Wettability Modification Research Articles

Potential applications of cyclodextrins in enhanced oil recovery

• We tested the use of cyclodextrins (CD) as additives for enhanced oil recovery. • The CD decreased the oil-water contact angle for a dodecane drop immersed in brine in contact with a quartz surface. • Molecular dynamics calculations indicated that the observed effects are due to the formation of inclusion complexes at the brine/dodecane interface. In the present work, cyclodextrins (CD) were tested as potential agents for enhanced petroleum recovery. For this purpose, wettability was evaluated through a combination of experimental measurements of the contact angle of a hydrocarbon drop (dodecane) on a quartz surface and molecular dynamics (MD) simulations. The whole system was immersed in a 0.6 M NaCl aqueous solution containing the CD. Here, the dodecane, the quartz and the NaCl solution represent the oil, the rock surface and the reservoir brine, respectively, thus mimicking the situation occurring in actual oil reservoirs. It was found that the presence of the CD in the aqueous phase consistently decreased the oil–water contact angle for the dodecane drop on quartz, indicating that the CD have an effect in displacing the hydrocarbon from the rock surface. The results show that cyclodextrins are potential candidates as additives in enhanced oil recovery. Complementary, MD calculations were performed to clarify the molecular mechanisms involved in the wettability modification due to the presence of the CD. Two different strategies were employed to determine the contact angles through MD, the first of them employing the Young–Laplace equation and the second using direct geometric measurements. The calculated contact angles were in good agreement with the experimental data. The MD results suggest that the decreased contact angles are mainly due to two effects: (i) formation of inclusion complexes between the CD and dodecane at the oil:water interface; and (ii) formation of CD monolayer on the quartz surface, resulting in a decreased surface wettability for the dodecane drop.

J1130203 レーザ照射による石英表面の官能基制御

Functional group on silica surface is controlled for modification of wettability. Silica substrate is firstly terminated with trifluoromethyl group (-CF_3) by silane coupling treatment, which exhibits high hydrophobicity. The surface is then modified by laser irradiation with various power and scan speed to control quantity of released -CF_3 group. Contact angle decreases with the increasing of irradiated laser energy from 110° to 40°. The quantity of the released -CF_3 group is evaluated by X-ray photoelectron spectroscopy (XPS) and the result indicates gradual decreasing of the group. Its trend is well corresponding to the decreasing of the contact angle. Transmittance of visible light and surface morphology observed by SEM are not changed by the laser irradiation, therefore it is indicated that there is not physical damage during the modification. The proposed modification is applied to surface channel drawing by laser and purified water selectively expands within the modified area.

X-ray irradiation-induced reversible wettability modification of titanium NRAs

The reversible transition between hydrophilicity and hydrophobicity in Ti NRAs induced by alternating X-ray irradiation and ethanol immersion was revealed.

Automatic droplet transportation on a plastic microfluidic device having wettability gradient surface

This paper presents a microfluidic device that can automatically transport a droplet on a plastic plate. This device consists of a Cyclo Olefin Polymer (COP) plate and a SiO2 membrane and has wettability gradient surface. Lithographic patterns of hydrophilic SiO2 permitted wettability modification of a hydrophobic COP surface. A series of alternate hydrophobic and hydrophilic wedge-shaped patterns generated a required gradient in wettability. When we dropped a droplet on the wettability gradient surface, it moved along the wettability gradient due to an imbalance between surface tension forces acting on the opposite sides of the droplet edge. The droplet transportation test was carried out using water of 5 μl. As a result, we succeeded in automatically transporting the droplet on the SiO2/COP wettability gradient pattern. We also carried out droplet transportation in an enclosed microchannel for preventing droplet evaporation using DI (Deionized) water of 5 μl. In this case, the droplet was automatically transported by forming the wettability gradient pattern at the top and bottom in an enclosed microchannel without evaporation.

Mechanistic Study of the Wettability Modification in Carbonate and Sandstone Reservoirs during Water/Low Salinity Water Flooding

The paper pertains to the analysis of the chemical interaction between sea water ions, asphaltene colloids and silicate /calcite mineral as a substrate during water/low salinity water flooding. The work tackles modeling of salinity dependent relative permeability and capillary pressure functions from contact angle to estimate oil recovery during water/low salinity water. The paper has two main parts. In the first part, static contact angle is calculated based on disjoining pressure and compared to the experimental values, reported in the literature. In the second part, the model is used to demonstrate that water film is more stable in presence of low salinity water compared to distilled water and sea water, for carbonate and silicate minerals. Increasing temperature enhances the stability of the water film around the substrate for both types of minerals. This could be future interpreted as an indication for extra oil recovery applying low salinity water injection at elevated temperature. It is interesting to observe from the model that, increasing the Mg2+ ion concentration enhances the hydrophilicity characteristics for calcite mineral modified by asphaltene while for silicate surface modified by asphaltene, SO42- ion enhances the hydrophobicity behaviour.

Modification of the PTFE wettability by oxygen plasma treatments: influence of the operating parameters and investigation of the ageing behaviour

The effects of O2 plasma treatments on poly(tetrafluoroethylene) (PTFE) sheets are deeply investigated. The chemical modifications owing to the plasma treatment are studied by means of attenuated total reflectance Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy (XPS), while the surface topography of the plasma-treated samples is assessed by atomic force microscopy (AFM) analyses. Results are correlated with the wettability characteristics of the plasma-modified PTFE sheets, which is studied by means of contact angle (CA) and roll-off angle measurements. Finally, the ageing of the plasma-treated surfaces is investigated. The RF power input and the treatment time influence the chemical/morphological characteristics and the wettability of the plasma-treated samples. PTFE samples treated at low-power input (up to 50 W) are more hydrophilic than the untreated one. The XPS analysis reveals that OH functionalization of the outermost layers of polymeric chains decreases by increasing the RF power input, and dynamic CAs gradually increase. The AFM analysis shows a strong increase in the surface roughness as a consequence of the differential etching of the PTFE surface for samples treated at power inputs ⩾100 W, with formation of globular structures. XPS analyses of the aged samples reveal a post-plasma oxidation. However, the dynamic CAs measured after 30 days are greater than those measured immediately after treatment, and for power input ⩾100 W the aged plasma-treated PTFE surfaces are super-hydrophobic. This result suggests a decrease in the surface density of the exposed hydroxyl groups during ageing time, as a consequence of surface adaptation.

Super Hydrophobic Parylene-C Produced by Consecutive <inline-formula> <tex-math notation="TeX">${\rm O}_{2}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="TeX">${\rm SF}_{6}$ </tex-math></inline-formula> Plasma Treatment

The wetting behavior of polymeric biomaterials is of great importance for biomedical research and pharmaceutical applications. Tailoring of polymer surface wettability is particularly effective to address biomedical issues such as biofouling control and biocompatibility improvement. In this paper, we conducted comprehensive experiments and analytical modeling to understand the effects of a consecutive-O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> plasma treatment on the super hydrophobicity of parylene-C. Experimentally, super hydrophobic parylene-C surfaces with a maximum water contact angle of ~169° have been successfully achieved. Atomic force microscopy and X-ray photoelectron spectroscopy results strongly suggest that the modification of surface wettability can be attributed to the variation in surface roughness and the plasma-induced surface chemistry. Analytically, a transition of droplet status from the Wenzel state to the Cassie state on hydrophobic parylene-C surfaces has been demonstrated after sufficient roughening by O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> plasma pre-treatment. The surface morphology of plasma-treated parylene-C films has also been analyzed and the hexagonal-close-packed model of downward crowns shows the best agreement with experimental results. Our simple and time-efficient treatment eliminates the need for creating well-defined patterns, is completely compatible with conventional microfabrication techniques, and can also be applied to curved parylene surfaces.

Preparation of TiO&lt;sub&gt;2&lt;/sub&gt; Nanotube Array by Anodic Oxidation Method and its Wetting Applications

In the overreview, the effects of anodic oxidation parameters on the characterstics of TiO2 nanotube array are discussed at first. Then, the wettability modification methods of the TiO2 nanotube array and its application in anit-corrosion, photocatalysis and medical science are presented.

Electron beam induced surface modifications of PET film

The semi-crystalline poly (ethylene terephthalate) PET film was treated by low energy electrons with different fluences and the surface wettability modification is investigated. Contact angle technique is employed to prove PET surface wettability enhancement. The contact angle decreases due to alteration of surface chemistry, morphology and free energy after electrons irradiation. Fourier transform infrared spectroscopy (FT-IR) shows the creation of polar groups on the surface which are responsible for surface wettability improvement. Atomic force microscope (AFM) observations reveal that the surface roughness changes after electrons–PET interactions. Surface free energy analysis has been observed as well. Low energy electrons irradiation of PET film improves and controls its wettability, adhesion and then biocompatibility.

Numerical Simulation of Surfactant Flooding in Darcy Scale Flow

One of the methods that is used nowadays in enhanced oil recovery is surfactant flooding. The main mechanisms of surfactant flooding in reservoir consist of reduction of interfacial tension between water and oil and modification of rock wettability. In this study, the authors simulate the surfactant injection process in Darcy scale and in one-dimensional, multicomponent, multiphase state, and effects of physical phenomena such as adsorption, dispersion, convection, and exchange between fluids and solids are considered. Wettability alteration of reservoir rock due to presence of surfactant in injected fluid is detected in relative permeability and capillary pressure curves. First, the authors express the governing flow equations in the system and then discretize them. The variables consist of water and oil saturations, surfactant concentration in water phase, water and oil pressures, and velocities in each block. Second, the discretized equations are solved by IMPES method and pressure and saturation variables are calculated and after that, the concentration of surfactant in water phase is calculated. Finally, results of simulation are shown.

Nucleate pool boiling heat transfer augmentation on hydrophobic self-assembly mono-layered alumina nano-porous surfaces

In this study, we have observed substantial pool boiling heat transfer augmentation by creating one-dimensionally grown Alumina Nano Porous Surface (1-D ANPS). Pre-organized numerous nano pores have structural uniqueness such as enlarged surface area, increase in active nucleation sites, and liquid thin film evaporation at vapor–liquid menisci of the pore mouth. At the same time, the surface wetting of a cylindrical heater is modified with a hydrophobic Self-Assembled Monolayer (SAM) coating. Enhanced water contact angle of the 1-D ANPS yields substantial active nucleation site increase by preventing liquid impregnation into nano pores, which play a role of trapping non-condensible gas. The combination of structural uniqueness of the 1-D ANPS and surface wettability modification achieves significant heat transfer coefficient (HTC) enhancement in the nucleate pool boiling regime. Also, HTC improvement is closely related to bubble interactions on the cylindrical heating surface while they are moving along the periphery. For a hydrophobic surface, bubble sweeps along the heater periphery and efficiently removes adjacent premature bubbles. It leads to reduced waiting time. Enlarged bubbles carry more heat from the surface and yield huge internal/external convection. In order examine bubble motions, an analytical model and high speed camera were used.

Membranes with tailored wettability properties for the generation of uniform emulsion droplets with high efficiency

Membrane emulsification is a promising technology for the production of micro–nano particles, which is able to compete with the conventional mechanical emulsification processes. The production of emulsions with narrow droplet size distribution at dispersed phase fluxes (productivity) sufficiently high to make the process suitable for industrial application is still a considerable challenge. The interfacial tension between the dispersed phase and the membrane pore wall is a crucial parameter to maintain droplets shape while enhancing productivity. In the present paper, a membrane thickness with asymmetric properties in terms of wettability between external and internal sides has been tested in the preparation of W/O emulsions. The membrane surface wettability modification was obtained by adsorption of hydrophobic macromolecules on the lumen side of hydrophilic membrane. Lipase was used as a model macromolecule. W/O emulsion droplets with smaller droplets size have been produced with lipase-loaded membrane compared with the unmodified hydrophilic membrane. High dispersed phase flux of 30Lh−1m−2 was also obtained with a significant increase of process productivity compared to the use of hydrophobic membranes. These results show that membrane–protein interaction can be used to functionalize opportunely the membrane for membrane emulsification application reducing emulsification time and increasing dispersed phase flux without modifying the control on droplets properties in terms of size and size distribution.

Formation and characterization of hydrophobic glass surface treated by atmospheric pressure He/CH4 plasma

Atmospheric pressure helium plasmas, generated in the open air by 13.56 MHz rf power, were applied for the glass surface wettability modification. The plasma gas temperature, measured by the spectroscopic method, was under 400 K which is low enough to treat the samples without thermal damages. The hydrophobicity of the samples determined by the water droplet contact angle method was dependent on the methane gas content and the plasma exposure time. Adding the methane gas by a small amount of 0.25%, the contact angle was remarkably increased from 10° to 83° after the 10 s plasma treatment. From the analysis of the treated surface and the plasma, it was shown that the deposition of alkane functional groups such as C-H stretch, CH2 bend, and CH3 bend was one of the contributing factors for the hydrophobicity development. In addition, the hydrophobic properties lasted over 2 months even after the single treatment. From the results, the atmospheric pressure plasma treatment promises the fast and low-cost method for the thermally-weak surface modification.

Wettability characterization and adhesion enhancement of arc-treated surface of aluminum alloys

The aim of this study is to determine the wettability-enhancing effects of an atmospheric pressure, direct current (DC) plasma arc discharge on the surface of aluminum alloys. Wettability is a critical factor in engineering applications such as biomedical implants, painting, and adhesive bonding. For example, in the realm of adhesive bonding, greater wettability improves a metal substrate's attraction to an adhesive material and results in a higher bond quality. In this study, the contact angle was determined and compared as a measure of the wettability using two different techniques: the sessile drop and the ballistic deposition with water as a test liquid. The effect of different arc discharge process parameters on the wettability, including arc current and plasma torch velocity, was studied. A two-dimensional finite element analysis based on the volume-of-fluid model was carried out to explore the behavior of droplet (e.g., spreading and stabilization) on an ideal surface. Additionally, the values of the dynamic receding contact angle were measured through the simulation by applying the tilted plate method and considering the surface roughness to compare the results with the values obtained from the ballistic deposition method. Studying the wettability alteration of the surface of aluminum alloys subjected to the arc treatment revealed the wettability reduction over time. Additionally, it was found that there was a linear correlation between the contact angle value and the strength of adhesively bonded joints using two structural adhesives. The results of this study in the wettability modification of aluminum subjected to the arc treatment and wettability alteration of the treated substrate over time may be used as a quality assurance tool to design the production process and achieve the desired quality and strength in adhesively bonded joints.

Design of Biomimetic and Bioactive Cold Plasma-Modified Nanostructured Scaffolds for Enhanced Osteogenic Differentiation of Bone Marrow-Derived Mesenchymal Stem Cells

The objective of this study was to design a biomimetic and bioactive tissue-engineered bone construct via a cold atmospheric plasma (CAP) treatment for directed osteogenic differentiation of human bone morrow mesenchymal stem cells (MSCs). Porous nanocrystalline hydroxyapatite/chitosan scaffolds were fabricated via a lyophilization procedure. The nanostructured bone scaffolds were then treated with CAP to create a more favorable surface for cell attachment, proliferation, and differentiation. The CAP-modified scaffolds were characterized via scanning electron microscope, Raman spectrometer, contact angle analyzer, and white light interferometer. In addition, optimal CAP treatment conditions were determined. Our in vitro study shows that MSC adhesion and infiltration were significantly enhanced on CAP modified scaffolds. More importantly, it was demonstrated that CAP-modified nanostructured bone constructs can greatly promote total protein, collagen synthesis, and calcium deposition after 3 weeks of culture, thus making them a promising implantable scaffold for bone regeneration. Moreover, the fibronectin and vitronection adsorption experiments by enzyme-linked immunosorbent assay demonstrated that more adhesion-mediated protein adsorption on the CAP-treated scaffolds. Since the initial specific protein absorption on scaffold surfaces can lead to further recruitment as well as activation of favorable cell functions, it is suggested that our enhanced stem cell growth and osteogenic function may be related to more protein adsorption resulting from surface roughness and wettability modification. The CAP modification method used in this study provides a quick one-step process for cell-favorable tissue-engineered scaffold architecture remodeling and surface property alteration.

Alkyl- and fluoroalkyltrialkoxysilanes for wettability modification

Alkyl- and fluoroalkyltriethoxysilanes were investigated as potential surface modifiers. Many aspects concerning trialkoxysilanes were discussed, starting from hydrolysis of silanes in water solutions, the effect of this hydrolysis on the surface tension, wettability of the modified surface to the morphology of the modified surface.Surface tension and contact angle measurements as well as scanning electron microscopy were used to characterise alkyl- and fluoroalkyltriethoxysilanes and their ability to modify the wettability of glass. The effect of such modification was superhydrophobic surface with high values of contact angles. Superhydrophobic behaviour was observed as a result of two-step modification providing increased surface roughness thanks to the use of different size silica particles and surface chemical modification with fluorosilane molecules.

Enhancing the onset of pool boiling by wettability modification on nanometrically smooth surfaces

Pool boiling experiments are performed with degassed water on highly smooth surfaces of two different wettabilities: hydrophilic and hydrophobic cases. Boiling curves and visual observations on the boiling have been performed. The onset of nucleate boiling (ONB) has been measured and the influence of the wettability has been quantified. As the inherent mean roughness of the glass substrates was lower than one nanometer it was possible to show the sole effect of the wettability. No hysteresis in the boiling curve was observed for both cases. The ONB was observed after 3.5°C superheat on the hydrophobic case and the heat transfer coefficient (HTC) changed suddenly from the one of a convection regime (1.5kW/m2K) to the one of a nucleate boiling regime (4kW/m2K). On the contrary for the hydrophilic case, despite superheat above 37°C and presence of boiling, the HTC was kept as the one of the convection regime.

A novel main chain benzoxazine polymer with the ability of UV-induced self-surface modification

In this paper, a series of benzophenone-based polybenzoxazine (PBD) was synthesized through the formation of oxazine rings, and the structures of the obtained polymers were confirmed by FTIR, 1H NMR and UV–visible analysis. As the existence of benzophenone units in the main chain, PBD could initiate photopolymerization of various monomers. The photo-initiative behavior of PBD was tested by differential scanning photocalorimetry, which shows the high photopolymerization efficiency. Meanwhile, PBD could be used as film substrates for initiating photopolymerization of the monomers and change the surface performance without additional initiator. Through this method, the surface properties of PBD film could be tailored conveniently. The surface wettability modifications through the surface photo-polymerization of styrene (St) and N-isopropyl acrylamide (NiPAM) were carried out for example, and the surface properties were investigated by water contact angle measurements (WCA), X-ray photoelectron spectroscopy (XPS) and Atom Force Microscopy (AFM) and the results showed that the surface properties PBD film could be well designed by selecting different kind of monomer through photopolymerization to realize an easy-tuned surface with desired wettability required.

Atmospheric pressure plasma with a flat spiral electrode

Abstract A new kind of electrically isolated flat spiral electrode for generating homogeneous atmospheric pressure plasmas is proposed. A sinusoidal voltage (5 kVpk–pk, 48 kHz) has been applied to the electrode. The high voltage is generated with a dc supply voltage of only 4 V, based on the electrical characteristics of a resonant circuit. Plasma was generated in closed spaces in helium with air impurities, with or without using a second grounded electrode. The gas temperature was of around 324 K and the plasma was tested for the paperboard hydrophilicity and transparent film for printer wettability modifications.

激光辐照改变几种氧化物单晶表面浸润性的研究

激光辐照改变几种氧化物单晶表面浸润性的研究