Robust Superhydrophobic Surfaces Research Articles

Design and Synthesis of a Robust and Multifunctional Superhydrophobic Coating with a Three-Dimensional Network Structure on a Paper-Based Material.

A fundamental challenge in artificial superhydrophobic papers is their poor resistance to mechanical abrasion, which limits their practical application in different fields. Herein, a robust and multifunctional superhydrophobic paper is successfully fabricated via a facile spraying method by combining silver nanowires and fluorinated titania nanoparticles through a common paper sizing agent (alkyl ketene dimer) onto paper. It is shown that the surface of the paper-based material presents a three-dimensional network structure due to the cross-linking of silver nanowires with a high aspect ratio. Further hydrophilic and hydrophobic performance test results show that it exhibits exceptional water repellency, with a desirable static contact angle of 165° and roll-off angle of 6.2°. The superhydrophobic paper showcases excellent mechanical durability and maintains its superhydrophobicity even after enduring 130 linear sandpaper abrasion cycles or high-velocity water jetting impact benefited from interfacial van der Waals and hydrogen bonding. Simultaneously, the robust superhydrophobic surface can effectively prevent the penetration of acid or alkali solutions, as well as UV light, resulting in excellent chemical stability. Additionally, the superhydrophobic paper offers supplementary features such as self-cleaning, electrical conductivity, and antibacterial capability. Further development of this strategy paves a way toward next-generation superhydrophobic paper composed of nanostructures and characterized by multiple (or additional) functionalities.

Oxygen-Terminated Polycrystalline Boron-Doped Diamond Superhydrophobic Surface with Excellent Mechanical and Thermal Stabilities.

Superhydrophobic surfaces are of great interest because of their remarkable properties. Due to its maximal hardness and chemical inertness, diamond film has great potential in fabricating robust superhydrophobic surfaces. In the present study, an oxygen-terminated polycrystalline boron-doped diamond (O-PBDD) superhydrophobic surface with micro/nano-hierarchical porous structures is developed. The preparation method is very simple, requiring only sputtering and dewetting procedures. The former involves sputtering gold and copper particles onto the hydrogen-terminated polycrystalline boron-doped diamond (H-PBDD) to form gold/copper films, whereas the latter involves placing the samples in an atmospheric tube furnace to form hierarchical pores. By controlling the etching parameters, the wettability of the O-PBDD surface can be adjusted from hydrophilic to superhydrophobic, which is significantly different to the normal hydrophilicity feature of O-termination diamonds. The water contact angle of the obtained O-PBDD surface can reach 165 ± 5°, which is higher than the superhydrophobic diamond surfaces that are reported in the literature. In addition, the O-PBDD surface exhibits excellent durability; it can maintain satisfactory superhydrophobicity even after high-pressure, high-temperature, and sandpaper friction tests. This work provides a new research direction for fabricating robust superhydrophobic materials with diamond film.

Fabrication of robust superhydrophobic surface on TC4 alloy by wire electrical discharge machining

Superhydrophobic metal surfaces have significant applications in various areas such as surface self-cleaning, resistance reduction, anti-corrosion, etc. However, inexpensive preparation methods for superhydrophobic surfaces with a good mechanical stability are still to be developed. In this study, microarray structures on TC4 alloy were readily fabricated using a wire electrical discharge machining technology. Following the treatment with a fluorinating reagent, the microarray surface exhibited excellent superhydrophobic properties, where the largest contact angle and the smallest sliding angle reached 159° and 3°, respectively. Influences of the dimensions of microarray structure on the TC4 alloy surface wettability were also investigated in this study. Experiments show that this superhydrophobic surface possesses favorable self-cleaning, good mechanical stability, and promising anti-corrosion properties. In addition, by controlling the dimensions of the microstructure a superhydrophobic surface with a gradient wettability was also fabricated, which exhibits the property of doing nondestructive transportation of liquids.

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 and anti-corrosion performances of robust superhydrophobic surface on NAB via solution-etching

A labyrinth microstructure interconnected by micron and submicron acicular structures was successfully prepared by immersing nickel-aluminum bronze in 9 wt% FeCl3·6H2O solution at room temperature for 40 min. After being modified with 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (FAS-17), the microstructure surface displays robustly low-adhesion superhydrophobicity, and the water contact angle is above 160 ° on it. In addition, the superhydrophobic surface exhibits excellent corrosion resistance and stability in 3.5wt % NaCl aqueous solution and corrosion solution with different pH values.

A hyperbranched-topology-mediated self-roughness approach toward robust all-organic superhydrophobic surfaces

Biomimetic superhydrophobic surfaces (SHSs) have shown promising applications in versatile scenarios. However, due to limitations of complicated templates, expensive instruments, and insufficient adhesion between adhesives and inorganic/organic nanoparticles, simultaneous implementation of facile fabrication and highly robustness of SHSs remains difficult. Here, we demonstrate a hyperbranched-topology-mediated self-roughness approach to construct an all-organic SHS. Because of the stable covalent linkages, the SHS can be applied for versatile surfaces, exhibiting high resistance to mechanical abrasions and chemical corrosions. Additionally, once wetted with alcohol, the surface turns from superhydrophobic to hydrophilic, enabling the manipulation of liquid and gas motion as well as applications as micro-reactors. This topology-mediated self-roughness strategy paves a foundation for future development of liquid-repellent coatings.

Fluorine-free, robust and self-healing superhydrophobic surfaces with anticorrosion and antibacterial performances

Superhydrophobic surfaces with water-repelling ability have important applications, such as self-cleaning, antibacterial and corrosion protection. However, the using of harmful fluorinated materials and its poor mechanochemical stability limit its practical application. Herein, a fluorine-free, robust and self-healing superhydrophobic surface is prepared through a two-step method of laser processing and spraying coating for anticorrosion and antibacterial applications. Laser processing is used to construct periodic micron-sized pillars for obtaining strong interface bonding between coating and substrate by mechanical interlocking effect, and as an ‘armor’, preventing the removal of the coating. The coating consists of epoxy resin (EP), hexadecyltrimethoxysilane (HDTMS) and γ-aminopropyltriethoxysilane treated Cu2O (KH550-Cu2O). The superhydrophobic surface can withstand various mechanical durability tests, such as multiple sandpaper abrasion and tape peeling cycles. It exhibits excellent corrosion inhibition efficiency (ηp > 99 %) on Mg alloy, Tinplate and Al alloy, which results from superhydrophobicity and organic coating. The superhydrophobicity endows surface with excellent antibacterial adhesion performance in a static liquid environment. The bactericidal activity of KH550-Cu2O can effectively inactivate the bacteria in contact with the surface and the free bacteria, providing excellent antibacterial ability in a dynamic liquid environment. It still exhibits good anticorrosion and antibacterial abilities after multiple mechanical abrasion cycles due to the outstanding mechanical durability. Moreover, it exhibits outstanding self-healing ability to plasma etching and oil contamination, self-cleaning ability under air and oil conditions, and chemical stability against acids and alkalis solution. All the above excellent performances promote its application in a wider range of fields.

Stretchable Superhydrophobic Surfaces: From Basic Fabrication Strategies to Applications

Superhydrophobic surfaces find extensive applications in various fields, including self-cleaning, liquid manipulation, anti-icing, and water harvesting. To achieve superhydrophobicity, the surfaces are designed with hierarchical nano- and/or microscale protrusions. These structures result in a static contact angle above 150° and a sliding/rolling-off angle below 10° when water droplets deposit on the surface. The combination of hierarchical structures and low-surface energy materials contributes to this unique liquid-repellent property. In addition to liquid repellency, the durability of these surfaces is crucial for practical applications, which has prompted the exploration of stretchable superhydrophobic surfaces as a viable solution. The flexibility of these surfaces means that they are effectively safeguarded against mechanical damage and can withstand daily wear and tear. Over the last decade, considerable research has been dedicated to developing stretchable superhydrophobic surfaces to expand their potential applications. This review provides an overview of stretchable superhydrophobic surfaces, specifically emphasizing current processing strategies and their prospective applications. Additionally, we present a forward-looking perspective on future fabrication methods to create robust superhydrophobic surfaces, further enhancing their practicality and versatility.

Chemically robust superhydrophobic surfaces with a self‐replenishing nanoscale liquid coating

AbstractDue to poor chemical robustness, superhydrophobic surfaces become susceptible to failure, especially in a highly oxidative environment. To ensure the long‐term efficacy of these surfaces, a more stable and environmentally friendly coating is required to replace the conventional salinization layers. Here, soot‐templated surfaces with re‐entrant nanostructures are precoated with polydimethylsiloxane (PDMS) brushes. An additional nanometer‐thick lubricant layer of PDMS was then applied to increase chemical stability. The surface is superhydrophobic with a nanoscale liquid coating. Since the lubricant layer is thin, ridge formation is suppressed, which leads to low drop sliding friction and fast drop shedding. By introducing a bottom “reservoir” of a free lubricant as an oil source for self‐replenishing to the upper layer, the superhydrophobic surface becomes more stable and heals spontaneously in response to alkali erosion and O2 plasma exposure. This design also leads to a higher icing delay time and faster removal of impacting cooled water drops than for uncoated surfaces, preventing icing at low temperatures.

Fabrication of robust superhydrophobic surface on silicone rubber

Robust superhydrophobic surfaces with periodic array structures composed of circular silica islands on silicone rubber substrates were fabricated using a combination of multi-laser exposure and chemical modification. Abrasion tests with sandpaper demonstrate that hard silica regions on the surface can protect the silicone rubber region from external damage, resulting in long-lasting superhydrophobicity. Moreover, with an increase in area fraction and a decrease in array hole radius, the wear of the filled superhydrophobic silica is slowed while the protection for the silicone rubber region is enhanced. Particularly, the optimum surface geometry had an area fraction of 35 % and array hole radius of 100 μm retaining its hydrophobicity up to 63 times of abrasion, eight times more than that of the superhydrophobic surface processed by lasers alone. The results of a sand impact test confirmed the resulting surface's resilience in an aeolian sand environment. This research demonstrated the feasibility of producing robust, superhydrophobic surfaces on flexible silicone rubber substrates and providing a foundation for improving and innovating related products.

Preparation of a robust and stable superhydrophobic coating with self-cleaning and mold resistance properties on natural bamboo substrate

Bamboo, as an excellent natural material, has received widespread attention and application. However, its defects, including hydrophilicity and poor mold resistance, shorten its service life. Therefore, the best strategy to address the defects of bamboo is to prepare robust and stable superhydrophobic surfaces. This study reports a simple two-step method to prepare superhydrophobic surfaces, using only two materials: rosin and nano-CaCO3. The method is easy to operate, replicable, cost-effective and safe. The prepared superhydrophobic bamboo (SHB) has a water contact angle (WCA) of 153 ± 3°. After being soaked in water at 0 ℃, 20 ℃, 40 ℃, 60 ℃, 80 ℃ and 100 ℃ for 2 h, the WCA of SHB maintained superhydrophobic in a wide range of 0–80 ℃. After being soaked in water at 100 ℃ for 2 h, the WCA of SHB sightly decreased to 147 ± 3°. After 2000 circles of weight friction, the WCA of SHB was 151°. After 1000 circles of tape peeling, the WCA of SHB was 150°. The WCA of SHB was greater than 151 ± 2° after soaked in acidic or alkaline solutions with pH values of 3, 5, 7, 9 and 11 for 2 h. After 6 weeks of fungal culture, the infection rate of SHB was 0%, while the infection rate of clean bamboo (CB) was 100%. In a word, SHB not only has good robustness, chemical stability, high and low temperature resistance, and mold resistance, but also can self-cleaning the dust on superhydrophobic surfaces through liquid droplets.

Rapid surface texturing to achieve robust superhydrophobicity, controllable droplet impact, and anti-frosting performances

Robust superhydrophobic surfaces with excellent capacities of repelling water and anti-frosting are of importance for many mechanical components. In this work, wear-resistant superhydrophobic surfaces were fabricated by curing a mixture of polyurethane acrylate (PUA) coating and 1H,1H,2H,2H-Perfluorodecyltrichlorosilane (HFTCS) on titanium alloy (TC4) surfaces decorated with micropillars pattern, thus, composite functional surfaces with PUA coating in the valleys around the micropillars pattern of TC4 were achieved. Apparent contact angle on fabricated surfaces could reach 167°. Influences of the geometric parameters of micropillars pattern on the apparent contact angle were investigated, and the corresponding wear-resistant property was compared. Droplet impact and anti-frosting performances on the prepared surfaces were highlighted. An optimized design of surface texture with robust superhydrophobicity, controllable droplet impact, and anti-frosting performances was proposed. This design principle is of promising prospects for fabricating superhydrophobic surfaces in traditional mechanical systems.

One-pot coatable fluorinated polyurethane resin solution for robust superhydrophobic anti-fouling surface

Superhydrophobic coating materials have considerable potential in a wide range of industrial applications because of their anti-fouling properties. However, their application is limited due to the instability caused by their fragile structure, resulting in superhydrophobic failure. Moreover, achieving superhydrophobic materials requires complex processes and specialized equipment. Polyurethane (PU) is a promising as a material for superhydrophobic coatings because of its inherent advantages such as adhesion properties and mechanical toughness. In this study, a fluorinated polyurethane (FPU) solution was synthesized using a one-pot method. Further, two types of particles with varying solvent miscibility were blended into an FPU solution. The alterations in surface morphologies, resulting from variations in evaporation conditions due to the different particle compositions, were confirmed through scanning electron microscopy (SEM), which leads to a difference in hydrophobicity. The prepared coating material was shown to tiny thorn-like surface morphology, which allowed it to demonstrate a high water contact angle of 157°, along with additional anti-fouling properties. Furthermore, the resulting superhydrophobic coating materials demonstrate mechanical robustness under cyclic tape peel test even after 10 cycles and cross-cut test Our study offers an effective approach for achieving superhydrophobic properties while maintaining mechanical durability, thereby advancing the development of high-performance superhydrophobic materials.

Photothermal superhydrophobic surface with good corrosion resistance, anti-/de-icing property and mechanical robustness fabricated via multiple-pulse laser ablation

Corrosion and ice accumulation occurring on carbon steel bring about huge economy lost, resource waste, and even hazard event. Fabricating black superhydrophobic surfaces is an effective method for improving the anti-corrosion and anti-/de-icing properties of metallic materials. However, it is still a challengeable task to fabricate a robust black superhydrophobic surface on carbon steel through an eco-friendly method. Herein, a black superhydrophobic surface was obtained on 45 steel substrate via a simple and fluorine-free method, i.e., multiple-pulse laser ablation followed by chemical modification with hexadecyltrimethoxysilane (HDTMS). The obtained surface exhibits a water contact angle of 156° and possesses a low reflectance (<9%) in the wavelength range of 400 ∼ 2500 nm. The surface displays an excellent photothermal property with a temperature rise of 52 °C under 1 sun of illumination within 8 min. Electrochemistry data reveals that the surface has good corrosion resistance with 64.78-times lower corrosion current density and 73.81-times higher charge transfer resistance than the steel substrate. Anti-icing test shows that the surface possesses 2547 s longer freezing delay time and at least ∼ 3 times lower de-icing force than the steel substrate, and photothermal de-icing test demonstrates that the ice on the surfaces starts thawing within 60 s under 0.5 sun of illumination, indicating that the surface has excellent anti-/de-icing property. Moreover, after impacting by 2000 g of sands or 400 times of tape peeling tests, the surface still maintains superhydrophobicity, indicating the good mechanical robustness of the surface.

Tailoring flower-like Zn(OH)2 nanoarchitectures and stearic acid on cellulosic fibers for structurally robust superhydrophobic surface

Structurally robust nanostructures on the surface of matrix highly determine the durability of superhydrophobic surface of cellulosic materials. Traditionally, the hydrophobic inorganic-organic nanocomposites were physically coated on the surface of cellulose fibers, whereas the nanocomposite was easy to fall off under external force due to the weak interfacial interaction between inorganic materials and cellulose, restricting their practical application. In this work, a sort of structurally stable superhydrophobic cellulosic materials was elaborately designed by successive in situ synthesis of Zn(OH)2 nanoarchitectures and coating stearic acid (STA). The unique flower-like micro/nano structures as well as the presence of hydrophobic STA imparted the cellulosic materials with superhydrophobic behavior and the optimized water contact angle of synthesized STA@Zn(OH)2/paper nanocomposite was enhanced to 171°. Moreover, the resultant cellulosic nanocomposite also possesses excellent structural stability without STA and Zn(OH)2 fall off as well as hydrophobicity reduction after bending 100 times. Compared to bare filter paper, both tensile stress and elongation at break of optimized flower-like nanocomposite reached 14.04 MPa and 25.24% with 109.6% and 323.5% improvement, respectively. Furthermore, such superhydrophobic cellulose-based material also presented excellent anti-fouling and antibacterial performances. This work proposed a facial and efficient strategy to construct structurally stable superhydrophobic cellulose-based materials, displaying great potential application in food packaging and outdoor anti-fouling fields.

Investigation on the Corrosion Resistance Properties of Cobalt-Chromium-Molybdenum Alloy Artificial Human Body Components with Robust Biomimetic Superhydrophobic and Slippery Surfaces Based on Laser Texturing.

Cobalt-chromium-molybdenum alloy is used as a material for artificial human body components such as artificial hip joint and artificial denture and is often affected by electrochemical corrosion in human body fluids and saliva, which leads to inflammatory reactions and damage to the surrounding tissues as well as loosening and failure of the body components themselves. Few studies have been conducted to prepare corrosion-resistant coatings on the surface of Co28Cr6Mo. In this study, we used laser texturing to process a bionic 3D micronanocomposite structure on the surface of Co28Cr6Mo and quickly prepared a superhydrophobic and slippery surface coating with excellent corrosion resistance using polydimethylsiloxane solution and silicone oil modification. This surface had ultralow surface adhesion and good robustness of durability and abrasion resistance, reducing bacterial colonization or tissue adhesion and solving the problem of the lack of stability of the superhydrophobic surface. Microgrid grooves and layered nanoparticles were structurally responsible for the variation in wettability. The formation mechanism and composition of the prepared coatings were further analyzed. Electrochemical corrosion experiments were conducted on the surface in simulating body fluid and saliva environments, which showed the enhanced corrosion resistance of the prepared surface in the human body. These findings can further develop the surface functional modification of Co28Cr6Mo, accelerating basic and applied research studies on artificial human components.

Preparation of a Wear-Resistant, Superhydrophobic SiO2/Polymethyl Methacrylate Composite Coating on Aluminum Surface Processed with Nanosecond Laser.

Superhydrophobic coatings are limited by complex preparation processes and poor mechanical durability in practical applications. In this study, a mechanically robust superhydrophobic composite coating was applied to an aluminum surface that underwent processing with a nanosecond laser (referred to as a superhydrophobic aluminum surface). It exhibits a high water contact angle (WCA) of 158.81°, a low sliding angle (SA) of less than 5°, and excellent self-cleaning ability. The wear test shows its durability, and the corrosion test shows its excellent corrosion resistance. This study provides a framework for the preparation of robust superhydrophobic surfaces that may have potential applications in many fields.

In-situ grown SiO2 on amino-silane modified polyacrylonitrile nanofibrous membranes and its waterproof-breathable and light-shielding properties

Waterproof and breathable (W&B) materials with light-shielding properties are expected to provide new choices for outdoor clothing. Herein, SiO2@PAN nanofibrous membranes were fabricated by a facile and eco-friendly strategy. Firstly, amino-silane modified polyacrylonitrile (PAN-APS) nanofibrous membranes were prepared by electrospinning. Subsequently, a hierarchical rough structure and robust superhydrophobic surface were formed by a one-step in-situ growing SiO2 and coating with hexadecyltrimethoxysilane (HDTMS). The results showed that SiO2@PAN nanofibrous membranes displayed durable water repellency (the water contact angle above 150° and the sliding angle of about 5.3°), and high breathability (the air permeability of 47.23 mm/s and the moisture permeability of 3.92 kg·m−2·d-1). And SiO2@PAN nanofibrous membranes had a certain durability, which water repellency could maintain even after mechanical abrasion, or after 24 h of immersion in acid-base solutions with pH values of 1, 4, 7, 10 and 13. Moreover, SiO2@PAN nanofibrous membranes showed light-shielding properties. After 10 min exposure to sunlight irradiation, the surface temperature of SiO2@PAN membrane was about 10 °C lower than that of PAN membrane and 20 °C lower than the temperature of the surface without covering membrane. This work provides a promising candidate for protective clothing.

Low temperature-curable superhydrophobic surface with ultra-mechanical durable and anti-corrosion properties through structural engineering of coniferous ZnO

Superhydrophobic surfaces (SHS) receive considerable attention because of their wide applications, such as building materials, biomedical materials, and different metallic coatings. This study reports a simple and cost-effective approach for fabricating a robust superhydrophobic surface consisting of 1H,1H,2H,2H-perfluorooctyltriethoxysilane-modified SiO2 and coniferous ZnO nanoparticles dispersed in fluoroethylene vinyl ether (FEVE/FS@ZnO) on a stainless steel substrate. The prepared SHS coatings were curable at room temperature and easy to handle. They exhibited unique hierarchical and re-entrant structures, reducing surface energy and resulting in a long lifetime, significant adhesion enhancement, and superhydrophobic and self-cleaning properties. The highest water contact angle (CA) and roll-off angle were 156° and 3°, respectively, achieved at an optimized ZnO:fluoroalkylsilane mass ratio of 10:0.6. The SHS coatings also showed a significant anti-corrosion effect in a corrosion solution (3.5 wt% NaCl solution) and high stability against various acidic (H2SO4, pH = 1) and basic (NaOH, pH = 13) solutions. In addition, the SHS coating layer exhibited improved durability and stability in sandpaper abrasion and tape peel tests, with a CA of 153° after 130 sandpaper abrasion cycles. These results provide a pathway for the future development of multifunctional coating materials. The robust FEVE/FS@ZnO SHS coating with superhydrophobic and self-cleaning properties could be applied to various functionalized solid surfaces.

One-step rapid synthesis of robust superhydrophobic surfaces through acrylate crosslinking/polymerization

A new synthetic approach is proposed to fabricate highly durable and eco-friendly superhydrophobic surfaces using acrylate click chemistry. This approach does not require complex or time-consuming fabrication processes and can be used for the rapid fabrication of durable anti-fouling materials/coatings. The use of long-chain acrylates provides the surface with extreme water repellency, and the resulting surface exhibits long-term stability under various harsh conditions, including prolonged exposure to chemicals, mechanical stress, and physical abrasions. Unlike existing techniques that suffer from poor durability and stability, the proposed method is facile and uses a temperature-initiated acrylate crosslinking/polymerization chemistry that provides a hierarchical morphology with low surface energy to the surface during the reaction. This technique results in highly robust 3D superhydrophobic surfaces that can be easily molded or sprayed onto various flexible and rigid substrates. These surfaces have potential applications in the fabrication of emerging advanced and functional materials. Furthermore, the superhydrophobic gel materials can be extended in 3D print molding using silicone templates, and the spray coating exhibits self-cleaning performance even after harsh physical abrasion. Overall, this new approach is a promising step towards the development of durable and eco-friendly superhydrophobic materials and coatings that can be used in practical applications.