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The COVID‐19 pandemic has highlighted the need to improve understanding of droplet transport during expiratory emissions. While historical emphasis has been placed on violent events such as coughing and sneezing, the recognition of asymptomatic and presymptomatic spread has identified the need to consider other modalities, such as speaking. Accurate prediction of infection risk produced by speaking requires knowledge of both the droplet size distributions that are produced, as well as the expiratory flow fields that transport the droplets into the surroundings. This work demonstrates that the expiratory flow field produced by consonant productions is highly unsteady, exhibiting extremely broad inter‐ and intra‐consonant variability, with mean ejection angles varying from ≈+30° to −30°. Furthermore, implementation of a physical mouth model to quantify the expiratory flow fields for fricative pronunciation of [f] and [θ] demonstrates that flow velocities at the lips are higher than previously predicted, reaching 20–30 m/s, and that the resultant trajectories are unstable. Because both large and small droplet transport are directly influenced by the magnitude and trajectory of the expirated air stream, these findings indicate that prior investigations of the flow dynamics during speech have largely underestimated the fluid penetration distances that can be achieved for particular consonant utterances.

The impingement of a droplet on a rigid square obstacle in a microchannel is simulated numerically using a high-density-ratio pseudo-potential multi-relaxation time LBM. The effects of Reynolds (Re) number, Weber (We) number, contact angle, obstacle size and kinematic viscosity ratio on the droplet dynamics after impact are investigated. It was found that the formation of the liquid film around the obstacle, the expansion of the droplet and its rupture time are all affected by these factors. As the Re number increases, the process of droplet falling along the obstacle is faster and the droplet demonstrates a more intense dynamic behavior. Increasing the We number makes the liquid film around the obstacle thinner and more stretched. Hydrophilicity and hydrophobicity of the obstacle surface play a major role in its surface wetting. For the hydrophobic obstacle wall, the separated sub-droplets move more rapidly toward the channel walls. As the hydrophobicity increases, the small droplet left on the upper surface of the obstacle will bounce upward. The bouncing tendency increases as the kinematic viscosity ratio decreases. As the obstacle size increases, the droplet expands more around it and approaches the channel walls faster.

A counterflow two-phase diffusion flame with polydisperse spray is numerically studied in a 2D configuration, using a Lagrangian formalism for the liquid phase and accurate combustion chemistry. Results exhibit a very complex double flame structure with diffusion and premixed flames, as well as group and individual droplet burning. Monodisperse two-phase counterflow flames are also computed to help analyse the polydisperse flame, and confirm the strong link between droplet diameter and flame regime. For small droplet diameters, the flame has the same structure than a gaseous flame at a different equivalence ratio, and the total heat release of the flame increases with the droplet size. For larger droplets, the premixed mode becomes dominant and the total heat release of the flame exceeds the maximum gaseous diffusion one.

Convincing arguments have been presented testifying that that the surface tension of a small spherical droplet must decrease upon diminishing droplet radius in correspondence with a positive constant Tolman length. The solution of the Gibbs–Tolman–Koenig–Buff equation has been found in the most compact form. The surface tension of a small spherical droplet has been calculated within the framework of the continual approximation using the Mie–Lennard-Jones interatomic pair potential.

This paper investigates the droplet formation and motion characteristics in seven-wire rotating arc electrogas welding. A high-speed video camera was used to observe the droplet formation and motion behaviors. The forces on the droplet in different welding parameters were analyzed to explain the droplet formation and motion processes. The results show that the small droplets at the end of six peripheral wires accumulate and grow toward the small droplet at the end of the center wire under the action of the electromagnetic force, and the coupled droplet forms under the action of electromagnetic force and surface tension at the end of the center wire. Gravity, plasma flow force, and rotating force affect the fall of the coupled droplet through the arc space and show non-axial motion and axial motion with different welding currents.

Nanoemulsions are emulsions with droplet size in the order of 100 nm and are kinetically stabilized dispersions formulated by combination and stabilization of two immiscible phases using a surfactant. They exhibit useful properties due to small droplet size leading to high surface area per unit volume, higher stability, optically transparent appearance, flexible fluidity and increased bioavailability of lipophilic components. Recently, interdisciplinary applications of nanoemulsions in consumer products, i.e. pharmaceuticals, pesticides, cosmetics, food, paint and environmental applications have attracted interest in its research. Various authors have focussed on preparing nanoemulsions through different methods, including high-energy and low-energy. High energy methods mainly includes microfluidization, high pressure homogenization and ultrasonication whereas, low energy methods comprise of phase transition temperature, phase inversion composition, spontaneous emulsification, micro emulsion dilution and recently developed approach such as D phase emulsification (DPE). In this review article, we address the growing usefulness of low energy method due to ease in its scale-up, less consumption of energy and increased stability in formulation of nanoemulsions. It also includes review on characterization techniques, applications of nanoemulsions and optimization studies for industrial scale up.

Carbon nanotubes based on mechanical deformation for controlling mass transport have various promising potential applications in nanofluidic devices. The thermophoresis of water nanodroplets through carbon nanotubes with deformation imposed by nanoindentation is explored using molecular dynamics simulations. We find that deforming the carbon nanotubes can effectively control the thermophoretic motion of the confined droplet. When the carbon nanotubes are deformed to a certain level, the migration of the droplet is significantly limited. Under strong deformation, the exchange of water molecules between separated droplets is blocked by narrow passage. Moreover, we identify some interesting phenomena and important physical mechanisms, and explain them via the relationship between the molecular interactions between the interfacial water and the thermophoretic effect. The thermophoretic dynamics of a small droplet confined in the carbon nanotubes with a larger radius reveals that the interfacial interactions b...

There is a growing interest for using of nano/sub-micron particles in the technology of pharmaceutical, cosmetic and also food. Especially, this interest has been increasing parallel with better emulsification techniques and stabilization mechanisms. There are two main groups of nanoemulsion preparation methods, namely high-energy and low-energy spontaneous emulsification methods. Preparation processes and components used are significant parameters that affect stability from few hours to years. Problems such as creaming, coalescence sedimentation and flocculation are not concern for nanoemulsions due to their small droplet size. However, the main destabilization mechanism is Ostwald ripening for them. In this paper, a comprehensive review is presented to give basic ideas about nanoemulsions, their preparation methods, and evaluations. Keywords: Nanoemulsion, preparation methods, evaluation

Horizontal oscillations of small droplet clusters (from one to four droplets) levitating over a locally heated water layer in upward vapor–air flow are investigated experimentally. These oscillatio...

The movement of a small droplet in the boundary layer of the liquid–vapor flow in a horizontal channel with large velocity gradients is considered. The influence of the Magnus and Saffman lift forces on this droplet and the distance of its separation from the channel wall was investigated. The velocity components of the droplet and its reach distance were determined from the numerical solution of the system of nonlinear differential equations with the use of the Mathcad program.

In this study, the numerical computation is used to investigate the transient movement of a water droplet in a microchannel. For tracking the evolution of the free interface between two immiscible fluids, we employed the finite element method with the two-phase level set technique to solve the Navier-Stokes equations coupled with the energy equation. Both the upper wall and the bottom wall of the microchannel are set to be an ambient temperature. 40mW heat source is placed at the distance of 1 mm from the initial position of a water droplet. When the heat source is turned on, a pair of asymmetric thermocapillary convection vortices is formed inside the droplet and the thermocapillary on the receding side is smaller than that on the advancing side. The temperature gradient inside the droplet increases quickly at the initial times and then decreases versus time. Therefore, the actuation velocity of the water droplet first increases significantly, and then decreases continuously. The dynamic contact angle is strongly affected by the oil flow motion and the net thermocapillary momentum inside the droplet. The advancing contact angle is always larger than the receding contact angle during actuation process.

A detailed experimental study on the evolution process of charged liquid deformation and breakup in another immiscible liquid from a capillary channel was conducted at micro-scale. By means of high-speed microscopy technique, various liquid spray modes and droplet formation processes were illustrated in detail at different flow rates and voltages. The effects of Reynolds (Re) and electric Bond (BoE) number on droplet size distribution were analyzed. It was found that droplet sizes rose with increasing Re while declined with increasing BoE. The experimental results show that electric field could promote interfacial area through decreasing interfacial tension to augment mass transfer between immiscible liquids at low flow rates. Besides, liquid spray experienced drip, deformation, breakup and jet modes with the increase of flow rate and electric potential. A critical Re of 170 was obtained beyond which electric field had little effect on liquid dynamic behaviors.

Emulsions have widely been used in various application, e.g. in energy system as a potential second refrigerant. However, there is a lack of comprehensive study on extraordinary effective thermal conductivity enhancement in the oil-in-water (O/W) emulsions, and effects of temperature and droplet size were not considered in the widely used models of effective thermal conductivity for the O/W emulsions. In this study, non-Fourier heat conduction characteristics in the O/W emulsions were investigated experimentally. The O/W emulsions were prepared with different droplet sizes by controlling the ultrasonic processing time. The O/W emulsions containing small droplets are stable. Effective thermal conductivity of O/W emulsions nonlinearly varies with droplet size, concentration, fluid properties and temperature. Small droplet size is beneficial for effective thermal conductivity enhancement of O/W emulsions. Thermal conductivity of fluids can be enhanced significantly especially at low concentration although thermal conductivity of oil is much lower than water conductivity, which could be due to non-Fourier heat conductions in O/W emulsions. Time lag ratio less than 1 indicates that no thermal waves exist in O/W emulsions, and diffusion-dominant non-Fourier heat conduction could exist in the O/W emulsions. A new model of effective thermal conductivity, which considers effects of fluid thermosphysical properties, oil concentration, droplet size and temperature, was developed for the O/W emulsions based on the measured data. This study could be helpful for exploring the mechanisms behind extraordinary heat conductivity enhancement phenomena of oil-in-water emulsions.

Objective Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spreads through person-to-person contact via small droplet particles, especially in poorly ventilated indoor settings such as households, estimating at 16.6% of secondary attack rate. This study aimed to explore the secondary attack rate in Thai households during the new SARS-CoV-2 variant outbreak. Methods We obtained a retrospective study of exposed members in households among 30 sets of patients with reverse transcriptase-polymerase chain reaction (RT-PCR) confirmed SARS-CoV-2 infection (index cases) at Chulabhorn Hospital, Bangkok, Thailand, from May 1 to June 30, 2021. Characteristic of index cases and households were extracted from medical records and analyzed. Results The 30 index cases were associated with 157 exposed household close contacts. Seventy-six were RT-PCR confirmed SARS-CoV-2 infections within 14 days after being exposed from an index case, with a secondary attack rate of 48%. However, there was no difference between secondary attack rates among the age of contact, household size, or SARS-CoV-2 variants. Conclusion Our data show high transmissibility of SARS-CoV-2, which was notably exaggerated compared to previous studies. Therefore, developing preventive strategies such as post-exposure prophylaxis (PEP) in close contact with SARS-CoV-2 infection would be a novel supplement to the current standard of care.

The fall of a small droplet from a height H = 20 mm onto the surface of a sessile drop leads to a change in its shape: the drop is periodically stretched and then compressed. At H = 500 mm, after the fall of a small droplet, the formation of splashes and fingers is observed. Subsequently, the sessile droplet is compressed with the formation of closely spaced smaller droplets. The PIV method was used to obtain experimental data on the change in velocity in the horizontal section a sessile drop after the fall of a small droplet. The fall of one droplet onto the surface of another drop from a height of H = 20 mm leads to the formation of vortices in the drop and the flow velocity in the drop increases many times from 0.035-0.5 mm/s to 4.1-4.8 mm/s. After 5 s the drop, the flow velocity in the sitting drop approaches the velocity before the fall, and a toroidal vortex is formed in the drop.

We measure aerosol persistence to assess the risk of transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in public spaces. Direct measurement of aerosol concentrations, however, has proven to be technically difficult; we propose the use of handheld particle counters as a novel and easily applicable method to measure aerosol concentrations. This allows us to perform measurements in typical public spaces, each differing in volume, the number of people, and the ventilation rate. These data are used to estimate the relation between the aerosol persistence time and the risk of infection with SARS-CoV-2.

The effects of electric charges and fields on droplet collision–coalescence and the evolution of cloud droplet size distribution are studied numerically. Collision efficiencies for droplet pairs with radii from 2 to 1024 µm and charges from −32 r2 to +32 r2 (in units of elementary charge; droplet radius r in units of µm) in different strengths of downward electric fields (0, 200, and 400 V cm−1) are computed by solving the equations of motion for the droplets. It is seen that the collision efficiency is increased by electric charges and fields, especially for pairs of small droplets. These can be considered as being electrostatic effects. The evolution of the cloud droplet size distribution with the electrostatic effects is simulated using the stochastic collection equation. Results show that the electrostatic effect is not notable for clouds with the initial mean droplet radius of r¯=15 µm or larger. For clouds with the initial r¯=9 µm, the electric charge without a field could evidently accelerate raindrop formation compared to the uncharged condition, and the existence of electric fields further accelerates it. For clouds with the initial r¯=6.5 µm, it is difficult for gravitational collision to occur, and the electric field could significantly enhance the collision process. The results of this study indicate that electrostatic effects can accelerate raindrop formation in natural conditions, particularly for polluted clouds. It is seen that the aerosol effect on the suppression of raindrop formation is significant in polluted clouds, when comparing the three cases with r¯=15, 9, and 6.5 µm. However, the electrostatic effects can accelerate raindrop formation in polluted clouds and mitigate the aerosol effect to some extent.

Nanoemulsions are kinetically stable biphasic dispersions of two immiscible liquids in which nanodroplets are stabilized by utilizing surfactants. Recently, nanoemulsions have been widely applied in various fields such as the pharmaceutical, cosmetic, and food sector due to their unique favorable size and formulation. The small droplet size leads to a high surface area, eventually affecting the bioavailability. Additionally, nanoemulsions may serve as protective shields for the bioactive functional components encapsulated within. Herein, a comprehensive study of the various methods used for the preparation of nanoemulsions, as well as their stability, characterization, and potential application in various sectors, is presented.

Multiple Water-in-Water-in-Water (W/W/W) emulsions were prepared, stabilized and characterized. The main objective was to find a simple and low-cost method for the preparation of W/W/W emulsions. The system composed of gelatin, maltodextrin and water was used, and two different methods were studied for producing multiple emulsions in this system. In the first method, maltodextrin-in-gelatin (M/G) emulsions with small droplet size were formed by pH-induced nucleation of maltodextrin droplets, and afterwards, maltodextrin-in-gelatin-in-maltodextrin (M/G/M) multiple emulsions were obtained by dispersing M/G droplets into maltodextrin solutions. The second method consisted in cooling down gelatin-in-maltodextrin (G/M) emulsions, leading to the spontaneous formation of inner maltodextrin droplets. The latter method allowed producing more homogenous M/G/M multiple emulsion droplets. The colloidal stability of such emulsions greatly improved with the addition of mucin particles, which is a glycoprotein that adsorbs on the G/M interface. Stable M/G/M multiple emulsions have been prepared and characterized by fluorescence optical microscopy, where contrast has been enhanced through covalently labelling the various components with fluorescent dyes. To our knowledge, this is the first report of a simple and cost-effective method for the production of multiple W/W/W emulsions, without using microfluidic techniques. Moreover, the present work also demonstrates that mucin microparticles can be effective stabilizers for protein-in-polysaccharide emulsions, and these dispersions can be easily prepared by phase transition methods., The authors greatly acknowledge the financial support from the Spanish Ministry of Economy and Competitiveness (CTQ2017-84998-P and CTQ2016-80645-R projects) and Marie Sklodowska Curie Initial Training Networks (FP7-PEOPLE-2013-ITN-606713, BIBAFOODS project). Support from Generalitat de Catalunya (2017SGR1778 and TECCIT15-1-0009) and Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), is also acknowledged. The authors also acknowledge the “Grupo de Nanotecnología Farmacéutica”, of the University of Barcelona (UB), in the Faculty of Pharmacy, which forms an Associated Unit to CSIC. Authors are also very grateful to the European Regional Development Fund (Fondo Europeo de Desarrollo Regional, FEDER), which provides support to these government programs.Characterization, except Confocal Microscopy, have been performed by the Nanostructured Liquid Characterization Unit, located at the Institute of Advanced Chemistry of Catalonia (IQAC), belonging to the Spanish National Research Council (CSIC) and affiliated to the NANBIOSIS ICTS of the Biomedical Networking Centre (CIBER-BBN), which is financed by Instituto de Salud Carlos III. Laser Confocal Optical Microscopy was performed at the Advanced Optical Microscopy Unit of the Scientific and Technological Centres of University of Barcelona. The authors also greatly thank Carlos Rodríguez-Abreu and Conxita Solans (IQAC-CSIC), and Allan Mackie and Josep Bonet (Universitat Rovira i Virgili, Spain) for very useful discussions.

This study aims to produce and optimize palm oil-based nano-emulsion to encapsulate curcumin using microfluidizer and Response Surface Methodology (RSM). Encapsulation of curcumin is essential to overcome curcumin's poor bioavailability through the formation of nano-sized droplets in order to harvest its outstanding anti-inflammatory and anti-cancer medicinal properties. Among the parameters of concern are microfluidizer's pressure, number of cycles and surfactant concentration (Tween 80). Optimisations were performed by employing RSM. Characterisations were conducted for the droplet size, poly-dispersity index (PDI), zeta potential (ZP) and viscosity. Stable palm oil-based oil in water nano-emulsion encapsulating curcumin was achieved at a droplet size of 275.5 nm, PDI of 0.257, ZP of −36.2 and viscosity of 446 cP using microfluidizer. The optimized conditions were at 350 bar, 5 cycles and 1 wt% surfactant. Optimized microfluidizer with the aid of RSM is deemed capable to produce palm oil-based oil in water nano-emulsion encapsulating curcumin with small droplet size using low surfactant concentration and under optimum energy consumption.

Donor organ shortage stimulated an active use of donors with expanded evaluation criteria. The main evaluation method was a histological examination of liver graft biopsy specimens before (time-zero biopsy) and after reperfusion (time-1 biopsy). Severe ischemic and reperfusion injuries among recipients who received a liver graft made 20.4% and 16.6% respectively. The study showed no impact of small droplet, medium droplet, or even large droplet steatosis (less than 50%) on graft reperfusion injury.

In this study, we formulated and stabilized oil-in-water nanoemulsions using a crude extract from argan press-cake as sole emulsifier. Various extracts from argan press-cake were prepared in order to select the most surface-active one(s) foreseeing emulsions preparation. Fifty percent (v/v) ethanolic extract reduced the interfacial tension to a minimum value at both MCT oil and soybean oil interfaces (12.7 and 10.5 mN m-1 respectively). This extract was also effective at producing fine emulsions with small droplet sizes (d3,2 < 115 nm) and good physical stability using different oils such as soybean oil, MCT oil and fish oil and at conventional homogenization conditions (100 MPa for 4 passes). On the other hand, the emulsions were very sensitive to NaCl addition (≥25 mM) and to acidic pH (

Generating individual, small droplets offers unique possibilities for various applications where precise volume and concentration control are necessary. This paper presents a systematic method for generating ultra-small droplets based on a controllable meniscus break-up procedure. The method utilizes two nozzles that are connected to a computer-controlled syringe through a three-way junction. A syringe is used to extrude the liquid from both orifices until they are connected by a liquid meniscus. Next, draining the liquid out of the meniscus and back into the nozzle will cause the meniscus to thin, which will ultimately result in its break-up and the formation of one small droplet. Both experimental and theoretical studies are presented to demonstrate the validity of the proposed method. It is shown that droplets with volumes from femtoliters to nanoliters can be generated.

A three-stage collector was used to collect size-resolved cloud samples at the summit of Mt. Tai. Subsequently, analyses of pH values, water-soluble ions, and trace metals were performed and bacterial community were conducted using MiSeq amplicon sequencing. The pH values of the samples decreased as droplet sizes decreased. Sulfate (SO42–), nitrate (NO3–) and ammonium (NH4+) were the main secondary inorganic ions which their concentration distributed significantly different from size-resolved cloud water. The NH4+ concentration was higher in smaller droplets. The SO42– and NO3– concentrations were higher in larger droplets. The Ca2+ concentration increased as droplet size increased. Small droplet samples tended to have lower pH value, mainly because of the more acidic (SO42– and NO3–) and less acid-neutralizing (NH4+ and Ca2+) components. The bacterial community in size-resolved cloud samples were firstly recognized and dominated by the genera of Lactococcus (average abundance 34.9%) and Bacillus (average abundance 34.0%). Linear discriminant analysis effect size (LEfSe) revealed differences of the bacterial community in size-resolved cloud water samples, which was probably caused by the bacterial size. Redundancy analysis suggested several minor correlations that the H2O2, NO2– concentrations, and trace metals exert effects on the bacterial community.

Turbine blades operate under a harsh environmental condition, and the inlet temperature of gas turbines is increasing with requirement of high engine efficiency. Some cooling schemes are adopted to prevent these blades from the thermal erosion of the hot mainstream. Film cooling technology is used widely and effectively in gas turbines. The coolant air is suppressed to the wall by the mainstream after jetting out of the film hole. A new hole configuration is first proposed to improve the film cooling characteristics in this paper. Comparison between a conventional cylindrical hole and a new combined hole is conducted by computational fluid dynamics, and effects of various blowing ratios and droplet sizes are also investigated. Results show that the combined hole configuration provides a wider coverage than that in the cylindrical hole configuration case at high blowing ratios (M = 1.0 and M = 1.5). In addition, the film cooling with mist injection also provides a significant enhancement on cooling performance especially for the combined hole case with a small droplet size (10−5 m).

Small clusters of condensed microdroplets can levitate above a heated water surface. Vertical oscillations of small clusters (one, two, and three droplets) in the frequency range below 90 Hz are studied and compared with recently reported horizontal oscillations. Two reproducible peak frequencies are at 41.6 ± 0.4 Hz and at 49.5 ± 0.2 Hz. These frequencies are much higher than those for horizontal oscillations (between 1.61 Hz and 5.96 Hz); however, corresponding amplitudes are much smaller, which suggests equal energy distributions between the degrees of freedom. The values of effective stiffness constants are obtained from the data on equilibrium height of levitation of droplets of different sizes, and possible sources of oscillations are discussed. The oscillations are caused by aerodynamic forces, and these are same forces which are responsible for the stability of the droplet cluster.

Nanoemulsions are currently of interest in the functional food sector because their small droplet size (100–500 nm) provides a number of potential advantages over conventional emulsions. This study concerned the behavior of nanoemulsions stabilized with whey proteins and two synthetic emulsifiers (Tween 80 and Croduret), and exposed to conditions simulating the human upper gastrointestinal tract. In particular, the effect of synthetic emulsifiers (food additives) on the interfacial composition and digestion rate of milk proteins at the interface of nanoemulsions was determined. The results indicate that the protein was partially co-absorbed with only one synthetic emulsifier (Croduret) at the interface, which made protein more resistant to digestion in the nanoemulsion system. This suggests that the degree of protein digestion can be controlled by appropriate selection of synthetic emulsifiers and presenting the protein in nanoemulsion system.

To study water droplet dynamic behavior in the silicone oil under a uniform DC electric field, a visual experiment system is set up. Two parallel plates are placed to form a uniform DC electric field. Results show when the electric field intensity is less than 2.33 kV/cm, with the increase of the electric field intensity, the droplet stretches in the vertical direction. The droplet detaches from the lower plate at 2.45 kV/cm. The droplet breaks into two daughter droplets at 3.67 kV/cm. Two daughter droplets coalesce at 4.67 kV/cm. A liquid bridge is formed at 4.93 kV/cm.

Soybean lipophilic protein (LP) is a promising emulsifier for nanoemulsion delivery systems. Herein, the influence of pH on the stability, rheological properties, and encapsulation efficiency of a nanoemulsion formed by ultrasonically modified LP was determined, and its influence mechanism was explored. The delivery system exhibited a high absolute zeta potential value (18–30 mV) in neutral and alkaline environments (pH 7.0 or 9.0) and uniform particle size distribution (100–350 nm). Cryo-scanning electron microscopy showed that LPs in neutral and alkaline environments covered the oil–water interface more evenly than those in acidic environments. Moreover, the LP nanoemulsion has excellent rheological properties and exhibit high emulsification performance, vitamin E encapsulation efficiency, and oxidation stability. These improvements occurred because the nanoemulsion prepared using ultrasonicated LP had a high absolute zeta potential value (maximum 30 mV), small droplet size (minimum 190 nm), uniform protein film, high viscosity, and good viscoelasticity in different pH environments. In summary, the nanoemulsion delivery system prepared by LP ultrasonication can resist the influence of different pH environments and maximize the delivery efficiency in neutral and alkaline environments. The research results identified a suitable pH environment for LP nanoemulsions and provide a theoretical reference for their further application.

We report new experimental investigations of the response of single superheated emulsion detectors with small droplet (

Consumer demands for natural and clean label ingredients is promoting food and beverage manufacturers to replace synthetic emulsifiers with natural alternatives. This study examined the potential use of quillaja saponin (Q-Naturale 200®) as a natural emulsifier in model coffee creamers. The model liquid creamer was an oil-in-water emulsion (2% quillaja saponin, 10% medium chain triglycerides) that had a whitish milk color (lightness, L* = 86–90) similar to a commercial liquid creamer (L* = 91–93). The model creamer was stable to droplet aggregation and creaming from pH 3.5 to 7.0, which was attributed to the small droplet diameter (d

There has been growing interest in the use of edible nanoemulsions as delivery systems for lipophilic active substances, such as oil-soluble vitamins, antimicrobials, flavors, and nutraceuticals, because of their unique physicochemical properties. Oil-in-water nanoemulsions consist of oil droplets with diameters typically between approximately 30 and 200 nm that are dispersed within an aqueous medium. The small droplet size usually leads to an improvement in stability, gravitational separation, and aggregation. Moreover, the high droplet surface area associated with the small droplet size often leads to a high reactivity with biological cells and macromolecules. As a result, lipid digestibility and bioactive bioavailability are usually higher in nanoemulsions than conventional emulsions, which is an advantage for the development of bioactive delivery systems. In this review, the most important factors affecting nanoemulsion formation and stability are highlighted, and a critical analysis of the potential benefits of using nanoemulsions in food systems is presented.

Tightly confined water within a small droplet behaves differently from bulk water. This notion is obtained on the basis of several reports showing unusual behaviors of water droplet residing at the core of a reverse micelle. In this study, we have shown a well-known hydrophobic dye, coumarin 153 (C153), which prefers to reside at the water-rich region inside the dendrimer molecule. Optical density (OD) measurement at the absorption peak of C153 shows that it is almost insoluble in bulk water but highly soluble in aqueous dendrimer solution. The OD of C153 increases several times in the latter case as compared to that in the former. We found the most interesting observation when we compared the data from fluorescence correlation spectroscopy (FCS) with the fluorescence anisotropy decay of C153 in aqueous dendrimer solution. The FCS measurement reveals a much slower translational diffusion time (τD) of C153 attached to a dendrimer molecule as compared to that of free C153 in bulk water in the absence of den...

The process of the droplet impact onto the liquid film on the rough solid surface, as one of the basic multiphase problems, is very important in many fields of science and engineering. On the other hand, the problem is also very complicated since there are many parameters that may influence the process of the droplet impact on the rough solid surface with a liquid film. Up to now, there are still little research on this problem, and to gain a better understanding on the physical mechanics of the droplet impact onto the film on the rough solid surface, it is desirable to conduct a detailed study. To clearly understand the physical phenomena appearing in the process of droplet impact on the liquid film, a parametric study on this problem is also carried out based on a recently developed lattice Boltzmann method in which a MRT lattice Boltzmann model is used to solve the Navier-Stokes equations, and the other is adopted to solve the Cahn-Hilliard equation that is used to depict the interface between different phases. In this paper, the effects of the relative thickness of film ( h ), the relative width of cavity ( d *) and the relative depth of cavity ( L *) on the dynamic behavior of interface are investigated in detail, and the velocity and pressure fields are also presented. In order to reduce the influence of lattice, we fix the lattice to be 600×120 for gas, which is fine enough to give accurate results. In addition, in our simulations, We =500, Re =480, viscosity ratio and density ratio are set to be 2:1. The numerical results first show that, the phenomena of crown and entrainment can be observed obviously during the process of droplet impact onto the liquid film on the rough interface when We and Re are large. The radius of spray ( r ), which is formed by the droplet impact onto liquid film, is related to time through the relation r / 2 R ≈ α U t / 2 R when h is small, which is coincident with the result of droplet impact onto the liquid film on smooth surface, and additionally the coefficient α would decrease with the increase of h . However, this relation seems not accurate for the case with a large h , and simultaneously, the splashing phenomenon has not been observed. Secondly, the relative width of cavity d * plays an important role on the phenomena of splashing. When d *=1, there will be two small droplets through the splashing phenomenon (left half part), then with this parameter increase, the number of small droplet and the point where the splashing occur will also change, and there also are much difference in relation of spray radius and time. Actually, if d * is small, the coefficient α would first decrease and then increase with the increase of d *, while if d *>8, the cavity width would only have a little influence on the behavior of spray. Finally, it is also found that the pressure change near the cavity bottom is small at different L *, that is to say, the relative depth of cavity L * seems to has no apparent effect on the formation of spray, but it brings a great influence on the splashing of spray and the movement of the droplet which is produced in the process of splashing.

We present a review of the very recent advances in the synthesis of block copolymer (BCP) Janus nanomaterials. Although Janus micelles can form by the self-assembly of BCPs in solution, patchy or core–shell structures are usually dominant. Structural transformation of the core–shell structure or disassembly of the patchy structure is further employed to achieve Janus nanomaterials. Disassembly of ABC tri-block terpolymer supramolecular structures is advantageous in tuning much more easily the shapes of the Janus nanomaterials from spherical to cylindrical and sheet/disc-like. Narrow molecular weight distributions and strict processing conditions are required. Emulsion droplet confined self-assembly of BCPs can directly achieve Janus nanomaterials in a sufficiently small droplet and/or at low polymer concentration. A neutral emulsion interface is required using proper surfactants. Alternatively, a general method has been proposed to prepare Janus nanomaterials by guided self-assembly of BCPs within a confined environment by the strong interaction and the selective crosslinking of one block. The aforementioned Janus nanomaterials are in the form of a polymer cluster. Single chain Janus nanomaterials of BCPs can be prepared by intramolecular crosslinking of one block in a very dilute solution. It remains challenging to synthesize single chain Janus nanomaterials at high solid content for example tens of percent. At the end of this review, a perspective on BCP Janus nanomaterials is provided.

Molecular migration of gum Arabic (GA) fragments was investigated, when thermodynamic phase separation occurred in mixtures of konjac glucomannan (KGM) and GA at different concentrations. It has been quantitatively analyzed by GPC-MALLS. After reaching phase equilibrium, GA with the small molecular weight migrated into KGM-rich phase, resulting in a decrease of its relative content (from 13.58% to 0.05%) in GA-rich phase. GA was dyed with fluorochrome, and aggregations of GA in separated phase were recorded using fluorescence microscopy. When KGM content was fixed at 0.4 wt%, increasing GA concentration led to the simultaneous formation of larger aggregates of GA. In the process of phase separation, the amount of coexisted KGM in GA-rich phase decreased as a function of time. To collect the separated phases, the fractionated GA was named as FGA. FGA showed better interfacial properties than original GA, resulting in decreasing of oil-water interfacial tension and increasing of the moduli of interfacial adsorption layer. The proposed reason was that fractions of GA maintained in GA-rich phase, which has proved to possess larger molecular weight, contributed to the better emulsifying capacity. So FGA was the concentrated sample of large molecular fractions that has high emulsifying capacity. Optimized FGA-stabilized emulsions presented small droplet size (around 20 μm), high surface charge at neutral pH (about −30 mV) and high stabilities under various pH range or NaCl concentration. Taken together, this paper provides a flexible method for separating and concentrating GA with high emulsifying capability and has great potentials to be applied in in developing new food ingredients.

Oil–air lubrication supplies lubricants in the form of droplets to elastohydrodynamic lubrication (EHL) contacts, such as those in high-speed spindle bearings. However, there is a paucity of information related to understanding the lubrication behaviors of oil droplets within EHL contacts. In this study, behaviors of lubricant droplets, in terms of spreading around a static contact as well as passing through a rolling contact, were studied with an optical ball-on-disk EHL test rig. Influences of oil droplet size, viscosity, and surface tension on droplet spreading were examined. Lubricating film formation was also investigated when droplets traveled through the EHL contact region. The results indicated that droplet size and running speed significantly influenced film profiles. With increasing entrainment speeds, a small droplet passed through the contact without spreading and generated films with a significant depression in the central contact region.

Droplet manipulation is playing an important role in various fields, including scientific research, industrial production, and daily life. Here, inspired by the microstructures and functions of Namib desert beetles, Nepenthes pitcher plants, and emergent aquatic plants, we present a multibioinspired slippery surface for droplet manipulation by employing combined strategies of bottom-up colloidal self-assembly, top-down photolithography, and microstructured mold replication. The resultant multilayered hierarchical wettability surface consists of hollow hydrogel bump arrays and a lubricant-infused inverse opal film as the substrate. Based on capillary force, together with slippery properties of the substrate and wettability of the bump arrays, water droplets from all directions can be attracted to the bumps and be collected through hollow channels to a reservoir. Independent of extra energy input, droplet condensation, or coalescence, these surfaces have shown ideal droplet pumping and water collection efficiency. In particular, these slippery surfaces also exhibit remarkable features including versatility, generalization, and recyclability in practical use such as small droplet collection, which make them promising candidates for a wide range of applications.

Currently, nanoencapsulation of bioactive compounds is promising, and is one of the methods that has been proven very effective. The development of food-grade nanoemulsions is in a state of constant innovation due to the interesting features that this method of encapsulation has, such as small droplet size, kinetic stability and appearance. With this technology, it is possible to control some food properties, such as texture, taste and stability. In this article, we present a review of the most commonly used methods in the creation of nanoemulsions, the recent developments of these dispersions, the relevant applications of nanoemulsions in food matrices, the most commonly used food-grade materials and the functionality of nanoemulsions, which are designed primarily to encapsulate compounds with biological activity. Nanoemulsions have been shown to be effective in preventing degradation and improving the bioavailability of bioactive compounds, such as oil-soluble vitamins, antimicrobials, flavours and antioxidants. At the end of this article, facts of interest about acceptance issues and nanotechnology regulatory policies in the food industry are presented.

This study aimed to optimize ultrasound-assisted palm oil-in-water nanoemulsions. The influence of hydrophilic-lipophilic balance (HLB), oil and surfactants concentrations, ultrasound intensity and processing time were investigated by means of two experimental designs. Desirability profiles were applied to detect the optimal conditions for preparing the nanoemulsion. Stable nanoemulsions with small droplet size and polydispersity index (PDI) were obtained at an HLB of 6.5, oil and surfactant concentrations of 2.8 wt%, ultrasound intensity of 200 W.cm-2 and processing time of 15 minutes. The nanoemulsion presented stability for 30 days at three different temperatures (4°C, 25°C and 40°C), which makes it suitable for application in the food and cosmetic industries. Ultrasound was shown to be a promising technology to produce nanoemulsions containing palm oil.