Sliding Angle Research Articles

Preparation of robust superhydrophobic surface on PET substrate using Box-Behnken design and facile sanding method with PTFE powder

Superhydrophobic surfaces have attracted increasing interests due to their excellent features, while achieving facile preparation of superhydrophobic surface with good mechanical stability is still a challenging work. In this paper, we prepared a superhydrophobic surface by sanding polytetrafluoroethylene powder directly onto the surface of a polyethylene terephthalate (PET) film by means of a simple sanding method with sandpaper. The fabrication parameters were firstly optimized using response surface methodology. Surface morphology and chemical composition of the fabricated surface were characterized by field emission scanning electron microscopy, Fourier transform infrared and x-ray photoelectron spectroscopy. The mechanical performance of the superhydrophobic PET surfaces was evaluated by tape peeling test, and potential applications of this surface in self-cleaning and anti-icing were finally carried out. The results showed that the water contact angle up to 153.5° and sliding angle less than ∼3° on PET surface could be prepared under the optimum conditions, and its superhydrophobicity of surfaces was attributed to the synergistically effect of low surface energy and surface roughness. The fabricated superhydrophobic surfaces also exhibited good resistance to abrasion, and they have great potential for application in the fields of self-cleaning and anti-icing.

Fabrication of high-durability superhydrophobic coatings based on dual-sized SiC particles

In recent years, inspired by “biomimicry”, superhydrophobic surfaces have gained significant attention. Superhydrophobic surfaces demonstrate notable advantages in addressing interfacial issues, and superhydrophobic coatings exhibit excellent waterproofness, anti-fouling, self-cleaning, anti-corrosion, and additional capabilities, making them promising next-generation waterproof materials. However, the complex preparation process, coupled with poor wear resistance and environmental durability, severely limits their practical applications. Therefore, this article started from simplifying the preparation process and improving the durability of the coatings. Epoxy resin (E51) was used as the film-forming material, and carbon nanotubes (CNTs) and dual-sized SiC particles (nano-SiC and micro-SiC) were used as the fillers. Room temperature vulcanized silicone rubber (RTV) was used as a binder interacting with epoxy resin to promote the interface interaction between the fillers and the polymers. This process resulted in the successful preparation of superhydrophobic coatings with outstanding comprehensive performance. When the ratio of μ-SiC to n-SiC was 1:1, the prepared coating exhibited the best superhydrophobic properties with a water contact angle (WCA) of 167.4° and a sliding angle (SA) of 4.6°. Even after undergoing severe mechanical tests, such as sandpaper abrasion for 1000 cycles, sand impact for 100 cycles, cross-cut test, and tape-peeling for 70 cycles, the coatings still maintained their non-wetting Cassie-Baxter state. Furthermore, even after immersion in strong acid, strong alkali and 3.5 wt% NaCl solutions for 6 days, keeping at 500 ℃ for 2 hours, and exposure to ultraviolet for 6 days, the coatings still exhibited excellent superhydrophobicity. This suggested that the prepared coating had excellent chemical stability and high-temperature resistance. In addition, the superhydrophobic coating exhibited exceptional capabilities in self-cleaning, anti-corrosion, anti-icing, and de-icing properties. Furthermore, this coating, applicable to diverse substrates including board, steel, paper, and glass, demonstrated an impressive water contact angle (WCA) and sliding angle (SA). The spraying method offers the benefits of simplicity and cost-effectiveness. This is poised to significantly broaden its practical applications in various fields, including construction, transportation, and the chemical industry.

Hydrophobic Solid Photothermal Slippery Surfaces with Rapid Self-repairing, Dual Anti-icing/Deicing, and Excellent Stability Based on Paraffin and Etching.

Ice and snow disasters have greatly affected both the global economy and human life, and the search for efficient and stable anti-icing/deicing coatings has become the main goal of much research. Currently, the development and application of anti-icing/deicing coatings are severely limited due to their complex preparation, structural fragility, and low stability. This work presents a method for preparing hydrophobic solid photothermal slippery surfaces (SPSS) that exhibit rapid self-repairing, dual anti-icing/deicing properties, and remarkable stability. A photothermal layer of copper oxide (CuO) was prepared by using chemical deposition and etching techniques. The layer was then impregnated with stearic acid and solid paraffin wax to create a hydrophobic solid photothermal slippery surface. This solves the issue of low stability on superhydrophobic surfaces caused by fragile and irretrievable micro/nanostructures. In addition, the underlying photothermal superhydrophobic surface provides good anti-icing/deicing properties even if the paraffin on the surface evaporates or is lost during operation. The findings indicate that when subjected to simulated light irradiation, the coating's surface temperature increases to 80 °C within 12 min. The self-repair process is completed rapidly in 170 s, and at -15 °C, it takes only 201 s for the ice on the surface to melt completely. The surface underneath the paraffin exhibited good superhydrophobic properties, with a contact angle (CA) of 154.1° and a sliding angle (SA) of 6.8° after the loss of paraffin. Simultaneously, the surface's mechanical stability and durability, along with its self-cleaning and antifouling properties, enhance its service life. These characteristics provide promising opportunities for practical applications that require long-term anti-icing/deicing surfaces.

Durable and highly hydrophobic flax fabrics designing via “grafting to” method using catalysed hydrosilylation

Highly hydrophobic flax fabrics with durable properties were prepared via “grafting to” method for self-cleaning application. Flax fabrics were firstly functionalized with vinyl groups using 1,3-divinyltetramethyldisilazane (DVTS). Then, the vinyl functionalized flax fabrics were grafted by poly(hydromethylsiloxane-co-dimethylsiloxane) (PDMS-co-PHMS) via a hydrosilylation reaction using Karstedt catalyst, between Si-H groups present in PDMS-co-PHMS and vinyl groups present onto the vinyl functionalized flax fabrics. The prepared fabrics were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-rays fluorescence, confocal laser scanning microscopy (CLSM) and tensile test. The modified fabrics displayed highly hydrophobic properties with contact angle (θ) about 147° ± 5 and a sliding angle (SA) of about 15° ± 2, making them ideal for practical self-cleaning applications. Furthermore, good durability with excellent washing resistance was also obtained for these fabrics.

Fabrication of Superhydrophobic Coating by Spraying PDMS-SiO2 Suspension for Self-Cleaning Application

Superhydrophobic surfaces that mimic lotus leaf surfaces have been widely studied due to their unique self-cleaning ability. Herein, we have fabricated a self-cleaning superhydrophobic coating on a glass substrate using the facile sol-gel spray coating method. The silica particles were synthesized via the sol-gel method in acidic conditions. A self-cleaning superhydrophobic coating was achieved by spraying a suspension of synthesized SiO2 particles and PDMS on a glass substrate at room temperature. The incorporation of SiO2 particles in the PDMS matrix resulted in the formation of a rough structure on the glass surface. This surface exhibited excellent superhydrophobic properties with a high water contact angle (WCA) of 154° and a low sliding angle (SA) of 4°. In addition, the prepared samples showed strong mechanical resistance against various tests such as multiple adhesive tape peeling, sandpaper abrasion, and pencil hardness. As a result, the developed superhydrophobic coating holds great potential for self-cleaning applications on a larger scale.

Anti-corrosion and anti-fouling superhydrophobic silicone coating with continuous micro/nano structure

At present, silicone superhydrophobic coatings are attracting much attention in the fields of anti-corrosion and antifouling, so they have a broad application prospect. In this paper, superhydrophobic surfaces with continuous micro/nano structure were prepared on various substrates using a simple blending method similar to the conventional preparation of RT vulcanized silicone rubber. The difference was that the new kinds of crosslinker (MF-S) was synthesized by 3-glycidyloxypropyltrimethocysilane and 3-aminopropyltriethoxysilane. Linear fluorinated copolymer (L-SF) was prepared by free radical polymerization of 3-mercaptopropyltriethoxysilane (MPTES) and 1H, 1H, 7H-dodecafluoroheptyl methacrylate (DFMA). And the condensation reaction with α, ω-dihydroxypodimethylsiloxane (PDMS), tetraethyl orthosilicate (TEOS), and inorganic nanoparticles constructed superhydrophobic coatings with continuous micro- and nanostructures. The coating had a water contact angle (WCA) of up to 162° and a sliding angle (SA) as low as 2°. What's more, the WCA of the coating remained around 160° and the SA stayed below 5° after sandpaper abrasion, UV irradiation, and hot and cold treatment. The adhesion of the coating on different substrates was higher than 2 MPa. Due to the synergistic effect of the superhydrophobicity of the coating and the photocatalytic activity of the TiO2 nanoparticles, the coating achieves an antimicrobial efficiency of 97.8 % against Staphylococcus aureus. The synergistic effect of the air layer and the densification of the coating resulted in the electrical impedance modulus at the lowest frequency of the coating remaining two orders of magnitude higher than that of the bare carbon steel plate after several days of immersion in sodium chloride solution. The work showed great potential for application in anti-corrosion and anti-fouling coatings.

Superhydrophobic concrete coating with excellent mechanical robustness and anti-corrosion performances

In this study, an environmentally friendly superhydrophobic surface for concrete (S-concrete) with excellent mechanical robustness and anti-corrosion performances was put forward. By introducing geopolymer material, a novel inorganic gelling material act as binders to enhance the stability of the S-concrete, the suspension based on stearic acid (STA) modified by micro diatomaceous earth (DE) and nano alumina (Al2O3) were intensely attached to the substrate. The structure morphologies, chemical compositions, surface wetting behavior of this S-concrete were systematically investigated by SEM, XRD, FT-IR and wettability measurements. The results showed that the S-concrete coating was successfully constructed by achieving a desirable static contact angle of 159.1° and a small slide angle 4.5°. The S-concrete features Cassie-Baxter phase contacts, liquids repellency, anti-fouling and self-cleaning properties. The S-concrete exhibited excellent resistance to chloride corrosion, which was reduced by about 2 orders of magnitude compared to ordinary concrete. What is more, this S-concrete coating showed remarkable robustness against sandpaper abrasion and tape-peeling, while retaining its superhydrophobicity even suffering 200 abrasion cycles and 60 tape-peeling. The improved durable mechanical robustness and interfacial bonding force can be attributed to the cross-linked three-dimensional hierarchical structures formed by the combination of geopolymer material and embedded DE/Al2O3@STA micro-nanoparticles.

Fabrication of a sustainable superhydrophobic surface of Ag-NPs@SA on copper alloy for corrosion resistance, photocatalysis, and simulated distribution of Ag atoms.

Artificial superhydrophobic surfaces that do not absorb water, like the lotus leaf, show tremendous promise in numerous applications. However, superhydrophobic surfaces are rarely used because of their low stability and endurance. A stable organic superhydrophobic surface (SHS) composed of novel morphology Ag-nanoparticles (NPs) has been fabricated on a copper alloy via etching, immersion, spraying, and annealing treatment, along with a static water contact angle (WCA) of 158 ± 1° and sliding angle (SA) less than 2°. The surface texture, composition, and morphology of the substrate surfaces were explored by using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, and DFT-based Ag atom distribution. The anti-corrosion study of non-coated and Ag-NP-coated copper alloy was undertaken using electrochemical impedance spectroscopy. Ag-NPs +SA@SHS enhanced the corrosion resistance as compared with bare Cu alloy. The water droplet rolled down the coated Cu alloy, removed the chalk powder from the surface, and indicated an excellent self-cleaning function. Photodegradation of Congo red (CR) and methylene blue (MB) dye samples was assessed by measuring the absorbance through UV-Visible spectrophotometry, where the Ag-NPs coated on the copper alloy were used as a catalyst. The performance of the SHS@Ag-NPs in the aqueous solution was 99.31% and 98.12% for industrial pollutants (CR and MB), with degradation rates of 5.81 × 10-2 s-1 and 5.89 × 10-2 s-1, respectively. These findings demonstrated a simple, rapid, and low-energy fabrication technique for SHS@Ag-NPs. This research reveals a valuable approach for the fabrication of SHS@Ag-NPs on various substrates to extend the superhydrophobic surfaces with ultra-fast self-healing properties, for outdoor applications such as anti-corrosion, for an innovative approach for the remediation of polluted water treatment, and for industrial applications.

Application of 3D printing for fabrication of superhydrophobic surfaces with reversible wettability.

Control of surface wettability is needed in many applications. The potential use of 3D printing technology to gain control over wettability remains largely unexplored. In this paper, Fused Deposition Molding (FDM) 3D printing technology was utilized to print polylactic acid (PLA) microplate array structures to generate superhydrophobic surfaces with reversable wetting properties. This was achieved by spraying polydimethylsiloxane (PDMS) and silica (SiO2) solutions, over microplate surfaces. Anisotropic wetting properties were also achieved based on the surface structure design. Due to the shape memory properties of PLA, the morphology of the microplate arrays could be switched between the original upright shape and deformed shape. Through alternating pressing and heating treatments, the microplate arrays showed anisotropic wettability switching. The difference between the contact angle (CA) and sliding angle (SA) of water droplets on the original surface parallel to and perpendicular to the microplate array direction were ΔCA = 7° and ΔSA = 3° respectively, and those on the surface of the deformed microplate array were ΔCA = 7° and ΔSA = 21°, respectively. This process enabled reversible alteration in the wetting behavior of water droplets on the original and deformed surfaces between sliding and sticking states. PLA-based shape memory anisotropic superhydrophobic surfaces with tunable adhesion were successfully applied to rewritable platforms, micro droplet reaction platforms, and gas sensing.

One-step candle soot-PDMS dip-coated superhydrophobic stainless steel mesh for oil-water separation

We presented a superhydrophobic stainless steel mesh (SSM) developed by facile one-step dip coating of candle soot (CS)-polydimethylsiloxane (PDMS) using chloroform as solvent for effective and durable oil-water separation. SSM dip coated with chloroform solution of 200 mg CS and 0.5 mL PDMS yielded water contact angle (WCA), oil contact angle (OCA) and sliding angle (SA) of 162 ± 2°, 0° and 4 ± 1°, respectively. In series of oil-water separation studies, superhydrophobic mesh revealed >98 % separation efficiency with high separation flux of 7810 L·m−2·h−1. The superhydrophobic mesh revealed excellent mechanical, chemical and thermal durability.

Robust and applicable superhydrophobic coatings with multi-layer self-similar structure and self-healing properties

To prepare durable superhydrophobic coatings with low-cost is of great importance for its practical application. How to improve the mechanical endurance by a facile method is rarely mentioned in reports. Achieving thicker coating with multi-layer micro-nano structures is critical for obtaining the robust superhydrophobic coating due to the high abrasion resistance to mechanical damage. Herein, a superhydrophobic coating with a multi-layer self-similar structure was fabricated by a facile blending and spraying method. Epoxy resin, neutral silicone glue, polysiloxane and nano-SiO2 are the main composition of the ESPS coating which are important for the multi-layer micro-nano structure construction and adhesion stability between the coating and the substrate. The water contact angle (WCA) and sliding angle (SA) of the ESPS coating were 162.5 ± 0.5° and 4.6 ± 0.4°, respectively. Notably, the ESPS coating with four layers can be abraded with 1500-grid sandpaper under the load of 400 Pa for 24 m. In addition, the prepared samples were put in an outdoor environment for 180 days and exhibited excellent durability and stability. These outstanding properties could be attributed to the hierarchical self-similar structure of the composited coating and the good resistance and adhesion stability provided by polysiloxane. Additionally, the ESPS coating could restore its superhydrophobic characteristic by self-healing realized by the neutral silicone glue in the composition. The good stability and operability of the ESPS coating make it applicable to a wide range of applications.

Superhydrophobic F-SiO2/tea polyphenol coating with high efficiency photothermal anti-icing and de-icing properties

Ice accumulation is an important challenge for daily life and industrial production. The photothermal effect offers a promising approach for active de-icing to address this issue. While the photothermal effect of polyphenol-metal ion complex is extensively studied in photothermal cancer therapy, its application in de-icing remains relatively unexplored. Herein, a durable photothermal superhydrophobic coating was designed by combining F-SiO2 @Tp/Fe (Tea polyphenol-Fe3+) nanoparticles and silicone resin using a one-step spray method. Due to the unique micro-nano structure, the resulting coating exhibited excellent superhydrophobicity, characterized by water contact angle (CA) of up to 159° and sliding angle (SA) of less than 2.5°. Additionally, the coating demonstrated reliable mechanical durability and chemical stability, as evidenced by its good performance in sandpaper abrasion, tape peeling and electrochemical corrosion tests. Moreover, owing to the efficient photothermal conversion of F-SiO2 @Tp/Fe nanoparticles, surface temperature of the coating can quickly reach 81 ℃ under 1 kW/m2 simulated sunlight irradiation (1 Sun). The prepared coating exhibits over three times delayed icing time under 1 sun irradiation at − 25 °C in comparison to the absence of light. And the coating also exhibits stable de-icing and defrosting cycle performance. These findings demonstrate effective synergistic effect of anti-icing and de-icing in the F-SiO2 @Tp/Fe photothermal superhydrophobic coating, showcasing its promising application potential in practical engineering.

Fabrication and Characterizations of Superhydrophobic Surface with Superior Corrosion Inhibition on Q345b Steel Substrate

AbstractIn this work, a coherent and cost‐effective method is developed to achieve superhydrophobicity and excellent corrosion resistance on Q345B steel surfaces. The method involves sequential etching with hydrochloric acid and hydrofluoric acid, passivation with potassium permanganate, treatment with bis‐(γ‐triethoxysilylpropyl)‐tetrasulfide (KHSi69，BT), and modification with hydrophobic SiO2 nanoparticles. The effects of etching and passivation time, including SiO2 doping ratio on the wettability and corrosion resistance of the prepared surfaces are investigated. The results demonstrate that the surface exhibits a micro–nano multilayer and modified nano‐multiscale cluster structure which has a contact angle (CA) of 155.8 ± 1.7° and a sliding angle (SA) of 5 ± 0.5° by employing the following conditions: hydrochloric acid etching time of 10 min, hydrofluoric acid etching time of 25 min, passivation time of 300 min, and a 3 wt% SiO2 doping ratio. Moreover, the surface displays extremely weak droplet adhesion and excellent self‐cleaning properties. Furthermore, the corrosion inhibition of the prepared steel surface is evaluated using potentiodynamic polarization curves and electrochemical impedance spectroscopy. The results indicate that the corrosion inhibition efficiency of the superhydrophobic surface is enhanced by about 89.95% compared to the traditional two‐step processing involving etching and modification. These findings expand the potential applications of steel.

Effect of heating self-healing and construction of composite structure on corrosion resistance of superhydrophobic phosphate ceramic coating in long-term water environment

Despite superhydrophobic ceramic coatings have been successfully prepared, there lacks an improvement in their corrosion resistance in long-term saltwater environments due to the porous properties. In this paper, two coatings were prepared again by heat repair treatment and construction of double-layer composite structure, and the surface characteristics of the coatings were determined by scanning electron microscope, infrared spectrometer and contact angle measuring instrument, and the electrochemical performance and corrosion resistance of the coatings were evaluated by electrochemical test and immersion test. The results showed that the original porous ceramic coating had superhydrophobic property, and the water contact angle (CA) and sliding angle (SA) were 150.4°and 8.7°, respectively. Through knife scratching, sandpaper abrasion and tape peeling tests, the coating had good bond strength and mechanical durability. Compared with the original coating, the corrosion resistance of heat repair coating and composite coating had better corrosion resistance and a protective effect on the substrate. This protective mechanism can be attributed to the repair effect of heat treatment on the hydrophobicity of the coating, and the composite structure resists the penetration of external liquids. Based on these results, heat repair and double-layer composite structures can improve the defects of long-term insufficient durability of superhydrophobic ceramic coatings, which have potential marine application prospects.

Preparation of a UV anti-aging and superhydrophobic self-cleaning coating by loading nano-rutile on sericite and being modified with HDTMS

To enhance the anti-aging property of a superhydrophobic self-cleaning coating, rutile nano-TiO2 was loaded onto the surface of sericite via wet grinding method to prepare sericite-rutile composite particles. Then, the composite was modified with hexadecyltrimethoxysilane (HDTMS) and sprayed onto the substrates surfaces to prepare sericite-rutile/HDTMS composite coatings with both UV shielding and superhydrophobic self-cleaning properties. The structure, properties, and mechanism of the coating were studied. The research showed that the micro-nanoscale hierarchical structure has been constructed by compositing sericite and rutile, which were the structure foundation of superhydrophobic coatings. The sericite-rutile composite was modified with HDTMS and sprayed onto the substrates forming a superhydrophobic self-cleaning coating. Water contact angles (WCAs) and slide angles (SAs) of the coating were 155.3° and 1.3°, respectively. The sericite-rutile/HDTMS coating exhibited good UV shielding and anti-aging properties. Its UV shielding rate was 93.53%, which was equivalent to that of pure rutile (94.27%). After UV irradiation for 80 h, the surface maintained superhydrophobicity, and the chromaticity of the coating surface did not change. The superhydrophobicity and low adhesion to water of the sericite-rutile/HDTMS coating are due to the micro-nano hierarchical structure of the sericite-rutile composite and the low surface energy of HDTMS. The UV shielding effect of the coating is mainly due to the strong absorption of UV light by the sericite-rutile composite. This work provides a simple and environmentally friendly method for constructing a coating with UV shielding and superhydrophobic self-cleaning properties.

Developing RobEVELOPING DURABLE SUPERAMPHIPHOBIC COATING ON ROUGH ALUMINUM USING RESIDUAL FROM BURNED RECYCLED SILICONE RUBBER FOR ANTI-CORROSIONust Superamphiphobic Coating on Rough Aluminum Substrates Using Recycled Silicon Rubber and Simple Spray Pyrolysis Technique for Anticorrosion Applications

This study presents a new, cost-effective, and environmentally friendly approach for creating a superamphiphobic coating. The method involves using a spray coating technique to apply silicone rubber onto smooth and micro-rough aluminum (Al) substrates. To enhance the coating's surface energy reduction, a thin layer of silicone rubber – trifluorotoluene (SR-TFT) was added. The morphology and chemistry of the coatings were analyzed utilizing scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and Fourier Transform Infrared Spectrometer (FTIR). The coatings displayed superamphiphobic properties with contact angles (CAs) of 170° for water and over 150° for both glycerol and ethylene glycol. Additionally, a remarkably low water droplet sliding angle (SA) of less than 2° was observed for surfaces coated with silicone rubber (SR)- trifluorotoluene (TFT), whether smooth or roughened. The coatings were tested for mechanical and chemical durability by impinging water droplets and immersing them in an acidic liquid respectively. The results showed that SR-TFT-coated silicone rubber on micro-rough Al substrates maintained its superamphiphobic property and exhibited excellent corrosion resistance compared to hydrophilic Al plates. Furthermore, the coatings displayed self-cleaning properties when water droplets were poured over a dusty surface, as the rolling water droplets effectively collected contaminant particles, leaving the surface of the sample clean. These findings indicate potential applications for the developed coatings as self-cleaning surfaces in challenging environmental conditions.

Experimental and Statistical Study on the Formation Characteristics and Discrimination Criteria of River Blockages Caused by Landslides

The discrimination of river blockages is very important for the risk assessment of landslide disasters and secondary hazards. Experimental studies and statistical analyses were carried out to explore the formation process and discriminant criteria of river blockages caused by landslides. An adjustable slide chute was designed and built to conduct forty-five landslide experiments. According to the experimental results, river blockage was identified as having six types based on the differences between the water depth and the height of the landslide dam, and the degree of river blockage increased from 70% to 100% as the chute angle, particle size, and landslide volume increased. It is also found that landslide volume controls the landslide dam height and degree of blockage, and particle size and slide angle control both the landslide velocity as it enters the river and the cross-section shape of the landslide dam. To investigate more influence factors, a statistical investigation of 60 real landslide cases was carried out, and it revealed that some geometric attributes related to landslide volume have the highest correlation with river blockage, especially landslide thickness. Finally, an improved probability model was proposed to assess the possibility of complete blockage, and it has overall accuracies of 91.1% and 83.3% when applied to predict experimental landslide cases and real landslide cases, respectively.

Achieving superhydrophobicity of Zr-based metallic glass surface with anti-corrosion and anti-icing properties by nanosecond laser ablation and subsequent heat treatment

Water repellency of superhydrophobic surfaces offers an opportunity to enhance the corrosion and icing resistance of metallic glasses (MGs). Inspired by the “lotus effect” in nature, hierarchical micro/nanostructures were constructed on a Zr-based MG surface using nanosecond laser ablation. By subsequent heat treatment in air, the structured surface showed a water contact angle (CA) of 168.2 ± 1.5° and a sliding angle (SA) of 4 ± 0.7° (adhesion force of 9.8 ± 1.7 μN), exhibiting repellency and low adhesion to water. Specifically, the superhydrophobic surface stored in air and immersed in water possessed stability and durability, and the superhydrophobic surface still maintained superhydrophobicity after mechanical scratching. The heat treatment temperature worked as a switch for controlling the wettability transition, and by tuning the temperature, the structured surface can switch from superhydrophobicity (CA: 168.2 ± 1.5°) to superhydrophilicity (CA: ~0°). Furthermore, compared to the polished MG surface, the superhydrophobic surface increased the corrosion resistance and freezing time, and delayed the freezing temperature. This study provides a facile non-fluorinated method for fabricating superhydrophobic MG surfaces with anti-corrosion and anti-icing properties, which would enhance the application of MGs as structural and functional materials under extreme conditions.

Preparation and analysis of tridirectionally anisotropic superhydrophobic surface with biomimetic wedge-shaped structure

A novel biomimetic wedge-shaped structure (BWSS) has been fabricated using nanosecond laser etching method. The BWSS as-processed exhibits superhydrophilicity (contact angle (CA) = 0°) and transforms to superhydrophobicity (CA > 160°) after chemical modification. Sliding angles (SAs) on the superhydrophobic surface show the tridirectional anisotropy: SAs in perpendicular anti outside radial direction (⊥Anti-RO) > SAs in perpendicular outside radial direction (⊥RO) > SAs in parallel direction (∥). Mechanisms of tridirectional anisotropy are discussed in detail. The original phenomenon indicates the superhydrophobic surface with BWSS possesses excellent tridirectionally anisotropic wettability, which can provide enormous potential applications in microfluidic fields.

A rapid one-step preparation method of the repairable three-dimensional antifouling superhydrophobic 2.5EPZF coating on magnesium alloys

Although three-dimensional (3D) superhydrophobic coating has been gradually prepared on the surface of metal substrate for anticorrosion and antifouling, their complex preparation steps and equipment requirements limit their practical application. Herein, by a rapid one-step spray preparation method the fabricating 3D superhydrophobic 2.5EPZF (2.5 g epoxy resin/polycaprolactone (PCL)/zinc oxide/perfluorodecyltriethoxysilane) coating is prepared. This method utilizes a certain degree of directional arrangement of macromolecular long chain polymers (PCL) as solvent evaporation during the spraying process to form a filamentous structure to construct the 3D coating. This preparation mechanism provides us a novel theoretical guidance method for preparing 3D coating. Further, the silk thickness and mesh density of the 3D mesh structure is controlled by adding epoxy resin. When the amount of epoxy resin is 2.5 g, the surface of 2.5EPZF coating is with about 1–3 μm thick branch frame and 0.1–0.4 μm thin treetop. And the water-contact angle (CA) of 2.5EPZF is 156.6 ± 1.5° and the sliding angle (SA) is < 10° . The 2.5EPZF coating exhibits durable antifouling, strong mechanical&chemical durability, and corrosion resistance. The corrosion current of the 2.5EPZF coating for 0 day's immersion and 35 days’ immersion in NaCl solution is 1.043 × 10−12 A•cm−2 and 1.1703 × 10−11 A•cm−2, respectively. Under solar irradiation and at 50 °C for 30 min, the 2.5EPZF coating is with scratching recovering. Additionally, the composite coating can be prepared by a large area. It is expected that this method is readily used and shows great application potentials.