Submicron Droplets Research Articles

A hydrophilic–lipophilic deviation model in formulating microemulsion for topical application

The hydrophilic–lipophilic deviation (HLD) model is firmly established in oil recovery and can be potentially applied in various other fields. In this work, the HLD concept is systematically used to prepare microemulsion for topical application using isopropyl myristate (IPM), squalane, water, mixed nonionic surfactants and magnesium ascorbyl phosphate (MAP). The clear water-in-oil (W/O) microemulsion formed spontaneously and has a consistent submicron droplet size below 30 nm. The microemulsion was characterized by particle size, electrical conductivity, electrophoretic mobility, viscosity and in vitro diffusion. The addition of one part of squalane to three parts of IPM in the oil blend prevented the percolation phenomenon and reduced the electrophoretic mobility of MAP. The inclusion of squalane to IPM in the oil phase reduced the cumulative amount of MAP permeated from the microemulsion, reduced the permeation coefficient of MAP and increased the lag time, reduced the steady-state flux and permeability coefficient as well. The microemulsion provided an alternative approach to encapsulate the water-soluble MAP in an oil matrix as a cosmetic active ingredient for the manufacture of personal care products.

Comparison between acetonitrile-water separation by betaine and betaine hydrochloride

Acetonitrile and water are miscible solvents. This study compares their separation by betaine and betaine hydrochloride. Acetonitrile is a hydrogen (H) bond acceptor and so is betaine, because of its -CO and -CO- groups. Therefore, betaine competes with acetonitrile for interactions with the hydrogens of water molecules, as indicated by attenuated total reflectance - Fourier transform infrared spectroscopy (ATR-FTIR). Therefore, when added to acetonitrile-water mixtures, betaine displaces acetonitrile. Separation into bulk phases occurs with 5–10 wt% betaine (relative to water), for acetonitrile concentrations between 50 and 80 wt% (relative to the aqueous phase). At lower acetonitrile concentrations (e.g., 1 wt%), betaine separates acetonitrile from water to yield emulsified acetonitrile droplets, detected by light scattering. With 1 wt% acetonitrile and betaine, acetonitrile droplets in water are negatively charged due to the -CO- group of betaine, as shown by electrophoretic measurements. In the case of betaine hydrochloride, the negative charge of the -CO- group is shielded by a proton, and interactions with water are weaker. As a result, bulk separation is not observed. Nonetheless, betaine hydrochloride also competes against acetonitrile for interactions with hydrogen atoms of water molecules, albeit not as effectively as betaine. This is shown by ATR-FTIR. Therefore, betaine hydrochloride emulsifies acetonitrile in water into sub-micron droplets. These droplets are positively charged, owing to the positively charged nitrogen atom of betaine hydrochloride. Acidifying mixtures of betaine, acetonitrile and water (with HCl) impedes bulk separation. This result confirms the importance of electrostatic interactions between the hydrogens of water and the unshielded, negative -CO- group of betaine.

Droplets for acoustic vaporization: Formulations, properties and applications

The Acoustic Droplet Vaporization (ADV) (1), a phase-change of the droplets core from liquid to vapor phase upon ultrasound irradiation, burst renewed interest in droplet emulsions, a traditional topic of colloidal science, opening up innovative applications in biomedicine. Droplets undergoing ADV share similar liquid cores, typically perfluorocarbons (PFCs), however, the nature of the shells can be polymeric (2) or lipidic (3, 4). Such difference imparts to phase-change droplets diverse acoustic and mechanical behaviors (5). In this contribution we present some results concerning a general strategy for the formulation of polymer or lipid shelled submicron droplets. Other key points for the use of ADV-responsive in biomedical applications will be addressed. Recently we have extended the concepts of ADV to radiation responsive droplets for dosimetry in cancer treatment with hadronic radiation. Results on this activity will be also reported (6).

Electrochemical Characterization of Neurotransmitters in a Single Submicron Droplet.

Single-entity electrochemistry, which employs electrolysis during the collision of single particles on ultramicroelectrodes, has witnessed significant advancements in recent years, enabling the observation and characterization of individual particles. Information on a single aqueous droplet (e.g., size) can also be studied based on the redox species contained therein. Dopamine, a redox-active neurotransmitter, is usually present in intracellular vesicles. Similarly, in the current study, the electrochemical properties of neurotransmitters in submicron droplets were investigated. Because dopamine oxidation is accompanied by proton transfer, unique electrochemical properties of dopamine were observed in the droplet. We also investigated the electrochemical properties of the adsorbed droplets containing DA and the detection of oxidized dopamine by the recollision phenomenon.

Cellulose nanocrystal stabilized pickering nanoemulsions and their coalescence stability studied by fluorescence microscopy

Cellulose nanocrystals (CNCs) have been used as Pickering emulsifiers by forming rigid interfacial layer coated around oil droplets. Sulfated and desulfated CNCs were used to emulsify squalane oil to produce Pickering nanoemulsions. The formation of CNCs-Pickering nanoemulsions was investigated and their stability against mechanical stresses was studied using fluorescence microscopy with a lab-made image analysis program. The formation of Pickering nanoemulsions using CNC particles was tuned by screening their surface charges with cations. Sulfated and desulfated CNC nanoemulsions showed submicron droplet size of 619 and 555 nm, respectively. The mechanical stresses could induce droplet encounter leading to physical instability. The sulfated CNCs displayed superior stability than the desulfated CNCs in terms of droplet aggregation after treatment with mechanical stresses. Fluorescence microscopy image analysis revealed the physical instability of Pickering nanoemulsions at the microscopic level, which is a useful tool for studying the destabilization mechanisms.

Experimental study on the removal of submicron droplets by fibrous filter media in a sound field

The acoustic agglomeration technology is proposed as pretreatment to effectively reduce the concentration of particles produced in the industrial process, thus to improve the filtration efficiency of subsequent filter devices. However, the removal of submicron droplets by sound waves has not yet received attention. In this paper, a new method is proposed for high-efficient filtration of submicron droplets based on sound waves. According to the entrainment mechanism of sound waves on the submicron droplets, a sound field is introduced in the filtration system to enhance the collision probability between the droplets and the fibers in filter materials. The effects of sound pressure level (SPL) and sound frequency on the droplet removal were experimentally investigated at different filtration gas velocities. The results show that there is no shift for the upstream particle size distribution, however, the downstream droplet concentration decreases when the sound field is introduced. The effect of the sound field on filtration performance is determined by the vibration amplitude and the vibration period of the droplets. In the SPL range of 130–145 dB, the improvement of the filtration performance is better with the increase of the SPL for a fixed sound frequency. In the frequency range of 500–900 Hz, the optimal filtration performance of the filter material is obtained at 700 Hz. When the filtration gas velocity is between 0.2 and 0.4 m/s, the improvement of the filtration performance gradually weakens as the filtration velocity increases. Furthermore, the reduction of the downstream droplet concentration is more significant for low-efficient filters or those with fewer layers under the same condition in the sound field.

STABILIZATION OF PICKERING EMULSIONS WITH HETEROAGGREGATES OF DETONATION NANODIAMONDS AND SIO2 NANOPARTICLES

The stabilization of Pickering emulsions with mixtures of similarly and oppositely charged detonation nanodiamonds and silica nanoparticles has been studied. Dynamic light scattering has been employed to study the influence of pH and the mass ratio of the particles on the sizes and ζ-potentials of aggregates. The formation of heteroaggregates from mixtures of similarly charged nanoparticles and the efficient stabilization of dodecane droplets have been shown and theoretically substantiated. Submicron droplets of Pickering emulsion stabilized with the mixtures of oppositely charged silica nanoparticles and detonation nanodiamondshave been obtained.

Fabrication of Assembled FeS2 Nanosheet and Application for High-Performance Supercapacitor Electrodes.

To overcome the low-energy-density limitation of supercapacitors, we aimed to achieve a material with a high specific capacitance by manipulating the nanostructure of FeS2, which comprises the most abundant and affordable elements. In this study, nanosheet-assembled FeS2 (NSA-FeS2) was fabricated using a novel method. Sub-micron droplets of sulfur particles stabilized with polyvinylpyrrolidone were formed in silicone oil medium, and Fe(CO)5 was absorbed and reacted on the surface to form core-shell particles, ES/[Fe], with a sulfur core and an iron-containing outer shell. The high temperature treatment of ES/[Fe] produced NSA-FeS2, in which pyrite FeS2 nanosheets grew and were partially interconnected. In a three-electrode system, the as-prepared NSA-FeS2 and NSA-FeS2/polyaniline (PANI) composites exhibited specific capacitances of 763 and 976 Fg-1, respectively, at a current density of 0.5 Ag-1, with corresponding capacitance retentions of 93 and 96% after 3000 charge-discharge cycles. The capacitance retention of the NSA-FeS2/PANI composites was 49% when the current density was increased from 0.5 to 5 Ag-1. Notably, the obtained specific capacitances exhibited the highest values in pure FeS2 and FeS2-based composites, indicating the significant potential for the utilization of iron sulfide in pseudocapacitive electrode materials.

Effects of Salinity Beyond Coalescence on Submicron Aerosol Distributions

AbstractBubbles entrained by ocean waves rise to the surface and burst, creating a shower of droplets which contribute to sea spray aerosols. Submicron‐sized droplets, of which an estimated 60%–80% come from a bursting bubble film cap, play a key role in global climate atmospheric processes. However, many aspects of predicting the number and size of submicron drops emitted from a bursting bubble remain unknown. It is well‐documented that higher salinity increases submicron droplet production, which has been attributed to the role of salt in the suppression of bubble coalescence. We experimentally show that submicron drop production increases with salinity despite using a salt that does not affect bubble coalescence, indicating that salinity plays a role in the physics of submicron aerosol formation beyond coalescence. Laboratory experiments are conducted using sodium acetate solutions of salinity S = 0.001–0.1 M with millimeter‐sized bubbles generated via a needle. Unlike previous studies, the measured droplet size distributions are converted to formation diameter, revealing that the peak aerosol formation diameter decreases with higher salinity. Applying this diameter conversion to past studies, we find the peak formation diameter exhibits a scaling of Dform ∼ S−0.32 across three orders of magnitude in salinity and for a variety of salts, bubble coalescence behaviors, and bubble generation mechanisms. This result suggests that salinity has a systematic effect on the length scale of the rupturing bubble film which generates the aerosols. Consequently, salinity likely impacts the submicron aerosol production in oceanic environments even if bubble coalescence is negligible.

Microfluidic Methods for Generation of Submicron Droplets: A Review.

Submicron droplets are ubiquitous in nature and widely applied in fields such as biomedical diagnosis and therapy, oil recovery and energy conversion, among others. The submicron droplets are kinetically stable, their submicron size endows them with good mobility in highly constricted pathways, and the high surface-to-volume ratio allows effective loading of chemical components at the interface and good heat transfer performance. Conventional generation technology of submicron droplets in bulk involves high energy input, or relies on chemical energy released from the system. Microfluidic methods are widely used to generate highly monodispersed micron-sized or bigger droplets, while downsizing to the order of 100 nm was thought to be challenging because of sophisticated nanofabrication. In this review, we summarize the microfluidic methods that are promising for the generation of submicron droplets, with an emphasize on the device fabrication, operational condition, and resultant droplet size. Microfluidics offer a relatively energy-efficient and versatile tool for the generation of highly monodisperse submicron droplets.

The role of size effects in microextraction

Size effects during phase transformations change the composition of coexisting phases in ternary mixtures. The consequence is a change in the distribution coefficients of the components, which is of interest for microextraction. The concentration dependence of the degree of extraction for separable mixtures (aniline-methylcyclopentane-hexane and water-phenol-toluene) in submicron drops was simulated by the methods of equilibrium chemical thermodynamics. The concentration dependence of the degree of extraction during microextraction for submicron droplets is constructed. Keywords: phase equilibria, microextraction, thermodynamic modeling, size effect, ternary system.

Роль размерных эффектов при микроэкстракции

Size effects during phase transformations change the composition of coexisting phases in ternary mixtures. The consequence is a change in the distribution coefficients of the components, which is of interest for microextraction. The concentration dependence of the degree of extraction for separable mixtures (aniline - methylcyclopentane - hexane and water - phenol - toluene) in submicron drops was simulated by the methods of equilibrium chemical thermodynamics. The concentration dependence of the degree of extraction during microextraction for submicron droplets is constructed.

Preparation of combined oleophobic fibre filters with pore size gradients and their high-efficiency removal of oil mist droplets

Pore size is a key factor that influences the removal of oil mist droplets by a coalescence filter. However, the influence of the pore size distribution among different filter layers on filtration performance has not been thoroughly explored. In this work, a method for preparing glass fibre filtration media with a specific structure as well as good oleophobic properties and mechanical strength was developed by combining the wet-spinning method and immersive modification. The prepared single-layer media were combined in various three-layer structures with increasing pore size gradient, decreasing pore size gradient and uniform pore size distribution. The trends in the pressure drop and droplet penetration ratio of the resulting combined filters over time were analysed systematically. The results demonstrated that in the combined filter, the first layer material had a significant influence on the filtration process and steady-state performance. Throughout filtration, the pressure drop of the filter with a decreasing pore size gradient had layering characteristics, which was conducive to capturing droplets within different particle size intervals in different stages and thereby relieving the operational pressure on different layers. Hence, the filter with a decreasing pore size gradient had a relatively low steady-state pressure drop and the best comprehensive filtration performance for submicron droplets. However, the filter with an increasing pore size gradient had the highest separation efficiency for submicron droplets and its concentration of steady-state downstream droplets was 19% lower than that in the filter composed of three layers of minimum pore size materials. The proposed mechanism by which the filter with the increasing pore size gradient improved the coalescence filtration efficiency for submicron droplets was based on capillary theory.

Particle Image Velocimetry in a High-Speed Short-Duration Turbine Rig

AbstractThis article presents the implementation of a particle image velocimetry (PIV) into the high-speed short-duration rotating turbine facility of the von Karman Institute. The advantage of PIV as a whole-field measurement is emphasized in such circumstances for which the use of optical technique can drastically reduce the number of tests and the need for multiple intrusive expensive probes, ultimately lowering the testing cost. Practical solutions were demonstrated that address various challenges for the effective application of PIV. An endoscope delivered the laser sheet to the region of interest and a plano-concave window provided optical access for the measurement in the annular test section. Sub-micron scale oil droplets were seeded into the main flow through custom-made probes located upstream of the nozzle guide vane and into a pipeline supplying rim seal purge flow. A high-speed laser system and a high-speed camera were synchronized at 1 kHz sampling rate. Complementary measurements and dedicated image processing were performed to ensure the synchronization of the PIV images with the rotor position that was monitored through an encoder. The region of interest was the blade-to-blade plane at the 58% span turbine exit on a rectangular field of view covering approximately one rotor pitch and 0.15 rotor axial chord from the rotor trailing edge. Phase-locked-average velocity fields are obtained from PIV and compared against steady-state Reynolds-averaged Navier–Stokes (RANS) simulations along with four-hole probe measurement results. Together with uncertainty analysis, the results demonstrate the promising robustness and accuracy of PIV. A practical guideline for PIV application in such kinds of turbine test rigs is provided as a conclusion of the paper.

Fluorescent Tracer Particles For PIV Measurement In Gas Flows

This paper presents the development and employment of fluorescent tracer particles which allow removal of undesired strong light reflections in gas-phase Particle Image Velocimetry measurements. A spectroscopic investigation on fluorescent dye-doped solutions at different concentrations provided fluorescent emission spectra ranging their peak between 540 and 585 nm when excited by 527 nm wavelength Nd:YLF laser. The fluorescence intensity of the solutions in a form of sub-micron droplet was examined through comparison of statistical pixel intensities of raw particle images. Within the investigated concentration range, the intensity was found to be almost proportional to the dye concentration. The developed particle was tested in a wind tunnel at 5 m/s mean flow speed with a metal turbine blade placed in the channel and laser sheet oriented to impinge the blade surface. With the employment of an adequate optical band-stop filter, the undesired light reflections were successfully removed and reasonable vector calculations were enabled in proximity to the reflective surfaces. Lastly, the fluorescent PIV was performed in a high-speed short-duration rotating turbine test rig in order to demonstrate the effectiveness of the technique in industrial or extreme applications comprise severe conditions.

Ultrasonic attenuation model of mixed particle three-phase system based on Monte Carlo method

From the perspective of calculating ultrasonic absorption and scattering properties of individual solid particle and droplet, the ultrasonic wave is treated as discrete phonons. And by tracking their motion process and event statistics, a new prediction model of ultrasonic attenuation of spherical mixed particles in gaseous medium is established with Monte Carlo method. Considering the difference in physical properties between solid particles and liquid particles, the ultrasonic absorption characteristics of the two kinds of particles are obviously different, and when dimensionless particle size <i>kR</i> ≤ 1, the backscattering of particles is uniform and dominant, then the ultrasonic scattering pressures gradually transit from the dominant position of backscattering to the trend of forward enhancement with the increase of dimensionless particle size. The numerical simulation results for the system with a single particle type are compared with those from various standard models such as classical ECAH model and McC model, showing that they are in good agreement. Similarly, the results are then compared with experimental results, which accord with each other in general. After calculating and verifying the ultrasonic attenuation of aluminum particles and submicron droplets respectively in air, the method is extended to the three-phase monodisperse and polydisperse mixed particle system composed of aluminum particles and liquid droplets. In the three-phase system of gas-liquid-solid mixed particles, the particle type has a significant influence on ultrasonic attenuation, and the attenuation contribution of different particles against mixing ratio does not follow the linear gradient with the increase of volume concentration. For a polydisperse system, the ultrasonic attenuation spectrum is greatly affected by the average particle size, but it is insensitive to the width of particle size distribution. The numerical results also show that both the particle type and particle distribution size should be carefully take into account in the polydisperse system. Moreover, the MCM model can be further extended to non-spherical particles and combined with mathematical inversion to form the theoretical basis for the measurement of mixed particle system.

Droplette: A Platform Technology to Directly Deliver Nucleic Acid Therapeutics and Other Molecules into Cells and Deep into Tissue Without Transfection Reagents.

Droplette (US 9,700,686 B2 and PCT/US2016/035695) is the first portable and contact-free transdermal technology comprising the unique combination of a piezoelectric transducer and a pneumatic diaphragm pump to deliver large biomolecules including nucleic acid therapeutics (NATs) deep into cells, and into skin and soft tissue for effective delivery over short timescales. The droplets that come out of the device are 10-50× smaller upon impact than what is created through other commercial atomizers, such as the piezoelectric transducer alone. This device has been tested extensively in vitro, in vivo and in IRB approved human studies. The Droplette device delivers metered doses using a water droplet dispersal technology already commonly used in humidifier devices, by utilizing a piezoelectric material. Three key innovations make this device technically novel and tailored specifically for both field and lab use: (1) The combination of the piezo and pump to generate sub-micron drug-loaded droplets that penetrate cells, skin, and soft tissue to effectively deliver a range of large molecules, proteins, and nucleic acids. (2) Their assembly in a modular manner which enables portability, safe sterilization, and ejection without direct device-surface contact or significant force, allowing for improved safety and ease of use in both research and clinical settings. (3) The integration of a single-use, sterile cartridge that contains a therapeutic formulation and allows easy integration of a large number of molecules. The platform has broad applications across multiple fields, such as delivery of drugs for inflammatory skin diseases, antibiotics for skin infections, and gene delivery for gene therapy and biomedical research. In this chapter, we briefly introduce the Droplette delivery technology, instructions for building your own setup (note that fully built devices are available for purchase from Droplette, Inc), and provide protocols for directly transfecting adherent cell cultures and for direct in vivo transfection using the Droplette system without the need for traditional transfection reagents or methods.

Improving the Performance of Polysulfone-nano ZnO Membranes for Water Treatment in Oil Refinery with Modified UV Irradiation and Polyvinyl Alcohol

Refinery wastewater is generated from the process of refining large amounts of oil. Oil refined wastewater contains micron-scaled emulsion droplets, and sub-micron droplets that are difficult to remove from water, which poses problems for researchers. Membrane technology is widely used in water treatment because it is very selective and effective in the filtration process. This research focuses on oil refinery water treatment using polysulfone (PSF) membrane ZnO nano composites modified with ultraviolet (UV) irradiation and polyvinyl alcohol. This membrane was prepared using the dry / wet phase inversion method. Then-the membrane was modified using UV irradiation and coated with polyvinyl alcohol (PVA). PSF-nano ZnO modifications have an impact on membrane performance; UV irradiation showed an increase in the value of membrane pure water flux from 4.5 Lm–2h–1 to 5.7 Lm–2h–1. However, after UV irradiation, the rejection value decreased after UV irradiation, whereas the presence of PVA as a coating agent increased the rejection value to 77.2 % for Total Dissolve Solid (TDS) rejection, 76 % for Chemical Oxyugen Demand COD rejection, and 65.3 % for ammonia rejection. This value was higher than that obtained for membranes without PVA coating, namely only 47.3 % for TDS, 51.1 % for (COD), and 29.4 % for ammonia rejection. Modifications with UV and PVA irradiation provide interrelated effects to improve membrane performance.

Features of metastable superheated water atomization when being discharged through convergent-divergent nozzles at different superheat values

Experiments with the metastable superheated water atomization proved the significant increase of the submicron droplets mass fraction at the outlet of convergent-divergent nozzle from 0.45-0.55 to 0.75-0.9 with an increase of the inlet water temperature from170to255°C. Two different approaches to dimensionless treatment of the atomization processdata and determining the boundary of the zone of flashing predominance are compared. The analysis of two approaches to dimensionless treatment of experimental and calculating results concerning transition to predominating role of nucleation in the process of superheated liquid atomization in convergent-divergent nozzles is done.

Specificfeatures of evolution of dense atomized superheated water plumes and peculiarities of its diagnostics

Experimental study of evolution of plumes of atomized metastable superheated water during its discharge through convergent-divergent nozzles is conducted. Dispersion characteristics of dense plumes in micron and submicron droplet diameter ranges are obtained. Theoretical and prediction analyses of different coagulation mechanisms in the considered two-phase flow are performed. The negligible effect of Brown-type coagulation is shown. It is also demonstrated that turbulent coagulation can change the fraction of micron-diameter droplets within 9%. In addition, for the first time, an “inertial” mechanism of coagulation is considered for the studied plumes under the conditions of plume baking in a cocurrent flow or in the ambient air. It can lead to a considerable decrease in the submicron-droplet mass fraction, which is observed in experiments even at a small distance from the nozzle cut. The predicted data are compared with experimental ones obtained at theexperimental setup.