High Water Contact Angle Research Articles

Comparison of biodegradable chitosan-based composite films reinforced by different micron-sized plant fibers for food packaging

To provide a fully degradable food packaging film with excellent performance, a chitosan (CS)-based film containing micron-sized plant fibers was prepared by the casting method. With the addition of different plant fibers—wheat straw fiber (WF), maize straw fiber (MF), rice straw fiber (RF), and sisal fiber (SF), a significant improvement in mechanical, water resistance, water vapor barrier, and thermal properties was observed. By comparison, the most significant enhancement effect was observed in CS/SF-based film. The tensile strength and elongation at break of this film were 58.44 MPa and 14.42%, respectively. Moreover, it exhibited excellent properties such as the highest water contact angle (118°), a moisture absorption rate of 5.14%, a low water vapor transmission rate (110.73 g·m-2·d-1), and high thermal stability. Considering the sustainability and attractive physical properties, the improved films showed great potential for food packaging.

Bio‐based fluorine‐free branched polyurethane@organosilicon water‐repellent agent for cotton fabric

AbstractIn recent years, with the increasing consciousness on environment protection, fluorine‐free water‐repellent agents in textile industry have attracted considerable attention. Herein, we proposed a new strategy to prepare bio‐based fluorine‐free branched polyurethane@organosilicon water‐repellent agent for cotton fabric (CF). Branched polyurethane (BPU) with long alkyl chains was firstly synthesized through the reaction of glycerin monostearate extracted from natural palm fruit, toluene diisocyanate, trimethylopropane and N‐methyl diethanolamine, and then utilized to coat the C24‐28 olefin modified hydroxyl silicone oil (C24‐28 HSO) by emulsification procedure to obtain branched polyurethane@organosilicon (BPU@C24‐28 HSO) water‐repellent agent. Fourier transform infrared spectroscopy and1H nuclear magnetic resonance spectroscopy confirmed the chemical structures of BPU, C24‐28 HSO and BPU@C24‐28 HSO water‐repellent agent. The biomass carbon content of the water‐repellent agent reached 54.0%. Transmission electron microscope demonstrated that the BPU@C24‐28 HSO water‐repellent agent appeared obvious spherical shape with core‐shell structure. Owing to the introduction of organosilicon, the water‐repellent agent significantly improved the softness of the CF. In addition, the CF finished by the BPU@C24‐28 HSO water‐repellent agent also exhibited excellent water‐repellent score of 90+, high water contact angle of 141.6° and superior surface stability. Our findings provided a direction to prepare environmental‐friendly and high‐performance water‐repellent agents for various fabrics.

An expanding horizon: Recyclable dual-functional size-adjusted fluorinated mesh devices for large-scale oily wastewater remediation

The general lack of water resources makes the treatment of oily wastewater as an urgent concern, which causes catastrophic damage to ecosystems and environment. Construction of a universal oil/water separator is not an easy task, because the reported processes are relatively complex and it is difficult to achieve industrial large-scale production. To overcome this problem, herein, using the low-cost and frequently-used metal (stainless steel, etc.) meshes as raw materials, two kinds of oil/water separators with different moving models have firstly designed via a universal technique of a facile chemical etching and fluoridation coating process. The newly synthesized superhydrophobic/superoilphilic stainless steel or copper mesh with surface morphology, high purity and structure stability displayed an excellent anti-wetting property (high water contact angle of >157°) after a series of tests of immersion, droplet rolling-off, anti-impacting process, 30days exposure aging in open-air, etc. In addition, experimental results revealed that the fresh and aging separators can maintain excellent oily wastewater remediation efficiency up to ∼99% even after 25 separation cycles, making them economical and commercially viable. This study provides a novel perspective for advancement in designing oil/water separator with low cost, less energy consumption and high efficiency for universal application.

Soda pulping of sunn hemp (Crotalaria juncea L.) and its usage in molded pulp packaging

Petroleum-based materials are often used in the packaging industry. However, the single use value of such products can be problematic with regard to proper waste disposal. As such, molded pulp packaging can be used as an alternative, given its ease of recycling, composting, and eventual biodegradation. In this work, we aims to study the pulp properties of sunn hemp and its usage as molded pulp products. For this purpose, unbleached beaten and unbeaten soda pulps derived from the whole stem of sunn hemp were examined for their fiber morphology, fibrillation, fiber classification, and physical properties. The sunn hemp pulp was subsequently molded using a batch molding machine. To determine the hydrophobicity of the molded pulp products, the molded samples were manufactured with and without additives. Finally, some properties of the molded pulp products were examined and compared with the commercially available bleached bagasse molded pulp products. It was observed that the molded products made from sunn hemp pulp with additives had a higher water contact angle than that of the commercial products. In terms of general usage, the molded products from sunn hemp pulp with additives were found to be capable of storing hot water, hot cooking oil, as well as microwaving water. We concluded that the sunn hemp pulp could be used as an alternative fibrous raw material in the production of molded pulp packaging.

Development of sustainable superhydrophobic coatings on aluminum substrate using magnesium nanoparticles for enhanced catalytic activity, self-cleaning, and corrosion resistance

This study focuses on the development of sustainable superhydrophobic surfaces (SHSs) using magnesium nanoparticles (Mg-NPs) for catalytic applications and achieved excellent SHSs on the aluminum substrate along with a high static water contact angle of 160° and a low sliding angle of 2° via etching, immersion, and annealing method. The changes in surface chemistry, structural composition, and surface morphology were examined by using various characterization techniques, such as X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Herein, we describe the creation of Mg-NPs @SHS which is facile, eco-friendly, mechanically stable and fluorine-free, along with surface robustness as compared to other SHP coatings present in the literature whose surface textures become fragile and poor wear-resistance due to direct/indirect involvement of toxic chemicals such as fluorocarbons along with complicated preparation processes and costly processing procedures. It showed a low value of Ecorr (−0.425 V) and a high value of Icorr (2.016 × 10−5 A cm−2) than a non-coated Al plate of Ecorr is (−0.801 V) and Icorr (4.998 × 10−3 A cm−2). It has also remarkable self-cleaning, super buoyancy, anti-icing property, and excellent catalytic reduction of 4-NP to 4-AP with efficiency of 99.82% in the 1st and 84% in 13th cycle. These findings suggest that Mg-NPs @SHS on the aluminum substrate have promising applications in sustainable environmental practices and provide valuable insights for the fabrication of superhydrophobic surfaces on different materials. This work offers a new avenue for the development of high-performance catalysts with reusability and durability composed of magnesium particles.

Preparation and Properties of a Novel Cross-Linked Network Waterborne Polyurethane for Wood Lacquer.

Waterborne polyurethane (WPU) is a waterborne coating with excellent physicochemical properties. Its deficiencies of water resistance, chemical resistance, staining, and hardness have limited the wide application of polyurethane in the wood lacquer market. In this study, polycarbonate diols (PCDL) were used as soft segments and WPCU was modified by cross-linking using Trimethylolpropane (TMP) to prepare polycarbonate type WPU (WPCU) with cross-linked network structure. The new wood lacquer was prepared by adding various additives and tested by applying it on wood board. The successful synthesis of WPCU was determined by FTIR testing, and the cross-linking degree of WPCU was probed by low-field NMR. The viscosity of the cross-linked WPCU emulsion showed a decreasing trend compared to the uncross-linked WPCU emulsion, and WPCU-2 had the smallest particle size. Compared with the uncrosslinked WPCU film, the crosslinked WPCU film had lower water absorption (2.2%), higher water contact angle (72.7°), excellent tensile strength (44.02 MPa), higher thermomechanical, and better water and alcohol resistance. The effect of crosslinker content on the microphase separation of WPCU chain segments on the surface roughness of the film was investigated by SEM. The wood paint prepared by WPCU emulsion has good dry heat resistance, chemical resistance, and adhesion, and the hardness of the wood paint when the TMP content is 3% reaches H. It also has good resistance to sticky stains, which can be used to develop new wood lacquer.

A new hydrophobin candidate from Cladosporium macrocarpum with super-hydrophobic surface

Hydrophobins are amphipathic proteins with small molecular weights produced in filamentous fungi. These proteins are highly stable due to the disulfide bonds formed between the protected cysteine residues. They have great potential for usage in many different fields such as surface modifications, tissue engineering, and drug transport systems because hydrophobins are surfactants and soluble in harsh mediums. In this study, it was aimed to determine the hydrophobin proteins responsible for the hydrophobicity of the super-hydrophobic fungi isolates in the culture medium and to carry out the molecular characterization of the hydrophobin producer species. As a result of measuring surface hydrophobicity by determining the water contact angle, five different fungi with the highest hydrophobicity were classified as Cladosporium by classical and molecular (ITS and D1-D2 regions) methods. Also, protein extraction according to the recommended method for obtaining hydrophobins from spores of these Cladosporium species indicated that the isolates have similar protein profiles. Ultimately, the isolate named A5 with the highest water contact angle was identified as Cladosporium macrocarpum, and the 7 kDa band was appointed as a hydrophobin since it was the most abundant protein in protein extraction for this species.

Nanoscale chemical heterogeneity enables the co-existence of opposing superhydrophobic and hygroscopic properties

Superhydrophobicity and hygroscopicity are two properties that are theoretically exclusive to each other. The fabrication of functional fabrics with these two properties remains very challenging. In this work, it is demonstrated that a non-sticky superhydrophobic and hygroscopic fabric coating can be prepared via the photo polymerization of hexadecyl acrylate and methacrylic acid. On coating surface, the phase-separation-induced chemical heterogeneity has a unique feature of possessing elevated continuous hydrophobic domain and depressed hydrophilic domain, as evidenced by atomic force microscopy measurement. The elevation of hydrophobic domain (i.e., depression of hydrophilic domain) allows the hydrophilic domain to make negligible contribution to the surface wettability to water drop, but can absorb water molecules, thus inducing the unique superhydrophobic but hygroscopic property. The coating has a very low total surface energy of 22.61 mN m−1, with its polar part (0.01 mN m−1) being negligible, thereby showing a high static water contact angle of ~112° on flat glass slide. The coated polyester fabric shows a non-sticky superhydrophobicity with a static water contact angle of ~151° and a water shedding angle of ~10°, as well as good hygroscopic and anti-static properties. We anticipate that this novel coating and the reported strategy of generating the particular chemical heterogeneity may lead to the development of advanced special wettability coatings for various applications.

Fabrication of high-strength and multi-recyclable supramolecular polysiloxane by incorporating quadruple hydrogen bonds into main-chains for adhesive and oil-water separation

Studies are currently exploring strategies for development of recyclable materials that do not rely on petrochemical resources to alleviate increased environmental pollution. Polysiloxane is a non-toxic and non-hazardous polymeric material that is not produced from petrochemical resources, but has limited application due to its poor mechanical properties. In the present study, a novel supramolecular polysiloxane (SPSO) with excellent mechanical properties, exceptional reprocessing molding, and superior multiple recyclability was fabricated through incorporation of 2-ureido-4[1H]-pyrimidinone (UPy) into the main chains. The quadruple hydrogen bond interaction of UPy induces the aggregation of UPy, leading to phase separation and physical crosslinking in the SPSO. The rigid hard phase region acts as a reinforcing filler to further enhance the mechanical strength of the SPSO. The maximum tensile strength of the material was 7.28 MPa, which was significantly higher than that of traditional silicone rubber at 0.5 MPa. The mechanical properties of the SPSO retained 100% of the original properties even after three generations of recycling, indicating excellent multiple recyclability. The material exhibited excellent adhesive properties due to the high number of hydrogen bonds. The maximum adhesive strength of the SPSO to wood was 4.8 MPa. SPSO composite sponge was prepared by adding chopped carbon fiber reinforcement. The superhydrophobic SPSO composite sponge had a high water contact angle of 153°, indicating that it can be used for oil-water separation. The maximum separation efficiency of the material was 96%. A simple and versatile approach was used to introduce hydrogen bonds into the backbone of polysiloxane to form physical cross-links and enhance microphase separation. The findings from this study provide a basis for constructing polysiloxane materials with high recyclability and strong mechanical properties.

Efficient adsorption of aromatic and aliphatic hydrocarbons by electrospun hydrophobic PTFE-NiO composite nanofiber filter mats

Aromatic and aliphatic hydrocarbons (AAHs) are comprised of a variety of gaseous chemicals that may affect human and environmental health. To remove AAHs from air, polytetrafluoroethylene-nickel oxide (PTFE-NiO) composite nanofiber filter mats (NFMs) were synthesized and characterized for their ability to effectively adsorb AAHs. The NiO-nanoparticle-doped mats were fabricated by green electrospinning of PTFE and polyvinyl alcohol (PVA) mixtures added with nickel (II) nitrate hexahydrate in the spinning solution followed by surface heat treatment. FE-SEM FTIR, Raman spectroscopy, sessile drop and Jar methods were applied as characterization techniques. The diameter of the electrospun nanofibers without NiO dopant ranged from 0.34 ± 21.61 to 0.23 ± 10.12 µm, whereas a reduction in diameter of NiO-doped nanofibers was obtained, ranging between pristine to 0.25 ± 24.12 µm and 0.12 ± 85.75 µm with heat treatment. 6% (by weight) NiO-doped PTFE composite NFMs exhibited a high water-contact angle of 120 ± 2.20 degrees; the high hydrophobicity value aided self-cleansing property of NFMs for practical applications. UV adsorption capability for heat-treated PTFE-NiO NFMs was evaluated for three AAHs, and the results showed that 6 wt% NiO adsorbed 1.41, 0.67, and 0.73 µg/mg of toluene, formaldehyde and acetone, respectively. These findings reveal the potential applicability of the prepared filter mats for capturing various AAHs from polluted air.

Hydrophobic, Mechanical, and Physical Properties of Polyurethane Nanocomposite: Synergistic Impact of Mg(OH)2 and SiO2.

Polyurethane (PU) is one of the most well-known polymer coatings because of its favorable characteristics, which include its low density, nontoxicity, nonflammability, longevity, adhesion, simple manufacture, flexibility, and hardness. However, PU does come with several major drawbacks, among which are poor mechanical properties as well as low thermal and chemical stability, particularly in the high-temperature mode, where becomes gets flammable and loses adhesion ability. The limitations have inspired researchers to develop a PU composite to improve the weaknesses by adding different reinforcements. Magnesium hydroxide, having the ability to be produced with exceptional properties such as flammability, has consistently attracted the interest of researchers. Additionally, silica nanoparticles with high strength and hardness are one of the excellent reinforcements of polymers these days. The hydrophobic, physical, and mechanical properties of pure polyurethane and the composite type (nano, micro, and hybrid) fabricated with the drop casting method were examined in this study. 3-Aminopropyl triethoxysilane was applied as a functionalized agent. To confirm that hydrophilic particles turned into hydrophobic, FTIR analysis was carried out. The impact of size, percentage, and kind of fillers on different properties of PU/Mg(OH)2-SiO2 was then investigated using different analyses including spectroscopy and mechanical and hydrophobicity tests. The resultant observations demonstrated that different surface topographies can be obtained from the presence of particles of different sizes and percentages on the hybrid composite's surface. Surface roughness allowed for exceptionally high water contact angles, which confirmed the hybrid polymer coatings' superhydrophobic properties. According to the particle size and content, the distribution of fillers in the matrix also improved the mechanical properties.

DEVELOPMENT OF AN ANTIMICROBIAL LIPID COATING TO PREVENT INFECTIONS IN UNCEMENTED JOINT REPLACEMENTS

Preventing infections in joint replacements is a major ongoing challenge, with limited effective clinical technologies currently available for uncemented knee and hip prostheses. This research aims to develop a coating for titanium implants, consisting of a supported lipid bilayer (SLB) encapsulating an antimicrobial agent. The SLB will be robustly tethered to the titanium using self-assembled monolayers (SAMs) of octadecylphosphonic acid (ODPA). The chosen antimicrobial is Novobiocin, a coumarin-derived antibiotic known to be effective against resistant strains of Staphylococcus aureus.ODPA SAMs were deposited on TiO2-coated quartz crystal microbalance (QCM) sensors using two environmentally friendly non-polar solvents (anisole and cyclopentyl methyl ether, CPME), two concentrations of ODPA (0.5mM and 1mM) and two processing temperatures (21°C and 60°C). QCM, water contact angle measurements, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and temperature-programmed desorption mass spectrometry (TPD-MS) were used to characterise the ODPA SAM. A SLB with encapsulated Novobiocin was subsequently developed on the surface of the ODPA SAM using fluorescent lipids and a solvent assisted method. The prototype implant surface was tested for antimicrobial activity against S. aureus.A well-ordered, uniform ODPA SAM was rapidly formed using 0.5 mM ODPA in CPME at 21°C during 10 min, as confirmed by high Sauerbrey mass (≍285-290 ng/cm2), high atomic percentage phosphorus (detected using XPS) and high water contact angles (117.6±2.5°). QCM measurements combined with fluorescence microscopy provided evidence of complete planar lipid bilayer formation on the titanium surface using a solvent assisted method. Incorporation of Novobiocin into the SLB resulted in reduced attachment and viability of S. aureus.Key parameters were established for the rapid, robust and uniform formation of an ODPA SAM on titanium (solvent, temperature and concentration). This allowed the successful formation of an antimicrobial SLB, which demonstrated potential for reducing attachment and viability of pathogens associated with joint replacement infections.

Transparent and superhydrophobic room temperature vulcanized (RTV) polysiloxane coatings loaded with different hydrophobic silica nanoparticles with self-cleaning characteristics

Superhydrophobic coatings based on room temperature vulcanized (RTV) polysiloxane matrix loaded with organically modified silica (ORMOSIL) nanoparticles were successfully prepared using the cost-effective and scalable one-step spraying coating approach. ORMOSIL nanoparticles were prepared by sol-gel treatment at ambient conditions through the reaction between the commercial hydrophilic silica (R200) and octyl-triethoxysilane (R200.OTS), (1H,1H,2H,2H-nonafluorohexyl)-triethoxysilane (R200.NFS) and a mixture of both (R200.OTS/NFS). The functionalization of the silica was followed by Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). Commercial hydrophobic silica particles functionalized with siloxane (R202) and octyl-silane (R805) were also used for comparison. The presence of 20 % of R202 and R200.NFS resulted in coatings with water contact angle (WCA) higher than 160°, sliding angle <5°, high transparency and an effective self-cleaning behavior. Increasing the amount of nanoparticles increased the superhydrophobic response but the translucence decreased. Coatings containing R200.OTS particles presented high translucence and high WCA, but the sliding angle was also high, which limits their use as self-cleaning material.

Hierarchical ‘rose-petal’ ZnO/Si surfaces with reversible wettability reaching complete water repellence without chemical modification

Smart surfaces with externally controlled wettability patterns are ubiquitous building blocks for micro-/nanofluidic and lab-on-chip devices, among others. We develop hierarchical surfaces of ZnO nanorods grown on laser-microstructured silicon with reversible photo-induced and heat-induced wettability. The as-prepared surfaces are superhydrophilic, with very low water contact angles (~ 10°), and transition to a wetting state with high water contact angles (~ 150°) when annealed in vacuum. As the annealing temperature increases to 400 °C, the surfaces become completely water-repellent. Even though the annealed surfaces present high water contact angles, at the same time, they are very adhesive for water droplets, which do not roll off even when tilted at 90° or 180o (rose-petal effect), unlike standard hydrophobic surfaces which typically combine high water contact angles with low roll-off angles. The surfaces return to the superhydrophilic state when irradiated with UV light, which indicates a reversible wettability with external stimuli. Based on this transition, we demonstrate local modification of the wetting state of the surfaces by UV irradiation through a mask, which results in directed liquid motion, useful for microfluidic applications. The high contact angles obtained in this work are usually obtained only after chemical modification of the ZnO surface with organic coatings, which was not necessary for the hierarchical surfaces developed here, reducing the cost and processing steps of the fabrication route. These rose-petal surfaces can be used as “mechanical hands” in several applications, such as no-loss transport of small liquid volumes, precision coatings, spectroscopy, and others. Furthermore, the completely water-repellent surfaces, rarely reported elsewhere, may find important applications in frictionless liquid transport for microfluidic and other devices.

Fabrication of superhydrophobic surfaces for applications in total internal reflection effects

Superhydrophobic surfaces have attracted significant attention in the applied science community. This paper presents three different methods for fabricating superhydrophobic surfaces, which can be applied in liquid light guides with the total internal reflection effect playing a central role. The selective bi-polymer etching only produces a hydrophobic porous poly(methyl methacrylate) surface but is simple and versatile for use on an arbitrary surface. In metal-assisted chemical etching, wet etching of a silver layer on a silicon sample creates porous silicon with superhydrophobicity, characterized by a water contact angle of 160°. The metal-assisted chemical etching method modified with the presence of polystyrene nanoparticles further improved the water contact angle to 164° by creating a nanopillar silicon structure. The metal-assisted chemical etching methods are more complicated but can produce superhydrophobic surfaces with very high water contact angles. These results show that superhydrophobic surfaces fabricated by methods in this study can be used for total internal reflection effect at the interface between water with huge potential applications in liquid light guides.

Biochar based self cleaning superhydrophobic surface with aqueous DESphobic properties

In this work, facile fabrication of chemically stable superhydrophobic surfaces based on biocompatible, fluorine free, carbon rich biochar has been reported. Biochar synthesized from dried rice straw by pyrolysis at 550˚C, which was characterized using Fourier Transform Infrared (FTIR) and Scanning Electron Microscopy (SEM). The biochar coated surface demonstrated superhydrophobic behaviour with static water CA > 150°. Aqueous drops remain in superhydrophobic state due to stability of Cassie-Baxter wetting regime and can shows very high-water contact angle (WCA > 160°) and self-cleaning behaviour. Such a very high WCA have been achieved typically by combination of low energy chemicals (fluorine based) and surface textures. However, no harsh chemical treatment of biochar was performed and a simple methodology of creating biochar layer onto the substate was adopted. Such surface also demonstrated repellent properties against aqueous mixtures of deep eutectic solvent (DES). A spherical aqueous DES drop can be easily formed onto the biochar surface for image analysis. The density of the liquid sample with a small sample volume can be assessed using this drop shape that was measured on the superhydrophobic biochar surface.

Fabrication and characterization of super-hydrophobic surfaces based on sandpapers and nano-particle coatings

In this work, we fabricate a series of super-hydrophobic surfaces by sprayed-coating a layer of hydrophobic nano-particles on sandpapers that contain micro-scale abrasive particles. Sandpapers with a range of grit sizes from 60 to 1500 are investigated. We find that the coated sandpaper with grit sizes of 240, 400, 800, 1000, and 1500 exhibit super-hydrophobicity with a high water contact angle ranging from 158° to 165° and a low sliding angle varying from 10° to 2°. However, other coated sandpapers with grit sizes of 60, 120, and 600 do not show super-hydrophobicity, possibly for the reason that the Cassie-Baxter state is not stable. Furthermore, we study the impacts of hydrostatic pressure and liquid flow on the robustness of the super-hydrophobic sandpapers. We find that the percentage of surface area covered by gas reduces due to pressure and liquid flow as expected, but the samples remain in the partial Cassie-Baxter state at the highest pressure (2.4 atm) and highest flow speed (5.0 m/s). After the pressure and flow tests, all samples retain their super-hydrophobic properties. The robustness of the air plastron on the fabricated samples could be attributed to the hierarchical roughness structures. In conclusion, we develop a method that could significantly reduce the cost of fabricating robust super-hydrophobic surfaces. Future work is required to evaluate the performance of the super-hydrophobic sandpapers for applications such as drag reduction, anti-biofouling, and anti-icing.

Composition of Organically Modified Silica for the Superhydrophobic Surface with Low Sliding Angle

Extremely water-repellent surfaces with low sliding angle (SA) have been obtained with a facile single-step sol-gel strategy via co-condensation of tetraethoxysilane (TEOS) and hexadecyltrimethoxysilane (HDTMS) in basic media with an efficient self-cleaning property. We investigated the effect of the molar ratio of HDTMS and TEOS on the properties of the modified silica-coated poly(ethylene terephthalate) (PET) film. A high water contact angle (WCA) of 165° and a low SA of 1.35° were obtained at a molar ratio of 0.125. The dual roughness pattern for the low SA was developed by a one-step coating of the modified silica with a molar ratio of 0.125. The evolution of the surface to the dual roughness pattern by nonequilibrium dynamics depended on the size and shape factor of modified silica. The primitive size and the shape factor of the organosilica with a molar ratio of 0.125 were 70 nm and 0.65, respectively. We also presented a new method to determine the superficial surface friction (ζ) of the superhydrophobic surface. The ζ was a physical parameter that characterized the slip and rolling behavior of water droplets on the superhydrophobic surface along with the equilibrium property WCA and the static frictional property SA.

A novel two-step strategy to construct multifunctional superhydrophobic wood by liquid-vapor phase deposition of methyltrimethoxysilane for improving moisture resistance, anti-corrosion and mechanical strength

The increased application of wood products has raised new demands for chemically modified wood, such as enhanced water resistance and use of nontoxic fluorine-free compounds, but less attention has been paid to such requirements to date. Herein, superhydrophobic wood (SH-Wood) with high water contact angle (> 150°) and low sliding angle (< 10°) was prepared successfully by using liquid-vapor phase deposition of methyltrimethoxysilane (MTMS) combining vacuum-pressure impregnation and chemical vapor deposition methods for the first time. Covalent grafting of methyl groups with low-surface-energy on SH-Wood substrate was confirmed via Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) with energy dispersive X-ray scanning (EDS) analyses showed that the cell wall inside the wood was successfully filled by MTMS in situ grafting and a dense polymethylsiloxane protective layer was formed on the surface of SH-Wood. The SH-Wood generated exhibited excellent moisture resistance, a dramatic decrease in the water uptake (WU) from 116.3 % (control) to 23.5 %, and a diminished water vapor absorption (WVA) from 9.5 % compared to control wood (14.3 %). Moreover, the SH-Wood also demonstrated good anti-corrosion, abrasive resistance, mechanical strength and multi-functions of stain-resistance, anti-adhesion and self-cleaning, which will undoubtedly facilitate greatly expanded applications for wood.

An omniphobic membrane with macro-corrugation for the treatment of real pharmaceutical wastewater via membrane distillation

Treatment of realistic pharmaceutical wastewater with hazardous compound, complex composition and high concentration under certain scenarios is critical to environmental protection. Membrane distillation (MD) offers the potential to concentrate the wastewater, extract clean water and reduce the volume to be treated in further downstream processing. In this work, an omniphobic membrane with macro-corrugation was fabricated for MD against realistic pharmaceutical wastewater. The membrane was fabricated by electrospinning technique, followed by heat-pressing, physical compression for imprinting of patterns and omniphobic coating. The pattern was imprinted by a simple and cheap approach and can potentially be applied to larger scale applications. The as-prepared membrane showed high water contact angle (142.5 ± 2.3°), low water sliding angle (25.8 ± 3.8°) and fouling/scaling resistance in the presence of salt and surfactants. Furthermore, it demonstrated excellent stability during the concentration of challenging realistic pharmaceutical wastewater with complex composition, due to the simultaneous wetting resistance by Teflon coating and enhanced turbulence to interrupt aggregation by surface patterns. This work gives useful insights on the design and application of MD membranes for treating challenging pharmaceutical wastewater.