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Hypothesis: When an aqueous colloidal drop dries on a solid substrate, the final pattern of the dried deposit can be manipulated through controlling the internal flow states of the drop., Experiments: We report a strategy to control the dried patterns of aqueous colloidal drop by controlling the drop configurations and relative humidity. For this purpose, both sessile and pendant drops are studied., Finding: The capillary flow, which is responsible for coffee-ring, is suppressed by increasing the relative humidity. Then, surprisingly, the internal convection in the pendant drop is significantly stronger than that in the sessile drop. This phenomenon leads to the formation of the disc-like and spot-like dried patterns in the sessile and pendant drop, respectively, which are the results of different interactions between the Marangoni and (buoyancy-induced) natural convections in the sessile and pendant drops. In the sessile drop, the Marangoni and natural convections mutually restrain each other due to their opposite flow directions. In contrast, in the pendant drop, the two convections mutually enhance each other, due to their same flow directions. Thisnew strategy offers a foreign-material-free and external-force-free means to control the dried patterns of the drop., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021. Published by Elsevier Inc.)

The synthesis in one pot(1) of opposing 'rose petal' and 'lotus leaf' superhydrophobic materials from commercially available superhydrophilic cloth substrates of varying texture is described for the first time. Surfaces of 'rough' textured cloth and 'smooth' textured cloth were simultaneously rendered superhydrophobic by growing zinc oxide (ZnO) nanorods by a hydrothermal process in the same chemical bath. Contact angle hysteresis and water pendant drop tests revealed strong water adhesion to ZnO microrod-treated rough cloth. The combination of water contact angle >150° and strong adhesion is indicative of the 'rose petal effect' with potential for water pinning. Smooth cloth with ZnO nanorods exhibited no adhesion to water droplets with facilitative roll-off. The combination of water contact angle >150° and weak to no adhesion with water is indicative of the 'lotus leaf effect' with potential for self-cleaning. Pendant water drop tests indicated cohesive failure of water on rough cloth coated with ZnO nanorods. Natural rose petals demonstrated adhesive failure between the petal surface and water droplet. A parsimonious explanation is presented. We also describe the development of superhydrophobic clothes without the need for special conditions or further chemical modification., (Copyright © 2013 Elsevier Inc. All rights reserved.)

The purpose of this communication is to draw attention to a puzzling inconsistency in the published data for the interfacial tension between methane and water at high-pressure and high-temperature conditions. The published data sets fall into two categories – those exhibiting linear dependence of interfacial tension on temperature, in agreement with the phenomenological Eötvös rule, and others exhibiting a peculiar and seemingly reproducible non-linear trend. The inconsistency seems to have gone largely unnoticed. That is somewhat disconcerting considering that the methane/water system is a commonly used reference system for evaluation of fluid interfacial tension models. The literature data are reviewed, discussed, and compared with a novel set of interfacial tension data for the methane/water system obtained in this study. [ABSTRACT FROM AUTHOR]

Highlights: [•] Effect of two different families of ILs on IFT between crude oil and water was examined. [•] The used two different families of ILs were namely imidazolium and pyridinium. [•] Results revealed more successful IFT reduction using imidazolium compared with pyridinium. [•] Results revealed significant effect of salinity on reduction of IFT especially for imidazolium. [Copyright &y& Elsevier]

Highlights: [•] An experimental method is presented for the interfacial tension between two liquids. [•] The bubble contour is evaluated by image processing. [•] A force balance is used for the interfacial tension. [•] The Laplace equation relating internal pressure and curvature is not involved. [Copyright &y& Elsevier]

Abstract: The effect of ultrasound on flow through a capillary using the pendant drop method was investigated. Water was injected into a 0.1mm Hastelloy C-276 capillary tube submersed into several mineral oils with different viscosity, and kerosene. The average drop rate per minute was measured at several ultrasonic intensities. We observed that there exists a peak drop rate at a characteristic intensity, which strongly depends on oil viscosity and the interfacial tension between water and the oil. The semi-quantitative results reveal that the remarkable change in the interfacial forces between oil and water could be the explanation to the enhancement of oil recovery when the ultrasonic waves are applied. [Copyright &y& Elsevier]

Abstract: Interfacial tension of water–CO2 interface was measured by pendant drop method in the presence of a surfactant of various concentrations. The surfactants used were three surfynols which are non-ionic blanched hydrocarbon with different length of the alkyl side chain. Prior to the interfacial tension measurements, the solubility of the surfynols in CO2 were determined from cloud point method. The measured interfacial tensions indicated that an addition of small amount surfactant did reduce the interfacial tension. The interfacial activities of surfactants were evaluated from the slope of the interfacial tension reduction curve against the surfactant concentration and rationalized in terms of the molecular natures such as hydrophobic alkyl chain length. [Copyright &y& Elsevier]

Abstract: A novel apparatus, PeDro, was used to measure interfacial tension in a two-component system made of water and compressed carbon dioxide at temperatures ranging 278–335K and pressures 0.1–20MPa. Our optimized experimental setup utilized the quasi-static pendant drop method and ensured experimental errors below 2%. The interfacial tension showed a pronounced dependence on pressure and temperature. A regression function was derived that allows to interpolate between the experimental data with high precision. Molecular dynamics simulations were performed for liquid–liquid and liquid–vapor interfaces between water and carbon dioxide at elevated pressures. The interfacial tension was obtained from long constant-volume production runs as the difference between normal and tangential pressure components. The results showed a good agreement with experimental data, with our model system reproducing faithfully the pressure–temperature dependence of the interfacial tension. [Copyright &y& Elsevier]

Dynamic interfacial tension (JET) measurements were used to investigate the interactions between a dissociated model naphthenic acid (p-(n-dodecyl) benzoic acid) and various divalent metallic cations (Mg2+, Ca2+, Sr2+, and Ba2+) across a toluene/hexadecane-water interface. The measurements were performed by using the pendant drop technique. The results obtained, plotted as IFT vs. time gave curves with similar shapes but different slopes and levels of the equilibrium IFT, depending upon the acid and salt concentrations and the type of cation added. Due to differences in degree of hydration of the various cations, the products of the reaction between dissociated acid monomers and the cations showed differences in solubility, which, in turn, affected the IFT. Based on the shapes of the curves, the mechanisms of the reactions involved in the process are discussed. [ABSTRACT FROM AUTHOR]

Interfacial properties of the (CH 4 + CO 2 + H 2 O) system are of great importance in many geotechnical engineering applications. In this study, we report the first experimental measurements of the interfacial tensions in the (CH 4 + CO 2 + H 2 O) system under both three-phase (VLLE) and biphasic conditions. The measurements were made by the pendant drop method. The compositions of the coexisting phases were obtained from a previous study of the phase behavior and the phase densities were then calculated from an equation of state. IFTs along five isotherms in the VLLE region and along six isotherms in biphasic region are reported. In the VLLE region, the IFT between the water-rich liquid and the gas phase varied between (33 and 39) mN·m−1, with a sharp increase as the pressure increased along an isotherm towards the upper critical end point. In the same region, the IFT between the water-rich and CO 2 -rich liquids varied between (30 and 33) mN·m−1. The IFT between the gas phase and the CO 2 -rich liquid phase was too small to measure accurately but an approximate value was obtained which is consistent with Antonov's equality. In the biphasic region, measurements were made at temperatures up to 423 K and at pressures up to 30 MPa. As observed in other water-gas systems, the IFT declines monotonically along isotherms with increasing pressure and decreases with increasing temperature at constant pressure. Image 1 [ABSTRACT FROM AUTHOR]