Conductive Woven Fabrics Research Articles

Influence of woven fabric construction parameters on electromagnetic shielding effectiveness: Part I – weave influence

The development of textiles with the ability to shield an electromagnetic field is still of great interest, and the influences of the construction parameters of woven fabric (weave, input fibrous material composition, three-dimensional (3D) construction) on the resulting electromagnetic shielding efficiency have still not been sufficiently investigated. The main goal of this study is therefore to analyze the weaves of special electrically conductive woven fabrics and evaluate their impact on electromagnetic shielding effectiveness (SE) using statistical methods. Here, the interlacing structure cells of woven fabric are newly used to describe the weave. The results confirmed that the proposed theory of the interlacing of woven fabric is satisfactory for evaluating and, especially, for prediction of the SE of electromagnetic shielding woven fabrics. For this study, the input yarn (made from a mixture of traditional and extremely thin discrete stainless steel fibers) is used for the production of 21 types of dobby woven fabrics with different weaves and its SE was analyzed using the coaxial transmission-line technique. This contribution can be used as theoretical guidance for the construction, design, and production of special woven fabrics (dobby and jacquard pattern) with controlled SE.

Preparation and Characterization of PEDOT:PSS/TiO2 Micro/Nanofiber-Based Gas Sensors.

In this study, we employed electrospinning technology and in situ polymerization to prepare wearable and highly sensitive PVP/PEDOT:PSS/TiO2 micro/nanofiber gas sensors. PEDOT, PEDOT:PSS, and TiO2 were prepared via in situ polymerization and tested for characteristic peaks using energy-dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FT-IR), then characterized using a scanning electron microscope (SEM), a four-point probe resistance measurement, and a gas sensor test system. The gas sensitivity was 3.46–12.06% when ethanol with a concentration between 12.5 ppm and 6250 ppm was measured; 625 ppm of ethanol was used in the gas sensitivity measurements for the PEDOT/composite conductive woven fabrics, PVP/PEDOT:PSS nanofiber membranes, and PVP/PEDOT:PSS/TiO2 micro/nanofiber gas sensors. The latter exhibited the highest gas sensitivity, which was 5.52% and 2.35% greater than that of the PEDOT/composite conductive woven fabrics and PVP/PEDOT:PSS nanofiber membranes, respectively. In addition, the influence of relative humidity on the performance of the PVP/PEDOT:PSS/TiO2 micro/nanofiber gas sensors was examined. The electrical sensitivity decreased with a decrease in ethanol concentration. The gas sensitivity exhibited a linear relationship with relative humidity lower than 75%; however, when the relative humidity was higher than 75%, the gas sensitivity showed a highly non-linear correlation. The test results indicated that the PVP/PEDOT:PSS/TiO2 micro/nanofiber gas sensors were flexible and highly sensitive to gas, qualifying them for use as a wearable gas sensor platform at room temperature. The proposed gas sensors demonstrated vital functions and an innovative design for the development of a smart wearable device.

Highly Sensitive and Flexible Capacitive Pressure Sensor Based on a Dual-Structured Nanofiber Membrane as the Dielectric for Attachable Wearable Electronics

Wearable devices are an indispensable part of modern life, and flexible capacitive pressure sensors as their luminous subset have assumed a significant role in this day and age owing to ultralow power consumption. In recent years, a fierce debate as well as numerous studies have been conducted to improve the sensitivity of capacitive pressure sensors, but a vital challenge of the mass production of a highly sensitive sensor by a low-cost method still remains. In this paper, to meet industrial demands, we propose a simple method to fabricate sandwich-structured capacitive pressure sensors on an industrial scale and at low cost; as the electrospinning collector, stainless steel screens with regular patterns and structures were utilized to gain the dielectric with both external microstructure and internal pores (dual structure). The prepared pressure sensor is composed of a thermoplastic-urethane electrospun nanofiber film, as a dielectric, in the middle and two conductive woven fabrics on the upper and lower sides as electrodes. Benefiting from the prolific air in the dielectric layer, the designed sensor demonstrates outstanding sensing performance, such as high sensitivity (0.28 kPa–1) in the low-pressure region (0–2 kPa), fast response/relaxation time (65/78 ms), and high-grade durability (1000 cycles). Moreover, the produced pressure sensor is employed for not only detecting human limb movements and object grasping but also detecting pressure distribution in sensor array state, so demonstrating the application potential in attachable wearable electronics.

Study on frequency selective/absorption/reflection multilayer composite flexible electromagnetic interference shielding fabric

Three kinds of electromagnetic functional materials, frequency selective surface, carbonyl iron coated absorbing fabric and conductive woven fabric, were laminated to filter, absorb and reflect electromagnetic waves. Through equivalent circuit analysis, the frequency selection characteristics and the correlation between the shape and size of the periodic structure of cross-shaped and Jerusalem-shaped frequency selective surfaces were studied. It is found that frequency selective surfaces can reduce the transmission coefficient of carbonyl iron coated fabric at the resonance point, so that the working frequency band of the composite shielding material can be controlled and adjusted. The stacking order has no effect on the frequency selective surface/frequency selective surface double-layer materials, but influence the transmission coefficient of composite materials with frequency selective surface superimposed carbonyl iron coated fabric and/or conductive woven fabric. Among all samples, the transmission coefficient of Jerusalem-shaped/carbonyl iron coated fabric-3/conductive woven fabric has the most strong shielding effect, which is up to −51.72 dB at 10.48 GHz. It is proved that using flexible fabric as the matrix and compounding materials with different electromagnetic functions is an effective method to realize high efficiency and adjustable electromagnetic shielding ability.

Electromagnetic shielding performance of copper and silver-plated hybrid yarn based multilayer fabrics in C & X band frequency range

In the present study, a strategic designing of multilayer shield was planned to enhance the multiple reflection phenomenon to achieve maximum absorption properties in microwave frequency (C & X band) range. Multi-layer EMR shields were developed using pure cotton fabric and conductive woven fabrics, incorporated with copper- based & silver-plated hybrid yarn. First of all, single layer fabrics were produced in five variants, nomenclature as L1A (pure cotton) L1B, L1C (copper-based hybrid yarn), LS1B and LS1C (silver plated hybrid yarn). These five variants were used to prepare four sets of double & triple layer fabric. In both double and triple layer composition, L1A fabric (pure cotton) was used as top layer followed by B and C series fabrics, containing copper and silver-plated hybrid yarn. The EMSE performance in C and X band frequency range of single layer, double layer and triple layers in terms of scattering parameters S11(reflectance) & S21 (transmittance) in vertical and horizontal wave polarization was studied. It was found that number of layers, layer composition, orientation of metallic yarn, frequency and EM wave polarization have significant influence on overall electromagnetic shielding effectiveness.

Study on frequency selective/absorption/reflection multilayer composite flexible electromagnetic wave absorbing fabric

In order to realize wide-band, high-efficiency and flexible electromagnetic wave absorption, an effective method is the combination of different electromagnetic functional materials. How to use and make the multilayer materials with individual absorption, reflection and selective transmission characteristics is very important. In this work, multilayer composite flexible absorbing fabrics made of a frequency selective surface (FSS), carbonyl iron coated fabrics (CIFs) and copper-nickel plated conductive woven fabrics (CWFs) were prepared. The layered composite materials have a thin thickness, good flexibility and adjustable absorption band, which provide a reference for the development of lightweight and efficient electromagnetic wave absorbing materials. The influence of the resonance point, wave absorbent content and conductive layer on the absorbing properties were studied. CIF-3 with a surface density of 2046.9 g/m2 has the best absorption performance with a minimum reflectivity of –20.52 dB at 12.56 GHz. A one-layer FSS can broaden the absorption bandwidth; the broadening degree varies with the resonance point of the FSS, which also makes the absorption band adjustable. The bandwidth of f12/CIF-3 with reflectivity of less than –10 dB can reach 5.68 GHz. Besides, CWF is beneficial to increase the absorption intensity, and the best reflectivity of CIF-3/CWF can reach –27.73 dB. Furthermore, three-layer composites can improve the absorption strength and bandwidth of CIF at low frequency. Compared with CIF-3, the reflectivity of f14/CIF-3/CWF decreases 8.06 dB at 11.28 GHz, and the bandwidth is 4.72 GHz, which widens by 0.32 GHz.

High-strength conductive yarns and fabrics: mechanical properties, electromagnetic interference shielding effectiveness, and manufacturing techniques

The aim of this study is to combine conductive polymer composite with conductive fabrics for the acquisition of electromagnetic interference shielding effectiveness (EMI SE) materials. HS-PET filaments, 316 L stainless steel (SS) wires, and bamboo charcoal (BC) roving are made into woven fabrics and knitted fabrics. Unlike the nonwoven fabrics that consist of entangled staple fibers, the resulting shielding materials have greater air permeability. Accordingly, HS-PET filaments, 316 L SS filaments, and BC roving are made into conductive yarns with different twists per inch (T.P.I.) using a ring spinning manufacture. The conductive yarns are made into woven and knitted fabrics, the electromagnetic interference shielding effectiveness (EMI SE) of which are then evaluated in order to examine the influences of the number of fabric layers, lamination angle, and laminated fabric type. The test results show that with a T.P.I being 8, the conductive yarns have an optimal tensile strength of 43.74 N with the lowest CV% of 4.72%. In the meantime, the conductive yarns have good uniformity but do not demonstrate any significant trend on the linear resistance. In addition, the conductive woven fabrics have better tensile strength along the weft direction (712.49 N). Regardless of whether it is a woven fabric or a knitted fabric, the surface resistivity is 107 Ω/sq. Single-layered knitted fabrics have the optimal air permeability (262.6 cm3/s/cm2), and the three-layered woven fabrics laminated at angle of 0°/90°/45° exhibit the maximum EMI SE (-45.96 dB). Therefore, the three parameters are correlated with the metallic conductive network that directly changes the EMI SE of the resulted fabrics and composites.

Electromagnetic wave shielding and mechanical properties of vapor-grown carbon nanofiber/polyvinylidene fluoride composite fibers

The demand for multifunctional requirements in aerospace, military, automobile, sports, and energy applications has encouraged the investigation of new conductive composite fibers. This study focuses on the development of Vapor-grown carbon nanofibers (VGCNFs) filled Polyvinylidene Fluoride (PVDF) composite fibers. Polyvinylidene fluoride (PVDF) reinforced with (1, 3, 5, and 8 wt.%) carbon nanofibers were produced as a masterbatch. The production of PVDF and PVDF/CNF composite fibers have been done successfully by using melt spinning processing technique. Conductive woven fabrics were produced with composite fibers on handloom machines to measure electromagnetic interference (EMI) shielding efficiency. Tensile strength of fibers increased with increase in CNF loading up to 3%. The tensile strength displayed a decrease of 5% and 8% CNF loading. Electromagnetic shielding effectiveness (EMSE) of woven fabrics with composite fibers were tested by using the coaxial transmission line method for planar materials standard that is based on ASTM D 4935-10. The electromagnetic shielding effectiveness of woven fabric which is consist of conductive composite fibers were increased with increasing CNFs loading and amount of fabric layers. It can be seen that the woven fabrics displayed between 2–10 dB and 2–4 dB EMSE values in the 15–600 MHz and 600–3000 MHz-frequency range, respectively. Nevertheless, it was observed that conductive filler content, dispersion, and network formation within the composite fibers were highly influent on the electromagnetic shielding effectiveness performance of the structures.

Easy-to-Build Textile Pressure Sensor.

This article presents the design, construction, and evaluation of an easy-to-build textile pressure resistive sensor created from low-cost conventional anti-static sheets and conductive woven fabrics. The sensor can be built quickly using standard household tools, and its thinness makes it especially suitable for wearable applications. Five sensors constructed under such conditions were evaluated, presenting a stable and linear characteristic in the range 1 to 70 kPa. The linear response was modeled and fitted for each sensor individually for comparison purposes, confirming a low variability due to the simple manufacturing process. Besides, the recovery times of the sensors were measured for pressures in the linear range, observing, for example, an average time of 1 s between the moment in which a pressure of 8 kPa was no longer applied, and the resistance variation at the 90% of its nominal value. Finally, we evaluated the proposed sensor design on a classroom application consisting of a smart glove that measured the pressure applied by each finger. From the evaluated characteristics, we concluded that the proposed design is suitable for didactic, healthcare and lifestyle applications in which the sensing of pressure variations, e.g., for activity assessment, is more valuable than accurate pressure sensing.

Textile-based batteries with nanofiber interlayer

Textile batteries are of utmost interest for the emerging field of electronic textiles. Several research groups work on this topic, developing either fiber-based batteries or planar alternatives, e.g. by coating textile fabrics with metallic electrodes and an electrolyte between them. Since usual non-toxic electrolytes are fluid, using them in a textile battery necessitates gelling them or embedding them in a sponge-like matrix to avoid diffusion through the textile electrodes. Here we report on measurements of textile batteries, prepared from different conductive woven fabrics with a nanofiber mat as an interlayer filled with iodine-triiodide solution. Firstly, the highest voltages were achieved combining metal electrodes with a carbon electrode, showing that the electrolyte in this system is part of the redox system. Second, the metal electrodes were destroyed after short times, suggesting that iodine-triiodide is not an ideal choice for an electrolyte, although this material is often used. Finally, we show that even without setting up the complete battery, the electrolyte slowly destroys the metal layers, while it is itself degraded by photo-oxidation, underlining the necessity to find non-toxic, environmentally-friendly alternatives for iodine-triiodide to enable long-term storage. Assuming non-solid state for electrolytes, the level of their confinement by different types of corrugated materials was tested.

A simulation model of electrical resistance applied in designing conductive woven fabrics – Part II: fast estimated model

Limited researches have been proposed regarding the theoretical model of conductive woven fabric. In a previous study, one type of simulation model was derived to compute the resistance of conductive woven fabric. This paper proposed another fast estimated method to obtain the electrical resistance of conductive thermal woven fabrics (CTWFs) based on the previous model but design oriented. This new model has a similar predicted effect, for which the maximum deviation is less than 1.2% compared to the previous one. The cover factor was a major factor in this model, which assists designers to comprehend and manage the method rapidly. The results revealed that the proposed fast estimated model was well fitted ( P-value < 0.05) and could well simulate the electrical resistance of CTWFs within a certain error variation. According to this model, designers can independently estimate the electrical resistance and design customized products of CTWFs, which will be produced effectively by reducing extra waste of energy and cost.

A simulation model of electrical resistance applied in designing conductive woven fabrics

Numerous studies have performed analyses of knitted fabric integrating conductive yarn in textile-based electronic circuits, some of which established simulative models such as the resistive network model for knitting stitches. Compared to conductive knitted fabrics, limited studies have been presented regarding the resistive theoretical model of conductive woven fabric. In this paper, a simulation model was derived to compute the resistance of conductive woven fabric in terms of the following fabric parameters: structure, density and conductive yarn arrangement. The results revealed that the model is well fitted ( P value < 0.01) and can predict the resistance of woven fabrics, which makes it possible to estimate the fabric parameters and thus to meet the required resistance. Based on this model, thermal conductive woven fabric with maximum energy management and cost control can be efficiently designed.

Electromagnetic shielding, wicking, and drying characteristics of CSP/AN/SSW hybrid yarns-incorporated woven fabrics

To improve the wearing comfort, durability, and antibacterial properties of the electromagnetic (EM) shielding property, a type of multifunction EM shielding woven fabrics which having great liquid transport and drying ability were fabricated in this study. This study aims to investigate theirs liquid transport, drying, and electromagnetic (EM) shielding properties. For this purpose, initially six types of multifunctional crisscross-section polyester (CSP)/antibacterial nylon (AN)/stainless steel wire (SSW) metal hybrid yarns with different wrapping amounts were produced using hollow spindle spinning technique. Conductive woven fabrics were then woven with CSP/AN/SSW metal hybrid yarns as weft yarns, and PET filaments as the warp yarns. The liquid transport and drying ability of the conductive woven fabrics were evaluated in terms of wicking ability and water evaporation rate, which are two vital factors that affect the physiological comfort level of personal protective clothing (PPC). Results indicated that adding CSP yarn in the fabricated EM shielding woven fabric could obviously improve the drying rate of the fabric. The EM shielding behavior of these woven fabrics were analyzed using a vector network analyzer in the frequency range of 300 kHz–3 GHz. Results showed that the wrapping amounts of the metal hybrid yarns significantly affect the wicking and drying abilities of the woven fabrics. In addition, the lamination angles of the fabrics with different amounts of layers remarkably affect their EM shielding characteristics.

Polyaniline Based Conductive Textiles

The conductive polymers were mixed with binder and coated on cotton, polyester and wool fabric, keeping conductive polymer concentration at 5 %. Conductive woven fabrics were obtained by pad-dry-cure coating technique. The surface and bulk conductivity behaviour of the coating paste with respect to temperature were studied using four probe and two probe technique. The conductivity studies show that the coated fabrics have good electrical conductivity in the range of 33.2 μS/cm–3281 μS/cm and there was an increase in conductivity with rise in temperature.