With the development and prosperity of Internet of Things (IoT) technology, wearable electronics have brought fresh changes to our lives. The demands for low power consumption and mini-type wearable power systems for wearable electronics are more urgent than ever. Thermoelectric materials can efficiently convert the temperature difference between body and environment into electrical energy without the need for mechanical components, making them one of the ideal candidates for wearable power systems. In recent years, a variety of high-performance thermoelectric materials and processes for the preparation of large-scale single-fiber devices have emerged, driving the application of flexible fiber-based thermoelectric generators. By weaving thermoelectric fibers into a textile that conforms to human skin, it can achieve stable operation for long periods even when the human body is in motion. In this review, the complete process from thermoelectric materials to single-fiber/yarn devices to thermoelectric textiles is introduced comprehensively. Strategies for enhancing thermoelectric performance, processing techniques for fiber devices, and the wide applications of thermoelectric textiles are summarized. In addition, the challenges of ductile thermoelectric materials, system integration, and specifications are discussed, and the relevant developments in this field are prospected.
The lithium-ion (Li-ion) battery has received considerable attention in the field of energy conversion and storage due to its high energy density and eco-friendliness. Significant academic and commercial progress has been made in Li-ion battery technologies. One area of advancement has been the addition of nanofiber materials to Li-ion batteries due to their unique and desirable structural features including large aspect ratios, high surface areas, controllable chemical compositions, and abundant composite forms. In the past few decades, considerable research efforts have been devoted to constructing advanced nanofiber materials possessing conductive networks to facilitate efficient electron transport and large specific surface areas to support catalytically active sites, both for the purpose of boosting electrochemical performance. Herein, we focus on recent advancements of nanofiber materials with carefully designed structures and enhanced electrochemical properties for use in Li-ion batteries. The synthesis, structure, and properties of nanofiber cathodes, anodes, separators, and electrolytes, and their applications in Li-ion batteries are discussed. The research challenges and prospects of nanofiber materials in Li-ion battery applications are delineated.
Hemodialysis, the most common modality of renal replacement therapy, is critically required to remove uremic toxins from the blood of patients with end-stage kidney disease. However, the chronic inflammation, oxidative stress as well as thrombosis induced by the long-term contact of hemoincompatible hollow-fiber membranes (HFMs) contribute to the increase in cardiovascular diseases and mortality in this patient population. This review first retrospectively analyzes the current clinical and laboratory research progress in improving the hemocompatibility of HFMs. Details on different HFMs currently in clinical use and their design are described. Subsequently, we elaborate on the adverse interactions between blood and HFMs, involving protein adsorption, platelet adhesion and activation, and the activation of immune and coagulation systems, and the focus is on how to improve the hemocompatibility of HFMs in these aspects. Finally, challenges and future perspectives for improving the hemocompatibility of HFMs are also discussed to promote the development and clinical application of new hemocompatible HFMs.
The manipulation of cell behaviors is essential to maintaining cell functions, which plays a critical role in repairing and regenerating damaged tissue. To this end, a rich variety of tissue-engineered scaffolds have been designed and fabricated to serve as matrix for supporting cell growth and functionalization. Among others, scaffolds made of electrospun fibers showed great potential in regulating cell behaviors, mainly owing to their capability of replicating the dimension, composition, and function of the natural extracellular matrix. In particular, electrospun fibers provided both topological cues and biofunctions simply by adjusting the electrospinning parameters and/or post-treatment. In this review, we summarized the most recent applications and advances in electrospun nanofibers for manipulating cell behaviors. First, the engineering of the secondary structures of individual fibers and the construction of two-dimensional nanofiber mats and nanofiber-based, three-dimensional scaffolds were introduced. Then, the functionalization strategies, such as endowing the fibers with bioactive, physical, and chemical cues, were explored. Finally, the typical applications of electrospun fibers in controlling cell behaviors (i.e., cell adhesion and proliferation, infiltration, migration, neurite outgrowth, stem cell differentiation, and cancer cell capture and killing) were demonstrated. Taken together, this review will provide valuable information to the specific design of nanofiber-based scaffolds and extend their use in controlling cell behaviors for the purpose of tissue repair and regeneration.
Prevention of spreading viral respiratory disease, especially in case of a pandemic such as coronavirus disease of 2019 (COVID-19), has been proved impossible without considering obligatory face mask-wearing protocols for both healthy and contaminated populations. The widespread application of face masks for long hours and almost everywhere increases the risks of bacterial growth in the warm and humid environment inside the mask. On the other hand, in the absence of antiviral agents on the surface of the mask, the virus may have a chance to stay alive and be carried to different places or even put the wearers at risk of contamination when touching or disposing the masks. In this article, the antiviral activity and mechanism of action of some of the potent metal and metal oxide nanoparticles in the role of promising virucidal agents have been reviewed, and incorporation of them in an electrospun nanofibrous structure has been considered an applicable method for the fabrication of innovative respiratory protecting materials with upgraded safety levels.
The huge gap between inadequate clean water supply and demanding human needs can be narrowed by sustainable and green methods of solar-driven evaporation, which effectively converts solar energy into thermal energy to purify seawater and wastewater. Electrospun materials produced from a facile electrospinning technique can be combined with functional photothermal materials, giving rise to various superior advantages in solar water evaporation. However, to date, few reviews have focused on this topic. This article reviews the recent progress of electrospun nanofiber-based evaporation systems focusing on polymer selection, available solar materials, incorporation strategies of solar materials, system configurations, factors influencing the performance, and applications of electrospun nanofiber evaporation systems. The incorporation strategies of solar materials and system configurations in electrospun nanofiber evaporators are classified and systematically discussed. Finally, the challenges and perspectives of the electrospun nanofiber evaporation systems are also presented. This review updates the progress of electrospun nanofiber evaporation systems and simultaneously stimulates attractive research on designing electrospun nanofiber-based photothermal systems for applications in solar water evaporation, photothermal therapy, electricity generation, and other related areas.
The inhospitable niche at the injury site after spinal cord injury (SCI) brings several challenges to neural stem cell (NSC) therapy, such as limited NSC retention and neuronal differentiation. Biomaterial-based stem cell transplantation has become a promising strategy for building a favorable niche to stem cells. Herein, an aligned fibrin nanofiber hydrogel modified with N-Cadherin-Fc (AFGN) was fabricated by electrospinning and biochemical conjugation to deliver NSCs for SCI repair. The AFGN hydrogel provides multimodal cues, including oriented nanofibrous topography, soft stiffness, and specific cell binding ligand, for directing NSC functions and nerve regeneration. The conjugated N-Cadherin-Fc recapitulated the homophilic cell–cell interaction for NSCs’ adhesion on AFGN and modulated cellular mechanosensing in response to AFGN for NSC differentiation. In addition, the AFGN hydrogel carrying exogenous NSCs was implanted in a rat 2 mm-long complete transected SCI model and significantly promoted the grafted NSCs retention, immunomodulation, neuronal differentiation, and in vivo integration with inherent neurons, thus finally achieved renascent neural relay formation and an encouraging locomotor functional recovery. Altogether, this study represents a valuable strategy for boosting NSC-based therapy in SCI regeneration by engineering an NSC-specific niche.
Intense heat waves pose a serious threat to public health and well-being, especially in outdoor spaces. Outdoor high-temperature environments without air conditioners are major challenges for humanity. However, an achievable approach that can provide outdoor cooling without consuming any energy is lacking. Hence, this work presents a novel hierarchical fabric emitter (HFET) used for sunshade sheds to provide radiative outdoor cooling for humanity, the HFET is composed of polyethylene/silicon dioxide/silicon nitride film, melt-blown polypropylene film, and polydimethylsiloxane film from top to bottom. In addition to reflecting 94% solar irradiance by its top surface, the HFET shows selective emission (0.82 in the atmospheric window and 0.38 outside the atmospheric window) on its top surface to outer space and broadband absorption (0.80 in the longwave infrared band) on its bottom surface from the inside. This bidirectional asymmetric emission enables the simulated skin to avoid overheating by 2–11 °C relative to the reverse HFET and bare cases under direct sunlight. Due to its excellent cooling capability, the HFET will be one of the most considerable solutions for outdoor cooling in hot summer environments.
Wearable tensile strain sensors have attracted substantial research interest due to their great potential in applications for the real-time detection of human motion and health through the construction of body-sensing networks. Conventional devices, however, are constantly demonstrated in non-real world scenarios, where changes in body temperature and humidity are ignored, which results in questionable sensing accuracy and reliability in practical applications. In this work, a fabric-like strain sensor is developed by fabricating graphene-modified Calotropis gigantea yarn and elastic yarn (i.e. Spandex) into an independently crossed structure, enabling the sensor with tunable sensitivity by directly altering the sensor width. The sensor possesses excellent breathability, allowing water vapor generated by body skin to be discharged into the environment (the water evaporation rate is approximately 2.03 kg m−2 h−1) and creating a pleasing microenvironment between the sensor and the skin by avoiding the hindering of perspiration release. More importantly, the sensor is shown to have a sensing stability towards changes in temperature and humidity, implementing sensing reliability against complex and changeable wearable microclimate. By wearing the sensor at various locations of the human body, a full-range body area sensing network for monitoring various body movements and vital signs, such as speaking, coughing, breathing and walking, is successfully demonstrated. It provides a new route for achieving wearing-comfortable, high-performance and sensing-reliable strain sensors.
High-performance wearable sensors that detect complex, multidimensional signals are indispensable in practical applications. Most existing sensors can only detect axial deformations or single stimuli, dramatically limiting their application fields. In this study, anisotropic strain and deformation-insensitive pressure sensors were effectively constructed based on a rigid-flexible synergistic stretchable substrate. Furthermore, we developed a three-dimensional integrated sensor with highly directional selective sensing through reasonable design and assembly. This integrated sensor recognizes the amplitude and direction of strain in the plane with a maximum gauge factor of 635 and an unprecedented selectivity of 13.99. Additionally, this device can also monitor the pressure outside the plane with a sensitivity of 0.277 kPa−1. We further investigated the working mechanism of sensor anisotropy and confirmed the application of the sensor in detecting complex multifreedom human joint movements. This research discovery provides new ideas and methods for developing multidimensional sensors, which is essential for broadening the application field of wearable electronic products.
Flexible electronics are essential for the rapid development of human–machine interface technology, encompassing sensors and energy storage systems. Solid-state supercapacitors with 1D nanofiber electrodes are critical for enhancing ion transport. In this study, a flexible supercapacitor integrated with a strain sensor was designed using a polyvinyl alcohol/polymethyl methacrylate (PVA/PMMA)-based electrolyte and a metal–organic framework (MOF)-derived Zr–nanoporous carbon mat (Zr–NPC). The sensor showed remarkable sensitivity over a broad strain range, enabling reliable and precise detection of mechanical deformation. The supercapacitor with Zr–NPC@PVDF electrode also demonstrated a specific capacitance of 286 mF cm−2 at 0.5 mA cm−2, maintaining high flexibility and mechanical strength. The fabricated supercapacitor maintained around 81% charge retention after 10,000 cycles. Ultimately, the self-powered integrated model was directly connected to the human body to detect physical motion, accentuating its potential for widespread applications in wearable technology.
Wearable sensors have drawn vast interest for their convenience to be worn on body to monitor and track body movements or exercise activities in real time. However, wearable electronics rely on powering systems to function. Herein, a self-powered, porous, flexible, hydrophobic and breathable nanofibrous membrane based on electrospun polyvinylidene fluoride (PVDF) nanofiber has been developed as a tactile sensor with low-cost and simple fabrication for human body motion detection and recognition. Specifically, effects of multi-walled carbon nanotubes (CNT) and barium titanate (BTO) as additives to the fiber morphology as well as mechanical and dielectric properties of the piezoelectric nanofiber membrane were investigated. The fabricated BTO@PVDF piezoelectric nanogenerator (PENG) exhibits the high β-phase content and best overall electrical performances, thus selected for the flexible sensing device assembly. Meanwhile, the nanofibrous membrane demonstrated robust tactile sensing performance that the device exhibits durability over 12,000 loading test cycles, holds a fast response time of 82.7 ms, responds to a wide pressure range of 0–5 bar and shows a high relative sensitivity, especially in the small force range of 11.6 V/bar upon pressure applied perpendicular to the surface. Furthermore, when attached on human body, its unique fibrous and flexible structure offers the tactile sensor to present as a health care monitor in a self-powered manner by translating motions of different movements to electrical signals with various patterns or sequences.
Radioactive iodine element mainly in CH3I is a key fission product of concern in the nuclear fuel cycle, which directly threatens human health if released into the environment. Effective capture of the I element is essential for human health protection. The iodine filter, consisting of an activated carbon inner core and cotton filter, is the most common radioactive iodine protection product. Currently, the activated carbon inside the iodine filter suffers from the weak adsorption efficiency and high cost. Herein, a process based on a strong alkali activation method was developed to significantly improve iodine absorption and reduce the cost. A series of flexible porous carbon fibers with a high specific surface area (up to about 1,500 ~ 2,200 m2/g) were prepared by carbonation of the phenolic resin fibers (PF, prepared through melt spinning and crosslink) followed by activation via KOH treatment. Meanwhile, the nitrogen-doped sp2-heterogeneous carbon atoms were prepared by adding nitrogen sources such as urea which led to a high surface area nano-porous fibers with an average pore size of ~ 2.4 nm. The nitrogen-doped porous carbon fibers exhibit very high adsorption for liquid iodine and iodine vapor. The liquid iodine adsorption capacity of nitrogen-doped porous carbon NDAC-4 prepared under 800 °C reaches 2,120 mg/g, which is 2.1 times higher than that of the commercial iodine filter, and for iodine vapor the capacity can reach 5,330 mg/g. Meanwhile, the CH3I adsorption capacity is 510 mg/g, which is 3.4 times higher than that of commercial unmodified viscose fibers and has greater stability and circularity. Importantly, the research has met the requirements of industrial production, and the fabrication of phenolic-fibers-based protection equipment can be widely used in the nuclear radiation industry.
Achieving efficient hemostasis and wound management is vital to preserve life and restore health in case of extensive hemorrhagic skin damage. Here, we develop a filter pump-like hierarchical porous-structure (HPS) dressing based on a non-woven substrate, konjac glucomannan (KGM) aerogel, and bi-functional microporous starch (BMS). The KGM aerogel intercalates into the non-woven network structure, forming a hydrophilic frame to stimulate the plasma permeation toward the interior in synergy with the hydrophilic pores of the BMS. The BMS surface forms a hydrophobic matrix that fills the spaces of the KGM hydrophilic frame, contributing to the isolation and aggregation of blood cells on the surface of the HPS dressing to establish rapid hemostasis. Animal model experiments suggest reliable HPS dressing hemostatic capacity, as it is able to stop ear artery and liver bleeding within 97.6 ± 15.2 s and 67.8 ± 5.4 s, respectively. Furthermore, the dressings exhibit antibacterial properties and enabled wound healing within 2 weeks. In vitro hemolysis and cytotoxicity tests also confirm the biocompatibility of HPS dressings. This novel “two-in-one” hemostatic dressing facilitates tissue repair of bleeding wounds over the entire recovery period, thereby providing a convenient strategy for wound management.
A Gemini HPS dressing for both hemostasis and wound healing was proposed using amphiphilic hierarchical-porous structures to isolate and aggregate blood cells to promote hemostasis, and alloy nanoparticles to inhibit bacterial proliferation to accelerate wound healing.
Improving the accuracy of shape sensors based on multicore fibers (MCFs) is challenging but of great importance for real-time 3D shape detection, especially in visually inaccessible areas. In this work, a novel approach is proposed to improve MCF shape sensor accuracy using an ultraviolet transparent liquid mediated fiber Bragg grating (FBG) inscription technique and a twist-isolating packaging method. A newly developed UV index matching liquid (UV-IML) is used to generate uniform light field at all the MCF cores, enabling FBG inscription with high accuracy. Additionally, a new stress fully released (SFR) packaging method is implemented to isolate the sensor from any external twists. The MCF shape sensor shows a maximum relative error of only 3.33% and the lowest reported relative sensitivity error of 1.11% cm−1. Moreover, a real-time 3D shape sensing system with a response frequency larger than 30 Hz is constructed using the unique MCF shape sensor. The highly accurate real-time 3D shape sensing results indicate potential applications for in vivo shape estimation of endoscopies and soft robots.
A highly accurate MCF shape sensor for real-time 3D shape detection in visually inaccessible areas is developed. The MCF shape sensor shows a maximum relative error of 3.33% and the lowest reported relative sensitivity error of 1.11% cm−1. The novel ultraviolet index matching liquid FBG inscription method and stress fully released packaging method ensures high accuracy.
Casualties are frequent in high-risk environments, particularly in high-risk chemical and high-temperature fire environments, due to improper protection or accidents. While wearable sensors can offer real-time biomechanical monitoring in fire and chemical environments, they cause discomfort, contain toxic heavy metals, and lack resistance to fire and acid/alkali. Herein, a facile approach to fabricating metal-free fire/acid/alkali-resistant poly(m-phenylene isophthalamide) fiber and carbon nanofiber composite triboelectric nanogenerator (PMIA/CNF-TENG) was demonstrated. The PMIA/CNF-TENG shows the advantages of textile construction including flexibility, waterproofing, and moisture permeability. It also exhibits unique functions, such as ultrahigh fire/temperature resistance, strong acid and alkali protection, the ability to monitor human signals in real time with self-power, handwritten input for danger signals, and sudden risk perception. The PMIA/CNF-TENG possessed an open-circuit voltage (VOC) retention rate of 96.8% even at 250 °C, thereby showing considerably higher thermal stability than conventional flame-retardant TENGs. When moved from room temperature to a simulated fire environment, the biomotion-generated VOC increased by 136.7% for bending the elbow and by over 900% for hand input, indicating good fire-sensing capability. In addition, output signal strength by solid–liquid contact depended on the solution type and corresponded to the laws—NaOH > HNO3 > H2SO4 > H2O, indicating potential applications in chemical splash detection and active acid–alkali liquid identification. Moreover, the PMIA/CNF-TENG could be built into wireless intelligent sensing systems to achieve remote biomotion and risk perception.
The fabrication of advanced radiation detectors is an important subject due to the wide use of radiation sources in scientific instruments, medical services, security check, non-destructive inspection, and nuclear industries. However, the manufacture of flexible and stretchable radiation detectors remains a challenge. Here, we report the scalable fabrication of super-elastic scintillating fibers and fabrics for visual radiation detection by thermal drawing and melt-spinning methods using styrene-b-(ethylene-co-butylene)-b-styrene, and scintillating Gd2O2S: Tb (GOS). Microstructure evolution, rheological properties, and radiation–composite interaction are studied to reveal the excellent processability, elasticity, and radiation detection ability of the fabricated fibers. Benefiting from the physical crosslinking structural features of the polymer matrix and the excellent radiation absorption capacities of GOS, the resulting fiber can sustain high strains of 765% with a high content of GOS dopants (2 wt.%) and has excellent X-ray detection performance with the limit down to 53 nGyair s−1. Furthermore, stretchable fabrics are constructed, and their applications in various fields, such as radiation warning, and X-ray imaging, are demonstrated. Our work not only provides a new type of super-elastic scintillating fibers and fabrics for smart textiles but also demonstrates their potential applications in the nuclear field.
Air pollution caused by the rapid development of industry has always been a great issue to the environment and human being’s health. However, the efficient and persistent filtration to PM0.3 remains a great challenge. Herein, a self-powered filter with micro–nano composite structure composed of polybutanediol succinate (PBS) nanofiber membrane and polyacrylonitrile (PAN) nanofiber/polystyrene (PS) microfiber hybrid mats was prepared by electrospinning. The balance between pressure drop and filtration efficiency was achieved through the combination of PAN and PS. In addition, an arched TENG structure was created using the PAN nanofiber/PS microfiber composite mat and PBS fiber membrane. Driven by respiration, the two fiber membranes with large difference in electronegativity achieved contact friction charging cycles. The open-circuit voltage of the triboelectric nanogenerator (TENG) can reach to about 8 V, and thus the high filtration efficiency for particles was achieved by the electrostatic capturing. After contact charging, the filtration efficiency of the fiber membrane for PM0.3 can reach more than 98% in harsh environments with a PM2.5 mass concentration of 23,000 µg/m3, and the pressure drop is about 50 Pa, which doesn’t affect people’s normal breathing. Meanwhile, the TENG can realize self-powered supply by continuously contacting and separating the fiber membrane driven by respiration, which can ensure the long-term stability of filtration efficiency. The filter mask can maintain a high filtration efficiency (99.4%) of PM0.3 for 48 consecutive hours in daily environments.
Reusable face masks are an important alternative for minimizing costs of disposable and surgical face masks during pandemics. Often complementary to washing, a prolonged lifetime of face masks relies on the incorporation of self-cleaning materials. The development of self-cleaning face mask materials requires the presence of a durable catalyst to deactivate contaminants and microbes after long-term use without reducing filtration efficiency. Herein, we generate self-cleaning fibers by functionalizing silicone-based (polydimethylsiloxane, PDMS) fibrous membranes with a photocatalyst. Coaxial electrospinning is performed to fabricate fibers with a non-crosslinked silicone core within a supporting shell scaffold, followed by thermal crosslinking and removal of the water-soluble shell. Photocatalytic zinc oxide nanoparticles (ZnO NPs) are immobilized on the PDMS fibers by colloid-electrospinning or post-functionalization procedures. The fibers functionalized with ZnO NPs can degrade a photo-sensitive dye and display antibacterial properties against Gram-positive and Gram-negative bacteria (Escherichia coli and Staphylococcus aureus) due to the generation of reactive oxygen species upon irradiation with UV light. Furthermore, a single layer of functionalized fibrous membrane shows an air permeability in the range of 80–180 L/m2s and 65% filtration efficiency against fine particulate matter with a diameter less than 1.0 µm (PM1.0).
High-performance yarn artificial muscles are highly desirable as miniature actuators, sensors, energy harvesters, and soft robotics. However, achieving a yarn artificial muscle that covers all the properties of excellent actuation performance, mechanical robustness, structural stability, and high scalability by a low-cost strategy is still a great challenge. Herein, a bio-inspired fasciated yarn structure is first reported for creating robust high-performance yarn artificial muscles. Unlike conventional strategies that leverage costly materials or complex processing, the developed yarn artificial muscles are constructed by hierarchically helical and sheath-core assembly design of cost-effective common fibers, such as viscose and polyester. The hierarchically helical sheath structure pushes the theoretical limit of the inserted twist in yarns and endows the yarn muscles with large stroke (5815° cm−1) and high work capacity (23.5 J kg−1). Due to the rapid water transfer and efficient energy conversion of inter-sheath–core coupling, the as-prepared yarn muscles possess fast response, high rotation accelerated speed, and low recovery hysteresis. Moreover, the inactive core yarn serves as support for internal tethering and load-bearing, enabling these yarn muscles to maintain a self-stable structure, robust life cycle and mechanics. We show that the yarn muscle fabricated in this method is readily available and highly scalable for achieving high-dimensional actuation deformations, which considerably broadens the application scenarios of artificial muscles.
The hierarchically helical and sheath-core structures are embraced to create high-performanceartificial muscles with a large stroke, a fast response, a high work capacity, a self-supportingmorphology and robust mechanical properties at a low-cost strategy, which boosts thescalable production and practical applications of artificial muscles and is expected to providenew opportunities in the development of miniature actuators, smart textiles and soft robotics.