Excellent Self-cleaning Properties Research Articles

A Fe3+-Doped TiO2 Superhydrophilic Coating with Transparent and Long-Lasting Antifogging Properties Constructed Based on Nanostructured Antireflective and Capillary Anchoring Effects.

Superhydrophilic surfaces have attracted great interest in antifogging applications. However, balancing long-lasting superhydrophilicity and high transparency on antifogging surfaces remains a serious problem to be solved. The objective of this work is to prepare superhydrophilic coatings with transparent and long-lasting antifogging properties. In the design, a three-step method was used to obtain the target coatings: (1) magnetron sputtering deposition of a TiN film to provide high intensity, (2) anodic oxidation of the TiN film to obtain TiO2 nanoparticles intended for nanostructured antireflective and capillary structures, and (3) the sol-gel method for the preparation of Fe3+-doped TiO2 coatings using spin-coating in order to achieve superhydrophilicity. The nanostructures, due to their subwavelength dimensions, not only provide high transparency but also recoverable superhydrophilicity owing to the presence of a capillary anchoring effect that prevents the coating from dissolving and peeling off after soaking. The doping of Fe3+ broadened the photoresponse range and maintained the long-lasting superhydrophilicity. Tests showed that the 2 mol % Fe3+-doped TiO2 coating with nanostructures exhibited the highest transparency, longest-lasting superhydrophilicity, and antifogging properties. Furthermore, the coating provided excellent self-cleaning properties, as well as mechanical and chemical stability.

Fabrication of flexible multifunctional graphene-based composite membrane with improved hydrophobicity and thermal conductivity characters for thermal management

The lifetime of electronic devices in complex environments is affected by the impact of high temperature water vapor on their performance. Equipping electronic devices with superhydrophobic properties and improved thermal conductivity will be the strategy of the future. In this paper, a surface material with high thermal conductivity and superhydrophobic properties is explored to address the problem of electronic device failure caused by heat and water vapor. To solve this problem, anti-temperature superhydrophobicity can be obtained by spraying alumina/nano-silicon carbide/thermoplastic elastomer composite powder (Al2O3/nano-SiC/SEBS) modified with 1 H,1 H,2 H,2H-perfluorooctyltriethoxysilane (POTS) on graphene membranes. A spherical Al2O3/nano-SiC composite superhydrophobic coating (ASS-GM) was formed on the surface of graphene-based composite membranes by spraying method. The results showed that the optimal ratio was m(Al2O3): m(SiC) = 8:1, and the static water contact angle of the coating was 162 ± 2.5°, and the surface energy was reduced. The ASS-GM significantly improves the thermal conductivity and superhydrophobicity of graphene-based composite membranes, achieving a double improvement in performance. The coating also offers excellent self-cleaning and antifouling properties compared to other materials. The ASS-GM is able to maintain a certain hydrophobicity angle (156 ± 1.5°) in harsh environments. This work provides practical applications for electronic coatings, which are important for improving the overall reliability and durability of electronic products.

Characteristics of natural corn starch/waste paper fiber composite foams treated by organic-inorganic hybrid hydrophobic coating technology.

With the growing global awareness of environmental protection, the demand for biodegradable materials to replace traditional plastic foam has become increasingly urgent. Starch-based foam, with its abundant availability, low cost, and biodegradability, has shown great potential as an alternative to plastic foam. However, its inherent high hydrophilicity and relatively low mechanical performance limit its widespread application. The aim of this study is to modify corn starch (NCS) and waste paper fiber (WPF) using citric acid (CA) and stearic acid (SA), and to develop an efficient hydrophobic coating through an organic-inorganic hybrid approach. This successfully resulted in the preparation of hydrophobic corn starch/waste paper fiber composite foam materials. Experimental results showed that the foam materials treated with a palmitic acid (PA)-modified nano-SiO2 coating (MCF@PA) exhibited excellent hydrophobic performance, with a water contact angle reaching as high as 138°, and a significant reduction in moisture absorption to 3.1%. In water immersion tests, the material maintained buoyancy and shape stability, demonstrating excellent self-cleaning properties. Additionally, the coating significantly enhanced the material's compressive strength, increasing by 90kPa, while also retaining thermal stability. However, the coating prepared by this method increased the material's hardness and reduced its biodegradability, which poses challenges for environmental sustainability. This study provides a new approach for preparing high-strength foam materials with excellent hydrophobicity and mechanical performance, paving an economical and efficient pathway for industrial production.

One-step hydrothermal method for long-term anti-corrosion lanthanum-based superhydrophobic coating on Mg alloy

The superhydrophobic coating was created on the surface of AZ31B using a one-step hydrothermal method. Various characterisation techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), contact angle goniometer, and electrochemical workstation, were employed to characterise its morphology, composition, hydrophobicity and corrosion resistance. The prepared coating from a 5-hour hydrothermal reaction exhibited a double-layer structure with a dense inner oxide layer and an outer layer of needle-like micro-nano structures. Achieving a water contact angle (WCA) as high as 159°, the superhydrophobic coating demonstrated low water adhesion and excellent self-cleaning properties. In a 3.5 wt-% NaCl aqueous solution, its corrosion rate was 5 orders of magnitude lower than that of the bare Mg alloy. Furthermore, the coating maintained a high impedance modulus value at 0.01 Hz (∼6.85 × 106 Ω cm2) after immersion in 3.5 wt-% NaCl solution for 25 days, which was attributed to the synergistic effect of the inner and outer layers. This study introduces a strategy for preparing long-term corrosion-resistant superhydrophobic coating on Mg alloy.

An environmentally friendly coating: Excellent self-cleaning, efficient antimicrobial, and durability properties

The development of non-polluting and non-toxic polymer antimicrobial agents is a prominent focus in contemporary research and development. Polymer quaternary ammonium salts are particularly promising for their antimicrobial efficacy. In this study, we synthesized quaternary imidazole derivatives using butylimidazole and 3-chloropropyltriethoxysilane. We then prepared PDMS/BIS/PPS hydrophobic antimicrobial composite coatings by incorporating quaternary ammonium salt chemically grafted silica (BIS), polyphenylene sulfide (PPS), and polydimethylsiloxane (PDMS). The resulting composite coating displayed a high contact angle of 136.4°±1° and a low sliding angle of less than 5°±1°, indicating its hydrophobic nature. Electrochemical assessments demonstrated exceptional corrosion resistance, with a corrosion inhibition rate of 99.967 %. Bacterial assays confirmed the coating's effectiveness in inhibiting bacterial proliferation, especially against E. coli. The quaternary ammonium-modified silica particles in the coating facilitate bacterial adsorption through electrostatic interactions, which compromise cell membrane permeability, obstruct nutrient uptake, and induce apoptosis. With its anti-fouling, self-cleaning, and anti-corrosion properties, this coating has substantial potential for applications in various fields, including medical devices, and food packaging.

Green synthesis of multifunctional bamboo-based nonwoven fabrics for medical treatment

Medical nonwovens fabrics are pivotal materials in modern healthcare systems, and find extensively application in surgical gowns, masks, nursing pads, and surgical instrument packaging. As healthcare requirements evolve and medical technology advances, the demand for functional nonwoven medical devices is continuously increasing. In addition, numerous environmental challenges and the need to transition to a sustainable society have increased the popularity of studies on environmentally friendly multifunctional nonwoven materials prepared from biomass fibers. Therefore, in this study, ecofriendly bamboo fibers were used to fabricate multifunctional medical nonwoven materials with superhydrophobic, antibacterial, flame-retardant, and biocompatible properties. Specifically, ZIF-67 was grown in situ on natural bamboo cellulose fibers (BCFs) extracted from natural bamboo and coated with polydimethylsiloxane to construct an environmentally friendly and versatile nonwoven fabric. The treated nonwoven fabric exhibited superhydrophobicity with contact angle of 163° and possess excellent self-cleaning properties. The antibacterial activity of the samples was investigated by the plate-counting method; the results showed that the untreated BCFs did not exhibit antibacterial activity, whereas the treated bamboo nonwoven fabrics demonstrated significant antibacterial activity (p < 0.001), with an antibacterial rate of >99 % against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus subtilis, and Candida albicans. In addition, when the samples were exposed to different temperatures (−4 and 50 °C) and humidities (0 % and 95 %), they demonstrated an antibacterial activity of >99 % against E. coli (F5,10 = 0.602; p = 0.670) and S. aureus (F4,10 = 0.289; p = 0.879). The heat release rate and smoke production rate of the nonwoven fabric decreased by 54.64 % and 93.18 %, respectively, compared to those of the BCFs, indicating excellent flame retardancy. The nonwoven fabric also exhibited satisfactory biocompatibility and breathability, ensuring user comfortability. This research not only has significant implications for producing low-cost, environmentally friendly, sustainable, and multifunctional medical products and openi up new pathways for the diversified utilization of bamboo, thereby expanding its applicability.

UV-driven self-replenishing liquid-infused surface with promising anti-algal adhesion performance.

Slippery liquid-infused porous surfaces (SLIPSs) inspired by Nepenthes have attracted much attention owing to their potential application in various cutting-edge fields. However, the performance of SLIPSs is impeded by surface damage and lubricant depletion, thereby limiting their further application. Herein, a UV-responsive slippery surface (SMEMG) was fabricated by introducing the UV-responsive functional group coumarin into the polymer side chain through random copolymerization, followed by crosslinking, curing and impregnation with vegetable oil. The self-healing ability and lubricant self-replenishing performance of the SMEMG were investigated. The results show that upon exposure to UV light, the damaged surface substrate can be repaired through a reversible photodimerization reaction between coumarin groups. Meanwhile, the lubricant oil within the bulk of the SMEMG substrate can be extruded to the surface during the photodimerization reaction, facilitating the recovery of surface wettability. The SMEMG exhibited excellent self-cleaning and anti-algal properties as well as durability in a harsh environment, demonstrating its promising application in marine anti-fouling.

Facile and sustainable upcycling of fly ash into multifunctional durable superhydrophobic coatings

Fly ash (FA), a hazardous byproduct of coal combustion in power plants, poses significant environmental and health risks due to improper disposal and utilization. This study introduces a facile, sustainable, and cost-effective method for converting FA into a robust superhydrophobic material for various substrates. -FA particles are modified with polydopamine (PD) in water and covalently grafted with octadecylamine (ODA) via the Michael Addition-Schiff Base reactions, resulting in robust superhydrophobic FA (SH-FA) with a water contact angle (WCA) of 163° (±3.1). When applied as a coating to jute, cotton, polyester fibers, PU sponge, and wood, they became superhydrophobic, with WCAs ranging from 154.7 to 161.2° except for the wood substrate, which achieved a WCA of 132° (±3°). The coated polyester fabric exhibited remarkable durability, retaining consistent WCA values after 70 abrasion cycles, 75 adhesive tape peelings, and 20 detergent washing cycles. It also showcased excellent self-cleaning properties, effectively repelling dust and various liquids. Additionally, the coated PU sponge demonstrated exceptional performance in separating oil from different oil/water mixtures, achieving rapid separation of organic solvents within seconds and maintaining a separation efficiency of over 98% even after 12 reuse cycles. These results indicate the potential for transforming FA through effective management.

PDMS-Based Hierarchical Superhydrophobic Fabric Coating Fabricated by Thermal Treatment and Electrostatic Flocking Technology.

Superhydrophobic coatings have broad applications in a variety of industries. By using a low-surface-energy material and creating nanoscale roughness, a superhydrophobic surface can be produced. To overcome the health and environmental concerns of fluorine-based materials and the limitations of large-scale rough microstructure fabrication, a poly(dimethylsiloxane) (PDMS)-based hierarchical superhydrophobic fabric coating prepared by simple thermal treatment and electrostatic flocking technology was introduced in this study. High-temperature thermal treatment is employed to create PDMS nanoparticle-decorated carbon fibers, which are further vertically implanted onto the surface of cotton fabric via electrostatic flocking technology. The environmentally friendly PDMS nanoparticles were adopted as low-surface-energy materials, and the electrostatic flocking technology was utilized to generate a vertically aligned carbon fiber array coating, mimicking a lotus leaf-like superhydrophobic surface microstructure. Therefore, an ultrahigh water contact angle of 173.9 ± 2.8° and a low sliding angle of 1 ± 0.5° can be obtained by the fabric coating with a PDMS-to-carbon fiber ratio of 20:1. The prepared superhydrophobic fabric also exhibits an excellent self-cleaning property and great durability after 60 cycles of washing. Through commercially available thermal treatment and electrostatic flocking processes, this strategy for fabricating fluorine-free superhydrophobic fabric can be easily scaled up for commercial manufacturing and promotes the design of superhydrophobic coatings for other substrates.

Robust superhydrophobic micro-nanostructures design based on polarity-opposite amorphous polymers

Superhydrophobicity exhibited by several natural surfaces has broad application prospects due to their excellent self-cleaning and low adhesion properties. However, designing a robust superhydrophobic coating via design strategy using amorphous polymers is allimportant for industrial applications, yet rather challenging. Here, we report a scalable strategy based on the phase separation and swelling treatment to construct an ultra-durable superhydrophobic coating with hierarchical micro-/nanostructures formed by two amorphous polymers (e.g. hydrophilic and lipophilic polymers). The controlled phase separation of two amorphous polymers creates uniformly distributed microprotrusions on the coating surface and the following swelling process produces submicro-/nanobumps on the microprotrusions. Notably, when both types of polymers achieve the hierarchical micro-/nanostructures, hydrophilic polymers exhibit strong adhesion with the substrates, whereas lipophilic polymers reduce the surface energy of the system. Benefitting from the self-similar structure and the adhesive effect, the polymer-based superhydrophobic coating displays superior mechanical and chemical robustness. Furthermore, our strategy will boost the practical application of robust superhydrophobic coatings for anti-corrosion application.

Durable superhydrophobic LTA-zeolite coating on PDMS surface with excellent self-cleaning property

Superhydrophobicity is a fundamental characteristic that plays a vital role in various applications, such as self-cleaning coatings, water vapor barriers for flexible electronics, and microfluidic chip fabrication. In this study, we developed a superhydrophobic surface coating on polydimethylsiloxane (PDMS) using Linde Type A (LTA) zeolite crystals, employing a silane coupling strategy. As part of this study, the LTA-zeolite-coated PDMS surface is characterized using various techniques to elucidate its superhydrophobic behavior, and a functionalization mechanism is proposed. The resulting substrate exhibited high surface roughness, with a water contact angle exceeding 155°, a sliding angle below 1°, and a contact angle hysteresis under 10°. This superhydrophobic surface coating effectively repelled water, confirming its excellent self-cleaning properties. Furthermore, the coating withstood three cycles of the Kapton adhesive tape peeling test, 5 h of water-jet hitting, and 72 h of UV light exposure, demonstrating its robustness and strong adhesion to PDMS.

Robust superhydrophobic self-cleaning coating prepared by silane modified multi-walled carbon nanotubes: A combined experimental and molecular dynamics study

As a functional material, superhydrophobic coating has been widely studied in the field of self-cleaning. However, obtaining superhydrophobic coatings with robustness through simple preparation processes remains a challenge. In this paper, a robust superhydrophobic coating is prepared based on multi-walled carbon nanotubes modified by octyltrimethoxysilane, and its performance and hydrophobic mechanism are studied by experiments and molecular dynamics simulation. The superhydrophobic coating is prepared by one-step spraying method. The coating is characterized and analyzed by scanning electron microscopy and Fourier transform infrared spectroscopy, and the properties of the coating are tested by experiments. Molecular dynamics simulation is used in the study to construct a molecular model system, and the molecular modification mechanism and coating wettability are simulated under the COMPASSII force field. The results show that octyltrimethoxysilane successfully modified carbon nanotubes, and the hydroxyl groups at the head of the molecular chain are bound to the surface of the carbon nanotubes in the form of hydrogen bonds, while the tail of the molecular chain is far away from the surface. After modification, the surface of carbon nanotubes changed from hydrophilic to hydrophobic. The prepared superhydrophobic coating not only has excellent self-cleaning properties, but also exhibits corrosion resistance to acid and alkali solutions. The coating still has superhydrophobic when the wear length is in the range of 400 cm. It can be seen that a robust superhydrophobic self-cleaning coating is successfully prepared by a simple one-step spraying method. The modification mechanism and the hydrophobic mechanism of the coating were obtained by the combination of experiment and molecular dynamics simulation, which provided theoretical support for the superhydrophobic of the coating at the micro level.

Self-cleaning and anti-corrosion superhydrophobic coatings of PA-TiO2@SiO2 copolymerized hetero compound

Inspired by leaf lotus effect, superhydrophobic surfaces have developed rapidly in recent years. In this paper, anatase nano TiO2 with particles size of about 70 nm was successfully loaded on the surface of SiO2 by sol-gel method. SiO2 and TiO2 were chemically bonded by Ti-O-Si and constructed a certain micro- and nano-composite structure. After superhydrophobic composite PA-TiO2@SiO2 was obtained by copolymerizing with acrylate and other monomers. The coating was prepared by drop coating plus spraying coating on glass substrates with water contact angles >160° and excellent self-cleaning properties, which could maintain the performance of the superhydrophobic coating by immersion in acidic solutions or water for 2 days. Meanwhile, the coating on the surface of the glass plate at −20 °C significantly delayed the freezing time of the ice. The rough structure of the surface and the presence of fluorine-containing hydrophobic groups gave the superhydrophobic coating an advantage over acrylate polymers in reducing the corrosion rate of steel surfaces.

Robust, breathable and antibacterial superamphiphobic cotton fabrics prepared by layer-by-layer dip coating

Superamphiphobic fabrics with both antibacterial and breathable properties are essential for medical applications i.e. stain protection, while challengeable in preparation. In this work, a novel multifunctional superamphiphobic fabric is freshly prepared using a simple layer-by-layer dip-coating strategy. The polydopamine (PDA), polytetrafluoroethylene (PTFE), branched poly (ethylenimine) (bPEI), silicon dioxide (SiO2), octadecylamine (ODA), poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS) are successfully grafted on cotton fabrics. Attributed to the hierarchical micro-nano structure and low surface energy of the coating, the prepared breathable superamphiphobic fabric (B-SAF) exhibits super-repellency and stain resistance against water and oily liquids, even the liquid surface tension is as low as 27.5 mN/m. Moreover, high breathability, good moisture resistance, excellent self-cleaning property were obtained, and good durability were maintained after varied mechanical and chemical damage, high temperatures, and continuous light exposure. More importantly, benefiting from the superamphiphobicity and the presence of amines, B-SAF demonstrates excellent resistance to blood staining and antibacterial activity, which exhibits strong application potentials in the fields of advanced functional textiles, protective clothing, antifouling and chemical engineering.

Self-cleaning of metal-organic framework membranes achieved by photocatalytic ZIFs for dye and antibiotic separation

The progress of membrane-based applications is hindered by widespread membrane fouling, which leads to a significant decrease in separation effectiveness and lifespan, even though membrane separations have shown great potential in the treatment of dye wastewater. The metal-organic framework MOFs (ZIF-8) display strong thermal and chemical stability and an exceptional capacity to degrade organic molecules under visible light, making them extremely promising for the development of self-cleaning membranes. In this investigation, a ZIF-8/L-DOPA/PVDF mixed matrix membrane with excellent self-cleaning properties was constructed using the in-situ growth technique. The characterization results confirmed the formation of a continuous ZIF-8 coating layer, considerably increasing the surface roughness of the composite membrane from 22.9 nm to 76.3 nm compared to L-DOPA/PVDF substrates. The ZIF-8 layer deposited on the L-DOPA/PVDF membrane surface reduced the contact angle from 75.71° to 40.94°. The highest-performing ZIF-8/L-DOPA/PVDF membranes show a higher water permeability of 159.63 (L·m−2 h−1 bar−1) and superior dye rejection rates (Congo red: 97.3 %, Methylene Blue: 98.32 %, Methyl Blue: 98.62 %), along with enhanced removal of antibiotics (e.g., Tetracycline: 95.3 % and Ciprofloxacin: 93.34 %), and long-term nanofiltration stability. Furthermore, the treated membrane recovers almost all of its initial separation efficacy after exposure to visible light due to the successful removal of attached dyes from the membrane surface through photocatalysis. This work presents the potential to fabricate membranes with advantageous photocatalytic properties and effectively treat dye wastewater using self-cleaning membranes.

Superhydrophobic PCTFE-based microporous membrane for water/oil emulsion separation in various environments

The separation of oil from oily water is a critical endeavor owing to the escalating global oil pollution. Membrane separation technology has gained widespread adoption for oily water treatment. Inspired by the vertical segregation phenomenon in drying multi-component suspensions, this study proposed an evaporation-induced stratification coupled with sacrificial template method to prepare superhydrophobic polychlorotrifluoroethylene (PCTFE) membrane for fast gravity-driven oil/water separation. The precursor of PCTFE microporous membranes, PCTFE/fluoroelastomer/hydrophobic silica nanoparticles (PCTFE/FR/SiO2) composite films, were fabricated via a solvent-assisted method. Induced by solvent evaporation, the pre-fabricated composite films exhibited a stratified structure, where SiO2 nanoparticles enriched near the top surfaces, making it easily tailor the surficial wettability. For the matrix, PCTFE-rich domains and FR-rich domains intersected, forming a bicontinuous structure. After sacrificing FR, PCTFE porous membranes were obtained. Meanwhile, the PCTFE-based porous skeletons combining with surface enriched SiO2 nanoparticles constructed a multi-level roughness, thus achieving superhydrophobicity. The optimized membrane possessed an average pore size of ∼1.84 μm, a porosity of ∼60 %, and a WCA above 155°, owning excellent self-cleaning properties and efficient oil/water separation ability. The membrane exhibited remarkable capability in various oil/water mixtures, including emulsified water-in-oil. The separation flux and oil recovery purity for water-in-dichloromethane emulsion were up to 2843 ± 84 L/(m2·h) and 99.95 wt%, respectively. Furthermore, though being immersed into various organic solvents for 7 days or experiencing 15 separation cycles, the performances of the membranes hardly changed. Accordingly, this work provides a practical approach for tailoring surficial wettability and fabricating PCTFE-based membranes suitable for oil/water separation fields.

Innovative Treatment of Ancient Architectural Wood Using Polyvinyl Alcohol and Methyltrimethoxysilane for Improved Waterproofing, Dimensional Stability, and Self-Cleaning Properties

This study introduced a novel two-step treatment to enhance the waterproofing, dimensional stability, and self-cleaning capabilities of ancient architectural wood. The process was initiated with the immersion of wood in an organic hybrid sol, composed of an acidic methyltrimethoxysilane (MTMS)-based silica sol and polyvinyl alcohol (PVA), which effectively sealed the wood’s inherent pores and cracks to mitigate degradation effects caused by aging, fungi, and insects. Subsequently, the treated wood surface was modified with an alkaline MTMS-based silica sol to form a functional superhydrophobic protective layer. The modification effectiveness was meticulously analyzed using advanced characterization techniques, including scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The results demonstrated substantial improvements: the modified wood’s water contact angle (WCA) reached 156.0°, and the sliding angle (SA) was 6.0°. Additionally, the modified wood showed a notable reduction in water uptake and moisture absorption, enhancing its dimensional stability. The superhydrophobic surface endowed the wood with excellent self-cleaning properties and robust resistance to pollution. Enhanced mechanical durability of superhydrophobic surface was observed under rigorous testing conditions, including sandpaper abrasion and tape peeling. Furthermore, the modification improved the thermal stability, compressive strength, and storage modulus of the wood. Collectively, these enhancements render this modification a potent methodology for the preservation and functional augmentation of historic architectural woodwork.

Radiative cooling and indoor light management enabled by a transparent and self-cleaning polymer-based metamaterial

Transparent roofs and walls offer a compelling solution for harnessing natural light. However, traditional glass roofs and walls face challenges such as glare, privacy concerns, and overheating issues. In this study, we present a polymer-based micro-photonic multi-functional metamaterial. The metamaterial diffuses 73% of incident sunlight, creating a more comfortable and private indoor environment. The visible spectral transmittance of the metamaterial (95%) surpasses that of traditional glass (91%). Furthermore, the metamaterial is estimated to enhance photosynthesis efficiency by ~9% compared to glass roofs. With a high emissivity (~0.98) close to that of a mid-infrared black body, the metamaterial is estimated to have a cooling capacity of ~97 W/m2 at ambient temperature. The metamaterial was about 6 °C cooler than the ambient temperature in humid Karlsruhe. The metamaterial exhibits superhydrophobic performance with a contact angle of 152°, significantly higher than that of glass (26°), thus potentially having excellent self-cleaning properties.

Superhydrophobic finishing of cotton fabric via nonsolvent-induced phase separation of polystyrene–perfluoropolyether block copolymer

This paper reports synthesis of polystyrene–perfluoropolyether block copolymer@cotton fabric (PS–PFPE@CF) with a rough structure through nonsolvent-induced phase separation. The factors affecting the hydrophobicity of the coating, such as solvent quality, the molecular weight of the PS segments, and the volume ratio of tetrahydrofuran/1,3-di(trifluoromethyl)benzene (THF/DTFMB) and THF–MeOH, were all investigated, and the relation between the coating structure and hydrophobicity was also analyzed. In the THF–DTFMB system, PS–PFPE@CF (4 h, 80 mg/mL) appeared as a secondary structure with the superposition of small spheres on large spheres. For this structure, the water-contact angle reached 156.2° ± 0.5° and the sliding angle was 9.5° ± 1.5°. Furthermore, scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, and thermogravimetric analysis confirmed that PS–PFPE coated the cotton fabric. Finally, application tests were performed to assess the application prospects of PS–PFPE@CF. Oil-water separation, self-cleaning, and antifouling applications were studied, and the experimental results showed that the separation efficiency of the superhydrophobic fabric was nearly constant, from 99.4 % to 98.3 % after 10 oil-water separation tests. PS–PFPE@CF exhibited excellent self-cleaning properties and performed well in the sandpaper abrasion and tape peeling tests. This research thus used a degradable PFPE block copolymer to produce cotton fabrics with excellent hydrophobicity, self-cleaning, and wear resistance.

Role of coating techniques and low surface energy materials on long-term performance of superhydrophobic titanium

This study, for the first time, compares the performance of robust superhydrophobic (SHP) titanium (CP-Ti) surfaces developed by two different coating methods, (i) dip / immersion coating and (ii) spin coating, using two different low surface energy materials, (i) stearic acid and (ii) polydimethylsiloxane (PDMS). A facile two-step method for the fabrication of SHP Ti surface is followed, wherein the CP-Ti was first anodized and followed by the coating. The anodization of CP-Ti increased its surface roughness by developing a homogeneous coverage of randomly distributed micro-clusters, whose chemical composition was TiO2-xCly. Subsequent low surface energy organic coatings did not alter the surface morphology. The XPS analysis of stearic acid coated SHP Ti showed that the molecular structure of stearic acid is retained intact whereas the PDMS coated sample showed a partial modification of PDMS molecular structure with the presence of additional -[Si(O)2-O]- bonds apart from the inherent -[Si(CH3)2-O]- bonds. The water contact angle (WCA) and sliding angle (SA) values of SHP Ti were 170±5° and 6±2°, respectively. The SHP Ti showed excellent self-cleaning properties for both hydrophobic and hydrophilic contaminants. The adhesion test of the coatings showed the detachment of coating was within 5%. The coatings prepared by dip / immersion method retained their superhydrophobicity for an abrasion distance of about twice the length, (75±25 cm), due to a higher coating thickness, as compared to those obtained by the spin coating technique (40±20 cm). Further, the stearic acid-coated CP-Ti showed a better abrasion resistance while the stability of the PDMS-coated samples in different pH and Cl- environments was better. Nevertheless, both the stearic acid and PDMS-coated SHP CP-Ti samples showed excellent long-term stability against ambient atmosphere and UV exposure.