Electrocardiogram (ECG) electrodes are important sensors for detecting heart disease whose performance determines the validity and accuracy of the collected original ECG signals. Due to the large drawbacks (e.g., allergy, shelf life) of traditional commercial gel electrodes, textile electrodes receive widespread attention for their excellent comfortability and breathability. This work demonstrated a dry electrode for ECG monitoring fabricated by screen printing silver/silver chloride (Ag/AgCl) conductive ink on ordinary polyester fabric. The results show that the screen-printed textile electrodes have good and stable electrical and electrochemical properties and excellent ECG signal acquisition performance. Furthermore, the resistance of the screen-printed textile electrode is maintained within 0.5 Ω/cm after 5000 bending cycles or 20 washing and drying cycles, exhibiting excellent flexibility and durability. This research provides favorable support for the design and preparation of flexible and wearable electrophysiological sensing platforms.

Nowadays, the chipless radio frequency identification (RFID) tag is attracting significant attention owing to its immense potential in tracking. However, most of the chipless tags are fabricated on hard printed circuit boards, and the wearable fabric-based chipless tag is still in the research stage. In this paper, a symmetrical 3^rd L-shaped multi-resonator wearable chipless RFID tag is designed and screen-printed onto fabric. In order to investigate the influence of the non-uniform conductive layer on the signal transmission at high frequency, the surface and cross-sectional topographies of the printed conductive film are analyzed and the frequency response characteristics are simulated and measured. The obtained results show that the common fabric can be used as the substrate to screen print the L-shaped multi-resonators of the chipless RFID tag, and the quality of the screen printed line, especially a narrow line, significantly affects the radio frequency performance. For the screen-printed 3^rd L-shaped stub resonators, the relative frequency shift compared with the simulation results are 0.99%, 0.88% and 2.26%, respectively. Generally, the surface morphology of fabric and screen-printed precision are critical in improving the performance of L-shaped multi-resonators.

Nowadays, fabric-based antennas, resonators, and sensors are attracting significant attention due to their excellent comfortability and flexibility compared with the rigid commercial printed circuit boards (PCBs). Both the dielectric constant () and dielectric loss tangent () of substrate materials have a great influence on their frequency response characteristics. However, the effect of dielectric loss is usually ignored, since traditional radio frequency (RF) devices are fabricated on commercial PCBs with much lower . As the differences of dielectric loss vary widely with different fabric materials, it is of great significance to explore the influence of dielectric loss on the frequency response characteristics. Therefore, this paper systematically studied the influence of substrate properties on RF performance of microstrip multiresonator. Firstly, the models of microstrip multiresonators with different and were created by HFSS simulation. By parametrically sweeping, it showed that the was the key factor for the notch depth. And the larger the , the bigger the electromagnetic loss of the material, resulting in a smaller notch depth of the resonator. Then, three representative materials with different orders of magnitude of (AD-450: 0.002, FR-4: 0.015, and denim fabric: 0.114) were chosen to verify the simulation. The results showed that the common fabric-based resonator has poor RF characteristics for their big dielectric loss compared with those of commercial PCBs. This study is of great significance for designing wearable electronic devices with flexible substrate materials with large dielectric loss.

Smart clothes equipped with flexible sensing systems provide a comfortable means to track health status in real time. Although these sensors are flexible and small, the core signal-processing units still rely on a conventional printed circuit board (PCB), making current health-monitoring devices bulky and inconvenient to wear. In this study, a printed fabric-based hybrid circuit was designed and prepared—with a series of characteristics, such as surface/sectional morphology, electrical properties, and stability—to study its reliability. Furthermore, to verify the function of the fabric-based circuit, simulations and measurements of the circuit, as well as the collection and processing of a normal adult’s electrophysiological signals, were conducted. Under 10,000 stretching and bending cycles with a certain elongation and bending angle, the resistance remained 0.27 Ω/cm and 0.64 Ω/cm, respectively, demonstrating excellent conductivity and reliability. Additionally, the results of the simulation and experiment showed that the circuit can successfully amplify weak electrocardiogram (ECG) signals with a magnification of 1600 times with environmental filtering and 50 Hz of industrial frequency interference. This technology can monitor human electrophysiological signals, such as ECGs, electromyograms (EMGs), and joint motion, providing valuable practical guidance for the unobtrusive monitoring of smart clothes.

To reveal the engineering relationship among the electrical properties of embroidered conductive lines, the electrical properties and arrangements of conductive yarns, it is necessary to establish their equivalent resistance model. Embroidered conductive lines in textiles are usually fabricated by single-layer (conductive and nonconductive yarn used as upper and lower yarn) or double-layer embroidery technology (conductive yarns used as upper and lower yarn). Several researchers have proposed the simple resistance model for single-layer embroidered conductive line based on geometric structure of single conductive yarn in fabric. However, the double-layer conductive line has the contact resistance periodically interlaced by the upper and lower conductive yarns, and it made its equivalent circuit different from that of single-layer conductive line. In this work, a geometric model was built to describe the trace of conductive yarn in fabric, and in combination with Wheatstone Bridge theory, was applied to establish the equivalent resistance models of double-layer conductive lines with a certain width, consisted of various courses. First, the equivalent resistance model of double-layer conductive lines consisting of single course was proposed to calculate the contact resistance. Then, to obtain the electrical resistance of double-layer conductive lines with a certain width, the equivalent resistance model was extended from single course to multiple courses ($n\ge 3$ ). Finally, to validate the proposed equivalent resistance model, double-layer conductive lines with different embroidery parameters (stitch length and stitch spacing) on nonwoven fabric were fabricated and evaluated. The experimental results revealed that the proposed model accurately predicted the resistances of double-layer conductive lines.

Silver/silver chloride (Ag/AgCl)‐coated electronic textiles (e‐textiles) provide breathable, flexible, and stable substitutes to traditional medical gel electrodes or flexible film‐based electrodes for electrocardiogram (ECG) monitoring. In this electrode system, Ag transfers electrons to maintain strong electrical conductivity, while AgCl converts ions to electrons at the skin–electrode interface to ensure good electrochemical properties. Nevertheless, the fabrication techniques and electronical characteristics are the main focus, which ignores the impact of the amount of AgCl on the performances of textile electrodes. In this paper, three different weight percentages of Ag/AgCl textile electrodes were compared here; the weight percentage of Ag/AgCl is 8/2, 7/3, and 6/4, respectively. The surface and cross‐section morphology, elemental content, and electrical/electrochemical properties and the ability of ECG signal acquisition were comprehensively characterized. The results show that all the three textile electrodes fabricated by microelectronic printer exhibited uniform surfaces and outstanding electrical/electrochemical properties, and all of them were able to acquire ECG signals effectively. Furthermore, with the increase of AgCl content, the electrochemical performance of textile electrode is more excellent and the better the quality signal acquisition, especially under dynamic conditions with minimal motion artifacts. By analyzing the acquired signals and metrics such as signal‐to‐noise ratio (SNR) and mean square deviation of R‐wave peaks, it can be concluded that when the proportion of AgCl for a textile electrodes is 40%, the level of ECG signal acquisition can be comparable to that of medical disposable gel electrodes. This research offers constructive guidance for material selection of wearable electrodes and electrophysiological sensing platforms.