Emulsion Drops Research Articles

Predictive modeling of emulsion stability and drop characteristics using machine learning: A study on surfactant influence and time dynamics

This study explores the application of empirical and machine learning techniques to assess the impact of surfactants and time on the stability of oil-water emulsions and the characteristics of droplets. It utilizes a novel machine learning approach to forecast cumulative mass percentages by considering parameters such as drop size and time. The actual data was at 1st, 30, and 60 minutes after emulsion preparation and were forecasted up to 180 minutes with a Long-Short Term Memory (LSTM) machine learning model. The model demonstrates promising results in capturing the intricate relationships characterized by achieving an R-Squared (R2) score of 0.898 and Mean Squared Error (MSE) 0.00466. Under similar conditions and analysis, the results predicted for all three surfactants Gum Arabic (GA), Tween-20 (T20), and Poly Vinyl Alcohol (PVA) demonstrated similar behavior. Overall change in cumulative mass is lower confirming emulsion stability; however, at time stamps coalescence occurs, that can be neglected due to little impact. The results also show that interfacial tension is directly related to emulsion stability. Gum Arabic having highest interfacial tension (16mN/m) resulted in the most stable emulsion as compared to lowest interfacial tension surfactant Tween-20 (4mN/m). It is important to acknowledge certain limitations such as variations in surfactant concentration, temperature fluctuations, and shear forces, which may impact the experimental results and model performance. In conclusion, the current finding indicates that predictive modeling with LSTM in understanding emulsion dynamics is providing a foundation for future developments aimed at improving product performance and stability in a variety of industrial sectors like oil/gas, food and pharmaceutical.

Preparation of PDMS permeation membrane by emulsion dilution method and its separation performance for aromatics

Natural aroma compounds are a kind of important food additive. Taking bis(2-ethylhexyl) sodium sulfosuccinate (AOT) as the surfactant, water-in-n-heptane emulsions were prepared. Then, the emulsions were adopted as the diluter to prepare polydimethylsiloxane (PDMS) pervaporation membranes using the emulsion templating method (ePDMS), of which the separation layer was controlled by the template action of emulsion drops. The ePDMS membranes were utilized to separate aroma compounds. Field-emission scanning electron microscope (FESEM) analysis revealed that the surface of the ePDMS membrane remained smooth, and white light interferometry confirmed the membrane’s surface smoothness. FESEM cross-sectional analysis exposed the voids left by the evaporation of the emulsion, rendering the separation layer of the ePDMS membrane more porous. Water contact angle measurements demonstrated the hydrophobicity of the ePDMS membrane, which is advantageous for the pervaporation of aromatic compounds. Fourier transform infrared spectrometry analysis confirmed the evaporation and separation of the emulsion, retaining the original chemical properties of the PDMS membrane. In an ethanol–water system, the permeation flux of ethanol in ePDMS membranes prepared with 1 emulsion (Vwater:Vn-heptane = 1:9; mass concentration of AOT of 1.0 mg/ml) is 90.6% higher than that in PDMS membranes, while the separation factor does not change obviously. The separation performance of ePDMS membranes for linalool in water was further studied. Results show that the permeation flux and separation factor of linalool in ePDMS composite membranes at 50 °C are 786 g m−2 h−1 and 17.69, which separately increase by 84.7% and 27.1% compared with those in PDMS membranes. This indicates that adding ethanol exerts a significant synergistic effect on the separation of linalool.

Flowerlike Spreading of Micellar Films during Emulsion Drop Evaporation.

We investigated the film spreading during the evaporation of submillimeter oil-in-water emulsion droplets on a solid surface, and observed a novel phenomenon where the film follows a two-layer spreading. In combination with the instability at the film front, the spreading front acquires a flowerlike pattern. The emergence of the two-layer structure is attributed to micelles within the oil film that yield an oscillating disjoining pressure. By considering both the slipping condition and the disjoining pressure, a scaling analysis is carried out that agrees well with the observed film spreading dynamics. The film spreading follows Tanner's law initially, while it becomes faster at a later stage, where the film radius follows r∼t^{1/2} for weak slip and r∼t^{3/8} for strong slip conditions.

Effect of gamma radiation on the crack pattern of a styrene-acrylic emulsion dry droplet

We present findings on the influence of gamma radiation on the crack pattern of dried drops of an aqueous styrene-acrylic emulsion. An increase in the dose of gamma radiation reduces the number of cracks and expands the edge of the dried droplet. Furthermore, gamma radiation induces a reduction in the branching of the crack pattern and an increase in the frequency of cracks, with a magnitude comparable to the width of the edge of the dried droplet. The results of the infrared analysis indicated that the micelles surrounding the styrene-acrylic copolymer in the emulsion exerted a protective effect, preventing indirect damage caused by radicals formed due to water radiolysis. The results of the zeta potential and particle size measurements demonstrated that gamma radiation caused an increase in the average size of the micelles, a widening of the size distribution, and a redistribution of surface charges. Doses above 100 kGy induce a loss of emulsion stability. The effects of gamma radiation on the crack patterns were interpreted by considering the dynamics of micelle deposition at the edge of the drop during drying and the appearance of mechanical instabilities in the deposit that lead to cracks. The larger micelles produced due to gamma radiation on the emulsion modify the microstructure formation at the edge of the dried drop, thereby alleviating the formation of mechanical stresses that result in the appearance of cracks.

Hydrogen Sulfide Delivery System Based on Salting-Out Effect for Enhancing Synergistic Photothermal and Photodynamic Cancer Therapies.

The simultaneous application of photothermal therapy (PTT) and photodynamic therapy (PDT) offers substantial advantages in cancer treatment. However, their synergistic anticancer efficacy is often limited by tumor hypoxia, and thermotolerance induced by high expression of heat shock proteins (HSP). Fortunately, hydrogen sulfide (H2S), known for its direct cytotoxic effect on tumor cells, has been recognized for its ability to enhance PTT and PDT. The effectiveness of H2S in these therapies is challenged by its low loading efficiency, poor stability, and short diffusion distance. To address these issues, a nanoscale emulsion drop template created through the salting-out effect is employed to construct a robust H2S delivery system. Polydopamine (PDA), chosen for its interfacial polymerization tendency and excellent photothermal conversion rate, is utilized as a carrier for the H2S donor (ADT) and Zinc phthalocyanine (ZnPc) to fabricate a novel nanomedicine termed APZ NPs. The temperature-responsive APZ NPs are designed to release H2S during the PTT process. Elevated H2S levels promoted vasodilation, thereby enhancing the enhanced permeability and retention effect (EPR) of APZ NPs within solid tumors. This strategy effectively alleviated tumor hypoxia by disrupting the mitochondrial respiratory chain and mitigated tumor cell heat tolerance by inhibiting HSP expression.

How does an emulsion drop's viscosity influence its impact on various meshes?

The impact of emulsion drops on a mesh is studied. These drops find applications in various fields, e.g., agricultural sprays, where the drop passes through a mesh for atomization. Both penetration (full or partial) and lateral spreading are observed in most cases. The maximum spread's variation with Weber number (We) shows liquid independence for drops impacting a given mesh. The variations can be concluded into one. However, when both lateral spread and penetration are concerned, the emulsion drop with the highest water content tested stands out as different. It shows dissimilar characteristics due to its higher viscosity. The drop's lateral spread Reynolds number is lower than the others, indicating a significant dependence on the liquid viscosity. Rising viscosity resists the lateral inertia. Surface tension (ST) and density do not have much influence. The balance between the downward and after-impact lateral inertia and their resistance makes the lateral spread on a given mesh independent of liquid. Three regimes, full, partial, and no penetration, can be defined. A dissimilarity in the after-penetration jet length is detected. The length is inversely proportional to the emulsion's rising water content. The drop with the highest viscosity, together with ST, provides the highest resistance to penetration. Thus, the length reduces abruptly. When the after-impact penetration cone angle is studied, the average angle reduces with We for the highest viscosity emulsions. An abrupt rise in resistance is detected. The study's novelty lies in bringing out the viscosity's influence on the emulsion drop's impact on a mesh.

Self-shaping of triglyceride and alkane drops: Similarities and differences

Small emulsion drops typically exhibit spherical shape at positive interfacial tension due to the energy minimization principle. However, in a series of studies (Denkov et al., Nature, 2015, 528, 392–395; Cholakova et al., Nature Phys., 2021, 17, 1050–1055) we showed that alkane droplets stabilized by appropriate saturated long-chain surfactants may spontaneously change their shape upon cooling, morphing into various polyhedra; hexagonal, tetragonal and triangular platelets; rod-like particles and even synthetic swimmers. These deformations are governed by the formation of thin plastic rotator phases adjacent to the drop surface. Although alkanes have numerous industrial applications, they cannot be used in food and pharma related products, in which most often triglyceride molecules are employed. The possibility for self-shaping of triglyceride drops has been demonstrated, but the detailed understanding of the process is currently missing. In the present study, we performed model experiments aimed to reveal the conditions under which the triglyceride emulsion drops may change their shape upon cooling. We show that most of the various non-spherical shapes known for alkanes can be reproduced with triglyceride droplets providing that the surfactant adsorption layer freezes before the nucleation of the oily molecules inside the drops. By comparing the behavior of triglyceride and alkane droplets, we draw unified picture and provide guiding principles which can be used for selection of appropriate surfactants enabling the spontaneous shape deformations upon cooling of oily drops of different chemical compositions.

Chitin nanocrystals/alginate complex for tuning stability, rheology and bioavailability of cholecalciferol in Pickering emulsions

In this paper we investigate polyelectrolyte complexes of sodium alginate (Alg) and chitin nanocrystals (ChNC). Formation, stability and transport properties of sunflower oil-in-water emulsions stabilized by ChNC-Alg complex were studied using dynamic light scattering (DLS), laser Doppler electrophoresis, optical microscopy, potentiometric titration, rheology and simulated digestion. It has been established that during emulsions formation, the ChNC-Alg complex is rearranged at the interface and the formation of a two-layer coating of the droplet occurs. Stabilized O/W emulsions are stable during storage, in the pH range 2–9 and centrifugal acceleration up to 2000 RCF. Presence of Ca2+ and Na+ ions in the range up to 150 mM has virtually no effect on the droplet size. Inclusion of 5 wt% Alg in the ChNC-based emulsion stabilizer system leads to a drop in Gibbs adsorption >16 times compared to the ChNC-stabilized emulsion, increase in viscosity and rheopexy index of the systems. We found that chemical properties of colloidal phase surface and rheological properties of emulsions stabilized by ChNC-Alg are mostly dependent on the droplet size, not the type of oil as a result of a comparative study of sunflower oil/liquid paraffin oil. Emulsion drops of an optimized composition are stable in the upper parts of the model gastrointestinal tract system and transport vitamin D3 to the small intestine without significant losses. The bioavailability of vitamin D3 in emulsions stabilized with the ChNC-Alg complex is higher than for emulsions stabilized with ChNC alone.

Ultralight, Robust, Thermal Insulating Silica Nanolace Aerogels Derived from Pickering Emulsion Templates.

Synthesis of silica aerogel insulators with ultralight weight and strong mechanical properties using a simplified technique remains challenging for functional soft materials. This study introduces a promising method for the fabrication of mechanically reinforced ultralight silica aerogels by employing attractive silica nanolace (ASNLs)-armored Pickering emulsion templates. For this, silica nanolaces (SiNLs) are fabricated by surrounding a cellulose nanofiber with necklace-shaped silica nanospheres. In order to achieve amphiphilicity, which is crucial for the stabilization of oil-in-water Pickering emulsions, hydrophobic alkyl chains and hydrophilic amine groups are grafted onto the surface of SiNLs by silica coupling reactions. Freeze-drying of ASNLs-armored Pickering emulsions has established a new type of aerogel system. The ASNLs-supported mesoporous aerogel shows 3-fold greater compressive strength, 4-fold reduced heat transfer, and a swift heat dissipation profile compared to that of the bare ASNL aerogel. Additionally, the ASNL aerogel achieves an ultralow density of 8 mg cm-3, attributed to the pore architecture generated from closely jammed emulsion drops. These results show the potential of the ASNL aerogel system, which is ultralight, mechanically stable, and thermally insulating and could be used in building services, energy-saving technologies, and the aerospace industry.

In Vitro and In Vivo Performance of Pickering Emulsion-Based Powders of Omega-3 Polyunsaturated Fatty Acids.

Omega-3 polyunsaturated fatty acids (n-3 PUFA) are essential nutrients for human health and have been linked to a variety of health benefits, including reducing the risk of cardiovascular diseases. In this paper, a spray-dried powder formulation based on Pickering emulsions stabilized with cellulose nanocrystals (CNC) and hydroxypropyl methylcellulose (HPMC) has been developed. The formulation was compared in vitro and in vivo to reference emulsions (conventional Self-Emulsifying Drug Delivery System, SEDDS) to formulate n-3 PUFA pharmaceutical products, specifically in free fatty acid form. The results of in vivo studies performed in fasted dogs showed that Pickering emulsions reconstituted from powders are freely available (fast absorption) with a similar level of bioavailability as reference emulsions. In the studies performed with dogs in the fed state, the higher bioavailability combined with slower absorption observed for the Pickering emulsion, compared to the reference, was proposed to be the result of the protection of the n-3 PUFAs (in free fatty acid form) against oxidation in the stomach by the solid particles stabilizing the emulsion. This observation was supported by promising results from short-term studies of chemical stability of powders with n-3 PUFA loads as high as 0.8 g oil/g powder that easily regain the original emulsion drop sizes upon reconstitution. The present work has shown that Pickering emulsions may offer a promising strategy for improving the bioavailability and stability as well as providing an opportunity to produce environmentally friendly (surfactant free) and patient-acceptable solid oral dosage forms of n-3 PUFA in the free fatty acid form.

USE OF AQUEOUS EMULSIONS OF WASTE MOTOR OILS AS HIGH-EFFICIENCY FUEL

This work presents the methodology of using wasted lubricants as a highly efficient fuel as water-fuel emulsions, which containing up to 70% water. They burning in burners under conditions of action high-frequency electrical discharges. It has been shown that the viscosity of a water-oil emulsion with a high water part (more than 50%) outweighs the viscosity of pure oil. With a low water part (10-20%), the emulsion is the most stable. With more water, the semi-delamination time decreases. Therefore, it is necessary to spray the emulsion near the site of the making. The results of natural experiments and prospects of the proposed methodology are given. Combustion of a water-in-oil emulsion with a volume content of 50-70% water is possible in the presence of a discharge of high-frequency signals. Independent combustion of the emulsion without the support of a small diesel fuel torch is possible with sufficient heating of the combustion chamber. To implement combustion, the burner for liquid fuels was modernized by adding a pre-chamber between the burner and the nozzle or boiler. To organize effective spraying of water-oil emulsion with a large amount of water (up to 70%), it is necessary to ensure sufficient heating of the emulsion in the pipelines. First, this reduces its viscosity, making it easier to pump the emulsion through the supply systems of the spraying device. Otherwise, it is necessary to serve under a pressure, so that the water at a high temperature (above 100 ° C) is remained liquid. When leaving the nozzle under pressure, the water “boils” (“micro-bump” drops of emulsion), which further disperses the burning liquid. The peculiarity of this burner is the action of a high-frequency streamer in the area of spraying emulsion droplets inside the forechamber. The use of water-fuel emulsions allows to reduce emissions of nitrogen oxides and carbon monoxide, reduce its fire and explosion hazard during transportation and storage. Effectiveness assessment of this complex showed that energy expenditures can reach percents of levels compared to full heat release.Thus, the possibility of using such water-oil emulsions as alternative fuels is shown. Keywords: water-oil emulsion, high-frequency electric discharge, combustion, torch.

Visualization and Quantification of Mobility Reduction in Porous Media Flow Associated with Pore Blocking by Emulsion Drops

Visualization and Quantification of Mobility Reduction in Porous Media Flow Associated with Pore Blocking by Emulsion Drops

Structure of Rotator Phases Formed in C13–C21 Alkanes and Their Mixtures: In Bulk and in Emulsion Drops

Structure of Rotator Phases Formed in C₁₃–C₂₁ Alkanes and Their Mixtures: In Bulk and in Emulsion Drops

Evaporation of flammable liquids droplets in an electric discharge

Evaporation of a liquid drop under the action of a high-frequency electric discharge is considered. The drops were suspended on a thermocouple and were in air at room temperature. The analysis was carried out under the assumption that the action of the discharge is thermal. It is shown that pure liquid fuel drop (ethanol and diesel fuel) evaporates according to the d2-law. At the same time, the rate of evaporation takes a maximum value depending on the distance to the electrode. Analysis of the rate of drop mass reduction made it possible to estimate the thermal power of the discharge, which also passes through a maximum when the electrode is moved away from the drop. When evaporating emulsion droplets (50%/50% fuel/water) after the heating stage, pulsations of geometric size are observed. The drop size periodically changes near some average value with a certain frequency, which decreases with the time of "evaporation". A physico-mathematical model of droplet heating under the thermal action of a discharge was constructed. The pulsations are explained by the evaporation of water globules inside the emulsion drop, the subsequent increase in the size of the vapor bubbles before the "micro-explosion" of the drop. The loss of emulsion material under the action of an electric discharge occurs mainly due to emissions during microexplosions. That is, the electric discharge leads to the dispersion of emulsions droplets with a high water content, in contrast to individual flammable liquids droplets. A decrease in the water content and the power of the electric discharge leads to an increase in the period of pulsations.

Demixing behavior of Pickering emulsions stabilized by Janus particles and uniform Pickering particles at different pH values

This work investigates the demixing behavior of Pickering emulsions consisting of water, n-hexadecane, and two different types of Pickering particles. The first type is uniform, and the second consists of one-side modified Janus particles influencing the emulsion behavior significantly. Both particle types are able to stabilize the emulsions, but lead to clear differences in the emulsion drop size and size distribution. This results in different creaming times varying between minutes and hours and different clearance processes of the water excess phase. Large pH effects were found in addition. At some conditions, non-adsorbed particles were observed that sediment over time in addition to the creaming of the emulsion.

Water-in-oil emulsion drop-wall impact: Effect of viscosity and water particles on slip length over an oleophilic surface

The study is focused on the numerical simulation of the boundary slip of a water-in-oil (W/O) emulsion along an oleophilic surface in a 2D axisymmetric formulation of the Navier–Stokes equations for an incompressible laminar flow. Drops of emulsions with a volume fraction of the dispersed phase of 0.04–0.34 collide with a smooth glass wall at initial velocities of 1.2–3.6 m/s; the motion of the interface between the liquid and gas phases is resolved by the level set method. The influence of the wall wettability by oily liquids is demonstrated by varying the static contact angle up to 0.5° and by considering the dynamic one as a function of the empirically measured contact line velocity of the liquid drop according to Tanner's law. Numerical simulation of emulsion drop spreading dynamics reveals that the boundary slip of a heterogeneous liquid along a smooth oleophilic wall is different from that of a homogeneous. The temporal changes in the average viscous stress allowed the illustration of the interrelated effects of emulsion viscosity and the presence of disperse phase particles on the boundary slip of a heterogeneous liquid and its motion in the viscous boundary layer. The analytical expression evaluating the slip length for an arbitrary W/O emulsion was derived using the effective properties of the liquid. In testing the expression, the values of the maximum spreading factor of drops of an arbitrary W/O emulsion predicted by numerical simulation correspond to those determined from experiments at a moderate error of 7.4%.

Two Convenient Methods for Detection of Non-Dairy Fats in Butter by Dynamic Light Scattering and Luminescence Spectroscopy

We propose two convenient methods to quickly detect the presence of non-milk fat (palm oil) in butter, as well as to determine its amount in the product. For the first time, we have experimentally obtained the dependence of the size of drops of an alcoholic emulsion of oil or spread on the content of palm oil in it by the dynamic light scattering (DLS) method. We have also obtained the dependence of intensity ratio of the components of spread luminescence spectrum on palm oil content when excited at a wavelength λ = 266 nm. These results allowed us to propose two methods for determining the adulteration of butter with palm oil using DLS and measuring luminescence spectra. The two methods are physically independent but successfully supplement each other. DLS and luminescent methods for determining the proportion of palm oil give errors of no more than 10% and 6%, respectively.

A triple emulsion droplet in an extensional flow

In this theoretical report we analytically explore the deformation and breakup of an initially spherical triple emulsion drop undergoing an axisymmetric extensional creeping flow. The triple emulsion, suspended in an external fluid (fluid 1), is originally made from an inner spherical drop (fluid 4), engulfed by a spherical shell (fluid 3), which is subsequently engulfed by another spherical shell (fluid 2). The problem is described by eight dimensionless parameters: the external capillary number (Ca), three viscosity ratios (λ21, λ32, λ43), two radii ratios (K, k), and two surface tensions ratios (M, m). When the triple emulsion is subjected to an external uniaxial extensional flow (Ca > 0), the outer interface (21) and the inner drop interface (43) deform into prolate spheroids, while the interface between them (32) deforms into an oblate spheroid. The reverse occurs for an external biaxial flow (Ca < 0), the outer interface (21) and the inner drop interface (43) deform into oblate spheroids and the middle interface (32) becomes a prolate spheroid. Three types of breakup mechanisms are to be expected: when the outer and the middle interfaces are in contact, when the middle and the inner interfaces are in contact, and when the inner drop breaks while the two shell phases remain continuous. Finally, an analytical expression for the effective viscosity of a dilute emulsion containing spherical triple emulsion droplets is suggested. For a triple emulsion which behaves like a solid: a very viscous or a very thin outer shell (λ21→∞ or K→ 1), the effective viscosity reduces to Einstein’s formula, and when the triple emulsion behaves like a single drop: a very thick outer shell such that the inner shell and the inner drop disappear (K→ 0), Taylor’s expression is recovered.

Synthesis of gold nanoparticles in emulsion–emulsion precipitation route: Experiment, mechanism and simulation

Soft templates like water-in-oil emulsion drops (of 1-100μm diameter), have been used for synthesis of nanoparticles; with specific mean particle diameter and narrow particle size distribution. In this context, two separate emulsions have been reacted by an emulsion–emulsion precipitation route. Consequently, two different kinds of interacting populations coexist — emulsion drops evolving through drop coalescence and breakage, with multiple nanoparticle populations growing inside each emulsion drop. However, no model framework currently exists to simulate these two highly interacting populations, for predicting evolution of nanoparticle size. To this end, presently gold nanoparticles (GNPs) have been used as a model system, to explore the nanoparticle formation mechanism. The metal salt precursor and reducing agent (NaBH4 or N2H4) are prepared in two separate water-in-oil emulsions and are reacted upon mixing to form GNPs. A kinetic Monte Carlo (kMC) scheme accounting for drop coalescence, drop breakage, nucleation, particle growth and particle–particle coagulation was developed to handle simultaneous size and number evolution of aqueous emulsion drops and GNP populations. We find that, the mean GNP diameter decreases (from 6.9 to 3.5 nm) with increasing molar ratio (M) of reducing agent to precursor concentration. Further, increasing the precursor concentration at a fixed M, does not affect the final particle size. Our kMC simulation results not only agree well with experimental mean particle diameter and coefficient of variation (COV) of particle diameter, but was also validated with full particle size distribution of GNPs. So, M can be used as a tunable parameter for controlling GNP diameter experimentally.

New emulsion electrospun biodegradable fibers and films PLA/PVP, containing green synthesized hydrozincite – Antibacterial and photocatalytic activity

New Poly(lactic acid)/Polyvinylpyrrolidone, containing green synthesized Hydrozincite (GHZ) emulsion electrospun fibers and drop spread films possessing antibacterial and photocatalytic activity were prepared. The PLA/PVP/GHZ films possess higher photocatalytic efficiency towards Malachite Green (MG) dye discoloration (85%) than that of the fibers (62%). The films demonstrate better antibacterial activity to E. coli K-12 with about 6.58 Log CFU/ml in comparison with fibers which expressed about 2.20 Log CFU/ml reduction for 120 h contact.