Durable Superhydrophobicity Research Articles

Transparent superhydrophobic film with anti-fouling and anti-scaling ability by facile method of dip-coating SiO2 Sol

In the past decades, the studies of materials with transparency and durable superhydrophobicity have captured much attention because of the versatile uses in outdoor glass wall, automobile windshield and solar panel. In this paper, a superhydrophobic and transparent SiO2 film with transmittance over 44% was obtained on glass substrate with a facile method of dip-coating without further modification. The contact angle and sliding angle of water droplet on the superhydrophobic film is 163.1° and 4°, respectively. The results reveal the performance of superhydrophobicity originates from the synergistic effects of rough SiO2 structures and hydrophobic alkyl with low surface energy. The SiO2 coating exhibits self-cleaning ability, anti-fouling property and anti-scaling performances. Furthermore, the SiO2 coatings have good thermal stability and resistance ability to acid and base. The techniques adopted here have the advantage of simple process, low cost and fluorine-free treatment, which may provide an useful reference for the preparation of transparent and superhydrophobic film in practice.

Wodyetia Bifurcate Structured Fibrous Fabrics with Durable Superhydrophobicity for High-Efficiency Oil-Water Separation

Wodyetia Bifurcate Structured Fibrous Fabrics with Durable Superhydrophobicity for High-Efficiency Oil-Water Separation

Hierarchical Artificial Compound Eyes with Wide Field-of-View and Antireflection Properties Prepared by Nanotip-Focused Electrohydrodynamic Jet Printing.

Artificial compound eyes (ACEs) endowed with durable superhydrophobicity, wide field-of-view (FOV), and antireflection properties are extremely appealing in advanced micro-optical systems. However, the simple and high-efficiency fabrication of ACEs with these functions is still a major challenge. Herein, inspired by moth eyes, ACEs with hierarchical macro/micro/nano structures were fabricated using the combination of nanotip-focused electrohydrodynamic jet (NFEJ) printing and air-assisted deformation processes. The NFEJ printing enables the direct and maskless fabrication of hierarchical micro/nanolens arrays (M/NLAs) without intermediate steps. The introduction of M/NLAs on the eye surface significantly improves the water hydrophobic performance with a water contact angle of 161.1° and contact angle hysteresis (CAH) of 4.2° and generally decreases the reflectance by 51% in the wavelength range of 350-1600 nm in comparison to the macroeye without any structures. The contact angle remains almost unchanged, and the CAH slightly increases from 4.2° to 8.7° after water jet impact for 20 min, indicating a durable superhydrophobicity. Moreover, the results confirm that the durable superhydrophobic ACEs with antireflection properties exhibit excellent imaging quality and a large FOV of up to 160° without distortion.

Superhydrophobic Copper Materials with Excellent Durability and Regeneration Based on Self-Similarity in Structure and Composition

The widespread application of artificial superhydrophobic material is hindered by the poor durability and regeneration of artificial superhydrophobicity. The problem is expected to be resolved by endowing the superhydrophobic material with self-similarity. Herein, Copper-based superhydrophobic material intensified by furfuryl alcohol resin (Cu/FAR) with long-term durability and high strength is developed, and the obtained Cu/FAR composite reveals excellent and durable superhydrophobicity. Moreover, it is a remarkable fact that the as-prepared superhydrophobic Cu/FAR exhibits outstanding durability and maintenance of superhydrophobicity grounded on the good self-similarity in micro-structure, chemical structure and composition both externally and internally. Consequently, the superhydrophobicity can be maintained or regenerated without difficulty even if superhydrophobic surface has been damaged or fouled accidentally. Therefore, the method provides a new thought to prepare superhydrophobic material with robust durability and outstanding maintenance.

Ultra-thin self-healing vitrimer coatings for durable hydrophobicity

Durable hydrophobic materials have attracted considerable interest in the last century. Currently, the most popular strategy to achieve hydrophobic coating durability is through the combination of a perfluoro-compound with a mechanically robust matrix to form a composite for coating protection. The matrix structure is typically large (thicker than 10 μm), difficult to scale to arbitrary materials, and incompatible with applications requiring nanoscale thickness such as heat transfer, water harvesting, and desalination. Here, we demonstrate durable hydrophobicity and superhydrophobicity with nanoscale-thick, perfluorinated compound-free polydimethylsiloxane vitrimers that are self-healing due to the exchange of network strands. The polydimethylsiloxane vitrimer thin film maintains excellent hydrophobicity and optical transparency after scratching, cutting, and indenting. We show that the polydimethylsiloxane vitrimer thin film can be deposited through scalable dip-coating on a variety of substrates. In contrast to previous work achieving thick durable hydrophobic coatings by passively stacking protective structures, this work presents a pathway to achieving ultra-thin (thinner than 100 nm) durable hydrophobic films.

Multifunctional Superhydrophobic Composite Coatings with Remarkable Passive Heat Dissipation and Anticorrosion Properties

Effective surface passive heat dissipation and durable superhydrophobicity are highly desired for promoting more flexible applications of power-intensive energy systems of aluminum and aluminum-bas...

One-Step Methods to Fabricate Durable Superhydrophobic Coatings for Flexible Electronic Sensors

Inspired by lotus leaves in nature, superhydrophobic surfaces have attracted extensive attention in many fields. However, their complex preparation process, poor durability and high cost seriously restrict their large-scale application in industrial production. Based on the good flexibility and durability of carbon nanofibers, several simple modifier-free one-step approaches were adopted to fabricate a durable CNF/PVDF/PDMS conductive superhydrophobic coating. The fabricated coating not only possesses good superhydrophobicity to many kinds of liquids, but also has excellent self-cleaning and anti-fouling properties. In addition, the superhydrophobicity of the obtained multifunctional coating is stable even after harsh bending fatigue deformation, long immersion times and high-temperature treatment. Due to its strong adhesion and excellent conductivity, the CNF/PVDF/PDMS coating displays reliable mechanical stability and superior sensitivity. These distinct features make the obtained conductive superhydrophobic coating a good candidate for multifunctional smart sensors, with great application prospects in gesture detectors, waterproof wearable electronics and health monitors.

Development of Highly Durable Superhydrophobic Coatings by One-Step Plasma Spray Methodology

This study aims to minimize the mechanical, chemical and thermal damages on the blades of a compressor used in aerospace engines by developing a superhydrophobic coating on the blade surface. In the absence of any information in open literature for the fabrication of such coatings, an one-step plasma spray process was implemented. For this, a well mixed powder of Ni and Ti was used as feedstock material. The superhydrophobicity characteristic of the coating was confirmed by the measurement of the contact (165°) and sliding angles (8 ± 1°) by the sessile drop technique. The adhesion test of the coating showed the high force of adhesion at the interface with a failure limit of 40.85 MPa. Furthermore, the abrasion test depicted an excellent abrasion resistance of the coating. These two investigations indicated that the coatings had a very high mechanical durability. The coatings also showed an excellent thermal stability up to 400 °C. Beyond this temperature (at 600 and 900 °C), the superhydrophobic characteristic changed for hydrophobic. The pH and corrosion tests were also performed to assess the chemical stability of coatings. They showed that the coatings retained the superhydrophobic property for pH ranging between 9.5 and 2.4. Beyond this range, at pH = 10 and pH = 2, the contact angles were 138° and 143°, respectively. In addition, the coatings exhibited a better corrosion resistance than the substrate and coatings developed by using other deposition techniques.

Robust Microcapsules with Durable Superhydrophobicity and Superoleophilicity for Efficient Oil-Water Separation.

The poor ultraviolet (UV) resistance and insufficient solvent compatibility are challenges for long-term storage and service of oil-water separation materials in practical applications. Herein, a superhydrophobic/superoleophilic surface with nano- to microscale hierarchical structures was formed spontaneously on robust microcapsules (MCs) via in situ polymerization and a sol-gel surface treatment. The resultant MCs possessed superior UV-resistant and solvent-proof superhydrophobicity. The water contact angles (WCAs) of the MC coating remained above 160° and the sliding angles (SAs) were below 3° after 9 days of UV aging test or 20 days of nonpolar and polar aprotic solvent immersion tests. More interestingly, these MCs can be used to separate the oil phase from its aqueous emulsion effectively, achieving a high and reusable separation efficiency with over 90% oil purity after 10 cycles of filtrations even after 13 days of UV aging. Therefore, these novel MCs will exhibit effective oil-water separation performance, superior chemical stability, outstanding reusability, and long-term storage stability for promising practical applications.

Wood-inspired superelastic MXene aerogels with superior photothermal conversion and durable superhydrophobicity for clean-up of super-viscous crude oil

It remains a great challenge to develop functional aerogels with superior mechanical robustness, durable superhydrophobicity, and excellent photothermal conversion ability for the promising next generation of oil/water separation materials and energy regulation systems. Herein, inspired by wood structures, we proposed a facile strategy to develop MXene aerogels with super-elasticity, self-cleaning, excellent joule heating and superior photothermal conversion ability. Functionalized cellulose nanocrystal was synthesized via green mechanochemistry, which served as a wetting modifier and dispersant. MXene was applied to construct functional networks in waterborne polyurethane. With fine-tuning of nucleation-driving, the desirable microstructures could be controllably diversified for structure-adaptable functionality. The wood-inspired MXene aerogel showed durable superhydrophobicity (CA ≈ 152°), mechanical superelasticity (76.2% strain remaining after 100 compress-release cycles), highly efficient absorption capacity of light oil (63 g/g) and superior photothermal conversion ability. Also, the as-prepared MXene aerogel demonstrated ultrahigh viscosity crude oil (c.a.130000 mPa.s) absorption capacity of 24.5 g/g under 1 sun irradiation and recyclability of 76% after 5 cycles, much higher than those of the reported. This study provides a promising strategy for constructing integrated multifunctional aerogels with superior mechanical robustness to meet the increasing demands in many fields such as energy regulation devices and crude oil absorbents.

Facile Fabrication of Non-fluorinated Durable Superhydrophobic Cotton Fabric

The superhydrophobic surface is easy to lose the superhydrophobicity in the practical applications, due to the fact that the micro- and nanoscale rough structure is easily damaged. Therefore, it is one of the challenges to endow solid surface with durable superhydrophobic property. In this work, the environment-friendly superhydrophobic cotton fabric was prepared by dip-coating methodology. Meanwhile, the cotton fabric was endowed with durable superhydrophobicity. Herein, the octadecylamine was utilized to reduce the surface free energy of cotton fabric. However, octadecylamine was only adsorbed on the fabric surface. Therefore, the hydrophobic resin was employed to supply enough adhesion force. As a result, the limitation that traditional methods frequently utilize additional nanoparticles to construct hierarchical rough surfaces was broken. The water contact angles of the coated cotton fabric at room temperature and 70 °C reached 154.4±0.6° and 120±1.1 °, respectively. Moreover, the coated cotton fabric still reserved superhydrophobic property after 30th cycle’s abrasion and exhibited excellent hydrophobicity after 500th cycle’s abrasion. In addition, the surface free energy of original cotton fabric reduced by 54.7 % so that the coated cotton fabric had outstanding repellency to hydrochloric acid, sodium hydroxide solution, coffee and sodium chloride solution, respectively.

Copper nanoparticle decorated non-woven polypropylene fabrics with durable superhydrophobicity and conductivity

In this study, a facile method was prepared to fabricate highly flexible, conductive and superhydrophobic polymer fabrics. Copper nanoparticles (CuNPs) were decorated on polypropylene fabrics using a simple spraying method and superhydrophobicity was obtained after vacuum drying for 4 h without any surface modifier. Accumulation of CuNPs constituted coral-like rough micro-nano structures, forming a stable Cassie model and endowing the surface with dense charge transport pathways, thus resulting in excellent superhydrophobicity (water contact angle ∼159°, sliding angle ∼2.3°) and conductivity (sheet resistance ∼0.92 Ω sq−1). The fabrics displayed superior waterproof and self-cleaning properties, as well as great sustainability in the water. Additionally, the superhydrophobicity and conductivity can be almost maintained after heat treatment, wear testing, water droplet impinging, weak alkali/acid treatment and repeated bending-kneading tests. These superhydrophobic and conductive fabrics that are free from moisture and pollution can be a reliable candidate to solve the water-penetration issue in the rapid development of flexible electronics.

Highly compressible and durable superhydrophobic cellulose aerogels for oil/water emulsion separation with high flux

Nowadays high porosity aerogels are widely applied in wastewater purification, while the fragility and unversatility of nascent cellulose aerogels limited the application in oil/water filtering separation. Here, highly compressible, elastic, superhydrophobic cellulose/poly(vinyl alcohol) (PVA) composite aerogels were fabricated via combination of chemical cross-linking, freeze drying and silanization. The obtained cellulose/PVA aerogels exhibited durable superhydrophobicity with WCA of 156.6 °, even maintaining 155.0 ° after 30 days. Synergistic effects of physical entanglement, chemical cross-linking and H-bond network between cellulose and PVA molecular chains endowed the aerogels with excellent compressibility and recoverability. The aerogels exhibited maximum compressive stress of 490.7 kPa at 90% strain, even without reduction in mechanical strength under 70% compressive strain for 10 cycles. More importantly, the strengthened aerogels exhibited remarkable separation performances for both immiscible oil/water mixtures and surfactant-stabilized water-in-oil emulsions. Fascinating permeation flux of up to 7176.3 L m−2 h−1 and total separation amount as high as 4550.6 L m−2 with separation efficiency of 98.5% for water-in-cyclohexane emulsion were harvested. Thus, this work provides a green, sustainable and mass-producible cellulose-based aerogel for high-efficiency oily wastewater remediation.

Fabrication and Potential Applications of Highly Durable Superhydrophobic Polyethylene Terephthalate Fabrics Produced by In-Situ Zinc Oxide (ZnO) Nanowires Deposition and Polydimethylsiloxane (PDMS) Packaging.

Considerable attention has been devoted to the in-situ deposition of zinc oxide (ZnO) nanowires (ZnO-NWs) on the surface of organic supports, due to their very wide applications in superhydrophobicity, UV shielding, and nanogenerators. However, the poor interfacial bond strength between ZnO-NWs and its support limits their applications. Herein, we developed a facile process to grow robust ZnO-NWs on a polyethylene terephthalate (PET) fabric surface through simultaneous radiation-induced graft polymerization, hydrothermal processing, and in-situ nano-packaging; the obtained materials were denoted as PDMS@ZnO-NWs@PET. The introduction of an adhesion and stress relief layer greatly improved the attachment of the ZnO-NWs to the support, especially when the material was subjected to extreme environment conditions of external friction forces, strong acidic or alkaline solutions, UV-irradiation and even washing with detergent for a long time. The PDMS@ZnO-NWs@PET material exhibited excellent UV resistance, superhydrophobicity, and durability. The ZnO-NWs retained on the fabric surface even after 30 cycles of accelerated washing. Therefore, this process can be widely applied as a universal approach to overcome the challenges associated with growing inorganic nanowires on polymeric support surfaces.

Study on dynamics and freezing behaviors of water droplet on superhydrophobic aluminum surface

In this work, a kind of superhydrophobic aluminum surface (treated-Al-SA) is fabricated by chemical etching using hydrochloric acid and hydrogen peroxide, and then treated by stearic acid. The surface of treated-Al-SA has typical hierarchical structure, which hold its durable superhydrophobicity under water droplet impact test, bending test, temperature test, humidity test and corrosive liquids test. Moreover, treated-Al-SA show excellent self-cleaning property at the different tilt angle under room temperature. Results on the dynamic behavior of water droplet is indicated the good anti-adhesion and superhydrophobicity of the treated-Al-SA. The whole freezing process of the water droplets on the surface of untreated-Al and treated-Al-SA is observed. The freezing time of treated-Al-SA is 59 s, which is longer than that of untreated-Al. It is estimated that the different anti-freezing behavior is caused by the thermal conductivity between the water droplet and plate, which is provided an insight into freezing characteristics of water droplet. This study is offered the novel opinion of the superhydrophobic aluminum surface produced by chemical etching, which may help the application of structured aluminum surface.

Efficient fabrication of lightweight polyethylene foam with robust and durable superhydrophobicity for self-cleaning and anti-icing applications

The poor robustness and durability of superhydrophobic surfaces under various externally imposed stresses have become a challenging issue for practical applications. Here, an efficient dissolution and modification strategy is proposed for facilely fabricating superhydrophobic polyethylene (F-PE/SiO2) foam with 98.6% porosity using sodium chloride (NaCl) as a sacrificial template and superhydrophobic nano-silica particles as a surface chemical modifier. A microscale porous and interconnected 3D framework is formed when NaCl is dissolved and the nano-silica particles adsorb on the surface of interconnected pores to form nanoscale structures. The F-PE/SiO2 foam exhibits a water contact angle (CA) of 158 ± 2° and a sliding angle (SA) of 4 ± 2°. Interestingly, the F-PE/SiO2 foam could maintain its superhydrophobicity under 980 Pa pressure of water droplet impacting and 8.1 kPa pressure of water flow impacting. Besides robust dynamic superhydrophobicity, the F-PE/SiO2 foam exhibits exceptional mechanical durability against knife scratching, tape-peeling, bending-twisting, and ultrasonication in ethanol because of unique hierarchical micro-nanostructure and the stably adsorbed nano-silica particles. Impressively, the F-PE/SiO2 foam maintains superhydrophobicity upon abrasion damage until all the thickness is worn away, which are potentially advantageous in practical applications. Moreover, this F-PE/SiO2 foam also demonstrated excellence in anti-wetting, self-cleaning and anti-icing, which makes the product can effectively reduce the damage caused by surface pollution, ice formation, and other natural factors when applied to oil-water separation and insulation material of refrigerator.

Preparation of superhydrophobic and superoleophilic cotton-based material for extremely high flux water-in-oil emulsion separation

Highly stable emulsified water-in-oil mixtures from industrial processes have severe impact on the environment. As their abundance is increasing worldwide, the methods to effectively separate these emulsified water–oil mixtures have attracted significant interest in recent years. Herein, a durable superhydrophobic cotton-based material (SCM) using poly(vinyl phenol), 1,3-phenylene bisoxazoline, and raw cotton was developed. The as-prepared SCM possesses superhydrophobicity (water contact angle > 150°) and superoleophilicity (oil contact angle < 5°). The SCM has excellent repellence not only toward pure water, but also hot water and corrosive aqueous liquids. The superwetting composite also exhibits durable superhydrophobicity after long-term immersion in organic solvents. Moreover, after the compression process, the superwetting material exhibits a remarkable oil–water separation performance. Very high permeation flux values of up to 10,400 ± 400 L m−2h−1 and 867,500 ± 30,300 L m−2h−1 bar−1 are observed for the surfactant-stabilized water-in-oil emulsion by employing gravity-driven and external pressure filtration, respectively, with excellent efficiencies (oil purity of ≥ 99.97 wt%). The outstanding separation performance for various oils and organic solvents, stability in harsh chemical and physical environments, robustness, and recyclability of the superhydrophobic composite make SCM an excellent candidate for large scale application.

Ultradurable Superhydrophobic Natural Rubber‐Based Elastomer Enabled by Modified Multiscale Leather Collagen Fibers

AbstractSuperhydrophobicity is vital to natural rubber‐based materials and can endow materials with intriguing features, such as self‐cleaning. Normally, low surface energy and surfacial micro/nanostructure are the two premises of superhydrophobicity. However, the fragility of micro/nanostructures in natural rubber (NR) composite surfaces makes the maintenance of durable superhydrophobicity under external forces difficult. Thus, the application of NR composite elastomers is limited in industrial fields. In this work, a novel NR‐based elastomer is prepared by uniquely dispersing perfluorooctytriethoxysilane‐modified leather collagen fibers (M‐LCF) with multiscale structures into rubber matrix. The as‐prepared NR composite with 40% M‐LCF content displays excellent superhydrophobicity with a water contact angle of 156°, and the endowed superhydrophobicity is ultradurable and can be retained after 2000 cycles of mechanical abrasion under a pressure of 100 kPa. Moreover, the prepared material features superior self‐cleaning performance and mechanical properties. The reported work may serve as a basic for fabricating materials with durable superhydrophobicity.

Green Fabrication of a Multifunctional Sponge as an Absorbent for Highly Efficient and Ultrafast Oil-Water Separation.

Oil leakage results in serious environmental pollution and severe waste of resources, which makes the development of low-cost, environmentally friendly, high-capacity, and durable oil absorbents an urgent task. In this paper, superhydrophobic coatings of activated carbon (AC)–TiO2–PDMS@PDMS were developed without using any fluorine-containing reagents. The TiO2 particles were grown on the AC surface to form AC–TiO2 powders. The hydrophilic AC–TiO2 powders were further grafted with polydimethylsiloxane (PDMS) molecules (AC–TiO2–PDMS) to achieve superhydrophobicity through covalent reaction between PDMS and TiO2 under UV light. The AC–TiO2–PDMS powder was mixed with a PDMS polymer to form a superhydrophobic coating solution, which made the commercial sponge obtain durable superhydrophobicity. It showed high liquid repellency and antifouling ability toward various liquids and drinks. Taking advantage of the large surface area and high absorption capacity of AC, the coated sponge showed superior high absorption capacity (up to 100–158 g/g) toward various oils and organic solvents with a high absorption speed. Besides, the sponge showed high reusability that could be repeatedly used to absorb various oils and organic solvents. Moreover, the sponge also presented photocatalytic capability, which could repeatedly photodegrade the oil contaminants without influencing the superhydrophobicity, therefore largely increasing the recyclability and lifetime of the sponge. It also could separate immiscible oil–water mixtures with high efficiency and continuously remove oils from water. It was chemically stable and mechanically durable and could resist various harsh conditions without losing its superhydrophobicity. This study developed a facile, cost-effective, and environmentally friendly method to fabricate very promising absorbents for large-scale oil and solvent cleanups and recovery.

Facile synthesis of composite films featuring bulk superhydrophobicity, durability, and repairability for aquatic show

Synthesis of bulk superhydrophobic composite materials with durable and repairable properties is of important theoretical and practical significance. Herein, a bulk superhydrophobic composite film (BSCF) is fabricated by integrating organic polymer components, polyurethane acrylate (PUA) and polydimethylsiloxane (PDMS), and inorganic component, silica particles (SiO2). Due to the bulk deposition and construction of the covalently cross-linking polymer scaffolding, the composite film exhibits a unique bulk superhydrophobic property, which is capable of being exposed to the surface under mechanical shear to preserve durable superhydrophobicity. Therefore, the extreme water repellency of the BSCF maintains unaltered even cyclic sandpaper abrasion is conducted (>150 cycles). By exploiting the advantage of the extreme water repellency inside the composite film bulk, the BSCF is also able to repair its deprived superhydrophobicity via a sanding treatment (>30 cycles), which is completely different from the depletion of healing agents. Furthermore, the aquatic light-reflective function of superhydrophobic materials is exploited in this work for the first time and the exploitation of it may broaden the potential application fields of superhydrophobic materials in deep-sea exploitation, undersea transportation, and aquatic decoration. Based on the aquatic light-reflective principle, a series of patterns on the BSCF surface display dazzling light under the illumination of a flashlight and the aquatic show is successfully realized on each layer of the BSCF. Our studies convincingly show a new direction to synthesize composite materials featuring bulk superhydrophobic, durable, and repairable performances for various potential applications.