Aerogel fiber has broad applications in thermal insulation, pollution adsorption, biomedicine, energy storage, and aerospace. However, the large-scale and continuous production of aerogel fibers remains a significant challenge. Wet spinning technology transforms the static sol–gel process into rapid dynamic gel fiber molding, and is the preferred spinning method for continuous molding and large-scale production of aerogel fibers. This review provides a systematic overview of the production process of wet-spun aerogel fibers and the obstacles it encounters in the forming and drying stages. It also discusses the progress of different spinning strategies in optimizing the structure and properties of aerogel fibers. Recent advances in the properties of aerogel fibers, such as thermal insulation, adsorption, and optical and electromagnetic shielding, which are affected by the structural characteristics of aerogel fibers, are presented. Finally, this review provides a brief conclusion and discusses the technical challenges and future directions for wet-spun aerogel fibers. This review is expected to offer fresh perspectives and innovative strategies for the continuous production of aerogel fibers, the development of high-performance and multifunctional aerogel fibers, and their diverse applications.
Hydrogel fibers have gained considerable attention, but their large-scale production and industrial application are currently constrained. The key lies in precise diameter control and industrial manufacturing with a straightforward, energy-saving, and efficient strategy. Herein, we introduce a hydrodynamic drafting spinning platform inspired by water vortices. It employs the rotation of a nonsolvent to generate vortices and further facilitate the efficient drafting of hydrogel fibers. Through supporting equipment, we have achieved impressive results, including scalable production capabilities (1 h, single channel output of 2 × 103 m of fibers) and extensive adaptability. Subsequently, by simply regulating the velocity difference between fiber extrusion and fluid vortex, hydrogel fibers can be drafted to any diameter from about 1 mm to 5 × 10–2 mm (for chitosan system). Notably, this platform endows hydrogel fibers to carry functional hydrophilic or hydrophobic drugs. Equally significant, these delicate hydrogel fibers seamlessly integrate with subsequent manufacturing technologies. This allows the production of various end products, such as fiber bundles, yarns, fabrics, and nonwovens. Furthermore, the immense potential in biomedical applications has been demonstrated after obtaining hydrogel fiber-based nonwoven as wound dressings. In summary, the hydrodynamic drafting spinning platform offers an effective solution for the large-scale production of diameter-controllable, multifunctional hydrogel fibers.
NdFeB magnets are third-generation permanent magnets that are employed as indispensable components in various industries. Notably, rare-earth elements (REEs) such as Dy and Nd must be efficiently recovered from end-of-life magnets to enable resource circulation and reinforce unstable supply chains. To that end, this paper reports synergistically performing core/shell-structured composite fibers (CSCFs) containing sodium polyacrylate and nanoporous zeolitic imidazolate framework-8 (NPZIF-8) nanocrystals as a readily recoverable adsorbent with an exceptional REE-adsorbing ability. The CSCF core forms an NPZIF-8 nanocrystal shell on the fiber surface as well as draws REEs using its dense sodium carboxylate groups into the NPZIF-8 nanocrystal lattice with high specific surface area. The CSCFs exhibit significantly higher maximum adsorption capacities (468.60 and 435.13 mg·g−1) and kinetic rate constants (2.02 and 1.92 min−1) for the Nd3+ and Dy3+ REEs than those of previously reported REE adsorbents. Additionally, the simple application of the CSCFs to an adsorption reactor considerably mitigates the adsorbent-shape-induced pressure drop, thereby directly influencing the energy efficiency of the recovery. Moreover, the high REE-recovery ability, tractability, and recyclability of the CSCFs offers a pragmatic pathway to achieving cost-effective REE recovery. Overall, this study provides new insights into designing synergistically performing core/shell architectures for feasible REE recovery.
Clinical diagnosis and early intervention employ pedobarometry, which analyzes gait, posture, and foot health. Athletes utilize smart insoles to track step count, distance, and other parameters to improve performance. Current sensor platforms are bulky and limited to indoor or clinical environments, despite the trend of developing specialized insoles for recuperation and therapy. Hence, we presented a fully flexible, typically portable, and multi-functional insole monitoring technology powered by Archimedean algorithmic spiral TENG-based power system strictly produced from biopolymers such as bacterial cellulose, conjugate-blend of polydimethylsiloxane (PDMS), poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), and more. Along with exceptional mechanical and electrical performance [current density (J SC) ≈ 40–50 μA/cm2 and power density (P D) ≈ 500–600 μW/cm2], the smart insole system exhibited good sensor-human foot interfacial analysis results, proving to be capable of biomechanical analysis of gait, posture, and many other podiatry-related conditions, albeit being soft, portable, and having compatibility potential for IoT integration.
Passive cooling holds tremendous potential in improving thermal comfort because of its zero energy consumption and cost-effectiveness. However, currently reported radiative cooling materials primarily focus on hydrophobic polymer films, inevitably leading to sweat accumulation and limited cooling efficiency in hot-humid environments. Herein, an advanced Janus membrane with excellent temperature–moisture management capabilities is developed, which combines radiative cooling and evaporative heat dissipation. Modification with Calcium sulfite (CaSO3) nanoparticles not only enhances the optical properties (state-of-the-art solar reflectance of 96.6%, infrared emittance of 96.1%) but also improves the wettability of the polylactic acid fiber membrane. Especially 15% emittance improvement is achieved due to the strong infrared radiation ability of CaSO3. The membranes with opposite wettability realize the directional sweat transport (high one-way transport index of 945%). Excellent radiative cooling capability is demonstrated with sub-ambient cooling of 5.8 °C in the dry state. The Janus membranes covering sweaty skin exhibit a 46% shorter drying time and a 2 °C lower average evaporation temperature compared to cotton fabric, indicating highly efficient thermal and moisture management. This work provides an efficient route to achieving smart textiles that enable the human body to adapt to complex environmental conditions.
Delayed healing of diabetic wounds poses a major challenge to human health due to severe vascular dysfunction, sustained inflammation, and vulnerability to microbial infection. Herein, we constructed multidimensionally nano-topologized electrospun polycaprolactone (PCL) fibrous membranes with shish-kebab nanoarrays on each fiber through self-induced crystallization, on which the CuO2–MgO2 bimetallic peroxide nanodots (BPNs) were anchored by polydopamine (PDA) as the bridging layer. When activated by the acidic microenvironment (typically infected diabetic wound), BPNs on fibers reacted immediately to release Cu2+ and Mg2+ ions together with hydrogen peroxide (H2O2) molecules, which were then transferred into ·OH radicals through Fenton-type reactions catalyzed by Cu2+ for instant bacteria elimination. At the same time, the released Cu2+ and Mg2+ ions were retained to improve the angiogenesis and suppress the inflammation infiltration, thus remodeling the wound microenvironment. Meanwhile, the one-dimensional (1D)-constructed nano shish-kebabs and PDA coating on fibers provided additional topological activation for cell adhesion and directed migration along the aligned fiber orientation. Through the meticulous design, the resultant membranes markedly accelerated the infected wound healing in the diabetic rat model. This study pioneers a unique design to develop a nanocomposite fibrous membrane that combines multidimensional topologies with chemodynamic therapy (CDT), for efficiently combating infected diabetic wounds.
Graphene composite yarns have demonstrated significant potential in the development of multifunctional wearable electronics, showcasing exceptional conductivity, mechanical properties, flexibility, and lightweight design. However, their performance is limited by the weak interfacial interaction between the fibers and graphene. Herein, a polydopamine–reduced graphene oxide (PDA–RGO) interfacial modulation strategy is proposed to prepare graphene-coated cotton yarns with high electrical conductivity and strength. PDA–RGO serves as an interfacial bonding molecule that interacts with the cotton yarn (CY) substrate to establish a hydrogen interface, while interconnecting with highly conductive graphene through π–π interactions. The developed interface-designed graphene-coated yarn demonstrates an impressive average electrical conductivity of (856.27 ± 7.02) S/m (i.e., average resistance of (57.57 ± 5.35) Ω). Simultaneously, the obtained conductive yarn demonstrates an exceptional average tensile strength of (172.03 ± 8.03) MPa, surpassing that of primitive CY by approximately 1.59 times. The conductive yarns can be further used as low-voltage flexible wearable heaters and high-sensitivity pressure sensors, thus showcasing their remarkable potential for high-performance and multifunctional wearable devices in real-world applications.
Fiber-based material systems are emerging as key elements for next-generation wearable devices due to their remarkable advantages, including large mechanical deformability, breathability, and high durability. Recently, greatly improved mechanical stability has been established in functional fiber systems by introducing atomic-thick two-dimensional (2D) materials. Further development of intelligent fibers that can respond to various external stimuli is strongly needed for versatile applications. In this work, helical-shaped semiconductive fibers capable of multifunctional sensing are obtained by wet-spinning MoS2 liquid crystal (LC) dispersions. The mechanical properties of the MoS2 fibers were improved by exploiting high-purity LC dispersions consisting of uniformly-sized MoS2 nanoflakes. Notably, three-dimensional (3D) helical fibers with structural chirality were successfully constructed by controlling the wet-spinning process parameters. The helical fibers exhibited multifunctional sensing characteristics, including (1) photodetection, (2) pH monitoring, (3) gas detection, and (4) 3D strain sensing. 2D materials with semiconducting properties as well as abundant surface reactive sites enable smart multifunctionalities in one-dimensional (1D) and helical fiber geometry, which is potentially useful for diverse applications such as wearable internet of things (IoT) devices and soft robotics.
Currently, the development of clean and green energy-harvesting solutions is becoming increasingly critical. Batteries have long been considered as the most traditional and efficient technology for powering electronic devices. However, they have a limited lifetime and require constant observation and replacement. To address this issue, triboelectric nanogenerator (TENG) has garnered considerable attention as a prospective sustainable power source for smart devices. Further, several approaches for improving their output performance have been investigated. Herein, we created a unique TENG based on densely packed molybdenum disulfide (MoS2) petals grown on electrospun polyacrylonitrile (PAN) fibers (MPF) using a hydrothermal technique. Designed MPF-TENG is used for mechanical energy-harvesting and smart study room touch sensor applications. The effects of pure MoS2 powder, PAN fibers, and MoS2 grown on the PAN fibers were investigated. MoS2 addition enhanced the surface charge, surface roughness, and electrical performance. The MPF-TENG had a maximum triboelectric output voltage, current, charge, and average power density of 245.3 V, 5.12 µA, 60.2 nC, and 1.75 W/m2, respectively. The MPF-TENG remained stable for more than 10,000 cycles. The MPF-TENG successfully illuminated blue LEDs, turned on a timer clock, and could be used in smart study rooms to generate energy. This study provides an effective method for improving the performance of TENG by growing MoS2 petals on PAN fibers, with promising applications in power supplies for portable electronic devices. Furthermore, the fabricated MPF-TENG was demonstrated to be a potential touch sensor for smart study rooms to save electricity.
Developing an advanced individual protection cloth is a pivotal factor in combating global pathogen epidemics. However, formidable challenges are posed by the triangularity imbalance effect, necessitating the simultaneous fulfillment of requirements for high comfort, high safety, and mass production. In this study, a mass-producible hybrid polytetrafluoroethylene nanofiber mat (HPNFM) was developed by integrating technologies of organic–inorganic hybridization and membrane asynchronous stretching. Exceptional comfort was attained by conferring waterproofing and breathability attributes, achieved through the radial island-chain architecture exhibiting hydrophobicity and nanoporosity. Furthermore, through the incorporation of high-efficiency anti-pathogen nanoparticles, the HPNFM ensures high safety, demonstrating active antibacterial and antiviral effects. This is achieved through the synergistic effects of electrostatic induction and reactive oxygen species-based pathogen inactivation. More significantly, an HPNFM-based individual protective suit is designed and manufactured, which successfully encapsulates the advantages of high comfort, safety, and mass production, displaying competitiveness as a commercial product. Positioned as a viable strategy, this work holds substantial potential for practical applications in responding to future epidemics.
Improving the osteogenic properties of bone grafts plays a critical role in the repair and functional restoration of critical-sized bone defects. The endogenous electric field, one of the most crucial physiological signals, has been confirmed to maintain physiological function and reconstruct the structure of bone, which is inadequate in bone defect sites. Strategies for the development of electroactive osteogenic biomaterials arise to remodel and promote the electrophysiological microenvironment. Among the electroactive materials, electret biomaterials can provide a stable and persistent endogenous electrical stimulation, which better conforms to the physiological microenvironment and has long-term effectiveness in the bone repair process. Herein, an electret hybrid electrospun fibrous mat (EHFM) was developed to mimic the structure of the natural extracellular matrix (ECM) with a suitable and persistent electrophysiological microenvironment. The EHFM was constructed with a core–shell structure, in which silicon dioxide electrets were loaded in the core-layer to remodel and maintain the electrical microenvironment over the long term. The EHFM significantly promoted the osteogenesis of bone mesenchymal stem cells (BMSCs) in vitro and showed remarkable ability in bone repair, which was three times better than that of the control group in a critical-sized rat calvarial defect model. Furthermore, it was verified that EHFM-derived osteogenesis was related to the activation of the calcium ion-sensing receptor (CaSR), while increasing intracellular calcium ion concentration of BMSCs. This study puts forward a novel engineering strategy to promote bone defect repair by remodeling a stable and persistent electrophysiological microenvironment, showing potential for clinical applications.
A bimodal coupled multifunctional tactile perceptron for contactless gesture recognition and material identification is proposed to address the challenges posed by limited functionality, signal interference from multimodal collaborative work, and the high power consumption of traditional tactile sensors. This perceptron integrates a capacitive sensor and a triboelectric sensor symmetrically, employing an energy complementarity strategy to reduce power consumption and implementing symmetrical distribution of two sensors for physical isolation to prevent signal interference. The capacitive sensor detects external pressure, providing information on material properties such as hardness, softness, and deformation, with a wide linear response range of 0–745.3 kPa. The triboelectric sensor captures the electron affinity of measured object. Further, by utilising machine learning algorithms, a system for contactless gesture recognition and material identification is engineered. This system demonstrates a remarkable accuracy rate of 98.5% when recognising 5 gestures, and achieves a perfect identification (100%) of 10 different materials aided by incorporating capacitive and triboelectric response. These results greatly advance the progress of tactile perceptrons with high integration, low power consumption, and multifunctionality, enhancing their effectiveness and reliability in smart device applications.
Spiral fibers with high energy storage and high output efficiency are highly desirable for soft robots and actuators. However, it is still a great challenge to achieve spiral fibers with excellent water actuation performance, structural stability, and high scalability in a low-cost strategy. A coaxial spiral structure is reported for the fabrication of high-performance fiber actuators. The developed shell–core helical fiber actuators were based on alginate/poly(ethylene glycol) acrylate shell and alginate/GO core with green and excellent spinnability. Owing to the high water-absorbing-swelling capacity and energy storage of the shell, the prepared spiral fibers are characterized by fast response, high energy output, and good repeatability of cycling. On the other hand, the core endows the spiral fibers with the additional features of strong force retention and photothermal response. The shell–core spiral structure promotes the output efficiency of the twisted fiber actuator with a large rotation (2500°/cm), untwisting speed (2250 rpm), and recovery speed (2700 rpm). In addition, the tertiary spiral structure based on TAPG fibers exhibits excellent humidity and photothermal response efficiency. The application of fibers to smart textiles enables efficient human epidermal thermal management.
Stretchable conductive fibers composed of conductive materials and elastic substrates have advantages such as braiding ability, electrical conductivity, and high resilience, making them ideal materials for fibrous wearable strain sensors. However, the weak interface between the conductive materials and elastic substrates restricts fibers flexibility under strain, leading to challenges in achieving both linearity and sensitivity of the as-prepared fibrous strain sensor. Herein, cryo-spun drying strategy is proposed to fabricate the thermoplastic polyurethane (TPU) fiber with anisotropic conductive networks (ACN@TPU fiber). Benefiting from the excellent mechanical properties of TPU, and the excellent interface among TPU, silver nanoparticles (AgNPs) and polyvinyl alcohol (PVA), the prepared ACN@TPU fiber exhibits an outstanding mechanical performance. The anisotropic conductive networks enable the ACN@TPU fiber to achieve high sensitivity (gauge factor, $GF$ = 4.68) and excellent linearity within a wide working range (100% strain). Furthermore, mathematical model based on AgNPs is established and the resistance calculation equation is derived, with a highly matched fitting and experimental results ($R^{2}$ = 0.998). As a conceptual demonstration, the ACN@TPU fiber sensor is worn on a mannequin to accurately and instantly detect movements. Therefore, the successful construction of ACN@TPU fiber with anisotropic conductive networks through the cryo-spun drying strategy provides a feasible approach for the design and preparation of fibrous strain sensing materials with high linearity and high sensitivity.
In the last decade, numerous physical modification methods have been introduced to enhance triboelectric nanogenerator (TENG) performance although they generally require complex and multiple fabrication processes. This study proposes a facile fabrication process for Poly(vinylidene fluoride) (PVDF) nanofiber (NF) mats incorporating additive and nonadditive physical modifications. Patterned PVDF NF mats are prepared by electrospinning using a metal mesh as the NF collector. As a negative triboelectric material, the TENG with the patterned PVDF NF mat exhibits superior performance owing to the engineered morphology of the contact layer. PVDF is crucial in TENGs owing to its superior ferroelectric properties and surface charge density when combined with specific electroceramics. Hence, the synergy of the physical modification methods is achieved by incorporating BaTiO3 (BTO) nanoparticles (NPs) into the PVDF. By functionalizing BTO NPs with polydopamine, the TENG performance is further improved owing to the enhanced dispersion of NPs and improved crystallinity of the PVDF chains. Utilizing large NPs produces a nanopatterning effect on the NF surface, thereby resulting in the hierarchical structure of the NF mats. The source of the voltage signals from the TENG is analyzed using fast Fourier transform.
Fiber supercapacitors (FSs) based on transition metal oxides (TMOs) have garnered considerable attention as energy storage solutions for wearable electronics owing to their exceptional characteristics, including superior comfortability and low weights. These materials are known to exhibit high energy densities, high specific capacitances, and fast redox reactions. However, current fabrication methods for these structures primarily rely on chemical deposition, often resulting in undesirable material structures and necessitating the use of additives, which can degrade the electrochemical performance of such structures. Herein, physically deposited TMO nanoribbon yarns generated via delamination engineering of nanopatterned TMO/metal/TMO trilayer arrays are proposed as potential high-performance FSs. To prepare these arrays, the target materials were initially deposited using a nanoline mold, and subsequently, the nanoribbon was suspended through selective plasma etching to obtain the desired twisted yarn structures. Because of the direct formation of TMOs on Ni electrodes, a high energy/power density and excellent electrochemical stability were achieved in asymmetric FS devices incorporating CoNixOy nanoribbon yarns and graphene fibers. Furthermore, a triboelectric nanogenerator, pressure sensor, and flexible light-emitting diode were synergistically combined with the FS. The integration of wearable electronic components, encompassing energy harvesting, energy storage, and powering sensing/display devices, is promising for the development of future smart textiles.
Conventional wound dressings only protect passively against bacterial infection. Emerging mechanically active adhesive dressings (AADs) are inspired by the active closure of embryonic wounds. It can promote wound healing by actively contracting the wound bed. AADs meet the requirements of high toughness, stimulus–response, and dynamic adhesion properties, which are challenging. Hence, we construct a water-responsive shape memory polyurea fibrous membrane (PU-fm) featuring favorable toughness, wet-adhesion, breathability, absorbency of four times its weight, and antibacterial. First, the water-toughened electrospun PU-fm is fabricated using a homemade polyurea (PU) elastomer with multistage hydrogen bond networks as a spinning solution. Furthermore, a Janus-structured polyurea-polydopamine-silver fibrous membrane (PU@PDA@Ag-fm) is engineered, integrating antibacterial properties without compromising mechanical robustness. It demonstrates strong adhesion to the skin, actively promotes wound contraction, and enables adaptive wrapping of tissues of varying sizes by the water-driven shape memory effect. Antibacterial tests and wound healing experiments indicate that the PU@PDA@Ag-fm has favorable antibacterial properties against Escherichia coli (E.coli) and accelerates the wound healing rate by 20%. For the first time, water-responsive shape memory PU-fm as the AADs is constructed, providing a new strategy for wound management. This can be extended to applications in other smart devices for biomedicine such as tendon repair, and bioelectronic interfaces.
Wearable sensors have been rapidly developed for application in various human monitoring systems. However, the wearing comfort and thermal properties of these devices have been largely ignored, and these characteristics urgently need to be studied. Herein, we develop a wearable and breathable nanofiber-based sensor with excellent thermal management functionality based on passive heat preservation and active Joule heating effects. The multifunctional device consists of a micropatterned carbon nanotube (CNT)/thermoplastic polyurethane (TPU) nanofiber electrode, a microporous ionic aerogel electrolyte and a microstructured Ag/TPU nanofiber electrode. Due to the presence of a supercapacitive sensing mechanism and the application of microstructuration, the sensor shows excellent sensing performance, with a sensitivity of 24.62 kPa−1. Moreover, due to the overall porous structure and hydrophobicity of TPU, the sensor shows good breathability (62 mm/s) and water repellency, with a water contact angle of 151.2°. In addition, effective passive heat preservation is achieved by combining CNTs with high solar absorption rates (85%) as the top layer facing the outside, aerogel with a low thermal conductivity (0.063 W m−1 k−1) as the middle layer for thermal insulation, and Ag with a high infrared reflectance rate as the bottom layer facing the skin. During warming, this material yields a higher temperature than cotton. Furthermore, the active Joule heating effect is realized by applying current through the bottom resistive electrode, which can quickly increase the temperature to supply controlled warming on demand. The proposed wearable and breathable sensor with tunable thermal properties is promising for monitoring and heat therapy applications in cold environments.
We reported a wearable and breathable nanofiber-based sensor with excellent thermal management functionality based on passive heat preservation and active Joule heating effects.
Development of novel electrode materials with the integration of structural and compositional merits can essentially improve the electrosorption performance. Herein, we demonstrate a new strategy, named as carbothermal diffusion reaction synthesis (CDRS), to fabricate binder-free CrN/carbon nanofiber electrodes for efficient electrosorption of fluoride ions from water. The CDRS strategy involves electrospinning MIL-101(Cr) particles with polyacrylonitrile (PAN) to form one-dimensional nanofiber, followed by spatial-confined pyrolysis process in which the nitridation reaction occurred between nitrogen element from PAN and chromium element from MIL-101(Cr), resulting macroscopic, free-standing electrodes with well dispersed ultrafine CrN nanoparticles on porous nitrogen enriched carbon matrix. As expected, the F− adsorption capacity reached 47.67 mg g−1 and there was no decrease in F− removal after 70 adsorption regenerations in 50 mg L−1 F− solution at 1.2 V. The adsorption mechanism of F− was explored by X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT). The enhanced F− adsorption capacity was achieved by the reversible Cr4+/Cr3+ redox pair provided by CrN and the electrical double layer capacitance produced by carbon skeleton. This study provides guidance on synergistic modulation of shaping and composition optimization of novel functional materials for electrosorption, catalysis, and supercapacitor applications.
In recent years, the collection and monitoring of human physiological signals have garnered increasing attention due to their wide-ranging applications in healthcare, human–machine interaction, sports, and other fields. However, the continuous fabrication of flexible gel fiber electrodes with high mechanical performance, high conductivity, and durability for extreme environments using a simple, efficient, and universal strategy remains challenging for physiological signal acquisition. Here, we have employed a strategy of solvent replacement and multi-level hydrogen bond enhancement to construct eutectogel fibers with continuous solid–liquid structure, achieving continuous production of fibers with high strength, high conductivity, and low-temperature resistance. In the fiber, PVA serves as the solid-state elastic phase, DES as the liquid ionic conductive phase, and CNF as the reinforcement phase. The resulting eutectogel fibers exhibit excellent tensile strength (37.3 MPa), good elongation (> 700%), high electrical conductivity (0.543 S/m), and resistance to extreme dry and −60 °C low-temperature environments. Furthermore, these eutectogel fibers demonstrate high sensitivity for monitoring joint movements and effectively detecting in vitro and in vivo signals, show casing their potential for wearable strain sensors and monitoring physiological signals.