Smart fibers are considered as promising materials for the fabrication of wearable electronic skins owing to their features such as superior flexibility, light weight, high specific area, and ease of modification. Besides, piezoelectric or triboelectric electronic skins can respond to mechanical stimulation and directly convert the mechanical energy into electrical power for self-use, thereby providing an attractive method for tactile sensing and motion perception. The incorporation of sensing capabilities into smart fibers could be a powerful approach to the development of self-powered electronic skins. Herein, we review several aspects of the recent advancements in the development of self-powered electronic skins constructed with smart fibers. The summarized aspects include functional material selection, structural design, pressure sensing mechanism, and proof-to-concept demonstration to practical application. In particular, various fabrication strategies and a wide range of practical applications have been systematically introduced. Finally, a critical assessment of the challenges and promising perspectives for the development of fiber-based electronic skins has been presented.

Rapid industrialization is accompanied by the deterioration of the natural environment. The deepening crisis associated with the ecological environment has garnered widespread attention toward strengthening environmental monitoring and protection. Environmental sensors are one of the key technologies for environmental monitoring, ultimately enabling environmental protection. In recent decades, micro/nanomaterials have been widely studied and applied in environmental sensing owing to their unique dimensional properties. Electrospinning has been developed and adopted as a facile, quick, and effective technology to produce continuous micro- and nanofiber materials. The technology has advanced rapidly and become one of the hotspots in the field of nanomaterials research. Environmental sensors made from electrospun nanofibers possess many advantages, such as having a porous structure and high specific surface area, which effectively improve their performance in environmental sensing. Furthermore, by introducing functional nanomaterials (carbon nanotubes, metal oxides, conjugated polymers, etc.) into electrospun fibers, synergistic effects between different materials can be utilized to improve the catalytic activity and sensitivity of the sensors. In this review, we aimed to outline the progress of research over the past decade on electrospinning nanofibers with different morphologies and functional characteristics in environmental sensors.

Airborne particulate matter (PM) has been the leading contributor to air pollution, posing a substantial risk to human health, and effective filtration technologies are required. Two-dimensional (2D) materials, such as graphene, graphitic carbon nitride (g-C₃N₄), molybdenum disulfide (MoS₂), and MXenes have emerged in recent years for PM filtration due to their exceptionally large specific surface area and unique electrical properties. Here, the most extensively used 2D materials for PM filtration followed by a summary of their fabrication methods and corresponding morphologies were introduced. Among them, the coating is the most cost-effective technique for achieving large-scale and quick fabrication. Electrospinning can effectively enhance filtration efficiency and reduce pressure drop by upgrading electrostatic force and lowering the fiber diameter. The initial and long-term performance of 2D-material-based filters was summarized. Among all 2D materials, GO is the most studied and shows the best performance by upgrading the dipole–dipole and electrostatic interaction between filters and PM. Future study is expected to explore various 2D materials beyond GO, to evaluate filtration efficiency for submicron PM at m/s level air velocity, and to extend the service life for potential applications.

In this study, an antibacterial nanofiber membrane [polyvinylidene fluoride/Bi₄Ti₃O₁₂/Ti₃C₂T_x (PVDF/BTO/Ti₃C₂T_x)] is fabricated using an electrostatic spinning process, in which the self-assembled BTO/Ti₃C₂T_x heterojunction is incorporated into the PVDF matrix. Benefiting from the internal electric field induced by the spontaneously ferroelectric polarization of BTO, the photoexcited electrons and holes are driven to move in the opposite direction inside BTO, and the electrons are transferred to Ti₃C₂T_x across the Schottky interface. Thus, directed charge separation and transfer are realized through the cooperation of the two components. The recombination of electron–hole pairs is maximumly inhibited, which notably improves the yield of reactive oxygen species by enhancing photocatalytic activity. Furthermore, the nanofiber membrane with an optimal doping ratio exhibits outstanding visible light absorption and photothermal conversion performance. Ultimately, photothermal effect and ferroelectric polarization enhanced photocatalysis endow the nanofiber membrane with the ability to kill 99.61% ± 0.28% Staphylococcus aureus and 99.71% ± 0.16% Escherichia coli under 20 min of light irradiation. This study brings new insights into the design of intelligent antibacterial textiles through a ferroelectric polarization strategy.

Hard-to-dissolve polymers provide next-generation alternatives for high-performance filter materials owing to their intrinsically high chemical stability, superior mechanical performance, and excellent high-temperature resistance. However, the mass production of hard-to-dissolve nanofibers still remains a critical challenge. A simple, scalable, and low-cost ionic solution blow-spinning method has herein been provided for the large-scale preparation of hard-to-dissolve Nomex polymeric nanofibers with an average diameter of nearly 100 nm. After rapidly dissolving Nomex microfibers in the lithium chloride/dimethylacetamide (LiCl/DMAc) solution system, the conductive solution can be stably and conductivity-independently processed into nanofibers. The method optimizes electrospinning and avoids spinnability degradation and potential safety hazards caused by high electrical conductivity. Owing to nanofibrous structure and high dipole moment, Nomex nanofibrous filters show a stable high filtration efficiency of 99.92% for PM_0.3 with a low areal density of 4.6 g m⁻², as well as a low-pressure drop of 189.47 Pa. Moreover, the flame-retardant filter can work at 250 °C and 280 °C for a long and short time without shrinking or burning, respectively, exhibiting a high filtration efficiency of 99.50% for PM_0.3−10.0. The outstanding properties and low cost enable the efficient capture of PM from various high-temperature exhausts, making Nomex nanofibrous membrane an even more ideal industrial-grade air filter than polypropylene, polytetrafluoroethylene, polyimide, and ceramic nanofibrous filters.

Hard-to-dissolve nanofibers provide alternatives for high-efficiency and low-resistant air filtration but are limited by the universality and economics of fabrication methods. A scalable and efficient ionic solution blow-spinning strategy has herein been proposed in preparing hard-to-dissolve nanofibrous filters.

Monofilament type of polyaromatic amide (PA) and carbon nanotube (CNT) composite fibers is presented. A concept of a lyotropic liquid crystal (LLC) constructed via a spontaneous self-assembly is introduced to mitigate the extremely low compatibility between PA and CNT. These approaches provide an effective co-processing route of PA and CNT simultaneously to fabricate the uniform, continuous, and reliable composite fibers through a wet-spinning. Interestingly, the addition of a small amount PA into the dope solution of CNT governs the LLC mesophase not only in a spinneret stage but also in a coagulant region. Thus, the developed PA/CNT composite fibers have the high uniaxial orientational order and the close interfacial packing compared to the pure CNT fibers. The PA/CNT composite fibers achieve the outstanding tensile strength, electrical conductivity, and electrochemical response, while maintaining a lightweight. They also exhibit the chemical, mechanical, and thermal robustness. All of these advantages can make flexible, sewable, and washable PA/CNT composite fibers ideal nanocomposite materials for use in next-generation information and energy transporting system by replacing conventional metal electrical conductors.

The lyotropic liquid crystal self-assembly governed by doping the aramid polymers shows the ability to construct mechanically strong and continuous carbon nanotube-based composite fibers that can be used in the lightweight and robust electrical wiring for extreme environmental applications.

Obtaining detailed insight into the photocatalytic performance of heterogeneous photocatalytic materials, is important for evaluating material properties as well as guiding material design. However, capture of the detailed matter changes on a photocatalyst surface in real time, and in situ during photocatalysis remains challenging. This work reports a promising optical microfiber sensor integrating a photocatalytic reaction monolayer on an optical microfiber surface to monitor reaction kinetics using Cu₂O-based heterogeneous photocatalysts, as an example. The evanescent field of microfiber is used to track the photocatalytic process in real time, through the interaction with the catalytic layer, by monitoring the surface refractive index changes caused by adsorption and degradation. Since the catalytic layer is less than 1 µm thick, the typical high-power light source can be replaced by low-power light irradiation. This method successfully reveals that relative to the pristine Cu₂O microspheres, the photocatalytic activity is enhanced by the incorporation of Ti₃C₂Tx MXene into Cu₂O, whereas incorporation of CdS into Cu₂O suppresses the activity. Compared with the existing methods used for photocatalysis evaluation, this optical microfiber can be directly employed in real matrices to track local photocatalytic performance. It can also provide details about the different adsorption/degradation kinetics of photocatalysts. It is suitable for most photocatalytic processes and is not limited to pollutants with characteristic UV–visible absorption spectra. This study provides important inspiration for the future development of in situ, real-time reaction assessment.

Durable superamphiphobic surfaces are highly desired for real-world applications such as self-cleaning, anti-fouling, personal protection, and functional sportswear. However, challenges still exist in constructing robust superamphiphobic surfaces by using short-fluorinated polymers as one of the promising alternatives for environmentally unfriendly long perfluorinated side-chain polymers. Hierarchical patterns on biological skins endow the creatures with a specific surface for survival. Here, a facile strategy was proposed to generate hierarchical wrinkles for ultradurable superamphiphobic fabrics by simulating the deformation adaptability of snakeskin. Snake-like hierarchical winkling was constructed by the infusion of reactive perfluorooctyltriethoxysilane (FOS) in a wet chemical plus vapor polymerization process. Upon the infusion of FOS, the mismatch of shrinkage caused by gradient crosslinking leads to the formation of a soft wrinkled poly (perfluorooctyl triethoxysilane) (poly-FOS) surface. Such a snakeskin-like hierarchical wrinkled surface and high fluorine density of poly-FOS endowed the treated superamphiphobic fabrics with high water resistance (contact angle 169°), castor oil resistance (154°), and extraordinary durability (withstanding 100 standard laundries, 15,000 rubbing cycles and strong acid and alkali solutions). Moreover, a superamphiphobic surface can be formed on various substrates, including fabric, wood, paper, and glass. This work thus gives new insights into the environmentally friendly manufacture of ultradurable superamphiphobic fabrics.

Injuries to the nervous system account for the widespread morbidity, mortality, and discomfort worldwide. Artificial nerve guidance conduits (NGCs) offer a promising platform for nerve reconstruction, however, they require extracellular matrix (ECM)-like features to better mimic the in vivo microenvironment. Consequently, this research was aimed to fabricate heparin/growth factors (GFs)-immobilized artificial NGCs. Heparin was covalently immobilized onto aligned electrospun polycaprolactone/gelatin (PCL/Gel) nanofibers. Thereafter, basic fibroblast growth factor (bFGF) and nerve growth factor (NGF) were preferentially immobilized on heparinized nanofibers; the immobilization efficiency of GFs was found to be 50% with respect to (w.r.t.) their initial loaded amounts. The in vivo implantation of NGCs in a sciatic nerve defect model revealed the successful retention (~ 10% w.r.t the initial loaded amount) and bioactivity of NGF for up to 5 days. The permeability of bovine serum albumin (BSA) from nanofibrous membranes was further assessed and found to be comparable with the commercialized cellulose acetate membranes. The bioactivity of NGCs was assessed in a sciatic nerve defect model in rats for short-term (1 week) and long-term (1-month). The NGCs displayed good structural stability and biocompatibility in vivo. The in vivo evaluation revealed the accumulation of host cells into the transplanted NGCs. Taken together; these heparin/GFs-immobilized artificial NGCs may have broad implications for nerve regeneration and related tissue engineering disciplines.

Excessive exudate at wound sites increases treatment difficulty and severely decelerates the healing process. In wound exudate management, dressings with unidirectional liquid transport capability have exhibited enormous potential. However, it remains challenging to improve the one-way liquid transport efficiency. Herein, a trilayered fibrous dressing is constructed by sequentially electrospinning polyurethane (PU) and polyvinylidene fluoride (PVDF) onto cotton fabric. Through hot pressing, a stable wettability gradient is formed across the PVDF/PU/cotton dressing due to the melting and bridging of PU nanofibers. The trilayered dressing exhibited rapid unidirectional transport with water penetrating from the hydrophobic side to the hydrophilic side in 6 s. The hydrostatic pressure from the hydrophilic side to the hydrophobic side is 569% higher than that from the hydrophobic side to the hydrophilic side, indicating that the dressing has a profound unidirectional conductivity. In vivo experiments demonstrates that the trilayered dressing can accelerate the wound healing process, especially in the early stages of wound occurrence, by quickly draining the excessive exudate. This study provides a new method to construct wound dressings with wettability gradients, which are advantageous for efficient exudate removal.

Currently, most of the materials for oil–water separation membranes are limited to fluorine-based polymers with low surface energy. However, it is not biodegradable and requires large amounts of organic and toxic solvents in the membrane manufacturing process. Therefore, interest in the development of a new eco-friendly oil–water separation membrane that does not cause secondary pollution and exhibits selective wettability characteristics in water or oil is increasing. The biopolymeric nanofibrous membranes inspired by fish skin can provide specific underwater oleophobicity, which is effective for excellent oil–water separation efficiency and prevention of secondary contamination. Fish gelatin, which is highly soluble in water and has a low gelation temperature, can be electrospun in an aqueous solution and has the same polar functional groups as the hydrophilic mucilage of fish skin. In addition, the micro/nanostructure of fish skin, which induces superoleophobicity in water, introduces a bead-on-string structure using the Rayleigh instability of electrospinning. The solubility of fish gelatin in water was removed using an eco-friendly crosslinking method using reducing sugars. Fish skin-mimicking materials successfully separated suspended oil and emulsified oil, with a maximum flux of 2086 Lm⁻² h⁻¹ and a separation efficiency of more than 99%. The proposed biopolymeric nanofibrous membranes use fish gelatin, which can be extracted from fish waste and has excellent biodegradability with excellent oil–water separation performance. In addition, polymer material processing, including membrane manufacturing and crosslinking, can be realized through eco-friendly processes. Therefore, fish skin-inspired biopolymeric membrane is expected to be a promising candidate for a sustainable and effective oil–water separation membrane in the future.

Electrospinning is a simple and versatile method to produce nanofiber filters. However, owing to bending instability that occurs during the electrospinning process, electrospinning has frequently produced a non-uniform-thickness nanofiber filter, which deteriorates its air filtration. Here, an adaptive electrospinning system based on reinforcement learning (E-RL) was developed to produce uniform-thickness nanofiber filters. The E-RL accomplished a real-time thickness measurement of an electrospun nanofiber filter by measuring the transmitted light through the nanofiber filter using a camera placed at the bottom of the collector and converting it into thickness using the Beer–Lambert law. Based on the measured thickness, the E-RL detected the non-uniformity of the nanofiber filter thickness and manipulated the movable collector to alleviate the non-uniformity of the thickness by a pre-trained reinforcement learning (RL) algorithm. For the training of the RL algorithm, the nanofiber production simulation software based on the empirical model of the deposition of the nanofiber filter was developed, and the training process of the RL algorithm was repeated until the optimal policy was achieved. After the training process with the simulation software, the trained model was transferred to the adaptive electrospinning system. By the movement of the collector under the optimal strategy of RL algorithm, the non-uniformity of such nanofiber filters was significantly reduced by approximately five times in standard deviation and error for both simulation and experiment. This finding has great potential in improving the reliability of electrospinning process and nanofiber filters used in research and industrial fields such as environment, energy, and biomedicine.

Micro- and nano-fibers of shape memory polymers (SMP) offer multiple advantages like high specific surface area, porosity, and intelligence, and are suitable for biomedical applications. In this study, biodegradable poly (p-dioxanone) (PPDO) materials were incorporated to improve the brittleness of shape memory polylactic acid (PLA), and plasticizers were used to reduce the transition temperature of SMP composites such that their transitions could be induced close to body temperature. Furthermore, an electrostatic spinning technology was applied to prepare SMP fibers with wrinkled structures and regulate their microstructures and morphologies such that the intelligent transition of wrinkled and smooth morphologies can be achieved on the fiber surface. The application of this controllable-morphology fiber membrane in intelligent controlled drug release and scar inhibition after Ahmed Glaucoma Valve (AGV) implantation was also studied. The drug release from the stretched and deformed drug-loaded fiber membranes was faster than those from membranes with the original shape. This membrane with micro- and nano-fibers had good anti-scarring effects that improved after drug loading. The achievement of intelligent controlled drug release and the evident anti-scarring effects of the membrane broaden the application of SMP fibers in the biomedical field.

Yarn-based batteries with the dual functions of wearable and energy storage have demonstrated promising potential in wearable energy textiles. However, it is still an urgent problem to construct efficient and flexible electrodes while optimize the configuration of yarn-based batteries to maintain excellent electrochemical performance under different mechanical deformations. Herein, NiCo₂S_4−x nanotube arrays with tunable S-vacancies are constructed on carbon yarn (CY) (NiCo₂S_4−x@CY) by a facile hydrothermal strategy. The aqueous zinc-ion batteries (ZIBs) with NiCo₂S_4−x@CY as cathodes exhibit exceptional discharge capacity (271.7 mAh g⁻¹) and outstanding rate performance (70.9% capacity retention at 5 A g⁻¹), and reveal a maximum power density of 6,059.5 W kg⁻¹ and a maximum energy density of 432.2 Wh kg⁻¹. It is worth noting that the tunable S-vacancies promote the surface reconfiguration and phase transitions of NiCo₂S_4−x, thereby enhancing the conductivity and charge storage kinetics. The high reactivity and cycling stability of NiCo₂S_4−x@CY can be related to the discharge products of S-doped NiO and CoO. Furthermore, flexible stretchable yarn-based ZIBs with wrapped yarn structures are constructed and exhibit excellent tensile stability and durability under a variety of mechanical deformations. As a proof of concept, the ZIBs integrated into the fabric show excellent electrochemical performance even in response to simultaneous stretching and bending mechanical deformations. The proposed strategy provides novel inspiration for the development of highly efficient and economical yarn-based ZIBs and wearable energy textiles.

Insufficient bionic performance is a structural obstacle and makes urethral repair unobtainable. To overcome this challenge, we mimicked the urethral matrix and applied two electrospinning techniques to build a double-layer sponge tube of nanofibers and nanoyarns. Intriguingly, silk fibroin (SF) and vitamin B5 (VitB5) could be introduced to increase the elasticity of the outer layer and reduce the hydrophobicity to further improve mesenchymal cell proliferation. Systematic experiments validated the bionic structure, biocompatibility, and exosome delivery capacity in this scaffold. We achieved scarless urethral repair by delivering the bioactive growth factors from adipose-derived stem cell exosomes by physical absorption. Biological regeneration of the urethra can be accomplished with continuous epithelium in animals. Furthermore, bioinformatics studies revealed that the expression of cell proliferation and fibrotic genes (e.g., Wnt7a, cfa-miR-574) was responsible for the biological regeneration of the adipose-derived stem cells exosomes (ADSC-exos) by delivering poly l-lactide-co-caprolactone/SF/VitB5 bilayer sponge (PSVBS) via reduced fibrosis gene expression, as well as improved epithelial formation and blood vessel formation. Therefore, the PSVBS design appeared to be an instructive approach for urethral and other tubular organ regeneration.

TOC figure: The electrospun double-layer sponge fabricated by electrospinning simulated the microstructure of the urethra. The sponge can deliver the exosomes through a physical absorption style. The P(LLA-CL)/SF/VitB5 bilayer sponge has great potential to promote vascular regeneration and wound healing and can effectively inhibit fibrosis.

Flexible wearable ultraviolet (UV) shielding, monitoring and warning devices have important applications in civil and military fields. However, most flexible wearable UV devices show unsatisfactory performance due to their poor stability and easy failure at large strains. Herein, inspired by tree rings, we engineered a hierarchical composite nanofibrous helix with an alternately stacked Archimedes spiral structure via a cost-effective strategy. Based on a photo-electricity-acoustic energy conversion system, we fabricated an all-in-one device exhibiting strain-insensitive UV protection at 0–500% strain for UV shielding as well as strain-sensitive UV monitoring at 500–1500% strain for UV early warning. Compared with previously reported common nanofibrous membrane devices, the as-prepared composite nanofibrous helix shows great advantages in terms of stability and UV protection, especially at large strains. Furthermore, the helix demonstrates multiple functions of wear resistance, antibacterial properties, biodegradation and knittability. This versatile strategy holds great promise for wearable electronics and multifunctional devices.