Droplet Phase Research Articles

Preparation of oil-in-water core-sheath nanofibers through emulsion electrospinning for phase change temperature regulation

In the present work, the phase change material dodecanol (DD) and the polymer polyvinyl alcohol (PVA) was used as the oil phase and water phase, respectively, to prepare the oil-in-water (O/W) core-sheath structured nanofibers. The forming mechanism of the core-sheath structure of O/W emulsion electrospun nanofibers has been studied. During emulsion electrospinning, the oil phase droplets are polarized, stretched, deformed and merged under the dual action of water phase and electric field force, resulting in the phase separation within jet to form core-sheath structured fibers. Then, the influences of the contents of water phase and oil phase materials on the fiber structures and phase change performances were explored. With a water phase content ≥10 wt% and an oil phase content ≤8 wt%, the fibers can exhibit an obvious core-sheath structure. It was shown that the nanofibers prepared using 10 wt% PVA and 8 wt% DD have a phase transition enthalpy as high as 67 J/g and a good thermal cycle stability with a loss rate of melting enthalpy as low as 0.3%. The results reported would be useful for the phase change temperature regulation based on the emulsion electrospun core-sheath structured nanofibers.

Interface effects of quark matter: Light-quark nuggets and compact stars

The interface effects of quark matter play important roles in the properties of compact stars and small nuggets, such as strangelets and nonstrange quark matter ($ud\mathrm{QM}$) nuggets. By introducing a density derivative term to the Lagrangian density and adopting Thomas-Fermi approximation, we find it is possible to reproduce the results obtained by solving Dirac equations. Adopting certain parameter sets, the energy per baryon of $ud\mathrm{QM}$ nuggets decreases with baryon number $A$ and become more stable than nuclei at $A\ensuremath{\gtrsim}300$. The effects of quark matter symmetry energy are examined, where $ud\mathrm{QM}$ nuggets at $A\ensuremath{\approx}1000$ can be more stable than others if large symmetry energy is adopted. In such cases, larger $ud\mathrm{QM}$ nuggets will decay via fission and the surface of a $ud\mathrm{QM}$ star will fragment into a crust made of $ud\mathrm{QM}$ nuggets and electrons, which resembles the cases of a strange star's crust. The corresponding microscopic structures are then investigated adopting spherical and cylindrical approximations for the Wigner-Seitz cells, where the droplet phase is found to be the most stable configuration with $ud\mathrm{QM}$ stars' crusts and $ud\mathrm{QM}$ dwarfs made of $ud\mathrm{QM}$ nuggets ($A\ensuremath{\approx}1000$) and electrons. For the cases considered here, the crust thickness of $ud\mathrm{QM}$ stars is typically $\ensuremath{\sim}200\text{ }\text{ }\mathrm{m}$, which reaches a few kilometers if we neglect the interface effects and adopt Gibbs construction. The masses and radii of $ud\mathrm{QM}$ dwarfs are smaller than typical white dwarfs, which would increase if the interface effects are neglected.

Influence of phase separation microstructure on the mechanical properties of transparent modifier-free glasses

In this work, we use heat treatment to vary the size of nanoscale droplets in a phase-separated B2O3-SiO2-Al2O3-P2O5 glass without traditional modifiers and explore the effect of phase separation on the mechanical properties. The melt-quenched version of this glass already exhibits phase separation with a droplet phase rich in B2O3. The glass transition temperature (Tg) of the droplet phase is lower than that of silica-rich glass matrix. Upon heat treatment at a temperature below the Tg of the droplet phase, the size of droplets decreases but the fraction of the droplet phase increases. Consequently, the crack initiation resistance more than doubles. Upon heat treatment at the Tg of the matrix phase, the fracture toughness increases from 0.61 to 0.73 MPa·m0.5, which is primarily due to the aggregation of individual droplets. Upon the different heat treatments, the phase-separated glasses retain their optical transparency, while the hardness increases slightly.

On-site microextraction technologies for the comprehensive investigation of breath composition in lung cancer patients

Breath composition analysis is a fast and non-invasive alternative to commonly used methods of detecting lung cancer, such as biopsy. One issue in the study of breath composition is the availability of appropriate sampling and sample-preparation methods that are able to fully capture the gas and droplet phases of exhaled breath. In this article, we detail the application of a filter-incorporated needle-trap device (NTD) to capture gaseous compounds and droplets in breath samples. In addition, a thin-film microextraction method was also employed to conduct extractions from only the gas phase. In comparing the NTD (total concentration) and TFME (free concentration) results, it is possible to obtain a more comprehensive view of the sample, as this approach captures both the free and droplet-bound concentrations, which can in turn provide a better characterization of the cancer. Furthermore, the developed devices were applied for the on-site sampling of lung cancer patients. The complete interpretation of the results and their relationship to the state of the disease and patient health status requires a large cohort of patients and considerable medical expertise; therefore, this study focuses on method development and the application of the proposed device for fast and sensitive on-site detection of biomarkers in patients.

Tuning the Size of Large Dense-Core Vesicles and Quantal Neurotransmitter Release via Secretogranin II Liquid-Liquid Phase Separation.

Large dense‐core vesicles (LDCVs) are larger in volume than synaptic vesicles, and are filled with multiple neuropeptides, hormones, and neurotransmitters that participate in various physiological processes. However, little is known about the mechanism determining the size of LDCVs. Here, it is reported that secretogranin II (SgII), a vesicle matrix protein, contributes to LDCV size regulation through its liquid–liquid phase separation in neuroendocrine cells. First, SgII undergoes pH‐dependent polymerization and the polymerized SgII forms phase droplets with Ca2+ in vitro and in vivo. Further, the Ca2+‐induced SgII droplets recruit reconstituted bio‐lipids, mimicking the LDCVs biogenesis. In addition, SgII knockdown leads to significant decrease of the quantal neurotransmitter release by affecting LDCV size, which is differently rescued by SgII truncations with different degrees of phase separation. In conclusion, it is shown that SgII is a unique intravesicular matrix protein undergoing liquid–liquid phase separation, and present novel insights into how SgII determines LDCV size and the quantal neurotransmitter release.

Suppression of Liquid-Liquid Phase Separation and Aggregation of Antibodies by Modest Pressure Application.

The high colloidal stability of antibody (immunoglobulin) solutions is important for pharmaceutical applications. Inert cosolutes, excipients, are generally used in therapeutic protein formulations to minimize physical instabilities, such as liquid–liquid phase separation (LLPS), aggregation and precipitation, which are often encountered during manufacturing and storage. Despite their widespread use, a detailed understanding of how excipients modulate the specific protein‐protein interactions responsible for these instabilities is still lacking. In this work, we demonstrate the high sensitivity to pressure of globulin condensates as a suitable means to suppress LLPS and subsequent aggregation of concentrated antibody solutions. The addition of excipients has only a minor effect. The high pressure sensitivity observed is due to the fact that these flexible Y‐shaped molecules create a considerable amount of void volume in the condensed phase, leading to an overall decrease in the volume of the system upon dissociation of the droplet phase by pressure already at a few tens of to hundred bar. Moreover, we show that immunoglobulin molecules themselves are highly resistant to unfolding under pressure, and can even sustain pressures up to about 6 kbar without conformational changes. This implies that immunoglobulins are resistant to the pressure treatment of foods, such as milk, in high‐pressure food‐processing technologies, thereby preserving their immunological activity.

Copper-alumina hybrid nanofluid droplet phase change dynamics over heated plain copper and porous residue surfaces

Droplet phase change is the key phenomenon for high heat transfer rates in spray or drop-wise cooling applications. Despite high cooling efficiency of the spray cooling technology, conventional fluids, such as water, cannot be used for thermal management of modern high heat flux devices due to their immense power density, resulting in early device failures. To address this issue, in this research, we experimentally study the evaporation performance for various volumes of the copper-alumina hybrid nanofluid (CAHF) droplet on a plain copper substrate and compare it with water (H2O) droplet in sub-boiling and boiling regimes (i.e., for substrate temperatures of 25–170 °C). We also numerically investigate and compare the internal velocity and thermal fields of CAHF and H2O droplets on a heated plain copper substrate. Besides the plain copper surface, we examine the phase change behaviour of the subsequent CAHF droplet over a heated residue surface that was obtained from the phase transition of the first CAHF droplet on a heated plain copper substrate. Our results demonstrate that the evaporation rate of CAHF droplets on a plain copper surface is up to 24% and an order of magnitude higher than water droplets in sub-boiling and nucleate boiling regimes, respectively. Moreover, the evaporation rate of the CAHF droplet on a residue surface increases up to 141% and 800% compared to that on a plain copper surface in sub-boiling and nucleate boiling regimes, respectively. Furthermore, the latent heat flux up to 10 times can be achieved using the CAHF droplet compared to H2O droplet on a plain copper substrate in the nucleate boiling region, making the CAHF a potential fluid for high heat flux cooling applications.

The modeling of transient phase changes of water droplets in flue gas flow in the range of temperatures characteristic of condensing economizer technologies

Heat transfer and phase change processes of water droplets in humid air flow were investigated by performing experiments and numerical simulations of heat recovery from biofuel exhaust gas at 40–250 °C, which is characteristic for condensing heat exchangers. Compared to the experiments, the numerical investigation was performed within a wider range of boundary conditions considering droplet dispersity and flue gas parameters. The reliability of the simulation was justified through the coincidence between the calculated temperature of the equilibrium evaporation of droplets (convection heat transfer) in humid air and the wet-bulb thermometer temperature. In case of droplet combined heating (radiation and convection), the methodology was justified by coincidence between the calculated equilibrium evaporation velocity and experimental results obtained by other authors. When the temperature of radiation source is lower than 150 °C, the vapor flows calculated at the surface of the droplets in equilibrium evaporation in the cases of combined heating and convective heat transfer differs about 0.1%, therefore, the radiation influence can be neglected. Based on the results obtained in the investigation of the droplet's phase changes, the work includes practical recommendations for technological water injection to ensure optimal heat recovery from wet exhaust gas in condensing economizers.

Simulation of Separation of Salt Solution from Crude Oil in a Hydrocyclone

In this study, separating water from oil is studied numerically. In this simulation, the Reynolds Stress Model and the mixture multiphase model are used for coupling the velocity and pressure equations using the SIMPLE algorithm. The simulated geometry is taken from an experimental setup. It results that, in the case of the crude oil as the discrete phase, by increasing the diameter of the discrete phase (crude oil) droplets, the separation efficiency increases. If the diameter of the oil droplets is greater than 100 microns, the percentage of oil output from the spillway reaches 99.5%. In the case of the water phase as the discrete phase, if the water droplets size is considered equal to 200 microns, the water separation efficiency in the spillway reaches 69%.

Turbulent droplet breakage in a von Kármán flow cell

Droplet dispersion in liquid–liquid systems is a crucial step in many unit operations throughout the chemical, food, and pharmaceutic industries, where improper operation causes billions of dollars of loss annually. A theoretical background for the description of droplet breakup has been established, but many assumptions are still unconfirmed by experimental observations. In this investigation, a von Kármán swirling flow device was used to produce homogeneous, low-intensity turbulence suitable for carrying out droplet breakage experiments using optical image analysis. Individual droplets of known, adjustable, and repeatable sizes were introduced into an isotropic turbulent flow field providing novel control over two of the most important factors impacting droplet breakage: turbulence dissipation rate and parent droplet size. Introducing droplets one at a time, large data sets were gathered using canola, safflower, and sesame oils for the droplet phase and water as the continuous phase. Automated image analysis was used to determine breakage time, breakage probability, and child droplet size distribution for various turbulence intensities. Breakage time and breakage probability were observed to increase with increasing parent droplet size, consistent with the classic and widely used Coulaloglou–Tavlarides breakage model (C–T model). The shape of the child drop size distribution function was found to depend upon the size of the parent droplet.

Microemulsions; A Mini Review

The review goes into great detail about the microemulsions' characteristics, structure, kinds, theories, characterization, and applications. They may be made easily by mixing the various ingredients together without the need for special tools or circumstances. Unlike the o/w type microemulsion, which has an aqueous continuous phase and oil droplets distributed in it, the w/o type microemulsion has oil as the continuous phase and water as droplets are disseminated in it. Microemulsions are classified into four primary categories based on different phase systems, and they are often utilized in the pharmaceutical and cosmetics sectors as well as in analytical methods. The design of medicine formulations and cosmetics may benefit from having a thorough understanding of the physicochemical and biological characteristics of microemulsions.

Validation of a Two-Phase CFD Air/Mist Film Cooling Model With Experimental Details—Part II: Computational Model Validation

Abstract In this Part II of the paper, a numerical study has been performed to validate the multiphase computational fluid dynamics (CFD) model by comparing its results to the experimental data of an air/mist film cooling study presented in Part I. The complete experimental test section was simulated including all the details such as five holes, side walls effect, partially opened top wall, the conjugate bottom wall, the initial droplet distributions from the actual data, and the long boundary layer developing region upstream of the cooling holes. The effects of different particle distributions, the breakup and coalescence models, and the conjugate wall on the adiabatic film cooling effectiveness were investigated. The multiphase CFD model employs an Eulerian–Lagrangian approach. The Eulerian method is used for the continuous phase including air and water vapor, and the Lagrangian method in terms of the discrete phase model (DPM) is used to simulate the dispersed phase of liquid droplets in a continuous phase of air–water vapor mixture. The overall consistency between the computational prediction and experimental data is within 0.2% for the air-only case and 7% for the mist case. The results showed that considering the wall using the conjugate heat transfer technique significantly provided better agreement with the experimental data than without including the wall. The non-uniform particle distribution provided better agreement with the experimental results near the film cooling hole exit.

Universal Rapid Demulsification by Vacuum Suction Using Superamphiphilic and Underliquid Superamphiphobic Polyurethane/Diatomite Composites.

A process for universal rapid demulsification by vacuum suction using an as-prepared superamphiphilic and underliquid superamphiphobic polyurethane (PU)/diatomite composite has been developed and is used to demulsify kerosene-in-water and water-in-kerosene emulsions with and without a surfactant. The results show that the demulsification rate of all the emulsions exceeds 98.5% in long-term operation, with a stable demulsification speed exceeding 0.303 L/m2 min. When a superhydrophobic channel for separation is added, the oil/water separation efficiency exceeds 99.0%, and the final products are qualified oil and water. This attractive universal demulsification capability of PU/diatomite originates from its underliquid superamphiphobicity, which attracts a continuous phase to form a stable liquid film and thus repels dispersed phase droplets, which have a similar interaction with the surface but are much less abundant. The vacuum forces emulsion droplets into the microstructure of the PU/diatomite cake, where they are compressed, coalesce, and finally demulsified. This observed mechanism suggests a promising strategy to avoid the negative effects of oil fouling in demulsification and achieve large-scale universal continuous rapid demulsification.

Computational DNA Droplets Recognizing miRNA Sequence Inputs Based on Liquid–Liquid Phase Separation

AbstractPhase‐separated biomolecular droplets are formed in cells to regulate various biological processes. This phenomenon can be applied to constructing self‐assembled dynamic molecular systems such as artificial cells and molecular robots. Recently, programmable phase‐separated droplets called DNA droplets have been reported as a possible method to construct such dynamic molecular systems. This study reports a computational DNA droplet that can recognize a specific combination of tumor biomarker microRNAs (miRNAs) as molecular inputs and output a DNA logic computing result by physical DNA droplet phase separation. A mixed DNA droplet consisting of three DNA nanostructures with orthogonal sticky‐end sequences and two linker DNAs to cross‐bridge the orthogonal DNA nanostructures is proposed. By the hybridization of miRNAs with the linkers, the cross‐bridging ability is lost, causing the phase‐separation of the mixed DNA droplet into three DNA droplets, resulting in executing a miRNA pattern recognition described by a logical expression ((miRNA‐1 ∧ miRNA‐2) ∧ (miRNA‐3 ∧ ¬miRNA‐4)). This experimentally demonstrates that the computational DNA droplets recognize the above specific pattern of chemically synthesized miRNA sequences as a model experiment. In the future, this method will provide potential applications such as diagnosis and therapy with integration to biomolecular robots and artificial cells.

Effect of particle morphology on reactivity, ignition and combustion of boron powders

Spherical boron powders with 2–20 µm sized particles were prepared by ball milling commercial boron in the presence of emulsion with hexane and acetonitrile serving as the continuous and droplet phases, respectively. A small amount of Fluorel®, a fluorocarbon serving as binder was dissolved in the acetonitrile. For comparison, an irregularly-shaped boron powder was prepared by milling commercial boron with the same acetonitrile/Fluorel® solution. Reactivity of the spherical boron powders was compared to those of milled and as received commercial powders with irregularly-shaped particles. Thermo-gravimetric measurements in Ar/O2 gas flow showed that milling boron with or without Fluorel® shifts the onset of boron oxidation to lower temperatures. The rate of initial oxidation was greater for the finer spherical powders compared to coarser spheres and to irregularly shaped milled powder. The milling did not appreciably change the activation energy of oxidation of boron and the observed accelerated oxidation was attributed to its increased specific surface area. Two of the finer prepared spherical powders could be ignited when coated on an electrically heated filament in the temperature range of ca. 600 – 1000 °C. Commercial powders, irregularly-shaped milled powder, and coarser spherical powders did not ignite. All boron powders aerosolized and ignited in an enclosed vessel in air generated similar pressures. In another experiment, blended boron and potassium nitrate powders were heated to ignition in room air using a laser beam. The ignition delays for the blends made with spherical powders were substantially shorter vs. similar blends with commercial powder. Combustion of the blends with spherical powders was more vigorous than with commercial boron. Particles were ejected more rapidly, and had shorter apparent burn times.

Pickering emulsions: structure, properties and the use as colloidosomes and stimuli-responsive emulsions

Pickering emulsions are emulsions that are stabilized by solid micro- and nanoparticles. These emulsions are in most demand for applications where the use of surfactants is restricted. The review addresses stabilization of Pickering emulsions. The attention is focused on the flocculation, coalescence, sedimentation and Ostwald ripening processes taking place in these emulsions. The structures formed by particles in the emulsion dispersion medium and in thin interlayers between the dispersed phase droplets are analyzed. Methods for preparing colloidosomes, that is, microcapsules of assembled particles, from Pickering emulsions are considered. Colloidosomes are promising for the encapsulation and prolonged release of active substances. Conversely, Pickering stimuli-responsive emulsions provide intense release of encapsulated substances upon the change in the environmental parameters. This can be used not only in medicine and pharmacology, but also in sensors, food industry, paint and varnish industry, petroleum production, etc.The bibliography includes 340 references.

Potential one-pot synthesis of spherical magnesium silicate powder by mechanical milling

Synthetic magnesium silicate finds applications in adsorbents, catalysis, pharmaceuticals, foods, cosmetics, and in oil industry. This study introduces a method for potential one-pot preparation of narrowly sized, spherical magnesium silicate powders. After initial synthesis by precipitation from magnesium sulphate and sodium metasilicate solutions, the magnesium silicate precursor was ball-milled with two immiscible liquids, forming a particle-loaded emulsion. Hexane formed the continuous phase; the droplet phase was formed by either acetonitrile, methanol, or water-methanol mixtures. Suspended precursor particles were refined, their fragments became trapped in the droplets, where they were eventually compacted into composite spheres. Prepared spherical powders were characterized using scanning electron microscopy, nitrogen sorption, and low angle laser light scattering. The synthesized powders exhibited narrow size distributions with modes from 3.3 to 92 μm. The spherical powders showed an enhanced flowability and had specific surface areas comparable to or higher than the precipitated precursor powders.

Numerical simulation of fluidized bed coating process considering particle abrasion

A coupled methodology was developed to model the fluidized bed coating process considering particle abrasion. Interactions of gas phase, particle phase and droplet phase were coupled with multiphase flow. Evaporation, coating and abrasion models were involved and verified by experimental data. The coupled method was evaluated by NaCl coating cases. Under the conditions of two experimental cases, quantitative proportion of the adhered precipitation abrased from the coated particle surface was obtained, which is attributed to frequent particle collisions. Another fluidized bed coating process, in-situ preparation of the Calcium-based supported sorbent for flue gas desulfurization, was simulated to validate the coupled model and investigate the effects of operating conditions on the net coating efficiency. When the nozzle was arranged near the dense phase zone, the conditions had little effect on the efficiency. Otherwise, higher efficiency can be achieved by increasing the bed inventory, droplet diameter, and droplet initial velocity. This research offers an efficient approach for modeling of fluidized bed coating process where particle abrasion is exigent, as well as providing guidelines for practical application of in-situ desulfurizer preparation.

Spinor boson droplets stabilized by spin fluctuations

Self-trapped droplets stabilized by quantum fluctuations have been experimentally realized in dipolar gases and binary boson mixtures. In this paper, we propose spinor Bose gases as another candidate for droplet formation. For spin-1 gas, we find that spin fluctuations give a dilute but self-trapped state for two different order parameters where the mean-field picture predicts collapse. A polar droplet phase can be stabilized by spin fluctuations for both antiferromagnetic and ferromagnetic spin-dependent coupling. An antiferromagnetic droplet phase can be stabilized similarly with a negative quadratic Zeeman shift. Furthermore, the beyond mean-field energy of the system depends on the quadratic Zeeman coupling, which provides a mechanism to tune the droplet formation and its density. We discuss the parameters necessary for the experimental realization of such spinor droplets.

A geometrical criterion for the dynamic snap-off event of a non-wetting droplet in a rectangular pore–throat microchannel

In porous media, non-wetting phase droplets snapping off in a constricted microchannel are one of the most common phenomena in two-phase flow processes. In this paper, the application range of the classic quasi-static criterion in rectangular cross section microchannels is obtained. For three different droplet breakup phenomena—total breakup, partial breakup, and non-breakup—observed in experiments when a non-wetting phase droplet passes through a microchannel constriction, the breakup is caused by the droplet neck snapping off in a channel constriction. A critical criterion for the dynamic snap-off event in a two-phase flow is proposed considering the effect of viscous dissipation by mechanical analysis, energy dissipation analysis, and many microfluidic experiments. When the droplet front flows out of the constriction, snap-off will occur if the surface energy release exceeds the required energy for viscous dissipation and kinetic energy conversion. The unique partial breakup phenomenon is affected by droplet surfactant distribution and the acceleration effect in the constriction center. This partial breakup phenomenon in experiments is an essential evidence for the non-uniform distribution of surfactants in the droplet surface. The results of this study contribute to understanding pore-scale mass transfer and flow pattern changes within porous media.