on the flow field and evaporation process using a high-speed camera. In the case of ethanol, water/ethanol mixtures with initial ethanol fractions of 50 and 70 wt%, and hexane droplets, microlayered toroidal vortexes are generated in the vicinity of the droplet interface. Experimental results indicate the presence of two stages in the evaporation process of ethanol and binary mixture droplets for ethanol content >10%. The internal and external flow fields of the acoustically levitated droplet of pure and binary mixtures are clearly observed. The binary mixture of the levitated droplet shows the interaction between the configurations of the internal and external flow fields of the droplet and the concentration of the volatile fluid. Our findings can contribute to the further development of existing theoretical prediction.

  6. The Liquid Droplet Radiator - an Ultralightweight Heat Rejection System for Efficient Energy Conversion in Space

    Science.gov (United States)

    Mattick, A. T.; Hertzberg, A.

    1984-01-01

    A heat rejection system for space is described which uses a recirculating free stream of liquid droplets in place of a solid surface to radiate waste heat. By using sufficiently small droplets ( 100 micron diameter) of low vapor pressure liquids the radiating droplet sheet can be made many times lighter than the lightest solid surface radiators (heat pipes). The liquid droplet radiator (LDR) is less vulnerable to damage by micrometeoroids than solid surface radiators, and may be transported into space far more efficiently. Analyses are presented of LDR applications in thermal and photovoltaic energy conversion which indicate that fluid handling components (droplet generator, droplet collector, heat exchanger, and pump) may comprise most of the radiator system mass. Even the unoptimized models employed yield LDR system masses less than heat pipe radiator system masses, and significant improvement is expected using design approaches that incorporate fluid handling components more efficiently. Technical problems (e.g., spacecraft contamination and electrostatic deflection of droplets) unique to this method of heat rejectioon are discussed and solutions are suggested.

  7. 3D trajectories re-construction of droplets ejected in controlled tungsten melting studies in ASDEX Upgrade

    International Nuclear Information System (INIS)

    Yang, Zhongshi; Krieger, K.; Lunt, T.; Brochard, F.; Briancon, J.-L.; Neu, R.; Dux, R.; Janzer, A.; Potzel, S.; Pütterich, T.

    2013-01-01

    Two fast visible range camera systems with vertically and tangentially oriented crossed viewing fields in the divertor region of ASDEX Upgrade were used to observe tungsten (W) droplets ejected from a melting W-pin into the divertor plasma. To obtain the spatial (3D) trajectories of the tungsten droplets, the trajectory of a given droplet in the (2D) camera image coordinate system was derived for each view separately. From these data, the 3D droplet position was derived by computing the shortest line segment connecting crossed viewing chords to a given droplet taking the centre coordinate of the line segment as actual coordinate. The experimental error of the derived position was estimated from the length of the connecting line segment. In the toroidal direction, the computed trajectories can be described by an analytical transport model for the droplets assuming an initial droplet diameter in the range of 60–100 μm. In the vertical direction the vertical distance droplets travelled when reaching the edge of the viewing field also agrees with the model predictions. However, discrepancies are found with respect to the time point whence a droplet reverts its initial downwards motion due to centrifugal forces exceeding gravity and plasma generated force components

  8. Experimental Observations on the Deformation and Breakup of Water Droplets Near the Leading Edge of an Airfoil

    Science.gov (United States)

    Vargas, Mario; Feo, Alex

    2011-01-01

    This work presents the results of an experimental study on droplet deformation and breakup near the leading edge of an airfoil. The experiment was conducted in the rotating rig test cell at the Instituto Nacional de Tecnica Aeroespacial (INTA) in Madrid, Spain. An airfoil model placed at the end of the rotating arm was moved at speeds of 50 to 90 m/sec. A monosize droplet generator was employed to produce droplets that were allowed to fall from above, perpendicular to the path of the airfoil at a given location. High speed imaging was employed to observe the interaction between the droplets and the airfoil. The high speed imaging allowed observation of droplet deformation and breakup as the droplet approached the airfoil near the stagnation line. A tracking software program was used to measure from the high speed movies the horizontal and vertical displacement of the droplet against time. The velocity, acceleration, Weber number, Bond number, Reynolds number, and the drag coefficients were calculated along the path of a given droplet from beginning of deformation to breakup and/or hitting the airfoil. Results are presented for droplets with a diameter of 490 micrometers at airfoil speeds of 50, 60, 70, 80 and 90 m/sec

  9. Droplet Vaporization In A Levitating Acoustic Field

    Science.gov (United States)

    Ruff, G. A.; Liu, S.; Ciobanescu, I.

    2003-01-01

    Combustion experiments using arrays of droplets seek to provide a link between single droplet combustion phenomena and the behavior of complex spray combustion systems. Both single droplet and droplet array studies have been conducted in microgravity to better isolate the droplet interaction phenomena and eliminate or reduce the effects of buoyancy-induced convection. In most experiments involving droplet arrays, the droplets are supported on fibers to keep them stationary and close together before the combustion event. The presence of the fiber, however, disturbs the combustion process by introducing a source of heat transfer and asymmetry into the configuration. As the number of drops in a droplet array increases, supporting the drops on fibers becomes less practical because of the cumulative effect of the fibers on the combustion process. To eliminate the effect of the fiber, several researchers have conducted microgravity experiments using unsupported droplets. Jackson and Avedisian investigated single, unsupported drops while Nomura et al. studied droplet clouds formed by a condensation technique. The overall objective of this research is to extend the study of unsupported drops by investigating the combustion of well-characterized drop clusters in a microgravity environment. Direct experimental observations and measurements of the combustion of droplet clusters would provide unique experimental data for the verification and improvement of spray combustion models. In this work, the formation of drop clusters is precisely controlled using an acoustic levitation system so that dilute, as well as dense clusters can be created and stabilized before combustion in microgravity is begun. While the low-gravity test facility is being completed, tests have been conducted in 1-g to characterize the effect of the acoustic field on the vaporization of single and multiple droplets. This is important because in the combustion experiment, the droplets will be formed and

  10. Slip of Spreading Viscoplastic Droplets.

    Science.gov (United States)

    Jalaal, Maziyar; Balmforth, Neil J; Stoeber, Boris

    2015-11-10

    The spreading of axisymmetric viscoplastic droplets extruded slowly on glass surfaces is studied experimentally using shadowgraphy and swept-field confocal microscopy. The microscopy furnishes vertical profiles of the radial velocity using particle image velocimetry (PIV) with neutrally buoyant tracers seeded in the fluid. Experiments were conducted for two complex fluids: aqueous solutions of Carbopol and xanthan gum. On untreated glass surfaces, PIV demonstrates that both fluids experience a significant amount of effective slip. The experiments were repeated on glass that had been treated to feature positive surface charges, thereby promoting adhesion between the negatively charged polymeric constituents of the fluids and the glass surface. The Carbopol and xanthan gum droplets spread more slowly on the treated surface and to a smaller radial distance. PIV demonstrated that this reduced spreading was associated with a substantial reduction in slip. For Carbopol, the effective slip could be eliminated entirely to within the precision of the PIV measurements; the reduction in slip was less effective for xanthan gum, with a weak slip velocity remaining noticeable.

  11. Cough aerosol in healthy participants: fundamental knowledge to optimize droplet-spread infectious respiratory disease management.

    Science.gov (United States)

    Zayas, Gustavo; Chiang, Ming C; Wong, Eric; MacDonald, Fred; Lange, Carlos F; Senthilselvan, Ambikaipakan; King, Malcolm

    2012-03-21

    The Influenza A H1N1 virus can be transmitted via direct, indirect, and airborne route to non-infected subjects when an infected patient coughs, which expels a number of different sized droplets to the surrounding environment as an aerosol. The objective of the current study was to characterize the human cough aerosol pattern with the aim of developing a standard human cough bioaerosol model for Influenza Pandemic control. 45 healthy non-smokers participated in the open bench study by giving their best effort cough. A laser diffraction system was used to obtain accurate, time-dependent, quantitative measurements of the size and number of droplets expelled by the cough aerosol. Voluntary coughs generated droplets ranging from 0.1 - 900 microns in size. Droplets of less than one-micron size represent 97% of the total number of measured droplets contained in the cough aerosol. Age, sex, weight, height and corporal mass have no statistically significant effect on the aerosol composition in terms of size and number of droplets. We have developed a standard human cough aerosol model. We have quantitatively characterized the pattern, size, and number of droplets present in the most important mode of person-to-person transmission of IRD: the cough bioaerosol. Small size droplets (< 1 μm) predominated the total number of droplets expelled when coughing. The cough aerosol is the single source of direct, indirect and/or airborne transmission of respiratory infections like the Influenza A H1N1 virus. Open bench, Observational, Cough, Aerosol study. © 2012 Zayas et al; licensee BioMed Central Ltd.

  12. Shear-driven redistribution of surfactant affects enzyme activity in well-mixed femtoliter droplets.

    Science.gov (United States)

    Liu, Yu; Jung, Seung-Yong; Collier, C Patrick

    2009-06-15

    We developed a microfluidic platform for splitting well-mixed, femtoliter-volume droplets from larger water-in-oil plugs, where the sizes of the daughter droplets were not limited by channel width. These droplets were separated from mother plugs at a microfabricated T-junction, which enabled the study of how increased confinement affected enzyme kinetics in droplets 4-10 microm in diameter. Initial rates for enzyme catalysis in the mother plugs and the largest daughter drops were close to the average bulk rate, while the rates in smaller droplets decreased linearly with increasing surface to volume ratio. Rates in the smallest droplets decreased by a factor of 4 compared to the bulk rate. Traditional methods for detecting nonspecific adsorption at the water-oil interface were unable to detect evidence of enzyme adsorption, including pendant drop tensiometry, laser scanning confocal microscopy of drops containing labeled proteins in microemulsions, and epifluorescence microscopy of plugs and drops generated on-chip. We propose the slowing of enzyme reaction kinetics in the smaller droplets was the result of increased adsorption and inactivation of enzymes at the water-oil interface arising from transient interfacial shear stresses imparted on the daughter droplets as they split from the mother plugs and passed through the constricted opening of the T-junction. Such stresses are known to modulate the interfacial area and density of surfactant molecules that can passivate the interface. Bright field images of the splitting processes at the junction indicate that these stresses scaled with increasing surface to volume ratios of the droplets but were relatively insensitive to the average flow rate of plugs upstream of the junction.

  13. Experimental test of liquid droplet radiator performance

    International Nuclear Information System (INIS)

    Mattick, A.T.; Simon, M.A.

    1986-01-01

    This liquid droplet radiator (LDR) is evolving rapidly as a lightweight system for heat rejection in space power systems. By using recirculating free streams of submillimeter droplets to radiate waste energy directly to space, the LDR can potentially be an order of magnitude lighter than conventional radiator systems which radiate from solid surfaces. The LDR is also less vulnerable to micrometeoroid damage than are conventional radiators, and it has a low transport volume. Three major development issues of this new heat rejection system are the ability to direct the droplet streams with sufficient precision to avoid fluid loss, radiative performance of the array of droplet streams which comprise the radiating elements of the LDR, and the efficacy of the droplet stream collector, again with respect to fluid loss. This paper reports experimental results bearing on the first two issues - droplet aiming in a multikilowatt-sized system, and radiated power from a large droplet array. Parallel efforts on droplet collection and LDR system design are being pursued by several research groups

  14. Multicomponent droplet vaporization in a convecting environment

    International Nuclear Information System (INIS)

    Megaridis, C.M.; Sirignano, W.A.

    1990-01-01

    In this paper a parametric study of the fundamental exchange processes for energy, mass and momentum between the liquid and gas phases of multicomponent liquid vaporizing droplets is presented. The model, which examines an isolated, vaporizing, multicomponent droplet in an axisymmetric, convecting environment, considers the different volatilities of the liquid components, the alteration of the liquid-phase properties due to the spatial/temporal variations of the species concentrations and also the effects of multicomponent diffusion. In addition, the model accounts for variable thermophysical properties, surface blowing and droplet surface regression due to vaporization, transient droplet heating with internal liquid circulation, and finally droplet deceleration with respect to the free flow due to drag. The numerical calculation employs finite-difference techniques and an iterative solution procedure that provides time-varying spatially-resolved data for both phases. The effects of initial droplet composition, ambient temperature, initial Reynolds number (based on droplet diameter), and volatility differential between the two liquid components are investigated for a liquid droplet consisting of two components with very different volatilities. It is found that mixtures with higher concentration of the less volatile substance actually vaporize faster on account of intrinsically higher liquid heating rates

  15. Droplet behavior analysis in consideration of droplet entrainment from liquid film in annular dispersed flow

    International Nuclear Information System (INIS)

    Matsuura, Keizo; Otake, Hiroshi; Kataoka, Isao; Serizawa, Akimi

    2000-01-01

    A method of droplet behavior simulation in an annular dispersed flow has been developed. In this method, both droplet deposition and entrainment from liquid film are considered. The Lagrangian method and stochastic model are used to analyze droplet diffusion and deposition behavior in a turbulent flow, and droplet entrainment from liquid film is calculated by an entrainment correlation. For the verification of this method, Gill's experiment is analyzed, in which the transition from annular flow with no entrainment to equilibrium annular dispersed flow was observed. Analysis results can also show the similar transition tendency. The experimental results of radial distribution of droplet mass flux are compared with analysis results. The agreement is good for low liquid flow rate, but entrainment rate must be adjusted for high liquid flow rate, in which gas turbulence is thought to be modified by high droplet density. In future work the effect of high droplet density on turbulence should be considered. (author)

  16. Droplet formation in Hele-Shaw T-junction.

    Science.gov (United States)

    Ricouvier, Joshua; Yazhgur, Pavel; Leshansky, Alexander; Tabeling, Patrick; Microflusa Team

    The development of digital microfluidics has attracted considerable interest towards generation of highly monodisperse microdroplets. T-junction has become an essential element of most of microfluidic chips. Despite its importance, theoretical analysis of droplet formation at T-junction is still incomplete due to complexity of physics involved. We focused on droplet generation at the Hele-Shaw T-junction. The effect of various experimental parameters, such as channel geometry, flow rates, surface tension and fluid viscosities, was thoroughly investigated. Our results show that the experimental system exhibits three distinct regimes (squeezing, dripping and jetting regimes) and point out the effect of confinement on the transitions. We demonstrate that the size of the ''plug'' droplet depends not only on the flow rate ratio (as described in the literature), but also on the capillary number and the channel cross-section aspect ratio. Quasi-2D flow equations allow us to perform numerical simulations and to compare them with experimental results. The Microflusa project receives funding from the European Union's Horizon 2020 research and innovation programme under Grant Agreement No. 664823.

  17. Preparation and nucleation of spherical metallic droplet

    Directory of Open Access Journals (Sweden)

    Bing-ge Zhao

    2015-03-01

    Full Text Available The preparation and solidification of metallic droplets attract more and more attention for their significance in both engineering and scientific fields. In this paper, the preparation and characterization of Sn-based alloy droplets using different methods such as atomization and consumable electrode direct current arc (CDCA technique are reviewed. The morphology and structure of these droplets were determined by optical microscopy, X-ray diffraction (XRD and scanning electron microscopy (SEM. The solidification behavior of single droplet was systematically studied by means of scanning calorimetry (DSC, and the nucleation kinetics was also calculated. In particular, the development of fast scanning calorimetry (FSC made it possible to investigate the evolution of undercooling under ultrafast but controllable heating and cooling conditions. The combination of CDCA technique and FSC measurements opens up a new door for quantitative studies on droplet solidification, which is accessible to demonstrate some theories by experiments.

  18. New models for droplet heating and evaporation

    KAUST Repository

    Sazhin, Sergei S.

    2013-02-01

    A brief summary of new models for droplet heating and evaporation, developed mainly at the Sir Harry Ricardo Laboratory of the University of Brighton during 2011-2012, is presented. These are hydrodynamic models for mono-component droplet heating and evaporation, taking into account the effects of the moving boundary due to evaporation, hydrodynamic models of multi-component droplet heating and evaporation, taking and not taking into account the effects of the moving boundary, new kinetic models of mono-component droplet heating and evaporation, and a model for mono-component droplet evaporation, based on molecular dynamics simulation. The results, predicted by the new models are compared with experimental data and the prehctions of the previously developed models where possible. © 2013 Asian Network for Scientific Information.

  19. Settling of fixed erythrocyte suspension droplets

    Science.gov (United States)

    Omenyi, S. N.; Snyder, R. S.

    1983-01-01

    It is pointed out that when particles behave collectively rather than individually, the fractionation of micron-size particles on the basis of size, density, and surface characteristics by centrifugation and electrophoresis is hindered. The formation and sedimentation of droplets containing particles represent an extreme example of collective behavior and pose a major problem for these separation methods when large quantities of particles need to be fractionated. Experiments are described that measure droplet sizes and settling rates for a variety of particles and droplets. Expressions relating the particle concentration in a drop to measurable quantities of the fluids and particles are developed. The number of particles in each droplet is then estimated, together with the effective droplet density. Red blood cells from different animals fixed in glutaraldehyde provide model particle groups.

  20. Droplet size in a rectangular Venturi scrubber

    Directory of Open Access Journals (Sweden)

    M. A. M. Costa

    2004-06-01

    Full Text Available The Venturi scrubber is a device which uses liquid in the form of droplets to efficiently remove fine particulate matter from gaseous streams. Droplet size is of fundamental importance for the scrubber performance. In the present experimental study, a laser diffraction technique was used in order to measure droplet size in situ in a Venturi scrubber with a rectangular cross section. Droplet size distribution was measured as a function of gas velocity (58.3 to 74.9 m/s, liquid-to-gas ratio (0.07 to 0.27 l/m³, and distance from liquid injection point (64 to 173 mm. It was found that all these variables significantly affect droplet size. The results were compared with the predictions from correlations found in the literature.

  1. Modelling the Evolution of Sea Spray Droplets on a Global Scale

    Science.gov (United States)

    Staniec, A.; Vlahos, P.; Monahan, E. C.

    2017-12-01

    Sea spray droplets are an important mechanism for the transport of moisture, heat, and organic material between the ocean and the atmosphere. Spume droplets are the largest of the size spectrum and as such have the potential to transport significant amounts of energy and gases despite their generally short residence time in the atmosphere. A model is developed based on the physical parameterizations from Andreas et al. (1995, 2005)and a range of spume generation functions, coupled with a biogeochemical exchange model for gases developed here to examine the equilibrium temperature and gas exchange of spume droplets under representative open ocean conditions. The modelling approach uses micro-physics to simulate the expected changes to the droplet as it equilibrates with the atmospheric temperature and relative humidity. The effect of temperature differentials and relative humidity variations is explored. A global approach is simulated by using average summer and winter values for SST, salinity, and air temperature throughout the various ocean basins.

  2. Droplet-fused microreactors for room temperature synthesis of nanoscale needle-like hydroxyapatite

    International Nuclear Information System (INIS)

    Liu Kaiying; Qin Jianhua

    2013-01-01

    A microfluidic device using droplet-fused microreactors is introduced for room temperature synthesis of nanoscale needle-shaped hydroxyapatite (HAp, Ca 10 (PO 4 ) 6 (OH) 2 ). The device is integrated with multifunctional units, e.g., T-junctions for droplet generation and fusion, winding channels for rapid mixing, and a delay line for simple visualization of the HAp formation process. The necessary conditions such as surfactant and fluid flow rate for an aqueous stream to merge with water-in-oil droplets are investigated. The nanoscale morphologies of the HAp produced by this method are also compared with HAp prepared by conventional bulk mixing. This paper shows that further reaction could be initiated by flowing additional reagent streams directly into the droplets of the initial reaction mixture, which is a novel approach for synthesizing a needle-like morphology of the HAp with a high aspect ratio under room temperature. (paper)

  3. Hydrodynamics and PIV study in the impingement zone formed by a droplet train

    Science.gov (United States)

    Kanjirakat, Anoop; Sadr, Reza; Zhang, Taolue; Muthusamy, Jayaveera; Alvarado, Jorge; Texas A; M University at Qatar Collaboration; Texas A; M University College Station Collaboration

    2016-11-01

    Droplet impingement is encountered in numerous technical applications, such as ink jet printing, spray cooling, and fuel injection in internal combustion engines. Even though many studies in droplet impingement were conducted in past, not many have measured the near-wall velocities in the droplet impingement zone. With the goal of gaining a better understanding of the hydrodynamics in the impingement zone, well-controlled experiments are performed in combination with micro-PIV measurements and numerical simulations. Hydrodynamics of HFE-7100 droplets generated using a piezoelectric droplet generator, impinging on a pre-wetted surface is investigated. Micro-PIV studies in the high-velocity impingement zone are performed using one-micron meter fluorescent particles dispersed in HFE-7100 along with the double exposed images. Three-dimensional and 2D-axisymmetric numerical modeling for a transient droplet crown development is performed. The interface between the gas and the liquid is modeled using a Volume of Fluid (VOF) method. Numerical simulation results obtained are observed to be in good agreement with that of the experimental observations. Supported by National Priority Research Program (NPRP) of Qatar National Research Fund (QNRF), Grant No.: NPRP 6-1304-2-525.

  4. On-chip real-time single-copy polymerase chain reaction in picoliter droplets

    Energy Technology Data Exchange (ETDEWEB)

    Beer, N R; Hindson, B; Wheeler, E; Hall, S B; Rose, K A; Kennedy, I; Colston, B

    2007-04-20

    The first lab-on-chip system for picoliter droplet generation and PCR amplification with real-time fluorescence detection has performed PCR in isolated droplets at volumes 10{sup 6} smaller than commercial real-time PCR systems. The system utilized a shearing T-junction in a silicon device to generate a stream of monodisperse picoliter droplets that were isolated from the microfluidic channel walls and each other by the oil phase carrier. An off-chip valving system stopped the droplets on-chip, allowing them to be thermal cycled through the PCR protocol without droplet motion. With this system a 10-pL droplet, encapsulating less than one copy of viral genomic DNA through Poisson statistics, showed real-time PCR amplification curves with a cycle threshold of {approx}18, twenty cycles earlier than commercial instruments. This combination of the established real-time PCR assay with digital microfluidics is ideal for isolating single-copy nucleic acids in a complex environment.

  5. Controlled production of droplets by in-flight electrospraying.

    Science.gov (United States)

    Kim, Oleg V; Dunn, Patrick F

    2010-10-19

    Diameter, velocity, and charge measurements of progeny droplets produced in-flight by a millimeter-size parent drop subjected to electric and ionic fields are reported. Different drop breakup modes were studied using phase doppler anemometry and high-speed digital photography. Drop breakup occurred in applied electric (∼1 kV/cm to ∼10 kV/cm) and ionic (∼10(13)/m(3) to ∼10(15)/m(3)) fields that were generated using a DC-corona discharge in a needle-plate configuration. Effects of the external electric field and the diameter of the parent drop are considered. Several models are summarized, including simulations of the electrohydrodynamics of the corona discharge, electrocapillary stability analysis of the jet, and progeny droplets mobility analysis. Using experimental and model results, the charge of progeny drops is shown to vary as the three-halves power of their diameter.

  6. Seed-mediated synthesis of silver nanocrystals with controlled sizes and shapes in droplet microreactors separated by air.

    Science.gov (United States)

    Zhang, Lei; Wang, Yi; Tong, Limin; Xia, Younan

    2013-12-17

    Silver nanocrystals with uniform sizes were synthesized in droplet microreactors through seed-mediated growth. The key to the success of this synthesis is the use of air as a carrier phase to generate the droplets. The air not only separates the reaction solution into droplets but also provides O2 for the generation of reducing agent (glycolaldehyde). It also serves as a buffer space for the diffusion of NO, which is formed in situ due to the oxidative etching of Ag nanocrystals with twin defects. For the first time, we were able to generate Ag nanocrystals with controlled sizes and shapes in continuous production by using droplet microreactors. For Ag nanocubes, their edge lengths could be readily controlled in the range of 30-100 nm by varying the reaction time, the amount of seeds, and the concentration of AgNO3 in the droplets. Furthermore, we demonstrated the synthesis of Ag octahedra in the droplet microreactors. We believe that the air-driven droplet generation device can be extended to other noble metals for the production of nanocrystals with controlled sizes and shapes.

  7. Entropy Analyses of Droplet Combustion in Convective Environment with Small Reynolds Number

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiaobin; ZHANG Wei; ZHANG Xuejun

    2013-01-01

    This paper analyzes the entropy generation rate of simple pure droplet combustion in a temperature-elevated air convective environment based on the solutions of flow,and heat and mass transfer between the two phases.The flow-field calculations are carried out by solving the respective conservation equations for each phase,accounting for the droplet deformation with the axisymmetric model.The effects of the temperature,velocity and oxygen fraction of the free stream air on the total entropy generation rate in the process of the droplet combustion are investigated.Special attention is given to analyze the quantitative effects of droplet deformation.The results reveal that the entropy generation rate due to chemical reaction occupies a large fraction of the total entropy generated,as a result of the large areas covered by the flame.Although,the magnitude of the entropy generation rate per volume due to heat transfer and combined mass and heat transfer has a magnitude of one order greater than that due to chemical reaction,they cover a very limited area,leading to a small fraction of the total entropy generated.The entropy generation rate due to mass transfer is negligible.High temperature and high velocity of the free stream are advantageous to increase the exergy efficiency in the range of small Reynolds number (<1) from the viewpoint of the second-law analysis over the droplet lifetime.The effect of droplet deformation on the total entropy generation is the modest.

  8. Comparison of capacitive and radio frequency resonator sensors for monitoring parallelized droplet microfluidic production

    KAUST Repository

    Conchouso Gonzalez, David

    2016-06-28

    Scaled-up production of microfluidic droplets, through the parallelization of hundreds of droplet generators, has received a lot of attention to bring novel multiphase microfluidics research to industrial applications. However, apart from droplet generation, other significant challenges relevant to this goal have never been discussed. Examples include monitoring systems, high-throughput processing of droplets and quality control procedures among others. In this paper, we present and compare capacitive and radio frequency (RF) resonator sensors as two candidates that can measure the dielectric properties of emulsions in microfluidic channels. By placing several of these sensors in a parallelization device, the stability of the droplet generation at different locations can be compared, and potential malfunctions can be detected. This strategy enables for the first time the monitoring of scaled-up microfluidic droplet production. Both sensors were prototyped and characterized using emulsions with droplets of 100-150 μm in diameter, which were generated in parallelization devices at water-in-oil volume fractions (φ) between 11.1% and 33.3%.Using these sensors, we were able to measure accurately increments as small as 2.4% in the water volume fraction of the emulsions. Although both methods rely on the dielectric properties of the emulsions, the main advantage of the RF resonator sensors is the fact that they can be designed to resonate at multiple frequencies of the broadband transmission line. Consequently with careful design, two or more sensors can be parallelized and read out by a single signal. Finally, a comparison between these sensors based on their sensitivity, readout cost and simplicity, and design flexibility is also discussed. © 2016 The Royal Society of Chemistry.

  9. Spreading of a granular droplet

    Science.gov (United States)

    Clement, Eric; Sanchez, Ivan; Raynaud, Franck; Lanuza, Jose; Andreotti, Bruno; Aranson, Igor

    2008-03-01

    The influence of controlled vibrations on the granular rheology is investigated in a specifically designed experiment in which a granular film spreads under the action of horizontal vibrations. A nonlinear diffusion equation is derived theoretically that describes the evolution of the deposit shape. A self-similar parabolic shape (the``granular droplet'') and a spreading dynamics are predicted that both agree quantitatively with the experimental results. The theoretical analysis is used to extract effective friction coefficients between the base and the granular layer under sustained and controlled vibrations. A shear thickening regime characteristic of dense granular flows is evidenced at low vibration energy, both for glass beads and natural sand. Conversely, shear thinning is observed at high agitation.

  10. Visual measurement of the evaporation process of a sessile droplet by dual-channel simultaneous phase-shifting interferometry.

    Science.gov (United States)

    Sun, Peng; Zhong, Liyun; Luo, Chunshu; Niu, Wenhu; Lu, Xiaoxu

    2015-07-16

    To perform the visual measurement of the evaporation process of a sessile droplet, a dual-channel simultaneous phase-shifting interferometry (DCSPSI) method is proposed. Based on polarization components to simultaneously generate a pair of orthogonal interferograms with the phase shifts of π/2, the real-time phase of a dynamic process can be retrieved with two-step phase-shifting algorithm. Using this proposed DCSPSI system, the transient mass (TM) of the evaporation process of a sessile droplet with different initial mass were presented through measuring the real-time 3D shape of a droplet. Moreover, the mass flux density (MFD) of the evaporating droplet and its regional distribution were also calculated and analyzed. The experimental results show that the proposed DCSPSI will supply a visual, accurate, noncontact, nondestructive, global tool for the real-time multi-parameter measurement of the droplet evaporation.

  11. Internal flow inside droplets within a concentrated emulsion during droplet rearrangement

    Science.gov (United States)

    Leong, Chia Min; Gai, Ya; Tang, Sindy K. Y.

    2018-03-01

    Droplet microfluidics, in which each droplet serves as a micro-reactor, has found widespread use in high-throughput biochemical screening applications. These droplets are often concentrated at various steps to form a concentrated emulsion. As part of a serial interrogation and sorting process, such concentrated emulsions are typically injected into a tapered channel leading to a constriction that fits one drop at a time for the probing of droplet content in a serial manner. The flow physics inside the droplets under these flow conditions are not well understood but are critical for predicting and controlling the mixing of reagents inside the droplets as reactors. Here we investigate the flow field inside droplets of a concentrated emulsion flowing through a tapered microchannel using micro-particle image velocimetry. The confining geometry of the channel forces the number of rows of drops to reduce by one at specific and uniformly spaced streamwise locations, which are referred to as droplet rearrangement zones. Within each rearrangement zone, the phase-averaged velocity results show that the motion of the droplets involved in the rearrangement process, also known as a T1 event, creates vortical structures inside themselves and their adjacent droplets. These flow structures increase the circulation inside droplets up to 2.5 times the circulation in droplets at the constriction. The structures weaken outside of the rearrangement zones suggesting that the flow patterns created by the T1 process are transient. The time scale of circulation is approximately the same as the time scale of a T1 event. Outside of the rearrangement zones, flow patterns in the droplets are determined by the relative velocity between the continuous and disperse phases.

  12. Spontaneous droplet trampolining on rigid superhydrophobic surfaces

    Science.gov (United States)

    Schutzius, Thomas M.; Jung, Stefan; Maitra, Tanmoy; Graeber, Gustav; Köhme, Moritz; Poulikakos, Dimos

    2015-11-01

    Spontaneous removal of condensed matter from surfaces is exploited in nature and in a broad range of technologies to achieve self-cleaning, anti-icing and condensation control. But despite much progress, our understanding of the phenomena leading to such behaviour remains incomplete, which makes it challenging to rationally design surfaces that benefit from its manifestation. Here we show that water droplets resting on superhydrophobic textured surfaces in a low-pressure environment can self-remove through sudden spontaneous levitation and subsequent trampoline-like bouncing behaviour, in which sequential collisions with the surface accelerate the droplets. These collisions have restitution coefficients (ratios of relative speeds after and before collision) greater than unity despite complete rigidity of the surface, and thus seemingly violate the second law of thermodynamics. However, these restitution coefficients result from an overpressure beneath the droplet produced by fast droplet vaporization while substrate adhesion and surface texture restrict vapour flow. We also show that the high vaporization rates experienced by the droplets and the associated cooling can result in freezing from a supercooled state that triggers a sudden increase in vaporization, which in turn boosts the levitation process. This effect can spontaneously remove surface icing by lifting away icy drops the moment they freeze. Although these observations are relevant only to systems in a low-pressure environment, they show how surface texturing can produce droplet-surface interactions that prohibit liquid and freezing water-droplet retention on surfaces.

  13. Electronic states and nature of bonding of the molecule PdGe by all electron ab initio HF–CI calculations and mass spectrometric equilibrium experiments

    DEFF Research Database (Denmark)

    Shim, Irene; Kingcade, Joseph E. , Jr.; Gingerich, Karl A.

    1986-01-01

    In the present work we present all-electron ab initio Hartree–Fock (HF) and configuration interaction (CI) calculations of six electronic states of the PdGe molecule. The molecule is predicted to have a 3Pi ground state and two low-lying excited states 3Sigma− and 1Sigma+. The electronic structure...

  14. Foam droplet separation for nanoparticle synthesis

    International Nuclear Information System (INIS)

    Tyree, Corey A.; Allen, Jonathan O.

    2008-01-01

    A novel approach to nanoparticle synthesis was developed whereby foam bubble bursting produced aerosol droplets, an approach patterned after the marine foam aerosol cycle. The droplets were dried to remove solvent, leaving nanometer-sized particles composed of precursor material. Nanoparticles composed of sodium chloride (mean diameter, D-bar p ∼ 100 nm), phosphotungstic acid (D-bar p ∼ 55 nm), and bovine insulin (D p ∼ 5-30 nm) were synthesized. Foam droplet separation can be carried out at ambient temperature and pressure. The 'soft' nature of the process makes it compatible with a wide range of materials

  15. Diffusion and evaporation of a liquid droplet

    Science.gov (United States)

    Shukla, K. N.

    1980-06-01

    The process of evaporation and diffusion of a spherical liquid droplet in an atmosphere of noncondensable gas is studied theoretically. An equation for the shrinkage of the radius of the droplet is derived on the basis of continuity and momentum equations. Further, a conjugate problem consisting of the energy and mass balance for the gaseous environment is formulated. An approximation of thin thermal and diffusion boundary-layers is introduced to simplify the analysis. Results are presented for methanol-nitrogen, ammonia-nitrogen, and sodium-argon systems. It has been observed that the droplet of highly viscous fluid exhibits rapid contraction.

  16. Electronically droplet energy harvesting using piezoelectric cantilevers

    KAUST Repository

    Al Ahmad, Mahmoud Al

    2012-01-01

    A report is presented on free falling droplet energy harvesting using piezoelectric cantilevers. The harvester incorporates a multimorph clamped-free cantilever which is composed of five layers of lead zirconate titanate piezoelectric thick films. During the impact, the droplet kinetic energy is transferred into the form of mechanical stress forcing the piezoelectric structure to vibrate. Experimental results show energy of 0.3 μJ per droplet. The scenario of moderate falling drop intensity, i.e. 230 drops per second, yields a total energy of 400 μJ. © 2012 The Institution of Engineering and Technology.

  17. Heat exchanges between droplets and atmosphere

    International Nuclear Information System (INIS)

    Yadigaroglu, Georges.

    1975-01-01

    Data necessary for calculating the droplet cooling in wet cooling systems are surveyed. This cooling obeys the laws of simultaneous heat and mass transfer. Exchanges with a solid sphere moving inside a surrounding fluid medium are first examined. The corrections needed for taking into account various secondary effects (circulation in the droplet, lack of sphericity, oscillations, etc...) are then dealt with. Some data necessary for calculating the trajectories of the droplets and their behavior in a cooling system are included (diameter distribution, limit velocities, decay thresholds, etc...). Finally, calculation methods applying to spray systems, as well as wet towers broadly outlined [fr

  18. A flow-free droplet-based device for high throughput polymorphic crystallization.

    Science.gov (United States)

    Yang, Shih-Mo; Zhang, Dapeng; Chen, Wang; Chen, Shih-Chi

    2015-06-21

    Crystallization is one of the most crucial steps in the process of pharmaceutical formulation. In recent years, emulsion-based platforms have been developed and broadly adopted to generate high quality products. However, these conventional approaches such as stirring are still limited in several aspects, e.g., unstable crystallization conditions and broad size distribution; besides, only simple crystal forms can be produced. In this paper, we present a new flow-free droplet-based formation process for producing highly controlled crystallization with two examples: (1) NaCl crystallization reveals the ability to package saturated solution into nanoliter droplets, and (2) glycine crystallization demonstrates the ability to produce polymorphic crystallization forms by controlling the droplet size and temperature. In our process, the saturated solution automatically fills the microwell array powered by degassed bulk PDMS. A critical oil covering step is then introduced to isolate the saturated solution and control the water dissolution rate. Utilizing surface tension, the solution is uniformly packaged in the form of thousands of isolating droplets at the bottom of each microwell of 50-300 μm diameter. After water dissolution, individual crystal structures are automatically formed inside the microwell array. This approach facilitates the study of different glycine growth processes: α-form generated inside the droplets and γ-form generated at the edge of the droplets. With precise temperature control over nanoliter-sized droplets, the growth of ellipsoidal crystalline agglomerates of glycine was achieved for the first time. Optical and SEM images illustrate that the ellipsoidal agglomerates consist of 2-5 μm glycine clusters with inner spiral structures of ~35 μm screw pitch. Lastly, the size distribution of spherical crystalline agglomerates (SAs) produced from microwells of different sizes was measured to have a coefficient variation (CV) of less than 5%, showing

  19. Metal Droplet Formation in Gas Metal Arc Welding

    International Nuclear Information System (INIS)

    Haidar, J.

    2000-01-01

    A two-dimensional dynamic treatment has been developed for description of arc and electrode properties in gas metal arc welding (GMAW). The theory is a unified treatment of the arc the welding wire anode and the cathode, and includes a detailed account of sheath effects near the anode. The wire anode is included as a dynamic entity and the volume of fluid method is used to handle the movement of the free surface of the molten metal at the tip of the wire, accounting for effects of surface tension, inertia, gravity, arc pressure, viscous drag force of the plasma, magnetic forces and Marangoni effect, and also for the effects of wire feed rate in GMAW. Results of calculations made for a mild steel wire of diameter 0.16 cm are in good agreement with experimental measurements of droplet diameter and droplet detachment frequency at currents between 150 and 330 A, which includes the transition between ''globular'' and ''spray'' transfer. Quantitative predictions are also made of the amount of metal vapour that is generated from the welding droplets at the tip of the welding wire. (author)

  20. Internal flow and evaporation characteristic inside a water droplet on a vertical vibrating hydrophobic surface

    International Nuclear Information System (INIS)

    Kim Hun; Lim, Hee Chang

    2015-01-01

    This study aims to understand the internal flow and the evaporation characteristics of a deionized water droplet subjected to vertical forced vibrations. To predict and evaluate its resonance frequency, the theories of Lamb, Strani, and Sabetta have been applied. To visualize the precise mode, shape, and internal flow inside a droplet, the experiment utilizes a combination of a high-speed camera, macro lens, and continuous laser. As a result, a water droplet on a hydrophobic surface has its typical shape at each mode, and complicated vortices are observed inside the droplet. In particular, large symmetrical flow streams are generated along the vertical axis at each mode, with a large circulating movement from the bottom to the top and then to the triple contact line along the droplet surface. In addition, a bifurcation-shaped flow pattern is formed at modes 2 and 4, whereas a large ellipsoid-shape flow pattern forms at modes 6 and 8. Mode 4 has the fastest internal flow speed and evaporation rate, followed by modes 8 then 6, with 2 having the slowest of these properties. Each mode has the fastest evaporation rate amongst its neighboring frequencies. Finally, the droplet evaporation under vertical vibration would lead to more rapid evaporation, particularly for mode 4

  1. Assessment of the influence factors on nasal spray droplet velocity using phase-Doppler anemometry (PDA).

    Science.gov (United States)

    Liu, Xiaofei; Doub, William H; Guo, Changning

    2011-03-01

    Droplet velocity is an important parameter that can be used to characterize nasal spray products. In this study, a phase-Doppler anemometry (PDA) system was used to measure the droplet velocities of nasal sprays. A survey of seven commercial nasal spray products showed a range of droplet velocities from 6.7 to 19.2 m/s, all significantly different from each other. A three-level, four-factor Box-Behnken design of experiments (DOE) methodology were applied to investigate the influences of actuation parameters and formulation properties on nasal spray droplet velocity using a set of placebo formulations. The DOE study shows that all four input factors (stroke length, actuation velocity, concentration of the gelling agent, and concentration of the surfactant) have significant influence on droplet velocity. An optimized quadratic model generated from the DOE results describes the inherent relationships between the input factors and droplet velocity thus providing a better understanding of the input factor influences. Overall, PDA provides a new in vitro characterization method for the evaluation of inhalation drugs through assessment of spray velocity and may assist in product development to meet drug delivery equivalency requirements. © 2011 American Association of Pharmaceutical Scientists

  2. Internal flow and evaporation characteristic inside a water droplet on a vertical vibrating hydrophobic surface

    Energy Technology Data Exchange (ETDEWEB)

    Kim Hun; Lim, Hee Chang [School of Mechanical Engineering, Pusan National University, Busan (Korea, Republic of)

    2015-07-15

    This study aims to understand the internal flow and the evaporation characteristics of a deionized water droplet subjected to vertical forced vibrations. To predict and evaluate its resonance frequency, the theories of Lamb, Strani, and Sabetta have been applied. To visualize the precise mode, shape, and internal flow inside a droplet, the experiment utilizes a combination of a high-speed camera, macro lens, and continuous laser. As a result, a water droplet on a hydrophobic surface has its typical shape at each mode, and complicated vortices are observed inside the droplet. In particular, large symmetrical flow streams are generated along the vertical axis at each mode, with a large circulating movement from the bottom to the top and then to the triple contact line along the droplet surface. In addition, a bifurcation-shaped flow pattern is formed at modes 2 and 4, whereas a large ellipsoid-shape flow pattern forms at modes 6 and 8. Mode 4 has the fastest internal flow speed and evaporation rate, followed by modes 8 then 6, with 2 having the slowest of these properties. Each mode has the fastest evaporation rate amongst its neighboring frequencies. Finally, the droplet evaporation under vertical vibration would lead to more rapid evaporation, particularly for mode 4.

  3. Numerical simulation code for combustion of sodium liquid droplet and its verification

    International Nuclear Information System (INIS)

    Okano, Yasushi

    1997-11-01

    The computer programs for sodium leak and burning phenomena had been developed based on mechanistic approach. Direct numerical simulation code for sodium liquid droplet burning had been developed for numerical analysis of droplet combustion in forced convection air flow. Distributions of heat generation and temperature and reaction rate of chemical productions, such as sodium oxide and hydroxide, are calculated and evaluated with using this numerical code. Extended MAC method coupled with a higher-order upwind scheme had been used for combustion simulation of methane-air mixture. In the numerical simulation code for combustion of sodium liquid droplet, chemical reaction model of sodium was connected with the extended MAC method. Combustion of single sodium liquid droplet was simulated in this report for the verification of developed numerical simulation code. The changes of burning rate and reaction product with droplet diameter and inlet wind velocity were investigated. These calculation results were qualitatively and quantitatively conformed to the experimental and calculation observations in combustion engineering. It was confirmed that the numerical simulation code was available for the calculation of sodium liquid droplet burning. (author)

  4. Phononic fluidics: acoustically activated droplet manipulations

    Science.gov (United States)

    Reboud, Julien; Wilson, Rab; Bourquin, Yannyk; Zhang, Yi; Neale, Steven L.; Cooper, Jonathan M.

    2011-02-01

    Microfluidic systems have faced challenges in handling real samples and the chip interconnection to other instruments. Here we present a simple interface, where surface acoustic waves (SAWs) from a piezoelectric device are coupled into a disposable acoustically responsive microfluidic chip. By manipulating droplets, SAW technologies have already shown their potential in microfluidics, but it has been limited by the need to rely upon mixed signal generation at multiple interdigitated electrode transducers (IDTs) and the problematic resulting reflections, to allow complex fluid operations. Here, a silicon chip was patterned with phononic structures, engineering the acoustic field by using a full band-gap. It was simply coupled to a piezoelectric LiNbO3 wafer, propagating the SAW, via a thin film of water. Contrary to the use of unstructured superstrates, phononic metamaterials allowed precise spatial control of the acoustic energy and hence its interaction with the liquids placed on the surface of the chip, as demonstrated by simulations. We further show that the acoustic frequency influences the interaction between the SAW and the phononic lattice, providing a route to programme complex fluidic manipulation onto the disposable chip. The centrifugation of cells from a blood sample is presented as a more practical demonstration of the potential of phononic crystals to realize diagnostic systems.

  5. Janus droplets: liquid marbles coated with dielectric/semiconductor particles.

    Science.gov (United States)

    Bormashenko, Edward; Bormashenko, Yelena; Pogreb, Roman; Gendelman, Oleg

    2011-01-04

    The manufacturing of water droplets wrapped with two different powders, carbon black (semiconductor) and polytetrafluoroethylene (dielectric), is presented. Droplets composed of two hemispheres (Janus droplets) characterized by various physical and chemical properties are reported first. Watermelon-like striped liquid marbles are reported. Janus droplets remained stable on solid and liquid supports and could be activated with an electric field.

  6. Self-propelled oil droplets consuming "fuel" surfactant

    DEFF Research Database (Denmark)

    Toyota, Taro; Maru, Naoto; Hanczyc, Martin M

    2009-01-01

    A micrometer-sized oil droplet of 4-octylaniline containing 5 mol % of an amphiphilic catalyst exhibited a self-propelled motion, producing tiny oil droplets, in an aqueous dispersion of an amphiphilic precursor of 4-octylaniline. The tiny droplets on the surface of the self-propelled droplet wer...

  7. Aerosol indirect effect from turbulence-induced broadening of cloud-droplet size distributions

    Energy Technology Data Exchange (ETDEWEB)

    Chandrakar, Kamal Kant; Cantrell, Will; Chang, Kelken; Ciochetto, David; Niedermeier, Dennis; Ovchinnikov, Mikhail; Shaw, Raymond A.; Yang, Fan

    2016-11-28

    The influence of aerosol concentration on cloud droplet size distribution is investigated in a laboratory chamber that enables turbulent cloud formation through moist convection. The experiments allow steady-state microphysics to be achieved, with aerosol input balanced by cloud droplet growth and fallout. As aerosol concentration is increased the cloud droplet mean diameter decreases as expected, but the width of the size distribution also decreases sharply. The aerosol input allows for cloud generation in the limiting regimes of fast microphysics (τc < τt) for high aerosol concentration, and slow microphysics (τc > τt) for low aerosol concentration; here, τc is the phase relaxation time and τt is the turbulence correlation time. The increase in the width of the droplet size distribution for the low aerosol limit is consistent with larger variability of supersaturation due to the slow microphysical response. A stochastic differential equation for supersaturation predicts that the standard deviation of the squared droplet radius should increase linearly with a system time scale defined as τs-1c-1 + τt-1, and the measurements are in excellent agreement with this finding. This finding underscores the importance of droplet size dispersion for the aerosol indirect effect: increasing aerosol concentration not only suppresses precipitation formation through reduction of the mean droplet diameter, but perhaps more importantly, through narrowing of the droplet size distribution due to reduced supersaturation fluctuations. Supersaturation fluctuations in the low aerosol / slow microphysics limit are likely of leading importance for precipitation formation.

  8. Simulating oil droplet dispersal from the Deepwater Horizon spill with a Lagrangian approach

    Science.gov (United States)

    North, Elizabeth W.; Schlag, Zachary; Adams, E. Eric; Sherwood, Christopher R.; He, Ruoying; Hyun, Hoon; Socolofsky, Scott A.

    2011-01-01

    An analytical multiphase plume model, combined with time-varying flow and hydrographic fields generated by the 3-D South Atlantic Bight and Gulf of Mexico model (SABGOM) hydrodynamic model, were used as input to a Lagrangian transport model (LTRANS), to simulate transport of oil droplets dispersed at depth from the recent Deepwater Horizon MC 252 oil spill. The plume model predicts a stratification-dominated near field, in which small oil droplets detrain from the central plume containing faster rising large oil droplets and gas bubbles and become trapped by density stratification. Simulated intrusion (trap) heights of ∼ 310–370 m agree well with the midrange of conductivity-temperature-depth observations, though the simulated variation in trap height was lower than observed, presumably in part due to unresolved variability in source composition (percentage oil versus gas) and location (multiple leaks during first half of spill). Simulated droplet trajectories by the SABGOM-LTRANS modeling system showed that droplets with diameters between 10 and 50 μm formed a distinct subsurface plume, which was transported horizontally and remained in the subsurface for >1 month. In contrast, droplets with diameters ≥90 μm rose rapidly to the surface. Simulated trajectories of droplets ≤50 μm in diameter were found to be consistent with field observations of a southwest-tending subsurface plume in late June 2010 reported by Camilli et al. [2010]. Model results suggest that the subsurface plume looped around to the east, with potential subsurface oil transport to the northeast and southeast. Ongoing work is focusing on adding degradation processes to the model to constrain droplet dispersal.

  9. A simple and low-cost fully 3D-printed non-planar emulsion generator

    KAUST Repository

    Zhang, Jiaming; Li, Erqiang; Aguirre-Pablo, Andres A.; Thoroddsen, Sigurdur T

    2015-01-01

    Droplet-based microfluidic devices provide a powerful platform for material, chemical and biological applications based on droplet templates. The technique traditionally utilized to fabricate microfluidic emulsion generators, i.e. soft

  10. Relationship between concentration of surfactant and pressure for droplet creation, and effect on droplet size in microchannel O/W emulsification; Maikurochaneru ni yoru O/W nyukaho ni okeru kaimen kasseizai nodo to ekiteki seisei atsuryoku no kankei, oyobi koreraga ekitekikei ni oyobosu eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Kawakatsu, T.; Komori, H.; Oda, N.; Yonemoto, T. [Tohoku Univ., Sendai (Japan). Graduate School of Engineering

    1998-03-01

    O/W (oil in water) emulsion is produced by micro-channel emulsification method, and the effects of surfactant concentration on the pressures at which droplet generation starts and stops are evaluated in connection with the water phase and oil phase interfacial tension. In addition, the effects of surfactant concentration and operational pressure on the droplet size are investigated by measuring the generated droplet distribution, mean droplet size, standard deviation, geometrical standard deviation, and the possibility of producing mono-dispersion emulsion whose droplet size is large than 10 micron. The breakthrough pressure and the minimum pressure for droplet generation become low with the increase of SDS (sodium lauryl sulfate) concentration. The surfactant concentration, however, is found to have no effect on the breakthrough pressure and the minimum pressure for droplet generation when the SDS concentration exceeds the critical micelle concentration. It is true also for a system added with NaCl. As regards droplet size, uniform 20{mu}m droplet is obtained irrespective of the surfactant concentration and pressure. 13 refs., 10 figs., 2 tabs.

  11. 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.

  12. Effects of droplet interactions on droplet transport at intermediate Reynolds numbers

    Science.gov (United States)

    Shuen, Jian-Shun

    1987-01-01

    Effects of droplet interactions on drag, evaporation, and combustion of a planar droplet array, oriented perpendicular to the approaching flow, are studied numerically. The three-dimensional Navier-Stokes equations, with variable thermophysical properties, are solved using finite-difference techniques. Parameters investigated include the droplet spacing, droplet Reynolds number, approaching stream oxygen concentration, and fuel type. Results are obtained for the Reynolds number range of 5 to 100, droplet spacings from 2 to 24 diameters, oxygen concentrations of 0.1 and 0.2, and methanol and n-butanol fuels. The calculations show that the gasification rates of interacting droplets decrease as the droplet spacings decrease. The reduction in gasification rates is significant only at small spacings and low Reynolds numbers. For the present array orientation, the effects of interactions on the gasification rates diminish rapidly for Reynolds numbers greater than 10 and spacings greater than 6 droplet diameters. The effects of adjacent droplets on drag are shown to be small.

  13. Multi-scale simulation of droplet-droplet interactions and coalescence

    CSIR Research Space (South Africa)

    Musehane, Ndivhuwo M

    2016-10-01

    Full Text Available Conference on Computational and Applied Mechanics Potchefstroom 3–5 October 2016 Multi-scale simulation of droplet-droplet interactions and coalescence 1,2Ndivhuwo M. Musehane?, 1Oliver F. Oxtoby and 2Daya B. Reddy 1. Aeronautic Systems, Council... topology changes that result when droplets interact. This work endeavours to eliminate the need to use empirical correlations based on phenomenological models by developing a multi-scale model that predicts the outcome of a collision between droplets from...

  14. Substrate curvature gradient drives rapid droplet motion.

    Science.gov (United States)

    Lv, Cunjing; Chen, Chao; Chuang, Yin-Chuan; Tseng, Fan-Gang; Yin, Yajun; Grey, Francois; Zheng, Quanshui

    2014-07-11

    Making small liquid droplets move spontaneously on solid surfaces is a key challenge in lab-on-chip and heat exchanger technologies. Here, we report that a substrate curvature gradient can accelerate micro- and nanodroplets to high speeds on both hydrophilic and hydrophobic substrates. Experiments for microscale water droplets on tapered surfaces show a maximum speed of 0.42  m/s, 2 orders of magnitude higher than with a wettability gradient. We show that the total free energy and driving force exerted on a droplet are determined by the substrate curvature and substrate curvature gradient, respectively. Using molecular dynamics simulations, we predict nanoscale droplets moving spontaneously at over 100  m/s on tapered surfaces.

  15. Strange particle production from quark matter droplets

    International Nuclear Information System (INIS)

    Werner, K.; Hladik, M.

    1995-01-01

    We recently introduced new methods to study ultrarelativistic nuclear scattering by providing a link between the string model approach and a thermal description. The string model is used to provide information about fluctuations in energy density. Regions of high energy density are considered to be quark matter droplets and treated macroscopically. At SPS energies, we find mainly medium size droplets---with energies up to few tens of Gev. A key issue is the microcanonical treatment of individual quark matter droplets. Each droplet hadronizes instantaneously according to the available n-body phase space. Due to the huge number of possible hadron configurations, special Monte Carlo techniques have been developed to calculate this disintegration. We present results concerning the production of strange particles from such a hadronization as compared to string decay. copyright 1995 American Institute of Physics

  16. Manipulation of microfluidic droplets by electrorheological fluid

    KAUST Repository

    Zhang, Menying; Gong, Xiuqing; Wen, Weijia

    2009-01-01

    Microfluidics, especially droplet microfluidics, attracts more and more researchers from diverse fields, because it requires fewer materials and less time, produces less waste and has the potential of highly integrated and computer

  17. Electronically droplet energy harvesting using piezoelectric cantilevers

    KAUST Repository

    Al Ahmad, Mahmoud Al; Jabbour, Ghassan E.

    2012-01-01

    A report is presented on free falling droplet energy harvesting using piezoelectric cantilevers. The harvester incorporates a multimorph clamped-free cantilever which is composed of five layers of lead zirconate titanate piezoelectric thick films

  18. Numerical modeling of a vaporizing multicomponent droplet

    Science.gov (United States)

    Megaridis, C. M.; Sirignano, W. A.

    The fundamental processes governing the energy, mass, and momentum exchange between the liquid and gas phases of vaporizing, multicomponent liquid droplets have been investigated. The axisymmetric configuration under consideration consists of an isolated multicomponent droplet vaporizing in a convective environment. The model considers different volatilities of the liquid components, variable liquid properties due to variation of the species concentrations, and non-Fickian multicomponent gaseous diffusion. The bicomponent droplet model was employed to examine the commonly used assumptions of unity Lewis number in the liquid phase and Fickian gaseous diffusion. It is found that the droplet drag coefficients, the vaporization rates, and the related transfer numbers are not influenced by the above assumptions in a significant way.

  19. Collisions of droplets on spherical particles

    Science.gov (United States)

    Charalampous, Georgios; Hardalupas, Yannis

    2017-10-01

    Head-on collisions between droplets and spherical particles are examined for water droplets in the diameter range between 170 μm and 280 μm and spherical particles in the diameter range between 500 μm and 2000 μm. The droplet velocities range between 6 m/s and 11 m/s, while the spherical particles are fixed in space. The Weber and Ohnesorge numbers and ratio of droplet to particle diameter were between 92 deposition and splashing regimes, a regime is observed in the intermediate region, where the droplet forms a stable crown, which does not breakup but propagates along the particle surface and passes around the particle. This regime is prevalent when the droplets collide on small particles. The characteristics of the collision at the onset of rim instability are also described in terms of the location of the film on the particle surface and the orientation and length of the ejected crown. Proper orthogonal decomposition identified that the first 2 modes are enough to capture the overall morphology of the crown at the splashing threshold.

  20. Electronic structure of Ge-2 and Ge-2 and thermodynamic properties of Ge-2 from all electron ab initio investigations and Knudsen effusion mass spectroscopic measurements

    DEFF Research Database (Denmark)

    Shim, Irene; Baba, M. Sai; Gingerich, K.A.

    2002-01-01

    The low-lying states of the molecule Ge-2 and of the ion Ge-2(-) have been investigated by all electron ab initio multiconfiguration self-consistent field (CASSCF) and multi-reference configuration interaction (MRCI) calculations. The relativistic corrections for the Darwin contact term and for t......The low-lying states of the molecule Ge-2 and of the ion Ge-2(-) have been investigated by all electron ab initio multiconfiguration self-consistent field (CASSCF) and multi-reference configuration interaction (MRCI) calculations. The relativistic corrections for the Darwin contact term...... excited states are presented. Thermal functions based on the theoretically determined molecular parameters were used to derive the thermodynamic properties of the Ge-2 molecule from new mass spectrometric equilibrium data. The literature value for the dissociation energy of Ge-2 has been re...

  1. Pseudobinary eutectics in Cu–Ag–Ge alloy droplets under containerless condition

    International Nuclear Information System (INIS)

    Ruan, Y.; Wang, X.J.; Lu, X.Y.

    2013-01-01

    Highlights: ► Two pseudobinary eutectics form in Cu–Ag–Ge alloy. ► It is influenced by thermodynamic and kinetic factors of the alloy in the drop tube. ► As droplet size reduces, anomalous → lamellar → anomalous transition happens in (Ag + ζ). ► (Ag + ε 2 ) is a product of both peri-eutectic and pseudobinary eutectic transitions. -- Abstract: Pseudobinary eutectic generated by pseudobinary eutectic transition or peri-eutectic transition is a crucial structure in ternary alloy systems. Its formation mechanism strongly influences mechanical properties of these metallic materials. However, it was customarily neglected. In this paper, two pseudobinary eutectics, i.e. (Ag + ζ) and (Ag + ε 2 ), were investigated during the rapid solidification of Cu–Ag–Ge ternary alloy in a 3 m-drop tube. The sharp temperature variations and dramatic kinetic activities of the falling alloy droplets before solidification cause special microstructural characteristics. (Ag) dendrite is the heterogeneous nucleus for anomalous (Ag + ζ) pseudobinary eutectic in large droplets. Lamellar (Ag + ζ) pseudobinary eutectic grain forms independently on condition that primary (Ag) dendrite cannot form and its eutectic morphology becomes anomalous with the decrease of droplet size. Nanoscaled (Ag + ε 2 ) pseudobinary eutectic generating at the last stage of solidification is the product of both peri-eutectic and pseudobinary eutectic transitions. It distributes in the gaps of (Ag + ζ) pseudobinary eutectic grains and its morphology remains lamellar regardless of droplet size

  2. Mode pattern of internal flow in a water droplet on a vibrating hydrophobic surface.

    Science.gov (United States)

    Kim, Hun; Lim, Hee-Chang

    2015-06-04

    The objective of this study is to understand the mode pattern of the internal flow in a water droplet placed on a hydrophobic surface that periodically and vertically vibrates. As a result, a water droplet on a vibrating hydrophobic surface has a typical shape that depends on each resonance mode, and, additionally, we observed a diversified lobe size and internal flows in the water droplet. The size of each lobe at the resonance frequency was relatively greater than that at the neighboring frequencies, and the internal flow of the nth order mode was also observed in the flow visualization. In general, large symmetrical flow streams were generated along the vertical axis in each mode, with a large circulating movement from the bottom to the top, and then to the triple contact line along the droplet surface. In contrast, modes 2 and 4 generated a Y-shaped flow pattern, in which the flow moved to the node point in the lower part of the droplet, but modes 6 and 8 had similar patterns, with only a little difference. In addition, as a result of the PIV measurement, while the flow velocity of mode 4 was faster than that of model 2, those of modes 6 and 8 were almost similar.

  3. Equilibrium Droplets on Deformable Substrates: Equilibrium Conditions.

    Science.gov (United States)

    Koursari, Nektaria; Ahmed, Gulraiz; Starov, Victor M

    2018-05-15

    Equilibrium conditions of droplets on deformable substrates are investigated, and it is proven using Jacobi's sufficient condition that the obtained solutions really provide equilibrium profiles of both the droplet and the deformed support. At the equilibrium, the excess free energy of the system should have a minimum value, which means that both necessary and sufficient conditions of the minimum should be fulfilled. Only in this case, the obtained profiles provide the minimum of the excess free energy. The necessary condition of the equilibrium means that the first variation of the excess free energy should vanish, and the second variation should be positive. Unfortunately, the mentioned two conditions are not the proof that the obtained profiles correspond to the minimum of the excess free energy and they could not be. It is necessary to check whether the sufficient condition of the equilibrium (Jacobi's condition) is satisfied. To the best of our knowledge Jacobi's condition has never been verified for any already published equilibrium profiles of both the droplet and the deformable substrate. A simple model of the equilibrium droplet on the deformable substrate is considered, and it is shown that the deduced profiles of the equilibrium droplet and deformable substrate satisfy the Jacobi's condition, that is, really provide the minimum to the excess free energy of the system. To simplify calculations, a simplified linear disjoining/conjoining pressure isotherm is adopted for the calculations. It is shown that both necessary and sufficient conditions for equilibrium are satisfied. For the first time, validity of the Jacobi's condition is verified. The latter proves that the developed model really provides (i) the minimum of the excess free energy of the system droplet/deformable substrate and (ii) equilibrium profiles of both the droplet and the deformable substrate.

  4. Liquid films and droplet deposition in a BWR fuel element

    International Nuclear Information System (INIS)

    Damsohn, M.

    2011-01-01

    time-averaged liquid film thickness decreases with decreasing liquid flow rate, increasing gas flow rate and increasing gas density. By the introduction of spacers, the liquid film is strongly structured into streaks downstream of the spacer in a distinct pattern depending on the spacer shape. The streaks are mainly generated by the effect of circumferential vector components of the gas shear stresses on the gas-liquid interface, which are generated by the spacer. The resulting local decrease of liquid mass flow rate can be interpreted as a deficiency of a given spacer geometry, since it may promote dryout under BWR conditions in close proximity to the spacer. Furthermore spacers increase the droplet deposition compared to an open channel flow, thus increasing the mass flow rate in the liquid film and the dryout margin. Spacer vanes enhance the droplet deposition by an enhanced turbulence of the gas core, a deflection of the gas streamlines and the direct impact of droplets on the spacer vanes. The contribution of each phenomenon to the deposition rate depends on the spacer design and flow conditions present. For the studied generic spacer geometries and experimental conditions, the contribution of the direct impact is dominant, while the contribution of enhanced turbulence seems to be negligible. Additional to the described phenomenon, droplet break-up occurs in spacer proximity, either by the impact on the spacer or by the high velocity gradients of the gas flow in the spacer. This break-up may change the contribution of the deposition effects. It is shown that a Lagrangian droplet tracking on basis of the same gas flow field used as input for the film thickness model can qualitatively reproduce most of the relevant effects observed in the experiments. Furthermore the model gives the right quantitative tendencies when flow parameters are varied. The combination of adiabatic experiments of the presented kind, complemented by the proposed simplified CFD modeling, can

  5. Evaluation of droplet deposition in rod bundle

    International Nuclear Information System (INIS)

    Ji, W.; Gu, C.Y.; Anglart, H.

    1997-01-01

    Deposition model for droplets in gas droplet two-phase flow in rod bundle is developed in this work using the Lagrangian method. The model is evaluated in a 9-rod bundle geometry. The deposition coefficient in the bundle geometry are compared with that in round tube. The influences of the droplet size and gas mass flow rate on deposition coefficient are investigated. Furthermore, the droplet motion is studied in more detail by dividing the bundle channel into sub-channels. The results show that the overall deposition coefficient in the bundle geometry is close to that in the round tube with the diameter equal to the bundle hydraulic diameter. The calculated deposition coefficient is found to be higher for higher gas mass flux and smaller droplets. The study in the sub-channels show that the ratio between the local deposition coefficient for a sub-channel and the averaged value for the whole bundle is close to a constant value, deviations from the mean value for all the calculated cases being within the range of ±13%. (author)

  6. Thermocapillary droplet actuation on structured solid surfaces

    Science.gov (United States)

    Karapetsas, George; Chamakos, Nikolaos T.; Papathanasiou, Athanasios G.

    2017-11-01

    The present work investigates, through 2D and 3D finite element simulations, the thermocapillary-driven flow inside a droplet which resides on a non-uniformly heated patterned surface. We employ a recently proposed sharp-interface scheme capable of efficiently modelling the flow over complicate surfaces and consider a wide range of substrate wettabilities, i.e. from hydrophilic to super-hydrophobic surfaces. Our simulations indicate that due to the presence of the solid structures and the induced effect of contact angle hysteresis, inherently predicted by our model, a critical thermal gradient arises beyond which droplet migration is possible, in line with previous experimental observations. The migration velocity as well as the direction of motion depends on the combined action of the net mechanical force along the contact line and the thermocapillary induced flow at the liquid-air interface. We also show that through a proper control and design of the substrate wettability, the contact angle hysteresis and the induced flow field it is possible to manipulate the droplet dynamics, e.g. controlling its motion along a predefined track or entrapping by a wetting defect a droplet based on its size as well as providing appropriate conditions for enhanced mixing inside the droplet. Funding from the European Research Council under the Europeans Community's Seventh Framework Programme (FP7/2007-2013)/ERC Grant agreement no. [240710] is acknowledged.

  7. Structural Transitions in Cholesteric Liquid Crystal Droplets

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-07-26

    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.

  8. Statistical steady states in turbulent droplet condensation

    Science.gov (United States)

    Bec, Jeremie; Krstulovic, Giorgio; Siewert, Christoph

    2017-11-01

    We investigate the general problem of turbulent condensation. Using direct numerical simulations we show that the fluctuations of the supersaturation field offer different conditions for the growth of droplets which evolve in time due to turbulent transport and mixing. This leads to propose a Lagrangian stochastic model consisting of a set of integro-differential equations for the joint evolution of the squared radius and the supersaturation along droplet trajectories. The model has two parameters fixed by the total amount of water and the thermodynamic properties, as well as the Lagrangian integral timescale of the turbulent supersaturation. The model reproduces very well the droplet size distributions obtained from direct numerical simulations and their time evolution. A noticeable result is that, after a stage where the squared radius simply diffuses, the system converges exponentially fast to a statistical steady state independent of the initial conditions. The main mechanism involved in this convergence is a loss of memory induced by a significant number of droplets undergoing a complete evaporation before growing again. The statistical steady state is characterised by an exponential tail in the droplet mass distribution.

  9. Snap evaporation of droplets on smooth topographies.

    Science.gov (United States)

    Wells, Gary G; Ruiz-Gutiérrez, Élfego; Le Lirzin, Youen; Nourry, Anthony; Orme, Bethany V; Pradas, Marc; Ledesma-Aguilar, Rodrigo

    2018-04-11

    Droplet evaporation on solid surfaces is important in many applications including printing, micro-patterning and cooling. While seemingly simple, the configuration of evaporating droplets on solids is difficult to predict and control. This is because evaporation typically proceeds as a "stick-slip" sequence-a combination of pinning and de-pinning events dominated by static friction or "pinning", caused by microscopic surface roughness. Here we show how smooth, pinning-free, solid surfaces of non-planar topography promote a different process called snap evaporation. During snap evaporation a droplet follows a reproducible sequence of configurations, consisting of a quasi-static phase-change controlled by mass diffusion interrupted by out-of-equilibrium snaps. Snaps are triggered by bifurcations of the equilibrium droplet shape mediated by the underlying non-planar solid. Because the evolution of droplets during snap evaporation is controlled by a smooth topography, and not by surface roughness, our ideas can inspire programmable surfaces that manage liquids in heat- and mass-transfer applications.

  10. Magnetic fluid droplet in a harmonic electric field

    Energy Technology Data Exchange (ETDEWEB)

    Kvasov, D., E-mail: kvasovdmitry@gmail.com [Lomonosov Moscow State University, Moscow (Russian Federation); Naletova, V. [Lomonosov Moscow State University, Moscow (Russian Federation); Beketova, E.; Dikanskii, Yu. [North-Caucasus Federal University, Stavropol (Russian Federation)

    2017-06-01

    A magnetic fluid droplet immersed in oil in an applied harmonic electric field is studied experimentally and theoretically. It is shown that deformations of the droplet observed experimentally are not described by the well-known theory. New double-layer droplet model which describes experimental data well is proposed. - Highlights: • The magnetic fluid droplet in the oil in a harmonic electric field is studied. • The paradoxical flattening effect of the droplet is observed experimentally. • For explaining this effect the model of the double-layer droplet is proposed. • Numerical and experimental data coincide qualitatively and quantitatively.

  11. Experimental investigation on the effect of liquid injection by multiple orifices in the formation of droplets in a Venturi scrubber

    Energy Technology Data Exchange (ETDEWEB)

    Guerra, V.G.; Goncalves, J.A.S. [Department of Chemical Engineering, Federal University of Sao Carlos, Via Washington Luiz, Km. 235, 13565-905 Sao Carlos, SP (Brazil); Coury, J.R. [Department of Chemical Engineering, Federal University of Sao Carlos, Via Washington Luiz, Km. 235, 13565-905 Sao Carlos, SP (Brazil)], E-mail: jcoury@ufscar.br

    2009-01-15

    Venturi scrubbers are widely utilized in gas cleaning. The cleansing elements in these scrubbers are droplets formed from the atomization of a liquid into a dust-laden gas. In industrial scrubbers, this liquid is injected through several orifices so that the cloud of droplets can be evenly distributed throughout the duct. The interaction between droplets when injected through many orifices, where opposite clouds of atomized liquid can reach each other, is to be expected. This work presents experimental measurements of droplet size measured in situ and the evidence of cloud interaction within a Venturi scrubber operating with multi-orifice jet injection. The influence of gas velocity, liquid flow rate and droplet size variation in the axial position after the point of the injection of the liquid were also evaluated for the different injection configurations. The experimental results showed that an increase in the liquid flow rate generated greater interaction between jets. The number of orifices had a significant influence on droplet size. In general, the increase in the velocity of the liquid jet and in the gas velocity favored the atomization process by reducing the size of the droplets.

  12. Experimental investigation on the effect of liquid injection by multiple orifices in the formation of droplets in a Venturi scrubber

    International Nuclear Information System (INIS)

    Guerra, V.G.; Goncalves, J.A.S.; Coury, J.R.

    2009-01-01

    Venturi scrubbers are widely utilized in gas cleaning. The cleansing elements in these scrubbers are droplets formed from the atomization of a liquid into a dust-laden gas. In industrial scrubbers, this liquid is injected through several orifices so that the cloud of droplets can be evenly distributed throughout the duct. The interaction between droplets when injected through many orifices, where opposite clouds of atomized liquid can reach each other, is to be expected. This work presents experimental measurements of droplet size measured in situ and the evidence of cloud interaction within a Venturi scrubber operating with multi-orifice jet injection. The influence of gas velocity, liquid flow rate and droplet size variation in the axial position after the point of the injection of the liquid were also evaluated for the different injection configurations. The experimental results showed that an increase in the liquid flow rate generated greater interaction between jets. The number of orifices had a significant influence on droplet size. In general, the increase in the velocity of the liquid jet and in the gas velocity favored the atomization process by reducing the size of the droplets

  13. Experimental investigation on the effect of liquid injection by multiple orifices in the formation of droplets in a Venturi scrubber.

    Science.gov (United States)

    Guerra, V G; Gonçalves, J A S; Coury, J R

    2009-01-15

    Venturi scrubbers are widely utilized in gas cleaning. The cleansing elements in these scrubbers are droplets formed from the atomization of a liquid into a dust-laden gas. In industrial scrubbers, this liquid is injected through several orifices so that the cloud of droplets can be evenly distributed throughout the duct. The interaction between droplets when injected through many orifices, where opposite clouds of atomized liquid can reach each other, is to be expected. This work presents experimental measurements of droplet size measured in situ and the evidence of cloud interaction within a Venturi scrubber operating with multi-orifice jet injection. The influence of gas velocity, liquid flow rate and droplet size variation in the axial position after the point of the injection of the liquid were also evaluated for the different injection configurations. The experimental results showed that an increase in the liquid flow rate generated greater interaction between jets. The number of orifices had a significant influence on droplet size. In general, the increase in the velocity of the liquid jet and in the gas velocity favored the atomization process by reducing the size of the droplets.

  14. Comparison of capacitive and radio frequency resonator sensors for monitoring parallelized droplet microfluidic production

    KAUST Repository

    Conchouso Gonzalez, David; McKerricher, Garret; Carreno, Armando Arpys Arevalo; Castro, David; Shamim, Atif; Foulds, Ian G.

    2016-01-01

    with droplets of 100-150 μm in diameter, which were generated in parallelization devices at water-in-oil volume fractions (φ) between 11.1% and 33.3%.Using these sensors, we were able to measure accurately increments as small as 2.4% in the water volume fraction

  15. Single-enzyme analysis in a droplet-based micro- and nanofluidic system

    NARCIS (Netherlands)

    Arayanarakool, Rerngchai; Shui, Lingling; Kengen, Servé W.M.; van den Berg, Albert; Eijkel, Jan C.T.

    2013-01-01

    The kinetic activity of individual enzyme molecules was determined in aqueous droplets generated in a nano- and microfluidic device. To avoid high background noise, the enzyme and substrate solution was confined into femtoliter carriers, achieving high product concentrations from single-molecule

  16. Influence of complex interfacial rheology on the thermocapillary migration of a surfactant-laden droplet in Poiseuille flow

    Science.gov (United States)

    Das, Sayan; Chakraborty, Suman

    2018-02-01

    The effect of surface viscosity on the motion of a surfactant-laden droplet in the presence of a non-isothermal Poiseuille flow is studied, both analytically and numerically. The presence of bulk-insoluble surfactants along the droplet surface results in interfacial shear and dilatational viscosities. This, in turn, is responsible for the generation of surface-excess viscous stresses that obey the Boussinesq-Scriven constitutive law for constant values of surface shear and dilatational viscosities. The present study is primarily focused on finding out how this confluence can be used to modulate droplet dynamics in the presence of Marangoni stress induced by nonuniform distribution of surfactants and temperature along the droplet surface, by exploiting an intricate interplay of the respective forcing parameters influencing the interfacial stresses. Under the assumption of negligible fluid inertia and thermal convection, the steady-state migration velocity of a non-deformable spherical droplet, placed at the centerline of an imposed unbounded Poiseuille flow, is obtained for the limiting case when the surfactant transport along the interface is dominated by surface diffusion. Our analysis proves that the droplet migration velocity is unaffected by the shear viscosity whereas the dilatational viscosity has a significant effect on the same. The surface viscous effects always retard the migration of a surfactant-laden droplet when the temperature in the far-field increases in the direction of the imposed flow although the droplet always migrates towards the hotter region. On the contrary, if a large temperature gradient is applied in a direction opposite to that of the imposed flow, the direction of droplet migration gets reversed. However, for a sufficiently high value of dilatational surface viscosity, the direction of droplet migration reverses. For the limiting case in which the surfactant transport along the droplet surface is dominated by surface convection, on

  17. Microphysics of mass-transport in coupled droplet-pairs at low Reynolds number and the role of convective dynamics

    Science.gov (United States)

    Dong, Qingming; Sau, Amalendu

    2016-06-01

    Interfacial mass-transport and redistribution in the micro-scale liquid droplets are important in diverse fields of research interest. The role of the "inflow" and the "outflow" type convective eddy-pairs in the entrainment of outer solute and internal relocation are examined for different homogeneous and heterogeneous water droplet pairs appearing in a tandem arrangement. Two micro-droplets of pure (rain) water interact with an oncoming outer air stream (Re ≤ 100) contaminated by uniformly distributed SO2. By virtue of separation/attachment induced non-uniform interfacial shear-stress gradient, the well-defined inflow/outflow type pairs of recirculating eddy-based convective motion quickly develops, and the eddies effectively attract/repel the accumulated outer solute and control the physical process of mass-transport in the droplet-pair. The non-uniformly shear-driven flow interaction and bifurcation of the circulatory internal flow lead to growth of important micro-scale "secondary" eddies which suitably regroup with the adjacent "primary" one to create the sustained inflow/outflow type convective dynamics. The presently derived flow characteristics and in-depth analysis help to significantly improve our understanding of the micro-droplet based transport phenomena in a wider context. By tuning "Re" (defined in terms of the droplet diameter and the average oncoming velocity of the outer air) and gap-ratio "α," the internal convective forcing and the solute entrainment efficiency could be considerably enhanced. The quantitative estimates for mass entrainment, convective strength, and saturation characteristics for different coupled micro-droplet pairs are extensively examined here for 0.2 ≤ α ≤ 2.0 and 30 ≤ Re ≤ 100. Interestingly, for the compound droplets, with suitably tuned radius-ratio "B" (of upstream droplet with respect to downstream one) the generated "inflow" type coherent convective dynamics helped to significantly augment the centre

  18. Core-electron binding energies from self-consistent field molecular orbital theory using a mixture of all-electron real atoms and valence-electron model atoms

    International Nuclear Information System (INIS)

    Quinn, C.M.; Schwartz, M.E.

    1981-01-01

    The chemistry of large systems such as clusters may be readily investigated by valence-electron theories based on model potentials, but such an approach does not allow for the examination of core-electron binding energies which are commonly measured experimentally for such systems. Here we merge our previously developed Gaussian based valence-electron model potential theory with all-electron ab initio theory to allow for the calculation of core orbital binding energies when desired. For the atoms whose cores are to be examined, we use the real nuclear changes, all of the electrons, and the appropriate many-electron basis sets. For the rest of the system we use reduced nuclear charges, the Gaussian based model potentials, only the valence electrons, and appropriate valence-electron basis sets. Detailed results for neutral Al 2 are presented for the cases of all-electron, mixed real--model, and model--model SCF--MO calculations. Several different all-electron and valence electron calculations have been done to test the use of the model potential per se, as well as the effect of basis set choice. The results are in all cases in excellent agreement with one another. Based on these studies, a set of ''double-zeta'' valence and all-electron basis functions have been used for further SCF--MO studies on Al 3 , Al 4 , AlNO, and OAl 3 . For a variety of difference combinations of real and model atoms we find excellent agreement for relative total energies, orbital energies (both core and valence), and Mulliken atomic populations. Finally, direct core-hole-state ionic calculations are reported in detail for Al 2 and AlNO, and noted for Al 3 and Al 4 . Results for corresponding frozen-orbital energy differences, relaxed SCF--MO energy differences, and relaxation energies are in all cases in excellent agreement (never differing by more than 0.07 eV, usually by somewhat less). The study clearly demonstrates the accuracy of the mixed real--model theory

  19. Droplet printing through bubble contact in the laser forward transfer of liquids

    International Nuclear Information System (INIS)

    Duocastella, M.; Fernandez-Pradas, J.M.; Morenza, J.L.; Serra, P.

    2011-01-01

    The deposition process of the laser-induced forward transfer of liquids at high laser fluences is analyzed through time-resolved imaging. It has been found that, at these conditions, sessile droplets are deposited due to the contact of a generated cavitation bubble with the receptor substrate, in contrast to the jet contact mechanism observed at low and moderate laser fluences. The bubble contact results in droplets with a larger diameter, a smaller contact angle and a lower uniformity than those of the jet mechanism. Therefore, in order to attain a high degree of resolution this mechanism should be prevented.

  20. Droplet printing through bubble contact in the laser forward transfer of liquids

    Energy Technology Data Exchange (ETDEWEB)

    Duocastella, M. [Universitat de Barcelona, Departament de Fisica Aplicada i Optica, Marti i Franques 1, E-08028 Barcelona (Spain); Fernandez-Pradas, J.M., E-mail: jmfernandez@ub.edu [Universitat de Barcelona, Departament de Fisica Aplicada i Optica, Marti i Franques 1, E-08028 Barcelona (Spain); Morenza, J.L.; Serra, P. [Universitat de Barcelona, Departament de Fisica Aplicada i Optica, Marti i Franques 1, E-08028 Barcelona (Spain)

    2011-01-15

    The deposition process of the laser-induced forward transfer of liquids at high laser fluences is analyzed through time-resolved imaging. It has been found that, at these conditions, sessile droplets are deposited due to the contact of a generated cavitation bubble with the receptor substrate, in contrast to the jet contact mechanism observed at low and moderate laser fluences. The bubble contact results in droplets with a larger diameter, a smaller contact angle and a lower uniformity than those of the jet mechanism. Therefore, in order to attain a high degree of resolution this mechanism should be prevented.

  1. 3D metal droplet printing development and advanced materials additive manufacturing

    Directory of Open Access Journals (Sweden)

    Lawrence E. Murr

    2017-01-01

    Full Text Available While commercial additive manufacturing processes involving direct metal wire or powder deposition along with powder bed fusion technologies using laser and electron beam melting have proliferated over the past decade, inkjet printing using molten metal droplets for direct, 3D printing has been elusive. In this paper we review the more than three decades of development of metal droplet generation for precision additive manufacturing applications utilizing advanced, high-temperature metals and alloys. Issues concerning process optimization, including product structure and properties affected by oxidation are discussed and some comparisons of related additive manufactured microstructures are presented.

  2. Droplet condensation in rapidly decaying pressure fields

    International Nuclear Information System (INIS)

    Peterson, P.F.; Bai, R.Y.; Schrock, V.E.; Hijikata, K.

    1992-01-01

    Certain promising schemes for cooling inertial confinement fusion reactors call for highly transient condensation in a rapidly decaying pressure field. After an initial period of condensation on a subcooled droplet, undesirable evaporation begins to occur. Recirculation within the droplet strongly impacts the character of this condensation-evaporation cycle, particularly when the recirculation time constant is of the order of the pressure decay time constant. Recirculation can augment the heat transfer, delay the onset of evaporation, and increase the maximum superheat inside the drop by as much as an order of magnitude. This numerical investigation identifies the most important parameters and physics characterizing transient, high heat flux droplet condensation. The results can be applied to conceptual designs of inertial confinement fusion reactors, where initial temperature differences on the order of 1,500 K decay to zero over time spans the order of tens of milliseconds

  3. Lattice-Boltzmann simulations of droplet evaporation

    KAUST Repository

    Ledesma-Aguilar, Rodrigo; Vella, Dominic; Yeomans, Julia M.

    2014-01-01

    © the Partner Organisations 2014. We study the utility and validity of lattice-Boltzmann (LB) simulations to explore droplet evaporation driven by a concentration gradient. Using a binary-fluid lattice-Boltzmann algorithm based on Cahn-Hilliard dynamics, we study the evaporation of planar films and 3D sessile droplets from smooth solid surfaces. Our results show that LB simulations accurately reproduce the classical regime of quasi-static dynamics. Beyond this limit, we show that the algorithm can be used to explore regimes where the evaporative and diffusive timescales are not widely separated, and to include the effect of boundaries of prescribed driving concentration. We illustrate the method by considering the evaporation of a droplet from a solid surface that is chemically patterned with hydrophilic and hydrophobic stripes. This journal is

  4. Lattice-Boltzmann simulations of droplet evaporation

    KAUST Repository

    Ledesma-Aguilar, Rodrigo

    2014-09-04

    © the Partner Organisations 2014. We study the utility and validity of lattice-Boltzmann (LB) simulations to explore droplet evaporation driven by a concentration gradient. Using a binary-fluid lattice-Boltzmann algorithm based on Cahn-Hilliard dynamics, we study the evaporation of planar films and 3D sessile droplets from smooth solid surfaces. Our results show that LB simulations accurately reproduce the classical regime of quasi-static dynamics. Beyond this limit, we show that the algorithm can be used to explore regimes where the evaporative and diffusive timescales are not widely separated, and to include the effect of boundaries of prescribed driving concentration. We illustrate the method by considering the evaporation of a droplet from a solid surface that is chemically patterned with hydrophilic and hydrophobic stripes. This journal is

  5. Droplet sizes, dynamics and deposition in vertical annular flow

    International Nuclear Information System (INIS)

    Lopes, J.C.B.; Dukler, A.E.

    1985-10-01

    The role of droplets in vertical upwards annular flow is investigated, focusing on the droplet size distributions, dynamics, and deposition phenomena. An experimental program was performed based on a new laser optical technique developed in these laboratories and implemented here for annular flow. This permitted the simultaneous measurement of droplet size, axial and radial velocity. The dependence of droplet size distributions on flow conditions is analyzed. The Upper-Log Normal function proves to be a good model for the size distribution. The mechanism controlling the maximum stable drop size was found to result from the interaction of the pressure fluctuations of the turbulent flow of the gas core with the droplet. The average axial droplet velocity showed a weak dependence on gas rates. This can be explained once the droplet size distribution and droplet size-velocity relationship are analyzed simultaneously. The surprising result from the droplet conditional analysis is that larger droplet travel faster than smaller ones. This dependence cannot be explained if the drag curves used do not take into account the high levels of turbulence present in the gas core in annular flow. If these are considered, then interesting new situations of multiplicity and stability of droplet terminal velocities are encountered. Also, the observed size-velocity relationship can be explained. A droplet deposition is formulated based on the particle inertia control. This permitted the calculation of rates of drop deposition directly from the droplet size and velocities data

  6. Interface-Resolving Simulation of Collision Efficiency of Cloud Droplets

    Science.gov (United States)

    Wang, Lian-Ping; Peng, Cheng; Rosa, Bodgan; Onishi, Ryo

    2017-11-01

    Small-scale air turbulence could enhance the geometric collision rate of cloud droplets while large-scale air turbulence could augment the diffusional growth of cloud droplets. Air turbulence could also enhance the collision efficiency of cloud droplets. Accurate simulation of collision efficiency, however, requires capture of the multi-scale droplet-turbulence and droplet-droplet interactions, which has only been partially achieved in the recent past using the hybrid direct numerical simulation (HDNS) approach. % where Stokes disturbance flow is assumed. The HDNS approach has two major drawbacks: (1) the short-range droplet-droplet interaction is not treated rigorously; (2) the finite-Reynolds number correction to the collision efficiency is not included. In this talk, using two independent numerical methods, we will develop an interface-resolved simulation approach in which the disturbance flows are directly resolved numerically, combined with a rigorous lubrication correction model for near-field droplet-droplet interaction. This multi-scale approach is first used to study the effect of finite flow Reynolds numbers on the droplet collision efficiency in still air. Our simulation results show a significant finite-Re effect on collision efficiency when the droplets are of similar sizes. Preliminary results on integrating this approach in a turbulent flow laden with droplets will also be presented. This work is partially supported by the National Science Foundation.

  7. The Influence of Acoustic Field Induced by HRT on Oscillation Behavior of a Single Droplet

    Directory of Open Access Journals (Sweden)

    Can Ruan

    2017-01-01

    Full Text Available This paper presents an experimental and theoretical study on the effects of an acoustic field induced by Hartmann Resonance Tube (HRT on droplet deformation behavior. The characteristics of the acoustic field generated by HRT are investigated. Results show that the acoustic frequency decreases with the increase of the resonator length, the sound pressure level (SPL increases with the increase of nozzle pressure ratio (NPR, and it is also noted that increasing resonator length can cause SPL to decrease, which has rarely been reported in published literature. Further theoretical analysis reveals that the resonance frequency of a droplet has several modes, and when the acoustic frequency equals the droplet’s frequency, heightened droplet responses are observed with the maximum amplitude of the shape oscillation. The experimental results for different resonator cavity lengths, nozzle pressure ratios and droplet diameters confirm the non-linear nature of this problem, and this conclusion is in good agreement with theoretical analysis. Measurements by high speed camera have shown that the introduction of an acoustic field can greatly enhance droplet oscillation, which means with the use of an ultrasonic atomizer based on HRT, the quality of atomization and combustion can be highly improved.

  8. Synthesis of colloidal metal nanocrystals in droplet reactors: the pros and cons of interfacial adsorption.

    Science.gov (United States)

    Zhang, Lei; Wang, Yi; Tong, Limin; Xia, Younan

    2014-07-09

    Droplet reactors have received considerable attention in recent years as an alternative route to the synthesis and potentially high-volume production of colloidal metal nanocrystals. Interfacial adsorption will immediately become an important issue to address when one seeks to translate a nanocrystal synthesis from batch reactors to droplet reactors due to the involvement of higher surface-to-volume ratios for the droplets and the fact that nanocrystals tend to be concentrated at the water-oil interface. Here we report a systematic study to compare the pros and cons of interfacial adsorption of metal nanocrystals during their synthesis in droplet reactors. On the one hand, interfacial adsorption can be used to generate nanocrystals with asymmetric shapes or structures, including one-sixth-truncated Ag octahedra and Au-Ag nanocups. On the other hand, interfacial adsorption has to be mitigated to obtain nanocrystals with uniform sizes and controlled shapes. We confirmed that Triton X-100, a nonionic surfactant, could effectively alleviate interfacial adsorption while imposing no impact on the capping agent typically needed for a shape-controlled synthesis. With the introduction of a proper surfactant, droplet reactors offer an attractive platform for the continuous production of colloidal metal nanocrystals.

  9. Simulation of High-Speed Droplet Impact Against Dry Substrates with Partial Velocity Slip

    Science.gov (United States)

    Kondo, Tomoki; Ando, Keita

    2017-11-01

    High-speed droplet impact can be used to clean substrates such as silicon wafers. Radially spreading shear flow after the impact may allow for mechanically removing contaminant particles at substrate surfaces. Since it is a big challenge to experimentally explore such complicated flow that exhibits contact line motion and water hammer, its flow feature is not well understood. Here, we aim to numerically evaluate shear flow caused by the impact of a spherical water droplet (of submillimeter sizes) at high speed (up to 50 m/s) against a dry rigid wall. We model the flow based on compressible Navier-Stokes equations with Stokes' hypothesis and solve them by a high-order-accurate finite volume method equipped with shock and interface capturing. To treat the motion of a contact line between the three phases (the droplet, the rigid wall, and the ambient air) in a robust manner, we permit velocity slip at the wall with Navier's model, for wall slip is known to come into play under steep velocity gradients that can arise from high-speed droplet impact. In our presentation, we will examine radially spreading flow after the droplet impact and the resulting wall shear stress generation from the simulation. This work was supported by JSPS KAKENHI Grant Number JP17J02211.

  10. Mixing efficiency inside micro-droplets coalesced by two components in cross-structure

    Science.gov (United States)

    Ren, Yanlin; Liu, Zhaomiao; Pang, Yan

    2017-11-01

    The mixing of micro-droplets is used in analytical chemistry, medicine production and material synthesis owing to its advantages including the encapsulation and narrow time residence distribution. In this work, droplets are coalesced by two dispersed phase with different flow rates, generated in cross-structure and mixed in planar serpentine structure. The mixing efficiency of micro-droplets under control characters including the width of entrance and the flow rate of dispersed phases have been investigated by experiments and numerical simulations. The UDS (user-defined scalar) as dimensionless concentration of the solution is adopted in simulation, and is used to calculate the concentration and the mixing effect. By changing the flow rates and the entrances` width, the changing rules of the mixing characters have been obtained. The asymmetry distributions of components make rapid mixing process in half part of each droplet when travel through a straight channel. Increasing of the ratio of entrance width result into larger droplet and weaken the chaotic mixing effect. Meanwhile, the coalesced mechanism can be performed by ranging the ratio of flow rates, the ranges are also determined by the widths of entrances. The authors gratefully acknowledge the support of National Natural Science Foundation of China (Grant No. 11572013).

  11. Real-time image processing for label-free enrichment of Actinobacteria cultivated in picolitre droplets.

    Science.gov (United States)

    Zang, Emerson; Brandes, Susanne; Tovar, Miguel; Martin, Karin; Mech, Franziska; Horbert, Peter; Henkel, Thomas; Figge, Marc Thilo; Roth, Martin

    2013-09-21

    The majority of today's antimicrobial therapeutics is derived from secondary metabolites produced by Actinobacteria. While it is generally assumed that less than 1% of Actinobacteria species from soil habitats have been cultivated so far, classic screening approaches fail to supply new substances, often due to limited throughput and frequent rediscovery of already known strains. To overcome these restrictions, we implement high-throughput cultivation of soil-derived Actinobacteria in microfluidic pL-droplets by generating more than 600,000 pure cultures per hour from a spore suspension that can subsequently be incubated for days to weeks. Moreover, we introduce triggered imaging with real-time image-based droplet classification as a novel universal method for pL-droplet sorting. Growth-dependent droplet sorting at frequencies above 100 Hz is performed for label-free enrichment and extraction of microcultures. The combination of both cultivation of Actinobacteria in pL-droplets and real-time detection of growing Actinobacteria has great potential in screening for yet unknown species as well as their undiscovered natural products.

  12. Lipid Droplet Formation Is Dispensable for Endoplasmic Reticulum-associated Degradation*

    Science.gov (United States)

    Olzmann, James A.; Kopito, Ron R.

    2011-01-01

    Proteins that fail to fold or assemble in the endoplasmic reticulum (ER) are destroyed by cytoplasmic proteasomes through a process known as ER-associated degradation. Substrates of this pathway are initially sequestered within the ER lumen and must therefore be dislocated across the ER membrane to be degraded. It has been proposed that generation of bicellar structures during lipid droplet formation may provide an “escape hatch” through which misfolded proteins, toxins, and viruses can exit the ER. We have directly tested this hypothesis by exploiting yeast strains defective in lipid droplet formation. Our data demonstrate that lipid droplet formation is dispensable for the dislocation of a plant toxin and the degradation of both soluble and integral membrane glycoproteins. PMID:21693705

  13. Measurement and interpretation of growth and evaporation of monodispersed droplets in a shock tube

    Science.gov (United States)

    Peters, F.; Paikert, B.

    1994-01-01

    A special gasdynamic shock tube process in combination with a Mie light scattering method is used to study growth and subsequent evaporation of monodispersed droplets carried in argon or air. The droplets are generated by homogeneous nucleation and observed in the micrometer range (0.15-6 micrometer radius). Droplet concentrations range from 10-1000/cu mm. Four different substances, i.e. water, n-propanol, methanol and n-hexane are tested for a wide range of properties. A model covering the entire range between large (Kn much greater than 1) and small Knudsen numbers (K much less than 1) is applied to interpret the experimental data. Excellent agreement is found.

  14. DNS of droplet-vortex interaction with a Karman vortex street

    International Nuclear Information System (INIS)

    Burger, M.; Schmehl, R.; Koch, R.; Wittig, S.; Bauer, H.-J.

    2006-01-01

    Predicting fuel spray interaction with large scale vortex structures still is a major challenge for state-of-the-art CFD codes. In order to elucidate the mechanisms involved, a fundamental study has been carried out in which the interaction of water droplets with a Karman vortex street is investigated. The disperse two-phase flow around a cylinder has been computed taking into account the mass, momentum and heat transfer between both phases. Flow conditions are chosen such that large scale vortices are generated by periodic flow separations of the well known Karman vortex street. A homogeneous distribution of water droplets is injected into the hot air up-stream of the computational domain. The mixing process as well as the impact of the droplets on the gas phase instabilities is analyzed in the downstream region where large scale vortex structures are present

  15. Big savings from small holes. [Liquid Droplet Radiator project for space vehicles

    Science.gov (United States)

    White, Alan

    1989-01-01

    The status and results to date of the NASA-Lewis/USAF Astronautics study of technology for large spacecraft heat-dissipation by means of liquid-droplet radiation (LDR) are discussed. The LDR concept uses a droplet generator to create billions of 200-micron droplets of a heatsink fluid which will cool through radiation into deep space as they fly toward a dropet collector. This exposure to the space environment entails the maintenance of vapor pressure as low as 10 to the -7th torr; the fluid must also be very stable chemically. While certain oils are good fluids for LDR use at low temperatures, higher-temperature heatsink fluids include Li, Sn, and Ga liquid metals.

  16. Study on condensation of biomass pyrolysis gas by spray bio-oil droplets

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Kun; Cheng, Wen-Long [University of Science and Technology of China (China)], email: wlcheng@ustc.edu.cn; Chen, Jing [Anhui Electric Power Design Institute (China); Shi, Wen-Jing [Anhui Heli Co., Ltd (China)

    2011-07-01

    This is a study of bio-oil generated by fast pyrolysis; a biomass feedstock is heated to pyrolyze at a rapid rate, the gas pyrolyzed is then condensed rapidly. The interesting result is a potential alternative fuel oil. An analysis was made of the effects of the initial pyrolysis gas temperatures, the initial bio-oil droplets temperatures and diameters, and the flow ratio of the gas and the liquid droplets on the heat and mass transfer between the gas and the liquid droplets. A few criterion equations were achieved with respect to the spray condenser. This paper established the gas-liquid phase equilibrium of an aqueous multi-composition system and the spray condensation model coupling heat and mass transfer. Model calculation and analysis showed that: spray condensation can effectively cool the high-temperature pyrolysis gas quickly; with gas liquid flowing, mass transfer rate reduces; and the relationship of gas and liquid flow ratio can achieve good accuracy.

  17. Fluorescence detection system for microfluidic droplets

    Science.gov (United States)

    Chen, Binyu; Han, Xiaoming; Su, Zhen; Liu, Quanjun

    2018-05-01

    In microfluidic detection technology, because of the universality of optical methods in laboratory, optical detection is an attractive solution for microfluidic chip laboratory equipment. In addition, the equipment with high stability and low cost can be realized by integrating appropriate optical detection technology on the chip. This paper reports a detection system for microfluidic droplets. Photomultiplier tubes (PMT) is used as a detection device to improve the sensitivity of detection. This system improves the signal to noise ratio by software filtering and spatial filter. The fluorescence intensity is proportional to the concentration of the fluorescence and intensity of the laser. The fluorescence micro droplets of different concentrations can be distinguished by this system.

  18. Droplets bouncing on a standing wave field

    Science.gov (United States)

    Pucci, Giuseppe; Tambasco, Lucas; Harris, Daniel; Bush, John

    2017-11-01

    A liquid bath subject to a vertical vibration becomes unstable to standing surface waves at a critical vibrational acceleration known as the Faraday threshold. We examine the behavior of a millimetric droplet bouncing on the surface of a quasi-one-dimensional fluid channel above the Faraday threshold. We identify a sequence of bifurcations that occurs as the vibrational acceleration is increased progressively, ultimately leading to the erratic, diffusive motion of the droplet along the length of the channel. A simple theoretical model is presented. This work was supported by the US National Science Foundation through Grants CMMI-1333242 and DMS-1614043.

  19. TRAJECTORY AND INCINERATION OF ROGUE DROPLETS IN A TURBULENT DIFFUSION FLAME

    Science.gov (United States)

    The trajectory and incineration efficiency of individual droplet streams of a fuel mixture injected into a swirling gas turbulent diffusion flame were measured as a function of droplet size, droplet velocity, interdroplet spacing, and droplet injection angle. Additional experimen...

  20. 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

  1. 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.

  2. Velocity and rotation measurements in acoustically levitated droplets

    International Nuclear Information System (INIS)

    Saha, Abhishek; Basu, Saptarshi; Kumar, Ranganathan

    2012-01-01

    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. Charge Transfer into Aqueous Droplets via Kilovolt Potentials

    Science.gov (United States)

    Hamlin, B. S.; Rosenberg, E. R.; Ristenpart, W. D.

    2012-11-01

    When an aqueous droplet immersed in an insulating oil contacts an electrified surface, the droplet acquires net charge. For sufficiently large field strengths, the charged droplet is driven back and forth electrophoretically between the electrodes, in essence ``bouncing'' between them. Although it is clear that the droplet acquires charge, the underlying mechanism controlling the charge transfer process has been unclear. Here we demonstrate that the chemical species present in the droplet strongly affect the charge transfer process into the drop. Using two independent charge measurement techniques, high speed video velocimetry and direct current measurement, we show that the charge acquired during contact is strongly influenced by the droplet pH. We also provide physical evidence that the electrodes undergo electroplating or corrosion for droplets with appropriate chemical species present. Together, the observations strongly suggest that electrochemical reactions govern the charge transfer process into the droplet.

  4. Encapsulation of emulsion droplets by organo–silica shells

    NARCIS (Netherlands)

    Zoldesi, C.; Steegstra, Patrick; Imhof, Arnout

    2007-01-01

    Surfactant-stabilized emulsion droplets were used as templates for the synthesis of hollow colloidal particles. Monodisperse silicone oil droplets were prepared by hydrolysis and polymerization of dimethyldiethoxysiloxane monomer, in the presence of surfactant: sodium dodecyl sulphate (SDS, anionic)

  5. Thermophoretically driven water droplets on graphene and boron nitride surfaces

    Science.gov (United States)

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

    2018-05-01

    We investigate thermally driven water droplet transport on graphene and hexagonal boron nitride (h-BN) surfaces using molecular dynamics simulations. The two surfaces considered here have different wettabilities with a significant difference in the mode of droplet transport. The water droplet travels along a straighter path on the h-BN sheet than on graphene. The h-BN surface produced a higher driving force on the droplet than the graphene surface. The water droplet is found to move faster on h-BN surface compared to graphene surface. The instantaneous contact angle was monitored as a measure of droplet deformation during thermal transport. The characteristics of the droplet motion on both surfaces is determined through the moment scaling spectrum. The water droplet on h-BN surface showed the attributes of the super-diffusive process, whereas it was sub-diffusive on the graphene surface.

  6. A novel coarsening mechanism of droplets in immiscible fluid mixtures

    Science.gov (United States)

    Shimizu, Ryotaro; Tanaka, Hajime

    2015-06-01

    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.

  7. The Evaporation of Liquid Droplets in Highly Turbulent Gas Streams

    National Research Council Canada - National Science Library

    Gould, Richard

    1998-01-01

    Single acetone and heptane droplets were suspended from a hypodermic needle in turbulent airflow, and the Nusselt number was obtained from direct measurements of the droplet diameter and evaporation rate...

  8. Flow field induced particle accumulation inside droplets in rectangular channels.

    Science.gov (United States)

    Hein, Michael; Moskopp, Michael; Seemann, Ralf

    2015-07-07

    Particle concentration is a basic operation needed to perform washing steps or to improve subsequent analysis in many (bio)-chemical assays. In this article we present field free, hydrodynamic accumulation of particles and cells in droplets flowing within rectangular micro-channels. Depending on droplet velocity, particles either accumulate at the rear of the droplet or are dispersed over the entire droplet cross-section. We show that the observed particle accumulation behavior can be understood by a coupling of particle sedimentation to the internal flow field of the droplet. The changing accumulation patterns are explained by a qualitative change of the internal flow field. The topological change of the internal flow field, however, is explained by the evolution of the droplet shape with increasing droplet velocity altering the friction with the channel walls. In addition, we demonstrate that accumulated particles can be concentrated, removing excess dispersed phase by splitting the droplet at a simple channel junction.

  9. The influence of gas phase velocity fluctuations on primary atomization and droplet deformation

    Science.gov (United States)

    Kourmatzis, A.; Masri, A. R.

    2014-02-01

    The effects of grid-generated velocity fluctuations on the primary atomization and subsequent droplet deformation of a range of laminar liquid jets are examined using microscopic high-speed backlit imaging of the break-up zone and laser Doppler anemometry of the gas phase separately. This is done for fixed gas mean flow conditions in a miniature wind tunnel experiment utilizing a selection of fuels, turbulence-generating grids and two syringe sizes. The constant mean flow allows for an isolated study of velocity fluctuation effects on primary atomization in a close approximation to homogeneous decaying turbulence. The qualitative morphology of the primary break-up region is examined over a range of turbulence intensities, and spectral analysis is performed in order to ascertain the break-up frequency which, for a case of no grid, compares well with the existing literature. The addition of velocity fluctuations tends to randomize the break-up process. Slightly downstream of the break-up region, image processing is conducted in order to extract a number of metrics, which do not depend on droplet sphericity, and these include droplet aspect ratio and orientation, the latter quantity being somewhat unconventional in spray characterization. A turbulent Weber number which takes into account gas phase fluctuations is utilized to characterize the resulting droplet shapes, in addition to a mean Weber number . Above a a clear positive relationship exists between the mean aspect ratio of droplets and the turbulent Weber number where is varied by altering all relevant variables including the velocity root mean square, the initial droplet diameter, the surface tension and the density.

  10. Effect of injection angle, density ratio, and viscosity on droplet formation in a microfluidic T-junction

    Directory of Open Access Journals (Sweden)

    Mohammad Yaghoub Abdollahzadeh Jamalabadi

    2017-07-01

    Full Text Available The T-junction microchannel device makes available a sharp edge to form micro-droplets from bio-material solutions. This article investigates the effects of injection angle, flow rate ratio, density ratio, viscosity ratio, contact angle, and slip length in the process of formation of uniform droplets in microfluidic T-junctions. The governing equations were solved by the commercial software. The results show that contact angle, slip length, and injection angles near the perpendicular and parallel conditions have an increasing effect on the diameter of generated droplets, while flow rate, density and viscosity ratios, and other injection angles had a decreasing effect on the diameter. Keywords: Microfluidics, Droplet formation, Flow rate ratio, Density ratio

  11. Sensitive and predictable separation of microfluidic droplets by size using in-line passive filter.

    Science.gov (United States)

    Ding, Ruihua; Ung, W Lloyd; Heyman, John A; Weitz, David A

    2017-01-01

    Active manipulation of droplets is crucial in droplet microfluidics. However, droplet polydispersity decreases the accuracy of active manipulation. We develop a microfluidic "droplet filter" that accurately separates droplets by size. The droplet filter has a sharp size cutoff and is capable of distinguishing droplets differing in volume by 20%. A simple model explains the behavior of the droplets as they pass through the filter. We show application of the filter in improving dielectric sorting efficiency.

  12. Droplet Traffic at a Simple Junction at Low Capillary Numbers

    Science.gov (United States)

    Engl, Wilfried; Roche, Matthieu; Colin, Annie; Panizza, Pascal; Ajdari, Armand

    2005-11-01

    We report that, when a train of confined droplets flowing through a channel reaches a junction, the droplets either are alternately distributed between the different outlets or all collect into the shortest one. We argue that this behavior is due to the hydrodynamic feedback of droplets in the different outlets on the selection process occurring at the junction. A “mean field” model, yielding semiquantitative results, offers a first guide to predict droplet traffic in branched networks.

  13. Method for Measuring Cooling Efficiency of Water Droplets Impinging onto Hot Metal Discs

    Directory of Open Access Journals (Sweden)

    Joachim Søreng Bjørge

    2018-06-01

    Full Text Available The present work outlines a method for measuring the cooling efficiency of droplets impinging onto hot metal discs in the temperature range of 85 °C to 400 °C, i.e., covering the boiling regimes experienced when applying water to heated objects in fires. Stainless steel and aluminum test discs (with 50-mm diameter, 10-mm thickness, and a surface roughness of Ra 0.4 or Ra 3 were suspended horizontally by four thermocouples that were used to record disc temperatures. The discs were heated by a laboratory burner prior to the experiments, and left to cool with and without applying 2.4-mm diameter water droplets to the discs while the disc temperatures were recorded. The droplets were generated by the acceleration of gravity from a hypodermic injection needle, and hit the disc center at a speed of 2.2 m/s and a rate of 0.02 g/s, i.e., about three droplets per second. Based on the recorded rate of the temperature change, as well as disc mass and disc heat capacity, the absolute droplet cooling effect and the relative cooling efficiency relative to complete droplet evaporation were obtained. There were significant differences in the cooling efficiency as a function of temperature for the two metals investigated, but there was no statistically significant difference with respect to whether the surface roughness was Ra 0.4 or Ra 3. Aluminum showed a higher cooling efficiency in the temperature range of 110 °C to 140 °C, and a lower cooling efficiency in the temperature range of 180 °C to 300 °C compared to stainless steel. Both metals gave a maximum cooling efficiency in the range of 75% to 85%. A minimum of 5% cooling efficiency was experienced for the aluminum disc at 235 °C, i.e., the observed Leidenfrost point. However, stainless steel did not give a clear minimum in cooling efficiency, which was about 12–14% for disc temperatures above 300 °C. This simple and straightforward technique is well suited for assessing the cooling efficiency of

  14. Dynamics of droplet breakup in a T-junction

    NARCIS (Netherlands)

    Hoang, D.A.; Portela, L.M.; Kleijn, C.R.; Kreutzer, M.T.; Van Steijn, V.

    2013-01-01

    The breakup of droplets due to creeping motion in a confined microchannel geometry is studied using three-dimensional numerical simulations. Analogously to unconfined droplets, there exist two distinct breakup phases: (i) a quasi-steady droplet deformation driven by the externally applied flow; and

  15. New models for droplet heating and evaporation

    KAUST Repository

    Sazhin, Sergei S.; Elwardani, Ahmed Elsaid; Gusev, Ivan G.; Xie, Jianfei; Shishkova, Irina N.; Cao, Bingyang; Snegirev, Alexander Yu.; Heikal, Morgan Raymond

    2013-01-01

    and evaporation, taking into account the effects of the moving boundary due to evaporation, hydrodynamic models of multi-component droplet heating and evaporation, taking and not taking into account the effects of the moving boundary, new kinetic models of mono

  16. Droplet microfluidics in (bio) chemical analysis

    Czech Academy of Sciences Publication Activity Database

    Basova, E. Y.; Foret, František

    2015-01-01

    Roč. 140, č. 1 (2015), s. 22-38 ISSN 0003-2654 R&D Projects: GA ČR(CZ) GBP206/12/G014 Institutional support: RVO:68081715 Keywords : droplet chemistry * bio analysis * microfluidics * protein Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 4.033, year: 2015

  17. Droplet microfluidics in (bio) chemical analysis

    Czech Academy of Sciences Publication Activity Database

    Basova, E. Y.; Foret, František

    2015-01-01

    Roč. 140, č. 1 (2015), s. 22-38 ISSN 0003-2654 R&D Projects: GA ČR(CZ) GBP206/12/G014 Institutional support: RVO:68081715 Keywords : droplet chemistry * bioanalysis * microfluidics * protein Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 4.033, year: 2015

  18. Droplet Manipulations in Two Phase Flow Microfluidics

    NARCIS (Netherlands)

    Pit, Arjen; Duits, Michael H.G.; Mugele, Friedrich Gunther

    2015-01-01

    Even though droplet microfluidics has been developed since the early 1980s, the number of applications that have resulted in commercial products is still relatively small. This is partly due to an ongoing maturation and integration of existing methods, but possibly also because of the emergence of

  19. Droplet microfluidic platform for cell electrofusion

    NARCIS (Netherlands)

    Schoeman, R.M.

    2015-01-01

    In this thesis a lab on a chip platform is described which is capable of electrofusing cells in a picoliter droplet. The platform consist out of glass part containing recessed platinum electrodes plasma bonded to a PDMS slab containing microchannels. First the two cell populations are introduced

  20. Droplet bubbling evaporatively cools a blowfly.

    Science.gov (United States)

    Gomes, Guilherme; Köberle, Roland; Von Zuben, Claudio J; Andrade, Denis V

    2018-04-19

    Terrestrial animals often use evaporative cooling to lower body temperature. Evaporation can occur from humid body surfaces or from fluids interfaced to the environment through a number of different mechanisms, such as sweating or panting. In Diptera, some flies move tidally a droplet of fluid out and then back in the buccopharyngeal cavity for a repeated number of cycles before eventually ingesting it. This is referred to as the bubbling behaviour. The droplet fluid consists of a mix of liquids from the ingested food, enzymes from the salivary glands, and antimicrobials, associated to the crop organ system, with evidence pointing to a role in liquid meal dehydration. Herein, we demonstrate that the bubbling behaviour also serves as an effective thermoregulatory mechanism to lower body temperature by means of evaporative cooling. In the blowfly, Chrysomya megacephala, infrared imaging revealed that as the droplet is extruded, evaporation lowers the fluid´s temperature, which, upon its re-ingestion, lowers the blowfly's body temperature. This effect is most prominent at the cephalic region, less in the thorax, and then in the abdomen. Bubbling frequency increases with ambient temperature, while its cooling efficiency decreases at high air humidities. Heat transfer calculations show that droplet cooling depends on a special heat-exchange dynamic, which result in the exponential activation of the cooling effect.

  1. 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

  2. Interaction between liquid droplets and heated surface

    Energy Technology Data Exchange (ETDEWEB)

    Nigmatulin, B I [Research and Engineering Centre, LWR Nuclear Plants Safety, Elektrogorsk (Russian Federation); Vasiliev, N I [Research and Engineering Centre, LWR Nuclear Plants Safety, Elektrogorsk (Russian Federation); Guguchkin, V V [Research and Engineering Centre, LWR Nuclear Plants Safety, Elektrogorsk (Russian Federation)

    1993-06-01

    In this paper, experimental methods and investigation results of interaction between droplets of different liquids and a heated surface are presented. Wetted area, contact time period and transition boundary from wetted to non-wetted interaction regimes are experimentally evaluated. A simple connection of the wetted area value and contact time period with the heat removal efficiency is shown. (orig.)

  3. Deformable nematic droplets in a magnetic field

    NARCIS (Netherlands)

    Otten, R.H.J.; van der Schoot, P. P. A. M.

    2012-01-01

    We present a Frank-Oseen elasticity theory for the shape and structure of deformable nematic droplets with homeotropic surface anchoring in the presence of a magnetic field. Inspired by recent experimental observations, we focus on the case where the magnetic susceptibility is negative, and find

  4. Adjuvants for single droplet application of glyphosate

    DEFF Research Database (Denmark)

    Mathiassen, Solvejg Kopp; Kudsk, Per; Lund, Ivar

    2016-01-01

    Retention and biological activity of droplets of glyphosate deposited onto plant leaves using a Drop on Demand inkjet printer application system, was examined on pot-grown Brassica napus, Solanum nigrum, Chenopodium album, Silene noctiflora and Echinocloa crus-galli plants. Retention was measured...

  5. Droplet-model electric dipole moments

    International Nuclear Information System (INIS)

    Myers, W.D.; Swiatecki, W.J.

    1991-01-01

    Denisov's recent criticism of the droplet-model formula for the dipole moment of a deformed nucleus as derived by Dorso et al., it shown to be invalid. This helps to clarify the relation of theory to the measured dipole moments, as discussed in the review article by Aberg et al. (orig.)

  6. Hydrodynamic clustering of droplets in turbulence

    Science.gov (United States)

    Kunnen, Rudie; Yavuz, Altug; van Heijst, Gertjan; Clercx, Herman

    2017-11-01

    Small, inertial particles are known to cluster in turbulent flows: particles are centrifuged out of eddies and gather in the strain-dominated regions. This so-called preferential concentration is reflected in the radial distribution function (RDF; a quantitative measure of clustering). We study clustering of water droplets in a loudspeaker-driven turbulence chamber. We track the motion of droplets in 3D and calculate the RDF. At moderate scales (a few Kolmogorov lengths) we find the typical power-law scaling of preferential concentration in the RDF. However, at even smaller scales (a few droplet diameters), we encounter a hitherto unobserved additional clustering. We postulate that the additional clustering is due to hydrodynamic interactions, an effect which is typically disregarded in modeling. Using a perturbative expansion of inertial effects in a Stokes-flow description of two interacting spheres, we obtain an expression for the RDF which indeed includes the additional clustering. The additional clustering enhances the collision probability of droplets, which enhances their growth rate due to coalescence. The additional clustering is thus an essential effect in precipitation modeling.

  7. Characterization of extreme ultraviolet emission from tin-droplets irradiated with Nd:YAG laser plasmas

    International Nuclear Information System (INIS)

    Aota, T; Nakai, Y; Fujioka, S; Shimomura, M; Nishimura, H; Nishihara, N; Miyanaga, N; Izawa, Y; Mima, K; Fujiwara, E

    2008-01-01

    EUV emission from spherical and planer targets were precisely characterized as an experimental database for use in EUV source generation at high repetition rates. In the single-shot base experiments, conversion efficiency as high as those for the plasma geometry has been demonstrated. The integrated experiment was made with 10 Hz plasma generation, obtained conversion efficiency is low mainly due to unstable positioning of the droplets

  8. Electronic structure and bonding in the RhC molecule by all-electron ab initio HF–Cl calculations and mass spectrometric measurements

    DEFF Research Database (Denmark)

    Shim, Irene; Gingerich, K. A.

    1984-01-01

    In the present study we present all-electron ab initio Hartree–Fock (HF) and configuration interaction (CI) calculations of the 2Sigma+ ground state as well as of 16 excited states of the RhC molecule. The calculated spectroscopic constants of the lowest lying states are in good agreement...... with the experimental data. The chemical bond in the electronic ground state is mainly due to interaction of the 4d orbitals of Rh with the 2s and 2p orbitals of C. The bond is a triple bond composed of two pi bonds and one sigma bond. The 5s electron of Rh hardly participates in the bond formation. It is located...

  9. Operator formulation of the droplet model

    International Nuclear Information System (INIS)

    Lee, B.W.

    1987-01-01

    We study in detail the implications of the operator formulation of the droplet model. The picture of high-energy scattering that emerges from this model attributed the interaction between two colliding particles at high energies to an instantaneous, multiple exchange between two extended charge distributions. Thus the study of charge correlation functions becomes the most important problem in the droplet model. We find that in order for the elastic cross section to have a finite limit at infinite energy, the charge must be a conserved one. In quantum electrodynamics the charge in question is the electric charge. In hadronic physics, we conjecture, it is the baryonic charge. Various arguments for and implications of this hypothesis are presented. We study formal properties of the charge correlation functions that follow from microcausality, T, C, P invariances, and charge conservation. Perturbation expansion of the correlation functions is studied, and their cluster properties are deduced. A cluster expansion of the high-energy T matrix is developed, and the exponentiation of the interaction potential in this scheme is noted. The operator droplet model is put to the test of reproducing the high-energy limit of elastic scattering quantum electrodynamics found by Cheng and Wu in perturbation theory. We find that the droplet model reproduces exactly the results of Cheng and Wu as to the impact factor. In fact, the ''impact picture'' of Cheng and Wu is completely equivalent to the droplet model in the operator version. An appraisal is made of the possible limitation of the model. (author). 13 refs

  10. Engineering plant membranes using droplet interface bilayers.

    Science.gov (United States)

    Barlow, N E; Smpokou, E; Friddin, M S; Macey, R; Gould, I R; Turnbull, C; Flemming, A J; Brooks, N J; Ces, O; Barter, L M C

    2017-03-01

    Droplet interface bilayers (DIBs) have become widely recognised as a robust platform for constructing model membranes and are emerging as a key technology for the bottom-up assembly of synthetic cell-like and tissue-like structures. DIBs are formed when lipid-monolayer coated water droplets are brought together inside a well of oil, which is excluded from the interface as the DIB forms. The unique features of the system, compared to traditional approaches (e.g., supported lipid bilayers, black lipid membranes, and liposomes), is the ability to engineer multi-layered bilayer networks by connecting multiple droplets together in 3D, and the capability to impart bilayer asymmetry freely within these droplet architectures by supplying droplets with different lipids. Yet despite these achievements, one potential limitation of the technology is that DIBs formed from biologically relevant components have not been well studied. This could limit the reach of the platform to biological systems where bilayer composition and asymmetry are understood to play a key role. Herein, we address this issue by reporting the assembly of asymmetric DIBs designed to replicate the plasma membrane compositions of three different plant species; Arabidopsis thaliana , tobacco, and oats, by engineering vesicles with different amounts of plant phospholipids, sterols and cerebrosides for the first time. We show that vesicles made from our plant lipid formulations are stable and can be used to assemble asymmetric plant DIBs. We verify this using a bilayer permeation assay, from which we extract values for absolute effective bilayer permeation and bilayer stability. Our results confirm that stable DIBs can be assembled from our plant membrane mimics and could lead to new approaches for assembling model systems to study membrane translocation and to screen new agrochemicals in plants.

  11. Chemotactic droplet swimmers in complex geometries

    Science.gov (United States)

    Jin, Chenyu; Hokmabad, Babak V.; Baldwin, Kyle A.; Maass, Corinna C.

    2018-02-01

    Chemotaxis1 and auto-chemotaxis are key mechanisms in the dynamics of micro-organisms, e.g. in the acquisition of nutrients and in the communication between individuals, influencing the collective behaviour. However, chemical signalling and the natural environment of biological swimmers are generally complex, making them hard to access analytically. We present a well-controlled, tunable artificial model to study chemotaxis and autochemotaxis in complex geometries, using microfluidic assays of self-propelling oil droplets in an aqueous surfactant solution (Herminghaus et al 2014 Soft Matter 10 7008-22 Krüger et al 2016 Phys. Rev. Lett. 117). Droplets propel via interfacial Marangoni stresses powered by micellar solubilisation. Moreover, filled micelles act as a chemical repellent by diffusive phoretic gradient forces. We have studied these chemotactic effects in a series of microfluidic geometries, as published in Jin et al (2017 Proc. Natl Acad. Sci. 114 5089-94): first, droplets are guided along the shortest path through a maze by surfactant diffusing into the maze from the exit. Second, we let auto-chemotactic droplet swimmers pass through bifurcating microfluidic channels and record anticorrelations between the branch choices of consecutive droplets. We present an analytical Langevin model matching the experimental data. In a previously unpublished experiment, pillar arrays of variable sizes and shapes provide a convex wall interacting with the swimmer and, in the case of attachment, bending its trajectory and forcing it to revert to its own trail. We observe different behaviours based on the interplay of wall curvature and negative autochemotaxis, i.e. no attachment for highly curved interfaces, stable trapping at large pillars, and a narrow transition region where negative autochemotaxis makes the swimmers detach after a single orbit.

  12. An interface tracking model for droplet electrocoalescence.

    Energy Technology Data Exchange (ETDEWEB)

    Erickson, Lindsay Crowl

    2013-09-01

    This report describes an Early Career Laboratory Directed Research and Development (LDRD) project to develop an interface tracking model for droplet electrocoalescence. Many fluid-based technologies rely on electrical fields to control the motion of droplets, e.g. microfluidic devices for high-speed droplet sorting, solution separation for chemical detectors, and purification of biodiesel fuel. Precise control over droplets is crucial to these applications. However, electric fields can induce complex and unpredictable fluid dynamics. Recent experiments (Ristenpart et al. 2009) have demonstrated that oppositely charged droplets bounce rather than coalesce in the presence of strong electric fields. A transient aqueous bridge forms between approaching drops prior to pinch-off. This observation applies to many types of fluids, but neither theory nor experiments have been able to offer a satisfactory explanation. Analytic hydrodynamic approximations for interfaces become invalid near coalescence, and therefore detailed numerical simulations are necessary. This is a computationally challenging problem that involves tracking a moving interface and solving complex multi-physics and multi-scale dynamics, which are beyond the capabilities of most state-of-the-art simulations. An interface-tracking model for electro-coalescence can provide a new perspective to a variety of applications in which interfacial physics are coupled with electrodynamics, including electro-osmosis, fabrication of microelectronics, fuel atomization, oil dehydration, nuclear waste reprocessing and solution separation for chemical detectors. We present a conformal decomposition finite element (CDFEM) interface-tracking method for the electrohydrodynamics of two-phase flow to demonstrate electro-coalescence. CDFEM is a sharp interface method that decomposes elements along fluid-fluid boundaries and uses a level set function to represent the interface.

  13. Formation of radial aligned and uniform nematic liquid crystal droplets via drop-on-demand inkjet printing into a partially-wet polymer layer

    Science.gov (United States)

    Parry, Ellis; Kim, Dong-Jin; Castrejón-Pita, Alfonso A.; Elston, Steve J.; Morris, Stephen M.

    2018-06-01

    This paper investigates the drop-on-demand inkjet printing of a nematic liquid crystal (LC) onto a variety of substrates. Achieving both a well-defined droplet boundary and uniformity of the LC director in printed droplets can be challenging when traditional alignment surfaces are employed. Despite the increasing popularity of inkjet printing LCs, the mechanisms that are involved during the deposition process such as drop impact, wetting and spreading have received very little attention, in the way of experiments, as viable routes for promoting alignment of the resultant LC droplets. In this work, radial alignment of the director and uniformity of the droplet boundary are achieved in combination via the use of a partially-wet polymer substrate, which makes use of the forces and flow generated during droplet impact and subsequent wetting process. Our findings could have important consequences for future LC inkjet applications, including the development of smart inks, printable sensors and lasers.

  14. On-chip Magnetic Separation and Cell Encapsulation in Droplets

    Science.gov (United States)

    Chen, A.; Byvank, T.; Bharde, A.; Miller, B. L.; Chalmers, J. J.; Sooryakumar, R.; Chang, W.-J.; Bashir, R.

    2012-02-01

    The demand for high-throughput single cell assays is gaining importance because of the heterogeneity of many cell suspensions, even after significant initial sorting. These suspensions may display cell-to-cell variability at the gene expression level that could impact single cell functional genomics, cancer, stem-cell research and drug screening. The on-chip monitoring of individual cells in an isolated environment could prevent cross-contamination, provide high recovery yield and ability to study biological traits at a single cell level These advantages of on-chip biological experiments contrast to conventional methods, which require bulk samples that provide only averaged information on cell metabolism. We report on a device that integrates microfluidic technology with a magnetic tweezers array to combine the functionality of separation and encapsulation of objects such as immunomagnetically labeled cells or magnetic beads into pico-liter droplets on the same chip. The ability to control the separation throughput that is independent of the hydrodynamic droplet generation rate allows the encapsulation efficiency to be optimized. The device can potentially be integrated with on-chip labeling and/or bio-detection to become a powerful single-cell analysis device.

  15. The Lipid Droplet – A Well-Connected Organelle

    Directory of Open Access Journals (Sweden)

    Qiang eGao

    2015-08-01

    Full Text Available Our knowledge of inter-organellar communication has grown exponentially in recent years. This review focuses on the interactions that cytoplasmic lipid droplets have with other organelles. Twenty-five years ago droplets were considered simply particles of coalesced fat. Ten years ago there were hints from proteomics studies that droplets might interact with other structures to share lipids and proteins. Now it is clear that the droplets interact with many if not most cellular structures to maintain cellular homeostasis and to buffer against insults such as starvation. The evidence for this statement, as well as probes to understand the nature and results of droplet interactions, are presented.

  16. Droplet Epitaxy Image Contrast in Mirror Electron Microscopy

    Science.gov (United States)

    Kennedy, S. M.; Zheng, C. X.; Jesson, D. E.

    2017-01-01

    Image simulation methods are applied to interpret mirror electron microscopy (MEM) images obtained from a movie of GaAs droplet epitaxy. Cylindrical symmetry of structures grown by droplet epitaxy is assumed in the simulations which reproduce the main features of the experimental MEM image contrast, demonstrating that droplet epitaxy can be studied in real-time. It is therefore confirmed that an inner ring forms at the droplet contact line and an outer ring (or skirt) occurs outside the droplet periphery. We believe that MEM combined with image simulations will be increasingly used to study the formation and growth of quantum structures.

  17. Post-dryout heat transfer and entrained droplet sizes at low pressure and low flow conditions

    International Nuclear Information System (INIS)

    Jeong, H.Y.; No, H.C.

    1997-01-01

    The entrainment mechanisms and the entrained droplet sizes with relation to the flow regimes are investigated. Through the analysis of many experimental post-dryout data, it is shown that the most probable flow regime near dryout or quench front is not annular flow but churn-turbulent flow when the mass flux is low. A correlation describing the initial droplet size just after the CHF position at low mass flux is suggested through regression analysis. The history-dependent post-dryout model of Varone and Rohsenow replaced by the Webb-Chen model for wall-vapor heat transfer is used as a reference model in the analysis. In the post-dryout region at low pressure and low flow, it is found that the suggested one-dimensional mechanistic model is not applicable when the vapor superficial velocity is very low. This is explained by the change of main entrainment mechanism with the change of flow regime. In bubbly or slug flow a number of tiny droplets generated from bubble burst become important in the heat transfer after dryout. Therefore, the suggested correlation is valid only in the churn-turbulent flow regime (j g * = 0.5∼4.5). It is also suggested that the droplet size generated from the churn-turbulent surface is dependent not only on the pressure but also on the vapor velocity. It turns out that the present model can predict the measured cladding and vapor temperatures within 20% and 25%, respectively

  18. Lithography-free nanofluidic concentrator based on droplets-on-demand system

    Science.gov (United States)

    Yu, Miao; Zhou, Hongbo; Yao, Shuhuai

    2013-11-01

    Biomarkers are usually low-abundance proteins in biofluids and below detection limit of conventional biosensors. Nanofluidic concentration devices allow efficient biomolecules trapping by utilizing ion concentration polarization near nanochannels. However, once the electric field is turned off, the electrokinetic concentration plug cannot maintain its concentration status and starts to diffuse. In order to maintain the high concentration and extract the concentrated sample for further analysis, a good approach is to encapsulate these plugs into water-in-oil droplets. Here we developed a nanofluidic concentrator based on droplet-on-demand generator to encapsulate concentrated sample in nL droplets. The lithography-free nanochannels were patterned by thermal cracking on the surface of PS Petri-dish. The resulting nanochannel arrays were 30 nm in depth. In combination with microchannels on PDMS, the micro-nano hybrid chip was developed. We used FITC solution to demonstrate that the chip significantly increased the sample concentration for more than 100 folds within 5 minutes. By tuning the pulsed pressure imposed by the solenoid valve connected to the concentration channel, the system can generate a desired volume of droplet with a target sample concentration at a prescribed time. This work was supported by the Research Grants Council of Hong Kong under General Research Fund (Grant No. 621110).

  19. Fusion of microlitre water-in-oil droplets for simple, fast and green chemical assays.

    Science.gov (United States)

    Chiu, S-H; Urban, P L

    2015-08-07

    A simple format for microscale chemical assays is proposed. It does not require the use of test tubes, microchips or microtiter plates. Microlitre-range (ca. 0.7-5.0 μL) aqueous droplets are generated by a commercial micropipette in a non-polar matrix inside a Petri dish. When two droplets are pipetted nearby, they spontaneously coalesce within seconds, priming a chemical reaction. Detection of the reaction product is accomplished by colorimetry, spectrophotometry, or fluorimetry using simple light-emitting diode (LED) arrays as the sources of monochromatic light, while chemiluminescence detection of the analytes present in single droplets is conducted in the dark. A smartphone camera is used as the detector. The limits of detection obtained for the developed in-droplet assays are estimated to be: 1.4 nmol (potassium permanganate by colorimetry), 1.4 pmol (fluorescein by fluorimetry), and 580 fmol (sodium hypochlorite by chemiluminescence detection). The format has successfully been used to monitor the progress of chemical and biochemical reactions over time with sub-second resolution. A semi-quantitative analysis of ascorbic acid using Tillman's reagent is presented. A few tens of individual droplets can be scanned in parallel. Rapid switching of the LED light sources with different wavelengths enables a spectral analysis of multiple droplets. Very little solid waste is produced. The assay matrix is readily recycled, thus the volume of liquid waste produced each time is also very small (typically, 1-10 μL per analysis). Various water-immiscible translucent liquids can be used as the reaction matrix: including silicone oil, 1-octanol as well as soybean cooking oil.

  20. Emulsion oil droplet size significantly affects satiety: A pre-ingestive approach.

    Science.gov (United States)

    Lett, Aaron M; Norton, Jennifer E; Yeomans, Martin R

    2016-01-01

    Previous research has demonstrated that the manipulation of oil droplet size within oil-in-water emulsions significantly affects sensory characteristics, hedonics and expectations of food intake, independently of energy content. Smaller oil droplets enhanced perceived creaminess, increased Liking and generated greater expectations of satiation and satiety, indicating that creaminess is a satiety-relevant sensory cue within these systems. This paper extends these findings by investigating the effect of oil droplet size (d4,3: 2 and 50 μm) on food intake and appetite. Male participants (n = 34 aged 18-37; BMI of 22.7 ± 1.6 kg/m(2); DEBQ restricted eating score of 1.8 ± 0.1.) completed two test days, where they visited the laboratory to consume a fixed-portion breakfast, returning 3 h later for a "drink", which was the emulsion preload containing either 2 or 50 μm oil droplets. This was followed 20 min later with an ad libitum pasta lunch. Participants consumed significantly less at the ad libitum lunch after the preload containing 2 μm oil droplets than after the 50 μm preload, with an average reduction of 12% (62.4 kcal). Despite the significant differences in intake, no significant differences in sensory characteristics were noted. The findings show that the impact that an emulsion has on satiety can be enhanced without producing significantly perceivable differences in sensory properties. Therefore, by introducing a processing step which results in a smaller droplets, emulsion based liquid food products can be produced that enhance satiety, allowing covert functional redesign. Future work should consider the mechanism responsible for this effect. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Hydrodynamics of Leidenfrost droplets in one-component fluids

    KAUST Repository

    Xu, Xinpeng; Qian, Tiezheng

    2013-01-01

    Using the dynamic van der Waals theory [Phys. Rev. E 75, 036304 (2007)], we numerically investigate the hydrodynamics of Leidenfrost droplets under gravity in two dimensions. Some recent theoretical predictions and experimental observations are confirmed in our simulations. A Leidenfrost droplet larger than a critical size is shown to be unstable and break up into smaller droplets due to the Rayleigh-Taylor instability of the bottom surface of the droplet. Our simulations demonstrate that an evaporating Leidenfrost droplet changes continuously from a puddle to a circular droplet, with the droplet shape controlled by its size in comparison with a few characteristic length scales. The geometry of the vapor layer under the droplet is found to mainly depend on the droplet size and is nearly independent of the substrate temperature, as reported in a recent experimental study [Phys. Rev. Lett. 109, 074301 (2012)]. Finally, our simulations demonstrate that a Leidenfrost droplet smaller than a characteristic size takes off from the hot substrate because the levitating force due to evaporation can no longer be balanced by the weight of the droplet, as observed in a recent experimental study [Phys. Rev. Lett. 109, 034501 (2012)].

  2. Hydrodynamics of Leidenfrost droplets in one-component fluids

    KAUST Repository

    Xu, Xinpeng

    2013-04-24

    Using the dynamic van der Waals theory [Phys. Rev. E 75, 036304 (2007)], we numerically investigate the hydrodynamics of Leidenfrost droplets under gravity in two dimensions. Some recent theoretical predictions and experimental observations are confirmed in our simulations. A Leidenfrost droplet larger than a critical size is shown to be unstable and break up into smaller droplets due to the Rayleigh-Taylor instability of the bottom surface of the droplet. Our simulations demonstrate that an evaporating Leidenfrost droplet changes continuously from a puddle to a circular droplet, with the droplet shape controlled by its size in comparison with a few characteristic length scales. The geometry of the vapor layer under the droplet is found to mainly depend on the droplet size and is nearly independent of the substrate temperature, as reported in a recent experimental study [Phys. Rev. Lett. 109, 074301 (2012)]. Finally, our simulations demonstrate that a Leidenfrost droplet smaller than a characteristic size takes off from the hot substrate because the levitating force due to evaporation can no longer be balanced by the weight of the droplet, as observed in a recent experimental study [Phys. Rev. Lett. 109, 034501 (2012)].

  3. Binary particle separation in droplet microfluidics using acoustophoresis

    Science.gov (United States)

    Fornell, Anna; Cushing, Kevin; Nilsson, Johan; Tenje, Maria

    2018-02-01

    We show a method for separation of two particle species with different acoustic contrasts originally encapsulated in the same droplet in a continuous two-phase system. This was realized by using bulk acoustic standing waves in a 380 μm wide silicon-glass microfluidic channel. Polystyrene particles (positive acoustic contrast particles) and in-house synthesized polydimethylsiloxane (PDMS) particles (negative acoustic contrast particles) were encapsulated inside water-in-oil droplets either individually or in a mixture. At acoustic actuation of the system at the fundamental resonance frequency, the polystyrene particles were moved to the center of the droplet (pressure node), while the PDMS particles were moved to the sides of the droplet (pressure anti-nodes). The acoustic particle manipulation step was combined in series with a trifurcation droplet splitter, and as the original droplet passed through the splitter and was divided into three daughter droplets, the polystyrene particles were directed into the center daughter droplet, while the PDMS particles were directed into the two side daughter droplets. The presented method expands the droplet microfluidics tool-box and offers new possibilities to perform binary particle separation in droplet microfluidic systems.

  4. Evaluation of droplet size distributions using univariate and multivariate approaches

    DEFF Research Database (Denmark)

    Gauno, M.H.; Larsen, C.C.; Vilhelmsen, T.

    2013-01-01

    of the distribution. The current study was aiming to compare univariate and multivariate approach in evaluating droplet size distributions. As a model system, the atomization of a coating solution from a two-fluid nozzle was investigated. The effect of three process parameters (concentration of ethyl cellulose...... in ethanol, atomizing air pressure, and flow rate of coating solution) on the droplet size and droplet size distribution using a full mixed factorial design was used. The droplet size produced by a two-fluid nozzle was measured by laser diffraction and reported as volume based size distribution....... Investigation of loading and score plots from principal component analysis (PCA) revealed additional information on the droplet size distributions and it was possible to identify univariate statistics (volume median droplet size), which were similar, however, originating from varying droplet size distributions...

  5. Supersonic laser-induced jetting of aluminum micro-droplets

    Energy Technology Data Exchange (ETDEWEB)

    Zenou, M. [Racah Institute of Physics and the Harvey M. Kruger Family Center for Nano-science and Nanotechnology, The Hebrew University of Jerusalem, 91904 Jerusalem (Israel); Additive Manufacturing Lab, Orbotech Ltd., P.O. Box 215, 81101 Yavne (Israel); Sa' ar, A. [Racah Institute of Physics and the Harvey M. Kruger Family Center for Nano-science and Nanotechnology, The Hebrew University of Jerusalem, 91904 Jerusalem (Israel); Kotler, Z. [Additive Manufacturing Lab, Orbotech Ltd., P.O. Box 215, 81101 Yavne (Israel)

    2015-05-04

    The droplet velocity and the incubation time of pure aluminum micro-droplets, printed using the method of sub-nanosecond laser induced forward transfer, have been measured indicating the formation of supersonic laser-induced jetting. The incubation time and the droplet velocity were extracted by measuring a transient electrical signal associated with droplet landing on the surface of the acceptor substrate. This technique has been exploited for studying small volume droplets, in the range of 10–100 femto-litters for which supersonic velocities were measured. The results suggest elastic propagation of the droplets across the donor-to-acceptor gap, a nonlinear deposition dynamics on the surface of the acceptor and overall efficient energy transfer from the laser beam to the droplets.

  6. Supersonic laser-induced jetting of aluminum micro-droplets

    International Nuclear Information System (INIS)

    Zenou, M.; Sa'ar, A.; Kotler, Z.

    2015-01-01

    The droplet velocity and the incubation time of pure aluminum micro-droplets, printed using the method of sub-nanosecond laser induced forward transfer, have been measured indicating the formation of supersonic laser-induced jetting. The incubation time and the droplet velocity were extracted by measuring a transient electrical signal associated with droplet landing on the surface of the acceptor substrate. This technique has been exploited for studying small volume droplets, in the range of 10–100 femto-litters for which supersonic velocities were measured. The results suggest elastic propagation of the droplets across the donor-to-acceptor gap, a nonlinear deposition dynamics on the surface of the acceptor and overall efficient energy transfer from the laser beam to the droplets

  7. Global rainbow refractometry for droplet temperature measurement

    International Nuclear Information System (INIS)

    Pascal Lemaitre; Emmanuel Porcheron; Amandine Nuboer; Philippe Brun; Pierre Cornet; Jeanne Malet; Jacques Vendel; Laurent Bouilloux; Gerard Grehan

    2005-01-01

    Full text of publication follows: In order to establish an accurate database to characterize the heat and mass transfers between a spray and the atmosphere with thermal-hydraulic conditions representative of a hypothetical nuclear reactor accident in the containment enclosure of a pressurized water reactor (PWR), the French Institut de Radioprotection et de Surete Nucleaire (IRSN) has developed the TOSQAN experimental facility. This experiment is highly instrumented with non-intrusive diagnostics allowing to measure droplet size and velocity and gas concentrations [1]. The aim of this work is to present the Global Rainbow Thermometry (GRT), which is an advanced non-intrusive optical diagnostic, developed to measure the mean temperature of a set of falling droplets, in a measurement volume of 1 cm 3 . The final paper will be divided in three parts. In the first one, we will explain the principle of the rainbow formation and how droplet temperature can be deduced from the rainbow analysis [2]. This part will be illustrated with the theoretical background on the rainbow and numerical simulations of the global rainbow. The second part will be devoted to present the global rainbow experimental set-up we have developed on optical table, its experimental qualification and finally its implementation on the TOSQAN facility [3]. Finally, we will present the temperature measurements achieved in TOSQAN for thermal-hydraulic conditions representative of a hypothetical nuclear reactor accident. These measurements are useful to characterize the heat and mass transfers between the spraying droplets and the air-steam mixture composing the atmosphere. This analysis will be exposed in a two companion papers. References: [1] E. Porcheron, P. Brun, P. Cornet, J. Malet, J. Vendel. Optical diagnostics applied for single and multi-phase flow characterization in the TOSQAN facility dedicated for thermal hydraulic containment studies. NURETH-10 Seoul, Korea, October 5-9, 2003. [2] P

  8. Global rainbow refractometry for droplet temperature measurement

    Energy Technology Data Exchange (ETDEWEB)

    Pascal Lemaitre; Emmanuel Porcheron; Amandine Nuboer; Philippe Brun; Pierre Cornet; Jeanne Malet; Jacques Vendel; Laurent Bouilloux [Institut de Radioprotection et de Surete Nucleaire DSU/SERAC, BP 68, 91192 Gif-sur-Yvette Cedex (France); Gerard Grehan [UMR 6614 CORIA, Laboratoire d' Electromagnetisme et Systemes Particulaires Site Universitaire du Madrillet, Avenue de l' universite BP 12, 76 801 Saint Etienne du Rouvray Cedex, (France)

    2005-07-01

    Full text of publication follows: In order to establish an accurate database to characterize the heat and mass transfers between a spray and the atmosphere with thermal-hydraulic conditions representative of a hypothetical nuclear reactor accident in the containment enclosure of a pressurized water reactor (PWR), the French Institut de Radioprotection et de Surete Nucleaire (IRSN) has developed the TOSQAN experimental facility. This experiment is highly instrumented with non-intrusive diagnostics allowing to measure droplet size and velocity and gas concentrations [1]. The aim of this work is to present the Global Rainbow Thermometry (GRT), which is an advanced non-intrusive optical diagnostic, developed to measure the mean temperature of a set of falling droplets, in a measurement volume of 1 cm{sup 3}. The final paper will be divided in three parts. In the first one, we will explain the principle of the rainbow formation and how droplet temperature can be deduced from the rainbow analysis [2]. This part will be illustrated with the theoretical background on the rainbow and numerical simulations of the global rainbow. The second part will be devoted to present the global rainbow experimental set-up we have developed on optical table, its experimental qualification and finally its implementation on the TOSQAN facility [3]. Finally, we will present the temperature measurements achieved in TOSQAN for thermal-hydraulic conditions representative of a hypothetical nuclear reactor accident. These measurements are useful to characterize the heat and mass transfers between the spraying droplets and the air-steam mixture composing the atmosphere. This analysis will be exposed in a two companion papers. References: [1] E. Porcheron, P. Brun, P. Cornet, J. Malet, J. Vendel. Optical diagnostics applied for single and multi-phase flow characterization in the TOSQAN facility dedicated for thermal hydraulic containment studies. NURETH-10 Seoul, Korea, October 5-9, 2003. [2] P

  9. Monodisperse Picoliter Droplets for Low-Bias and Contamination-Free Reactions in Single-Cell Whole Genome Amplification.

    Directory of Open Access Journals (Sweden)

    Yohei Nishikawa

    Full Text Available Whole genome amplification (WGA is essential for obtaining genome sequences from single bacterial cells because the quantity of template DNA contained in a single cell is very low. Multiple displacement amplification (MDA, using Phi29 DNA polymerase and random primers, is the most widely used method for single-cell WGA. However, single-cell MDA usually results in uneven genome coverage because of amplification bias, background amplification of contaminating DNA, and formation of chimeras by linking of non-contiguous chromosomal regions. Here, we present a novel MDA method, termed droplet MDA, that minimizes amplification bias and amplification of contaminants by using picoliter-sized droplets for compartmentalized WGA reactions. Extracted DNA fragments from a lysed cell in MDA mixture are divided into 105 droplets (67 pL within minutes via flow through simple microfluidic channels. Compartmentalized genome fragments can be individually amplified in these droplets without the risk of encounter with reagent-borne or environmental contaminants. Following quality assessment of WGA products from single Escherichia coli cells, we showed that droplet MDA minimized unexpected amplification and improved the percentage of genome recovery from 59% to 89%. Our results demonstrate that microfluidic-generated droplets show potential as an efficient tool for effective amplification of low-input DNA for single-cell genomics and greatly reduce the cost and labor investment required for determination of nearly complete genome sequences of uncultured bacteria from environmental samples.

  10. Volume-of-fluid simulations in microfluidic T-junction devices: Influence of viscosity ratio on droplet size

    Science.gov (United States)

    Nekouei, Mehdi; Vanapalli, Siva A.

    2017-03-01

    We used volume-of-fluid (VOF) method to perform three-dimensional numerical simulations of droplet formation of Newtonian fluids in microfluidic T-junction devices. To evaluate the performance of the VOF method we examined the regimes of drop formation and determined droplet size as a function of system parameters. Comparison of the simulation results with four sets of experimental data from the literature showed good agreement, validating the VOF method. Motivated by the lack of adequate studies investigating the influence of viscosity ratio (λ) on the generated droplet size, we mapped the dependence of drop volume on capillary number (0.001 1. In addition, we find that at a given capillary number, the size of droplets does not vary appreciably when λ 1. We develop an analytical model for predicting the droplet size that includes a viscosity-dependent breakup time for the dispersed phase. This improved model successfully predicts the effects of the viscosity ratio observed in simulations. Results from this study are useful for the design of lab-on-chip technologies and manufacture of microfluidic emulsions, where there is a need to know how system parameters influence the droplet size.

  11. A lattice Boltzmann simulation of coalescence-induced droplet jumping on superhydrophobic surfaces with randomly distributed structures

    Science.gov (United States)

    Zhang, Li-Zhi; Yuan, Wu-Zhi

    2018-04-01

    The motion of coalescence-induced condensate droplets on superhydrophobic surface (SHS) has attracted increasing attention in energy-related applications. Previous researches were focused on regularly rough surfaces. Here a new approach, a mesoscale lattice Boltzmann method (LBM), is proposed and used to model the dynamic behavior of coalescence-induced droplet jumping on SHS with randomly distributed rough structures. A Fast Fourier Transformation (FFT) method is used to generate non-Gaussian randomly distributed rough surfaces with the skewness (Sk), kurtosis (K) and root mean square (Rq) obtained from real surfaces. Three typical spreading states of coalesced droplets are observed through LBM modeling on various rough surfaces, which are found to significantly influence the jumping ability of coalesced droplet. The coalesced droplets spreading in Cassie state or in composite state will jump off the rough surfaces, while the ones spreading in Wenzel state would eventually remain on the rough surfaces. It is demonstrated that the rough surfaces with smaller Sks, larger Rqs and a K at 3.0 are beneficial to coalescence-induced droplet jumping. The new approach gives more detailed insights into the design of SHS.

  12. An experimental study on suspended sodium droplet combustion (3)

    International Nuclear Information System (INIS)

    Sato, Kenji

    2005-03-01

    As part of studies for phenomenological investigation of sodium droplet burning behavior, in our previous experimental studies for suspended single sodium droplet, behavior of ignition process and succeeding combustion, ignition delay time, and droplet temperature history had been investigated. In this study, combustion experiments of suspended sodium droplet were performed in upward dry air flow by expanding the range of free-stream velocity U of air flow into 400 cm/s with initial droplet temperature Ti=300, 350, and 400degC and initial droplet diameter 4 mm at first. Then, the combustion experiments were also performed by changing the initial droplet diameter from 2.3 to 4.4 mm with Ti=350 and 400degC and U=100 cm/s. From the experimental results, the effects of free-stream velocity, initial droplet temperature, and initial droplet diameter on the ignition/burning behavior and ignition delay time were examined. The obtained results are as follows: (1) Ignition phenomena of suspended droplet were observed for all examined experimental conditions up to 400 cm/s. The orange emission observed at the moment of ignition occurs simultaneously over whole droplet surface except the top region of it. (2) The feature of the dependence of ignition delay time on the free-stream velocity is independent of the initial droplet temperature. With the increase of the free-stream velocity, up to 300 cm/s the ignition delay time decreases with decreasing dependency, and then the dependency increases more. (3) The ignition delay time increases with the increase of initial droplet diameter. The dependency increases as the initial droplet diameter increases. The ignition delay time extrapolated toward zero diameters from the obtained results becomes to be essentially zero. (author)

  13. Optoelectronic properties of XIn2S4 (X = Cd, Mg) thiospinels through highly accurate all-electron FP-LAPW method coupled with modified approximations

    International Nuclear Information System (INIS)

    Yousaf, Masood; Dalhatu, S.A.; Murtaza, G.; Khenata, R.; Sajjad, M.; Musa, A.; Rahnamaye Aliabad, H.A.; Saeed, M.A.

    2015-01-01

    Highlights: • Highly accurate all-electron FP-LAPW+lo method is used. • New physical parameters are reported, important for the fabrication of optoelectronic devices. • A comparative study that involves FP-LAPW+lo method and modified approximations. • Computed band gap values have good agreement with the experimental values. • Optoelectronic results of fundamental importance can be utilized for the fabrication of devices. - Abstract: We report the structural, electronic and optical properties of the thiospinels XIn 2 S 4 (X = Cd, Mg), using highly accurate all-electron full potential linearized augmented plane wave plus local orbital method. In order to calculate the exchange and correlation energies, the method is coupled with modified techniques such as GGA+U and mBJ-GGA, which yield improved results as compared to the previous studies. GGA+SOC approximation is also used for the first time on these compounds to examine the spin orbit coupling effect on the band structure. From the analysis of the structural parameters, robust character is predicted for both materials. Energy band structures profiles are fairly the same for GGA, GGA+SOC, GGA+U and mBJ-GGA, confirming the indirect and direct band gap nature of CdIn 2 S 4 and MgIn 2 S 4 materials, respectively. We report the trend of band gap results as: (mBJ-GGA) > (GGA+U) > (GGA) > (GGA+SOC). Localized regions appearing in the valence bands for CdIn 2 S 4 tend to split up nearly by ≈1 eV in the case of GGA+SOC. Many new physical parameters are reported that can be important for the fabrication of optoelectronic devices. Optical spectra namely, dielectric function (DF), refractive index n(ω), extinction coefficient k(ω), reflectivity R(ω), optical conductivity σ(ω), absorption coefficient α(ω) and electron loss function are discussed. Optical’s absorption edge is noted to be 1.401 and 1.782 for CdIn 2 S 4 and MgIn 2 S 4 , respectively. The prominent peaks in the electron energy spectrum

  14. Experimental investigation on the droplet entrainment from interfacial waves in air-water horizontal stratified flow

    International Nuclear Information System (INIS)

    Bae, Byeong Geon; Yun, Byong Jo; Kim, Kyoung Du

    2014-01-01

    It was mainly due to the fact that droplet entrainment affects the Peak Cladding Temperature (PCT) of the nuclear fuel rod in the Postulated accident conditions of NPP. Recently, droplet entrainment in the horizontally arranged primary piping system for the NPP is of interest because it affects directly the steam binding phenomena in the steam generators. Pan and Hanratty correlation is the only applicable one for the droplet entrainment rate model for horizontal flow. Moreover, there are no efforts for the model development on the basis of the droplet entrainment principal and physics phenomena. More recently, Korea Atomic Energy Research Institute (KAERI) proposed a new mechanistic droplet generation model applicable in the horizontal pipe for the SPACE code. However, constitutive relations in this new model require three model coefficients which have not yet been decided. The purpose of present work is determining three model coefficients by visualization experiment. For these model coefficients, the major physical parameters regarding the interfacial disturbance wave should be measured in this experiments. There are the wave slope, liquid fraction, wave hypotenuse length, wave velocity, wave frequency, and wavelength in the major physical parameters. The experiment was conducted at an air water horizontal rectangular channel with the PIV system. In this study, the experimental conditions were stratified-way flow during the droplet generation. Three coefficients were determined based on several data related to the interfacial wave. Additionally, we manufactured the parallel wire conductance probe to measure the fluctuating water level over time, and compared the wave height measured by the parallel wire conductance probe and image processing from images taken by high speed camera. Experimental investigation was performed for droplet entrainment from phase interface wave in an air-water stratified flow. In the experiments, we measured major physical parameters

  15. Laser-induced fluorescence imaging of acetone inside evaporating and burning fuel droplets

    Science.gov (United States)

    Shringi, D. S.; Shaw, B. D.; Dwyer, H. A.

    2009-01-01

    Laser-induced fluorescence was used to visualize acetone fields inside individual droplets of pure acetone as well as droplets composed of methanol or 1-propanol initially mixed with acetone. Droplets were supported on a horizontal wire and two vaporization conditions were investigated: (1) slow evaporation in room air and (2) droplet combustion, which leads to substantially faster droplet surface regression rates. Acetone was preferentially gasified, causing its concentration in droplets to drop in time with resultant decreases in acetone fluorescence intensities. Slowly vaporizing droplets did not exhibit large spatial variations of fluorescence within droplets, indicating that these droplets were relatively well mixed. Ignition of droplets led to significant variations in fluorescence intensities within droplets, indicating that these droplets were not well mixed. Ignited droplets composed of mixtures of 1-propanol and acetone showed large time-varying changes in shapes for higher acetone concentrations, suggesting that bubble formation was occurring in these droplets.

  16. Mechanism of supercooled droplet freezing on surfaces.

    Science.gov (United States)

    Jung, Stefan; Tiwari, Manish K; Doan, N Vuong; Poulikakos, Dimos

    2012-01-10

    Understanding ice formation from supercooled water on surfaces is a problem of fundamental importance and general utility. Superhydrophobic surfaces promise to have remarkable 'icephobicity' and low ice adhesion. Here we show that their icephobicity can be rendered ineffective by simple changes in environmental conditions. Through experiments, nucleation theory and heat transfer physics, we establish that humidity and/or the flow of a surrounding gas can fundamentally switch the ice crystallization mechanism, drastically affecting surface icephobicity. Evaporative cooling of the supercooled liquid can engender ice crystallization by homogeneous nucleation at the droplet-free surface as opposed to the expected heterogeneous nucleation at the substrate. The related interplay between droplet roll-off and rapid crystallization is also studied. Overall, we bring a novel perspective to icing and icephobicity, unveiling the strong influence of environmental conditions in addition to the accepted effects of the surface conditions and hydrophobicity.

  17. Magnetic droplet soliton nucleation in oblique fields

    Science.gov (United States)

    Mohseni, Morteza; Hamdi, M.; Yazdi, H. F.; Banuazizi, S. A. H.; Chung, S.; Sani, S. R.; Åkerman, Johan; Mohseni, Majid

    2018-05-01

    We study the auto-oscillating magnetodynamics in orthogonal spin-torque nano-oscillators (STNOs) as a function of the out-of-plane (OOP) magnetic-field angle. In perpendicular fields and at OOP field angles down to approximately 50°, we observe the nucleation of a droplet. However, for field angles below 50°, experiments indicate that the droplet gives way to propagating spin waves, in agreement with our micromagnetic simulations. Theoretical calculations show that the physical mechanism behind these observations is the sign changing of spin-wave nonlinearity (SWN) by angle. In addition, we show that the presence of a strong perpendicular magnetic anisotropy free layer in the system reverses the angular dependence of the SWN and dynamics in STNOs with respect to the known behavior determined for the in-plane magnetic anisotropy free layer. Our results are of fundamental interest in understanding the rich dynamics of nanoscale solitons and spin-wave dynamics in STNOs.

  18. Ballistic model to estimate microsprinkler droplet distribution

    Directory of Open Access Journals (Sweden)

    Conceição Marco Antônio Fonseca

    2003-01-01

    Full Text Available Experimental determination of microsprinkler droplets is difficult and time-consuming. This determination, however, could be achieved using ballistic models. The present study aimed to compare simulated and measured values of microsprinkler droplet diameters. Experimental measurements were made using the flour method, and simulations using a ballistic model adopted by the SIRIAS computational software. Drop diameters quantified in the experiment varied between 0.30 mm and 1.30 mm, while the simulated between 0.28 mm and 1.06 mm. The greatest differences between simulated and measured values were registered at the highest radial distance from the emitter. The model presented a performance classified as excellent for simulating microsprinkler drop distribution.

  19. Swimming droplets driven by a surface wave

    Science.gov (United States)

    Ebata, Hiroyuki; Sano, Masaki

    2015-02-01

    Self-propelling motion is ubiquitous for soft active objects such as crawling cells, active filaments, and liquid droplets moving on surfaces. Deformation and energy dissipation are required for self-propulsion of both living and non-living matter. From the perspective of physics, searching for universal laws of self-propelled motions in a dissipative environment is worthwhile, regardless of the objects' details. In this article, we propose a simple experimental system that demonstrates spontaneous migration of a droplet under uniform mechanical agitation. As we vary control parameters, spontaneous symmetry breaking occurs sequentially, and cascades of bifurcations of the motion arise. Equations describing deformable particles and hydrodynamic simulations successfully describe all of the observed motions. This system should enable us to improve our understanding of spontaneous motions of self-propelled objects.

  20. Lipid Structure in Triolein Lipid Droplets

    DEFF Research Database (Denmark)

    Chaban, Vitaly V; Khandelia, Himanshu

    2014-01-01

    of a mass of hydrophobic lipid esters coved by phospholipid monolayer. The small size and unique architecture of LDs makes it complicated to study LD structure by modern experimental methods. We discuss coarse-grained molecular dynamics (MD) simulations of LD formation in systems containing 1-palmitoyl-2...... to coarse-grained simulations, the presence of PE lipids at the interface has a little impact on distribution of components and on the overall LD structure. (4) The thickness of the lipid monolayer at the surface of the droplet is similar to the thickness of one leaflet of a bilayer. Computer simulations......Lipid droplets (LDs) are primary repositories of esterified fatty acids and sterols in animal cells. These organelles originate on the lumenal or cytoplasmic side of endoplasmic reticulum (ER) membrane and are released to the cytosol. In contrast to other intracellular organelles, LDs are composed...

  1. Direct printing of miniscule aluminum alloy droplets and 3D structures by StarJet technology

    Science.gov (United States)

    Gerdes, B.; Zengerle, R.; Koltay, P.; Riegger, L.

    2018-07-01

    Drop-on demand printing of molten metal droplets could be used for prototyping 3D objects as a promising alternative to laser melting technologies. However, to date, only few printheads have been investigated for this purpose, and they used only a limited range of materials. The pneumatically actuated StarJet technology enables the direct and non-contact printing of molten metal microdroplets from metal melts at high temperatures. StarJet printheads utilize nozzle chips featuring a star-shaped orifice geometry that leads to formation of droplets inside the nozzle with high precision. In this paper, we present a novel StarJet printhead for printing aluminum (Al) alloys featuring a hybrid design with a ceramic reservoir for the molten metal and an outer shell fabricated from stainless steel. The micro machined nozzle chip is made from silicon carbide (SiC). This printhead can be operated at up to 950 °C, and is capable of printing high melting point metals like Al alloys in standard laboratory conditions. In this work, an aluminum–silicon alloy that features 12% silicon (AlSi12) is printed. The printhead, nozzle, and peripheral actuation system are optimized for stable generation of AlSi12 droplets with high monodispersity, low angular deviation, and miniaturized droplet diameters. As a result, a stable drop-on-demand printing of droplets exhibiting diameters of d droplet  =  702 µm  ±  1% is demonstrated at 5 Hz with a low angular deviation of 0.3°, when a nozzle chip with 500 µm orifice diameter is used. Furthermore, AlSi12 droplets featuring d droplet  =  176 µm  ±  7% are printed when using a nozzle chip with an orifice diameter of 130 µm. Moreover, we present directly printed objects from molten Al alloy droplets, such as high aspect ratio, free-standing walls (aspect ratio 12:1), and directly printed, flexible springs, to demonstrate the principle of 3D printing with molten metal droplets.

  2. Structures, stability, magnetic moments and growth strategies of the Fe_nN (n = 1–7) clusters: All-electron density functional theory calculations

    International Nuclear Information System (INIS)

    Li, Zhi; Zhao, Zhen

    2017-01-01

    The geometries, electronic properties, magnetic moments and growth strategies of the Fe_nN (n = 1–7) clusters are investigated using all-electron density functional theory. The results show that N doping significantly distorts the Fe_n clusters. Fe_4N and Fe_6N clusters are more stable structures than other considered Fe_nN clusters. Local peaks of HOMO-LUMO gap curve are found at n = 3, 7, implying that the chemical stability of the Fe_3N and Fe_7N clusters is higher. Fe_2N, Fe_4N and Fe_6N clusters have larger magnetic moments compared to other considered Fe_nN (n = 1–7) clusters. It can be seen that the Fe_5 clusters are easier to adsorb a Fe atom while the Fe_4 clusters are easier to adsorb a N atom. The considered Fe_mN clusters prefer to adsorb a Fe atom and larger Fe_mN clusters are easier to grow. - Highlights: • The structural stability of the Fe_4N and Fe_6N clusters is higher. • The chemical stability of the Fe_3N and Fe_7N clusters is higher. • Fe_5 clusters are easier to adsorb a Fe atom while Fe_4 clusters are easier to adsorb a N atom. • Fe_nN clusters prefer to adsorb a Fe atom.

  3. Characteristics of droplet motion in effervescent sprays

    Directory of Open Access Journals (Sweden)

    Jedelský Jan

    2014-03-01

    Full Text Available Time resolved droplet size and velocity measurement was made using Phase-Doppler anemometry in an effervescent spray at GLR of 6 % and operation pressure drops 21 – 52 kPa. The spray shows a size dependent variation of mean as well as fluctuating axial and radial velocities of droplets similarly for all operation regimes. Particles under 13 μm follow the gas flow, axially decelerated due to gas expansion. Velocity of medium sized particles is positively size correlated and larger particles keep high velocity, given them during discharge. Fluctuating radial velocity of small particles is larger than that of large particles while fluctuating axial velocity increases with size. Small particles thus reach a ratio of radial to axial velocity fluctuations ~ 0.6 but large particles only ~ 0.1, which indicates large transverse dispersion of small particles. Overall fluctuating velocity ratios smaller than 0.5 document an anisotropic character of the liquid mass fluctuations. Power spectral density (PSD of axial velocity fluctuations of large droplets is uniform up to 1 kHz, while PSD of smaller particles drops down with frequency for frequencies > 100 Hz. Large particles thus preserve the fluctuations imposed during discharge while the gas turbulence drops with frequency. Turbulence intensity reaches 14 to 21 % depending on pressure. Such high-turbulence character of the flow probably results from a heterogeneous gas–liquid mixture at the discharge.

  4. Characteristics of droplet motion in effervescent sprays

    Science.gov (United States)

    Jedelský, Jan; Zaremba, Matouš; Malý, Milan; Jícha, Miroslav

    2014-03-01

    Time resolved droplet size and velocity measurement was made using Phase-Doppler anemometry in an effervescent spray at GLR of 6 % and operation pressure drops 21 - 52 kPa. The spray shows a size dependent variation of mean as well as fluctuating axial and radial velocities of droplets similarly for all operation regimes. Particles under 13 μm follow the gas flow, axially decelerated due to gas expansion. Velocity of medium sized particles is positively size correlated and larger particles keep high velocity, given them during discharge. Fluctuating radial velocity of small particles is larger than that of large particles while fluctuating axial velocity increases with size. Small particles thus reach a ratio of radial to axial velocity fluctuations ~ 0.6 but large particles only ~ 0.1, which indicates large transverse dispersion of small particles. Overall fluctuating velocity ratios smaller than 0.5 document an anisotropic character of the liquid mass fluctuations. Power spectral density (PSD) of axial velocity fluctuations of large droplets is uniform up to 1 kHz, while PSD of smaller particles drops down with frequency for frequencies > 100 Hz. Large particles thus preserve the fluctuations imposed during discharge while the gas turbulence drops with frequency. Turbulence intensity reaches 14 to 21 % depending on pressure. Such high-turbulence character of the flow probably results from a heterogeneous gas-liquid mixture at the discharge.

  5. Water droplet evaporation from sticky superhydrophobic surfaces

    Science.gov (United States)

    Lee, Moonchan; Kim, Wuseok; Lee, Sanghee; Baek, Seunghyeon; Yong, Kijung; Jeon, Sangmin

    2017-07-01

    The evaporation dynamics of water from sticky superhydrophobic surfaces was investigated using a quartz crystal microresonator and an optical microscope. Anodic aluminum oxide (AAO) layers with different pore sizes were directly fabricated onto quartz crystal substrates and hydrophobized via chemical modification. The resulting AAO layers exhibited hydrophobic or superhydrophobic characteristics with strong adhesion to water due to the presence of sealed air pockets inside the nanopores. After placing a water droplet on the AAO membranes, variations in the resonance frequency and Q-factor were measured throughout the evaporation process, which were related to changes in mass and viscous damping, respectively. It was found that droplet evaporation from a sticky superhydrophobic surface followed a constant contact radius (CCR) mode in the early stage of evaporation and a combination of CCR and constant contact angle modes without a Cassie-Wenzel transition in the final stage. Furthermore, AAO membranes with larger pore sizes exhibited longer evaporation times, which were attributed to evaporative cooling at the droplet interface.

  6. Droplet ejection and sliding on a flapping film

    Directory of Open Access Journals (Sweden)

    Xi Chen

    2017-03-01

    Full Text Available Water recovery and subsequent reuse are required for human consumption as well as industrial, and agriculture applications. Moist air streams, such as cooling tower plumes and fog, represent opportunities for water harvesting. In this work, we investigate a flapping mechanism to increase droplet shedding on thin, hydrophobic films for two vibrational cases (e.g., ± 9 mm and 11 Hz; ± 2 mm and 100 Hz. Two main mechanisms removed water droplets from the flapping film: vibrational-induced coalescence/sliding and droplet ejection from the surface. Vibrations mobilized droplets on the flapping film, increasing the probability of coalescence with neighboring droplets leading to faster droplet growth. Droplet departure sizes of 1–2 mm were observed for flapping films, compared to 3–4 mm on stationary films, which solely relied on gravity for droplet removal. Additionally, flapping films exhibited lower percentage area coverage by water after a few seconds. The second removal mechanism, droplet ejection was analyzed with respect to surface wave formation and inertia. Smaller droplets (e.g., 1-mm diameter were ejected at a higher frequency which is associated with a higher acceleration. Kinetic energy of the water was the largest contributor to energy required to flap the film, and low energy inputs (i.e., 3.3 W/m2 were possible. Additionally, self-flapping films could enable novel water collection and condensation with minimal energy input.

  7. Electrostatic field and charge distribution in small charged dielectric droplets

    Science.gov (United States)

    Storozhev, V. B.

    2004-08-01

    The charge distribution in small dielectric droplets is calculated on the basis of continuum medium approximation. There are considered charged liquid spherical droplets of methanol in the range of nanometer sizes. The problem is solved by the following way. We find the free energy of some ion in dielectric droplet, which is a function of distribution of other ions in the droplet. The probability of location of the ion in some element of volume in the droplet is a function of its free energy in this element of volume. The same approach can be applied to other ions in the droplet. The obtained charge distribution differs considerably from the surface distribution. The curve of the charge distribution in the droplet as a function of radius has maximum near the surface. Relative concentration of charges in the vicinity of the center of the droplet does not equal to zero, and it is the higher, the less is the total charge of the droplet. According to the estimates the model is applicable if the droplet radius is larger than 10 nm.

  8. Electrostatic field and charge distribution in small charged dielectric droplets

    International Nuclear Information System (INIS)

    Storozhev, V.B.

    2004-01-01

    The charge distribution in small dielectric droplets is calculated on the basis of continuum medium approximation. There are considered charged liquid spherical droplets of methanol in the range of nanometer sizes. The problem is solved by the following way. We find the free energy of some ion in dielectric droplet, which is a function of distribution of other ions in the droplet. The probability of location of the ion in some element of volume in the droplet is a function of its free energy in this element of volume. The same approach can be applied to other ions in the droplet. The obtained charge distribution differs considerably from the surface distribution. The curve of the charge distribution in the droplet as a function of radius has maximum near the surface. Relative concentration of charges in the vicinity of the center of the droplet does not equal to zero, and it is the higher, the less is the total charge of the droplet. According to the estimates the model is applicable if the droplet radius is larger than 10 nm

  9. 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.

  10. In vitro characterization of perfluorocarbon droplets for focused ultrasound therapy

    International Nuclear Information System (INIS)

    Schad, Kelly C; Hynynen, Kullervo

    2010-01-01

    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 x 10 6 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.

  11. 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.

  12. A study on the contact angles of a water droplet on smooth and rough solid surfaces

    International Nuclear Information System (INIS)

    Park, Ju Young; Ha, Man Yeong; Choi, Ho Jin; Hong, Seung Do; Yoon, Hyun Sik

    2011-01-01

    We investigated the wetting characteristics such as contact angle, wetting radius and topography of water droplets on smooth and random solid surfaces. Molecular dynamic simulation is employed to analyze the wetting behavior of water droplets on smooth and rough surfaces by considering different potential energy models of bond, angle, Lennard-Jones and Coulomb to calculate the interacting forces between water molecules. The Lennard-Jones potential energy model is adopted as an interaction model between water molecules and solid surface atoms. The randomly rough surface is generated by changing the standard deviation of roughness height from 1 A to 3 A with the fixed autocorrelation length. The size of water droplet considered is in the range from 2,000 to 5,000 molecules. The contact angles increase generally with increasing number of water molecules. For a hydrophobic surface whose characteristic energy is 0.1 kcal/mol, the contact angles depend rarely on the standard deviation of the roughness height. However, when the surface energy is 0.5 and 1.0 kcal/mol, the contact angles depend on both the roughness height of surfaces and droplet size

  13. [Synthesis of hollow titania microspheres by using microfluidic droplet-template].

    Science.gov (United States)

    Ma, Jingyun; Jiang, Lei; Qin, Jianhu

    2011-09-01

    Droplet-based microfluidics is of great interest due to its particular characteristics compared with the conventional methods, such as reduced reagent consumption, rapid mixing, high-throughput, shape controlled, etc. A novel method using microfluidic droplet as soft template for the synthesis of hollow titania microspheres was developed. A typical polydimethylsiloxane (PDMS) microfluidic device containing "flow-focusing" geometry was used to generate water/oil (W/O) droplet. The mechanism for the hollow structure formation was based on the interfacial hydrolysis reaction between the continuous phase containing titanium butoxide precursor and the dispersed containing water. The continuous phase mixed with butanol was added in the downstream of the channel after the hydrolysis reaction. This step was used for drawing the water out of the microgels for further hydrolysis. The microgels obtained through a glass pipe integrated were washed, dried under vacuum and calcined after aging for a certain time. The fluorescence and scanning electron microscope (SEM) image of the microspheres indicated the hollow structure and the thickness of the shell. In addition, these microspheres with thin shell (about 2 microm) were apt to rupture and collapse. Droplet-based microfluidic offered a gentle and size-controllable manner to moderate this problem. Moreover, it has potential applications in photocatalysis combined with some modification realized on the chip simultaneously.

  14. Acoustic separation of oil droplets, colloidal particles and their mixtures in a microfluidic cell

    KAUST Repository

    Vakarelski, Ivan Uriev; Li, Erqiang; Abdel-Fattah, Amr I.; Thoroddsen, Sigurdur T

    2016-01-01

    Here we report direct macroscopic and microscopic observations of acoustic driven separation of dodecane oil droplets in water in the presence and absence of colloidal silica particles suspended in the water phase. The experiments were conducted in a simple rectangular channel glass microfluidic cell in which an ultrasound standing wave pattern was generated at 300 KHz frequency. The separation process of both oil droplets and colloidal particles inside the cell was recorded using a high-speed video camera equipped with a macro-objective lens for macroscopic observation or with a high-speed camera attached to an inverted optical microscope for a higher resolution microscopic observation. We characterize the clustering process in the case of emulsion droplets or solid colloidal particles and ultimately demonstrate the emulsion droplets separation from the solid particles in the mixtures based on their different acoustic contrast factors. Finally, we conduct proof of concept experiment to show that the same approach can be used in a continuous fluid flow process.

  15. Detection of avian influenza antigens in proximity fiber, droplet, and optical waveguide microfluidics

    Science.gov (United States)

    Yoon, Jeong-Yeol; Heinze, Brian C.; Gamboa, Jessica; You, David J.

    2009-05-01

    Virus antigens of avian influenza subtype H3N2 were detected on two different microfluidic platforms: microchannel and droplet. Latex immunoagglutination assays were performed using 920-nm highly carboxylated polystyrene beads that are conjugated with antibody to avian influenza virus. The bead suspension was merged with the solutions of avian influenza virus antigens in a Y-junction of a microchannel made by polydimethylsiloxane soft lithography. The resulting latex immunoagglutinations were measured with two optical fibers in proximity setup to detect 45° forward light scattering. Alternatively, 10 μL droplets of a bead suspension and an antigen solution were merged on a superhydrophobic surface (water contact angle = 155°), whose movement was guided by a metal wire, and 180° back light scattering is measured with a backscattering optical probe. Detection limits were 0.1 pg mL-1 for both microchannel with proximity fibers and droplet microfluidics, thanks to the use of micro-positioning stages to help generate reproducible optical signals. Additionally, optical waveguide was tested by constructing optical waveguide channels (filled with mineral oil) within a microfluidic device to detect the same light scattering. Detection limit was 0.1 ng mL-1 for an optical waveguide device, with a strong potential of improvement in the near future. The use of optical waveguide enabled smaller device setup, easier operation, smaller standard deviations and broader linear range of assay than proximity fiber microchannel and droplet microfluidics. Total assay time was less than 10 min.

  16. Acoustic separation of oil droplets, colloidal particles and their mixtures in a microfluidic cell

    KAUST Repository

    Vakarelski, Ivan Uriev

    2016-06-15

    Here we report direct macroscopic and microscopic observations of acoustic driven separation of dodecane oil droplets in water in the presence and absence of colloidal silica particles suspended in the water phase. The experiments were conducted in a simple rectangular channel glass microfluidic cell in which an ultrasound standing wave pattern was generated at 300 KHz frequency. The separation process of both oil droplets and colloidal particles inside the cell was recorded using a high-speed video camera equipped with a macro-objective lens for macroscopic observation or with a high-speed camera attached to an inverted optical microscope for a higher resolution microscopic observation. We characterize the clustering process in the case of emulsion droplets or solid colloidal particles and ultimately demonstrate the emulsion droplets separation from the solid particles in the mixtures based on their different acoustic contrast factors. Finally, we conduct proof of concept experiment to show that the same approach can be used in a continuous fluid flow process.

  17. Dynamics of Water Absorption and Evaporation During Methanol Droplet Combustion in Microgravity

    Science.gov (United States)

    Hicks, Michael C.; Dietrich, Daniel L.; Nayagam, Vedha; Williams, Forman A.

    2012-01-01

    The combustion of methanol droplets is profoundly influenced by the absorption and evaporation of water, generated in the gas phase as a part of the combustion products. Initially there is a water-absorption period of combustion during which the latent heat of condensation of water vapor, released into the droplet, enhances its burning rate, whereas later there is a water-evaporation period, during which the water vapor reduces the flame temperature suffciently to extinguish the flame. Recent methanol droplet-combustion experiments in ambient environments diluted with carbon dioxide, conducted in the Combustion Integrated Rack on the International Space Station (ISS), as a part of the FLEX project, provided a method to delineate the water-absorption period from the water-evaporation period using video images of flame intensity. These were obtained using an ultra-violet camera that captures the OH* radical emission at 310 nm wavelength and a color camera that captures visible flame emission. These results are compared with results of ground-based tests in the Zero Gravity Facility at the NASA Glenn Research Center which employed smaller droplets in argon-diluted environments. A simplified theoretical model developed earlier correlates the transition time at which water absorption ends and evaporation starts. The model results are shown to agree reasonably well with experiment.

  18. Numerical investigation of the droplet condensation on the horizontal surface with patterned wettability

    Science.gov (United States)

    Cho, Jaeyong; Lee, Joonsang

    2017-11-01

    The condensation is the one of the efficient heat transfer phenomenon that transfers the heat along an interface between two phases. This condensation is affected by the wettability of surface. Heat transfer rate can be improved by controlling the wettability of surface. Recently, the researches with patterned wettability, which is composed by a combination of hydrophilic and hydrophobic surface, have been performed to improve the heat transfer rate of condensation. In this study, we performed numerical simulation for condensation of droplet on the patterned wettability, and we analyze condensation phenomenon on the wettability pattered surface through the kinetic energy, heat flux curve, and droplet shape in the vicinity of the droplet. When we performed numerical simulations and analyzing the condensation with patterned wettability, we used the lattice Boltzmann method for the base model, and phase change was solved by Peng-Robinson equation of sate. We can find that the droplet is generated at the bottom surface and high condensation rate can be maintained on the patterned wettability. This work was also supported by the National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MSIP) (No. 2015R1A5A1037668) and BrainKorea21plus.

  19. Syrlic: a Lagrangian code to handle industrial problems involving particles and droplets

    International Nuclear Information System (INIS)

    Peniguel, C.

    1997-01-01

    Numerous industrial applications require to solve droplets or solid particles trajectories and their effects on the flow. (fuel injection in combustion engine, agricultural spraying, spray drying, spray cooling, spray painting, particles separator, dispersion of pollutant, etc). SYRLIC is being developed to handle the dispersed phase while the continuous phase is tackled by classical Eulerian codes like N3S-EF, N3S-NATUR, ESTET. The trajectory of each droplet is calculated on unstructured grids or structured grids according the Eulerian code with SYRLIC is coupled. The forces applied to each particle are recalculated along each path. The Lagrangian approach treats the convection and the source terms exactly. It is particularly adapted to problems involving a wide range of particles characteristics (diameter, mass, etc). In the near future, wall interaction, heat transfer, evaporation more complex physics, etc, will be included. Turbulent effects will be accounted for by a Langevin equation. The illustration shows the trajectories followed by water droplets (diameter from 1 mm to 4 mm) in a cooling tower. the droplets are falling down due to gravity but are deflected towards the center of the tower because of a lateral wind. It is clear that particles are affected differently according their diameter. The Eulerian flow field used to compute the forces has been generated by N3S-AERO, on an unstructured mesh

  20. Structures, stability, magnetic moments and growth strategies of the Fe{sub n}N (n = 1–7) clusters: All-electron density functional theory calculations

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhi, E-mail: lizhi81723700@163.com [School of Materials and Metallurgy, University of Science and Technology Liaoning, Anshan, 114051 (China); Zhao, Zhen [School of Chemistry and Life Science, Anshan Normal University, Anshan, 114007 (China)

    2017-02-01

    The geometries, electronic properties, magnetic moments and growth strategies of the Fe{sub n}N (n = 1–7) clusters are investigated using all-electron density functional theory. The results show that N doping significantly distorts the Fe{sub n} clusters. Fe{sub 4}N and Fe{sub 6}N clusters are more stable structures than other considered Fe{sub n}N clusters. Local peaks of HOMO-LUMO gap curve are found at n = 3, 7, implying that the chemical stability of the Fe{sub 3}N and Fe{sub 7}N clusters is higher. Fe{sub 2}N, Fe{sub 4}N and Fe{sub 6}N clusters have larger magnetic moments compared to other considered Fe{sub n}N (n = 1–7) clusters. It can be seen that the Fe{sub 5} clusters are easier to adsorb a Fe atom while the Fe{sub 4} clusters are easier to adsorb a N atom. The considered Fe{sub m}N clusters prefer to adsorb a Fe atom and larger Fe{sub m}N clusters are easier to grow. - Highlights: • The structural stability of the Fe{sub 4}N and Fe{sub 6}N clusters is higher. • The chemical stability of the Fe{sub 3}N and Fe{sub 7}N clusters is higher. • Fe{sub 5} clusters are easier to adsorb a Fe atom while Fe{sub 4} clusters are easier to adsorb a N atom. • Fe{sub n}N clusters prefer to adsorb a Fe atom.

  1. Droplet networks with incorporated protein diodes show collective properties

    Science.gov (United States)

    Maglia, Giovanni; Heron, Andrew J.; Hwang, William L.; Holden, Matthew A.; Mikhailova, Ellina; Li, Qiuhong; Cheley, Stephen; Bayley, Hagan

    2009-07-01

    Recently, we demonstrated that submicrolitre aqueous droplets submerged in an apolar liquid containing lipid can be tightly connected by means of lipid bilayers to form networks. Droplet interface bilayers have been used for rapid screening of membrane proteins and to form asymmetric bilayers with which to examine the fundamental properties of channels and pores. Networks, meanwhile, have been used to form microscale batteries and to detect light. Here, we develop an engineered protein pore with diode-like properties that can be incorporated into droplet interface bilayers in droplet networks to form devices with electrical properties including those of a current limiter, a half-wave rectifier and a full-wave rectifier. The droplet approach, which uses unsophisticated components (oil, lipid, salt water and a simple pore), can therefore be used to create multidroplet networks with collective properties that cannot be produced by droplet pairs.

  2. Phase rainbow refractometry for accurate droplet variation characterization.

    Science.gov (United States)

    Wu, Yingchun; Promvongsa, Jantarat; Saengkaew, Sawitree; Wu, Xuecheng; Chen, Jia; Gréhan, Gérard

    2016-10-15

    We developed a one-dimensional phase rainbow refractometer for the accurate trans-dimensional measurements of droplet size on the micrometer scale as well as the tiny droplet diameter variations at the nanoscale. The dependence of the phase shift of the rainbow ripple structures on the droplet variations is revealed. The phase-shifting rainbow image is recorded by a telecentric one-dimensional rainbow imaging system. Experiments on the evaporating monodispersed droplet stream show that the phase rainbow refractometer can measure the tiny droplet diameter changes down to tens of nanometers. This one-dimensional phase rainbow refractometer is capable of measuring the droplet refractive index and diameter, as well as variations.

  3. Printing microstructures in a polymer matrix using a ferrofluid droplet

    International Nuclear Information System (INIS)

    Abdel Fattah, Abdel Rahman; Ghosh, Suvojit; Puri, Ishwar K.

    2016-01-01

    We print complex curvilinear microstructures in an elastomer matrix using a ferrofluid droplet as the print head. A magnetic field moves the droplet along a prescribed path in liquid polydimethylsiloxane (PDMS). The droplet sheds magnetic nanoparticle (MNP) clusters in its wake, forming printed features. The PDMS is subsequently heated so that it crosslinks, which preserves the printed features in the elastomer matrix. The competition between magnetic and drag forces experienced by the ferrofluid droplet and its trailing MNPs highlight design criteria for successful printing, which are experimentally confirmed. The method promises new applications, such as flexible 3D circuitry. - Highlights: • Magnetically guided miscible ferrofluid droplets print 3D patterns in a polymer. • Printing mechanism depends on the dynamics between the fluid and magnetic forces. • Droplet size influences the width of the printed trail. • The Colloidal distribution of the ferrofluid is important for pattern integrity. • Particle trajectories and trails are simulated and validated through experiments.

  4. Stochastic growth of cloud droplets by collisions during settling

    Science.gov (United States)

    Madival, Deepak G.

    2018-04-01

    In the last stage of droplet growth in clouds which leads to drizzle formation, larger droplets begin to settle under gravity and collide and coalesce with smaller droplets in their path. In this article, we shall deal with the simplified problem of a large drop settling amidst a population of identical smaller droplets. We present an expression for the probability that a given large drop suffers a given number of collisions, for a general statistically homogeneous distribution of droplets. We hope that our approach will serve as a valuable tool in dealing with droplet distribution in real clouds, which has been found to deviate from the idealized Poisson distribution due to mechanisms such as inertial clustering.

  5. Printing microstructures in a polymer matrix using a ferrofluid droplet

    Energy Technology Data Exchange (ETDEWEB)

    Abdel Fattah, Abdel Rahman [Department of Mechanical Engineering, Hamilton, Ontario (Canada); Ghosh, Suvojit [Department of Engineering Physics, McMaster University, Hamilton, Ontario (Canada); Puri, Ishwar K. [Department of Mechanical Engineering, Hamilton, Ontario (Canada); Department of Engineering Physics, McMaster University, Hamilton, Ontario (Canada)

    2016-03-01

    We print complex curvilinear microstructures in an elastomer matrix using a ferrofluid droplet as the print head. A magnetic field moves the droplet along a prescribed path in liquid polydimethylsiloxane (PDMS). The droplet sheds magnetic nanoparticle (MNP) clusters in its wake, forming printed features. The PDMS is subsequently heated so that it crosslinks, which preserves the printed features in the elastomer matrix. The competition between magnetic and drag forces experienced by the ferrofluid droplet and its trailing MNPs highlight design criteria for successful printing, which are experimentally confirmed. The method promises new applications, such as flexible 3D circuitry. - Highlights: • Magnetically guided miscible ferrofluid droplets print 3D patterns in a polymer. • Printing mechanism depends on the dynamics between the fluid and magnetic forces. • Droplet size influences the width of the printed trail. • The Colloidal distribution of the ferrofluid is important for pattern integrity. • Particle trajectories and trails are simulated and validated through experiments.

  6. Trace of a water droplet exerted by coulomb force. 2

    International Nuclear Information System (INIS)

    Sugita, Hideaki; Murakami, Takuro; Nakazawa, Takeshi; Nakasako, Makoto; Yoshimura, Takuma; Osarakawa, Toshihiro

    2002-01-01

    The movement of water droplets in the air-water separator is based on the principle of the electrostatic precipitator with positive and negative poles. The mechanism of separation is that the water droplets charged negative ions or electrons by corona discharge are collected on the positive pole by Coulomb force operating between the both poles. This paper describes the theoretical analyses that how the movement of a water droplet is affected by Coulomb force in the air-water separator. (author)

  7. Droplet-Wall/Film Impact in IC Engine Applications

    Science.gov (United States)

    2017-08-14

    Report: Droplet-Wall/ Film Impact in IC Engine Applications (ARO Topic 1.4.1 under ARO’s Dr. Ralph A. Anthenien) The views, opinions and/or findings...Participants: RPPR Final Report as of 12-Oct-2017 Agreement Number: W911NF-16-1-0449 Organization: Princeton University Title: Droplet-Wall/ Film Impact...droplets impacting a wet surface under various film thickness, which plays a critical role in controlling the efficiency of applications such as those

  8. Radioactive droplet moisture transfer from nuclear power plant spray pool

    International Nuclear Information System (INIS)

    Elokhin, A.P.

    1995-01-01

    Problem on transfer of radioactive droplet moisture with an account of its evaporation from the nuclear power plant spray pool (NPP coolant) is considered. Formulae enabling evaluation of droplet and radioactive water admixture lifetime as a whole, as well as the maximum distance (by wind), over which it can extend, are obtained. Recommendations for decrease in the droplet dispersed composition and reduction in scale of radioactive contamination of underlying surface are given. 10 refs.; 3 figs.; 1 tab

  9. A Modeling of Compressible Droplets in a Fluid

    OpenAIRE

    Boudin, Laurent; Desvilletter, Laurent; Motte, Renaud

    2003-01-01

    In this work, we are interested in a complex fluid-kinetic model that aims to take into account the compressibility of the droplets of the spray. The ambient fluid is described by Euler-like equations, in which the transfer of momentum and energy form the droplets is taken into account, while the spray is represented by a probability density function satisfying a Vlasov-like equation. Implicit terms crop up because of the compressibility of the droplets. After having derived...

  10. Hot Surface Ignition of A Composite Fuel Droplet

    Directory of Open Access Journals (Sweden)

    Glushkov Dmitrii O.

    2015-01-01

    Full Text Available The present study examines the characteristics of conductive heating (up to ignition temperature of a composite fuel droplet based on coal, liquid petroleum products, and water. In this paper, we have established the difference between heat transfer from a heat source to a fuel droplet in case of conductive (hot surface and convective (hot gas heat supply. The Leidenfrost effect influences on heat transfer characteristics significantly due to the gas gap between a composite fuel droplet and a hot surface.

  11. Droplet Combustion and Non-Reactive Shear-Coaxial Jets with and without Transverse Acoustic Excitation

    Science.gov (United States)

    2012-01-01

    node, there is no droplet deflection, but there is limited evidence for this. Recent studies at UCLA and at NASA Glenn Research Center by Dattarajan et...generator supplied continuous sine wave signals, which were amplified via Trek PZD2000A high-voltage amplifiers, to each piezo-siren. The waveform...1.3. Verify the wire on Channel 1 of the Tenma oscilloscope (Model No. 72-6800) comes from the output voltage monitor on the Trek -1 amplifier and the

  12. Droplet Combustion and Non-Reactive Shear-Coaxial Jets with Transverse Acoustic Excitation

    Science.gov (United States)

    2012-06-01

    for this. Recent studies at UCLA and at NASA Glenn Research Center by Dattarajan et al. [20, 21] have focused on methanol droplet combustion...via Trek PZD2000A high-voltage amplifiers, to each piezo-siren. The waveform generators output signals were locked in frequency. However, their phase...1.3. Verify the wire on Channel 1 of the Tenma oscilloscope (Model No. 72-6800) comes from the output voltage monitor on the Trek -1 amplifier

  13. Lipid Droplet Formation Is Dispensable for Endoplasmic Reticulum-associated Degradation*

    OpenAIRE

    Olzmann, James A.; Kopito, Ron R.

    2011-01-01

    Proteins that fail to fold or assemble in the endoplasmic reticulum (ER) are destroyed by cytoplasmic proteasomes through a process known as ER-associated degradation. Substrates of this pathway are initially sequestered within the ER lumen and must therefore be dislocated across the ER membrane to be degraded. It has been proposed that generation of bicellar structures during lipid droplet formation may provide an “escape hatch” through which misfolded proteins, toxins, and viruses can exit ...

  14. Enhancing Protease Activity Assay in Droplet-Based Microfluidics Using a Biomolecule Concentrator

    Science.gov (United States)

    Chen, Chia-Hung; Sarkar, Aniruddh; Song, Yong-Ak; Miller, Miles A.; Kim, Sung Jae; Griffith, Linda G.; Lauffenburger, Douglas A.; Han, Jongyoon

    2011-01-01

    We introduce an integrated microfluidic device consisting of a biomolecule concentrator and a microdroplet generator, which enhances the limited sensitivity of low-abundance enzyme assays by concentrating biomolecules before encapsulating them into droplet microreactors. We used this platform to detect ultra low levels of matrix metalloproteinases (MMPs) from diluted cellular supernatant and showed that it significantly (∼10-fold) reduced the time required to complete the assay and the sample volume used. PMID:21671557

  15. On the interfacial thermodynamics of nanoscale droplets and bubbles

    Science.gov (United States)

    Corti, David S.; Kerr, Karl J.; Torabi, Korosh

    2011-07-01

    We present a new self-consistent thermodynamic formalism for the interfacial properties of nanoscale embryos whose interiors do not exhibit bulklike behavior and are in complete equilibrium with the surrounding mother phase. In contrast to the standard Gibbsian analysis, whereby a bulk reference pressure based on the same temperature and chemical potentials of the mother phase is introduced, our approach naturally incorporates the normal pressure at the center of the embryo as an appropriate reference pressure. While the interfacial properties of small embryos that follow from the use of these two reference pressures are different, both methods yield by construction the same reversible work of embryo formation as well as consistency between their respective thermodynamic and mechanical routes to the surface tension. Hence, there is no a priori reason to select one method over another. Nevertheless, we argue, and demonstrate via a density-functional theory (with the local density approximation) analysis of embryo formation in the pure component Lennard-Jones fluid, that our new method generates more physically appealing trends. For example, within the new approach the surface tension at all locations of the dividing surface vanishes at the spinodal where the density profile spanning the embryo and mother phase becomes completely uniform (only the surface tension at the Gibbs surface of tension vanishes in the Gibbsian method at this same limit). Also, for bubbles, the location of the surface of tension now diverges at the spinodal, similar to the divergent behavior exhibited by the equimolar dividing surface (in the Gibbsian method, the location of the surface of tension vanishes instead). For droplets, the new method allows for the appearance of negative surface tensions (the Gibbsian method always yields positive tensions) when the normal pressures within the interior of the embryo become less than the bulk pressure of the surrounding vapor phase. Such a

  16. Variable focus microscopy using a suspended water droplet

    International Nuclear Information System (INIS)

    Chowdhury, F A; Chau, K J

    2012-01-01

    We explore a low-technology methodology to dispense and shape water droplets for application as the magnifying element in a microscope using either reflection-mode or transmission-mode illumination. A water droplet is created at the end of a syringe and then coated with a thin layer of silicone oil to mitigate evaporation. By applying mechanical pressure to the water droplet using a metal tip, the shape of the droplet is tuned to yield focusing properties amenable for microscopy. Images captured using the microscope demonstrate micron-scale resolution, variable magnification and imaging quality comparable to that obtained by a conventional, laboratory-grade microscope. (paper)

  17. Prediction of water droplet evaporation on zircaloy surface

    International Nuclear Information System (INIS)

    Lee, Chi Young; In, Wang Kee

    2014-01-01

    In the present experimental study, the prediction of water droplet evaporation on a zircaloy surface was investigated using various initial droplet sizes. To the best of our knowledge, this may be the first valuable effort for understanding the details of water droplet evaporation on a zircaloy surface. The initial contact diameters of the water droplets tested ranged from 1.76 to 3.41 mm. The behavior (i.e., time-dependent droplet volume, contact angle, droplet height, and contact diameter) and mode-transition time of the water droplet evaporation were strongly influenced by the initial droplet size. Using the normalized contact angle (θ*) and contact diameter (d*), the transitions between evaporation modes were successfully expressed by a single curve, and their criteria were proposed. To predict the temporal droplet volume change and evaporation rate, the range of θ* > 0.25 and d* > 0.9, which mostly covered the whole evaporation period and the initial contact diameter remained almost constant during evaporation, was targeted. In this range, the previous contact angle functions for the evaporation model underpredicted the experimental data. A new contact angle function of a zircaloy surface was empirically proposed, which represented the present experimental data within a reasonable degree of accuracy. (author)

  18. Dynamic Wetting Behavior of Vibrated Droplets on a Micropillared Surface

    Directory of Open Access Journals (Sweden)

    Zhi-hai Jia

    2016-01-01

    Full Text Available The dynamical wetting behavior has been observed under vertical vibration of a water droplet placed on a micropillared surface. The wetting transition takes place under the different processes. In compression process, the droplet is transited from Cassie state to Wenzel state. The droplet undergoes a Wenzel-Cassie wetting transition in restoring process and the droplet bounces off from the surface in bouncing process. Meanwhile, the wetting and dewetting models during vibration are proposed. The wetting transition is confirmed by the model calculation. This study has potential to be used to control the wetting state.

  19. Investigation on Electrostatical Breakup of Bio-Oil Droplets

    Directory of Open Access Journals (Sweden)

    John Z. Wen

    2012-10-01

    Full Text Available In electrostatic atomization, the input electrical energy causes breaking up of the droplet surface by utilizing a mutual repulsion of net charges accumulating on that surface. In this work a number of key parameters controlling the bio-oil droplet breakup process are identified and these correlations among the droplet size distribution, specific charges of droplets and externally applied electrical voltages are quantified. Theoretical considerations of the bag or strip breakup mechanism of biodiesel droplets experiencing electrostatic potential are compared to experimental outcomes. The theoretical analysis suggests the droplet breakup process is governed by the Rayleigh instability condition, which reveals the effects of droplets size, specific charge, surface tension force, and droplet velocities. Experiments confirm that the average droplet diameters decrease with increasing specific charges and this decreasing tendency is non-monotonic due to the motion of satellite drops in the non-uniform electrical field. The measured specific charges are found to be smaller than the theoretical values. And the energy transformation from the electrical energy to surface energy, in addition to the energy loss, Taylor instability breakup, non-excess polarization and some system errors, accounts for this discrepancy. The electrostatic force is the dominant factor controlling the mechanism of biodiesel breakup in electrostatic atomization.

  20. Research into spectra transformation of cooling tower droplet drift

    International Nuclear Information System (INIS)

    Mandrykin, G.P.

    1990-01-01

    Empirical droplet-diameter distributions in a cooling tower and outside are well approximated by the Rosin-Rammler-Bennet two-parameter function. Fractional efficiency of eliminators is also approximated by the above function fairly well. The design formulas proposed are universal and allow evaluation of droplet spectra transformation as well as the efficiency of measures for preventing droplet emissions from cooling towers both at the design and operation stages. Estimates of cooling tower droplet emissions calculated by the formulas suggested may be recommended as input data applied to the solution of environmental pollution problems and their assessment

  1. Recent Advances in Controlling the Depositing Morphologies of Inkjet Droplets.

    Science.gov (United States)

    Sun, Jiazhen; Bao, Bin; He, Min; Zhou, Haihua; Song, Yanlin

    2015-12-30

    Inkjet printing has been widely used in functional material patterning for fabrication of optical/electrical devices. The depositing morphologies of inkjet droplets are critical to the resolution and performance of resulted functional patterns. This review summarizes various strategies to control the depositing morphologies of inkjet droplets, including suppressing and utilizing coffee-ring effect, employing liquid substrates, developing patterned substrates and controlling droplets coalescence. Moreover, the remaining challenges in controlling inkjet droplets are presented, and the broad research and application prospects of controlling nanomaterial patterning by inkjet printing are proposed.

  2. Dynamic interactions of Leidenfrost droplets on liquid metal surface

    Science.gov (United States)

    Ding, Yujie; Liu, Jing

    2016-09-01

    Leidenfrost dynamic interaction effects of the isopentane droplets on the surface of heated liquid metal were disclosed. Unlike conventional rigid metal, such conductive and deformable liquid metal surface enables the levitating droplets to demonstrate rather abundant and complex dynamics. The Leidenfrost droplets at different diameters present diverse morphologies and behaviors like rotation and oscillation. Depending on the distance between the evaporating droplets, they attract and repulse each other through the curved surfaces beneath them and their vapor flows. With high boiling point up to 2000 °C, liquid metal offers a unique platform for testing the evaporating properties of a wide variety of liquid even solid.

  3. Controlling Active Liquid Crystal Droplets with Temperature and Surfactant Concentration

    Science.gov (United States)

    Shechter, Jake; Milas, Peker; Ross, Jennifer

    Active matter is the study of driven many-body systems that span length scales from flocking birds to molecular motors. A previously described self-propelled particle system was made from liquid crystal (LC) droplets in water with high surfactant concentration to move particles via asymmetric surface instabilities. Using a similar system, we investigate the driving activity as a function of SDS surfactant concentration and temperature. We then use an optical tweezer to trap and locally heat the droplets to cause hydrodynamic flow and coupling between multiple droplets. This system will be the basis for a triggerable assembly system to build and couple LC droplets. DOD AROMURI 67455-CH-MUR.

  4. Modeling Evaporation and Particle Assembly in Colloidal Droplets.

    Science.gov (United States)

    Zhao, Mingfei; Yong, Xin

    2017-06-13

    Evaporation-induced assembly of nanoparticles in a drying droplet is of great importance in many engineering applications, including printing, coating, and thin film processing. The investigation of particle dynamics in evaporating droplets can provide fundamental hydrodynamic insight for revealing the processing-structure relationship in the particle self-organization induced by solvent evaporation. We develop a free-energy-based multiphase lattice Boltzmann method coupled with Brownian dynamics to simulate evaporating colloidal droplets on solid substrates with specified wetting properties. The influence of interface-bound nanoparticles on the surface tension and evaporation of a flat liquid-vapor interface is first quantified. The results indicate that the particles at the interface reduce surface tension and enhance evaporation flux. For evaporating particle-covered droplets on substrates with different wetting properties, we characterize the increase of evaporate rate via measuring droplet volume. We find that droplet evaporation is determined by the number density and circumferential distribution of interfacial particles. We further correlate particle dynamics and assembly to the evaporation-induced convection in the bulk and on the surface of droplet. Finally, we observe distinct final deposits from evaporating colloidal droplets with bulk-dispersed and interface-bound particles. In addition, the deposit pattern is also influenced by the equilibrium contact angle of droplet.

  5. Evaluation of droplet size distributions using univariate and multivariate approaches.

    Science.gov (United States)

    Gaunø, Mette Høg; Larsen, Crilles Casper; Vilhelmsen, Thomas; Møller-Sonnergaard, Jørn; Wittendorff, Jørgen; Rantanen, Jukka

    2013-01-01

    Pharmaceutically relevant material characteristics are often analyzed based on univariate descriptors instead of utilizing the whole information available in the full distribution. One example is droplet size distribution, which is often described by the median droplet size and the width of the distribution. The current study was aiming to compare univariate and multivariate approach in evaluating droplet size distributions. As a model system, the atomization of a coating solution from a two-fluid nozzle was investigated. The effect of three process parameters (concentration of ethyl cellulose in ethanol, atomizing air pressure, and flow rate of coating solution) on the droplet size and droplet size distribution using a full mixed factorial design was used. The droplet size produced by a two-fluid nozzle was measured by laser diffraction and reported as volume based size distribution. Investigation of loading and score plots from principal component analysis (PCA) revealed additional information on the droplet size distributions and it was possible to identify univariate statistics (volume median droplet size), which were similar, however, originating from varying droplet size distributions. The multivariate data analysis was proven to be an efficient tool for evaluating the full information contained in a distribution.

  6. Experimental study on oxidation and combustion characteristics of sodium droplets

    International Nuclear Information System (INIS)

    Zhang Zhigang; Sun Shubin; Liu Chongchong; Tang Yexin

    2015-01-01

    In the operation of the sodium-cooled fast reactor, the accident caused by the leakage and combustion of liquid sodium is common and frequent. In this paper, the oxidation and combustion characteristics of sodium droplets were studied by carrying out the experiments of the oxidation and combustion under different conditions of initial temperatures (140-370℃) of the sodium droplets and oxygen concentrations (4%-21%). The oxidation and combustion behaviors were visualized by a set of combustion apparatus of sodium droplet and a high speed camera. The experiment results show that the columnar oxides grow longer as the initial temperature of sodium droplet and oxygen concentration become lower. Under the same oxygen concentration condition, the sodium droplet with the higher initial temperature is easier to ignite and burn. When the initial temperature of sodium droplet is below 200℃, it is very difficult to ignite. If there is a turbulence damaging the oxide layer on the surface, the sodium droplet will also burn gradually. When the initial temperature ranges from 140℃ to 370℃ and the oxygen fraction is equal to or higher than 12%, the sodium droplet could burn completely and the maximum combustion temperature could roughly reach 600-800℃. When the oxygen concentration is below 12%, the sodium droplet could not burn completely and the highest combustion temperature is below 600℃. The results are helpful to the research on the columnar flow and spray sodium fire. (authors)

  7. An experimental study on suspended sodium droplet combustion

    International Nuclear Information System (INIS)

    Sato, Kenji

    2003-03-01

    As part of studies for phenomenological investigation of sodium droplet burning behavior, in our previous experimental studies, ignition process and succeeding combustion of suspended single sodium droplet had been investigated by using high speed movie camera, and a temperature measurement system feasible for the experiment had been developed. In the present study, by using 4 mm diam. suspended sodium droplet, combustion experiments were performed for the free-stream velocity of dry air flow of 20 to 60 cm/s, and for the initial droplet temperature of 280 to 400degC, and the effects of the free-stream velocity and initial droplet temperature on the ignition behavior and droplet temperature variation with time were examined by using high speed movie camera and sheath-type fine thermocouple. The experimental results are as follows: (1) When the initial droplet temperature is less than 290degC, before ignition the oxide film accompanied with vertical streak appeared and the droplet turned to teardrop shape. (2) The ignition delay time defined as the time to evolution of orange color light emission zone or flame zone decreases with the increase o the free-stream velocity or of initial droplet temperature. Examples of typical ignition time are 1.4 s at the free-stream velocity 20 cm/s and initial droplet temperature 300degC, and 0.65 s at 60 cm/s and 400degC. (3) the dependence of the ignition delay time on the free-stream velocity decreases as the free stream velocity increases. (4) The droplet temperatures at the moment of melting extending all over the surface and at the moment of ignition are around 460degC and 500 to 600degC (mostly around 575degC), respectively. These values are essentially independent of the free-stream velocity and initial droplet temperature. (5) The rate of temperature rise does not change through the moment of ignition. (6) The asymptotic droplet temperature at approaching to quasi-steady combustion state following ignition is independent of

  8. Correcting saturation of detectors for particle/droplet imaging methods

    International Nuclear Information System (INIS)

    Kalt, Peter A M

    2010-01-01

    Laser-based diagnostic methods are being applied to more and more flows of theoretical and practical interest and are revealing interesting new flow features. Imaging particles or droplets in nephelometry and laser sheet dropsizing methods requires a trade-off of maximized signal-to-noise ratio without over-saturating the detector. Droplet and particle imaging results in lognormal distribution of pixel intensities. It is possible to fit a derived lognormal distribution to the histogram of measured pixel intensities. If pixel intensities are clipped at a saturated value, it is possible to estimate a presumed probability density function (pdf) shape without the effects of saturation from the lognormal fit to the unsaturated histogram. Information about presumed shapes of the pixel intensity pdf is used to generate corrections that can be applied to data to account for saturation. The effects of even slight saturation are shown to be a significant source of error on the derived average. The influence of saturation on the derived root mean square (rms) is even more pronounced. It is found that errors on the determined average exceed 5% when the number of saturated samples exceeds 3% of the total. Errors on the rms are 20% for a similar saturation level. This study also attempts to delineate limits, within which the detector saturation can be accurately corrected. It is demonstrated that a simple method for reshaping the clipped part of the pixel intensity histogram makes accurate corrections to account for saturated pixels. These outcomes can be used to correct a saturated signal, quantify the effect of saturation on a derived average and offer a method to correct the derived average in the case of slight to moderate saturation of pixels

  9. Propagation of capillary waves and ejection of small droplets in rapid droplet spreading

    KAUST Repository

    Ding, Hang; Li, Erqiang; Zhang, F. H.; Sui, Yi; Spelt, Peter D M; Thoroddsen, Sigurdur T

    2012-01-01

    A new regime of droplet ejection following the slow deposition of drops onto a near-complete wetting solid substrate is identified in experiments and direct numerical simulations; a coalescence cascade subsequent to pinch-off is also observed for the first time. Results of numerical simulations indicate that the propagation of capillary waves that lead to pinch-off is closely related to the self-similar behaviour observed in the inviscid recoil of droplets, and that motions of the crests and troughs of capillary waves along the interface do not depend on the wettability and surface tension (or Ohnesorge number). The simulations also show that a self-similar theory for universal pinch-off can be used for the time evolution of the pinching neck. However, although good agreement is also found with the double-cone shape of the pinching neck for droplet ejection in drop deposition on a pool of the same liquid, substantial deviations are observed in such a comparison for droplet ejection in rapid drop spreading (including the newly identified regime). This deviation is shown to result from interference by the solid substrate, a rapid downwards acceleration of the top of the drop surface and the rapid spreading process. The experiments also confirm non-monotonic spreading behaviour observed previously only in numerical simulations, and suggest substantial inertial effects on the relation between an apparent contact angle and the dimensionless contact-line speed. © 2012 Cambridge University Press.

  10. Propagation of capillary waves and ejection of small droplets in rapid droplet spreading

    KAUST Repository

    Ding, Hang

    2012-03-12

    A new regime of droplet ejection following the slow deposition of drops onto a near-complete wetting solid substrate is identified in experiments and direct numerical simulations; a coalescence cascade subsequent to pinch-off is also observed for the first time. Results of numerical simulations indicate that the propagation of capillary waves that lead to pinch-off is closely related to the self-similar behaviour observed in the inviscid recoil of droplets, and that motions of the crests and troughs of capillary waves along the interface do not depend on the wettability and surface tension (or Ohnesorge number). The simulations also show that a self-similar theory for universal pinch-off can be used for the time evolution of the pinching neck. However, although good agreement is also found with the double-cone shape of the pinching neck for droplet ejection in drop deposition on a pool of the same liquid, substantial deviations are observed in such a comparison for droplet ejection in rapid drop spreading (including the newly identified regime). This deviation is shown to result from interference by the solid substrate, a rapid downwards acceleration of the top of the drop surface and the rapid spreading process. The experiments also confirm non-monotonic spreading behaviour observed previously only in numerical simulations, and suggest substantial inertial effects on the relation between an apparent contact angle and the dimensionless contact-line speed. © 2012 Cambridge University Press.

  11. Direct Observations of Isoprene Secondary Organic Aerosol Formation in Ambient Cloud Droplets

    Science.gov (United States)

    Zelenyuk, A.; Bell, D.; Thornton, J. A.; Fast, J. D.; Shrivastava, M. B.; Berg, L. K.; Imre, D. G.; Mei, F.; Shilling, J.; Suski, K. J.; Liu, J.; Tomlinson, J. M.; Wang, J.

    2017-12-01

    Multiphase chemistry of isoprene photooxidation products has been shown to be one of the major sources of secondary organic aerosol (SOA) in the atmosphere. A number of recent studies indicate that aqueous aerosol phase provides a medium for reactive uptake of isoprene photooxidation products, and in particular, isomeric isoprene epoxydiols (IEPOX), with reaction rates and yields being dependent on aerosol acidity, water content, sulfate concentration, and organic coatings. However, very few studies focused on chemistry occurring within actual cloud droplets. We will present data acquired during recent Holistic Interactions of Shallow Clouds, Aerosols, and Land Ecosystems (HI-SCALE) Campaign, which provide direct evidence for IEPOX-SOA formation in cloud droplets. Single particle mass spectrometer, miniSPLAT, and a high-resolution, time-of-flight aerosol mass spectrometer were used to characterize the composition of aerosol particles and cloud droplet residuals, while a high-resolution, time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) was used to characterize gas-phase compounds. We find that the composition of cloud droplet residuals was markedly different than that of aerosol particles sampled outside the cloud. Cloud droplet residuals were comprised of individual particles with high relative fractions of sulfate and nitrate and significant fraction of particles with mass spectra that are nearly identical to those of laboratory-generated IEPOX-SOA particles. The observed cloud-induced formation of IEPOX-SOA was accompanied by simultaneous decrease in measured concentrations of IEPOX and other gas-phase isoprene photooxidation products. Ultimately, the combined cloud, aerosol, and gas-phase measurements conducted during HI-SCALE will be used to develop and evaluate model treatments of aqueous-phase isoprene SOA formation.

  12. 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.

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

    International Nuclear Information System (INIS)

    Kim, Han-sol; Lee, Jae-Young; Kim, Jong-Rok; Euh, Dong-Jin

    2016-01-01

    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

  14. 1-Million droplet array with wide-field fluorescence imaging for digital PCR.

    Science.gov (United States)

    Hatch, Andrew C; Fisher, Jeffrey S; Tovar, Armando R; Hsieh, Albert T; Lin, Robert; Pentoney, Stephen L; Yang, David L; Lee, Abraham P

    2011-11-21

    Digital droplet reactors are useful as chemical and biological containers to discretize reagents into picolitre or nanolitre volumes for analysis of single cells, organisms, or molecules. However, most DNA based assays require processing of samples on the order of tens of microlitres and contain as few as one to as many as millions of fragments to be detected. Presented in this work is a droplet microfluidic platform and fluorescence imaging setup designed to better meet the needs of the high-throughput and high-dynamic-range by integrating multiple high-throughput droplet processing schemes on the chip. The design is capable of generating over 1-million, monodisperse, 50 picolitre droplets in 2-7 minutes that then self-assemble into high density 3-dimensional sphere packing configurations in a large viewing chamber for visualization and analysis. This device then undergoes on-chip polymerase chain reaction (PCR) amplification and fluorescence detection to digitally quantify the sample's nucleic acid contents. Wide-field fluorescence images are captured using a low cost 21-megapixel digital camera and macro-lens with an 8-12 cm(2) field-of-view at 1× to 0.85× magnification, respectively. We demonstrate both end-point and real-time imaging ability to perform on-chip quantitative digital PCR analysis of the entire droplet array. Compared to previous work, this highly integrated design yields a 100-fold increase in the number of on-chip digitized reactors with simultaneous fluorescence imaging for digital PCR based assays.

  15. The liquid droplet radiator: Status of development

    Science.gov (United States)

    Persson, J.

    1991-12-01

    The ever greater amounts of power to be dissipated onboard future spacecraft, together with their limited external dimensions, will make it increasingly difficult to use conventional radiator technology without imposing a severe mass penalty. Hunting for lightweight alternatives to current heat rejection systems has become a matter of growing urgency, which explains the great interest that the Liquid Droplet Radiator (LDR) has attracted. Tradeoff analyses indicate that an LDR may be as much as an order of magnitude lighter than a comparable conventional radiator. A literature study examining the progress of the LDR research and some of its possible applications is reviewed. An investigation of the LDR heat rejection capability is presented.

  16. Quark matter droplets in neutron stars

    Science.gov (United States)

    Heiselberg, H.; Pethick, C. J.; Staubo, E. F.

    1993-01-01

    We show that, for physically reasonable bulk and surface properties, the lowest energy state of dense matter consists of quark matter coexisting with nuclear matter in the presence of an essentially uniform background of electrons. We estimate the size and nature of spatial structure in this phase, and show that at the lowest densities the quark matter forms droplets embedded in nuclear matter, whereas at higher densities it can exhibit a variety of different topologies. A finite fraction of the interior of neutron stars could consist of matter in this new phase, which would provide new mechanisms for glitches and cooling.

  17. Parallelization of Droplet Microfluidic Systems for the Sustainable Production of Micro-Reactors at Industrial Scale

    KAUST Repository

    Conchouso Gonzalez, David

    2017-04-01

    At the cutting edge of the chemical and biological research, innovation takes place in a field referred to as Lab on Chip (LoC), a multi-disciplinary area that combines biology, chemistry, electronics, microfabrication, and fluid mechanics. Within this field, droplets have been used as microreactors to produce advanced materials like quantum dots, micro and nanoparticles, active pharmaceutical ingredients, etc. The size of these microreactors offers distinct advantages, which were not possible using batch technologies. For example, they allow for lower reagent waste, minimal energy consumption, increased safety, as well as better process control of reaction conditions like temperature regulation, residence times, and response times among others. One of the biggest drawbacks associated with this technology is its limited production volume that prevents it from reaching industrial applications. The standard production rates for a single droplet microfluidic device is in the range of 1-10mLh-1, whereas industrial applications usually demand production rates several orders of magnitude higher. Although substantial work has been recently undertaken in the development scaled-out solutions, which run in parallel several droplet generators. Complex fluid mechanics and limitations on the manufacturing capacity have constrained these works to explore only in-plane parallelization. This thesis investigates a three-dimensional parallelization by proposing a microfluidic system that is comprised of a stack of droplet generation layers working on the liquid-liquid ow regime. Its realization implied a study of the characteristics of conventional droplet generators and the development of a fabrication process for 3D networks of microchannels. Finally, the combination of these studies resulted in a functional 3D parallelization system with the highest production rate (i.e. 1 Lh-1) at the time of its publication. Additionally, this architecture can reach industrially relevant

  18. Hydrophobic polymer covered by a grating electrode for converting the mechanical energy of water droplets into electrical energy

    Science.gov (United States)

    Helseth, L. E.; Guo, X. D.

    2016-04-01

    Water contact electric harvesting has a great potential as a new energy technology for powering small-scale electronics, but a better understanding of the dynamics governing the conversion from mechanical to electrical energy on the polymer surfaces is needed. Important questions are how current correlates with droplet kinetic energy and what happens to the charge dynamics when a large number of droplets are incident on the polymer simultaneously. Here we address these questions by studying the current that is generated in an external electrical circuit when water droplets impinge on hydrophobic fluorinated ethylene propylene film containing a grating electrode on the back side. Droplets moving down an inclined polymer plane exhibit a characteristic periodic current time trace, and it is found that the peak current scales with sine of the inclination angle. For single droplets in free fall impinging onto the polymer, it is found that the initial peak current scales with the height of the free fall. The transition from individual droplets to a nearly continuous stream was investigated using the spectral density of the current signal. In both regimes, the high frequency content of the spectral density scales as f -2. For low frequencies, the low frequency content at low volume rates was noisy but nearly constant, whereas for high volume rates an increase with frequency is observed. It is demonstrated that the output signal from the system exposed to water droplets from a garden hose can be rectified and harvested by a 33 μF capacitor, where the stored energy increases at a rate of about 20 μJ in 100 s.

  19. Experimental study of sodium droplet burning in free fall. Evaluation of preliminary test results

    International Nuclear Information System (INIS)

    Miyahara, Shinya; Ara, Kuniaki

    1998-08-01

    To study a sodium leak and combustion behavior phenomenologically and to construct the mechanistic evaluation method, an experimental series of a sodium droplet burning in free fall is under way. In this study, the accuracy of measurement technique used in the preliminary test was assessed and the modified technique was proposed for the next test series. Analytical study of the test results was also conducted to deduce dominant parameters and important measurement items which would play an important role in the droplet combustion behavior. The results and conclusions are as follows: (1) Assessment of measurement accuracy and modified technique proposed for the next test series. a) Control accuracy of sodium supply system using β-alumina solid electrolyte was sufficient for generation of objective size of single droplet. However, it is necessary to calibrate the correlation between the quantity of electric charge for sodium supply system and that of supplied sodium. b) Measurement accuracy of falling velocity using high-speed video was ±0.33 m/s at an upper part and ±0.48 m/s at a lower part of the measurement. To reduce the error, a high-speed stroboscopic method is recommended to measure the falling velocity of droplet. (2) Results of analytical study and deduced dominant parameters and important measurement items. a) The falling behavior of a burning droplet was described solving the equation of free falling motion for a rigid sphere. In the case of higher falling height, it is necessary to study the burning effects on the falling behavior. b) The mass burned of a falling droplet was calculated using the combustion model according to 'D 2 ' law during the full burning phase. It is necessary to study the dominant chemical reaction in the burning flame because the mass burned depends on the composition of the reaction products. c) The mass burned was calculated using surface oxidation model for preignition phase together with above model. However, it is

  20. Oxidation of SO{sub 2} and formation of water droplets under irradiation of 20 MeV protons in N{sub 2}/H{sub 2}O/SO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Tomita, Shigeo [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Nakai, Yoichi, E-mail: nakaiy@riken.jp [Radioactive Isotope Physics Laboratory, RIKEN Nishina Center, Wako, Saitama 351-0198 (Japan); Funada, Shuhei; Tanikawa, Hideomi; Harayama, Isao [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Kobara, Hitomi [National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8569 (Japan); Sasa, Kimikazu [Tandem Accelerator Complex, University of Tsukuba, Tsukuba, Ibaraki 305-8577 (Japan); Pedersen, Jens Olaf Pepke [National Space Institute, Technical University of Denmark, DK-2800 Kgs. Lyngby (Denmark); Hvelplund, Preben [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark)

    2015-12-15

    We have performed an experiment on charged droplet formation in a humidified N{sub 2} gas with trace SO{sub 2} concentration and induced by 20 MeV proton irradiation. It is thought that SO{sub 2} reacts with the chemical species, such as OH radicals, generated through the reactions triggered by N{sub 2}{sup +} production. Both droplet number and droplet size increased with SO{sub 2} consumption for the proton irradiation. The total charged droplet numbers entering the differential mobility analyzer per unit time were proportional to the 0.68 power of the SO{sub 2} consumption. These two findings suggest that coagulation among the small droplets contributes to the formation of the droplets. The charged droplet volume detected per unit time is proportional to the SO{sub 2} consumption, which indicates that a constant amount of sulfur atoms is contained in a unit volume of droplet, regardless of different droplet-size distributions depending on the SO{sub 2} consumption.

  1. Probing droplets with biological colloidal suspensions on smart surfaces by synchrotron radiation micro- and nano-beams

    KAUST Repository

    Marinaro, Giovanni

    2015-03-01

    Droplets with colloidal biological suspensions evaporating on substrates with defined wetting properties generate confined environments for initiating aggregation and self-assembly processes. We describe smart micro- and nanostructured surfaces, optimized for probing single droplets and residues by synchrotron radiation micro- and nanobeam diffraction techniques. Applications are presented for Ac-IVD and β-amyloid (1-42) peptides capable of forming cross-β sheet structures. Complementary synchrotron radiation FTIR microspectroscopy addresses secondary structure formation. The high synchrotron radiation source brilliance enables fast raster-scan experiments. © 2015 Elsevier Ltd.

  2. Probing droplets with biological colloidal suspensions on smart surfaces by synchrotron radiation micro- and nano-beams

    KAUST Repository

    Marinaro, Giovanni; Accardo, Angelo; Benseny-Cases, Nú ria; Burghammer, Manfred C.; Castillo-Michel, Hiram A.; Cotte, Marine; Dante, Silvia; De Angelis, Francesco De; Di Cola, Emanuela; Di Fabrizio, Enzo M.; Hauser, C.; Riekel, Christian

    2015-01-01

    Droplets with colloidal biological suspensions evaporating on substrates with defined wetting properties generate confined environments for initiating aggregation and self-assembly processes. We describe smart micro- and nanostructured surfaces, optimized for probing single droplets and residues by synchrotron radiation micro- and nanobeam diffraction techniques. Applications are presented for Ac-IVD and β-amyloid (1-42) peptides capable of forming cross-β sheet structures. Complementary synchrotron radiation FTIR microspectroscopy addresses secondary structure formation. The high synchrotron radiation source brilliance enables fast raster-scan experiments. © 2015 Elsevier Ltd.

  3. Direct numerical simulation of droplet-laden isotropic turbulence

    Science.gov (United States)

    Dodd, Michael S.

    Interaction of liquid droplets with turbulence is important in numerous applications ranging from rain formation to oil spills to spray combustion. The physical mechanisms of droplet-turbulence interaction are largely unknown, especially when compared to that of solid particles. Compared to solid particles, droplets can deform, break up, coalesce and have internal fluid circulation. The main goal of this work is to investigate using direct numerical simulation (DNS) the physical mechanisms of droplet-turbulence interaction, both for non-evaporating and evaporating droplets. To achieve this objective, we develop and couple a new pressure-correction method with the volume-of-fluid (VoF) method for simulating incompressible two-fluid flows. The method's main advantage is that the variable coefficient Poisson equation that arises in solving the incompressible Navier-Stokes equations for two-fluid flows is reduced to a constant coefficient equation. This equation can then be solved directly using, e.g., the FFT-based parallel Poisson solver. For a 10243 mesh, our new pressure-correction method using a fast Poisson solver is ten to forty times faster than the standard pressure-correction method using multigrid. Using the coupled pressure-correction and VoF method, we perform direct numerical simulations (DNS) of 3130 finite-size, non-evaporating droplets of diameter approximately equal to the Taylor lengthscale and with 5% droplet volume fraction in decaying isotropic turbulence at initial Taylor-scale Reynolds number Relambda = 83. In the droplet-laden cases, we vary one of the following three parameters: the droplet Weber number based on the r.m.s. velocity of turbulence (0.1 ≤ Werms ≤ 5), the droplet- to carrier-fluid density ratio (1 ≤ rhod/rho c ≤ 100) or the droplet- to carrier-fluid viscosity ratio (1 ≤ mud/muc ≤ 100). We derive the turbulence kinetic energy (TKE) equations for the two-fluid, carrier-fluid and droplet-fluid flow. These equations allow

  4. Self-peeling of impacting droplets

    Science.gov (United States)

    de Ruiter, Jolet; Soto, Dan; Varanasi, Kripa K.

    2018-01-01

    Whether an impacting droplet sticks or not to a solid surface has been conventionally controlled by functionalizing the target surface or by using additives in the drop. Here we report on an unexpected self-peeling phenomenon that can happen even on smooth untreated surfaces by taking advantage of the solidification of the impacting drop and the thermal properties of the substrate. We control this phenomenon by tuning the coupling of the short-timescale fluid dynamics--leading to interfacial defects upon local freezing--and the longer-timescale thermo-mechanical stresses--leading to global deformation. We establish a regime map that predicts whether a molten metal drop impacting onto a colder substrate will bounce, stick or self-peel. In many applications, avoiding adhesion of impacting droplets around designated target surfaces can be as crucial as bonding onto them to minimize waste or cleaning. These insights have broad applicability in processes ranging from thermal spraying and additive manufacturing to extreme ultraviolet lithography.

  5. Post-Tanner spreading of nematic droplets

    International Nuclear Information System (INIS)

    Mechkov, S; Oshanin, G; Cazabat, A M

    2009-01-01

    The quasistationary spreading of a circular liquid drop on a solid substrate typically obeys the so-called Tanner law, with the instantaneous base radius R(t) growing with time as R∼t 1/10 -an effect of the dominant role of capillary forces for a small-sized droplet. However, for droplets of nematic liquid crystals, a faster spreading law sets in at long times, so that R∼t α with α significantly larger than the Tanner exponent 1/10. In the framework of the thin film model (or lubrication approximation), we describe this 'acceleration' as a transition to a qualitatively different spreading regime driven by a strong substrate-liquid interaction specific to nematics (antagonistic anchoring at the interfaces). The numerical solution of the thin film equation agrees well with the available experimental data for nematics, even though the non-Newtonian rheology has yet to be taken into account. Thus we complement the theory of spreading with a post-Tanner stage, noting that the spreading process can be expected to cross over from the usual capillarity-dominated stage to a regime where the whole reservoir becomes a diffusive film in the sense of Derjaguin.

  6. Lipid Droplets and Mycobacterium leprae Infection

    Science.gov (United States)

    Elamin, Ayssar A.; Stehr, Matthias; Singh, Mahavir

    2012-01-01

    Leprosy is a chronic infectious disease and is a major source of morbidity in developing countries. Leprosy is caused by the obligate intracellular bacterium Mycobacterium leprae, which infects as primary target Schwann cells. Lepromatous leprosy exhibits multiple lesions of the skin, eyes, nerves, and lymph nodes. The sites of infection are characterized by the presence of foamy macrophages, fully packed with lipid droplets (LDs), which are induced by M. leprae. In the last years, it has become evident that M. tuberculosis imports lipids from foamy macrophages and is dependent on fatty acids for growth in infected macrophages. M. leprae seems to have similar mechanisms for scavenging lipids from the host. But due to the inability to culture M. leprae on laboratory media, research progresses only slowly. However, in the last years, substantial progress has been made in the field of lipid metabolism in M. leprae. Herein, we will present and summarize the lipid droplets formation and the metabolism of lipids during M. leprae infection. PMID:23209912

  7. Accelerating Yeast Prion Biology using Droplet Microfluidics

    Science.gov (United States)

    Ung, Lloyd; Rotem, Assaf; Jarosz, Daniel; Datta, Manoshi; Lindquist, Susan; Weitz, David

    2012-02-01

    Prions are infectious proteins in a misfolded form, that can induce normal proteins to take the misfolded state. Yeast prions are relevant, as a model of human prion diseases, and interesting from an evolutionary standpoint. Prions may also be a form of epigenetic inheritance, which allow yeast to adapt to stressful conditions at rates exceeding those of random mutations and propagate that adaptation to their offspring. Encapsulation of yeast in droplet microfluidic devices enables high-throughput measurements with single cell resolution, which would not be feasible using bulk methods. Millions of populations of yeast can be screened to obtain reliable measurements of prion induction and loss rates. The population dynamics of clonal yeast, when a fraction of the cells are prion expressing, can be elucidated. Furthermore, the mechanism by which certain strains of bacteria induce yeast to express prions in the wild can be deduced. Integrating the disparate fields of prion biology and droplet microfluidics reveals a more complete picture of how prions may be more than just diseases and play a functional role in yeast.

  8. Extended lattice Boltzmann scheme for droplet combustion.

    Science.gov (United States)

    Ashna, Mostafa; Rahimian, Mohammad Hassan; Fakhari, Abbas

    2017-05-01

    The available lattice Boltzmann (LB) models for combustion or phase change are focused on either single-phase flow combustion or two-phase flow with evaporation assuming a constant density for both liquid and gas phases. To pave the way towards simulation of spray combustion, we propose a two-phase LB method for modeling combustion of liquid fuel droplets. We develop an LB scheme to model phase change and combustion by taking into account the density variation in the gas phase and accounting for the chemical reaction based on the Cahn-Hilliard free-energy approach. Evaporation of liquid fuel is modeled by adding a source term, which is due to the divergence of the velocity field being nontrivial, in the continuity equation. The low-Mach-number approximation in the governing Navier-Stokes and energy equations is used to incorporate source terms due to heat release from chemical reactions, density variation, and nonluminous radiative heat loss. Additionally, the conservation equation for chemical species is formulated by including a source term due to chemical reaction. To validate the model, we consider the combustion of n-heptane and n-butanol droplets in stagnant air using overall single-step reactions. The diameter history and flame standoff ratio obtained from the proposed LB method are found to be in good agreement with available numerical and experimental data. The present LB scheme is believed to be a promising approach for modeling spray combustion.

  9. Using droplet-on-demand based printing to guide self-assembly in a peptide-protein based bioink

    Science.gov (United States)

    Hedegaard, Clara; Collin, Estelle; Redondo-Gomez, Carlos; Nguyen, Luong T. H.; Ng, Kee Woei; Castrejon-Pita, Alfonso A.; Castrejon-Pita, J. Rafael; Mata, Alvaro

    2017-11-01

    Tissue engineering aims to capture details of the extracellular matrix (ECM) that stimulate tissue regeneration. Advanced biofabrication techniques have enabled structural complexity, however they are restricted by the choice of material due to stringent printing requirements, leading to a lack of nanoscale control and molecular versatility. In this project, we exploit the dynamics of droplet fluid interactions combined with the co-assembly of peptide amphiphiles (PAs) with biomolecules/proteins to develop a new approach to droplet-based biofabrication. A custom-made droplet generator was developed and used to controllably dispense droplets of PA into a protein solution resulting in gel formation within milliseconds. Taking advantage of the interfacial and inertial forces during the droplet/liquid interaction, it is possible to control the co-assembly kinetics, to give rise to aligned or disordered nanofibers, hydrogel structures of different geometries and sizes, surface topographies, and higher-ordered structures made from multiple hydrogels. The process allows multiple cell types to be spatially distributed on the outside or embedded within the ECM mimetic scaffolds, whilst exhibiting high cell viability (>88%). ERC Starting Grant (STROFUNSCAFF), FP7-PEOPLE-2013-CIG Biomorph and the Royal Society.

  10. Numerical study on morphology and solidification characteristics of successive droplet depositions on a substrate

    Science.gov (United States)

    Adaikalanathan, Vimalan

    Successive droplet impingement finds extensive applications in additive manufacturing technologies such as 3D printing, Liquid Metal Jetting and Net Form Manufacturing. Deposition, deformation and solidification of droplets are the constitutive stages in the process which determine the final outcome. Detailed knowledge about the flow behaviour, phase transformation and free surface deformation is required to have a complete understanding and optimization of the process parameters. Experimental research in this field is only limited to imaging techniques and post solidification analysis which only provide superficial information while overlooking most of the governing phenomenon. Knowledge of the physics governing the fluid and thermal behaviours can be applied to study the process with real time data pertaining to flow field, temperature profiles and solidification. However, free surface tracking, surface tension modelling, non-isothermal solidification and convection dominant heat transfer pose mathematical challenges in the solution of the governing equations. Moreover, deposition of droplets on pre-solidified splats or non-flat surfaces requires accurate special attention. The objective of the present work is to model the successive droplet impacts and simultaneous solidification and deformation. The highly non-linear flow field governed by the Navier Stokes equation is solved using a Two Step Projection method. The surface tension effects are accounted for through a Continuum Surface Force technique. One of the crucial elements in the study is the interface tracking algorithm. A Coupled Level Set Volume of Fluid (CLSVOF) method is formulated to give an accurate orientation of the drastically deforming interface and also facilitates generation of multiple droplets in a fixed domain at a user defined frequency, thereby conserving computational resources. The phase change is modelled using an enthalpy formulation of the energy equation with an implicit source term

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

    International Nuclear Information System (INIS)

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

    2013-01-01

    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. (paper)

  12. Analytical detection techniques for droplet microfluidics—A review

    International Nuclear Information System (INIS)

    Zhu, Ying; Fang, Qun

    2013-01-01

    Graphical abstract: -- Highlights: •This is the first review paper focused on the analytical techniques for droplet-based microfluidics. •We summarized the analytical methods used in droplet-based microfluidic systems. •We discussed the advantage and disadvantage of each method through its application. •We also discuss the future development direction of analytical methods for droplet-based microfluidic systems. -- Abstract: In the last decade, droplet-based microfluidics has undergone rapid progress in the fields of single-cell analysis, digital PCR, protein crystallization and high throughput screening. It has been proved to be a promising platform for performing chemical and biological experiments with ultra-small volumes (picoliter to nanoliter) and ultra-high throughput. The ability to analyze the content in droplet qualitatively and quantitatively is playing an increasing role in the development and application of droplet-based microfluidic systems. In this review, we summarized the analytical detection techniques used in droplet systems and discussed the advantage and disadvantage of each technique through its application. The analytical techniques mentioned in this paper include bright-field microscopy, fluorescence microscopy, laser induced fluorescence, Raman spectroscopy, electrochemistry, capillary electrophoresis, mass spectrometry, nuclear magnetic resonance spectroscopy, absorption detection, chemiluminescence, and sample pretreatment techniques. The importance of analytical detection techniques in enabling new applications is highlighted. We also discuss the future development direction of analytical detection techniques for droplet-based microfluidic systems

  13. Modeling the evaporation of sessile multi-component droplets

    NARCIS (Netherlands)

    Diddens, C.; Kuerten, Johannes G.M.; van der Geld, C.W.M.; Wijshoff, H.M.A.

    2017-01-01

    We extended a mathematical model for the drying of sessile droplets, based on the lubrication approximation, to binary mixture droplets. This extension is relevant for e.g. inkjet printing applications, where ink consisting of several components are used. The extension involves the generalization of

  14. Droplet Impacting on Liquid Film: Evolution of Entrapped Air Layer

    Science.gov (United States)

    Tang, Xiaoyu; Saha, Abhishek; Law, Chung K.

    2014-11-01

    In this work we experimentally studied the dynamics of droplet impacting films of various thicknesses within a range of h / R <= 1 (h: film thickness; R: droplet radius). High speed imaging and color interferometry enabled the investigation of the evolution of the air layer trapped between two surfaces, which plays a critical role in determining the collision outcome. Globally, two distinct regimes of impaction outcome, namely bouncing and merging, are observed at low and high impact inertia, respectively. Impaction with high inertia depletes the air layer before the droplet significantly deforms, resulting in permanent merging. At low impact inertia, however, color interferometry shows the existence of three phases prior to bouncing. Upon impaction, droplet endures significant deformation trapping the air layer between the interfaces, hence increasing the resistance force. This phase is characterized by fast deformation of the air film, followed by a period of pseudo equilibrium, with minimal changes in the interfacial air-film profile. The droplet also lacks kinetic energy to penetrate further into the film, resulting in a temporary balance between the droplet weight and air-film pressure. The deformed droplet eventually relaxes towards spherical shape to destroy the equilibrium. Fast change occurs in air-layer and pressure distribution favoring the droplet bouncing.

  15. Numerical simulation of the drying of inkjet-printed droplets

    NARCIS (Netherlands)

    Siregar, D.P.; Kuerten, J.G.M.; Geld, van der C.W.M.

    2013-01-01

    In this paper we study the behavior of an inkjet-printed droplet of a solute dissolved in a solvent on a solid horizontal surface by numerical simulation. An extended model for drying of a droplet and the final distribution of the solute on an impermeable substrate is proposed. The model extends the

  16. Oil droplets of bird eyes : Microlenses acting as spectral filters

    NARCIS (Netherlands)

    Stavenga, Doekele G.; Wilts, Bodo D.

    2014-01-01

    An important component of the cone photoreceptors of bird eyes is the oil droplets located in front of the visual-pigment-containing outer segments. The droplets vary in colour and are transparent, clear, pale or rather intensely yellow or red owing to various concentrations of carotenoid pigments.

  17. Development of Two Way Coupled Euler – Euler Droplets Model

    Directory of Open Access Journals (Sweden)

    Vojtěch BĚTÁK

    2010-12-01

    Full Text Available A development of droplet solver for 3D complex geometry is described in this work. This solver is composed of solvers for turbulent flow field and droplets. This code is based on the finite volume method. An open source CFD code OpenFOAM was chosen for its first implementation and first results are shown.

  18. Droplet impact on superheated micro-structured surfaces

    NARCIS (Netherlands)

    Tran, Tuan; Staat, Erik-Jan; Susarrey Arce, A.; Foertsch, T.C.; van Houselt, Arie; Gardeniers, Johannes G.E.; Prosperetti, Andrea; Lohse, Detlef; Sun, Chao

    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

  19. Rheological properties of soybean protein isolate gels containing emulsion droplets

    NARCIS (Netherlands)

    Kim, K.H.; Renkema, J.M.S.; Vliet, van T.

    2001-01-01

    Rheological properties of soybean protein gels containing various volume fractions oil droplets have been studied at small and large deformations. Dynamic viscoelastic properties of soybean protein isolate gels were determined as a function of the volume fraction of oil droplets stabilised by the

  20. Experimental investigation of flash pyrolysis oil droplet combustion

    DEFF Research Database (Denmark)

    Ibrahim, Norazana; Jensen, Peter A.; Dam-Johansen, Kim

    2013-01-01

    at a temperature ranging between 1000 and 1400°C with an initial gas velocity of 1.6 m/s and oxygen concentration of 3%. The evolution of combustion of bio-oil droplets was recorded by a digital video camera. It was observed that the combustion behaviour of pyrolysis oil droplet differ from the heavy oil in terms......The aim of this work is to investigate and compare the combustion behaviour of a single droplet of pyrolysis oil derived from wheat straw and heavy fossil oil in a single droplet combustion chamber. The initial oil droplet diameters were in between 500 μm to 2500 μm. The experiments were performed...

  1. 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.

  2. Probing droplets on superhydrophobic surfaces by synchrotron radiation scattering techniques

    KAUST Repository

    Accardo, Angelo

    2014-06-10

    Droplets on artificially structured superhydrophobic surfaces represent quasi contact-free sample environments which can be probed by X-ray microbeams and nanobeams in the absence of obstructing walls. This review will discuss basic surface wettability concepts and introduce the technology of structuring surfaces. Quasi contact-free droplets are compared with contact-free droplets; processes related to deposition and evaporation on solid surfaces are discussed. Droplet coalescence based on the electrowetting effect allows the probing of short-time mixing and reaction processes. The review will show for several materials of biological interest that structural processes related to conformational changes, nucleation and assembly during droplet evaporation can be spatially and temporally resolved by raster-scan diffraction techniques. Orientational ordering of anisotropic materials deposited during solidification at pinning sites facilitates the interpretation of structural data. 2014 International Union of Crystallography.

  3. Composition measurements of binary mixture droplets by rainbow refractometry.

    Science.gov (United States)

    Wilms, J; Weigand, B

    2007-04-10

    So far, refractive index measurements by rainbow refractometry have been used to determine the temperature of single droplets and ensembles of droplets. Rainbow refractometry is, for the first time, to the best of our knowledge, applied to measure composition histories of evaporating, binary mixture droplets. An evaluation method is presented that makes use of Airy theory and the simultaneous size measurement by Mie scattering imaging. The method further includes an empirical correction function for a certain diameter and refractive index range. The measurement uncertainty was investigated by numerical simulations with Lorenz-Mie theory. For the experiments, an optical levitation setup was used allowing for long measurement periods. Temperature measurements of single-component droplets at different temperature levels are shown to demonstrate the accuracy of rainbow refractometry. Measurements of size and composition histories of binary mixture droplets are presented for two different mixtures. Experimental results show good agreement with numerical results using a rapid-mixing model.

  4. Composition measurements of binary mixture droplets by rainbow refractometry

    International Nuclear Information System (INIS)

    Wilms, J.; Weigand, B.

    2007-01-01

    So far, refractive index measurements by rainbow refractometry have been used to determine the temperature of single droplets and ensembles of droplets. Rainbow refractometry is, for the first time, to the best of our knowledge, applied to measure composition histories of evaporating, binary mixture droplets. An evaluation method is presented that makes use of Airy theory and the simultaneous size measurement by Mie scattering imaging. The method further includes an empirical correction function for a certain diameter and refractive index range. The measurement uncertainty was investigated by numerical simulations with Lorenz-Mie theory. For the experiments, an optical levitation setup was used allowing for long measurement periods. Temperature measurements of single-component droplets at different temperature levels are shown to demonstrate the accuracy of rainbow refractometry. Measurements of size and composition histories of binary mixture droplets are presented for two different mixtures. Experimental results show good agreement with numerical results using a rapid-mixing model

  5. METHANE GAS STABILIZES SUPERCOOLED ETHANE DROPLETS IN TITAN'S CLOUDS

    International Nuclear Information System (INIS)

    Wang, Chia C.; Lang, E. Kathrin; Signorell, Ruth

    2010-01-01

    Strong evidence for ethane clouds in various regions of Titan's atmosphere has recently been found. Ethane is usually assumed to exist as ice particles in these clouds, although the possible role of liquid and supercooled liquid ethane droplets has been recognized. Here, we report on infrared spectroscopic measurements of ethane aerosols performed in the laboratory under conditions mimicking Titan's lower atmosphere. The results clearly show that liquid ethane droplets are significantly stabilized by methane gas which is ubiquitous in Titan's nitrogen atmosphere-a phenomenon that does not have a counterpart for water droplets in Earth's atmosphere. Our data imply that supercooled ethane droplets are much more abundant in Titan's clouds than previously anticipated. Possibly, these liquid droplets are even more important for cloud processes and the formation of lakes than ethane ice particles.

  6. Rayleigh Instability-Assisted Satellite Droplets Elimination in Inkjet Printing.

    Science.gov (United States)

    Yang, Qiang; Li, Huizeng; Li, Mingzhu; Li, Yanan; Chen, Shuoran; Bao, Bin; Song, Yanlin

    2017-11-29

    Elimination of satellite droplets in inkjet printing has long been desired for high-resolution and precision printing of functional materials and tissues. Generally, the strategy to suppress satellite droplets is to control ink properties, such as viscosity or surface tension, to assist ink filaments in retracting into one drop. However, this strategy brings new restrictions to the ink, such as ink viscosity, surface tension, and concentration. Here, we report an alternative strategy that the satellite droplets are eliminated by enhancing Rayleigh instability of filament at the break point to accelerate pinch-off of the droplet from the nozzle. A superhydrophobic and ultralow adhesive nozzle with cone morphology exhibits the capability to eliminate satellite droplets by cutting the ink filament at breakup point effectively. As a result, the nozzles with different sizes (10-80 μm) are able to print more inks (1 printing electronics and biotechnologies.

  7. Bioreactor droplets from liposome-stabilized all-aqueous emulsions

    Science.gov (United States)

    Dewey, Daniel C.; Strulson, Christopher A.; Cacace, David N.; Bevilacqua, Philip C.; Keating, Christine D.

    2014-08-01

    Artificial bioreactors are desirable for in vitro biochemical studies and as protocells. A key challenge is maintaining a favourable internal environment while allowing substrate entry and product departure. We show that semipermeable, size-controlled bioreactors with aqueous, macromolecularly crowded interiors can be assembled by liposome stabilization of an all-aqueous emulsion. Dextran-rich aqueous droplets are dispersed in a continuous polyethylene glycol (PEG)-rich aqueous phase, with coalescence inhibited by adsorbed ~130-nm diameter liposomes. Fluorescence recovery after photobleaching and dynamic light scattering data indicate that the liposomes, which are PEGylated and negatively charged, remain intact at the interface for extended time. Inter-droplet repulsion provides electrostatic stabilization of the emulsion, with droplet coalescence prevented even for submonolayer interfacial coatings. RNA and DNA can enter and exit aqueous droplets by diffusion, with final concentrations dictated by partitioning. The capacity to serve as microscale bioreactors is established by demonstrating a ribozyme cleavage reaction within the liposome-coated droplets.

  8. Theoretical study of liquid droplet dispersion in a venturi scrubber.

    Science.gov (United States)

    Fathikalajahi, J; Talaie, M R; Taheri, M

    1995-03-01

    The droplet concentration distribution in an atomizing scrubber was calculated based on droplet eddy diffusion by a three-dimensional dispersion model. This model is also capable of predicting the liquid flowing on the wall. The theoretical distribution of droplet concentration agrees well with experimental data given by Viswanathan et al. for droplet concentration distribution in a venturi-type scrubber. The results obtained by the model show a non-uniform distribution of drops over the cross section of the scrubber, as noted by the experimental data. While the maximum of droplet concentration distribution may depend on many operating parameters of the scrubber, the results of this study show that the highest uniformity of drop distribution will be reached when penetration length is approximately equal to one-fourth of the depth of the scrubber. The results of this study can be applied to evaluate the removal efficiency of a venturi scrubber.

  9. An interfacial mechanism for cloud droplet formation on organic aerosols.

    Science.gov (United States)

    Ruehl, Christopher R; Davies, James F; Wilson, Kevin R

    2016-03-25

    Accurate predictions of aerosol/cloud interactions require simple, physically accurate parameterizations of the cloud condensation nuclei (CCN) activity of aerosols. Current models assume that organic aerosol species contribute to CCN activity by lowering water activity. We measured droplet diameters at the point of CCN activation for particles composed of dicarboxylic acids or secondary organic aerosol and ammonium sulfate. Droplet activation diameters were 40 to 60% larger than predicted if the organic was assumed to be dissolved within the bulk droplet, suggesting that a new mechanism is needed to explain cloud droplet formation. A compressed film model explains how surface tension depression by interfacial organic molecules can alter the relationship between water vapor supersaturation and droplet size (i.e., the Köhler curve), leading to the larger diameters observed at activation. Copyright © 2016, American Association for the Advancement of Science.

  10. Universal evaporation dynamics of a confined sessile droplet

    Science.gov (United States)

    Bansal, Lalit; Hatte, Sandeep; Basu, Saptarshi; Chakraborty, Suman

    2017-09-01

    Droplet evaporation under confinement is ubiquitous to multitude of applications such as microfluidics, surface patterning, and ink-jet printing. However, the rich physics governing the universality in the underlying dynamics remains grossly elusive. Here, we bring out hitherto unexplored universal features of the evaporation dynamics of a sessile droplet entrapped in a 3D confined fluidic environment. We show, through extensive set of experiments and theoretical formulations, that the evaporation timescale for such a droplet can be represented by a unique function of the initial conditions. Moreover, using same theoretical considerations, we are able to trace and universally merge the volume evolution history of the droplets along with evaporation lifetimes, irrespective of the extent of confinement. We also showcase the internal flow transitions caused by spatio-temporal variation of evaporation flux due to confinement. These findings may be of profound importance in designing functionalized droplet evaporation devices for emerging engineering and biomedical applications.

  11. A new kind of droplet space distribution measuring method

    International Nuclear Information System (INIS)

    Ma Chao; Bo Hanliang

    2012-01-01

    A new kind of droplet space distribution measuring technique was introduced mainly, and the experimental device which was designed for the measuring the space distribution and traces of the flying film droplet produced by the bubble breaking up near the free surface of the water. This experiment was designed with a kind of water-sensitivity test paper (rice paper) which could record the position and size of the colored scattering droplets precisely. The rice papers were rolled into cylinders with different diameters by using tools. The bubbles broke up exactly in the center of the cylinder, and the space distribution and the traces of the droplets would be received by analysing all the positions of the droplets produced by the same size bubble on the rice papers. (authors)

  12. Role of cavitation in high-speed droplet impact problems

    Science.gov (United States)

    Kondo, Tomoki; Ando, Keita

    2014-11-01

    High-speed droplet impact is found in physical cleaning using liquid jets, but its mechanisms for particle removal from target surfaces are yet unclear. In this study, we explore the possibility of having cavitation inside the droplet. The pressure evolution within a droplet colliding with a flat surface of deformable materials is determined by multicomponent Euler equations. Dynamics of cavitation bubbles heterogeneously nucleated from preexisting nuclei are determined from Rayleigh-Plesset calculations according to the pressure evolution within the droplet in one-way-coupling manner. The simulation shows that cavitation indeed occurs due to tension that arises from the water hammer shock reflection at the droplet interface. The role of cavitation including pressure emission from its collapse is to be discussed based on the one-way-coupling computations.

  13. Probing droplets on superhydrophobic surfaces by synchrotron radiation scattering techniques

    KAUST Repository

    Accardo, Angelo; Di Fabrizio, Enzo M.; Limongi, Tania; Marinaro, Giovanni; Riekel, Christian

    2014-01-01

    Droplets on artificially structured superhydrophobic surfaces represent quasi contact-free sample environments which can be probed by X-ray microbeams and nanobeams in the absence of obstructing walls. This review will discuss basic surface wettability concepts and introduce the technology of structuring surfaces. Quasi contact-free droplets are compared with contact-free droplets; processes related to deposition and evaporation on solid surfaces are discussed. Droplet coalescence based on the electrowetting effect allows the probing of short-time mixing and reaction processes. The review will show for several materials of biological interest that structural processes related to conformational changes, nucleation and assembly during droplet evaporation can be spatially and temporally resolved by raster-scan diffraction techniques. Orientational ordering of anisotropic materials deposited during solidification at pinning sites facilitates the interpretation of structural data. 2014 International Union of Crystallography.

  14. Gallium-Based Room-Temperature Liquid Metals: Actuation and Manipulation of Droplets and Flows

    Directory of Open Access Journals (Sweden)

    Leily Majidi

    2017-08-01

    Full Text Available Gallium-based room-temperature liquid metals possess extremely valuable properties, such as low toxicity, low vapor pressure, and high thermal and electrical conductivity enabling them to become suitable substitutes for mercury and beyond in wide range of applications. When exposed to air, a native oxide layer forms on the surface of gallium-based liquid metals which mechanically stabilizes the liquid. By removing or reconstructing the oxide skin, shape and state of liquid metal droplets and flows can be manipulated/actuated desirably. This can occur manually or in the presence/absence of a magnetic/electric field. These methods lead to numerous useful applications such as soft electronics, reconfigurable devices, and soft robots. In this mini-review, we summarize the most recent progresses achieved on liquid metal droplet generation and actuation of gallium-based liquid metals with/without an external force.

  15. Experimental study of micron size droplets in a two phase flow in a converging - diverging nozzle

    International Nuclear Information System (INIS)

    Jurski, Kristine

    1997-01-01

    The fluid present in a pressurized vessel in normal operation is generally a mono-phase one. In accidental regime (a breach for example), a two-phase (ring and/or dispersed) flow appears and the flow is submitted to large accelerations when passing through the breach, and is then dispersed in the atmosphere. This research thesis reports an experimental simulation of an accident by generating, through a discharge of an upstream vessel into a downstream vessel, a strongly accelerated gaseous-liquid two-phase flow, with an essentially dispersed configuration in a convergent-divergent nozzle. In order to characterize the speed and diameter evolution of the dispersed liquid phase, the author reports a comparative study of two different liquid aerosols: micron-size droplets of di-octyl phthalate (DOP) of known concentration and diameter, and water droplets obtained by heterogeneous spontaneous condensation [fr

  16. Computational Thermodynamics Analysis of Vaporizing Fuel Droplets in the Human Upper Airways

    Science.gov (United States)

    Zhang, Zhe; Kleinstreuer, Clement

    The detailed knowledge of air flow structures as well as particle transport and deposition in the human lung for typical inhalation flow rates is an important precursor for dosimetry-and-health-effect studies of toxic particles as well as for targeted drug delivery of therapeutic aerosols. Focusing on highly toxic JP-8 fuel aerosols, 3-D airflow and fluid-particle thermodynamics in a human upper airway model starting from mouth to Generation G3 (G0 is the trachea) are simulated using a user-enhanced and experimentally validated finite-volume code. The temperature distributions and their effects on airflow structures, fuel vapor deposition and droplet motion/evaporation are discussed. The computational results show that the thermal effect on vapor deposition is minor, but it may greatly affect droplet deposition in human airways.

  17. Lipid droplets as ubiquitous fat storage organelles in C. elegans

    Directory of Open Access Journals (Sweden)

    Guo Fengli

    2010-12-01

    Full Text Available Abstract Background Lipid droplets are a class of eukaryotic cell organelles for storage of neutral fat such as triacylglycerol (TAG and cholesterol ester (CE. We and others have recently reported that lysosome-related organelles (LROs are not fat storage structures in the nematode C. elegans. We also reported the formation of enlarged lipid droplets in a class of peroxisomal fatty acid β-oxidation mutants. In the present study, we seek to provide further evidence on the organelle nature and biophysical properties of fat storage structures in wild-type and mutant C. elegans. Results In this study, we provide biochemical, histological and ultrastructural evidence of lipid droplets in wild-type and mutant C. elegans that lack lysosome related organelles (LROs. The formation of lipid droplets and the targeting of BODIPY fatty acid analogs to lipid droplets in live animals are not dependent on lysosomal trafficking or peroxisome dysfunction. However, the targeting of Nile Red to lipid droplets in live animals occurs only in mutants with defective peroxisomes. Nile Red labelled-lipid droplets are characterized by a fluorescence emission spectrum distinct from that of Nile Red labelled-LROs. Moreover, we show that the recently developed post-fix Nile Red staining method labels lipid droplets exclusively. Conclusions Our results demonstrate lipid droplets as ubiquitous fat storage organelles and provide a unified explanation for previous studies on fat labelling methods in C. elegans. These results have important applications to the studies of fat storage and lipid droplet regulation in the powerful genetic system, C. elegans.

  18. A compact and facile microfluidic droplet creation device using a piezoelectric diaphragm micropump for droplet digital PCR platforms.

    Science.gov (United States)

    Okura, Naoaki; Nakashoji, Yuta; Koshirogane, Toshihiro; Kondo, Masaki; Tanaka, Yugo; Inoue, Kohei; Hashimoto, Masahiko

    2017-10-01

    We have exploited a compact and facile microfluidic droplet creation device consisting of a poly(dimethylsiloxane) microfluidic chip possessing T-junction channel geometry, two inlet reservoirs, and one outlet reservoir, and a piezoelectric (PZT) diaphragm micropump with controller. Air was evacuated from the outlet reservoir using the PZT pump, reducing the pressure inside. The reduced pressure within the outlet reservoir pulled oil and aqueous solution preloaded in the inlet reservoirs into the microchannels, which then merged at the T-junction, successfully forming water-in-oil emulsion droplets at a rate of ∼1000 per second with minimal sample loss. We confirmed that the onset of droplet formation occurred immediately after turning on the pump (<1 s). Over repeated runs, droplet formation was highly reproducible, with droplet size purity (polydispersity, <4%) comparable to that achieved using other microfluidic droplet preparation techniques. We also demonstrated single-molecule PCR amplification in the created droplets, suggesting that the device could be used for effective droplet digital PCR platforms in most laboratories without requiring great expense, space, or time for acquiring technical skills. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Investigation and classification of spume droplets production mechanisms at hurricane winds

    Science.gov (United States)

    Troitskaya, Yuliya; Kandaurov, Alexander; Ermakova, Olga; Kozlov, Dmitry; Sergeev, Daniil; Zilitinkevich, Sergey

    2016-04-01

    Sea sprays are typical element of the marine atmospheric boundary layer of important environmental effect. There are still significant uncertainties in estimations of these effects due to insufficient knowledge on the sea spray generation function. The reason for that are difficulties of direct measurements and insufficient knowledge about the mechanisms of the spume droplet's formation. This study is concerned with the laboratory experiments for identification of mechanisms due to which a strong wind tears off water from the crest of the waves made at the high-speed wind-wave flume of IAP RAS. In order to obtain statistical data for the events on the surface, leading to the spray generation a high-speed video-filming was made using a horizontal and vertical shadow methods at rates of up to 10,000 fps in a wide range of wind speeds (20 - 35 m/s). Classification of phenomena responsible for generation of spume droplets was made. It was observed for the friction velocities from 0.8 to 1.5 m/s that the generation of the spume droplets is caused by 3 types of local phenomena: breaking of "projections" see e.g.[1], bursting of submerged bubbles [2,3] and bag breakup - it begins with increase of small-scale elevation of the surface, transforming to small "sails" then inflated to a water film bordered by a thicker rim and at last blows up, so the droplets are produced from rupture of the water film and fragmentation of the rim (the first report on the observation of a new mechanism of spume droplets', similar to bag-breakup regime was made in [4]). Statistical analysis of number of these phenomena at different winds showed that the "bag-breakup" is the major mechanism of spume droplets generation at strong and hurricane winds. Statistical distributions of observed "bags" geometrical parameters at different airflow velocities were retrieved from video-filming using specially developed software which allowed semi-automatic registering of image features. Acknowledgements

  20. Droplet Splashing by a Slingshot Mechanism

    KAUST Repository

    Thoroddsen, Sigurdur T.

    2011-01-18

    When a drop impacts onto a liquid pool, it ejects a thin horizontal sheet of liquid, which emerges from the neck region connecting the two liquid masses. The leading section of this ejecta bends down to meet the pool liquid. When the sheet touches the pool, at an “elbow,” it ruptures and sends off microdroplets by a slingshot mechanism, driven by surface tension. High-speed imaging of the splashing droplets suggests the liquid sheet is of submicron thickness, as thin as 300 nm. Experiments in partial vacuum show that air resistance plays the primary role in bending the sheet. We identify a parameter regime where this slingshot occurs and also present a simple model for the sheet evolution, capable of reproducing the overall shape.

  1. Droplet Splashing by a Slingshot Mechanism

    KAUST Repository

    Thoroddsen, Sigurdur T; Thoraval, M.-J.; Takehara, K.; Etoh, T. G.

    2011-01-01

    When a drop impacts onto a liquid pool, it ejects a thin horizontal sheet of liquid, which emerges from the neck region connecting the two liquid masses. The leading section of this ejecta bends down to meet the pool liquid. When the sheet touches the pool, at an “elbow,” it ruptures and sends off microdroplets by a slingshot mechanism, driven by surface tension. High-speed imaging of the splashing droplets suggests the liquid sheet is of submicron thickness, as thin as 300 nm. Experiments in partial vacuum show that air resistance plays the primary role in bending the sheet. We identify a parameter regime where this slingshot occurs and also present a simple model for the sheet evolution, capable of reproducing the overall shape.

  2. Interaction of Droplets Separated by an Elastic Film.

    Science.gov (United States)

    Liu, Tianshu; Xu, Xuejuan; Nadermann, Nichole; He, Zhenping; Jagota, Anand; Hui, Chung-Yuen

    2017-01-10

    The Laplace pressure of a droplet placed on one side of an elastic thin film can cause significant deformation in the form of a bulge on its opposite side. Here, we show that this deformation can be detected by other droplets suspended on the opposite side of the film, leading to interaction between droplets separated by the solid (but deformable) film. The interaction is repulsive when the drops have a large overlap and attractive when they have a small overlap. Thus, if two identical droplets are placed right on top of each other (one on either side of the thin film), they tend to repel each other, eventually reaching an equilibrium configuration where there is a small overlap. This observation can be explained by analyzing the energy landscape of the droplets interacting via an elastically deformed film. We further demonstrate this idea by designing a pattern comprising a big central drop with satellite droplets. This phenomenon can lead to techniques for directed motion of droplets confined to one side of a thin elastic membrane by manipulations on the other side.

  3. Prediction of oil droplet size distribution in agitated aquatic environments

    International Nuclear Information System (INIS)

    Khelifa, A.; Lee, K.; Hill, P.S.

    2004-01-01

    Oil spilled at sea undergoes many transformations based on physical, biological and chemical processes. Vertical dispersion is the hydrodynamic mechanism controlled by turbulent mixing due to breaking waves, vertical velocity, density gradients and other environmental factors. Spilled oil is dispersed in the water column as small oil droplets. In order to estimate the mass of an oil slick in the water column, it is necessary to know how the droplets formed. Also, the vertical dispersion and fate of oil spilled in aquatic environments can be modelled if the droplet-size distribution of the oil droplets is known. An oil spill remediation strategy can then be implemented. This paper presented a newly developed Monte Carlo model to predict droplet-size distribution due to Brownian motion, turbulence and a differential settling at equilibrium. A kinematic model was integrated into the proposed model to simulate droplet breakage. The key physical input of the model is the maximum droplet size permissible in the simulation. Laboratory studies were found to be in good agreement with field studies. 26 refs., 1 tab., 5 figs

  4. Measurement of droplet vaporization rate enhancement caused by acoustic disturbances

    Science.gov (United States)

    Anderson, T. J.; Winter, M.

    1992-10-01

    Advanced laser diagnostics are being applied to quantify droplet vaporization enhancement in the presence of acoustic fields which can lead to instability in liquid-fueled rockets. While models have been developed to describe the interactions between subcritical droplet vaporization and acoustic fields in the surrounding gases, they have not been verified experimentally. In the super critical environment of a rocket engine combustor, little is understood about how the injected fluid is distributed. Experiments in these areas have been limited because of the lack of diagnostic techniques capable of providing quantitative results. Recently, however, extremely accurate vaporization rate measurements have been performed on droplets in a subcritical environment using morphology-dependent resonances (MDR's) in which fluorescence from an individual droplet provides information about its diameter. Initial measurements on methanol droplets behind a pressure pulse with a pressure ratio of 1.2 indicated that the evaporation rate in the first few microsec after wave passage was extremely high. Subsequent measurements have been made to validate these results using MDR's acquired from similarly-sized droplets using a pulse with a 1.1 pressure ratio. A baseline measurement was also made using a non evaporative fluid under similar Weber and Reynolds number conditions. The MDR technique employed for these measurements is explained and the facilities are described. The evaporation measurement results are shown and the rates observed from different droplet materials and different wave strengths are compared.

  5. Mechanism and simulation of droplet coalescence in molten steel

    Science.gov (United States)

    Ni, Bing; Zhang, Tao; Ni, Hai-qi; Luo, Zhi-guo

    2017-11-01

    Droplet coalescence in liquid steel was carefully investigated through observations of the distribution pattern of inclusions in solidified steel samples. The process of droplet coalescence was slow, and the critical Weber number ( We) was used to evaluate the coalescence or separation of droplets. The relationship between the collision parameter and the critical We indicated whether slow coalescence or bouncing of droplets occurred. The critical We was 5.5, which means that the droplets gradually coalesce when We ≤ 5.5, whereas they bounce when We > 5.5. For the carbonate wire feeding into liquid steel, a mathematical model implementing a combined computational fluid dynamics (CFD)-discrete element method (DEM) approach was developed to simulate the movement and coalescence of variably sized droplets in a bottom-argon-blowing ladle. In the CFD model, the flow field was solved on the premise that the fluid was a continuous medium. Meanwhile, the droplets were dispersed in the DEM model, and the coalescence criterion of the particles was added to simulate the collision- coalescence process of the particles. The numerical simulation results and observations of inclusion coalescence in steel samples are consistent.

  6. Computational/experimental studies of isolated, single component droplet combustion

    Science.gov (United States)

    Dryer, Frederick L.

    1993-01-01

    Isolated droplet combustion processes have been the subject of extensive experimental and theoretical investigations for nearly 40 years. The gross features of droplet burning are qualitatively embodied by simple theories and are relatively well understood. However, there remain significant aspects of droplet burning, particularly its dynamics, for which additional basic knowledge is needed for thorough interpretations and quantitative explanations of transient phenomena. Spherically-symmetric droplet combustion, which can only be approximated under conditions of both low Reynolds and Grashof numbers, represents the simplest geometrical configuration in which to study the coupled chemical/transport processes inherent within non-premixed flames. The research summarized here, concerns recent results on isolated, single component, droplet combustion under microgravity conditions, a program pursued jointly with F.A. Williams of the University of California, San Diego. The overall program involves developing and applying experimental methods to study the burning of isolated, single component droplets, in various atmospheres, primarily at atmospheric pressure and below, in both drop towers and aboard space-based platforms such as the Space Shuttle or Space Station. Both computational methods and asymptotic methods, the latter pursued mainly at UCSD, are used in developing the experimental test matrix, in analyzing results, and for extending theoretical understanding. Methanol, and the normal alkanes, n-heptane, and n-decane, have been selected as test fuels to study time-dependent droplet burning phenomena. The following sections summarizes the Princeton efforts on this program, describe work in progress, and briefly delineate future research directions.

  7. Evaluation method for radiative heat transfer in polydisperse water droplets

    International Nuclear Information System (INIS)

    Maruyama, Shigenao; Nakai, Hirotaka; Sakurai, Atsushi; Komiya, Atsuki

    2008-01-01

    Simplifications of the model for nongray radiative heat transfer analysis in participating media comprised of polydisperse water droplets are presented. Databases of the radiative properties for a water droplet over a wide range of wavelengths and diameters are constructed using rigorous Mie theory. The accuracy of the radiative properties obtained from the database interpolation is validated by comparing them with those obtained from the Mie calculations. The radiative properties of polydisperse water droplets are compared with those of monodisperse water droplets with equivalent mean diameters. Nongray radiative heat transfer in the anisotropic scattering fog layer, including direct and diffuse solar irradiations and infrared sky flux, is analyzed using REM 2 . The radiative heat fluxes within the fog layer containing polydisperse water droplets are compared with those in the layer containing monodisperse water droplets. Through numerical simulation of the radiative heat transfer, polydisperse water droplets can be approximated by using the Sauter diameter, a technique that can be useful in several research fields, such as engineering and atmospheric science. Although this approximation is valid in the case of pure radiative transfer problems, the Sauter diameter is reconfirmed to be the appropriate diameter for approximating problems in radiative heat transfer, although volume-length mean diameter shows better accordance in some cases. The CPU time for nongray radiative heat transfer analysis with a fog model is evaluated. It is proved that the CPU time is decreased by using the databases and the approximation method for polydisperse particulate media

  8. Numerical study of droplet impact and rebound on superhydrophobic surface

    Science.gov (United States)

    Cai, Xuan; Wu, Yanchen; Woerner, Martin; Frohnapfel, Bettina

    2017-11-01

    Droplet impact and rebound on superhydrophobic surface is an important process in many applications; among them are developing self-cleaning or anti-icing materials and limiting liquid film formation of Diesel Exhaust Fluid (DEF) in exhaust gas pipe. In the latter field, rebound of DEF droplet from wall is desired as an effective mean for avoiding or reducing unwanted solid deposition. Our goal is to numerically study influence of surface wettability on DEF droplet impact and rebound behavior. A phase-field method is chosen, which was implemented in OpenFOAM by us and validated for wetting-related interfacial flow problems. In the present contribution we first numerically reproduce relevant experimental studies in literature, to validate the code for droplet impact and rebound problem. There we study droplet-surface contact time, maximum/instantaneous spreading factor and droplet shape evolution. Our numerical results show good agreement with experimental data. Next we investigate for DEF droplets the effects of diameter, impact velocity and surface wettability on rebound behavior and jumping height. Based on Weber number and equilibrium contact angle, two regimes are identified. We show that surface wettability is a deciding factor for achieving rebound event. This work is supported by Foundation ``Friedrich-und-Elisabeth Boysen Stiftung fuer Forschung und Innovation'' (BOY-127-TP1).

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

    International Nuclear Information System (INIS)

    Fujisawa, Nobuyuki; Yamagata, Takayuki; Takano, Shotaro; Saito, Kengo; Morita, Ryo; Fujiwara, Kazutoshi; Inada, Fumio

    2015-01-01

    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

  10. Recent Advances In Science Support For Isolated Droplet Combustion Experiments

    Science.gov (United States)

    Dryer, F. L.; Kazakov, A.; Urban, B. D.; Kroenlein, K.

    2003-01-01

    In a joint program involving Prof. F.A. Williams of the University of California, San Diego and Dr. V. Nayagam of the National Center for Microgravity Research, the combustion characteristics of isolated liquid fuel droplets of n-heptane, n-decane, methanol, methanol-water, ethanol and ethanol-water having initial diameters between about 1 mm and 6 mm continues to be investigated. The objectives of the work are to improve fundamental knowledge of droplet combustion dynamics for pure fuels and fuel-water mixtures through microgravity experiments and theoretical analyses. The Princeton contributions support the engineering design, data analysis, and data interpretation requirements for the study of initially single component, spherically symmetric, isolated droplet combustion studies through experiments and numerical modeling. UCSD contributions are described in a companion communication in this conference. The Princeton effort also addresses the analyses of Fiber Supported Droplet Combustion (FSDC) experiments conducted with the above fuels and collaborative work with others who are investigating droplet combustion in the presence of steady convection. A thorough interpretation of droplet burning behavior for n-heptane and n-decane over a relatively wide range of conditions also involves the influences of sooting on the combustion behavior, and this particular aspect on isolated burning of droplets is under consideration in a collaborative program underway with Drexel University. This collaboration is addressed in another communication at this conference. The one-dimensional, time-dependent, numerical modeling approach that we have continued to evolve for analyzing isolated, quiescent droplet combustion data has been further applied to investigate several facets of isolated droplet burning of simple alcohols, n-heptane, and n-decane. Some of the new results are described below.

  11. Quantum dissipative dynamics and decoherence of dimers on helium droplets

    International Nuclear Information System (INIS)

    Schlesinger, Martin

    2011-01-01

    In this thesis, quantum dynamical simulations are performed in order to describe the vibrational motion of diatomic molecules in a highly quantum environment, so-called helium droplets. We aim to reproduce and explain experimental findings which were obtained from dimers on helium droplets. Nanometer-sized helium droplets contain several thousands of 4 He atoms. They serve as a host for embedded atoms or molecules and provide an ultracold ''refrigerator'' for them. Spectroscopy of molecules in or on these droplets reveals information on both the molecule and the helium environment. The droplets are known to be in the superfluid He II phase. Superfluidity in nanoscale systems is a steadily growing field of research. Spectra obtained from full quantum simulations for the unperturbed dimer show deviations from measurements with dimers on helium droplets. These deviations result from the influence of the helium environment on the dimer dynamics. In this work, a well-established quantum optical master equation is used in order to describe the dimer dynamics effectively. The master equation allows to describe damping fully quantum mechanically. By employing that equation in the quantum dynamical simulation, one can study the role of dissipation and decoherence in dimers on helium droplets. The effective description allows to explain experiments with Rb 2 dimers on helium droplets. Here, we identify vibrational damping and associated decoherence as the main explanation for the experimental results. The relation between decoherence and dissipation in Morse-like systems at zero temperature is studied in more detail. The dissipative model is also used to investigate experiments with K 2 dimers on helium droplets. However, by comparing numerical simulations with experimental data, one finds that further mechanisms are active. Here, a good agreement is obtained through accounting for rapid desorption of dimers. We find that decoherence occurs in the electronic manifold of the

  12. Transport of expiratory droplets in an aircraft cabin.

    Science.gov (United States)

    Gupta, Jitendra K; Lin, Chao-Hsin; Chen, Qingyan

    2011-02-01

    The droplets exhaled by an index patient with infectious disease such as influenza or tuberculosis may be the carriers of contagious agents. Indoor environments such as the airliner cabins may be susceptible to infection from such airborne contagious agents. The present investigation computed the transport of the droplets exhaled by the index patient seated in the middle of a seven-row, twin-aisle, fully occupied cabin using the CFD simulations. The droplets exhaled were from a single cough, a single breath, and a 15-s talk of the index patient. The expiratory droplets were tracked by using Lagrangian method, and their evaporation was modeled. It was found that the bulk airflow pattern in the cabin played the most important role on the droplet transport. The droplets were contained in the row before, at, and after the index patient within 30 s and dispersed uniformly to all the seven rows in 4 minutes. The total airborne droplet fraction reduced to 48, 32, 20, and 12% after they entered the cabin for 1, 2, 3, and 4 min, respectively, because of the ventilation from the environmental control system. It is critical to predict the risk of airborne infection to take appropriate measures to control and mitigate the risk. Most of the studies in past either assume a homogenous distribution of contaminants or use steady-state conditions. The present study instead provides information on the transient movement of the droplets exhaled by an index passenger in an aircraft cabin. These droplets may contain active contagious agents and can be potent enough to cause infection. The findings can be used by medical professionals to estimate the spatial and temporal distribution of risk of infection to various passengers in the cabin. © 2010 John Wiley & Sons A/S.

  13. 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.

  14. Sectorial oscillation of acoustically levitated nanoparticle-coated droplet

    Science.gov (United States)

    Zang, Duyang; Chen, Zhen; Geng, Xingguo

    2016-01-01

    We have investigated the dynamics of a third mode sectorial oscillation of nanoparticle-coated droplets using acoustic levitation in combination with active modulation. The presence of nanoparticles at the droplet surface changes its oscillation amplitude and frequency. A model linking the interfacial rheology and oscillation dynamics has been proposed in which the compression modulus ɛ of the particle layer is introduced into the analysis. The ɛ obtained with the model is in good agreement with that obtained by the Wilhelmy plate approach, highlighting the important role of interfacial rheological properties in the sectorial oscillation of droplets.

  15. Structural morphology of acoustically levitated and heated nanosilica droplet

    International Nuclear Information System (INIS)

    Kumar, Ranganathan; Tijerino, Erick; Saha, Abhishek; Basu, Saptarshi

    2010-01-01

    We study the vaporization and precipitation dynamics of a nanosilica encapsulated water droplet by levitating it acoustically and heating it with a CO 2 laser. For all concentrations, we observe three phases: solvent evaporation, surface agglomeration, and precipitation leading to bowl or ring shaped structures. At higher concentrations, ring reorientation and rotation are seen consistently. The surface temperature from an infrared camera is seen to be dependent on the final geometrical shape of the droplet and its rotation induced by the acoustic field of the levitator. With nonuniform particle distribution, these structures can experience rupture which modifies the droplet rotational speed.

  16. The behavior of volatile droplets in a controlled atmosphere

    International Nuclear Information System (INIS)

    Perrault, Gerard

    1971-01-01

    A technique permitting constant temperature and atmospheric composition to be obtained in a few minutes in a closed container allowed the equilibrium, evaporation and growth of several types of droplets to be studied. A critical review is presented on the thermodynamics of equilibria and the kinetics of evaporation and growth in the different cases. Fair agreement was reached between theory and experiment. Coefficients of evaporation, condensation, and accommodation were calculated for water and water-ClNa droplets; the theory is extended to a few particular cases of droplets containing two volatile constituents. (author) [fr

  17. Polarizability of Fluid Droplets and the Kerr Effect on Microemulsions

    CERN Document Server

    Lisy, V

    2001-01-01

    Spheroidal fluid droplets immersed in another fluid and thermally fluctuating in the shape are considered. The polarizability of the droplet is evaluated up to the second order in the fluctuation amplitudes. The correlation functions of the polarizability tensor components are found and used to describe the polarized and depolarized scattering of light, and the Kerr effect on microemulsions. By comparison of the theoretical results with the Kerr constant measurements from the literature, we estimate the bending rigidity of the surfactant monolayer that separates the oil and water phases in droplet microemulsions.

  18. Nanospiral Formation by Droplet Drying: One Molecule at a Time

    Directory of Open Access Journals (Sweden)

    Wan Lei

    2011-01-01

    Full Text Available Abstract We have created nanospirals by self-assembly during droplet evaporation. The nanospirals, 60–70 nm in diameter, formed when solvent mixtures of methanol and m-cresol were used. In contrast, spin coating using only methanol as the solvent produced epitaxial films of stripe nanopatterns and using only m-cresol disordered structure. Due to the disparity in vapor pressure between the two solvents, droplets of m-cresol solution remaining on the substrate serve as templates for the self-assembly of carboxylic acid molecules, which in turn allows the visualization of solution droplet evaporation one molecule at a time.

  19. Towards a high throughput droplet-based agglutination assay

    KAUST Repository

    Kodzius, Rimantas; Castro, David; Foulds, Ian G.

    2013-01-01

    This work demonstrates the detection method for a high throughput droplet based agglutination assay system. Using simple hydrodynamic forces to mix and aggregate functionalized microbeads we avoid the need to use magnetic assistance or mixing structures. The concentration of our target molecules was estimated by agglutination strength, obtained through optical image analysis. Agglutination in droplets was performed with flow rates of 150 µl/min and occurred in under a minute, with potential to perform high-throughput measurements. The lowest target concentration detected in droplet microfluidics was 0.17 nM, which is three orders of magnitude more sensitive than a conventional card based agglutination assay.

  20. An experimental study on suspended sodium droplet combustion (2)

    International Nuclear Information System (INIS)

    Sato, Kenji

    2004-03-01

    As part of studies for phenomenological investigation of sodium droplet burning behavior, in our previous experimental studies for suspended single sodium droplet, behavior of ignition process and succeeding combustion, ignition delay time, and droplet temperature history had been investigated. In the present study, by using 4 mm diam. suspended sodium droplet, combustion experiments were performed for extended free-stream velocity range of dry air up to 200 cm/s, and for the initial droplet temperature T i =300degC and 400degC, and the effects of the free-stream velocity and initial droplet temperature on the ignition/burning behavior and ignition delay time were examined by using high speed video camera. The obtained experimental results are as follows: (1) Ignition phenomena of suspended spherical shape droplet were observed for all examined experimental conductions except the case of free-stream velocity U=200 cm/s at 300degC, where detachment of droplet from the support due to strained oxide film occurred. (2) The ignition delay time defined as the time to evolution of orange-light emitting zone or flame zone decreases with the increase of the free-stream velocity or of initial droplet temperature. Examples of typical ignition delay time are 0.68 s at U=20 cm/s, 0.52 s at U=100 cm/s, and 0.37 s at 200 cm/s for T i =400degC. (3) The orange-light emission at the moment of ignition occurs simultaneously over whole surface except the top region of the droplet. The intensity of the emission at the moment of ignition takes its maximum at the bottom region or upstream region of the droplet, and the emission intensity during the stable burning period increases with the increase of U. (4) When T i is 300degC, formation of temporal multiple short projections are observed before ignition for all examined free-stream velocities. The projections often do not disappear before ignition when the velocity is relatively high. (5) The layer or cloud composed of aerosol is formed

  1. 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.

  2. Towards a high throughput droplet-based agglutination assay

    KAUST Repository

    Kodzius, Rimantas

    2013-10-22

    This work demonstrates the detection method for a high throughput droplet based agglutination assay system. Using simple hydrodynamic forces to mix and aggregate functionalized microbeads we avoid the need to use magnetic assistance or mixing structures. The concentration of our target molecules was estimated by agglutination strength, obtained through optical image analysis. Agglutination in droplets was performed with flow rates of 150 µl/min and occurred in under a minute, with potential to perform high-throughput measurements. The lowest target concentration detected in droplet microfluidics was 0.17 nM, which is three orders of magnitude more sensitive than a conventional card based agglutination assay.

  3. Interaction mechanisms between ceramic particles and atomized metallic droplets

    Science.gov (United States)

    Wu, Yue; Lavernia, Enrique J.

    1992-10-01

    The present study was undertaken to provide insight into the dynamic interactions that occur when ceramic particles are placed in intimate contact with a metallic matrix undergoing a phase change. To that effect, Al-4 wt pct Si/SiCp composite droplets were synthesized using a spray atomization and coinjection approach, and their solidification microstructures were studied both qualitatively and quantitatively. The present results show that SiC particles (SiCp) were incor- porated into the matrix and that the extent of incorporation depends on the solidification con- dition of the droplets at the moment of SiC particle injection. Two factors were found to affect the distribution and volume fraction of SiC particles in droplets: the penetration of particles into droplets and the entrapment and/or rejection of particles by the solidification front. First, during coinjection, particles collide with the atomized droplets with three possible results: they may penetrate the droplets, adhere to the droplet surface, or bounce back after impact. The extent of penetration of SiC particles into droplets was noted to depend on the kinetic energy of the particles and the magnitude of the surface energy change in the droplets that occurs upon impact. In liquid droplets, the extent of penetration of SiC particles was shown to depend on the changes in surface energy, ΔEs, experienced by the droplets. Accordingly, large SiC particles encoun- tered more resistance to penetration relative to small ones. In solid droplets, the penetration of SiC particles was correlated with the dynamic pressure exerted by the SiC particles on the droplets during impact and the depth of the ensuing crater. The results showed that no pene- tration was possible in such droplets. Second, once SiC particles have penetrated droplets, their final location in the microstructure is governed by their interactions with the solidification front. As a result of these interactions, both entrapment and rejection of

  4. Fluid Flow and Mixing Induced by AC Continuous Electrowetting of Liquid Metal Droplet

    Directory of Open Access Journals (Sweden)

    Qingming Hu

    2017-04-01

    Full Text Available In this work, we proposed a novel design of a microfluidic mixer utilizing the amplified Marangoni chaotic advection induced by alternating current (AC continuous electrowetting of a metal droplet situated in electrolyte solution, due to the linear and quadratic voltage-dependence of flow velocity at small or large voltages, respectively. Unlike previous researchers exploiting the unidirectional surface stress with direct current (DC bias at droplet/medium interface for pumping of electrolytes where the resulting flow rate is linearly proportional to the field intensity, dominance of another kind of dipolar flow pattern caused by local Marangoni stress at the drop surface in a sufficiently intense AC electric field is demonstrated by both theoretical analysis and experimental observation, which exhibits a quadratic growth trend as a function of the applied voltage. The dipolar shear stress merely appears at larger voltages and greatly enhances the mixing performance by inducing chaotic advection between the neighboring laminar flow. The mixer design developed herein, on the basis of amplified Marangoni chaotic advection around a liquid metal droplet at larger AC voltages, has great potential for chemical reaction and microelectromechanical systems (MEMS actuator applications because of generating high-throughput and excellent mixing performance at the same time.

  5. CFD Lagrangian Modeling of Water Droplet Transport for ISS Hygiene Activity Application

    Science.gov (United States)

    Son, Chang H.

    2013-01-01

    The goal of this study was to assess the impacts of free water propagation in the Waste and Hygiene Compartment (WHC) installed in Node 3. Free water can be generated inside the WHC in small quantities due to crew hygiene activity. To mitigate potential impact of free water in Node 3 cabin the WHC doorway is enclosed by a waterproof bump-out, Kabin, with openings at the top and bottom. At the overhead side of the rack, there is a screen that prevents large drops of water from exiting. However, as the avionics fan in the WHC causes airflow toward the deck side of the rack, small quantities of free water may exit at the bottom of the Kabin. A Computational Fluid Dynamics (CFD) analysis of Node 3 cabin airflow enable identifying the paths of water transport. To simulate the droplet transport the Lagrangian discrete phase approach was used. Various initial droplet distributions were considered in the study. The droplet diameter was varied in the range of 5-20 mm. The results of the computations showed that most of the drops fall to the rack surface not far from the WHC curtain.

  6. Behavior of the polygonal HEPA filter exposed to water droplets carried by the offgas flow

    International Nuclear Information System (INIS)

    Jannakos, K.; Potgeter, G.; Legner, W.

    1991-01-01

    A polygonal high-efficiency particulate air (HEPA) filter element has been developed and tested with a view to cleaning the dissolver offgas from reprocessing plants. It is likewise suited to filter process offgases generated in other plants. Due to its high dew point (about 30 degree C) the dissolver offgas, before being directed into the HEPA filter, is heated with a gas heater to approx. 100 degree C so that condensation in the pipework upstream of the filter and in the filter proper is avoided. In case of failure of the heater the offgas may undergo condensation upstream of the HEPA filter until it is bypassed to a standby heater or a standby filter system. Consequently, the filter may be loaded with water droplets. therefore, experiments have been performed with a view to estimating the behavior of the polygonal filter element when exposed to condensate droplets in a real plant. According to the experiments performed so far it can be anticipated that in case of failure of the heater the amount of condensate produced until bypassing to a standby system will not damage a new or little loaded polygonal filter element. The experiments will be carried on with the goal of investigating the behavior of a heavily loaded polygonal filter element exposed to water droplets

  7. Sizing of single evaporating droplet with Near-Forward Elastic Scattering Spectroscopy

    Science.gov (United States)

    Woźniak, M.; Jakubczyk, D.; Derkachov, G.; Archer, J.

    2017-11-01

    We have developed an optical setup and related numerical models to study evolution of single evaporating micro-droplets by analysis of their spectral properties. Our approach combines the advantages of the electrodynamic trapping with the broadband spectral analysis with the supercontinuum laser illumination. The elastically scattered light within the spectral range of 500-900 nm is observed by a spectrometer placed at the near-forward scattering angles between 4.3 ° and 16.2 ° and compared with the numerically generated lookup table of the broadband Mie scattering. Our solution has been successfully applied to infer the size evolution of the evaporating droplets of pure liquids (diethylene and ethylene glycol) and suspensions of nanoparticles (silica and gold nanoparticles in diethylene glycol), with maximal accuracy of ± 25 nm. The obtained results have been compared with the previously developed sizing techniques: (i) based on the analysis of the Mie scattering images - the Mie Scattering Lookup Table Method and (ii) the droplet weighting. Our approach provides possibility to handle levitating objects with much larger size range (radius from 0.5 μm to 30 μm) than with the use of optical tweezers (typically radius below 8 μm) and analyse them with much wider spectral range than with commonly used LED sources.

  8. Encapsulation of Single Nanoparticle in Fast-Evaporating Micro-droplets Prevents Particle Agglomeration in Nanocomposites.

    Science.gov (United States)

    Pan, Ming; Shi, Xinjian; Lyu, Fengjiao; Levy-Wendt, Ben Louis; Zheng, Xiaolin; Tang, Sindy K Y

    2017-08-09

    This work describes the use of fast-evaporating micro-droplets to finely disperse nanoparticles (NPs) in a polymer matrix for the fabrication of nanocomposites. Agglomeration of particles is a key obstacle for broad applications of nanocomposites. The classical approach to ensure the dispersibility of NPs is to modify the surface chemistry of NPs with ligands. The surface properties of NPs are inevitably altered, however. To overcome the trade-off between dispersibility and surface-functionality of NPs, we develop a new approach by dispersing NPs in a volatile solvent, followed by mixing with uncured polymer precursors to form micro-droplet emulsions. Most of these micro-droplets contain no more than one NP per drop, and they evaporate rapidly to prevent the agglomeration of NPs during the polymer curing process. As a proof of concept, we demonstrate the design and fabrication of TiO 2 NP@PDMS nanocomposites for solar fuel generation reactions with high photocatalytic efficiency and recyclability arising from the fine dispersion of TiO 2 . Our simple method eliminates the need for surface functionalization of NPs. Our approach is applicable to prepare nanocomposites comprising a wide range of polymers embedded with NPs of different composition, sizes, and shapes. It has the potential for creating nanocomposites with novel functions.

  9. Temporal and spatial effects of ablation plume on number density distribution of droplets in an aerosol measured by laser-induced breakdown

    International Nuclear Information System (INIS)

    Yashiro, H.; Kakehata, M.

    2013-01-01

    We proposed and experimentally demonstrated a novel method of evaluating the number density of droplets in an aerosol by laser-induced breakdown. The number density of droplets is evaluated from the volume in which the laser intensity exceeds the breakdown threshold intensity for droplets, and the number of droplets in this volume, which is evaluated by the experimentally observed breakdown probability. This measurement method requires a large number of laser shots for not only precise measurement but also highly temporally and spatially resolved density distribution in aerosol. Laser ablation plumes ejected from liquid droplets generated by breakdown disturb the density around the measurement points. Therefore, the recovery time of the density determines the maximum repetition rate of the probe laser irradiating a fixed point. The expansion range of the ablation plume determines the minimum distance at which the measurement points are unaffected by a neighboring breakdown when multiple laser beams are simultaneously irradiated. These laser irradiation procedures enable the measurement of the number density distribution of droplets in an aerosol at a large number of points within a short measurement time.

  10. Temporal and spatial effects of ablation plume on number density distribution of droplets in an aerosol measured by laser-induced breakdown

    Energy Technology Data Exchange (ETDEWEB)

    Yashiro, H.; Kakehata, M. [Electronics and Photonics Research Institute (ESPRIT), National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan)

    2013-05-07

    We proposed and experimentally demonstrated a novel method of evaluating the number density of droplets in an aerosol by laser-induced breakdown. The number density of droplets is evaluated from the volume in which the laser intensity exceeds the breakdown threshold intensity for droplets, and the number of droplets in this volume, which is evaluated by the experimentally observed breakdown probability. This measurement method requires a large number of laser shots for not only precise measurement but also highly temporally and spatially resolved density distribution in aerosol. Laser ablation plumes ejected from liquid droplets generated by breakdown disturb the density around the measurement points. Therefore, the recovery time of the density determines the maximum repetition rate of the probe laser irradiating a fixed point. The expansion range of the ablation plume determines the minimum distance at which the measurement points are unaffected by a neighboring breakdown when multiple laser beams are simultaneously irradiated. These laser irradiation procedures enable the measurement of the number density distribution of droplets in an aerosol at a large number of points within a short measurement time.

  11. Study on pipe wastage mechanism by liquid droplet impingement erosion

    International Nuclear Information System (INIS)

    Higashi, Yuma; Narabayashi, Tadashi; Shimazu, Yoichiro; Tsuji, Masashi; Ohmori, Shuichi; Mori, Michitsugu; Tezuka, Kenichi

    2009-01-01

    Evaluation of wastage speed for nuclear power plant maintains plant reliability and power up rating is important. There are two main cause of wastage flow accelerated corrosion (FAC) and mechanical erosion. This study is to develop evaluating the wastage speed by liquid droplet impingement erosion (LDIE). LDIE often occurs at downstream of corner of pipe or orifice. In this study, the liquid drop impinging tests were conducted with the test pieces mounted on a high speed rotating disk that cross thin water down jet and produced LDIE phenomena. The amount of the wastage by LDIE was evaluated by changing the rotational speed, the impingement frequency, and test piece materials. In addition, the generation mechanism of erosion was investigated by observing the surface of the test piece with a microscope. There is a method of evaluating by the mass difference before and after experiments. But this method is not correct because error becomes larger for mass measurement in the experiment, for the lost mass by LDIE is very little amount. Therefore, the method was developed to measure the volume in the erosion part. In this method, depth of LDIE was measured by the accuracy of ±0.01μm; therefore accurate measurement of the wastage can be improved. (author)

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

    International Nuclear Information System (INIS)

    Alger, T.W.

    1978-01-01

    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 μm and a nominal mass-mean droplet diameter of 2.4 μm. 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 μm, which are approximately equal to the maximum stable droplet diameters within the nozzle jet flow

  13. 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.

  14. AC electric field induced droplet deformation in a microfluidic T-junction.

    Science.gov (United States)

    Xi, Heng-Dong; Guo, Wei; Leniart, Michael; Chong, Zhuang Zhi; Tan, Say Hwa

    2016-08-02

    We present for the first time an experimental study on the droplet deformation induced by an AC electric field in droplet-based microfluidics. It is found that the deformation of the droplets becomes stronger with increasing electric field intensity and frequency. The measured electric field intensity dependence of the droplet deformation is consistent with an early theoretical prediction for stationary droplets. We also proposed a simple equivalent circuit model to account for the frequency dependence of the droplet deformation. The model well explains our experimental observations. In addition, we found that the droplets can be deformed repeatedly by applying an amplitude modulation (AM) signal.

  15. Three-axis acoustic device for levitation of droplets in an open gas stream and its application to examine sulfur dioxide absorption by water droplets.

    Science.gov (United States)

    Stephens, Terrance L; Budwig, Ralph S

    2007-01-01

    Two acoustic devices to stabilize a droplet in an open gas stream (single-axis and three-axis levitators) have been designed and tested. The gas stream was provided by a jet apparatus with a 64 mm exit diameter and a uniform velocity profile. The acoustic source used was a Langevin vibrator with a concave reflector. The single-axis levitator relied primarily on the radial force from the acoustic field and was shown to be limited because of significant droplet wandering. The three-axis levitator relied on a combination of the axial and radial forces. The three-axis levitator was applied to examine droplet deformation and circulation and to investigate the uptake of SO(2) from the gas stream to the droplet. Droplets ranging in diameters from 2 to 5 mm were levitated in gas streams with velocities up to 9 ms. Droplet wandering was on the order of a half droplet diameter for a 3 mm diameter droplet. Droplet circulation ranged from the predicted Hadamard-Rybczynski pattern to a rotating droplet pattern. Droplet pH over a central volume of the droplet was measured by planar laser induced fluorescence. The results for the decay of droplet pH versus time are in general agreement with published theory and experiments.

  16. Droplet deposition above a quench front during reflood after a large break LOCA

    International Nuclear Information System (INIS)

    Lee, R.

    1982-01-01

    Droplet deposition or migration towards the wall in a dispersed flow has been the subject of many investigations due to its industrial applications such as combustion of sprays of liquid fuel, evaporators, spray cooling, nuclear reactors, etc. Dispersed flow is characterized by high void and hence low droplet concentration and the theoretical study of droplet deposition is the treatment of a single droplet trajectory in the dispersed. As the droplet is travelling towards the wall, whether it will eventually be deposited on the wall or not, will be determined by the competing forces acting on it and by the boundary layer it is traversing through towards the wall. The mechanism of droplet deposition will be examined. The prediction of the boundary layer thickness will take into account the droplet size and density difference between the fluid and the droplet. Given the condition above the quench front, the minimum lateral velocity required for droplet deposition could be determined as a function of droplet diameter

  17. Transport mechanism of an initially spherical droplet on a combined hydrophilic/hydrophobic surface

    Energy Technology Data Exchange (ETDEWEB)

    Myong, Hyon Kook; Kwon, Young Hoo [Dept. of Mechanical Engineering, Kookmin University, Seoul (Korea, Republic of)

    2015-11-15

    Fluid transport is a key issue in the development of microfluidic systems. Recently, Myong (2014) has proposed a new concept for droplet transport without external power sources, and numerically validated the results for a hypothetical 2D shape, initially having a hemicylindrical droplet shape. Myong and Kwon (2015) have also examined the transport mechanism for an actual water droplet, initially having a 3D hemispherical shape, on a horizontal hydrophilic/hydrophobic surface, based on the numerical results of the time evolution of the droplet shape, as well as the total kinetic, gravitational, pressure and surface free energies inside the droplet. In this study, a 3D numerical analysis of an initially spherical droplet is carried out to establish a new concept for droplet transport. Further, the transport mechanism of an actual water droplet is examined in detail from the viewpoint of the capillarity force imbalance through the numerical results of droplet shape and various energies inside the droplet.

  18. Modeling of droplet dynamic and thermal behaviour during spray ...

    Indian Academy of Sciences (India)

    Unknown

    Supersonic atomization; droplets; thermal history; solid fraction; secondary dendrite arm spacing. 1. Introduction .... velocity with distance as illustrated in (1) (Eon-Sik Lee and Ahn ...... Uhlenwinkel and U Fritsching (Bremen, Germany: Univer-.

  19. Novel mixing method for cross linker introduction into droplet emulsions

    CSIR Research Space (South Africa)

    Land, KJ

    2013-10-01

    Full Text Available the introduction of cross linker after droplet formation, together with the utilisation of topological microfluidic channel structures, allowing for the novel manufacture of particles. Flow over these structures has been simulated in order to choose the most...

  20. Growth Kinetics of the Homogeneously Nucleated Water Droplets: Simulation Results

    International Nuclear Information System (INIS)

    Mokshin, Anatolii V; Galimzyanov, Bulat N

    2012-01-01

    The growth of homogeneously nucleated droplets in water vapor at the fixed temperatures T = 273, 283, 293, 303, 313, 323, 333, 343, 353, 363 and 373 K (the pressure p = 1 atm.) is investigated on the basis of the coarse-grained molecular dynamics simulation data with the mW-model. The treatment of simulation results is performed by means of the statistical method within the mean-first-passage-time approach, where the reaction coordinate is associated with the largest droplet size. It is found that the water droplet growth is characterized by the next features: (i) the rescaled growth law is unified at all the considered temperatures and (ii) the droplet growth evolves with acceleration and follows the power law.