Superhydrophobic Functions Research Articles

Synthesis of super-hydrophobic CuO/ZnO layered composite nano-photocatalyst

The introduction of super-hydrophobicity into the field of photocatalysis has attracted the attention of many researchers nowadays. Here, CuO nanowires were synthesized via thermal oxidation method. The flower-like ZnO nanostructures were self-assembled with CuO nanowires by hydrothermal growth method. The functionalized super-hydrophobic CuO/ZnO layered composite nano-photocatalyst was obtained though polydimethylsiloxane (PDMS) grafting. We analyzed the effects of zinc sources, hydrothermal reaction time, solution concentration and surfactant concentration on the properties of the composite nano-photocatalyst. FESEM micrographs revealed CuO/ZnO layered composite nanostructures, which were composed of CuO nanowires with uniform morphology and carnation-like ZnO nanoflowers. XRD spectrum showed CuO/ZnO layered composite nano-photocatalyst possessed pure CuO phase and the wurtzite structure of ZnO. UV–vis spectrum manifested that the composite nanostructures had desired light absorption for ultraviolet light band and the contact angle (CA) results confirmed the successful modification of super-hydrophobic functionalization. After the modification of PDMS, the CuO/ZnO layered composite nano-photocatalyst prepared with the optimal conditions shows desired photocatalytic properties and super-hydrophobicity. The stable super-hydrophobic property after photocatalytic degradation is expected to improve self-cleaning and broaden the application field of photocatalyst.

Antiliquid-Interfering, Antibacteria, and Adhesive Wearable Strain Sensor Based on Superhydrophobic and Conductive Composite Hydrogel.

Conductive hydrogels are promising multifunctional materials for wearable sensors, but their practical applications require combined properties that are difficult to achieve. Herein, we developed a flexible wearable sensor with double-layer structure based on conductive composite hydrogel, which included the outer layer of silicone elastomer (Ecoflex)/silica microparticle composite film and the inner layer of P(AAm-co-HEMA)-MXene-AgNPs hydrogel. Through covalently cross-linking silicone elastomer on the surface of the hydrogel polymer, we bonded a thin Ecoflex film (100 μm) on the P(AAm-co-HEMA)-MXene-AgNPs hydrogel with robust interface, which can easily adhere to the Ecoflex/SiO2 microparticle composite film by silicone glue. The Ecoflex/SiO2 microparticle composite film endows the strain wearable sensor with superhydrophobic function that could maintain the stability under stretching or bending. Moreover, it can effectively resist the interference of water droplets and water flow. The P(AAm-co-HEMA)-MXene-AgNPs hydrogel exhibits outstanding antibacterial activity to inhibit Staphylococcus aureus, Escherichia coli, and even drug-resistant Escherichia coli. In addition, the flexible wearable sensor exhibited good self-adhesive performance by changing the reaction temperature of hydrogel and can adhere strongly onto various materials. The conductive composite hydrogel reported in this work contributes an innovative strategy for the preparation of multifunctional flexible wearable sensor.

A flower-like waterborne coating with self-cleaning, self-repairing properties for superhydrophobic applications

A durable waterborne coating with superhydrophobic function has great application in construction, wooden furniture, vehicles, electronic instruments, and leather finishes. Here, we exploit a facile and scalable strategy for constructing durable wood products with superhydrophobic, self-cleaning, and self-repairing properties through a microencapsulation approach, which includes sodium dodecylbenzene sulfonate as a carrier, polytetrafluoroethylene (PTFE) as wall material, and vinyl triethoxy silane (VTES) as core material. The superhydrophobic character is attributed to the –CH3 in stearic acid molecules that successfully grafted onto zinc acetate to generate zinc stearate (ZnSt2), forming a micron flower-like arrayed on the surface of the wood. Combining an uncomplicated immersion and heat treatment route, the collapsed coating can be recovered and the surfaces with the superhydrophobic structure can be regained. This durable coating strategy has high application value in many fields, for instance, wooden furniture, wooden structure buildings, and the protection of historic sites.

Machine learning model for understanding laser superhydrophobic surface functionalization

A general machine learning (ML) framework of surface wetting is proposed by considering a broad range of factors, including solid surface topography, solid surface chemistry, liquid properties, and environmental conditions. In particular, an XGBoost-based ML model is demonstrated for learning the surface wetting behaviors processed by a laser-based surface functionalization process, namely nanosecond laser-based high-throughput surface nanostructuring (nHSN). This is the first known attempt to apply machine learning to surface wetting by considering both surface topography and surface chemistry properties. Novel microscale and nanoscale topography parameters viz., roughness, fractal, entropy, feature periodicity are defined with suitable computer algorithms to comprehensively describe the surface topography. A novel set of surface chemistry parameters such as polarity, volume, and amount of functional groups are also used as the machine learning model input. Upon analyzing the importance of each parameter for the nHSN process, surface chemistry shows the greatest importance in determination of surface wettability, while surface morphology also plays a part in influencing the wettability. • A machine learning model is firstly proposed for surface wettability considering both topography and chemistry. • Fractal dimension, 2D-entropy, and periodicity are used to describe surface morphology. • Polarity and functional groups are used to describe surface chemistry. • The results showed that the surface chemistry is the dominant feature while surface topography plays a supportive role.

Fabrication of Superhydrophobic Ni-Co-BN Nanocomposite Coatings by Two-Step Jet Electrodeposition

The stability of hydrophobic surface has an important influence on the application of superhydrophobic function. The destruction of hydrophobic micro-nano structures on the material surface is the main factor leading to the loss of superhydrophobic property. In order to improve the corrosion resistance of superhydrophobic surface, Ni-Co-BN nanocomposite coatings with superhydrophobic property were prepared on 45 steel by two-step jet electrodeposition. The surface morphology, water contact angle, and corrosion resistance of the samples were measured and characterized by scanning electron microscope, surface contact angle measuring instrument, and electrochemical workstation. The results of electrochemical analysis show that the superhydrophobic property improved the corrosion resistance of Ni-Co-BN nanocomposite coating. The enhanced corrosion resistance is of great significance to the integrity of the microstructure and the durability of the superhydrophobic function.

A cost effective strategy to fabricate STA@PF@Cu2O hierarchical structure on wood surface: aimed at superhydrophobic modification

Cuprous oxide nanoparticles (Cu2O NPs), phenol formaldehyde (PF) resin, and stearic acid (STA) were used to fabricate hierarchical core/shell structures to endow wood with superhydrophobic function, in which the preparation of Cu2O NPs and the synthesis of PF were carried out simultaneously in one system. The Cu2O NPs with the shape of a symmetrical tetrahexahedron were prepared in this work, and this novel shape is beneficial for creating a superhydrophobic surface. A relatively rough structure in micro/nanoscale was formed on the wood surface after being sprayed with PF@Cu2O coating, which played a vital role in the fabrication of superhydrophobic wood surfaces, as expected. Morphological analysis and surface free energy calculations verified that STA reduced the surface free energy. Application of 12 layers of PF@Cu2O coating followed by 2 h immersion in STA ethanol solution produced wood surfaces with low water permeability and high water contact angles of 153.3°, 153.2°, 150.5° on cross, radial, and tangential sections, respectively. Abrasion tests coupled with subsequent exposure to acidic and alkaline conditions indicated that the coating was resistant to both mechanical wear and chemical degradation. This two-step coating strategy used inexpensive ingredients and could have potential to application as water repellency protection of wood timber.

Fabrication of biomimetic superhydrophobic and anti-icing Ti6Al4V alloy surfaces by direct laser interference lithography and hydrothermal treatment

Nature gives us a large number of inspirations in designing functional materials. Many plant leaves with self-cleaning properties are ubiquitous in nature. These plants have hierarchical structures, which have extreme repellency to liquids and have considerable technical potential in various applications. Herein, we present a method for fabricating bionic taro leaf surfaces by direct laser interference lithography (DLIL) and hydrothermal treatment. The micro-pillar array structure (MPA) was fabricated by DLIL, and a layer of nano-grass structure (NG) was grown on it by hydrothermal treatment. Experiments indicate that the hierarchical composite structures not only have a satisfactory superhydrophobic function with the apparent contact angle (CA) of 172° and sliding angle (SA) of 4°, but also have a strong anti-icing ability with the delay time (DT) of 3723 s. The method is simple and high-efficient for fabricating bionic self-cleaning and anti-icing surfaces.

Superhydrophobic Functionalization of Cotton Fabric via Reactive Dye Chemistry and a Thiol–ene Click Reaction

A straightforward method for imparting superhydrophobic character to cotton textiles using methods based in textile processing and organic synthesis was developed. Cotton fabric was first treated with a common dye anchor, cyanuric chloride, which was subsequently reacted with cysteamine to yield a thiol function on the surface. Thiol–ene click chemistry was employed to attach alkyl chains to render the surface hydrophobic. Effects of temperature and reaction time on the click reaction step were investigated to optimize the process, and a water contact angle exceeding 150° was obtained after reaction at 100 °C and 60 min. Furthermore, it was shown that both AIBN and hydrogen peroxide are effective initiators for the click reaction. The efficacy of the resulting textile in separating hydrocarbons from water was demonstrated. This straightforward preparation of a superhydrophobic textile is most promising in that it is accomplished without incorporating perfluorinated functional groups or nanoparticles.

A Tunable Optical Bragg Grating Filter Based on the Droplet Sagging Effect on a Superhydrophobic Nanopillar Array.

Nanostructures have been widely applied on superhydrophobic surfaces for controlling the wetting states of liquid microdroplets. Many modern optic devices including sensors are also integrated with micro- or nanostructures for function enhancement. However, it is rarely reported that both microfluidics and optics are compatibly integrated in the same nanostructures. In this paper, a novel microfluidic-controlled tunable filter composed of an array of periodic micro/nanopillars on top of a planar waveguide is proposed and numerically simulated, in which the periodic pillars endow both the Bragg grating and the superhydrophobic functions. The tunability of grating is achieved by controlling the sagging depth of a liquid droplet into the periodic pillars. Simulation results show that a narrow bandwidth of 0.4 nm and a wide wavelength tuning range over 25 nm can be achieved by such a microfluidic-based tunable optofluidic waveguide Bragg grating filter. Moreover, this proposed scheme can be easily modified as a refractive index sensor with a sensitivity of 103 nm per refractive index unit.

PEA/V-SiO2 core-shell structure for superhydrophobic surface with high abrasion performance

Organic/inorganic core-shell nanostructure of PEA/V-SiO2 emulsion has been firstly synthesized along with comparison of conventional SiO2 and pure PEA materials . Their chemical bondings and morphology properties have been observed though characterization methods such as transmission electron microscopy, X-ray photon spectrum and infrared spectrum, etc. The nanoparticle of mean diameter within 200 nm has been obtained that was well dispersed into the pure solvent. After that, the water repelling textile has been prepared to measure the surface contact angle which reached above 151.5°. The super hydrophobic function abrasion resistance is also characterized and such improvement is attributed to the highly entanglements and nanostructure established by PEA/V-SiO2 above the textile surface.

Hierarchical, Self-Healing and Superhydrophobic Zirconium Phosphate Hybrid Membrane Based on the Interfacial Crystal Growth of Lyotropic Two-Dimensional Nanoplatelets.

We demonstrate a facile route to in situ growth of lyotropic zirconium phosphate (ZrP) nanoplates on textiles via an interfacial crystal growing process. The as-prepared hybrid membrane shows a hierarchical architecture of textile fibers (porous platform for fluid transport), ZrP nanoplatelets (layered scaffolds for chemical barriers), and octadecylamine (organic species for superhydrophobic functionalization). Interestingly, such a hybrid membrane is able to separate the oily wastewater with a high separation efficiency of 99.9%, even at in harsh environments. After being chemically etched, the hybrid membrane is able to restore its hydrophobicity autonomously and repeatedly, owing to the hierarchical structure that enables facile loading of healing agent. We anticipate that the concept of implanting superhydrophobic self-healing features in anisotropic structure of lyotropic nanoparticles will open up new opportunities for developing advanced multifunctional materials for wastewater treatment, fuel purification, and oil spill mitigation.

Inkjet Printing Enabled Controllable Paper Superhydrophobization and Its Applications.

Papers' intrinsic interconnected porous structures and hydrophilic properties usually results in difficulty and complexity in partial functionalization and regulation processes because the capillary effect may lead to the fast diffusion of modifiers from one side to the other. Here, we report a simple and innovative inkjet printing approach that led to precise hydrophobic functionalization controllable in both planar and steric dimensions. Fabrication of Janus superwetting papers and superwettable patterned papers with high precision was achieved by computer-controlled inkjet printing. Elaborate controls of ink quantity enabled superhydrophobic functionalization on one side of the paper substrate, with the opposite side superhydrophilic. Static water contact angles up to 154° were obtained on the inkjet-printed side of the paper, thanks to an appropriate combination of surface chemistry with dual-scale surface roughness. Furthermore, paper-based microfluidics were fabricated and the resolution of which were estimated to be ca. 600 μm. Meanwhile, a paper-based analytical device for colorimetric sensing of Ni(II) was designed and demonstrated based on superwettable patterned papers by inkjet printing. The inkjet printing approach reported here represents a key step forward in fabricating Janus materials and complicate patterns for practical applications.

Rationally Designed, Multifunctional Self-Assembled Nanoparticles for Covalently Networked, Flexible and Self-Healable Superhydrophobic Composite Films

For constructing bioinspired functional films with various superhydrophobic functions, including self-cleaning, anticorrosion, antibioadhesion, and oil-water separation, hydrophobic nanomaterials have been widely used as crucial structural components. In general, hydrophobic nanomaterials, however, cannot form strong chemical bond networks in organic-inorganic hybrid composite films because of the absence of chemically compatible binding components. Herein, we report the rationally designed, multifunctional self-assembled nanoparticles with tunable functionalities of covalent cross-linking and hydrophobicity for constructing three-dimensionally interconnected superhydrophobic composite films via a facile solution-based fabrication at room temperature. The multifunctional self-assembled nanoparticles allow the systematic control of functionalities of composite films, as well as the stable formation of covalently linked superhydrophobic composite films with excellent flexibility (bending radii of 6.5 and 3.0 mm, 1000 cycles) and self-healing ability (water contact angle > 150°, ≥10 cycles). The presented strategy can be a versatile and effective route to generating other advanced functional films with covalently interconnected composite networks.

Study on properties and mechanisms of luminescent cement-based pavement materials with super-hydrophobic function

In this study, super-hydrophobic and luminescent cement pavement materials (SLCPM) were prepared, and the effects of the long afterglow luminescent materials and hydrophobic materials on luminescent properties and hydrophobicity of SLCPM were investigated. The results indicated that the mechanical performance of SLCPM was improved with the addition of luminescent powder (LP), but the opposite was true for the addition of reflective powder (RP). The superior luminescent properties of SLCPM could be found when the content of the LP was about 25% and the optimum content of the RP was maintained at 10%. The initial brightness could reach 96.56% of the maximum initial brightness after lighting for 30 min, which have more stable long afterglow performance and higher identification. The super-hydrophobic surface coating has excellent stability, self-cleaning performance and long-term stability, which can effectively reduce the liquid infiltration. After the test was finished, the surface contact angle and rolling angle could still reach 152.2° and 5.4°, respectively. It is concluded that doping appropriate LP can not only optimize the distribution of hydration products, but also improve compactness and initial brightness of SLCPM; while doping a large amount of RP can obviously reduce its strength due to its reaction with hydration products. These obtained results would provide a new thought on the design of the road pavement in low lighting environment.

Low cost and facile preparation of robust multifunctional coatings with self-healing superhydrophobicity and high conductivity

Superhydrophobic and conductive multifunctional coatings have been receiving great attention in recent years due to their wide potential applications. Nevertheless, a simple and cost-effective approach is still lacked. Herein, photocatalytic TiO2 nanoparticles and graphite particles were blended with fluorinated polysiloxane and methyltris(methylethylketoxime)silane, and followed by simply spraying onto various substrates for superhydrophobic functionalization under ambient-drying, in which the graphite particles and TiO2 nanoparticles could not only lead to the micro/nano-roughness structures for coatings but also endow the coatings with the conductivity and photocatalysis. These as-prepared coatings are not only superhydrophobic but also have the high conductivity. They also can be coated on the fabrics for the oil/water separation and deposited on flammable objects as the fire-shielding layer. This multifunctional coating is robust under the external taped or pressed forces and very stable whether in the acid-alkali and salty environment or during long hours of UV irradiation. And most of all, this coating could repair its superhydrophobicity even after mechanically abraded or polluted with organics. The design and fabrication of this multifunctional coating may find immediate usage in a wide range of areas.

基于大理石石粉的超疏水涂层制备及性能

本文以固化后的有机硅聚合物为低表面能物质，大理石石粉纳米颗粒为无机填料，喷涂在不同基材的表面后，制备了具有超疏水性能的PTFMS-TEOS杂化涂层。考察了大理石石粉与有机硅聚合物复合的比例及温度对涂层疏水性的影响。用接触角测量仪和扫描电子显微镜分别对超疏水表面进行了结构分析和形貌表征。结果显示，当大理石石粉与PTFMS-TEOS质量比1:3时杂化涂层表面具有较好的超疏水功能，静态接触角可达153˚，这主要是涂层表面含有低表面能氟原子及具有纳米粗糙结构共同作用的结果。 A super hydrophobic PTFMS-TEOS hybrid coating was prepared after solidified silicone polymer as low surface energy material, marble powder and nano particle as inorganic filler and sprayed on different substrates. The effect of the proportion and temperature of marble stone powder and organosilicon polymer on the hydrophobicity of the coating was investigated. The surface of the superhydrophobic surface was analyzed and characterized by the contact angle measuring instrument and the scanning electron microscope respectively. The results show that when the marble powder and PTFMS-TEOS mass ratio is 1:3, the surface of the hybrid coating has super hydrophobic function, and the static contact angle can reach 153 degrees, which is mainly due to the joint action of low surface energy fluorine atoms and nano rough structure on the coating surface.

Corrosion resistance of a superhydrophobic micro-arc oxidation coating on Mg-4Li-1Ca alloy

A micro-arc oxidation (MAO)/zinc stearate (ZnSA) composite coating was fabricated via MAO processing and subsequent sealing with electrodeposition of a superhydrophobic ZnSA. The surface morphologies, chemical composition and corrosion resistance of the coatings were investigated using field-emission scanning electron microscopy, Fourier transform infrared, X-ray diffraction and electrochemical and hydrogen evolution measurements. Results indicated that the MAO coating was efficiently sealed by the following superhydrophobic ZnSA coating. The MAO/ZnSA composite coating significantly enhanced the corrosion resistance of Mg alloy Mg-4Li-1Ca due to its superhydrophobic function. Additionally, corrosion mechanism was suggested and discussed for the composite coating.

Controllable Superhydrophobic Coating on Cotton Fabric by UV Induced Thiol‐ene Reaction for Wettability Patterning and Device Metallization

Superhydrophobic surfaces in nature have attracted a great deal of interest not only for fundamental understanding but also for practical applications through mimicking the nature. Fluorochemicals, due to their intrinsic low surface energy, have been widely applied as artificial superhydrophobic functionalization materials with excellent performance. However, the use of these materials for practical applications might be restricted due to the relative high cost and potential hazards to human health. In this work, a low‐cost and environmentally friendly short silane chain material is developed for fabricating superhydrophobic surfaces. A transparent photoactive coating is obtained by polycondensation of trichlorovinylsilane on cotton fabrics. The coating shows excellent superhydrophobicity. After being grafted with vinyl group, the coating can be easily functionalized using a photoclick thiol‐ene reaction. The thiol‐ene reaction has resulted in highly uniform polymer networks, which makes it possible to realize the rapid wettability switch from superhydrophobic to superhydrophilic state. Such ability makes it potentially viable to prepare well‐defined cotton patterning by printing, and realize flexible electronic devices when electrodes are printed on the fabrics.

Superoleophobic surfaces on stainless steel substrates obtained by chemical bath deposition

Superhydrophobic surfaces have shown great potential in domestic and industrial applications. However, these surfaces lose their superhydrophobic functions once being contaminated by oily liquids. In this work a simple chemical bath deposition method is reported to fabricate superoleophobic surfaces on steel substrates that repel both water and oil. The synthesis of superoleophobic surfaces involves the fabrication of the micro/nanometre-scale origami-ball-like structures on steel substrates, followed by the modification of low surface energy material. The fabricated surfaces have glycerol, peanut oil and hexadecane contact angles larger than 150° and roll-off angles smaller than 10°. This method is highly efficient because it takes only 5 min to create the surface re-entrant structures that are required by superoleophobicity. The prepared surfaces showed remarkable durability and retained superoleophobicity even after exposure to high and low temperatures (−30 and 100°C), and UV irradiation. This work will enrich the processing methods of the superoleophobic surfaces on stainless steel substrates.

Superhydrophobic functionalization of cutinase activated poly(lactic acid) surfaces

Controlled enzymatic hydrolysis of PLA surfaces, followed by ring opening of AKD, leads to superhydrophobic surfaces (WCA >150°).