Stable Contact Angle Research Articles

Enhanced buoyancy and propulsion in 3D printed swimming micro-robots based on a hydrophobic nano-fibrillated cellulose aerogel and porous lead-free piezoelectric ceramics

This paper provides the first demonstration of additively manufactured swimming micro-robots which combine a hydrophobic nanofibrillated cellulose aerogel, to provide long-term buoyancy, with a low acoustic impedance porous piezoelectric ceramic for improved propulsion. The hydrophobic nanocellulose aerogel is shown to exhibit a high and stable contact angle that was maintained for extended periods of time, which facilitates long-term and stable buoyancy of the micro-robot. To quantify the benefits of introducing porosity into the active piezoelectric element, a new analysis model was developed to inform material design and maximize the acoustic propulsion force. Detailed characterisation and modelling of the swimming robots demonstrated that a swimming robot based on a lead-free porous Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramic exhibited a higher acoustic radiation propulsion force and a faster swimming speed compared to a robot fabricated using a dense ceramic element. These benefits were associated with the lower elastic modulus, density and acoustic impedance of the porous piezoelectric material. The lower dielectric constant, reduced device capacitance, and lower resonant frequency of the porous piezoelectric element also significantly reduced the driving current and power requirements of the robot. This work therefore provides new insights on the impact of hydrophobic and acoustically matched piezoelectric materials on the performance of swimming micro-robots, and successfully demonstrates the use of porosity to improve acoustic impedance matching of resonant piezoelectric devices, such as micro-robots and ultrasonic transducers.

Hydrophobic Aerogels from Vinyl Polymers Derived from Radical Polymerization: Proof-of-Concept.

Hydrophilicity is one important drawback of bio-based aerogels. To overcome this issue, a novel approach for the preparation of mesoporous, water repellent aerogels is introduced, which combines synthesis of cross-linked bio-based copolymers from methacrylate copolymerizations, followed by solvent exchange and supercritical drying steps. The influence of monomers with different nonpolar ester groups (methyl, vanillin, tetrahydrofurfuryl) on textural properties and water contact angles of the dry products is assessed. Final aerogels show generally high overall porosities (≈96%), low densities (0.07-0.11gcm-3) as well as fine, mainly mesoporous networks, and specific surface areas in the range of 120-240m2g-1. Hereby, choice of the methacrylate ester groups results in differences of the resulting pore-size distributions. Water repellency tests show stable static water contact angles in the hydrophobic range (≈100°) achieved for the substrate containing the vanillin ester group. On the contrary the other substrates absorb water quickly, which indicates a decisive role of the ester group. The presented approach opens up a new pathway to bio-based aerogels with intrinsic hydrophobicity. It is suggested that the properties are tailored by the choice of the monomer structure, hence enabling further adaption and optimization of the products.

Hierarchical 0D CuO Wrapped by Petal-like 2D ZnO: A Strategic Approach of Superhydrophobic Melamine Sponge toward Wastewater Treatment.

In addressing the pressing environmental challenges posed by frequent oil spills, this work presents a novel approach of synthesizing a superhydrophobic three-dimensional (3D) porous melamine sponge (MS). CuO and ZnO nanoparticles were grown on the MS via a hydrothermal method to create MS/CuO/ZnO with multiscale hierarchical nanostructures. The resulting material exhibited a stable water contact angle of 155° through various tests. MS/CuO/ZnO demonstrated exceptional oil absorption capacities (40-145 g/g and 0.83-0.99 mL.cm-3), surpassing 98% efficiency in oil separation, and retained reusability for 10 cycles. Impressively, the sponge achieved successful separation of oil/water emulsions with a permeation flux of 14870 L m-2 h-1. The composite sponge, distinguished by its high photodegradation ability, can degrade both water- and oil-targeted pollutants under visible light irradiation from light-emitting diode (LED). With its remarkable attributes including superior oil absorption, excellent oil/water separation, mechanical resistance, and excellent photocatalytic ability, it exhibits considerable potential for applications in both wastewater treatment and large-scale marine oil spill response. The easily prepared MS/CuO/ZnO emerges as a versatile solution capable of addressing pressing challenges and marking a significant leap toward sustainable and impactful environmental remediation.

Upcycling of waste brick powder and PET as robust and flexible Janus membrane with asymmetric wettability for switchable emulsion separation

Superwetting membranes were widely studied in the field of oil/water separation due to their excellent separation efficiency and good recoverability, but they still suffer from the disadvantages of expensive reagents, complicated processes, and narrow scope of application. Herein, a robust and flexible Janus membrane with asymmetric wetting properties was constructed using discarded PET and bricks powder as building blocks, for various types of emulsions separation. Given the cross-linking effect of acrylic resin, the superhydrophilic crushed waste bricks powder (WBP) was orderly assembled on the electrospinning PET nanofiber membrane, achieving asymmetric wettability on each side: the high-hydrophobic PET side had underwater superoleophilicity, while superhydrophilic WBP side had underwater superoleophobicity. Janus membrane exhibit excellent corrosion resistance and can maintain stable contact angles in different pH environments. Due to its highly porous and surface anisotropic nature, Janus membrane showed excellent separation efficiency and separation flux for both oil-in-water emulsions (separation efficiency up to 99.4%, separation flux up to 196 L m−2 h−1) and oil-in-water emulsions (separation efficiency up to 99.3%, separation flux up to 792 L m−2 h−1 bar−1). More importantly, Janus membranes exhibited outstanding reusability. This Janus membrane shows great potential in the fields of waste upcycling and emulsion separation.

Systematic Study of Wettability Alteration of Glass Surfaces by Dichlorooctamethyltetrasiloxane Silanization-A Guide for Contact Angle Modification.

To investigate the effects of wettability on multiphase flow in porous media, glass bead packs or micromodels are commonly used. Their wettability can be altered by the surface treatment method-silanization. Although silanization is widely used for glass wettability modification, comparable systematic approaches over a large range of geometries, treatment conditions, and measurement systems are scarce. In this work, dichlorooctamethyltetrasiloxane (Surfasil) treatment was systematically investigated, resulting in a guide for achieving a wide range of contact angles. Initially, the influence of the Surfasil solvent, treatment time, and Surfasil-to-solvent ratio was investigated on glass plates using the sessile drop method. By varying these variables, it was possible to achieve a wide range of comparable, repeatable, and stable contact angles, from approximately 20-95° for air-water systems. Due to the linear increase of contact angle with larger Surfasil exposure, either due to the time or concentration, contact angle tuning is possible until the critical point. Beyond the critical point of exposure, a system-specific plateau value is reached, independent of the approach. After establishing a clear relationship between the parameters and contact angles, the same treatment parameters were applied to single beads, micromodels, and beadpacks with heptane as the chosen solvent. Optical image analysis was used for the microchips, and micro CT data analysis was used for the bead packs. The treatment appeared to be transferable to all geometries, resulting in similar wetting conditions within the limitations of the measurements. It is concluded that a glass plate can be used as an analogue for obtaining the contact angle alteration trends for more complex porous media with similar compositions. Data analysis methods and surface roughness could have an effect on the obtained contact angle spread.

Super gas wet and gas wet rock surface: State of the art evaluation through contact angle analysis

Recently, super gas wet and gas wet surfaces have been extensively attended in petroleum industry, as supported by the increasing number of publications in the last decade related to wettability alteration in gas condensate reservoirs. In many cases, contact angle measurement has been employed to assess the wettability alteration. Even though contact angle measurement seems to be a straightforward approach, there exist many misuses of this technique and consequently misinterpretation of the corresponding results. In this regard, a critical inspection of the most recent updated concepts and the intervening parameters in the contact angle based wettability evaluation of liquid-solid-gas systems could aid to provide some remediation to alleviate this problem. To this end, this work presents a survey on the accurate terms and rigorous protocols based on the community of surface science and chemistry. As a preliminary step, advancing, receding, static, and the most stable contact angle terminology are defined. The study is followed by the definition of the contact angle hysteresis effect. The application of surface free energy in the selection of the best gas wet agent is then analyzed. Afterward, the impact of the size-dependent behavior of drop on contact angle is discussed. Finally, a sessile drop experiment is explained to achieve the defined parameters. For future contributions to petroleum industry journals, like this journal, this work could offer an easy use of the conceptual framework for analyzing the results and comparative evaluations in chemical wettability modifier agents.

Wetting and spreading behavior of molten CMAS on the laser textured thermal barrier coatings with the assistance of Pt-modification

Gadolinium zirconate (Gd2Zr2O7, GZO) is a promising next-generation material for thermal barrier coatings (TBCs). The molten CMAS (calcium-magnesium–aluminium silicates) will react with GZO and quickly produce dense Ca4Y6(SiO4)6 phase, which can prevent the further penetration of the molten CMAS. However, the large thermal expansivity difference between the dense reaction production and the GZO substrate leads to the delamination of the production layer when encountering the thermal shock effect. Therefore, it is essential to reduce the accumulation of molten CMAS. In this paper, the surface texture was fabricated on the surface of EB-PVD (electron beam physical vapor deposition) GZO-TBCs. And then a thin layer of Pt film was deposited on the laser-textured surface. The purpose is to increase the wetting contact angle between the molten CMAS and TBCs, thus decreasing the accumulation of the CMAS. The results show that the stable contact angle of the molten CMAS on the laser-textured GZO-TBCs increased from the original 16° to 66.3°, but the surface texture was completely corroded after high-temperature wetting. By introducing a thin layer of Pt film over the laser-textured coatings, a stable contact angle of 111.6° was achieved. This is because Pt film successfully prevents the molten CMAS react with GZO.

Fluid droplet spreading and adhesion studied with a microbalance: a review

A contact angle observed for a liquid–solid system is not necessarily a unique value, and a few contact angles need to be considered carefully in relation to liquid spreading, adhesion and phase separation. Understanding of the significance of different contact angles has improved in the last few years through direct measurements of interactive forces between droplets/bubbles and solids together with the simultaneous visualization of the changes in their shapes. A microelectronic balance system is employed to measure the force of spreading after either liquid droplet or gas bubble attachment to a substrate surface and the droplet/bubble–substrate adhesion forces after droplet/bubble compression, retraction and detachment. Equipped with a camera in flank and data-acquisition software, the instrument measures directly the forces, monitors droplet/bubble–surface separation with respect to distances over which the droplet/bubble stretches and collects optical images simultaneously. The images are used to analyze capillary pressure and surface tension forces based on the measured droplet/bubble dimensions, shapes of surfaces and values of contact angles. These measurements allow researchers to correlate the advancing, receding and most stable contact angles with liquid–solid interactive forces and analyze their scientific meaning. This review summarizes the very recent literature reports on measurements and interpretation of liquid droplet/gas bubble interactive forces and associated contact angles.

Width effect on contact angle hysteresis in a patterned heterogeneous microchannel

The width effect on contact angle hysteresis in a microchannel with patterned heterogeneous surfaces is systematically investigated. In the model, identical defects periodically appear on the background surface. To this end, a droplet's evaporation and condensation processes inside the microchannel are studied by theoretical analysis and numerical simulation based on a diffuse-interface lattice Boltzmann method. The microchannel width effect on the system's equilibrium properties is studied. The results demonstrate that the number of equilibrium configurations increases linearly with the microchannel width ( $b$ ), and has a quadratic relationship with the cosine of the reference contact angle and the heterogeneity strength ( $\varepsilon$ ). The average most stable contact angle is independent of $b$ and is always equal to the contact angle predicted by the Cassie–Baxter equation. For contact angle hysteresis ( $H$ ), when the microchannels are narrow and wide, there are individual-effect-dominated hysteresis (IDH) and collective-effect-dominated hysteresis (CDH), respectively. The IDH and CDH are hysteresis modes corresponding to the jumping behaviour of contact lines affected by individual defects and two neighbouring defects, respectively. Based on the graphical force balance approach, we establish a scaling law to quantify the connection between $H$ , $b$ and $\varepsilon$ . Specifically, in the IDH mode, $H\sim b \varepsilon ^2$ , while in the CDH mode, $H$ increases linearly with $\varepsilon$ but nonlinearly with $b$ .

Preparation of corrosion-resistant hydrophobic composite films on magnesium alloy

ABSTRACT Magnesium alloy has attracted wide attention for excellent properties but poor corrosion resistance hinders its application. The method of preparing high-performance corrosion-resistant films with low cost and easy operation is significantly crucial to the corrosion protection of magnesium alloy. By synthesizing zeolite film directly on AZ91D magnesium alloy, the work presented a simple, efficient and environmentally-friendly preparation method. In this study, a one-step synthesis method of multi-structure composite film on AZ91D magnesium alloy was explored. The prepared film surface had dense Mg(OH)2 bottom layer and K2Al2Si4O12·xH2O upper layer with porous support microstructure. Compared with the substrate, the corrosion current on the sample surface modified by stearic acid was reduced by about three orders of magnitude, and the corrosion inhibition rate reached 99.96% with a stable contact angle of about 125°. The results showed the excellent corrosion resistance and stable hydrophobicity of the prepared sample.

Modification of PVDF membranes using BiOBr precursor in-situ deposition and tannic acid self-assembly for effectively removing organic pollutants

Currently, conventional technologies for water treatment are not sufficiently efficient to completely mineralize refractory organic pollutants, and most of the existing reports only deal with multiple organic pollutants individually. Therefore, designing a hydrophilic membrane that is easy to fabricate and has multiple active sites for simultaneous separation of blended complex organic pollutants is urgently required. Therefore, the aim of this study was to share a new perspective for designing high-performance membranes by functionally modifying the membranes. First, we combined water-induced precipitation properties of BiOBr with polyvinylidene fluoride (PVDF) phase inversion to enable in-situ growth and firm enchasing of hydrophilic BiOBr nanomaterials in the micro-clusters of the PVDF membrane, avoiding the disadvantages of easy aggregation and masking of nanomaterials. Second, we adopted a simple method to self-assemble the tannic acid (TA) and halloysite nanotubes on the membrane surface enhanced hydrophilicity and anti-fouling performance. The electrostatic force between TA and the [Bi2O2]2+ electric double layer of BiOBr makes the two stably combined. The TA/BiOBr/PVDF membrane designed herein demonstrated high efficiency in the instantaneous separation of recalcitrant blended organic molecules. The removal efficiency of the TA/BiOBr/PVDF membrane for methylene blue, methyl orange, rhodamine B, tetracycline, and bisphenol A was 99.6%, 97.7%, 99.8%, 90.7%, and 85.5%, respectively. The evaluation of SEM, EDS, atomic force microscopy, XRD and XPS results demonstrated not only the compatibility of in-situ preferential deposition of BiOBr for PVDF but also a hydrophilic nano-layer of TA self-assembled on the surface of the BiOBr/PVDF membrane. The stable blended pollutants flux (Jw, 144.4 L·m−2·h−1·bar−1) and water contact angle (47.46°) of the TA/BiOBr/PVDF membrane were higher than those of a pristine PVDF membrane (102.7 L·m−2·h−1·bar−1 and 87.08°, respectively). In addition, the composite membrane showed high stability for recycling and anti-pollution activities.

Wetting behaviour of a Green cutting fluid (GCF); influence of surface roughness and surface energy of AA5052, Ti6Al4V and EN31

Green Cutting fluids (GCFs) are biodegradable and eco-friendly alternatives that can be employed in metalworking processes. They facilitate better tool service life and surface quality by removing the heat built, reducing coefficients of friction at tool-chip, and tool-work interfaces, flushing away the chip and preventing the formation of Built-up edges (BUEs). Conventionally, mineral oil (MO) based CFs are used, which can cause serious health hazards in humans as well as negatively impact the environment. Sustainable Green-cutting fluids (GCF) were found to be the solution for reducing the issues raised by the MO-based cutting fluids. The GCF used in the present study was synthesized using coconut oil (Cocos Nucifera) as the base, which is a clean, bio-degradable and eco-friendly substitute for petroleum-based mineral oils. This work is focused on experimentally determining the effectiveness of green cutting fluids on surfaces of (Aluminium)AA5052, (Titanium alloy)Ti6AL4V and Steel(EN31) with various surface topographies. In order to do so, the wetting properties were measured by a stable contact angle θ between the solid–liquid surface and the vapour-liquid interface. Wettability responses from the roughened surfaces in the range of 0.06–2.1 µm was evaluated using a profilometer and contact angle goniometer. Results show that the wetting characteristics of GCF are comparable to that of the MO-based CFs and can be a viable alternative, thus reducing the adverse effects on the environment. In conclusion, this study shows the potential of GCFas an alternative to MO-based cutting fluids used in machining operations in the manufacturing industries.

Comb-like poly(dodecyl methacrylate) modified SiO2 nanoparticles as nanohybrid coatings: Electron beam grafting and tuning superhydrophobic/water-repellent surface studies

The current research focuses on tailoring silica nanoparticles (SiO2NPs) with comb-like poly(dodecyl methacrylate) (PDMA) brushes and tuning coating parameters based on roller coating process for confining surface morphology towards hydrophobic and superhydrophobic including water-repellent surface. Electron beam (EB) induced a simultaneous “graft-from” polymerization of DMA monomer onto vinyl modified SiO2NPs (SiO2NPs-V) was established in an inventive castor oil/ethanol mixed solvent. Functional surface chemistry of SiO2NPs and nanorough surface topography controlled by NPs content and coating thickness mainly influences the hydrophobic/superhydrophobic, water-repellent, and water absorption properties including gloss values, whiteness and yellowness index of coated papers. The papers coated with SiO2NPs-V-PDMA/PVA of 6–10 wt% with the thickness of ~10–14 μm exhibited matt surface and provided superhydrophobic and water-repellent properties. The coated paper has a desirable and stable water contact angle of 152°, low droplet adhesion with lower dynamic tilting angle (<5°), and 5.3-folds reduced water absorption. Our investigation provides compelling evidence that the SiO2NPs-V-PDMA obtained from EB modification and the developed coating formula for roller-based coating process are realistic approaches for hydrophobic/superhydrophobic coatings and printing inks for paper-based industries.

Modification of the copper wettability by nanosecond laser texturing

Nanosecond laser microstructuring of copper surfaces was performed in this work. The contact angle value immediately after laser treatment decreased sharply and all samples were hydrophilic or superhydrophilic. Hydrophobization of the textured samples occurs as a result of environmental exposure over time. Oxidation and adsorption of carbon and its compounds from the atmosphere leads to a change in the wettability of the irradiated surfaces. The acceleration of hydrophobization process with decrease of fluence was found. It is shown that the stable contact angle, reached after one month, does not depend on the value of the fluence and is about 140°.

Multifunctional cellulose membranes with antibacterial activity and infrared insulation properties for personal thermal management application

ABSTRACT In this work, multifunctional cellulose membranes (Ag-NWs/CMs@Ag) with antibacterial activities, high air permeability, and infrared preservation properties were successfully prepared for personal thermal management application. Infrared radiation preservation was observed by modifying surface’s physical and chemical properties. Additionally, Ag-NWs/CMs@Ag exhibits high air permeability of 3.00 mg/cm2·hour, the excellent antibacterial activity against E. coli and S. aureus and hydrophobic properties with a stable water contact angle of 129.35°. Overall, the results of this study demonstrate Ag-NWs/CMs@Ag offers great potential in personal thermal management application and provide an effective strategy for the development of wearable textiles.

Janus poly(vinylidene fluoride)-graft-(TiO2 nanoparticles and PFDS) membranes with loose architecture and asymmetric wettability for efficient switchable separation of surfactant-stabilized oil/water emulsions

Janus membranes, with extremely asymmetric wettability, superior flux and rejection, facile fabrication route, and versatile in complex environment, is urgently needed in fields of ideal oil/water separation. In this work, a facile poly (vinylidene fluoride)-graft-(TiO2 nanoparticles and 1H, 1H, 2H, 2H-perfluorodecyltri-ethoxysilane) (PVDF-g-(TiO2-PFDS)) membrane with loose architecture and asymmetric wettability was successfully fabricated by one-step surface grafting and further single-side chemical vapor deposition (CVD) strategies. Amino-functionalized TiO2 (TiO2–NH2) nanoparticles immobilized could not only improve surface energy and roughness of the PVDF-g-poly(acrylic acid) (PAA) membrane, but also decrease pore size adequately. PFDS was further deposited on one side of PVDF-g-TiO2 NPs membrane for constructing asymmetric interface. The fabricated Janus membrane showed superhydrophilic (a water contact angle of 0°) and superhydrophobic (a stable water contact angle of 151°) properties on forward/reverse surfaces. These characteristics endowed the membrane with high separation flux of ∼2500 L·m-2·h-1 under 0.1 MPa, and high rejection rate of above 99.70% for separating surfactant-stabilized dodecane-in-water and water-in-chloroform emulsions, respectively. Furthermore, the PVDF-g-(TiO2-PFDS) membrane showed excellent cycling performance during separation process. This work shows a potential way to fabricate Janus membranes with dual wettability for efficient oil/water separation facilely.

Wettability and infiltration of Si melt on SiO2-Si3N4 composite ceramic

Non-wettable material with Si melt is preferred to manufacture crucible in order to avoid adhesion between Si and traditional fused silica crucible. In this work, wetting and infiltration behaviors of Si drop on porous/dense SiO2-Si3N4 ceramic and SiO2 ceramic were systematically studied via the sessile drop technology and microstructural analysis method. The porous SiO2-Si3N4 ceramic exhibited non-wetting behavior with stable contact angle of about 130 °. Nevertheless, dense SiO2-Si3N4 ceramic and SiO2 ceramic displayed wetting features with Si drop. For both SiO2-Si3N4 ceramics, three kinds of infiltrations were observed, including infiltration under Si drop, infiltration under substrate surface (beyond drop) and infiltration on substrate surface. Notably, the infiltration under Si drop had the slowest speed with tiny infiltration depth. The above non-wetting behavior and tiny infiltration under drop of porous SiO2-Si3N4 ceramic were closely related to material pore characteristics and Si/substrate interfacial reaction.

Facile fabrication and repair of superhydrophobic metal surfaces via electric spark deposition with oil

Recent research has focused on the durability of superhydrophobic surfaces, and some methods have reported improvements in the resistance of surfaces to abrasion from several sandpaper treatment cycles with the goal of maintaining a contact angle (CA) > 150°. However, the surface water repellency is lost because of the numerous abrasive cycles causing significant mechanical damage. Repairing the superhydrophobicity of the material is necessary when the surface is damaged. Current repair methods have different limitations, such as special abrasion conditions or limits on the substrate size and working conditions. Here, we demonstrate that using electric spark deposition with oil can create a superhydrophobic surface in a single step. This represents a facile method that can be carried out by hand with fewer limitations on its working conditions and the substrate location and shape. The morphology and chemical composition of the coating was investigated. The addition of octadecanoic acid to the oil provided a stable CA > 150° for the coated surface. The coated surface lost superhydrophobicity after being subject to three different damaging processes, and the superhydrophobicity could be recovered after recoating.

The study of water wettability on solid surfaces by molecular dynamics simulation

The wetting of nanodroplets on solid surfaces was studied by molecular dynamics simulations. Through investigation of the contact angle of nanodroplets with different sizes, a relatively stable and accurate contact angle was obtained for a droplet radius of larger than 43 Å (1 Å = 10−10 m). The contact angles for droplets at different levels of solid-liquid forces were quantitatively evaluated. The results show that there is an excellent linear correlation between them in the angle range of 28° to 167°. Under a strong solid-liquid force, thin liquid film expansion in the three-phase line was found in nanometer-level simulations. The thin film spreading range increased with increasing solid-liquid force.

Click preparation and mechanism on amphiphilic oleophobic/hydrophilic behavior of fluorinated diblock copolymers

AbstractIn this article, amphiphilic fluorinated diblock copolymers of poly(perfluorohexylethyl acrylate)‐block‐allylpolyethyleneglycol (PF6A‐b‐APEG1200) are synthesized by reversible addition‐fragmentation transfer (RAFT) polymerization and sequential thiol‐ene click reaction. The molecular structure is characterized by 1H nuclear magnetic resonance (1H NMR) spectra and Fourier transform infrared (FTIR) spectra. Morphology and particle size of resultant copolymer micelles in aqueous solution are analyzed by transmission electron microscope (TEM) and dynamic light scattering (DLS). The wettability and relative element contents of PF6A‐b‐APEG1200 coatings are investigated with contact angle (CA) and X‐ray photoelectron spectroscopy (XPS). When PF6A‐b‐APEG1200 coating is stimulated by water, the fluorine content at the top fluoropolymer‐air interface decreases and the water contact angle of the surface decreases over time, showing the hydrophilicity. While stimulated by n‐hexadecane, the fluorine content of the film surface increases, showing the oleophobicity with a stable apparent oil contact angle of 72 ± 1°. According to the detailed analysis of XPS results, the stimuli‐responsive behavior of the amphiphilic polymers can be ascribed to the migration and rearrangement of the two blocks in PF6A‐b‐APEG1200, which might probably be one of the universally accepted oleophobic/hydrophilic mechanisms.