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Contact angle measurement by sessile drop (SD) and captive bubble (CB) method is calculated by the four software, i.e. 'Angle Tool' plugin, Drop Snake (DS) plugin, and LB-ADSA plugin of the ImageJ®; and the Ossila® with their advantages and disadvantages. In this study, the ease of use and precision were tested by standard deviation calculation for different hydrophilic membranes. Angle Tool plugin, and DS plugin of ImageJ®; and the Ossila software gave high standard deviations due to rough cut membranes edges giving background shadows misleading the software algorithm. LB-ADSA plugin of the ImageJ® had both advantages of manual drop edge selection and algorithmic calculation of contact angle giving the lowest standard deviation. Therefore, we found that the LB-ADSA plugin of ImageJ® is precise for hydrophilic membranes by both SD and CB methods. [ABSTRACT FROM AUTHOR]

[Display omitted] • Contact angles of anode and cathode materials are modified using plasma modification. • Interactions between plasma parameters are evaluated by Box-Behnken design. • Plasma treatment enhances flotation separation selectivity of electrode materials. • Flotation of anode and cathode materials obeys to the first order-kinetic model. • The contact angle increase of anode materials plays a major role in plasma treatment. The recycling of spent lithium-ion batteries (LIBs) can not only reduce the potential harm caused by solid waste piles to the local environment but also provide raw materials for manufacturing new batteries. Flotation is an alternative approach to achieve the selective separation of cathode and anode active materials from spent LIBs. However, the presence of organic binder on the surface of hydrophilic lithium transition-metal oxides results in losses of cathode materials in the froth phase. In this study, plasma treatment was utilized to remove organic layers from cathode and anode active materials. Firstly, the correlations between plasma treatment parameters (e.g., input power, air flowrate, and treatment time) were explored and the contact angles of cathode and anode active materials were investigated by the response surface methodology. Secondly, differences in the flotation recoveries of cathode and anode active materials were enhanced with plasma modification prior to flotation, which is consistent with the contact angle measurement. Finally, the plasma-modification mechanisms of hydrophobicity of cathode and anode active materials were discussed according to Fourier Transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses. The proposed method could be a promising tool to enhance the flotation separation efficiency of cathode and anode active materials for the recycling of spent LIBs. [ABSTRACT FROM AUTHOR]

The underground storage of CO2 in a depleted carbonate formation is a suitable method for limiting its anthropogenic release and minimize global warming. The rock wettability is an essential factor controlling the mechanisms of CO2 trapping and its containment safety in the geo-storage formation. The geo-storage rock contains innate organic acids which alters the wettability of the rock surface from the hydrophilic condition to the hydrophobic state, thus reduce the CO2 storage capacity. In this study, methyl orange which is a toxic dye that is generally released into environment was used as wettability modifier to change the wettability of stearic acid aged calcite (oil wet) to water wet. This study uses the contact angle technique (sessile drop method) to examine the effects of various concentration of methyl orange (10-100 mg/L) on the wettability of the CO2/brine/stearic-acid aged calcite system under geo-storage conditions (i.e., temperatures of 25 and 50 °C and pressures of 5-20 MPa). The results indicate that the advancing and receding contact angles (qa and qr) of the organic-acid contaminated rock surface were drastically reduced upon exposure to methyl orange, attaining the minimum values of 62°C and 58°C respectively, in the presence of 100 mg/L methyl orange at 20 MPa and 50 °C. Thus, the present results suggest that rather than discharging methyl orange into the environment, it could be injected into underground reservoirs in order to reduce the level of environmental pollution and at the same time increase the CO2 storage capacity of carbonate formations. [ABSTRACT FROM AUTHOR]

The measurement of solid-liquid contact angle holds significant importance in physical chemistry experiments. In this study, we have enhanced this experiment by incorporating the latest advancements in scientific research, specifically focusing on the application of special wettability materials for treating oily wastewater. The resulting comprehensive and innovative experiment integrates ideological and political elements, aiming to not only enhance students’ learning interest but also guide them in applying theory to practical scenarios, utilizing their specialized knowledge to protect the environment and remediate nature. By fostering students’ sense of social responsibility and professional pride, this teaching reform effectively achieves the goal of cultivating innovative talents. [ABSTRACT FROM AUTHOR]

[Display omitted] Contact angle can be a key parameter in chemical engineering. However, the development and the optimization of numerous processes using supercritical CO 2 , considered as environmentally friendly, require new measurements under dense CO 2 atmosphere. Besides, the influence of the roughness or the wetting regime on the contact angle is known at ambient conditions but remains to be discussed for systems under high pressure. Contact angle measurements of ethanol, water, and their mixtures, with ethanol mass fractions ranging from 0.25 to 0.75, on two stainless steels in saturated CO 2 at pressures ranging from 0.1 MPa to 15.1 MPa, and at 313 K and 333 K were carried out in a set-up improving mass transfer between the studied liquid and the continuous fluid phase. Stainless steel surfaces have been characterized by atomic force and scanning electron microscopies allowing the application of the Wenzel equation. Ethanol wetted totally both stainless steels while contact angles of all other liquids were increased by the rise of pressure, with contact angles up to 128° for water at 15.1 MPa. Trapped bubbles were observed at the solid/liquid interface and the bubble formation is discussed. Furthermore, the potential influence of bubble presence on the wetting regime is prospected through the question: could the pressure rise modify the wetting regime? [ABSTRACT FROM AUTHOR]

Aluminium foil is a versatile material used in various industries, but its inherent low wettability limits its application. Surfactant can be used as effective agents for enhancing the wettability, enabling improved surface interactions and performance. In this study, we investigated the wettability of anionic (SDS and AOT) and cationic (CTAB) surfactants prepared in water as well as in isopropanol-water solvents with the four different volume fractions (0.1, 0.2, 0.3 and 0.4) on aluminium foil surfaces by measuring the contact angle. As the volume fraction of isopropanol on aluminium foil increases, the contact angle of SDS, CTAB, and AOT increases whereas the surface free energy decreases, indicating the hydrophobic nature of the surface. This trend is observed with the increasing concentrations of various solvents used. The adhesion work exhibits a linear increase with alcohol surface tension. A curvilinear variation is observed in the plots between cos θ and 1/ γ SL . The plots of adhesion work versus contact angles show non-linear variation. Additionally, the plot of cos θ against the surface tension of alcohol and adhesion work against log C exhibit curvilinear variation. With these results, the article aims to provide valuable insights into the application of surfactants for improving the wettability of aluminium foil. [ABSTRACT FROM AUTHOR]

In this study, we report the synthesis of a new fluorinated vinyl monomer, that is, pentafluorophenyl vinyl ketone [1‐(pentafluorophenyl)prop‐2‐en‐1‐one], its radical polymerization and copolymerization with styrene, methyl vinyl ketone, or phenyl vinyl ketone. The obtained homo‐ and co‐polymers were subjected to thermal analysis, contact angle measurement, and an assay of resistance to UV irradiation. The results showed that the poly(pentafluorophenyl vinyl ketone) has a slightly greater contact angle and a lower temperature of the maximum decomposition rate when compared to the nonfluorinated analog: poly(phenyl vinyl ketone). [ABSTRACT FROM AUTHOR]

The economical fabrication of one-dimensional dielectric reflectors using the hybrid sol-gel spin coating process is significant compared to sophisticated chemical and physical vapor deposition techniques. In this work, we opted for alternate layers of TiO2 and SiO2 films to fabricate nearinfrared dielectric reflectors owing to their high refractive index contrast and easy tunability of the reflection window in the desired spectral range. X-ray diffraction (XRD) studies of the monolayer TiO2 and SiO2 confirmed the existence of anatase-TiO2 and amorphous-SiO2 phases, respectively. Spectroscopic ellipsometry investigation of TiO2 and SiO2 films revealed the refractive indices of 2.6 and 1.5, respectively. The field-emission scanning electron microscopy (FESEM) analyses evidenced the fabrication of 2.5 stacks/bilayers of TiO2/SiO2 (TiO2/SiO2)2.5 S. The reflectance measurement demonstrated 100% reflection in the near-infrared region with its center wavelength of 833 nm. In addition, we have examined the water contact angle of various samples using the sessile drop technique, and 2.5 stacks-based reflector showed its lowest contact angle of 29.3°, which suggests its anti-fogging and self-cleaning applications. [ABSTRACT FROM AUTHOR]

Abstract Abstract This article presents a cost-effective ultraviolet-ozone cleaner (UV/O3 Cleaner) for surface pre-treatment of substrates in the field of semiconductor technology. The cleaner consists of two chambers, the upper one contains the electronics, including the time counter. The lower chamber contains the two UV sterilisation lamps and a UV reflector of anodized aluminium, which confines the area of high Ozone concentration in the area of interest. The device is successfully used for surface cleaning and modification of different materials. To this end, the two important wavelengths 253.7 nm (excitation of organic residues) and 184.9 nm (production of ozone from the atmospheric environment as a strong oxidant) were first detected. The effectiveness of UV/O3 cleaning is demonstrated by improving the properties of indium tin oxide (ITO) for OLED fabrication. The contact angle of water to ITO could be reduced from 90° to 3° and for diiodomethane, it was reduced from 55° to 31° within the 10 min of irradiation. This greatly improved wettability for polar and non-polar liquids can increase the flexibility in further process control. In addition, an improvement in wettability is characterized by measuring the contact angles for titanium dioxide (TiO2) and polydimethylsiloxane (PDMS). The contact angle of water to TiO2 decreased from 70° to 10°, and that of diiodomethane to TiO2 from 54° to 31°. The wettability of PDMS was also greatly increased. Here, the contact angle of water was reduced from 109° to 24° and the contact angle to diiodomethane from 89° to 49°. Article Highlights We report a cost-effective dry-cleaning device for surface cleaning and modification based on ultraviolet-ozone irradiation. Contact angle measurements show an increase of wettability for different materials due to surface modification. The UVO3 pre-treatment improves layer formation and optoelectrical properties of OLEDs.

Flax fiber-containing polypropylene-based polymer matrix composites (PMCs) with different lignite fly ash (LFA) contents were synthesized using the formula (80 − x) PP − 20 F – x LFA (where x = 0, 2.5, 5.0, 7.5, and 10.0 wt.%) and analyzed. The added LFA acted as a filler material in the polymer network to re-formulate the microstructure of PMCs. The structural changes in the PMCs were induced to alter their thermal stability and mechanical strength. A linear increase in Tg, density, and compressive strength values was observed up to addition of 10 wt.% LFA in the prepared PMCs. Fourier transform infrared spectra revealed the structural changes that occurred in the polymer network for all the samples during the addition of LFA. Results of the X-ray diffraction studies confirmed the crystalline phase of the added LFA in the PMCs. Contact angle and surface energy studies showed a higher contact angle and lower surface energy in the PMC sample containing 5 wt.% LFA. The low wear depth in the sample containing 5 wt.% LFA confirmed its better wear than other samples. The obtained results confirmed that the flax fiber-added polypropylene composite with 5 wt.% LFA is suitable for aerospace, construction, and automobile applications.

One of the most efficient ways to extract hydrocarbons is to use nanoparticles for wettability alteration, to address dwindling reservoirs and growing energy demand. Another crucial factor is inhibiting asphaltene precipitation, which can cause damage to production components and alter the rock's wettability and permeability. This study investigates the impact of synthesized Fe 3 O 4 , SiO 2 , and Fe 3 O 4 /SiO 2 nanomaterials on wettability alteration and asphaltene removal in an oil/water system at two temperatures (25 °C and 80 °C). The nanocomposites with various ratios were manufactured with the aid of the sol-gel method and characterized using FTIR, XRD, and dynamic light scattering analysis. The stability of different concentrations of nanofluids was assessed via sedimentation tests and zeta potential measurements. According to the results, there was a reduction in both surface energy and oil area fraction from 89.46 to 8.13 mN/m and from about 1–0.075, respectively. Maximum wettability alteration (from 155° to 32°) was achieved at the optimum condition (0.075 wt% of C1000 at 80 °C). The C1000 nanocomposite played a significant role as an inhibitor in shifting the onset point to higher concentrations of n-heptane compared to Fe 3 O 4 and SiO 2 nanoparticles. Furthermore, nanomaterials have a better association with the Langmuir model, and the asphaltene particles are adsorbed homogeneously and in the form of one layer of adsorbents. The results of this study can assist the petroleum sector in better controlling asphaltene precipitation and enhancing oil recovery by C1000 nanoparticles, leading to a higher recovery rate and a more cost-effective production approach. [Display omitted] • The strongly oil-wet surface becomes water-wet in presence of various ratio of nanoparticles. • The asphaltene particles are adsorbed homogeneously and in the form of one layer on the adsorbents. • Optimization of different nanocomposites and nanofluid concentrations. • The static and dynamic contact angles of the rock surface were measured. [ABSTRACT FROM AUTHOR]

[Display omitted] Characterizing the microstructure of an ice/surface interface and its effect on the icephobic behavior of surfaces remains a significant challenge. Introducing X-ray Computed Tomography (XCT) can provide unprecedented insights into the internal (porosity) and interfacial structures, i.e. wetting regime, between (super)hydrophobic surfaces and ice by visualizing these optically inaccessible regions. Frozen droplets with controlled volume were deposited on top of metallic and polymeric substrates with different levels of wettability. Different modes of XCT (3D and 4D) were utilized to obtain information on the internal and interfacial structure of the ice/surface system. The results were supplemented by conventional surface analysis techniques, including optical profilometry and contact angle measurements. Using XCT on ice/surface systems, the 3D and 4D (imaging with temporal resolution) structural information can be visualized. From these datasets, qualitative and quantitative results were obtained, not only for characterizing the interface but also for analyzing the entire droplet/surface system, e.g., measurement of porosity size, shape, and location. These results highlight the potential of XCT in the characterization of both droplets and substrates and proves that the technique can aid to develop hydrophobic surfaces for use as icephobic materials. [ABSTRACT FROM AUTHOR]

The accurate segmentation of liquid drop image is an important part of high precision contact Angle measurement.Aiming at the problems of inaccurate target, incomplete contour, and poor effect of solid-liquid-vapor intersection and boundary details in the process of liquid drop segmentation, a neural network model suitable for liquid drop segmentation is proposed.The model is based on U-Net network, and a 1×1 convolution layer is added at its input to summarize image features to avoid losing information from the initial image.Resnet18 structure is used as the feature learning encoder of U-Net to enhance the expression ability of the network and promote the propagation of gradient.The feature fusion technology of dense connection is added in the decoding process, which improves the detail information of segmented target and reduces the network parameters.Finally, a batch normalization operation is added after each convolution layer to further optimize the network performance.Experimental results show that the improved U-Net model can effectively improve the accuracy of droplet identification and segmentation effect, and has a certain reference value in the field of contact Angle measurement.

Spontaneous capillary flow in open microchannels is a phenomenon driven by surface energies. The contact angle that the liquid forms with the channel's substrate material and the cross-section of the microchannel decide whether liquid from a connected reservoir will automatically fill the channel or not. In this work we show how this behavior can be used to design a passive contact angle measurement device (CAMD) based on parabolic open microgrooves. To that end, we present a theory of open capillary flow in such microgrooves and compare the results to minimal energy surface simulations. Additionally, we discuss that the condition for capillary flow of curved microchannels is essentially equal to the condition for their straight counterparts having the same cross-section.Lastly, we present two demonstrators of our CAMD made out of micromilled poly(methyl methacrylate). The devices consist of five open microchannels with different cross-sections which are connected to a common liquid reservoir. We show how the behavior of a liquid placed into that reservoir can be used to evaluate the contact angle between the liquid and the substrate material. A comparison to conventional contact angle goniometry shows that our approach is able to successfully estimate contact angles with an accuracy of 10° by design which can be improved by employing a greater number of microchannels. Since our devices were automatically designed and can be tuned to specific applications, this provides an easy approach to include contact angle measurement into existing lab-on-a-chip devices.

The contact angle of droplets on the surface is an important parameter to characterize the surface properties of materials. It has critical applications in fluid mechanics, surface chemistry, medicine, and other disciplines. High-precision contact angle measurement is closely related to the accurate positioning of three-phase contact points and the degree of coincidence of fitting curves. Therefore, a new contact angle measurement method was proposed. Firstly, the three-phase contact point of the droplet was automatically detected based on the Harris corner detection algorithm. The distance between corners was screened, and sub-pixel corner detection was performed based on screened corners to obtain the accurate position of the three-phase contact point. Secondly, in order to solve the problem that the hydrophobic and superhydrophobic droplet contours are not accurate in polynomial curve fitting, the logarithmic spiral and Archimedes spiral were used to fit the droplet contours. The tangent line of the fitted curve at the contact point of the three phases was obtained to obtain the accurate contact Angle measurement value. Finally, several droplet pictures were measured and verified. The results show that this method is not only suitable for measuring static contact angles, but also for measuring dynamic contact angles. The automatic contact angle measurement results are basically consistent with the electronic protractor measurement results. [ABSTRACT FROM AUTHOR]

The aim of this work is to provide a better understanding of the interface between graphite and different molecular and ionic liquids. Experimental measurements of the liquid surface tension and of the graphite-liquid contact angle for sixteen ionic liquids and three molecular liquids are reported. These experimental values allowed the calculation of the solid/liquid interfacial energy that varies, for the ionic liquids studied, between 14.5 mN m−1 for 1-ethyl-3-methylimidazolium dicyanamide and 37.8 mN m−1 for 3-dodecyl-1-(naphthalen-1-yl)-1H-imidazol-3-ium tetrafluoroborate. Imidazolium-based ionic liquids with large alkyl side-chains or functionalized with benzyl groups seem to interact more favourably with freshly peeled graphite surfaces. Even if the interfacial energy seems a good descriptor to assess the affinity of a liquid for a carbon-based solid material, we conclude that both the surface tension of the liquid and the contact angle between the liquid and the solid can be significant. Molecular dynamics simulations were used to investigate the ordering of the ions near the graphite surface. We conclude that the presence of large alkyl side-chains in the cations increases the ordering of ions at the graphite surface. Benzyl functional groups in the cations lead to a large affinity towards the graphite surface. [ABSTRACT FROM AUTHOR]

Atomistic molecular dynamics simulations were conducted to study the wetting states of 1-ethyl-3-methylimidazolium bis(trifluoro-methylsulfonyl)-imide ionic liquid (IL) nanodroplets on surfaces with different strengths of van der Waals (VDW) interactions and in the presence of an electric field. By adjusting the depth of Lennard-Jones potential, the van der Waals interaction between the solid surface and ionic liquid was systematically varied. The shape of the droplets was analyzed to extract the corresponding contact angle utilized to characterize wetting states of the nanodroplets. The explored range of surface-IL interactions allowed contact angles ranging from complete IL spreading on the surface to poor wettability. The effect of the external electrical field was explored by adding point charges to the surface atoms. Systems with two charge densities (±0.002 e/atom and ±0.004 e/atom) that correspond to 1.36 V/nm and 2.72 V/nm electric fields were investigated. Asymmetrical wetting states were observed for both cases. At 1.36 V/nm electric field, contributions of IL-surface VDW interactions and Coulombic interactions to the wetting state were competitive. At 2.72 V/nm field, electrostatic interactions dominate the interaction between the nanodroplet and surface, leading to enhanced wettability on all surfaces. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Natural Fibers is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recently, nanofluids and microorganisms -as environmentally friendly agents- have indicated superb potential in the enhanced oil recovery process. Herein, the interface properties of nanofluid and rock surfaces were surveyed by a synergistic combination of nano and biomaterials. The stability of the synthesized TiO 2 nanofluid with the aid of steric and electrostatic methods (at 25 and 80 °C) was studied by sedimentation tests, particle size distribution, and zeta potential analysis. The growth rate of bioproducts from three bacteria (Acinetobacter, Bacillus, and Klebsiella) in different carbon sources was optimized. The high stability of nanofluid was achieved by the use of sodium dodecyl sulfate surfactant and pH = 8 for 30-day at temperatures of 25 °C and 80 °C as the base fluid. The optimal growth media for bacteria is a 3-day incubation at 37 °C in a shaking incubator with whey as the carbon source. Finally, the simultaneous use of nano (0.005 wt%) and biomaterials (0.01 wt%) showed the highest wettability alteration, transforming it from strongly oil-wet to water-wet at an optimal concentration of materials. Overall, the findings of this study can help to reduce environmental concerns and operating expenses. [Display omitted] • Use of Nano and biomaterials simultaneously for EOR at temperatures of 25 and 80 °C. • Three bacteria were screened in various culture media for MEOR applications. • Preparation of a stable nanofluid via the steric and electrostatic methods. • Whey is a better carbon source for biosurfactant production. • The synergistic of nano and biomaterials revealed an 80% wettability alternation. [ABSTRACT FROM AUTHOR]

Streptomyces are known for their ability to produce various secondary metabolites used in biotechnology, human medicine and agriculture. Understanding of surface properties is very interesting in the control of interfacial phenomena. The objective of this study was to investigate the effect of consistency and composition of growth medium on the physicochemical properties of the surface of Streptomyces strains. To achieve this objective, Six Streptomyces strains belonging to bioprocess and bio-interfaces laboratory are cultivated in two media Bennett (rich) and GBA (minimum). Both media are tested in solid (agar) and liquid (broth) mode. The wettability θw, electron donor character ˠ (-), electron acceptor character ˠ (+) and Surface free energy ΔGiwi are determined using contact angle measurements. On the two solid media Bennett and GBA, Streptomyces strains develop a hydrophobic surface (96.9°

This study investigates the suitability of Piezoelectric Direct Discharge Plasma as a tool for wetting behaviour modification of PEEK and dentin, and compares the results of this method with low-pressure plasma treatment and phosphoric acid etching. Static contact angle measurements were made, roughness was assessed using tactile measurement, and AFM and SEM images were taken. An optimum operating distance of ≤15 mm was determined for the plasma based on the water contact angle. Furthermore, it was demonstrated that despite only a fraction of the power, the PDD plasma also produces hydrophilic and nanostructured PEEK surfaces with a 38° water contact angle in the same plasma time. In contrast, the gold standard of dental surface modification of dentin—phosphoric acid etching—showed no measurable contact angle due to the exposed dentin tubules. Treatment with PDD plasma reduces the water contact angle of dentin from 65° to 43° and is not negative affected by water. Wet, PDD plasma-treated dentin samples show a water contact angle of only 26.5°. The dentin tubules exposed by chemical etching led to a significantly increased roughness. No comparable effect could be demonstrated for plasma treatment on dentin, but based on the contact angle measurements, a chemically strongly activated surface with strongly polar interaction behaviour can be assumed. The additional use of the PDD plasma technique to improve wetting could therefore have a positive effect on the adhesive bond between human dentin and polymeric dental restorative materials or, depending on the adhesive system, replace the etching process altogether.

Surface energy calculation of materials in production technology has become even more important in terms of surface quality with interfacial phenomena. In this study, geometric-harmonic mean equation, OWRK, Schultz and Dorris–Gray methods were applied to characterize surface energy of paragonite mica by contact angle measurement technique (CAMT) and inverse gas chromatography (IGC) at room temperature. Total energy ranges from 49 to 122 mN/m. While values obtained from Dorris–Gray and Schultz methods are higher than others, the dispersive component result of Dorris–Gray is slightly higher than Schultz method. This work clearly shows that the surface energy of even superhydrophilic surfaces can be calculated by both CAMT and IGC. However, it was obtained with a comparative study that IGC with Dorris–Gray method is a well beneficial measurement tool to calculate surface energy. [ABSTRACT FROM AUTHOR]

In this work, we report on the controlled change of the wetting behaviour of silica thin films deposited by a reactive e-beam evaporation. The as-deposited coated surfaces were treated with acetone solvent using an ultra-sonic bath followed by characterising their contact angles. As confirmed by a repeated contact angle measurement, the silica thin films changed their wetting behaviour from superhydrophilic to hydrophilic which we attributed to the creation of OH groups and hydroxylation process. X-ray photoelectron spectroscopy analysis suggested a SiOx stoichiometry of SiO1.85 for the non-treated samples and SiO1.91 for the solvent-treated ones. Such promising results pave the way to develop a cost-effective and efficient anti-soiling and self-cleaning coating for a large-scale application. [ABSTRACT FROM AUTHOR]

This paper proposes a design methodology for a six-wheeled rover that adapt to different stairs and maintain its stability based on the robot's parameters, the kinematics constraints, the maximum height, and the minimum length of the step required to climb up and down. We also propose an emergency controller to prevent falls during the climb up or down using the contact angle measurement between wheel–ground by a laser scanner sensor on each side of the robot. Thus, the geometry terrain information and the wheel contact loss detection with the ground can be obtained. This loss of contact with the ground is a determining factor in an emergency case where the robot's stability is at risk. Therefore, the controllers kick in to regain the wheel contact with the step, preventing the robot from falling. Simulations and experimental results when the robot climbs up and down stairs demonstrate the ability to react to possible falls. [ABSTRACT FROM AUTHOR]

The present study aims to evaluate effect of hydroxyapatite (HA, Ca10(PO4)6OH2), a ceramic similar to natural bone, into AZ31B Mg alloy matrix on biomineralization and biocompatibility. The novel friction stir processing additive manufacturing route was employed to fabricate Mg-HA composites. Various HA contents (5, 10, 20 wt%) were incorporated into Mg matrix.Microstructural observation and chemical composition analysis revealed that refined Mg grains and dispersion of HA particles at micro/nanoscales were achieved in Mg-HA composites after the friction stir processing. The biomineralization evaluation were carried out using immersion experiments in simulated body fluid followed by mineral morphology observation and chemical composition analysis. The wettability measurements were conducted to correlate the biomineralization behavior. The results showed improvement in wettability and bone-like Ca/P ratio in apatite deposit on the composites compared to as-received Mg. In addition, the increase of blood compatibility, cell viability and spreading were found in the higher HA content composites, indicating the improved biocompatibility. Therefore, friction stir processed Mg-20 wt%HA composite exhibited the highest wettability and better cell adhesion among other composites due to the effect of increased HA content within Mg matrix.

Calotropis Gigantea (CG) is a shrub plant that grows rampantly in South Asia. Here we report the development of CG bast fibre yarns, which could yield replacements for artificial fibres in engineering applications. Most of the researchers concentrated only in the short form of natural fibres, this leads to dropping the fibre reinforcement in continuous and lengthy products. An attempt has been made in this research by taking CG fibre in the form of twisted yarn as reinforcement. The surface treatment is done to enhance the properties of the CG fibres and to reduce hydrophilic and hygroscopic behaviour using NaOH (aq.). Determining the appropriate NaOH concentration in the treatment solution is essential to reduce the hydrophilicity of the fibres while retaining its mechanical properties. Generally optimised NaOH concentration found by completing fibre characterization, which is a very lengthy and time-consuming process. In this research work, the optimum concentration of NaOH found by a quick and short process using simple techniques. Two techniques were used such as Contact angle measurement of fibre surface and microscopic observation of xylem structure to find an optimum concentration of NaOH in the aqueous solution. On treated CG fibres, the contact angle is found to be as high as 112° for 4 wt.% NaOH (aq.) concentration; indicating that the treatment renders the fibre hydrophobic and the observation of xylem structure (voids) confirms in a minimum amount in the same 4 wt.% NaOH treated fibre. The mechanism involved is rationalized using infrared/vibrational spectroscopy based measurements of untreated and treated sampled. The orientation of the fibre helps with optimization of the properties. The elastic modulus (measured as per ASTM standards) obtained are 4.18 GPa (along the fibres) and 3.05 GPa (perpendicular to the fibres).

In this article, we study the formation of nanomeniscus around a nanoneedle using molecular dynamics simulation approach. The results reveal three distinct phases in the time-evolution of meniscus before equilibrium according to the contact angle, meniscus height, and potential energy. In addition, we investigated the correlation between the nanoneedle diameter and nanomeniscus characteristics. The results have applications in various fields such as scanning probe microscopy and rheological measurements. [ABSTRACT FROM AUTHOR]

[Display omitted] The drop deposition technique can impact contact angle measurements. We hypothesized that the drop pinch-off, during the traditionally used pendant drop technique, significantly alters the static contact angle. The capillary waves and dynamic wetting pressure generated during the pendant drop deposition are the source for forced spreading, which can be circumvented by alternative liquid-needle drop deposition techniques. To compare the role of drop pinch-off and resultant dynamic wetting pressure, we meticulously observed and quantified the entire drop deposition process using high speed imaging until the drop attains the static contact angle in both cases, namely pendant drop and liquid needle deposition technique. Conventionally used standard substrates are compared using both techniques and further compared using literature data. The capillary waves and corresponding drop shape variations are analysed for quantifying the dynamic wetting pressure by measuring drop base diameter, contact angle and centre of mass. We compared three parameters - drop pinch-off, spreading behaviour and respective static contact angles along with the resultant dynamic wetting pressure for both the techniques, i.e., pendant drop and liquid-needle. For the pendant drop technique we observed a pronounced drop volume dependency of these parameters even though the corresponding Bond numbers are less than unity. In contrast, for the liquid needle there is no such dependency. With a theoretical argument corroborating experimental observations, this work highlights the importance of a well controlled drop deposition, with a minimum wetting pressure, in order to guarantee contact angle data that is independent of drop deposition effects, thereby only reflecting the substrate properties. [ABSTRACT FROM AUTHOR]

This research work deals with the development of a polymeric super-hydrophobic surface involving nano silica–titania core–shell particles. This core–shell structure enhanced the properties of two different materials in a single nanoparticle in an outstanding manner; polymeric coatings containing core silica and shell titania have improved the mechanical behavior and hydrophobicity of coating surfaces, respectively. This nano core–shell was synthesized through two different methodologies which were prepared at high and low processing temperature separately, that is, called sol–gel and peptization synthesis. Further surface properties of the prepared nanoparticles were investigated individually in solvent-based emulsions and water-based emulsions. Nanocoating formulations were developed on mild steel substrate for analysis on the mechanical behavior of the coating and contact angle measurement. In the coating formulation, nano core–shell concentrations ranged from 1% (wt) to 6% (wt), and used nanoparticles were functionalized with methyl trimethoxy silane for better surface properties. Based on the results of the experiment, core–shell nanocoatings have been found mechanically robust and superhydrophobic (∼145.1° ± 2°) coating. [ABSTRACT FROM AUTHOR]

Recent advances in scanning probe methods that provide direct access to the surface free energy of inorganic layered materials in terms of the Hamaker constant yield energetic values for monolayer graphene that differ substantially, by a factor of around 0.4, from bulk graphite. The onset of bulk deviating energy values was observed at a multilayer slab thickness of ~3 nm, corresponding to a layer number of 10. The findings, complemented with extractions from water contact angle measurements and calculated interlayer binding energies, find short-range ordinary van der Waals interactions to be most prominently affected by dimensional constraints and many-body interactions. [ABSTRACT FROM AUTHOR]

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The purpose of this paper consists in the evaluation of the contact angle at the interface of Co-Cr sintered samples by DMLS process. The sintered samples supported a post treatment and were coated by HA using sol-gel method and were immersed in simulated biological fluid SBFx1 for 7 days. The Co-Cr (ST2724G) sintered disks by Direct Metal Laser Sintering (DMLS) process using a Phenix Systems machine, were coated by hydroxyapatite sol-gel method for improving the bioactivity of dental implants. KSV CAM 101 apparatus is used for static contact angle measurements performed on dried films. After wetting angle determination, we can notice that the sintered samples of Co-Cr alloy, which supported a post treatment, after DMLS process show better roughness surfaces and the layers of HA are uniformly deposited. The contact angle values are very important to characterize the surfaces and the roughness of the solid materials used for implantology. In this paper, the contact angles at the interface between Co-Cr sintered disks coating with HA and distilled water reveal a hydrophilic character. Scanning electronic microscopy SEM and EDS techniques were employed for morphological investigation of the sintered samples manufactured by DMLS process. They were also used for semi-quantitative and qualitative chemical and metallographic analyses.

Streptomyces are known for their ability to produce various secondary metabolites used in biotechnology, human medicine and agriculture. Understanding of surface properties is very interesting in the control of interfacial phenomena. The objective of this study was to investigate the effect of consistency and composition of growth medium on the physicochemical properties of the surface of Streptomyces strains. To achieve this objective, Six Streptomyces strains belonging to bioprocess and bio-interfaces laboratory are cultivated in two media Bennett (rich) and GBA (minimum). Both media are tested in solid (agar) and liquid (broth) mode. The wettability θw, electron donor character ˠ (-), electron acceptor character ˠ (+) and Surface free energy ΔGiwi are determined using contact angle measurements. On the two solid media Bennett and GBA, Streptomyces strains develop a hydrophobic surface (96.9° <θw<167.9°) with a weak electron donor character (0.3 mJm-2 < (ˠ (-)) <12.14 mJm-2) and a strong electron acceptor character (0.26 mJm-2 < ˠ (+) < 17.8 mJm-2) and a negative surface free energy ((- 11.8 mJm-2) < ΔGiwi < (-110 mJm-2)). Whereas on both Bennett and GBA liquid media, the surfaces of Streptomyces strains are generally hydrophilic (1.3° < θw < 9.33°) with a strong electron donor character (13.76 mJm-2 < ( ˠ (-)) < 70.06 mJm-2) and a positive surface free energy. By changing the composition of the culture medium, only a slight change in the degree of hydrophobicity and surface free energy of Streptomyces is observed. Regarding the effect of medium composition on the surface properties of Streptomyces, the degree of wettability and the values of surface free energy are no longer the same when the composition of the medium changes. These results could be applied in further studies interested in interfacial phenomena and microbial adhesion in biotechnological fields. [ABSTRACT FROM AUTHOR]

The present work's target is to study the impact of fly ash or TiC nanoparticles or both on the characteristics of coir fiber epoxy hybrid composites. Mechanical characteristics like tensile, flexural, inter‐laminar shear strength, impact strength, shore D hardness, and thermal stability or degradation characteristics were determined. The microstructure of the samples was observed from a scanning electron microscopy. It was observed that the addition of coir fiber, fly ash, and TiC nanoparticles in the epoxy polymer enhanced the mechanical and thermal characteristics of composites. It can be assigned to the better interaction and uniform distribution between the fillers and the epoxy polymer. Fillers acted a critical role in enhancing the characteristics of epoxy hybrid composites. Additionally, water absorption characteristics were also investigated for all specimens. A comparative examination was performed between various fabricated composite specimens. Results exhibited that, the water absorption of the composites improves considerably with the addition of reinforcements. Also, thermogravimetric analysis exhibited that the fabricated epoxy hybrid composites were stable thermally. [ABSTRACT FROM AUTHOR]

Measurements of contact angle on graphene sheets show a notable dependence on the nature of the underlying substrate, a phenomenon termed wetting transparency. Our molecular modeling studies reveal analogous transparency in case of submerged graphene fragments in water. A combined effect of attractive dispersion forces, angle correlations between aqueous dipoles, and repulsion due to the hydrogen-bond-induced orientation bias in polarized hydration layers acting across graphene sheet, enhances apparent adhesion of water to graphene. We show wetting free energy of a fully wetted graphene platelet to be about 8 mNm-1 lower than for graphene wetted only on one side, which gives close to 10° reduction in contact angle. This difference has potential implications for predictions of water absorption vs. desorption, phase behavior of water in aqueous nanoconfinements, solvent-induced interactions among graphitic nanoparticle and concomitant stability in aqueous dispersions, and can influence permeability of porous materials such as carbon nanotubes by water and aqueous solutions. [ABSTRACT FROM AUTHOR]

The renal capsule tissue of lamb was irradiated with ultraviolet-C light and the treated samples were analyzed by uniaxial tensile test, dynamic mechanical analysis, attenuated total reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and contact angle measurements. It was shown that the skin cross-linking is dominant in low doses in accordance with the contact angle assessment. Conversely, the strong bulk degradation takes place at high doses. Similarly, the bulk cross-linking affects the mechanical tests as to enhance the stiffness at low doses, whereas strong degradation occurs at high doses that mainly arises from the strong bulk chain scission. [ABSTRACT FROM AUTHOR]

• A natural relaxation of as-placed water drops on PDMS surfaces was observed. • Actual contact angle hysteresis on deformable surfaces is hidden. • Slow moving contact lines on elastic surfaces are out of "quasi-static" regimen. • The "braking effect" developed on soft surfaces affects contact line dynamics. • The drop formation by controlled volume variation resolves steady contact angles. Characterization of contact angle hysteresis on soft surfaces is sensitive to the measurement protocol and might present adventitious time-dependencies. Contact line dynamics on solid surfaces is altered by the surface chemistry, surface roughness and/or surface elasticity. We observed a "slow" spontaneous relaxation of static water sessile drops placed on elastic surfaces. This unexpected drop motion reveals unresolved equilibrium configurations that may affect the observed values of contact angle hysteresis. Drop relaxation on deformable surfaces is partially governed by a viscoelastic dissipation located at the contact line. In this work, we studied the natural relaxation of water drops formed on several smooth PDMS surfaces with different elastic moduli. We monitored in time the contact angle and contact radius of each drop. For varying the initial contact angle, we used the growing-shrinking drop method. We postulate that the so-called "braking effect", produced by the surface deformability, affects the contact line velocity and in consequence, the contact angle measurements. We conclude that the wetting properties of elastic surfaces should be properly examined with reliable values of contact angle measured after drop relaxation. [ABSTRACT FROM AUTHOR]

The simulation of fluid flow over solid surfaces is important in many applications, for example, in automotive applications where good visibility and the performance of external sensors are essential. Multiphase CFD simulation methods such as level set or coupled level set–volume of fluid typically require a validated dynamic contact angle model as a function of capillary number to accurately resolve the near wall behaviour. This paper explores an experimental approach to identify a suitable contact angle model for pure and contaminated water on glass and painted surfaces. Applying image processing methods to high-resolution digital images of droplets descending flat plate samples of the required surfaces, the dynamic advancing and receding contact angles and capillary number are determined. Cox–Voinov, de Gennes and Yokoi models are parameterised from the experimental data, and the Yokoi model is shown to be the most suited to these surface/fluid combinations where hysteresis is significant. A multiphase simulation implementing the Yokoi model demonstrates good correlation for the Bond number between simulation and experiment. [ABSTRACT FROM AUTHOR]

This paper proposes a design methodology for a six-wheeled rover that adapt to different stairs and maintain its stability based on the robot’s parameters, the kinematics constraints, the maximum height, and the minimum length of the step required to climb up and down. We also propose an emergency controller to prevent falls during the climb up or down using the contact angle measurement between wheel–ground by a laser scanner sensor on each side of the robot. Thus, the geometry terrain information and the wheel contact loss detection with the ground can be obtained. This loss of contact with the ground is a determining factor in an emergency case where the robot’s stability is at risk. Therefore, the controllers kick in to regain the wheel contact with the step, preventing the robot from falling. Simulations and experimental results when the robot climbs up and down stairs demonstrate the ability to react to possible falls.

Nowadays, many self-healing strategies are available for recovering mechanical damage of bulk polymeric materials. The recovery of surface-dependent functionalities on polymer films is, however, equally important and has been less investigated. In this work we study the ability of low surface energy cross-linked poly(ester urethane) networks containing perfluorinated dangling chains to self-replenish their surface, after being submitted to repeated surface damage. For this purpose we used a combined experimental-simulation approach. Experimentally, the cross-linked films were intentionally damaged by cryo-microtoming to remove top layers and create new surfaces which were characterized by water Contact Angle measurements and X-Ray Photoelectron Spectroscopy. The same systems were simultaneously represented by a Dissipative Particles Dynamics simulation method, where the damage was modeled by removing the top film layers in the simulation box and replacing it by new "air" beads. The influence of different experimental parameters, such as the concentration of the low surface energy component and the molecular mobility span of the dangling chains, on the surface recovery is discussed. The combined approach reveals important details of the self-replenishing ability of damaged polymer films such as the occurrence of multiple-healing events, the self-replenishing efficiency, and the minimum "healing agent" concentration for a maximum recovery. [ABSTRACT FROM AUTHOR]

In tissue engineering applications, various synthetic biodegradable polymers have got attention due to their excellent physical as well as biological properties. Polycaprolactone (PCL) has been identified as one of the best biocompatible polymers, which have wide applications in biomedical engineering. The surface properties of PCL have limited its utilization in tissue engineering. The researchers have also focused on the development of the PCL blends to enhance the surface characteristics. In the present study, carbonyl iron powder (CIP) reinforced PCL blends were fabricated by the solvent cast 3D printing (SC‐3DP) technique. The characterization techniques such as X‐ray diffraction, atomic force microscopy, and surface energy measurement by contact angle were used. The surface free energy of all the surfaces with their polar components was determined by Owens Wendt method. The fibroblasts cell responses were also examined for the assessment of biological properties. The results revealed that the increase in the percentage of CIP in the PCL matrix enhanced the value of surface free energy. The CIP reinforcement influenced the topography and surface roughness of the prepared composites. The change in surface properties affected the cell interactions on the surfaces, as investigated by cell viability test. The cell adhesion and viability were improved at a lower percentage of CIP. [ABSTRACT FROM AUTHOR]

Practical considerations on the measurement of the dynamic contact angle and the spreading diameter of impacting droplets are discussed in this paper. The contact angle of a liquid is commonly obtained either by a polynomial or a linear fitting to the droplet profile around the triple-phase point. Previous works have focused on quasi-static or sessile droplets, or in cases where inertia does not play a major role on the contact angle dynamics. Here, we study the effect of droplet shape, the order of the fitting polynomial and the fitting domain, on the measurement of the contact angle on various stages following droplet impact where the contact line is moving. Our results, presented in terms of the optical resolution and the droplet size, show that a quadratic fitting provides the most consistent results for a range of various droplet shapes. As expected, our results show that contact angle values are less sensitive to the fitting conditions for the cases where the droplet can be approximated to a spherical cap. Our experimental conditions include impact events with liquid droplets of different sizes and viscosities on various substrates. In addition, validating past works, our results show that the maximum spreading diameter can be parameterised by the Weber number and the rapidly advancing contact angle. [ABSTRACT FROM AUTHOR]

This work proposes an approach to fabricate micro patterned surfaces on PA2200 polyamide in order to improve its performance in terms of wettability and adhesion. In more detail, the present work aims to change the wettability of the surface and decrease their bacteria adhesion tendency. The experimental procedure consists of imprinting a set of erentffdi micro patterned structures over the polymer in order to verify the effectiveness of the methodology to change the contact angle of the surface, and in turn, reduce the occurrence of bacteria adhesion. Four different surface patterning were produced by laser ablation of a commercially pure titanium alloy, and then imprinted over the polyamide by surface stamping. The resulting surfaces were analyzed by topographical characterization and scanning electron microscopy. The wettability was probed by contact angle measurements while the bacteria adhesion was analyzed by adhesion test. The experimental results demonstrate the effectiveness of the method to modify the surface characteristics and to obtain a reliable patterned surface without using chemical hazardous material; opening to the possibility to replicate more complex structures and to obtain graded engineering surfaces. [ABSTRACT FROM AUTHOR]

This paper investigates the wettability of selected wood species from Indonesian community forests, namely (Indonesian name–Latin name) surian (Toona sinensis), jabon (Anthocephalus cadamba), gmelina (Gmelina arborea.), Manglid (Manglietia glauca), rubber wood (Hevea brasiliensis), and sengon (Paraserianthes falcataria). The study measures the contact angle and evaluates the suitability of these wood species for plywood production. Logs from a community forest were processed to convert into thin slices of veneer using the rotary cutting method at a plywood plant. Subsequently, the study analyzed the wetting behavior of the veneer samples resulting from a rotary process on tangential surfaces without smoothing treatment with distilled water. The veneer was then made into plywood using an adhesive nanofiller of phenol formaldehyde mixed with wood bark powder. Ball milling produced nanofillers from the bark of jabon, gmelina, and surian with nanoscale particle diameter size (10–1000 nm). The bonding strength of the plywood was evaluated under cyclic and dry test conditions according to Japanese Standards. The study shows that P. falcataria, H. brasiliensis, and A. cadamba have a smaller contact angle than T. sinensis, G. arborea, and M. glauca. Thus, the higher wettability of P. falcataria, H. brasiliensis, and A. cadamba results in a better adhesive spread and more intimate contact between the wood surface and the adhesive. However, the study found higher bonding strength values for H. brasiliensis and T. sinensis plywood using jabon nanofiller, followed by T. sinensis plywood using surian nanofiller and H. brasiliensis plywood using gmelina nanofiller. [ABSTRACT FROM AUTHOR]