Search Results (486)

Backgroun/Objectives: Recent pharmaceutical research has increasingly focused on eutectic systems to improve the formulation and delivery of active pharmaceutical ingredients (APIs). This study presents the preparation and characterization of three therapeutic eutectic systems (THEESs) based on ibuprofen and menthol at various molar ratios. Methods: The THEESs were prepared and analyzed by assessing their physicochemical properties and rheological properties were evaluated to determine flow behavior. Cytotoxicity assays were conducted on HaCaT and HepG2 cell lines to assess biocompatibility. Results: All systems formed monophasic, homogeneous, clear and viscous liquids. Key physicochemical properties, including density, refractive index, surface tension, speed of sound and isobaric heat capacity, showed a temperature-dependent, inverse proportional trend. Viscosity followed the Vogel–Fulcher–Tammann equation, and rheological analysis revealed non-Newtonian behavior, which is important for pharmaceutical processing. Notably, cytotoxicity assays revealed that Ibu-M3 and Ibu-M4 showed lower toxicity than pure compounds in HaCaT cells, while Ibu-M5 was more toxic; in HepG2 cells, only Ibu-M3 was less toxic, whereas Ibu-M4 and Ibu-M5 were more cytotoxic than the pure compounds. Conclusions: These findings highlight the potential of ibuprofen–menthol eutectic systems for safer and more effective pharmaceutical formulations. Full article

We present a theoretical model for the electrophoresis of a weakly charged oil drop migrating through an uncharged polymer gel medium saturated with an aqueous electrolyte solution. The surface charge of the drop arises from the specific adsorption of ions onto its interface. Unlike solid particles, liquid drops exhibit internal fluidity and interfacial dynamics, leading to distinct electrokinetic behavior. In this study, the drop motion is driven by long-range hydrodynamic effects from the surrounding gel, which are treated using the Debye–Bueche–Brinkman continuum framework. A simplified version of the Baygents–Saville theory is adopted, assuming that no ions are present inside the drop and that the surface charge distribution results from linear ion adsorption. An approximate analytical expression is derived for the electrophoretic mobility of the drop under the condition of low zeta potential. Importantly, the derived expression explicitly includes the Marangoni effect, which arises from spatial variations in interfacial tension due to non-uniform ion adsorption. This model provides a physically consistent and mathematically tractable basis for understanding the electrophoretic transport of oil drops in soft porous media such as hydrogels, with potential applications in microfluidics, separation processes, and biomimetic systems. These results also show that the theory could be applied to more complicated or biologically important soft materials. Full article

Janus nanoparticles (JNPs) extend the concept of amphiphilicity beyond classical molecular surfactants into the nanoscale. Amphiphilic behavior is defined by the presence of hydrophobic and hydrophilic moieties within a single molecular structure. Traditionally, such molecular structures are known as surfactants or amphiphiles and are capable of reducing interfacial tension, adsorbing spontaneously at interfaces, stabilizing emulsions and foams, and forming micelles, bilayers, or vesicles. Recent experimental, theoretical, and computational studies demonstrate that these behaviors are scalable to nanostructured colloids such as JNPs. Amphiphilic JNPs, defined by anisotropic surface chemistry on distinct hemispheres, display interfacial activity driven by directional wetting, variable interfacial immersion depth, and strong interfacial anchoring. They can stabilize liquid/liquid and liquid/gas interfaces, and enable templated or spontaneous self-assembly into supra-structures, such as monolayer sheets, vesicles, capsules, etc., both in bulk and at interfaces. Their behavior mimics the “soft” molecular amphiphiles but also includes additional particularities given by their “hard” structure, as well as contributions from capillary, van der Waals, hydrophobic, and shape-dependent forces. This review focuses on compiling the evidence supporting amphiphilicity as a scalable property, discussing how JNPs function as colloidal amphiphiles and how geometry, polarity contrast, interfacial interactions, and environmental parameters influence their behavior. By comparing surfactant behavior and JNP assembly, this work aims to clarify the transferable principles, the knowledge gap, as well as the emergent properties associated with amphiphilic Janus colloids. Full article

Over recent years, ultrasonic atomization, especially with regard to liquid metals, has become an object of increased interest, mainly from industry, for additive manufacturing, but also from investigators, for research purposes. A strong correlation between the average particle size, distribution of particle sizes, and other process parameters like frequency and vibration amplitude was noted based on the analysis of available theoretical studies, simulations and experiments. The influence of parameters of the atomized fluid-like viscosity and surface tension on process parameters was also mentioned. The objective of this study is further research on the feasibility of using ultrasonic atomization to examine the properties of liquids, especially metals in liquid state. It attempts to close a gap in existing knowledge in searching for a new, possibly simple and cost-effective method to study the properties of liquid metals and further clarify the relationship between ultrasonic atomization parameters (amplitude, frequency, characteristics of metal being spilled on a vibrating surface) and obtained atomization results meant by average particle size and atomization time. Using numerical modeling (finite element method and computational fluid dynamics) as a methodology, combined with tests of using ultrasonic atomization as an instrument to determine properties of liquid metals, was considered as an introduction to a series of experiments. These tests were followed by real experiments that are also presented. At the first stage, numerical modeling was applied to a case of a specific liquid being spilled over a vibrating surface of different angles of inclination and specified, constant frequency and amplitude. The results of the simulation are in line with the current state of knowledge about ultrasonic atomization. Moreover, they can provide some more information on scalability, thus easing the comparison of the results of other experiments presented in the available literature. As a result, the relationship between fluid properties and the average size of atomized particles was demonstrated independently of the surface inclination angle. In the same way, the dependence of successful atomization on a sufficiently thin layer of a liquid was demonstrated. Thirdly, a correlation between the aforementioned layer thickness and the value of vibration amplitude has also been shown. Taking all the above into consideration, ultrasonic atomization can also be considered a research method and can be applied to study the properties of liquid metals. Further research, simulations and experimentation will be conducted to verify, develop and describe this method in full. Full article

In bulk liquid or on solid surfaces, nanobubbles (NBs) are gaseous domains at the nanoscale. They stand out due to their extended (meta)stability and great potential for use in practical settings. However, due to the high energy cost of bubble generation, maintenance issues, membrane bio-fouling, and the small actual population of NBs, significant advancements in nanobubble engineering through traditional mechanical generation approaches have been impeded thus far. With the introduction of the electric field approach to NB creation, which is based on electrostrictive NB generation from an incoming population of “electro-fragmented” meso-to micro bubbles (i.e., with bubble size broken down by the applied electric field), when properly engineered with a convective-flow turbulence profile, there have been noticeable improvements in solid-state operation and energy efficiency, even allowing for solar-powered deployment. Here, these innovative methods were applied to a selection of upstream and downstream activities in the oil–water–fuels nexus: advancing core flood tests, oil–water separation, boosting the performance of produced-water treatment, and improving the thermodynamic cycle efficiency and carbon footprint of internal combustion engines. It was found that the application of electric field NBs results in a superior performance in these disparate operations from a variety of perspectives; for instance, ~20 and 7% drops in surface tension for CO₂- and air-NBs, respectively, a ~45% increase in core-flood yield for CO₂-NBs and 55% for oil–water separation efficiency for air-NBs, a rough doubling of magnesium- and calcium-carbonate formation in produced-water treatment via CO₂-NB addition, and air-NBs boosting diesel combustion efficiency by ~16%. This augurs well for NBs being a potent agent for sustainability in the oil and fuels sector (whether up-, mid-, or downstream), not least in terms of energy efficiency and environmental sustainability. Full article

To address the unclear coupling mechanism between bubble detachment behavior and acoustic characteristics in gas–liquid two-phase flow, this paper systematically studied bubble behavior and acoustic characteristics under different conditions by building a high-precision synchronous measurement system, combining acoustic signal analysis and bubble dynamics observation. The influence mechanism of liquid surface tension, dynamic viscosity, and orifice diameter on the critical gas flow velocity of bubble flow transition was analyzed, and a flow pattern classification criterion system was established. The experimental results showed that the bubble flow state could be divided into three states according to the characteristics of the acoustic signals: discrete bubble flow, single-chain bubble flow, and dual-stage chain bubble flow. The liquid surface tension and dynamic viscosity had no significant effect on the critical gas flow velocity of the transition from discrete bubble flow to single-chain bubble flow, but significantly increased the critical gas flow velocity of the transition from single-chain bubble flow to dual-stage chain bubble flow. The increase in the orifice diameter reduced the critical gas flow velocity of the two types of flow transition. In addition, the Weber number (We) and Galileo number (Ga) were introduced to construct a quantitative classification system of flow pattern, which provided theoretical support for the optimization of industrial gas–liquid two-phase flow. Full article

To investigate the degradation mechanisms of the surrounding rock in abandoned mine roadways used for oil storage, this study combined uniaxial compression tests with digital image correlation (DIC), scanning electron microscopy (SEM), and other techniques to analyze the evolution of the rock mechanical properties under the coupled effects of oil–water soaking and initial damage. The results indicate that oil–water soaking induces the loss of silicon elements and the deterioration of microstructure, leading to surface peeling, crack propagation, and increased porosity of the sample. The compressive strength decreases linearly with the soaking time. Acoustic emission (AE) monitoring showed that after 24 h of soaking, the maximum ringing count rate and cumulative count decreased by 81.7% and 80.4%, respectively, compared to the dry state. As the liquid saturation increases, the failure mode transitions from tension dominated to shear failure. The synergistic effect of initial damage and oil–water erosion weakens the rock’s energy storage capacity, with the energy storage limit decreasing by 45.6%, leading to reduced resistance to external forces. Full article

Drying constitutes an essential step in aerogel fabrication, where the drying method directly determines the pore structure and consequently influences the material’s functionality. This study employed various drying techniques to prepare balsa-wood-derived aerogels, systematically investigating their effects on microstructure, density, and performance characteristics. The results demonstrate that different drying methods regulate aerogels through distinct pore structure modifications. Supercritical CO₂ drying optimally preserves the native wood microstructure, yielding aerogels with superior thermal insulation performance. Freeze-drying induces the formation of ice crystals, which reconstructs the microstructure, resulting in aerogels with minimal density, significantly enhanced permeability, and exceptional cyclic water absorption capacity. Vacuum drying, oven drying, and natural drying all lead to significant deformation of the aerogel pore structure. Among them, oven drying increases the pore quantity of aerogels through volumetric contraction, thereby achieving the highest specific surface area. However, aerogels prepared by air drying have the highest density and the poorest thermal insulation performance. This study demonstrates that precise control of liquid surface tension during drying can effectively regulate both the pore architecture and functional performance of wood-derived aerogels. The findings offer fundamental insights into tailoring aerogel properties through optimized drying processes, providing valuable guidance for material design and application development. Full article

Biosurfactants are becoming increasingly popular, but industrial production of biosurfactants is difficult, partly due to high production costs resulting from the need to use expensive substrates. One economically feasible candidate is vegetable oils, which can be directly metabolized without pretreatment. The aim of this work is therefore to investigate the possibility of using vegetable oils for lipopeptide production by Serratia marcescens G8-1. The genetic background of this strain for the production of lipopeptides was investigated using a genomic approach. The biosurfactants were analysed by Ultra-Performance Liquid Chromatography coupled with Electrospray Ionisation Mass Spectrometry. The ability to reduce surface tension was investigated using a tensiometer. The results showed that the best effect in reducing surface tension was achieved by adding waste rapeseed oil. Sunflower and linseed oil also showed good results. Significantly poorer results were obtained when fresh rapeseed oil, sesame oil and pumpkin seed oil were used. The putative gene cluster for cyclic lipopeptides NRPS was identified in the genome of S. marcescens G8-1. The results obtained confirmed that serrawettin W1 is the major biosurfactant produced by S. marcescens G8-1. Of particular interest, the results showed the presence of vinylamycin when rapeseed oil was used. Full article

Polyols derived from poly(vinyl alcohol) (PVA) have not been reported before. The hydroxyalkylation of PVA with oxiranes leads to powdered or gum-like products that are not miscible with isocyanates and therefore useless as sources of polyurethane foams. Glycidol and ethylene carbonates were used to dissolve and convert PVA into liquid polyol. The physical properties of the PVA-derived polyol, such as the density, viscosity, and surface tension, were determined. The polyol was then used to obtain rigid polyurethane foams (PUFs). Foaming conditions were optimized, and the apparent density, volume water uptake, dimensional stability, heat conductance coefficient, pore size, thermal resistance, compressive strength, and glass transition temperature of the obtained PUFs were determined. The properties of the obtained PUFs were similar to those of classic rigid PUFs, but the thermal resistance of the former is better. Specifically, PVA-derived PUFs are thermally resistant at temperatures of up to 150 °C. Furthermore, they are ecologically safe; in standard soil conditions, 54.6% or 100% biodegradation of the foams in cube and powder form, respectively, was observed, as measured by BOD after 28 days of storage. Full article

We experimentally studied the effect of a surfactant on bubble formation on a superhydrophobic surface (SHS). The bubble was created by injecting gas through an orifice on the SHS at a constant flow rate in the quasi-static regime. The surfactant, 1-pentanol, was mixed with water at concentration C ranging from 0 to 0.08 mol/L, corresponding to surface tension σ ranging from 72 to 43 mN/m. We found that as C increased, the bubble detachment volume (V_d) and maximum bubble base radius (R_d^max) decreased. For a low surfactant concentration, the static contact angle θ₀ remained nearly constant, and V_d and R_d^max decreased due to lower surface tensions, following the scaling laws R_d^max~σ^1/2 and V_d~σ^3/2. The bubble shapes at different concentrations were self-similar. The bubble height, bubble base radius, radius at the bubble apex, and neck radius all scaled with the capillary length. For high surfactant concentrations, however, θ₀ was greatly reduced, and V_d and R_d^max decreased due to the combined effects of reduced θ₀ and smaller σ. Lastly, we found that the surfactant had a negligible impact on the forces acting on the bubble, except for reducing their magnitudes, and had little effect on the dynamics of bubble pinch-off, except for reducing the time and length scales. Overall, our results provide a better understanding of bubble formation on complex surfaces in complex liquids. Full article

Three oleyl-based sulfosuccinates with different polyoxyethylene (EO) chain length (MS-OE_n, where n = 3, 5, 7) were synthesized, and their structure were confirmed using FT-IR and ¹H NMR analyses. The surfactant’s adsorption properties, aggregation behavior and practical performance were systematically investigated. Equilibrium surface tension measurements elucidated the surface adsorption properties such as critical micelle concentration (cmc) values and the corresponding surface tensions at cmc (γ_cmc). Dynamic surface tension analysis indicated slower adsorption kinetics for surfactants with longer EO chains. Aggregation studies demonstrated that MS-OE₃ formed vesicles, whereas no such vesicular structures were observed in the aqueous solutions of MS-OE₅ and MS-OE₇ at equivalent concentrations. Further, it was observed that foam stability decreased with an increase in EO units, while MS-OE₃ exhibited the best wetting ability. Notably, the liquid crystal emulsion formulated with MS-OE₇ demonstrated exceptional long-term stability. Full article

Surfactants are often used in the process of coal dust suppression, and the wetting effect is greatly affected by the surfactant hydrophilic group structures. In order to explore the influence of hydrophilic groups of surfactants on their adsorption states and wetting effect on coal dust, three surfactants with similar hydrophilic groups were selected, namely, anionic surfactant sodium dodecyl sulfate (SDS), anionic-nonionic surfactant alkyl ether sulfate (AES), and nonionic surfactant alkyl polyoxyethylene ether-3 (AEO-3). To assess surfactant efficiency, surface tension, wetting time, infrared spectra, and wetting heat were analyzed. These parameters provide insights into molecular adsorption, interfacial behavior, and energy changes during wetting. The different adsorption states of surfactants on the coal dust surface due to EO and SO₄²⁻ hydrophilic groups were analyzed. Results show that both anionic surfactant SDS and nonionic surfactant AEO-3 form the monolayer adsorption structure on the coal dust surface. Due to the electrostatic repulsion of SO₄²⁻ groups, the adsorption density of SDS is lower than that of AEO-3, which results in the higher wetting heat of AEO-3 compared to SDS. In addition, the EO groups without electrostatic repulsion make AEO-3 molecules more tightly adsorbed at the air–liquid interface, causing the minimal surface tension. Therefore, the wetting time of AEO-3 is shorter than that of SDS. The anionic-nonionic surfactant AES has both EO and SO₄²⁻ groups. Because the EO groups in the inner surfactant adsorption layer can attract Na⁺ ions to distribute around them, the free AES molecules further form the outer adsorption layer under the electrostatic attraction between SO₄²⁻ groups and Na⁺ ions. The double-layer adsorption structure causes the hydrophobic groups of the outer AES molecules to face outward, the hydrophobic sites on the coal dust surface are not completely transformed into hydrophilic sites. Although AES exhibits the highest adsorption density, it has the lowest wetting heat and the longest wetting time. The research results can provide theoretical guidance for the selection of suitable surfactants for coal dust suppression. Full article

In this study, we introduce a novel Electrowetting-on-Dielectric (EWOD) sensor designed to quantify marine dispersants at the spill point. The sensor quantifies changes in the surface tension of liquid droplets at varying dispersant concentrations through the deformation response of the droplet under applied voltage. Analyzed responses include droplet length and contact angle (CA) on the device surface upon sensor activation. This sensor offers significant advantages over existing chemical methods, which are costly and complex. Moreover, compared to conventional methods based on the same principle, it demonstrates enhanced sensitivity at low concentrations. Additionally, the sensor’s portability enables instantaneous and in situ measurements of marine dispersant concentrations, thus providing a crucial tool for effective oil spill response by facilitating on-site decision-making and offering higher temporal resolution for studies on the marine dispersant’s environmental impact. The device’s potential extends beyond marine dispersants to detecting various contaminants affecting surface tension. Its adaptability underscores the EWOD device’s role as a versatile tool for environmental monitoring and on-site analysis, addressing the urgent need for efficient and sustainable solutions in environmental management. Full article

To support computational studies and process optimization that require temperature-dependent thermophysical properties, this study characterized the wettability, surface tension, liquid–solid interfacial tension (IFT), and work of adhesion of Al 7075-T6 alloy from 923–1073 K under argon on porous alumina, tungsten, and nonporous alumina substrates using sessile drop experiments and Young’s and Young–Dupre equations, respectively. Furthermore, the substrates’ room-temperature surface free energy (SFE) characteristics were characterized using the Owens–Wendt–Rabel–Kaelble model. The contact angle results revealed the alloy’s poor wettability on all substrates. The surface tension data ranged from 718.87–942.90 mN·m⁻¹ in decreasing order of tungsten, porous alumina, and nonporous alumina. The SFE results of the porous alumina, nonporous alumina, and tungsten substrates were 44.92, 43.32, and 42.03 mN·m⁻¹, respectively. Also, the calculated liquid–solid IFT values ranged from 539.24–835.51 mN·m⁻¹ in decreasing order of porous alumina, tungsten, and nonporous alumina. Additionally, the calculated work of adhesion values ranged from 123.97–479.44 mN·m⁻¹ in decreasing order of nonporous alumina, tungsten, and porous alumina, respectively. Thus, the wettability, surface tension, and liquid–solid IFT of Al 7075-T6 alloy on the substrates were affected by the substrates’ SFE characteristics, thereby affecting the work of adhesion. Full article