Environmentally Friendly and Breathable Fluorinated Polyurethane Fibrous Membranes Exhibiting Robust Waterproof Performance

Balsam-Pear-Skin-Like-Structure Polyvinylidene Fluoride/Ethylene-Vinyl Alcohol Fibrous Membrane for Highly Efficient Oil/Water Separation Through One-Step Electrospinning

The rapid growth of industrial activities has significantly increased oil demand, leading to wastewater contamination with oil and causing severe environmental pollution. Traditional oil-water separation techniques, such as gravity separation, filtration, and chemical treatments, are hindered by low efficiency, high energy consumption, and secondary pollution. Membrane separation technology has emerged as a promising solution due to its simplicity, low energy consumption, and high efficiency. In this study, we report the fabrication of a novel polyvinylidene fluoride/ethylene-vinyl alcohol (PVDF/EVOH) nanofibrous membrane (NFM) with a unique balsam-pear-skin-like structure using a one-step electrospinning process. The membrane's superhydrophobicity and superoleophilicity were achieved via water vapor-induced phase separation (WVIPS), by optimizing the rheological properties and mixing ratio of EVOH and PVDF precursor solutions. The resulting PVDF/EVOH (PE12-3) NFM exhibits exceptional properties, achieving separation efficiencies of 99.4% for heavy oil and 98.9% for light oil, with a heavy oil flux of 18,020 L m-2 h-1-significantly surpassing previously reported performances. Additionally, the membrane shows excellent recyclability, making it ideal for large-scale oil-water separation in wastewater treatment and environmental remediation. This one-step fabrication strategy offers an efficient and scalable approach for developing high-performance membranes to tackle oil pollution in water.

Porous polymers: structure, fabrication and application

The porous polymer is a common and fascinating category within the vast family of porous materials. It offers valuable features such as sufficient raw materials, easy processability, controllable pore structures, and adjustable surface functionality by combining the inherent properties of both porous structures and polymers. These characteristics make it an effective choice for designing functional and advanced materials. In this review, the structural features, processing techniques and application fields of the porous polymer are discussed comprehensively to present their current status and provide a valuable tutorial guide and help for researchers. Firstly, the basic classification and structural features of porous polymers are elaborated upon to provide a comprehensive analysis from a mesoscopic to macroscopic perspective. Secondly, several established techniques for fabricating porous polymers are introduced, including their respective basic principles, characteristics of the resulting pores, and applied scopes. Thirdly, we demonstrate application research of porous polymers in various emerging frontier fields from multiple perspectives, including pressure sensing, thermal control, electromagnetic shielding, acoustic reduction, air purification, water treatment, health management, and so on. Finally, the review explores future directions for porous polymers and evaluates their future challenges and opportunities.

One-Step Fabrication of Poly(vinylidene Fluoride-Co-Hexafluoropropylene)/Perfluorodecyltriethoxysilane Fibrous Membranes with Waterproof, Breathable, and Radiative Cooling Properties

Functional membranes with waterproof, breathable, and thermal regulation capabilities are increasingly sought after across various industries. However, developing such functional membranes commonly involves complex multi-step preparation processes. Herein, we introduced perfluorodecyltriethoxysilane (FAS) into the poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) solution for one-step electrospinning, successfully fabricating membranes that combine these properties. The hydrophobicity of the PVDF-HFP/FAS membrane was greatly improved with the water contact angle increased from 120.6° to 142.9° and the solar reflectance rising from 72% to 92% due to the presence of fluorocarbon segments. The synergistic effect of enhanced hydrophobicity, small pore size, and elevated solar reflectivity resulted in robust water resistance (62 kPa), excellent water vapor transmission rate (12.4 kg m-2 d-1), and superior cooling performance (6.4 °C lower than commercial cotton fabrics). These findings suggest that the proposed PVDF-HFP/FAS membranes, characterized by desired multifunction characteristics and scalable production, hold great potential for application in diverse strategic fields.

Preparation and Properties of GMS/HTSF-Modified Waterborne Polyurethane Fluorine-Free Waterproof and Breathable Film

Developing a fluorine-free, durable, high-performance waterproof breathable film for fabrics remains a formidable challenge. In this paper, a strategy for the preparation of fluorine-free, durable, and high-efficiency fabric waterproof and breathable membranes using glyceryl monostearate (GMS)/double-ended hydroxy silicone oil (HTSF)-modified waterborne polyurethane was proposed. The orderly orientation of GMS and HTSF gives the fabric excellent water-repellent properties, and the polyurethane macromolecular chain ensures strong adhesion of long-chain alkanes and silicones to the fabric surface. In this paper, the effects of different GMS contents on the stability, chemical structure, particle size, viscosity, water absorption performance, surface morphology, and XPS of a waterborne polyurethane fluorine-free waterproof and breathable membrane (GHWPU) were studied. At the same time, the application properties of GHWPU-treated fabrics, such as waterproof performance, antifouling performance, surface energy, morphology, and air permeability, were discussed. Through the analysis of SEM and XPS, it was found that the folds on the surface of the film were more and more orderly with the increasing content of GMS, and this orderly distribution of water-repellent groups endowed the film with excellent water-repellent ability. When the GMS content was 28 wt %, the finished fabrics had excellent comprehensive properties such as static contact angle of 141.6°, hydrostatic pressure of 96.7 KPa, resistance to more than 30 washes, and air permeability of 119.3 mm/s.

Progress in the Preparation and Application of Breathable Membranes

Breathable membranes with micropores enable the transfer of gas molecules while blocking liquids and solids, and have a wide range of applications in medical, industrial, environmental, and energy fields. Breathability is highly influenced by the nature of a material, pore size, and pore structure. Preparation methods and the incorporation of functional materials are responsible for the variety of physical properties and applications of breathable membranes. In this review, the preparation methods of breathable membranes, including blown film extrusion, cast film extrusion, phase separation, and electrospinning, are discussed. According to the antibacterial, hydrophobic, thermal insulation, conductive, and adsorption properties, the application of breathable membranes in the fields of electronics, medicine, textiles, packaging, energy, and the environment are summarized. Perspectives on the development trends and challenges of breathable membranes are discussed.

Directional vapor transported and water-proof nanofibrous membranes for liquid desiccant dehumidification systems

The membrane-based liquid desiccant dehumidification system is a newly developed method in the field of air dehumidification. In this study, double-layer nanofibrous membranes (DLNMs) with directional vapor transport and water repellency for liquid dehumidification were fabricated by a simple electrospinning process. Specifically, the combination of thermoplastic polyurethane nanofibrous membrane and polyvinylidene fluoride (PVDF) nanofibrous membrane forms a cone-like structure in DLNMs, resulting in directional vapor transportation. The nanoporous structure and rough surface of PVDF nanofibrous membrane provide waterproof performance for DLNMs. Compare with the commercial membranes, the proposed DLNMs have a significantly higher water vapor permeability coefficient, which is as high as 539.67 g·μm m^-2·24 h·Pa. This study not only provides a new route to construct a directional vapor transport and waterproof membrane, but also demonstrates the huge application prospect of the nanofibrous membrane formed by electrospinning in the field of solution dehumidification.

Fluorine-Free, Highly Durable Waterproof and Breathable Fibrous Membrane with Self-Clean Performance

Lightweight, durable waterproof and breathable membranes with multifunctional properties that mimic nature have great potential for application in high-performance textiles, efficient filtering systems and flexible electronic devices. In this work, the fluoride-free triblock copolymer poly(styrene-b-butadiene-b-styrene) (SBS) fibrous membrane with excellent elastic performance was prepared using electrospinning. According to the bionics of lotus leaves, a coarse structure was built onto the surface of the SBS fiber using dip-coating of silicon dioxide nanoparticles (SiO₂ NPs). Polydopamine, an efficient interfacial adhesive, was introduced between the SBS fiber and SiO₂ NPs. The hydrophobicity of the modified nanofibrous membrane was highly improved, which exhibited a super-hydrophobic surface with a water contact angle large than 160°. The modified membrane retained super-hydrophobic properties after 50 stretching cycles under 100% strains. Compared with the SBS nanofibrous membrane, the hydrostatic pressure and WVT rate of the SBS/PDA/SiO₂ nanofibrous membrane improved simultaneously, which were 84.2 kPa and 6.4 kg·m^-2·d^-1 with increases of 34.7% and 56.1%, respectively. In addition, the SBS/PDA/SiO₂ nanofibrous membrane showed outstanding self-cleaning and windproof characteristics. The high-performance fibrous membrane provides a new solution for personal protective equipment.

Electrospun Nanofibrous Membranes: A Versatile Medium for Waterproof and Breathable Application

Waterproof and breathable membranes that prevent liquid water penetration, while allowing air and moisture transmission, have attracted significant attention for various applications. Electrospun nanofiber materials with adjustable pore structures, easily tunable wettability, and good pore connectivity, have shown significant potential for constructing waterproof and breathable membranes. Herein, a systematic overview of the recent progress in the design, fabrication, and application of waterproof and breathable nanofibrous membranes is provided. The various strategies for fabricating the membranes mainly including one-step electrospinning and post-treatment of nanofibers are given as a starting point for the discussion. The different design concepts and structural characteristics of each type of waterproof and breathable membrane are comprehensively analyzed. Then, some representative applications of the membranes are highlighted, involving personal protection, desalination, medical dressing, and electronics. Finally, the challenges and future perspectives associated with waterproof and breathable nanofibrous membranes are presented.

Waterproof, breathable and infrared-invisible polyurethane/silica nanofiber membranes for wearable textiles

Waterproof and breathable membranes, which have great potential in applications such as membrane distillation, self-cleaning, and multifunctional clothing, have attracted a lot of attention due to their superior performance. Superhydrophobic and infrared-invisible polyurethane (PU)/silica (SiO₂) nanofiber microporous membranes were prepared by facile electrospinning and a hydrothermal-assisted sol-gel method. Compared with pure PU nanofiber membranes, silica nanoparticles act as an adhesion layer, which can provide the rough surface and low surface energy of fibrous membranes. Therefore, the grafted PU/SiO₂ nanofiber membrane was endowed with a good superhydrophobic effect, and its water contact angle (WCA) reached 161°. The nanofiber membrane exhibited comfortable waterproof and breathable properties, in which the air permeability and water vapor transfer rate was 5.18 mm s^-1 and 7.85 kg m^-2 d^-1, respectively. When the PU/SiO₂ nanofiber membrane was irradiated by infrared light, the surface of the fiber membrane showed a green, low-temperature state. These waterproof and breathable nanofiber membranes with superhydrophobic properties could be used in anti-icing, outdoor concealment, and camouflage applications.

Recent Progress in Protective Membranes Fabricated via Electrospinning: Advanced Materials, Biomimetic Structures, and Functional Applications

Electrospinning is a significant micro/nanofiber processing technology and has been rapidly developing in the past 2 decades. It has several applications, including advanced sensing, intelligent manufacturing, and high-efficiency catalysis. Here, multifunctional protective membranes fabricated via electrospinning in terms of novel material design, construction of novel structures, and various protection requirements in different environments are reviewed. To achieve excellent comprehensive properties, such as, high water vapor transmission, high hydrostatic pressure, optimal mechanical property, and air permeability, combinations of novel materials containing nondegradable/degradable materials and functional structures inspired by nature have been investigated for decades. Currently, research is mainly focused on conventional protective membranes with multifunctional properties, such as, anti-UV, antibacterial, and electromagnetic-shielding functions. However, important aspects, such as, the properties of electrospun monofilaments, development of "green electrospinning solutions" with high solid content, and approaches for enhancing adhesion between hydrophilic and hydrophobic layers are not considered. Based on this systematic review, the development of electrospinning for protective membranes is discussed, the existing gaps in research are discussed, and solutions for the development of technology are proposed. This review will assist in promoting the diversified development of protective membranes and is of great significance for fabricating advanced materials for intelligent protection.

Environmentally Friendly, Durably Waterproof, and Highly Breathable Fibrous Fabrics Prepared by One-Step Fluorine-Free Waterborne Coating

Waterproof and breathable membranes (WBMs) have drawn broad attention due to their widespread applications in various scientific and industry fields. However, creating WBMs with environment-friendliness and high performance is still a critical and challenging task. Herein, an environmentally friendly fluorine-free WBM with high performance was prepared through electrospinning and one-step dip-coating technology. The fluorine-free waterborne hydroxyl acrylic resin (HAR) emulsion containing long hydrocarbon chains endowed the electrospun polyacrylonitrile/blocked isocyanate prepolymer (PAN/BIP) fibrous membranes with superior hydrophobicity; meanwhile, crosslinking agent BIP ensured strong chemical binding between hydrocarbon segments and fiber substrate. The as-prepared PAN/BIP@HAR fibrous membranes achieve ideal properties with waterproofness of 112.5 kPa and moisture permeability of 12.7 kg m^-2 d^-1, which are comparable to the existing high-performance fluorinated WBMs. Besides, the PAN/BIP@HAR membranes also display impressive tensile strength and durability. Significantly, the proposed technology was also applicable to other hydrophilic fiber substrates, such as cellulose acetate and polyamide 6. The successful synthesis of environmentally friendly, durably waterproof, and highly breathable PAN/BIP@HAR membranes not only opens a new avenue to materials design, but also provides promising candidates with tremendous potential in various areas.

Superelastic, Breathable, and High-Barrier Nanofibrous Membranes with Biomimetic ECM Structure for Toxic Chemical Protection

As the last line of protection for humans, chemical protective suits provided safe and effective protection where chemical warfare agents (CWAs) or chemical reagents leaked; however, the existing chemical protective clothing had poor wearing pressure comfort due to the limitation of inherent materials. Herein, we reported a scalable strategy to fabricate chemical protective fabric (CPF) with a biomimetic extracellular matrix (ECM) barrier layer composed of an elastic fiber framework based on the cross-linked nanofiber membrane and the styrene-butadiene-styrene block copolymer (SBS)/acticarbon matrix. The construction of the reliable and strategical biomimetic ECM structure succeeded in fulfilling hazardous chemical barrier properties, recoverable deformation, and thermal comfort improvement. The resulting CPF exhibited waterproofness with exceeding 200 kPa hydrostatic pressure and exceptional WVT of 550.96 g m^-2 d^-1, rapid elastic recovery from a strain of 80%, high-cycle fatigue resistance, superior barrier performance against toxic chemicals, and keeping CEES resistance after 100 tensile loading cycles. The successful preparation of the fascinating biomimetic nanofibrous membrane may provide a particular research foundation for developing chemical protective clothing in the future.

Ultralight, Superelastic, and Washable Nanofibrous Sponges with Rigid-Flexible Coupling Architecture Enable Reusable Warmth Retention

Nanofibrous sponges enable promising potentials in warmth retention but are impeded by short service life and nonwashability, owing to their inadequate mechanical properties. Herein, a scalable strategy is reported to develop ultralight, superelastic, and washable micro/nanofibrous sponges (MNFSs) with a rigid-flexible coupling architecture created by bridging high-modulus polyethylene terephthalate microfibers with flexible polyacrylonitrile nanofibers via robust bonding structures. Meanwhile, the in situ doping of fluoropolymer endows micro/nanofibers with desirable amphiphobicity. The resultant MNFSs present high resilience, superior compressive fatigue resistance (5.7% residual strain at 1000th), low-temperature-resistant superelasticity (up to -196 °C), and unique washing-invariant superelasticity. Moreover, the fascinating structures of high porosity, high tortuosity, and small pores enable MNFSs both ultralight property (7.5 mg cm^-3) and effective warmth retention (28.51 mW m^-1 K^-1). Additionally, the MNFSs possess remarkable antifouling, robust stability, and long service life. The work might provide an avenue to develop mechanically robust nanofibrous sponges for various applications.

3D-cellulose acetate-derived hierarchical network with controllable nanopores for superior Li+ transference number, mechanical strength and dendrites hindrance

The dendrites is deemed to be one of the most crucial problems for lithium-ion batteries because it hampers their safety and cycling performance severely. Herein, a cellulose acetate-based separator with uniformly distributed nanopores was engineered and successfully prepared through a simple one-step process. The controlled nanopores promoted uniform transmission of ions and the cellulose acetate backbone inhibited the transference of anions, and prevented large-scale accumulation of lithium ions, thereby restricting the nucleation and growth of dendrites. The 3D-networked separator exhibited capacity retention of 78.6% after 900 cycles at 1C, with the breaking elongation and the strength increased by 620% and 28.4%, respectively, which originated from the porosity controlling of the nanofiber inter-bridging. The nanopore-assembled structure of 3D-hierarchy with MOFs provided the channels for the lithium ions transference through the separator and hence tackled the major challenge of mechanical vulnerability and electrochemical instability, which have never been reported before. Therefore, the developed strategy may offer a powerful and effective alternative for conventional approach of occurring dendrites post-treatments for higher ionic conductivity.

Integrated All-Fiber Electronic Skin toward Self-Powered Sensing Sports Systems

The development of wearable electronic skins (E-skins) requires devices with high flexibility, breathability, and antibacterial activity, as in sports sensing technology. Here, we report a flexible, breathable, and antibacterial triboelectric nanogenerator (TENG)-based E-skin for self-powered sensing in volleyball reception statistics and analytics, which is fabricated by sandwiching a silver nanowire (Ag NW) electrode between a thermoplastic polyurethane (TPU) sensing layer and a poly(vinyl alcohol)/chitosan (PVA/CS) substrate. Benefiting from an outstanding breathability of 10.32 kg m^-2 day^-1 and biocidal properties of CS and Ag NW, the E-skin offers excellent thermal-moisture comfort and a remarkable antibacterial effect on Escherichia coli and Staphylococcus aureus. A pressure sensitivity of 0.3086 V kPa^-1 is demonstrated in the sensing range of 6.65-19.21 kPa. Besides, a volleyball reception statistical and analytical system is further developed based on a 2 × 3 E-skin array. According to this work, the integration of wearable electronic devices with self-powered sensors may expand practical applications in sports.

Electrospinning fabrication of polystyrene-silica hybrid fibrous membrane for high-efficiency air filtration

The development of new materials for air filtration and particulate matter (PM) pollution is critical to solving global environmental issues that threaten human health and accelerate the greenhouse effect. In this study, a novel electrospun polystyrene-SiO2 nanoparticle (PS-SNP) fibrous membrane was explored by a single-step strategy to obtain the composite multi-layered filter masks. In addition, the air filtration performance of this fibrous membrane for PM was evaluated. The effects of SiO2 on the composition, morphology, mechanical property, and surface wetting of PS-SNP membranes were studied. Allowing SiO2 to be incorporated into the PS polymer was endowed with promising superhydrophobicity and demonstrated excellent mechanical properties. As-prepared PS-SNP membranes possess significantly better filtration efficiency than pure PS membrane. Furthermore, a three-layered air filter media (viscose/PS-SNP/polyethylene terephthalate) used in this study has considerable performances compared to the commercial masks. Since this air filtration membrane has excellent features such as high air filtration and permeability, we anticipate it to have huge potential application in air filtration systems, including cleanroom, respirator, and protective clothing.

Asymmetric Wettable, Waterproof, and Breathable Nanofibrous Membranes for Wound Dressings

Despite the progression in wound treatment, the development of wound dressings with considerable skin regeneration capability and improved patient comfort still faces huge challenges. In this study, a type of asymmetric wettable gradient nanofibrous membrane, which is composed of a hydrophobic polyvinyl butyral (PVB)-polydimethylsiloxane (PDMS) upper layer, a PVB-PDMS/gelatin middle layer, and a hydrophilic gelatin lower layer, has been fabricated. The PVB-PDMS upper layer gave dramatically elevated water contact angles from 71.27° to 125.45° as compared with the gelatin membrane, indicating an asymmetric wettability. The composite membrane exhibited outstanding waterproof capability with a hydrostatic pressure of 58.21 kPa, excellent breathability with a water vapor transmission rate of 8.80 kg m^-2 d^-1, improved stretchability and tear resistance, and dramatic improvement in mesenchymal stem cell recruitment with the immobilization of stromal-cell-derived factor-1α for accelerating skin regeneration. The development of asymmetric wettable nanofibrous membranes offers insight into wound-dressing design.

Fabrication of waterproof gas separation membrane from plastic waste for CO2 separation

In this study, waste polystyrene (wPS) plastic was used to prepare gas-separation membranes with hot-pressing technology to reduce the accumulation of plastic waste. Polystyrene is a commonly used polymer for the production of plastic products, and it is also used in the synthesis of membranes for gas separation. Compared to the traditional synthesis process, hot-pressing is environmentally friendly because it does not require organic solvents. The mobility of the polymer chain and the integrity and free volume of the membrane are affected by the temperature, pressure, duration, and annealing environment of the hot-pressing process, thereby altering the performance of the membrane. Additionally, when the wPS contained polybutadiene, the gas separation membranes showed a selectivity of 17.14 for CO₂/N₂. The membranes also exhibited ideal waterproof performance when the membranes were operated under water pressures of 1-5 bar. Therefore, membranes derived from wPS through hot pressing are waterproof and can be used for gas separation. Furthermore, they are expected to maintain their separation performance in complex environments.

Short-Branched Fluorinated Polyurethane Coating Exhibiting Good Comprehensive Performance and Potential UV Degradation in Leather Waterproofing Modification

In the current leather market, waterproof leather occupies a large proportion, where waterproofness has become one of the important standards for leather selection. However, the most advanced fluorine-containing waterproofing agents on the market always have long chains of over eight carbons (C8), whose use has been restricted due to their bioaccumulation and recalcitrance in natural environment. Consequently, creating waterproof materials characterized by their environmentally friendly qualities and high performance is of great significance. Herein, we report a novel strategy for preparation of the fluorinated polyurethanes containing short branched fluorocarbon chains, and apply it in leather waterproofing. Because the fluorine-containing chain segments are enriched on the coating surface, the waterproof agent coating shows good hydrophobicity, low water absorption, high wear resistance and potential photodegradation of performances. Additionally, the water and oil proof performances of the coating are comparable to that of the marketed C8 waterproofing agent. Its solvent-resistant and antifouling performances are also outstanding. Therefore, the coating can meet the property requirements for daily use and has broad application prospects.

In-situ electrospinning of thymol-loaded polyurethane fibrous membranes for waterproof, breathable, and antibacterial wound dressing application

Skin-like flexible membrane with excellent water resistance and moisture permeability is an urgent need in the wound dressing field to provide comfort and protection for the wound site. Despite efforts that have been made in the development of waterproof and breathable (W&B) membranes, the in-situ electrospinning of W&B membranes suitable for irregular wound surfaces as wound dressings still faces huge challenges. In the current work, a portable electrospinning device with multi-functions, including adjustable perfusion speed for a large range from 0.05 mL/h to 10 mL/h and high voltage up to 11 kV, was designed. The thymol-loaded ethanol-soluble polyurethane (EPU) skin-like W&B nanofibrous membranes with antibacterial activity were fabricated via the custom-designed device. Ultimately, the resultant nanofibrous membranes composed of EPU, fluorinated polyurethane (FPU), and thymol presented uniform structure, robust waterproofness with the hydrostatic pressure of 17.6 cm H₂O, excellent breathability of 3.56 kg m^-2 d^-1, the high tensile stress of 1.83 MPa and tensile strain of 453%, as well as high antibacterial activity. These results demonstrate that the new-type device has potential as a portable electrospinning apparatus for the fabrication of antibacterial membranes directly on the wound surface and puts a new way for the development of portable electrospinning devices.

Green-Solvent-Processed Fibrous Membranes with Water/Oil/Dust-Resistant and Breathable Performances for Protective Textiles

Waterproof and breathable membranes (WBMs) are highly demanded worldwide due to their promising applications in outdoor protective clothing, medical hygiene, and electronic devices. However, the design of such materials integrated with environmental friendliness and high functionality has been considered a long-standing challenge. Herein, we report the green-solvent-processed polyamide fibrous membranes with amphiphobicity and bonding structure via ethanol-based electrospinning and water-based impregnating techniques, endowing the fibrous membranes with outstanding water/oil/dust-resistant and good breathable properties. The developed green smart fibrous membranes exhibit integrated properties with robust water and oil intrusion pressures of 101.2 and 32.4 kPa, respectively, excellent dust removal efficiency of above 99.9%, good water vapor transmission rate of 11.2 kg m^-2 d^-1, air permeability of 2.6 mm s^-1, tensile strength of 15.6 MPa, and strong toughness of 22.8 MJ m^-3, enabling the membranes to protect human beings and electronic devices effectively. This work may shed light on designing the next generation green smart fibrous WBMs for protective textiles.

Multifunctional, Waterproof, and Breathable Nanofibrous Textiles Based on Fluorine-Free, All-Water-Based Coatings

Developing environmentally benign, multifunctional waterproof and breathable membranes (WBMs) is of great importance but still faces enormous challenges. Here, an environmentally benign fluorine-free, ultraviolet (UV) blocking, and antibacterial WBM with a high level of waterproofness and breathability is developed on a large scale by combining electrospinning and step-by-step surface coating technology. Fluorine-free water-based alkylacrylates with long hydrocarbon chains were coated onto polyamide 6 fibrous membranes to construct robust hydrophobic surfaces. The subsequent titanium dioxide nanoparticle emulsion coating prominently decreased the maximum pore size, leading to higher water resistance, endowing the membranes with efficient UV-resistant and antibacterial properties. The resulting fibrous membranes possessed excellent waterproofness of 106.2 kPa, exceptional breathability of 10.3 kg m^-2 d^-1, a significant UV protection factor of 430.5, together with a definite bactericidal efficiency of 99.9%. We expect that this methodology for construction of environmentally benign and multifunctional WBMs will shed light on the material design, and the prepared membranes could implement their promising applications in covering materials, outdoor equipment, protective clothing, and high-altitude garments.

Emerging Developments in the Use of Electrospun Fibers and Membranes for Protective Clothing Applications

There has been increased interest to develop protective fabrics and clothing for protecting the wearer from hazards such as chemical, biological, heat, UV, pollutants etc. Protective fabrics have been conventionally developed using a wide variety of techniques. However, these conventional protective fabrics lack breathability. For example, conventional protective fabrics offer good protection against water but have limited ability in removing the water vapor and moisture. Fibers and membranes fabricated using electrospinning have demonstrated tremendous potential to develop protective fabrics and clothing. These fabrics based on electrospun fibers and membranes have the potential to provide thermal comfort to the wearer and protect the wearer from wide variety of environmental hazards. This review highlights the emerging applications of electrospinning for developing such breathable and protective fabrics.

Fluorine-Free Waterborne Coating for Environmentally Friendly, Robustly Water-Resistant, and Highly Breathable Fibrous Textiles

Waterproof and breathable membranes (WBMs) with simultaneous environmental friendliness and high performance are highly desirable in a broad range of applications; however, creating such materials still remains a tough challenge. Herein, we present a facile and scalable strategy to fabricate fluorine-free, efficient, and biodegradable WBMs via step-by-step dip-coating and heat curing technology. The hyperbranched polymer (ECO) coating containing long hydrocarbon chains provided an electrospun cellulose acetate (CA) fibrous matrix with high hydrophobicity; meanwhile, the blocked isocyanate cross-linker (BIC) coating ensured the strong attachment of hydrocarbon segments on CA surfaces. The resulting membranes (TCA) exhibited integrated properties with waterproofness of 102.9 kPa, breathability of 12.3 kg m^-2 d^-1, and tensile strength of 16.0 MPa, which are much superior to that of previously reported fluorine-free fibrous materials. Furthermore, TCA membranes can sustain hydrophobicity after exposure to various harsh environments. More importantly, the present strategy proved to be universally applicable and effective to several other hydrophilic fibrous substrates. This work not only highlights the material design and preparation but also provides environmentally friendly and high-performance WBMs with great potential application prospects for a variety of fields.

Facile fabrication of fluorine-free breathable poly(methylhydrosiloxane)/polyurethane fibrous membranes with enhanced water-resistant capability

HYPOTHESIS

Ideal breathable and waterproof materials contain two key elements: hydrophobic matrix and small pore size. Current high-performing breathable waterproof membranes usually employ fluorinated materials to construct hydrophobic surface, which possess alarming potential environmental hazards. Fluorine-free waterproof agents through coating treatment to obtain hydrophobicity suffer from complicated fabrication process and poor durability. Hence, non-fluorinated chemicals incorporated into fibers via a facile one-step electrospinning may be an effective approach to attain durable hydrophobic membranes.

EXPERIMENTS

Poly(methylhydrosiloxane)/polyurethane (PMHS/PU) solution with various PMHS concentration was formulated and electrospun to fibrous membranes, followed by a facile thermal treatment process. A systematic study including morphologies, porous structure, and surface wettability was performed. Breathable waterproof performance and tensile strength were also investigated.

FINDINGS

Added PMHS imparted mighty hydrophobicity to the membranes with a water contact angle of 130.2°, and the subsequent heat treatment greatly improved waterproofness, meanwhile doubled the tensile strength. The resultant membranes exhibited robust hydrostatic pressure of 54.1 kPa, medium breathability of 9.5 kg m^-2 d^-1, and excellent stretching stress of 14.1 MPa, which can meet the requirements of general use. The presented strategy on membrane fabrication is feasible and scalable, which may be considered as an effective remedy for environmental protection.

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

Among superhydrophobic materials, non-wettable textiles are probably the ones that come in contact or interact with the human body most frequently. Hence, textile treatments for water or oil repellency should be non-toxic, biocompatible, and comply with stringent health standards. Moreover, considering the volume of the worldwide textile industry, these treatments should be scalable, sustainable, and eco-friendly. Due to this awareness, more and more non-wettable textile treatments with eco-friendly processes and green or non-toxic chemicals are being adopted and reported. Although fluorinated alkylsilanes or fluorinated polymers with C8 chemistry (with ≥ 8 fluorinated carbon atoms) are the best performing materials to render textiles water or oil repellent, they pose substantial health and environmental problems and are being banned. For this reason, water/solvent-borne, C8-free vehicles for non-wettable treatment formulations are probably the only ones that can have commercialization prospects. Hence, researchers have come up with a variety of new, non-toxic, green formulations and materials to render fabrics liquid repellent that constitute the focus of this review paper. As such, this review article discusses and summarizes recent developments and techniques on various sustainable superhydrophobic treatments for textiles, with comparable performance and durability to formulations based on fluorinated C8 compounds. The current state-of-the-art technologies, potential commercialization prospects, and relevant limitations are discussed and summarized with examples. The review also attempts to indicate promising future strategies and new materials that can transform the process for non-wettable textiles into an all-sustainable technology.

Effect of the hyaluronic acid-poloxamer hydrogel on skin-wound healing: in vitro and in vivo studies

BACKGROUND

Recent research into skin injury and wound healing has focused mainly on post-trauma hemostasis, infection prevention, dermal regeneration and angiogenesis. However, less attention has been paid to air permeability and moisture loss prevention which also play important roles in injury healing.

METHODS

In the present work, we prepared a hyaluronic acid-poloxamer (HA-POL) hydrogel and tested the therapeutic effect of the hydrogel on skin-wound healing.

RESULTS

The HA-POL hydrogel transformed from sol to gel at 30°C, close to body temperature, and had stable moisturizing properties. HA-POL hydrogel promoted skin-wound healing and increased protein accumulation in the wound area. HA-POL hydrogel allowed greater air permeability than Band-aid, a typical wound covering. Results from transwell assays showed that the HA-POL hydrogel effectively isolated skin-wounds from bacterial invasion.

CONCLUSION

This work demonstrates the advantages of using HA-POL gel materials in the treatment of cutaneous wounds.

Biomimetic Fibrous Murray Membranes with Ultrafast Water Transport and Evaporation for Smart Moisture-Wicking Fabrics

Both antigravity directional water transport and ultrafast evaporation are critical to achieving a high-performance moisture-wicking fabric. The transpiration in vascular plants possess both of these features, which is due to their optimized hierarchical structure composed of multibranching porous networks following Murray's law. However, it remains a great challenge to simultaneously realize the ultrafast water transport and evaporation by mimicking nature's Murray networks in the synthetic materials. Here, we report a synergistic assembly strategy to create a biomimetic micro- and nanofibrous membrane with antigravity directional water transport and quick-dry performance by combining a multibranching porous structure and surface energy gradient, overcoming previous limitations. The resulting fiber-based porous Murray membranes exhibit an ultrahigh one-way transport capability ( R) of 1245%, a desired overall moisture management capability (OMMC) of 0.94, and an outstanding water evaporation rate of 0.67 g h^-1 (5.8 and 2.1 times higher than the cotton fabric and Coolmax fabric, respectively). Overall, the successful synthesis of these biomimetic porous Murray membranes should serve as a source of inspiration for the development of moisture-wicking technologies, providing personal comfort in hot or humid environments.

Waterproof and Breathable Electrospun Nanofibrous Membranes

Waterproof and breathable (W&B) membranes combine fascinating properties of resistance to liquid water penetration and transmitting of water vapor, playing a key role in addressing problems related to health, resources, and energy. Electrospinning is an efficient and advanced way to construct nanofibrous materials with easily tailored wettability and adjustable pore structure, therefore providing an ideal strategy for constructing W&B membranes. In this review, recent progress on electrospun W&B membranes is summarized, involving materials design and fabrication, basic properties of electrospun W&B membranes associated with waterproofness and breathability, as well as their applications. In addition, challenges and future trends of electrospun W&B membranes are discussed.

Human Skin-Like, Robust Waterproof, and Highly Breathable Fibrous Membranes with Short Perfluorobutyl Chains for Eco-Friendly Protective Textiles

Flexible smart membranes with superior waterproofness and extreme breathability are highly desirable for wearable uses. However, present waterproof and breathable materials suffer from limited performance efficiency, alarming environmental risks, and complicated fabrication procedures. We report on eco-friendly fibrous membranes with human skin-like, robust waterproof, and highly breathable capabilities that can be prepared via a facile electrospinning strategy. A novel polyurethane elastomer (C4FPU) possessing double-terminal short perfluorobutyl (-C₄F₉) chain is synthesized for the first time and incorporated into the polyurethane (PU) fiber matrix, endowing the membrane with mighty and durable hydrophobicity. Additionally, the employment of AgNO₃ greatly decreased the maximum pore size ( d_max), contributing to the dramatically enhanced waterproofness. The resulting PU/C4FPU/AgNO₃ fibrous membranes exhibit comprehensive properties of exceptional hydrostatic pressure (102.8 kPa), excellent water vapor transmission rate (12.9 kg m^-2 d^-1), high mechanical property (9.8 MPa), and significant antibacterial efficacy against Escherichia coli and Staphylococcus aureus. The successful synthesis of these intriguing membranes may provide a promising candidate for the new generation of key building blocks of the upscale protective garments.

Microsphere-Fiber Interpenetrated Superhydrophobic PVDF Microporous Membranes with Improved Waterproof and Breathable Performance

Superhydrophobic membranes with extreme liquid water repellency property are good candidates for waterproof and breathable application. Different from the mostly used strategies through either mixing or postmodifying base membranes with perfluorinated compounds, we report in this work a facile methodology to fabricate superhydrophobic microporous membranes made up of pure poly(vinylidene fluoride) (PVDF) via a high-humidity induced electrospinning process. The superhydrophobic property of the PVDF microporous membrane is contributed by its special microsphere-fiber interpenetrated rough structure. The effective pore size and porosity of the PVDF membranes could be well tuned by simply adjusting the PVDF concentrations in polymer solutions. The membrane with optimized superhydrophobicity and porous structure exhibits improved waterproof and breathable performance with hydrostatic pressure up to 62 kPa, water vapor transmission rate (WVT rate) of 10.6 kg m^-2 d^-1, and simultaneously outstanding windproof performance with air permeability up to 1.3 mm s^-1. Our work represents a rather simple and perfluorinated-free strategy for fabricating superhydrophobic microporous membranes, which matches well with the environmentally friendly requirement from the viewpoint of practical application.

Continuous, Spontaneous, and Directional Water Transport in the Trilayered Fibrous Membranes for Functional Moisture Wicking Textiles

Directional water transport is a predominant part of functional textiles used for continuous sweat release in daily life. However, it has remained a great challenge to design such textiles which ensure continuous directional water transport and superior prevention of water penetration in the reverse direction. Here, a scalable strategy is reported to create trilayered fibrous membranes with progressive wettability by introducing a transfer layer, which can guide the directional water transport continuously and spontaneously, thus preventing the skin from being rewetted. The resulting trilayered fibrous membranes exhibit a high one-way transport index R (1021%) and a desired breakthrough pressure (16.1 cm H₂ O) in the reverse direction, indicating an ultrahigh directional water transport capacity. Moreover, on the basis of water transport behavior, a plausible mechanism is proposed to provide insight into the integrative and cooperative driving forces at the interfaces of trilayered hydrophobic/transfer/superhydrophilic fibrous membranes. The successful synthesis of such fascinating materials would be valuable for the design of functional textiles with directional water transport properties for personal drying applications.

Breathable and Colorful Cellulose Acetate-Based Nanofibrous Membranes for Directional Moisture Transport

Textiles with excellent moisture transport characteristics play key role in regulating comfort of the body, and use of color in textiles helps in developing aesthetically pleasing apparels. Herein, we report an aesthetically pleasing and breathable dual-layer cellulose acetate (CA) based nanofibrous membranes with exceptional directional moisture transport performance. The outer layer was synthesized by subjecting CA nanofibers to hydrolysis and reactive dyeing processes, which converted moderately hydrophobic CA nanofibers into uniformly colored superhydrophilic CA nanofibers with an excellent wettability. In addition to excellent wettability and superhydrophilic nature, dyed CA (DCA) nanofibers also offered high color yield and dye fixation as well as considerable colorfastness performance against washing and light, thus, were used as the outer layer. However, pristine CA nanofibers were chosen as the inner layer for their moderate hydrophobicity. The subsequent CA/DCA nanofiber membrane produced a high wettability gradient, which facilitated directional moisture transport from CA to DCA layers. The resultant dual-layer nanofiber membranes offered a high color yield of 16.33 with ∼82% dye fixation, excellent accumulative one-way transport capacity (919%), remarkable overall moisture management capacity (0.89), and reasonably high water vapor transport rate (12.11 kg d^-1 m^-2), suggesting them to be a potential substrate for fast sweat-release applications.

Biomimetic fabrication of superhydrophobic loofah sponge: robust for highly efficient oil-water separation in harsh environments

Oil/water separation has become an increasingly important field due to frequent industrial oily wastewater emission and crude oil spill accidents. Herein, we fabricate a robust superhydrophobic loofah sponge via a versatile, environmentally friendly, and low-cost dip coating strategy, which involves the modification of commercial loofah sponge with waterborne polyurea and fused SiO2 nanoparticles without the modification of any toxic low-surface-energy compound. The as-prepared loofah sponge showed excellent superhydrophobic/superoleophilic properties and exhibited robustness for effective oil-water separation in extremely harsh environments (such as 1 M HCl, 1 M NaOH, saturated NaCl solution and hot water higher than 95 °C) due to the remarkably high chemical stability. In addition, the as-prepared loofah sponge was capable of excellent anti-fouling, has self-cleaning ability and could act as the absorber for effective separation of surfactant-free oil-in-water emulsions. More importantly, the as-prepared loofah sponge demonstrated remarkable robustness against strong sandpaper abrasion and finger wipes, while retaining its superhydrophobicity and efficient oil/water separation efficiency even after more than 50 abrasion cycles. This facile and green synthesis approach presented here has the advantage of large-scale fabrication of a multifunctional biomass-based adsorbent material as a promising candidate in anti-fouling, self-cleaning, and versatile water-oil separation.

Electrospun Hydrophilic Janus Nanocomposites for the Rapid Onset of Therapeutic Action of Helicid

The oral delivery of active ingredients for the fast onset of therapeutic effects is a well-known method in patients. In this study, a new kind of hydrophilic Janus structural nanocomposite was designed for the rapid dissolution and transmembrane permeation of helicid, an herbal medicine with poor water solubility. A side-by-side electrospinning process characterized by an eccentric spinneret was developed to fabricate the Janus nanocomposites. The morphology, inner structure, incorporated components and their physical states, hydrophilicity, and functional performances of the Janus nanocomposites were investigated. The experimental results demonstrated that an unspinnable fluid (polyvinylpyrrolidone K10-sodium dodecyl sulfate) could be simultaneously treated with an electrospinnable fluid (polyvinylpyrrolidone K90-helicid) to create Janus structural nanocomposites. The prepared Janus nanofibers exhibited linear morphology and notable side-by-side inner structure with all the incorporated components present in an amorphous state. Both the control of monolithic nanocomposites and the Janus composites can provide more than 10-fold the transmembrane rates of crude helicid particles. Compared with monolithic nanocomposites, the Janus nanocomposites exhibited improved hydrophilicity and can further promote the dissolution and transmembrane permeation of helicid for a potentially faster onset of therapeutic actions. The generation mechanisms and functional performance of Janus nanocomposites were suggested. The preparation protocols reported here can provide a useful approach for designing and developing new functional nanocomposites in the form of Janus structures. Meanwhile, the medicated hydrophilic Janus nanocomposites represent a newly developed kind of nano drug delivery system for the fast onset of therapeutic action of orally administered water-insoluble drugs.