Conductive Fabrics Research Articles

Recent advances in electromagnetic interference (EMI) shielding textiles: A comprehensive review

The rapid growth of 5 G wireless networks and modern electronic communication equipment has resulted in electromagnetic interference (EMI) and radiation pollution which led to the detrimental effects on sensitive precision electronics and on human health. A substantial amount of research has been done to develop efficient products for electromagnetic interference (EMI) shielding. In this concern, electromagnetic interference shielding textiles have gained huge attention to protect human beings from these radiations. This review gives an overview of the basic introduction of conductive textiles, effects of electromagnetic radiation, EMI shielding mechanisms, and factors that are responsible for EMI shielding. The synthesis and characterization of conductive inks and advanced materials which are utilized for EMI shielding textiles are discussed in detail. Metals, conductive polymers, and carbon-based materials have gained huge intention to develop EMI shielding textiles. Moreover, the dominant mechanism of shielding, frequency range, and conductivity of materials has also been discussed. On the basis of our comprehensive analysis the outlooks for future research are also discussed.

Feasibility of conductive embroidered threads for I2C sensors in microcontroller-based wearable electronics

In recent years, the importance of flexible and textile electronics in the field of wearable devices has continuously increased, as they are expected to replace conventional wires that exhibit limited resistance to the mechanical stress occurring in on-body applications. Wearable health devices (WHDs) can provide physiological information about various body parts and employ distributed sensor networks. Among the sensors typically integrated within WHDs, those based on the I2C communication protocol are very common and exploit signals transmitted at frequencies up to hundreds of kilohertz. Therefore, robust communication is required to guarantee a proper transmission of the signal at those frequencies. In this context, we have realized embroidered conductive threads exhibiting a lower resistance, appositely designed to replace conventional wires in a microcontroller-based wearable device employing I2C sensors. A commercial conductive thread (silver coated polyamide) was used to embroider the conductive lines on to cotton fabric. Preliminary measurements were performed to characterize the response of these materials to signals typically operated within the I2C communication protocol at different path lengths. Resistive measurements have also been performed to stimulate different environmental conditions, that is, temperature, the effect of sweating, and repeated washing cycles, also apply mechanical stress, i.e. twisting, with promising results that validate our conductive paths for digital signal communication.

Stretchable and wash durable reactive silver ink coatings for electromagnetic interference shielding, Joule heating, and strain sensing textiles

In this paper, we demonstrate a highly conductive, stretchable, and wash-durable fabric for a variety of electronic textile applications such as electromagnetic interference (EMI) shielding, Joule heating, and strain sensing by utilizing a chemical etchant pretreatment that promotes covalent bonding, a reactive silver ink with conformal in situ silver reduction, and the use of a polymer coating for a protective barrier. Reactive ink coated on polyethylene terephthalate (PET) knitted textiles exhibit an average EMI shielding efficiency of 74.8 dB in the X band (frequency range of 8–12 GHz) and 76.6 dB in the Ku band (12–18 GHz). The conductive textiles show high Joule heating performance, where a temperature of 152 °C can be achieved at only 1.3 V DC applied voltage. This Joule heating performance is maintained after stretching and washing. Furthermore, the textile may be used for strain sensing and monitoring human movement. As prepared silver films do not degrade after 1000 stretching cycles at 50 % strain and maintain EMI SE higher than 70 dB after 300 min washing. The demonstrated textiles may be used for wearable electronics, personal medical devices, and next generation communications.

Fabrication and Characterization of Single‐Layer Textile‐Based Flexible Pressure Sensors for Smart Wearable Electronics Applications

Textile‐based sensors have been widely studied for wearable monitoring. The sensor systems demand a large sensing area, flexibility, and scalable fabrication method. Herein, single‐layer piezoresistive sensors are developed by a machine stitching technique using metallic and graphene nanoplatelets‐coated conductive threads and fabrics. The pressure‐sensing mechanism is based on measuring the electrical resistance due to the change in the contact area between the conductive thread and fabric as pressure on the sensor varies. The single‐layer sensor design provides flexibility and overcomes the physical drift of the sensor during human activities, which enhances wearability and performance. The coated textiles are characterized by scanning electron microscopy and Fourier‐transform infrared spectroscopy. Physical and electromechanical tests are performed on the sensors to evaluate their wearability and sensing performance. The sensors exhibit a wide working range of up to 100 kPa and good sensitivity with excellent durability against repeated mechanical deformations. The application potential of the sensors in real‐time monitoring is demonstrated by embedding them into clothing as a wearable device. Moreover, the effectiveness of the sensors is tested for posture correction. This article suggests a novel technique to fabricate durable, flexible, and highly efficient pressure sensors for smart wearable applications.

The Influence of Titanium Oxide Nanoparticles and UV Radiation on the Electrical Properties of PEDOT:PSS-Coated Cotton Fabrics.

With the rapid growth of electronic textiles, there is a need for highly conductive fabrics containing fewer conductive materials, allowing them to maintain flexibility, low cost and light weight. Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS), is one of the most promising conductive materials for the production of conductive fabrics due to its excellent properties such as solubility, relatively high conductivity, and market availability. Moreover, its electrical conductivity can be enhanced by polar solvents or acid treatment. The aim of this work was to fabricate conductive cotton fabrics with a small fixed amount of PEDOT:PSS and to investigate how titanium dioxide (TiO2) nanoparticles affect the electrical, thermal and structural properties of PEDOT:PSS-coated cotton fabrics. The change in electrical conductivity of the nanocomposite fabric was then related to morphological analysis by scanning electron microscopy and X-ray diffraction. We found that the sheet resistance of the nanocomposite cotton fabric depends on the TiO2 concentration, with a minimum value of 2.68 Ω/□ at 2.92 wt% TiO2. The effect of UV light on the sheet resistance of the nanocomposite cotton fabric was also investigated; we found that UV irradiation leads to an increase in conductivity at an irradiation time of 10 min, after which the conductivity decreases with increasing irradiation time. In addition, the electrical behavior of the nanocomposite cotton fabric as a function of temperature was investigated. The nanocomposite fabrics exhibited metallic behavior at high-TiO2 concentrations of 40.20 wt% and metallic semiconducting behavior at low and medium concentrations of 11.33 and 28.50 wt%, respectively. Interestingly, cotton fabrics coated with nanocomposite possessed excellent washing durability even after seven steam washes.

Pressure Sensors Combining Porous Electrodes and Electrospun Nanofiber-Based Ionic Membranes

It is one of the most urgent development directions and crucial challenges for flexible pressure sensors to have both characteristics of high sensitivity and wide measuring range. To address this challenging problem, this paper proposes an innovative, convenient, and industrially scalable capacitive pressure sensor that combines porous electrodes and electrospun nano ionic membranes with surface microstructure. The advantage of this sensor is that nano ionic nanofiber membranes are directly prepared on porous conductive fabrics by electrospinning with high reliability and good repeatability. The prepared dielectric layer of the sensor is in complete contact with the electrode, which effectively eliminates the uncertainty of air gap interference in traditional packaging methods. The sensing mechanism of the designed sensor is also persuasively revealed by finite-element and theoretical analysis in this paper. First, the porosity of both the conductive fabric and dielectric layer expands the measurement range. Second, the surface microstructure of the nano ion membrane increases the effective contact area between the dielectric layers when external pressure is applied to the sensor, thus increasing the conduction path of the ions. The increase of the ionizing degree under pressure leads to the change of the interface capacitance. These make the sensor have high sensitivity in the wide measurement range. The designed sensor exhibits a sensitivity of up to 1254.5 kPa–1 over a low-pressure measurement range of 0–10 kPa, providing an amazingly wide measurement range of 0–800 kPa, with an extremely high sensitivity of 128.1 kPa–1 over the entire measurement range. The designed sensor illustrates both a fairly fast response time of 10 ms and a relaxation time of 16 ms, in addition to the durability of up to 3000 cycles. The above exceptional performance demonstrates its remarkable potential applications in smart wearable devices and pneumatic pressure monitoring.

Conductive Thread-Based Immunosensor for Pandemic Influenza A (H1N1) Virus Detection

Infectious agents such as viruses pose significant threats to human health, being transmitted via direct contact as well as airborne transmission without direct contact, thus requiring rapid detection to prevent the spread of infectious diseases. In this study, we developed a conductive thread-based immunosensor (CT-IS), a biosensor to easily detect the presence of airborne viruses. CT-IS utilizes an antibody that specifically recognizes the HA protein of the pandemic influenza A (pH1N1) virus, which is incorporated into the conductive thread. The antigen-antibody interaction results in increased strain on the conductive thread in the presence of the pH1N1 virus, resulting in increased electrical resistance of the CT-IS. We evaluated the performance of this sensor using the HA protein and the pH1N1 virus, in addition to samples from patients infected with the pH1N1 virus. We observed a significant change in resistance in the pH1N1-infected patient samples (positive: n = 11, negative: n = 9), whereas negligible change was observed in the control samples (patients not infected with the pH1N1 virus; negative). Hence, the CT-IS is a lightweight fiber-type sensor that can be used as a wearable biosensor by combining it with textiles, to detect the pH1N1 virus in a person's vicinity.

Emerging passive thermoregulatory textiles through tailoring different heat transfer routes

Personal thermal management systems play significant roles in improving personal thermal comfort and decreasing energy consumption resulting from traditional thermoregulation methods such as air conditioning. Thermoregulatory textiles passively regulating human body heat transfer routes through their engineered properties are an effective and promising way to offer personal thermophysiological comfort without extra energy consumption. In this paper, we reviewed recent progress on passive thermoregulatory textiles and classified them into four categories: radiative thermoregulatory textiles, conductive thermoregulatory textiles, single phase convective thermoregulatory textiles, and phase transition convective cooling textiles. By comparing and summarizing their thermoregulatory paths and performance, we found that radiative thermoregulatory textiles are the most promising because of their wide temperature regulation paths, superior thermoregulatory performance, and bidirectional temperature regulation. Furthermore, we provided critical considerations on the various characterization and calculation methods for thermoregulatory performance used in these research works, and pointed out future perspectives in such a burgeoning field.

Enhancement of the vertical thermal conductivity in conductive silicone composites using hybrid fillers and double-sided coating process

Herein, we propose an effective method for improving the vertical thermal conductivity of conductive silicone composites using thermally conductive hybrid fillers and a double-sided coating process. By applying the resin mixing and screen-printing method instead of the conventional spray coating, it was possible to prevent the shrinkage of the conductive composite fabric. It was found that a higher graphene content in the hybrid filler resulted in a higher thermal conductivity for the conductive composites. Moreover, a double-sided coating of conductive silicone additionally improved the vertical thermal conductivity of the fabric due to the formation of a double-sided heat transfer network.

Effect of coating direction of conductive silicone polymer on the electrical and mechanical properties of silicone-embedded conductive textiles

We propose an elegant method for fabricating mechanically robust and electrically conductive composite textiles for next-generation smart clothing by controlling coating direction of the silicone polymer. A typical additive-type silicon polymer containing conductive fillers was coated on the pristine fabric in the wale and course direction. The conductive textile coated in the wale direction showed better elastic recovery than that coated in the course direction. Moreover, the conductive fabrics coated in the wale direction exhibited small cracks and low electrical resistance due to the deep penetration of conductive silicone polymer, leading to the construction of stable conductive network.

Design and Fabrication of Embroidered Textile Strain Sensors: An Alternative to Stitch-Based Strain Sensors.

Smart textile sensors have been gaining popularity as alternative methods for the continuous monitoring of human motion. Multiple methods of fabrication for these textile sensors have been proposed, but the simpler ones include stitching or embroidering the conductive thread onto an elastic fabric to create a strain sensor. Although multiple studies have demonstrated the efficacy of textile sensors using the stitching technique, there is almost little to no information regarding the fabrication of textile strain sensors using the embroidery method. In this paper, a design guide for the fabrication of an embroidered resistive textile strain sensor is presented. All of the required design steps are explained, as well as the different embroidery design parameters and their optimal values. Finally, three embroidered textile strain sensors were created using these design steps. These sensors are based on the principle of superposition and were fabricated using a stainless-steel conductive thread embroidered onto a polyester-rubber elastic knit structure. The three sensors demonstrated an average gauge factor of 1.88±0.51 over a 26% working range, low hysteresis (8.54±2.66%), and good repeatability after being pre-stretched over a certain number of stretching cycles.

Textile Electronic Circuits from Laser‐Patterned Conductive Fabric

Textile electronics have shown very promising results in remote health monitoring or personal thermal management. Meanwhile, textile‐based generators are researched to harvest energy from human motion and supply the electronics required for signal acquisition and transmission. Hence, there is a need to fully integrate electronic circuits directly onto textile to achieve self‐powered smart garments. Herein, a thermoadhesive conductive fabric is considered to realize textile electronic circuits. A laser‐based method is developed to pattern the circuit design. After optimizing the spatial resolution, the electrical and mechanical resistances of the resulting textile conductive tracks are evaluated. Heterogeneous interconnections with rigid electronic components are considered with different methods such as soldering and bonding. The interconnections are characterized and compared regarding their electrical contact resistances. Finally, demonstrators are realized to show a proof of concept of “textronic circuits.”

Fabric Electrode Monitoring of Dynamic and Static ECG Signal and Comfort Performance

To monitor dynamic ECG for a long time, fabric electrodes must have excellent comfort and electrical properties. In addition, the quality of the collected ECG should be as free as possible from interference by motion artifacts due to dry skin and body movement. This study explores the comfort of four different materials and structures of silver-plated fabric electrodes, analyzing the acquisition effect of ECG signals under dynamic and static conditions. To obtain fabric electrodes with good comfort levels and stable ECG signal monitoring under dynamic and static conditions, four kinds of electroless silver-plated conductive fabrics were selected and assembled into fabric electrodes. Permeability, electrochemical impedance spectrum, static opening voltage, and dynamic static electrocardiogram were tested and evaluated for each of the four fabric electrodes; additionally, the comfort of the four fabric electrodes and the mass of ECG monitored under dynamic and static conditions were assessed. The results showed that the highly hygroscopic knitted fabric electrode showed better comfort than the other three samples. The electrochemical impedance spectrum curve of the highly hygroscopic knitted fabric electrode was relatively smooth and stable, and it had lower impedance than the other electrodes; moreover, the static open-circuit voltage changed more stably with the increase of processing time compared to the other samples. The four kinds of fabric electrodes all collected clear and stable ECG in the resting state. However, in dynamic conditions, only the highly hygroscopic knitted fabric electrodes collected stable ECG under the conditions of seven daily life actions, clearly distinguishing between the P-wave, QRS wave group, and T-wave. The knitted fabric electrode has a high correlation with the ECG measured by a disposable gel electrode, meeting the standards needed to monitor ECG during the human body’s daily activities.

Investigation of the Functional Ageing of Conductive Coated Fabrics under Simulated Washing Conditions.

Conductive textiles play an important role in recent electronics development; however, one of the major challenges remains their machine-washing durability. For the investigation of the basic wash ageing mechanisms, we used copper-plated polyamide 66 and cellulose fabrics and developed a wet and dry operable flex tester with online resistance recording. The evaluation was supported by abrasion tests, cyclic elongation tests and tribological investigation of dry and wet textile-textile friction. It was found that the contribution of mechanical and chemical ageing to wash ageing strongly depends on the substrate material. A bad adhesion of copper on polyamide 66 leads to early fatigue while better stability of the copper on cellulose leads to a stronger resistance against ageing. For both substrates, the delamination of the copper layer was the root cause of the fatigue, which is facilitated by the washing solution. Finally, a cumulative fatigue model was developed and the determination of the end of lifetime by the intended use is discussed.

Design and Measurement of a Vibrating Intrinsic Reverberation Chamber Working in Tuned Mode

In this letter, a vibrating intrinsic reverberation chamber (VIRC) working in mode tuning is designed and fabricated; the designed RC is made of a highly electrically conductive silver fabric. A stepper motor is used to tune the cavity surface step by step along its normal direction, and an RC with vibrating wall is realized. The corresponding relationship between the vibrating amplitude and frequency of use is calculated. A test system is developed and the performance of VIRC is experimentally verified. Measurement results show that the measured E-field samples follow a Rician distribution, and the standard deviation of the space E-field is less than 3 dB, which meets the requirements of statistical uniformity tolerance in IEC 61000-4-21.

Water vapor transmission and electromagnetic shielding characteristics of stainless steel/viscose blended yarn woven fabrics

In this study, stainless steel/viscose blended yarn was prepared and different structured woven fabrics were prepared for studying the moisture transmission and electromagnetic shielding behaviour. By doubling viscose spun yarn with SS filament yarn, the SS/viscose blended yarn was prepared. The woven fabrics were made in a sample loom using viscose yarn and SS/viscose blended yarn. By changing the metal content, thread density and conductive fibre proportions at different levels, the developed fabrics were analyzed for maximum shielding effectiveness in the frequency of 300 kHz to 1.5 GHz. The fabric having conductive threads in warp and weft directions showed larger shielding effectiveness (SE) compared to fabric having conductive threads in one direction. The increase in weft density, proportions of conductive threads (in weft direction) and metal content increases the shielding level of fabric. The highest SE of 56 dB was observed for plain woven fabric compared to 3/1 twill, 2/2 twill and 2/2 basket fabrics in the frequency of 700 MHz. The influence of environmental factors such as relative humidity and pH on shielding behaviour of fabrics were also studied. As the relative humidity was increased, the SE was also increased. The fabric treated with acidic (or) basic condition exhibited better SE than the fabric in neutral condition. Similarly, air permeability and water vapour transmission characteristics of the developed conductive fabrics were also analyzed. The air permeability of the fabric was higher when the metal content in the fabric was low. The fabric having more floats showed higher air permeability compared to fabrics with less floats. Similarly, the water vapour transmission rate was also high for long float fabrics. The developed conductive fabrics could be used as wall covering and personal protective clothing in defense industry.

High performance additional mass enhanced film structure triboelectric nanogenerator for scavenging vibration energy in broadband frequency range

It is highly desired to develop high performance vibration energy scavengers to power amounted and distributed sensors along with the era of Internet of Things. This study proposes a novel additional mass enhanced film structure triboelectric nanogenerator (AMF-TENG) for efficiently scavenging broadband vibration energy. The AMF-TENG is composed of an additional mass, a fluorinated ethylene propylene (FEP) film with a carbon electrode, and a conductive fabric fixed on a hollow frame. The additional mass can enhance the electrical output of the AMF-TENG by 25.5 times due to the vibration amplitude and contact forces between the FEP film and conductive fabric are greatly amplified. The utilization of a hollow frame makes the electrical output of AMF-TENG 150% higher than the enclosed frame. Theoretical analysis and experimental studies were carried out to investigate the design parameters. The experimental results indicate that the AMF-TENG shows good electrical performance in the broadband frequency range from 15 to 70 Hz. Under the vibration condition of 40 Hz and 30 m/s2, it can generate a maximum power density of 622.59 W/m3, which is higher than previous studies by 155.2%. Finally, the AMF-TENG is proven to power temperature and humidity sensors continuously under actual machine vibration. In brief, the AMF-TENG provides a new method for efficiently scavenging of vibration energy in the broadband frequency range.

Effect of Fabric Electrode Surface Coating Medium on ECG Signal Quality under Dynamic and Static Conditions

This study intends to explore the influence of a fabric electrode skin interface filling medium on ECG signals under dynamic and static conditions, so as to be able to better monitor both stable and dynamic ECG signals. In this paper, cotton fabric electrodes were prepared using electroless silver-plated conductive cotton fabric, and then the electrodes were integrated into a physiotherapy-grade elastic bandage to assemble the fabric ECG tape. The electrode impedance tester and the BIOPAC physiological recorder were used to measure the fabric electrode-skin impedance and electrocardiogram under dynamic and static conditions, respectively. Later, the influence of the fabric electrode coated medium on the acquisition effect of an electrocardiogram signal under dynamic and static conditions is discussed. The results show that in the absence of a dielectric reagent coating, the cotton fabric electrode is easily disturbed by external noise which leads to large electrode-skin contact impedance. However, the electrode-skin contact impedance is greatly reduced after coating the fabric electrode with the dielectric reagent. At the same time, after applying the conducive paste coating, the corresponding change curve of the fabric electrode became more stable, and the impedance value was less than 0.005 MΩ·cm2, which meets the standard requirement for textile dry electrode skin impedance. In a state of rest, a clear and stable ECG can be collected regardless of whether the medium reagent is coated or not. However, only after applying the conductive paste can a stable ECG signal be collected under the three motion modes, or can a P wave, QRS wave group, or T wave be clearly distinguished. In addition, there is a high correlation with the disposable gel electrode, which can satisfy the requirements of the long-term monitoring of ECG signals under dynamic conditions.

Effect of multiscale hybrid fillers on the electrical conductivity of silicone-based conductive textiles

Synergistic combinations of the microsized copper filler and nanosized conductive fillers were applied to silicone-based conductive textile for improvement of electrical conductivity. Conductive composite textiles (CCTs) were manufactured through screen-printing and subsequent thermal curing of polydimethylsiloxane containing hybrid fillers. We examined changes in the electrical properties of the CCTs according to the type and concentration of nanosized fillers including silver nanowires, graphene nanoparticles, and carbon nanotubes. It was found that upon the addition of 0.5 wt% graphene, the electrical resistance was improved by 27% compared to that of the original CCT owing to the formation of an excellent conductive network.

Changes in characteristics of silver conductive fabrics owing to perspiration and washing.

The original appearance and physical properties of smart clothing as well as the electrical properties of the conductive fabric applied, despite utilization and the management environment, need to be maintained. Previous research has only investigated the washability and functional changes of smart textiles according to the environment from the perspective of sensors and fabric material; however, they have not comprehensively considered actual usage conditions. In this study, changes in the appearance, color, chemical components, wettability, and electrical properties of silver-coated conductive knitted fabrics due to exposure to perspiration and washing were investigated based on the manufacturing methods of conductive fabrics. The conductive knitted fabric exposed to perspiration exhibited the most prominent color change, and the surface became rough and hydrophilic as AgCl and AgO were formed through a chemical reaction between perspiration and silver. In contrast, the conductivity of the fabric was enhanced by the release of Ag+ ions via perspiration. After washing, the silver layer on the surface of the conductive knitted fabric peeled off due to the interference and friction between the fabrics caused by the mechanical force generated during the cleaning process. There was no obvious chemical change, but the contact angle decreased as the nano-roughness decreased owing to the removal of silver particles. The conductivity slightly increased after washing but did not show a significant difference at 10% elongation. Finally, as the frequency of exposure to perspiration and washing increased, the silver layer coating the fiber or fabric surface peeled off and was damaged, resulting in a significant color change. Additionally, the chemical composition of the silver layer was significantly altered by perspiration and water and became hydrophilic. Surface resistance also increased linearly as the frequency of exposure to perspiration and washing increased. In terms of hand value, softness and smoothness decreased, and warmness increased after several cycles. Under all conditions, the conductive fabric with silver-coated yarn maintained a more optimized appearance and electrical properties than the silver-coated fabric according to the manufacturing method. Therefore, conductive yarn is more suitable for manufacturing conductive knitted fabrics for smart clothing in terms of durability. Additionally, specific management plans based on the actual use and environment of smart clothing using conductive knitted fabric are urgently needed.