One-step fabrication of multi-scaled, inter-connected hierarchical fibrous membranes for directional moisture transport

Construction of Janus structures on thin silk fabrics via misting for wet-thermal comfort and antimicrobial activity

Owing to their small fiber diameter (10-15 μm), silk fabrics are always thin (32-90 g m-2). Therefore, construction of the Janus surfaces of silk fabrics that possess excellent multifunctionality remains a formidable challenge. Herein, first, silk fabrics were grafted using glycidyltrimethylammonium chloride to form a superhydrophilic surface (G-side). Then, a unilateral hydrophobic surface (O-side) was readily fabricated by mist coating octadecyltrichlorosilane-functionalized SiO2 nanoparticles (NPs) to produce hierarchical surface textures. To prevent NP penetration from the G-side to the O-side, a "fireproof isolation" method was employed. Consequently, Janus silk fabrics (JanSFs) bearing asymmetric wettability were prepared, and their wetting gradient could be conveniently regulated. With the mist time ranging from 4 to 7 min, the unidirectional transport index and efficiency of the unidirectional water transport increased and decreased by 13.2 and 10.4 times, respectively. Sweat could be effectively drained away from human skin to ensure that the skin was dry and comfortable. Compared with the surface temperature of the raw fabric, the raw fabric of JanSFs increased by 2.7 °C. Furthermore, the breathability of JanSF was negligibly affected, and the outer O-side of the JanSF showed substantial antibacterial activity. This study is important for designing JanSFs that exhibit unidirectional water transport.

A sandwich-like silk fibroin/polysaccharide composite dressing with continual biofluid draining for wound exudate management

Optimal wound healing requires a wet microenvironment without over-hydration. Inspired by capillarity and transpiration, we have developed a sandwich-like fibers/sponge dressing with continuous exudate drainage to maintain appropriate wound moisture. This dressing is prepared by integrating a three-layer structure using the freeze-drying method. Layer I, as the side that contacts with the skin directly, consists of a hydrophobic silk fibroin membrane; Layer II, providing the pumping action, is made of superabsorbent chitosan-konjac glucomannan sponge; Layer III, accelerating evaporation sixfold compared to natural evaporation, is constructed with a graphene oxide soaked hydrophilic cellulose acetate membrane. Animal experiments showed that the composite dressing had superior wound-healing characteristics, with wounds decreasing to 24.8% of their original size compared to 28.5% for the commercial dressing and 43.2% for the control. The enhanced wound healing can be ascribed to the hierarchical porous structure serves as the fluid-driving factor in this effort; the hydrophilicity of a membrane composed of silk fibroin nanofibers is adjustable to regulate fluid-transporting capacity; and the photothermal effect of graphene oxide guarantees exudates that have migrated to the top layer to evaporate continuously. These findings indicate the unidirectional wicking dressing has the potential to become the next generation of clinical dressings.

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.

Advanced functional nanofibers: strategies to improve performance and expand functions

Nanofibers have a wide range of applications in many fields such as energy generation and storage, environmental sensing and treatment, biomedical and health, thanks to their large specific surface area, excellent flexibility, and superior mechanical properties. With the expansion of application fields and the upgrade of application requirements, there is an inevitable trend of improving the performance and functions of nanofibers. Over the past few decades, numerous studies have demonstrated how nanofibers can be adapted to more complex needs through modifications of their structures, materials, and assembly. Thus, it is necessary to systematically review the field of nanofibers in which new ideas and technologies are emerging. Here we summarize the recent advanced strategies to improve the performances and expand the functions of nanofibers. We first introduce the common methods of preparing nanofibers, then summarize the advances in the field of nanofibers, especially up-to-date strategies for further enhancing their functionalities. We classify these strategies into three categories: design of nanofiber structures, tuning of nanofiber materials, and improvement of nanofibers assemblies. Finally, the optimization methods, materials, application areas, and fabrication methods are summarized, and existing challenges and future research directions are discussed. We hope this review can provide useful guidance for subsequent related work.

Graphical abstract

Customizable bio-based coating of phase-transited lysozyme-COS for durable antibacterial and moisture management on wool fabric

Textiles with efficient moisture management provide a comfortable microenvironment for human body. However, little attention has been paid to sweat-induced bacterial growth alongside. In this study, chitooligosaccharide (COS) was used to modify lysozyme (Lyz-COS) to obtain more excellent antibacterial activity. Lyz-COS could undergo an amyloid-like aggregation by reducing its disulfide bond and hydrogen bond triggered by thiourea dioxide (TD). The Phase-Transited Lyz-COS (PTL-COS) coating increases the hydrophilicity and antibacterial properties of wool fabrics, which can withstand 50 washing cycles and 100 rubbing cycles. In addition, two methods are proposed to customize Janus wool fabrics as desired. Method 1: The PTL-COS film was prepared first, and then the film was transferred to one side of the wool fabric. Method 2: Simply spray the PTL-COS solution on one side of the wool fabric. These two processes are simple to operate and can be customized on demand, enabling single transport of sweat and inhibiting sweat-induced bacterial growth. This work underlines the significance of chitooligosaccharide-modified PTL coatings for functionalization of textile surfaces and provides new insights into the development of more adaptable and smarter textiles and clothing.

A Trilayered Composite Fabric with Directional Water Transport and Resistance to Blood Penetration for Medical Protective Clothing

Functional textiles with enhanced moisture management can facilitate sweat transport away from the skin to improve personal comfort. However, porous materials exhibit low capability of preventing the intrusion of external liquids, becoming a bottleneck in the design of medical protective clothing. Herein, a trilayered composite fabric based on a gradient wettability structure is demonstrated for directional water transport and resistance to blood penetration. The proposed fabric shows distinct advantages, including a high water breakthrough pressure of 2.43 kPa from the external side, an outstanding positive water transport index (1522%), and an antiblood penetration resistance of 2.71 kPa. Moreover, the fabric shows improved comfort with a high moisture transmission (320 g m^-2 h^-1) and desired water evaporation rate (0.36 g h^-1). This work addressed the concern of directional water transport and resistance to blood penetration while providing a comfortable wearing microenvironment, leading to a promising research direction for multifunctional medical textiles.

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.

Review on the Development and Application of Directional Water Transport Textile Materials

Moisture (sweat) management in textile products is crucial to regulate human thermo-physiological comfort. Traditional hydrophilic textiles, such as cotton, can absorb sweat, but they retain it, leading to undesired wet adhesion sensation and even excessive cooling. To address such issues, the development of functional textiles with directional water transport (DWT) has garnered great deal of interest. DWT textile materials can realize directional water transport and prevent water penetration in the reverse direction, which is a great application for sweat release in daily life. In this review article, the mechanism of directional water transport is analyzed. Then, three key methods to achieve DWT performance are reviewed, including the design of the fabric structure, surface modification and electrospinning. In addition, the applications of DWT textile materials in functional clothing, electronic textiles, and wound dressing are introduced. Finally, the challenges and future development trends of DWT textile materials in the textile field are discussed.

Moisture-Wicking, Breathable, and Intrinsically Antibacterial Electronic Skin Based on Dual-Gradient Poly(ionic liquid) Nanofiber Membranes

Electronic skin can detect minute electrical potential changes in the human skin and represent the body's state, which is critical for medical diagnostics and human-computer interface development. On the other hand, sweat has a significant effect on the signal stability, comfort, and safety of electronic skin in a real-world application. In this study, by modifying the cation and anion of a poly(ionic liquid) (PIL) and employing a spinning process, a PIL-based multilayer nanofiber membrane (PIL membrane) electronic skin with a dual gradient is created. The PIL electronic skin is moisture-wicking and breathable due to the hydrophilicity and pore size-gradients. The intrinsically antimicrobial activities of PILs allow the safe collection of bioelectrical signals from the human body, such as electrocardiography (ECG) and electromyography (EMG). In addition, a robotic hand may be operated in real-time, and a preliminary human-computer interface can be accomplished by simple processing of the collected EMG signal. This study establishes a novel practical approach for monitoring and using bioelectrical signals in real-world circumstances via the multifunctional electronic skin.

Nanoarchitectonics for Electrospun Membranes with Asymmetric Wettability

Membranes with asymmetric wettability have attracted significant interest by virtue of their unique transport characteristics and functionalities arising from different wetting behaviors of each membrane surface. The cross-sectional wettability distinction enables a membrane to realize directional liquid transport or multifunction integration, resulting in rapid advance in applications, such as moisture management, fog collection, oil-water separation, and membrane distillation. Compared with traditional homogeneous membranes, these membranes possess enhanced transport performance and higher separation efficiency owing to the synergistic or individual effects of asymmetric wettability. This Review covers the recent progress in fabrication, transport mechanisms, and applications of electrospun membranes with asymmetric wettability and provides a perspective on future development in this important area.

An All-Hydrophobic Fluid Diode for Continuous and Reduced-Wastage Water Transport

Directional water transport that occurs in natural insects and plants is important to both organisms and advanced science and technology. Despite the many studies conducted to facilitate directional liquid transport by constructing double-layered hydrophilic/hydrophobic materials, it remains difficult to achieve continuous water transport and reduce liquid wastage due to the hydrophilic regions. Herein, a directional water transport fabric (DWTF) was fabricated using a simple single-side coating method based on entirely hydrophobic materials. With coating thicknesses of 13-29 μm, the fabric could guide the continuous water motion from the coated to the uncoated side and can be utilized as a "liquid diode". In addition, the DWTF exhibited a water wastage reduction during the transport process, benefiting from the intrinsic hydrophobic properties of the material. Moreover, a plausible mechanism of water transport is proposed to explain the water droplet transfer in the bilayered hydrophobic materials. Consequently, the resulting DWTF exhibited an excellent accumulative one-way transport capability (AOTC) of 965.7% and a desirable overall moisture management capability (OMMC) of 0.92. This work provides an avenue for fabricating smart fluid delivery materials to various applications such as flexible microfluidics, wound dressing, oil-water separation processes, and engineered desiccant materials.

Mussel-Inspired Design of a Self-Adhesive Agent for Durable Moisture Management and Bacterial Inhibition on PET Fabric

Functional textiles with advanced moisture management can enhance human comfort and physiological health. However, conventional wet finishing processes used for textiles are usually highly polluting and exhibit poor fastness. Inspired by the strong underwater adhesion properties of mussels based on cation-π interaction, a novel superhydrophilic polymeric molecule with strong cohesion and adhesion property is designed on a poly(ethylene terephthalate) (PET) fabric. The cation-π hydrophilic agent (CPHA) can efficiently transform the hydrophobic PET fabric to a superhydrophilic one, and its superhydrophilicity can withstand 150 home laundry cycles. In addition, the cationic moieties in the CPHA self-adhere to the PET fabric without any finishing auxiliary that would cause pollution. Due to its strong adhesion, CPHA can be applied to one side of the PET fabric via spray coating and curing to form a Janus hydrophobic/superhydrophilic fabric capable of diode-like one-way sweat transportation (with forward transportation capability of 1115% and backward transportation capability of -1509%). Moreover, the Janus fabric inhibits bacterial growth and invasion, while simultaneously preserving the inner ecological healthy balance of the skin's microflora. This work opens up a pathway to develop adhesives in textile wet processing for more diverse, smarter applications, e.g., quick-dry sportswear, protective suits, or air-conditioning fabrics.

Antibacterial Hybrid Hydrogels

Bacterial infectious diseases and bacterial-infected environments have been threatening the health of human beings all over the world. In view of the increased bacteria resistance caused by overuse or improper use of antibiotics, antibacterial biomaterials are developed as the substitutes for antibiotics in some cases. Among them, antibacterial hydrogels are attracting more and more attention due to easy preparation process and diversity of structures by changing their chemical cross-linkers via covalent bonds or noncovalent physical interactions, which can endow them with various specific functions such as high toughness and stretchability, injectability, self-healing, tissue adhesiveness and rapid hemostasis, easy loading and controlled drug release, superior biocompatibility and antioxidation as well as good conductivity. In this review, the recent progress of antibacterial hydrogel including the fabrication methodologies, interior structures, performances, antibacterial mechanisms, and applications of various antibacterial hydrogels is summarized. According to the bacteria-killing modes of hydrogels, several representative hydrogels such as silver nanoparticles-based hydrogel, photoresponsive hydrogel including photothermal and photocatalytic, self-bacteria-killing hydrogel such as inherent antibacterial peptides and cationic polymers, and antibiotics-loading hydrogel are focused on. Furthermore, current challenges of antibacterial hydrogels are discussed and future perspectives in this field are also proposed.