Wearable electromagnetic interference (EMI) shielding devices are highly demanded to reduce the endlessly emerging EM pollution. Undesired durability and limited scale-up production capacity are the main obstacles to hinder the industrialized application of flexible EMI wearables. Here, a scalable Fe3O4/polypyrrole (PPy) embedded cotton/polypropylene (FP@CP) fabric is introduced for EMI shielding and Joule heating, which is achieved by a unique particle flow spinning method. This method can continually manufacture functional yarns in large quantities, followed by weaving into fabrics. The core-sheath yarn structure can highly embed Fe3O4/PPy shielding layer by polypropylene (PP) strips, which protects internal functional components from leakage or damage by the environment. Consequently, the obtained fabrics present greater durability (50 washing and 465 abrasion cycles) in comparison with most reported EMI devices. The EMI shielding mechanism was investigated through both experimental and simulation methods. It suggests that the combination of EMI reflection and absorption modes synergistically contributes to enhancing the EMI shielding property of obtained fabrics, reaching a maximum total shielding effectiveness (SET) of 47 dB. Besides, the composite fabric achieves a high Joule heating temperature to 105 ℃ at 3 V within 10 s due to its efficient electric-thermal property. This work paves a cost-effective way to realize scale-up manufacturing of versatile EM protection textiles to be applied in daily, military and aerospace fields.
Polyvinylidene fluoride (PVDF) is a piezoelectric polymer for the potential massive production of smart textiles, facing the difficulty of synergetic improving its fiber strength and softness. Strengthening of flexible PVDF fibers via drawing incurs the reduction of fiber softness. Here, inspired by the cotton fibers, this study aimed to construct a strong and soft PVDF fiber by regulating its cross-sectional shape and longitudinal convolution. Mechanism of increasing softness by longitudinal spiral twisting was conducted during the strengthening of PVDF fibers with favorable cross-sectional shapes. Then circular, flat and kidney shaped PVDF fibers were prepared to conduct drawing and twisting under different parameters. The influences of cross-sectional shapes and convolutions on PVDF fiber properties were examined using scanning electron microscope (SEM), X ray diffraction (XRD), universal stretch meter and AFM. Results indicated that all the fibers became strong but rigid with increased drawing ratios, mainly due to their corresponding attenuation to increase fiber inner crystallization and surface smoothness. In specialty, the circular fiber had a higher crystallization increase ratio (106.3%) than that of kidney (74.7%) and flat (73.1%) fibers. Surprisingly, all drawn fibers became flexible and further strengthened after tensile twisting within 400 T/m. Overall the optimum strong and flexible fibers were obtained by 400 T/m tensile twisting of the 2 times drawn flat PVDF fibers.
Electrochemical degradation is a commonly used strategy to remove organic contaminations in water. However, in some remote areas where electricity is insufficient, electrochemical degradation may become ineffective due to the absence of a power supply. Here, a unique self‐powered electrochemical system (SPES) is proposed to accomplish the power‐free degradation of tetracyclines (TCs) and organic dyes in water with the assistance of flexible magnetoelectric flag generators (MFGs). These MFGs convert wind energy into electricity. Under a wind speed of 6.3 m s −1 , a 22 × 30 cm 2 MFG yields a peak open‐circuit voltage of 3.5 V and an ultra‐high peak short‐circuit current of ≈13 mA. A suchlike MFG charges large capacitors of 5 F to 1 V in 184 min. Powered by a series of MFGs, 5 ppm of tetracycline hydrochloride (TCH) or organic dyes in water are totally degraded with SPES in only 10 min. Moreover, the MFG is fully foldable and portable, which is well‐suited for the migrating feature of the nomadic people in remote areas. The study opens up a new solution to the persistent problem of TCs contamination in natural waters in some remote regions where electricity is lacking.
The fiber micro-leveled diameter limits the ultimate cohesion between twisted fibers of conventional yarn. Electrospun nanofibers have a large specific surface area, high surface energy and massive active sites. However, the application of nanofibers is limited by their ultra-fine diameter, low absolute strength, and poor wear resistance. To take advantage of the micro and nanofibers, a spinning method of online twisting polyurethane nanofibers and micron cotton fibers together was proposed to form a core-sheath nano-composite yarn. The experimental spinning result and its analysis showed that the composite yarn sheath was wrapped with highly orientated nanofibers, endowing the yarn with super-smooth properties (3 mm hairiness number averaged as only 0.9) and super-hydrophobic function (contact angle 112.1°). Furthermore, other properties of spun yarns were also improved after online nano-composition such as yarn strength (5.53% stronger than conventional yarn) and unevenness (30.36% lower than conventional yarn).
Nanocomposites with carbon nanotubes (CNTs) can combine the stiffness and multi-functionality of carbon nanotubes with the advantages of high toughness and processability of polymers giving rise to properties different from that of general composites. However, when the content of CNTs increases gradually, the flexibility of the composite fibre can reduce. In this paper, we propose a simple method of softening the composite fibre via dimensional helical deformation of fibre inner macromolecule bundles to avoid the deterioration of fibre flexibility. The theoretical simulations were conducted to predict proper helical deformations of the single fibre to increase fibre softness, followed by practical softening of the polyvinylidene difluoride (PVDF)/CNTs composite by tensional twisting of the single fibres. The fibres with and without tensional twisting were tested by Fourier-transformed infrared spectroscopy, scanning electron microscopy, X-ray diffraction and mechanical drawing. Results showed the reinforcement of the PVDF/multi-walled CNTs composite fibres (tensile strength enhanced from 4.71 to 5.19 cN/dtex) with an evident softness reduction (initial modulus increased from 16.8 to 20.52 cN/dtex) as the CNTs content increased from 0 to 1.5 wt%. After the tensional twisting, the initial modulus of the composite fibre was reduced by 62.5% while the fibre strength remained reinforced because biomimetic helix formation improved the internal structure deformation ability of the fibre.
Electromagnetism, which has been used to harvest energy from human motion, is expected to power an increasing number of wearable electronic devices upon fabrics. However, most reported electromagnetism‐based approaches necessitate rigid and heavy setups. Here, a scalable‐manufactured flexible magnetoelectrical clothing generator is demonstrated that can generate electricity through the swinging of the arms. A “particle flow spinning” (PFS) method can produce continuous magnetic yarns, resulting in a magnetic fabric through an industrial weaving machine. Fabrics can be prepared in large quantities and have a lower cost. The magnetic fabrics and conductive wires are built on two sides of the armpit parts of the clothing, leading to continuous and stable voltage and current when swinging arm, 14.3 V peak voltage, 31.2 mA peak current, and 96 mW peak power (3197 mW m −2 peak power density) in series to a low‐impedance load (750 ohms). Furthermore, the magnetic fabrics can work under water without sealing treatment, in acidic/alkaline environments or at extreme temperatures. The magnetoelectrical clothing generator can power diverse electronic devices in many fields, such as LED lights, calculators, wireless communication, and health monitoring devices. This approach opens a path toward exploring electromagnetic energy harvesting strategies to realize power generation for the development of clothing electronics.
Bonding among fibers is critical to developing a high strength fabric. Chemical adhesive (polyvinyl butyral, abbreviated as PVB) can improve the bonding between fibers to improve yarn strength to the required level. However, retaining the fabric strength after abrasion and washing without the loss of chemical adhesive is challenging. In this study, a novel method has been applied to intra-layer PVB-paste spinning to improve yarn strength. The forming mechanism and PVB flow/fibers compaction model of PVB-paste spun yarn were analyzed. The optimum process parameters of intra-layer PVB-paste spinning combined with orthogonal experiments were established, which maximally increased the binding force between the filament and staple fibers to improve the yarn strength. Moreover, in comparison to original yarn, PVB-paste spun yarn strength can be increased up to 32.3 % in the best case. Therefore, the yarn strength could be improved via intra-layer PVB-paste spinning. Meanwhile, the tearing and breaking strength of PVB-paste fabric were approximately 27.8 % and 7.2 % more than those of cotton fabric, respectively. Additionally, the fabric made by that yarn also maintains good strength performance during abrasion and washing, while also having good hand-feel characteristics. Overall, the successful manufacture of these PVB-paste fabric should promote the development of high-performance fabric.
Self-powered fabric electronic devices are critical for next-generation wearable technologies, biomedical applications, and human-machine interfaces. The flexible magnetoelectric strategy is an emerging self-powered approach that can adapt to diverse environments and yield efficient electric outputs. However, there is an urgent need to develop a continuous manufacturing method for fabricating self-powered sensing magnetoelectric yarns with a high magnetic powder ratio and resistance to severe surroundings. In this study, we report particle flow spinning mass-manufactured magnetoelectric yarns for self-powered mechanical sensing. It has been shown that mechanical stretching/bending forces can be sensed and recognized by magnetoelectric yarns without an additional power supply. Through a combination of parameter optimization experiments and Maxwell modeling, we reveal the mechanism behind this mechanical-to-electric conversion capability. We further show that these self-powered sensing magnetoelectric yarns can monitor human motions after being attached to texture clothing. We expect that our results will stimulate further research on fabric electronics in a self-powered manner and will substantially advance the field.
Sustainability and environmental consciousness directed attention toward research and innovation in the field of natural fiber composites. Baobab (Adansonia digitata L.) is tropical tree of the silk-cotton family that is native to Africa. The aim of this study is to pore over the use of baobab bast fibers as potential reinforcement in polymer composites. The baobab bast fibers were extracted from the bark of baobab tree in Sudan. Fibers were investigated by chemical analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and single fiber tensile test. Further, the density and relative humidity of fibers were determined.The cellulose, hemicellulose, lignin, ash, and moisture contents present in the fiber are 60.70%, 21.98%, 5.91%, 5.32%, 13%, respectively. The fiber has a density of 1.1041 g/cm3. FTIR spectra for cellulose and nanocellulose confirms absorption bands characteristic of pure celluloses at 3330, 2919, 1640, 1028. Scanning electron micrographs showed roughening of the fiber surface and crack-like lines indicate fiber clusters being held together. The baobab fiber possessed a crystallinity index of 48.01% with thermal stability up to 250°C. The results revealed that baobab fiber can be utilized as reinforcement in polymer composites.