Excellent Self-cleaning Properties Research Articles

Cerium Stearate Electrodeposited Superhydrophobic Coatings for Active Corrosion Protection of Anodized AA2024-T3

The present study investigated the active corrosion protection provided by superhydrophobic cerium stearate coatings. Superhydrophobic cerium stearate was deposited on anodized AA2024-T3 at 40 V with different electrodeposition times using a simple DC electrodeposition technique to know the role of electrodeposition time on surface morphology, hydrophobicity, and corrosion resistance. The structure and morphology of cerium stearate was characterized to understand its formation mechanism. Electrodeposition process at 40 V for 120 min resulted in the formation of dual-scale Allium giganteum like micro/nano hierarchical texture of cerium stearate with a water contact angle of 165±1.6°. The cerium stearate coating obtained for 120 min process time had excellent self-cleaning property and good chemical stability, environmental stability, and mechanical durability acceptable for industrial applications. Electrochemical impedance spectroscopy and scanning vibrating electrode technique were used to investigate the active corrosion protection of cerium stearate coating. The electrodeposited cerium stearate coating showed active corrosion protection based on self-healing ability by releasing cerium (Ce3+) ions.

Preparation of carbon nanotube/tannic acid/polyvinylpyrrolidone membranes with superwettability for highly efficient separation of crude oil-in-water emulsions

Oil spills and oily industrial wastewater contain insoluble toxic organic molecules, which are harmful to the environment and human health. The preparation of separation membranes with favorable superwettability is crucial for oil-contaminated water treatment. In this study, we prepared a membrane from carbon nanotubes (CNTs), tannic acid (TA), and polyvinylpyrrolidone (PVP) via a green method, without using organic solvents. This membrane exhibited superhydrophilicity and underwater superoleophobicity, along with excellent self-cleaning and anti-fouling properties towards highly viscous crude oil. Furthermore, the CNT/TA/PVP membrane exhibited excellent oil/water separation performance, with very high permeation flux values of up to 7570 and 2634 L m−2 h−1 bar−1for surfactant-free and -stabilized oil-in-water emulsions, respectively. Remarkably, we separated a stabilized crude oil-in-water emulsion using the CNT/TA/PVP membrane. Moreover, these CNT/TA/PVP membranes were resilient under oil accumulation at intermittent pressure during oil/water separation, maintaining a high flux. The high performance of this CNT/TA/PVP membrane, and its green, low-energy, cost-effective preparation, indicate considerable potential for practical applications.

Surface engineering of cellulose film with myristic acid for high strength, self-cleaning and biodegradable packaging materials

Developing sustainable, renewable, hydrophobic, and biodegradable packaging material to replace petroleum-based plastic products remains a challenge. Herein, original cellulose/myristic acid composite films were fabricated by solvent-vaporized controllable crystallization of natural myristic acid on anisotropic cellulose films. The myristic acid crystals that evenly distributed on the surface of cellulose film generated micronano binary structure and the interstitial space between microplates, resulting in high hydrophobicity (water contact angle = 132°) and excellent self-cleaning property of the composite film. The resultant film exhibited good tensile strength and toughness under both dry (188.7 MPa, 34.4 MJ m−3) and humid conditions (119.9 MPa, 28.7 MJ m−3). Moreover, these composite films could be degraded completely after approximately 102 days in soil with an average environment temperature of 32 °C. This work provided a low-cost and sustainable pathway for the fabrication of high-strength, self-cleaning, and waterproof packaging materials instead of plastics.

A facile method to prepare stearic acid-TiO2/zinc composite coating with multipronged robustness, self-cleaning property, and corrosion resistance

Despite that some superhydrophobic coatings have been developed to enhance the corrosion resistance of steel, there lacks a solution that also fulfills both robustness and service durability. Taking advantage of the controlled generation of particles during electrodeposition, a multifunctional stearic acid (STA)-TiO2/zinc composite (TZC) coating with hierarchical micro/nanostructures by codeposition of TiO2 nanoparticles and zinc ions was prepared on carbon steel substrates. The structures of STA-TZC coating were characterized by a series of means. The micro/nanoscale structured surface based on TZC with STA overcoat imparted the prepared STA-TZC coating with outstanding superhydrophobic property; the water contact angle and sliding angle were 160±1.4° and 5.4±0.2°, respectively. According to the tests of knife scratching, adhesive tape peeling, sandpaper abrasion, and chemical corrosion resistance, the STA-TZC coating presented good mechanical and chemical stabilities. Additionally, STA-TZC coating showed excellent self-cleaning property, corrosion resistance, and superhydrophobic stability. The results indicated that filling the voids of porous zinc coating with TiO2 nanoparticles and subsequently modifying with STA film could greatly improve the coating’s resistance to corrosion and mechanical abrasion. This electrochemical codeposition-modification method has broad application prospects for exploring and preparing metal-based superhydrophobic coatings.

Synthesis of a novel anti-fog and high-transparent coating with high wear resistance inspired by dry rice fields

During the outbreak of COVID-19, the fogging of goggles was a fatal problem for doctors. At present, there are many ways to prevent fogging by adjusting surface wettability. However, the mechanical properties of most super-hydrophilic antifogging coatings are poor, easy to lose their antifogging properties when encountering fingers or cloth friction. To address this issue, the Konjac Glucomannan was cross-linked with water-soluble silicone fluid to form a binder, then being combined with the modified Ecokimera to prepare an eco-friendly super-hydrophilic coating that possessed excellent super-hydrophilicity, and the water contact angle (WCA) was 2.51 ± 1°. In addition, the WCA is still about 5° after 180 times of antifogging tests. The friction resistance of the coating was as high as 24 m. Moreover, the light transmittance was only reduced by 3%. Besides, they also had the excellent self-cleaning property. After being stored in the laboratory environment for 90 days, it can still maintain the hydrophilic property (WCA is about 5°). In general, the method proposed in this study is low-cost and eco-friendly, and can be widely used in the preparation of antifogging coatings.

Fabricating low-cost, robust superhydrophobic coatings with re-entrant topology for self-cleaning, corrosion inhibition, and oil-water separation

HypothesisThe superhydrophobic surfaces with re-entrant microstructures are known to provide robust superhydrophobicity by enhancing the energy barrier for Cassie-Baxter to Wenzel transition. However, the fabrication of such structured surfaces often involves sophisticated techniques and expensive ingredients. ExperimentsHerein, a multifunctional, low-cost, and fluorine-free superhydrophobic coating with re-entrant surface topology was fabricated using fly ash (FA) and room-temperature-vulcanizing silicone. A systematic study was performed to evaluate the coating properties and durability. The robustness was evaluated as a function of particle size and inter-particle spacing. The performance in self-cleaning, corrosion inhibition and oil-water separation has been presented. FindingsThe synthesized coatings are substrate-versatile and demonstrate superhydrophobic behavior. The close-packed coating of re-entrant FA particles attained via vibration compaction was seen to provide high robustness. The coatings retain their superhydrophobicity after multiple cycles of tape-peeling and exposure to environmental factors including temperature, pH, and UV radiation. These coatings exhibit excellent corrosion inhibition (corrosion efficiency > 99.999%), outperforming the majority of the previously reported superhydrophobic coatings. It also displays excellent self-cleaning property and high separation efficiencies in oil-water separation (>99%). We envision that such FA-based superhydrophobic coatings can solve the issues of synthesizing cheaper, sustainable, and robust superhydrophobic surfaces while simultaneously opening new avenues for FA utilization.

Tannic acid-based complex coating modified membranes with photo-Fenton self-cleaning property for sustainable oil-in-water emulsion separation

The separation of oil-in-water emulsions containing surfactants has been a challenge in the field of water purification. The main reason limiting the use of membrane separation technology for emulsions is the reduction in flux due to membrane fouling. Introducing photo-Fenton self-cleaning reaction into membrane filtration to reduce the adverse effects of membrane fouling represents a promising direction in membrane fields. In this study, a two-step immersion method was used to prepare tannic acid (TA)-Fe(III) as a composite coating on a pristine polyvinylidene fluoride (PVDF) membrane, and then HPO42- was added to the coating, which greatly improved the hydrophilicity and compactness of the coating. The resulting membrane had separation fluxes of more than 1500 L m-2 h−1 for various oil-in-water emulsions at a transmembrane pressure of 0.1 bar, and the carbon content of all filtrates was less than 50 ppm. The prepared membranes exhibit satisfactory antifouling ability. After 50 min of continuous high-efficiency separation, the membrane undergoes a photo-Fenton reaction under ultraviolet light to restore the original wettability and flux. After 5 self-cleaning cycles, it can still recover to 96.96% of the original flux. The high permeation and excellent self-cleaning property of the PVDF/TA-Fe(III)-HPO4 membrane manifest its attractive potential application in water purification.

Are telechelic polysiloxanes better than hemi-telechelic for self-cleaning applications?

HypothesisPolysiloxanes are becoming new trend in self-cleaning (oil- and water‐repellent) applications due to their low-cost and environmentally friendly nature. Lower phase separation of polysiloxanes in coating matrix is critical to obtain excellent self-cleaning properties. We hypothesize that telechelic polysiloxanes can bind to coating matrix at both ends and thus will suppress phase separation of polysiloxane as compared to hemi-telechelic analog and thus will offer excellent self-cleaning properties. ExperimentEight PDMS additives were prepared via the free-radical polymerization of telechelic and hemi-telechelic methacryloxypropyl-based PDMS precursors with methylmethacrylate (MMA) and glycidylmethacrylate (GMA). The compositions of the prepared polysiloxane additives were optimized to obtain excellent self-cleaning performance. FindingsOur breakthrough development confirms that telechelic polysiloxanes (PDMS-T) incorporated into epoxy-based anti-smudge coatings outperform hemi-telechelic polysiloxanes (PDMS-HT) by offering excellent repellency against difficult to repel liquids. These breakthrough findings will vertically advance Science and innovations in the self-cleaning field by offering robust guidelines for choosing suitable polysiloxane for self-cleaning applications.

Enhancing the Oil-Fouling Resistance of Polymeric Membrane Ion-Selective Electrodes by Surface Modification of a Zwitterionic Polymer-Based Oleophobic Self-Cleaning Coating

Due to the frequent oil spill accidents and pollution of industrial oily wastewater, oil fouling has become a great challenge to polymeric membrane ion-selective electrodes (ISEs) for applications in oil-contaminated areas. Herein, a simple approach is proposed to enhance the oil-fouling resistance of polymeric membrane ISEs by surface modification of a zwitterionic polymer-based underwater oleophobic coating. As a proof-of-concept, a classical poly(vinyl chloride) membrane-based calcium ion-selective electrode (Ca2+-ISE) is chosen as a model sensor. The zwitterionic polymer-based coating can be readily modified on the sensor's surface by immersion of the electrode into a mixture solution of dopamine and a zwitterionic acrylate monomer (i.e., sulfobetaine methacrylate, SBMA). The formed poly(SBMA) (PSBMA) coating alters the oleophilic membrane surface to an oleophobic one, which endows the surface with excellent self-cleaning properties without loss of the sensor's analytical performance. Compared to the pristine Ca2+-ISE, the PSBMA-modified Ca2+-ISE exhibits an improved analytical stability when exposed to oil-containing wastewater. The proposed approach can be explored to enhance the oil-fouling resistance of other polymeric membrane-based electrochemical sensors for use in the oil-polluted environment.

Fabrication of multifunctional PET fabrics with flame retardant, antibacterial and superhydrophobic properties

The multifunctional polyethylene terephthalate (PET) fabrics with flame retardant, antibacterial and superhydrophobic properties were successfully fabricated by a simple coating approach to enhance the properties of PET fabrics and to make them extensively applicable in a number of fields. The composite coating was composed of ammonium polyphosphate (APP), polydopamine (PDA), PDMS-silica (PDMS-SiO2), and silver nanoparticles (AgNPs). ATR-FTIR spectra, XPS analysis, and SEM-EDS spectrometer were employed to investigate the morphological properties and constitution of these coatings. The flame retardant performance of the multifunctional PET fabrics was determined by LOI, vertical flame test (VFT) and cone calorimeter test (CCT). The results revealed that the APP@SiO2-PDA@Ag PET fabrics' LOI value reached 29.0 %, which was 9.5 % higher than that of pristine PET fabrics. Besides, the APP@SiO2-PDA@Ag PET fabrics could self-extinguish the fire quickly in the VFT. The peak heat release rate and total heat release of the APP@SiO2-PDA@Ag PET fabrics were 34 % and 26 % lower than those of the pristine one. Notably, the multifunctional PET fabrics had excellent antibacterial activity against E. coli and S. aureus. The multifunctional fabrics exhibited superhydrophobicity with a water contact angle (CA) greater than 150° and showed excellent self-cleaning and antifouling properties. More importantly, the multifunctional PET fabrics still retained excellent flame retardant performance and antibacterial properties after multiple washing cycles.

Durable and Regenerable Superhydrophobic Coating on Steel Surface for Corrosion Protection

Corrosion limits the usage of steel and leads to the tremendous loss of the economy. Superhydrophobic coating is proven an effective way to prevent corrosion due to its excellent water repellent nature. Herein, we describe the successful preparation of superhydrophobic coating on steel surface which is synthesized by using chemical etching technique with mixture of hydrochloric and nitric acid followed by treatment with lauric acid. By optimizing the etching process parameters, superhydrophobicity with water static contact angle of 170° and tilt angle of 5° is successfully achieved. Coated steel is found to be thermal, chemical, and mechanical stable. Besides, coating has also good regenerability. Furthermore, coating exhibits the excellent self-cleaning and anti-fogging properties. The electrochemical study is revealed the enhancement of corrosion resistance of steel after coating. This facile strategy inspires the large-scale fabrication of multifunctional steel surfaces for practical applications in self-cleaning, anti-fogging, and corrosion protection.

Fabrication of durable and sustainable superhydrophobic‐superoleophilic paper for efficient oil/water separation

Traditional superhydrophobic materials for oil/water separation not only depend on non-renewable materials but also lead to secondary environmental pollution after use due to their non-biodegradation and introduction of toxic fluorochemicals. Herein, we reported a facile method to prepare durable and sustainable superhydrophobic-superoleophilic paper, which is combination of layer-by-layer (LBL) assembly of ZnO nanoparticles and carrageenan (CR) together with following polydimethylsiloxane (PDMS) modification. The surface chemical composition, zeta potential, surface morphology, surface wettability and strength property of the modified paper were investigated. The PDMS/(ZnO/CR)7 multilayer-modified paper showed superhydrophobic-superoleophilic property and 2.6 % improvement in tensile strength compared with original paper. Meanwhile, this superhydrophobic paper exhibited excellent anti-bacterial adhesion ability and photodynamic bactericidal activity, which were more effective in preventing and eliminating bacterial contamination. Besides, the resultant paper had excellent self-cleaning, anti-fouling and water repellency properties, showed excellent separation performances for stratified oil-water mixture and water-in-oil emulsion as well as good recyclability. The obtained superhydrophobic paper also presented excellent mechanical robustness and environmental stability. We believed that superhydrophobic paper prepared in this study could have promising potential as an environmental-benign and effective oil/water separation material.

Preparation of durable superamphiphobic cotton fabrics with self-cleaning and liquid repellency

A durable superamphiphobic cotton fabric was obtained by coating SiO2 aerogel particles, polydimethylsiloxane (PDMS), and 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFTES) on a cotton fabric via the dip-pad-dry process. The surface morphology, chemical composition, and thermal degradation behavior characterization of the as-prepared cotton fabric (PFTES/PDMS/SiO2@Cotton fabric) were performed, respectively. It was proved that the coated cotton fabric was successfully covered with PFTES/PDMS/SiO2. The porous rough surface topology structure due to the SiO2 aerogel particles along with low surface energy because of the fluorinated chains and PDMS adhesive layer on the as-obtained PFTES/PDMS/SiO2@Cotton fabric can trap a layer of air, endowing the coated fabric durable superamphiphobicity. The prepared superamphiphobic cotton fabric with a water contact angle (WCA) of 159.0 ± 0.8° and an oil contact angle (OCA) of 154.5 ± 0.7° showed good liquid repellence for common liquids in daily life like orange juice, cola, coffee, and milk, exhibiting excellent self-cleaning and stain-resistance property. Moreover, the superamphiphobic cotton fabric possessed good durability and still maintained superamphiphobicity after mechanical abrasion for 1500 cycles or ultraviolet (UV) irradiation for 96 h. This superamphiphobic cotton fabric exhibited potential applications in various fields due to the high repellency to various liquids.

A Facile and Cost-Effective Method to Prepare a Robust Superhydrophobic RTV Silicone Coating

A facile and cost-effective layer-by-layer assembly method is reported for the fabrication of a superhydrophobic coating using room temperature vulcanized silicone rubber and silica particles of different diameters. The superhydrophobic coating shows a contact angle of 154.6° and a rolling angle of 9°. The coating exhibits excellent self-cleaning properties and corrosion resistance with good softness and mechanical durability. The sample maintains its good superhydrophobicity, even after a series of tests by knife scratching, cutting, and hammering. The fabrication method has great advantages in terms of efficiency, cost, simple procedure and conditions. Its wide application in different substrates and the use of environment-friendly materials are also beneficial to the large-scale production of the coating.

Synthesis of a novel superamphiphobic coating with a hierarchical three-dimensional structure inspired by bird's nest

Based on the stability of bird's nest multi scaffold structure, a hierarchical three-dimensional bionic structure (Wax-PFDMS-Pal-TiOx coating) with superamphiphobic (SAP) properties, high stiffness and good stability was designed with carnauba wax as barrier and binder, palygorskite (Pal) as structural framework, TiOx as nano filler and 1H, 1H, 2H, 2H-Perfluorodecyltrimethoxysilane (PFDMS) as modifier. In addition, the morphology, structure and chemical composition of the coating were proved by scanning electron microscope (SEM), atomic force microscopy (AFM), Fourier transform infrared spectrometer (FI-TR), X-ray photoelectron spectroscopy (XPS) and other characterization methods. Studies have demonstrated that the nano-rough structure of Pal and TiOx can form submicron-nano composite hierarchical structure with carnauba wax, and hydrolyze and condense with PFDMS respectively to obtain the three-dimensional structure with high roughness and low surface energy. Under optimal conditions, the contact angles of water and oil on the coating surface are both over 160°. Meanwhile, the results of friction resistance test, salt resistance and pH resistance test show that the coating has excellent mechanical stability. The coating also has excellent self-cleaning property to resist the pollution of particles and mixture of water and oil. The current research is based on natural raw materials and provides a new idea for a stable bionic structure with SAP properties.

Sustainable self-cleaning evaporator for long-term solar desalination using gradient structure tailored hydrogel

Interfacial solar evaporation has been demonstrated as a promising strategy to mitigate water scarcity. However, for practical application in marine environment, the accumulation of salt and growth of microorganisms such as bacteria will cause scarring and fouling of the evaporators, depressing the potential for long-term sustainable use. Here, we report a hydrogel evaporator (chitosan/PAAm/PPy) with integrated three-layer structure containing individual functions for heat localization to improve solar evaporation efficiency, salt redissolution and antibacterial growth for sustainable long-term use, as well as management of thermal energy loss, respectively. The as-fabricated hydrogel evaporator presented a high-water evaporation rate of 2.41 kg m-2h−1 under 1-sun illumination, and excellent self-cleaning property against the salt accumulation and bacteria growth. During a two-week continuous evaporation experiment in simulated marine water with 3.5 wt% salinity and mixture of bacteria, the evaporator generated vapor stably in a range of 2.30 ~ 2.41 kg m-2h−1, without noticeable performance decay. Additionally, the hydrogel evaporator shows a stable vapor generation rate during cycled dehydration-hydration processes, as well as against repeated weight loading–unloading tests, indicating its convenience for long-term use and storage.

Fabrication of durable corrosion-resistant polyurethane/SiO2 nanoparticle composite coating on aluminium

In this work, SiO2 nanoparticle–embedded polyurethane superhydrophobic coating on aluminium substrate was fabricated using spin coating technique. By embedding SiO2 nanoparticles into the polyurethane matrix, superhydrophobicity is successfully achieved with water static contact angle of 156 ± 3° and tilt angle of 6 ± 1°. Coating exhibits excellent self-cleaning and antifouling properties. Wetting stability of coating was further evaluated by performing water jet, bending, sand falling, tape peeling, floating, annealing, and chemical stability tests. It is found that coating is mechanically, thermally, and chemically stable. Water droplet impact test shows the bouncing, pinning, and splashing behaviour of water droplets at different impact velocities. The electrochemical experiment has demonstrated that the corrosion potential of aluminium after coating increases and the corrosion current density decreases, revealing the corrosion resistance property of coating. We envision that the self-cleaning, antifouling, and anticorrosive superhydrophobic coating of the polyurethane/SiO2 nanoparticle composite can effectively prevent the corrosion of aluminium and the aforesaid coating has great industrial applications.

Durable superhydrophobic PVDF/FEVE/GO@TiO2 composite coating with excellent anti-scaling and UV resistance properties

Biomimetic superhydrophobic surfaces with excellent self-cleaning, antifouling and anticorrosion properties often suffer from mechanical damage and stop functioning when exposed to corrosive solutions or UV light in practical applications. In this study, a robust superhydrophobic PVDF/FEVE/GO@TiO2 composite coating with a high water contact angle of 158 ± 1.6° and low sliding angle of 6 ± 0.5° has been successfully fabricated via the combination of hydrothermal synthesis and spraying techniques. The GO@TiO2 composite particles were synthesized by in-situ growth of TiO2 on the GO surface through chemical condensation with the active sites of GO under hydrothermal conditions. Owing to the interfacial enhancement of GO@TiO2 and the adhesion enhancement of FEVE, the prepared superhydrophobic coating demonstrated excellent mechanical durability and retained its superhydrophobicity after 1000 abrasion cycles. Moreover, due to the orientation of lamellar GO, TiO2 was evenly distributed on the coating surface to construct uniform micro-/nanostructures, which can capture stable air film to prevent the permeation of H+, Cl−, OH− from water and simultaneously absorb more UV irradiation. Thus, the prepared coating demonstrated outstanding chemical stability under strong acidic and alkaline conditions for 7 days and after exposure to UV radiation (300 W) for 20 days. Furthermore, under the cooperative effect of the air film and hierarchical structures, the prepared superhydrophobic coating can inhibit the nucleation of CaCO3 scale and induce the formation of unstable needle-like CaCO3 on the coating surface. Therefore, it is anticipated that this durable superhydrophobic coating will be an excellent candidate for technological applications, such as anti-scaling, antifouling, and self-cleaning materials.

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.

Rapid Fabrication of Superhydrophobic Surface on Magnesium Alloy with Excellent Corrosion-Resistant and Self-Cleaning Properties

Abstract A bilayer coating superhydrophobic surface was developed by a simple one-step solvothermal method. This strategy can realize the introduction of low surface energy myristic acid/n-dodecyltrimethoxysilane and the fabrication of complex bionic micro/nano structure in one step, thereby further simplifying the manufacturing process. The as-obtained superhydrophobic surface has a CA of 157.6° and a SA of 2.0°. The bionic micro/nano structures are like the common herb sowthistle. The bilayer coating superhydrophobic surface has excellent self-cleaning properties, chemical stability and corrosion resistance. In addition, this strategy can effectively broaden the application of magnesium alloys and extend to other conductive metal materials.