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The interfacial structure and adsorption behavior of 1-butyl-3-methylimidazolium thiocyanate ionic liquids (ILs) aqueous solutions were investigated using sum-frequency generation vibrational spectroscopy (SFG-VS) and surface tension measurements. Polarization-dependent measurements revealed a dramatic increase in the SFG signal for both CH and CN stretching modes with increasing ILs concentration, reaching a maximum at a mole fraction of 0.01. This concentration dependence was accompanied by a dramatic drop in surface tension. Upon further increasing the concentration, surface tension varied slightly and reached a constant value, while the SFG signal decreased significantly. Quantitative polarization analysis showed that as the bulk concentration increased, the apparent molecular orientation of the SCN− transition dipole at the interface changed from 51° to 46°, and the tilt angle of CH3 group of the butyl chain attached to the imidazole cationic ring changed from 18° to 32°. The decrease in the SFG signal can be explained by the formation of a double layer adsorption structure at the air/water interface. It was also demonstrated that the anions were adsorbed at the interface simultaneously with the cationic group, rather than by successive adsorption as proposed in a previous study. Using the Shereshefsky model, the thermodynamic Gibbs free energy of adsorption deduced from surface tension data was compared with SFG results. [ABSTRACT FROM AUTHOR]

A central aim of multiscale modeling is to use results from the Schrödinger equation to predict phenomenology on length scales that far exceed those of typical molecular correlations. In this work, we present a new approach rooted in classical density functional theory (cDFT) that allows us to accurately describe the solvation of apolar solutes across length scales. Our approach builds on the Lum–Chandler–Weeks (LCW) theory of hydrophobicity [K. Lum et al., J. Phys. Chem. B 103, 4570 (1999)] by constructing a free energy functional that uses a slowly varying component of the density field as a reference. From a practical viewpoint, the theory we present is numerically simpler and generalizes to solutes with soft-core repulsion more easily than LCW theory. Furthermore, by assessing the local compressibility and its critical scaling behavior, we demonstrate that our LCW-style cDFT approach contains the physics of critical drying, which has been emphasized as an essential aspect of hydrophobicity by recent theories. As our approach is parameterized on the two-body direct correlation function of the uniform fluid and the liquid–vapor surface tension, it straightforwardly captures the temperature dependence of solvation. Moreover, we use our theory to describe solvation at a first-principles level on length scales that vastly exceed what is accessible to molecular simulations. [ABSTRACT FROM AUTHOR]

The Martini model, a coarse-grained forcefield for biomolecular simulations, has experienced a vast increase in popularity in the past decade. Its building-block approach balances computational efficiency with high chemical specificity, enabling the simulation of organic and inorganic molecules. The modeling of coarse-grained beads as Lennard-Jones particles poses challenges for the accurate reproduction of liquid–vapor interfacial properties, which are crucial in various applications, especially in the case of water. The latest version of the forcefield introduces refined interaction parameters for water beads, tackling the well-known artifact of Martini water freezing at room temperature. In addition, multiple sizes of water beads are available for simulating the solvation of small cavities, including the smallest pockets of proteins. This work focuses on studying the interfacial properties of Martini water, including surface tension and surface thickness. Employing the test-area method, we systematically compute the liquid–vapor surface tension across various combinations of water bead sizes and for temperatures from 300 to 350 K. These findings are of interest to the Martini community as they allow users to account for the low interfacial tension of Martini water by properly adjusting observables computed via coarse-grained simulations to allow for accurate matching against all-atom or experimental results. Surface tension data are also interpreted in terms of local enrichment of the various mixture components at the liquid–vapor interface by means of Gibbs' adsorption formalism. Finally, the critical scaling of the Martini surface tension with temperature is reported to be consistent with the critical exponent of the 3D Ising universality class. [ABSTRACT FROM AUTHOR]

Self-propelled synthetic particles have attracted scientific interest due to their potential applications as nanomotors in drug delivery and their insight into bacterial taxis. Research on their dynamics has focused on understanding phoresis and self-phoresis in catalytic Janus particles at both the nano- and microscale. This study explores the combined effects of self-diffusiophoresis and self-thermophoresis induced by exothermic chemical reactions on the surface of active particles moving in non-electrolyte media. We examine how these phoretic phenomena interact, influenced by the coupling between chemical reactions, heat generation, and the concentration and temperature fields at the particle interface. Using a theoretical framework based on the induction of surface tension gradients at the particle interface, we analyze the phoretic dynamics, quantifying parameters such as effective diffusivities, transport coefficients, and, most importantly, phoretic coefficients. Our findings provide insights into the conditions that dictate coupled or independent phoretic behaviors, with implications for drug delivery and nanomotor applications, enabling customized transport processes at the nanoscale. [ABSTRACT FROM AUTHOR]

Regarding the rheological properties of fluids, certain nanoparticles can markedly modify the rheological behavior of low surface tension solutions by interacting with surfactant molecules. In this work, a low surface tension fluid with cetyltrimethylammonium chloride was prepared, and the silica nanoparticles were uniformly dispersed into it by ultrasonic dispersion. By adjusting the size, shape, and concentration of nanoparticles, the fluid behavior can be changed from Newtonian to non-Newtonian with finely tuned viscosity and characterized by a shear-thinning rheological behavior. In addition, this work explored how variations in environmental temperature and solution pH affect the rheological responses of the low surface tension suspension system. The experimental findings revealed that increasing the temperature substantially decreases the system's viscosity and induces a shear-thickening behavior. It is particularly significant that, under extreme pH conditions (either strongly acidic or alkaline), the viscosity of the nanoparticle suspensions was markedly enhanced at a particle concentration of 10 000 ppm. This interesting result coincided with a notable reduction in the zeta potential and an increase in the average particle size, suggesting an intensified aggregation of particles within the suspension system. A mechanism detailing the interaction between silica nanoparticles and surfactant micelles was proposed. This work indicates that the incorporation of nanoparticles into surfactant solutions offers a powerful approach to modulating fluid rheology across various conditions. [ABSTRACT FROM AUTHOR]

We calculate thermodynamic and structural quantities of a fluid of hard spheres of diameter σ in a quasi-one-dimensional pore with accessible pore width W smaller than σ by applying a perturbative method worked out earlier for a confined fluid in a slit pore [Franosch et al. Phys. Rev. Lett. 109, 240601 (2012)]. In a first step, we prove that the thermodynamic and a certain class of structural quantities of the hard-sphere fluid in the pore can be obtained from a purely one-dimensional fluid of rods of length σ with a central hard core of size σ W = σ 2 − W 2 and a soft part at both ends of length (σ − σW)/2. These rods interact via effective k-body potentials v eff (k) (k ≥ 2). The two- and the three-body potential will be calculated explicitly. In a second step, the free energy of this effective one-dimensional fluid is calculated up to leading order in (W/σ)2. Explicit results for, e.g., the perpendicular pressure, surface tension, and the density profile as a function of density, temperature, and pore width are presented and partly compared with results from Monte-Carlo simulations and standard virial expansions. Despite the perturbative character of our approach, it encompasses the singularity of the thermodynamic quantities at the jamming transition point. [ABSTRACT FROM AUTHOR]

Surface tension and interfacial tension are crucial to the study of nanomaterials. Herein, we report a solubility method using magnesium oxide nanoparticles of different radii (1.8–105.0 nm, MgO NPs) dissolved in pure water as a targeted model; the surface tension and interfacial tension (and their temperature coefficients) were determined by measuring electrical conductivity and combined with the principle of the electrochemical equilibrium method, and the problem of particle size dependence is discussed. Encouragingly, this method can also be used to determine the ionic (atomic or molecular) radius and Tolman length of nanomaterials. This research results disclose that surface/interfacial tension and their temperature coefficients have a significant relationship with particle size. Surface/interfacial tension decreases rapidly with a radius <10 nm (while the temperature coefficients are opposite), while for a radius >10 nm, the effect is minimal. Especially, it is proven that the value of Tolman length is positive, the effect of particle size on Tolman length is consistent with the surface/interfacial tension, and the Tolman length of the bulk does not change much in the temperature range. This work initiates a new era for reliable determination of surface/interfacial tension, their temperature coefficients, ionic radius, and Tolman length of nanomaterials and provides an important theoretical basis for the development and application of various nanomaterials. [ABSTRACT FROM AUTHOR]

At the line of triple contact of an elastic body with two immiscible fluids, the body is subjected to a force concentrated on this line, the fluid–fluid surface tension. In the simple case of a semi-infinite body, limited by a plane, a straight contact line on this plane, and a fluid–fluid surface tension normal to the plane, the classical elastic solution leads to an infinite displacement at the contact line and an infinite elastic energy. By taking into account the body–fluid surface tension (i.e., isotropic surface stress) and applying Kolosov's approach of plane strain elasticity, we present a new and simple expression of the solution concerning the semi-infinite body, which gives a finite displacement and a ridge at the contact line, and finite elastic energy. A detailed description of the displacements, strains, and stresses in the neighborhood of the contact line is given. This solution also shows that Green's formulae, in the volume and on the surfaces, are valid (these formulae play a central role in the theory). [ABSTRACT FROM AUTHOR]

The focus of our study is an in-depth investigation of the quantum effects associated with the surface tension and other thermodynamic properties of nanoscopic liquid drops. The behavior of drops of quantum Lennard-Jones fluids is investigated with path-integral Monte Carlo simulations, and the test-area method is used to determine the surface tension of the spherical vapor–liquid interface. As the thermal de Broglie wavelength, λB, becomes more significant, the average density of the liquid drop decreases, with the drop becoming mechanically unstable at large wavelengths. As a consequence, the surface tension is found to decrease monotonically with λB, vanishing altogether for dominant quantum interactions. Quantum effects can be significant, leading to values that are notably lower than the classical thermodynamic limit, particularly for smaller drops. For planar interfaces (with infinite periodicity in the direction parallel to the interface), quantum effects are much less significant with the same values of λB but are, nevertheless, consequential for values representative of hydrogen or helium-4 at low temperatures corresponding to vapor–liquid coexistence. Large quantum effects are found for small drops of molecules with quantum interactions corresponding to water, ethane, methanol, and carbon dioxide, even at ambient conditions. The notable decrease in the density and tension has important consequences in reducing the Gibbs free-energy barrier of a nucleating cluster, enhancing the nucleation kinetics of liquid drops and of bubble formation. This implies that drops would form at a much greater rate than is predicted by classical nucleation theory. [ABSTRACT FROM AUTHOR]

We determine the surface tension of aqueous electrolyte solutions in contact with non-polar dielectric media using a thermomechanical approach, which involves deriving the stress tensor from the thermodynamic potential of an inhomogeneous fluid. To obtain the surface tension, we calculate both the normal and tangential pressures using the components of the stress tensor, recently derived by us [Y. A. Budkov and P. E. Brandyshev, J. Chem. Phys. 159, 174103 (2023)] within the framework of Wang's variational field theory. Using this approach, we derive an analytical expression for the surface tension in the linear approximation. At low ionic concentrations, this expression represents the classical Onsager–Samaras limiting law. By utilizing only one fitting parameter, which is related to the affinity of anions to the dielectric boundary, we successfully approximated experimental data on the surface tension of several aqueous electrolyte solutions. This approximation applies to both the solution–air and solution–dodecane interfaces, covering a wide range of electrolyte concentrations. [ABSTRACT FROM AUTHOR]

Two-dimensional colloidal crystals assembled from polystyrene nanospheres have emerged as a pivotal foundation for fabricating large-area nano-functional surfaces. These assemblies, defined by their hexagonal close-packed configuration and interlaced with grain boundaries, have garnered significant attention for applications in plasmonic structures, catalysts, photonic crystals, and inverse opals. Nonetheless, achieving consistent large-scale regularity has proven challenging due to unpredictable crystal growth and the introduction of defects. Utilizing acoustic waves excited from the airside, our experiments demonstrate the significant effects of such waves on the self-assembly process, leading to larger crystal domains and reduced defects. In comparison to the extensively studied water-end excitation techniques, our air-end excitation method introduces a novel dynamic in regulating colloidal monolayer crystallization and presents a comprehensive analysis of varying acoustic parameters, frequency, amplitude, and waveform. These findings reveal the potential of airside acoustic annealing in refining the structure of two-dimensional colloidal arrays. To elucidate our experimental observations, we delve into the theoretical underpinnings of particle dynamics, driven by classical hydromechanical constraints like surface tension and gravity. Using a qualitative estimate, we shed light on the resonant excitations and their potential role in optimizing the self-assembly process, especially focusing on resonances pertinent for enhancing cluster enlargements. Conclusively, our research, steeped in robust theoretical frameworks and groundbreaking experimental techniques, offers a multifaceted solution for perfecting two-dimensional colloidal arrays. This combined approach not only broadens the scope of acoustically induced crystallization but also charts a path for its adoption across diverse environments, signaling transformative prospects for nanomanufacturing and optical research. [ABSTRACT FROM AUTHOR]

Grazing-incidence x-ray diffraction (GIXRD) is a scattering technique that allows one to characterize the structure of fluid interfaces down to the molecular scale, including the measurement of surface tension and interface roughness. However, the corresponding standard data analysis at nonzero wave numbers has been criticized as to be inconclusive because the scattering intensity is polluted by the unavoidable scattering from the bulk. Here, we overcome this ambiguity by proposing a physically consistent model of the bulk contribution based on a minimal set of assumptions of experimental relevance. To this end, we derive an explicit integral expression for the background scattering, which can be determined numerically from the static structure factors of the coexisting bulk phases as independent input. Concerning the interpretation of GIXRD data inferred from computer simulations, we extend the model to account also for the finite sizes of the bulk phases, which are unavoidable in simulations. The corresponding leading-order correction beyond the dominant contribution to the scattered intensity is revealed by asymptotic analysis, which is characterized by the competition between the linear system size and the x-ray penetration depth in the case of simulations. Specifically, we have calculated the expected GIXRD intensity for scattering at the planar liquid–vapor interface of Lennard-Jones fluids with truncated pair interactions via extensive, high-precision computer simulations. The reported data cover interfacial and bulk properties of fluid states along the whole liquid–vapor coexistence line. A sensitivity analysis shows that our findings are robust with respect to the detailed definition of the mean interface position. We conclude that previous claims of an enhanced surface tension at mesoscopic scales are amenable to unambiguous tests via scattering experiments. [ABSTRACT FROM AUTHOR]

When a cubic lattice is confined by a surface layer, the effective thermoelastic properties can be tailored by the prestress produced by the surface. The thermal expansion coefficient, temperature derivative of elasticity, and the equation of state (EOS) of the solid depend on the potential of each bond and the lattice structure, which can be predicted by the recently developed singum model. This paper first uses a granular lattice confined by a spherical shell to demonstrate singum modeling of the thermoelastic behavior of the cubic lattices and then extends it to atomic crystal lattices by considering the surface tension and long-range interactions. Given the elasticity and the EOS of a cubic crystal, the interatomic potential can be inversely derived. As the bond length changes with thermal expansion and pressure, the singum model predicts the temperature- and pressure-dependent elasticity. Using the orientational average, isotropic elastic constants can be obtained for polycrystals. The case study of copper (Cu) demonstrates the versatility of the model for different cubic lattices and predicts the experimental results of pressure- and temperature-dependent elasticity. The singum model is general for different lattice types and EOS forms and provides clear physical and mechanical meanings to correlate the interatomic potential, EOS, and elasticity in the closed-form formulation, which is very useful in engineering design and analysis of metal structural members in fire, geothermal, and space applications without the needs of large-scale numerical simulations. [ABSTRACT FROM AUTHOR]

In this work, we implemented an off-axis digital holographic microscopy (DHM) setup to study the behavior of liquid drops on nanostructured porous silicon (PS) membranes. When a liquid comes into contact with the PS structure, capillary action and surface tension give rise to imbibition of the liquid into the intricate volume of the pores. At the same time, the vapor field developed around the drop enhances liquid condensation and evaporation into and from the pores. The complex interplay between these phenomena (capillary driven internal flows, condensation, and evaporation) is not yet fully understood but the methods we propose can provide new insights. We demonstrate how DHM allows determining the filling fraction of the porous membrane around drying drops of water and isobutyl alcohol. The phase information obtained from registered holograms provides quantitative information that permits to reconstruct the filling fraction along the porous membrane and its evolution during the drying process. Additionally, relevant parameters such as speed and contact angle during retraction of the drops can be measured. These methods can be further extended to other porous materials, such as porous alumina, micro- and macro-PS, to develop better fluid-dynamic models for describing fluid behavior in highly confined structures. [ABSTRACT FROM AUTHOR]

Chemical reactions can induce Marangoni flows by changing the surface tension of a solution open to the air, either by changing the composition and/or by modifying the temperature. We consider the case of a simple A + B → C reaction front propagating in a thin horizontal system open to air. The effect of the three chemical species on the surface tension of the aqueous solution is quantified by three solutal Marangoni numbers, while the effect of temperature changes is determined by the thermal Marangoni number. By integrating numerically the incompressible Navier–Stokes equations coupled to reaction-diffusion-convection equations for the chemical concentrations and temperature taking into account the Lewis number (ratio between heat and mass diffusivities), we emphasize the importance of thermal changes occurring due to the heat of reaction on the dynamics of chemically induced Marangoni convection. Based on the reaction-diffusion profiles of concentrations and temperature, asymptotic analytical solutions for the surface tension profiles are obtained and classified as a function of the Marangoni numbers and the Lewis number. This new classification allows for the prediction of the convective patterns in thermo-solutal Marangoni flows. The analytical predictions are further confirmed by numerical results and additional extrema in surface tension profiles induced by the thermal effects are found to affect the nonlinear dynamics. [ABSTRACT FROM AUTHOR]

The dynamics of many multiphase fluid systems involve the thinning and eventual break up of a slender fluid filament or a liquid jet. The interfacial instability that controls the rate of jet thinning depends on the relative magnitudes of capillary, viscous, and inertial stresses. Surfactants add an additional layer of physicochemical dynamics by reducing the surface tension of the interface and introducing reverse Marangoni flows in response to surface concentration gradients. Surfactants may also introduce an intrinsic surface rheology that affects jet thinning. Quantifying these effects has been a significant problem in chemical physics and a topic of key research interest. Recent studies have shown that insoluble surfactants delay thread thinning and suppress instabilities in Newtonian jets. However, the role of surfactant solubility in liquid jet stability is still unknown. In this work, we use linear stability analysis to quantitatively show the stabilizing effects of Marangoni stresses, surfactant adsorption and desorption time, and intermolecular forces upon adsorption. We highlight the seemingly indistinguishable way in which various surfactant properties result in the same outcome. We also identify a surface dissipative contribution that arises from the interplay of Marangoni flows with finite adsorption and desorption, which acts as an "apparent" surface viscosity. We verify predictions of our linear stability results against numerical simulations and conclude by noting that tuning surface activity and kinetics of adsorbed surfactants or particles can potentially suppress droplet formation, which is of significant impact in the printing industry and in the control of the spread of aerosols. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations in the microcanonical ensemble are performed to study the collapse of a bubble in liquid water using the single-site mW and the four-site TIP4P/2005 water models. To study system size effects, simulations for pure water systems are performed using periodically replicated simulation boxes with linear dimensions, L, ranging from 32 to 512 nm with the largest systems containing 8.7 × 106 and 4.5 × 109 molecules for the TIP4P/2005 and mW water models, respectively. The computationally more efficient mW water model allows us to reach converging behavior when the bubble dynamics results are plotted in reduced units, and the limiting behavior can be obtained through linear extrapolation in L−1. Qualitative differences are observed between simulations with the mW and TIP4P/2005 water models, but they can be explained by the models' differences in predicted viscosity and surface tension. Although bubble collapse occurs on time scales of only hundreds of picoseconds, the system sizes used here are sufficiently large to obtain bubble dynamics consistent with the Rayleigh–Plesset equation when using the models' thermophysical properties as input. For the conditions explored here, extreme heating of the interfacial water molecules near the time of collapse is observed for the larger mW water systems (but the model underpredicts the viscosity), whereas heating is less pronounced for the TIP4P/2005 water systems because its larger viscosity contribution slows the collapse dynamics. The presence of nitrogen within the bubble only starts to affect bubble dynamics near the very end of the initial collapse, leading to an incomplete collapse and strong rebound for the mW water model. Although nitrogen is non-condensable at 300 K, it becomes highly compressed and reaches a liquid-like density near the collapse point. We find that the dissolution of nitrogen is much slower than the movement of the collapsing water front, and the re-expansion of the dense nitrogen droplet gives rise to bubble rebound. The incompatibility of the collapse and dissolution time scales should be considered for continuum-scale modeling of bubble dynamics. We also confirm that the diffusion coefficient for dissolved nitrogen is insensitive to pressure as the liquid transitions from a compressed to a stretched state. [ABSTRACT FROM AUTHOR]

In view of the current situation in which non-polarizable rigid water models have been scarcely examined against surface-specific properties, we appraise TIP4P-type models at the liquid water surface on the basis of heterodyne-detected sum frequency generation (HD-SFG) spectroscopy. We find in the HD-SFG spectrum of the water surface that the peak frequency of the hydrogen-bonded OH band, the half width at half maximum of the hydrogen-bonded OH band, and the full width at half maximum of the free OH band are best reproduced by TIP4P, TIP4P/Ew, and TIP4P/Ice, respectively, whereas it is already well known that TIP4P/2005 best reproduces the surface tension. These TIP4P-type models perform better at the water surface in terms of the present appraisal items than some polarizable models in the literature. [ABSTRACT FROM AUTHOR]

The work W to form a nucleus (also known as the critical nucleus) is a key quantity in the description of nucleation phenomena because of its exponentially strong effect on the nucleation rate. The present study provides a general approximate expression for W, which comprises a hierarchy of approximations to the dependence of W on the experimentally controlled overpressure Δp of a nucleating multicomponent phase. This general expression is used to derive explicit formulas for the lowest-order members of the W(Δp) hierarchy as well as for the respective lowest-order approximations to the Δp dependences of the nucleus surface tension, the nucleus radius, the Gibbs–Tolman length, and the stationary nucleation rate. The second-order and the third-order approximations to the W(Δp) dependence are confronted with available W(Δp) data, and the latter is found to agree very well with the data. The results obtained are applicable to homogeneous single-component or multicomponent nucleation from the binodal to the spinodal of the old phase, i.e., in the entire range of the old-phase metastability. [ABSTRACT FROM AUTHOR]

Thermocapillary convection was investigated in a metallic system of pure Ni, at the nanoscale, by molecular dynamics. The system interface was irradiated by a heat flux, mimicking a focused laser source. The melt pool was submitted to a large temperature gradient that modified the surface tension along the interface. In liquid metal, because surface tension typically decreases with increasing temperature, the result is a gradient of surface tension along the free surface. The liquid metal, therefore, started to flow in the direction of high surface tension. Two counter-rotating convection cells developed, characteristic of those observed in welding and other material processing. A systematic estimation of relevant parameters in hydrodynamics allowed us to interpret the results in terms of Prandtl, Marangoni, and Péclet numbers. This study demonstrates the influence of laser power and system size on pool shape and flow characteristics. [ABSTRACT FROM AUTHOR]

We present a surface-tension driven electrochemical liquid metal (LM) actuator without the gas-producing side-reaction and capable of fabrication/operation in ambient air for practical applications. A hybrid supercapacitor is introduced to inhibit the common counter electrode side reactions, and the use of quasi-solid-state ionic hydrogel instead of liquid electrolyte further enables non-volatile operations. A 2×4 LM droplet array is demonstrated to actuate by a low driving voltage of 3.5 V for a maximum force of ~8.5 mN and a displacement of 0.56 mm in only 1.75 s. With the favorable scaling law of surface tension, further miniaturization could provide new opportunities in applications such as micro-robots, microfluidics, soft robots, and so on.

A series of epoxy modified polymethylpenylsiloxane (EPMPS) emulsions for oil agent in carbon fibers production were synthesized with EPMPS resins and non-ionic emulsifier by phase inversion emulsification. The EPMPS resins with different epoxy content were prepared by non-hydrolytic sol–gel method. The influence of epoxy content on the chemical structure, molecular weight, surface tension and thermal stability of EPMPS resins were investigated by Fourier transform infrared (FTIR), gel permeation chromatography (GPC), contact angle meter and thermogravimetric analysis (TGA), respectively. The properties of EPMPS emulsions and their effects on polyacrylonitrile (PAN) precursor were investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). It was found that the increase of epoxy content not only obviously decreased the molecular weight and surface tension of EPMPS, but also conduced to the processing of PAN precursor. With the decreasing of surface tension, the oil agent was easier to spread and film on the surface of PAN precursors. In addition, the TGA curves showed that the EPMPS resins had good thermal stability at low temperature and can be completed volatilized under high temperature conditions. Hence, the EPMPS emulsions could be used as oil agent for PAN precursors. [ABSTRACT FROM AUTHOR]

A series of imidazolium gemini surfactants with three different hydrophobic chains have been synthesised and analysed by 1HNMR, 13CNMR, FTIR, ESI-MS and TGA. The conductivity of these surfactants has been taken at 293, 298, 303 and 308 K in water, and results have indicated that these gemini surfactants act as weak electrolytes. Thermodynamic properties calculated from conductance have confirmed that micellization was spontaneous and more favourable in comparison to dissociation process. Density as well as viscosity measurements were indicating that there exist significant interactions between these gemini surfactants and solvent (water) molecules. Surface active properties have confirmed that imidazolium gemini surfactants are excellent candidates to lower the surface tension at air/water interface and having affinity to form aggregates in the bulk solution after CMC. Thermogravimetric analysis (TGA) has indicated that all the three surfactants have thermal stability up to 535–600 °C. The thermal stability was increasing with increasing hydrophobic chain, and the activation energy for thermal decomposition was found in the range of 20.43–36.55 kJ/mol. Moreover, antimicrobial activities were examined and inferred that these compounds exhibit excellent antimicrobial activity against B. cereus and C. albicans. [ABSTRACT FROM AUTHOR]

The authors have investigated the potential of a plant-based natural surfactant in the modification of various bubble parameters. Bubble dynamics at the orifice were studied in natural surfactant solutions extracted from the plant Sapindus mukorossi at concentrations below and above its critical micellar concentration (CMC). The results were compared to the ones obtained with Sodium Dodecyl Sulfate solutions. The CMC values of Sapindus mukorossi and Sodium Dodecyl Sulfate are 7.5 × 10−3 g/cc and 2.39 × 10−3 g/cc, respectively. A photographic method was employed to observe bubble formation at the orifice. The results show that biosurfactants, like chemical surfactants, have a comparable effect on bubble density, size, and rise velocity. Experimentally determined bubble radius, volume, and radial velocity were used to calculate various forces contributing to the bubble dynamics. The buoyancy, pressure, and surface tension forces were significantly stronger in magnitude in comparison to the gas momentum, viscous drag, and added mass forces. Our findings suggest that the significance of various dynamic forces involved in bubble growth dynamics varies according to the bubble generation frequency regimes. We report for the first time the potential of Sapindus mukorossi in altering bubble properties and surface forces at the orifice and its usage in various bubble-related industrial applications. [ABSTRACT FROM AUTHOR]

Valacyclovir hydrochloride (VC) possesses more oral bioavailability among all the anti-herpes drugs and more effective performance than acyclovir. The goal of the current research was to synthesize and characterize the inclusion complex of VC (ICVC) with gamma-cyclodextrin (γ-CD) utilizing various spectroscopic and physicochemical techniques like UV-vis, 1H-NMR, FTIR, conductance, surface tension, and SEM analysis. The studies confirmed that the 1 : 1 stoichiometry of the formed ICVC was well supported by molecular docking and DFT study. After complexation with γ-CD, the photostability was enhanced. The purpose of the current study was to create topical gels loaded with VC and ICVC and assess their potential to increase VC penetration through the topical route by enhancing their pharmacokinetic profile. The optimized topical gels containing VC and ICVC have zeta potentials of −3.8 ± 1.0 mV and −5.7 ± 0.9 mV, respectively. An in vitro drug release study showed that at the end of 8 h, 32.3% and 23.38% release of VC was observed from the VC-loaded and ICVC-loaded gel. An ex vivo skin permeation study of the ICVC-loaded gel showed poor permeability and negligible flux value in comparison to the VC-loaded gel, which implies the retainability of the drug at the dermal site as a depot formulation from which the drug will be released and act in a sustained manner. Based on these findings, it was confirmed that the efficacy of VC can be much improved through the topical delivery of ICVC-loaded gel for the treatment of herpes with minimum dose requirements, less toxicity, rapid action, and improved bioavailability of the VC. [ABSTRACT FROM AUTHOR]

Hypothesis Atomistically-detailed models of surfactants provide quantitative information on the molecular interactions and spatial distributions at fluid interfaces. Hence, it should be possible to extract from this information, macroscopical thermophysical properties such as interfacial tension, critical micelle concentrations and the relationship between these properties and the bulk fluid surfactant concentrations. Simulations and Experiments Molecular-scale interfacial of systems containing n- dodecyl β -glucoside (APG 12) are simulated using classical molecular dynamics. The bulk phases and the corresponding interfacial regions are all explicitly detailed using an all-atom force field (PCFF+). During the simulation, the behaviour of the interface is analyzed geometrically to obtain an approximated value of the critical micelle concentration (CMC) in terms of the surfactant area number density and the interfacial tension is assessed through the analysis of the forces amongst molecules. New experimental determinations are reported for the surface tension of APG 12 at the water/air and at the water/ n -decane interfaces. Findings We showcase the application of a thermodynamic framework that inter-relates interfacial tensions, surface densities, CMCs and bulk surfactant concentrations, which allows the in silico quantitative prediction of interfacial tension isotherms. • We present a method to relate molecular observations to interfacial tensions. • Atomistic simulation results are provided for n -dodecyl β -glucoside; (APG 12). • New experimental determinations are reported for the water/air and water/ n -decane interfacial tension. • Consistency is seen between simulations, experiments and machine learning predictions. [ABSTRACT FROM AUTHOR]

[Display omitted] Our hypothesis is that dynamic interfacial tension values as measured by the partitioned-Edge-based Droplet GEneration (EDGE) tensiometry can be connected to those obtained with classical techniques, such as the automated drop tensiometer (ADT), expanding the range of timescales towards very short ones. Oil-water and air–water interfaces are studied, with whey protein isolate solutions (WPI, 2.5 – 10 wt%) as the continuous phase. The dispersed phase consists of pure hexadecane or air. The EDGE tensiometer and ADT are used to measure the interfacial (surface) tension at various timescales. A comparative assessment is carried out to identify differences between protein concentrations as well as between oil–water and air–water interfaces. The EDGE tensiometer can measure at timescales down to a few milliseconds and up to around 10 s, while the ADT provides dynamic interfacial tension values after at least one second from droplet injection and typically is used to also cover hours. The interfacial tension values measured with both techniques exhibit overlap, implying that the techniques provide consistent and complementary information. Unlike the ADT, the EDGE tensiometer distinguishes differences in protein adsorption dynamics at protein concentrations as high as 10 wt% (which is the highest concentration tested) at both oil–water and air–water interfaces. [ABSTRACT FROM AUTHOR]

The emergence of macroscopic self‐propelled oscillatory motion based on molecular design has attracted continual attention in relation to autonomous systems in living organisms. Herein, a series of perylenediimides (PDIs) with various imide side chains was prepared to explore the impact of molecular design and alignment on the self‐propelled motion at the air‐water interface. When placed on an aqueous solution containing a reductant, a solid disk of neutral PDI was reduced to form the water‐soluble, surface‐active PDI dianion species, which induces a surface tension gradient in the vicinity of the disk for self‐propelled motion. We found that centimeter‐scale oscillatory motion could be elicited by controlling the supply rate of PDI dianion species through the reductant concentration and the structure of the imide side chains. Furthermore, we found that the onset and speed of the self‐propelled motion could be changed by the crystallinity of PDI at the water surface. This design principle using π‐conjugated molecules and their self‐assemblies could advance self‐propelled, non‐equilibrium systems powered by chemical energy. [ABSTRACT FROM AUTHOR]

The degummed wastewater from silk processing contains a huge amount of amino acids and polypeptides from sericin. The silk degumming water is far from being exploited fully. Sericin in the degumming water is generally wasted and causes environmental pollution. In this study, simulated silk degumming water was hydrolyzed by alkaline protease to produce abundant amino acids and polypeptides. After enzymatic hydrolysis, the maximum free amino groups concentration in the silk degumming water was approximately 54 mM. It facilitated the recycling of silk degumming water for the production of melanin-like amino acid surfactants as raw materials. 4-Tert-butylcatechol was used as the starting material to generate o-quinone via oxidation by ceric ammonium nitrate. o-Quinone was coupled with free amino groups in enzymatic hydrolysates of silk degumming water to synthesize a sericin-based amino acid surfactant as hydrophobic and hydrophilic group, respectively. Through the green and simple synthesis route, the product was characterized to have a novel melanin-like structure. The product exhibited superior surface-active properties by lowering the surface tension to 32.39 mN m−1. Furthermore, it demonstrated good foaming ability and foam stability, with the initial foam volume of 37 mL and the foam half-life time of more than 25 min. The product owned a good emulsification ability in the oil-water emulsion with delamination time of 297 s and 291 s for emulsion formed by soybean oil and liquid paraffin, respectively. The wetting time of the canvas sheet was only 134 s. Consequently, the product showed low surface tension, good foaming, emulsifying, and wetting properties. • Utilization of silk degumming water as renewable source for amino acid surfactants. • Novel structure similar with melanin by coupling amino acid to o-quinone. • Simultaneous treatment of silk degumming water. • Green route composed of only easy oxidation and spontaneous coupling reaction. • Production of surfactants with superior foaming, emulsifying, and wetting capacity. [ABSTRACT FROM AUTHOR]

Paper-based microfluidic devices offer an ideal platform for biological and environmental detection because they are low-cost, small, disposable, and fill by natural capillary action. In this tutorial review, we discuss the surface modification of paper-based microfluidic devices with functional polymers using the initiated chemical vapor deposition (iCVD) process. The iCVD process is solventless and therefore ideal for coating cellulose paper because there are no surface tension effects or solvent compatibility issues. The process can also be scaled up for roll-to-roll manufacturing. The chemical functionality of the iCVD coating can be tuned by varying the monomer and the structure of the coating can be tuned by varying the processing parameters. [ABSTRACT FROM AUTHOR]

The effect of surface roughness and temperature on wettability of polyethylene terephthalate (PET) melt on steel substrates is assessed. A plot of contact angle, Φ, Vs. time, τ, revealed the significant effect of temperature on wetting compared to surface roughness. The surface free energy of the steel substrate decreased by about 22% with increase in surface roughness from 0.21 to 3.8 μm. The measured surface tension of the polymer melt was 31.36 mN m−1 at 260°C. The variation in the cooling rate of the solidifying molten PET resulted in varying degree of polymer opacity. The opacity variations were quantified as a function of pixel intensity. The opacity of the solidified PET melt drops sharply declines at lower cooling rates before stabilizing at higher rates. No significant difference in the mean pixel intensity is observed between PET melts solidified at different substrate temperatures. Three distinct regimes in PET melt solidification are identified: (i) increased crystallization propensity at lower cooling rates (<8°C min−1), (ii) dominance of amorphous characteristics at higher rates (>199°C min−1), and (iii) a transitional regime at intermediate cooling rates. [ABSTRACT FROM AUTHOR]

The saffron composition is being widely studied for authenticity and traceability, but very few works have been carried out to investigate the relationship between the chemical and physico-chemical properties of saffron solutes and their technological functionality in colloidal systems. This study aims at evaluating the surface properties of saffron extracts obtained using solvents of different polarities to achieve extracts with different compositions in terms of the pattern and content of polar and medium polarity crocins. The air–water surface was evaluated alone and in the presence of Tween 20 at different surfactant–extract ratios. Saffron extracts were able to decrease the surface tension of the aqueous phase, indicating the presence of surface-active compounds. In the mixed saffron extract–Tween 20 systems, competitive adsorption at the air–water interface occurred when the surfactant was present at a low concentration, while at concentrations higher than the CMC, Tween 20 hindered the adsorption of the extract surface-active compounds. The results highlight the interesting technological functionality of saffron extracts for applications in colloidal systems. To better exploit their use in the design and development of formulated foods, nutraceutics and pharma products, further studies are needed to unravel the relationship between the composition of saffron extracts and corresponding surface activity. [ABSTRACT FROM AUTHOR]

Wire-based additive manufacturing (AM) is at the forefront of complex metal fabrication because of its scalability for large components, potential for high deposition rates, and ease of use. A common goal of wire directed energy deposition (DED) is preserving a stable process throughout deposition. If too little energy is put into the deposition, the wire will stub into the substrate and begin oscillating, creating turbulence within the meltpool. If too much energy exists, the wire will overheat, causing surface tension to take over and create liquid drips as opposed to a solid bead. This paper proposes a computer vision technique to work as both a state detection and event detection system for wire stability. The model utilizes intensity variations along with frame-to-frame difference calculations to determine process stability. Because the proposed model does not rely on machine learning techniques, it is possible for an individual to interpret and adjust as they see fit. The first part of this paper describes creation and implementation of the model. The model's capability was then evaluated using a 1D laser power experiment, which generated a wide range of stability states across varying powers. The model's accuracy was evaluated through 3D geometry data gathered from the experimentally deposited beads. The model proved to be both capable and accurate and has potential to be used as a real-time control system with future work. [ABSTRACT FROM AUTHOR]

This study focuses on formulating a low-surface-energy, water-resistant, and anti-condensation coating utilizing a fluorocarbon and acrylic resins composite (FAC), enhanced by six functional additives: antistatic agents, water-repellent agents, nanofillers, anti-mold and anti-algae agent, leveling agents, and wetting and dispersing agents. An orthogonal experimental design was implemented to systematically investigate the effects of varying concentrations of these additives on the surface tension of the coating. The results show that the optimized combination of fluorocarbon and acrylic resins composite (OFAC)with functional additives significantly reduces the surface tension, thereby improving both water resistance and anti-condensation properties. This research advances the development of more efficient surface treatment technologies, particularly for applications requiring enhanced water resistance and anti-condensation performance. [ABSTRACT FROM AUTHOR]

Deionized water is replacing fluorinated liquids as the preferred choice for two-phase immersion cooling in data centers. Yet, insufficient bubble removal capability at low saturated pressure is a key challenge hindering the widespread application. To solve this issue, this study employs non-ionic surfactant (Tween 20) and asymmetric structures (expanding microchannel) to enhance the boiling performances of deionized water under sub-atmospheric pressure. The research examines the effects of pressure (8.8~38.5 kPa), surfactant concentration (0.1~0.5 mL/L), and heat flux density (10~180 W/cm2) on the boiling heat transfer characteristics and analyzes the mechanism of unusual temperature oscillations induced by surfactants. It was found that the trade-off between the sub-atmospheric pressure, surface tension coefficient, and reduced static contact angle results in pronounced intermittent boiling on the heated surface. Even with the addition of surfactants, the improvement in heat transfer requires demanding conditions. Boiling enhancement throughout all heat flux conditions was achieved when the surfactant concentration was higher than 0.2 mL/L for the expanding microchanneled surface. The heat transfer coefficient reached 6.89 W·cm−2·K−1 under 8.8 kPa, which was 45% higher than without the surfactant. Under the same heat flux and sub-atmospheric pressure, as the concentration increased from 0.1 to 0.5 mL/L, the amplitudes of temperature fluctuation of the plane surface and expanding microchanneled surface decreased from 10 K to 2 K and 18 K to 1 K, respectively. The onset of nucleate boiling and wall superheat of the expanding microchanneled surface gradually decreased with the increase in surfactant concentration, where the onset of nucleate boiling decreased by 10.54 K. When the heat flux is 160 W/cm2, the wall superheat is reduced by 12.8 K. [ABSTRACT FROM AUTHOR]

Significant progress has recently been made in the biosynthesis of germacrene A using microbial cell factories. Germacrene A is a crucial precursor for the synthesis of anti‐cancer active compounds. However, its hydrophobic characteristics lead to its aggregation in cell membranes and cause severe cytotoxicity. In the present study, we found that rhamnolipids (RLs), as toxicity antidotes, could promote the production of germacrene A. An optimal RLs concentration of 1.25 g L−1 resulted in an increase of over 30% in the germacrene A titer at both shake flask and bioreactor scales. Mechanistic analysis showed that the addition of RLs could dramatically reduce aqueous‐phase surface tension and cell surface hydrophobicity (CSH), and increase the cell membrane permeability. This, in turn, promoted an efficient transfer of germacrene A from cell membrane to extraction phases. The addition of RLs also increased the adenosine triphosphate (ATP) concentration and the nicotinamide adenine dinucleotide (NAD+/NADH) ratio, while reducing reactive oxygen species (ROS) levels. Correspondingly, gene transcripts for key enzymes associated with germacrene A biosynthesis, the respiratory chain, and ROS scavenging were upregulated significantly. This study provides an effective RLs‐regulated fermentation method for the biosynthesis of hydrophobic natural products. [ABSTRACT FROM AUTHOR]

The development of aviation biofuels is a key strategy for reducing carbon emissions in the aviation industry. This study aimed to establish a surrogate model for aviation biofuels using a hybrid approach that combined explicit equations with an artificial neural network (ANN). The low heating value was calculated using an explicit equation, whereas the ANN predicted changes in density, viscosity, surface tension with temperature, and the distillation curve of the surrogate model. An optimization algorithm was then employed to identify suitable substitutes, which consisted of 11.44% n‐decane, 43.43% n‐dodecane, 43.11% n‐tetradecane, and 2.02% methylcyclohexane. The maximum error between the physical properties of the surrogate components and the measured biofuels did not exceed 7%. The ignition delay time of the substitute components matched that of real aviation biofuels at an equivalence ratio of 1.0 and a pressure of 10 bar. [ABSTRACT FROM AUTHOR]

The oil and water holding capacities, surface activity, and gelling ability of sodium carbonate-soluble pectin (NSP) extracted from the cell wall of bulb and foliage leaves of yellow and red onion (Allium cepa L.) were investigated and compared with those of commercial citrus pectin. Pectin chemical composition and properties its aqueous dispersions (e.g. the viscosity, pH) were studied. Homogalacturonan was the main component of the low-methoxylated pectin, with a small amount of rhamnogalacturonan I (more branched in the bulb pectin). Both the oil (35–41 g/gd.m.) and water (20 g/gd.m) holding capacities of NSP were higher than citrus pectin (1 and 17 g/gd.m, respectively). The surface activity of NSP was comparable (foliage leaves; surface tension (γ) decrease to 62 mN/m) or higher (bulb; γ decrease to 56 mN/m) than commercial pectin. The ability of NSP, especially extracted from the bulb, to form larger structures with increasing viscosity and neutralizing the negative surface charge, was significantly higher than that of citrus pectin. Therefore, NSP of bulb and foliage leaves may be useful as a carrier of oil- or water-soluble substances, a surface active agent, texturizer and gelling agent in the food, pharmaceutical, cosmetic and agricultural branches of industry. [ABSTRACT FROM AUTHOR]

The thermophysical properties (viscosity, density, and surface tension) of the secondary metallurgical slags with various CaO/Al2O3 ratios (0.56–1.99) and SiO2 (1–20 wt%) contents are investigated. The results show that the addition of SiO2 increases the viscosity of the cleanness and desulfurization slags (CaO/Al2O3 ratios ≥1). In slag with a higher Al2O3 content (CaO/Al2O3 < 1) and constant CaO content, the viscosity shows a first decreased and then increased phenomenon with the addition of SiO2. Moreover, the breakpoints of the viscosity are strongly lowered with the addition of SiO2. Both the density and surface tension of slags show a decreasing tendency with the SiO2 addition. Moreover, the single hot thermocouple technique method is applied to investigate the crystallization process of the slags, and the result shows that with high SiO2 contents, glassy layers are formed on the molten slags. [ABSTRACT FROM AUTHOR]

Nanofluids play an important role in machining processes for lubrication and cooling action. However, conventional fluids put the environment and operator health in risk due to its hazardous nature. This paper attempts to develop and characterize a novel sustainable and eco-friendly nanofluids for machining applications. In this study, deionized water-based Al2O3, TiO2 and MWCNT nanoparticles dispersed nanofluids and its hybrids Al2O3–TiO2 (50:50) and Al2O3-MWCNT (90:10) with varying concentration (0.5, 1.0, 1.5 and 2.0 vol%) having sodium lauryl sulfate as surfactant were developed and characterized for rheological, thermal and wettability properties at near room temperature. The experimental results show that nanofluid's thermophysical properties were better than the base fluid. The thermal conductivity of all the nanofluids produced in this study is more than 0.611238 W/m K which is more than the thermal conductivity for deionized water. Similarly, surface tension obtained for various nanofluids is comparatively lower than deionized water, i.e., 0.072 N/m. As the concentration of nanoparticles increases from 0.5 to 1.5 vol%, it leads to an increase in thermal conductivity, but the increase of nanoparticles concentration beyond 2% has a very minimal effect on thermal conductivity. The rate of transmittance % is as follows: 0.5 vol% > 1.0 vol% > 1.5 vol% > 2.0 vol%. It has been observed that zeta potential values are above ± 30 mV, thus indicating a stable formation of nanofluids due to non-agglomeration of nanoparticles. Hence, the following properties of nanofluids will help in high-speed machining applications. [ABSTRACT FROM AUTHOR]

We compared the accuracy of volume of fluid (VOF) methods in unstructured solvers using the following five different methods: 1 - the algebraically compressive VOF method, 2 – simple coupled VOF method with Level Set (S-CLSVOF) method, 3 - interface-compressing VOF method incorporated with Laplacian filter (VOFL), 4 - isoAdvector method, and 5 - isoAdvector method incorporated with Laplacian filter (isoAdvectorL) by incorporating them into OpenFOAM®, an open-source software. To evaluate these methods under proper conditions, we compared the calculation accuracy using the optimized parameters, which are explored by Bayesian optimization. The test cases for advection accuracy of volume fraction and for imbalance of surface tension force in static multiphase fluid fields were considered. In this study, we found that the compression parameters and maximum Courant number should be adjusted to obtain high accuracy simulation according to the simulation condition in VOF and S-CLSVOF method. In VOFL and isoAdvectorL methods, the spurious current can be extremely reduced, which means that these methods are suitable for slow flow with higher Laplace number conditions. [ABSTRACT FROM AUTHOR]

The median filter scheme is an elegant, monotone discretization of the level set formulation of motion by mean curvature. It turns out to evolve every level set of the initial condition precisely by another class of methods known as threshold dynamics. Median filters are, in other words, the natural level set versions of threshold dynamics algorithms. Exploiting this connection, we revisit median filters in light of recent progress on the threshold dynamics method. In particular, we give a variational formulation of, and exhibit a Lyapunov function for, median filters, resulting in energy based unconditional stability properties. The connection also yields analogues of median filters in the multiphase setting of mean curvature flow of networks. These new multiphase level set methods do not require frequent redistancing, and can accommodate a wide range of surface tensions. [ABSTRACT FROM AUTHOR]

The pinning dynamic of oil droplet on micropore surface has a significant impact on the stability of the oil film. Herein, the numerical model of the oil droplet generated in situ at the orifices is established. The influence of pore parameters and the inlet pressure on the movement of the three‐phase contact line are explored. The transformation mechanism between pinning and spreading of the droplet is revealed. The result shows that due to the competition between the surface tension and the driving force, the flow field parameters at the pinning point become unstable. Until the three‐phase contact line is unpinned, the droplet spreads on the micropore surface. With the reduce of the contact angle or the increase of the diameter of the pore, the pinning time of the droplet is shortened, and the droplets spread faster on the micropore surface. As the inlet pressure increases, the droplets grow faster at the orifice and spread from the orifice until the apparent contact angle reaches its maximum forward angle. The spread promotes the regeneration of the lubricating film, which is conducive to improving the stability of the oil film on micropore surface. [ABSTRACT FROM AUTHOR]

Thermophysical properties have wide applications in various fields like chemical industries, mass and heat transfer processes, design and engineering calculations of industrial plants and their evaluation in liquid mixtures gives us a better understanding of intermolecular interactions taking place therein. The binary liquid mixtures under the current study comprise a range of alkanones viz. 2-Propanone, 2-Butanone, 2-Pentanone and 2-Heptanone with aromatic amines like Aniline, N-methylaniline and Pyridine at temperatures 293.15 K to 303.15 K which have multifarious industrial applications. In the present investigation, ultrasonic velocity (u) studies have been carried out using five approaches at three temperatures. Furthermore, surface tension (σ) , acoustical impedance (z) and thermoacoustical parameters along with non-linearity parameters (B/A) have been evaluated. The variations in molecular interactions are well understood through interaction parameters (χ) . The obtained results indicate that the order of interactions is Pyridine < N-methylaniline < Aniline for a specific alkanone and 2-Propanone > 2-Butanone > 2-Pentanone > 2-Heptanone for a given amine at all three temperatures. The study of thermophysical properties have been elaborated to understand the order of the interactions between various amines and alkanones. [ABSTRACT FROM AUTHOR]

This paper considers a mathematical model of steady flows of an inviscid and incompressible fluid moving in the azimuthal direction. The water density varies with depth and the waves are propagating under the force of gravity, over a flat bed and with a free surface, on which acts a force of surface tension. Our solution pertains to large scale equatorial dynamics of a fluid with free surface expressed in cylindrical coordinates. We also prove a regularity result for the free surface. [ABSTRACT FROM AUTHOR]

In this paper, we consider a resolvent problem arising from the free boundary value problem for the compressible fluid model of Korteweg type, which is called as the Navier–Stokes–Korteweg system, with surface tension in the half-space. The Navier–Stokes–Korteweg system is known as a diffuse interface model for liquid–vapor two-phase flows. Our purpose is to show the R -boundedness for the solution operator families of the resolvent problem, which gives us the maximal regularity estimates in the L p -in-time and L q -in-space setting by applying the Weis’s operator valued Fourier multiplier theorem (Weis in Math Ann 319:735–758, 2001). [ABSTRACT FROM AUTHOR]

Ionic liquids' (ILs) surface tension, vital in liquid interface research, faces challenges in measurement methods—time‐consuming and labor‐intensive. The Structure‐Surface Tension Relationship (SSTR) is crucial for understanding the surface tension laws of ionic liquids, helping to predict surface tension and design ionic liquids that meet target requirements. In this study, SMILES string and group contribution methods were used to generate descriptors, and the random forest and multi‐layer perceptron (MLP) models were cross combined with the two descriptor generation methods to establish the SSTR model, providing a comprehensive framework for predicting the surface tension of ionic liquids. String‐MLP excels with high accuracy (R2 = 0.995, RMSE = 0.686, AARD% = 0.71%) for diverse ILs' surface tension values. Meanwhile, the Shapley Additive exPlanning (SHAP) method was used to test the impact of different features on model prediction, increasing the transparency and interpretability of the model. [ABSTRACT FROM AUTHOR]

We report measurements performed to understand the effects of gas (QG) and liquid (QL) flow rates, surface tension (σGL), liquid viscosity (μL), and particle diameter (dp) on dynamics of local liquid spreading, pressure drop, and overall liquid holdup in a pseudo‐2D trickle bed. We show that an increase in the gas‐phase inertia leads to a decrease in the lateral liquid spreading, whereas an increase in the liquid‐phase inertia leads to an increase in the lateral liquid spreading. We also show that an increase in dp causes a reduction in the lateral liquid spreading. Using dimensionless numbers (AB and We), we propose a regime map showing contributions of different forces to the local liquid spreading. We show that the interplay between the inertia and capillary forces governs the liquid distribution near the inlet, whereas the relative contribution of gravitational force increases toward the outlet. Finally, we propose a relation between AB and We for "bed‐scale" liquid spreading. [ABSTRACT FROM AUTHOR]

In this study, a new method was introduced to induce micellar transitions by using vesicles formed from mixed surfactants, which offer enhanced stability. Different physicochemical analysis methods were used to study the transition mechanism and the aggregation behavior of the mixed aqueous system composed of the double‐chain cationic didodecyldimethylammonium bromide (DDAB) and a single‐chain nonionic fluorinated surfactant undecafluoro n‐pentyl decaoxyethylene ether (C5F11(EO)10), by varying the fraction of DDAB, then the total surfactant concentration of DDAB/C5F11(EO)10 mixed system at XDDAB = 0.9. The obtained results indicated that the addition of the fluorinated surfactant C5F11(EO)10 to the mixed system resulted in a reduction of the surface tension (γ) and a decrease in the Electrical conductivity (K). Furthermore, even at high total concentrations of the mixed system, the conductivity and charge density at the surface remained stable. As XDDAB values increased, a higher degree of dissociation (α) was observed, along with negative values in the thermodynamic parameters of micellization (ΔGCMC°$$ {G}_{\mathrm{CMC}}^{{}^{\circ}} $$, ΔGCVC°$$ {G}_{\mathrm{CVC}}^{{}^{\circ}} $$, and ΔGads°$$ {G}_{\mathrm{ads}}^{{}^{\circ}} $$), confirming the transition from micelles to vesicles. The dynamic light scattering (DLS) analysis revealed the formation of two stable types of aggregates at both low and high concentrations, as supported by the zeta potential (ζ). Upon increasing the concentration of surfactants, UV–Vis absorption measurements indicated that small spherical micelles grow into large multilamellar vesicles, as evidenced by an increase in turbidity and confirmed transmission electron microscopy images. [ABSTRACT FROM AUTHOR]