Super-Toughness Carbon Nanotube Yarns by Bio-Inspired Nano-Coiling Engineering.

Lightweight structural materials are commonly used as effective fillers for advanced composites with high toughness. This study focused on enhancing the toughness of direct-spun carbon nanotube yarns (CNTYs) by controlling the micro-textural structure using a water-gap-based direct spinning. Drawing inspiration from the structural features of natural spider silk fibroin, characterized by an α-helix in the amorphous region and ß-sheet in the crystalline region, multiscale bundles within CNTYs are reorganized into a unique nano-coil-like structure. This nano-coiled structure facilitated the efficient dissipation of external mechanical loads through densification with the rearrangement of multiscale bundles, improving specific strength and strain. The resulting CNTYs exhibited exceptional mechanical properties with toughness reaching 250 J g-1, making them promising alternatives to commercially available fibers in lightweight, high-toughness applications. These findings highlight the significance of nano-coiling engineering for emulating bio-inspired micro-textural structures, achieving remarkable enhancement in the toughness of CNTYs.

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.

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 5.5 N tex-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, ≈200 nm in thickness, evolve from the assembly of elementary bundles, 30 nm 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.

Multimodal collective swimming of magnetically articulated modular nanocomposite robots.

Magnetically responsive composites can impart maneuverability to miniaturized robots. However, collective actuation of these composite robots has rarely been achieved, although conducting cooperative tasks is a promising strategy for accomplishing difficult missions with a single robot. Here, we report multimodal collective swimming of ternary-nanocomposite-based magnetic robots capable of on-demand switching between rectilinear translational swimming and rotational swimming. The nanocomposite robots comprise a stiff yet lightweight carbon nanotube yarn (CNTY) framework surrounded by a magnetic polymer composite, which mimics the hierarchical architecture of musculoskeletal systems, yielding magnetically articulated multiple robots with an agile above-water swimmability (~180 body lengths per second) and modularity. The multiple robots with multimodal swimming facilitate the generation and regulation of vortices, enabling novel vortex-induced transportation of thousands of floating microparticles and heavy semi-submerged cargos. The controllable collective actuation of these biomimetic nanocomposite robots can lead to versatile robotic functions, including microplastic removal, microfluidic vortex control, and transportation of pharmaceuticals.

High-Performance Thermoelectric Fabric Based on a Stitched Carbon Nanotube Fiber.

With the continuous development of flexible and wearable thermoelectric generators (TEGs), high-performance materials and their integration into convenient wearable devices have to be considered. Herein, we have demonstrated highly aligned wet-spun carbon nanotube (CNT) fibers by optimizing the liquid crystalline (LC) phase via hydrochloric acid purification. The liquid crystalline phase facilitates better alignment of CNTs during fiber extrusion, resulting in the high power factor of 2619 µW m-1 K-2, which surpasses those of the dry-spun CNT yarns. A flexible all-carbon TEG was fabricated by stitching a single CNT fiber and doping selected segments into n-type by simple injection doping. The flexible TEG shows the maximum output power densities of 1.9 mW g-1 and 10.3 mW m-2 at ΔT = 30 K. Furthermore, the flexible TEG was developed into a prototype watch-strap TEG, demonstrating easy wearability and direct harvesting of body heat into electrical energy. Combining high-performance materials with scalable fabrication methods ensures the great potential for flexible/or wearable TEGs to be utilized as future power-conversion devices.

High-Energy Density Li-O2 Battery with a Polymer Electrolyte-Coated CNT Electrode via the Layer-by-Layer Method.

Li-O2 batteries have attracted considerable attention for several decades due to their high theoretical energy density (>3400 Wh/kg). However, it has not been clearly demonstrated that their actual volumetric and gravimetric energy densities are higher than those of Li-ion batteries. In previous studies, a considerable quantity of electrolyte was usually employed in preparing Li-O2 cells. In general, the electrolyte was considerably heavier than the carbon materials in the cathode, rendering the practical energy density of the Li-O2 battery lower than that of the Li-ion battery. Therefore, air cathodes with significantly smaller electrolyte quantities need to be developed to achieve a high specific energy density in Li-O2 batteries. In this study, we propose a core-shell-structured cathode material with a gel-polymer electrolyte layer covering the carbon nanotubes (CNTs). The CNTs are synthesized using the floating catalyst chemical vapor deposition method. The polymeric layer corresponding to the shell is prepared by the layer-by-layer (LbL) coating method, utilizing Li-Nafion along with PDDA-Cl [poly(diallyldimethylammonium chloride)]. Several bilayers of Li-Nafion and PDDA, on the CNT surface, are successfully prepared and characterized via X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The porous structure of the CNTs is retained after the LbL process, as confirmed by the nitrogen adsorption-desorption profile and BJH pore-size distribution analysis. This porous structure can function as an oxygen channel for facilitating the transport of oxygen molecules for reacting with the Li ions on the cathode surface. These polymeric bilayers can provide an Li-ion pathway, after absorbing a small quantity of an ionic liquid electrolyte, 0.5 M LiTFSI EMI-TFSI [1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide]. Compared to a typical cathode, where only liquid electrolytes are employed, the total quantity of electrolyte in the cathode can be significantly reduced; thereby, the overall cell energy density can be increased. A Li-O2 battery with this core-shell-structured cathode exhibited a high energy density of approximately 390 Wh/kg, which was assessed by directly weighing all of the cell components together, including the gas diffusion layer, the interlayer [a separator containing a mixture of LiTFSI, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (PYR-14), and PDDA-TFSI], the lithium anode, and the LbL-CNT cathode. The cycle life of the LbL-CNT-based cathode was found to be 31 cycles at a limited capacity of 500 mAh/gcarbon. Although this is not an excellent performance, it is almost 2 times better than that of a CNT cathode without a polymer coating.

Rational Design of 1D Partially Graphitized N-Doped Hierarchical Porous Carbon with Uniaxially Packed Carbon Nanotubes for High-Performance Lithium-Ion Batteries.

N-doped hierarchical porous carbon with uniaxially packed carbon nanotubes (CNTs) was prepared by copolymer single-nozzle electrospinning, carbonization, and KOH activation. Densely and uniaxially aligned CNTs improve the electrical conductivity and act as a structural scaffold, enhancing the electrochemical performance of the anode. A partially graphitized N-doped carbon shell, which has a rapid ion accessible pore network and abundant redox sites, was designed to expand the redox sites from the surface of the material to the whole material, including the inner part. As an anode, this material exhibited a superior reversible capacity of 1814.3 mA h g-1 at 50 mA g-1 and of 850.1 mA h g-1 at 1000 mA g-1. Furthermore, the reversible capacity decreased by only 36% after 400 cycles and showed superior rate capability to that of the same material without CNTs, indicating that the CNT acted successfully as a structural scaffold and enhanced the electrical conductivity. This study not only allowed the rational design of the ideal structure of CNT-based carbonaceous anode material, which has both a rapid ion accessible structure and fast electron-transfer path, but also shed light on a potential strategy by which to use CNTs to modify the nitrogen bonding configuration in N-doped carbon for better electrochemical performance.

Metal-Phenolic Carbon Nanocomposites for Robust and Flexible Energy-Storage Devices.

Future electronics applications such as wearable electronics depend on the successful construction of energy-storage devices with superior flexibility and high electrochemical performance. However, these prerequisites are challenging to combine: External forces often cause performance degradation, whereas the trade-off between the required nanostructures for strength and electrochemical performance only results in diminished energy storage. Herein, a flexible supercapacitor based on tannic acid (TA) and carbon nanotubes (CNTs) with a unique nanostructure is presented. TA was self-assembled on the surface of the CNTs by metal-phenolic coordination bonds, which provides the hybrid film with both high strength and high pseudocapacitance. Besides 17-fold increased mechanical strength of the final composite, the hybrid film simultaneously exhibits excellent flexibility and volumetric capacitance.

Experimental consideration of the Hansen solubility parameters of as-produced multi-walled carbon nanotubes by inverse gas chromatography.

The Hansen solubility parameters (HSPs) of as-produced multi-walled carbon nanotubes (APMWCNTs) were determined by means of the inverse gas chromatography (IGC) technique. Due to non-homogeneous surfaces of the APMWCNTs arising from defects and impurities, it was necessary to establish adequate working conditions for determining the HSPs of the CNTs. We then obtained the HSPs of the APMWCNTs and compared these results with earlier reports as determined by using sedimentation and molecular dynamics simulation methods. It was found that the determination of the HSPs of the CNTs by IGC can give an enhanced determination range based on the adsorption thermodynamic parameters, compared to the HSPs determined using sedimentation methods. And the HSPs of the APMWCNTs, determined here, provided good guidelines for the selection of feasible solvents that can improve the dispersion of the APMWCNTs.

Development of a quantitative sandwich enzyme-linked immunosorbent assay for detecting the MPT64 antigen of Mycobacterium tuberculosis.

PURPOSE: Tuberculosis (TB) is a major infectious disease and is responsible for two million deaths annually. For the identification and quantitation of Mycobacterium tuberculosis (M. tuberculosis), a causative agent of TB, a sandwich enzyme-linked immunosorbent assay (ELISA) against the MPT64 protein of M. tuberculosis, an antigen marker of the M. tuberculosis complex, was developed. MATERIALS AND METHODS: The MPT64 protein was expressed, and anti-MPT64 monoclonal antibodies were prepared. A sandwich ELISA was established using recombinant MPT64 protein and anti-MPT64 monoclonal antibodies. The sandwich MPT64 ELISA was evaluated using reference and clinical mycobacterial strains. RESULTS: The sandwich MPT64 ELISA detected MPT64 protein from 2.1 ng/mL to 250 ng/mL (equivalent to 1.7×104 CFU/mL and 2.0×106 CFU/mL). All 389 clinical M. tuberculosis isolates tested positive in the sandwich MPT64 ELISA (sensitivity, 100%), and the assay showed no cross reactivity to any tested nontuberculous mycobacterial strain (specificity, 100%). CONCLUSION: The sandwich MPT64 ELISA is a highly sensitive and quantitative test for MPT64 protein, which can identify M. tuberculosis.

Development of a Specific and Rapid Diagnostic Method for Detecting Influenza A (H1N1) pdm09 Virus Infection Using Immunochromatographic Assay.

OBJECTIVES: The aim of this study was to develop an immunochromatographic assay (ICA) for the detection of influenza A (H1N1) pdm09 virus infection. MATERIALS AND METHODS: Several monoclonal antibodies against influenza A (H1N1) pdm09 virus were generated and an ICA (pdm09-ICA) was developed for the rapid and specific detection of influenza A (H1N1) pdm09 virus infection. The specificity and sensitivity of the developed assay were compared with that of hemagglutination assay and real-time reverse-transcription polymerase chain reaction (rRT-PCR). RESULTS: The detection limit was estimated to be 1/2 (8) hemagglutinating unit; the sensitivity and specificity rates of pdm09-ICA were 75.86% (110/145) and 100% (43/43), respectively, compared with rRT-PCR. The cross-reactivity for 20 influenza viruses, including seasonal H1N1 viruses, was found to be negative except for the H1N1 virus (A/Swine/Korea/GC0503/2005). CONCLUSION: These results indicate that the proposed method can be easily used for rapid and specific detection of the pdm09 infection. The assay developed in this study would be a useful tool for distinguishing the pdm09 infection from seasonal influenza A and B infections.

[Evaluation of SD BIOLINE Chagas Ab Rapid kit].

BACKGROUND: Chagas' disease is caused by Trypanosoma cruzi, a protozoan parasite, which is transmitted by blood-sucking bugs or through blood transfusion or organ transplantation. It is endemic in Central and South America. The objective of this study was to compare the performance of immunochromatographic SD Bioline Chagas Ab Rapid (Standard Diagnostics, Korea) with three immunochromatographic kits for the detection of antibodies to T. cruzi. METHODS: A total of 320 serum specimens (140 positive and 180 negative) from National Reference Laboratory for Chagas and Leishmaniasis (NRLCL, Honduras) were used for the evaluation of four different test kits: SD Bioline Chagas Ab Rapid, Chagas Stat-Pak Assay (Chembio Diagnositc Systems, USA), OnSite Chagas Ab Rapid test-Cassette (CTK Biotech, USA), and Trypanosoma Detect Rapid Test (InBios International, USA). The results of four kits were compared with those of NRLCL. Cross-reactivity with other parasites was also evaluated. RESULTS: Compared with the results of NRLCL, sensitivity and specificity were 99.3% and 100% for both of SD and Chembio kits, 97.2% and 100% for InBios kit, and 97.9% and 98.8% for CTK kit. None of other parasites showed cross-reactivity. CONCLUSIONS: SD Bioline Chagas Ab Rapid kit showed test results highly correlating with those of National Reference Laboratory for Chagas and Leishmaniasis. It can be used for a rapid detection of Chagas' disease in endemic region and monitoring the disease among overseas travelers in Korea.

One-step immunochromatography assay kit for detecting antibodies to canine parvovirus.

This study was performed to determine the feasibility of using whole serum to detect antibodies to canine parvovirus (CPV) under nonlaboratory conditions and to evaluate the performance characteristics of an immunochromatography assay kit. Precise detection of levels of antibody against CPV in puppies can be used to determine a vaccination schedule, because maternal antibodies frequently result in the failure of protective vaccination, and can also be used to determine the antibody levels of infected puppies. Several methods for the titration of CPV antibodies have been reported, including the hemagglutination inhibition (HI) assay, which is considered the "gold standard." These methods, however, require intricate and time-consuming procedures. In this study, a total of 386 serum specimens were tested. Compared to the HI assay, the rapid assay had a 97.1% sensitivity and a 76.6% specificity (with a cutoff HI titer of 1:80). This single-step assay could be performed rapidly and easily without special equipment. The kit provides a reliable method for detection of anti-CPV antibody where laboratory support and personnel are limited.