Carbon Nanotube Sheets Research Articles

High-Performance Artificial Ligament Made from Helical Polyester Fibers Wrapped with Aligned Carbon Nanotube Sheets.

Repairing high-load connective tissues, such as ligaments, by surgically implanting artificial grafts after injury is challenging because they lack biointegration with host bones for stable interfaces. Herein, a high-performance helical composite fiber (HCF) ligament by wrapping aligned carbon nanotube (CNT)sheets around polyester fibers is proposed. Anterior cruciate ligament (ACL)reconstruction surgery shows that HCF grafts could induce effective bone regeneration, thus allowing the narrowing of bone tunnel defects. Such repair of the bone tunnel is in strong contrast to the tunnel enlargement of more than 50% for commercial artificial ligaments made from bare polyester fibers. Rats reconstructed with this HCF ligamentshow normal jumping, walking, and running without limping. This work allows bone regeneration in vivo through a one-step surgery without seeding cells or transforming growth factors, thereby opening an avenue for high-performance artificial tissues.

Designing Reflective Hybrid Counter Electrode for Fiber Dye‐Sensitized Solar Cell with Record Efficiency

AbstractFiber solar cells can be woven into textiles to effectively supply electricity for wearables and have attracted increasing interests in the past decade. However, achieving high power conversion efficiencies in real‐world applications remains a significant challenge for power supply textiles. Here a unique hybrid counter electrode made from metal current collector fiber with high electrical conductivity, aligned carbon nanotube sheet with high electrocatalytic property, and porous titanium dioxide/poly(vinylidene fluoride‐co‐hexafluoropropylene) film with high light reflectance is designed. For the resulting fiber dye‐sensitized solar cell, a rapid charge collection and transport are achieved, and the unique advantage of absorbing light from all directions is effectively realized, producing a record power conversion efficiency of 12.52%. The power conversion efficiency varies below 10% after bending, twisting, or pressing for 1000 cycles. These fiber dye‐sensitized solar cells are further integrated with fiber batteries as power systems for a smart bracelet, demonstrating the effective power solution for wearables.

Fusion joining of thermoplastic composites with a carbon fabric heating element modified by multiwalled carbon nanotube sheets

Fusion joining of thermoplastic composites with a carbon fabric heating element modified by multiwalled carbon nanotube sheets

One-step method for the fabrication of pure and metal-decorated densified CNT films for effective electromagnetic interference shielding

Light-weight, thin, and robust electromagnetic shielding materials with high electrical conductivity are needed for advanced modern electronics and telecommunication technologies to protect circuits from electromagnetic interference. Carbon nanotubes (CNT) are ideal candidates for electromagnetic shielding materials due to their excellent mechanical strength, high electrical conductivity, and light weight. However, the relatively poor electrical conductivity of CNT films, a result of the many points of contact resistance between neighboring CNTs, is an obstacle towards their utilization as a shielding material. Here, we propose a facile CNT film fabrication method that enhances the conductivity of CNT films by collapsing the separation between neighboring CNTs (i.e., densifying the material) in the CNT network. The dense CNT films resulting from this facile method exhibit high electrical conductivity (∼106 S m-1), and achieve excellent shielding of 99.999992% (71 dB) at frequencies between 8.2 GHz and 12.4 GHz with a thickness of 14.3 μm. The remarkable absolute shielding effectiveness (3.50 × 105 dB cm-2 g-1) is due to the material's low density (i.e., ∼1.0 g/cm3), thinness (i.e., 1.3–14.3 μm), and metal-like conductivity. Also, the produced CNT sheet is an ideal substrate for gold decoration that can dramatically enhance the EMI shielding performance further (EMI SE increased from 43.90 dB in the loose film to 56.67 dB in the dense film, which further increased to 66.12 dB when the dense CNT film was coated with a thin gold layer). The outstanding properties of gold-decorated dense CNT films make them strong candidates to meet the electromagnetic shielding needs of modern cutting-edge, lightweight, and compact electronic devices.

Highly Uniform Fabrication of Gold Nanoparticles on Carbon Nanotube Sheets for Sensors Based on Surface-Enhanced Raman Spectroscopy with Improved Reproducibility

Uniform deposition of metal nanoparticles (NPs) on carbon-based substrates is of importance for practical applications as sensors, catalysts, devices, and so forth. Here, we report a one-step wet-chemistry approach that realizes the highly uniform decoration of gold NPs (Au NPs) onto carbon nanotube (CNT) sheets. We first use plasma treatment to make the CNT bundles separated, namely, applying the “debundling” effect onto the film. We also reveal that dimethyl sulfoxide (DMSO) not only promotes the CNT debundling, providing more interstitial space for gold deposition, but also attracts the gold cluster nucleation due to molecule interactions. The reproducibility of surface-enhanced Raman scattering (SERS) signals from this well-engineered CNT/Au NPs substrate is significantly enhanced, as the relative standard deviation from G and D peaks are decreased from 18.8 and 21.3% to 5.6 and 6.2%, respectively. We have fabricated a flexible SERS substrate based on Au NPs/CNT hybrid, which can effectively detect the analyte Rhodamine 6G (R6G) at a concentration as low as 1 × 10–8 M.

Dry-spun carbon nanotube ultrafiltration membranes tailored by anti-viral metal oxide coatings for human coronavirus 229E capture in water

Although waterborne virus removal may be achieved using separation membrane technologies, such technologies remain largely inefficient at generating virus-free effluents due to the lack of anti-viral reactivity of conventional membrane materials required to deactivating viruses. Here, a stepwise approach towards simultaneous filtration and disinfection of Human Coronavirus 229E (HCoV-229E) in water effluents, is proposed by engineering dry-spun ultrafiltration carbon nanotube (CNT) membranes, coated with anti-viral SnO2 thin films via atomic layer deposition. The thickness and pore size of the engineered CNT membranes were fine-tuned by varying spinnable CNT sheets and their relative orientations on carbon nanofibre (CNF) porous supports to reach thicknesses less than 1 µm and pore size around 28 nm. The nanoscale SnO2 coatings were found to further reduce the pore size down to ∼21 nm and provide more functional groups on the membrane surface to capture the viruses via size exclusion and electrostatic attractions. The synthesized CNT and SnO2 coated CNT membranes were shown to attain a viral removal efficiency above 6.7 log10 against HCoV-229E virus with fast water permeance up to ∼4 × 103 and 3.5 × 103 L.m−2.h−1.bar−1, respectively. Such high performance was achieved by increasing the dry-spun CNT sheets up to 60 layers, orienting successive 30 CNT layers at 45°, and coating 40 nm SnO2 on the synthesized membranes. The current study provides an efficient scalable fabrication scheme to engineer flexible ultrafiltration CNT-based membranes for cost-effective filtration and inactivation of waterborne viruses to outperform the state-of-the-art ultrafiltration membranes.

Intertwined CNT Assemblies as an All-Around Current Collector for Volume-Efficient Lithium-Ion Hybrid Capacitors

The increasing demands for conversion systems for clean energy, wearable devices powered by energy storage systems, and electric vehicles have greatly promoted the development of innovative current collectors to replace conventional metal-based foils, including those in multidimensional forms. In this study, carbon nanotubes (CNTs) with desirable features and ease of processing are used in the preparation of floating catalyst-chemical vapor deposition-derived CNT sheets for potential use as all-around current collectors in two representative energy storage devices: batteries and electrochemical capacitors. Due to their short and multidirectional electron pathways and multimodal porous structures, CNT-based current collectors enhance ion transport kinetics and provide many ion adsorption and desorption sites, which are crucial for improving the performance of batteries and electrochemical capacitors, respectively. By assembling activated carbon-CNT cathodes and prelithiated graphite-CNT anodes, high-performance lithium-ion hybrid capacitors (LIHCs) are successfully demonstrated. Briefly, CNT-based LIHCs exhibit 170% larger volumetric capacities, 24% faster rate capabilities, and 21% enhanced cycling stabilities relative to LIHCs based on conventional metallic current collectors. Therefore, CNT-based current collectors are the most promising candidates for replacing currently used metallic materials and provide a valuable opportunity to possibly redefine the roles of current collectors.

High platinum utilization for proton exchange membrane fuel cells via low-temperature substrate sputtering on acid-treated carbon nanotube sheet

Low-temperature substrate sputtering on an acid-treated carbon nanotube (ATCNT) sheet result in high platinum (Pt) utilization. A thin catalyst layer (CL, ∼300 nm) with a high density of Pt and vacancies was formed on the ATCNT sheet (Pt-deposited ATCNT). It replaced the commercial carbon-supported Pt and microporous layers of the proton exchange membrane fuel cells. The substrate temperature (Tsub: 20, 5, −10, −30, and −50 ℃) contributed to crack formation in the porous Pt thin film and restrained the growth of Pt grain (average grain size from 8.60 to 3.97 nm). Below −10 ℃, the crack and grain size changed significantly. The increased crack and smaller grain size enlarged the Pt surface area while forming vacancies; this was confirmed via physical and electrochemical characterizations. When compared to Pt-deposited ATCNT (Tsub = 20 ℃, 47.61 m2 g-1Pt), the electrochemical surface area of Pt-deposited ATCNT (Tsub = -50 ℃, 72.06 m2 g-1Pt) increased by 51.35%. We present a high Pt mass-specific peak power density (5.93 kW g-1Pt), focusing on a strategy to increase Pt utilization.

Carbon nanotube sheet as a current collector for low-temperature solid oxide fuel cells

The utilization of Carbon Nanotube (CNT) sheets as current collectors for Solid Oxide Fuel Cells (SOFCs) was investigated in this study. A direct spinning method was employed for the synthesis of the 15 μm thick CNT sheet, which demonstrated high efficiency and cost-effectiveness. The material properties of the CNT sheet were characterized as a cathodic current collector and were subsequently integrated into 500 μm thick yttria-stabilized zirconia pellet-based SOFCs. The electrochemical performance of the SOFCs was evaluated at a temperature of 500 °C, resulting in a significant increase of 34.7% compared to the traditional SOFCs employing Pt mesh current collectors. Electrochemical Impedance Spectroscopy (EIS) analysis was performed to demonstrate that the observed performance enhancement was attributed to a reduction in both ohmic and charge transfer resistance. This highlights the potential of CNT sheet current collectors in not only decreasing ohmic resistance but also facilitating the reaction kinetics in solid oxide cells.

Pore-controlled carbon nanotube sheet anodes for proton/anion-exchange membrane water electrolyzers

The commercialization of proton/anion-exchange membrane water electrolyzers (PEMWEs/AEMWEs) requires the development of high-performance and durable anodes. Herein, pore-controlled electrodes (C@PCEs) that incorporate carbon nanotube sheets with square pores and catalyst nanoparticles are designed. Ir and NiFe catalysts, which promote the oxygen evolution reaction under acidic and alkaline conditions, respectively, are applied in PEMWEs and AEMWEs. The C@PCEs have higher catalytic activities than the corresponding conventional densely packed electrodes (C@DPEs). Additionally, the PEMWEs and AEMWEs with C@PCEs exhibit improved performance with reduced overpotentials compared to those with C@DPEs. This enhancement in performance is ascribed to the pore structure of the C@PCEs, in which the electrocatalyst is well dispersed without agglomeration, thus increasing the electrochemical surface area. In addition, the highly conductive and porous carbon nanotube framework promotes electron and mass transfer. These results demonstrate that the C@PCE design is promising for anodes in both PEMWEs and AEMWEs.

Carbon Hybrid Materials-Design, Manufacturing, and Applications.

Carbon nanotubes (CNTs) have extraordinary properties and are used for applications in various fields of engineering and research. Due to their unique combination of properties, such as good electrical and thermal conductivity and mechanical strength, there is an increasing demand to produce CNTs with enhanced and customized properties. CNTs are produced using different synthesis methods and have extraordinary properties individually at the nanotube scale. However, it is challenging to achieve these properties when CNTs are used to form macroscopic sheets, tapes, and yarns. To further improve the properties of macroscale forms of CNTs, various types of nanoparticles and microfibers can be integrated into the CNT materials. The nanoparticles and microfibers can be chosen to selectively enhance the properties of CNT materials at the macroscopic level. In this paper, we propose a technique to manufacture carbon hybrid materials (CHMs) by combining CNT non-woven fabric (in the form of sheets or tapes) with microfibers to form CNT-CF hybrid materials with new/improved properties. CHMs are formed by integrating or adding nanoparticles, microparticles, or fibers into the CNT sheet. The additive materials can be incorporated into the synthesis process from the inlet or the outlet of the reactor system. This paper focuses on CHMs produced using the gas phase pyrolysis method with microparticles/fibers integrated at the outlet of the reactor and continuous microfiber tapes integrated into the CNT sheet at the outlet using a tape feeding machine. After synthesis, characterizations such as microscopy and thermogravimetric analysis were used to study the morphology and composition of the CNTs, and examples for potential applications are discussed in this paper.

Electrocatalytic ultrafiltration membrane reactors designed from dry-spun self-standing carbon nanotube sheets

The development of electrochemically active ultrafiltration membrane reactors offers promising perspectives to achieve simultaneous separation and degradation of persistent organic pollutants and support triggered self-cleaning of membrane materials upon surface fouling. Here, electro-responsive ultrafiltration membranes were synthesised from drawable carbon nanotubes (CNT) dry-spun as ultra-thin sheets onto preformed carbon nanofibre (CNF) supports to generate a unique class of electrically conductive and flexible ultrafiltration membranes. The pore size of the CNT-based membranes, on the order of ∼ 28 nm, was fine-tuned by controlling the dry layering and orientation of the CNT sheets to manage the membrane selectivity. The CNT-based membranes were used as effective conductive platforms to promote charge transfer during electrocatalytic degradation of acetaminophen, as a model contaminant. The CNT-based membranes, besides offering water permeance up to 2.77 × 103 L.m−2.h−1.bar−1, yielded electrocatalytic kinetic constant up to 46.5 × 10−3 min−1 during combined electrochemical reaction and ultrafiltration process, which is 1.4 to 39 times larger than previously reported values. Such high performance was maintained quite stable even after 8 reuse cycles. These results demonstrate the potential of CNT dry spinning technology for the scalable fabrication of highly permeable, but selective CNT-based membranes with remarkable electrochemical properties towards cost-effective water treatment at an exceptional reaction rate.

Super aligned carbon nanotubes for interfacial modification of hole transport layer in polymer solar cells

This work presents a facile and innovative method for the insertion of super aligned carbon nanotubes (CNTs) as sheets over and within poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as an efficient hole transport layer (HTL) in the inverted type polymer solar cell. CNTs sheets drawn from the vertically grown CNTs arrays were extracted via a sharp-edge blade and were directly transferred to the surface of PEDOT:PSS followed by the deposition of thermally evaporated silver electrode. All the characteristic photovoltaic parameters of the device have been improved with the insertion of special patterened CNTs sheets as compared to the standards device (without CNTs sheets). Power conversion efficiency (PCE) improved from 2.14% to 3.69% with the increased short circuit current density from 9.12 mAcm−2 to 11.58 mAcm−2 and fill factor from 0.48 to 0.58, respectively. Scanning electron microscopy (SEM) images revealed the successful insertion of CNTs without any destructive impact on the integrity of CNTs structure. Moreover, the performance and stability of the device have also been optimized by increasing the thickness of CNTs sheets. Electrochemical impedance spectroscopy (EIS) showed the reduction in charge transfer resistance on replacement of CNTs sheets-modified PEDOT:PSS as HTL as compared to simple PEDOT:PSS, which may be attributed to the creation of ordered steps which provided cascade routes for the better charge (holes) collection. Facile modification of the anode materials with improved device performance for designing of new device architecture will help scale-up production of low-cost, stable, and efficient polymer solar cells.

Multifunctional microneedle patches with aligned carbon nanotube sheet basement for promoting wound healing

Wound healing has become a health concern and economic burden worldwide for its high incidence and complexity. Attempts to improve wound treatment tend to develop biomedical patches with delicate structure design and functionality. In this paper, we present novel multifunctional microneedle patches with aligned carbon nanotube (CNT) sheet basement for promoting wound healing. Because of the outstanding biocompatibility, biodegradability and non-immunogenicity, hyaluronic acid (HA) is utilized to construct the CNT-integrated microneedle patch with vascular endothelial growth factor (VEGF) encapsulation. It was found that the aligned CNT layer basement could not only impart the composite microneedle patch with orientation morphology, but also endow the patch with controllable release performance, due to its photo-thermal or electro-thermal conversion capacity. Based on these features, we have demonstrated that the highly ordered microstructure of CNT could effectively induce the orientation of fibroblasts; while VEGF release could facilitate tubular formation of endothelial cells. Thus, the aligned CNT and VEGF-loaded multifunctional patch is beneficial to the wound repair process in a typical animal experiment. These results indicate that the proposed microneedle patch is potentially promising for regeneration medicine.

Elastomeric Core/Conductive Sheath Fibers for Tensile and Torsional Strain Sensors.

Motion sensing, aimed at detecting and monitoring mechanical deformation, has received significant attention in various industrial and research fields. In particular, fiber-structured mechanical strain sensors with carbon-based materials have emerged as promising alternatives for wearable applications owing to their wearability and adaptability to the human body. Various materials, structures, sensing mechanisms, and fabrication methods have been used to fabricate high-performance fiber strain sensors. Nevertheless, developing multi-modal strain sensors that can monitor multiple deformations remains to be accomplished. This study established core/sheath fiber multi-modal strain sensors using polymer and carbon nanotubes (CNTs). Specifically, a flexible and conductive CNT sheet was wrapped onto the elastomeric core fiber at a certain angle. This wrapping angle allowed the CNTs to mechanically deform under tensile and torsional deformations without fatal structural damage. The CNTs could sense both tensile and torsional strains through reversible structural changes during deformations. The fiber strain sensor exhibited an increase of 124.9% and 9.6% in the resistance during tensile and torsional deformations of 100% and 1250 rad/m, respectively.

Crystallinity-limited thermoelectric properties of single-wall carbon nanotube sheets prepared using high-speed laminar flow dispersion

Crystallinity-limited thermoelectric properties of single-wall carbon nanotube sheets prepared using high-speed laminar flow dispersion

Electrochemically Activated CNT Sheet as a Cathode for Zn-CO2 Batteries.

High demand for electrochemical storage devices is increasing the need for high-performance batteries. A Zn-CO2 battery offers a promising solution for CO2 reduction as well as energy storage applications. For this study, a Zn-CO2 battery was fabricated using a Carbon Nanotube (CNT) sheet as a cathode and a Zn plate as an anode. The electrochemical activation technique was used to increase the surface area of the CNT electrode by roughly 4.5 times. Copper (Cu) as a catalyst was then deposited onto the activated CNT electrode using electrodeposition method and different Cu loadings were investigated to optimize CO2 reduction. The final assembled Zn-CO2 battery has a 1.6 V output voltage at a current density of 0.063 mA/cm2, which is higher than most devices reported in the literature. This study demonstrates the importance of activation process which enabled more catalyst loading on the cathode resulted in additional active sites for electroreduction process. This paper presents the activated CNT sheet as a promising cathode material for Zn-CO2 batteries.

Real-Time Position Detecting of Large-Area CNT-based Tactile Sensors based on Artificial Intelligence

For medical device and artificial skin applications, etc., large-area tactile sensors have attracted strong interest as a key technology. However, only complex and expensive manufacturing methods such as fine pattern alignment technology have been considered. To replace the existing smart sensor, which has to go through a complicated process, a new approach including a simple piezoresistive patch based on artificial intelligence has been suggested. Specifically, a 16-electrode terminal was connected to the edge of a polydimethylsiloxane pad where multi-walled carbon nanotube sheets are well dispersed, and a voltage input to the center of the specimen. The collected data was calculated using a voltage divider circuit to collect the voltage data. 54 random positions were marked on the pad. 4 positions were configured as the validation data set and 50 positions as the training data set. We examined whether it was possible to determine points in untrained positions using a deep neural network (DNN) and 12 different machine learning (ML) algorithms. The result of a deep neural network for untrained point location identification was MSE: 0.00026, R2: 0.991158, and the result of Random Forest, an ensemble model among ML algorithms, was MSE: 0.00845, R2: 0.971239. Real-time position detection is possible using smart sensors created by combining simple bulk materials and artificial intelligence models from research results.

Crystallinity-limited thermoelectric properties of single-walled carbon nanotube sheets prepared using high-speed laminar flow dispersion

Crystallinity-limited thermoelectric properties of single-walled carbon nanotube sheets prepared using high-speed laminar flow dispersion

Localized Liquid Zones Assisted Highly Crystalline Single-Wall Carbon Nanotube Sheets: Implications for Conducting Shields in Coaxial Cables

The electrical conductivity of carbon nanotube (CNT) macro assemblies can be influenced by their crystallinity. Herein, we present the synthesis of high-quality SWCNT sheets for which an appropriate optimization parametric research of synthesis temperature, precursor flow rate, and H2 flow rate was carried out in this approach. It was found that highly crystalline SWCNT sheet (IG/ID = 180.3) was synthesized by floating catalyst chemical vapor deposition technique at 12 mL/h precursor flow rate and 1000 sccm H2 flow rate. Three distinct Raman laser wavelengths (514, 532, and 785 nm) were used to study the as-synthesized sheet, and the maximum calculated IG/ID ratio was found to be 180.3 (@ λ = 514 nm). Due to high concentration of H2 gas, the number of localized liquid zones or CNT nucleation sites increased which has an impact on both the quality as well as the diameter of CNTs. The I–V characteristics of CNT sheet were studied via four-probe technique, yielding a measured value of electrical conductivity of 9.21 × 106 S/m. Further, the R-T measurement showed the positive temperature coefficient up to the 108 K which indicates the metallicity of as produced CNT sheets. These highly conducting SWCNT sheets are the best solution for a wide range of applications in many fields, including conducting shields in coaxial cables, flexible and nano scale electrical and electronic devices, displays, biosensors, field-effect transistors and gas sensing materials.