Durable Superhydrophobic Coatings Research Articles

One-Step Methods to Fabricate Durable Superhydrophobic Coatings for Flexible Electronic Sensors

Inspired by lotus leaves in nature, superhydrophobic surfaces have attracted extensive attention in many fields. However, their complex preparation process, poor durability and high cost seriously restrict their large-scale application in industrial production. Based on the good flexibility and durability of carbon nanofibers, several simple modifier-free one-step approaches were adopted to fabricate a durable CNF/PVDF/PDMS conductive superhydrophobic coating. The fabricated coating not only possesses good superhydrophobicity to many kinds of liquids, but also has excellent self-cleaning and anti-fouling properties. In addition, the superhydrophobicity of the obtained multifunctional coating is stable even after harsh bending fatigue deformation, long immersion times and high-temperature treatment. Due to its strong adhesion and excellent conductivity, the CNF/PVDF/PDMS coating displays reliable mechanical stability and superior sensitivity. These distinct features make the obtained conductive superhydrophobic coating a good candidate for multifunctional smart sensors, with great application prospects in gesture detectors, waterproof wearable electronics and health monitors.

Waterborne, non-fluorinated and durable anti-icing superhydrophobic coatings based on diatomaceous earth

Superhydrophobic coatings have great potential for anti-icing compared with conventional techniques (e.g., thermal melting, chemical release and mechanical vibration), but suffer from short water freezing time, environment-unfriendliness, low stability, etc.

Development of Highly Durable Superhydrophobic Coatings by One-Step Plasma Spray Methodology

This study aims to minimize the mechanical, chemical and thermal damages on the blades of a compressor used in aerospace engines by developing a superhydrophobic coating on the blade surface. In the absence of any information in open literature for the fabrication of such coatings, an one-step plasma spray process was implemented. For this, a well mixed powder of Ni and Ti was used as feedstock material. The superhydrophobicity characteristic of the coating was confirmed by the measurement of the contact (165°) and sliding angles (8 ± 1°) by the sessile drop technique. The adhesion test of the coating showed the high force of adhesion at the interface with a failure limit of 40.85 MPa. Furthermore, the abrasion test depicted an excellent abrasion resistance of the coating. These two investigations indicated that the coatings had a very high mechanical durability. The coatings also showed an excellent thermal stability up to 400 °C. Beyond this temperature (at 600 and 900 °C), the superhydrophobic characteristic changed for hydrophobic. The pH and corrosion tests were also performed to assess the chemical stability of coatings. They showed that the coatings retained the superhydrophobic property for pH ranging between 9.5 and 2.4. Beyond this range, at pH = 10 and pH = 2, the contact angles were 138° and 143°, respectively. In addition, the coatings exhibited a better corrosion resistance than the substrate and coatings developed by using other deposition techniques.

Feasible fabrication of durable superhydrophobic SiO2 coatings with translucency and self-cleaning performance

In this work, a versatile strategy was proposed to fabricate translucent superhydrophobic coatings by spraying the suspension of modified SiO2/polydimethylsiloxane (PDMS) on various substrates. The wettability can be adjusted by changing the mass ratio of modified SiO2 nanoparticles in the suspension. By optimizing the parameters in the spraying process, a superhydrophobic surface with a water contact angle of 164.1 ± 3.4° and a sliding angle of 4.2 ± 0.4° was achieved. As prepared translucent superhydrophobic SiO2/PDMS coatings show good mechanical durability, chemical stability, and self-cleaning performances.

Dehydrogenation-driven assembly of transparent and durable superhydrophobic ORMOSIL coatings on cellulose-based substrates

A novel dehydrogenation-driven assembly method was proposed to fabricate durable superhydrophobic SiO2/PMHS ORMOSIL (organically modified silica) coatings on cellulose-based substrates. Poly(methylhydrogen)siloxane (PMHS) played the key role in the durability of ORMOSIL coatings and the assembly process. The dehydrogenation-driven assembly mechanism of ORMOSIL was discussed in detail. Results indicated that the chemical property and microstructure of ORMOSIL could be controlled easily by varying the weight ratio of SiO2 to PMHS. The lotus-like ORMOSIL coating could be realized as the weight ratio of SiO2 to PMHS was 1:1. The ORMOSIL coating on wood surface was of self-cleaning property, good transparency and durability (including water-repellency and dimensional stability, mechanical and chemical stability, and UV-resistance). In addition, the SiO2/PMHS ORMOSIL gave cotton good oil/water separation ability. Finally, the dehydrogenation-driven assembly method was simple and low-cost, and it can be applied to fabricate durable superhydrophobic coatings on any other hydroxyl-containing substrates besides the cellulose-based substrates.

A facile cross-linking approach to fabricate durable and self-healing superhydrophobic coatings of SiO2-PVA@PDMS on cotton textile

Superhydrophobic surfaces with long-lasting stability through simple fabrication procedures have attracted considerable attention. The application of existing superhydrophobic surfaces is limited, considering the use of toxic ingredients and their poor longevity. Herein, we report the novel fabrication of durable, fluorine-free, and self-healing superhydrophobic cotton textiles by utilising boric acid (H3BO3) as a cross-linker to silica nanoparticles and poly (vinyl alcohol) followed by polydimethylsiloxane (PDMS) modification through a simple dip-dry coating technique. Boric acid possessed a noticeable micro/nanoporous structure with silica and poly (vinyl alcohol) via cross-linking on the surface, which showed excellent superhydrophobicity, and PDMS modification on the textile surface created a lower surface energy than unmodified textile. The fabricated surface exhibited a maximum water-contact angle of 156.84°±1.5° with a small rolling angle of 1.8°±0.3°, presenting outstanding superhydrophobicity for cotton textiles. The modified cotton textile surface had excellent durability against mechanical and chemical disturbances. The experimental findings indicated that the fabricated textile had adequate mechanical strength that could withstand sandpaper abrasion for 120 cycles, tape-peeling repetition 60 times, knife scratching for 20 cycles and washing by surfactant solutions for 80 cycles. Additionally, the modified textiles exhibited oil–water separation and self-healing abilities, therefore showing multifunctional properties that have potential in a wide range of cotton textile surface treatments.

Hexadecyltrimethoxysilane-Modified SiO2 Nanoparticle-Coated Halloysite Nanotubes Embedded in Silicone–Acrylic Polymer Films as Durable Fluorine-Free Superhydrophobic Coatings

Superhydrophobic coatings have received considerable attention owing to their potential applications. There has been an increasing demand for the construction of durable superhydrophobic coatings u...

Development of novel superhydrophobic coatings using siloxane-modified epoxy nanocomposites

The extensive research and interest in superhydrophobic surfaces have not yet resulted in their widespread utilization. Limitations include high cost, complex fabrication techniques, and poor durability. Herein, we report a facile, economic, and scalable spray-coating fabrication technique that utilizes an epoxy-silica nanocomposite to create robust and durable superhydrophobic coatings. To overcome its inherent high surface energy, the epoxy was modified using an amino-functionalized polysiloxane. The newly developed nanocomposite coating demonstrated excellent water repellency with contact angles of ~165° and sliding angles of ~3° for different substrate materials such as metals, wood, glass, and textile. Our results revealed that a nanocomposite coating with a silica concentration of ~28 wt% provides an optimum balance between superhydrophobicity and durability. We also investigated the effect of solvent volatility on the hierarchical structure and superhydrophobicity of the coated samples, which is rarely considered in the literature. It was found that a spray emulsion with lower solvent volatility results in an enhanced surface microstructure that improves water repellency. Moreover, the coated samples demonstrated excellent robustness and durability against peeling, abrasion, corrosion (pH 1 to 13), and high temperature (up to 150 °C) environments exposure tests. The outcome of our efforts confirms that the epoxy modification process leads to enhanced superhydrophobicity without compromising the robustness and durability of the coating. This remarkable performance offers a great potential for large-scale production of superhydrophobic surfaces operating in harsh working conditions.

Synthesis of Durable Superhydrophobic Coating and Its Applications in Oil/Water Separation

Superhydrophobic surfaces have received enormous attention thanking to their potential applications in the areas of anti-icing, anti-contamination, and oil/water separation. Herein, we have successfully prepared superhydrophobic surfaces, which were synthesized by using the polydimethylsiloxane (PDMS) as adhesive and the magnesium palmitate (Mg-P) were evently coated to form roughness on the surfaces of glass, textile, stainless steel mesh, and paper. The as-fabricated superhydrophobic surfaces possessed excellent water-resistance, self-cleaning properties, durability, and robustness. Remarkably, in the actual oil/water separation, the water contact angle and oil collection efficiency of the superhydrophobic mesh were still more than 150° and 91% even after separation over 10 cycles, respectively. Thus, the superhydrophobic coating has applications potential in self-cleaning, anti-contamination, and oil/water separation fields.

The Superhydrophobic State Stability of Coatings Based on Copolymers of Glycidyl Methacrylate and Alkyl Methacrylates on Cotton Fabric Surface

We suggest a simple and reproducible strategy for fabricating durable superhydrophobic coatings on the basis of series of functional random copolymers of alkyl methacrylates and glycidyl methacrylate on cotton fabric surface. The procedure consists of the fabric treatment by solutions of copolymers in methylethylketone and following heating at 140 °C. The initial contact angles of obtained coatings on fabric surface achieve 165°. The dependence of superhydrophobic properties of coatings based on copolymers of glycidyl methacrylate and alkyl (meth)acrylates (with alkyl radicals С4–С18 in side chains) attached to the cotton fabric surface was studied. The comparative analysis of superhydrophobic state stability of polymer coatings during long-term contacts with aggressive media is presented. We evaluated the contact angles stability as a function of prolonged contact of polymer coatings with water under saturated vapor conditions, organic solvents, and synthetic detergents. Polymeric coatings based on a copolymer of lauryl methacrylate (С12) and glycidyl methacrylate provide better stability of superhydrophobic properties compared with other copolymers of alkyl methacrylates.

Fabrication of robust superhydrophobic surfaces by one-step spray coating: Evaporation driven self-assembly of wax and nanoparticles into hierarchical structures

Mechanically durable superhydrophobic coatings have enormous application potential in almost all aspects of our daily lives. In this study, we present a practical strategy for one-step fabrication of robust superhydrophobic coatings based on evaporation driven self-assembly of hydrophobic nanoparticles and wax into hierarchical structures. Depending on the solvent and coating distance, spray-coating a dispersion composed of alkyl-silane functionalized nanoparticles and wax results in extremely water repellent surfaces with a water contact angle of 175° and a sliding angle of 3°. The formation of hierarchically structured surfaces upon evaporation of the solvent enables fabrication of fluorine-free, highly water repellent surfaces and provides high level of structural protection against mechanical abrasion. The coating retains its superhydrophobicity even after 1000 cycles of water spray impact, 45 min of water jet impact, and 180 cm of linear abrasion. The low-cost, scalable, one-step, and fluorine-free fabrication of superhydrophobic coatings that can be applied onto virtually any type of material surface with a satisfactory mechanical robustness based on eco-friendly and industrially available materials presents promising avenues for practical applications.

Functional Superhydrophobic Coating Systems for Possible Corrosion Mitigation

Because of their repellent, corrosion-mitigating, anti-icing, and self-cleaning properties, superhydrophobic coatings have numerous applications from windshields to textiles. A superhydrophobic coating is defined as one having a water contact angle (WCA) greater than 150° with a surface sliding angle less than 10°, and very low hysteresis between the advancing and receding angles. Its surface exhibits the so-called “lotus leaf effect,” whereby water bounces and balls up on contact. Here, water droplets run off readily, taking along dirt and dust for a self-cleaning effect that keeps the surface dry. The chemical composition of a surface affects the WCA, which can rise to 120°, but to achieve a WCA greater than 150°, which is considered superhydrophobic, an additional micro- and nanostructural component is needed. This functional hierarchical micro- and nanomorphology is exhibited in nature by plants and insects. A superhydrophobic coating on metallic substrates promises to provide corrosion mitigation by blocking oxygen and electrolytes, which are needed for the initiation of corrosion at the surface and interface. The methods used for preparing functional superhydrophobic coatings include sol-gel processing, layer-by-layer assembly, etching, lithography, chemical and electrochemical depositions, chemical vapor deposition, electrospinning, hydrothermal synthesis, and one-pot reactions. In this work, some research studies conducted to develop robust and durable superhydrophobic coatings are discussed in detail and analyzed for possible corrosion mitigation on the surfaces of metals and alloys. Scientists, engineers, students, and other participants in automotive, aircraft, energy, defense, electronics, and other industries will benefit greatly from this work.

Fabrication of transparent, durable and self-cleaning superhydrophobic coatings for solar cells

A superhydrophobic coating with high transparency and ultrahigh adhesive force is prepared for application on the glass covers of solar cells, which also exhibits excellent thermal stability and strong acid–base corrosion resistance.

Durable Superhydrophobic Silica Aerogel Coating from Hydrophobic Gel Synthesis

Silica aerogel is a nanostructured porous solid material. It has a low bulk density, low thermal conductivity and can be hydrophobic. In this work, hydrophobic silica gel, a material used to form aerogel, is used instead of its powder form to avoid ultrafine air particles pollution. It is used to surface modified materials to make the materials superhydrophobic and still withstand physical abrasion that ordinary aerogel would not able to do. The superhydrophobic silica aerogel coating was designed by mixing the hydrophobic gel with DOW CORNING® 2405 resin as binder and varying DOWSIL™ Z-6137 silane and tetraethyl orthosilicate (TEOS). The coating is characterized by the static contact angles (CA) and abrasion test. Scanning electron micrographs of different coating compositions were investigated. Results show that the hydrophobic gel mixed with resin and Z-6137 silane have contact angle >179º. Superhydrophobic silica aerogel coating can be utilized as material coatings for glass, fiber, polymer, etc.

Durable and Multifunctional Superhydrophobic Coatings with Excellent Joule Heating and Electromagnetic Interference Shielding Performance for Flexible Sensing Electronics

Superhydrophobic coatings have wide applications in many fields. However, superhydrophobic and smart coatings with multifunctionality and their applications in flexible sensing electronics are seldom reported. In this work, durable, superhydrophobic, and anticorrosive coatings with excellent Joule heating and electromagnetic interference (EMI) shielding performance are prepared on the basis of Ag precursor reduction and synchronous nonsolvent induced phase separation. Silver nanoparticles (AgNPs) coated with the copolymer (polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene: SEBS) are uniformly distributed on the target substrate, forming mechanically durable conductive network. SEBS could not only endow the surface coating with superhydrophobicity but also improve the interaction among individual Ag nanoparticles and the interfacial adhesion between AgNPs and the substrate. The multifunctional coating possesses excellent anticorrosive, self-cleaning, and deicing properties. The high conductivity endows the coatings with excellent Joule heating and EMI shielding performance. The multifunctional coating can be applied to a variety of different substrates with outstanding surface stability and reliability. The conductivity for the smart coating can reach as high as 107 S/cm with the EMI shielding effectiveness up to 37.8 dB. At a low applied voltage of 1 V, the conductive fabric can be heated up to over 80 °C in 60 s and displays good recyclability during dozens of heating and cooling cycles. The Joule heating-induced temperature increase could be used for efficient surface deicing. When used for the flexible and wearable strain sensors, the multifunctional coating has a very low strain detection limit of 0.5% and large sensitivity (with the gauge factor as high as 1075) and excellent repeatability. In addition, it can be used for precisely monitoring different body motions, including both large and subtle joint movement.

Facile Fabrication of Durable Superhydrophobic Films from Carbon Nanotube/Main-Chain Type Polybenzoxazine Composites.

Superhydrophobic materials have immense applications in the fields of industry and research. However, their durability is still a cause for concern. A facile method for preparing durable superhydrophobic films from carbon nanotubes (CNTs) and the main-chain type polybenzoxazine precursors is reported herein. We used probe ultrasonicator to prepare CNT/polybenzoxazine coatings. Compared with the general sonicating dispersion process, the dispersion time was greatly reduced from a few hours to 5 minutes and the prepared suspension exhibited film-forming characteristics well. The CNT/polybenzoxazine films, which do not contain any fluorinated compounds, exhibit remarkable durability against thermal treatment, organic solvents, corrosive liquids, and sandpaper abrasion, while retaining their superhydrophobicity. Furthermore, these CNT/polybenzoxazine films also showed durable superhydrophobicity after ultraviolet (UV) irradiation for 100 h. This CNT/polybenzoxazine film can be readily used for practical applications to make durable superhydrophobic coatings.

Fabrication of fluorine-free superhydrophobic coatings from montmorillonite with mechanical durability and chemical stability

In this study, durable superhydrophobic coatings were successfully prepared by modifying montmorillonite with stearic acid and organosiloxane, and this procedure was simple, efficient, and environmentally friendly. Different from the previously reported methods, the micro-/nanostructures of the superhydrophobic coatings were constructed by using the abundant natural montmorillonite as the building blocks. The surface topography of the coating was analyzed with a scanning electron microscope, while element compositions and functional groups were characterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, respectively. The as-prepared superhydrophobic coatings showed excellent wear resistance, and could maintain their superhydrophobicity after sandpaper abrasion for 180 cm in length. Apart from the superb wear resistance, the obtained superhydrophobic coatings also displayed strong acid resistance and anti-UV properties. In addition, the as-coated fabric not only possessed superhydrophobicity and the ability of oil–water separation, but also exhibited excellent fire resistance because of the thermal stability of MMT particles. Notably, the favorable comprehensive performance of the as-prepared coatings was indicative of their potential applications in oil/water separation and some harsh conditions, and as outdoor protective materials.

Mechanically durable superhydrophobic PDMS-candle soot composite coatings with high biocompatibility

To realize practical applications, the development of superhydrophobic coatings with high durability against harsh environmental conditions has been of interest, especially coatings that are susceptible to mechanical damage. Herein, we present mechanically durable superhydrophobic polydimethylsiloxane (PDMS)-candle soot (CS)-based composite coatings through simple and rapid casting and soot processes, which can be fabricated on various substrates, such as glass, woods, stainless steel meshes, and plastics. The reported extremely water-repellent coatings consist of a PDMS basic binding layer, candle soot clusters (CSC), and an outside CS layer, which has exhibited long-lived superwettability and resistance against mechanical damage in multi-cycle abrasion tests and ultrasonication treatments over a long duration. The resulting mechanical durability was mainly a result of three-dimensional topography-protected and carbon nanoparticle-mixed structures, which decreased the contact area and created highly hydrophobic bulk coatings. Moreover, the durable performances of the three types of CS-based superhydrophobic coatings to resist mechanical damage, involving CS, PDMS-CS, and PDMS-CSC-CS coatings, were compared on a glass substrate, and the results indicated higher robustness of the present PDMS-CSC-CS coatings. In addition, it showed higher biocompatibility than a PDMS film surface, and can therefore be employed as a promising material for further modification for applications in prospective multifunctional biomedical devices.

Large-scale fabrication of durable and robust super-hydrophobic spray coatings with excellent repairable and anti-corrosion performance

Some drawbacks such as complicated preparation processes, more expensive modification, and lack of durability have restricted the practical applications of super-hydrophobic coatings. In this paper, we present a simple and inexpensive approach to fabricating a robust super-hydrophobic coating by spraying a fluorine-free suspension composed of epoxy resin (EP), polydimethylsiloxane (PDMS), and modified SiO2 on various substrates. This coating exhibited excellent super-hydrophobicity with a contact angle of 159.5° and a sliding angle of 3.8°. The as-prepared super-hydrophobic EP + PDMS@SiO2 coating retained super-hydrophobicity after exposure to harsh conditions including immersion in boiling water for 2 h or liquid nitrogen for 1 h, intense UV radiation for 48 h, and intense chemical corrosion. Moreover, the resulting super-hydrophobic coating can withstand various mechanical durability experiments such as tape peeling after knife scraping, hand kneading, and 100 sandpaper abrasion cycles. Furthermore, the fabricated coatings also exhibit a self-healing ability against O2 plasma etching, excellent self-cleaning in air and oil conditions and outstanding anti-corrosion performance. We believe that this easy, environmentally friendly method has great potential for large-scale practical applications in numerous fields.

Environmentally benign and durable superhydrophobic coatings based on SiO2 nanoparticles and silanes

The literatures about superhydrophobic coatings (SHCs) are increasing every year, however, undesirable chemicals including organic solvents and fluorinated compounds are intensively used in the existing preparation methods, which seriously hinder their large scale production and practical applications. Herein, a simple approach for preparation of totally waterborne, fluorine-free and durable SHCs is reported. First, a waterborne suspension of hexadecyl polysiloxane modified SiO2 (SiO2@HD-POS) was prepared via HCl-catalyzed hydrolytic condensation of hexadecyltrimethoxysilane (HDTMS) and tetraethoxysilane with SiO2 nanoparticles. The SHCs with high water contact angles (CA = 163.9°) and low sliding angles (SA = 3.7°) were prepared simply by sequentially spray-coating a polyurethane (PU) waterborne solution and the SiO2@HD-POS waterborne suspension onto glass slides. The influences of SiO2, HDTMS, reaction time and fabrication temperature on superhydrophobicity were investigated. The SHCs can withstand 80 m of reciprocating abrasion against A4 paper at 4.5 kPa and impacting of at least 50 g of sand microparticles with 30 cm release height. Moreover, the coatings also show exceptional thermostability in boiling water. The SHCs showed promising applications in various areas including oil/water separation and preventing scald, as the method is environmental benign and the coatings are applicable onto various substrates.