Surface Tension Measurement Method Research Articles

Morphology Observation of Two-Dimensional Monolayers of Model Proteins on Water Surface as Revealed by Dropping Method.

We have investigated the morphology of two-dimensional monolayers of gramicidin-D (GD) and alamethicin (Al) formed on the water surface by the dropping method (DM) using surface tension measurement (STm), Brewster angle microscopy (BAM), and atomic force microscopy (AFM). Dynamic light scattering (DLS) revealed that GD in alcoholic solutions formed a dimeric helical structure. According to the CD and NMR spectroscopies, GD molecules existed in dimer form in methanol and lipid membrane environments. The STm results and BAM images revealed that the GD dimer monolayer was in a liquid expanded (LE) state, whereas the Al monolayer was in a liquid condensed (LC) state. The limiting molecular area (A0) was 6.2 ± 0.5 nm2 for the GD-dimer and 3.6 ± 0.5 nm2 for the Al molecule. The AFM images also showed that the molecular long axes of both the GD-dimer and Al were horizontal to the water surface. The stability of each monolayer was confirmed by the time dependence of the surface pressure (π) observed using the STm method. The DM monolayer preparation method for GD-dimer and Al peptide molecules is a useful technique for revealing how the model biological membrane's components assemble in two dimensions on the water surface.

Exploration of surface tension measurement methods for pharmaceutical excipients

Surface tension is a crucial functional indicator for various classes of pharmaceutical excipients, as highlighted in both the Pharmacopoeia of the People’s Republic of China (ChP) < 9601 Guidelines for Functionality-related Characteristics of Pharmaceutical Excipients > and the United States Pharmacopoeia (USP) < 1059 Excipient Performance >. However, there are few systematic studies on surface tension measurement of pharmaceutical excipients, resulting in a lack of stable parameter support in practical applications. In this study, we aim to fill this gap by exploring three different methods for measuring surface tension. These methods were carefully developed taking into account the actual measurement process and statistical theory, thus ensuring their applicability and reliability. Through comparative analyses, we have identified the most suitable measurement methods for different classes of pharmaceutical excipients. In addition, this paper describes the surface adsorption behavior of various excipients. Therefore, this study provides valuable guidance for the determination of surface tension and the study of surface adsorption behavior, which lays the foundation for further comprehensive research in the field of surface tension of pharmaceutical excipients and the improvement of general pharmacopoeia specification.

Benchmarking surface tension measurement method using two oscillation modes in levitated liquid metals

The Faraday forcing method in levitated liquid droplets has recently been introduced as a method for measuring surface tension using resonance. By subjecting an electrostatically levitated liquid metal droplet to a continuous, oscillatory, electric field, at a frequency nearing that of the droplet’s first principal mode of oscillation (known as mode 2), the method was previously shown to determine surface tension of materials that would be particularly difficult to process by other means, e.g., liquid metals and alloys. It also offers distinct advantages in future work involving high viscosity samples because of the continuous forcing approach. This work presents (1) a benchmarking experimental method to measure surface tension by excitation of the second principal mode of oscillation (known as mode 3) in a levitated liquid droplet and (2) a more rigorous quantification of droplet excitation using a projection method. Surface tension measurements compare favorably to literature values for Zirconium, Inconel 625, and Rhodium, using both modes 2 and 3. Thus, this new method serves as a credible, self-consistent benchmarking technique for the measurement of surface tension.

Spherical Spontaneous Capillary-Wave Resonance on Optically Trapped Aerosol Droplet

We report a contactless surface tension measurement method of micrometer-sized aerosol droplets. In this method, we assume spherical spontaneous resonance of a thermally induced capillary wave. Fir...

Faraday forcing of high-temperature levitated liquid metal drops for the measurement of surface tension

In this work, a method for the measurement of surface tension using continuous periodic forcing is presented. To reduce gravitational effects, samples are electrostatically levitated prior to forcing. The method, called Faraday forcing, is particularly well suited for fluids that require high temperature measurements such as liquid metals where conventional surface tension measurement methods are not possible. It offers distinct advantages over the conventional pulse-decay analysis method when the sample viscosity is high or the levitation feedback control system is noisy. In the current method, levitated drops are continuously translated about a mean position at a small, constant forcing amplitude over a range of frequencies. At a particular frequency in this range, the drop suddenly enters a state of resonance, which is confirmed by large executions of prolate/oblate deformations about the mean spherical shape. The arrival at this resonant condition is a signature that the parametric forcing frequency is equal to the drop’s natural frequency, the latter being a known function of surface tension. A description of the experimental procedure is presented. A proof of concept is given using pure Zr and a Ti39.5Zr39.5Ni21 alloy as examples. The results compare favorably with accepted literature values obtained using the pulse-decay method.

Effects of different activating fluxes on the surface tension of molten metal in gas tungsten arc welding

Surface tension is an important factor in arc welding and affects weld microstructure and flow mode in the weld pool. A novel surface tension measurement method based on the principle of weld pool oscillation is proposed to sense the surface tension of the weld pool without and with TiO2, NaCl, and CaF2 activating fluxes during tungsten inert gas welding process. Experimental results reveal that the TiO2 activating flux can convert the surface tension gradient from negative to positive but exerts minimal effect on arc behavior. The surface tension gradient is mainly controlled by the oxygen content in the weld pool, which determines the Marangoni convection and penetration depth. High oxygen content decreases the surface tension gradient and weakens the Marangoni convection in the weld pool. The NaCl and CaF2 activating fluxes can reduce the absolute value of average surface tension but exert negligible effects on the sign of surface tension gradient. The varied surface tension and increased penetration depth with NaCl and CaF2 activating fluxes are caused by arc constriction and increased arc temperature, respectively.

Non-contact surface tension measurement method

Non-contact surface tension measurement method

Development of Maximum Bubble Pressure Method for Surface Tension Measurement of High Viscosity Molten Silicate

A surface tension measurement method based on the maximum bubble pressure (MBP) method was developed in order to precisely determine the surface tension of molten silicates in this study. Specifically, the influence of viscosity on surface tension measurements was quantified, and the criteria for accurate measurement were investigated. It was found that the MBP apparently increased with an increase in viscosity. This was because extra pressure was required for the flowing liquid inside the capillary due to viscous resistance. It was also expected that the extra pressure would decrease by decreasing the fluid velocity. For silicone oil with a viscosity of $$1000\,\hbox {mPa}{\cdot }\hbox {s}$$ , the error on the MBP could be decreased to +1.7 % by increasing the bubble detachment time to $$300\,\hbox {s}$$ . However, the error was still over 1 % even when the bubble detachment time was increased to $$600\,\hbox {s}$$ . Therefore, a true value of the MBP was determined by using a curve-fitting technique with a simple relaxation function, and that was succeeded for silicone oil at $$1000\,\hbox {mPa}{\cdot } \hbox {s}$$ of viscosity. Furthermore, for silicone oil with a viscosity as high as $$10\,000\,\hbox {mPa}{\cdot }\hbox {s}$$ , the apparent MBP approached a true value by interrupting the gas introduction during the pressure rising period and by re-introducing the gas at a slow flow rate. Based on the fundamental investigation at room temperature, the surface tension of the $$\hbox {SiO}_{2}$$ –40 $$\hbox {mol}\%\hbox {Na}_{2}\hbox {O}$$ and $$\hbox {SiO}_{2}$$ –50 $$\hbox {mol}\%\hbox {Na}_{2}\hbox {O}$$ melts was determined at a high temperature. The obtained value was slightly lower than the literature values, which might be due to the influence of viscosity on surface tension measurements being removed in this study.

Effects of electrolytes on the surface and micellar characteristics of Sodium dodecyl sulphate surfactant solution

The effect of some electrolytes (namely sodium acetate and calcium acetate) on their critical micelle concentration (CMC), have been determined by spectrophotometric, conductometeric and surface tension measurement method at 298K, 308K and 318K. From the surface tension data physico-chemical properties such as surface excess concentration (Γmax) and minimum area per molecule (Amin) at surface have been obtained. From the observed CMC data, free energy of micellization (∆Gmic), entropy change of micellization (∆Smic), and enthalpy change of micellizaton (∆Hmic) for the studied surfactant solutions with or without electrolyte have been obtained. The results have been interpreted in light of inter-molecular interaction.

Micellization and Synergistic Effect in an Aqueous Solution of an AOS-TX100 Mixture: Before and After Equilibrium in the Presence of Clay

In this research, a novel surfactant mixture consisting of anionic (alpha olefin sulfonate [AOS]) and nonionic (TX100) type was developed. Possible synergistic effect in micelle formation in different mass ratios of the mixture (1:2, 1:1, and 2:1) was studied by surface tension measurement method. Rubingh's Regular Solution theory was used to evaluate the interaction parameters (β) and activity coefficient (f) for both binary mixture and single surfactants, before and after equilibrium in the presence of clay minerals (kaolinite and illite). The differences between experimentally obtained CMC values and ideally calculated values, showed nonideality of the mixtures. In addition, the lower CMC values of mixtures in comparison with individual surfactants were an indication of synergism. The synergistic effect was maintained before and after equilibrium with clay minerals. The β values of the mixture before equilibrium were in the range –1.5 to –2.6. However, after equilibrium with kaolinite, the values were in the range of –1.9 to –3.9 while after equilibrium with illite they were in the range –1 to –3. For the mixture, before and after equilibrium, the synergism became more severe as mole fractions of AOS increased in the mixture.

Surface tension of dimethyl ether in the temperature range 120–214 K

The capillary constant a 2 was measured by the differential capillary method of surface tension measurement. The surface tension σ of dimethyl ether was calculated. The experiments were performed both above the triple point temperature (T t = 131.66 K) and below it in the range in which the coexisting liquid and gas are metastable. Equations that approximate the temperature dependences of a 2 and σ were suggested. The excess surface entropy and energy were determined. The surface entropy had a maximum at T ≈ 190 K.

A Novel Surface Tension Coefficient Measurement Method Based on Microposts Array Microfluidic Chip

A novel surface tension measurement method based on microposts array microfluidic chip is presented and the fabrication process is studied. When the surface tension balance was broken due to evaporation, the tips of the microposts array submerged in aqueous solvent were pulled as vertical micro-cantilever at the liquid-air interface and displaced. In micro- or nanometers scale, the surface area to volume ratio becomes higher comparably, which means that the surface tension is dominant. The surface tension can be calculated by measuring microposts deformation. Microposts array was fabricated by templating the PDMS (poly-dimethylsiloxane) in the pores of polycarbonate track-etched (PCTE) membranes and filling the membrane pores by capillarity. Subsequently microposts were released by dissolving the template in an organic solvent and bond with micro-chamber collecting with micro-channel. By choosing appropriate membranes, different lengths and diameters of the microposts and the densities of the microposts arrays can be fabricated. The experiment result shows that the surface tension measurement method based on microposts array microfluidic chip is effective and the resolution can reach nN/μm.

Sensitivity Analysis of the Pressure-Based Direct Integrity Test for Membranes Used in Drinking Water Treatment

We conducted a sensitivity analysis of the commonly employed pressure-based direct integrity test (DIT), the most sensitive test for defects in low-pressure hollow fiber (LPHF) microfiltration and ultrafiltration systems used in drinking water treatment. Incorporating uncertainty to assess the practice of DIT, we find the resolution in some tests may be insufficient to verify the presence of a barrier to oocysts of Cryptosporidium. Applying distributions and boundaries derived from literature and practice, we solved for the defect size resolution (DSR) using Monte Carlo and Probability Bounds Analysis for five commercial membrane designs. Surface tension was modeled using annual temperature profiles from three rivers. Contact angle measurement error and variability were derived from literature, respectively, as a standard deviation of 5.7 degrees and +/- 9.6 degrees median change due to natural organic matter (NOM) fouling. These measures of contact angle uncertainty and variability were combined in a normal distribution with the discrete values currently applied. Additionally we considered model uncertainty, applying the maximum bubble pressure method, an established method of surface tension measurement in liquids in which the maximum air pressure in a submerged capillary is developed after the contact angle becomes zero prior to bubble formation. Where the DSR exceeds 3 microm the test design is not compliant with applicable drinking water regulations. Implications include uncertain and variable log-removal values (LRV) as determined by DIT due to the possible emergence of defects large enough to allow oocysts to pass without detection by the DIT. Specifically, we found the DSR may exceed 3 microm and may be as large as 8 microm. With the variable contact angle model, all lower bound possibilities are compliant, whereas the upper bound is over 80% noncompliant for three of five commercial designs. Using the Maximum Bubble Pressure Method, the lower bounds in three designs start to exceed 3 microm for between 50 and 100% of the produced water, whereas the upper bounds of the DSR completely exceed 3 microm for four of five commercial designs examined.

The liquid–gas interface of oxygen–nitrogen solutions: 1. Surface tension

The capillary method of surface tension measurement has been used to measure the surface tension of oxygen–nitrogen solutions in the temperature range from 80 to 132 K. At temperatures below the nitrogen critical temperature ( T c = 126.2 K) the capillary constant and the surface tension of solutions are smaller than their additive values and vary linearly with the temperature. Experimental data are compared with the results of calculating the surface tension by the theories of Pinnes and Rowlinson.

Measurement of Surface Tension of Epoxy Resins Used in Dispensing Process for Manufacturing Thin Film Transistor-Liquid Crystal Displays

This paper presents an inverse method for measuring the surface tension of the epoxy resins used in the dispensing process for manufacturing TFT-LCD based on droplet images. A direct method, which is capable of predicting the profile of an axisymmetric liquid droplet, is developed, and then the direct method is incorporated with a droplet imaging system to build up a measurement system for determination of the surface tension of the epoxy resins. When applying the surface tension measurement method, one only needs to give the density of the liquid and identify the geometric parameters of the liquid droplet, such as the droplet volume and the contact angle, through the imaging system. This approach has been used to determine surface tension of various epoxy resins. Finally, for testing the accuracy of the approach, some commonly used fluids are tested. Results show that the approach leads to satisfactory accuracy.

Surface Tension Measurement at High Temperatures by using Dynamics of Melt Flow

Surface tension of melts at high temperature has significant effects on different industrial processes. In a new containerless method for surface tension measurement, an atmospheric radio-frequency inductively coupled plasma melts metallic or ceramic rods and a high-speed charge-coupled device records the drop formation caused by melting. Pendant drops produced by the melt flow are compared with the theoretical Young–Laplace (YL) profiles. Moreover, the dynamics of the melt flow is mimicked by using numerical simulations of drop injection from a nozzle. The numerical model solves the axisymmetric Navier–Stokes equations for both the melt and the surrounding gas by using the finite volume method. Since the YL equations provide theoretical pendant drop profiles based on an inviscid quasiequilibrium condition, a detailed study of the differences between experimental, numerical, and theoretical profiles demonstrates some of the hydrodynamic effects influencing the surface tension measurement methods, which are based on drop profiles. Results from this surface tension measurement method, in addition to a discussion on the hydrodynamic effects, are presented.

Influence of Capillary Effects on Precision of Pressure Measurement by Liquid-Level Manometer

A dependence of the radius of curvature of a meniscus on the diameter of a manometer tube is found by means of a numerical solution of a differential equation. A modification of the hanging drop method of surface tension measurement based on computer processing of the photographic image of the drop is developed to measure the coefficient of surface tension of a working fluid. Interferometric investigations of the fluctuations of the curvature that determine the error of the manometer are conducted.

Process Management Based on Analysis of Surfactant Properties

Abstract One goal of optimising cleaning processes is the economic use of surfactant. To find the optimum concentration of active surfactants for a stable and high cleaning quality, a measurement technique to determine this concentration is required, in order to establish a correlation to the cleaning result. The article introduces a modified surface tension measurement method to determine the concentration of active surfactants in process conditions. Based on this method, a new generation of inline tensiometers had been developed. These Instruments allow continuously monitoring the active surfactant concentration in a cleaning bath. The article shows how to interpret the measurement results for the process control. Exemplarily at the use of online measurement in metal cleaning processes, the potential to provide a higher level of process quality control will be illustrated.

Modeling the Wilhelmy Surface Tension Method for Nematic Liquid Crystals

A general model for the Wilhelmy (fiber) surface tension measurement method for uniaxial nematic liquid crystals has been derived using fundamental principles and classical liquid-crystal physics. A rigorous formulation of the contributions of surface and bulk nematic elasticity was implemented for the Wilhelmy method. The surface contribution is a function of the surface anchoring strength of the liquid-crystal free surface and the director surface orientation at the solid−nematic−vapor common line. The exact bulk elasticity contribution is a function of the director field in the meniscus, which is a function of the nematic−fiber interactions, the size of the fiber, and the temperature, among other things. The specific form of the Wihelmy model equation for four typical nematic textures was developed and analyzed. It is found that the effect may depend on the size of the fiber, the presence of disclinations, and the representative Frank elastic constants. The expression representing the actual measuremen...

The pendant drop method of surface tension measurement: equation interpolating the shape factor tables for several selected planes

For evaluation of the surface tension by the pendant drop method, the method of selected plane is often preferred to more precise and sophisticated treatments. The several selected planes method, which implies better verification of data, is used only seldom, which is likely due to low accessibility of data for other planes in a suitable form. This article presents equations which express the parameter 1/H with a maximum deviation of 10−4, in terms of the shape parameter Sk for 5 planes with the distance from drop apex equal to 0.8–1.2 multiple of the equatorial diameter de. The aim of this paper is only to introduce this tool for easier use of the method; the analysis of advantages and disadvantages of using several planes was made prior by several authors.