Applications Of Superhydrophobic Surfaces Research Articles

Recent advances in biomimetic superhydrophobic surfaces: focusing on abrasion resistance, self-healing and anti-icing.

Superhydrophobic materials have been widely used in the fields of materials engineering and the coating industry due to their excellent abrasion resistance, corrosion resistance, anti-icing and antibacterial properties and have also attracted the attention of many researchers. However, in the process of application, their superhydrophobic surface is susceptible to external factors such as physical or chemical effects, resulting in the loss of low surface energy materials or the destruction of micro- and nano-rough structures, thus losing their superhydrophobic properties. This review describes the research progress in three aspects of superhydrophobic surfaces: abrasion resistance, self-healing, and anti-icing. Firstly, the definition and application of superhydrophobic surfaces, as well as the basic principle and mechanism of superhydrophobic surfaces are introduced. Then, the research status and improvement methods of superhydrophobic surfaces are presented in detail from three aspects, such as abrasion resistance, self-healing, and anti-icing. Finally, the research process of superhydrophobic surfaces is evaluated and prospected in order to provide a new perspective for the preparation of superhydrophobic surfaces with a wide range of applications and better performance.

Designing a Robust Ni-P/CeO2 Superhydrophobic Composite Coating for Synergistically Enhanced Corrosion Protection and Friction Reduction Performance.

Superhydrophobic surfaces have received widespread attention for their unique hydrophobicity in metal corrosion protection. However, the shortcomings of mechanical stability and long-term corrosion resistance limit their practical application. In this work, we designed and fabricated an anticorrosive and friction reducing Ni-P/CeO2 superhydrophobic composite (SC) coating on a copper surface. The fabricated coating shows good superhydrophobicity with a water contact angle of up to 154°. The Ni-P support structure and CeO2 nanoparticles form a multilayer micro/nanostructure by electrodeposition, ensuring excellent mechanical stability of the Ni-P/CeO2 SC coating. Electrochemical tests indicate that the coating has excellent corrosion resistance due to the superhydrophobic air film, Ni-P barrier layer, and CeO2 inhibition. Moreover, the friction coefficient of the coating is only 0.11 under dry friction conditions, showing excellent friction-reducing performance, which is attributed to the cooperation of the low adhesion coefficient of superhydrophobic surfaces, the ball-rolling effect of CeO2 nanoparticles, and the self-healing effect of the Ni-P micro/nanostructure. This work provides a novel strategy for designing a robust superhydrophobic coating with mechanical stability, corrosion protection, and friction reduction abilities to inspire new applications of superhydrophobic surfaces.

Superhydrophobic Surfaces with Excellent Ice Prevention and Drag Reduction Properties Inspired by Iridaceae Leaf.

The anti-icing and drag-reduction properties of diverse microstructured surfaces have undergone extensive study over the past decade. Nonetheless, tough environments enforce stringent demands on the composite characteristics of superhydrophobic surfaces (SHS). In this study, fresh composite structures were fabricated on a metal substrate by nanosecond laser machining technology, drawing inspiration from the hardy plant Iridaceae. The prepared sample surface mainly consists of a periodic microrhombus array and irregular nanosheets. To comprehensively investigate the effect of its special structure on surface properties, three surfaces with different sizes of rhombic structures were used for comparative analysis, and the results show that the SH-S2 sample is optimal. This can significantly delay the freezing time by an impressive 1404 s at -10 °C while revealing the sample surface anti-icing strategy. In addition, the rheological experiments determined over 300 μm of slip length for the SH-S2 sample, and the drag reduction rate of the surface reaches nearly 40%, which is well aligned with the results of the delayed icing experiments. Finally, the mechanical durability of the SH-S2 surface was investigated through scratch damage, sandpaper abrasion, reparability trials, and icing and melting cycle tests. This research presents a new approach and methodology for the application of SHS on polar ship surfaces.

A novel superhydrophobic Al conductor with excellent anti-icing performance and its mechanism

Overhead conductor icing is one of the main factors causing transmission line failures. Superhydrophobic surface (SHS) with composite pore structure exhibits excellent anti-icing effectiveness and durability. Herein, this novel SHS was prepared on complex aluminum conductors by two-step anodic oxidation technology, and the motion behavior of droplets on the SHS conductor in the glaze icing environment was studied experimentally to analyze the anti-icing mechanism. The simulated glaze icing experiment results show that the SHS conductor significantly reduces the ice accumulation, and the icing weight is only 23 % of the untreated conductor. Compared with the flat surface, the groove structure of the SHS conductor enhances the ability of millimeter-sized droplets to bounce, and the contact time is less than 9 ms. Also, micron-sized spraying droplets exhibit excellent mobility on the SHS conductor surface, and the contact time is further reduced. Moreover, the SHS conductor has a good ability to delay the freezing of spraying droplets. The above factors endow the SHS conductor excellent anti-icing performance. This work lays a foundation for the anti-icing application of SHS on transmission lines.

Plastron restoration for underwater superhydrophobic surface by porous material and gas injection

Restoring and maintaining the gas layer (plastron) on underwater superhydrophobic surface (SHS) is critical for the real-world application of SHS, such as reducing friction drag in high-Reynolds number turbulent flows. In this work, we experimentally investigated the capability of a technology based on porous material and gas injection to restore the plastron on an underwater SHS from a fully wetted state. The SHS was created by sprayed coating a commercial superhydrophobic coating on a porous steel plate. In the experiments, the SHS was immersed in stationary liquid, the gas injection pressure and gas injection duration were independently controlled. The status of gas layer on SHS was examined by a high-speed camera. We found that the surface area being restored with a plastron increased with increasing gas injection pressure and gas injection duration, and that the plastron restoration process involved bubble formation, merging and detachment. A layer of gas was left on the surface after bubble detachment. The size of the detached bubble increased with time due to bubble merging, and became stable when there was no more bubble merging. Increasing gas injection pressure led to higher gas flow rates, larger detached bubble sizes and faster plastron restorations. A plastron restoration within 0.3 s was achieved at the highest pressure, faster than the in-situ gas generation methods. Furthermore, we found that the gas flow rate through the underwater SHS can be described by a modified Darcy’s law. Our results highlighted the potential of using porous material and gas injection to restore the plastron and made possible the real-world implementation of SHS.

Natural superhydrophobic surfaces and recent advances in synthetic superhydrophobic surfaces: A review

This review uses modern technologies to discuss the hydrophobicity mechanism of various natural surfaces found and studied in recent decades and their chemical components and delicate surface structure. It also contains many invent inspired by lifelike superhydrophobic characters, and tons of human living has been solved with the help of these applications. Also, the theories of how low hysteresis is induced by high contact angle devoted to the ability of water-repellent, drag reduction, and self-cleaning of a bunch of natural creatures are presented along with their characteristics. Besides, some of the recent fast, eco-friendly fabrication methods of superhydrophobic are discussed with the application of superhydrophobic surfaces in industry. Furthermore, the problems and challenges currently facing how to make the fabrication methods of the superhydrophobic characters better fit the industrial manufacture.

Regulation of droplet impacting on superhydrophobic surfaces: Coupled effects of macrostructures, wettability patterns, and surface motion

Superhydrophobic surfaces have shown great application prospects due to their excellent water repellency in many applications involving fluid–surface interactions. As a ubiquitous fluid–surface interaction phenomenon, droplet impacting dynamics has a crucial effect on the application of superhydrophobic surfaces. In this Perspective, we summarize the basic process of droplet impacting on superhydrophobic surfaces and introduce the two most concerned parameters that describe the droplet impacting dynamics, i.e., the maximum spreading coefficient and the contact time. We then review two improvement strategies for superhydrophobic surfaces: one is to construct macrostructures and the other is to set wettability patterns on the surface. The former strategy shows great potential in reducing the droplet contact time, and the latter one can accurately regulate the behavior of impacting droplets. The motion of superhydrophobic surfaces also changes the droplet impacting dynamics due to the additional aerodynamic effect or energy input, which arouses attention recently. However, only the individual influence of each factor (e.g., macrostructures, wettability patterns, or surface motion) on the droplet impacting dynamics has been focused in literature, so we write this Perspective to emphasize the importance and urgency of studying the coupled effects of these three factors.

Study on anti-icing performance of carbon fiber composite superhydrophobic surface

The icing phenomenon widely exists in the nature and has become an urgent problem to be solved in the fields of aerospace, wind power generation, and other fields. Scholars have been undertaking much research on surface anti-icing technology, but it has always been a challenge to develop an efficient, energy-saving, environmentally friendly, stable and durable anti-icing surface. In this study, hydrophobic silica nanoparticles were used to hydrophobically modify the matrix material, and a metal screen was used as a template, combined with hot-pressing process. The superhydrophobic surface of carbon fiber composite material with anti-icing property was prepared. The results showed that the water contact angle of the surface was 156 ± 2°, the sliding angle was 2 ± 1.5°, and the number of water drops bouncing on the surface was 7 times. Compared with the untreated test sample, the surface ice content decreased by 4 times, and the ice adhesion strength decreased by 2 times. Besides, the surface also had excellent contact state recovery and mechanical stability. During the process of icing and thawing, the contact state between the droplet and the surface changed spontaneously from Wenzel model to Cassie model. After 30 cycles of icing and de-icing, the surface still maintained a water contact angle of more than 150°and an ice adhesion strength of less than 50 KPa. The preparation method of this study is simply, rapid, low-cost, green and environment-friendly, which provides reliable theoretical guidance and design ideas for surface anti-icing technology and effectively promotes the large-scale production and application of superhydrophobic surfaces in the field of anti-icing.

Advances in Bioinspired Superhydrophobic Surfaces Made from Silicones: Fabrication and Application.

As research on superhydrophobic materials inspired by the self-cleaning and water-repellent properties of plants and animals in nature continues, the superhydrophobic preparation methods and the applications of superhydrophobic surfaces are widely reported. Silicones are preferred for the preparation of superhydrophobic materials because of their inherent hydrophobicity and strong processing ability. In the preparation of superhydrophobic materials, silicones can both form micro-/nano-structures with dehydration condensation and reduce the surface energy of the material surface because of their intrinsic hydrophobicity. The superhydrophobic layers of silicone substrates are characterized by simple and fast reactions, high-temperature resistance, UV resistance, and anti-aging. Although silicone superhydrophobic materials have the disadvantages of relatively low mechanical stability, this can be improved by the rational design of the material structure. Herein, we summarize the superhydrophobic surfaces made from silicone substrates, including the cross-linking processes of silicones through dehydration condensation and hydrosilation, and the surface hydrophobic modification by grafting hydrophobic silicones. The applications of silicone-based superhydrophobic surfaces have been introduced such as self-cleaning, corrosion resistance, oil-water separation, etc. This review article should provide an overview to the bioinspired superhydrophobic surfaces of silicone-based materials, and serve as inspiration for the development of polymer interfaces and colloid science.

Recent Advances in Superhydrophobic and Antibacterial Coatings for Biomedical Materials

In recent years, biomedical materials have been used in the response to the emergence of medical infections that pose a serious threat to the health and life of patients. The construction of superhydrophobic coatings and antimicrobial coatings is among the most effective strategies to address this type of medical derived infection. Firstly, this paper reviews the preparation methods of superhydrophobic surface coatings and their applications; summarizes the advantages and disadvantages of superhydrophobic surface preparation schemes based on the template method, spraying methods, etching methods, and their respective improvement measures; and focuses on the applications of superhydrophobic surfaces in self-cleaning and antibacterial coatings. Then, the action mechanisms of contact antibacterial coatings, anti-adhesion bacteriostatic coatings, anti-adhesion bactericidal coatings, and intelligent antibacterial coatings are introduced, and their respective characteristics, advantages, and disadvantages are summarized. The application potential of antimicrobial coatings in the field of biomedical materials is highlighted. Finally, the applications of superhydrophobic and antimicrobial coatings in medical devices are discussed in detail, the reasons for their current difficulties in commercial application are analyzed, and the future directions of superhydrophobic coatings and antimicrobial coatings are considered.

Fluorine-free, short-process and robust superhydrophobic cotton fabric and its oil-water separation ability

Superhydrophobic (SH) fabric is widely used in production and life because of its excellent water repellency, self-cleaning, and anti-fouling properties, however, long process and poor durability against repeated laundering and abrasion of SH fabrics remain challenges. In this study, we report a fluorine-free, short-process and robust SH cotton fabric obtained by dip-coating with SH coatings based on UV induced thiol–ene click reactions among 3-mercaptopropyltriethoxysilane (MPTES), octavinyloctasilasesquioxane (OV-POSS) and 2 %–3 % (mercaptopropyl)methylsiloxane-dimethylsiloxane co-polymers (S-PDMS), and the coated fabric is enough durable against repeated laundering, abrasion, chemical corrosion and UV aging. Furthermore, its self-healing ability owing to heat treatment (140 °C, 30 min) can further improve the coating durability, based on which the coating can withstand at least 28 cycles of repeated accelerated washing (equivalent to 140 cycles of normal home laundering) and maintain its superhydrophobicity. Additionally, the coating can separate oil-water mixtures, and the separation efficiency is more than 99 %, even after 10 cycles of repeated oil-water separation processes. The combination of short-process and self-healing ability makes it very promising in the large-scale manufacturing and application of SH surfaces.

Laser-Induced Graphene Superhydrophobic Surface Transition from Pinning to Rolling for Multiple Applications.

The fabrication and applications of superhydrophobic surfaces (contact angle >150°,sliding angle <10°) have attracted worldwide interest with respect to materials and devices. In this work, the laser-induced graphene (LIG) superhydrophobic surface transition from pinning to rolling via an extremely simple solvent treatment of LIG in air is reported. By adding a certain solvent (e.g., ethanol) to the surface, the LIG superhydrophobic surface changes from pinning (sliding angle = 180°) to rolling (sliding angle <6°), which is attributed to the chemically changed surface properties and surface morphology of LIG. Three applications are demonstrated with the developed superhydrophobic LIG, including surface-enhanced Raman spectroscopy, water-oil separation, and anti-icing.

Robust network-like superhydrophobic magnesium hydroxide surface via cathodic electrodeposition with xanthan gum

Economic cost of raw materials has become an important limiting factor for the further application of superhydrophobic surface. Magnesium hydroxide is an innocuous, antibacterial, eco-friendly, and especially cheap material. Superhydrophobic surface fabricated with magnesium hydroxide was safe, environment friendly, and of very low cost. However, magnesium hydroxide superhydrophobic surfaces prepared through traditional electrodeposition method was always fragile and easy to peel off substrate, due to the discontinuous platelet-like structure which led to weak mechanical property. In this work, we electrodeposited a robust network-like magnesium hydroxide layer on iron substrate under the structure direction of xanthan gum which formed network with helical conformation at low temperature and proper pH value in aqueous solution. Electrodeposition factors such as concentrations of xanthan gum and glucose, bath temperature, pH value of electrolyte and current intensity were studied. The magnesium hydroxide layer fabricated at the optimum condition (0.5 mol/L magnesium nitrate, 4 mg/L XG, 4 mg/L glucose, 2.6 pH value and 35 mA at 15°C for 20 min) was with network-like structure, and exhibited excellent superhydrophobicity (water contact angle, 153.56° sliding angle, 2.2°) and self-cleaning property after stearic acid modification. The robust layer kept superhydrophobic until 600 mm abrasion length facing 1000 grit SiC sandpaper under 100 g weight, and with detachment less than 5% after cross hatch tape adhesion test. The layer also demonstrated good long-term immersion stability, and was still superhydrophobic with 48 h immersion in 3.5 wt% NaCl aqueous solution at room temperature. The inhibition efficiency of the layer reached 99.03%, due to its extremely high corrosion resistance (Rct = 2.87 × 105 Ω/cm2, Rf = 2.53 × 106 Ω/cm2). The introduced method of electrodepositing robust network-like MH layer made the further application of low-cost superhydrophobic surface with magnesium hydroxide possible.

Fabrication of recyclable, superhydrophobic-superoleophilic quartz sand by facile two-step modification for oil-water separation

With the highly frequency of oil spillages and chemical leakages, the application of superhydrophobic surface in oil-water separation is promising. Herein, the myristic acid/TiO2 @raw quartz sand (MATC@sand) with superhydrophobic-superoleophilic properties has been judiciously designed and synthesized that could be utilized for oil-water separation. The as-prepared samples were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectrometer (XPS) and Fourier transform infrared spectroscopy (FTIR). The wetting behavior was evaluated by contact angle measurer and the result showed that the MATC@sand had a water contact angle of 165.0°, a sliding angle less than 5° and an oil contact angle of 0°, which endowed the modified quartz sand with efficiently implement oil-water separation in various modes. The mechanism of oil-water separation using MATC@sand was exploited and it demonstrated the excellent ability of oil-water separation was mainly attributed to the synergistic effect between rough hierarchical micro/nanostructures and low surface energy. Moreover, for the sake of demonstrating its performance in practice application of oil-water separation, the durability, self-cleaning capacity, thermostability and anticorrosion of the MATC@sand are also measured to ensure the practical application. The results proved that the functional quartz sand is recyclable, economical and readily available, which made it have great prospects in practical application.

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.

Application of Superhydrophobic Surface on Boiling Heat Transfer Characteristics of Nanofluids

Boiling heat transfer is a mode using the phase change of working medium to strengthen the heat exchange due to its good heat exchange capability, and it is widely used in heat exchange engineering. Nanofluids have been used in the direction of enhanced heat transfer for their superior thermophysical property. The wetting, spreading and ripple phenomena of superhydrophobic surfaces widely exist in nature and daily life. It has great application value for engineering technology. In this article, the boiling heat exchange characteristics of nanofluids on superhydrophobic surface are numerically studied. It was found that with the increase of superheating degree, the steam volume ratio of unmodified heated surface increases to saturation, while the steam volume and evaporation ratio of modified superhydrophobic surface increase firstly and then decrease. At the same time, bubbles are generated and accumulated more fully on superhydrophobic surface. It was also found that nanofluids with low viscosity are more affected by superhydrophobic surface characteristics, and the increase is more significant with high superheating degree, and the superhydrophobic surface is beneficial to enhancing boiling heat exchange. Compared with the simulation results, it could be concluded that the boiling heat exchange performance of CuO-water nanofluids on the modified superhydrophobic surface is better than that of CuO-ethylene glycol nanofluids under high superheating degree.

The concept, deposition routes, and applications of superhydrophobic surfaces – Review

The superhydrophobic surface (SHS) is the surface with a high apparent contact angle (> 150 °), low hysteresis in the contact angle (< 10 °), and low sliding angle. Owing to many applications of SHS (such as water-resistant surfaces, antifogging surfaces, anti-icing surfaces, anticorrosion surfaces, etc.), the artificial SHS could be prepared. This review article focuses on the deposition, behavior and application of the SHS. It includes an introduction, fundamental principles of superhydrophobicity, main factors for SHS fabrications, deposition methods used to prepare the SHS, and factors affecting the electrochemical synthesis of electroconducting polymers. Moreover, the mechanism of the electrochemical synthesis of polymers, applications of SHS in different fields, and the stability of SHS have been presented. Finally, the challenges of SHS have been discussed.

Superhydrophobic Surfaces: Insights from Theory and Experiment.

Biomimetic nanosurfaces with distinct wettability and versatility have found special enthusiasm in both fundamental research and industrial applications. With the advent of nanotechnology, it is doable to acclimate surface architecture and surface chemistry to attain superhydrophobicity. The uniqueness of superhydrophobic surfaces arises from various phenomenal advances, and its progress is expected to continue for decades in the future. In this Review Article, we discuss recent progress made in defining physical aspects of numerical modeling, experimental practices adopted, and applications of superhydrophobic surfaces. First, we revisit various classical models of superhydrophobicity and recent theoretical advances achieved related to the wetting phenomena. Subsequently, we emphasize various precursors and advance fabrication strategies adopted to fabricate superhydrophobic surfaces. In the following section, we take up various potential applications and appropriate working principles to explain wettability phenomena. Finally, some general conclusions are drawn along with proposed guidelines for designing robust superhydrophobic coatings.

A bio-inspired superhydrophobic surface for fog collection and directional water transport

Simple methods for the collection and transportation of water droplets can solve complex problems, but developing technologies to achieve this is a challenge. To this end, widespread attention in recent years has focused on the preparation and application of superhydrophobic surfaces. Inspired by the structures of trichomes (hairs) of Sarracenia, a genus of carnivorous pitcher plants, we report a bionic high-low rib-like microstructure with superhydrophobic and directional water transport properties. At the same time, we can accelerate fog-collection efficiency by preparing a surface enabling directional slip of liquid. This work provides a good strategy for liquid transportation and fog collection, which has broad application prospects in the collection of rainwater in desert areas and the transmission of microfluidics in mechanical engineering.

Combinational Biomimicking of Lotus Leaf, Mussel, and Sandcastle Worm for Robust Superhydrophobic Surfaces with Biomedical Multifunctionality: Antithrombotic, Antibiofouling, and Tissue Closure Capabilities.

Surface wetting occurring in daily life causes undesired contaminations, which are critical issues in various fields. To solve these problems, the nonwetting property of a superhydrophobic (SH) surface has proven its utility by preventing contaminant infiltration, serious infections, or malfunction. However, the application of SH surfaces in the biomedical field has been limited due to the weak durability and toxicity of the related components. To overcome these limitations, we developed a robust and biocompatible SH surface through combinational biomimicking of three natural organisms, lotus leaf, mussel, and sandcastle worm, for the first time. Using the water-immiscible and polycationic characteristics of mussel adhesive protein (iMglue), an SH iMglue-SiO2(TiO2/SiO2)2 coating was fabricated by solution-based electrical charge-controlled layer-by-layer growth of nanoparticles (NPs). The fabricated iMglue-SiO2(TiO2/SiO2)2 SH surface showed excellent durable nonwetting properties and was applied to an intracatheter tube coating to develop antithrombotic catheters under blood flow. Furthermore, we developed a iMglue-employed SH patch for a tissue closure bandage by spraying hydrophobic SiO2 NPs on the iMglue-covered cotton pads. The prepared iMglue-employing SH patch showed perfect bifunctionality with excellent antibiofouling and tissue closure capabilities. Our work presents a novel, useful strategy for fabricating a biomedically multifunctional, robust SH surface through combinational mimicking of natural organisms.