Producing functional soft fibers via existing spinning methods is environmentally and economically costly due to the complexity of spinning equipment, involvement of copious solvents, intensive ...consumption of energy, and multi-step pre-/post-spinning treatments. We report a nonsolvent vapor-induced phase separation spinning approach under ambient conditions, which resembles the native spider silk fibrillation. It is enabled by the optimal rheological properties of dopes via engineering silver-coordinated molecular chain interactions and autonomous phase transition due to the nonsolvent vapor-induced phase separation effect. Fiber fibrillation under ambient conditions using a polyacrylonitrile-silver ion dope is demonstrated, along with detailed elucidations on tuning dope spinnability through rheological analysis. The obtained fibers are mechanically soft, stretchable, and electrically conductive, benefiting from elastic molecular chain networks via silver-based coordination complexes and in-situ reduced silver nanoparticles. Particularly, these fibers can be configured as wearable electronics for self-sensing and self-powering applications. Our ambient-conditions spinning approach provides a platform to create functional soft fibers with unified mechanical and electrical properties at a two-to-three order of magnitude less energy cost under ambient conditions.
Atmospheric pollution has emerged as causing irreversible harm to the ecosystem and people. Sub-micron fibrous filters play an incomparable role in effective air purification, owing to their ...excellent internal connectivity. Herein, three-dimensional sub-micron fibrous webs with various aligned degrees were conveniently fabricated via free surface electrospinning with different rotation speeds of the roller with a large diameter in large quantity, applied in air filtration. The influence of the orientation degrees of fibers on the performances of the fibrous filter was analyzed systematically. Results showed that the filtration performance of fibrous filters was inversely proportional to the orientation degree of the sub-micron fibers. Random fibrous webs with areal densities of ≤2.0 g m−2 exhibited high porosity (∼90%), ensuring qualified air permeability and outstanding filtration efficiency from 92% to 99.5% for ultra-fine aerosol particles (∼0.26 µm) under a higher air velocity of 14.1 cm s−1. The internal aperture channels were twists and turns with irregular polygon shape for random fibrous webs, while they were a narrow strip in the horizontal and straight in the longitudinal for aligned ones, which influenced the filter’s performances. Fibrous webs with better orientation of fibers and larger pore size are beneficial for energy efficiency and exhibited good filtration performance, better air permeability, and an improved mechanical property along the longitudinal direction. A cost-effective uniform sub-micron fibrous filter with different aligned degrees could be produced rapidly via free surface electrospinning with a mass production rate, which is beneficial for industrial production and commercial applications in respiratory protection and indoor air purification for precise purification of air pollution.
Breathable, flexible, and highly sensitive pressure sensors have drawn increasing attention due to their potential in wearable electronics for body‐motion monitoring, human‐machine interfaces, etc. ...However, current pressure sensors are usually assembled with polymer substrates or encapsulation layers, thus causing discomfort during wearing (i.e., low air/vapor permeability, mechanical mismatch) and restricting their applications. A breathable and flexible pressure sensor is reported with nonwoven fabrics as both the electrode (printed with MXene interdigitated electrode) and sensing (coated with MXene/silver nanowires) layers via a scalable screen‐printing approach. Benefiting from the multi‐layered porous structure, the sensor demonstrates good air permeability with high sensitivity (770.86–1434.89 kPa−1), a wide sensing range (0–100 kPa), fast response/recovery time (70/81 ms), and low detection limit (≈1 Pa). Particularly, this sensor can detect full‐scale human motion (i.e., small‐scale pulse beating and large‐scale walking/running) with high sensitivity, excellent cycling stability, and puncture resistance. Additionally, the sensing layer of the pressure sensor also displays superior sensitivity to humidity changes, which is verified by successfully monitoring human breathing and spoken words while wearing a sensor‐embedded mask. Given the outstanding features, this breathable sensor shows promise in the wearable electronic field for body health monitoring, sports activity detection, and disease diagnosis.
A high‐performance, breathable, and multifunctional pressure sensor is fabricated via a facile and scalable screen‐printing method. The fabricated pressure sensor has high sensitivity of 770.86–1434.89 kP−1, exhibits good poking resistance and high sensitivity for the humidity, which can be used for full‐scale human motion detection, health monitoring and language recognition.
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•The slip effect on nanofibrous was modeled and numerically simulated to determine the optimal membrane structure.•Slip effect was utilized to design the low-resistance bimodal ...nanofibrous membrane filter.•The bimodal and sandwich structured fibers ware easily prepared via free surface electrospinning.•A sandwich structured fibrous membrane filter with gradient air passageway was fabricated for ultrafine-particle filtration.
Nanofiber materials have great potential in air filtration, especially to deal with the micro-/nano-particulate matters (PM). However, there still remains a challenge to reduce pressure drop while maintaining ultra-high filtration efficiency for fibrous membrane filters. In the present article, the high-efficiency and low-resistance bimodal nanofibrous membrane filter based on slip effect was designed and fabricated. By modelling and numerically simulating the air flow field around single fiber, the fiber with diameter of 70 nm was found to be most effective for slip flow to reduce air resistance. To introduce the slip effect into fibrous membrane, bimodal structured fibrous membrane filters which consisted of scaffold fibers (200 nm) and the optimal slip effect functional fibers (70 nm) were designed to increase the gap between the fibers. Furthermore, a sandwich structured fibrous membrane filter was fabricated via one-step free surface electrospinning, in which the bimodal fibers (70 + 200 nm) was in the middle layer, while the upper and lower layers were consisted of unimodal fibers of 110 and 70 nm, separately, to form gradient air passageway. The sandwich structured fibrous membrane presented a filtration efficiency of 99.984% for PM0.26, meeting the requirements of precision filtration under the premise of low-resistance (85.02 Pa), with a QF (quality factor) as high as 0.1028 Pa−1. The results shown in the current work provide an efficient way for the design and fabrication of nanofibrous membrane for high-efficiency and low-resistance air purification against PM.
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•A 3D sub-micro fibrous material was fabricated via free surface electrospinning.•The PAN/PI composite fibrous filter was electrospun for precise filtration of PM0.26.•PI waste short ...fibers were utilized as raw materials.•The cost-effective PAN/PI filter with high yield is promising for application.
Particulate matter (PM) pollution has enormously threatened ecosystem and public health. Among various air filtration medium, fibrous ones are very attracting and promising, with an array of advantages such as high specific surface area, and good internal connectivity. Even so, the large-scale fabrication of fibrous filtration materials still remains challenging. Here, three-dimensional polyacrylonitrile/polyimide (PAN/PI) composite sub-micro fibrous membranes were fabricated facilely via free surface electrospinning for precise filtration of PM0.26 pollutants, where the waste PI short fibers were utilized as raw material. The resultant composite fibrous membranes, featuring thin fiber diameter (~150 nm), low areal density (<0.8 g m−2), large porosity, and highly tortuous airflow channels with uniform poresize distribution, possessed excellent mechanical property with tensile strength of 4.95 MPa (twice that of pristine PAN), high thermal durability as well as remarkable filtration performance for ultrafine NaCl aerosol particles (≤0.26 µm) even after multiple filtration tests at high airflow velocity of 14.1 cm s−1. The deepened aperture channels inside three-dimensional sub-micro fibrous membranes are tortuous enough for capturing ultrafine PMs from the airstream mainly via diffusion, interception, and impaction mechanisms, and the reported large-scale fabrication of cost-effective homogeneous PAN/PI fibrous filter media is promising for industrial production and commercial applications.
Sorption‐based atmospheric water harvesting (AWH) is a promising approach for mitigating worldwide water scarcity. However, reliable water supply driven by sustainable energy regardless of diurnal ...variation and weather remains a long‐standing challenge. To address this issue, a polyelectrolyte hydrogel sorbent with an optimal hybrid‐desorption multicyclic‐operation strategy is proposed, achieving all‐day AWH and a significant increase in daily water production. The polyelectrolyte hydrogel possesses a large interior osmotic pressure of 659 atm, which refreshes sorption sites by continuously migrating the sorbed water within its interior, and thus enhancing sorption kinetics. The charged polymeric chains coordinate with hygroscopic salt ions, anchoring the salts and preventing agglomeration and leakage, thereby enhancing cyclic stability. The hybrid desorption mode, which couples solar energy and simulated waste heat, introduces a uniform and adjustable sorbent temperature for achieving all‐day ultrafast water release. With rapid sorption–desorption kinetics, an optimization model suggests that eight moisture capture–release cycles are capable of achieving high water yield of 2410 mLwater kgsorbent−1 day−1, up to 3.5 times that of single‐cyclic non‐hybrid modes. The polyelectrolyte hydrogel sorbent and the coupling with sustainable energy driven desorption mode pave the way for the next‐generation AWH systems, significantly bringing freshwater on a multi‐kilogram scale closer.
A polyelectrolyte hydrogel sorbent with free and coordinated hygroscopic salt is described, which exhibits fast sorption due to the large interior osmotic pressure and prevention of salt aggregation and leakage through the strong salt–polymer electrostatic interactions. By using a multicyclic operation strategy and a hybrid desorption mode, the sorbent achieves high‐yield water production, outperforming single‐cyclic solar‐driven mode by three times.
The electronic textile has been evolving into a multifunctional flexible electronics platform. However, due to processing methods, e.g., coating, the fabric is endowed with electronic functionality ...while weakening its original performances. Thus, there is still a long way for electronic fabrics. Here, a nano/micro core-sheath yarn-based waterproof and breathable fabric triboelectric nanogenerator (CSYF TENG) is continuously fabricated for energy harvesting, self-powered humidity, and subtle force sensing systems. Different from coated yarns, our uniaxially aligned CSYs with ordered nanofibers tightly wrapping around the conductive fibers are manufactured via a one-step conjugate electrospinning technique. Owing to the hierarchical structure and tremendous specific surface areas, CSYF TENGs exhibit unparalleled electrical outputs with excellent durability and biomechanical pressure sensitivity, demonstrating superior comfortability, i.e., waterproof property, breathability, and flexibility, without sacrificing fabric's original properties. Furthermore, based on the micro/nano radial expansion fiber-based fabric architecture, the excellent humidity management properties are manifested, resulting in a fast response (8 s)/recovery of electrical outputs toward humidity, making CSYF TENG an ideal self-powered humidity sensor. Besides, this TENG can be used as a bioenergy harvester, a self-powered tiny force sensor, and a fabric-based e-skin with excellent machine-washable and abrasion resistance properties. This work highlights the numerous applications of CSYs for wearable TENGs and self-powered electronic textiles.
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•A nano/micro core-sheath yarn based breathable fabric TENG is continuously fabricated.•The hierarchical architecture strategy enables CSYF TENG as a subtle force sensor.•Excellent humidity management makes CSYF TENG as an ideal humidity sensor.•CSYF TENG exhibits superior comfortability, huge potential in wearable e-textile.
Textile-based triboelectric nanogenerators (TENG) that can effectively harvest biomechanical energy and sense multifunctional posture and movement have a wide range of applications in next-generation ...wearable and portable electronic devices. Hence, bulk production of fine yarns with high triboelectric output through a continuous manufacturing process is an urgent task. Here, an ultralight single-electrode triboelectric yarn (SETY) with helical hybridized nano-micro core–shell fiber bundles is fabricated by a facile and continuous electrospinning technology. The obtained SETY device exhibits ultralightness (0.33 mg cm–1), extra softness, and smaller size (350.66 μm in diameter) compared to those fabricated by conventional fabrication techniques. Based on such a textile-based TENG, high energy-harvesting performance (40.8 V, 0.705 μA cm–2, and 9.513 nC cm–2) was achieved by applying a 2.5 Hz mechanical drive of 5 N. Importantly, the triboelectric yarns can identify textile materials according to their different electron affinity energies. In addition, the triboelectric yarns are compatible with traditional textile technology and can be woven into a high-density plain fabric for harvesting biomechanical energy and are also competent for monitoring tiny signals from humans or insects.
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•The hierarchical-structured electrospun fibrous web is fabricated with high yield.•The fibrous filter with tortuous channels shows superior air filtration performance.•Through-air ...thermally bonded composite exhibits more rigid, better physical property.•Reinforced filter bonded thermally with save-energy and low cost has good prospect.
Air pollution has steadily worsened in recent years, and the coronavirus disease 2019 has been spreading since 2020. The electrospun fibrous filters present superior filtration performance, while the low mechanical property and yield of them limit their applications, which must be addressed urgently. Herein, polyacrylonitrile (PAN) sub-micron fibrous membrane with hierarchical structure was easily manufactured using free surface electrospinning in mass production for air purification. The “sandwich” structured fibrous filter was thermally bonded with bi-component nonwoven through traditional bonding procedures, due to melting and bonding of the cortex of bi-component fibers, in which the electrospun fibrous web as the mid layer with tortuous channels showed superior filtration performance for aerosol particles with diameter of 260 nm, which could effectively intercept different-sized particles suspended in the air. In addition, the impact of the processing parameters on the characteristics and filtration mechanisms of thermally bonded composite materials was thoroughly investigated. The results showed that composite material with “dendrites” and “axon” morphologies presented the best formability, outstanding peeling strength and breaking strength, and steady filtration performance, following an easy through-air bonding procedure, making it useful for post-processing in air purification. The reinforced composite filter, which is thermally bonded with sub-micron fibers with high yield and nonwoven, is save-energy and has a low operation cost, indicating its promising commercial possibilities.
Moisture-induced electric generation has emerged as a promising powering solution for next-generation wearable electronics since moisture is ubiquitous in the atmosphere. However, the practical ...applications of current film-shaped generators are limited by the challenge of wearable comfort and large-scale integration into wearables. Herein, we reported a strategy to prepare flexible and high-performance core-shell yarn-shaped moisture-induced electric generator (YMEG) via employing metal wire as the core electrode, polymer-salt solution-treated electrospun nanofiber mats as the active layer, and deposited sliver as the shell electrode. Through the moisture induced interaction between active layer and electrode, the obtained best performance of YMEG with length of 2 cm can produce a highly stable voltage of ∼0.8 V and a current density of 14.3 μA/cm2, reaching the state-of-the-art level among the reported one-dimensional fiber/yarn-shaped MEGs. Furthermore, benefiting from the weavability of YMEG, a dislocation ordered stacking strategy is created for effective integration of YMEG units into fabric, and realizing the simultaneous enhancement of output voltage and current. Such integrated fabric device can work normally under deformation and show successful practical use in power electronics and sensing system, demonstrating great potential to serve as an advanced energy accessory for wearable electronics.
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•A novel flexible and high-performance core-shell yarn-shaped moisture-induced electric generator (MIEG) is developed via core-spun electrospinning technique followed with dip-drying treatment and sliver deposition.•The conjugated electrospinning technique is applied for yarn-shape MEG.•A dislocation-ordered stacking strategy is created for realizing the simultaneous enhancement of output voltage and current.•The integrated devices can work normally under deformation and shows successful practical use in power electronics and sensing humidity from humans.
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