Inside Front Cover: In article number 1800428 by Markus Gallei and coworkers, a side‐chain ferrocene‐containing polymer as a matrix for a metallopolymer inverse opal structure is presented as a ...redox‐active material. Vivid structural colors are obtained due to the well‐ordered voids within the metallopolymer‐containing matrix, and redox‐responsiveness is also demonstrated, revealing both a change of surface wettability and structural reflection colors.
The literatures about superhydrophobic coatings (SHCs) are increasing every year, however, undesirable chemicals including organic solvents and fluorinated compounds are intensively used in the ...existing preparation methods, which seriously hinder their large scale production and practical applications. Herein, a simple approach for preparation of totally waterborne, fluorine-free and durable SHCs is reported. First, a waterborne suspension of hexadecyl polysiloxane modified SiO
(SiO
@HD-POS) was prepared via HCl-catalyzed hydrolytic condensation of hexadecyltrimethoxysilane (HDTMS) and tetraethoxysilane with SiO
nanoparticles. The SHCs with high water contact angles (CA = 163.9°) and low sliding angles (SA = 3.7°) were prepared simply by sequentially spray-coating a polyurethane (PU) waterborne solution and the SiO
@HD-POS waterborne suspension onto glass slides. The influences of SiO
, HDTMS, reaction time and fabrication temperature on superhydrophobicity were investigated. The SHCs can withstand 80 m of reciprocating abrasion against A4 paper at 4.5 kPa and impacting of at least 50 g of sand microparticles with 30 cm release height. Moreover, the coatings also show exceptional thermostability in boiling water. The SHCs showed promising applications in various areas including oil/water separation and preventing scald, as the method is environmental benign and the coatings are applicable onto various substrates.
Wettability measurement is important in production development to newly discovered as well as mature reservoirs. Evaluating the wettability is exceptionally important (for its significant-yields in ...hydrocarbon quantities) in oil and gas production schemes for newly discovered reservoirs such as shale reservoirs and other unconventional plays. Shale wettability has its unique fluid-mineral distribution relationships, which makes both pore morphology as well as mineral composition very significant factors controlling its wettability. The complex shale physical, chemical, and crystollgraphical constituent's mineralogy as well as its physical pore morphology heterogeneity can complicate the wettability measurement further inside the pore structure fabrication, and hence the ultimate oil/gas recovery. The main objective of this study is to investigate the complexity of heterogeneous mineral structure of shale as well as its complex pore structure and its attributes toward the unconventional imaging method of wettability contact angle measurement.
•Novel microstructured surfaces were fabricated with spatially-controlled mixed wettability.•Area ratio of hydrophobic region on pillar tops greatly affects the boiling performance of mixed wetting ...microstructured surfaces.•Synergistic enhancement mechanism was explored by optimally utilizing the combined effects of mixed wettability and microstructures.
Surface wettability is a very important factor that affects the pool boiling heat transfer performance and the surfaces with mixed wettability have attracted much attention in recent years for enhancing pool boiling. However, the existing experimental studies were mainly focused on plain surfaces with mixed wettability or microstructured surfaces whose tops of microstructures were entirely subjected to wettability modification. In this work, we fabricated microstructured surfaces with spatially-controlled mixed wettability by controlling the size of the hydrophobic spots on the tops of microstructures. Saturated pool boiling of water on the surfaces was experimentally investigated to explore the synergistic enhancement of pool boiling by optimally utilizing the combined effects of mixed wettability and microstructures. The experimental results indicate that the size of the hydrophobic spots on the tops of microstructures has a significant influence on the boiling performance of microstructured surfaces with mixed wettability. By controlling the size of the hydrophobic spots on the tops of microstructures to optimize the combined effects of mixed wettability and microstructures, the novel microstructured surface performs much better than a base microstructured surface without wettability modification and the one whose tops of pillars are entirely subjected to wettability modification. The heat transfer coefficient (HTC) was found to be significantly enhanced together with a higher critical heat flux (CHF). Specifically, the achieved largest HTC and highest CHF are 257.6 kW/(m2 K) and 2190.8 kW/m2, respectively, which are 4.55 times and 1.87 times, respectively, over those of the plain copper surface.
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•Caprock geological formations depict intermediate-wet conditions.•Increased pressure and reduced temperature inversely affect hydrogen wettability.•Hydrophilic caprock geological ...formations become intermediate wet in the presence of organic acids.
Actualization of the hydrogen (H2) economy and decarbonization goals can be achieved with feasible large-scale H2 geo-storage. Geological formations are heterogeneous, and their wetting characteristics play a crucial role in the presence of H2, which controls the pore-scale distribution of the fluids and sealing capacities of caprocks. Organic acids are readily available in geo-storage formations in minute quantities, but they highly tend to increase the hydrophobicity of storage formations. However, there is a paucity of data on the effects of organic acid concentrations and types on the H2-wettability of caprock-representative minerals and their attendant structural trapping capacities.
Geological formations contain organic acids in minute concentrations, with the alkyl chain length ranging from C4 to C26. To fully understand the wetting characteristics of H2 in a natural geological picture, we aged mica mineral surfaces as a representative of the caprock in varying concentrations of organic molecules (with varying numbers of carbon atoms, lignoceric acid C24, lauric acid C12, and hexanoic acid C6) for 7 days. To comprehend the wettability of the mica/H2/brine system, we employed a contact-angle procedure similar to that in natural geo-storage environments (25, 15, and 0.1 MPa and 323 K).
At the highest investigated pressure (25 MPa) and the highest concentration of lignoceric acid (10−2 mol/L), the mica surface became completely H2 wet with advancing (θa= 106.2°) and receding (θr=97.3°) contact angles. The order of increasing θa and θr with increasing organic acid contaminations is as follows: lignoceric acid > lauric acid > hexanoic acid. The results suggest that H2 gas leakage through the caprock is possible in the presence of organic acids at higher physio-thermal conditions. The influence of organic contamination inherent at realistic geo-storage conditions should be considered to avoid the overprediction of structural trapping capacities and H2 containment security.
Wastewater contaminated with oil or organic compounds poses threats to the environment and humans. Efficient separation of oil and water are highly desired yet still challenging. This paper reports ...the fabrication of a smart fiber membrane by depositing pH-responsive copolymer fibers on a stainless steel mesh through electrospinning. The cost-effective precursor material poly(methyl methacrylate)-block-poly(4-vinylpyridine) (PMMA-b-P4VP) was synthesized using copper(0)-mediated reversible-deactivation radical polymerization. The pH-responsive P4VP and the underwater oleophilic/hydrophilic PMMA confer the as-prepared membrane with switchable surface wettability toward water and oil. The three-dimensional network structure of the fibers considerably strengthens the oil/water wetting property of the membrane, which is highly desirable in the separation of oil and water mixtures. The as-prepared fiber membrane accomplishes gravity-driven pH-controllable oil/water separations. Oil selectively passes through the membrane, whereas water remains at the initial state; after the membrane is wetted with acidic water (pH 3), a reverse separation is realized. Both separations are highly efficient, and the membrane also exhibits switchable wettability after numerous cycles of the separation process. This cost-effective and easily mass-produced smart fiber membrane with excellent oil-fouling repellency has significant potential in practical applications, such as water purification and oil recovery.
As a growing hot research topic, manufacturing smart switchable surfaces has attracted much attention in the past a few years. The state-of-the-art study on reversibly switchable wettability of smart ...surfaces has been presented in this systematic review. External stimuli are brought about to render the alteration in chemical conformation and surface morphology to drive the wettability switch. Here, starting from the fundamental theories related to the surfaces wetting principles, highlights on different triggers for switchable wettability, such as pH, light, ions, temperature, electric field, gas, mechanical force, and multi-stimuli are discussed. Different applications that have various wettability requirement are targeted, including oil-water separation, droplets manipulation, patterning, liquid transport, and so on. This review aims to provide a deep insight into responsive interfacial science and offer guidance for smart surface engineering. It ends with a summary of current challenges, future opportunities, and potential solutions on smart switch of wettability on superwetting surfaces.
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•Advances on smart surfaces with reversibly switchable wettability are critically reviewed.•Fundamental theory behind switchable wetting and the inherent principles for smart surfaces are presented.•The influence of various external stimuli on tunable wetting state is highlighted and discussed.•Promising applications with on-demanded wettability requirement are targeted.•A summary of current challenges, future opportunities and potential solutions on superwetting surfaces are proposed.
This study investigates the ability of hydrogen (H2) to wet clay surfaces in the presence of brine, with implications for underground hydrogen storage in clay-containing reservoirs. Rather than ...measuring contact angles directly with hydrogen gas, a suite of other gases (carbon dioxide (CO2), argon (Ar), nitrogen (N2), and helium (He)) were employed in the gas-brine-clay system under storage conditions (moderate temperature (333 K) and high pressures (5, 10, 15, and 20 MPa)), characteristic of a subsurface environment with a shallow geothermal gradient. By virtue of analogies to H2 and empirical correlations, wettabilities of hydrogen on three clay surfaces were mathematically derived and interpreted. The three clays were kaolinite, illite, and montmorillonite and represent 1:1, 2:1 non-expansive, and 2:1 expansive clay groups, respectively. All clays showed water-wetting behaviour with contact angles below 40° under all experimental set-ups. It follows that the presence of clays in the reservoir (or caprock) is conducive to capillary and/or residual trapping of the gas. Another positive inference is that any tested gas, particularly nitrogen, is suitable as cushion gas to maintain formation pressure during hydrogen storage because they all turned out to be more gas-wetting than hydrogen on the clay surfaces; this allows easier displacement and/or retrieval of hydrogen during injection/production. One downside of the predominant water wettability of the clays is the upstaged role of biogeochemical reactions at the wetted brine-clay/silicate interface and their potential to affect porosity and permeability. Water-wetting decreased from kaolinite as most water-wetting clay over illite to montmorillonite as most hydrogen-wetting clay. Their wetting behaviour is consistent with molecular dynamic modelling that establishes that the accessible basal plane of kaolinite's octahedral sheet is highly hydrophilic and enables strong hydrogen bonds whereas the same octahedral sheet in illite and montmorillonite is not accessible to the brine, rendering these clays less water-wetting.
•Determination of contact angles for the clay-brine-H2 system; studied clays were kaolinite, illite, and montmorillonite.•Wettabilities change as function of clay type.•Kaolinite is most water-wet, followed by illite and finally montomorillonite, which is only moderately water-wet.•Octahedral clay sheet (the ‘O’ in ‘TO’ and ‘TOT’) is reasoned to cause varying water-wetting character of the clays.•Presence of clays in reservoir/caprock will help in capillary and/or residual trapping of hydrogen.
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