Preparation Of Superhydrophobic Surfaces Research Articles

Preparation and properties of polytetrafluoroethylene superhydrophobic surface

Polytetrafluoroethylene (PTFE), as a typical hydrophobic material, has a very wide range of applications in various industries. However, the surface contact angle cannot reach the superhydrophobic effect, increasing cleaning costs. Here, we successfully prepared PTFE superhydrophobic surface by ball milling and spraying. The results show that the low surface energy is an important reason why the droplets remain spherical on the surface of the material and do not spread. The micro-nano secondary structure can support the droplets, and the air cushion formed helps the material surface to have a higher contact angle. The surface contact angle of the PTFE plate sprayed with 3% graphene/hydrophobic nano-SiO2 composite powder is 161.05°. After 10 times of tape stripping, the contact area between droplets and air remains above 85.00%. After 10 times of friction and wear, the contact angle remains above 150°. The wettability of the material is not significantly affected due to structural similarity and material consistency. This approach may carve a feasible way for the preparation of superhydrophobic surfaces and reduces the cleaning cost of PTFE surfaces.

Sustainable and Practical Superhydrophobic Surfaces via Mechanochemical Grafting

AbstractThe broad adoption of superhydrophobic surfaces in practical applications is hindered by limitations of existing methods in terms of excessive usage of solvents, the need for tedious and lengthy chemical processes, insufficient biocompatibility, and the high cost of materials. Herein, a mechanochemical approach for practical and solvent‐free manufacturing of superhydrophobic surfaces is reported. This approach enables solvent‐free and ultra‐rapid preparation of superhydrophobic surfaces in a single‐step without the need for any washing, separation, and drying steps. The hydrolytic rupture of siloxane bonds and generation of free radicals induced by mechanochemical pathways play a key role in covalent grafting of silicone to the surface of nanoparticles that leads to superhydrophobic surfaces with a water contact angle of >165° and a sliding angle of <2°. The direct use of industrially available and non‐functional silicone materials together with demonstrated applicability to inorganic nanoparticles of varied composition greatly contribute to the scalability of the presented approach. The resulting superhydrophobic surfaces are highly biocompatible as demonstrated by fibroblast cells using two different assays. Monolith materials fabricated from silicone‐grafted nanoparticles exhibit bulk and durable superhydrophobicity. The presented approach offers tremendous potential with sustainability, scalability, cost‐effectiveness, simplicity, biocompatibility, and universality.

Preparation of superhydrophobic surface from raspberry like particles of bifunctional polyssesquioxane

AbstractIn this article, we selected MTMS and ETMS as mixed precursors to generate polysiloxane particles on the surface of styrene copolymer microspheres, forming raspberry‐like particles. The best experimental formula was obtained by orthogonal test. When the ratio of MTMS and ETMS was 3:1, the hydrophobic properties of composite particles reached the best, with a water contact angle (WCA) of 163° and a WSA of 3°. The hydrophobic models of raspberry particles were established. And the influence of gas–liquid contact components, surface roughness and precursor ratio on hydrophobic properties was clarified by theoretical calculation, Fourier transform infrared and X‐ray diffraction analysis. The prepared superhydrophobic surface shows great application potential in self‐cleaning, antifouling and other fields.

The effect of high temperature annealing on surface wettability, mechanical and chemical properties of laser ablated nitinol surface

Nitinol shape memory alloys are widely used in medical devices due to their special properties. However, the release of nickel ions into human liquid during corrosion process would cause great harm to human body. It has been found that super-hydrophobic surface with superior anti-corrosion performance could greatly solve this issue. Therefore, the preparation of green and healthy super-hydrophobic layer on nickel-titanium alloy surface has significant medical value. In this work, we explored a newly method of fabricating healthy super-hydrophobic surface with contact angle (WCA) of 153.2° ± 1.5°, and roll angle (RA) of 6° ± 0.5°by combination of nitinol alloy laser irradiation. Particularly, high temperature annealing was firstly adopted in the fabrication procession of super-hydrophobic surface, which can bring great reference value to the research in this filed. Besides, the formation mechanism was also revealed via the analysis of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Furthermore, corrosion behavior was also investigated by electrochemical impedance (EIS) analysis to illustrate preventing nickel ions release performance. Unlike the traditional super-hydrophobic surface preparation methods, this method does not introduce any toxic substances, which has great application prospects in the medical field.

Preparation of Superhydrophobic Surfaces and Their Application in Oily Wastewater Treatment: Design of a Comprehensive Physical Chemistry Innovation Experiment

Preparation of Superhydrophobic Surfaces and Their Application in Oily Wastewater Treatment: Design of a Comprehensive Physical Chemistry Innovation Experiment

A durable superhydrophobic surface with protective nest-like micro-containers

The preparation of superhydrophobic surfaces is a promising potential strategy for protecting metal substrates and allowing their utilization in a broader range of applications. Many studies have investigated metal-based superhydrophobic surfaces, and various methods for fabricating these surfaces have been reported. However, the fragility of their structure and composition has long puzzled researchers and hindered the development of superhydrophobic surfaces for practical use. Moreover, nanostructures are notoriously more delicate than microstructures. Therefore, developing surfaces with durable structures at both the nanoscale and microscale is crucial. Herein, a novel method was developed to rapidly prepare many nest-like “micro-containers”. Green ingredients were then stored and protected in these nest-like micro-containers as nanostructures and low surface energy components. The approach reported herein allows for the fabrication of a favorable hierarchical structure with a well-protected structure and composition. Characterization and a variety of measurements were performed to confirm that the unique structural design of this superhydrophobic surface produced an ultra-high water contact angle with low adhesion. Furthermore, the superhydrophobic surface exhibited good resistance to mechanical damage, good corrosion resistance, high environmental durability, and self-cleaning properties. • A structural protection strategy to fabricate durable superhydrophobic surfaces is proposed. • Low surface energy components are stored, protected, and recovered. • Preparation methods are green, low-cost and easy to implement. • Formation mechanism is analyzed in detail. • Excellent durability, anti-corrosion and self-cleaning are performed.

Retardation of superhydrophobicity for the air plasma sprayed ceria coating surface

Ceria has become a potential candidate for the preparation of superhydrophobic surfaces due to the apparent intrinsic hydrophobicity reported in recent years. In the present study, a CeO2 coating with bi-scale structures imitating lotus leaf surface was deposited by air plasma spraying (APS). It was found that the wettability of the coating surface exhibited a special delayed phenomenon, that the surface needed to be stored in the atmosphere for a period of time before it could change from superhydrophilicity in the fresh as-sprayed state to superhydrophobicity. To elucidate the mechanism, the research focused on analyzing the changes in the chemical composition of the surface. The results showed that adsorption effect was the main factor dominated the surface wettability. During atmospheric storage, the coating surface spontaneously adsorbed low surface free energy substances, mainly carboxylates containing alkane chain and alkanes, resulting in the transition of wettability. The bombardment of argon plasma jet to ceria during APS led to the valence state change of Ce atoms, resulting in the generation of coordinatively unsaturated metal cations acted as active adsorption sites, which was the reason for the spontaneous adsorption. Due to the restrictions on the location of the active sites and the limited concentration of airborne adsorbates, the spontaneous adsorption proceeded slowly, which led to the retardation of superhydrophobicity for the coating surface. The study laid a theoretical foundation for the preparation of CeO2 superhydrophobic coatings by APS, and provided further insights into the underlying mechanism of the apparent hydrophobicity of CeO2.

Eco-Friendly Fabrication of Transparent Superhydrophobic Coating with Excellent Mechanical Robustness, Chemical Stability, and Long-Term Outdoor Durability.

Surfaces that possess both superhydrophobicity and high transparency at the same time recently have attracted extensive attention in outdoor applications. However, fabrication and application of transparent superhydrophobic coating usually face following challenges: the micro-nano hierarchical structure required for superhydrophobicity usually leads to a decrease in the light transmittance due to its light trapping effect; fluorine-containing materials used in the preparation of superhydrophobic surfaces are potentially harmful to humans and the environment; and the superhydrophobic surface is easily destroyed by external factors. In this work, a transparent superhydrophobic coating was fabricated via an inexpensive and eco-friendly two-step method, that is, dipping glass substrate into the polydimethylsiloxane/SiO2 suspension followed by calcination treatment. The prepared coating showed superhydrophobicity with a water contact angle of 164° and a sliding angle less than 1.0°. In the visible light region with the wavelength range of 300-900 nm, the maximal transmittance of the superhydrophobic coating was ∼91.4%, which is higher than that of the untreated glass substrate (∼90.9%). Moreover, the coating can maintain superhydrophobicity and high transmittance after sandpaper abrasion, water flow impact, immersion in strong acid/alkaline solution, UV irradiation, and long-term outdoor exposure. We believing that the coating has huge potential value in outdoor applications.

Preparation of super-hydrophobic surface with micro-nano layered structure on 316 stainless steel by one-step wet chemical method

In order to simplify the traditional preparation procedure of super-hydrophobic stainless steel (SLS), a novel one-step method was developed to produce super-hydrophobic surface on 316 SLS under the simultaneous chemical etching and surface modification with cofunction of hydrogen peroxide (H2O2), hydrofluoric acid (HF) and perfluorooctyl trichlorosilane (PFOS). The effects of the mixing ratio of reagents (H2O2, HF and PFOS) and reaction time were explored by orthogonal experiments. The results indicated that H2O2 showed the most significant effect on the hydrophobicity of SLS. When the molar ratio of H2O2/HF ranged between 0.2/1–0.4/1, the prepared samples showed excellent super-hydrophobicity, with the maximum water contact angle of 161.78° and the minimum slip angle of 1.94°. The influencing mechanism of H2O2 on the etching and modification was further explored by X-ray photoelectron spectroscopy (XPS) and Scanning electron microscopy (SEM). The results showed that the ratio of H2O2/HF markedly affected the grafting of PFOS onto the surface of SLS. According to the tests of corrosion resistance and durability, the corrosion resistance of super-hydrophobic surface was 6 times higher than that of raw SLS, and the super-hydrophobicity of SLS hardly changed after 3 months of exposure in the ambient air. The water contact angle was still close to 150° after peeling adhesive tape for 12 times. The results of this study indicated a promising perspective for industrial application of the one-step method.

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.

Effect of Hydrophobic Nano-SiO2 Particle Concentration on Wetting Properties of Superhydrophobic Surfaces.

As a unique surface wettability, superhydrophobicity has great application value. A variety of preparation methods for superhydrophobic surfaces have been reported, which have the disadvantages of high cost and complicated process. In order to design a method that is easy to operate, low-cost, and suitable for large-scale preparation of superhydrophobic surfaces, in this paper, hydrophobic nano-SiO2 particles are used as spray fillers, and superhydrophobic surfaces are successfully obtained by the spraying process. According to the classical Cassie and Wenzel theory, the influence of the concentration change of hydrophobic nano-SiO2 particles on their wettability is explained, and the appropriate spray concentration parameters are obtained. The results show that the proportion of hydrophobic nano-SiO2 particles is lower than 0.05 g/mL, which will lead to insufficient microstructure on the surface of the coating, and cannot support the droplets to form the air bottom layer. However, an excessively high proportion of hydrophobic nano-SiO2 particles will reduce the connection effect of the silicone resin and affect the durability of the surface. Through theoretical analysis, there are Wenzel state, tiled Cassie state, and stacked Cassie state in the spraying process. When the substrate surface enters the Cassie state, the lower limit of the contact angle is 149°. This study has far-reaching implications for advancing the practical application of superhydrophobic surfaces.

Achieving amorphous micro-nano superhydrophobic structures on quartz glass with a PTFE coating by laser back ablation

Superhydrophobic surfaces are typically prepared by composite processing and coating with low-surface-energy materials. Transparent, hard, and brittle materials (e.g., glass) are typically covered with low-surface-energy coating to form a superhydrophobic surface. In addition, achieving superhydrophobicity generally requires aging or modification to obtain a low surface energy by composite processing. Therefore, the preparation of superhydrophobic surfaces using one-step method is more efficient and economical. In this study, a method of realizing a superhydrophobic structure by laser back-facing direct etching is proposed. A superhydrophobic structure was immediately realized in one step using glass as the substrate and polytetrafluoroethylene (PTFE) as a coating. In addition, the surface morphologies of microstructures were studied for different laser parameters (laser single pulse energy and scanning rate). The results showed that at a laser pulse energy of 12 μJ and scanning rate of 100 mm/s, the contact angle (CA) of the obtained surface structure was 153 ± 2°, and the rolling angle (RA) was less than 2°, implying superhydrophobicity. At a low laser energy (less than 10 μJ) and a scanning rate lower than 80 mm/s, the sample broke during etching. At scanning rates of 100 mm/s and higher, the surface was not superhydrophobic. Further, at high laser energies (more than 12 μJ), the samples disintegrated. Scanning electron microscopy (SEM) showed that micro/nano structures were formed on the surface. The results of the elemental content analysis and X-ray photoelectron spectroscopy (XPS) indicated that the sample surface was attached to fluorine-containing nanoparticles.

One-step fabrication of soft calcium superhydrophobic surfaces by a simple electrodeposition process.

A simple, one-step electrodeposition process was rapidly performed on a metal substrate to fabricate calcium superhydrophobic surfaces in an electrolyte containing calcium chloride (CaCl2), myristic acid (CH3(CH2)12COOH), and ethanol, which can avoid the intricate post-processing of surface treatment. The morphology and surface chemical compositions of the fabricated superhydrophobic surfaces were systematically examined by means of SEM, XRD, and FTIR, respectively. The results indicate that the deposited surfaces were mainly composed of calcium myristate, which can dramatically lower surface free energy. The shortest process for constructing a superhydrophobic surface is about 0.5 min, and the maximum contact angle of the as-prepared surfaces can reach as high as 166°, showing excellent superhydrophobicity. By adjusting the electrodeposition time, the structure of the cathodic surface transforms from the turfgrass structure, loose flower structures, larger and dense flower structures, secondary flower structures, and then into tertiary or more flower structures. The superhydrophobic surfaces showed excellent rebound performance with a high-speed camera. After a pressing force, their hardness increases, but the superhydrophobic performance is not weakened. Inversely, the bouncing performance is enhanced. This electrodeposition process offers a promising approach for large areas of superhydrophobic surfaces on conductive metals and strongly impacts the dynamics of water droplets.

Effects of the surface tension gradient and viscosity on coalescence-induced droplet jumping on superamphiphobic surfaces

With the development of superhydrophobic surface preparation technology, coalescence-induced droplet jumping shows broad application prospects in the fields of enhanced condensation heat transfer and self-cleaning. In this work, the coalescence-induced jumping process of heterogeneous and homogeneous droplets on superamphiphobic surfaces was studied by using glycerol–water mixtures with different glycerol volume fractions. The results showed that the surface tension gradient of heterogeneous droplets will lead to asymmetric deformation of droplets, asymmetric distribution of internal pressure of droplets, as well as decrease in the energy conversion efficiency and the vertical departure velocity. Our study also revealed that the effects of surface tension gradient and viscosity on droplet jumping are different in the two regions. When the glycerol volume fraction is less than 40%, the droplet velocity and energy conversion are dominated by the surface tension gradient, and the vertical departure velocity and the energy conversion efficiency of homogeneous droplets are larger. When the glycerol volume fraction is greater than 40%, the droplet velocity and energy conversion are dominated by the surface tension gradient and viscosity together, and the vertical departure velocity and the energy conversion efficiency of heterogeneous droplets are larger.

Preparation of Superhydrophobic Surfaces Based on Rod-Shaped Micro-Structure Induced by Nanosecond Laser

Solid–liquid frictional resistance is mainly attributed to the adhesion caused by the boundary layer effect. Superhydrophobic surfaces are expected to be an effective method to reduce frictional resistance. In this paper, a rod-shaped micro-structure was prepared on surfaces of Al alloy (5083) and Ti alloy (TC4) by line-by-line scanning with nanosecond laser. The inherent properties of the metal materials—such as their coefficient of thermal conductivity (CTC) and specific heat capacity (SHC)—had a major influence on the surface morphology and shape size of the rod-shaped micro-structure. Both two metals showed apparent oxidation on their surfaces during laser ablation, however, the degree of surface oxidation of the Al alloy was greater than that of the Ti alloy due to its more fragmentary rod-shaped micro-structure. The laser-treated surfaces could turn from hydrophilic to hydrophobic or even superhydrophobic after being left in the air for 20 days, which might be caused by the adsorption of low-surface energy matter in the air. In addition, the contact angle of the Al alloy was larger than that of the Ti alloy, which is due to the larger ratio of height to width of the micro–nano composite rod-shaped micro-structure on the surface of the Al alloy.

Study on Preparation of Superhydrophobic Surface by Selective Laser Melting and Corrosion Resistance

Superhydrophobic surfaces are used in aerospace, medical equipment, transportation, household appliances and other fields due to their special interface characteristics. In this paper, a superhydrophobic surface is prepared by Selective Laser Melting (SLM) 3D-printed technology, comparing the effects of different post-treatment methods and time on corrosion resistance, and revealing the root cause of the transition from hydrophilic to superhydrophobic. The test results show that for samples not treated with fluoro-silane, the microstructure adsorbs the organic matter in the air and reduces the surface energy, which is the root cause of the sample surface changing from hydrophilic to superhydrophobic. In addition, the corrosion resistance of 3D-printed, polished, 3D-printed + modified, and 3D-printed + corroded samples are analyzed. Among them, 3D-printed + modified samples have a longer resistance to corrosion, and after placing in outdoor natural conditions for 60 days, the contact angle of water droplets on the surface is 150.8°, which still has superhydrophobic properties and excellent natural durability.

Superhydrophobic micro-tube fabricated via one-step plasma polymerization for lossless droplet transfer

Lossless droplet transfer via micro-tube is urgently demanded in the fields of microfluidics and biomedicine. However, as the core component for the construction of lossless droplet transfer platform, the fabrication of low-adhesion micro-tubes is still a longstanding challenge. To solve the problems such as complex reaction procedures, difficult-to-clean reaction products, non-uniform wettability, etc. during the synthesis of the low-adhesion micro-tubes, a new one-step approach for the preparation of superhydrophobic micro-tubes has been developed, with the help of atmospheric pressure cold plasma (APCP) deposition technology. This method can break through the limitations of micro-tube materials, and achieve the preparation of superhydrophobic surface in glass and transparent Teflon tubes using a lab-made plasma generator. The mechanism of the superhydrophobic surface preparation by APCP deposition involves the formation of a micro-nano composite structure and hydrophobic functional groups. The results point out that the inner wall of the superhydrophobic micro-tube has good and consistent wettability, and uniform morphology. The reduction in transparency of the micro-tube was less than 5% within the wavelength range of 400 nm~1100 nm. Using the as-prepared superhydrophobic micro-tube as the core component, the lossless droplet transfer platform based on the non-contact ultrasonic driving was set up. Finally, the lossless droplet transfer under extreme conditions like in vertical micro-tubes, curve micro-tubes, spiral micro-tubes, using high-speed liquid feed at 850 μL/min was successfully achieved, with the transportation distance reaching hundreds of millimeters. With excellent performances, the lossless droplet transfer platform promises great potential applications in the fields like microfluidics, biomedicine and advanced device design.

Preparation of Superhydrophobic Surface on Copper Substrate and Its Corrosion Resistance

Preparation of Superhydrophobic Surface on Copper Substrate and Its Corrosion Resistance

Facile Electrochemical Method for the Fabrication of Stable Corrosion-Resistant Superhydrophobic Surfaces on Zr-Based Bulk Metallic Glasses.

Both surface microstructure and low surface energy modification play a vital role in the preparation of superhydrophobic surfaces. In this study, a safe and simple electrochemical method was developed to fabricate superhydrophobic surfaces of Zr-based metallic glasses with high corrosion resistance. First, micro–nano composite structures were generated on the surface of Zr-based metallic glasses by electrochemical etching in NaCl solution. Next, stearic acid was used to decrease surface energy. The effects of electrochemical etching time on surface morphology and wettability were also investigated through scanning electron microscopy and contact angle measurements. Furthermore, the influence of micro–nano composite structures and roughness on the wettability of Zr-based metallic glasses was analysed on the basis of the Cassie–Baxter model. The water contact angle of the surface was 154.3° ± 2.2°, and the sliding angle was <5°, indicating good superhydrophobicity. Moreover, the potentiodynamic polarisation test and electrochemical impedance spectroscopy suggested excellent corrosion resistance performance, and the inhibition efficiency of the superhydrophobic surface reached 99.6%. Finally, the prepared superhydrophobic surface revealed excellent temperature-resistant and self-cleaning properties.

Recent progress on the surface finishing of metals and alloys to achieve superhydrophobic surfaces: a critical review

ABSTRACT Superhydrophobicity is widely observed in nature with the tendency of a natural surface to be characterised by a water-repellent capability. Over the past thirty years, the production of superhydrophobic surfaces on metals and alloys has received growing interest because of its great significance in a wide range of industrial applications, such as water-proofing, anti-corrosion, anti-icing, drag reduction, self-cleaning, and phase change heat transfer enhancement. This paper presents a comprehensive review of the recent advances in the preparation of superhydrophobic surfaces on metals and alloys, largely focused on copper, aluminium, zinc, and related alloys. It starts with an introduction of the basic principle of superhydrophobicity and surface wettability characteristics. The fabrication methods, chemical and physical properties, advantages, and prospects are summarised and compared. Some promising and innovative applications of superhydrophobic metal/alloy surfaces are also briefly introduced. Finally, challenges affecting the development and application of superhydrophobic metal/alloy surfaces are outlined.