Use Of Surface Tension Research Articles

Examining the robustness and concentration dependency of PFAS air-water and NAPL-water interfacial adsorption coefficients

Determining robust values for the air-water or NAPL-water interfacial adsorption coefficient, KIA, is key to characterizing and modeling PFAS transport and fate in several environmental systems. Direct, high-resolution measurements of surfactant adsorption at the fluid-fluid interface were aggregated from the literature. This data set was used to examine the accuracy and applicability of Γ and KIA measurements determined for three PFAS from transport experiments and surface-tension data. The transport-measured Γ and KIA data were observed to be fully consistent with the directly-measured data. Specifically, Γ values for the two methods were entirely coincident in the region of overlapping concentrations, which spanned ~4 orders-of-magnitude. Furthermore, the two data sets adhered to an identical Γ-C profile. These results conclusively demonstrate the accuracy of the transport-measured values. Γ and KIA values determined from the application of the Gibbs adsorption equation to measured surface-tension data were fully consistent with the directly-measured and transport-measured data sets, demonstrating their applicability for representing PFAS transport in environmental systems. The directly-measured data were used to examine the concentration dependency of KIA values, absent the potential confounding effects associated with the use of surface-tension or transport-measured data. The directly-measured data clearly demonstrate that KIA attains a constant, maximum limit at lower concentrations. Two separate analyses of the transport-measured data both produced observations of constant KIA values at lower concentrations, consistent with the directly-measured data. These outcomes are discussed in terms of surface activities, relative surface coverages, and critical concentrations.

On the thin-film asymptotics of surface tension driven microfluidics

Abstract

The effect of Pseudomonas fluorescens biosurfactant pseudofactin II on the conformational changes of bovine serum albumin: Pharmaceutical and biomedical applications

Herein, we have investigated the binding interaction of bovine serum albumin (BSA) with a biosurfactant pseudofactin II (PF) in physiological buffer medium through the use of surface tension, fluorescence, circular dichroism (CD), isothermal titration calorimetry (ITC) and molecular docking studies. Fluorescence results showed that PF interacts with BSA through a static quenching mechanism. CD results demonstrate a conformational change in BSA upon PF combination. The negative Gibbs free energies obtained through ITC experiment suggest that the binding process is spontaneous. Molecular docking further provides an insight of various residues that are involved in this binding process, showing a binding energy of −58.6 kcal mol−1. The present study will help understand the binding mechanism of lipopeptide biosurfactant (PF) to proteins as well as the associated stability and conformational changes.

Review of Microfluidic Devices for On‐Chip Chemical Sensing

SUMMARYMicrofluidic techniques can be a basis to realize user‐friendly microanalytical devices of high performance. Required operations include injection of solutions to reaction chambers, volume measurement, and mixing of solutions. For this purpose, the use of surface tension is attractive. In hydrophobic flow channels, solutions can be moved stably in the form of plugs. Otherwise, solutions can be transported by capillary action in a hydrophilic flow channel and stopped at a hydrophobic valve. The valve can be opened autonomously by switching the mixed potential by wetting a zinc electrode formed in a controlling flow channel. In this review paper, we introduce some of our microfluidic devices particularly focusing on devices that work based on surface tension.

オンチップ化学センシングのためのマイクロフルイディックデバイスに関するレビュー

Microfluidic techniques can be a basis to realize user-friendly microanalytical devices of high performance. Required operations include injection of solutions to reaction chambers, volume measurement, and mixing of solutions. For this purpose, the use of surface tension is attractive. In hydrophobic flow channels, solutions can be moved stably in the form of plugs. Otherwise, solutions can be transported by capillary action in a hydrophilic flow channel and stopped at a hydrophobic valve. The valve can be opened autonomously by switching the mixed potential by wetting a zinc electrode formed in a controlling flow channel. In this review paper, we introduce some of our microfluidic devices particularly focusing on devices that work based on surface tension.

Exploration of interactions between decyl-β-d-glucopyranoside and bovine serum albumin in aqueous solution

The interactions between decyl-β-d-glucopyranoside (DG) and bovine serum albumin (BSA), in aqueous media, were investigated through the use of surface tension, steady-state fluorescence, and UV-vis absorption spectroscopy measurements.

Systematic procedure to parametrize force fields for molecular fluids.

A new strategy to develop force fields for molecular fluids is presented. The intermolecular parameters are fitted to reproduce experimental values of target properties at ambient conditions and also the critical temperature. The partial charges are chosen to match the dielectric constant. The Lennard-Jones parameters, εii and σii, are fitted to reproduce the surface tension at the vapor-liquid interface and the liquid density, respectively. The choice of those properties allows obtaining systematically the final parameters using a small number of simulations. It is shown that the use of surface tension as a target property is better than the choice of heat of vaporization. The method is applied to molecules, from all atoms to a coarse-grained level, such as pyridine, dichloromethane, methanol, and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM-BF4) at different temperatures and pressures. The heat of vaporization, radial distribution functions, and self-diffusion coeficient are also calculated.

Surface-tension phenomena in organismal biology: an introduction to the symposium.

Flows driven by surface tension are both ubiquitous and diverse, involving the drinking of birds and bees, the flow of xylem in plants, the impact of raindrops on animals, respiration in humans, and the transmission of diseases in plants and animals, including humans. The fundamental physical principles underlying such flows provide a unifying framework to interpret the adaptations of the microorganisms, animals, and plants that rely upon them. The symposium on "Surface-Tension Phenomena in Organismal Biology" assembled an interdisciplinary group of researchers to address a large spectrum of topics, all articulated around the role of surface tension in shaping biology, health, and ecology. The contributions to the symposium and the papers in this issue are meant to be a starting point for novices to familiarize themselves with the fundamentals of flows driven by surface tension; to understand how they can play a governing role in many settings in organismal biology; and how such understanding of nature's use of surface tension can, in turn, inspire humans to innovate.

Limitations in the use of surface tension and the Gibbs equation to determine surface excesses of cationic surfactants.

Neutron reflection (NR) and surface tension (ST) are used to show that there are serious limitations in applying the Gibbs equation accurately to ST data of cationic surfactants to obtain the limiting surface excess, Γ(CMC), at the critical micelle concentration (CMC). Nonionic impurities in C12TABr and C16TABr have been eliminated by extensive purification to give ST - ln(concentration) (σ - ln c) curves that are convex with respect to the ln c axis around the CMC, which is characteristic of a finite micellization width. Because NR shows that the surface excess often continues to increase at and above the CMC, this finite width makes it impossible to apply the Gibbs equation to obtain Γ(CMC) without knowledge of the effect of aggregation on the activity. NR data made it possible to apply the integrated Gibbs equation to the ST below the onset of the convex region of the σ - ln c curve and show that for C12TABr the micellization width causes the ST to underestimate Γ(CMC) by 12%. Hexadecyltrimethylammonium (C16TA) sulfate is used to show that divalent ion impurities are not a significant problem. For cationic surfactants, further errors are associated with ST methods that rely on complete wetting. Measurements using ring, plate, and bubble shape analyses indicate that with ring and plate incomplete wetting occurs at or above the CMC and may extend to lower concentrations and also causes the ST-Gibbs analysis to underestimate the surface excess. In combination with ion association and preaggregation in cationic gemini surfactants, this can cause errors as large as 100% in Γ(CMC). Comparison of ellipsometry and NR for C16TAX in 0.1 M KX (X = F or Cl) shows that ellipsometry cannot, as yet, be quantitatively modeled accurately enough for surface excess determination independent of NR calibration.

Adsorption of antibody onto Pluronic F68-covered nanoparticles: link with surface properties

The use of nanoparticles as drug delivery systems is an emerging application to improve intravenous therapy. Controlling the biocompatibility of the nanoparticles is a crucial step towards the optimal implementation of these systems. Adsorption of serum components onto the nanoparticles is driven mainly by hydrophobic forces. Thus, incorporation of hydrophilic polymers such as polyethylene oxide (PEO) derivatives to the nanostructure surface reduces the interaction of nanoparticles with blood stream components (IgG). The effectiveness of the poloxamer for reducing protein adsorption depends on the resistance of this coating layer. A fundamental understanding of the properties of this surface coating is crucial towards the rational design of these systems. Here, we have used an innovative combination of experimental techniques to evaluate the properties of the nanoparticles and more specifically, the mechanical properties of the coating. Electrophoretic mobility and colloidal stability data suggest similar surface characteristics between IgG–Pluronic–polystyrene (PS) and IgG–PS complexes, indicating that the protein adsorption is just slightly reduced by the presence of poloxamer. Nevertheless, the biological activity of the adhered antibodies suggests that the Pluronic F68 significantly altered their immunoactivity. The decrease in the activity might indicate a partial denaturation of the protein and/or changes in the preferential orientation when adsorbing caused by the surfactant–protein interactions. The surface characterisation of the IgG layers adsorbed onto a Pluronic covered surface importantly provides evidence of the conformational change undergone by the protein, supporting the partial protein denaturation suggested by the loss of immunoreactivity in the IgG–Pluronic–PS particles. The use of surface tension to obtain structural and mechanical information about the coating procedure is a novel approach to understand generic features of the biocompatibility of colloidal systems. These results may help to understand why drug nanocarriers coated by poloxamers improve their long-circulating properties in comparison with uncoated particles.

Improved wetting of bare and pre-coated steels by aqueous alumina sols for optimum coating success

Alumina coatings are a promising candidate for the protection of metals prone to high temperature corrosion. If applied via sol–gel process, especially by using so called aqueous modified Yoldas-sols, the deposition is hardened by differences in surface free energy of substrate and sol. In this paper the apparent surface properties of samples to be coated and sols were examined by contact angle measurements, IR-spectroscopy and tensiometry. The results imply, after consideration of possible uncertainties, the use of surface tension reducing 2-butanol already present during hydrolysis of the sols to obtain an easy and successful coating process.

Capillary Based Patterning of Cellular Communities in Laterally Open Channels

In order to offer an easier way to study interactions between multiple cellular populations, we have developed a novel method to precisely place cells in a variety of nonoverlapping patterns using surface tension in laterally open microchannels. Our design is fundamentally different from previous strategies such as compartmentalization, stamping, stenciling, or mechanical approaches. It relies on capillary action or the propensity for liquid to move more readily through narrow spaces as a result of surface tension. Until now, capillary based patterning has been limited to coating chemically isolated areas. Here, we demonstrate, through use of surface tension and controlled flooding, that it is possible to pattern multiple cells and proteins using laterally open channels in a variety of designs. We demonstrate the relevance of the concept by coculturing different mammalian cell types and evaluating the behavior of engineered quorum sensing circuits in E. coli. In the future, we believe the laterally open channel designs shown here can be useful for rapidly creating and studying cellular ecologies using simple pipetting.

Surface tension propulsion of fungal spores

Most basidiomycete fungi actively eject their spores. The process begins with the condensation of a water droplet at the base of the spore. The fusion of the droplet onto the spore creates a momentum that propels the spore forward. The use of surface tension for spore ejection offers a new paradigm to perform work at small length scales. However, this mechanism of force generation remains poorly understood. To elucidate how fungal spores make effective use of surface tension, we performed a detailed mechanical analysis of the three stages of spore ejection: the transfer of energy from the drop to the spore, the work of fracture required to release the spore from its supporting structure and the kinetic energy of the spore after ejection. High-speed video imaging of spore ejection in Auricularia auricula and Sporobolomyces yeasts revealed that drop coalescence takes place over a short distance ( approximately 5 microm) and energy transfer is completed in less than 4 mus. Based on these observations, we developed an explicit relation for the conversion of surface energy into kinetic energy during the coalescence process. The relation was validated with a simple artificial system and shown to predict the initial spore velocity accurately (predicted velocity: 1.2 m s(-1); observed velocity: 0.8 m s(-1) for A. auricula). Using calibrated microcantilevers, we also demonstrate that the work required to detach the spore from the supporting sterigma represents only a small fraction of the total energy available for spore ejection. Finally, our observations of this unique discharge mechanism reveal a surprising similarity with the mechanics of jumping in animals.

T1101-1-1 表面張力を利用した液滴の三次元輸送に関する研究(マイクロナノ理工学:nmからmmまでの表面制御とその応用(1))

This paper describes a new method for three-dimensional transportation of liquid droplets using EWOD (Electro Wetting on Dielectric). This method makes use of surface tension and electrostatic forces, which become dominant in microscale devices. The droplet transported on a vertical or upside down surface is affected by gravity force. In order to reduce the gravity effect, volume of water was reduced and shape and size of electrodes were changed. A water droplet was transported on a inclined plate, and the angle of inclination was changed from 10° to 360° by every 10°. The results show that water droplet can be transported on all inclined surfaces. Horizontal transportation of a droplet on a vertical surface was also made successfully.

Microfluidic device concept based on microoscillator dynamics at a liquid–liquid interface

Abstract Oscillating microbeams and microplates have been used extensively as sensing components for property detection in fluids. In liquids, their quality factor Q is drastically decreased, thus affecting a microsensor's resolution. To improve the Q -factor, we present a novel concept based on the positive use of surface tension on a mechanical oscillator composed of a microbeam–microplate assembly suspended at a liquid–liquid interface in a microfluidic channel. An analytical model is developed to investigate rotational dynamics of such an assembly. Surface tension effects at the liquid–liquid–solid perimeter line produce responses that are considerably different from those in a single fluid. It is shown that due to surface tension the Q -factor and the response are magnified by orders of magnitude, thus confirming that liquid–liquid interfaces enhance the oscillator's sensitivity. For two liquids the Q -factor varies as [ σ 2 - σ 1 ] 1 / 2 × ( μ 2 + μ 1 ) - 1 and for a single liquid as ρ 1 / 2 × μ - 1 , ( σ , μ ) being surface tension and viscosity, respectively. Microdevice design, actuation and sensing mechanisms, and optimal parameter selection are proposed.

Physical Properties of Ionic Liquids Consisting of the 1-Butyl-3-Methylimidazolium Cation with Various Anions and the Bis(trifluoromethylsulfonyl)imide Anion with Various Cations

Physical properties of 4 room-temperature ionic liquids consisting of the 1-butyl-3-methylimidazolium cation with various perfluorinated anions and the bis(trifluoromethylsulfonyl)imide (Tf2N-) anion with 12 pyrrolidinium-, ammonium-, and hydroxyl-containing cations are reported. Electronic structure methods are used to calculate properties related to the size, shape, and dipole moment of individual ions. Experimental measurements of phase-transition temperatures, densities, refractive indices, surface tensions, solvatochromic polarities based on absorption of Nile Red, 19F chemical shifts of the Tf2N- anion, temperature-dependent viscosities, conductivities, and cation diffusion coefficients are reported. Correlations among the measured quantities as well as the use of surface tension and molar volume for estimating Hildebrand solubility parameters of ionic liquids are also discussed.

Small-Prey Profitability: Field Analysis of Shorebirds’ use of Surface Tension of Water to Transport Prey

AbstractPrevious laboratory studies have shown that Red-necked Phalarope (Phalaropus lobatus), Wilson’s Phalarope (P. tricolor), Western Sandpiper (Calidris mauri), and Least Sandpiper (C. minutilla) use the surface tension of water surrounding a prey item to transport it from bill tip to mouth. Although such experimental work suggests that many species of shorebird may be capable of surface-tension feeding, no field studies have been done that examine this possibility. We studied the occurrence and interspecific variation in the performance of surface-tension transport (STT) in wild shorebirds feeding on identical prey items in shallow water. All shorebirds videotaped—Little Stint (C. minuta), Dunlin (C. alpina), Sanderling (C. alba), Curlew Sandpiper (C. ferruginea), Common Redshank (Tringa totanus), and Black-winged Stilt (Himantopus himantopus)—used STT to feed on small prey items. Individuals employing STT used one or several cycles of jaw spreading to transport the prey contained in a drop of water upward along the bill cavity, an action indicative of STT. Two distinct types of prey transport were observed: (1) use of STT in isolation by calidridine species following the description given in previous studies (i.e., an absence of other feeding mechanisms such as tongue movements, suction, or inertial transport), and (2) STT aided by inertial transport (head jerks) as seen in Common Redshank and Black-winged Stilt. Measured prey-transport variables (number of cycles, total time, and speed of transport) varied among species. The absence of significant relationships between these variables and measures of external morphology (bill length, bill length-to-width ratio, and bill length-to-depth ratio) suggests that some interspecific variations in STT performance may be attributable to differences in internal bill morphology. We show that STT is a common feeding mechanism in small or medium- sized shorebird species that feed on small prey items in shallow water. Birds using STT transported ≤3.6× faster than the theoretical value predicted by a previous model and can achieve high intake rates when foraging on high densities of available small prey items.Ventajas de las Presas Pequeñas: Análisis de Campo del Uso de la Tensión Superficial del Agua por las Aves Playeras para Transportar las Presas

Effect of hydrogen-bonding interactions on the self-assembly formation of sodium N-(11-acrylamidoundecanoyl)- l-serinate, l-asparaginate, and l-glutaminate in aqueous solution

Aggregation behavior of three N-acyl amino acid surfactants, sodium N-(11-acrylamidoundecanoyl)- l-serinate (SAUS), sodium N-(11-acrylamidoundecanoyl)- l-asparaginate (SAUAS), and sodium N-(11-acrylamidoundecanoyl)- l-glutaminate (SAUGL), was studied in aqueous solution by use of surface tension, fluorescence, dynamic light scattering, and transmission electron microscopic techniques. The amphiphiles have been shown to initially form flexible bilayer structures, which upon increase of surfactant concentration transform into closed spherical vesicles. The transmission electron micrographs of the aqueous solutions of the surfactants confirmed the existence of spherical vesicles. Dynamic light scattering measurements were performed to obtain hydrodynamic radii of the vesicles. Circular dichroism spectra of the amphiphiles indicated formation of chiral helical aggregates in the case of SAUS. The self-assembly formation of the amphiphiles has been discussed in light of the intermolecular hydrogen bonding interaction of the amide groups.

The Use of Surface Tension to Predict the Formation of 2D Arrays of Latex Spheres Formed via the Langmuir−Blodgett-Like Technique

Highly ordered hexagonal arrays of latex spheres on highly ordered pyrolytic graphite (HOPG) have been prepared from a Langmuir-Blodgett-like (LB-like) technique using both polymers and surfactants as spreading agents. The role of spreading agent concentration in forming a well-ordered, stable monolayer at the air-liquid interface was studied by means of atomic force microscopy, scanning electron microscopy, optical microscopy, and surface tension measurements for three different systems: a nonionic surfactant, octylphenoxy poly(ethyleneoxy)ethanol (Igepal CO 630); an anionic surfactant, sodium dodecyl sulfate; and a low-molecular-weight, water-soluble polymer, polyacrylamide. For both the anionic surfactant and the water soluble polymer, a correlation was found between a unique feature in surface tension measurements of the latex-spreading agent mixture and the concentrations at which hexagonal arrays of latex spheres form on the surface of HOPG. For the nonionic surfactant, no ordered structures were found on HOPG for any surfactant concentration, consistent with no appearance of the unique feature in surface tension measurements. These results show that a tensiometer can be used to determine the conditions under which well-ordered latex films have the possibility of forming on a substrate using the LB-like technique; however, other factors, such as pulling speed and surface chemistry, play a role as well.

高精度の表面張力測定 滴容法による自動測定の精度の調査（原標題は英語）

Surface tension is difficult to measure with high accuracy. This parameter was measured for pure water to determine conditions that would permit high accuracy. Sources of error in assessing stability, variance, reproducibility and time-dependency of surface tension were sought. The glass syringe, differences in inner and outer temperatures of the cell and its inner pressure, etc. were found to affect this parameter. With attention to these factors, greater accuracy was achieved. Use of a glass syringe and holder with exact control of temperature led to maximum elimination of error. The surface tension of pure water, surfactant solutions and volatile organic liquids were measured and compared with previous values. There was less variation and the results were much more reproducible. High accuracy is thus possible with elimination of sources of error. Significant interfacial phenomena such as phase transition in adsorbed film, not observed by usual surface tension measurement apparatus, may thus be effectively studied through use of surface tension obtained with the present apparatus.