Carbon Nanotube Yarns Research Articles

High-Resolution X-ray Spectromicroscopy Reveals Process-Structure Correlations in sub-5-μm Diameter Carbon Nanotube-Polymer Composite Dry-Spun Yarns.

A persistent lack of detailed and quantitative structural analysis of these hierarchical carbon nanotube (CNT) ensembles precludes establishing processing-structure-property relationships that are essential to enhance macroscale performance (e.g., in mechanical, electrical, thermal applications). Here, we use scanning transmission X-ray microscopy (STXM) to analyze the hierarchical, twisted morphology of dry-spun CNT yarns and their composites, quantifying key structural characteristics such as density, porosity, alignment, and polymer loading. As the yarn twist density increases (15,000 to 150,000 turns per meter), the yarn diameter decreased (4.4-1.4 μm) and density increased (0.55-1.26 g·cm-3), as intuitively expected. Yarn density, ρ, ubiquitously scaled with diameter d according to ρ ∼ d-2 for all parameters studied here. Spectromicroscopy probes with 30 nm resolution and elemental specificity were employed to analyze the radial and longitudinal distribution of the oxygen-containing polymer content (∼30% weight fraction), demonstrating nearly perfect filling of the voids between CNTs with a vapor-phase polymer coating and cross-linking process. These quantitative correlations highlight the intimate connections between processing conditions and yarn structure with important implications for translating the nanoscale properties of CNTs to the macroscale.

Nonlinear multiscale model for interstitial structures of densely ordered multi-walled carbon nanotube bundles

The microscopic structural changes upon mechanical deformation of coiled multi-walled carbon nanotube (MWCNT) yarns were investigated through a multiscale constitutive model. All-atom molecular dynamics simulations reveal a strong dependence of the nonlinear mechanical behavior on the diameter of the nanotubes composing the MWCNT bundles. Accordingly, the multiscale modeling is configured to predict the stress and interstitial area change experienced by each nanotube according to the diameter and position distribution of the nanotubes constituting the microstructure. From the proposed multiscale method, representative volume elements (RVEs) of MWCNT bundles with micrometer scale lengths are developed. The RVEs are applied to characterize the deformation of each nanotube due to the longitudinal sway and the stress concentration in the cross-section due to local tightening. The results are in good agreement with those of the all-atom cross-sectional model corresponding to each longitudinal position, which proves the validity of the developed RVEs.

Ionic Conduction and Dielectric Response of Nanoparticle-Coupled Hydrogel Network Polymer Electrolytes

The molecular level understanding of ion and polymer dynamics in nanoparticle-coupled hydrogel network polymer electrolytes is investigated by linear dielectric and viscoelastic measurements covering broad ranges of frequency and temperature. We prepare hydrogel polymer electrolytes (HPEs), composed of Li+ conducting hydrophilic poly(lithium acrylate) (PLiA) as the HPE matrix and vinyl-functionalized silica nanoparticles (NPs) as cross-linking points, via radical polymerization and sol–gel reaction. The NP content variation leads to changes in ionic conductivity (σDC), dielectric constant (εs), relaxation frequency, and elastic modulus, which are important characteristic factors for understanding ion transport. From the physical model of electrode polarization (EP), allowing for the determination of the number density of simultaneously conducting ions and their mobility, the NP-containing HPEs (HPE-NP) have simultaneously higher conducting ion concentration (p) and mobility (μ), resulting in higher ionic conductivity (σDC ∼ pμ), compared to the HPE without NPs. The temperature dependence of p and μ follows Arrhenius (thermally activated) and Vogel–Fulcher (segmentally driven) temperature dependences, respectively. In addition to the lower frequency EP, the HPEs show higher frequency relaxation (α2), attributed to ions rearranging. NP incorporation leads to faster α2 relaxation and higher static dielectric constant εs (shorter Bjerrum length lB). Time–temperature superposition (tTS) works well for these electrolytes and is applied to construct master curves of viscoelasticity and in-phase conductivity. In the end, the NP-containing HPE-based supercapacitor is fabricated using carbon nanotube yarn (CNTY) electrodes and shows stable electrochemical performance, demonstrating that our HPE can be a solid-state polymer electrolyte for energy storage devices.

Dynamic mechanical response of carbon nanotube yarns and their in situ electrical measurements

Carbon nanotube yarns (CNTYs) are outstanding hierarchical fibers with electrical properties that depend on temperature and mechanical stimuli, which makes them attractive as smart materials for sensing applications. In order to better understand the electrical response of CNTYs under a combination of dynamic loading and variations of temperature, their monotonic and cyclic tensile mechanical response, in situ Raman spectroscopy, mechanical hysteresis, and dynamic mechanical analysis (DMA) are investigated herein. The piezoresistivity and thermoresistivity of CNTYs were characterized to correlate the contribution of temperature and strain to the effective electrical response of the CNTY under DMA testing. It was found that the tensile load bearing of the CNTYs is governed mainly by structural changes of its bundles/fibrils, rather than by stretching of the carbon bonds. The large energy dissipation capabilities of the CNTYs arise mainly from friction among their fibrils and bundles, and also due to irreversible morphological changes in their hierarchical structure. The (mechanically constrained) thermoresistive characterization showed that the electrical resistance of the CNTYs decreases with increasing temperature, yielding an average temperature coefficient of resistance of −8.63 × 10−4 K−1. The electrical response of the CNTYs during DMA temperature scans is governed by their thermoresistive response.

Selective Interbundle Cross-Linking for Lightweight and Superstrong Carbon Nanotube Yarns.

In this study, a range of carbon nanotube yarn (CNTY) architectures was examined and controlled by chemical modification to gain a deeper understanding of CNTY load-bearing systems and produce lightweight and superstrong CNTYs. The architecture of CNTY, which has polymer layers surrounding a compact bundle without hampering the original state of the CNTs in the bundle, is a favorable design for further chemical cross-linking and for enhancing the load-transfer efficiency, as confirmed by in situ Raman spectroscopy under a stress load. The resulting CNTY exhibited excellent mechanical performance that exceeded the specific strength of the benchmark, high-performance fibers. This exceptional strength of the CNTY makes it a promising candidate for the cable of a space elevator traveling from the Earth to the International Space Station given its strength of 4.35 GPa/(g cm-3), which can withstand the self-weight of a 440 km cable.

High-performance novel asymmetric MXene@CNT//N-doped CNT flexible hybrid device with large working voltage for energy storage

We developed a novel fiber-shaped supercapacitor based on a hybrid MXene@CNT//N-doped CNT device. In particular, for the first time, electrophoretically deposited Ti3C2Tx MXenes on carbon nanotube yarns and microwave-assisted nitrogen-doped carbon nanotube yarns are proposed as negative and positive electrodes, respectively. Short-circuit encountered during cell assembly was prevented entirely by coating a reproducible polyvinylidene difluoride (PVDF) membrane directly on the electrodes. Based on the developed electrodes, the assembled cell exhibited a large operating voltage window of up to 2.0 V in a diluted 0.5 M H2SO4 liquid electrolyte. The device displayed excellent stability over 5000 cycles with a Coulombic efficiency of nearly 100 %. The device withstood a floating test for 70 h with approximately 100 % capacity retention and exhibited excellent resistance to mechanical stress. Areal energy density as high as 298.5 μWh cm−2 was recorded for a power density value of 855.5 μW.cm−2 at an areal current value of 0.5 mA cm−2. At a high current density of 10 mA cm−2, the energy density remained high at 99.0 μWh cm−2 for a corresponding power density of 8.11 mW cm−2. The reported values rank among the highest obtained for carbon nanotubes-based wired-shaped supercapacitors and show the potential of this flexible wired-shaped hybrid energy storage unit as a wearable device.

Enhanced Hydro-Actuation and Capacitance of Electrochemically Inner-Bundle-Activated Carbon Nanotube Yarns.

Recently, several attempts have been made to activate or functionalize macroscopic carbon nanotube (CNT) yarns to enhance their innate abilities. However, a more homogeneous and holistic activation approach that reflects the individual nanotubes constituting the yarns is crucial. Herein, a facile strategy is reported to maximize the intrinsic properties of CNTs assembled in yarns through an electrochemical inner-bundle activation (EIBA) process. The as-prepared neat CNT yarns are two-end tethered and subjected to an electrochemical voltage (vs Ag/AgCl) in aqueous electrolyte systems. Massive electrolyte infiltration during the EIBA causes swelling of the CNT interlayers owing to the tethering and subsequent yarn shrinkage after drying, suggesting activation of the entire yarn. The EIBA-treated CNT yarns functionalized with oxygen-containing groups exhibit enhanced wettability without significant loss of their physical properties. The EIBA effect of the CNTs is experimentally demonstrated by hydration-driven torsional actuation (∼986 revolutions/m) and a drastic capacitance improvement (approximately 25-fold).

Linear contracting and air-stable electrochemical artificial muscles based on commercially available CNT yarns and ionically selective ionogel coatings

Artificial muscles, or soft actuators, that could exhibit contractile stroke and operate in open-air, would be crucial for many applications, such as robotics, prosthetics, or powered exoskeletons. Amongst the different artificial muscle technologies, electrochemical carbon nanotube (CNT) yarn muscles, transducing capacitively ionic accumulation at the electrochemical double layer into linear contraction, are amongst the most promising candidates. However, their performances are either limited by an undesired bipolar behaviour or short lifetime due to the inevitable drying of water-based electrolytes. In this paper, we present here the fabrication of air-operating contractile linear artificial muscles from commercially available CNT yarns exhibiting outstanding performance. The synthesis and the junction of two ionogels based on cationic and anionic polyelectrolyte have been designed for the coating process on CNT yarns, and for selectively orienting the ionic flow allowing optimal electromechanical energy conversion. The dual-electrode CNT yarn actuators showed air-stable unipolar contractile stroke, reaching 9.7% without loss of performances after 2000 cycles.

Mechanical energy harvesters with tensile efficiency of 17.4% and torsional efficiency of 22.4% based on homochirally plied carbon nanotube yarns

Mechanical energy harvesters with tensile efficiency of 17.4% and torsional efficiency of 22.4% based on homochirally plied carbon nanotube yarns

Carboxylic multiwalled carbon nanotube aerogel-based macroscale fiber as a highly porous current collector

Carbon nanotube yarn is a potential substance for the fabrication of fiber-shaped energy storage devices owing to its lightweight, stiffness, and excellent electrical properties. However, it has a compact structure with a limited pore volume, leading to insufficient active material loading and inadequate gel electrolyte penetration. These seriously restrict its application in fiber-shaped energy storage devices made entirely of solid-state components. Herein, glycerol-functionalized polyacrylonitrile nanofibers (GPN) are electro-spun and collected on Ti wire. And they are chosen as hydrophilic support to load carboxylic multiwalled carbon nanotubes (CMWCNTs) via dip-coating. After oxidation, a 3D rolled O-CMWCNTs@GPN/Ti aerogel fiber-shaped structure with macroscopic thickness and excellent stability in water is fabricated. The O-CMWCNTs@GPN/Ti structure has a high length-specific capacitance value of 15.2 mF cm−1 itself. It also can be used as a current collector to load pseudocapacitive materials to improve capacity. With polyaniline (PANI) electrodeposited in this structure, the as-prepared hybrid aerogel electrode PANI@O-CMWCNTs@GPN/Ti displays a high specific capacitance of 52.6 mF cm−1 in a fiber-shaped supercapacitor device. All features suggest that O-CMWCNTs@GPN/Ti aerogel is an excellent candidate for flexible fiber-shaped energy storage devices.

Multifunctional and Washable Carbon Nanotube-Wrapped Textile Yarns for Wearable E-Textiles.

Carbon nanotube (CNT) yarns are promising for wearable electronic applications due to their excellent electromechanical and thermal properties and structural flexibility. A spinning system was customized to produce CNT-wrapped textile yarns for wearable applications. By adjusting the spinning parameters and core yarn, a highly tailored hybrid CNT yarn could be produced for textile processing, e.g., knitting and weaving. The electrical resistance and mechanical properties of the yarn are influenced by the core yarn. The high flexibility of the yarn enabled state-of-the-art three-dimensional (3D) knitting of the CNT-wrapped yarn for the first time. Using the 3D knitted technology, CNT-wrapped textile yarns were seamlessly integrated into a wrist band and the index finger of a glove. The knitted structure exhibited a large resistance change under strain and precisely recorded the signal under the different movements of the finger and wrist. When the knitted fabric was connected to a power source, rapid heating above skin temperature was observed at a low voltage. This work presents a novel hybrid yarn for the first time, which sustained 30 washing cycles without performance degradation. By changing the core yarn, a highly stretchable and multimodal sensing system could be developed for wearable applications.

High-Performance Biscrolled Ni-Fe Yarn Battery with Outer Buffer Layer.

The increasing demand for portable and wearable electronics has promoted the development of safe and flexible yarn-based batteries with outstanding electrochemical properties. However, achieving superior energy storage performance with a high active material (AM) load and long cycle life with this device format remains a challenge. In this study, a stable and rechargeable high-performance aqueous Ni-Fe yarn battery was constructed via biscrolling to embed AMs within helical carbon nanotube (CNT) yarn corridors. Owing to the high load of charge storage nanoparticles (NPs; above 97 wt%) and the outer neat CNT layer, the buffered biscrolled Ni-Fe yarn battery demonstrates excellent linear capacity (0.053 mAh/cm) and cycling stability (60.1% retention after 300 charge/discharge cycles) in an aqueous electrolyte. Moreover, our flexible yarn battery exhibits maximum energy/power densities of 422 mWh/cm3 and 7535 mW/cm3 based on the total volume of the cathode and anode, respectively, which exceed those reported for many flexible Ni-Fe batteries. Thus, biscrolled Ni-Fe yarn batteries are promising candidates for next-generation conformal energy solutions.

Carbon Nanotubes - Elastomer Actuator for Soft Prosthetics

Prosthetics play an important role as a substitute for any essential part of body. Soft prosthetic is an attempt at making these artificial devices more human-like. The main focus of this paper is the use of a carbon nanotube- elastomer based compound material as an actuator for prosthetic devices. One of the main limitations of Electroactive Polymer (EAP), which is high applied voltage, is overcome in this approach by using carbon nanotube (CNT) yarn permeated with a mixture of elastomer and methanol. The actuation is based on phase transition and this concept can be implemented for soft prosthetics.

PdO-Nanoparticle-Embedded Carbon Nanotube Yarns for Wearable Hydrogen Gas Sensing Platforms with Fast and Sensitive Responses

Hydrogen (H2) gas has recently become a crucial energy source and an imperative energy vector, emerging as a powerful next-generation solution for fuel cells and biomedical, transportation, and household applications. With increasing interest in H2, safety concerns regarding personal injuries from its flammability and explosion at high concentrations (>4%) have inspired the development of wearable pre-emptive gas monitoring platforms that can operate on curved and jointed parts of the human body. In this study, a yarn-type hydrogen gas sensing platform (HGSP) was developed by biscrolling of palladium oxide nanoparticles (PdO NPs) and spinnable carbon nanotube (CNT) buckypapers. Because of the high loading of H2-active PdO NPs (up to 97.7 wt %), when exposed to a flammable H2 concentration (4 vol %), the biscrolled HGSP yarn exhibits a short response time of 2 s, with a high sensitivity of 1198% (defined as ΔG/G0 × 100%). Interestingly, during the reduction of PdO to Pd by H2 gas, the HGSP yarn experienced a decrease in diameter and corresponding volume contraction. These excellent sensing performances suggest that the fabricated HGSP yarn could be applied to a wearable gas monitoring platform for real-time detection of H2 gas leakage even over the bends of joints.

Transition metal hydroxides@conducting MOFs on carbon nanotube yarns for ultra-stable quasi-solid-state supercapacitors with a ship-in-a-bottle architecture

A ship-in-a-bottle architecture on carbon nanotube yarn-based supercapacitor is prepared, in which transition metal hydroxide nanoparticles are confined in metal–organic frameworks anchored on carbon nanotubes and exhibits ultrahigh structural and electrochemical stability.

Nanoarchitectonics of cross-linked densified carbon nanotube yarn for stable conductivity and strain sensing

Nanoarchitectonics of cross-linked densified carbon nanotube yarn for stable conductivity and strain sensing

Superstrong Carbon Nanotube Yarns by Developing Multiscale Bundle Structures on the Direct Spin‐Line without Post‐Treatment (Adv. Sci. 2/2023)

Carbon Nanotubes In article number 2204250, Seung Jae Yang, Chong Rae Park, and co-workers report the superstrong carbon nanotube yarns with multiscale bundle structures inspired by the strengthening mechanism of natural cellulose fibers. This unique micro-texture of yarn enables one step forward to the realization of our ultimate goal, the space elevator.

Network Optimization of CNT Yarn Sensor Based on NNIA Algorithm in Damage Monitoring of 3D Braided Composites

In order to solve the optimization problem of carbon nanotube (CNT) yarn sensor network embedded in three-dimensional (3D) braided composite materials and realize the structural health monitoring of internal damage of aerospace parts, the multi-objective optimization of the number and location of sensors was studied using non-dominated neighborhood immune algorithm (NNIA). Through the research of 3D six-direction braiding process, stress sensitivity of single CNT yarn sensor, and damage location of 3D braided composites, the number, position, and coverage constraint functions based on NNIA algorithm are constructed. In addition, the number and position of three-dimensional braided composite embedded CNT yarn sensors with different sizes are solved. Through the stress experiment and data analysis of damaged parts, it is proved that the optimized configuration result of CNT yarn sensor obtained by NNIA algorithm is suitable for the damage monitoring of 3D braided composites. The damage location error is less than 1 mm. This study lays a foundation for the establishment of damage source localization model of 3D braided composites.

Twisted and coiled yarns for energy harvesting and storage, artificial muscles, refrigeration, and sensing

This overview focuses on our teams work on using twisted yarns and highly elastic coiled yarns for artificial muscles, energy harvesting, energy storage, sensing, and refrigeration. Despite the diversity of these applications for coiled carbon nanotube and polymer yarns, similar fabrication methods are applicable and conversion of coiling twist to yarn twist results in yarn elasticity, actuation, twistocaloric cooling, and the capacitance changes used for energy harvesting and sensing. Likewise, the same biscrolling method yields coiled yarns containing up to 95 weight percent of guest powders that provide various new properties. The obtained performance of the coiled polymer and carbon nanotube yarns are remarkable, such as artificial muscles that generate up to 98 times the output mechanical power than the maximum for the same weight human muscle and mechanical energy harvesters providing a higher peak electrical power per weight than prior art material-based mechanical energy harvesters for stretch frequencies between a few Hz and 600 Hz.

Superstrong Carbon Nanotube Yarns by Developing Multiscale Bundle Structures on the Direct Spin-Line without Post-Treatment.

Super strong fibers, such as carbon or aramid fibers, have long been used as effective fillers for advanced composites. In this study, the highest tensile strength of 5.5Ntex-1 for carbon nanotube yarns (CNTYs) is achieved by controlling the micro-textural structure through a facile and eco-friendly bundle engineering process in direct spinning without any post-treatment. Inspired by the strengthening mechanism of the hierarchical fibrillary structure of natural cellulose fiber, this study develops multiscale bundle structures in CNTYs whereby secondary bundles, ≈200nm in thickness, evolve from the assembly of elementary bundles, 30nm in thickness, without any damage, which is a basic load-bearing element in CNTY. The excellent mechanical performance of these CNTYs makes them promising substitutes for the benchmark, lightweight, and super strong commercial fibers used for energy-saving structural materials. These findings address how the tensile strength of CNTY can be improved without additional post-treatment in the spinning process if the development of the aforementioned secondary bundles and the corresponding orientations are properly engineered.