Water Drop Contact Angle Research Articles

A Study on Water Repellent Effectiveness of Natural Oil-Applied Soil as a Building Material

This study was performed to investigate the water repellent effectiveness of natural oil-applied soil when it is used as a building material. Natural oil types such as olive oil, bean oil, perilla oil and linseed oil, which are being used for producing water repellent timber, are selected for the experiments. It is expected that perilla oil and in seed oil, which are drying oil types will have better water repellent effectiveness than the other types. For the evaluation of water repellence of natural oil-applied soil, a contact angle test was performed. A contact angle of water drop on various surface conditions were tested, and large differences were seen between the natural oil-applied soil and untreated soil. As a result, it is showed that all natural oil types have water repellent effectiveness. However, linseed oil, which is a drying oil type, shows an outstanding water repellent effectiveness value, while perila oil, which is also a drying oil type, shows the lowest value. Additionally, results show that there is no link between water repellent effectiveness and the number of applications of natural oil. Nevertheless, existing commercial water repellents show better performance than natural oil, and it is anticipated that the results of this study will provide essential information for further research to enhance the water repellent effectiveness of soil as a building material.

Advantages and disadvantages of the addition of graphene nanoplatelets to epoxy resins

Graphene nanoplatelets (GNPs), in different contents, are added to epoxy resin. This work mainly consists of a deep characterization of the composites in order to evaluate their behavior regarding neat epoxy resin. In fact, their main properties, such as their morphological features, their thermo-mechanical and mechanical properties, their electrical conductivity and thermal diffusivity, their hydrophobic behavior and their barrier properties have been studied. It is confirmed that the GNP addition induces an important stiffing of thermosetting resin. However, the rest of mechanical properties, strength and elongation, are diminished due to a weak interface formed between the epoxy matrix and non-functionalized GNPs. The electrical conductivity and thermal diffusivity show an important increase. Electrical conductivity increases several orders of magnitude from a minimum value of percolation while the thermal diffusivity increases proportionally to GNP content. Other advantage of the GNP addition is the increase of the hydrophobic behavior of the composites, determined by measurements of contact angle of water drops. Finally, GNP/epoxy composites present higher barrier properties in humid environments. The addition of GNP decreases the maximum water content absorbed and the diffusion coefficient. However, this enhancement is not too large due to the weak interface and therefore the presence of hollows in the GNP/epoxy composites.

Surface memory effect enhanced by atmospheric pressure plasma jet treatment for liquid crystal alignment

In the present work we tried to study Polyimide (PI) film surface memory effect (SME) enhanced by atmospheric pressure plasma jet (APPJ) treatment for liquid crystal (LC) alignment. To evaluate and describe structural changes on the PI film surface, contact angle measurements and Fourier Transformed Infrared (FTIR) Spectroscopy methods were used. After each treatment cycle, the water drop contact angle to the treated surface decreases and FTIR spectra show an increase of CO bonds. When LCs in mesophase are injected into a cell flow alignment occurs, and SME imprints the LC flow alignment pattern onto the surface. Some materials like glass and PI films naturally have SME to some degree; however, in our work we show that treatment by APPJ leads to the enhancement of this effect. Kinetics of the alignment pattern imprinting process was investigated by varying the incubation duration, and at room temperature the minimum required time for the imprinting alignment pattern was found to be 20min. It was shown that the imprinted alignment of LCs on APPJ treated PI films has excellent heat resistance up to 150°C.

Single-Molecule Spectroscopic Imaging Studies of Polarity Gradients Prepared by Infusion-Withdrawal Dip-Coating

Sol–gel-derived thin films incorporating a one-dimensional polarity gradient are prepared by infusion-withdrawal dip-coating (IWDC) and characterized by single-molecule spectroscopic (SMS) imaging. Nonpolar phenyltrimethoxysilane (PTMOS) and polar tetramethoxysilane (TMOS) are used as precursor silanes during IWDC. Sessile drop water contact angle measurements demonstrate the presence of a wettability gradient in the resulting films, on macroscopic length scales. Raman maps of the phenyl C–H stretch at 3059 cm–1 confirm gradient formation. Material polarity is assessed by SMS imaging, using Nile Red as a polarity-sensitive probe. Polarity data are obtained by recording fluorescence videos of single-molecule emission simultaneously in two spectral bands (590 ± 20 and 640 ± 20 nm). The pairs of fluorescence spots produced by each molecule are identified and analyzed using automated spot-tracking software. The local film polarity is quantified via the Clausius–Mossotti factors calculated from the single-mole...

“Coffee ring” formation dynamics on molecularly smooth substrates with varying receding contact angles

A systematic study of “coffee-ring” formation dynamics was carried out using chemically and physically well-controlled substrates and colloids. Clean silicon wafers were reacted with tris(trimethylsiloxyl)chlorosilane in the vapor phase to yield molecularly smooth substrates with advancing and receding contact angles up to 84°/74° (θA/θR) and a constant hysteresis of 12±2°. Monodisperse gold nanoparticles (AuNPs) of 15nm in diameter were stabilized and functionalized with poly(vinyl alcohol) (PVOH) of 9nm in thickness in aqueous solution. The evolution of contact angle and contact diameter of water and colloid-containing drops on clean and modified silicon wafers was assessed as sessile drops evaporated. PVOH-AuNPs in the colloid-containing drop increase the energy barrier for contact line depinning and the pinning force. There are up to four drying stages for colloid-containing drops, initial pinning, depinning, secondary pinning, and final evaporation. The contribution of each stage to evaporation depends on substrate receding contact angle. It is established in this study that the secondary pinning is unique for colloid-containing drops and is only observed on substrates with receding contact angles greater than 35°. “Coffee rings” are formed on all modified silicon wafers, but not on clean silicon wafers with contact angles of 0°/0°.

Relationship between the severity, persistence of soil water repellency and the critical soil water content in water repellent soils

Soil water repellency (SWR) causes reduced soil water storage and enhanced runoff and reduced ecosystem productivity. As such, characterization of SWR is a prerequisite for effective environmental management. The objectives of this study were to determine the relationship between the severity of SWR and its persistence and to determine the soil critical water content (CWC). Soils were collected from thirteen soil sites; five from natural jack pine (Pinus banksiana) ecosites (AE1, AE2, SV 10, 26 and 27), six from reclaimed/disturbed sites (ALFH, CPA, SS trial, ATS, SCB, and SW30) located in the Athabasca Oil Sands region and two from agricultural sites (Goodale and Melfort) in Central Saskatchewan, Canada. The severity of SWR as a function of persistence was assessed by measuring the change of water drop contact angles (modified sessile drop method) with time (WDPT, water drop penetration time). The CWC was determined for all the soils by measuring water drop contact angles on soils with predetermined water contents from oven dried to 20% (kgkg−1). In natural, reclaimed and agricultural soils, a high severity (contact angle) of repellency does not necessarily denote long persistence (WDPT) or high CWC. Measurement of severity and persistence is related to the differences and changes in surface energy between water and the soil surface respectively. Although the CWC gives us the water content at which above it SWR is negligible, the trend between contact angle and increasing water content proved to be more informative. Characterizing and understanding the severity, persistence and CWC together are valuable when determining the effects of SWR on hydrological processes as they have different mechanisms compared to one another.

Coating a polystyrene well-plate surface with synthetic hematite, goethite and aluminium hydroxide for cell mineral adhesion studies in a controlled environment

Iron and aluminium oxides are available in many climatic regions and play a vital role in many environmental processes, including the interactions of microorganisms in contaminated soils and groundwater with their ambient environment. Indigenous microorganisms in contaminated environments often have the ability to degrade or transform those contaminants, a concept that supports an in situ remediation approach and uses natural microbial populations in order to bio-remediate polluted sites. These metal oxides have a relatively high pH-dependent surface charge, which makes them good candidates for studying mineral–bacterial adhesion. Given the importance of understanding the reactions that occur at metal oxide and bacterial cell interfaces and to investigate this phenomenon further under well-characterized conditions, some of the most common iron and aluminium oxides; hematite, goethite and aluminium hydroxide, were synthesized and characterized and a coating method was developed to coat polystyrene well-plates as a surface exposable to bacterial adhesion with these minerals (non-treated polystyrene-12 well-plates which are used for cell cultures). The coating process was designed in a way that resembles naturally coated surfaces in aquifers. Hematite, Fe2O3, was synthesized from acidic FeCl3 solution, while goethite, FeOOH, and aluminium hydroxide, Al(OH)3, were prepared from an alkaline solution of Fe(NO3)3 and Al(NO3)3. They were further characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), potentiometric titration and contact angle measurements. Characterization results show that the pure phases of hematite, goethite and aluminium hydroxides are formed with a point of zero charge (PZC) of 7.5, 8.5 and 8.9, respectively. The coating process was based on the direct deposition of mineral particles from an aqueous suspension by evaporation. Then, altered polystyrene surface properties were analyzed using X-ray photoelectron spectroscopy (XPS), attenuated total reflection-Fourier transform infrared (ATR-IR), water drop contact angle measurements and vertical scanning interferometry (VSI). The surface analysis tests prove that the coated polystyrene surface has physicochemical properties that are similar to the reference synthetic hematite, goethite and aluminium hydroxide minerals. These prepared and well-characterized mineral well-plates are similar to naturally occurring surfaces in aquifers and enable us to study the different steps of bacterial adhesion and biofilm formation on these metal oxides under laboratory-controlled conditions.

Surface Modification of Castor Oil‐Based Polyurethane by Polyacrylic Acid Graft using a Two‐Step Plasma Treatment for Biomedical Applications

ABSTRACTThe aim of this study is design and prepare medical grade polyurethane (PU) film based on castor oil without any additives. Acrylic acid (AAc) was grafted onto the surface of PU films using a two‐step oxygen plasma treatment. The first step of this method includes oxygen plasma pretreatment of the PU films, immersion in AAc monomeric solution, removal from the solution, and drying. The second step was carried out by plasma polymerization of preadsorbed reactive monomers on the surfaces of dried pretreated films. The effects of pretreatment time length and monomer concentration were studied on AAc graft amount. The surface of the modified PU films were characterized using attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy, scanning electron microscopy (SEM), and water drop contact angle measurements. The ATR‐FTIR results proved that the carbonyl (CO) and hydroxyl groups (OH) of AAc give rise to an absorption peak at 1698 cm–1, which was observed in the spectra of the modified PU. The SEM micrographs showed that poly(acrylic Acid) (PAAc)–grafted PU films have a different pattern compared with nonmodified PU films. Moreover, it was found that a decrease in contact angle indicated to a higher grafting amount of polymer. Finally, L929 fibroblast cell culture was done onto the PAAc–PU films. It was observed that cells are spherical and not uniformly distributed on the modified polymer surface.

Static contact angle algorithm selection for superhydrophobic surface hydrophobicity detection

The static contact angle calculation for superhydrophobic surfaces is systematically investigated. The water drop profiles with different volumes, contact angles, rotational angles and apex coordinates are numerically generated based on the Laplace equation. Thereafter, the goniometry, θ/2 method, circle and ellipse fitting algorithms and an improved axisymmetric drop shape analysis-profile (ADSA-P) algorithm are used to calculate the static contact angle. The results reveal that the contact angle errors by the θ/2 method, circle and ellipse fitting algorithms increase with the drop volume/contact angle. The goniometry will introduce significant error. The ADSA-P algorithm can accurately obtain the contact angles (error < 0.3°) for the drop profiles regardless of the water drop volume, contact angle, rotational angle and apex coordinate. The ADSA-P algorithm should be selected to calculate the static contact angles for the superhydrophobic surfaces. Static contact angle measurements of the superhydrophobic surfaces validate the aforementioned analysis.

In-vitro wettability of four silicone hydrogel lenses with differing surface properties

Purpose: To determine and compare the advancing sessile drop water contact angles (CAs) of four silicone hydrogel (SH) materials which utilise differing approaches to enhance wettability. These included a material that is plasma oxidized (balafilcon A), one with a plasma coating (lotrafilcon B), one with an internal wetting agent (senofilcon and also an untreated/unmodified material (comfilcon A).

Immobilization of [60]fullerene on silicon surfaces through a calix[8]arene layer

In this work, we report the functionalization of flat Si(100) surfaces with a calix[8]arene derivative through a thermal hydrosilylation process, followed by docking with [60]fullerene. Chemical grafting of calix[8]arene on silicon substrates was evaluated by X-ray photoelectron spectroscopy, whereas host-guest immobilization of fullerene was demonstrated by atomic force microscopy and sessile drop water contact angle measurements. Surface topographical variations, modelled on the basis of calix[8]arene and [60]fullerene geometrical parameters, are consistent with the observed morphological features relative to surface functionalization and to non-covalent immobilization of [60]fullerene.

Adhesion and Growth of Vascular Smooth Muscle Cells on Nanostructured and Biofunctionalized Polyethylene.

Cell colonization of synthetic polymers can be regulated by physical and chemical modifications of the polymer surface. High-density and low-density polyethylene (HDPE and LDPE) were therefore activated with Ar+ plasma and grafted with fibronectin (Fn) or bovine serum albumin (BSA). The water drop contact angle usually decreased on the plasma-treated samples, due to the formation of oxidized groups, and this decrease was inversely related to the plasma exposure time (50–300 s). The presence of nitrogen and sulfur on the polymer surface, revealed by X-ray photoelectron spectroscopy (XPS), and also by immunofluorescence staining, showed that Fn and BSA were bound to this surface, particularly to HDPE. Plasma modification and grafting with Fn and BSA increased the nanoscale surface roughness of the polymer. This was mainly manifested on HDPE. Plasma treatment and grafting with Fn or BSA improved the adhesion and growth of vascular smooth muscle cells in a serum-supplemented medium. The final cell population densities on day 6 after seeding were on an average higher on LDPE than on HDPE. In a serum-free medium, BSA grafted to the polymer surface hampered cell adhesion. Thus, the cell behavior on polyethylene can be modulated by its type, intensity of plasma modification, grafting with biomolecules, and composition of the culture medium.

Hydrophobic properties of cardboard coated with polylactic acid and ethylene scavengers

The corrugated cardboard used in food packaging readily absorbs moisture from the environment, especially when stored under high humidity conditions. In this research, the water barrier of cardboard was modified by changing the wettability of the cardboard surface, applying hydrophobic coatings of polylactic acid (PLA), alone or in combination with other substances that absorb gases (ethylene scavengers) such as clinoptilolite (C), sepiolite (S), and sepiolite permanganate (SP). The water barrier properties tested as water vapor permeability (WVP), water absorptiveness (WA), and water drop contact angle (CA) showed that the water resistance of the resulting cardboard was improved by the coating. The best results of these properties were obtained by using a coating of PLA 2% alone. In addition, PLA 2% with C 1.5% also showed good results, but the WA results were higher. The use of PLA coating produces a greater uniformity and smoothness of the coated cardboard surface due to the best filling of the pores or spaces between cellulose fibers. Our findings and the environmentally friendly nature of PLA strengthen the advantages of using these kinds of coatings on cardboard trays for the packaging, storage, and transport of foods such as fresh fruit and vegetables.

Effectiveness of Asphalt Rejuvenator

Abstract This paper presents an evaluation of maltene rejuvenator effectiveness. The rejuvenator was applied on the U.S.-40 highway in Henry County, IN, and its performance was monitored and evaluated using four different evaluation methods: (1) friction, (2) permeability test, (3) dynamic shear rheometer, and (4) contact-angle test. The results demonstrate that the rejuvenator has no significant effects on pavement permeability. However, the rejuvenator reduced the moduli (i.e., dynamic shear modulus, viscous modulus, and elastic modulus), increased the phase angle, and increased the water drop contact angle of the asphalt binder. The influence depth of the rejuvenator was approximately 12.5 mm from the surface for the test section. The influence life of the rejuvenator lasted longer than 391 days. Even though all average friction numbers (FNs) throughout the measurement period were above the INDOT minimum requirement (i.e., &amp;gt;20 FN), this depended to a large extent on the surface friction of the existing pavement before applying the rejuvenator. There was a significant FN reduction of a maximum of 47 % within a day after the application of the rejuvenator. Based on the friction performance, a friction test on existing pavements should be required prior to application of the rejuvenator. A pavement with a low FN should not receive the rejuvenator application.

Thermo-molded biocomposite from cassava starch, natural fibers and lignin associated by laccase-mediator system

Treatment of cellulose fibers and lignin by laccase-mediator system was conducted to enhance the binding efficiency of natural fibers and lignin compounds into cassava starch composite matrix. Violuric acid (VA) was tested for its effect as a mediator for laccase treatment. Influence of different fiber, lignin and water contents of biocomposite was statistically investigated. The results showed that adding 15% (w/w) fibers into biocomposite at 44% (w/w) water content increased flexural strength and modulus for 4 times compared with the control. A combination of fibers+VA gave the greatest enhancement of modulus for 1140% and flexural strength for 375.8% as much as neat starch biocomposite. The presence of fibers, lignin and VA as mediator for laccase treatment substantially enhanced water resistance of starch biocomposite detected by a change in water drop contact angle on biocomposite surface.

Amphiphiles as hydrophobicity regulator: Fine tuning the surface hydrophobicity of an electropolymerized film

Smart clean surfaces exhibiting reversible superhydrophilic to superhydrophobic transitions have been widely fabricated. A myriad of complex fabricating procedures have evolved over the years. Here, we demonstrate an apparently simple approach, wherein we utilized the attractive interaction between an unfabricated electropolymerized film and negative charge bearing amphiphilic molecules to precisely control the hydrophobicity of the surface of the film. We also demonstrate the use of different hydrophobic molecules to plug the voids created by the uneven distribution of the attached amphiphiles’ long hydrocarbon tails on the film surface. Water drop contact angle revealed that by the used technique, surface hydrophobicity can be tuned to any desired value. Moreover, the film surface exhibited a high adhesive force toward the water droplets, thus preventing them from rolling or dropping down. In addition, the tuning process can be completely reversed and repeated by altering the applied potential. The interaction between the amphiphiles and the film surface was confirmed by ATR-IR. Scanning electron micrographs revealed that the film surface underwent no morphological modifications upon interaction with the amphiphiles.

A Static Contact Angle Algorithm for Silicone Rubber Aging Experiments

To improve the accuracy of the static contact angle measurement in the silicone rubber aging experiments, a high accurate contact angle algorithm in combination with the circle fitting algorithm and ellipse fitting algorithm is proposed. The influence of the water drop volume and noise on the calculation accuracies of the two algorithms are analyzed. The results reveal that the circle fitting algorithm is more suitable for the images with small water drop volume and contact angle. However, the ellipse fitting algorithm is more suitable for the images with relatively large water drop volume and contact angle. The critical water drop volumes of the two algorithms in different hydrophobicities are obtained by the calculation of contact angle by the two algorithms. And it is used to select which algorithm to calculate contact angles in the proposed algorithm. The tangent line method, θ/2 method, circle fitting algorithm, ellipse fitting algorithm, and proposed algorithm are implemented. The numerically generated water drop profiles and real water drop images of aged silicone rubber are used to validate the new algorithm. The results indicate that the proposed algorithm is more accurate than the other algorithms in different water drop volumes, contact angles, and noise levels.

Chitosan/heparin surface modified polyacrylic acid grafted polyurethane film by two step plasma treatment

The aim of this study is to design an artificial skin dress. A multilayer skin dressing included synthesised castor oil based polyurethane (PU) as the outer layer and two biopolymeric layers of heparin and chitosan as the inner layers were prepared. The surface of PU film was activated using two steps oxygen radio frequency plasma treatment. The surface of the modified PU films characterised by attenuated total reflection Fourier transform infrared spectroscopy, scanning electron microscopy and water drop contact angle measurements. Scanning electron microscopy observations confirmed the presence of grafted poly acrylic acid on the surface of PU films. Also, heparin and chitosan were immobilised on PU films. In vitro cell culture showed that the samples have an excellent biocompatibility with L929 fibroblast cells. Cell adhesion and proliferation of cells on the chitosan/heparin immobilised surfaces showed better behaviours compared with poly (acrylic acid) grafted PU film.

Enrichment in hydrophobicity and scratch resistant properties of silica films on glass by grafted microporosity of the network

A simple fabrication method towards a novel morphology followed by hydrophobic and pencil scratch resistant film based on silica nanoparticles was successfully achieved from methyltrimethoxysilane on glass by spin coating technique. The polyvinyl alcohol was employed for grafting the microporous network of the silica nanoparticles. The enrichment in hydrophobicity and pencil scratch resistance properties of the silica nanoparticles was achieved by adapting a polymer route. Since, the silica particles are in the nanometer size the films are excellent in transmission of light in the visible region. The water drop contact angle was high, up to ~169 ± 1°, for 10 μL volume of water and the sliding angle was achieved minimum to 5 ± 1°. Non-wetting property was tested by keeping the film in the humidity chamber for over 60 days. The silica film demonstrated resistance to scratches by a pencil of 4 H grade as per the ASTM D 3363 method. The feasible potential approach towards the fabrication of the superhydrophobic silica film with tailored nanoporous network and scratch resistant assets is indispensable for many practical applications.

Synthesis and properties of polycarbonate-co-poly(siloxane-urethane-siloxane) block copolymers

Polycarbonate-co-poly(siloxane-urethane-siloxane) block copolymers (SiUrPC) were synthesized from siloxane-urethane monomer and polycarbonate (PC) oligomer, and their properties were compared with those of linear Bisphenol A PC (BPA-PC) and siloxane PC (SiPC). The synthesized polymers were characterized by 1H NMR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and gel permeation chromatography (GPC). The contact angle of the sessile water drop onto the polymer films was also measured. The thermal and mechanical properties of SiUrPC differed from those of BPA-PC and SiPC. SiUrPC exhibited superior flow properties and lower wettability than BPA-PC. Open image in new window