A flexible, lightweight and stretchable all-solid-state supercapacitor based on warp-knitted stainless-steel mesh for wearable electronics

Highly conductive, flexible, stretchable and lightweight electrode substrates are essential to meet the future demand on supercapacitors for wearable electronics. However, it is difficult to achieve the above characteristics simultaneously. In this study, ultrafine stainless-steel fibers (with a diameter of ≈30 μm) are knitted into stainless-steel meshes (SSMs) with a diamond structure for the fabrication of textile stretchable electrodes and current collectors. The electrodes are fabricated by utilizing an electrodeposited three-dimensional network graphene framework and poly(3,4-ethylenedioxythiophene) (PEDOT) coating on the SSM substrates via a two-step electrodeposition process, which show a specific capacitance of 77.09 F g−1 (0.14 A g−1) and superb cycling stability (91% capacitance retention after 5000 cycles). Furthermore, the assembled flexible stretchable supercapacitor based on the PEDOT/reduced graphene oxide (RGO)@SSM electrodes exhibits an areal capacitance (53 mF cm−2 at 0.1 mA cm−2), a good cycling stability (≈73% capacitance retention after 5000 cycles), rate capability (36 mF cm−2 at 5 mA cm−2), stretchable stability (≈78% capacitance retention at 10% strain for 500 stretching cycles) and outstanding flexibility and stability under various bending deformations. The assembled supercapacitors can illuminate a thermometer and a light-emitting diode, demonstrating their potential application as stretchable supercapacitors. This simple and low-cost method developed for fabricating lightweight, stretchable and stable high-performance supercapacitors offers new opportunities for future stretchable electronic devices.

The relevance of false-twist addition on ring spun yarns by means of rotary threaded surfaces

A novel concept of producing false-twist yarns by cyclical stress fluctuation was developed. The forming principle was introduced to analyze the formation process of false twists on rotary threaded contact surfaces. Geometric analysis indicates that cyclical stress variations produce extra rotations (false twists) on fiber strands in the yarn formation area, causing twist redistribution and fiber arrangement remodeling with the appearance of local fiber reversion. Theoretical analysis reveals that more false twists are produced when the spun yarn is in contact with surfaces of high traverse speeds. Then, a motion simulation model using different traverse speeds of the threaded contact surface was established to compare the yarn internal stress variation, verifying the false-twist efficiency at different traverse speeds. Finally, a systematic comparison was conducted between the yarns spun at different traverse speeds. It was shown that the yarn properties improved with higher traverse speeds of the threaded contact surface, achieving less hairiness, high yarn strength, and low residual torque.

A modified resistance to compression (RtC) test for evaluation of natural fiber softness

Comfort is a key feature of any clothing that relates significantly to softness of the fiber, yarn and fabric from which is it constructed. A known softness assessment method for fibers is the resistance to compression test. This traditional test only provides a single force value for the resistance of a loose fiber sample using a fixed mass under compression. In this research, a modified resistance to compression test was introduced to show the effects of repeated compression, providing more information about the softness and resilience of selected fibers. Three different natural fiber types, including wool, cotton and alpaca were compared using this new approach. The results showed compression profiles were quite different for different fiber types as well as for the same fibers with different diameters. While the diameters of the wool and alpaca samples were similar (18.5 μm), the modified resistance to compression values were significantly higher for wool (with a peak value at 9.5 kPa compared to 2.1 kPa for alpaca). Cotton was different from wool and alpaca but showed a similar modified resistance to compression value (10.4 kPa) to wool. During cycles of compression, modified resistance to compression peak values decreased slightly and then tended to be constant. Even though the structures of wool, cotton and alpaca were quite different, there was no significant difference in the magnitude of decline in modified resistance to compression peak values. This means that the modified resistance to compression test is able to provide additional information on the resilience characteristics of different natural fibers, and can reveal the resistance behavior of fiber samples during cyclic compression.

Investigation of ballistic performance on 3D compound structure fabric by finite element analysis

Ballistic performance and moldability are two important properties for 3D curved-surface ballistic applications. However, these two properties are contradictory to each other and impossible to improve at the same time, which is a technical issue that needs to be solved urgently in the research for ballistic materials for 3D curved-surface ballistic applications. In order to solve this issue, a new 3D compound structure fabric has been developed as part of our former research and has been shown to provide better ballistic performance with equivalent moldability compared to 3D angle-interlock fabric—a well-known 3D material for 3D curved-surface ballistic applications. Nevertheless, the ballistic performance of this new fabric itself is not clear, and further research is necessary. In this study, the ballistic performance of this new 3D compound structure fabric was investigated via the finite element analysis (FEA) model to examine energy absorption and penetration resistance. A ballistic test was also carried out to verify the results of the FEA model, and this demonstrated that the theoretical model was consistent with the experimental results.

Flexible carbonized cotton/thermoplastic polyurethane composites with outstanding electric heating and pressure sensing performance

Although flexible wearable conductive textiles for various applications have attracted great attention from researchers in recent years, it is still a great challenge to fabricate conductive textiles with the advantages of a simple fabrication process, excellent flexibility, environmental friendliness, and superior performance. Carbonized cellulose materials are gradually emerging in flexible electronics due to their flexibility, low cost, abundant raw materials, and electrical conductivity. Herein, carbonized cotton fabrics were fabricated from cotton fabrics via a simple carbonization process. Then carbonized cotton/thermoplastic polyurethane composites, with excellent electric heating performance and pressure sensing performance, were fabricated through a dip-and-dry method. Carbonized cotton/thermoplastic polyurethane composites show satisfactory electrical conductivity, electric heating temperature rising performance, heating stability, and resistance stability. The surface temperature of carbonized cotton/thermoplastic polyurethane composites can reach ≈53°C within 1.5 min at 5 V. Besides this, the fabricated flexible pressure sensor based on carbonized cotton/thermoplastic polyurethane composites exhibits the combined superiority of a wide working range (0–16 kPa), high sensitivity (98.77 kPa−1), and excellent durability (>4000 cycles). Moreover, the finger motions and wrist pulse can be monitored in real time. These results demonstrate the potential application value and broad developmental prospects of carbonized cotton/thermoplastic polyurethane composites in flexible wearable electronics.

Design of electronic cam for lower hook mechanism of fishing net-weaving machine based on polynomial fitting

The working efficiency and stability of the double hook-based fishing net-weaving machine is mainly determined by the lower hook mechanism. In this work, a new kind of lower hook mechanism, which is driven by four servo motors, is presented, and the electronic cam curve of the lower hook mechanism is introduced. First, cubic B-spline interpolation is used to get the basic motion path of the lower hook plate, and then the piecewise quintic polynomial fitting method is used to fit the motion path. Finally, self-adaptive mutation-based particle swarm optimization is put forward and used to obtain the optimal parameters of the quintic polynomial, which performs better compared with the other two particle swarm optimization algorithms in this study. Experiments suggest that the electronic cam curve generated by the piecewise quintic polynomial fitting has got 55.91% (horizontal motors) and 60.96% (vertical motors) optimization in maximum motor torque compared with curves generated by cubic B-spline interpolations. In addition, the new lower hook mechanism and its moving curve described in this paper improved the theoretical weaving speed of the fishing net-weaving machine, providing a basis for digital improvement of the knotted net-weaving industry.

Novel germanium-polyamide6 fibers with negative air ions release and far-infrared radiation as well as antibacterial property

There has been much concern about germanium because of its special atomic nuclear structure to generate negative electrons and far-infrared ray. In this study, novel germanium-polyamide6 fibers were prepared by using micro–nano structured germanium particles as a functional component via melt spinning. The effects of germanium concentration on the morphology, mechanical, negative air ion-releasing, and far-infrared radiation properties of the germanium-polyamide6 fibers were systematically investigated. Besides, the antibacterial activity and mechanism of the fibers against Staphylococcus aureus and Escherichia coli were also discussed. Even though the added germanium particles negatively affected the mechanical performance of the fiber, they were distributed well in the polyamide6 substrate when the concentration was increased from 2% to 6%. Increasing the temperature and pressure induced the germanium-polyamide6 fibers to produce more negative air ions and high far-infrared emissivity. The negative air ion-releasing property of the fiber led to antibacterial performance against S. aureus with more than 99% antibacterial rate. The results confirmed the great application potential of germanium in healthcare, medical, home, and apparel textiles.

A precise method of color space conversion in the digital printing process based on PSO-DBN

Neural networks have been widely used in color space conversion in the digital printing process. The shallow neural network easily obtains the local optimal solution when establishing multi-dimensional nonlinear mapping. In this paper, an improved high-precision deep belief network (DBN) algorithm is proposed to achieve the color space conversion from CMYK to L*a*b*. First, the PANTONE TCX color card is used as sample data, in which the CMYK value of the color block is used as input and the L*a*b* value is used as output; then, the conversion model from CMYK to L*a*b* color space is established by using DBN. To obtain better weight and threshold, DBN is optimized by a particle swarm optimization algorithm. Experimental results show that the proposed method has the highest conversion accuracy compared with Back Propagation Neural Network, Generalized Regression Neural Network, and traditional DBN color space conversion methods. It can also adapt to the actual production demand of color management in digital printing.

Establishment of the three-dimensional model of the nonwoven structure with fiber scale based on the GAN algorithm

The structure of nonwovens gives special functions, and the establishment of the structure model has important reference significance for the realization of functions. In this work, the two-dimensional configuration of polyester fibers in a spunlaced nonwoven fabric was extracted, and the configurational feature points of 2500 fibers were obtained. Combined with the generative adversarial nets algorithm, the generation model of the two-dimensional configuration of fibers was proposed after learning the configuration feature of 2500 fibers. Based on the assumption that the fibers are randomly distributed in the nonwoven fabric, we established a three-dimensional model of the spunlaced nonwoven fabric on the fiber scale using ABAQUS software. In addition, the water diffusion experiment and simulation were carried out to visualize the diffusion process of a water droplet in the nonwoven fabric, verifying the accuracy of the model. This method provides a novel idea for the modeling of textile structure on the fiber scale, which can be regarded as a model basis for the subsequent simulation analysis and function research.

Influence of the hydrodynamic degumming process on the quality of decorticated flax fibers

The study explored the impact of the hydrodynamic degumming process applied for decorticated monomorphic flax on fiber quality. The experiment was designed as the first stage of research leading to the development of a method for decorticated flax fiber elementarization and cottonization; in particular, effectively dividing the fiber bundles to ensure low linear density and reducing impurities in the content, to make the fibers suitable for cotton spinning systems. The degumming process of the decorticated fibers covered hydrodynamic disposal of the gluing substances, mainly pectins from the fibers, with use of a specially designed lab-scale Model Device for Physical Degumming of the Flax Fibers. The degummed fibers were tested for linear density, length, impurity content and chemical composition by thermogravimetric analysis combined with the analysis of evolved gases (Fourier transform infrared spectroscopy) and analysis of images of fiber cross-sections and longitudinal views from a scanning electron microscope. The study outcomes allowed us to determine the optimal parameters of the degumming process applied for decorticated flax fibers, in which the obtained fibers were of the highest quality. It was found that the optimal parameters of the process were a bath temperature of 30°C and a degumming process duration of 24 hours. These lab-scale process conditions were used in further work on the degumming process of flax fiber carried out on a semi-technical scale, followed by a mechanical cottonization of the fiber, at the final stage of the technological chain.