Carbon Nanotube Fibers Research Articles

A flexible precontact CNT-Al2O3 fiber sensor resistant to extreme temperatures.

As a new soft electronic product, a flexible precontact sensor provides spatial position sensing ability. However, the properties of traditional polymer materials change in industrial environments with extreme temperatures, which can cause the sensor function to decline or even fail. In this study, we propose a flexible fiber sensor based on the capacitor principle, which achieves a stable spatial positioning function and is not affected by a wide range of temperature changes. The fiber element of the sensor is obtained through the deposition of a flexible Al2O3 ceramic coating onto the surface of a carbon nanotube fiber (CNTF) via atomic layer deposition (ALD) technology. Coatings of different thicknesses (100 nm, 200 nm, and 300 nm) show different colors. The temperature resistance and flame retardancy of Al2O3 keep the morphology of the composite fiber unaffected by flame or high temperatures. Even at extreme temperatures (-78 °C to 500 °C), the sensor's sensing ability exhibits excellent stability. In addition, the spatial perception of the fibers remained viable after repeated bending (10 000 times). We demonstrate the potential of the sensor to acquire position information during high-temperature industrial pipe docking.

Controlled synthesis, properties, and applications of ultralong carbon nanotubes.

Carbon nanotubes (CNTs) are typical one-dimensional nanomaterials which have been widely studied for more than three decades since 1991 because of their excellent mechanical, electrical, thermal, and optical properties. Among various types of CNTs, the ultralong CNTs which have lengths over centimeters and defect-free structures exhibit superior advantages for fabricating superstrong CNT fibers, CNT-based chips, transparent conductive films, and high-performance cables. The length, orientation, alignment, defects, cleanliness, and other microscopic characteristics of CNTs have significant impacts on their fundamental physical properties. Therefore, the controlled synthesis and mass production of high-quality ultralong CNTs is the key to fully exploiting their extraordinary properties. Despite significant progress made in the study of ultralong CNTs during the past three decades, the precise structural control and mass production of ultralong CNTs remain a great challenge. In this review, we systematically summarize the growth mechanism and controlled synthesis strategies of ultralong CNTs. We also introduce the progress in the applications of ultralong CNTs. Additionally, we summarize the scientific and technological challenges facing the mass production of ultralong CNTs and provide an outlook and in-depth discussion on the future development direction.

A Miniaturized Flexible Patch Based on CNT Fiber Sensors and Highly Integrated SoC for Analysis of Sweat

A Miniaturized Flexible Patch Based on CNT Fiber Sensors and Highly Integrated SoC for Analysis of Sweat

A novel binder-free cathode catalyst Cu@NCNF/CP with three-dimensional self-supporting structure for Li-CO2 battery

The Li-CO2 battery is an emerging energy storage device that has garnered significant attention due to its high theoretical energy density and remarkable CO2 capture ability. However, the low reaction activity of Li2CO3 formation and decomposition may result in large overpotentials and poor cycling performance. In this work, a novel three-dimensional self-supporting high-performance cathode catalyst (Cu@NCNF/CP) was prepared. The Cu@NCNF/CP cathode catalyst is composed of Cu nanoparticles loaded on nitrogen-doped carbon nanotube fibers (NCNF) deposited on carbon paper (CP). The three-dimensional interconnected self-supporting structure of Cu@NCNF/CP eliminates the need for binders and can facilitate efficient electrolyte diffusion and electron transfer. Moreover, the nitrogen doping introduces enrichment active sites, and boosts the CO2 reduction reaction (CO2RR) activity, while the uniformly loaded Cu nanoparticles facilitate the adsorption and precipitation of CO2 molecules, thereby playing a crucial role in enhancing the electrocatalytic activity of the CO2 evolution reaction (CO2ER). Importantly, the Li-CO2 battery utilizing Cu@NCNF/CP as a cathode catalyst exhibits a large discharge capacity of 10.59 mAh cm−2 at a current density of 0.05 mA cm−2. When the cutoff capacity is limited to 0.15 mAh cm−2, the first-cycle overpotential is merely 1.28 V, and the cycle life can reach 1140 h due to the high reversibility of the Li2CO3 formation and decomposition. The successful application of a three-dimensional self-supporting Cu@NCNF/CP cathode catalyst in Li-CO2 battery systems introduces a novel concept for developing high-performance transition metal-based catalysts.

Understanding the torsional mechanical behavior of twisting carbon nanotube ribbon with different boundary conditions

Twisting can generate internal stress and store torsional energy, which is widely used as actuators and energy harvesters in electronic and biomedical fields. However, uncovering the effect of internal stress remains unclear. Herein, the experimental and theoretical mechanical model of the twisted ribbon with different boundary conditions was derived and analyzed. The dynamic experimental results indicate that the polymer inclines to constrain the unraveling process of carbon nanotube fiber. Then the elastic/plastic theoretical equations reveal that the internal stress gradually increases as the twisted angle, and the simulated internal stress agrees well with the theoretical results. The simulation results also indicate that the twisting-induced deformation and failure behavior of twisted ribbons are affected by the strain-rate sensitivity of the matrix and the loading velocity. Then, the releasing of the stored energy for twisted ribbons with different boundary conditions demonstrates the contraction and repulsion behaviors. This work investigating the mechanical behavior of twisted ribbons could provide a better guideline for designing twisted actuators with high reliability.

Dynamic asymmetric mechanical responsive carbon nanotube fiber for ionic logic gate

Inspired by biological ion channels, numerous artificial asymmetric ion channels have been synthesized to facilitate the fabrication of ionic circuits. Nevertheless, the creation of biomimetic asymmetric ion channels necessitates expensive scientific apparatus and intricate material processing procedures, which constrains its advancement within the realm of ionic devices. In this study, we have devised dynamic asymmetric ion channels with mechanical responsiveness by combining polymers of varying elastic modulus along the longitudinal axis of carbon nanotube fiber (CNTF). The ion rectification can be modulated via the disparate response of CNTF-based ion channels to mechanical stress. We have effectively employed these asymmetric ion channels with mechanical sensitivity in the design of a logic gate device, achieving logic operations such as “AND” and “OR”. The conception of these dynamic asymmetric ion channels with mechanical sensitivity offers a straightforward, cost-effective, and versatile approach for generating ion channels, highlighting their potential application in intricate, highly integrated ionic circuits.

Direct application of directly-spun carbon nanotube fiber as a fibrous nanocomposite catalyst for environmental remediation

Direct spinning process of carbon nanotube fiber (CNTF) is revisited as a scalable and continuous process to produce a fibrous nanocomposite catalyst for photocatalytic degradation of organic pollutants through photo-Fenton reaction. The directly-spun CNTF inevitably contains iron or iron oxide nanoparticles, which are widely used as a nanocatalyst for Fenton reaction, because they are essential catalysts to synthesize CNTF through decomposition of carbon source in chemical vapor deposition reaction. Therefore, CNTF is intrinsically a kind of nanocomposite fibers and has a strong potential to be utilized as a fibrous nanocomposite catalyst. Herein, it is demonstrated that CNTF is an efficient fibrous catalyst to decompose various organic pollutants through photo-Fenton reaction based on its stable reactivity in a wide pH range, weavability to prepare a textile (16 cm2), and recyclability without a structural deformation after washing and repeated usages.

Achieving High-Performance Aqueous Fiber-Shaped Zn-NixCoy Batteries through in-Situ Activation of Ni0.7Co0.3-MOFs

In the area of aqueous Zn-NixCoy batteries, the application of MOFs derivatives has greatly improved the battery capacity, but it is still far from their theoretical capacity (~372 mAh/g). One reason is that high-temperature annealing makes the internal structure of MOF collapse and agglomerate, which covers a large number of reactive sites resulting in the low capacity of the battery. Another reason is that the optimal ratio of cobalt/nickel is still not confirmed, which has important influences on the discharge platform and capacity of the batteries. Here, the NixCoy-MOFs in different ratios were deposited on the surface of carbon nanotube fibers (CNTFs) using cathodic electrochemical deposition methods. The NixCoy-MOFs were deposited in five Ni/Co ratios (Ni-MOFs, Ni0.7Co0.3-MOFs, Ni0.5Co0.5-MOFs, Ni0.3Co0.7-MOFs, and Co-MOFs). There were then converted into amorphous NixCoyOOH through in situ electrochemical oxidation (Ni-OOH, Ni0.7Co0.3-OOH, Ni0.5Co0.5-OOH, Ni0.3Co0.7-OOH, and Co-OOH). Ascribing to the sufficient reactive sites and optimal electronic structure, the material Ni0.7Co0.3-OOH reveals a large capacity of > 300 mAh/g at a current density of 1mA/cm2. The Zn//Ni0.7Co0.3-OOH battery also shows a high capacity of > 300 mAh/g with a discharge platform of > 1.8 V.

Additive-Free Continuous, Weavable Carbon Nanotube Fibers as Wearable Multifunctional Gas Sensor

Additive-Free Continuous, Weavable Carbon Nanotube Fibers as Wearable Multifunctional Gas Sensor

Electrodeposited polyaniline based carbon nanotubes fiber as efficient counter electrode in wire-shaped dye sensitized solar cells

Electrodeposited polyaniline over the carbon nanotubes fiber (CNTF) has been investigated as potential candidate to substitutes the Pt based auxiliary electrodes in unidimensional fibrous solar cells. CNTF, with excellent electrical and mechanical properties, modified with conducting polymer (polyaniline) via facile electrodeposition process which employed as cathodic materials showed efficient electrochemical reduction of triiodide ions in the fiber shaped dye-sensitized solar cells. Scanning electron microscopic analysis showed the efficacious integration of conducting polymer over the CNTF surface. The admirable electrocatalytic behavior of the fabricated electrode has investigated by electrochemical impedance spectroscopy and cyclic voltammetry. Current density and voltage (J–V) curves are used to quantify the photovoltaic performance of devices with different counter electrodes with fixed photoanode. With lower peak to peak separation, improved current density and better fill factor, exhibited the superior efficiency of modified electrode (PANI@CNTF). As compared to pristine fiber, polyaniline modification showed the outstanding performance with improved photovoltaics and electrochemical parameters measured by the J–V and CV curves, respectively.

Active Material‐Free Continuous Carbon Nanotube Fibers with Unprecedented Enhancement of Physicochemical Properties for Fiber‐Type Solid‐State Supercapacitors

AbstractFiber‐type solid‐state supercapacitors (FSSCs) are gaining traction as wearable energy storage devices, given their adaptability akin to traditional fibers. Carbon nanotube fibers (CNTFs) generated via a liquid crystalline (LC) wet‐spinning process demonstrate outstanding electrical conductivity, mechanical strength, and flexibility. However, their intrinsic “defect‐free” sp2 carbon surface restricts immediate FSSC application, limited by lower specific surface area and scant pseudocapacitive sites. This study develops LC‐spun CNTFs with inherent electrochemical activity, eliminating the need for post‐processing or additional active materials, a requirement typically essential in most previous research. This advancement arises from the wet‐spinning of functionalized CNTs from a LC solution with an exceptionally high concentration of 160 mg mL−1, facilitated by the manipulation of the LC phase transition range. The resultant CNTFs exhibit a refined internal structure, yielding an electrical conductivity of 1.9 MS m−1 and a mechanical strength of 0.93 GPa. Simultaneously, they demonstrate inherent electrical energy storage capabilities with a specific capacitance of 139.4 F g−1 and a volumetric capacitance of 192.4 F cm−3 at 0.5 A g−1. This innovation signifies a step forward in the potential for mass production without the burden of additional materials and steps.

Novel structured carbon nanotubes fiber based microelectrodes for efficient electrochemical water splitting and glucose sensing

An efficient electrocatalyst composed of nickel and cobalt selenide over unique structure carbon nanotubes (NiCo-Se@CNTs) fiber has been fabricated via a single-step hydrothermal method which showed efficient electrocatalytic performance towards electrochemical non-enzymatic glucose sensing and overall water splitting applications. The structural and elemental composition of a modified electrode (NiCo-Se@CNTs) was ascertained via transmission electron microscopy (TEM), X-rays diffraction (XRD) pattern, X-rays photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) along with energy dispersive X-ray spectroscopy (EDX) techniques. Modified fiber-based electrode was used for the electrochemical water splitting which showed a low overpotential value (η10 = 260 mV) with a corresponding Tafel slope of 138 mV dec−1. These values are far superior in contrast with pristine CNTs fiber, having 384 mV overpotential and 318 mV dec−1 of Tafel slope. In extension, while studying overall water splitting by engaging both modified CNTs fiber as anode and cathode, it exhibited excellent performance with an overpotential (η10) of 297 mV and corresponding Tafel slop of 159 mV dec−1. The fabricated electrode was further investigated for electrochemical glucose sensing which exhibited excellent performance towards the glucose detection with a linear dynamic range of up to 10 mM, a detection limit of 0.59 μM in an alkaline condition (pH=13) and high sensitivity of 813 mAmM−1cm−2. The outcomes demonstrated that fabricated fiber (NiCo-Se@CNTs) might be a promising material in future as a multifunctional electrocatalyst for flexible and wearable energy and sensing related applications.

Flextegrity arched structures for Lunar bases built from indigenous materials

Flextegrity is a broad structural concept, represented here by a chain of perforated massive segments in dry contact, coupled by a passing-through pre-tensioned tie-rod (tendon). Contact surfaces realize pure rolling along tailor-designed pitch lines, so that the relative rotation of adjacent segments determines the tendon elongation: the bending constitutive law can be optimized simply by re-shaping the contact surfaces. Flextegrity arches are placed side by side to form a vault, pressurized via an interposed air-tight membrane. The arch follows an almost complete circle (the vault approaches a tube), to minimize the actions on the foundations from internal pressure. The structure also supports a thick radiation shield above, made up of loose Lunar debris. The main characteristic is that the massive segments can be made from cast Lunar regolith, fused into solar-powered devices, whose weight is mitigated by the reduced Lunar gravity. Huge savings on mission budget are expected, because the only components from Earth are the tendons, made of high-performance lightweight carbon nanotube fibers, and the air-tight membrane. Small-scale prototypes are manufactured from cast concrete. The structural response is analyzed through a theoretical model. The concept is applied to a Moon base example, verifying compatibility with the strength of Lunar regolith under various actions, including meteoroid impact.

Long-term continuous degradation of carbon nanotubes by a bacteria-driven Fenton reaction

Very few bacteria are known that can degrade carbon nanotubes (CNTs), and the only known degradation mechanism is a Fenton reaction driven by Labrys sp. WJW with siderophores, which only occurs under iron-deficient conditions. No useful information is available on the degradation rates or long-term stability and continuity of the degradation reaction although several months or more are needed for CNT degradation. In this study, we investigated long-term continuous degradation of oxidized (carboxylated) single-walled CNTs (O-SWCNTs) using bacteria of the genus Shewanella. These bacteria are widely present in the environment and can drive the Fenton reaction by alternating anaerobic-aerobic growth conditions under more general environmental conditions. We first examined the effect of O-SWCNTs on the growth of S. oneidensis MR-1, and it was revealed that O-SWCNTs promote growth up to 30 μg/mL but inhibit growth at 40 μg/mL and above. Then, S. oneidensis MR-1 was subjected to incubation cycles consisting of 21-h anaerobic and 3-h aerobic periods in the presence of 30 μg/mL O-SWCNTs and 10 mM Fe(III) citrate. We determined key factors that help prolong the bacteria-driven Fenton reaction and finally achieved long-term continuous degradation of O-SWCNTs over 90 d. By maintaining a near neutral pH and replenishing Fe(III) citrate at 60 d, a degraded fraction of 56.3% was reached. S. oneidensis MR-1 produces Fe(II) from Fe(III) citrate, a final electron acceptor for anaerobic respiration during the anaerobic period. Then, ·OH is generated through the Fenton reaction by Fe(II) and H2O2 produced by MR-1 during the aerobic period. ·OH was responsible for O-SWCNT degradation, which was inhibited by scavengers of H2O2 and ·OH. Raman spectroscopy and X-ray photoelectron spectroscopy showed that the graphitic structure in O-SWCNTs was oxidized, and electron microscopy showed that long CNT fibers initially aggregated and became short and isolated during degradation. Since Shewanella spp. and iron are ubiquitous in the environment, this study suggests that a Fenton reaction driven by this genus is applicable to the degradation of CNTs under a wide range of conditions and will help researchers develop novel methods for waste treatment and environmental bioremediation against CNTs.

Tailoring fractal structure via 3D printing to achieve flexible stretchable electrodes based on Ecoflex/CNT/CF

Flexible electrodes are crucial for the widespread application of flexible electronics. Flexible stretchable electrodes are a research hotspot for finding a solution for the inability of flexible electrodes to withstand large deformations. In this study, the suitability of silicone rubber (Ecoflex), carbon nanotube (CNT), and carbon fiber (CF) composite materials for flexible devices and their ratios were evaluated for the first time. 3D-printed electrodes based on fractal structures with tensile insensitivity and high linearity were prepared to achieve integrated stretching of flexible devices. To demonstrate the benefits and impact of fractal structures on electrode performance, we fabricated flexible stretchable electrodes with four distinct designs: horseshoe, U-shaped, rectangular, and triangular. The tensile properties of these structures were theoretically calculated and validated through simulations and experiments; the horseshoe design proved to be the softest. Furthermore, we evaluated the performance of the prepared third-order flexible stretchable electrodes for gas-detection applications and achieved promising results, demonstrating the significant potential of these electrodes for wearable gas detection.

Cellulose/nanocarbon composite based multifunctional aerogels for thermal management

Renewable resource-based aerogels have attracted numerous attention due to the requirement on sustainable multifunctional materials for thermal management. A series of cellulose and nanocarbon composite aerogels have been prepared from a blend of carboxylated cellulose nanofibril (CCNF) with carbon nanotube (CNT), graphene oxide (GO), or carbon fiber (CF) using directional freezing method. CCNF/nanocarbon aerogels from bidirectional freezing exhibit higher compression strength due to bridge structures that are induced by temperature gradient horizontally and vertically. Meanwhile, CCNF/carbon aerogels from bidirectional freezing also have thermal conductivity coefficient (λ) as low as 0.0308 W/(m·K), which increases to 0.0388 W/(m·K) after calcination. The dispersed linear carbon materials CF and CNT in CCNF matrix lead to thermoelectric, Joule heating and photothermal performance of CCNF/nanocarbon aerogels, which is also promoted by calcination. The Seebeck coefficient of CCNF/nanocarbon aerogels ranges from 0.027 to 0.067 mV/K and change into 0.037–0.044 mV/K due to the more uniform carbon network formed after high temperature treatment. A 5–15 V input voltage can induce a temperature increase of 62 ∼ 303 °C for composite aerogel after calcination. A laser with 0.3 W power can result in a rapid temperature increase even to 200 °C in seconds for composite aerogel with and without calcination. These kinds of CCNF/nanocarbon based composite aerogels exhibit ability in thermal management, including thermal insulation, thermoelectric, electric and photo induced heating, which are good candidates for multifunctional aerogels.

Mass production of carbon nanotube fibers and hybrid yarns for high-performance helical auxetic yarn strain sensors

With the spectacular physical properties of electrical conductivity, mechanical strength and thermal conductivity, carbon nanotube (CNT) fibers are favored in many fields such as energy storage devices, sensing, electromagnetic shielding and structural reinforcement, especially in flexible sensing devices. However, the lower tensile properties of CNT fibers limit their further application in stretchable strain sensors, especially when monitoring large deformation variables. Here, large-scale continuous production of CNT fibers has achieved through floating catalytic chemical vapor deposition (FCCVD) technology. In the meantime, the CNT fibers were hybrid with Kevlar fibers to obtain hybrid CNT yarns with the strength of 168.4 MPa and the electrical conductivity of 7.78 × 104 S m−1. The strength of the hybrid CNT yarns produced by this method is higher than that of 40 count cotton yarns, which is perfectly suited for the fabrication of textile devices. Through knitting with three-dimensional elastic fabrics, the textile-based sensors exhibit promising sensing ability, washability, weather tolerance and sweat resistance, owing to the excellent physical and chemical properties of the hybrid CNT yarns. Moreover, stretchable strain sensors exhibit fast response and cycle stability, which provides unique opportunities in designing smart textiles with fast response and environmental durability.

High-Strength Carbon Nanotube Fibers from Purity Control by Atomized Catalytic Pyrolysis and Alignment Improvement by Continuous Large Prestraining.

Transferring the high strength of individual carbon nanotubes (CNTs) to macroscopic fibers is still a major technical challenge. In this study, CNT fibers are wound from a hollow cylindrical assembly. In particular, atomized catalytic pyrolysis is utilized to produce the fiber and control its purity. The pristine fiber is then continuously prestrained to have a highly aligned structure for subsequent full densification. Experimental measurements show that the final fiber possesses a high tensile strength (8.0 GPa), specific strength (5.54 N tex-1 (tex: the weight (g) of a fiber of 1 km long)), Young's modulus (350 GPa), and elongation at break (4%). Such an excellent combination is superior to that of any other existing fiber and attributed to the efficient stress transfer among the highly aligned and packed CNTs. Our study provides a new strategy involving atomized catalysis for developing superstrong CNT assemblies such as fibers and films for practical applications.

Carbon fiber-based multichannel solid-contact potentiometric ion sensors for real-time sweat electrolyte monitoring

Solid-contact ion-selective electrodes (SC-ISEs) feature miniaturization and integration that have gained extensive attention in non-invasive wearable sweat electrolyte sensors. The state-of-the-art wearable SC-ISEs mainly use polyethylene terephthalate, gold and carbon nanotube fibers as flexible substrates but suffer from uncomfortableness, high cost and biotoxicity. Herein, we report carbon fiber-based SC-ISEs to construct a four-channel wearable potentiometric sensor for sweat electrolytes monitoring (Na+/K+/pH/Cl−). The carbon fibers were extracted from commercial cloth, of which the starting point is addressing the cost and reproducibility issues for flexible SC-ISEs. The bare carbon fiber electrodes exhibited reversible voltammetric and stable impedance performances. Further fabricated SC-ISEs based on corresponding ion-selective membranes disclosed Nernstian sensitivity and anti-interface ability toward both ions and organic species in sweat. Significantly, these carbon fiber-based SC-ISEs revealed high reproducibility of standard potentials between normal and bending states. Finally, a textile-based sensor was integrated with a solid-contact reference electrode, which realized on-body sweat electrolytes analysis. The results displayed high accuracy compared with ex-situ tests by ion chromatography. This work highlights carbon fiber-based multichannel wearable potentiometric ion sensors with low cost, biocompatibility and reproducibility.

On-demand electrically controlled melatonin release from PEDOT/SNP composite improves quality of chronic neural recording.

Long-time and high-quality signal acquisition performance from implantable electrodes is the key to establish stable and efficient brain-computer interface (BCI) connections. The chronic performance of implantable electrodes is hindered by the inflammatory response of brain tissue. In order to solve the material limitation of biological interface electrodes, we designed sulfonated silica nanoparticles (SNPs) as the dopant of Poly (3,4-ethylenedioxythiophene) (PEDOT) to modify the implantable electrodes. In this work, melatonin (MT) loaded SNPs were incorporated in PEDOT via electrochemical deposition on nickel-chromium (Ni-Cr) alloy electrode and carbon nanotube (CNT) fiber electrodes, without affecting the acute neural signal recording capacity. After coating with PEDOT/SNP-MT, the charge storage capacity of both electrodes was significantly increased, and the electrochemical impedance at 1kHz of the Ni-Cr alloy electrodes was significantly reduced, while that of the CNT electrodes was significantly increased. In addition, this study inspected the effect of electrically triggered MT release every other day on the quality and longevity of neural recording from implanted neural electrodes in rat hippocampus for 1 month. Both MT modified Ni-Cr alloy electrodes and CNT electrodes showed significantly higher spike amplitude after 26-day recording. Significantly, the histological studies showed that the number of astrocytes around the implanted Ni-Cr alloy electrodes was significantly reduced after MT release. These results demonstrate the potent outcome of PEDOT/SNP-MT treatment in improving the chronic neural recording quality possibly through its anti-inflammatory property.