Search

Hydrofluoroethers (HFEs) belong to a family of promising fluids that find application potential both in scientific research and in many industrial areas. These include electronics cooling, cascade refrigeration, heat transfer fluids, lubricant carriers or even rinsing agents. However, the thermophysical properties of HFEs required for an effective design of technical applications are only vaguely described and the available experimental data for thermodynamic and transport properties are still limited. In order to improve the description of HFEs, new experimental measurements of liquid density and surface tension at pressure of 0.1 MPa and temperatures from 260 to 338 K were carried out with a series of five HFEs; namely HFE-7000, HFE-7100, HFE-7200, HFE-7300, and HFE-7500. Liquid density was determined from a single sinker buoyancy method with an expanded uncertainty of 0.50 kg•m−3. The Wilhelmy plate method and the du Nouy ring method were used for the measurement of surface tension with expanded uncertainties of 0.068 mN•m−1 and 0.18 mN•m−1, respectively. In the modelling part, a consistent fluid property model was developed based on the physically based equation of state PC-SAFT. Additionally, regarding polarity of HFEs, empirical correlation for dipole moment was addressed. In case of larger HFE molecules, it was determined that the polar modification named PCP-SAFT, provides only marginal correction. The equations were combined with the density gradient theory (DGT) in order to model vapor-liquid phase interface and predict the surface tension. DGT+PC-SAFT was found to provide good predictions for the surface tension of the five selected HFEs.

The purpose of this study is to investigate the surface activity of starch nanocrystals (SNC), material derived from starch, and confirm their usefulness as a surfactant. In order to evaluate the surface activity, the surface tension change of suspended SNC solution via the Wilhelmy plate method was measured and the values were compared with various synthetic surfactants. The effect of SNC as emulsifier was evaluated on emulsion formation and physical stability. The surface tension of the SNC-dispersed solution was decreased while its concentration was increased. When the 5.0% (w/v) of SNC was added, the surface tension was decreased from 70.3 to 49.5 mN/m. It was confirmed that the physical stability of the emulsion prepared by adding the SNC was improved compared to that of surface inactivity material (PEG 400). The phase separation was observed within 1 hour after preparation of the emulsion containing PEG 400, but the emulsion containing SNC was stable for 5 hours or more. To summarize this study, SNC, a natural-derived and non-toxic material, exhibits sufficient surface activity, thereby confirming the possibility of being applied to the food and pharmaceutical industry.

To quantitatively analyze and study the water stability of crushed gravel asphalt mixture by using surface energy theory, the surface energy parameters of crushed gravel samples at 20℃ are tested by using the gas sorption method, and the surface energy parameters of four anti-stripping agent asphalts with different dosages (0%, 0.2%, 0.4%, 0.6%) at 20℃ are tested by using the Wilhelmy plate method. Then, the binding energy of crushed gravel and anti-stripping agent asphalts with different dosages and the surface energy evaluation index of water stability are calculated. On this basis, quantitative analysis and sequencing of water stability of crushed gravel asphalt mixture were carried out. The microscopic mechanism of the anti-stripping agent's improvement on adhesion between crushed gravel and asphalt was analyzed from the angle of surface energy. Marshall test (immersion Marshall test, vacuum saturation Marshall test, freeze-thaw splitting test) with anti-stripping agent contents of 0%, 0.2%, 0.4%, and 0.6% was conducted through strict control of crushed gravel material, gradation, and oil-stone ratio. Results show that (1) the surface energy parameters of crushed gravel are dominated by polar alkali component; (2) the addition of anti-stripping agent will reduce the surface energy of asphalt, thus increasing the wettability of asphalt to aggregate; (3) the improvement of the adhesion between crushed gravel and asphalt by adding anti-stripping agent is mainly reflected in two aspects: reducing the cohesive energy of asphalt itself to increase its wettability to aggregate and increasing the surface energy acid component of asphalt to increase its adhesion binding energy to aggregate; and (4) the order of microscopic surface energy evaluation index of water stability of crushed gravel asphalt mixture is the same as that of macroscopic performance test index, thus demonstrating the accuracy of the surface energy system for quantitative analysis of the water stability of the crushed gravel asphalt mixture.

Objectives. This study focused on the quantification of the surface tension and the static and dynamic contact angles of epoxy oligomers, active diluents, and their mixtures of various compositions at different temperatures. The active diluents were aliphatic compounds based on glycidyl ethers, namely laproxides and a laprolate of different structure, functionality, molecular weight, and viscosity. Moreover, the preparation of effective polymer binders (matrices) for composites was explored.Methods. In this study, the epoxy oligomers ED-20 and DER-330, laproxides 201B, DEG-1, E-181, and 703, laprolate 301, and their mixtures in various compositions were investigated. Their surface tension and the static and dynamic contact angles were determined by the Wilhelmy plate and ring methods on a semiautomatic tensiometer at different temperatures (20–60 °C). The static contact angle was measured on a thin aluminum borosilicate glass plate, and the dynamic contact angles were determined using an installation for measuring surface tension developed by NPO Stekloplastik.Results. The surface tension and static and dynamic contact angles were obtained for all epoxy oligomers and active diluents, as well as for their mixtures at 20–60 °C. For binders based on systems of epoxy oligomers and active diluents, the impregnation rate of fiber reinforcement was also calculated. The introduction of laproxides or laprolates into the epoxy oligomers led to a decrease in surface tension and contact angles, while the increase in temperature increased the impregnation rate by 10–20 times.Conclusions. The temperature increase from 20 to 60 °C resulted in a decrease in the surface tension of mixed systems of epoxy oligomers and active diluents by almost two times. In addition, the contact angles changed by only 4°–7°, while the impregnation was significantly improved and the corresponding rate increased by 10–20 times.

A method for obtaining the elasticity, surface tension, and viscosity of ultrasonically levitated gel drops is presented. The drops examined were made of agarose, a hydrogel. In contrast to previous studies where fluid properties are obtained using ultrasonic levitation of a liquid drop, herein the material studied was a gel which has a significant elasticity. The work presented herein is significant in that gels are of growing importance in biomedical applications and exhibit behaviors partially determined by their elasticities and surface tensions. Obtaining surface tension for these substances is important but challenging since measuring this quantity using the standard Wilhelmy plate or DuNuoy ring methods is not possible due to breakage of the gel. The experiments were conducted on agarose gels having elasticities ranging from 12.2 to 200.3 Pa. A method is described for obtaining elasticity, surface tension, and viscosity, and the method is experimentally demonstrated for surface tension and viscosity. For the range of elasticities explored, the measured surface tension ranged from 0.1 to 0.3 N/m, and the viscosity ranged from 0.0084 to 0.0204 Pa s. The measurements of surface tension are, to the authors' knowledge, the first obtained of a gel using ultrasonic levitation.

Here, the effects of substituting portions of fossil-based phenol in phenol formaldehyde resin by renewable lignin from two different sources are investigated using a factorial screening experimental design. Among the resins consumed by the wood-based industry, phenolics are one of the most important types used for impregnation, coating or gluing purposes. They are prepared by condensing phenol with formaldehyde (PF). One major use of PF is as matrix polymer for decorative laminates in exterior cladding and wet-room applications. Important requirements for such PFs are favorable flow properties (low viscosity), rapid curing behavior (high reactivity) and sufficient self-adhesion capacity (high residual curing potential). Partially substituting phenol in PF with bio-based phenolic co-reagents like lignin modifies the physicochemical properties of the resulting resin. In this study, phenol-formaldehyde formulations were synthesized where either 30% or 50% (in weight) of the phenol monomer were substituted by either sodium lignosulfonate or Kraft lignin. The effect of modifying the lignin material by phenolation before incorporation into the resin synthesis was also investigated. The resins so obtained were characterized by Fourier Transform Infra-Red (FTIR) spectroscopy, Size Exclusion Chromatography (SEC), Differential Scanning Calorimetry (DSC), rheology, and measurements of contact angle and surface tension using the Wilhelmy plate method and drop shape analysis.

Surface texturing is an easy way to control wettability as well as bacterial adhesion. Air trapped in the surface texture of an immersed sample was often proposed as the origin of the low adhesion of bacteria to surfaces showing superhydrophobic properties. In this work, we identified two sets of femtosecond laser processing parameters that led to extreme superhydrophobic textures on a silicone elastomer but showed opposite behavior against Staphylococcus aureus (S. aureus, ATCC 25923) over a short incubation times (6 h). The main difference from most of the previous studies was that the air trapping was not evaluated from the extrapolation of the results of the classical sessile drop technique but from the drop rebound and Wilhelmy plate method. Additionally, all wetting tests were performed with bacteria culture medium and at 37 °C in the case of the Wilhelmy plate method. Following this approach, we were able to study the formation of the liquid/silicone interface and the associated air trapping for immersed samples that is, by far, most representative of the cell culture conditions than those associated with the sessile drop technique. Finally, the conversion of these superhydrophobic coatings into superhydrophilic ones revealed that air trapping is not a necessary condition to avoid Staphylococcus aureus retention on one of these two textured surfaces at short incubation times.

Two common test methods measure the surface energy of asphalt binders: the Wilhelmy plate method and the sessile drop method. In contrast to the sessile drop method, the Wilhelmy plate meth...

Solid–liquid interactions are ubiquitous phenomena in nature and industry. Wettability of a liquid on a solid is governed by the chemical heterogeneity and physical roughness of the solid surface and can be characterized by measuring the advancing and receding contact angles of the liquid droplet residing on the solid. To characterize contact angle, goniometry and the Wilhelmy plate method have been widely used. Although powerful, these methods have difficulty characterizing microdroplets, can be cumbersome and expensive, and have trouble handling surfaces with local wetting heterogeneity and deformed noncircular contact lines. Furthermore, past methods are incapable of measuring contact angle in situ during experiments (e.g., condensation). Here, we develop simple yet powerful contact angle measurement techniques using conventional optical microscopy that utilizes focal plane shift imaging, ray optics, and wave interference. We used our techniques to study the wetting characteristics for a wide range of ...

The time scale to attain equilibrium for interfacial tension measurement by means of the well known Wilhelmy plate method has been investigated. Despite that interfacial tension is independent of liquid viscosity, the measurement technique shows considerable dependency on viscosity in terms of relaxation time. For most practical liquids, density variation is insignificant, however, the viscosity often varies in the order of magnitude and indeed dictates the waiting or relaxation time for the measurement system to acquire steady equilibrium state. In this study, the quantified argument is made to define the relaxation time based on the known liquid properties while measuring unknown interfacial tension. This is of particular importance when assessing the dynamic interfacial tension of highly viscous liquids containing surface active molecules, as it allows to predict the time after which a reliable measurement of the interfacial tension is possible.

In this work, the surface tensions (γ) of the aqueous blends of 1-dimethylamino-2-propanol (DMA2P) + amino acid ionic liquids (AAILs) were studied using the Wilhelmy plate method at temperatures fr...

Contact angles are the characteristic angles made between the surface of a liquid and a solid surface. The measurement of contact angles can be done with multiple methods. However, because there ar...

N-lauroyl-L-Valine sodium (NLLVS) was synthesized and characterized by FT-IR, 1H-NMR spectrometry. Surface and interface tension were measured by wilhelmy plate and spinning drop method. The effect...

To avoid the restrictions of the captive bubble and the Wilhelmy plate techniques, a method was introduced for contact angle measurements under equilibrium conditions. It enables to determine even ultralow contact angles with high precision without prewetting the investigated surface because in this case, the capillary bridge of the test liquid is formed from a pendant drop and used as a probe. The contact angle is determined from the measured capillary force and liquid bridge geometry by using Delaunay's analytical solution. The method was experimentally proved to be valid. As a demonstration, contact angles less than 1° were measured with the uncertainty down to 0.1° on lightly corroded glass surfaces. Moreover, a new observation was obtained in complete wetting situations: the receding contact line starts to advance again during the increase of the bridge length. The contact angle is much lower in this readvancing phase compared to the advancing and receding values because the contact line finds prewetted surface in front of itself. Further advantage of the method is that the existing contact angle goniometers can be developed further into the presented measurement setup.

From the environmental conservation perspective, warm mix asphalt is more preferable compared to hot mix asphalt. This is because warm mix asphalt can be produced and paved in the temperature range 20–40°C lower than its equivalent hot mix asphalt. In terms of cost-effectiveness, warm mix asphalt can significantly improve the mixture workability at a lower temperature and thus reduce greenhouse gas emissions, to be environment friendly. However, the concern, which is challenging to warm mix asphalt, is its susceptibility to moisture damage due to its reduced production temperature. This may cause adhesive failure, which could eventually result in stripping of the asphalt binder from the aggregates. This research highlights the significance of Cecabase warm mix additive to lower the production temperature of warm mix asphalt and improvise the asphalt binder adhesion properties with aggregate. The binders used in the preparation of the test specimen were PG-64 and PG-76. The contact angle values were measured by using the dynamic Wilhelmy plate device. The surface free energy of Cecabase-modified binders was then computed by developing a dedicated algorithm using the C++ program. The analytical measurements such as the spreadability coefficient, work of adhesion, and compatibility ratio were used to analyze the results. The results inferred that the Cecabase improved the spreadability of the asphalt binder over limestone compared to the granite aggregate substrate. Nevertheless, the Cecabase-modified binders improved the work of adhesion. In terms of moisture sensitivity, it is also evident from the compatibility ratio indicator that, unlike granite aggregates, the limestone aggregates were less susceptible to moisture damage.

The objective of this work is the evaluation of chickpea protein adsorption at oil/water (O/W) interface as a function of protein concentration and pH value (2.5, 5.0 and 7.5). To assess molecular interpretation, interfacial tension is determined as a function of concentration with a Wilhelmy plate, whereas interfacial small amplitude oscillatory shear (i-SAOS) properties are determined using a double wall-ring (DWR) geometry controlled by a DHR3 rheometer (TA Instruments) and a pendant drop tensiometer (IT Concept) is used to determine linear viscoelastic dilatational measurements. This work provides a model which could predict both the linear and non-linear viscoelastic behavior of complex fluid-fluid interfacial layers. To this end, relaxation tests using the DWR device are carried out at the interface under the linear and non-linear regimes. Steady state viscosity values are also obtained to check the ability of the model to predict the interfacial flow behaviour. Results show that the Wagner-I model can reproduce fairly well the steady state flow behaviour of chickpea protein-adsorbed interfaces. This model is based on the use of a memory function calculated from the generalized Maxwell (obtained from i-SAOS measurements) and a damping function obtained by the Laun model from linear and non-linear relaxation tests.

Platinum cure for poly(dimethylsiloxane) (PDMS) coatings on a thermal gradient (45-140 °C) was carried out to study the effect of temperature on surface chemistry and wetting behavior. The motivation is the interest in surfaces with continuous gradients in wettability for applications such as protein adsorption, controlling bacterial adhesion, directional movement of cells, and biosensors. The Wilhelmy plate method and the advancing/receding drop method were employed for determining the positional dependence of θA and θR. A strong dependence of receding contact angles (θR) on cure temperature was found for Sylgard 184 (S-PDMS) and a Pt-cured laboratory-prepared analogue (Pt-PDMS) of known composition. Cure on the thermal gradient gave rise to striking "Big Dipper" Wilhelmy plate dynamic contact angle curves. High contact angle hysteresis (60-80°) was found for 45 °C cure (CAH = θΔ = θA - θR) but low CAH for 140 °C cure (10-20°). Drop addition/withdrawal using goniometry identified a similar trend. Attenuated total reflectance infrared spectroscopy showed absorptions for Si-OH (3500 cm-1) and Si-H (1250 cm-1) that were correlated with wetting behavior and near-surface chemistry. These studies revealed a complex relationship among hydrosilylation, Si-H autoxidation, and condensation of Si-OH. A model for advancing from a single network due to hydrosilylation to a double network for hydrosilylation plus Si-O-Si from condensation of Si-OH best explains evidence from spectroscopic and contact angle studies. These results are relevant to interactions of Pt-cured silicones at bio-interfaces, as receding contact angles determine work of adhesion, as well as applications that benefit from maximum hydrophobicity and minimizing water roll-off angles.

The antioil-fouling characteristic of an amorphous cellulose (a-cellulose) surface was elucidated using the sessile droplet method (static) and a modified Wilhelmy plate technique (dynamic). As compared to other hydrophilic surfaces (cellulose acetate, poly(vinyl alcohol), and glass), the oil (poly(dimethylsiloxane)) contact angle on the a-cellulose surface underwater shows the largest value (170.5 ± 5.0°), having the smallest deviation from its theoretical value (180.0°) as estimated by Young's equation. Also, the a-cellulose surface demonstrates the strongest affinity with water in an oil medium (stable hydrophilicity). Moreover, the work of adhesion between the receding oil phase and a-cellulose underwater is quantified to be 10.3 mN/m, approximately one-fourth of that in air (42.0 mN/m). The overall wetting study suggests a rather low oil/solid/water three-phase contact line (TPL) friction in the direction that water displaces oil. A proposed mechanism attributes these phenomena to the water-accessible rigid cellulose chains and supramolecular structure of a-cellulose. The former hinders molecular rearrangement during processing or upon exposure to oil, such that its polar hydroxyl groups are readily accessible to water, thereby retaining its hydrophilicity. The latter allows water to diffuse across the TPL, forming the hydration shells that weaken the van der Waals interactions between oil and cellulose chains. Such findings of the a-cellulose surface can be exploited to fabricate mesh membranes with high water permeation flux (375.4 ± 13.5 L m-2 h-1 Pa-1), high oil/water separation efficiency (93-98%), and long-lasting stability, which is suitable for offshore oil spill remediation.

This chapter will introduce fundamental aspects of molecular adsorption of proteins to a fluid-fluid interface. The focus of the chapter will be on the adsorption to an air-water interface, but several of the concepts can be applied to a liquid-solid or a liquid-liquid interface. Historically, the physical understanding of interfacial adsorption was developed from experiments and theory on small molecule surfactants. More recently, building from this perspective of surfactant adsorption, an understanding of protein-surface interactions has evolved largely based on examining proteins from the food and cosmetic industry. This chapter will highlight the thermodynamics of proteins partitioned into the air-water interface, focusing on the adsorption energy of the molecule as well as the ability of the molecule to change structure once adsorbed. Additionally, the fundamentals of surface hydrophobicity, structural stability and electrostatic interactions between the protein and the surface will be described by comparing the well-studied lysozyme, bovine serum albumin and β-casein proteins. Dynamics and orientation of adsorbed proteins will be discussed based on work that combines pendant bubble tensiometry, Wilhelmy plate methods, spectroscopic tools and scattering techniques. Finally, the chapter combines these experimental findings with theory and simulation-based results to give transport models that can capture the complexity of protein adsorption onto the air-water interface.

Due to their unique properties, nanoparticles have recently attracted lots of attention for enhanced oil recovery (EOR) and CO2 geo-sequestration (CGS) applications. The purpose of this research is to offer a better understanding of the role of nanoparticles on interfacial phenomena with a special focus on wettability alteration, interfacial tension and emulsification characteristics. Contact angle measurements were used to explore the effect of nanoparticles on wettability alteration of glass surfaces using sessile drop method in the absence and presence of NaCl. Scanning electron microscopy (SEM) images were collected to visualize how nanoparticles change the wettability of the surfaces. The effect of different parameters on morphology variation of glass surfaces and the consequent wettability alteration was examined. The investigated variables were nanoparticle concentration, exposure time, measurement time and salinity. Next, the effect of nanoparticles on interfacial tension (IFT) between water and n-octane was studied via the Wilhelmy plate method. The effect of nanoparticle concentration on IFT was investigated with and without added NaCl. Finally, a series of simple batch experiments were conducted to observe the effect of nanoparticles in emulsification behavior of a water-n-octane system. Photography and optical microscopy images were collected to analyze the stability and morphology of the formed emulsions for different nanoparticle concentrations in the absence and presence of NaCl. Our results show that the EOR-12 nanoparticles have excellent water-wetness properties and emulsification characteristics but do not necessarily change the IFT in a water-n-octane system. SEM micrographs taken from the nanofluid-treated glass surfaces showed a thick coverage of nanoparticles confirming the adsorption of nanoparticles onto the surface. Additionally, SEM images revealed a topography change of surfaces from smooth to rough after treatment with nanofluid which is the responsible mechanism for the observed wettability alteration. The higher the exposure time, the rougher the nanoparticle adsorption layer and consequently the better the performance of nanoparticles in wettability alteration of glass surfaces. Additionally, up to a threshold concentration, the contact angle decreased as the nanoparticle concentration increased, but above the threshold concentration, the measured contact angle did not show remarkable reduction. Conducting contact angle measurements in the presence of NaCl demonstrated that salinity can increase the adsorption rate, the final number of nanoparticles on the glass surface, the surface roughness and the intrinsic contact angle of nanoparticles leading to a better water-wetness. Testing different concentration of nanoparticles demonstrated that in the presence of NaCl, the wettability of the glass surface was not affected by the concentration and low concentrations of nanoparticles act as good as high concentrations. IFT measurements did not show any significant reduction in IFT between water and n-octane for all the tested concentrations with and without added NaCl mainly because of lack of the energy required to bring the nanoparticles at the interface. The results of batch emulsification experiments revealed that EOR-12 nanoparticles could serve as highly efficient Pickering emulsifiers in terms of both initial emulsion volume and its stability over time with and without NaCl. Adsorption of the nanoparticles at the interface was identified as the underlying mechanism for the emulsification characteristics of the nanoparticles. Photographs and optical microscopy measurement results illustrated that by tuning the nanoparticle concentration, emulsion droplet size and its uniformity can be adjusted. By utilizing higher concentrations of nanofluid, emulsions with smaller and more uniform droplet size and higher stability can be created.

We have given theoretical expressions for the forces exerted on a quasi-2D flat and smooth solid plate immersed into a liquid pool of a simple liquid. All forces given by the theory, the local forces on the top, the contact line and the bottom of the plate as well as the total force, showed an excellent agreement with the MD simulation results. We also revealed that the local forces around the bottom and top of the solid plate can be related to the SL and SV interfacial tensions \gamma_{SL} and \gamma_{SV}, and this was verified through the comparison with the SL and SV works of adhesion obtained by the thermodynamic integration. We have reached a conclusion that \gamma_{SL} and \gamma_{SV} as well as the liquid-vapor interfacial tension \gamma_{LV} can be extracted from a single equilibrium MD simulation without the computationally-demanding calculations., Comment: 11 Figures

We studied the dynamics of adsorption at the air-water interface of a cationic surfactant bearing two charges, Gemini 12-2-12, at concentrations below and above the critical micelle concentration (cmc). We used maximum bubble pressure and Wilhelmy plate techniques in order to access all time scales in the adsorption process. We found that the adsorption dynamics are controlled by diffusion at the initial stage of the adsorption process (milliseconds) and it is kinetically controlled by an electrostatic barrier (minute) approaching the equilibrium surfactant surface concentration. Between these two extremes, we found several relaxation phenomena, all following exponential decays with characteristic times spanning from one to hundreds of seconds. By means of time-resolved surface potential measurements, we show that these processes involve charge redistribution within the interfacial region. The surface tension data are analyzed and interpreted in the framework of the free energy approach. Fil: Fernández Leyes, Marcos Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina Fil: Gimenez Reyes, Santiago Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina Fil: Cuenca, Victor Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina Fil: Sánchez Morales, Jhon Freddy. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina Fil: Ritacco, Hernán Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina

Water repellency (hydrophobicity) of granular materials such as soil is usually assessed on bulk samples or arrays of grains, with their wettability being influenced by the often-variable properties of individual particles. Numerous methods exist to assess the wetting behaviour of granular bulk materials, whereas methods for determining the wettability of individual grains are scarce. Here we introduce a new technique, based on the Wilhelmy plate method and termed “micro-Wilhelmy plate method” (mWPM) that allows quantification of the water repellency of an individual particle. We developed two complementary variants of the methods, which involve the rupture of a water lamella after a particle has been brought into contact with water and then withdrawn from it. They were applied to individual wettable or water repellent spherical glass of diameter 120 and 270 µm and polymer particles (270 µm), as well as those of both wettable and natural water repellent particles (of similar size i.e. 120 to 270 µm) from sandy soils of the UK and the Netherlands. Spherical glass and polymer particles were examined in their native condition and following treatment with a hydrophobic (silicone-based water proofing) agent. In one method the break point of lamella was determined gravimetrically (g-mWPM, using an electronic 5-digit balance) and in the other it was determined optically (o-mWPM) from a video sequence obtained from a contact angle goniometer as the distance between the particle and the water surface at the point of lamella rupture. The latter required the use of image analysis and computation to estimate the potential energy of the water lamella. Both methods provided meaningful assessments of particle wettability. Man-made particles showed limited variability, whereas those drawn from naturally wettable or water repellent soils exhibited substantial variability, indicating that wettable soils contain water repellent particles and vice versa. Both methods introduced here offer a relatively quick examination of the wettability of individual particles. The o-mWPM is a particularly simple method only requiring a video camera, stepper-motor driven sample holder and a low magnification optical system. Additionally, it offers the possibility to investigate particle shape.

The objectives of this study are to evaluate long‐term wettability of novel surface‐engineered, clinically available dental implants, featuring a surface nanolayer of covalently linked hyaluronan, and to confirm the relationships between wetting properties and surface nanostructure and microstructure. Wettability measurements were performed on clinically available hyaluronan‐coated Grade 4 titanium implants, packaged and sterile, that is, in the “on the shelf” condition, after 1 year from production. Wetting properties were measured by the Wilhelmy plate method. Analysis of the surface structure and chemistry was perfomed by X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy‐dispersive X‐ray (EDX) analysis, atomic force microscopy (AFM), and ζ‐potential measurement, either on implants or disks or plates subjected to the same surface‐engineering process. Results show that hydrophilicity and ensuing capillary rise of the hyaluronan‐coated implant surface is unaffected by aging and dry storage. Chemical analysis of the implant surface by XPS and evaluation of the ζ potential indicate that hyaluronan chemistry and not that of titanium dictates interfacial properties. Comparison between XPS versus EDX and SEM versus AFM data confirm that the thickness of the hyaluronan surface layer is within the nanometer range. Data show that nanoengineering of the implant surface by linking of the hydrophilic hyaluronan molecule endows tested titanium implants by permanent wettability, without need of wet storage as presently performed to keep long‐term hydrophilic implant surfaces. From an analytical point of view, the introduction in routine clinical practice of nanoengineered implant surfaces requires upgrading of analytical methods to the nanoscale.

The densities and surface tensions of [Bmim][TFO]/H2SO4, [Hmim][TFO]/H2SO4 and [Omim][TFO]/H2SO4 binary mixtures were measured by pycnometer and Wilhelmy plate method respectively. The results show that densities and surface tensions of the mixtures decreased monotonously with increasing temperatures and increasing ionic liquid (IL) molar fraction. IL with longer alkyl side-chain length brings a lower density and a smaller surface tension to the ILs/H2SO4 binary mixtures. The densities and surface tensions of the mixtures are fitted well by Jouyban–Acree (JAM) model and LWW model respectively. Redlich−Kister (R–K) equation and modified Redlich−Kister (R–K) equation describe the excess molar volumes and excess surface tensions of the mixtures well respectively. Adding a small amount of ILs (xIL

Wilhelmy plate method does not consider viscous force in the force balance equation to measure the dynamic contact angle and this results in a significant error in the measurement. Differences between the results obtained by optical method and Wilhelmy plate method indicate the importance of viscous force in the force balance equation. A theoretical viscous model is proposed, which must be considered in the force balance equation in Wilhelmy plate method to increase the accuracy of the dynamic contact angle measurement, especially for the case of highly viscous liquids and for experiments at large speeds of the plate, which can lead to large shear rate along the surface of the plate.

Mucins, the main component of the mucus secretions of goblet and epithelial cells, are known for exhibiting a different behaviour in accordance with their surrounding environment (i.e. among others the environmental pH), which induces a drastic change in their measured mechanical properties. In this work, we have first employed Atomic Force Microscopy (AFM) in Force Spectroscopy mode to evaluate the adhesion of porcine mucin films at the nanoscale, and the changes caused in this particular factor by a pH variation between 7.0 and 4.0, both quite common values in biological conditions. Measurements also involved additional varying factors such as the indenting tip chemistry (hydrophobic vs hydrophilic), its residence time on the measured film (0, 1 and/or 2 seconds), and increasing pulling rates (ranging from 0.1 up to 10 µm/s). A second approach regarded the macroscale behaviour of the films, due to their potential applicability in the development of a new set of stimuli-responsive biomaterials. This was possible by means of complementary Wilhelmy plate method (to test the wetting properties) and cell proliferation studies on films previously exposed to the corresponding pH solution. According to our results, treatment with lowest pH (4.0) provides porcine mucin with a more hydrophilic character, showing a much stronger adhesion for analogous chemistries, as well as enhanced capability for cell attachment and proliferation, which opens new pathways for their future use and consideration as scaffold-forming material.

A semi-flexible polymer microtensiometer for local surface pressure measurements of Langmuir monolayers is presented. The current device geometry and read-out method via image analysis result in a theoretical accuracy of ±0.02mN⋅m-1 for a dynamic range between 0 and 75mN⋅m-1. The tensiometer sensitivity and dynamic range are easily tunable as they are solely based on the tensiometer spring dimensions. Finite element simulations are used to determine the response time of 20ms for a subphase viscosity of 1mPa⋅s. A poroviscomechanical model of the sensor is composed and the subphase viscosity is shown to dominate the transient behavior. The tensiometer performance is verified in a Langmuir trough by applying rapid local surface pressure oscillations. A Wilhelmy plate is used as an independent measurement tool and the results of both techniques correlate well.

A multicycle Wilhelmy plate method was applied to study the water and octane sorption behaviour of small Norway spruce veneers. Dry heart- and sapwood samples of varying density were investigated. ...

Small atmospheric aldehydes and ketones are known to play a significant role in the formation of secondary organic aerosols (SOA). However, many of them are difficult to experimentally isolate, as they tend to form hydration and oligomer species. Hydroxyacetone (HA) is unusual in this class as it contributes to SOA while existing predominantly in its unhydrated monomeric form. This allows HA to serve as a valuable model system for similar secondary organic carbonyls. In this paper the surface behavior of HA at the air-water interface has been investigated using vibrational sum frequency (VSF) spectroscopy and Wilhelmy plate surface tensiometry in combination with computational molecular dynamics simulations and density functional theory calculations. The experimental results demonstrate that HA has a high degree of surface activity and is ordered at the interface. Furthermore, oriented water is observed at the interface, even at high HA concentrations. Spectral features also reveal the presence of both cis and trans HA conformers at the interface, in differing orientations. Molecular dynamics results indicate conformer dependent shifts in HA orientation between the subsurface (∼5 Å deep) and surface. Together, these results provide a picture of a highly dynamic, but statistically ordered, interface composed of multiple HA conformers with solvated water. These results have implications for HA's behavior in aqueous particles, which may affect its role in the atmosphere and SOA formation.

The complex and diversified asphalt modification makes it harder for the assessment of testing methods capable of characterizing the performance of different modified asphalt in the presence of water. In this study, three representative test methods addressing the moisture performance of asphalt were evaluated and compared: surface free energy (SFE) test, binder bond strength (BBS) test and Hamburg wheel tracking device (HWTD) test. Results indicate that the HWTD test can be a benchmark test while the BBS test is a screening test in characterizing the moisture performance of various modified asphalt. In addition, the surface energy component obtained from the receding procedure in the Wilhelmy Plate Method correlated better with the adhesion property of asphalt than those based on the advancing procedure did. The various indices obtained from the three tests were classified as suitable or unsuitable indices on the basis of the analysis of specific additives. Furthermore, based on the degree of their improvement in the moisture performance, additives were classified into three grades: (1) the first grade including linear styrene–butadiene–styrene (SBS), branched SBS and gilsonite; (2) the second grade including high-density polyethylene, and polyphosphoric acid; (3) the third grade including asphalt rubber and terminal blend asphalt. Finally, it was found that base binders with shorter-chain structures and lower aromatics contents showed better moisture resistance in the HWTD test. High mobility of base asphalt binder negatively influenced the corresponding mixture’s moisture sensitivity.

Although 1- C n -3-methylimidazolium bromides are used in a variety of applications, their properties are still poorly studied and it is desirable to complete the experimental knowledge of them. This study presents 121 and 208 new experimental data on the density and surface tension, respectively, for [ C 1 IM][Br] and [ C n MIM][Br] with n = 2–10 at temperatures from (288 to 365) K and at the pressure of 0.1 MPa. The reported resultant data are means of sets of individual measurements performed at a given temperature. The density was measured by the buoyancy method and the surface tension concurrently by the Wilhelmy plate and du Nouy ring method. Their respective expanded combined uncertainties at the 0.95 confidence level do not exceed 0.86 kg · m−3 (0.007 ϱ ), 0.08 mN · m−1 and 0.8 mN · m−1. Models are presented generating density and surface tension values that represent the best current knowledge of these properties for the members of the studied homologous series. The estimated maximum deviations of the obtained recommended values from the true density and surface tension values are 0.1 kg · m−3 and 0.4 mN · m−1, respectively.

Platinum plate method based on Wilhelmy plate was used to measure the surface tension of hydrophilic nano-titanium dioxide-deionized water (nano-TiO2- DIW) fluids and hydrophilic lipophilic nano-TiO2-DIW fluids. Experimental results show that the surface adsorption of hydrophilic lipophilic nano-TiO2 is positive adsorption, and hydrophilic nano-TiO2 is negative adsorption. The hydrophilic nano-TiO2 in deionized water increases the surface tension of base fluid, and hydrophilic lipophilic nano-TiO2 in deionized water decreases. The surface tension of hydrophilic TiO2-DIW nanofluids increases, and hydrophilic lipophilic TiO2-DIW nanofluids decreases linearly with an increase in the natural logarithm of the molar concentration of nanofluids.

Many of the applications of ionic liquids rely on their bulk properties or their solvation abilities. However, it is their interactions with solid surfaces that underpin many of their potential applications in advanced technologies. Whether it is as lubricants for wind turbines or as electrolytes in supercapacitors, there are many areas where ionic liquids can provide an improvement in performance relative to more commonplace liquids. However, there are some barriers to their implementation in such applications. Foremost of these is the lack of systematic studies of their interactions with solid surfaces as well as neglecting the effect of the absorbed water on wetting. The present study explores the dynamic wetting of three ionic liquids (with a different length of hydrocarbon chain in the cation) on gold and glass substrates, both of which are relevant for nano-A nd micromechanical machine applications, under well-controlled environmental conditions. The form of data capture (Wilhelmy plate) allows for a direct analysis using analytical expressions for the two dominant approaches for dynamic wetting: The hydrodynamic and molecular kinetic models. All ionic liquids yield data that are described best by the molecular kinetic model. Substrate-ionic liquid and water-ionic liquid interactions contribute to the mechanisms involved in the wetting process. Refereed/Peer-reviewed

One of the most accurate methods for measuring the dynamic contact angle of liquids on solid surfaces is the Wilhelmy plate method. This method generally requires the use of rectangular samples having a constant perimeter in the liquid during advancing and receding cycles. A new formulation based on the Wilhelmy force balance equation to determine the contact angle for plate samples with irregular shapes has been developed. This method employs a profile plot obtained from an optical image to determine the perimeter (i.e. wetted length) of the sample as a function of the immersion depth. The raw force data measured by the force tensiometer is manipulated using the profile plot and the Wilhelmy equation to determine the wetting force and consequently advancing and the receding contact angle. This method is verified with both triangular and irregular PTFE samples in water, and measured contact angles are in good agreement with results from conventional regular shaped samples with a constant perimeter.

Exhaled air contains submicron droplets of alveolar lining fluid (ALF), which are generated in the small airways of human lungs and are in fact ALF micro-samples. The trapping of these droplets makes it possible to collect a native material from respiratory tract in a non-invasive manner, which holds great promise for lung diagnostics. In this work, we present an aerosol droplet sampling technique based on the exhaled breath barbotage (EBB) procedure. The proposed technique offers a unique opportunity to accumulate pulmonary surfactant (PS), a major constituent of ALF, on a liquid surface. The Wilhelmy plate method was used to measure the variation of the surface pressure over the surface area for the EBB samples collected in a Langmuir trough. A data processing algorithm was derived to evaluate the surface pressure ( π ) – surface concentration ( Γ ) isotherm from the raw data. With this algorithm, one can restore the isotherm even in the case when the amount of surfactant adsorbed on the surface is unknown. The ( π − Γ ) isotherms found for the samples collected in the groups of healthy volunteers and patients with pulmonary tuberculosis were compared with the isotherms obtained for artificial PS. It has been established that the isotherms measured for healthy people and artificial surfactant coincide, and the isotherms obtained in the TB group have lower inclination, which is indicative of a lower surface activity. The EBB method developed in this study can be used as a diagnostic tool for assessment of the functional status of PS in screening tests and subsequent treatment.

The density and surface tension values are presented that represent the best current knowledge of these properties for members of the homologous series of 1-C n -3-methylimidazolium chlorides. To identify these values, a method was used based on the consistency requirement between selected background experimental data and group contribution models of known best achievable accuracy. The models have been developed using our own and other authors' data. For this purpose 64 and 119 new experimental data on the density and surface tension, respectively, have been measured for [C 1 IM][Cl] and [C n MIM][Cl] with n = 2 , 3, 4, 6, and 10 at temperatures from (263 to 365) K and at the pressure of 0.1 MPa. The density was measured using the buoyancy method while the surface tension was measured by the Wilhelmy plate and du Nouy ring method in parallel. The respective expanded combined uncertainties at the 0.95 confidence level of the resultant means of sets of individual measurements performed at a given temperature do not exceed 1 kg ⋅ m −3 , 0.07 mN ⋅ m −1 and 1 mN ⋅ m −1 . The estimated maximum deviations of the obtained recommended values from the true density and surface tension values are 0.1 kg ⋅ m −3 and 0.15 mN ⋅ m −1 , respectively.