Superhydrophobic Fabrics Produced by Electrospinning and Chemical Vapor Deposition

One-Way Water Transport Fabrics Based on Roughness Gradient Structure with No Low Surface Energy Substances

Despite great recent progress in one-way water transport (OWT) fabrics, the development of these fabrics based on roughness gradient without low surface energy materials has yet to be achieved. In this work, we prepared OWT fabrics using five polymers with hydrophobic or hydrophilic groups by constructing a roughness gradient structure along the fabric thickness. Electrospraying was used to deposit a rough layer on fabric's single side. The surface energy gradient change across the fabric thickness derived from roughness gradient structure played a major part in determining the OWT performance. With the roughness gradient structure, even polymers with hydrophilic groups, such as polyacrylonitrile and polyamide 6, could become OWT fabrics. Besides, the layer deposited on the surface of the fabric showed no effects on the air permeability of the fabric. These novel results provided an opportunity for more polymers, especially for hydrophilic polymers, to be used to prepare OWT fabrics by designing a roughness gradient along the thickness of the fabric. The method would be applied in designing of OWT fabrics with high performance.

Super Water-Repellent Cellulose Acetate Mats

A single-step synthesis of super-water-repellent oil sorbents based on cellulose acetate (CA) mats is reported in this paper. Key phenomenological mechanisms involving roughness and changes in chemistry are used to describe the change in hydrophobic behavior of the CA mats. Contact angle calculations followed by Cassie's model apparent contact angle prediction have shown roughness alone is not capable of producing the super-hydrophobicity exhibited by as-spun mats. Fourier transform infrared spectroscopy of spin coated and electrospun mats shows a significant difference in the stretching of the hydroxyl bonds of the two materials. As it is this hydroxyl group which adds to the overall polarity of surface thus hydrophilicity of the material, we propose that the electrospinning process not only creates a rougher surface but also alters the chemistry of the electrospun cellulose acetate mats which ultimately gives rise to the reported hydrophobicity. Finally, due to their water repellent nature, and oleophilicity of the as-spun mats were tested as oil sorbent mats. The as-spun mats were capable of absorbing thirty times their weight in oil demonstrating their application for oil-water remediation.

Self-Cleaning, Chemically Stable, Reshapeable, Highly Conductive Nanocomposites for Electrical Circuits and Flexible Electronic Devices

Materials with multiple functions are highly desirable in practical applications. Developing multifunctional nanocomposites by a straightforward process is still a challenge. Here, a versatile nanocomposite has been developed by simple blending and pressing of multiwalled carbon nanotubes (MWCNTs) and modified polydimethylsiloxane (MPDMS). Because of the synergistic effect of MWCNTs and MPDMS, this nanocomposite exhibits outstanding hydrophobic property, striking self-cleaning capability, and excellent chemical stability against strong acid and strong base, which makes it possible to work under wet and even extreme chemical conditions. Besides, because of its flexibility, this nanocomposite can be reshaped, bended, twisted, and molded into on-demand patterns for special applications. Owing to the good distribution of MWCNTs, the nanocomposite shows high conductivity (with a sheet resistance of 86.33 Ω sq^-1) and high healing efficiency (above 96.53%) in an electrical field, and it also exhibits outstanding performance in various electrical circuits and flexible electroluminescent devices. Furthermore, the inherent portability, recyclability, and reusability of this nanocomposite make it more convenient and environmentally friendly for practical applications. Thus, our work provides a new strategy to develop a multifunctional nanocomposite, and it shows tremendous potential in flexible electronics.

Growth Regimes of Poly(perfluorodecyl acrylate) Thin Films by Initiated Chemical Vapor Deposition

Control over thin film growth (e.g., crystallographic orientation and morphology) is of high technological interest as it affects several physicochemical material properties, such as chemical affinity, mechanical stability, and surface morphology. The effect of process parameters on the molecular organization of perfluorinated polymers deposited via initiated chemical vapor deposition (iCVD) has been previously reported. We showed that the tendency of poly(1H,1H,2H,2H-perfluorodecyl acrylate) (pPFDA) to organize in an ordered lamellar structure is a function of the filament and substrate temperatures adopted during the iCVD process. In this contribution, a more thorough investigation of the effect of such parameters is presented, using synchrotron radiation grazing incidence and specular X-ray diffraction (GIXD and XRD) and atomic force microscopy (AFM). The parameters influencing the amorphization, mosaicity, and preferential orientation are addressed. Different growth regimes were witnessed, characterized by a different surface structuring and by the presence of particular crystallographic textures. The combination of morphological and crystallographic analyses allowed the identification of pPFDA growth possibilities between island or columnar growth.

Biodegradable bead-on-spring nanofibers releasing β-carotene for bone tissue engineering

Bead-on-string mats based on poly(lactide-co-glycolide) (PLGA) releasing β-carotene (βC) as a natural osteogen were fabricated and used for bone tissue engineering. Mesenchymal stem cells (MSCs) seeded on the scaffolds successfully differentiated to osteoblasts without using any a differential medium. The mats showed a small burst of β-carotene (24-27%) during the first day and a sustained slow release up to 21 days. The MTT and SEM results indicated good attachment and proliferation of MSCs on the scaffolds. Calcination of scaffolds and expression of RUNX2, SOX9, and osteonectin genes approved the differentiation of seeded MSCs to osteoblasts without using any external osteogenic differential agent. The scaffold loaded with 4% β-carotene not only induced the early phase of osteogenesis but also advanced the differentiation to the osteoblast maturation phase. Thus, these bead-on-string scaffolds can be used as a substrate for direct bone tissue engineering.

Imparting superhydrophobic and biocidal functionalities to a polymeric substrate by the sonochemical method

Multifunctional substrates with superhydrophobic and biocidal properties are gaining interest for a wide range of applications; however, the production of such surfaces remains challenging. Here, the sonochemical method is utilized to impart superhydrophobicity and antimicrobial properties to a polyethylene (PE) sheet. This is achieved by sonochemically depositing nanoparticles (NPs) of a hydrophobic fluoro-polymer (FP) on the PE sheets. The polymer is a flexible, transparent fluoroplastic composed of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride in the form of a powder. The NPs of polymers are generated and deposited on the surface of the PE using ultrasound irradiation. Optimizing the process results in a homogeneous distribution of 110-200 nm of NPs on the PE surface. The coated surface displays a water-contact angle of 160°, indicating excellent superhydrophobicity. This superhydrophobic surface shows high stability under outdoor conditions for two months, which is essential for various applications. In addition, metal-oxide nanoparticles (CuO or ZnO NPs) were integrated into the polymer coating to achieve antibacterial properties and increase the surface roughness. The metal oxides were also deposited sonochemically. The antibacterial activity of the FP@ZnO and FP@CuO PE composites was tested against the bacterium Staphylococcus aureus, and the results show that the FP@CuO PE can effectively eradicate the bacteria. This study highlights the feasibility of using the sonochemical method to deposit two separate functions, opening up new possibilities for producing "smart" novel surfaces.

Rational design of materials interface at nanoscale towards intelligent oil-water separation

Oil-water separation is critical for the water treatment of oily wastewater or oil-spill accidents. The oil contamination in water not only induces severe water pollution but also threatens human beings' health and all living species in the ecological system. To address this challenge, different nanoscale fabrication methods have been applied for endowing biomimetic porous materials, which provide a promising solution for oily-water remediation. In this review, we present the state-of-the-art developments in the rational design of materials interface with special wettability for the intelligent separation of immiscible/emulsified oil-water mixtures. A mechanistic understanding of oil-water separation is firstly described, followed by a summary of separation solutions for traditional oil-water mixtures and special oil-water emulsions enabled by self-amplified wettability due to nanostructures. Guided by the basic theory, the rational design of interfaces of various porous materials at nanoscale with special wettability towards superhydrophobicity-superoleophilicity, superhydrophilicity-superoleophobicity, and superhydrophilicity-underwater superoleophobicity is discussed in detail. Although the above nanoscale fabrication strategies are able to address most of the current challenges, intelligent superwetting materials developed to meet special oil-water separation demands and to further promote the separation efficiency are also reviewed for various special application demands. Finally, challenges and future perspectives in the development of more efficient oil-water separation materials and devices by nanoscale control are provided. It is expected that the biomimetic porous materials with nanoscale interface engineering will overcome the current challenges of oil-water emulsion separation, realizing their practical applications in the near future with continuous efforts in this field.

Making Nonsticky Surfaces of Sticky Materials: Self-Organized Microtexturing of Viscoelastic Elastomeric Layers by Tearing

Fabrication of large area, multiscale microtextured surfaces engineered for antiadhesion properties remains a challenge. Compared to an elastic surface, viscoelastic solids show much higher surface stickiness, tack, and adhesion owing to the increased contact area and energy dissipation. Here, we show a simple, low cost, large-area and high throughput method with roll-to-roll compatibility to fabricate multiscale, rough microstructures resistant to adhesion in a viscoelastic layer by controlled tearing of viscous film. Even a high adhesive strength viscoelastic solid layer, such as partially cured PDMS, is made nonsticky simply by its controlled tearing. The torn surface shows a fracture induced, self-organized leaflike micropattern resistant to sticking. The topography and adhesion strength of these structures are readily tuned by changing the tearing speed and the film thickness. The microtexture displays a springlike recovery, low adhesive strength, and easy release properties even under the high applied loads.

Water Droplet Dynamics on a Hydrophobic Surface in Relation to the Self-Cleaning of Environmental Dust

The dynamic motion of a water droplet on an inclined hydrophobic surface is analyzed with and without environmental dust particles on the surface. Solution crystallization of a polycarbonate surface is carried out to generate a hydrophobic surface with hierarchical texture composed of micro/nanosize spheroids and fibrils. Functionalized nanosize silica particles are deposited on the textured surface to reduce contact angle hysteresis. Environmental dust particles are collected and characterized using analytical tools prior to the experiments. The droplet motion on the hydrophobic surface is assessed using high-speed camera data, and then, the motion characteristics are compared with the corresponding analytical results. The influence of dust particles on the water droplet motion and the amount of dust particles picked up from the hydrophobic surface by the moving droplet is evaluated experimentally. A 40 μL droplet was observed to roll on the hydrophobic surface with and without dust particles, and the droplet slip velocity was lower than the rotational velocity. The rolling droplet removes almost all dust particles from the surface, and the mechanism for the removal of dust particles from the surface was determined to be water cloaking of the dust particles.

Optimization of the Synthesis of Superhydrophobic Carbon Nanomaterials by Chemical Vapor Deposition

Demand is increasing for superhydrophobic materials in many applications, such as membrane distillation, separation and special coating technologies. In this study, we report a chemical vapor deposition (CVD) process to fabricate superhydrophobic carbon nanomaterials (CNM) on nickel (Ni)-doped powder activated carbon (PAC). The reaction temperature, reaction time and H₂/C₂H₂ gas ratio were optimized to achieve the optimum contact angle (CA) and carbon yield (CY). For the highest CY (380%) and CA (177°), the optimal reaction temperatures were 702 °C and 687 °C, respectively. However, both the reaction time (40 min) and gas ratio (1.0) were found to have similar effects on CY and CA. Based on the Field emission scanning electron microscopy and transmission electron microscopy images, the CNM could be categorized into two main groups: a) carbon spheres (CS) free carbon nanofibers (CNFs) and b) CS mixed with CNFs, which were formed at 650 and 750 °C, respectively. Raman spectroscopy and thermogravimetric analysis also support this finding. The hydrophobicity of the CNM, expressed by the CA, follows the trend of CS-mixed CNFs (CA: 177°) > CS-free CNFs (CA: 167°) > PAC/Ni (CA: 65°). This paves the way for future applications of synthesized CNM to fabricate water-repellent industrial-grade technologies.

Reversible exchange of wetting state of a hydrophobic surface via phase change material coating

Reversible exchange of the wetting state of a hydrophobic surface is examined. Solution crystallization of a polycarbonate surface is carried out to form hierarchically distributed micro/nano size spherules and fibrils on the surface. Although the solution crystallized surface has hydrophobic characteristics, the contact angle hysteresis remains high. Functionalized silica particles are deposited on the crystallized polycarbonate surface to improve the droplet contact angle and lower contact angle hysteresis. The liquid film of n-octadecane with 1.5 μm thickness is formed on the functionalized silica particles deposited crystallized surface, which results in hydrophilic surface characteristics. The n-octadecane film solidifies upon reducing the temperature on the surface and solid flakes of n-octadecane are formed. This arrangement changes the surface wetting state to hydrophobic. Liquefaction and solidifying of the n-octadecane film at the functionalized silica deposited surface gives rise to reversible exchange of surface wetting state. This behavior is attributed to exposure of emerging functionalized silica particles to the free surface in the region of the solid n-octadecane flakes. The water droplet is cloaked by the liquid n-octadecane while forming a ridge around the droplet. In this case, the water droplet becomes mobile at the surface because flow develops in the n-octadecane liquid film at the onset of liquefaction.

Study on poly(tetrafluoroethylene-co-hexafluoropropylene) hollow fiber membranes with surface modification by a chemical vapor deposition method

FEP/PPy composite hollow fiber membranes were prepared by PPy layer polymerization on the outer surface of FEP hollow fiber membranesviaa chemical vapor deposition method.

Fabrication of Water Jet Resistant and Thermally Stable Superhydrophobic Surfaces by Spray Coating of Candle Soot Dispersion

A facile synthesis method for highly stable carbon nanoparticle (CNP) dispersion in acetone by incomplete combustion of paraffin candle flame is presented. The synthesized CNP dispersion is the mixture of graphitic and amorphous carbon nanoparticles of the size range of 20-50 nm and manifested the mesoporosity with an average pore size of 7 nm and a BET surface area of 366 m²g^-1. As an application of this material, the carbon nanoparticle dispersion was spray coated (spray-based coating) on a glass surface to fabricate superhydrophobic (water contact angle > 150° and sliding angle < 10 °) surfaces. The spray coated surfaces were found to exhibit much improved water jet resistance and thermal stability up to 400 °C compared to the surfaces fabricated from direct candle flame soot deposition (candle-based coating). This study proved that water jet resistant and thermally stable superhydrophobic surfaces can be easily fabricated by simple spray coating of CNP dispersion gathered from incomplete combustion of paraffin candle flame and this technique can be used for different applications with the potential for the large scale fabrication.

A review on the mechanical and thermodynamic robustness of superhydrophobic surfaces

Advancements in the fabrication and study of superhydrophobic surfaces have been significant over the past 10years, and some 20years after the discovery of the lotus effect, the study of special wettability surfaces can be considered mainstream. While the fabrication of superhydrophobic surfaces is well advanced and the physical properties of superhydrophobic surfaces well-understood, the robustness of these surfaces, both in terms of mechanical and thermodynamic properties, are only recently getting attention in the literature. In this review we cover publications that appeared over the past ten years on the thermodynamic and mechanical robustness of superhydrophobic surfaces, by which we mean the long term stability under conditions of wear, shear and pressure. The review is divided into two parts, the first dedicated to thermodynamic robustness and the second dedicated to mechanical robustness of these complex surfaces. Our work is intended as an introductory review for researchers interested in addressing longevity and stability of superhydrophobic surfaces, and provides an outlook on outstanding aspects of investigation.

Preparation of Stable Superhydrophobic Coatings on Wood Substrate Surfaces via Mussel-Inspired Polydopamine and Electroless Deposition Methods

Mussel-inspired polydopamine (PDA) chemistry and electroless deposition approaches were used to prepare stable superhydrophobic coatings on wood surfaces. The as-formed PDA coating on a wood surface exhibited a hierarchical micro/nano roughness structure, and functioned as an “adhesive layer” between the substrate and a metallic film by the metal chelating ability of the catechol moieties on PDA, allowing for the formation of a well-developed micro/nanostructure hierarchical roughness. Additionally, the coating acted as a stable bridge between the substrate and hydrophobic groups. The morphology and chemical components of the prepared superhydrophobic wood surfaces were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The PDA and octadecylamine (OA) modified surface showed excellent superhydrophobicity with a water contact angle (CA) of about 153° and a rolling angle (RA) of about 9°. The CA further increased to about 157° and RA reduced to about 5° with the Cu metallization. The superhydrophobic material exhibited outstanding stability in harsh conditions including ultraviolet aging, ultrasonic washing, strong acid-base and organic solvent immersion, and high-temperature water boiling. The results suggested that the PDA/OA layers were good enough to confer robust, degradation-resistant superhydrophobicity on wood substrates. The Cu metallization was likely unnecessary to provide significant improvements in superhydrophobic property. However, due to the amazing adhesive capacity of PDA, the electroless deposition technique may allow for a wide range of potential applications in biomimetic materials.

Biomolding Technique to Fabricate the Hierarchical Topographical Scaffold of POMA To Enhance the Differentiation of Neural Stem Cells

In this paper, a biomolding technique was first used to fabricate a scaffold of hierarchical topography with biomimetic morphology for tissue engineering. First, poly(ortho-methoxyaniline) (POMA) was synthesized by conventional oxidative polymerization, followed by characterizations with Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). Moreover, the POMA scaffold with 3D biomimetic morphology was fabricated using poly(dimethylsiloxane) (PDMS) as negative soft template from natural leaf surfaces of Xanthosoma sagittifolium, followed by transferring the pattern of PDMS template to POMA. The as-fabricated POMA scaffold with biomimetic morphology was investigated by scanning electron microscopy (SEM). Subsequently, cell-scaffold interactions were carried out by culturing rat neural stem cells (rNSCs) on biomimetic and nonbiomimetic, or flat, POMA scaffolds, as well as on poly(d-lysine) (PDL)-coated substrate, and evaluating the corresponding adhesion, cell viability, and differentiation of rNSCs. Results showed that there was no significant difference in the attachment of rNSCs on the three surface types, however, both the biomimetic and flat POMA scaffolds induced growth arrest relative to the PDL-coated substrate. In addition, the percentage of cells with elongated neurites after 19 days of culture was higher on the biomimetic POMA scaffold relative to flat POMA and PDL. In summary, the POMA scaffold with biomimetic morphology shows promise in promoting rNSCs differentiation and neurite outgrowth for long-term studies on nerve regenerative medicine.

Mussel-inspired chemistry for preparation of superhydrophobic surfaces on porous substrates

A facile and versatile mussel-inspired surface modification approach was used to fabricate a lotus-leaf-like hierarchical surface with superhydrophobicity.

Silicone oil impregnated nano silica modified glass surface and influence of environmental dust particles on optical transmittance

The behavior of environmental dust particles on a silicone oil impregnated glass surface is examined in relation to optical transparent surfaces for self-cleaning applications.

A Review on Development and Applications of Bio-Inspired Superhydrophobic Textiles

Bio-inspired engineering has been envisioned in a wide array of applications. All living bodies on Earth, including animals and plants, have well organized functional systems developed by nature. These naturally designed functional systems inspire scientists and engineers worldwide to mimic the system for practical applications by human beings. Researchers in the academic world and industries have been trying, for hundreds of years, to demonstrate how these natural phenomena could be translated into the real world to save lives, money and time. One of the most fascinating natural phenomena is the resistance of living bodies to contamination by dust and other pollutants, thus termed as self-cleaning phenomenon. This phenomenon has been observed in many plants, animals and insects and is termed as the Lotus Effect. With advancement in research and technology, attention has been given to the exploration of the underlying mechanisms of water repellency and self-cleaning. As a result, various concepts have been developed including Young's equation, and Wenzel and Cassie-Baxter theories. The more we unravel this process, the more we get access to its implications and applications. A similar pursuit is emphasized in this review to explain the fundamental principles, mechanisms, past experimental approaches and ongoing research in the development of bio-inspired superhydrophobic textiles.

Uniting Superhydrophobic, Superoleophobic and Lubricant Infused Slippery Behavior on Copper Oxide Nano-structured Substrates

Alloys, specifically steel, are considered as the workhorse of our society and are inimitable engineering materials in the field of infrastructure, industry and possesses significant applications in our daily life. However, creating a robust synthetic metallic surface that repels various liquids has remained extremely challenging. The wettability of a solid surface is known to be governed by its geometric nano-/micro structure and the chemical composition. Here, we are demonstrating a facile and economical way to generate copper oxide micro-nano structures with spherical (0D), needle (1D) and hierarchical cauliflower (3D) morphologies on galvanized steel substrates using a simple chemical bath deposition method. These nano/micro textured steel surfaces, on subsequent coating of a low surface energy material display excellent superhydrophobic, superoleophobic and slippery behavior. Polydimethylsiloxane coated textured surfaces illustrate superhydrophobicity with water contact angle about 160°(2) and critical sliding angle ~2°. When functionalized with low-surface energy perfluoroalkylsilane, these surfaces display high repellency for low surface tension oils as well as hydrocarbons. Among them, the hierarchical cauliflower morphology exhibits re-entrant structure thereby showing the best superoleophobicity with contact angle 149° for dodecane. Once infused with a lubricant like silicone oil, they show excellent slippery behavior with low contact angle hysteresis (~ 2°) for water drops.

Superhydrophobic materials for biomedical applications

Superhydrophobic surfaces are actively studied across a wide range of applications and industries, and are now finding increased use in the biomedical arena as substrates to control protein adsorption, cellular interaction, and bacterial growth, as well as platforms for drug delivery devices and for diagnostic tools. The commonality in the design of these materials is to create a stable or metastable air layer at the material surface, which lends itself to a number of unique properties. These activities are catalyzing the development of new materials, applications, and fabrication techniques, as well as collaborations across material science, chemistry, engineering, and medicine given the interdisciplinary nature of this work. The review begins with a discussion of superhydrophobicity, and then explores biomedical applications that are utilizing superhydrophobicity in depth including material selection characteristics, in vitro performance, and in vivo performance. General trends are offered for each application in addition to discussion of conflicting data in the literature, and the review concludes with the authors' future perspectives on the utility of superhydrophobic biomaterials for medical applications.

Complex, multi-scale small intestinal topography replicated in cellular growth substrates fabricated via chemical vapor deposition of Parylene C

Native small intestine possesses distinct multi-scale structures (e.g., crypts, villi) not included in traditional 2D intestinal culture models for drug delivery and regenerative medicine. The known impact of structure on cell function motivates exploration of the influence of intestinal topography on the phenotype of cultured epithelial cells, but the irregular, macro- to submicron-scale features of native intestine are challenging to precisely replicate in cellular growth substrates. Herein, we utilized chemical vapor deposition of Parylene C on decellularized porcine small intestine to create polymeric intestinal replicas containing biomimetic irregular, multi-scale structures. These replicas were used as molds for polydimethylsiloxane (PDMS) growth substrates with macro to submicron intestinal topographical features. Resultant PDMS replicas exhibit multiscale resolution including macro- to micro-scale folds, crypt and villus structures, and submicron-scale features of the underlying basement membrane. After 10 d of human epithelial colorectal cell culture on PDMS substrates, the inclusion of biomimetic topographical features enhanced alkaline phosphatase expression 2.3-fold compared to flat controls, suggesting biomimetic topography is important in induced epithelial differentiation. This work presents a facile, inexpensive method for precisely replicating complex hierarchal features of native tissue, towards a new model for regenerative medicine and drug delivery for intestinal disorders and diseases.

Electrospinning of Nanodiamond-Modified Polysaccharide Nanofibers with Physico-Mechanical Properties Close to Natural Skins

Electrospinning of biopolymers has gained significant interest for the fabrication of fibrous mats for potential applications in tissue engineering, particularly for wound dressing and skin regeneration. In this study, for the first time, we report successful electrospinning of chitosan-based biopolymers containing bacterial cellulous (33 wt %) and medical grade nanodiamonds (MND) (3 nm; up to 3 wt %). Morphological studies by scanning electron microscopy showed that long and uniform fibers with controllable diameters from 80 to 170 nm were prepared. Introducing diamond nanoparticles facilitated the electrospinning process with a decrease in the size of fibers. Fourier transform infrared spectroscopy determined hydrogen bonding between the polymeric matrix and functional groups of MND. It was also found that beyond 1 wt % MND, percolation networks of nanoparticles were formed which affected the properties of the nanofibrous mats. Uniaxial tensile testing of the woven mats determined significant enhancement of the strength (from 13 MPa to 25 MP) by dispersion of 1 wt % MND. The hydrophilicity of the mats was also remarkably improved, which was favorable for cell attachment. The water vapor permeability was tailorable in the range of 342 to 423 µg·Pa(-1)·s(-1)·m(-1). The nanodiamond-modified mats are potentially suitable for wound healing applications.

Environmental Applications of Interfacial Materials with Special Wettability

Interfacial materials with special wettability have become a burgeoning research area in materials science in the past decade. The unique surface properties of materials and interfaces generated by biomimetic approaches can be leveraged to develop effective solutions to challenging environmental problems. This critical review presents the concept, mechanisms, and fabrication techniques of interfacial materials with special wettability, and assesses the environmental applications of these materials for oil-water separation, membrane-based water purification and desalination, biofouling control, high performance vapor condensation, and atmospheric water collection. We also highlight the most promising properties of interfacial materials with special wettability that enable innovative environmental applications and discuss the practical challenges for large-scale implementation of these novel materials.

Recent Progress in Fabrication and Applications of Superhydrophobic Coating on Cellulose-Based Substrates

Multifuntional fabrics with special wettability have attracted a lot of interest in both fundamental research and industry applications over the last two decades. In this review, recent progress of various kinds of approaches and strategies to construct super-antiwetting coating on cellulose-based substrates (fabrics and paper) has been discussed in detail. We focus on the significant applications related to artificial superhydrophobic fabrics with special wettability and controllable adhesion, e.g., oil-water separation, self-cleaning, asymmetric/anisotropic wetting for microfluidic manipulation, air/liquid directional gating, and micro-template for patterning. In addition to the anti-wetting properties and promising applications, particular attention is paid to coating durability and other incorporated functionalities, e.g., air permeability, UV-shielding, photocatalytic self-cleaning, self-healing and patterned antiwetting properties. Finally, the existing difficulties and future prospects of this traditional and developing field are briefly proposed and discussed.

Durable and scalable icephobic surfaces: similarities and distinctions from superhydrophobic surfaces

Formation, adhesion, and accumulation of ice, snow, frost, glaze, rime, or their mixtures can cause severe problems for solar panels, wind turbines, aircrafts, heat pumps, power lines, telecommunication equipment, and submarines. These problems can decrease efficiency in power generation, increase energy consumption, result in mechanical and/or electrical failure, and generate safety hazards. To address these issues, the fundamentals of interfaces between liquids and surfaces at low temperatures have been extensively studied. This has lead to development of so called "icephobic" surfaces, which possess a number of overlapping, yet distinctive, characteristics from superhydrophobic surfaces. Less attention has been given to distinguishing differences between formation and adhesion of ice, snow, glaze, rime, and frost or to developing a clear definition for icephobic, or more correctly pagophobic, surfaces. In this review, we strive to clarify these differences and distinctions, while providing a comprehensive definition of icephobicity. We classify different canonical families of icephobic (pagophobic) surfaces providing a review of those with potential for scalable and robust development.