Water-repellent Properties Research Articles

Advanced functional photochromic wearables with fast photo-responsivity, long color-retention, and multi-environmental stability

Smart photochromic wearables have demonstrated attractive prospects in many emerging fields. However, their lower functional performance limits their applications. Herein, we have fabricated a novel photochromic wearable fabric via covalent grafting and chemical isolation technique grafting WO3 nanoflowers onto cellulose. In the charming system, exceptional photochromic properties of WO3 serve as the color-changing material. Besides, incorporated potassium persulfate as a fast-fading reagent is capable of slow oxygen release upon heating. These combined components give the photochromic fabric a rapid response time of 2 s, a fading time of 5 min, and an unprecedented long color-retention (>7 days). Moreover, this photochromic fabric exhibits outstanding rewritability (100 cycles) and exceptional water resistance, maintaining superb photochromic performance even after undergoing standard washing (50 cycles). Moreover, the activation barriers to the photochromic mechanism for the minimum energy pathway were calculated, which provides a theoretical basis for hydrophobic design. The fabric not only imparts water and oil repellence and antifouling properties but also has chemical stability in multi-environments. Notably, the fabrication process is cost-effective, environmentally friendly, and amenable to large-scale production. Such fabrics hold tremendous promise in household products, public facilities and wearable healthcare technologies.

Dual immobilization strategy for slippery surface to achieve durable anti-corrosion and excellent anti-icing

Aluminum alloys always suffer from the deficient corrosion resistance and anti-icing property. Slippery liquid infused porous surfaces (SLIPS) inspired by “Nepenthes” have exhibited great potential in corrosion protection and anti-icing. However, the rapid depletion of the infused lubricants often results in the unsatisfactory long-term protective performances of SLIPS. In this study, a dual immobilization strategy was employed to fabricate a slippery surface with robust lubricant layer. The active lubricants were infused in the nanopores of anodized aluminum oxide (AAO) and grafted on the surface of silanized phytic acid (PA) substrate support simultaneously. Due to the presence of infused and covalently grafted lubricants, the obtained slippery surface possessed excellent and durable water repellency and anticorrosion property. Throughout 21 days of immersion in the 3.5 wt% NaCl solution, the water sliding angle of the slippery surface was lower than 10° and the low frequency impedance of the slippery surface was higher than 2.0 × 106 Ω cm2. Moreover, the slippery surface also possesses self-healing capacities that can automatically seal the scratch and repair the protective performance within 24 h. Furthermore, the cooled water droplet can easily roll away from the slippery surface treated by low temperature freezing. The results suggest that the slippery surfaces prepared using dual immobilization strategy can effectively protect aluminum alloys from corrosion and icing. This study provides a novel insight into the design and construction of SLIPS with excellent durability, which can expand the applications of SLIPS in harsh environments.

Substrate-Independent Superhydrophobic Coating Capable of Photothermal-Induced Repairability for Multiple Damages Fabricated via Simple Blade Coating.

Repairable superhydrophobic surfaces have promising application potential in many fields. However, so far, it is still a challenge to develop a superhydrophobic surface with repairability for multiple types of damage through a simple method. In this paper, a repairable superhydrophobic coating was obtained on various substrates by blade-coating mixtures of polydimethylsiloxane (PDMS), polyvinylidene fluoride (PVDF), and multiwalled carbon nanotubes (MWCNTs) modified with dopamine (PDA) and octadecylamine (ODA). The obtained coating has a good liquid-repellent property with a water contact angle above 150° and a water sliding angle of ∼6° and possesses an excellent absorbance (∼97%) in the wavelength range of 250-2500 nm. Due to its high absorbance, the coating displays an outstanding photothermal effect with a temperature rise of ∼65 °C under irradiation by 1.0 kW/m2 of simulated sunlight. Furthermore, after being degraded by multiple stimuli, including plasma treatment, acid/alkali/oil immersion, sand impact, and the icing-thawing cycle, the coating can recover superhydrophobicity via sunlight irradiation, demonstrating the good photothermal-induced repairability of the coating. It can be expected that the good water-repellent property, photothermal effect, and repairability give this coating a promising prospect in practical applications.

Enhancing Antibacterial and Water-Repellent Properties for the Production of High-Performance Fabrics in Home Textiles

In this research, we aimed to enhance the antibacterial activity and water repellency functionalities of single-layer 100% cotton fabrics on both the face and back sides, utilizing conventional methods. Unlike conventional approaches that often rely on lamination or coating techniques to imbue fabric surfaces with distinct properties, our study pursued a cost-effective strategy using traditional textile finishing methods. By integrating double functionality into cotton fabric, we aimed to circumvent the need for additional equipment and high initial costs associated with other techniques. To achieve this, we improved the antibacterial activity of the fabrics through the incorporation of silver ions in the pad-dry process. Simultaneously, water repellency functionality was introduced through a printing application, where the printing paste, devoid of dyestuff, was combined with functional agents and applied using rotary printing to the fabric’s backside. Following these finishing applications, we conducted comprehensive tests encompassing washing durability, antibacterial efficacy, water repellency, mechanical strength, and fastness properties of the multifunctional fabrics. Characterization tests, including Fourier transform infrared attenuated total reflectance (FTIR-ATR) and scanning electron microscope analyses (SEM-EDX), were performed. The outcome of our study showcased the successful enhancement of double-functional cotton fabric, featuring water repellency and antibacterial efficiency on distinct sides. Furthermore, the results indicated that these functionalities endured up to 20 washing cycles, with fastness and performance tests consistently achieving peak levels.

Improving the water-repellent properties of carbon nanotube-polycarbonate composites by introducing nanoscale patterns into the injection molding process

In this study, we explore the impact of hydrophobic nanomaterials, specifically carbon nanotubes (CNTs), on the water repellency of composite materials. These composites are prepared by combining multilayered or single-layered CNTs with polycarbonate (PC). Our goal was to develop highly water-repellent materials by directly forming nanopatterns on the surface through injection molding to enhance water repellency. Irrespective of the CNT type, widening the spacing between surface patterns and increasing the CNT concentration from 0 to 30 wt% resulted in a notable increase in the water contact angle to 161°, surpassing that of Teflon (108°). Moreover, in the multilayered CNT/PC system, a reduction in the sliding angle was observed compared to that of pure polycarbonate, demonstrating a lotus effect-like trend. Conversely, in the case of single-layered CNTs, despite an increase in the contact angle, the sliding angle did not decrease as significantly as in the multilayered CNTs. This implies that the superior transferability during the injection molding process of multilayered CNT/PC compared to single-layered CNT/PC is the underlying factor. This technology holds promise not only in the realm of mobility, such as in the aviation and automotive industries, but also in the medical field, with applications in microfluidic devices.

Nanotechnology in Construction: Innovations, Applications, and Impacts

Nanotechnology has emerged as a transformative force in the construction industry, revolutionizing traditional building materials and methods. This paper delves into the multifaceted applications of nanotechnology in construction, focusing on its impact on building coatings, materials, colors, insulation, and sensors. By incorporating nanoparticles like carbon nanotubes and titanium dioxide, construction materials gain enhanced mechanical properties and durability. Nano-coatings applied to surfaces such as glass, wood, and concrete offer benefits like water repellence, UV resistance, and antibacterial properties, contributing to energy efficiency and cost savings. Furthermore, advancements in self[1]healing concrete, fire-resistant glass, and smart surfaces demonstrate the potential of nanotechnology to address longstanding challenges in construction. The paper also explores the use of nanotechnology in paints, insulation, and sensors, highlighting innovations such as self-cleaning paints, antistatic coatings, and nano-acoustic insulators. Overall, the integration of nanotechnology into the construction sector promises improved product quality, energy efficiency, and longevity, heralding a new era of sustainable and resilient built environments.

A Critical Review on Triboelectric Nanogenerators (TENGs) with Flame Retardant, Antibacterial, Self-Cleaning, or Water Repellent Properties

A Critical Review on Triboelectric Nanogenerators (TENGs) with Flame Retardant, Antibacterial, Self-Cleaning, or Water Repellent Properties

Holistic approach for fabrication of superhydrophobic MXene-based membrane for enhanced membrane distillation

There is growing interest in membrane distillation (MD) as a means of desalinating seawater with 100 % theoretical salt rejection which has the capacity to address freshwater scarcity. MD has huge potential for commercial applications owing to its low operating temperature and pressure requirements. However, wetting polymeric membranes inhibits water permeance and lowers salt rejection. MXene nanosheet-incorporated polyvinylidene (PVDF) membranes have been constructed for enhanced vapor transport with high water repellence and antiwetting properties. MXene nanosheets in PVDF polymeric matrices are responsible for their high super-hydrophobicity, which can mitigate membrane fouling and wetting during the MD process. As far as experimental outcomes are concerned, the pristine PVDF membrane exhibited severe wetting with salt leakage. Ti3C2Tx MXene nanosheets allow the formation of hierarchical polymeric micro/nanostructures, changing the intrinsic hydrophilicity to super-hydrophobicity. Surface engineering of a PVDF membrane with MXene nanosheets enables efficient saline desalination during the MD process. The surface-engineered MXene/PVDF membrane demonstrated a high-water contact angle of 143° with extremely high self-cleaning characteristics as compared to that of pristine PVDF membrane. As far as the performance of the membrane is concerned, the water flux of the pristine PVDF membrane decreased from 6.5 LMH to 6 LMH after the 14th hour which can be attributed to partial pores wetting during MD operation. Eventually, the pristine PVDF membrane exhibited a continuous salt flux (SF) increase. However, MXene/PVDF membrane showed stable water flux (8 LMH) and negligible SF. The study therefore demonstrates a facile and holistic approach for constructing MXene-based PVDF membranes that exhibit superior antiwetting performance during MD operation.

Nature-Inspired Superhydrophobic Coating Materials: Drawing Inspiration from Nature for Enhanced Functionality.

Superhydrophobic surfaces, characterized by exceptional water repellency and self-cleaning properties, have gained significant attention for their diverse applications across industries. This review paper comprehensively explores the theoretical foundations, various fabrication methods, applications, and associated challenges of superhydrophobic surfaces. The theoretical section investigates the underlying principles, focusing on models such as Young's equation, Wenzel and Cassie-Baxter states, and the dynamics of wetting. Various fabrication methods are explored, ranging from microstructuring and nanostructuring techniques to advanced material coatings, shedding light on the evolution of surface engineering. The extensive applications of superhydrophobic surfaces, spanning from self-cleaning technologies to oil-water separation, are systematically discussed, emphasizing their potential contributions to diverse fields such as healthcare, energy, and environmental protection. Despite their promising attributes, superhydrophobic surfaces also face significant challenges, including durability and scalability issues, environmental concerns, and limitations in achieving multifunctionality, which are discussed in this paper. By providing a comprehensive overview of the current state of superhydrophobic research, this review aims to guide future investigations and inspire innovations in the development and utilization of these fascinating surfaces.

Fabrication of micro/submicron hierarchical structures on ceramic sheet surfaces combining 2-step imprinting and in-plane compression processes

Many organisms have functional microstructured surfaces. Particularly, lotus leaves have hierarchical dual-scale micro/nanostructures on their surface and exhibit highly water repellent properties. We have developed techniques to fabricate patterns on inorganic material surfaces such as ceramics. Applying these techniques to fabricate hierarchical structures can make ceramic surfaces even more promising. In this paper, we prepared 2 kinds of mold with line-and-space patterns with pitches 50 μm and 2 μm and fabricated micro (rough patterns)/submicron (fine patterns) hierarchical structures on sintered ceramic sheets using a newly developed imprinting process with in-plain compression method. We proposed processes for the fabrication of such hierarchical structures, discussed the possibility of higher resolution of the patterns by comparison with the analytical results.

Clean and effective construction of SLIPS from porous polymer surface prepared by supercritical CO2 foaming technology

The gas-confined supercritical CO2 (scCO2) foaming technology is a clean method to prepare porous polymer surfaces but has never been applied to the construction of SLIPS due to the limitation of uneven and hard-controllable cell structure. In this paper, the surface of polystyrene (PS) is covered by a PS surface instead of the frequently-used rigid polymer films as a barrier, subsequently, both PS surfaces are foamed to prepare porous PS surfaces with uniform cell morphology and widely-adjustable cell size, which have active influences on the shear-resistant ability of SLIPS. Meanwhile, there is no solid waste generated in this process, and the production efficiency is at least doubled. The SLIPS with a cell-cell space of 0.07 μm and a mean cell diameter of 0.25 μm presents the optimal shear-resistant ability (CAH = 4.4° ± 0.8° after being sheared at 8500 rpm for 10 min). Consequently, this work proposes a clean, efficient, and facile path for preparing SLIPS with water-repellency, shear resistance, self-clean, and self-healing properties.

A top-down and in situ strategy for intrinsic acicular nanostructure enhanced ultradurable superhydrophobic and anti-icing aramid fabric

Essential requirements of protective clothing with multi-scenario practicability deserve intensive attention. Aramid fabric is widely used to protect industrial and outdoor workers operating under various hazardous conditions but is susceptible to fouling, subzero cold water and icing, resulting in severely deteriorated protective properties. However, the chemical inertness of aramid fabrics limits their further functionalization. This issue is addressed herein by developing a novel top-down strategy to construct an intrinsic densely packed acicular nanostructure on the surface of aramid fiber through the proton donor-assisted deprotonation-induced roughening (PAIR) method. The PAIR treatment consists of extracting hydrogen protons from the amide moiety and controllably dissociating the outer shell of the aramid fibers without destroying its hard-core structure. Such a “rough-surface-on-intact-core” texture endows the fabric with greatly enhanced water repellency, anti-icing and anti-fouling properties without sacrificing its impressive mechanical properties, moisture permeability and flame retardancy. Remarkably, the treated fabric can load 37 times its own weight in water, presenting an increased buoyancy and demonstrates an icing delay time of 1920 s, which is 1150 % that of a pristine aramid fabric. Featuring the easy processability, high endurance and multiple functions, the fabric is promising for applications in personal protective equipment and advanced functional textiles with multiple tasks under harsh weather events.

A Comparative Biodegradation Study to Assess the Ultimate Fate of Novel Highly Functionalized Hydrofluoroether Alcohols in Wastewater Treatment Plant Microcosms and Surface Waters.

Per- and polyfluoroalkyl substances (PFAS) are a class of chemicals present in a wide range of commercial and consumer products due to their water-repellency, nonstick, or surfactant properties, resulting from their chemical and thermal stability. This stability, however, often leads to persistence in the environment when they are inevitability released. We utilized microbial microcosms from wastewater treatment plant (WWTP) sludge to determine how employing different functional groups such as heteroatom linkages, varying chain lengths, and hydrofluoroethers (HFEs) will impact the ultimate fate of these novel PFAS structures. A suite of five novel fluorosurfactant building blocks (F7C3OCHFCF2SCH2CH2OH (FESOH), F3COCHFCF2SCH2CH2OH (MeFESOH), F7C3OCHFCF2OCH2CH2OH (ProFdiEOH), F7C3OCHFCF2CH2OH (ProFEOH), and F3COCHFCF2OCH2CH2OH (MeFdiEOH)) and their select transformation products, were incubated in WWTP aerobic microcosms to determine structure-activity relationships. The HFE alcohol congeners with a thioether (FESOH and MeFESOH) were observed to transform faster than the ether congeners, while also producing second-generation HFE acid products (F7C3OCHFC(O)OH (2H-3:2 polyfluoroalkyl ether carboxylic acid [PFECA]) and F3COCHFC(O)OH (2H-1:2 PFECA). Subsequent biodegradation experiments with 2H-1:2 PFESA and 2H-1:2 PFECA displayed no further transformation over 74 days. Surface water Photofate experiments compared 2H-1:2 PFECA, and 2H-1:2 polyfluorinated ether sulfonate (PFESA) with their fully fluorinated ether acid counterparts, and demonstrated the potential for both HFE acid species to completely mineralize over extended periods of time, a fate that highlights the value of studying novel PFAS functionalization. Environ Toxicol Chem 2024;43:2297-2305. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Preparation and Self-Cleaning Properties of a Superhydrophobic Composite Coating on a Stainless Steel Substrate

In order to improve the anti-fouling of stainless steel surfaces in outdoor or humid environments, a superhydrophobic modification is often used to improve its self-cleaning performance. However, the mechanical stability of superhydrophobic surfaces remains a challenge. In this paper, a two-step preparation method was adopted to prepare the micro–nanocomposite coating, which innovatively combined “top-down” and “bottom-up” approaches, and also coupled together two key factors that affect superhydrophobicity: a rough microstructure, and low surface energy. The silver mirror, adhesion, and pollution-resistance results show that the composite coating samples, which were obtained by optimizing the preparation process, have excellent water repellency and self-cleaning properties. Meanwhile, the samples demonstrate outstanding mechanical stability, and can resist damage from sandpaper and tape. The two-step preparation method was simple, fast, and efficient. This method could be popularized and applied to the preparation of superhydrophobic surfaces on metal substrates.

Engineering a robust, multifunctional superhydrophobic/oleophobic microporous aluminum surface via a two-step chemical etching process

Surfaces with unique wettability properties are gaining attention for their widespread applications. Particularly, superhydrophobic surfaces, known for their remarkable water-repellent properties and low adhesion, have gained substantial interest in recent years owing to their versatile applications. Despite their versatile applications, the durability of such surfaces faces challenges like mechanical abrasion, chemical deterioration, and environmental factors, limiting their effectiveness in real-world scenarios. In this study, we successfully fabricated a mechanically robust, cost-effective, and easy-to-process superhydrophobic surface on an aluminum substrate using a two-step chemical etching process. Initially, the hierarchical microporous (HMP) structure was created through chemical etching, followed by the deposition of a self-assembled layer of PFOTS onto the fabricated aluminum substrate, attaining superhydrophobic and oleophobic properties. The surface exhibits remarkable superhydrophobicity with a water contact angle of 162°, while coupled with oleophobic characteristics against a wide spectrum of oils with surface tensions ranging from 21.5–63.3 mN m − 1. We conducted comprehensive characterizations of surface morphology and chemical composition, while also investigating the impact of surface morphology on wettability, physicochemical stability, and antibacterial properties. Mechanical testing revealed that the surface maintained its superhydrophobicity even after undergoing linear abrasion for a distance of 120 cm under an applied pressure of 12.25 kPa. Furthermore, the surface displayed self-cleaning, and anti-fouling, along with significant antibacterial properties against Staphylococcus aureus bacteria, creating a 23 mm zone of inhibition. We believe the proposed method will inspire the fabrication of large-scale superhydrophobic metallic surfaces endowed with multifunctional properties, making them highly suitable for a wide range of industrial applications.

A review on application areas and surface geometry in superhydrophobic materials

Superhydrophobic surfaces offer many advantages beyond just being hydrophobic (water repellent) to the surface. The superhydrophobic property can be achieved by artificially creating geometric structures on the material surface. These geometric structures reduce the contact area between the liquid and the surface. The contact angle between the liquid and the surface gives rise to two conditions: hydrophobic and hydrophilic. If the contact angle between the surface and the liquid is above 90 degrees, a hydrophobic state occurs. If the angle is below 90 degrees, the surface is in a hydrophilic state. One of these two states is determined depending on the need and provides alternative solutions for many problems that currently await engineering interventions. Scientific studies in the field of superhydrophobia are increasing day by day. Interest in superhydrophobia is expected to grow further, as it offers environmentally friendly and economical solutions to ongoing challenges in various sectors. Superhydrophobic materials also offer a method of preventing icing due to their ability to prevent liquid retention on the material surface through their water repellent properties. Since the reduction of the contact area between the liquid and the material surface on superhydrophobic surfaces leads to a decrease in the friction factor, the friction of the flow on the material will also decrease. These properties of superhydrophobic materials generate interest in sectors such as aviation and marine. This study describes the properties of superhydrophobic surfaces created through various methods on materials, focusing on applications such as anti-icing and reduction of friction factor.

Reactive mesoporous organosoluble multifunctional hyperbranched polymer nanoparticles: Synthesis, post-polymerization reactions and clickable layer-by-layer coating

Synthesis of reactive organosoluble porous polymers, which can be useful for covalent layer-by-layer coatings, is synthetically challenging and not well known. In this work, we demonstrated a new approach to synthesize indole-decorated mesoporous hyperbranched polymer nanoparticles, which can be easily post-modified via triazolinedione (TAD)-indole click reaction. Importantly, further crosslinking of the polymer nanoparticles in solution leads to formation of insoluble mesoporous polymers, where porosity and surface area of the hyperbranched polymer nanoparticles further improved by ∼40%. Consequently, the nanoparticles are useful in layer-by-layer porous coatings and post-surface modifications. While studying their water repellent properties it was noted that nanoparticles having higher surface area/porosity results better water repellent surface which can be further enhanced via suitable surface functionalization using different long chain alkyl functionalities.

Design of functional coating with superior liquid repellency, self-cleaning, photodegradation and thermal insulation properties for building protection

A super-hydrophobic multifunctional coating (SMC) was designed and fabricated by combining commercial TiO2 with polydimethylsiloxane and perfluorodecyltrichlorosilane. The main objective of this research is to enhance the feasibility and effectiveness of SMC coating for building protection. After optimization, the comprehensive performance was significantly improved. The SMC not only significantly improves the water repellency of concrete (decreasing the capillary water absorption by 92.91 %), but also endows concrete with great self-cleaning and photodegradation properties. Additionally, ultraviolet–simulated (90 d) and practical environment (150 d) irradiation tests demonstrate the superior radiative cooling properties of SMC. COMSOL finite element simulation indicates about 20 % of ultraviolet light absorbance and 80 % of visible and near-infrared light reflectance on the SMC. The multifunctional SMC coating not only enhances the water repellency and self-cleaning properties of concrete, but also demonstrates excellent radiative cooling capabilities. These findings highlight the potential of the SMC coating as a promising material for sustainable and energy-efficient building applications.

Thin multifunctional coatings for textiles based on the layer-by-layer application of polyaromatic hybrid nanoparticles

Multifunctional textile coatings were developed using biobased nanoparticles from lignin and fatty acids, achieving significant water repellency, breathability, UV-shielding, and antibacterial properties, while remaining eco-friendly and durable.

Synthesis of Long Alkyl and Fluoroalkyl Substituted Siloxane Copolymers for the Water Repellency of Rammed Earth Walls.

Rammed earth in a built environment has vapor diffusion characteristics and humidity control abilities, each of which is respectively attributed to the porous structures and the hydrophilic properties. Indeed, these structures and properties allow for the easy absorbance of water particles, hence affecting the durability of a rammed earth wall. This paper presents the water-repellency method for rammed earth walls, which utilizes siloxane copolymers containing fluorine. The water-repellent properties are investigated by measuring the contact angle, water absorption rate, and compressive strength after spray-coating with the synthesized siloxane copolymers on the surface of the rammed earth specimens under study. The water contact angle of the specimen, coated with a siloxane copolymer containing 10 mol.% of a silane monomer with a fluorine group, is about 140°. The water absorption of the specimen obtained after immersing in water for 24 h is low, at about 3.5 wt.%. In addition, the compressive strength remains more than 80% of the corresponding strength of the specimen which is not immersed in water. It is confirmed that the use of a 10% by volume of the siloxane copolymer containing the fluorine group may enhance the water-repellent performance and economic competitiveness.