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.
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.
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.
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.
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.
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.
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.
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.