Fluoroalkylsilane Modification Research Articles

Rational Design of Oil-Resistant and Electrically Conductive Fluorosilicone Rubber Foam Nanocomposites for Sensitive Detectability in Complex Solvent Environments.

Recent years have witnessed the explosive development of highly sensitive smart sensors based on conductive polymer foam materials. However, the design and development of multifunctional polymeric foam composites as smart sensors applied in complex solvent and oil environments remain a critical challenge. Herein, we design and synthesize vinyl-terminated polytrifluoropropylmethylsiloxane through anionic ring-opening polymerization to fabricate fluorosilicone rubber foam (FSiRF) materials with nanoscale wrinkled surfaces and reactive Si-H groups via a green and rapid chemical foaming strategy. Based on the strong adhesion between FSiRF materials and consecutive oxidized ketjen black (OKB) nano-network, multifunctional FSiRF nanocomposites were prepared by a dip-coating strategy followed by fluoroalkylsilane modification. The optimized F-OKB@FSiRF nanocomposites exhibit outstanding mechanical flexibility in wide-temperature range (100 cycle compressions from -20 to 200 °C), structure stability (no detached particles after being immersed into various aqueous solutions for up to 15 days), surface superhydrophobicity (water contact angle of 154° and sliding angle of ∼7°), and tunable electrical conductivity (from 10-5 to 10-2 S m-1). Additionally, benefiting from the combined actions of multiple lines of defense (low surface energy groups, physical barriers, and "shielding effect"), the F-OKB@FSiRF sensor presents excellent anti-swelling property and high sensitivity in monitoring both large-deformation and tiny vibrations generated by knocking the beaker, ultrasonic action, agitating, and sinking objects in weak-polar or nonpolar solvents. This work conceivably provides a chemical strategy for the fabrication of multifunctional polymeric foam nanocomposite materials as smart sensors for broad applications.

Superhydrophobic and Anti‐Icing Surface by Femtosecond Laser Direct Writing

Glass fiber‐reinforced polymer (GFRP) is formed with glass fiber as the reinforcing material and resin as the matrix. It is widely used in wind turbine blades because of its lightweight, high strength, and corrosion resistance properties. Herein, a method to prepare superhydrophobic GFRP surfaces by femtosecond laser direct writing combined with fluoroalkylsilane modification is demonstrated. The prepared GFRP surface has excellent superhydrophobicity with contact angle of 163.9° and sliding angle of 3.8°. In the ice resistance tests, the icing delay time is extended from 33 to 273 s at −5 °C. The ice adhesion strength is reduced from 217.4 to 40.3 kPa. The surface still has superhydrophobicity and ice adhesion strength of less than 100 kPa after ten cycles of the test. The laser exposure conditions are optimized for water/ice repelling and are at high intensity of 4 TW cm−2 pulse−1 and 2.5 m s−1 beam travel speed, which make the presented approach efficient for fabrication over industrially large areas.

TiO2 Passivated Zno Nanoarray Layer Based Fluoroalkylsilane Film for Photovoltaic Optical Glass: Achieving UV Shielding, Acid Rain Resistance, and Self‐Cleaning Properties

AbstractPhotovoltaic technology is a prominent source of renewable energy, but maintenance costs and efficiency attenuation of large photovoltaic devices are significant issues due to their vast energy conversion area. To reduce costs and facilitate maintenance, superhydrophobic surfaces with self‐cleaning properties have been developed for photovoltaic glass. In this study, transparent ZnO nanoarrays (NAs) are synthesized on photovoltaic glass, with Eu3+ doping enhancing the ultraviolet radiation resistance of photovoltaic devices and slightly increasing visible transmittance. A TiO2 passivation layer is introduced on the ZnO NAs surface to enhance acid resistance and mitigate corrosion caused by acidic rainwater. Fluoroalkylsilane (POTS) modification achieves superhydrophobicity with a water contact angle of 160.25°, as demonstrated by droplet rolling experiments. Micro‐interaction of superhydrophobic properties is further investigated by force curve measurement using atomic force microscope, showing almost no nanometer water moisture on the superhydrophobic surface, but conspicuous water moisture on the control glass surface. Finally, simulated models and practical silicon crystal solar cells fabricated using the self‐cleaning glass show excellent acid rain resistance, self‐cleaning, and long service life properties, with no power conversion efficiency degeneration during a 40‐day outdoor application test.

Slippery Liquid‐Infused Porous Surface on Metal Material with Excellent Ice Resistance Fabricated by Femtosecond Bessel Laser

Slippery liquid‐infused porous surface (SLIPS) has shown great application prospects because of the great liquid repellency and ice resistance. However, there are a few types of research on different metal material to fabricate SLIPS. Here, a simple and effective method is developed on a stainless steel surface to manufacture microporous structure by femtosecond Bessel laser beam direct induce. By fluoroalkylsilane modification and infusing lubricant, SLIPS is successfully obtained. The ice restraint properties of the SLIPS are studied, including the characterization of icing delay and ice‐adhesion strength, which significantly increase the icing‐delay time and reduce the ice‐adhesion strength. Moreover, SLIPS exhibits great durability after hydraulic pressure, salt fog, high‐, and low‐temperature cycle. Based on this method, SLIPS can be produced on different metal substrates including Al, Zn, Ti, Cu with excellent liquid resistance and anti‐icing property, which greatly expand the application of SLIPS in the field of ice resistance.

Surface functionalization of Zr-based metallic glass by direct nanosecond laser texturing

The functional properties of metallic glasses (MGs) can be enhanced by introducing special micro/nano-structures on their surface. In this study, a nanosecond pulsed laser was used to texture micro-convex array structures with different pitches (P) on a Zr-based MG surface to enrich its engineering applications. The reflection characteristics and wettability of polished and textured surfaces were compared. The experimental results showed that unlike the bright spot reflected from the polished surface, the light reflected from the textured surface would induce a well-defined diffraction pattern. In addition, the wettability of the surfaces covered with micro-convex array structures was also different from that of the polished surface. That is, without post-processing, the textured array structures would promote hydrophilicity; while after exposing in the air for 100 days or fluoroalkylsilane modification, the textured array structures facilitated hydrophobicity.

Durable superhydrophobic surface with hierarchical microstructures for efficient water collection

Owing to the aggravation of water pollution and fresh water shortage, fabrication of functional materials with super-wettability surfaces for harvesting atmospheric water has gained widespread attention in recent years. In this paper, a superhydrophobic surface with combination of good robustness and efficient water-collecting performance was successfully fabricated via structuring multilevel microstructures. This hierarchically structured surface was prepared by photoetching, acid-etching, anodizing and fluoroalkylsilane modification treatments. The resultant surfaces exhibited great water repellency with the water contact angle (CA) of 173° and a low sliding angle (SA) of 1.5°, and showed good chemical stability both in air and severe acidic-alkaline environments. Furthermore, favorable water proofing property was still maintained after cyclical abrasion of the prepared superhydrophobic surface, with micrometer sized square frustum pillars to provide mechanical durability and the secondary bamboo shoots-like microstructure to provide water repellency. Water harvesting efficiency of this robust superhydrophobic surface was 5.3 g·cm − 2 ·h −1 , higher than those of the previous reported surfaces. This facilely fabricated superhydrophobic surface is expected to collect micro droplets from fog/mist environments so as to relieve the lack of water. • Micro-pillars and secondary bamboo shoots-like structures were fabricated. • The superhydrophobic surface shows good acid and alkali resistance. • As designed multi-level structures lead to well mechanical robustness. • Efficient water harvesting was realized via fast transportation of droplets.

Remote, selective, and in situ manipulation of liquid droplets on a femtosecond laser-structured superhydrophobic shape-memory polymer by near-infrared light

Droplet manipulation plays a significant role in the fields of biomedical detection, microfluidics, and chemical engineering. However, it still remains a great challenge to simultaneously achieve remote, selective, and in situ droplet manipulation on the same surface. Here, Fe3O4 nanoparticles were doped in a shape-memory polymer (SMP) to prepare a photothermal-responsive Fe3O4-SMP composite which showed remarkable near-infrared (NIR) light-triggered shape-memory property. Superhydrophobic micropillar array was constructed on such Fe3O4-SMP composite through femtosecond laser microfabrication and fluoroalkylsilane modification. The surface wettability of the as-prepared surface can transform from a low-adhesive sliding state to a high-adhesive pinning state as the micropillars are deformed by pressing. Interestingly, the deformed micropillars can stand up and restore to their original morphology under remote NIR light irradiation, resulting in the reversible and repeatable recovery of the ultralow-adhesive superhydrophobicity. With such light-triggered wettability switching, the droplets pinning on the sample surface can be remotely, selectively, and in situ released. Furthermore, the superhydrophobic Fe3O4-SMP surface is successfully applied in lossless liquid transfer, selective droplet release, and droplet-based microreactor. The as-fabricated superhydrophobic surfaces with NIR light-controlled reversible wettability will hold great promise in the fields of liquid manipulation, lab-on-a-chip, and microfluidics.

A SUPERHYDROPHOBIC COATING ON TITANIUM ALLOYS BY SIMPLE CHEMICAL ETCHING

In the present study, a scalable-manufactured and environmental-friendly method was proposed to fabricate the superhydrophobic coating on titanium alloy. The hierarchical binary surface structures were obtained by hydrothermal treatment of titanium alloy with oxalic acid and sodium hydroxide solutions successively. The hierarchical structure surfaces after fluoroalkyl-silane modification possessed a maximum contact angle of 158.7∘ and a sliding angle of 4.3∘. The low contact angle hysteresis surface can lead to efficient self-cleaning performance, which was confirmed by the bounce and roll off of water droplet on the surface. Furthermore, the anticorrosion behaviors of the superhydrophobic coating in 3.5[Formula: see text]wt.% NaCl solution was evaluated by the electrochemical impedance spectroscopy (EIS). It was found that the superhydrophobic coating can maintain its superhydrophobic state (150∘) within 48 h, thereby effectively preventing the corrosive medium from penetrating into the coating. This simple yet fast anti-corrosion/self-cleaning superhydrophobic coating manufacturing strategy will enlighten its potential application in the engineering fields.

Anisotropic, adhesion-switchable, and thermal-responsive superhydrophobicity on the femtosecond laser-structured shape-memory polymer for droplet manipulation

Smart superhydrophobic surfaces with reversible wettability are attracting increasing attention. However, most of the reported smart superhydrophobic surfaces switch their wettability through reversibly changing surface chemistry rather than surface microstructure. In this paper, femtosecond laser direct writing was exploited to create microgroove array structure on the shape-memory polymer (SMP) substrates. The groove-structured surface exhibited superhydrophobicity and anisotropic wettability after fluoroalkylsilane modification. Due to the excellent shape-memory property of the SMP substrate, the morphology of the microgroove array could be transformed between original stand shape and deformed shape in response to heat. Correspondingly, water droplet on the surface was reversibly changed between sliding and sticky states through alternant pressing and heating treatments, indicating switchable adhesion of the laser-induced microgroove array. Meanwhile, the anisotropic wettability could also recover with the restoration of the grooved microstructure. Such wettability conversion on the resultant surface could be cycled 10 times without decline of the superhydrophobicity and anisotropic wettability. The anisotropic superhydrophobic SMP surface with both ultralow and ultrahigh water adhesion was successfully applied in rewritable liquid pattern, droplet-based microreactor, and gas sensing. By taking advantage of femtosecond laser, reversible microstructures and surface wettability can be obtained on various SMP substrates. We believe that such surfaces with thermal-responsive superhydrophobicity, anisotropic wettability, and switchable adhesion will have enormous potential applications in non-loss droplet transfer, biological detection, and lab-on-chip devices.

Preparation of Superhydrophobic Surface on Titanium Alloy via Micro-milling, Anodic Oxidation and Fluorination.

The superhydrophobic surface has a great advantage of self-cleaning, inhibiting bacterial adhesion, and enhancing anticoagulant properties in the field of biomedical materials. In this paper, a superhydrophobic surface was successfully prepared on titanium alloy via high-speed micro-milling, anodic oxidation and fluoroalkylsilane modification. The surface morphology was investigated by scanning electron microscope and a laser scanning microscope. The surface wettability was investigated through the sessile-drop method. Firstly, regular microgrooves were constructed by micro-milling. Then, nanotube arrays were fabricated by anodic oxidation. Afterwards, fluoroalkylsilane was used to self-assemble a monolayer on the surface with a composite micro/nanostructure. Compared to polished titanium samples, the modified samples exhibited superhydrophobic properties with the water contact angle (CA) of 153.7° and the contact angle hysteresis of 2.1°. The proposed method will provide a new idea for the construction of superhydrophobic titanium surgical instruments and implants in the future.

A facile and less-polluting electrochemical method to fabricate multifunctional superhydrophobic film on iron materials

Iron materials have the extremely widespread applications and they are common in all kinds of frame structures, such as iron tower. However, it is well known that ironwork is easy to rust. Besides, in cold environment the freezing rain adhered to the iron facility can also bring huge potential security problems. Herein, we present a modified electrochemical machining (ECM) method by applying a mixed aqueous solution of Na2MoO4 and NaCl to fabricate superhydrophobic film on iron materials followed by fluoroalkylsilane (FAS) modification. The proposed ECM method can not only generate rough microstructures very rapidly even at low electrical parameters, but also reduce the pollution of the electrolyte by recycling the corrosion products. The sandpaper abrasion and knife scratch tests were utilized to demonstrate the mechanical strength of the obtained superhydrophobic surfaces. Good self-cleaning properties were also showed by using several kinds of contaminants and corrosive solutions. Furthermore, we demonstrated the good anti-fogging property by using atomizer and the anti-icing property by static and dynamic anti-icing tests in a cold environment to show the practical applications of the prepared film. We believe that the modified ECM method has broad application prospects.

A facile electrochemical machining process to fabricate superhydrophobic surface on iron materials and its applications in anti-icing

Iron materials are widely applied in electrical-tower. However, the freezing rain adhering to the electric-tower in winter can raise a huge potential safety hazard to the power facilities. Therefore, how to make ironworks possess anti-icing property has become a difficult problem. In order to resolve the aforementioned issue, a facile, low-cost and environment-friendly electrochemical machining method was developed to fabricate superhydrophobic surface on iron materials to endow anti-icing capacity in the freezing rain. After fluoroalkylsilane (FAS) modification, superhydrophobic surface could be obtained. The morphology of the surface film was examined using scanning electron microscopy (SEM) equipped with an energy-dispersive spectroscopy (EDS) and laser confocal microscope. The chemical composition was investigated by X-ray photoelectron spectroscopy (XPS). The influence of the applied processing time on wettability was also studied. The results showed that a rough surface, which consisted of many step-like structures, was formed on the surface of iron by the proposed electrochemical method. After FAS modification, the surface showed good superhydrophobicity with the water contact angle of 162° and water sliding angle of 3.33°. The mechanism of the generated rough structures was also discussed. Moreover, the static and dynamic anti-icing tests were conducted. The results showed that the superhydrophobic surface can not only significantly delay the freezing time, but also prevent the cold water from freezing on the iron surface, which could be a good solution to the freezing rain issue.

Investigation of Effects of Acid, Alkali, and Salt Solutions on Fluorinated Superhydrophobic Surfaces

Extensive studies have been carried out to investigate the stability of superhydrophobic surfaces under acid, alkali, and salt solutions. It is noted that previous literature studies just demonstrated a variety of experimental phenomena. However, very few works have focused on the protection mechanism or failure mechanism of fluorinated superhydrophobic surfaces from the perspective of chemical aspects. Herein, this paper aims to investigate the effects of acid, alkali, and salt solutions on the stability of fluorinated superhydrophobic surfaces, and the anticorrosion/corrosion mechanism will be further proposed. The superhydrophobic coating was obtained on silicon substrates by laser surface texturing followed by fluoroalkyl silane modification. The resultant surfaces presented a water contact angle (WCA) of 157.6 ± 0.4° with a small water sliding angle (WSA) of 1.3 ± 0.3°. The newly fabricated superhydrophobic surfaces were then immersed in different concentrations of corrosive solutions (acid, alkali, and salt solutions). The revolution of surface wettability and surface morphology on treated silicon surfaces was evaluated through WCAs, scanning electron microscopy, and white light confocal microscopy. The results indicate that the hydrogen ions (H+) played a positive role in the retention of superhydrophobicity. However, the hydroxyl (OH-) and chloride ions (Cl-) presented the negative influence. The protection mechanism or corrosion mechanism under different solutions was proposed based on the X-ray photoelectron spectroscopy results. In addition, the potentiodynamic polarization and electrochemical impedance spectroscopy measurements provided strong support in data and were conducted to verify the rationality of the proposed mechanism.

A contrastive investigation on anticorrosive performance of laser-induced super-hydrophobic and oil-infused slippery coatings

Nature inspired super-hydrophobic surface has aroused extensive attention on corrosion prevention. More works have investigated the instant corrosion resistance of fresh super-hydrophobic surface, but less research focused on its stability when immersed into corrosive solution for long time. Recently, another bio-mimic surface with slippery coating also presented great corrosion inhibition due to its excellent insulation between the corrosive medium and base material. However, which coating is suitable for long-term immersion into corrosive environments still remains to investigate. Herein, we firstly fabricated a super-hydrophobic coating on 316 L stainless steel by nanosecond laser ablation combining fluoroalkylsilane modification. Then a slippery coating was obtained by further infusing silicon oil into the as-prepared super-hydrophobic substrate. The PDP and EIS measurements indicate that both fresh super-hydrophobic and slippery surface were observed to improve the corrosion inhibition for the base substrate, and the performance of slippery surface was superior to that of super-hydrophobic surface. Immersion experiments infer that the air cushion of the super-hydrophobic surface was easily destroyed, resulting in a rapid failure of super-hydrophobicity and instability of corrosion resistance. In contrast, after immersed into 3.5 wt.% NaCl solution, the wetting property of oil-impregnated slippery surface almost remained the same. In addition, the electrochemical measurements reveal that the slippery coating presented exceptional anticorrosion behavior after long-term immersion into corrosive liquid. Therefore, the authors believe this study is expected to promote the development of anticorrosive coating for the steel materials. This work is of great importance for employing laser ablation to fabricate slippery surface, which is convenient and effective for metallic corrosion prevention in industrial fields.

Superhydrophilic–superhydrophobic patterned surfaces on glass substrate for water harvesting

Directional water harvesting is a special ability of flora and fauna in nature. Wettability-patterned surfaces inspired by natural structures have been extensively researched and could be a great potential avenue for easing water shortage. However, preparation strategies for these nature-inspired cases, including UV irradiation with mask technology, femtosecond laser direct writing and chemical treatment, are time-consuming, cost-ineffective and environmentally unfriendly. In this paper, robust and durable superhydrophobic (SHB) glass substrate was prepared by using laser-induced backward transfer technique and fluoroalkylsilane modification. Then wedge-shaped superhydrophilic (SHL) patterns on the SHB surfaces were rapidly constructed by inexpensive and commercially available fibre laser ablation for fog harvesting. This facile, cost-effective and non-corrosive preparation method described herein could be an alternative way to construct SHL–SHB patterns on glass substrate, which could be used for microfluidic devices, droplet manipulation and cell screening.

Fabrication of Superhydrophobic Surfaces on Metal Substrates by Nanosecond Laser

Superhydrophobic surfaces on aluminum, stainless steel, titanium alloy, and copper substrates were fabricated by nanosecond laser etching and fluoroalkylsilane modification. Compared with the existing laser beam machining technologies, such as femtosecond laser etching and picosecond laser etching, for fabricating superhydrophobic surface, the method developed by us is inexpensive and high efficiency. The influence of laser etching parameters on the surface morphology and wettability on the superhydrophobic surfaces were studied through orthogonal analysis method. The good superhydrophobicity with contact angle larger than 160° was achieved on the aforementioned 4 kinds of metals.

Electrochemical fabrication of superhydrophobic passive films on aeronautic steel surface

Aeronautic steel is widely used as the structural material in aircrafts. The inherent hydrophilicity of aeronautic steel will result in water clinging and ice adhesion in humid environment, which seriously affect the stability of aircrafts. Therefore, fabrication of superhydrophobic surface on aeronautic steel substrate has considerable industrial significance in improving its service life in humid environment. However, how to introduce superhydrophobicity on the aeronautic steel surface has been rarely focused. Herein, a facile electrochemical etching method was applied for forming passive films on 30Cr2Ni2WVA aeronautic steel surface, and the reduction of surface energy was achieved by fluoroalkylsilane modification. Experimental studies were implemented to investigate the influences of electrochemical process parameters on the wettability of prepared surfaces, and the relatively optimum technical parameters were obtained through comparative analysis of experimental results. The robustness of the superhydrophobic surface covered with passive films was carefully investigated by carrying out different tests including linear abrasion, solid particle impact, ultrasonic cleaning, ultraviolet exposure and thermal cycling. Additionally, we also studied the anti-icing property of the superhydrophobic surface.

Heat Transfer and Fouling Rate at Boiling on Superhydrophobic Surface with TiO2 Nanotube-Array Structure

A superhydrophobic surface coating of a nanotubes array grown directly on a titanium substrate was prepared by using the method of electrochemical anodic oxidation under ultrasonic assistance and fluoroalkyl silane modification. Experimental investigations of nucleate pool boiling and fouling behaviors were carried out to assess the heat transfer enhancement and fouling inhibition on a superhydrophobic titanium-based nanoporous coating. The superhydrophilic titanium-based nanoporous surface and the bare titanium substrate surface were also investigated as contrasts. The results indicate that the heat transfer performance of the superhydrophobic titanium-based nanoporous coating is superior to the bare titanium substrate and the superhydrophilic titanium-based nanoporous surface due to higher density of nucleation sites in the range of low heat fluxes. Besides, the superhydrophobic nanoporous coating also has lower fouling resistance and better antifouling performance at pool boiling of CaCO3 solution in comparison with bare and superhydrophilic surfaces.

Superhydrophobic modification of polyurethane sponge for the oil-water separation

In this work, the fluoroalkylsilane-modified SiO2 nanoparticles (NPs) were immobilized on the polyurethane sponges by a highly efficient drop-coating method using different polymers including poly(vinylidene fluoride), poly(vinylidene fluoride-ter-trifluoroethylene-ter-chlorotrifluoroethylene), polystyrene, and polyurethane as the adhesives to achieve the superhydrophobic modification of the polyurethane sponges for oil-water separation. The successful fluoroalkylsilane modification for the SiO2 NPs was confirmed by TEM, SEM, FITR, XPS, and TGA. Furthermore, the surface-modified polyurethane sponges were investigated by SEM and two-dimensional EDS mapping. The contact angles of the surface-modified polyurethane sponges were in the range of 151.6°–154.3°, which confirmed the realization of the superhydrophobic modification for the polyurethane sponges. The demonstration experiments showed that the resulting surface-modified polyurethane sponge could effectively remove oil from the oil-water mixture by direct absorption or gravity-driven filtration. Moreover, the surface-modified polyurethane sponges possessed not only high absorption capability for different oils including peanut oil, pump oil, and silicone oil but also good reusability. We believe that such novel surface-modified polyurethane sponges might be potential candidates for the oil-water separation.

An economical approach combining vacuum assisted soft imprinting and hydrothermal treatments to fabricate lotus leaf-like biomimetic hierarchical TiO2 structures

Here we report an low-cost method for fabricating 3D hierarchical TiO2 films with lotus-leaf-like micro/nano structures. With some low pressure provided by two middle-sized binder clips, the microscale pillar arrays of lotus leaf could be easily imprinted into the TiO2 sol film. In addition, if a low vacuum was introduced into the imprinting process, the complex laminar sub-microstructure on the micro pillars could also be duplicated with high fidelity. Hierarchical TiO2 micro/nano-structures were subsequently fabricated by the hydrothermal growth of TiO2 nanorods on the micro-structured TiO2 film. SEM observation and XRD analysis revealed that the micro-structured TiO2 film was anatase phase, which served as a nucleation layer for the growth of rutile TiO2 nanorods. This hierarchical surface exhibited a WCA of 155° after surface fluoroalkylsilane modification.