Yarn Sensors Research Articles

Design and development of a piezo-resistive sensor based on PEDOT: PSS applied to Sisal’s natural fiber for monitoring of 3D warp Interlock fabric

The aim of the current study is to develop and optimize a flexible sensor based on a natural sisal fiber. Based on this sensor yarn, different fibrous reinforcements of 3D warp interlock fabrics used in composite materials could be monitored. This natural yarn (Sisal) has been pre-coated with a layer of PVA solution which makes it possible to homogenize the surface of the yarn and serves as a substrate for the coating phase. A copper metal wire was used as a connecting device to the measurement acquisition system. Some Conductive Polymers Composite (CPC) based on PEDOT: PSS are compared and used as a coating layer in order to get the conductive appearance of the sensor yarn. A sensor calibration step was carried out which consists in testing the sensor yarn on a MTS traction bench while measuring their resistance variation simultaneously. The electromechanical behavior of the different types of sensors will be compared and discussed. Insertion of these developed sensors within 3D woven structures will be helpful for local monitoring and check the inner local elongation of the 3D warp interlock fabric during tensile tests.

Study on electromechanical property of polypyrrole-coated strain sensors based on polyurethane and its hybrid covered yarns

Fiber-based flexible electronics have become one of the most demanding sensing elements by various wearable applications. However, many of those flexible electronics are facing the major challenge of high electromechanical hysteresis. In this paper, polypyrrole-coated strain sensors based on polyurethane yarns and hybrid polyurethane yarns were fabricated and tested. To lower the mechanical and electromechanical hysteresis of the yarn and yarn-based sensors, micro-morphology and electromechanical property of the yarn-based sensors were observed and analyzed, especially the existence and generation of cracks on conductive films of the sensors. The effect of the covered yarn structure on the electromechanical property of the sensors was discussed. Through the results of tensile tests, the electromechanical properties of the yarn-based sensors were characterized, with contributing factors of electromechanical hysteresis examined and reason for the nonlinear electrical resistance-strain relationship elaborated. Furthermore, the covered yarn structure was found stable, with fewer cracks under tension. It’s recommended that hybrid PU yarns and corresponding yarn-based sensors shall be firstly considered for future research, for relatively small mechanical and electromechanical hysteresis.

Helical core-sheath elastic yarn-based dual strain/humidity sensors with MXene sensing layer

Flexible, stretchable and sensitive textile-based sensors play important roles in a wide variety of artificial intelligence because of its seamless integration with clothing and good comfort. Herein, MXene sensing layer is deposited on the surface of springlike helical core-sheath polyester yarns thanks to the capillarity effect and its intrinsic hydrophilic ability, and the resultant strain sensor and humidity sensor exhibit wide detection range from 0.3 to 120% strain and 30–100% relative humidity (RH) detection, owing to elastic core-sheath structures. The strain sensor shows excellent reproducibility (over 10000 cycles) and fast response time (120 ms). The core-sheath yarn sensor can detect various human motions such as walking, bending and twisting as well as physiological signal (pulse), which have great potential in real-time precise medicine and health care. The yarn sensor could also be an excellent humidity sensor because of the high specific area structure of yarn and intrinsic hydrophilic properties of MXene sensing layer.

Parameter Analysis of CNT Yarns in Smart 3-D Braiding Composites

Abstract An important method for making smart three-dimensional (3-D) braiding composites is to use embedded carbon nanotube (CNT) yarn sensors with 3-D braiding technology. According to the braiding structure of 3-D six-direction braiding composites, the mathematical model of carrier movement of braiding machine is constructed. The method for calculating the number and length of embedded CNT yarns with intelligent composites is proposed. The characteristics of resistance changing for CNT yarns under loading are analyzed. Experiments show that the error of the length and actual length of the CNT yarn calculated by the Bezier curve is less than 1 %. When the tensile strain exceeds 2 %, the strain of the embedded CNT yarns begins to appear nonlinear. The loading and unloading of the specimen have some influence on the resistance change of the CNT yarn. After the load is unloaded, the CNT yarn will produce the residual resistance.

Mechanical, electromagnetic shielding and gas sensing properties of flexible cotton fiber/polyaniline composites

Cotton fibers/polyaniline (PANI) composites were prepared by in situ polymerization acting as flexible sensors in order to avoid the waste brought by traditional sensing substrates. The uniform coating of PANI endowed the cotton strip loaded with PANI sensor (CSPS) and cotton yarn loaded with PANI sensor (CYPS) with good mechanical, electromagnetic shielding and gas sensing properties. Both CSPS and CYPS show high selectivity to NH3, high resistance to humidity and good repeatability between sensors. Compared with the strip shaped CSPS, quasi-one-dimensional CYPS shows higher sensitivity, faster response and recovery speed due to the higher surface exposure rate. The response of CYPS to 100 ppm NH3 increased from −32.1% of CSPS to −92.1%, and the recovery time was shortened from 30.1 s of CSPS to 20.1 s. In addition, quasi-one-dimensional CYPS also displayed the stability of sensing signals against mechanical bending from 0° to 60° and the change of effective sensing length. Importantly, the research has endowed cotton fibers with new diversified functions and expanded their application field.

Flexible Temperature Sensor Integration into E-Textiles Using Different Industrial Yarn Fabrication Processes.

Textiles enhanced with thin-film flexible sensors are well-suited for unobtrusive monitoring of skin parameters due to the sensors’ high conformability. These sensors can be damaged if they are attached to the surface of the textile, also affecting the textiles’ aesthetics and feel. We investigate the effect of embedding flexible temperature sensors within textile yarns, which adds a layer of protection to the sensor. Industrial yarn manufacturing techniques including knit braiding, braiding, and double covering were utilised to identify an appropriate incorporation technique. The thermal time constants recorded by all three sensing yarns was <10 s. Simultaneously, effective sensitivity only decreased by a maximum of 14% compared to the uncovered sensor. This is due to the sensor being positioned within the yarn instead of being in direct contact with the measured surface. These sensor yarns were not affected by bending and produced repeatable measurements. The double covering method was observed to have the least impact on the sensors’ performance due to the yarn’s smaller dimensions. Finally, a sensing yarn was incorporated in an armband and used to measure changes in skin temperature. The demonstrated textile integration techniques for flexible sensors using industrial yarn manufacturing processes enable large-scale smart textile fabrication.

Stretchable Graphene Thin Film Enabled Yarn Sensors with Tunable Piezoresistivity for Human Motion Monitoring

1D graphene based flexible sensors as wearable electronics have recently attracted considerable attentions because of lightweight, high extensibility, easy to wind and weave, and superior sensitivity. In this research, we established a facile and low-cost strategy to construct graphene thin film enabled yarn sensors (GYS) by combining the process of graphene oxide (GO) coating and reducing on polyester (PE) wound spandex yarns. According to systematic processing-property relationship study, a key finding of this work discovers that the degree of resistance recovery as well as gauge sensitivity of GYS can be well controlled and modulated by a pre-stretch treatment. Specifically, as the level of pre-stretch increases from 0 to 60%, the deformable range of sensor that guarantees full resistance recovery prolongs evidently from 0% to ~50%. Meanwhile, the gauge factor of GYS is tunable in the range from 6.40 to 12.06. To understand the pre-stretch process dependent sensing performance, SEM analysis was assisted to evidence the growing size of micro-cracks determining dominantly the behavior of electron transport. Lastly, to take better advantage of GYS, a new wearing mode was demonstrated by direct winding the yarn sensor on varied portions of human body for monitoring different body movements and muscle contracting & relaxing.

Self-Powered Coiled Carbon-Nanotube Yarn Sensor for Gastric Electronics.

The strong peristaltic contraction of the stomach facilitates mixing and emptying of ingested food, which occurs rhythmically at approximately 3 cycles/min (cpm) in humans. Generally, most patients with gastroparesis show gastric electrical dysrhythmia that is disrupted electrical signals controlling gastric contractions. For treatment of gastric electrical dysrhythmia, in vivo electrical impulses to the stomach via an implanted gastric stimulator have been known to restore these gastric deformations. Nevertheless, improved sensors to monitor gastric contractions are still needed in current gastric stimulators. Recently, we have developed a new technology converting mechanical motion to electrical energy by using stretch-induced capacitance changes of a coiled carbon-nanotube (CNT) yarn. For its potential use as a gastric deformation sensor, the performance of a coiled CNT yarn was evaluated in several biological fluids. For a sinusoidal stretch to 30%, the peak-to-peak open-circuit voltage (OCV) was consistently generated at frequencies below 0.1 Hz. This sinusoidal variation in OCV augmented as the strain increased from 10 to 30%. In an in vitro artificial gastric system, the OCV was approximately linearly proportional to the balloon volume, which can monitor periodic deformations of the balloon at 2, 3, and 4 cpm as shown for human gastric deformations. Moreover, stretchy coiled yarns generate the peak electrical voltage and power when deformed. The present study shows that a self-powered CNT yarn sensor can not only monitor the changes in frequency and amplitude of volumetric change but also generate electrical power by periodic deformations of the balloon. Therefore, it seems possible to automatically deliver accurate electrical impulses according to real-time evaluation of a patient's gastric deformation based on information on the frequency, amplitude, and rate of the OCV from CNT yarn.

Multilayered Glass Filament Yarn Surfaces as Sensor Yarn for In-situ Monitoring of Textile-reinforced Thermoplastic Composites

High-performance textile filament yarns, more precisely glass filament (GF) yarn, were used as base material for the development of sensor yarns (SY) because GFs offer high tensile strengths and moduli of elasticity in addition to beneficial decomposition temperatures and elongation. The aim of this work was the creation of a multifunctional sensor yarn (MFSY) based of GF. To achieve this aim, a homogeneous, completely coated first (1st) and second (2nd) silver (Ag) layer was built on the GF yarn surface by developing new technologies. The 1st Ag layer monitors damage within the thermoplastic composite globally, whereas the 2nd Ag layer monitors it locally and defects interface damage. Also, there was an insulation layer between two Ag layers, leading to a total of three layers built on the GF surface. Its surface morphology was determined by light and scanning electron microscopy (SEM) to assess Ag layer properties, such as structure, homogeneity, and cracking. For structural analysis, GFs were investigated using a Fourier transform infrared spectrometer (FTIR). The Ag layer thickness was determined after coating and metallization. Textile-physical tests of the GF in terms of tensile strength, elasticity modulus, elongation at break, yarn fineness and electric conductivity, were carried out before and after silvering.

Fabrication of capacitive yarn torsion sensors based on an electrospinning coating method

AbstractA yarn‐based capacitive torsion sensor was produced using a simple electrospinning coating method. It was expected that nonwoven nanofiber mats, as a coating layer, would exhibit excellent performance owing to their high surface area and porous three‐dimensional nonwoven structure, which is more deformable than that of films. The electrospinning process was investigated by image analysis to generate a suitable structure of the nanofiber coating layer. The thickness of the layer was controlled by varying the electrospinning coating time (10, 20 and 30 min). Yarn sensors with coating layers of different thicknesses were manufactured by twisting two coated fibers, while simultaneously measuring the capacitance. The best sensitivity was observed with the 10 min coated yarn, due to the largest valid twist level range. It is proposed that the distance between the electrodes and the dielectric constant of the material play an important and complex role in the capacitive response of the twisted yarn, caused by the porous three‐dimensional nonwoven structure of the coated layer and the molecular mobility of the polymer. This simple coating method is expected to be useful in a wide range of applications, such as wearable devices, by facilitating convenient fabrication and repair of the flexible sensors. Moreover, high performance of the sensor could be realized due to the structural advantage of the sensing layer. © 2019 Society of Chemical Industry

Analysis of Sensitivity, Linearity, Hysteresis, Responsiveness, and Fatigue of Textile Knit Stretch Sensors.

Wearable technology is widely used for collecting information about the human body and its movement by placing sensors on the body. This paper presents research into electronic textile strain sensors designed specifically for wearable applications which need to be lightweight, robust, and comfortable. In this paper, sixteen stretch sensors, each with different conductive stretch fabrics, are evaluated: EeonTex (Eeonyx Corporation), knitted silver-plated yarn, and knitted spun stainless steel yarn. The sensors’ performance is tested using a tensile tester while monitoring their resistance with a microcontroller. Each sensor was analyzed for its sensitivity, linearity, hysteresis, responsiveness, and fatigue through a series of dynamic and static tests. The findings show that for wearable applications a subset of the silver-plated yarn sensors had better ranked performance in terms of sensitivity, linearity, and steady state. EeonTex was found to be the most responsive, and the stainless steel yarn performed the worst, which may be due to the characteristics of the knit samples under test.

Thermal Properties of PEDOT-compl-PSS Sensor Yarns and Textile Reinforced Thermoplastic Composites

Smart textile structures such as sensor yarns provide real possibility for in situ structural health monitoring of textile reinforced thermoplastic composites. In this work thermal properties of E-glass/polypropylene (GF/ PP) and E-glass/poly(N,N’-hexamethylene adipamide) (GF/PA66) sensor yarns based on conductive polymer complex [3,4(ethylenedioxy)thiophene]-compl-poly(4-vinylbenzenesulfonic acid) (PEDOT-compl-PSS) and related composites were studied. Thermogravimetric analysis (TGA), microscale combustion calorimetry (MCC) and limiting oxygen index (LOI) methods were used to detect thermal behaviour of these structures and effect of coatings applied. According to TGA, GF/PP sensor yarn started to decompose at higher temperature, 345 °C, and showed higher pyrolysis residue, 28 %, compared to GF/PA66 sensor yarn that started to decompose at 316 °C and had lower pyrolysis residue, 23 % . The MCC showed that Heat Release Rate peaks of GF/PP sensor yarn, 341 W/g, and GF/PA66 sensor yarn, 348 W/g, occurred at similar Heat Release Temperature, ~ 430 °C. The additional peak, 51 W/g, was detected for GF/PP sensor yarn at 493 °C. Finally, LOI 22 and LOI 23 were detected only for GF/PP and GF/PA66 composites with integrated sensor yarns.

Highly sensitive polyaniline-coated fiber gas sensors for real-time monitoring of ammonia gas.

A single-yarn-based gas sensor has been made from conductive polyaniline coated on commercial yarns. This can detect ammonia gas concentration in an environment or a working area. Cotton, rayon and polyester are utilized as substrates using a dip-coating process. The conductive yarns show ohmic behavior with an electrical resistance of 15–31 kΩ cm−1. The conductive polyester yarn exhibits higher mechanical strength even after intensive chemical treatment. It also has the highest gas response of 57% of 50 ppm ammonia gas, the concentration at which health problems will occur. A linear gas response of the yarn sensor appears in a range of 5–25 ppm ammonia concentration. The polyester yarn sensor can be reused without any change in its sensing response. It can monitor gas levels continuously giving real-time results. By using a microcontroller as part of the circuitry, the gas detection results are transferred and updated wirelessly to a computer or to a smartphone. The textile-based gas sensor can be sewn directly onto the fabrics since it is made with the same fabric. This single-yarn-based gas sensor is suitable for mass production and is appropriate for sophisticated applications.

Experimental investigation of resistance-strain behavior of carbon nanotube fibers and yarns under single and cyclic loads

Carbon nanotube (CNT) fiber made from millions of carbon nanotubes (CNTs) that are highly-aligned in the axial direction, is lightweight and has many desirable properties, such as high strength and high ductility. CNT yarn is fabricated by twisting several CNT fibers to obtain improved electromechanical properties. In this paper, the mechanical behavior and electrical response of CNT fiber and their multi-ply yarns under uniaxial single and cyclic loads were investigated experimentally. The results reveal that the gauge factor of the CNT fiber is about 1.65. For CNT yarn, the sensitivity of the resistance variation decreases slightly with the number of fibers twisted in CNT yarn increasing, while the stability of resistance variation improves. The cyclic test result shows that the relative resistance changes linearly with strain. In addition, preload treatment will improve the stability of electromechanical property for CNT yarn sensors.

Novel temperature sensors based on strain-relieved braiding constructions

Novel textile temperature sensors based on strain-relieved braiding constructions offer attractive monitoring possibilities for numerous application fields involving e-textiles in general, and medical textiles in particular. Thus, the research work presented in this paper focused on theoretical foundations, manufacturing, and procedural, mechanical as well as thermal testing of these newly developed, textile-based sensors for temperature measurements. The median basic resistance of the scalable sensor yarns using a helical stainless steel wire is about 0.81 Ω/mm. Within the temperature range of 22 to 40℃, the developed sensor yarn has a mean linearity deviation of 0.028 K. The measured temperature coefficient is 0.68 × 10−3 K−1, which correlates with the properties of the stainless steel wire.

Human Machine Interface Glove Using Piezoresistive Textile Based Sensors

Human machine interface technology is focused upon new ways of interaction between human beings and machines. Gesture recognition gloves are getting increasingly popular as human-machine interface devices. Conventionally, these gloves use electronic sensors to sense different hand gestures. As electronic sensors are bulky and uncomfortable, we propose a glove with textile based piezoresistive yarn sensors. This glove is flexible, more comfortable and cheap as compared to the conventional human machine interface gloves. We have examined that this glove can effectively sense our gestures and can be used for teleoperations, sign language to speech conversion systems and gaming.

Multiple functional coating highly inert fiber surfaces of para-aramid filament yarn

High-performance textile filament yarns such as para-aramid filament yarn (p-AF) will be used as the base material for the development of sensor yarns (SY) because p-AF offer high tensile strengths and moduli of elasticity, as well as high decomposition temperatures and elongation. However, p-AF has an inert or hydrophobic surface, i.e. a lower polar fraction of the total surface energy that does not allow metallization. The aim of this work is the development of a multifunctional sensor yarn consisting of inert and hydrophobic p-AF. By applying new technologies developed at the Institute of Textile Machinery and Textile High Performance Materials Technology, a homogeneous, completely coated first (1st) and second (2nd) silver layer was built on the p-AF filament yarn surface. The first silver layer monitors the damage in the thermoplastic composite globally and the second silver layer locally. Between two silver layers is an insulation layer. Thus, three layers are built on the p-AF surface. The surface morphology has been determined by light and scanning electron microscopy to assess the Ag layer properties such as structure, homogeneity, and cracking. For structural analysis, p-AF were investigated using a Fourier transform infrared spectrometer. The dispersive and polar component of the surface energy of the treated and pretreated p-AF was measured by using a single fiber Tensiometer (Kruess K100. The Ag and insulation layer thickness was determined after coating and metallization. Textile physical tests of the tensile strength, elasticity modulus, elongation at break and filament yarn fineness of the p-AF before and after the silvering were carried out. The length related electrical resistance of the 1st and 2nd silver layer of the p-AF filament yarns was measured by a Multimeter Fluke 45 (Fluka Germany GmbH) with two wire methods.

Wearable strain sensing textile based on one-dimensional stretchable and weavable yarn sensors

Flexible, wearable, and even stretchable sensors are the key components of smart electronic textiles. However, most reported flexible and wearable sensors for wearable electronics are usually fabricated in two-dimensional (2D) planar strip configurations, which cannot be properly integrated into textile structures and thus greatly degrade intrinsic properties such as the softness, flexibility, and air permeability of textiles and the aesthetic feeling of clothing. In this work, a new one-dimensional weavable strain sensing yarn consisting of an elastic polyurethane (PU) core, a conductive Ag-nanoparticles/graphene-microsheets composite sheath, and a silicone encapsulation layer was designed and fabricated through an easily manipulated protocol. Arising from the reasonable structural design and appropriate material selection, the as-fabricated strain sensor not only exhibited excellent flexibility, stretchability, and highly repeatable electromechanical stability (a repeatability error of 1.56%) but also possessed both high sensitivity (a gauge factor of nearly 500) and a relatively wide working range (0–50% applied strain) with good linearity (a correlation coefficient of 0.98). In addition, the facile, nearly all-solution-based fabrication protocol enabled the scalable production of long conductive yarns. Thus, the proper yarn length and superb mechanical properties endowed the stretchable conductive yarn with good weavability. The excellent wearability of the stretchable conductive yarn was derived from the outermost isolating, hydrophobic, and biocompatible silicone encapsulation layer. A wearable high-sensitivity strain sensing textile, fabricated by directly weaving the as-prepared yarn-based sensor, showed great potential for application to wearable textile sensors for real-time monitoring of human motions from vigorous walking to subtle and complex pronunciations.

Local strain measurements of yarns inside of 3D warp interlock fabric during forming process

The final geometry of 3D warp interlock fabric needs to be check during the 3D forming step to ensure the right locations of warp and weft yarns inside the final structure. Thus, a new monitoring approach has been proposed based on sensor yarns located in the fabric thickness. To ensure the accuracy of measurements, the observation of the surface deformation of the 3D warp interlock fabric has been joined to the sensor yarns measurements. At the end, it has been revealed a good correlation between strain measurement done globally by camera and locally performed by sensor yarns. Additionally, sensor yarns located in the two directions of the 3D warp interlock fabric have revealed a different forming behaviour depending on the architecture and the different slope values of the punch.

Multi-layered sensor yarns for in situ monitoring of textile reinforced composites

In this contribution, the characteristic of yarns that have intrinsically conductivity as well as such with coaxial conductive coatings acting as in situ strain sensors are described. The objective of the based research projects is the real-time in situ sensing of both global stresses acting on fibre reinforced plastic (FRP) components and the detection of resulted local microscopic damages due to creep, delamination and micro-cracks in the fibre-matrix interphase of glass fibre (GFRP) and carbon fibre (CFRP) composites. Sensor materials similar to the particular FRP and its mechanical behaviour have been chosen. In the first approach, GF- and aramid-based sensor yarns have been developed with multiple tailored silver layer coating system capable to distinguish multiple scaled damage mechanism due to these effects globally and locally. The second approach bases on the piezoresistive effect of CF rovings for their usage as in situ strain sensors. In the next step, suitable fibre and polymer film-based cleading have been tested and evaluated, granting sufficient electrical isolation to avoid shortcircuits between the conductive sensor layers itself or between the sensor and intrinsically conductive CFRP respectively. Initially, the sensor performance of global strain measurement, means the accumulated strain along the integration length of the sensor yarn, has been evaluated during tensile stressing of FRP with integrated suchlike functionalised sensor yarns.