Theory Of Surface Tension Research Articles

Ion-Specific Surface Tension of Aqueous Electrolyte Solutions: Analytical Insights from a Restricted Primitive Model.

The ion-specific surface tension of aqueous electrolyte solutions is of fundamental importance in physical chemistry, solution chemistry, electrochemistry, and biochemistry, yet it remains a challenge to be qualitatively predicted. In this work, an analytical theory of ion-specific surface tension is developed. By modeling the solution to a restricted primitive model (RPM), the surface tension increment of the electrolyte solution reduces to the surface tension of the RPM, which is further determined analytically by using the integral equation theory and the morphological thermodynamics theory. According to our formula, the surface tension increment of the electrolyte solution consists of a dominant and positive hard sphere contribution, which depends on the salt concentration, and a secondary electrostatic contribution, which depends on the inverse Debye length and the salt concentration. Our theory is applied to 1:1, 2:2, 1:2, 2:1, 3:1, and 3:2 electrolyte solutions with typical salt concentrations up to several mol/L and compared with experimental data. Without introducing any adjustable parameters, our theory leads to a good prediction of the surface tension increment of more than 50 kinds of aqueous solutions. Such a good agreement demonstrates the great potential of our theory for a fundamental understanding of specific ion effects in a variety of electrolyte solutions.

Why Is the Baker Classification Inadequate for Classifying Silicone Implant Fibrous Capsules?

Baker's clinical classification is adopted as the gold standard for grading complications related to silicone implants. Despite being widely used for this purpose, the classification has several limitations, highlighting subjectivity, reproducibility, and interobserver agreement. In this technical report, we aim to present the reasons for the inadequacy of the Baker classification for breast implants and the main factors contributing to false-negative results using recent theories of surface tension of fluids and gel bleeding. We also present an alternative classification proposal using magnetic resonance imaging of the breasts.

Controllable pore size of super-hydrophobic magnetic core-shell nanospheres with dendritic architecture and their pore-dependent performances in oil/water separation

The fundamental properties of porous materials strongly rely on their pore sizes. Pore-size-dependent performances play significant roles in their applications like catalysis, adsorption, delivery, and so forth. In this work, a feasible pore-expanding approach has been successfully explored to control the pore size of magnetic core–shell nanospheres with dendritic architecture (Fe3O4@DMSNs). The size can be adjusted from ca. 10 nm to 25 nm and further to 60 nm in an unprecedented wide range. Further, a concise modification route has been adopted to endow Fe3O4@DMSNs particles with super-hydrophobic abilities by the usage of a long-chain silane (Fe3O4@DMSNs-OTES). The as-prepared nanospheres with magnetic response function can not only form magnetic liquid marbles (MLMs) easily, but also separate n-hexane in oil–water mixtures or oil-in-water emulsions rapidly and efficiently. However, the above three particles display certain differences in their basic properties (like pore volume) and application performances (like oil removal efficiency). Most importantly, Fe3O4@DMSNs-OTES with 60 nm pores exhibit the best super-hydrophobicity in contact angles of H2O and MLMs, Fe3O4@DMSNs-OTES with 25 nm pores possess the maximum adsorption capacity, while the ones with 10 nm pores show the quickest adsorption rate (removal efficiency). The relationship between the performances and the pore size has been thoroughly revealed and well deciphered by wettability theory (e.g., Cassie-Baxter equation) and surface tension theory. In a word, all Fe3O4@DMSNs-OTES hold promising potentials as candidates for the practical wastewater purification on the basis of their characteristics.

Futuristic Progress of Natural Emulsifiers in the Enhancement of Drug Delievery System and their Applications in Selected Medical Therapeutics

Food manufacturers are being encouraged to employ more natural and sustainable food components as a result of consumer concerns about human and environmental health. Synthetic components are being replaced with natural ingredients, while animal-based ingredients are being replaced with plant-based elements. Phospholipids, biosurfactants, proteins, polysaccharides, and natural colloidal particles are some of the natural emulsifiers that might be used in the food sector. Natural emulsifiers may be used more frequently in food items, resulting in a healthier and more sustainable food supply. More study is needed, however, to find, isolate, and characterize novel sources of economically viable natural emulsifiers suited for food applications. Foods, cosmetics, detergents, and personal care items are among the commercial products that are under increasing consumer demand to be more natural, sustainable, and ecologically friendly. As a result, the industry has attempted to develop natural alternatives to synthetic functional components in these goods. Natural emulsifiers such as amphiphilic proteins, polysaccharides, biosurfactants, phospholipids, and bioparticles are being used to replace synthetic surfactants. The physicochemical foundation of emulsion generation and stability by natural emulsifiers is explored in depth, as well as the benefits and limits of various natural emulsifiers. Single emulsions, such as water-in-oil and oil-in-water, and multiple emulsions, such as water-in-oil-in-water, are the most common types of emulsions. Emulsifier / emulgent is a chemical that increases the kinetic energy of an emulsion to stabilise it. Emulsifiers are separated into four types based on their chemical structure: synthetic, natural, finely split solids, and auxiliary agents; and three types based on their mode of action: monomolecular films, multimolecular films, and solid particle films. Surface tension theory, surface orientation theory, and plastic/interfacial film theory are some of the ideas that aid in the understanding of the emulsification process. emulsion, natural emulsifiers, biosurfactants, emulsion technology, water-in-oil.

Scarf for Lifshitz

Polarization of a vacuum as well as of dispersive and dissipative dielectric media with piece-wise and smooth inhomogeneities is studied with the goal to clarify the question of renormalizability of diverging electromagnetic stress-energy tensor. First, the stress tensor is computed with the Lifshitz approach to London forces in the non-retarded limit, which after the substraction of the leading free space ultraviolet divergencies still retains the divergencies associated with the presence of sharp boundaries between piece-wise inhomogeneities. We call these contributions finite because they become renormalized after a sharp interface is replaced with a dielectric permittivity changing according to a smooth function of spatial coordinates. In addition, such a smoothed out interface exhibits new subleading ultraviolet divergencies that appear due to its internal structure. To systematically deal with the polarization of inhomogeneous media, the Hadamard expansion is applied to single out both finite and subleading contributions and to unequivocally demonstrate incomplete renormalizability of the Lifshitz theory. The above approach also allows us to reveal the nature of surface tension, which proves to be purely quantum mechanical. The deduced theory of surface tension and its calculations for real dielectric media are favorably compared to the available experimental data. While the sharp interface limit recovers the classical boundary conditions for the electric field and uncovers the origin of the apparent local divergencies of the renormalized stresses in the sharp interface formulation previously pointed out in the literature, the problem of surface tension proves to be of a distinguished limit type because the sharp interface formulation loses the information about the internal structure of an interface and hence cannot explain the origin of surface tension.

Improving classification based on physical surface tension-neural net for the prediction of psychosocial-risk level in public school teachers.

BackgroundPsychosocial risks, also present in educational processes, are stress factors particularly critical in state-schools, affecting the efficacy, stress, and job satisfaction of the teachers. This study proposes an intelligent algorithm to improve the prediction of psychosocial risk, as a tool for the generation of health and risk prevention assistance programs.MethodsThe proposed approach, Physical Surface Tension-Neural Net (PST-NN), applied the theory of superficial tension in liquids to an artificial neural network (ANN), in order to model four risk levels (low, medium, high and very high psychosocial risk). The model was trained and tested using the results of tests for measurement of the psychosocial risk levels of 5,443 teachers. Psychosocial, and also physiological and musculoskeletal symptoms, factors were included as inputs of the model. The classification efficiency of the PST-NN approach was evaluated by using the sensitivity, specificity, accuracy and ROC curve metrics, and compared against other techniques as the Decision Tree model, Naïve Bayes, ANN, Support Vector Machines, Robust Linear Regression and the Logistic Regression Model.ResultsThe modification of the ANN model, by the adaptation of a layer that includes concepts related to the theory of physical surface tension, improved the separation of the subjects according to the risk level group, as a function of the mass and perimeter outputs. Indeed, the PST-NN model showed better performance to classify psychosocial risk level on state-school teachers than the linear, probabilistic and logistic models included in this study, obtaining an average accuracy value of 97.31%.ConclusionsThe introduction of physical models, such as the physical surface tension, can improve the classification performance of ANN. Particularly, the PST-NN model can be used to predict and classify psychosocial risk levels among state-school teachers at work. This model could help to early identification of psychosocial risk and to the development of programs to prevent it.

High-flux, anti-fouling dendrimer grafted PAN membrane: Fabrication, performance and mechanisms

Polyamidoamine (PAMAM) dendrimers grafted Polyacrylonitrile (PAN) UF membrane (PAN-PAMAM) was prepared for the first time. The optimized PAN-PAMAM membrane showed both a high flux (420 L m−2 h−1.bar−1) and a good BSA rejection (99%). To improve its hydrophilicity, the membrane was further modified with ethanolamine (ETA) under different conditions. The results suggest that PAN-PAMAM membrane modified by ETA/NaOH has an improved antifouling property for sodium alginate (SA), humic acid (HA) and bovine serum albumin (BSA), the flux recover ratio (FRR) increased from 61% to above 91%. Moreover, the modified membrane shows a better antifouling property in phosphate-buffered saline (PBS) solution than in water solution. DLS results showed that BSA aggregate morphology are different in two solutions. AFM image and BSA adsorption revealed that PBS decreases the coverage and amount of BSA adsorbed on the membrane surface, leading to an improved antifouling property. Surface tension and XDLVO theory were further used to analyze the fouling process. It was found that ETA/NaOH modification greatly increases the Lewis acid-base interfacial interaction of membrane. However, after the adsorption of BSA, Lewis acid-base interaction decreases greatly, leading to the irreversible fouling of membrane.

Analytical derivation of a pH dependent contact angle equation and the relationship to industrial processes of energy concerns

Regarding Young's equation, three fundamental interfacial energies of interfacial tensions can be identified. One of these interfacial energies relevant to our purpose is that related to the solid-liquid interface and it can be pH dependent. Intermolecular theory of surface tension links the solid-liquid interfacial tension or energy to surface charge species of solids. These species are electrostatic and depend on the pH of the aqueous medium in contact with the solid surface. Therefore, a theoretical relationship between contact angle and pH of some kind is worth exploring based on the fundamental theories of pH dependent solid-liquid interfacial tension, given the pH dependent electric double layer.A review of the literature dealing with the pH-dependent contact angle shows that polynomial curves have been fitted to contact angle versus pH data. Based on established theoretical works dealing with surface charge theories related to the electric double layer found in the literature, we have derived a pH dependent contact angle equation that describes trends in published experimental data with a high degree of regression coefficient. We have also theoretically and experimentally validated our model. The industrial significance of our model lies in the fact that the solution for pH, when the derivative is equated to zero, gives the point of zero charge pH of solid surface, which is an approach that has already been used in published works without any theoretical justification. The relationship of our model to industrial operations of energy and environmental significance has been discussed.

The Laplace Parallel Plates Problem in Capillarity Theory

When two parallel plates of perhaps different materials are immersed vertically into a fluid bath in a vertically downward gravity field, they may experience an attracting or repelling force. Following a framework introduced by Laplace, we seek explication based on surface tension theory, which we use to correlate the forces with estimates for the height of the liquid surface. In this context, we provide (as special cases of more general estimates), an exact formula for the mean rise height in the channel formed by the plates, together with a strict bound for the variation of rise height within the channel. We base our procedures directly on the nonlinear formulation of the governing equations as formulated by Young and by Laplace, and introduce no further structural hypotheses. As support for this decision we present an explicit example based on our Theorem 5, displaying errors of unlimited magnitude that can arise from customary linearization procedures, and which can also obscure physical phenomena of central interest. As corollary of the development, we obtain also a new characterization of the classes of attracting and repelling solutions. We establish further an asymptotically exact form of the Laplace discovery, that aside from an isolated exceptional case of repelling forces bounded from infinity above (and, as we show, bounded also from zero below), the force between the plates always becomes attracting and grows as the inverse square of the separation distance, as the plates are brought together with fixed contact angles. We continue our efforts, initiated by us in earlier publications, toward clarifying this exotic behavior in quantitative terms.

Capillary Graph-Interfaces “in-the-Large”

This paper continues ongoing investigations into questions initiated by seventeenth-century experiments of Mariotte on mutual attractions and repulsions of floating objects, later reformulated mathematically by Laplace in the context of idealized surface tension theory. The characteristic nonlinearity in the governing equations imposes restrictions on behavior of solutions as graphs in the Laplace model, to the effect that a priori relations connecting height and inclination of a presumed surface interface occur, severely restricting the heights that can be achieved by solution curves. We develop below some relevant consequences of that phenomenon. The initial section provides general (perhaps inadequate) background, characterizes global qualitative behavior of all solutions of the underlying equations, and elucidates the significant distinctions in behavior that occur for solutions over an interval that extends unboundedly in one base direction. The section next following presents a non-existence result ensuing from the limitations imposed on such solutions (this result is elaborated in the Appendix). Next follow individual properties of general solutions. The remainder of the paper addresses the forces arising between partially submerged bodies. Theorem 6 offers an alternative derivation of a discovery due to Aspley, He, and McCuan, which displays a remarkable identification of net horizontal force with a first integral of the basic equations. These relations simplify significantly some earlier literature; additionally, as indicated in Section 5, they open the way to consideration of a much larger class of partially immersed objects than appears in the Laplace formulation. We complete Section 5 with an illustrative example in a particular case, indicative of a general study currently underway.

Adhesive force measurement of steady-state water nano-meniscus: Effective surface tension at nanoscale

When the surface of water is curved at nanoscale as a bubble, droplet and meniscus, its surface tension is expected to be smaller than that of planar interface, which still awaits experimental studies. Here, we report static and dynamic force spectroscopy that measures the capillary force of a single nanoscale water meniscus at constant curvature condition. Based on the Young-Laplace equation, the results are used to obtain the effective surface tension (ST) of the meniscus, which decreases to less than 20% of the bulk value at the radius-of-curvature (ROC) below 25 nm, while indicating the bulk behaviour above ~130 nm ROC. Interestingly, such a possibility provides a qualitative resolution of the unsettled discrepancies between experiments and theories in the thermodynamic activation processes for the mentioned three types of nano-curvatured water. Our results may not only lead to development of microscopic theories of ST as well as further experimental investigations, but also help better understanding of the ST-induced nanoscale dynamics such as cluster growth or protein folding, and the ST-controlled design of nano-biomaterials using the nano-meniscus.

Flexible, Durable, and Unconditioned Superoleophobic/Superhydrophilic Surfaces for Controllable Transport and Oil–Water Separation

AbstractSuperoleophobic/superhydrophilic surfaces have incomparable advantages for oil–water separation and oil droplet manipulation; however, such surfaces are difficult to obtain on the basis of surface tension theory, and existing attempts are either not fully functional or are nondurable. Here, a solution to achieve the combination of superoleophobicity and superhydrophilicity by emphasizing the polar component of surface tension is proposed. The developed surfaces can be flexibly applied to almost any solid substrate and exhibit superoleophobic and instantaneous superhydrophilic property. The surfaces applied to certain substrates can be used for controllable oil transport, oil–water separation, and emulsion demulsification. Furthermore, a novel ferroconcrete‐like structure to substantially increase the durability of the developed surfaces without affecting the superwettability is developed. The coated steel meshes preserve the ability of the material to separate oil–water mixtures even after over 400 m abrasion, which can be a significant step toward its widespread application.

Self-stratifying coatings: a review

A self-stratifying coating is an economical coating containing multiresinous components with different functional groups, which spontaneously stratify after application to the substrate. These coating systems could be composed of two or more different layers to protect substrates against corrosion, by first layer, and simultaneously to create a desirable appearance, by second layer, with decorative properties. Conventional multilayer coating systems encounter some problems such as poor interfacial adhesion, application, and labor costs and also lengthy processing time. The concentration gradient of two layers would eliminate the inter-coating boundary which can be the point of failure in conventional coatings. In this paper, the surface tension and solubility theory regarding these coatings are discussed. In addition, the effects of different factors on the pigment location into the coating systems are studied. The main factors, including curing mechanisms, substrate effects, thickness, viscosity, kinetics of reaction, evaporation rate of solvents, dispersing agents, and surface properties of pigments have been reviewed. The models for prediction of self-stratifying coatings such as UNIFAC and computer simulation have also been addressed and taken into consideration. The prospect of these coatings and their application in different industries is presented.

A Variational Reduction and the Existence of a Fully Localised Solitary Wave for the Three-Dimensional Water-Wave Problem with Weak Surface Tension

Fully localised solitary waves are travelling-wave solutions of the three-dimensional gravity-capillary water wave problem which decay to zero in every horizontal spatial direction. Their existence has been predicted on the basis of numerical simulations and model equations (in which context they are usually referred to as `lumps'), and a mathematically rigorous existence theory for strong surface tension (Bond number $\beta$ greater than $\frac{1}{3}$) has recently been given. In this article we present an existence theory for the physically more realistic case $0<\beta<\frac{1}{3}$. A classical variational principle for fully localised solitary waves is reduced to a locally equivalent variational principle featuring a perturbation of the functional associated with the Davey-Stewartson equation. A nontrivial critical point of the reduced functional is found by minimising it over its natural constraint set.

Prediction of the gas hold-up in a large-diameter bubble column with liquid mixtures and electrolytes

Many correlations are available in the literature for computing the gas hold-up in bubble columns, mainly in pure liquids. Contrarily, very few works deal with the gas hold-up in liquid mixtures, giving different opinions about the successful application of Andrew’s dynamic surface tension model. This work further investigates this topic using more recent gas hold-up data presented in a previous work for the binary mixture comprising monoethylene glycol and water and measured for a large-diameter bubble column, which differs from the equipment used in the other few works that have pointed out the unusual behavior of the gas hold-up in binary liquid mixtures. The correlation proposed for representing the experimental data on the basis of the dynamic surface tension theory has been applied in the entire range of gas superficial velocities (0.004–0.20m/s) and it has been also generalized to predict the gas hold-up enhancement due to the presence of electrolytes. The results suggest that the dynamic surface tension model allows to reproduce the experimental gas hold-up data in a qualitative way, but a quantitative agreement is still lacking since the maximum frothing ability has been experimentally observed for a monoethylene glycol concentration lower than that predicted by Andrew’s theory.

Foamability of sodium dodecyl sulfate solutions: Anomalous effect of dodecanol unexplained by conventional theories

Conventional theories indicate that surfactant solutions with low surface tension, fast adsorption kinetics, and high interfacial viscoelasticity increase foamability. These theories are applicable to single surfactants of pre-CMC. Here, we examine whether these theories are applicable for surfactant mixtures. Specifically, we investigated the foamability of sodium dodecyl sulfate (SDS)-dodecanol (DOH) solutions. We found that the foamability of SDS–DOH solutions exhibited ‘anomalies’ that were unexplained by conventional theories. The remarkable decrease in the foamability of SDS solutions caused by the addition of DOH could not be easily explained by the theories of surface tension and surface viscoelasticity. Instead, we proposed alternative mechanisms to resolve these unexpected results. Below the DOH solubility limit, the replacement of SDS molecules by DOH molecules at the air–water interface results in a reduced surface potential, leading to a lower foamability. The antifoam effects of DOH droplets can account for the reduced foamability above this limit. This paper highlights the complex effect of surfactant mixtures on foamability.

Surface Tension and Adsorption without a Dividing Surface

The ingenious concept of a dividing surface of zero thickness that was introduced by Gibbs is the basis of the theory of surface tension and adsorption. However, some fundamental questions, mainly those related to the location of the dividing surface and the proper definition of relative adsorption, have remained open over the years. To avoid these questions, the present paper proposes to analyze an interfacial phase by defining a thermodynamic system of constant, but nonzero thickness. The interfacial phase is analyzed as it really is, namely a nonuniform three-dimensional entity. The current analysis redevelops the equation for calculating surface tension, though with different assumptions. However, the main point in the proposed model is that the thermodynamic interfacial system, due to its fixed thickness, conforms to the requirement of first-order homogeneity of the internal energy. This property is the key that allows using the Gibbs adsorption isotherm. It is also characteristic of the Gibbs dividing surface model, but has not always been discussed with regard to subsequent models. The resulting equation leads to a simple, "natural" expression for the relative adsorption. This expression may be compared with simulations and sophisticated surface concentration measurements, and from which the dependence of interfacial tension on the solution composition can be derived. Finally, it is important to point out that in order to calculate the interfacial tension as well as the relative adsorption from data on the properties of the interfacial phase, there is no need to know its exact thickness, as long as it is bigger than the actual thickness but sufficiently small.

Bursting water balloons

AbstractThe impact and rupture of a water-filled latex balloon on a flat, rigid surface is investigated using high-speed photography. Three distinct stages of the flow are observed, for which physical explanations are given. As the balloon lands and deforms, waves are formed on the balloon’s surface for which the restoring force is tension in the latex. These waves are shown to closely obey linear potential theory for constant surface tension. Should the balloon rupture, a crack forms, from which the membrane retracts. Spray is simultaneously ejected from the water’s surface, a consequence of a shear instability in the wake behind the retracting membrane. At later times, a larger-scale growth of the interfacial amplitude is observed, for which the generation mechanism is momentum in the water due to the preburst waves. However, it is argued that this is also a manifestation of the same mechanism that drives Richtmyer–Meshkov instability (RMI). Further, it is shown experimentally that this growth of the interface may also occur when there is no density difference across the balloon, a situation that does not arise for the standard RMI. An analytical model is then derived to predict the interfacial growth for such an interface, and is shown to predict the asymptotic growth rate of the interface accurately.

Application of the “online interdisciplinary expert panel” to the surface tension of condensed matter

In the short history of the “Online Interdisciplinary Expert Panel” approach, there were some essential “discoveries” concerning flaws in the contemporary theory of the surface tension of condensed matter. For liquids, it was proved that their surface tension force had no clearly defined subject to its application and consequently no correct definition of the surface tension; recently it was proposed for the first time. For solids, it was shown that multiple incorrect citations from Gibbs, for example of pseudo-notions like “cleavage,” “reversible cleavage” and “cutting up the body,” created the favorable conditions for the false theory of surface tension based on the Shuttleworth equation having no experimental confirmation.

A contact theory for surface tension driven systems

This paper presents a general model description for the contact of surface tension driven systems. The example system of a liquid droplet in contact with a deformable solid substrate is considered. This can be easily modified to consider two liquids or two solids in contact. The surface kinematics, essential to the modeling of surface tension, are described here in curvilinear coordinates. In particular modeling focus are the contact conditions at the contact boundary, where a wetting ridge may develop. It is shown that in the case of quasi-statics and hyperelasticity the governing equations can be derived from a global potential that accounts for contact as well as the energy storage within the bulk and surface domains. Altogether, 21 Euler–Lagrange equations are derived in this manner. Apart from these strong form equations, the governing weak form as well as its complete linearization, which are required for computational methods, are also discussed. It is shown that the governing equations can be further simplified into a reduced set of equations that are then suitable for an efficient computational implementation of the system. Computational solution methods are not discussed here, as the present focus is on the theory and its implications. A few remarks on analytical solutions, as well as a simple computational example, are given nonetheless. An auxiliary benefit of this work is a summary of the variation and linearization of the kinematical and constitutive equations of the system.