Robust biomimetic-structural superhydrophobic surface on aluminum alloy

Superior Anticorrosion Performance of Well-Dispersed MXene-Polymer Composite Coatings Enabled by Covalent Modification and Ambient Electron-Beam Curing

MXene-reinforced composite coatings have recently shown promise for metal anticorrosion due to their large aspect ratio and antipermeability; however, the challenges of the poor dispersion, oxidation, and sedimentation of MXene nanofillers in a resin matrix that are often encountered in the existing curing methods have greatly limited practical applications. Herein, we reported an efficient, ambient, and solvent-free electron beam (EB) curing technology to fabricate PDMS@MXene filled acrylate-polyurethane (APU) coatings for anticorrosion of 2024 Al alloy, a common aerospace structural material. We showed that the dispersion of MXene nanoflakes modified by PDMS-OH was dramatically improved in EB-cured resin and enhanced the water resistance through the additional water-repellent groups of PDMS-OH. Moreover, the controllable irradiation-induced polymerization enabled a unique high-density cross-linked network, presenting a large physical barrier against corrosive media. The newly developed APU-PDMS@MX₁ coatings achieved excellent corrosion-resistance with the highest protection efficiency of 99.9957%. The coating filled with uniformly distributed PDMS@MXene promoted the corrosion potential, corrosion current density, and corrosion rate to be -0.14 V, 1.49 × 10^-9 A/cm², and 0.0004 mm/year, respectively, and the impedance modulus was increased by 1-2 orders of magnitude compared to that of APU-PDMS coating. This work combining 2D material with EB curing technology broadens the avenue for designing and fabricating composite coatings for metal corrosion protection.

A wear and heat-resistant hydrophobic fluoride-free coating based on modified nanoparticles and waterborne-modified polyacrylic resin

Hydrophobic coatings have attracted extensive research due to their broad application prospects. However, hydrophobic coatings in practical applications are often limited by their insufficient stability and are difficult to be applied on a large scale. In this regard, wear and heat resistance are key aspects that must be considered. In this paper, a method for preparing a robust hydrophobic coating with modified ZrO₂ particles as the core component and modified acrylic resin is proposed. First, γ-aminopropyltriethoxysilane (APTES) was used to silanize ZrO₂ to obtain Si-ZrO₂ nanoparticles, which were grafted with amino groups. Then, the nanoparticles reacted with isocyanates to be grafted with hydrophobic groups. A simple spray method was developed to deposit a hydrophobic (141.8°) coating using the mixture containing the modified nanoparticles and non-fluorinated water-based silicon-modified acrylic resin (WSAR) that was prepared by free radical polymerization. The obtained coating exhibited a rough surface and the particles and resin were closely combined. Compared with pure resin coating, the composite coating exhibited 150% enhancement in wear resistance and it could wear 45 meters at a pressure of 20 kPa. Moreover, the coating could maintain the hydrophobic property even when it lost 70% quality or after it was heated at 390 °C. The thermogravimetric results showed that the temperature could reach 400 °C before the quality of the fluorine-free coating dropped to 90%. In addition, the coating could easily take away graphite or silicon carbide powder under the impact of water droplets, showing excellent self-cleaning performance.

Superhydrophobic Biological Fluid-Repellent Surfaces: Mechanisms and Applications

Superhydrophobic biological fluid-repellent surfaces (SBFRSs) have attracted great attention in the treatment of blood and urine-related diseases because of their unique wettability and compatibility, which creates a new path for the development of medical apparatus and instruments, and are expected to create advances in various fields. Here, this review provides an up-to-date summary of research progress on the repellent mechanism and application of SBFRSs. The underlying physical and chemical principles for designing superhydrophobic surfaces are first introduced. Then, the dialectical influences of solid-liquid interactions between superhydrophobic surfaces and biological fluids on the wettability and compatibility are emphatically expounded. Subsequently, attention is drawn to the recent applications of SBFRSs in biomedical fields, such as surgical medical apparatus, implant materials, extracorporeal circulation devices, and biological fluid detection. Finally, the outlook and challenges in terms of employing SBFRSs are also discussed. This review is expected to provide a comprehensive guidance for the preparation of SBFRSs with compatibility and long-term superhydrophobic stability that is closely related to clinical applications.

Bioinspired Pd-Cu Alloy Nanoparticles as Accept Agent for Dye Degradation Performances

Dye degradation is a key reaction in organic decomposition production through electron donor transferring. Palladium (Pd) is the best-known element for synthesis Pd-based catalyst, the surface status determines the scope of relative applications. Here we first prepare Pd-Cu alloy nanoparticles (NPs) by co-reduction of Cu(acac)₂ (acac = acetylacetonate) and Pd(C₅HF₆O₂)₂ in the presence of sodium borohydride (NaBH₄) and glutathione (GSH). The obtained Pd-Cu is about ~10 nm with super-hydrophilicity in aqueous mediums. The structural analysis clearly demonstrated the uniform distribution of Pd and Cu element. The colloidal solution keeps stability even during 30 days. Bimetallic Pd-Cu NPs shows biocompatibility in form of cell lines (IMEF, HACAT, and 239 T) exposed to colloidal solution (50 µg mL^-1) for 2 days. It shows the catalytic multi-performance for dye degradation such as methyl orange (MO), rhodamine B (RhB), and methylene blue (MB), respectively. The as-synthesized nanoparticles showed one of the best multiple catalytic activities in the industrially important (electro)-catalytic reduction of 4-nitrophenol (4-NP) to corresponding amines with noticeable reduced reaction time and increased rate constant without the use of any large area support. In addition, it exhibits peroxidase-like activity in the 3, 3', 5, 5'-Tetramethylbenzidine (TMB) color test and exhibit obvious difference with previous individual metal materials. By treated with high intensity focused ultrasound filed (HIFU), Pd-Cu NPs might be recrystallized and decreased the diameters than before. The enhancement in catalytic performance is observed obviously. This work expedites rational design and synthesis of the high-hierarchy alloy catalyst for biological and environment-friendly agents.

Metal organic frameworks (MOFs) as multifunctional nanoplatform for anticorrosion surfaces and coatings

Corrosion of metallic materials is a long-standing problem in many engineering fields. Various organic coatings have been widely applied in anticorrosion of metallic materials over the past decades. However, the protective performance of many organic coatings is limited due to the undesirable local failure of the coatings caused by micro-pores and cracks in the coating matrix. Recently, metal organic frameworks (MOFs)-based surfaces and coatings (MOFBSCs) have exhibited great potential in constructing protective materials on metallic substrates with efficient and durable anticorrosion performance. The tailorable porous structure, flexible composition, numerous active sites, and controllable release properties of MOFs make them an ideal platform for developing various protective functionalities, such as self-healing property, superhydrophobicity, and physical barrier against corrosion media. MOFs-based anticorrosion surfaces and coatings can be divided into two categories: the composite surfaces/coatings using MOFs-based passive/active nanofillers and the surfaces/coatings using MOFs as functional substrate support. In this work, the state-of-the-art fabrication strategies of the MOFBSCs are systematically reviewed. The anticorrosion mechanisms of MOFBSCs and functions of the MOFs in the coating matrix are discussed accordingly. Additionally, we highlight both traditional and emerging electrochemical techniques for probing protective performances and mechanisms of MOFBSCs. The remaining challenging issues and perspectives are also discussed.

Preparation and Application of a New Two-Component Superhydrophobic Coating on Aluminum Alloy

Superhydrophobic surfaces have been widely used for their corrosion resistance, self-cleaning and anti-icing characteristics. A new two-component superhydrophobic coating was prepared on aluminum alloy, and some application properties were studied. With appropriate silica, the contact angle of the two-component superhydrophobic coating can be 164.4°, and it has good resistance to the continuous hitting of water droplets and the corrosion of acid. Even when it had been continuous impacted by acid droplets for 300 min, the contact angle of the coating was still lager than 150°. However, the coating was easily corroded by sodium hydroxide. Moreover, it can not only reduce its freezing point by more than 5 °C, but also delay the freezing of droplets on aluminum alloy by about 20 s at the temperature of −20 °C. More than that, the growth of ice or frost on it can only cause extremely minor mechanical damage to it.

Robust and durable liquid-repellent surfaces

This review provides a comprehensive summary of characterization, design, fabrication, and application of robust and durable liquid-repellent surfaces.

Effect of Surface Structure Complexity on Interfacial Droplet Behavior of Superhydrophobic Titanium Surfaces for Robust Dropwise Condensation

In general, the dropwise condensation supported by superhydrophobic surfaces results in enhanced heat transfer relative to condensation on normal surfaces. However, in supersaturated environments that exceed a certain supersaturation threshold, moisture penetrates the surface structures and results in attached condensation, which reduces the condensation heat transfer efficiency. Therefore, when designing superhydrophobic surfaces for condensers, the surface structure must be resistant to attached condensation in supersaturated conditions. The gap size and complexity of the micro/nanoscale surface structure are the main factors that can be controlled to maintain water repellency in supersaturated environments. In this study, the condensation heat exchange performance was characterized for three different superhydrophobic titanium surface structures via droplet behavior (DB) mapping to evaluate their suitability for power plant condensers. In addition, it was demonstrated that increasing the surface structure complexity increases the versatility of the titanium surfaces by extending the window for improved heat exchange performance. This study demonstrates the usefulness of DB mapping for evaluating the performance of superhydrophobic surfaces regarding their applicability for industrial condenser systems.

Biologically Inspired Scalable-Manufactured Dual-layer Coating with a Hierarchical Micropattern for Highly Efficient Passive Radiative Cooling and Robust Superhydrophobicity

Bioinspired materials for temperature regulation have proven to be promising for passive radiation cooling, and super water repellency is also a main feature of biological evolution. However, the scalable production of artificial passive radiative cooling materials with self-adjusting structures, high-efficiency, strong applicability, and low cost, along with achieving superhydrophobicity simultaneously remains a challenge. Here, a biologically inspired passive radiative cooling dual-layer coating (Bio-PRC) is synthesized by a facile but efficient strategy, after the discovery of long-horned beetles' thermoregulatory behavior with multiscale fluffs, where an adjustable polymer-like layer with a hierarchical micropattern is constructed in various ceramic bottom skeletons, integrating multifunctional components with interlaced "ridge-like" architectures. The Bio-PRC coating reflects above 88% of solar irradiance and demonstrates an infrared emissivity >0.92, which makes the temperature drop by up to 3.6 °C under direct sunlight. Moreover, the hierarchical micro-/nanostructures also endow it with a superhydrophobic surface that has enticing damage resistance, thermal stability, and weatherability. Notably, we demonstrate that the Bio-PRC coatings can be potentially applied in the insulated gate bipolar transistor radiator, for effective temperature conditioning. Meanwhile, the coverage of the dense, super water-repellent top polymer-like layer can prevent the transport of corrosive liquids, ions, and electron transition, illustrating the excellent interdisciplinary applicability of our coatings. This work paves a new way to design next-generation thermal regulation coatings with great potential for applications.

Superamphiphobic Magnesium Alloys with Extraordinary Environmental Adaptability

The application of magnesium alloys is seriously limited by their poor environmental adaptability. In this work, we report a robust superamphiphobic coating, which endows magnesium alloys with extraordinary environmental adaptability. The coating was fabricated on magnesium alloys by a facile, cost-effective, and scalable method, one-step particle-free spraying. The as-treated magnesium alloys show excellent superamphiphobicity with the static contact angles (CAs) of water, ethylene glycol, benzyl alcohol, and cyclohexanol droplets of 157.5°, 155.1°, 151.7°, and 151.3°, respectively. These samples also display small dynamic CAs (0° for water and 10° for ethylene glycol) and water super-repellency, which endow magnesium surfaces with droplet impact resistance, self-cleaning, and oil-resistance functions. The simulating environmental-adaptability tests demonstrate that the as-treated magnesium alloys can remain superamphiphobic under various mechanical, chemical, and physical damages including sand impact (⩾10 cycles), water impact (v = 4.5 m·s^-1, 2 impacts·s^-1, 20 h), abrasion (1.0 kPa, 50 cycles), strong acid/alkaline solution (pH = 1-14), organic solvents immersion (ethylene glycol, n-hexane, ≥48 h), high temperature (200 °C, 72 h), and ultraviolet irradiation (λ = 254 nm, 672 h). The natural environmental-adaptability tests in the acidic industrial atmosphere for 40 days further confirm the robustness of the as-treated magnesium alloys under harsh environments. This work not only provides a promising method for industrially fabricating environmental-adaptable coatings on metallic materials but also paves the way for the much wider applications of magnesium alloys.

Robust superhydrophobicity: mechanisms and strategies

Superhydrophobic surfaces hold great prospects for extremely diverse applications owing to their water repellence property. The essential feature of superhydrophobicity is micro-/nano-scopic roughness to reserve a large portion of air under a liquid drop. However, the vulnerability of the delicate surface textures significantly impedes the practical applications of superhydrophobic surfaces. Robust superhydrophobicity is a must to meet the rigorous industrial requirements and standards for commercial products. In recent years, major advancements have been made in elucidating the mechanisms of wetting transitions, design strategies and fabrication techniques of superhydrophobicity. This review will first introduce the mechanisms of wetting transitions, including the thermodynamic stability of the Cassie state and its breakdown conditions. Then we highlight the development, current status and future prospects of robust superhydrophobicity, including characterization, design strategies and fabrication techniques. In particular, design strategies, which are classified into passive resistance and active regeneration for the first time, are proposed and discussed extensively.

Superhydrophobic Films with Enhanced Corrosion Resistance and Self-Cleaning Performance on an Al Alloy

In this article, a novel and facile method is used to construct superhydrophobic surfaces on aluminum alloys. A solution of aluminum chloride hexahydrate and N-dodecyltrimethoxysilane (DTMS) in ethanol was used as the electrolyte solution. The hydrolysis of DTMS was accelerated during the electrodeposition process, and the hydrolysate was bonded to a pretreated aluminum surface. The prepared aluminum alloy sample exhibits both superhydrophobicity (the surface water contact angle reached 155°) and excellent corrosion resistance. The inhibition efficiency of this sample is as high as 99.9% in 3.5 wt % NaCl solution, which remains at 98% even after 30 days of immersion. Thus, our fabrication can be well applied to the field of marine corrosion protection. Therefore, the working mechanism was discussed by confocal Raman microspectroscopy (CRM). In addition, the investigation by CRM and electrochemical impedance spectroscopy (EIS) also indicates that superhydrophobic samples show good stability in NaCl solution. The fabrication method can inspire new ideas for the construction of superhydrophobic aluminum alloys in the marine environment.

A superhydrophobic surface with aging resistance, excellent mechanical restorablity and droplet bounce properties

The use of a silicone rubber composite insulator has become an important aspect to ensure the safe operation of an electrical power grid. This study introduces a preparation method of a superhydrophobic silicone rubber surface using a simple preparation process at low cost and with excellent performance, which can be used in the mass production of silicone rubber composite insulators. In this study, the combination of a compression molding process and a template method was used to prepare the product. A microstructure composed of numerous boat-shaped grooves was constructed on the surface of silicone rubber. The modification of a low surface energy material is not required. The static contact angle with water after the high-temperature treatment exceeds 150°, and the rolling angle is under 10°. Excellent performance has been observed in terms of self-cleaning effect, aging resistance, and mechanical and droplet bounce properties. It has been shown that the loss of superhydrophobic properties, due to the prolonged immersion in water, can be restored by a high temperature heating process.

Fabrication of Self-Cleaning Superhydrophobic Surfaces with Improved Corrosion Resistance on 6061 Aluminum Alloys

Aluminum alloys are widely used, but they are prone to contamination or damage under harsh working environments. In this paper, a self-cleaning superhydrophobic aluminum alloy surface with good corrosion resistance was successfully fabricated via the combination of sand peening and electrochemical oxidation, and it was subsequently covered with a fluoroalkylsilane (FAS) film. The surface morphology, surface wettability, and corrosion resistance were investigated using a scanning electron microscope (SEM), an optical contact angle measurement, and an electrochemical workstation. The results show that binary rough structures and an FAS film with a low surface energy on the Al alloy surfaces confer good superhydrophobicity with a water contact angle of 167.5 ± 1.1° and a sliding angle of 2.5 ± 0.7°. Meanwhile, the potentiodynamic polarization curve shows that the corrosion potential has a positively shifted trend, and the corrosion current density decreases by three orders of magnitude compared with that of the original aluminum alloy sample. In addition, the chemical stability of the as-prepared superhydrophobic surface was evaluated by dripping test using solutions with different pH values for different immersion time. It indicates that the superhydrophobic surface could provide long-term corrosion protection for aluminum alloys. Consequently, the as-prepared superhydrophobic surface has excellent contamination resistance and self-cleaning efficacy, which are important for practical applications.

Phragmites Communis Leaves with Anisotropy, Superhydrophobicity and Self-Cleaning Effect and Biomimetic Polydimethylsiloxane (PDMS) Replicas

Phragmites communis leaf (PCL) is anisotropic, superhydrophobic and shows a self-cleaning effect. The water contact angle (WCA) values along the vertical and parallel vein directions on PCL are 153° ± 2° and 148° ± 2°, respectively. In contrast, the water sliding angle (WSA) values along the vertical and parallel vein directions for PCL are 12° ± 2° and 7° ± 2°, respectively. The epidermal wax makes the leaves intrinsically hydrophobic. The microstructure of the PCL surface shows sub-millimetre-, micron- and nanometre-scale structures. The sub-millimetre ridge structure is the main reason for the anisotropy of the leaves. The micron-scale papillae structure has a strong hydrophobic enhancement effect, and the nanoscale sheet structure is the key factor in achieving a stable Cassie state, as well as superhydrophobicity and self-cleaning activities. PCL-like polydimethylsiloxane (PDMS) samples fabricated by template transfer technology exhibited the sub-millimetre ridge structure and micron-scale papillae from the natural PCL; they also show obvious anisotropy and strong hydrophobicity and have a certain self-cleaning effect. The WCA and WSA values along the vertical and parallel vein directions on PCL are 146° ± 2°, 23° ± 2°, 142° ± 2° and 19° ± 2°, respectively. The preparation of a biomimetic PCL surface has broad application prospects in micro-fluidic control and the non-destructive transmission of liquids.

Facile synthesis of superhydrophobic three-metal-component layered double hydroxide films on aluminum foils for highly improved corrosion inhibition

A simple hydrothermal method was presented to obtain various superhydrophobic ZnMgAl layered double hydroxide films on aluminum foils (AF) with excellent corrosion inhibition.

One-Step Potentiostatic Deposition of Micro-Particles on Al Alloy as Superhydrophobic Surface for Enhanced Corrosion Resistance by Reducing Interfacial Interactions

Corrosion failure is a thorny problem that restricts the application of Al alloys. As a new technique for functional realization, hydrophobic preparation offers an efficient approach to solve corrosion problem. This work has developed a facile and low-cost method to endow Al alloy with enhanced water-repellent and anticorrosion abilities. The micro-particles have been firstly prepared by one-step deposition process. Furthermore, wetting and electrochemical behaviors of as-prepared structures have been investigated after silicone modification. Results show that the fabricated surface possesses excellent superhydrophobicity with a water contact angle (CA) of 154.7° and a sliding angle (SA) of 6.7°. Meanwhile, the resultant surface is proved with enhanced corrosion resistance by reducing interfacial interactions with seawater, owing to newly-generated solid-air-liquid interfaces. This work sheds positive insights into extending applications of Al alloys, especially in oceaneering fields.

Enhanced Corrosion Resistance of Superhydrophobic Layered Double Hydroxide Films with Long-Term Stability on Al Substrate

A superhydrophobic ZnAl-layered double hydroxide (LDH)-La film was prepared by a hydrothermal method and further modification by laurate anions in this work. Comprehensive characterizations of this film were performed in terms of morphology, composition, structure, roughness, and wettability by scanning electronic microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, three-dimensional laser scanning confocal microscopy. The long-term corrosion protection effect of this superhydrophobic film was investigated deeply by monitoring the changes of the electrochemical impedance spectra for a long time of up to a month in 3.5 wt % NaCl solution. In the meantime, the changes of the contact angle were also recorded with the evolution of the immersion time. The result indicated that the stable superhydrophobic ZnAl-LDH-La film was able to provide efficient protection for the underlying Al substrate for a long time. In addition, the capability of the superhydrophobic surface against harsh conditions, including chemical damages and physical damages, was emphatically investigated. It was found that the superhydrophobic surface was chemically stable toward acid (pH ≥ 3), alkali, and heating, and it also exhibited high ultraviolet (UV) radiation resistance. This superhydrophobic coating maintained superhydrophobicity for 7 days of radiation in an UV chamber equipped with a 40 W UV lamp (λ = 254 nm), indicating superior ability of adapting to outdoor environment. This comprehensive investigation of the superhydrophobic ZnAl-LDH-La film is considerably helpful for researchers and engineers to get deep insight into its potential for practical applications in the field of corrosion and protection.

Comprehensively durable superhydrophobic metallic hierarchical surfaces via tunable micro-cone design to protect functional nanostructures

Superhydrophobic surfaces have been intensively investigated in recent years. However, their durability remains a major challenge before superhydrophobic surfaces can be employed in practice. Although various works have focused on overcoming this bottleneck, no single surface has ever been able to achieve the comprehensive durability (including tangential abrasion durability, dynamic impact durability and adhesive durability) required by stringent industrial requirements. Within the hierarchical structures developed for superhydrophobicity in typical plants or animals by natural evolution, microstructures usually provide mechanical stability, strength and flexibility to protect functional nanostructures to enable high durability. However, this mechanism for achieving high durability is rarely studied or reported. We employed an ultrafast laser to fabricate micro/nanohierarchical structures on metal surfaces with tunable micro-cones and produced abundant nanostructures. We then systematically investigated their comprehensive mechanical durability by fully utilizing the protective effect of the microstructures on the functional nanostructures via the tunable design of micro-cones. We confirm that the height and spatial period of the microstructures were crucial for the tangential abrasion durability and dynamic impact durability, respectively. We finally fabricated optimized superhydrophobic tungsten hierarchical surfaces, which could withstand 70 abrasion cycles, 28 min of solid particle impact or 500 tape peeling cycles to retain contact angles of greater than 150° and sliding angles of less than 20°, which demonstrated exceptional comprehensive durability. The comprehensive durability, in particular the dynamic impact durability and adhesive durability, are among the best published results. This research clarifies the mechanism whereby the microstructures effectively protected the functional nanostructures to achieve high durability of the superhydrophobic surfaces and is promising for improving the durability of superhydrophobic surfaces and thus for practical applications.

Environmentally Benign Production of Stretchable and Robust Superhydrophobic Silicone Monoliths

Superhydrophobic materials hold an enormous potential in sectors as important as aerospace, food industries, or biomedicine. Despite this great promise, the lack of environmentally friendly production methods and limited robustness remain the two most pertinent barriers to the scalability, large-area production, and widespread use of superhydrophobic materials. In this work, highly robust superhydrophobic silicone monoliths are produced through a scalable and environmentally friendly emulsion technique. It is first found that stable and surfactantless water-in-polydimethylsiloxane (PDMS) emulsions can be formed through mechanical mixing. Increasing the internal phase fraction of the precursor emulsion is found to increase porosity and microtexture of the final monoliths, rendering them superhydrophobic. Silica nanoparticles can also be dispersed in the aqueous internal phase to create micro/nanotextured monoliths, giving further improvements in superhydrophobicity. Due to the elastomeric nature of PDMS, superhydrophobicity can be maintained even while the material is mechanically strained or compressed. In addition, because of their self-similarity, the monoliths show outstanding robustness to knife-scratch, tape-peel, and finger-wipe tests, as well as rigorous sandpaper abrasion. Superhydrophobicity was also unchanged when exposed to adverse environmental conditions including corrosive solutions, UV light, extreme temperatures, and high-energy droplet impact. Finally, important properties for eventual adoption in real-world applications including self-cleaning, stain-repellence, and blood-repellence are demonstrated.

Biomimetic multi-functional superhydrophobic stainless steel and copper meshes for water environment applications

The robust, multi-functional superhydrophobic metal meshes were fabricated by the one-step solution immersion method for water environment applications.

Facile Fabrication of Superomniphobic Polymer Hierarchical Structures for Directional Droplet Movement

We report a facile method for fabricating polymer hierarchical structures, which are the engineered, ratchet-like microscale structures with nanoscale dimples, for the directional movement of droplets. The fabricated polymer hierarchical structures with no surface modifier show hydrophobic, superhydrophobic, or omniphobic characteristics depending on their intrinsic polymer properties. Further treatment with a surface modifier endows the polymer surfaces with superomniphobicity. The fabricated polymer substrates with no surface modifier enable the movement of the water droplet along the designed track at almost no inclination of the substrate.

Hierarchical flower like double-layer superhydrophobic films fabricated on AZ31 for corrosion protection and self-cleaning

The designed sample is prepared by self-assembly of octadecyltrichlorosilane and deposition of ferric stearate, and the contact angle is 160°.

Robust superhydrophobic coating and the anti-icing properties of its lubricants-infused-composite surface under condensing condition

Water droplets on a slippery liquid-infused porous surface (SLIPS) could travel smoothly at low temperatures.

Superhydrophobic surfaces on brass substrates fabricated via micro-etching and a growth process

A superhydrophobic surface was fabricated on brass using a simple micro-etching technique. Numerous rough structures on the micro/nanometer scale were achieved, and the free energy of the surface was reduced using stearic acid modification.

Multifunctional substrate of Al alloy based on general hierarchical micro/nanostructures: superamphiphobicity and enhanced corrosion resistance

Aluminum alloys are vulnerable to penetrating and peeling failures in seawater and preparing a barrier coating to isolate the substrate from corrosive medium is an effective anticorrosion method. Inspired by the lotus leaves effect, a wetting alloy surface with enhanced anticorrosion behavior has been prepared via etch, deposition, and low-surface-energy modification. Results indicate that excellent superamphiphobicity has been achieved after the modification of the constructed hierarchical labyrinth-like microstructures and dendritic nanostructures. The as-prepared surface is also found with good chemical stability and mechanical durability. Furthermore, superior anticorrosion behaviors of the resultant samples in seawater are investigated by electrochemical measurements. Due to trapped air in micro/nanostructures, the newly presented solid-air-liquid contacting interface can help to resist the seawater penetration by greatly reducing the interface interaction between corrosive ions and the superamphiphobic surface. Finally, an optimized two-layer perceptron artificial neural network is set up to model and predict the cause-and-effect relationship between preparation conditions and the anticorrosion parameters. This work provides a great potential to extend the applications of aluminum alloys especially in marine engineering fields.

Bioinspired surfaces for turbulent drag reduction

In this review, we discuss how superhydrophobic surfaces (SHSs) can provide friction drag reduction in turbulent flow. Whereas biomimetic SHSs are known to reduce drag in laminar flow, turbulence adds many new challenges. We first provide an overview on designing SHSs, and how these surfaces can cause slip in the laminar regime. We then discuss recent studies evaluating drag on SHSs in turbulent flow, both computationally and experimentally. The effects of streamwise and spanwise slip for canonical, structured surfaces are well characterized by direct numerical simulations, and several experimental studies have validated these results. However, the complex and hierarchical textures of scalable SHSs that can be applied over large areas generate additional complications. Many studies on such surfaces have measured no drag reduction, or even a drag increase in turbulent flow. We discuss how surface wettability, roughness effects and some newly found scaling laws can help explain these varied results. Overall, we discuss how, to effectively reduce drag in turbulent flow, an SHS should have: preferentially streamwise-aligned features to enhance favourable slip, a capillary resistance of the order of megapascals, and a roughness no larger than 0.5, when non-dimensionalized by the viscous length scale.This article is part of the themed issue 'Bioinspired hierarchically structured surfaces for green science'.

Durable and scalable icephobic surfaces: similarities and distinctions from superhydrophobic surfaces

Formation, adhesion, and accumulation of ice, snow, frost, glaze, rime, or their mixtures can cause severe problems for solar panels, wind turbines, aircrafts, heat pumps, power lines, telecommunication equipment, and submarines. These problems can decrease efficiency in power generation, increase energy consumption, result in mechanical and/or electrical failure, and generate safety hazards. To address these issues, the fundamentals of interfaces between liquids and surfaces at low temperatures have been extensively studied. This has lead to development of so called "icephobic" surfaces, which possess a number of overlapping, yet distinctive, characteristics from superhydrophobic surfaces. Less attention has been given to distinguishing differences between formation and adhesion of ice, snow, glaze, rime, and frost or to developing a clear definition for icephobic, or more correctly pagophobic, surfaces. In this review, we strive to clarify these differences and distinctions, while providing a comprehensive definition of icephobicity. We classify different canonical families of icephobic (pagophobic) surfaces providing a review of those with potential for scalable and robust development.

A green miniemulsion-based synthesis of polymeric aggregation-induced emission nanoparticles

A green miniemulsion-based technique for preparing polymeric aggregation-induced emission nanoparticles was described.

Non-fluorinated superhydrophobic and micro/nano hierarchical Al doped ZnO film: the effect of Al doping on morphological and hydrophobic properties

The azo micro/nano hierarchical fluffy clew-like films and their superhydrophobic properties have been experimentally investigated and computationally simulated.