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

Recent advances of electrospun strategies in topical products encompassing skincare and dermatological treatments

As the potential applications of electrospinning in healthcare continue to be explored, along with advancements in industrial-scale solutions and the emergence of portable electrospinning devices, some researchers have explored electrospinning technology in topical products, including its application in skincare, such as facial masks, beauty patches, sunscreen, and dermatological treatments for conditions like atopic dermatitis, psoriasis, acne, skin cancer, etc. In this review, we first outline the fundamental principles of electrospinning and provide an overview of existing solutions for large-scale production and the components and functionalities of portable spinning devices. Based on the essential functionalities required for skincare products and the mechanisms and treatment methods for the aforementioned dermatological diseases, we summarize the potential advantages of electrospinning technology in these areas, including encapsulation, sustained release, large surface area, and biocompatibility, among others. Furthermore, considering the further commercialization and clinical development of electrospinning technology, we offer our insights on current challenges and future perspectives in these areas, including issues such as ingredients, functionality, residue concerns, environmental impact, and efficiency issues.

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.

Emerging Trends of Nanofibrous Piezoelectric and Triboelectric Applications: Mechanisms, Electroactive Materials, and Designed Architectures

Over the past few decades, significant progress in piezo-/triboelectric nanogenerators (PTEGs) has led to the development of cutting-edge wearable technologies. Nanofibers with good designability, controllable morphologies, large specific areas, and unique physicochemical properties provide a promising platform for PTEGs for various advanced applications. However, the further development of nanofiber-based PTEGs is limited by technical difficulties, ranging from materials design to device integration. Herein, the current developments in PTEGs based on electrospun nanofibers are systematically reviewed. This review begins with the mechanisms of PTEGs and the advantages of nanofibers and nanodevices, including high breathability, waterproofness, scalability, and thermal-moisture comfort. In terms of materials and structural design, novel electroactive nanofibers and structure assemblies based on 1D micro/nanostructures, 2D bionic structures, and 3D multilayered structures are discussed. Subsequently, nanofibrous PTEGs in applications such as energy harvesters, personalized medicine, personal protective equipment, and human-machine interactions are summarized. Nanofiber-based PTEGs still face many challenges such as energy efficiency, material durability, device stability, and device integration. Finally, the research gap between research and practical applications of PTEGs is discussed, and emerging trends are proposed, providing some ideas for the development of intelligent wearables.

Fabrication of Waterborne Silicone-Modified Polyurethane Nanofibers for Nonfluorine Elastic Waterproof and Breathable Membranes

Waterproof and breathable membranes have a huge market demand in areas, such as textiles and medical protection. However, existing fluorinated nanofibrous membranes, while possessing good waterproof and breathable properties, pose health and environmental hazards. Consequently, fabricating fluorine-free, eco-friendly waterborne membranes by integrating outstanding waterproofing, breathability, and robust mechanical performance remains a significant challenge. Herein, we successfully prepared waterborne silicone-modified polyurethane nanofibrous membranes with excellent elasticity, waterproofing, and breathability properties through waterborne electrospinning, using a small quantity of poly(ethylene oxide) as a template polymer and in situ doping of the poly(carbodiimide) crosslinking agent, followed by a simple hot-pressing treatment. The silicone imparted the nanofibrous membrane with high hydrophobicity, and the crosslinking agent enabled its stable porous structure. The hot-pressing treatment (120 °C) further reduced the pore size and improved the water resistance. This environmentally friendly nanofibrous membrane showed a high elongation at break of 428%, an ultra-high elasticity of 67.5% (160 cycles under 400% tensile strain), an air transmission of 13.2 mm s-1, a water vapor transmission rate of 5476 g m-2 d-1, a hydrostatic pressure of 51.5 kPa, and a static water contact angle of 137.9°. The successful fabrication of these environmentally friendly, highly elastic membranes provides an important reference for applications in healthcare, protective textiles, and water purification.

Bioinspired Hierarchical Multi-Protective Membrane for Extreme Environments via Co-Electrospinning-Electrospray Strategy

Extreme environments can cause severe harm to human health, and even threaten life safety. Lightweight, breathable clothing with multi-protective functions would be of great application value. However, integrating multi-protective functions into nanofibers in a facile way remains a great challenge. Here, a one-step co-electrospinning-electrospray strategy is developed to fabricate a superhydrophobic multi-protective membrane (S-MPM). The water contact angle of S-MPM can reach up to 164.3°. More importantly, S-MPM can resist the skin temperature drop (11.2 °C) or increase (17.2 °C) caused by 0 °C cold or 70 °C hot compared with pure electrospun membrane. In the cold climate (-5 °C), the anti-icing time of the S-MPM is extended by 2.52 times, while the deicing time is only 1.45 s due to the great photothermal effect. In a fire disaster situation, the total heat release and peak heat release rate values of flame retarded S-MPM drop sharply by 24.2% and 69.3%, respectively. The S-MPM will serve as the last line of defense for the human body and has the potential to trigger a revolution in the practical application of next-generation functional clothing.

High-Performance Liquid-Repellent and Thermal-Wet Comfortable Membranes Using Triboelectric Nanostructured Nanofiber/Meshes

Skin-like functional membranes with liquid resistance and moisture permeability are in growing demand in various applications. However, the membranes have been facing a long-term dilemma in balancing waterproofness and breathability, as well as resisting internal liquid sweat transport, resulting in poor thermal-wet comfort. Herein, a novel electromeshing technique, based on manipulating the ejection and phase separation of charged liquids, is developed to create triboelectric nanostructured nano-mesh consisting of hydrophobic ferroelectric nanofiber/meshes and hydrophilic nanofiber/meshes. By combining the true nanoscale diameter (≈22 nm), small pore size, and high porosity, high waterproofness (129 kPa) and breathability (3736 g m-2 per day) for the membranes are achieved. Moreover, the membranes can break large water clusters into small water molecules to promote sweat absorption and release by coupling hydrophilic wicking and triboelectric field polarization, exhibiting a satisfactory water evaporation rate (0.64 g h-1 ) and thermal-wet comfort (0.7 °C cooler than the cutting-edge poly(tetrafluoroethylene) protective membranes). This work may shed new light on the design and development of advanced protective textiles.

High-Performance Waterproof, Breathable, and Radiative Cooling Membranes Based on Nanoarchitectured Fiber/Meshworks

Smart membranes with protection and thermal-wet comfort are highly demanded in various fields. Nevertheless, the existing membranes suffer from a tradeoff dilemma of liquid resistance and moisture permeability, as well as poor thermoregulating ability. Herein, a novel strategy, based on the synchronous occurrence of humidity-induced electrospinning and electromeshing, is developed to synthesize a dual-network structured nanofiber/mesh for personal comfort management. Manipulating the ejection, deformation, and phase separation of spinning jets and charged droplets enables the creation of nanofibrous membranes composed of radiative cooling nanofibers and 2D nanostructured meshworks. With a combination of a true-nanoscale fiber (∼70 nm) in 2D meshworks, a small pore size (0.84 μm), and a superhydrophobic surface (151.9°), the smart membranes present high liquid repellency (95.6 kPa), improved breathability (4.05 kg m-2 d-1), and remarkable cooling performance (7.9 °C cooler than commercial cotton fabrics). This strategy opens up a pathway to the design of advanced smart textiles for personal protection.

Tri-Layered Bicomponent Microfilament Composite Fabric for Highly Efficient Cold Protection

Functional thin fabric with highly efficient cold protection properties are attracting the great attention of long-term dressing in a cold environment. Herein, a tri-layered bicomponent microfilament composite fabric comprised of a hydrophobic layer of PET/PA@C6 F13 bicomponent microfilament webs, an adhesive layer of LPET/PET fibrous web, and a fluffy-soft layer of PET/Cellulous fibrous web is designed and also successfully been fabricated through a facile process of dipping, combined with thermal belt bonding. The prepared samples exhibit a large resistance to wetting of alcohol, a high hydrostatic pressure of 5530 Pa, and brilliant water slipping properties, owing to the presence of dense micropores ranging from 25.1 to 70.3 µm, as well as to the smooth surface with an arithmetic mean deviation of surface roughness (Sa) ranging from 5.112 to 4.369 µm. Besides, the prepared samples exhibited good water vapor permeability, and a tunable CLO value ranging from 0.569 to 0.920, in addition to the fact that it exhibited a very suitable working temperature range of -5 °C to 15 °C. Additionally, it also showed excellent clothing tailorability including high mechanical strength with a remarkably soft texture and lightweight foldability that suitable for cold outdoor clothing applications.

Review of Waterproof Breathable Membranes: Preparation, Performance and Applications in the Textile Field

Waterproof breathable membranes (WBMs) characterized by a specific internal structure, allowing air and water vapor to be transferred from one side to the other while preventing liquid water penetration, have attracted much attention from researchers. WBMs combine lamination and other technologies with textile materials to form waterproof breathable fabrics, which play a key role in outdoor sports clothing, medical clothing, military clothing, etc. Herein, a systematic overview of the recent progress of WBMs is provided, including the principles of waterproofness and breathability, common preparation methods and the applications of WBMs. Discussion starts with the waterproof and breathable mechanisms of two different membranes: hydrophilic non-porous membranes and hydrophobic microporous membranes. Then evaluation criteria and common preparation methods for WBMs are presented. In addition, treatment processes that promote water vapor transmission and prominent applications in the textile field are comprehensively analyzed. Finally, the challenges and future perspectives of WBMs are also explored.

Moisture wicking textiles with hydrophilic oriented polyacrylonitrile layer: Enabling ultrafast directional water transport

Functional textiles with high-performance directional water transport for regulating human sweat are in high demand because of growing concerns about the role of comfort in the performance of wearer. However, the fabrication of such materials remains a critical job. Here, we report a facile strategy to develop hydrophilic oriented polyacrylonitrile (HOPAN)/hydrophilic polylactic acid @polyvinylidene fluoride (HPLA@PVDF) composite membrane with surface energy gradient for enhanced directional water transport. Three step fabrication strategy involves electrospinning of oriented polyacrylonitrile (OPAN fibers) on polylactic acid (PLA) nonwoven surface followed by dip-coating in hydrophilic agent, and single-side electrospray of PVDF dilute solution on HOPAN/HPLA. Combination of highly oriented fiber structure, differential pore size and asymmetric wettability between two layers enabled instant water transport. The resultant fabricated composite membranes offer superior properties with one-way transport capacity (R) of 1117%, overall moisture management capacity (OMMC) of 0.91, and excellent water vapor transmission rate of 11.6 kg m^-2 d^-1. The successful preparation of these fascinating directional water transport materials offers new insight into the role of fiber alignment along with differential apertures and asymmetric chemical structure for realizing membranes for quick-drying applications.

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.