Environmentally benign non-wettable textile treatments: A review of recent state-of-the-art

Micropatterned superhydrophobic meshes coated with low-cost carbon nanoparticles for efficient oil/water separation

Superhydrophobic and superoleophilic meshes have gained considerable attention in oil/water separation in recent years. To fabricate such meshes, surface roughness features can be introduced, and the surface free energy can be lowered, preferably, by utilizing low cost, safe, and readily available materials. Herein, we report a novel approach for fabricating a superhydrophobic copper mesh using low-cost carbon nanoparticles embedded within surface micropatterns. To create the micropatterns, a femtosecond laser was employed. The fabricated mesh exhibited a water contact angle of 168.9° and a roll-off angle of only 5.9°. Additionally, the mesh was highly durable and effectively retained its superhydrophobicity during water jet impact and tape-peeling tests. After 50 cycles of the water jet impact test and 5 cycles of the tape-peeling test, the water contact angle reduced by only 0.3° and 2.3°, respectively. When tested for separating n-hexane/water mixtures, the mesh exhibited a separation efficiency of up to 98%. The separation efficiency remained essentially constant after 10 cycles of n-hexane/water separation. It was observed that the surface micropatterns played a significant role in achieving superhydrophobicity and imparting high durability to the mesh. Meshes lacking these laser-induced micropatterns showed higher wettability, lower durability, and decreased separation performance with repeated use.

VAR Fabric Modification: Inducing Antibacterial Properties, Altering Wettability/Water Repellence, and Understanding Reactivity at the Molecular Level

The present work focuses on the surface coating of VAR technical fibers, consisting of 64% viscose (cellulose), 24% Kevlar, 10% other types of polyamides, and 2% antistatic polymers. Kevlar is an aramid material exhibiting excellent mechanical properties, while cellulose is a natural linear polymer composed of repeating β-d-glucose units, having several applications in the materials industry. Herein, we synthesized novel, tailor-designed organic molecules possessing functional groups able to anchor on VAR fabrics and cellulose materials, thus altering their properties on demand. To this end, we utilized methyl-α-d-glucopyranose as a model compound, both to optimize the reaction conditions, before applying them to the material and to understand the chemical behavior of the material at the molecular level. The efficient coating of the VAR fabric with the tailor-made compounds was then implemented. Thorough characterization studies using Raman and IR spectroscopies as well as SEM imaging and thermogravimetric analysis were also carried out. The wettability and water repellency and antibacterial properties of the modified VAR fabrics were also investigated in detail. To the best of our knowledge, such an approach has not been previously explored, among other factors regarding the understanding of the anchoring mechanism at the molecular level. The proposed modification protocol holds the potential to improve the properties of various cellulose-based materials beyond VAR fabrics.

Asphaltene-Derived Graphene Quantum Dots for Controllable Coatings on Glass, Fabrics, and Aerogels

Graphene quantum dots (GQDs) derived from natural asphaltene byproducts can produce controlled hydrophobic or hydrophilic interfaces on glass, fabrics, and aerogels. A set of facile solvent extraction methods were used to isolate and chemically prepare materials with different surface functionalities from a commercially derived asphaltene precursor. The organic-soluble fraction was used to create hydrophobic and water-repellent surfaces on glass and cotton fabrics. The GQD solutions could also penetrate the pores of a silica aerogel, rendering it hydrophobic. Alternatively, by extracting the more polar fraction of the GQDs and oxidizing their surfaces, we also demonstrate strongly hydrophilic coatings. This work shows that naturally abundant GQD-containing materials can produce interfaces with the desired wettability properties through a straightforward tuning of the solvent extraction procedure. Owing to their natural abundance, low toxicity, and strong fluorescence, asphaltene-derived GQDs could thus be applied, in bulk, toward a wide range of tunable surface coatings. This approach, moreover, uses an important large-scale hydrocarbon waste material, thereby offering a sustainable alternative to the disposal of asphaltene wastes.

Tetrapodal textured Janus textiles for accessible menstrual health

Menstruating individuals without access to adequate hygiene products often improvise with alternatives that pose health risks and limit their participation in society. We describe here a menstrual hygiene product based on low-cost materials, which are integrated onto fabrics to imbue unidirectional permeability. A body-facing "Janus" fabric top layer comprising ZnO tetrapods spray-coated onto polyester mosquito netting imparts hierarchical texturation, augmenting the micron-scale texturation derived from the weave of the underlying fabric. The asymmetric coating establishes a gradient in wettability, which underpins flash spreading and unidirectional permeability. The hygiene product accommodates a variety of absorptive media, which are sandwiched between the Janus layer and a second outward-facing coated densely woven fabric. An assembled prototype demonstrates outstanding ability to wick saline solutions and a menstrual fluid simulant while outperforming a variety of commercially alternatives. The results demonstrate a versatile menstrual health product that provides a combination of dryness, discretion, washability, and safety.

CdO-Nanografted Superhydrophobic Hybrid Polymer Composite-Coated Cotton Fabrics for Self-Cleaning and Oil/Water Separation Applications

The current study presents a simple and cost-competitive method for the development of high-performance superhydrophobic and superoleophilic cotton fabrics coated with cadmium oxide/cerotic acid (CdO/CE)-polycaprolactone (PCL)- and cadmium oxide/stearic acid (CdO/ST)-polycaprolactone-grafted hybrid composites. X-ray powder diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy are used to characterize the CdO/CE-PCL and CdO/ST-PCL and polycaprolactone-modified cotton fabrics. Using an optical contact angle meter, the wetting behavior of corrosive liquids such as coffee, milk, tea, water dyed with methylene blue, strong acids (HCl), strong alkali (NaOH), and saturated salt solution (NaCl) on the CdO-CE/ST/PCL-modified cotton fabrics is assessed as well as the durability of CdO-CE/ST/PCL-modified cotton fabrics in corrosive liquids. Data obtained from the oil-water separation experiment indicate remarkable separation efficiency with oil purity values of ≥99.97 wt %, and high permeation flux values of up to 11,700 ± 300 L m-2 h-1 are observed for surfactant-stabilized water-in-oil emulsions via a gravity-driven technique. From the data obtained, it is concluded that the nano-CdO-grafted superhydrophobic hybrid polymer composite-coated cotton fabrics (CdO-ST/(CE)/PCL/CFs) can be utilized for self-cleaning and oil/water separation applications.

Designing Non-Fluorinated Superhydrophobic Fabrics with Durable Stability and Photocatalytic Functionality

The ability of a superhydrophobic fabric to stay dry and clean has aroused great interest in daily life. Especially, the development of an eco-friendly non-fluorinated water-repellent textile has become a hot topic in recent years. We present a green strategy to achieve self-cleaning textile by in situ deposition of zinc oxide (ZnO) nanoparticles on cotton with subsequent polydimethylsiloxane modification. The prepared cotton fabric exhibits superior water repellency with a water contact angle of 157°. Meanwhile, this superhydrophobic surface can easily be ruined by oil contaminants and then exhibit a decreased water contact angle of 0°. However, the oil-contaminated surface can recover its water repellency after being irradiated. After six cycles of contamination using oleic acid and successive photodegradation, the fabric surface remains superhydrophobic. The obtained superhydrophobic surface does not adversely affect the fabric's strength and air permeability. Therefore, the developed superhydrophobic cotton fabrics have the potential to be used in a variety of industrial scenarios and in daily life.

Kevlar®, Nomex®, and VAR Modification by Small Organic Molecules Anchoring: Transfusing Antibacterial Properties and Improving Water Repellency

The surface modification of fabrics composed of Kevlar^®, Nomex^®, or VAR was extensively investigated. Kevlar^® and Nomex^® are widely-utilized aramid materials, whereas VAR is a technical fabric comprising 64% viscose, 24% para-aramid (Kevlar^®), 10% polyamide, and 2% antistatic fibers. Both aramid materials and cellulose/viscose exhibit exceptional mechanical properties that render them valuable in a wide range of applications. For the herein studied modification of Kevlar^®, Nomex^®, and VAR, we used small organic molecules 3-allyl-5,5-dimethylhydantoin (ADMH) and 3-(acrylamidopropyl)trimethylammonium chloride (APTAC), which were anchored onto the materials under study via graft polymerization. By doing so, excellent antibacterial properties were induced in the three studied fabrics. Their water repellency was improved in most cases as well. Extensive characterization studies were conducted to probe the properties of the modified materials, employing Raman and FTIR spectroscopies, Scanning Electron Microscopy (SEM), and thermogravimetric analysis (TGA).

One-Step Multifunctionalization of Flax Fabrics for Simultaneous Flame-Retardant and Hydro-Oleophobic Properties Using Radiation-Induced Graft Polymerization

This study concerns the one-step radiografting of flax fabrics with phosphonated and fluorinated polymer chains using (meth)acrylic monomers: dimethyl(methacryloxy)methyl phosphonate (MAPC1), 2-(perfluorobutyl)ethyl methacrylate (M4), 1H,1H,2H,2H-perfluorooctyl acrylate (AC6) and 1H,1H,2H,2H-perfluorodecyl methacrylate (M8). The multifunctionalization of flax fabrics using a pre-irradiation procedure at 20 and 100 kGy allows simultaneously providing them with flame retardancy and hydro- and oleophobicity properties. The successful grafting of flax fibers is first confirmed by FTIR spectroscopy. The morphology of the treated fabrics, the regioselectivity of grafting and the distribution of the fluorine and phosphorus elements are assessed by scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (SEM-EDX). The flame retardancy is evaluated using pyrolysis combustion flow calorimetry (PCFC) and cone calorimetry. The hydro- and oleophobicity and water repellency of the treated fabrics is established by contact angle and sliding angle measurements, respectively. The grafting treatment of flax irradiated at 100 KGy, using M8 and MAPC1 monomers (50:50) for 24 h, allows achieving fluorine and phosphorus contents of 8.04 wt% and 0.77 wt%, respectively. The modified fabrics display excellent hydro-oleophobic and flame-retardant properties with water and diiodomethane contact angles of 151° and 131°, respectively, and a large decrease in peak of heat release rate (pHRR) compared to pristine flax (from 230 W/g to 53 W/g). Relevant results are also obtained for M4 and AC6 monomers in combination with MAPC1. For the flame retardancy feature, the presence of fluorinated groups does not disturb the effect of phosphorus.

Flexible biomimetic materials with excellent photothermal performance and superhydrophobicity

Although thousands of superhydrophobic composites have been reported, it is still a challenge to develop eco-friendly superhydrophobic materials by a simple and low-cost strategy. Here, a paper-based superhydrophobic material was prepared by carbon fiber powders and polydimethylsiloxane through a facile spraying method. This obtained material has excellent liquid resistance and self-cleaning properties, whose contact angle reaches 155°. In addition, it possesses excellent photothermal conversion characteristics with a stable surface temperature of 73.4 °C and good water evaporation performance with an evaporation rate up to 1.08 kg/(m2·h) under one solar intensity (100 mW/cm2). Also, it has outstanding self-deicing performance, whose deicing time is 120 s earlier than that of the untreated surface under one solar intensity. An adaptability test shows this strategy of functional coatings can also be applied to other fiber substrates (coating paper, kraft paper, non-woven fabric, paulownia veneer, etc.). Overall, this superhydrophobic material has a promising application prospect in many fields such as waterproof packaging, deicing materials, water evaporation materials, etc.

Development of Cotton Fabrics via EVA/SiO2/Al2O3 Nanocomposite Prepared by γ-Irradiation for Waterproof and Fire Retardant Applications

Development of cotton fabric (CF) properties using nanocomposites via coating method was of considerable interest for wide applications. This article aims at developing CF properties by coating treatment using ethylene–vinyl-acetate (EVA), silicon dioxide (SiO2), aluminum oxide (Al2O3) nanoparticles and γ-irradiation widely used in waterproof and flame retardant applications. EVA-based nanocomposites, EVA/SiO2, EVA/Al2O3, and EVA/SiO2/Al2O3, were synthesized by γ-irradiation and the highest gel content of 81.2–95.3% was achieved at 30 kGy. The physicochemical properties of EVA-based nanocomposites were characterized by FT-IR, XRD, DSC and SEM techniques. Usage of irradiated EVA and EVA-based nanocomposites for treatment of CF by coating technique was successfully achieved. This technique provides a simple and versatile method leading to excellent uniform and smooth surface morphology without aggregation. The weight gain, mechanical properties, thermal properties, water vapor permeability and flame-retardant properties of the modified CF were evaluated. Moreover, compared with control CF, the resistivity of water absorptivity and hydrophobic property and the thermal stability were gained. The flame retardant properties of CF samples were performed using limited oxygen index (LOI) and vertical burning flame tests. LOI percentages of CF/EVA/SiO2, CF/EVA/Al2O3 and CF/EVA/SiO2/Al2O3 increased to 25.3, 27.5, and 29.3%, respectively. Untreated CF ignited and burned rapidly after 5 s. Meanwhile, the treated CF hold flame resistance properties and the burning time prolonged to 25 s. The results of the treated CF providing revealed hydrophobic and protective capability of the fabrics from being destroyed by burning, and support their further use in waterproof and flame retardant applications of fabrics.

Research progress on eco-friendly superhydrophobic materials in environment, energy and biology

In the past few years, bioinspired eco-friendly superhydrophobic materials (EFSMs) have made great breakthroughs, especially in the fields of environment, energy and biology, which have made remarkable contributions to the sustainable development of the natural environment. However, some potential challenges still exist, which urgently need to be systematically summarized to guide the future development of this field. Herein, in this review, initially, we discuss the five typical superhydrophobic models, namely, the Wenzel, Cassie, Wenzel-Cassie, "lotus", and "gecko" models. Then, the existence of superhydrophobic creatures in nature and artificial EFSMs are summarized. Then, we focus on the applications of EFSMs in the fields of environment (self-cleaning, wastewater purification, and membrane distillation), energy (solar evaporation, heat accumulation, and batteries), and biology (biosensors, biomedicine, antibacterial, and food packaging). Finally, the challenges and developments of eco-friendly superhydrophobic materials are highlighted.

Facile fabrication of self-roughened surfaces for superhydrophobic coatings via polarity-induced phase separation strategy

Rough structures have gained increasing attention since they are essential for surfaces with special wettability, which can be used for various applications. It is still a challenge to find a low-cost and simple way to fabricate rough surfaces despite extensive efforts. Herein, we report a facile strategy to fabricate self-roughened surfaces based on polarity-induced phase separation. The strategy relies on the migration of flexible chains of the nonpolar polysiloxane to airside, driven by surface tension and polarity difference with the polar crosslinker, which forms a self-roughened surface with numerous protrusions. It is worth noting that this strategy does not require strict control of procedures, since it is insensitive to environmental changes unlike other phase separation methods, as shown by the results of systematic studies on several key parameters. Modified fabrics and coatings exhibit excellent superhydrophobicity with a water contact angle higher than 160°. Moreover, due to the strong hydrogen bonds formed by the polar urea groups of the crosslinker with substrates, the abrasion resistance of the coating is significantly enhanced. It is believed that the proposed novel and facile strategy will be a promising candidate for industrial manufacturing.

Quality and Quantity Assessment of the Water Repellent Properties of Functional Clothing Materials after Washing

The aim of the research was to evaluate the changes in the surface properties of five functional clothing materials with water-repellent finishes (including PFC-free finish) after 1, 5, and 10 washes with three detergents. A new approach to the interpretation of the water-repellent properties of textile materials is presented, based on two techniques, i.e., the spray test method and contact angle measurements. The results showed that washing materials with hydrophobic finishes can cause significant changes in their properties, which are mainly dependent on the composition and structure of the material, as well as the type of hydrophobic finish. The PFC-free finish is the least resistant to washing. For all materials with PFC finishes, the water repellency depends on the fluorine content on the surface and fabric topography. It was also found that increasing washing frequency resulted in a gradual decrease in water repellency. The loss of water repellency below an acceptable level (Grade 3) occurred after the fifth washing for all materials. Significant differences in the interpretation of the results of the spray test and contact angle measurements were observed. Using these methods separately provides information on the changes in the surface properties of the tested materials; however, their parallel application allows for obtaining complementary data, which is important for the proper interpretation of results.

Advances in the development of superhydrophobic and icephobic surfaces

Superhydrophobicity and icephobicity are governed by surface chemistry and surface structure. These two features signify a potential advance in surface engineering and have recently garnered significant attention from the research community. This review aims to simulate further research in the development of superhydrophobic and icephobic surfaces in order to achieve their wide-spread adoption in practical applications. The review begins by establishing the fundamentals of the wetting phenomenon and wettability parameters. This is followed by the recent advances in modeling and simulations of the response of superhydrophobic surfaces to static and dynamic droplets contact and impingement, respectively. In view of their versatility and multifunctionality, a special attention is given to the development of these surfaces using nanocomposites. Furthermore, the review considers advances in icephobicity, its comprehensive characterization and its relation to superhydrophobicity. The review also includes the importance of the use of superhydrophobic surface to combat viral and bacterial contamination that exist in fomites.

Applications of nanotechnology in smart textile industry: A critical review

Background

In recent years, nanotechnology has been playing an important role in designing smart fabrics. Nanomaterials have been employed to introduce in a sustainable manner, antimicrobial, ultraviolet resistant, electrically conductive, optical, hydrophobic and flame-retardant properties into textiles and garments. Nanomaterial based smart devices are now also being integrated with the textiles so as to perform various functions such as energy harvesting and storage, sensing, drug release and optics. These advancements have found wide applications in the fashion industry and are being developed for wider use in defence, healthcare and on-body energy harnessing applications.

Aim of review

The objective of this work is to provide an insight into the current trends of using nanotechnology in the modern textile industries and to inspire and anticipate further research in this field. This review provides an overview of the most current advances concerning on-body electronics research and the wonders which could be realized by nanomaterials in modern textiles in terms of total energy reliance on our clothes.

Key scientific concepts of review

The work underlines the various methods and techniques for the functionalization of nanomaterials and their integration into textiles with an emphasis on cost-effectiveness, comfort, wearability, energy conversion efficiency and eco-sustainability. The most recent trends of developing various nanogenerators, supercapacitors and photoelectronic devices on the fabric are highlighted, with special emphasis on the efficiency and wearability of the textile. The potential nanotoxicity associated with the processed textiles due to the tendency of these nanomaterials to leach into the environment along with possible remediation measures are also discussed. Finally, the future outlook regarding progress in the integration of smart nano-devices on textile fabrics is provided.

Chitosan/sodium polyborate based micro-nano coating with high flame retardancy and superhydrophobicity for cotton fabric

In this work, a sustainable flame retardant and superhydrophobic cotton fabric was prepared by a two-step process: the cotton fabric was firstly treated with a chitosan/sodium polyborate polyelectrolyte complex water solution to obtain a flame retardant layer, and then treated with a polydimethylsiloxane (PDMS) tetrahydrofuran solution to construct a superhydrophobic layer. The phase-separated chitosan with a micro-nano roughness structure was covered by PDMS, which synergistically improved the hydrophobicity of the cotton fabric. The flammability evaluation indicated that the limiting oxygen index value of the treated fabric was increased to 40.0% from 18.2%, the peak of heat release rate was reduced by 63.8%, and the total heat release was reduced by 57.6% compared with that of the control sample. The enhanced flame retardancy was attributed to the excellent charring ability in the condensed phase. The treated fabric also showed anti-sticking, self-cleaning, and oil/water-separating properties. This coating treatment without any F, Cl, Br, P elements involved is regarded as a clean methodology for producing flame retardant and superhydrophobic cotton fabrics.

Development of polyester filters with polymer nanocomposite active layer for effective dye filtration

Organic dyes such as methyl orange (MO) and methylene blue (MB) are widely used in different industries and have become one of the leading emerging water contaminants. The purpose of the current research is to develop new polymer nanocomposite filters for the effective elimination of the dyes, which are non-biodegradable and not efficiently removed by traditional treatment methods. New padded and covered filters were produced applying polystyrene-acrylic/ZnO nanocomposite on the polyester surface by blade coating and one-bath pad methods. Principal results determined by SEM analysis confirm that functionalised layer can create unprecedented function of filter textile material depending on the way of treatment. Due to the modification, the surface area increased from 5.9 for untreated polyester to 85.2 (padded), 44.6 (covered) m²/g. The measured pore size of produced filters is around 3.4 nm, which corresponds to the mesoporous structure. Our study reported effective filters with the rate of MB and MO removal efficiencies up to 60%. Moreover, a colourless reduced form of MB-leuco-methylene blue (LMB) could be created. The functionalised layer of the developed filters through hydrogen bonding between the -OH groups of styrene-acrylic molecules and the -N(CH₃)₂ groups on LMB can stabilise LMB.

Disposition of Fluorine on New Firefighter Turnout Gear

Firefighter turnout gear is essential for reducing occupational exposure to hazardous chemicals during training and fire events. Per-and polyfluoroalkyl substances (PFASs) are observed in firefighter serum, and possible occupational sources include the air and dust of fires, aqueous film-forming foam, and turnout gear. Limited data exist for nonvolatile and volatile PFASs on firefighter turnout gear and the disposition of fluorine on the individual layers of turnout gear. Further implications for exposure to fluorine on turnout gear are not well understood. Three unused turnout garments purchased in 2019 and one purchased in 2008, were analyzed for 50 nonvolatile and 15 volatile PFASs by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-qTOF-MS) and gas chromatography-mass spectrometry (GC-MS), respectively. Particle-induced gamma ray emission (PIGE), a surface technique, and instrumental neutron activation analysis (INAA), a bulk technique, were used to measure total fluorine. Bulk characterization of the layers by pyrolysis-GC/MS (py-GC/MS) was used to differentiate fluoropolymer (e.g., PTFE) films from textile layers finished with side-chain polymers. The outer layer, moisture barrier, and thermal layers of the turnout gear all yielded measured concentrations of volatile PFASs that exceeded nonvolatile PFAS concentrations, but the summed molar concentrations made up only a small fraction of total fluorine (0.0016-6.7%). Moisture barrier layers comprised a PTFE film, as determined by py-GC-MS, and gave the highest individual nonvolatile (0.159 mg F/kg) and volatile PFAS (20.7 mg F/kg) as well as total fluorine (122,000 mg F/kg) concentrations. Outer and thermal layers comprised aromatic polyamide-based fibers (aramid) treated with side-chain fluoropolymers and had lower levels of individual nonvolatile and volatile PFASs. Equal concentrations of total fluorine by both PIGE and INAA on the outer and thermal layers is consistent with treatment with a side-chain fluoropolymer coating. New turnout gear should be examined as a potential source of firefighter occupational exposure to nonvolatile and volatile PFASs in future assessments.

Robust and durable liquid-repellent surfaces

This review provides a comprehensive summary of characterization, design, fabrication, and application of robust and durable liquid-repellent surfaces.

Creating superhydrophobic, abrasion-resistant and breathable coatings from water-borne polydimethylsiloxane-polyurethane Co-polymer and fumed silica

HYPOTHESIS

The high surface area and branched structure of fumed silica (FS) can be exploited in concert with the hydrophobic properties of polydimethylsiloxane (PDMS) and robustness of polyurethane (PU) to create PDMS-PU and FS grafted coatings with hierarchical structures and enhanced functionalities. The structural features of FS would add to superhydrophobicity; its open-branchlike characteristics would provide air permeability; the use of a tiered coating approach involving a FS-only layer on top of the PDMS-PU coat would create interlocking and strong abrasion-resistance, leading to a multifunctional coating with potential application in filtration and personal protection equipment (PPE).

EXPERIMENTS

PDMS-PU and PDMS-PU-Si copolymer dispersions are synthesized with different monomer molecular weights and FS concentration. Hydrophobicity is measured via water contact angle and wetting resistance measurements. Abrasion resistance is compared by investigating the fiber morphology and hydrophobicity of the coated fabrics after various abrasion cycles. Air flow versus pressure drop experiments are used to measure breathability. Interaction mechanism between substrate/components are explored using infrared spectroscopy.

FINDINGS

The interactions between the substrate, FS, and PDMS-PU can be manipulated to create a novel, tiered coating that exhibits superhydrophobicity, strong abrasion resistance together with desirable air-permeability, thereby providing a versatile and unique coating platform.

Advanced Switchable Molecules and Materials for Oil Recovery and Oily Waste Cleanup

Advanced switchable molecules and materials have shown great potential in numerous applications. These novel materials can express different states of physicochemical properties as controlled by a designated stimulus, such that the processing condition can always be maintained in an optimized manner for improved efficiency and sustainability throughout the whole process. Herein, the recent advances in switchable molecules/materials in oil recovery and oily waste cleanup are reviewed. Oil recovery and oily waste cleanup are of critical importance to the industry and environment. Switchable materials can be designed with various types of switchable properties, including i) switchable interfacial activity, ii) switchable viscosity, iii) switchable solvent, and iv) switchable wettability. The materials can then be deployed into the most suitable applications according to the process requirements. An in-depth discussion about the fundamental basis of the design considerations is provided for each type of switchable material, followed by details about their performances and challenges in the applications. Finally, an outlook for the development of next-generation switchable molecules/materials is discussed.

Multifunctional Textiles Based on Three-Dimensional Hierarchically Structured TiO2 Nanowires

The development of three-dimensional (3D) micro-/nanostructures with multiscale hierarchy offers new potential for the improvement of the pristine textile properties. In this work, a polyester fabric coated with 3D hierarchically structured rutile TiO₂ nanowires (THNWP) was fabricated by a facile hydrothermal strategy. The THNWP samples exhibit markedly improved photocatalytic activities and antibacterial properties owing to their 3D hierarchical architecture constructed by one-dimensional nanowire structures, good crystallinity, excellent light-harvesting capability, and fast electron-transfer rate. Furthermore, the unique 3D hierarchical nanostructures also combine with the monofilament to produce ternary-scale hierarchy, which endows the fabric surface with outstanding superamphiphobicity after further facile fluorination treatment. The supportive air-pockets trapped within the unique ternary-scale architectures are proved to be the crucial factor in the achievement of high liquid repellency, and the highest performing superamphiphobic surface is capable of repelling liquids down to a minimal surface tension of 23.4 mN m^-1. We envision that our findings may possess great potential in the bottom-up design of high-performance textiles.

Biobased Waterborne Polyurethane-Urea/SWCNT Nanocomposites for Hydrophobic and Electrically Conductive Textile Coatings

Waterborne polyurethane-urea dispersions (WPUD), which are based on 100% bio-based semi-crystalline polyester polyol and isophorone diisocyanate, have been successfully synthesized and doped with single-walled carbon nanotubes (SWCNT) to obtain a finishing agent that provides textiles with multifunctional properties. The chemical structure of WPUD has been characterized by Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The thermal properties have been evaluated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical thermal analysis (DMTA). Mechanical properties have been studied by tensile stress-strain analysis. Moreover, the particle size, particle size distribution (PSD), and stability of developed waterborne dispersions have been assessed by dynamic light scattering (DLS), Z-potential, and accelerated aging tests (analytical centrifugation). Subsequently, selected fabrics have been face-coated by the WPUD using knife coating method and their properties have been assessed by measuring water contact angle (WCA), water column, fabric stiffness, and air permeability. The electrical conductivity of textiles coated with SWCNT-doped WPUD has been evaluated by EN 1149 standard. Finally, the surface morphologies of uncoated and coated fabrics have been studied by scanning electron microscopy (SEM). All of the synthesized polyurethane-ureas provide the coated substrates with remarkable water-repellency and water column, being therefore a more sustainable alternative to waterproof coatings based on fluoropolymers, such as PTFE. The additivation of the polymeric matrices with SWCNT has led to textile coatings with excellent electrical conductivity, maintaining water column properties, giving rise to multifunctional coatings that are highly demanded in protective workwear and technical textiles.

Detection and diversity of fluorinated oil- and water-repellent coatings on apparel fibers

Fluorinated coatings, often used for oil and water repellency and stain resistance in fabrics, are potentially persistent forensic fiber markers. However, they have received limited attention because of challenges in their detection caused by the small size of a single fiber and thin nature of stain-resistant coatings. Here, we utilize a sensitive fluorine-selective analytical technique to detect and evaluate diversity of fluorinated coatings in apparel. Twelve clothing items marketed as stain-resistant were tested with nine showing oil- and water-repellent properties. Fluorinated pyrolysis products of single fibers from all of the nine items were detected by gas chromatography coupled to plasma-assisted reaction chemical ionization mass spectrometry (GC-PARCI-MS), indicating the prevalence of fluoropolymer coatings in stain-resistant clothing articles. Furthermore, three major classes of fluorinated coatings were identified via principal component analysis of pyrogram patterns. The classes were coating-specific and did not correlate with fiber core and color, highlighting a robust detection methodology. To evaluate the effect of fiber lifting in crime scenes, fibers from the 9 clothing items were used to develop a multinomial logistic regression model based on pyrogram principal components. The model was then tested using fibers subjected to contact with Post-it^® notes. The test set fibers were sampled from the clothing items of the training set and from three additional garments of differing color but the same brands as the training set. The coating classes were predicted with 98.4% accuracy, confirming robust classification of fiber coatings using py-GC-PARCI-MS regardless of fiber color, core, and fiber lifting.

Design of Experiment Approach to Optimize Hydrophobic Fabric Treatments

Polymer materials can be functionalized with different surface treatments. By applying nanoparticles in coating, excellent antimicrobial properties are achieved. In addition, antimicrobial properties are enhanced by hydrophobic surface modification. Therefore, the goal of this work was to modify the process parameters to achieve excellent hydrophobicity of polymer surfaces. For this purpose, a Design of Experiment (DoE) statistical methodology was used to model and optimize the process through six processing parameters. In order to obtain the optimum and to study the interaction between parameters, response surface methodology coupled with a center composite design was applied. The ANNOVA test was significant for all variables. The results of the influence of process parameters showed that, by increasing the pressure, concentration of hydrophobic compounds and dye concentration, water vapor permeability was enhanced, while by decreasing weight, its efficiency was enhanced. Moreover, the increase in the temperature enhanced water vapor permeability but decreased the resistance to water wetting. An optimal process with ecologically favorable 6C fluorocarbon (68.802 g/L) surpassed all preliminary test results for 21.15%. The optimal process contained the following parameters: 154.3 °C, 1.05 bar, 56.07 g/L dye, 220 g/m² fabric. Therefore, it is shown that DoE is an excellent tool for optimization of the parameters used in polymer surface functionalization.

Electrospun Hydrophobic Polyaniline/Silk Fibroin Electrochromic Nanofibers with Low Electrical Resistance

Electronic textiles (E-textiles) have been an area of intense industrial and academic research for years due to their advanced applications. Thus, the goal of this study was to develop highly conductive silk fibroin electrochromic nanofibers for use in E-textiles. The silk nanofibers were prepared by an electrospinning technique, and the conductive polyaniline (PANI) was added to impart the electrical conductivity and electroactive property to the resultant electrospun silk composite nanofibers. The experimental results showed that tuning the electrospinning procedure could control the morphology of the composite nanofibers, thus altering their mechanical properties and surface wettability. Furthermore, the developed PANI/silk composite fibers possess electroactive and electrochromic properties, such as adjusting the applied voltage. The developed strategy demonstrated the feasibility of incorporating not only electrical functionality but also electroactivity into sustainable silk nanofibers using electrospinning technique.

Elemental Fluorine Detection by Dielectric Barrier Discharge Coupled to Nanoelectrospray Ionization Mass Spectrometry for Nontargeted Analysis of Fluorinated Compounds

The growing use of fluorochemicals has elevated the need for nontargeted detection of unknown fluorinated compounds and transformation products. Elemental mass spectrometry (MS) coupled to chromatography offers a facile approach for such analyses by using fluorine as an elemental tag. However, efficient ionization of fluorine has been an ongoing challenge. Here, we demonstrate a novel atmospheric-pressure elemental ionization method where fluorinated compounds separated by gas chromatography (GC) are converted to Na₂F⁺ for nontargeted detection. The compounds are first introduced into a helium dielectric barrier discharge (DBD) for breakdown. The plasma products are subsequently ionized by interaction with a nanoelectrospray ionization (nano-ESI) plume of sodium-containing aqueous electrolytes. Our studies point to HF as the main plasma product contributing to Na₂F⁺ formation. Moreover, the results reveal that Na₂F⁺ is largely formed by the ion-neutral reaction between HF and Na₂A(NaA)_n⁺, gas-phase reagent ions produced by nano-ESI where A represents the anion of the electrolyte. Near-uniform fluorine response factors are obtained for a wide range of compounds, highlighting good efficiency of HF formation by DBD regardless of the chemical structure of the compounds. Detection limits of 3.5-19.4 pg of fluorine on-column are obtained using the reported GC-DBD-nano-ESI-MS. As an example of nontargeted screening, extractions from oil-and-water-repellent fabrics are analyzed via monitoring Na₂F⁺, resulting in detection of a fluorinated compound on a clothing item. Notably, facile switching of the ion source to atmospheric-pressure chemical ionization with the exact same chromatographic method allows identification of the detected compound at the flagged retention time.

Progress in Sol-Gel Technology for the Coatings of Fabrics

The commercial availability of inorganic/organic precursors for sol-gel formulations is very high and increases day by day. In textile applications, the precursor-synthesized sol-gels along with functional chemicals can be deposited onto textile fabrics in one step by rolling, padding, dip-coating, spraying or spin coating. By using this technology, it is possible to provide fabrics with functional/multi-functional characteristics including flame retardant, anti-mosquito, water- repellent, oil-repellent, anti-bacterial, anti-wrinkle, ultraviolet (UV) protection and self-cleaning properties. These surface properties are discussed, describing the history, basic chemistry, factors affecting the sol-gel synthesis, progress in sol-gel technology along with various parameters controlling sol-gel technology. Additionally, this review deals with the recent progress of sol-gel technology in textiles in addressing fabric finishing, water repellent textiles, oil/water separation, flame retardant, UV protection and self-cleaning, self-sterilizing, wrinkle resistance, heat storage, photochromic and thermochromic color changes and the improvement of the durability and wear resistance properties.

Advances in photocatalytic self-cleaning, superhydrophobic and electromagnetic interference shielding textile treatments

The use of nanomaterials in textiles provides many new opportunities and advantages for users and manufacturers; however, it comes with some of its downsides and challenges which need to be understood and overcome for enhancing the applicability of these products. This review article discusses the recent progress in developing self-cleaning and conductive textiles as two of the leading research fields of smart textiles. In particular, different aspects of fabricating nanocoatings for photocatalytic self-cleaning, superhydrophobic and electromagnetic interference (EMI) shielding effect will be brought to light. The theoretical concepts, mechanisms, latest fabrication methods along with their potential applications will be discussed. Moreover, the current drawbacks of these fields will be underlined and some recommendations for future research trajectories in terms of performance, current limitations, sustainability and safety will be proposed. This review article provides a comprehensive review on the state-of-the-art achievements in the field, which will be a valuable reference for researchers and decision makers.

Fabrication of Cotton Fabric with Superoleophilic/Superhydrophobic Characteristic on the Modified Surface by Using Fluoroalkylated Oligomeric Silica/Triazine Derivative Nanocomposites

Two fluoroalkylated vinyltrimethoxysilane oligomer (RF-(CH2CHSi(OMe)3)n-RF; n = 2, 3; RF = CF(CF3)OC3F7:RF-VMSi) in methanol reacted with aqueous sodium carbonate solution containing 2-hydroxy-4,6-dichloro-1,3,5-triazine sodium salt (TAZ) to provide two fluoroalkylated oligomeric silica/TAZ nanocomposites (RF-VMSiO2/TAZ). The original cotton fabric gives an oleophilic/hydrophilic property on its surface; however, modified cotton fabric surface with RF-VMSiO2/TAZ composites was demonstrated to provide highly oleophobic/superhydrophobic property on the surface. We can observe a remarkable time-dependent decrease of the contact angle of dodecane (oil) on the modified surfaces, and the contact angles of dodecane were found to decrease effectively from 55 ∘ –83 ∘ to 0 ∘ over 5–30 s to supply superoleophilicity with keeping the superhydrophobic property on the surfaces. The modified cotton fabric having superoleophilic/superhydrophobic property was applicable to the separation membrane to separate oil and water. Interestingly, modified cotton fabric was found to adsorb efficiently only droplets of oil spread on the water interface due to its unique surface wettability.

Progress in biomimetic leverages for marine antifouling using nanocomposite coatings

Because of the environmental and economic casualties of biofouling on maritime navigation, modern studies have been devoted toward formulating advanced nanoscale composites in the controlled development of effective marine antifouling self-cleaning surfaces.

Superhydrophobic Surface with Stepwise Multilayered Micro- and Nanostructure and an Investigation of Its Corrosion Resistance

We develop a fluorine-free preparation of the superhydrophobic surface on an aluminum alloy with anticorrosion performance and mechanical robustness. The surface morphology, chemical composition, and water repellency were determined with SEM, CLSM, EDS, FT-IR, TG, and contact-angle measurements, respectively. The aluminum matrix superhydrophobic surface (STA-PDMS-ZnO sample) was able to display excellent repellency to water with a WCA of 152° and a WSA of 2°. The outstanding superhydrophobicity on the as-prepared surface was greatly related to the construction of stepwise multilayered micro- and nanostructure within the superhydrophobic surface. Because of the special surface structure, the mechanical robustness and corrosion resistance of the STA-PDMS-ZnO sample were improved. Notably, the anticorrosion mechanism by air pockets was explained by the comparison of two superhydrophobic surfaces prepared with the same low-surface-energy chemicals. The superhydrophobic surface with a multilayered micro- and nanostructure (STA-PDMS-ZnO sample) showed greater corrosion resistance than the surface coated by superhydrophobic modification (control sample). This is because of the entrapments of numerous air pockets within the aluminum matrix superhydrophobic surface, thus strengthening the corrosion resistance. On the basis of the results, the multidimensional superhydrophobic surface is promising for having a good application future in the field of metal corrosion protection.

Environmentally responsive and anti-bugs textile finishes - Recent trends, challenges, and future perspectives

Bugs, such as microorganisms and insects, are present in the environment and sometimes can be health-hazardous if the living environment is not maintained following proper hygienic regulations. In the present scenario of increasing public awareness, environmental consciousness, and growing demand for easy-care, and disinfected textiles, the manufacturing of protective and easy-to-care textiles has become a key necessity of the modern world. Comfortable, clean, hygienic, antimicrobial, and insect repelling properties of textile goods are gaining the accelerating research momentum as a basic requirement to produce multifunctional textiles. These functional finishes have numerous applications such as in-home textiles, bed nets, and tenting, camping gear as well as in military uniforms. Synthetic antimicrobial and insect repellents are quite effective against insects and microscopic organisms but are slightly toxic to the human being and the environment. To overcome these problems, researchers are considering natural agents for functional finishes, but their effectiveness is less durable to textile material. Besides needful advantages, the excessive use of dyes in finishing processes heavily required washing cycles and ultimately release various types of hazardous dyes or wasteful effluents in the environment. This review reports the chemical composition and recent developments in textile finishes, particularly antimicrobial and insect repellent textile finishes. A large number of commonly used antimicrobial agents (i.e. chitosan, zwitterionic compounds, silver and silver-based compounds, titanium dioxide nanoparticles, imidazolium salts, triclosan and quaternary ammonium salts) and insect repellent textile finishes (i.e. N‑N‑diethyl‑m‑toluamide, permethrin, cypermethrin, pyrethrum, picaridin, bioallethrin, citriodiol and essential oils) have been presented. Finally, the review is wrapped up with major research gaps/challenges, concluding remarks, and future opportunities in this area of research.