Determination Of Contact Angle Research Articles

A New Type of Composite Membrane PVA-NaY/PA-6 for Separation of Industrially Valuable Mixture Ethanol/Ethyl Tert-Butyl Ether by Pervaporation.

Pervaporation is a membrane technique used to separate azeotropic and close boiling solvents. Heterogenous PVA composite membranes with NaY zeolite supported on polyamide-6 were fabricated and utilized in organic–organic pervaporation. The efficiency of prepared membranes was evaluated in the separation of ethanol/ethyl tert-butyl ether (EtOH/ETBE) using separation factor (β) and the thickness normalized pervaporation separation index (PSIN). Implementation of the fringe projection phase-shifting method allowed to the determined contact angle corrected by roughness. The influence of the presence of water traces in the feed on the overall separation efficiency was also discussed using the enrichment factor for water (EFwater). The incorporation of NaY into PVA matrix increases surface roughness and hydrophilicity of the composite membrane. It was found that membranes selectively transport ethanol from the binary EtOH/ETBE mixture. The values of β (2.3) and PSIN (288 μm g m−2 h−1) for PVA-NaY/PA6 membrane were improved by 143% and 160% in comparison to the values for the pristine PVA/PA6 membrane. It was found that membranes showed EFwater > 1, thus revealing the preferential transport of water molecules across membranes. These results are also significant for the design of membranes for the removal of water excess from the mixtures of organic solvents.

Determination of contact angles for three-phase flow in porous media using an energy balance

HypothesisWe define contact angles, θ, during displacement of three fluid phases in a porous medium using energy balance, extending previous work on two-phase flow. We test if this theory can be applied to quantify the three contact angles and wettability order in pore-scale images of three-phase displacement. TheoryFor three phases labelled 1, 2 and 3, and solid, s, using conservation of energy ignoring viscous dissipation (Δa1scosθ12-Δa12-ϕκ12ΔS1)σ12=(Δa3scosθ23+Δa23-ϕκ23ΔS3)σ23+Δa13σ13, where ϕ is the porosity, σ is the interfacial tension, a is the specific interfacial area, S is the saturation, and κ is the fluid–fluid interfacial curvature. Δ represents the change during a displacement. The third contact angle, θ13 can be found using the Bartell-Osterhof relationship. The energy balance is also extended to an arbitrary number of phases. FindingsX-ray imaging of porous media and the fluids within them, at pore-scale resolution, allows the difference terms in the energy balance equation to be measured. This enables wettability, the contact angles, to be determined for complex displacements, to characterize the behaviour, and for input into pore-scale models. Two synchrotron imaging datasets are used to illustrate the approach, comparing the flow of oil, water and gas in a water-wet and an altered-wettability limestone rock sample. We show that in the water-wet case, as expected, water (phase 1) is the most wetting phase, oil (phase 2) is intermediate wet, while gas (phase 3) is most non-wetting with effective contact angles of θ12≈48° and θ13≈44°, while θ23=0 since oil is always present in spreading layers. In contrast, for the altered-wettability case, oil is most wetting, gas is intermediate-wet, while water is most non-wetting with contact angles of θ12=134°±~10°,θ13=119°±~10°, and θ23=66°±~10°.

Wettability of welded wood-joints investigated by the Wilhelmy method: part 1. Determination of apparent contact angles, swelling, and water sorption

Abstract This study presents a novel application of the Wilhelmy plate method on welded joints of Scots pine sapwood and beech. Welding resulted in an increase in the contact angle (increased hydrophobicity) as well as a decrease in the water uptake and swelling of the welded pine-joint compared to non-welded pine. When the welding time was extended from 4 to 5 s, these properties were further pronounced. Welding of beech, on the other hand, led to an increase in the contact angle and a decrease in the water uptake, but an increase in the swelling. Fourier Transform Infrared spectroscopy showed that welding increased the aliphatic C–H and unsaturated C=C stretching absorption bands in pine and beech. Scanning electron microscopy showed a dense structure at the welded joints of the both species, giving evidence of a lower porosity that leads to a lower permeability as a result of the welding.

S-XCT experimental determination of local contact angle and meniscus shape in liquid moulding of composites

In-situ spontaneous wicking experiments were scanned using Synchrotron X-ray Computed Tomography (S-XCT) to study the meniscus shape at the fibre scale. To this end, a single tow of E-glass fibres was impregnated with a commercial epoxy resin by using a wicking fixture specially designed for such purpose. The high resolution of the S-XCT images recorded (0.325μm/pixel) allowed the direct access to the surface of the individual menisci formed between fibres and permitted a direct quantification of the contact angle as well as the local curvature measurement. The contact angle values measured were in good agreement with values reported in the literature. The experimental methodology employed was also compared with numerical results obtained using a surface minimization approach. The results obtained with the simulation tool, in terms of effective capillary pressure and meniscus shape, were in good agreement with the experimental data reported.

Hydrophilic Dual Layer Hollow Fiber Membranes for Ultrafiltration.

In this study, a triblock copolymer was used as additive to fabricate new dual layer hollow fiber membranes with a hydrophilic active inner surface in order to improve their fouling resistance. The polymeric components of the solutions for membrane fabrication were poly(ether sulfone), poly(N-vinyl pyrrolidone), and the triblock copolymer. The additive consists of three blocks: a middle hydrophobic poly(ether sulfone) block and two outer hydrophilic alkyl poly(ethylene glycol) blocks. By varying the additive concentration in the solutions, it was possible to fabricate dual layer hollow fiber membranes that are characterized by a hydrophilic inner layer, a pure water permeance of over 1800 L/(m2 bar h) and a molecular weight cut-off of 100 kDa similar to commercial membranes. Contact angle and composition determination by XPS measurements revealed the hydrophilic character of the membranes, which improved with increasing additive concentration. Rheological, dynamic light scattering, transmission, and cloud point experiments elucidated the molecular interaction, precipitation, and spinning behavior of the solutions. The low-molecular weight additive reduces the solution viscosity and thus the average relaxation time. On the contrary, slow processes appear with increasing additive concentration in the scattering data. Furthermore, phase separation occurred at a lower non-solvent concentration and the precipitation time increased with increasing additive content. These effects revealed a coupling mechanism of the triblock copolymer with poly(N-vinyl pyrrolidone) in solution. The chosen process parameters as well as the additive solutions provide an easy and inexpensive way to create an antifouling protection layer in situ with established recipes of poly(ether sulfone) hollow fiber membranes. Therefore, the membranes are promising candidates for fast integration in the membrane industry.

Antimicrobial packaging efficiency of ZnO-SiO2 nanocomposites infused into PVA/CS film for enhancing the shelf life of food products

Abstract In the current work, antimicrobial bionanocomposite films were fabricated based on chitosan (CS), poly (vinyl alcohol) (PVA) and nanocomposites comprised of silicon dioxide nanoparticles doped with zinc oxide nanoparticles (ZnO-SiO2). The ZnO-SiO2 nanocomposite was prepared and incorporated into a PVA/CS blend at different ratios (0.50, 1.0, 3.0 and 5.0 %) to generate the PVA/CS/ZnO-SiO2 bionanocomposites. The prepared ZnO-SiO2 nanocomposites as well as the PVA/CS/ZnO-SiO2 bionanocomposite films were evaluated using SEM, FT-IR, XRD and determination of the final contact angle. Furthermore, the mechanical properties, gas permeability (GTR) and water vapor transmission rate (WVTR) of the prepared PVA/CS/ZnO-SiO2 bionanocomposite films were evaluated. The fabricated bionanocomposite films displayed superior antibacterial activity against Gram-positive bacteria (staphylococcus aureus, S33R) as well as Gram-negative bacteria (Escherichia coli, IRAQ 3). Correspondingly, the prepared PVA/CS/ZnO-SiO2 bionanocomposites were used for bread packaging. The obtained result revealed the greatly improved visual appearance of the bread that was packaged in the PVA/CS/ZnO-SiO2 bionanocomposite film. Moreover, the totality of these various observations and testing methods led to an increase in the shelf life and reduced the amounts of food-borne pathogens in the packaged bread. This PVA/CS/ZnO-SiO2 bionanocomposite film is an antimicrobial packaging material that may reduce the current negative environmental footprint of packaging materials.

Simultaneous determination of wettability and shrinkage in an organic residue amended loamy topsoil

Abstract In agricultural land use, organic residues such as compost, digestate, and sewage sludge are discussed as costeffective soil conditioner that may improve the water holding capacity and crop available soil moisture. The objective of this study is to determine the effect of application of digestates with different compositions in maize, sugar beet and winter wheat, compost of shrub debris and sewage sludge on shrinkage behaviour and contact angle of till-derived loamy topsoil of a Haplic Luvisol under agricultural use. Novelty is the simultaneous determination of contact angle and shrinkage of soils amended with digestates composed of different composition in maize, sugar beet and winter wheat, compost of shrub debris and sewage sludge. The results suggest that the application of organic residues impacts the air capacity, while the contact angles remained in the subcritical range between > 0° and < 90°. The relationship between CA values and moisture ratios, ϑ, during proportional shrinkage was positive and linear (r2 of 0.98) and negative during residual- and zero-shrinkage (r2 of 0.93).

Evaluation of methods using topology and integral geometry to assess wettability

HypothesisThe development of high-resolution in situ imaging has allowed contact angles to be measured directly inside porous materials. We evaluate the use of concepts in integral geometry to determine contact angle. Specifically, we test the hypothesis that it is possible to determine an average contact angle from measurements of the Gaussian curvature of the fluid/fluid meniscus using the Gauss-Bonnet theorem. Theory and simulationWe show that it is not possible to unambiguously determine an average contact angle from the Gauss-Bonnet theorem. We instead present an approximate relationship: 2πn(1-cosθ)=4π-∫κG12dS12, where n is the number of closed loops of the three-phase contact line where phases 1 and 2 contact the surface, θ is the average contact angle, while κG12 is the Gaussian curvature of the fluid meniscus which is integrated over its surface S12. We then use the results of pore-scale lattice Boltzmann simulations to assess the accuracy of this approach to determine a representative contact angle for two-phase flow in porous media. FindingsWe show that in simple cases with a flat solid surface, the approximate expression works well. When applied to simulations on pore space images, the equation provides a robust estimate of contact angle, accurate to within 3°, when averaged over many fluid clusters, although individual values can have significant errors because of the approximations used in the calculation.

Membranes based on polyacrylamide coatings on metallic meshes prepared by a two-steps redox polymerization. Performance for oil-water separation and biofouling effects

Superhydrophilic oil–water separation membranes were prepared based on chemical (non-photo-induced) polymerization of acrylamide on metal meshes. Membranes were characterized by surface morphological analysis (SEM and AFM), determination of contact angles of water and oil drops, measurement of water flow through the membranes, analysis of dissolved organic in filtered water–oil systems, critical intrusion pressure of oil and surface coverage by bacterial biofilms. The main characteristics of the membranes were studied as function of coverage with polyacrylamide (PAM). The membranes presented efficiencies larger than 99% for toluene-water separation and lifetimes of several months. The intrusion pressure (0.25–1.25 kPa) and water flux (10–300 Lm-2s−1) varied depending on PAM coverage. A mathematical model was implemented for predicting the water flow as function of hydrogel coverage.The results indicate there is a degree of compromise between three factors that are related to the amount of PAM coating: avoiding biofouling (which can block the flow, induce corrosion, etc.), maintaining an important flow of water and sustaining a given intrusion pressure of oil on the membranes.

Fungal-induced water repellency in sand

Water infiltration into granular soils and the associated pore water pressure increase and reduction in shear strength can trigger landslides, instability of vertical cuts and failure of retaining walls. Water-repellent soils can reduce infiltration to maintain soil suction. Recent research has demonstrated the creation of synthetic water-repellent soils using chemical methods. This paper investigates a biological treatment for creating water-repellent sand by way of the growth of the fungus Pleurotus ostreatus. Water repellency was assessed using: (a) the water drop penetration test; (b) the molarity of ethanol drop test; and (c) the modified sessile drop method with contact angle (θ) determination by way of image analysis. Fungal-induced water repellency was found to be ‘extreme’ (θ > 110°) up to 4 weeks and ‘severe’ (θ > 105°) up to 12 weeks, even with no further supply of moisture or nutrients. A water-repellent layer was formed and maintained in saturated conditions, which is difficult to achieve using chemical methods.

Erratum: “Reliable determination of contact angle from the height and volume of sessile drops” [Am. J. Phys. 87(1), 28–32 (2019)

Erratum: “Reliable determination of contact angle from the height and volume of sessile drops” [Am. J. Phys. <b>87</b>(1), 28–32 (2019)

Using energy balance to determine pore-scale wettability

HypothesisBased on energy balance during two-phase displacement in porous media, it has recently been shown that a thermodynamically consistent contact angle can be determined from micro-tomography images. However, the impact of viscous dissipation on the energy balance has not been fully understood. Furthermore, it is of great importance to determine the spatial distribution of wettability. We use direct numerical simulation to validate the determination of the thermodynamic contact angle both in an entire domain and on a pore-by-pore basis. SimulationsTwo-phase direct numerical simulations are performed on complex 3D porous media with three wettability states: uniformly water-wet, uniformly oil-wet, and non-uniform mixed-wet. Using the simulated fluid configurations, the thermodynamic contact angle is computed, then compared with the input contact angles. FindingsThe impact of viscous dissipation on the energy balance is quantified; it is insignificant for water flooding in water-wet and mixed-wet media, resulting in an accurate estimation of a representative contact angle for the entire domain even if viscous effects are ignored. An increasing trend in the computed thermodynamic contact angle during water injection is shown to be a manifestation of the displacement sequence. Furthermore, the spatial distribution of wettability can be represented by the thermodynamic contact angle computed on a pore-by-pore basis.

Alignment of functionalized multiwalled carbon nanotubes in forward osmosis membrane support layer induced by electric and magnetic fields

A novel aligned polyphenylensulfone (PPSU)/cellulose acetate phthalate (CAP)/functionalized multiwalled carbon nanotube (FMWCNT) membrane support was prepared for forward osmosis (FO) application. The effect of applying the electric and/or magnetic fields on the horizontal and vertical alignment of FMWCNTs within PPSU/CAP membrane supports was investigated in detail. Field emission scanning electron microscopy (FESEM) confirmed the alignment of FMWCNTs under combined electric and magnetic fields. Furthermore, energy dispersive X-ray (EDX) spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, Raman spectroscopy, tensile test, thermogravimetric analysis (TGA), and water contact angle determination were conducted to further characterize the obtained samples. The performance of the obtained supports was studied in terms of pure water flux (PWF) and consequently, the vertically aligned nanocomposite membrane support prepared with 0.8 wt% FMWCNT, aligned under 0.6 kV/cm electric field followed by 2 T magnetic field demonstrated almost 6 times higher PWF in comparison with the unaligned one.

Relating nanofiltration membrane morphology to observed rejection of saccharides

Nanofiltration for the fractionation of uncharged solutes has become more interesting in recent times, due to the goal of valorizing side-streams and by-products of the food industry. Since the membranes suitable for this purpose are mainly utilized for demineralization processes, the specifications given by the manufacturer are insufficient for the prediction of the rejection of uncharged solutes. Nine membranes with a molecular weight cut-off between 150 and 1000 Da were investigated showing differences in their rejection of fructose at a transmembrane pressure difference ΔpTM of 1.0 MPa. These values were correlated with the root-mean-square roughness Sq and apparent pore size dap determined by atomic force microscopy, while the determined contact angle Θ did not influence the rejection. Thereby, a correlation between membrane morphology and rejection behavior was established.

Investigation of High Voltage Anodic Plasma (HVAP) Ag-DLC Coatings on Ti50Zr with Different Ag Amounts

The paper presents the investigation of a series of silver-incorporated diamond-like carbon (Ag-DLC) coatings with increasing Ag content on Ti50Zr and deposited using high voltage anodic plasma (HVAP). The coatings surface properties were analyzed with scanning electron microscope (SEM), atomic force microscope (AFM), and contact angle determinations. Electrochemical tests were performed in Afnor artificial saliva and evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy. Based on these properties, comparisons of coatings performance were linked with the amount of deposited Ag. Increasing the Ag content led to the increase of the corrosion resistance and to the decrease of the forces exhibited on the surface. The hydrophobic character of the coating with the highest Ag amount could prevent thrombosis, thus suggesting its possible use for medical implants.

Physical and Antibacterial Properties of Peppermint Essential Oil Loaded Poly (ε-caprolactone) (PCL) Electrospun Fiber Mats for Wound Healing.

The aim of this study was to fabricate and characterize various concentrations of peppermint essential oil (PEP) loaded on poly(ε-caprolactone) (PCL) electrospun fiber mats for healing applications, where PEP was intended to impart antibacterial activity to the fibers. SEM images illustrated that the morphology of all electrospun fiber mats was smooth, uniform, and bead-free. The average fiber diameter was reduced by the addition of PEP from 1.6 ± 0.1 to 1.0 ± 0.2 μm. Functional groups of the fibers were determined by Raman spectroscopy. Gas chromatography-mass spectroscopy (GC-MS) analysis demonstrated the actual PEP content in the samples. In vitro degradation was determined by measuring weight loss and their morphology change, showing that the electrospun fibers slightly degraded by the addition of PEP. The wettability of PCL and PEP loaded electrospun fiber mats was measured by determining contact angle and it was shown that wettability increased with the incorporation of PEP. The antimicrobial activity results revealed that PEP loaded PCL electrospun fiber mats exhibited inhibition against Staphylococcus aureus (gram-positive) and Escherichia coli (gram-negative) bacteria. In addition, an in-vitro cell viability assay using normal human dermal fibroblast (NHDF) cells revealed improved cell viability on PCL, PCLPEP1.5, PCLPEP3, and PCLGEL6 electrospun fiber mats compared to the control (CNT) after 48 h cell culture. Our findings showed for the first time PEP loaded PCL electrospun fiber mats with antibiotic-free antibacterial activity as promising candidates for wound healing applications.

Understanding surface and interface properties of modified Ti50Zr with nanotubes

The present work is a presentation of new results about the properties of nanostructures fabricated on Ti50Zr alloy surface in the context of the new trend in dentistry to extend Zr use as an alternative for Ti restorative works in the oral cavity. As a novelty, the present manuscript promotes a nanotubular Ti50Zr surface as a better choice than other TixZr alloys with and without modified nanostructured surfaces. The discussed modified nanostructured surfaces on Ti50Zr are mixtures of Ti and Zr nanotubes oxides fabricated via two steps anodizing and an ultrasonication stage between them leading to a nano cavities structure. The final surface nanotubes texture is able to improve mechanical properties and antibacterial effect. The surface characteristics were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), contact angle and atomic force microscopy (AFM) roughness determinations. Besides SEM and XRD characterization, the AFM extended investigation, developing more knowledge about adhesive and nano-mechanical properties, is a new approach, involving also the inverse Hall-Petch effect, in understanding surface and interface, able to introduce more performance in bio-applications.

Robust Contact Angle Determination for Needle-in-Drop Type Measurements.

One of the main approaches for contact angle determination using sessile drops with a missing apex (e.g., because of the presence of the needle tip) is the polynomial drop-profile fitting method. The major disadvantage of this fitting procedure is that the derived contact angle is highly sensitive to the polynomial order and the number of pixels involved in the actual fit. In the present work, an easily implementable method is introduced to effectively tackle these drawbacks. Instead of fitting the drop-profile itself, the polynomial fitting is applied to the difference between the drop profile and the circumcircle, independently for both sides of the drop. The derivative value of this difference at the contact point is used to correct the slope obtained analytically from the circumcircle. It is shown that this approach allows the robust determination of the contact angle with high (≤0.6°) accuracy in a straightforward manner, and the results are not affected by the actual contact angle, drop volume, or the resolution of the captured image. Validation of this new approach is also given in the contact angle range of 20°–150° by comparing the results to the values calculated by the Young–Laplace fit.

Novel hydrophobic PVDF membranes prepared by nonsolvent induced phase separation for membrane distillation

Polyvinylidene fluoride (PVDF) was used for membrane preparation using the nonsolvent induced phase separation (NIPS). In this paper, the effect of the polymer concentration in the dope solution and the nonsolvent bath composition is widely investigated. In particular, the effect of increasing concentrations of ethanol in the coagulation bath on the morphology and characteristics of the membranes, as well as on their performance in membrane distillation of pure water and a brine was evaluated. FESEM analysis, coupled with contact angle determination highlighted different coagulation paths that allowed to obtain superhydrophobic membranes at higher ethanol concentrations. Moreover, the polymer concentration had major effects on the overall porosity and pore size of the membrane. By tuning the membrane preparation conditions, it was possible to obtain membranes that showed great distillate flux as well as a complete salt rejection during the vacuum membrane distillation tests.

Osteogenic Differentiation of Mesenchymal Stem Cells with Silica-Coated Gold Nanoparticles for Bone Tissue Engineering.

Multifunctional nanofibrous scaffolds for effective bone tissue engineering (BTE) application must incorporate factors to promote neovascularization and tissue regeneration. In this study, silica-coated gold nanoparticles Au(SiO2) were tested for their ability to promote differentiation of human mesenchymal stem cells (hMSCs) into osteoblasts. Biocompatible poly-ε-caprolactone (PCL), PCL/silk fibroin (SF) and PCL/SF/Au(SiO2) loaded nanofibrous scaffolds were first fabricated by an electrospinning method. Electrospun nanofibrous scaffolds were characterized for fiber architecture, porosity, pore size distribution, fiber wettability and the relevant mechanical properties using field emission scanning electron microscopy (FESEM), porosimetry, determination of water contact angle, measurements by a surface analyzer and tabletop tensile-tester measurements. FESEM images of the scaffolds revealed beadless, porous, uniform fibers with diameters in the range of 164 ± 18.65 nm to 215 ± 32.12 nm and porosity of around 88–92% and pore size distribution around 1.45–2.35 µm. Following hMSCs were cultured on the composite scaffolds. Cell-scaffold interaction, morphology and proliferation of were analyzed by FESEM analysis, MTS (3-(4,5-dimethyl thiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt) and CMFDA (5-choromethyl fluorescein acetate) dye assays. Osteogenic differentiation of MSCs into osteogenic cells were determined by alkaline phosphatase (ALP) activity, mineralization by alizarin red S (ARS) staining and osteocalcin expression by immunofluorescence staining. The results revealed that the addition of SF and Au(SiO2) to PCL scaffolds enhanced the mechanical strength, interconnecting porous structure and surface roughness of the scaffolds. This, in turn, led to successful osteogenic differentiation of hMSCs with improved cell adhesion, proliferation, differentiation, mineralization and expression of pro-osteogenic cellular proteins. This provides huge support for Au(SiO2) as a suitable material in BTE.