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Highlights Continuously long carbon nanotube yarns (CNTYs) were integrated into glass fiber weave/vinyl ester composites to act as electrical sensing elements to self‐monitoring damage. A grid comprising one longitudinal and three transverse CNTYs, running through the 125 mm long flexural specimen, was integrated into the top and bottom layers of glass fiber weaves to allow monitoring of the electrical resistance and locate damage. Four‐point bending specimens were tested under cyclic flexural loading, alternating with low‐velocity impacts to monitor damage initiation and progression. The electrical response of the CNTY grid is able to pinpoint the region where damage initiates, accumulates, and propagates under cycling loading, triggered or not by impact. The damage location identified by the electrical response of CNTYs is supported by in situ in‐plane and through‐thickness strain fields measured by digital image correlation (DIC). The correlation between the electrical technique and the DIC‐measured strain fields indicate that the majority of damage occurs through interlaminar stresses at or near the supports and/or loading introduction elements of the flexural test rig. Integrating CNTYs into structural composites enables online damage monitoring, leading to intelligent condition‐based maintenance for naval ships, aircrafts, and other structures, ultimately extending service life and reducing costs. CNTYs were integrated into composites for damage self‐sensing. Electrical response of CNTYs pinpoints the region of damage. Damage caused by cyclic bending and low velocity impacts were identified. Electrically identified damage is supported by DIC. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) polymer composites have broad application prospects in thermal management as electrothermal heaters. Nevertheless, challenge remains in achieving high electrical conductivity for the composites due to the contradiction between CNTs and insulated polymers. To address this issue, herein, innovative use of interface strategy approach by constructing synergistic nanomaterial networks on carboxyl CNTs yarn winding composites for improving the interfacial adhesion and electrical performance. In the work, carboxyl CNTs yarn/CNTs‐graphene oxide (GO) polyvinyl alcohol (PVA) composites (C‐CY‐HP‐C) were proposed and manufactured via filament winding process. The as‐constructed C‐CY‐HP‐C demonstrated a remarkable interfacial shear strength of 2057.16 N mm−1, which was 53.59% higher than that of control CNTs yarn/PVA winding composites. In addition, the C‐CY‐HP‐C achieved an attractive electrical conductivity of 346.39 S cm−1 owing to the electronic transmission channels were formed. Notably, the superior electrical conductivity facilitated a rapid‐response of electrothermal performance for the C‐CY‐HP‐C. It reached a steady‐state temperature of 229.9°C within 10 s when the voltage was 1.2 V. Concurrently, it exhibited an impressive heating rate of 10.8°C min−1 at an ambient temperature of −20°C as the battery surface heater. These findings shed light on the development of technique for battery preheating system based on CNTs yarn/polymer composites. [ABSTRACT FROM AUTHOR]

The hierarchical structure and microscale dimensions of carbon nanotube yarns (CNTYs) make them great candidates for the development of integrated sensing applications. The change in the electrical resistance of CNTYs due to mechanical strain, known as piezoresistivity, is the principal mechanism in strain sensing using CNTYs. While the axial tensile properties of CNTYs have been studied widely, studies on the axial piezoresistive response of CNTYS under compression have been limited due to the complexities associated with the nature of the experiments involving subjecting a slender fiber to compression loading in its axial direction. In this study, the piezoresistive response of a single CNTY embedded into a polymeric resin (CNTY monofilament composite) was investigated under axial compression. The results suggest that the CNTY exhibits a strong piezoresistive response in the axial direction with sensitivity or gauge factor values in the order of 0.4–0.5 for CNTY monofilament composites. The piezoresistive response of the CNTY monofilament composites under compression was compared to that under tension and it was observed that the sensitivity appears to be slightly lower under compression. The potential change in sensitivity between the freestanding CNTY and the CNTY monofilament composite under compression is still unknown. Knowing the axial piezoresistive response of the CNTYs under both tension and compression will enable their use in sensing applications where the yarn undergoes compression including those in aerospace and marine structures, and civil or energy infrastructure. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) possess exceptional mechanical properties, surpassing stiffness and strength metrics of common materials such as steel alloys by 100× at the nanoscale. However, when myriads of individual CNTs are bundled together into macroscopic ensembles like fibers or sheets, the result is a 100-fold drop in strength compared to its individual components. Here we present a general strategy aimed to close this gap in property scaling. By using vapor-phase polymerization of a crosslinkable polymer, we reinforced the weak interlinkages among individual CNTs within both yarns and sheets to promote a better transference of mechanical load across the structure. After the treatment, dry-spun, low-density 2.3 μm thin yarns increased their elastic moduli by at least 300%, and free-standing CNT sheets exhibited a 10× boost. In-situ synchrotron small-angle X-ray scattering revealed that polymer-reinforced yarns undergo limited CNT bundle rearrangement when subjected to tensile loads compared to pristine yarns. This evidence supports the hypothesis that the polymer hinders CNTs slippage, the root cause of the poor scaling of mechanical properties in these materials. While we demonstrated this reinforcement method for CNT structures, it is not specific to CNTs and could be used in a wide variety of other hierarchical nanostructured ensembles.

Owing to increasing amount of research on energy harvesting, studies on harvesters for practical application and their performance are attracting attention. Therefore, studies on the use of continuous energy as an energy source for energy‐harvesting devices are being conducted, and fluid flows, e.g., wind, river flow, and sea wave, are widely used as input energy sources for continuous energy harvesting. A new energy‐harvesting technology has emerged based on the mechanical stretch and release of coiled carbon nanotube (CNT) yarns, which generate energy based on the change in the electrochemical double‐layer capacitance. First, this CNT yarn–based mechanical energy harvester is demonstrated, which is applicable to various environments where fluid flow exists. This environment‐adaptable harvester uses rotational energy as the mechanical energy source and is tested in river and ocean environments. Moreover, an attachable‐type harvester for the application of the existing rotational system is devised. In the case of a slow rotational environment, a square‐wave strain‐applying harvester has been implemented, which can convert sinusoidal strain motion into square‐wave strain motion for high output voltages. To achieve high performance of practical harvesting applications, a scale‐up method for powering signal‐transmitting devices has been implemented. [ABSTRACT FROM AUTHOR]

Developing efficient, sustainable, and high-performance energy storage systems is essential for advancing various industries, including integrated structural health monitoring. Carbon nanotube yarn (CNTY) supercapacitors have the potential to be an excellent solution for this purpose because they offer unique material properties such as high capacitance, electrical conductivity, and energy and power densities. The scope of the study included fabricating supercapacitors using various materials and characterizing them to determine the capacitive properties, energy, and power densities. Experimental studies were conducted to investigate the energy density and power density behavior of CNTYs embedded in various electrochemical-active matrices to monitor the matrices' power process and the CNTY supercapacitors' life-cyclic response. The results showed that the CNTY supercapacitors displayed excellent capacitive behavior, with nearly rectangular CV curves across a range of scan rates. The energy density and power density of the supercapacitors fluctuated between a minimum of 3.89 Wh/kg and 8 W/kg while the maximum was between 6.46 Wh/kg and 13.20 W/kg. These CNTY supercapacitors are being tailored to power CNTY sensors integrated into a variety of structures that could monitor damage, strain, temperature, and others. [ABSTRACT FROM AUTHOR]

Nanocarbon-based materials, including carbon nanotubes, have been considered to replace conventional metals for electrical wires, mainly due to their exceptional properties and the rapid increase in global demand for better electrical energy generation, transmission, and conversion. However, the numerical examination of the performance of the electrical machine with different novel carbon nano-based materials is still challenging. Advanced carbon-based materials are proposed as a hypothetical winding material to initiate discussion and examine potential possibilities. This study thoroughly examines and compares different carbon nanomaterials for winding material in a permanent magnet generator. The generator's performance was investigated for three stator winding materials: carbon nanotube (CNT) yarn, carbon nanotube aluminum composite (Al/CNT), and carbon nanotube copper composite (Cu/CNT). A finite-element model of a machine is used to provide the performance study and focuses on the machine-generated voltages, currents, and efficiencies. The simulation was carried out using COMSOL Multiphysics software. The findings illustrate that CNT yarn, Al/CNT, and Cu/CNT composite wire as a winding produces maximum voltages of 15.2, 50.1, and 70 V, respectively, when rotated at 100 rpm. It is observed that the proposed use of carbon nanomaterials is being explored as a possible way to replace the pure metal-based winding of the electrical machine. We conclude that carbon nanotube copper composite wire may be better for winding machine applications than carbon nanotube yarn. These results may be used to design a permanent magnet generator for industrial applications based on their requirements. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNT), CNT–aluminum (CNT–Al), and CNT–copper (CNT–Cu) composite wires have shown remarkable electrical and mechanical properties for developing windings of single-phase induction motor. A quest has been made that if these advanced carbon nanomaterials can outclass commonly used electrical wire metals to significantly leverage electrical machines. However, these advanced materials are still in laboratory stage and most material properties are not yet experimentally reaching to their expectations. Therefore, there is need to understand the potential of these nanomaterials for electrical machines and the numerical analysis of the performance of electrical machines with various advanced novel carbon nanomaterials is still a challenge. This paper presents a comprehensive study to compare the performance of a single induction motor with its stator and rotor made with different winding materials. In doing so, the traditional copper and aluminum rotor and stator coils have been replaced by windings made of pure CNT yarn, CNT–Al, and CNT–Cu wires. A 2-D induction machine model was developed for the simulation study conducted in COMSOL Multiphysics finite element-based software. General-purpose sizing and power equations were utilized during the computation. The simulated results of flux distribution, air-gap flux density, torque, and corresponding output power were used as criteria to determine the highest quality solution. The simulation results revealed that using CNT–Cu and CNT–Al wires as machine winding can achieve 25.9% and 16.8% higher efficiency, respectively, than using CNT wires. The motor torque from the proposed finite element model was validated against the experimental results under identical speed and input voltage, and an error of 5.9% suggests that the model can be used to predict the motor performance with reasonable accuracy. [ABSTRACT FROM AUTHOR]

[Display omitted] • A flexible n -type oleylamine/carbon nanotube hybrid yarn with a power factor of 876.25 μW m-1 K-2 was developed. • The oleylamine/carbon nanotube hybrid yarn exhibited a stable n -type behavior for over 370 days of continuous exposure to air. • The constructed thermoelectric generator yielded an output voltage of 705.94 mV and a maximum output power of 44.34 μW. Wearable thermoelectric generators (TEGs), envisioned to harness the temperature gradient (ΔT) between the human body and the environment into electricity, hold great promise for powering wearable electronics. However, their practical application has been hampered by the scarcity of flexible n -type thermoelectric (TE) materials boasting both high performance and long-term air stability. Here, we introduce a significant advancement by developing an n -type TE material through immersing carbon nanotube yarn (CNTY) into an oleylamine (OAm)/ethanol solution, followed by drying under atmospheric conditions. The resulting OAm/CNTY exhibits a Seebeck coefficient of -80.48 μV K-1, an electrical conductivity of 1353.18 S cm-1 and a power factor of 876.25 μW m-1 K-2, all while exhibiting exceptional mechanical flexibility. Notably, this hybrid yarn maintains stable n -type behavior even after enduring exposure to air for over 370 days, surpassing previous n -type TE materials based on CNT fibers and CNTY. Leveraging this advancement, we construct a prototype wearable TEG by alternately embroidering pristine p -type CNTY and n -type OAm/CNTY into a polyester spacer fabric, electrically connecting them in series using conductive silver paint. The resulting wearable TEG, featuring with 150 p - n couples, yields an output voltage of 705.94 mV and a maximum output power of 44.34 μW at a ΔT of 40 K. This groundbreaking work opens new avenues for the development of high-performance, air-stable, and flexible n -type TE material, ushering in a new era for wearable TEGs. [ABSTRACT FROM AUTHOR]

Twisted and coiled carbon nanotube (CNT) yarns utilize the capacitance change induced by mechanical deformation to convert mechanical energy into electrical energy without requiring a bias voltage. Improved techniques are needed for improving the energy generation of a single yarn. Here we report a sheath-core CNT yarn harvester (SCCH) using a twisted CNT sheath and a polymer fiber core, which increases the energy conversion efficiency to 6.1 %, up from 1.7 % for the neat coiled yarn. The SCCH generated a 2.2 times peak power density (233 W kg−1) than neat CNT yarn when cyclic stretched at 15 Hz. Additionally, the twistron was coated with gel electrolytes to create a sensor capable of monitoring human motion. The twistron was further employed to harness continuous rotational energy in diverse environments where fluid flow is present, facilitating the operation of temperature or humidity-sensing electronic devices. A sheath-core CNT yarn harvester (SCCH) was fabricated using a twisted CNT sheath and a high-mechanical-strength polymer core. The SCCH generates a higher gravimetric power than neat CNT yarn by reducing the matching impedance and increasing capacitance change. The input mechanical energy significantly decreased due to the soft yarn core, leading to a higher energy conversion efficiency. A self-powered humidity and temperature sensor based on SCCH has been created, capable of harvesting wind or flow energy from all directions. [Display omitted] • A sheath-core CNT yarn harvester (SCCH) was fabricated using a twisted CNT sheath and a polymer core. • The SCCH generates a higher gravimetric power than neat CNT yarn by reducing the matching impedance and increasing capacitance change. • The soft yarn core significantly decreased input mechanical energy, leading to a higher energy conversion efficiency. • A self-powered humidity and temperature sensor based on SCCH can harvest wind or flow energy from all directions. [ABSTRACT FROM AUTHOR]

The hierarchical structure and microscale dimensions of carbon nanotube yarns (CNTYs) make them great candidates for the development of integrated sensing applications. The change in the electrical resistance of CNTYs due to mechanical strain, known as piezoresistivity, is the principal mechanism in strain sensing using CNTYs. While the axial tensile properties of CNTYs have been studied widely, studies on the axial piezoresistive response of CNTYS under compression have been limited due to the complexities associated with the nature of the experiments involving subjecting a slender fiber to compression loading in its axial direction. In this study, the piezoresistive response of a single CNTY embedded into a polymeric resin (CNTY monofilament composite) was investigated under axial compression. The results suggest that the CNTY exhibits a strong piezoresistive response in the axial direction with sensitivity or gauge factor values in the order of 0.4–0.5 for CNTY monofilament composites. The piezoresistive response of the CNTY monofilament composites under compression was compared to that under tension and it was observed that the sensitivity appears to be slightly lower under compression. The potential change in sensitivity between the freestanding CNTY and the CNTY monofilament composite under compression is still unknown. Knowing the axial piezoresistive response of the CNTYs under both tension and compression will enable their use in sensing applications where the yarn undergoes compression including those in aerospace and marine structures, and civil or energy infrastructure.

Developing efficient, sustainable, and high-performance energy storage systems is essential for advancing various industries, including integrated structural health monitoring. Carbon nanotube yarn (CNTY) supercapacitors have the potential to be an excellent solution for this purpose because they offer unique material properties such as high capacitance, electrical conductivity, and energy and power densities. The scope of the study included fabricating supercapacitors using various materials and characterizing them to determine the capacitive properties, energy, and power densities. Experimental studies were conducted to investigate the energy density and power density behavior of CNTYs embedded in various electrochemical-active matrices to monitor the matrices’ power process and the CNTY supercapacitors’ life-cyclic response. The results showed that the CNTY supercapacitors displayed excellent capacitive behavior, with nearly rectangular CV curves across a range of scan rates. The energy density and power density of the supercapacitors fluctuated between a minimum of 3.89 Wh/kg and 8 W/kg while the maximum was between 6.46 Wh/kg and 13.20 W/kg. These CNTY supercapacitors are being tailored to power CNTY sensors integrated into a variety of structures that could monitor damage, strain, temperature, and others.

Carbon nanotube fibers or yarns (CNTYs) are lightweight, stiff, strong, electrically, and thermally conductive fiber-like materials that exhibit a piezoresistive response and could be integrated in glass-fiber/epoxy laminated composite materials to measure strain and to detect damage. Aiming at extending the scope of previous studies, this work is about the piezoresistive response of CNTY sensors integrated in composite laminates of industrial interest, accounting for interactions between the CNTY and the typical heterogeneous, anisotropic surrounding media, including the effects induced by the curing process of the composite matrix. This study reports experimental results on the mechanical response of laminated composite materials under quasi-static and vibration loading monitored using integrated CNTY sensors. A combination of CNTY sensor configurations and experimental setups were used to monitor the deformation and strains among the various layers of the laminated composites. As the laminated composites were mechanically loaded under quasi-static four-point bending, the CNTY sensors captured instantaneously the deformation as demonstrated by the change in their electrical resistance. Also, as the laminated composites were subjected to sinusoidal loading at specific frequencies, the integrated CNTY sensors were able to capture the loading cycles exactly including durations and peaks. Integrated sensing using CNTYs may offer a highly adaptive, practical, and sensitive structural monitoring method for a variety of applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon nanotube yarns (CNTYs) are hierarchical fibers with outstanding mechanical and electrical properties, with promising applications in the composite industry and as smart materials. In situ scanning electron microscopy observations are performed herein on individual dry-spun CNTYs during axial tensile testing in order to study their radial contraction response and structural changes. The CNTYs exhibited significant diameter reduction and untwisting due to the rearrangement of their fibrils during axial loading. In situ measurements of CNTY diameter reduction led to an exponential decrease of the radial contraction ratio with axial strain, with average values ranging between 5.43 and 1.08. The major failure mechanism was identified as fibril pull-out triggered by fibril slipping. The simultaneous stress and electrical resistance decay of CNTYs under axial tensile relaxation tests fit to a Wiechert's viscoelastic model using a Prony series. The rate of exponential decrease of the electrical resistance over time, however, is slower than that of the stress relaxation, indicating that additional charge carrier relaxation phenomena are present. Using the measured structural and material data input, a nonlinear analytical model based on classical theory of staple yarns is able to reproduce the mechanical response of the yarn. The model suggests that the most prominent parameters affecting the axial mechanical response of the CNTY are the radial contraction ratio, the slip factor, fibril radius, and fibril length. [Display omitted] • CNTYs exhibited nonlinear diameter reduction with the application of axial strain. • Radial contraction ratio of the CNTYs exponentially decreases with axial strain. • Failure mechanism of CNTYs is fibril pull-out caused by fibril slipping. • Mechanics of CNTYs is strongly influenced by radial contraction and slip factor. • Electrical relaxation requires more time than mechanical relaxation. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) fiber/yarn reinforced composites are considered as a new generation of advanced materials for applications in aerospace and space industry. In this study, two types of CNT composite yarns were produced by twisting CNT films and infiltrating with thermoset epoxy (EP) and thermoplastic poly vinyl alcohol (PVA) resins. The tensile strength of CNT/PVA and CNT/EP composite yarn was 409.91 MPa and 206.87 MPa, much higher than that of pure CNT yarn (129.94 MPa). After mono-cryogenic condition, the mechanical and electrical properties of CNT/EP and CNT/PVA composite yarns were both enhanced due to the structure reorder of the CNT bundles and improvement of interfacial bonding. However, after 60 times cyclic-cryogenic conditions, CNT/EP composite yarn showed a ∼10% degradation of tensile strength; while CNT/PVA composite yarn exhibited 6% increment. This study provides fundamental data of the CNT reinforced thermoset and thermoplastic composite yarns for their practical applications in cryogenic environment. [ABSTRACT FROM AUTHOR]

An ascorbic acid (AA) electrochemical sensor was fabricated by ferrocene methanol (Fc−OH) modified multi‐walled carbon nanotube yarn (CNTY). The prepared sensor (Fc−OH/CNTY) exhibited outstanding flexibility, highly stretchability, excellent bendability and obviously electrocatalytic activity for oxidation of ascorbic acid. The morphology of Fc−OH/CNTY was evaluated by scanning electron microscope. The electrochemical behaviour of Fc−OH/CNTY sensor was studied by cyclic voltammetry and amperometry measurements. Moreover, the influence of Fc−OH concentration, applied potential and electrolyte solution pH were also investigated to obtain the best sensor performance. The prepared sensor exhibited a wide linear range from 3 μM to 3.0 mM toward AA, and a detection limit of 1.32 μM (S/N=3). It also possessed a good lifetime and a fast response speed (2.83 s). In addition, the Fc−OH/CNTY sensor remained 90 % and 60 % of its initial activity after 100 and 500 times bending, respectively, which indicated a potential application on flexible, implantable and/or wearable electrochemical sensors. [ABSTRACT FROM AUTHOR]

Metal/carbon nanotube (CNT) composites are promising functional materials due to the various superior properties of CNTs in addition to the characteristics of metals, and consequently, many fabrication processes of these composites have been vigorously researched. In this paper, the fabrication process of metal/CNT composites by electrochemical deposition, including electrodeposition and electroless deposition, are comprehensively reviewed. A general introduction for fabrication of metal/CNT composites using the electrochemical deposition is carried out. The fabrication methods can be classified into three types: (1) composite plating by electrodeposition or electroless deposition, (2) metal coating on CNT by electroless deposition, and (3) electrodeposition using CNT templates, such as CNT sheets and CNT yarns. The performances of each type have been compared and explained especially from the view point of preparation methods. In the cases of (1) composite plating and (2) metal coating on CNTs, homogeneous dispersion of CNTs in electrochemical deposition baths is essential for the formation of metal/CNT composites with homogeneous distribution of CNTs, which leads to high performance composites. In the case of (3) electrodeposition using CNT templates, the electrodeposition of metals not only on the surfaces but also interior of the CNT templates is the key process to fabricate high performance metal/CNT composites. [ABSTRACT FROM AUTHOR]

The curing process and thermoresistive response of a single carbon nanotube yarn (CNTY) embedded in a room temperature vulcanizing (RTV) silicone forming a CNTY monofilament composite were investigated toward potential applications in integrated curing monitoring and temperature sensing. Two RTV silicones of different crosslinking mechanisms, SR1 and SR2 (tin- and platinumcured, respectively), were used to investigate their curing kinetics using the electrical response of the CNTY. It is shown that the relative electrical resistance change of CNTY/SR1 and CNTY/SR2 monofilament composites increased by 3.8% and 3.3%, respectively, after completion of the curing process. The thermoresistive characterization of the CNTY monofilament composites was conducted during heating-cooling ramps ranging from room temperature (RT~25 °C) to 100 °C. The thermoresistive response was nearly linear with a negative temperature coefficient of resistance (TCR) at heating and cooling sections for both CNTY/SR1 and CNTY/SR2 monofilament composites. The average TCR value was -8.36 × 10-4 °C-1 for CNTY/SR1 and -7.26 × 10-4 °C-1 for CNTY/SR2. Both monofilament composites showed a negligible negative residual relative electrical resistance change with average values of ~-0.11% for CNTY/SR1 and ~-0.16% for CNTY/SR2 after each cycle. The hysteresis amounted to ~21.85% in CNTY/SR1 and ~29.80% in CNTY/SR2 after each cycle. In addition, the effect of heating rate on the thermoresistive sensitivity of CNTY monofilament composites was investigated and it was shown that it reduces as the heating rate increases. [ABSTRACT FROM AUTHOR]

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The rapid development of robotics requires stretchable electrical conductors capable of large deformations and having high operational stability in terms of electrical and mechanical characteristics. Carbon nanotubes (CNT) have been considered as the primary component of stretchable conductors, and mechanically drawn CNT sheets have shown their functionality when combined with various elastomeric materials in the shape of yarns. Herein, an electrically passivated stretchable conductor with an elastomer sheath and a spandex–CNT coiled-yarn core structure is reported. Based on the proven performance of spandex–CNT coiled-yarn, the electrical insulation by the Ecoflex elastomer enhances its applicability in an actual situation without degrading the stretchable conductor functionality. The experimental results show a substantial working deformation range (up to 350%), high durability, and low resistance variation during repetitive stretch and release cycles. Additionally, its stability is confirmed over a wide temperature range (up to 150 °C) and even inside an acidic liquid environment where the elastomeric sheath protects the conducting core. The perfect cooperation between the Ecoflex sheath and spandex–CNT core opens the possibility of deploying this stretchable conductor technology under harsh conditions. [Display omitted] • Highly stretchable spandex-CNT coiled yarn is passivated by elastomer sheath layer. • Stretchable elastomer sheath provides electrical insulation and chemical protection. • Morphology variation of core at varying strain are visible inside elastomer sheath. • This design with substantial stability is versatile in wide range of applications. [ABSTRACT FROM AUTHOR]

The cross-linked hierarchical structure in biological systems provides insight into the development of innovative material structures. Specifically, the sarcoplasmic reticulum muscle is able to transmit electrical impulses in skeletal muscle due to its cross-linked hierarchical tubular cell structure. Inspired by the cross-linked tubular cell structure, we designed and built chemical cross-links between the carbon nanotubes within the carbon nanotube yarn (CNT yarn) structure by an esterification reaction. Consequently, compared with the pristine CNT yarn, its electrical conductivity dramatically enhanced 348%, from 557 S/cm to 1950 S/cm. Furthermore, when applied with three voltages, the electro-thermal temperature of esterified CNT yarn reached 261 °C, much higher than that of pristine CNT yarn (175 °C). In addition, the esterified CNT yarn exhibits a linear and stable piezo-resistive response, with a 158% enhanced gauge factor (the ratio of electrical resistance changing to strain change ~1.9). The superconductivity, flexibility, and stable sensitivity of the esterified flexible CNT yarn demonstrate its great potential in the applications of intelligent devices, smart clothing, or other advanced composites.

In order to evaluate the capability of carbon nanotube yarn (CNTY)-based composites for self-sensing of temperature, the temperature-dependent electrical resistance of CNTY monofilament composites was investigated using two epoxy resins: one that cures at 130 °C (CNTY/ERHT) and one that cures at room temperature (CNTY/ERRT). The effect of the curing kinetics of these epoxy resins on the electrical response of the embedded CNTY was investigated in prior studies. It was observed that the viscosity and curing kinetics affect the level of wetting and resin infiltration, which govern the electrical response of the embedded CNTY. In this work, the cyclic thermoresistive characterization of CNTY monofilament composites was conducted under heating–cooling, incremental heating–cooling, and incremental dwell cycles in order to study the effect of the curing temperature of the epoxy matrix on the electrical response of the CNTY monofilament composites. Both monofilament composites showed nearly linear and negative temperature coefficients of resistance (TCR) of −7.07 × 10−4 °C−1 for specimens cured at a high temperature and −5.93 × 10−4 °C−1 for specimens cured at room temperature. The hysteresis loops upon heating–cooling cycles were slightly smaller for high-temperature cured specimens in comparison to those cured at room temperature. A combination of factors, such as resin infiltration, curing mechanisms, intrinsic thermoresistivity of CNTY, variations in tunneling and contact resistance between the nanotubes and CNT bundles, and the polymer structure, are paramount factors in the thermoresistive sensitivity of the CNTY monofilament composites.

The vagus nerve carries sensory information from multiple organs in the body. The recording of its activity and further processing is a key step for neuromodulation treatments. This paper presents a specific algorithm for the processing and discrimination of intrafascicular recordings from the vagus nerve using the novel carbon nanotube yarn electrodes. Up to four different neural waveforms were found, whose occurrence corresponded to distinct levels of anesthesia depth. [ABSTRACT FROM AUTHOR]

The challenges of textiles that can generate and store energy simultaneously for wearable devices are to fabricate yarns that generate electrical energy when stretched, yarns that store this electrical energy, and textile geometries that facilitate these functions. To address these challenges, this research incorporates highly stretchable electrochemical yarn harvesters, where available mechanical strains are large and electrochemical energy storing yarns are achieved by weaving. The solid‐state yarn harvester provides a peak power of 5.3 W kg−1 for carbon nanotubes. The solid‐state yarn supercapacitor provides stable performance when dynamically deformed by bending and stretching, for example. A textile configuration that consists of harvesters, supercapacitors, and a Schottky diode is produced and stores as much electrical energy as is needed by a serial or parallel connection of the harvesters or supercapacitors. This textile can be applied as a power source for health care devices or other wearable devices and be self‐powered sensors for detecting human motion. [ABSTRACT FROM AUTHOR]

Continuous carbon nanotube (CNT) yarn fabricated from a floating catalyst chemical vapor deposition (FCCVD) method is treated under gamma-ray irradiation to enhance the mechanical properties of the CNT yarn and its unidirectional composite laminates. Gammy-ray doses varying from 50 kGy to 1200 kGy are used to irradiate CNT yarns and their microstructures, tensile properties and surface characterizations are studied. The graphitic structure change is not clear from the transmission electron microscopy, however, the specific tensile strength and modulus of yarn vary slightly within 10 % as the dose increased. This modulus trend coincides with mesoscopic distinct element modeling (mDEM) simulation results. Surface characterization shows additional oxygen functional groups and smaller contact angles after irradiation. Interestingly, the specific tensile properties of composite laminates also increase relative to the yarns, and the unidirectional laminate from CNT yarn treated with the optimal dose of 700 kGy achieves specific strength and modulus as high as 1.89 GPa/gcm−3 and 258 GPa/gcm−3, respectively, which are 30.9 % and 37 % increases compared to the control laminate. The results indicate that radiation-induced crosslinking among the CNTs and the formation of surface-active sites leads to enhanced load transfer in the yarns and promote CNT/resin interfacial bonding. [Display omitted] [ABSTRACT FROM AUTHOR]

The curing process and thermoresistive response of a single carbon nanotube yarn (CNTY) embedded in a room temperature vulcanizing (RTV) silicone forming a CNTY monofilament composite were investigated toward potential applications in integrated curing monitoring and temperature sensing. Two RTV silicones of different crosslinking mechanisms, SR1 and SR2 (tin- and platinum-cured, respectively), were used to investigate their curing kinetics using the electrical response of the CNTY. It is shown that the relative electrical resistance change of CNTY/SR1 and CNTY/SR2 monofilament composites increased by 3.8% and 3.3%, respectively, after completion of the curing process. The thermoresistive characterization of the CNTY monofilament composites was conducted during heating–cooling ramps ranging from room temperature (RT~25 °C) to 100 °C. The thermoresistive response was nearly linear with a negative temperature coefficient of resistance (TCR) at heating and cooling sections for both CNTY/SR1 and CNTY/SR2 monofilament composites. The average TCR value was −8.36 × 10−4 °C−1 for CNTY/SR1 and −7.26 × 10−4 °C−1 for CNTY/SR2. Both monofilament composites showed a negligible negative residual relative electrical resistance change with average values of ~−0.11% for CNTY/SR1 and ~−0.16% for CNTY/SR2 after each cycle. The hysteresis amounted to ~21.85% in CNTY/SR1 and ~29.80% in CNTY/SR2 after each cycle. In addition, the effect of heating rate on the thermoresistive sensitivity of CNTY monofilament composites was investigated and it was shown that it reduces as the heating rate increases.

Individual carbon nanotubes (CNTs) exhibit excellent mechanical, electrical and thermal properties, leading to development of a new generation of advanced lightweight materials and spacecraft electronics substituting the electronics based on silicon. The direct assembly of CNTs into macroscopic fibers or sheets has been a way to overcome their dispersion and processing challenges. Because of a wide range of applications of this material, we investigate effectively the defects on CNT yarns structures created by electron beam and gamma sources and their impact on the morphology and mechanical properties. The irradiated samples with electron beam at doses of 400, 600 and 800 kGy had a decrease in the strength from 219.60 ± 18.90 MPa for pristine yarn to 108.86 ± 23.77, 153.15 ± 21.63, 170.50 ± 25.78 MPa, respectively. The sample irradiated with gamma in air at dose of 100 kGy had the strength increased slightly as compared with the pristine sample and an increase in the elasticity modulus from 8.79 ± 1.19 to 19.63 ± 2.02 GPa as compared to CNT pristine yarn. The quality of the CNT yarns that was gamma irradiated in air with absorbed dose of 100 kGy was not affected by the radiation process with improvement of 123% of the Young’s modulus.

Carbon nanotubes (CNT) have remarkable mechanical properties and low density. Since length of the CNT is limited, CNT yarn is regarded as a reinforced fiber of carbon fiber reinforced plastics. However, the CNT yarn does not have remarkable mechanical properties such as the individual CNT. The most popular way for improving the mechanical properties of the CNT yarn is to make composites with polymer such as polyvinyl alcohol or polyimide. If some functional groups such as carboxyl groups are introduced on the surface of CNTs, interaction between the CNTs and the polymer is improved and high mechanical properties will be obtained. In this study, untwisted CNT yarns were prepared by drawing vertical aligned CNTs through a die and functionalized with mixed acid. Mixed acid introduced not only the functional groups but also defects on the surface of CNTs. For reducing the defects, the CNT yarn was graphitized at a temperature of 2800°C before the mixed acid treatment. By the graphitization treatment, crystallinity of the CNT yarn was improved and amorphous carbon was removed. As a result of XPS analysis, a graphitized CNT yarn treated with mixed acid did not contain the functional groups. On the other hand, a graphitized CNT yarn treated with hot mixed acid (90°C) contained the functional groups. Crystallinity of this yarn was 4.5 times higher than the as-received CNT yarn. In addition, as a result of single fiber tensile tests, tensile strength of this yarn was increased by 79 % and Young’s modulus was increased by 173 % compared to the as-received CNT yarn.

Carbon nanotube (CNT) yarn is enables CNTs to be used on macro scale. However, the mechanical properties of CNT yarns are smaller than CNT itself, and improvement of the mechanical properties is a challenge for practical application. In this study, untwisted CNT yarns were fabricated by a dry spinning method, and the yarns were graphitized and combined with polymer for the purpose of development of CNT yarns with high strength. As a result of the graphitized treatment to the as-received yarns under inert atmosphere at 2800°C, impure materials and defect structure on CNTs were removed and strength of the yarn was increased by 19%. After combining the as-received yarns with polyacrylic acid (PAA), the strength was increased by 174% and reached 2.3 GPa. Breaking form of the yarns were changed from pulling out of CNT bundles to rapture of CNT bundles by graphitization and combining with PAA, indicating an increase interactive force between the CNT bundles. However, the strengthening effect was limited when graphitized CNT yarns were combined with PAA. As a result of molecular dynamics simulations, it was revealed force transfer capability of PAA was low when the graphitized yarns was combined with PAA. There were functional groups on as-received CNT such as carboxyl groups. On the other hand, the functional groups were removed from CNTs after the graphitization treatment. Consequently, interaction such as hydrogen bond between as-received CNT and PAA was removed by the graphitization, and it lead to the decrease of the force transfer capability of PAA.

Previous electrochemically powered yarn muscles cannot be usefully operated between extreme negative and extreme positive potentials, since generated stresses during anion injection and cation injection partially cancel because they are in the same direction. We here report an ionomer-infiltrated hybrid carbon nanotube (CNT) yarn muscle that shows unipolar stress behavior in the sense that stress generation between extreme potentials is additive, resulting in an enhanced stress generation. Moreover, the stress generated by this muscle unexpectedly increases with the potential scan rate, which contradicts the fact that scan-rate-induced stress decreases for neat CNT muscles. It is revealed by the electro-osmotic pump effect that the effective ion size injected into the muscle increases with an increase in the scan rate. We demonstrate an electrochemically powered gel-elastomer-yarn muscle adhesive that generates and delivers muscle-contraction-mimicking stimulation to a target tissue.

The effect of polymerization kinetics and resin viscosity on the electrical response of a single carbon nanotube yarn (CNTY) embedded in a vinyl ester resin (VER) during polymerization was investigated. To analyze the effect of the polymerization kinetics, the concentration of initiator (methyl ethyl ketone peroxide) was varied at three levels, 0.6, 0.9, and 1.2 wt.%. Styrene monomer was added to VER, to reduce the polymer viscosity and to determine its effect on the electrical response of the CNTY upon resin wetting and infiltration. Upon wetting and wicking of the CNTY by VER, a transient decrease in the CNTY electrical resistance (ca. −8%) was observed for all initiator concentrations. For longer times, this initial decrease in electrical resistance may become a monotonic decrease (up to ca. −17%) or change its trend, depending on the initiator concentration. A higher concentration of initiator showed faster and more negative electrical resistance changes, which correlate with faster gel times and higher build-up of residual stresses. An increase in styrene monomer concentration (reduced viscosity) resulted in an upward shift of the electrical resistance to less negative values. Several mechanisms, including wetting, wicking, infiltration, electronic transfer, and shrinkage, are attributed to the complex electrical response of the CNTY upon resin wetting and infiltration.

Textiles, as a desired platform for wearable smart technology, can be integrated with smart elements in the hierarchical levels of the fabric structure. In this study, a new way to make strain sensing fabric was developed by embedding a single strain sensing carbon nanotube (CNT)-based yarn into the woven structure. To overcome the abrasion during insertion, the yarn was coated with poly(vinyl alcohol) (PVA) to achieve higher mechanical performance. The gauge factor of the yarn was improved from 0.91 to 1.64. The sensing properties of CNT/PVA yarn integrated strain sensing fabric showed a gauge factor of over 1.1, a degree of linearity of more than 97% and good stability and repeatability during cyclic loading. Fabric with different integrated yarn lengths, patterns and output connections has also been investigated. The results showed that the yarn length and bend over section had a great influence on the strain sensing properties of the fabric. Furthermore, the fabric strain sensor exhibited a quick and precise response to the finger motion detection, demonstrating potential in wearable electronics. [ABSTRACT FROM AUTHOR]

In this study, pristine carbon nanotubes (CNTs) and the CNTs functionalized through heat treatment were fabricated, and their hydrogen (H 2) gas sensing characteristics were evaluated at room temperature. Pristine CNTs exhibited relatively low reactivity toward H 2 gas, whereas functionalized CNTs demonstrated linear electrical response characteristics with an increase in the gas concentration due to the presence of functional groups (such as COOH and OH) on the CNT surface, which reduced the activation energy for the adsorption of H 2 molecules and provided additional reactive sites. Thus, functionalized CNTs can be potentially utilized in various fields because their operation does not require high-temperature environments (unlike the currently used metal oxide-based H 2 sensors), while the power consumption and explosion risks of these materials are easily reduced through a simple heat treatment process. • CNT sheet can be transferred easily another substrates to be used as a sensor. • Heat treatment could improve the sensitivity of the sensor. • The sensor exhibited higher sensitivity than that of the sensor fabricated by imprinting method. • Sensing performance could be enhanced by increasing the sensing area of the CNT surface [ABSTRACT FROM AUTHOR]

Abstract Perovskite solar cells (PSCs) have emerged as a promising photovoltaic technology on the lab scale due to their high power conversion efficiency, simple device fabrication, all solid-state structure and the possibility to integrate traditional devices into fiber format. In this work, a three-dimensional (3D) perovskite solar cell is demonstrated using functionalized carbon nanotube (CNT) yarn as both the cathode and anode material. TiO 2 and 2,2,7,-7-tetrakis(N , N -di-p-methoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD) are used as the electron transporting and hole transporting material respectively. The TiO 2 oxide layer is deposited on the top of the twisted carbon nanotube yarn and annealed with TiCl 4 to generate the uniform electron transport layer. A dip coating process is employed to produce a uniform perovskite layer on top of the TiO 2 oxide layer. Platinized carbon nanotube yarn is wrapped around on the top of the hole transporting layer and serves as the counter electrode. The photovoltaic characterization of the prepared cells was carried out at different cell lengths. Under AM 1.5 (100 mW cm−2) illumination it shows an enhanced power conversion efficiency (PCE) with a high open current voltage (V OC) of 0.825 V. This three-dimensional all solid-state perovskite solar cell shows a promising prospect in portable and wearable textile electronics. Graphical abstract Unlabelled Image Highlights • An all solid state carbon nanotube yarn based perovskite solar cell has been developed. • Three-dimensional perovskite solar cells based on CNT yarn exhibit high open current voltage. • Carbon nanotube yarn based cells are flexible and capable of harvesting incident photons from any direction. [ABSTRACT FROM AUTHOR]

Curing effects were investigated by using the electrical response of a single carbon nanotube yarn (CNTY) embedded in an epoxy resin during the polymerization process. Two epoxy resins of different viscosities and curing temperatures were investigated, varying also the concentration of the curing agent. It is shown that the kinetics of resin curing can be followed by using the electrical response of an individual CNTY embedded in the resin. The electrical resistance of an embedded CNTY increased (~9%) after resin curing for an epoxy resin cured at 130 °C with viscosity of ~59 cP at the pouring/curing temperature (“Epon 862”), while it decreased (~ −9%) for a different epoxy cured at 60 °C, whose viscosity is about double at the corresponding curing temperature. Lowering the curing temperature from 60 °C to room temperature caused slower and smoother changes of electrical resistance over time and smaller (positive) residual resistance. Increasing the concentration of the curing agent caused a faster curing kinetics and, consequently, more abrupt changes of electrical resistance over time, with negative residual electrical resistance. Therefore, the resin viscosity and curing kinetics play a paramount role in the CNTY wicking, wetting and resin infiltration processes, which ultimately govern the electrical response of the CNTY immersed into epoxy.

Carbon fiber-microelectrodes (CFMEs) have been the standard for neurotransmitter detection for over forty years. However, in recent years, there have been many advances of utilizing alternative nanomaterials for neurotransmitter detection with fast scan cyclic voltammetry (FSCV). Recently, carbon nanotube (CNT) yarns have been developed as the working electrode materials for neurotransmitter sensing capabilities with fast scan cyclic voltammetry. Carbon nanotubes are ideal for neurotransmitter detection because they have higher aspect ratios enabling monoamine adsorption and lower limits of detection, faster electron transfer kinetics, and a resistance to surface fouling. Several methods to modify CFMEs with CNTs have resulted in increases in sensitivity, but have also increased noise and led to irreproducible results. In this study, we utilize commercially available CNT-yarns to make microelectrodes as enhanced neurotransmitter sensors for neurotransmitters such as serotonin. CNT-yarn microelectrodes have significantly higher sensitivities (peak oxidative currents of the cyclic voltammograms) than CFMEs and faster electron transfer kinetics as measured by peak separation (ΔEP) values. Moreover, both serotonin and dopamine are adsorption controlled to the surface of the electrode as measured by scan rate and concentration experiments. CNT yarn microelectrodes also resisted surface fouling of serotonin onto the surface of the electrode over thirty minutes and had a wave application frequency independent response to sensitivity at the surface of the electrode.

Carbon nanotube yarn, which is an aggregation of Carbon nanotubes (CNTs), enables CNTs to be used on macro scale. However, tensile strength of the CNT yarn is much lower than CNT itself, and improvement of the mechanical properties is a challenge for practical application of the yarns. CNTs composing the yarns include some defect structures and impure materials, and their presence can cause a decrease in tensile strength of the yarn. In this study, untwisted CNT yarns were fabricated by dry spun method and graphitized at a temperature of 2800°C for the purpose of improving mechanical properties. Additionally, strength of a CNT composing the yarn and interactive force between the CNTs were evaluated to clarify strength development mechanism of the graphitized CNT yarn. Crystallinity of the CNT yarn was improved more than ten times, and defect structures and impure materials was removed by the graphitization treatment. As a result of single fiber tensile tests, strength of the yarn was increased by 20~35% after the graphitization. On the other hand, strength of the CNT composing the yarn was decreased. The breaking form of the CNT yarn was changed from pulling out of CNT bundles to rapture of the bundles by the graphitization, indicating an increase of interactive force between the bundles. In addition, as a result of pulling out simulations by molecular dynamics method, it was indicated that the pulling out of the CNT bundles were suppressed by increase in van der Waals force. Consequently, the improvement of mechanical properties of the untwisted CNT yarns was not due to the change in the strength of the CNT in the yarns but the main cause was the increase in the interactive force between the CNTs.

A theoretical model for the generation of thermo-acoustic waves from a heated point source in a free-space and a half-space is proposed, where the source is suspended over a substrate. By directly applying the analytical results of a point source to a thin line thermo-acoustic speaker, the acoustic pressure field generated by the periodically heated thin line can be derived using a mathematical integration technique. To further generalize the results from a thin line speaker to a thin line array, the acoustic pressure response generated by the line array speaker can also be implemented in both free- and half-spaces. In this work, the characteristics of pressure fields generated by the thin line array are investigated in detail. The established model is well validated by comparing with the existing experimental results. The present findings not only can be extended to investigate thermo-acoustic responses generated by arbitrary sources, and also it can provide important design guidelines for the manipulation and optimization of thin line array thermo-acoustic devices. [ABSTRACT FROM AUTHOR]

Materials that change color in response to external stimuli can cater to diverse applications from sensing to art. If made flexible, stretchable and weavable, they may even be directly integrated with advanced technologies such as smart textiles. A new class of engineered composite based on polydiacetylene (PDA) functionalized carbon nanotubes (CNT) shows tremendous potential in this regard. While the inherent multi stimuli chromatic response of the polymer (blue to red) is retained, the underlying conducting CNTs invoke electrochromism in PDA. Further, the fiber form factor of dry-spun CNT yarns facilitate direct weaving of large scale electrochromic fabrics, where current flow and thus color change can be accurately controlled. This review summarizes the fundamental aspects of CNT yarns and PDAs, focusing especially on their interaction chemistry which results in the scientifically and commercially appealing electrochromic transition in these hybrids. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) yarns are novel CNT-based materials that extend the advantages of CNT from the nanoscale to macroscale applications. Herein we have modeled the electrical properties of carbon nanotube yarn as a function of temperature and magnetic field. The conductivity was well explained by 3D Mott Variable Range Hopping (VRH) law at T  < 100 K. The hopping effective dimension is reduced with increasing of magnetic field. Negative magnetoresistance (MR) was observed at different magnetic field range. A quadratic MR was found at small magnetic fields up to B D2 , where a deviation occurred from the quadratic magnetic field dependence of the MR. In the intermediate magnetic field region, the negative MR shows linear magnetic field dependence up to the magnetic crossover field of B D1 . It was found that physical parameters such as the localization length and the density of states at the Fermi level are temperature and magnetic field dependent. In addition, a general scaling behavior was found for the MR as a function of ( B / B *) 1/3 , where B * is a crossover magnetic field. [ABSTRACT FROM AUTHOR]

Carbon nanotube yarns are micron-scale fibers comprised by tens of thousands of carbon nanotubes in their cross section and exhibiting piezoresistive characteristics that can be tapped to sense strain. This paper presents the details of novel foil strain gauge sensor configurations comprising carbon nanotube yarn as the piezoresistive sensing element. The foil strain gauge sensors are designed using the results of parametric studies that maximize the sensitivity of the sensors to mechanical loading. The fabrication details of the strain gauge sensors that exhibit the highest sensitivity, based on the modeling results, are described including the materials and procedures used in the first prototypes. Details of the calibration of the foil strain gauge sensors are also provided and discussed in the context of their electromechanical characterization when bonded to metallic specimens. This characterization included studying their response under monotonic and cyclic mechanical loading. It was shown that these foil strain gauge sensors comprising carbon nanotube yarn are sensitive enough to capture strain and can replicate the loading and unloading cycles. It was also observed that the loading rate affects their piezoresistive response and that the gauge factors were all above one order of magnitude higher than those of typical metallic foil strain gauges. Based on these calibration results on the initial sensor configurations, new foil strain gauge configurations will be designed and fabricated, to increase the strain gauge factors even more. [ABSTRACT FROM AUTHOR]

Chronic recording and stimulation in central and peripheral nerves require both high mechanical and biological compatibility. The biocompatible CNT yarn has shown promising mechanical advantage as a novel neural electrode. In this study, we quantitatively characterized the mechanical properties of CNT yarn electrodes from the perspective of the flexural limit and the flexural rigidity. The traditional test configuration was remedied for ultrafine samples with efficient elimination of the bias caused by the manual operation. As compared to the traditional Platinum-Iridium (Pt-Ir) wire electrode, CNT yarns with the similar diameter had a much more promising flexural-limit property, and thus can overcome the severe electrode failure in chronic neural recording or stimulation.

Stimulated by the previous findings that ion beam can induce carbon nanotube (CNT) welding, we studied the irradiation effects on CNT yarns by proton irradiation. A 2.5 MeV proton beam was transmitted through a 25 μm thick Ti window and irradiated CNT yarn in air. The yarn, of about 40 μm in diameter, was fabricated by pulling and spinning CNT bundles from a CNT aligned film. After irradiation to an ion fluence of 5 × 10 12 , 1 × 10 13 , 1 × 10 14 , and 1 × 10 15 cm −2 , Raman spectroscopy was performed to study defect behavior by comparing intensity changes to the D and G bands at 1350 cm − 1 and 1560 cm − 1 , respectively. The analysis revealed a decreasing defect level up to 1 × 10 13 cm −2 , followed by an increasing defect level with increasing fluence. The mechanical properties of the yarns are characterized by using a tensile tester with a strain rate of 0.2 mm/min at room temperature. The maximum tensile strength occurred at a fluence of 1 × 10 13 cm −2 . With increasing proton fluencies, the fracture strain shows gradual enhancement. [ABSTRACT FROM AUTHOR]

We report a highly stable electrical conductance of a compact and well-oriented carbon nanotube yarn under tensile strain. The gauge factor of the yarn was found to be extremely small of approximately 0.15 thanks to the improvements in the dry spinning process, including multi-web spinning and heat treatment. The threshold strain \varepsilon s , below which the yarn retains its electrical conductance stability, has also been determined to be approximately 15\times 10^3 ppm. Owing to its highly stable resistance under mechanical strain, the yarn has a good potential as a wiring material for niche applications, where light weight and resistance stability are required. [ABSTRACT FROM AUTHOR]