Durable Superhydrophobic Surfaces Research Articles

Durable and robust superhydrophobic fluororubber surface fabricated by template method with exceptional thermostability and mechanical stability

Superhydrophobic surfaces have a wide application prospect in daily life and industrial fields. However, these surfaces are vulnerable to various thermal and mechanical damages during service and lose their functions. Herein, a superhydrophobic fluororubber surface with orderly layered microprotrusion structure was successfully prepared by directly replicating the surface microstructure of stainless-steel mesh. The prepared superhydrophobic surface exhibited excellent superhydrophobic performance (153.93 ± 0.39°) and durability. Due to the excellent thermal stability of fluororubber, the surface can maintain its superhydrophobicity even heated, and can also endure continuous high-temperature exposure. Especially, the superhydrophobicity of the surface does not change when contacting high-temperature droplets. In addition, as a result of the direct formation of microstructure on the surface, the superhydrophobic fluororubber surface also shows excellent robustness to manual friction, sandpaper abrasion and cyclic bending and twisting. The superhydrophobic fluororubber surface has great potential of application in the fields of efficient heat exchange, seawater desalination and other.

Highly durable superhydrophobic surfaces based on a protective frame and crosslinked PDMS-candle soot coatings

Superhydrophobic surfaces can be applied to environmental, energy, and healthcare fields. However, the weak durability issue has significantly limited the practical industrial applications. To overcome the readily destroyed interfacial structures and chemical compositions, the superhydrophobic surfaces with high mechanical and chemical durability have been created on a stainless steel mesh (SSM) as a protective frame based on tightly crosslinked polydimethylsiloxane (PDMS)−candle soot (CS) composite coatings through simple mechanical transfer and candle burning processes, which abbreviated to SSM/PDMS−CS and showed a water contact angle (WCA) of 159.4° ± 1.6° and a sliding angle (SA) of 2.3° ± 0.5°. Harsh abrasion examinations based on sandpaper and fiber paper have been conducted by applying 100 g weight and 200 cm sliding distance. And the obtained WCAs and SAs were 155° ± 3.7°, 155.7° ± 2° and 3.7° ± 0.5°, 3.5° ± 0.3°. Scanning electron microscope showed scratches on the surface, but the superhydrophobic property has been well maintained. After 40 kHz ultrasonication treatment for 30 min, WCA and SA were 152° ± 0.9° and 4.1° ± 0.8°. Finally, SSM/PDMS−CS surfaces exhibit good chemical resistance to corrosive solutions even after pH 2, pH 10, 1 M NaCl, and toluene treatments for 15 days.

Optimization of coating parameters for fabrication of robust superhydrophobic (SHP) aluminum and evaluation of corrosion performance in aggressive medium

The huge interest in superhydrophobic surfaces originates from their potential engineering applications in corrosion protection, antifouling, oil recovery, self-cleaning, anti-adhesion, anti-icing, medical dressing, drag reduction and radiative cooling. Despite the progress made in developing superhydrophobic (SHP) coatings, a key challenge is the ability to fabricate mechanically robust SHP surfaces and a proper understanding of the corrosion performance of SHP surfaces in aggressive conditions. Here, we report a simple, rapid, inexpensive, scalable and eco-friendly method for fabrication of mechanically durable superhydrophobic (SHP) aluminum surfaces with self-cleaning properties using a scalable dip-coating method. The coating parameters were optimized to obtain a robust coating with desirable properties such as water contact angle (WCA), sliding angle, self-cleaning, abrasion and corrosion resistance. To obtain good adhesion between the substrate and the coating, chemical etching and hydroxylation of the Al surface were used. At an optimal withdrawal speed of the substrate in the precursor solutions, a maximum WCA of 172.3° ± 1.1° (SA ~ 1° ± 1°) was achieved. The hierarchical micro-nano roughness and the presence of the Si-(CH3)3 group were responsible for the superhydrophobic behavior. The existence of a covalent bond between the Al surface and the middle connecting layer and –O-Si-CH3 groups on the surface of the SHP Al are confirmed by LRS and XPS, respectively. The electrochemical studies in 3.5 wt% NaCl solution show that the Rct value of SHP Al during the initial state was ~2 orders higher than that of the bare sample. The Cdl value of SHP Al was 6 orders less than that of bare after 1 h of exposure in chloride solution. On the SHP surface, a droplet with an impinging velocity of 0.36 m/s showed approximately 7 bounces. The superhydrophobicity of the SHP sample was preserved up to 150 cm abrasion distance. The hierarchical surface morphology and superhydrophobicity (WCA ~151°) were retained by the SHP samples even after 120 h of immersion in 3.5 wt% NaCl, which indicates its suitability in seawater applications such as ships, underwater instruments and pipelines and marine structures. Further, our work provides a framework to develop mechanically robust SHP coating for various applications.

Facile fabrication of durable and flexible superhydrophobic surface with polydimethylsiloxane and silica nanoparticle coating on a polyethylene terephthalate film by hot-roll lamination

Practical applications of superhydrophobic surfaces have been limited by several disadvantages such as complex fabrication processes, high modification cost, and low mechanical durability. In this study, we present a facile and low-cost fabrication method to make flexible superhydrophobic films by a hot-roll lamination process. The film consists of a hydrophobic polydimethylsiloxane (PDMS) and hydrophobic silica nanoparticle (SNP) composite coating layer on a polyethylene terephthalate (PET) film. The coated film displayed excellent superhydrophobic properties with an apparent water droplet contact angle of 176.3° and a sliding angle of 2.4°. The surface morphology, roughness, and cross-section chemical composition of the coated films were investigated by field emission scanning electron microscopy and confocal laser scanning microscopy. The mechanical durability of the coated films was evaluated using several tests such as scratching with sandpaper, repeated bending deformation, and adhesion tape tests. The fabricated superhydrophobic films still showed superhydrophobic behavior after 20 tape tests. In addition, the fabricated superhydrophobic films exhibited strong mechanical durability, which preserved their very high contact angle >160° and very small sliding angle <10° after a 350 cm abrasion test with 240 grit sandpaper and a pressure of 1.2 kPa. Also, the coated sample exhibited very stable superhydrophobicity after 100 bending cycles due to the elasticity of PDMS. The chemical stability of flexible PDMS/SNP coated PET films was also investigated in acidic, neutral, and alkaline solutions and showed excellent chemical stability in acidic and neutral media in contrast to the alkaline medium. The obtained results demonstrated the outstanding robustness of the fabricated flexible superhydrophobic films that are promising for self-cleaning and water droplet bouncing performance. • Superhydrophobic surfaces were fabricated by a facile method without toxic chemicals. • The durability of the superhydrophobic films was demonstrated by abrasion and tape tests. • The fabricated films exhibited good flexibility in bending tests. • The self-cleaning property of the fabricated coated surfaces was also observed.

Fabrication of Durable Superhydrophobic Surface for Versatile Oil/Water Separation Based on HDTMS Modified PPy/ZnO.

Superhydrophobic materials have been widely applied in rapid removal and collection of oils from oil/water mixtures for increasing damage to environment and human beings caused by oil-contaminated wastewater and oil spills. Herein, superhydrophobic materials were fabricated by a novel polypyrrole (PPy)/ZnO coating followed by hexadecyltrimethoxysilane (HDTMS) modification for versatile oil/water separation with high environmental and excellent reusability. The prepared superhydrophobic surfaces exhibited water contact angle (WCA) greater than 150° and SA less than 5°. The superhydrophobic fabric could be applied for separation of heavy oil or light oil/water mixtures and emulsions with the separation efficiencies above 98%. The coated fabric also realized highly efficient separation with harsh environmental solutions, such as acid, alkali, salt, and hot water. The superhydrophobic fabric still remained, even after 80 cycles of separation and 12 months of storage in air, proving excellent durability. These novel superhydrophobic materials have indicated great development potentials for oil/water separation in practical applications.

Octadecylamine-functionalized cellulose nanocrystals as durable superhydrophobic surface modifier for polyester coating: Towards oil/water separation

The aim of this study is the elaboration of super-hydrophobicpolyester fabrics (PET) coated organophilic cellulose nanocrystals (CNC-ODA) using dip-coating approach. The CNC-ODA was successfully synthesized from microcrystalline cellulose via a chemical oxidation method, followed by carboxylation and chemical grafting of long chain fatty amine octadecylamine via an amidation reaction. PET fabrics loaded with different CNC-ODA contents, ranging from 1 to 5% wt. were successfully prepared and characterized by several techniques. FTIR confirmed the formation of interfacial interaction between the PET and CNC-ODA functional groups. The contact angle measurements revealed that treated PET fabrics displayed super-hydrophobic character with a contact angle of 153.1°. Tensile strength test revealed that the produced fabrics exhibited improved mechanical properties compared to pristine PET. Moreover, as a versatile application, the elaborated PET@CNC-ODA textile displayed excellent oil/water separation for different organic compounds/water mixtures. The obtained results are very motivating, in term of elaborating durable super-hydrophobic textiles.

Durable superhydrophobic polyvinylidene fluoride membranes via facile spray-coating for effective membrane distillation

Membrane wetting and fouling substantially limits application and deployment of membrane distillation process. Designing high-performance superhydrophobic membranes offers an effective solution to solve the challenge. In this work, a highly durable superhydrophobic surface (water contact angle of 170.8 ± 1.3°) was constructed via a facile and rapid spray-coating of extremely hydrophobic SiO2 nanoparticles onto a porous polyvinylidene fluoride (PVDF) substrate for membrane distillation. The superhydrophobic membrane coated by fluorinated SiO2 nanoparticles exhibited a superior physicochemical stability in a wide range of extreme environments (i.e., NaOH, HCl, hot water, rust water, humic acid solution, ultrasonication, and high-speed water scouring). During 8-h continuous membrane distillation desalination experiment, the coated superhydrophobic membrane experienced a consistently stable water vapor flux (ca. 19.1 kg·m−2·h−1) and desalination efficiency (99.99 %). Additionally, such a stable superhydrophobicity endowed the spray-coated PVDF membrane to overcome membrane wetting and fouling during membrane distillation of highly saline solutions containing foulants (i.e., humic acid and rust). Results reported in this study provides a useful concept and strategy in facile construction of robust superhydrophobic membranes via spray-coating for effective membrane distillation.

Investigation on fabrication of durable superhydrophobic surface based on multi-adhesive strategy

Poor mechanical stability, expensive cost, and complex preparation process still limit the practical application of artificial superhydrophobic surfaces. Improving the chemical durability and mechanical stability of superhydrophobic surfaces is an important research direction to promote its commercial application. Herein, we developed a cost-effective and simple method to produce a durable superhydrophobic surface based on a multi-adhesive strategy. Fluorocarbon resin and hydrophobic silica nanoparticles bring excellent hydrophobicity and low adhesion to the coating. And the introduction of bottom resin and phenolic amine adhesive can not only increase the adhesion between superhydrophobic coating and substrates but also increase the mechanical stability of the coating. Even after severe mechanical damage such as abrasion, rubbing, and scraping, the prepared surface can still maintain excellent superhydrophobicity. At the same time, stable resin and inorganic filler bring more than 99 % anticorrosion efficiency, excellent thermal stability, and chemical stability to the superhydrophobic surface. The outstanding performance of the superhydrophobic surfaces in the field of self-cleaning, anti-icing, and frost protection may attract attention for practical application in the industry. The convenience of surface preparation on various substrates by spraying and brushing methods, and the low cost of manufacturing can also greatly expand the application prospect of the developed superhydrophobic surface.

Micro-Nano-Nanowire Triple Structure-Held PDMS Superhydrophobic Surfaces for Robust Ultra-Long-Term Icephobic Performance.

Anti-icing superhydrophobic surfaces have attracted tremendous interests due to their repellency to water and extremely low ice affinity, whereas the weak durability has been the bottleneck for further applications. Surface durability is especially important in long-term exposure to low-temperature and high-humidity environments. In this study, a robust micro-nano-nanowire triple structure-held PDMS superhydrophobic surface was fabricated via a hybrid process: ultrafast-laser-prepared periodic copper microstructures were chemically oxidized, followed by modification of PDMS. The hedgehog-like surface structure was composed of microcones, densely grown nanowires, and tightly combined PDMS. The capillary force difference in micro-nanostructures drove PDMS solutions to distribute evenly, bonding fragile nanowires to form stronger composite cones. PDMS replaced the commonly used fragile fluorosilanes and protected nanowires from breaking, which endowed the surfaces with higher robustness. The ductile PDMS-nanowire composites possessed higher resiliency than brittle nanowires under a load of 1 mN. The surface kept superhydrophobic and ice-resistant after 15 linear abrasion cycles under 1.2 kPa or 60 icing-deicing cycles under -20 °C or 500 tape peeling cycles. Under a higher pressure of 6.2 kPa, the contact angle (CA) was maintained above 150° until the abrasion distance exceeded 8 m. In addition, the surface exhibited a rare spontaneously optimized performance in the icing-deicing cycles. The ice adhesion strength of the surface reached its lowest value of 12.2 kPa in the 16th cycle. Evolution of surface roughness and morphology were combined to explain its unique U-shaped performance curves, which distinguished its unique degradation process from common surfaces. Thus, this triple-scale superhydrophobic surface showed a long-term anti-icing performance with high deicing robustness and low ice adhesion strength. The proposed nanostructure-facilitated uniform distribution strategy of PDMS is promising in future design of durable superhydrophobic anti-icing surfaces.

Study on preparation and durability of surface microstructure of copper alloy

Superhydrophobic surfaces have huge applications in wetting fields. However, the surface is prone to mechanical abrasion and environmental damage in the application. This paper provides an alternative approach to preparing durable superhydrophobic surfaces, reveals the wear mechanism of the copper alloy surface and compares the tribological properties of different surfaces. Then, take the superhydrophobic surface of the circular truncated cone microstructure as an example to verify the durability under friction and wear, atmospheric environment, and acid and alkali media. The results show that compared with the polished surface, the copper alloy surface with microstructures can effectively reduce the friction coefficient of the surface and improve the tribological performance. The prepared superhydrophobic surface can endure abrasion under certain pressure and distance, and keep great stability in the atmospheric environment and acid–base conditions.

A durable and sustainable superhydrophobic surface with intertwined cellulose/SiO2 blends for anti-icing and self-cleaning applications

Poor wear resistance and the use of toxic chemicals restrict the marketization of most traditional superhydrophobic surfaces. The present work provides a method to prepare a durable and non-toxic superhydrophobic coating on the surface of a cotton fabric. Thermal polymerization of spray drying was used to obtain uniform structure of TEMPO-oxidized cellulose (TOC) with nano silica (SiO2), for achieving well-combined rough sphere-like micron particles with hierarchical dimensions, which were then immersed into isocyanate (IPDI) and polydimethylsiloxane (PDMS) respectively along with cotton fabric to construct a superhydrophobic coating on the fabric surface. The surface morphology, chemical structure, roughness and wettability of TOC-SiO2/PDMS surface were studied by adjusting the mass ratios of SiO2 to TOC. The optimal superhydrophobicity was obtained while the mass ratio of SiO2 to TOC was 1:1, displaying a water contact angle (CA) of 158.6°. The introduction of the intertwined TOC-SiO2 blends can construct a hierarchical micro-nano structure to enhance the hydrophobicity, simultaneously improve the mechanical durability of the superhydrophobic surface to prevent multiple peeling and friction damage, as well as outstanding chemical stability in a variety of harsh conditions.

Optimal condition for fabricating mechanically durable superhydrophobic titanium surface by rapid breakdown anodization: Self cleaning and bouncing characteristics

In this paper, we describe a simple, cost effective, fast, scalable and sustainable method for fabrication of mechanically durable superhydrophobic (SHP) surface of titanium by a rapid breakdown anodization (RBA) followed by molten stearic acid (MSA) chemical modification. In this new approach, the preparation time is only a minute. Instead of stearic acid- ethanol solution, molten stearic acid is the post surface modification, which made the preparation process rapid and simple. The anodized samples showed islands of TiO2 microclusters with complex hierarchical structures with nano pores uniformly distributed in the passive TiO2 matrix. Laser Raman spectroscopy (LRS) analysis revealed the TiO2 microclusters are polycrystalline in nature. The applied voltage, anodization time, immersion time and MSA bath temperature are optimized to obtain a robust mechanically durable SHP surface. FESEM images showed that both anodization and immersion parameters have significant effect on the surface morphology of microclusters. A maximum water contact angle (WCA) of 167.8° with a sliding angle of 6° was obtained for a Ti sample anodized at 50 V for 10 min after molten stearic acid immersion at 125 °C for 30 min. The prolonged anodization for 10 min promoted microcluster growth in all dimensions to form a highly hierarchical micro-nanostructure. The prepared samples showed vertical micro plate-like crystals of stearic acid on the micro clusters, which enhanced the very high WCA. The FTIR results revealed multiple bonding modes of stearic acid with TiO2 microclusters through surface hydroxyl groups. The prepared superhydrophobic samples showed excellent self-cleaning and abrasion resistance.

Functionally Integrated Device with Robust and Durable Superhydrophobic Surface for Efficient, Continuous, and Recyclable Oil–Water Separation

AbstractA cost‐efficient, universal adhesive layer‐involved strategy is demonstrated for the construction of robust superhydrophobic surfaces on a variety of materials. This strategy uses recycled rubber particles (RRPs) and low‐surface‐energy coating to generate superhydrophobicity, which are fixed on the substrates by a precoated E‐44 resin (ER) adhesive layer. Benefitting from the robust ER adhesive layer and wear‐resistant rubber particles, the ER/RRPs composite coated low‐surface‐energy coating (ER/RRPs/LSEC composite) shows high robustness under various harsh conditions including repeated abrasion, sunlight radiation, and acid/basic corrosion. When evaluated as functionally integrated device for oil spill cleanup, these superhydrophobic structures show excellent oil‐absorption and oil–water separation properties. For example, the copper foam device coated with the ER/RRPs/LSEC composite shows a high oil–water separating efficiency of 95% before and after mechanical abrasion. This strategy provides a new toolbox for constructing robust superhydrophobic surfaces with oil–water separation applications and offers a novel insight into the durability of artificial superhydrophobic surfaces.

Highly durable spray-coated superhydrophobic surface: Pre-anodizing and fatty acid chain length effect

Highly durable spray-coated superhydrophobic surface: Pre-anodizing and fatty acid chain length effect

Facile fabrication of hierarchical textures for substrate-independent and durable superhydrophobic surfaces.

On account of their wide range of applications in self-cleaning, anti-icing, frost suppression, etc., superhydrophobic surfaces have attracted considerate attention. However, most of the superhydrophobic surfaces can only be prepared on the surfaces of specific materials and are easily damaged in the case of friction. In this work, we propose a facile method to achieve superhydrophobicity on various substrate surfaces. By femtosecond laser direct processing, micron-level grooves and protrusions are constructed on substrates to form a protective layer. Then, the substrates covered by polytetrafluoroethylene (PTFE) were scanned to make the surfaces of the substrates superhydrophobic. Since the PTFE micro-nano-particles are evenly distributed on the grooves and protrusions, the surfaces exhibit robust superhydrophobicity with excellent anti-friction performance that is independent of the substrate properties. This work provides an efficient and environmentally friendly path for achieving robust superhydrophobic surfaces on various substrates.

Fabrication of durable underoil superhydrophobic surfaces with self-cleaning and oil-water separation properties.

In this study, a simple method without any additional chemical modification is proposed to fabricate underoil superhydrophobic surfaces with micro- and nano-hierarchical structures using a nanosecond laser system. The fabricated surfaces exhibited extreme superhydrophobicity and underoil superhydrophobicity with high contact angles of 153.8 ± 1.5° and 161.3 ± 1.1°, respectively. The results show that even after 20 abrasion cycles, the fabricated surfaces retained water repellency and self-cleaning performance under oil, while the superhydrophobicity in air was not resistant to wear. In addition, the fabricated brass meshes can also be used to separate oil in an oil–water mixture based on the prewetting induced underoil superhydrophobicity after being damaged. The separation efficiency was as high as 97.8%, which made them more appropriate for the oil–water separation than those based on superhydrophobicity. The proposed fabrication method is suitable for large-scale and mass production and provides a new avenue and possibility for further development of robust functional interface materials.

Robust and self-healing superhydrophobic aluminum surface with excellent anti-icing performance

Icing on the transmission line can cause disastrous consequence. At present, a lot of research has been conducted on related anti-icing technologies such as superhydrophobic surface (SHS). However, the application of SHS was limited by the poor durability. In this work, a durable superhydrophobic surface with an outstanding anti-icing property has been prepared via combining anodization and infusion of healing agent fluoroalkylsilane (FAS-17). The as-prepared SHS can efficiently prevent the icing process in glaze ice due to the effective repelling of the cooled water droplets at -8 °C. Beside, excellent anti-frosting performance has also been gained due to the self-transfer movement of condensation droplets. Furthermore, the as-prepared SHS surface can heal its superhydrophobicity after 8 times oxygen plasma or 64 times (7.68 m) of abrasion damage under the pressure of 12 kPa. The self-healing ability shows good stability even being heated at 80 °C after 30 days. The findings could provide developed insights into the design of high-performance anti-icing SHS based on the porous structure construction and self-healing modification.

Development of highly durable superhydrophobic and UV-resistant wood by E-beam radiation curing

Developing a practical strategy to fabricate an anti-abrasion and durable superhydrophobic wood surface with ultraviolet (UV) resistance has great practical significance for expanding the application of natural wood. In this study, a robust superhydrophobic layer with a hierarchical micro/nano-roughness structure was modified on the wood surface through in-situ mineralization and polymerization using a simple sol–gel method along with efficient electron beam (EB) curing technology. Hydrophobic agent (polydimethylsiloxane, PDMS), and crosslinking monomer (γ-methacryloxypropyl trimethoxysilane, MAPS) form new covalent bonds between TiO2 particle layer and wood substrate after EB radiation, which endows robust superhydrophobicity and remarkable UV resistance on the wood surface. The as-prepared wood exhibited a water contact angle of approximately 165.7° and obvious repellency to many aqua-phase liquids (cola, strongly acidic, alkaline droplets etc.). Furthermore, the hierarchical micro/nano-protrusion structures remained unchanged and micro/nano particles aggregated tightly on the as-prepared wood surface under harsh external environments (sandpaper abrasion and, ultrasonic treatment), confirming the desirable anti-abrasion and mechanically durable performance of the superhydrophobic surface. After the 18-day UV accelerated weathering test, the TiO2 particle layer conspicuously retained the discoloration and maintained its exceptional repellency toward water. The biomimetic superhydrophobic wood with excellent mechanical durability and UV resistance reveals its potential application in the furniture and architecture fields.

Thermally stable and durable superhydrophobic surfaces on stainless steel sheets with microholes via acid pretreatment and modification with self-assembled monolayers

Thermally stable and durable superhydrophobic surfaces on stainless steel sheets with microholes via acid pretreatment and modification with self-assembled monolayers

Facile Fabrication of Durable Superhydrophobic Aluminum Alloy Surfaces by HS-WEDM and Chemical Modification

Durable superhydrophobic aluminum alloy surfaces were prepared through a facile method: combining high-speed wire electrical discharge machining and chemical modification. Three types of pulse width were selected to machine the aluminum alloy surfaces with different levels of surface roughness. The effect of immersion time in perfluorooctanoic acid on the wettability of the aluminum alloy surfaces was examined. The contact angle of the superhydrophobic aluminum alloy surfaces was [Formula: see text], and the sliding angle was [Formula: see text]. After sanding with coarse sandpaper, the aluminum alloy surfaces still exhibited superhydrophobicity with a stroke of 450[Formula: see text]cm, indicating good mechanical durability. The prepared superhydrophobic aluminum alloy surface heated for 2[Formula: see text]h within the 190–240∘C temperature range showed favorable thermal stability. In addition, the superhydrophobic aluminum alloy surface exhibited self-cleaning property. Therefore, the superhydrophobic aluminum alloy surface prepared by using the simple mass production method showed good mechanical stability, thermal stability, and self-cleaning property, as well as broad application potential.