Durable and Recyclable Superhydrophobic Fabric and Mesh for Oil–Water Separation

The authors report durable and recyclable nanocomposite superhydrophobic coatings on two different substrates of fabric and mesh as prepared by titania nanoparticles and polydimethysiloxane (PDMS). The felted wool fabric and the steel mesh are initially coated with a thin layer of PDMS, which is followed by the deposition of nanocomposite coating of titania nanoparticles embedded in PDMS. The dual surface modification of two kinds of substrates generates highly hydrophobic surface character, which is retained after durability performance as measured in ultrasonication, sand, and emery paper abrasion tests. Oil–water separation experiments are performed using water mixtures with four oils, that is, n‐hexane, toluene, kerosene, and diesel to ensure the industrial applications of prepared composite materials. Moreover, nanocomposite coatings are tested for several cycles of oil–water separation in harsh conditions such as hot water, sodium chloride, and hydrochloric acid. The adopted approach improves the separation performance by inducing durability of the prepared nanocomposite coatings along with introducing recyclable character.     

Energy‐Efficient Oil–Water Separation of Biomimetic Copper Membrane with Multiscale Hierarchical Dendritic Structures

Membrane‐based materials with special surface wettability have been applied widely for the treatment of increasing industrial oily waste water, as well as frequent oil spill accidents. However, traditional technologies are energy‐intensive and limited, either by fouling or by the inability of a single membrane to separate all types of oil–water mixtures. Herein, a biomimetic monolayer copper membrane (BMCM), composed of multiscale hierarchical dendritic structures, is cleverly designed and successfully fabricated on steel mesh substrate. It not only possesses the ability of energy‐efficient oil–water separation but also excellent self‐recovery anti‐oil‐fouling properties (<150 s). The BMCM even keeps high separation efficiency (>93%) after ten‐time cycling tests. More importantly, it retains efficient oil–water separation capacity for five different oils. In fact, these advanced features are benefited by the synergistic effect of chemical compositions and physical structures, which is inspired by the typical nonwetting strategy of butterfly wing scales. The findings in this work may inspire a facile but effective strategy for repeatable and antipollution oil–water separation, which is more suitable for various applications under practical conditions, such as wastewater treatment, fuel purification, separation of commercially relevant oily water, and so forth.     

用于油水分离的静电纺纳米纤维膜研究进展

近年来,石油泄漏以及工业含油废水的排放对生态环境造成了严重的损害,高效节能的新型油水分离材料已成为研究热点。具有特殊亲液性的静电纺纳米纤维膜是一种可用于油水分离的新型膜材料,它具有较高的比表面积和孔隙率,既可以自发实现油水分离,又能减少能源消耗。主要介绍了超亲水疏油、超疏水亲油、智能切换亲水/亲油以及单向导油纳米纤维膜,及纤维膜的制备方法、亲液性以及油水分离过程和分离效率;并对静电纺油水分离纳米纤维膜所面临的挑战和应用前景进行了展望。     

Bioinspired Mechanically Robust Metal‐Based Water Repellent Surface Enabled by Scalable Construction of a Flexible Coral‐Reef‐Like Architecture

Mechanical robustness is a central concern for moving artificial superhydrophobic surfaces to application practices. It is believed that bulk hydrophilic materials cannot be use to construct micro/nanoarchitectures for superhydrophobicity since abrasion‐induced exposure of hydrophilic surfaces leads to remarkable degradation of water repellency. To address this challenge, the robust mechanical durability of a superhydrophobic surface with metal (hydrophilic) textures, through scalable construction of a flexible coral‐reef‐like hierarchical architecture on various substrates including metals, glasses, and ceramics, is demonstrated. Discontinuous coral‐reef‐like Cu architecture is built by solid‐state spraying commercial electrolytic Cu particles (15–65 µm) at supersonic particle velocities. Subsequent flame oxidation is applied to introduce a porous hard surface oxide layer. Owing to the unique combination of the flexible coral‐reef‐like architecture and self‐similar manner of the fluorinated hard oxide surface layer, the coating surface retains its water repellency with an extremely low roll‐off angle (<2°) after cyclic sand‐paper abrasion, mechanical bending, sand‐grit erosion, knife‐scratching, and heavy loading of simulated acid rain droplets. Strong adhesion to glass, ceramics, and metals up to 34 MPa can be achieved without using adhesive. The results show that the present superhydrophobic coating can have wide outdoor applications for self‐cleaning and corrosion protection of metal parts.     

Spray-Coating of Superhydrophobic Coatings for Advanced Applications

Superhydrophobic coatings are widely applicable, e.g., as self-cleaning surfaces or water–oil separation membranes, yet their wider usage is impeded due to costs of fabrication, size, or substrate limitation. Spray-coating is a versatile coating procedures and might offer a good solution for the fabrication of these superhydrophobic coatings, due to the fact that coatings can be fabricated on various materials in a simple, fast, and inexpensive manner. Most procedures rely on hybrid coatings of hydrophobized nanoparticles and a polymeric matrix, which have several drawbacks including the easy loss of nanoparticles and difficult waste handling. Here, the fabrication of the superhydrophobic material, called Fluoropor, for the first time, by spray-coating on various substrates including metals, tissues, concrete, and glass is presented. It is fabricated by spray-coating a mixture of a highly fluorinated monomer blended with porogens followed by photopolymerization. The superhydrophobicity of the material relies on the porous structure on the micro-/nanoscale across the bulk material and does not require any nanoparticles. Excellent self-cleaning ability of these coatings, resistance against thermal and abrasive impact, and their application as oil–water separation membranes are shown. This versatile applicability is highly promising for real-world application as self-cleaning coatings or oil–water separating membranes.     

静电纺丝制备PVDF多孔纳米纤维及其在吸油中的应用

采用静电纺丝和PEO模板相结合加工制备了具有超疏水性能的PVDF多孔纳米纤维.通过扫描电镜(SEM)观察所制备的PVDF纤维具有均匀微纳米二级孔道显微结构,测得该多孔纳米纤维表面接触角高达158°,呈现良好的超疏水特性.研究发现,将PVDF多孔纳米纤维作为溢油吸附材料具有良好的吸油效能,其对润滑油、柴油、植物油和汽油的...     

Ultrahigh‐Water‐Content,Superelastic, and Shape‐Memory Nanofiber‐Assembled Hydrogels Exhibiting Pressure‐Responsive Conductivity

High‐water‐content hydrogels that are both mechanically robust and conductive could have wide applications in fields ranging from bioengineering and electronic devices to medicine; however, creating such materials has proven to be extremely challenging. This study presents a scalable methodology to prepare superelastic, cellular‐structured nanofibrous hydrogels (NFHs) by combining alginate and flexible SiO₂ nanofibers. This approach causes naturally abundant and sustainable alginate to assemble into 3D elastic bulk NFHs with tunable water content and desirable shapes on a large scale. The resultant NFHs exhibit the integrated properties of ultrahigh water content (99.8 wt%), complete recovery from 80% strain, zero Poisson's ratio, shape‐memory behavior, injectability, and elastic‐responsive conductivity, which can detect dynamic pressure in a wide range (>50 Pa) with robust sensitivity (0.24 kPa^?1) and durability (100 cycles). The fabrication of such fascinating materials may provide new insights into the design and development of multifunctional hydrogels for various applications.     

One‐Pot Process to Control the Elaboration of Non‐Wetting Nanofibers

The surface wettability, such as superhydrophobic properties, of nanofibrous structures is highly depending on their size, length, spacing or orientation to the surface. Finding a way to control all these characteristics is extremely important in a theoretical point of view and for various applications. Here, we report the possible tuning of all these characteristics by adjusting the length (n) of the alkyl chains of electrodeposited poly(3,3‐dialkyl‐3,4‐propylenedioxythiophene), which allows the formation of horizontally or vertically oriented nanofibers of various dimensions and spacings. Here, we play especially on the hydrophilic/hydrophobic characteristics of the polymer to change the growth of a polymer on a substrate and the distance between the polymer backbones. For example, a change in the fiber orientation from horizontal to vertical is observed for n = 2. For n < 2, the polymer fibers are mainly horizontally aligned while for n > 2, the polymer fibers are vertically aligned.     

Ultrafiltration Membranes with Structure‐Optimized Graphene‐Oxide Coatings for Antifouling Oil/Water Separation

Fouling of ultrafiltration (UF) membranes in oil/water separation is a long‐standing issue and a major economic barrier to their use in a broad range of applications. Currently reported membranes typically show severe fouling, resulting from the strong oil adhesion on the membrane surface and/or oil penetration inside the membranes. This greatly degrades their performance and shortens service lifetime. Here, the use of graphene oxide (GO) as a novel coating material for the fabrication of fully recoverable, UF membranes with desired hierarchical surface roughness is accomplished by a facile vacuum filtration method for antifouling oil/water separation. The combination of ultrathin, “water‐locking” GO coatings with the optimized hierarchical surface roughness, provided by the inherent roughness of the porous supports and the corrugation of the GO coatings, minimizes underwater oil adhesion on the membrane surface. Cyclic membrane performance evaluation tests revealed approximately 100% membrane recovery by facile surface water flushing, establishing their excellent easy‐to‐recover capability. The novel GO functional coatings with optimized hierarchical structures may have broad applications in oil‐polluted environments.     

Mixed Fluorinated/Hydrogenated Self‐Assembled Monolayer‐Protected Gold Nanoparticles: In Silico and In Vitro Behavior

Gold nanoparticles (AuNPs) covered with mixtures of immiscible ligands present potentially anisotropic surfaces that can modulate their interactions at complex nano–bio interfaces. Mixed, self‐assembled, monolayer (SAM)‐protected AuNPs, prepared with incompatible hydrocarbon and fluorocarbon amphiphilic ligands, are used here to probe the molecular basis of surface phase separation and disclose the role of fluorinated ligands on the interaction with lipid model membranes and cells, by integrating in silico and experimental approaches. These results indicate that the presence of fluorinated amphiphilic ligands enhances the membrane binding ability and cellular uptake of gold nanoparticles with respect to those coated only with hydrogenated amphiphilic ligands. For mixed monolayers, computational results suggest that ligand phase separation occurs on the gold surface, and the resulting anisotropy affects the number of contacts and adhesion energies with a membrane bilayer. This reflects in a diverse membrane interaction for NPs with different surface morphologies, as determined by surface plasmon resonance, as well as differential effects on cells, as observed by flow cytometry and confocal microscopy. Overall, limited changes in monolayer features can significantly affect NP surface interfacial properties, which, in turn, affect the interaction of SAM‐AuNPs with cellular membranes and subsequent effects on cells.     

Signal Output of Triboelectric Nanogenerator at Oil–Water–Solid Multiphase Interfaces and its Application for Dual‐Signal Chemical Sensing

A liquid–solid contact triboelectric nanogenerator (TENG) based on poly(tetrafluoroethylene) (PTFE) film, a copper electrode, and a glass substrate for harvesting energy in oil/water multiphases is reported. There are two distinctive signals being generated, one is from the contact electrification and electrostatic induction between the liquid (water/oil) and the PTFE film (V_TENG and I_TENG); and the other is from the electrostatic induction in the copper electrode by the oil/water interfacial charges (ΔV_interface and I_interface), which is generated only when the liquid–solid contact TENG is inserted across the oil/water interface. The two signals show interesting opposite changing trends that the V_TENG and I_TENG decrease while the oil/water interfacial signals of ΔV_interface and I_interface increase after coating a layer of polydopamine on the surfaces of PTFE and glass via self‐polymerization. As an application of the observed phenomena, both the values of I_TENG and I_interface have a good linear relationship versus the natural logarithm of the concentration of the dopamine. Based on this, the first self‐powered dual‐signal detection of dopamine using TENG is demonstrated.     

Hyperfast Water Transport through Biomimetic Nanochannels from Peptide‐Attached (pR)‐pillar[5]arene

Synthetic water channels offer great promise to replace natural aquaporins (AQPs) for making new‐generation biomimetic membranes for water treatment. However, the water permeability of the current synthetic water channels is still far below that of AQPs. Here, peptide‐attached (pR)‐pillar[5]arene (pR‐PH) channels are reported to mimic the high permeability of AQPs. It is demonstrated that the pR‐PH channels with an open pore can transport water smoothly and efficiently. The pR‐PH channels are competitive with AQPs in terms of water permeability and are much superior to diastereomer peptide‐attached (pS)‐pillar[5]arene (pS‐PH) and other reported synthetic water channels. The exceptional water‐transport properties of the pR‐PH channels are further demonstrated in a composite polymeric membrane that incorporates the nanochannels into the top selective layer. This membrane gives a significantly improved water flux while retaining high salt rejection. The results establish a tangible foundation for developing highly efficient artificial water channel‐based biomimetic membrane for water purification applications.     

Microstructural and Interfacial Designs of Oxygen‐Permeable Membranes for Oxygen Separation and Reaction–Separation Coupling

Mixed ionic–electronic conducting oxygen‐permeable membranes can rapidly separate oxygen from air with 100% selectivity and low energy consumption. Combining reaction and separation in an oxygen‐permeable membrane reactor significantly simplifies the technological scheme and reduces the process energy consumption. Recently, materials design and mechanism investigations have provided insight into the microstructural and interfacial effects. The microstructures of the membrane surfaces and bulk are closely related to the interfacial oxygen exchange kinetics and bulk diffusion kinetics. Therefore, the permeability and stability of oxygen‐permeable membranes with a single‐phase structure and a dual‐phase structure can be adjusted through their microstructural and interfacial designs. Here, recent advances in the development of oxygen permeation models that provide a deep understanding of the microstructural and interfacial effects, and strategies to simultaneously improve the permeability and stability through microstructural and interfacial design are discussed in detail. Then, based on the developed high‐performance membranes, highly effective membrane reactors for process intensification and new technology developments are highlighted. The new membrane reactors will trigger innovations in natural gas conversion, ammonia synthesis, and hydrogen‐related clean energy technologies. Future opportunities and challenges in the development of oxygen‐permeable membranes for oxygen separation and reaction–separation coupling are also explored.     

Fabrication of micro-nano structure nanofibers by solvent etching

Micro-Nano structure nanofibrous affinity membranes of poly(ether sulfones) (PES) blended with a functional polymer poly(ethyleneimine) (PEI) were fabricated by electrospinning technique followed by solvent etching in crosslinking solution. The surface SEM image of the water washed PES/PEI nanofibrous membrane confirmed that PEI was concentrated on the fiber surface. The nanofibrous PES/PEI membranes were crosslinked in a mixture of acetone and water with glutaraldehyde (crosslinking agent, GA), and the micro-nano structural surface of the nanofibrous membranes was created by solvent etching due to the solvation between PEI and the solvent water in the crosslinking solution during the crosslinking process. The influence of the component of the crosslinking bath on the mophology of the resulting PES/PEI nanofibers was investigated. It was found that the relatively uniform micro-nano spherules grew on the surface of the nanofibers when the content of water in crosslinking solution was more than 20 wt%, and the diameters of the spherules were in the range of 50-250 nm. The advantage of the micro-nano structrue for the heavy metal ions removal in wastwater has been demonstrated by taking a series of static adsorption experiments. It was found that the micro-nano structrue of PES/PEI nanofibrous membranes could bring high performance of adsorption capacity for heavy metal ions, indicating that the unique morphology could bring much more large surface area per unit mass and high effectivity for heavy metal ions removal from aqueous solutions.     

Robust Flower‐Like TiO2@Cotton Fabrics with Special Wettability for Effective Self‐Cleaning and Versatile Oil/Water Separation

Inspired by the hierarchical structure of the mastoid on the micrometer and nanometer scale and the waxy crystals of the mastoid on natural lotus surfaces, a facile one‐step hydrothermal strategy is developed to coat flower‐like hierarchical TiO₂ micro/nanoparticles onto cotton fabric substrates (TiO₂@Cotton). Furthermore, robust superhydrophobic TiO₂@Cotton surfaces are constructed by the combination of hierarchical structure creation and low surface energy material modification, which allows versatility for self‐cleaning, laundering durability, and oil/water separation. Compared with hydrophobic cotton fabric, the TiO₂@Cotton exhibits a superior antiwetting and self‐cleaning property with a contact angle (CA) lager than 160° and a sliding angle lower than 5°. The superhydrophobic TiO₂@Cotton shows excellent laundering durability against mechanical abrasion without an apparent reduction of the water contact angle. Moreover, the micro/nanoscale hierarchical structured cotton fabrics with special wettability are demonstrated to selectively collect oil from oil/water mixtures efficiently under various conditions (e.g., floating oil layer or underwater oil droplet or even oil/water mixtures). In addition, it is expected that this facile strategy can be widely used to construct multifunctional fabrics with excellent self‐cleaning, laundering durability, and oil/water separation. The work would also be helpful to design and develop new underwater superoleophobic/superoleophilic materials and microfluidic management devices.     

Self‐Assembly of Enzyme‐Like Nanofibrous G‐Molecular Hydrogel for Printed Flexible Electrochemical Sensors

Conducting hydrogels provide great potential for creating designer shape‐morphing architectures for biomedical applications owing to their unique solid–liquid interface and ease of processability. Here, a novel nanofibrous hydrogel with significant enzyme‐like activity that can be used as “ink” to print flexible electrochemical devices is developed. The nanofibrous hydrogel is self‐assembled from guanosine (G) and KB(OH)₄ with simultaneous incorporation of hemin into the G‐quartet scaffold, giving rise to significant enzyme‐like activity. The rapid switching between the sol and gel states responsive to shear stress enables free‐form fabrication of different patterns. Furthermore, the replication of the G‐quartet wires into a conductive matrix by in situ catalytic deposition of polyaniline on nanofibers is demonstrated, which can be directly printed into a flexible electrochemical electrode. By loading glucose oxidase into this novel hydrogel, a flexible glucose biosensor is developed. This study sheds new light on developing artificial enzymes with new functionalities and on fabrication of flexible bioelectronics.     

A novel hydrophobic adsorbent of electrospun SiO<Subscript>2</Subscript>@MUF/PAN nanofibrous membrane and its adsorption behaviour for oil and organic solvents

With increasing oil spill accidents, the development of effective and low-cost adsorbents with good hydrophobicity is highly desirable. To cope with the clean-up of oil spill, a hydrophobic adsorbent was synthesized by electrospinning using inexpensive raw materials. By ingeniously combining melamine with polyacrylonitrile (PAN) as well as SiO₂ nanoparticles, a novel composite nanoadsorbent named SiO₂@MUF/PAN nanofibrous membrane was prepared and characterized. The adsorbents were conducted based on uniform nanofibre networks and were abundant with narrow slit-like pores, which are significant for the retention of oil and organic solvents. The hydrophobicity of the as-prepared membranes was enhanced with an increasing amount of SiO₂, and the highest water contact angle was 128.3°. Furthermore, the combination of SiO₂ and melamine increased the thermal stability of the membranes. With the unique pore structures and hydrophobicity, the membranes were able to selectively remove not only oil but also organic solvents from water surface. The adsorption capacities of the membranes with SiO₂ nanoparticles (0.9 wt%) were the highest and that for peanut oil, diesel, pump oil and engine oil were 19.09, 13.12, 18.48 and 22.67 g g^?1, respectively, while that for organic solvents ranged from 12.92 to 22.16 g g^?1. After 10 adsorption–regeneration cycles, the adsorption capacity was still around 35% of the initial value. Due to its high oil adsorption capacity, excellent reusability and the cost-effective hydrophobic, SiO₂@MUF/PAN have a great potential for oil spill clean-up.     

静电纺丝法制备聚乳酸纳米纤维及其吸油性能

本文采用静电纺丝法制备了聚乳酸(PLA)纳米纤维毡片,并首次研究了PLA纳米纤维微观结构对材料吸油性能的影响机制。扫描电子显微镜(SEM)表征显示前驱体溶液浓度对PLA静电纺丝纳米纤维直径具有显著影响,较高的浓度导致纳米纤维直径变大,10wt.%的前驱体溶液浓度可获得直径为50~100nm的均匀纳米纤维。接触角测定发现优化后的PLA纳米纤维材料具有超疏水超亲油特性。系统研究了PLA静电纺丝纳米纤维毡片对柴油、润滑油和植物油的吸附性能,发现PLA静电纺丝纳米纤维对柴油、润滑油和植物油的最大吸油倍率分别达到37、116和51g/g。实验模拟发现所制备的PLA纳米纤维材料具有吸油倍率高,吸水率低和可生物降解等特点,可用于吸附水面溢油。     

Calcinable Polymer Membrane with Revivability for Efficient Oily‐Water Remediation

Fouling of polymeric membranes remains a major challenge for long‐term operation of oily‐water remediation. The common reclamation methods to recycle fouled membranes have the issues of either incomplete degradation of organic pollutants or damage to filter membranes. Here, a calcinable polymer membrane with effective reclamation after fouling is reported, which shows full recovery of the original oil/water separation efficiency. The membrane is made of polysulfonamide/polyacrylonitrile fibers by emulsion electrospinning, followed by hydrothermal decoration of TiO₂ nanoparticles. The bonding structured fibrous membrane displays outstanding thermal stability in air (400 °C), strong acid/alkali resistance (at the pH range from 1 to 13), and robust tensile strength. As a result, the chemically fouled polymeric membrane can be easily reclaimed without decreasing in separation performance and mechanical properties by annealing treatment. As a proof‐of‐concept, the as‐prepared membrane is integrated into a wastewater separation tank, which achieves a high water flux over 3000 L m^?2 h^?1 and oil rejection efficiency of 99.6% for various oil‐in‐water emulsions. The presented strategy on membrane fabrication is believed to be an effective remedy for membrane fouling, and should apply in a wider field of filtration industry.     

Simulation‐Experimental Approach to Investigate the Role of Interfaces in Self‐Replenishing Composite Coatings

To investigate self‐replenishing on surface‐structured composite coatings a dual simulation‐experimental approach is employed to study the decisive role of polymer‐air and polymer‐particle interfaces. Experimentally, the composite system consists of a cross‐linked polymer network with fluorinated‐dangling chains, embedding colloidal SiO₂ nanoparticles which are incorporated in the network via covalent bonding. These particles provide the desired surface structure at the air‐interface before and after damage. Any damage replicates the rough surface, while the polymer layer on top of the particles serves as source of low surface energy groups which are able to reorient towards the new air‐interfaces. Using coarse‐grained simulations details of these self‐replenishing composite systems are revealed such as the minimum thickness of the polymer layer necessary for providing optimal self‐replenishing ability and the distribution profile of the dangling chains at the various interfaces. The principles and dual approach reported here may be applied to other self‐healing composite systems with applications in self‐cleaning, anti‐fouling or low adhesion materials.