Aligned 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.

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.

Superior Stable, Highly Efficient, and Anisotropic Electrothermal Composite Heater in Various Directions with Fast Response Based on Aligned Carbon Nanotube Sheets

Flexible electrothermal heaters have a great potential for applications of warm‐keeping and thermotherapy. However, those common electrothermal heaters are so sensitive to strain that they are hard to resistant to deformation while still keeping the stable and outstanding electrothermal performance. Here, a flexible and elastic composite heater with a stable electrothermal property under varied strain with large deformation is developed by mimicking the wrinkle feature of human skin in a carbon nanotube (CNT)/polydimethylsiloxane (PDMS) bilayered structure. The created wrinkle feature of CNT film from the resilience of PDMS makes the electrothermal heater a stable electrothermal performance within 30–40% strain in different directions. The aligned preference of CNTs in the CNT film gives the electrothermal heater an ability that shows different electrothermal performance depending on different angles between the direction of CNT alignment and the long axis of the sample. This composite electrothermal heater also presents a highly efficient electrothermal performance that can reach 200 °C within 30s upon 2 V.

Responsive Polymer Composite Fiber

Comprehensive SummaryWearable devices are a mainstream for our future daily life, where responsive polymer composite fibers represent one of the key components. However, their practical applications are hampered by several challenges, including poor responsive reversibility, poor controllability and low stability as well as single function. Herein, we share our recent studies on overcoming the above challenges for achieving novel responsive polymer composite fibers, especially focusing on chromatic fibers, deformational fibers and their integrations. Furthermore, we introduce a type of novel materials for these responsive fiber materials, i.e., aligned carbon nanotube sheets and fibers simultaneously with excellent electrical, optical and mechanical properties. For the future development, we further highlight the possible directions in this field. What is the most favorite and original chemistry developed in your research group?The conception and realization of display textile. Displays are the basic building blocks of electronics. Integrating displays into textiles offers exciting opportunities for smart electronic textiles, which are believed to change the future life of the human being. For instance, display textiles serve to bridge human‐machine interactions, and a real‐time communication tool may become true for individuals with voice or speech disorders. After hard work for over ten years, we have finally achieved this goal at lab and further produced such display textiles at large scale at industry.How do you get into this specific field? Could you please share some experiences with our readers?When I started to do research independently at Fudan University, I tried to do something unique. I just did not hope to simply follow the available direction. I majored at chemical fibers during my undergraduate study and later made research on electronic devices, so it was natural for me to combine fibers and electronics together. I do not remember the detail time I figured out the idea. In my mind, it should be very interesting and must be very cool. I did not know and even had not thought whether they were useful or not. After the paper was published in 2021, so many people contacted us for the use of display textiles for a spectrum of applications. During the study on the display textiles that have been also investigated for smart systems, we started to explore new smart fibermaterials almost at the same time. These smart fiber materials are discussed in this article.How do you supervise your students?First, it is important for me to understand them as every student is unique. Second, according to their characteristics, I may choose specific research projects, often following their interests. Third, I fully respect them when they start the research. They are totally free to decide the work time and work style. I trace the process mainly aiming at solving problems for them. Of course, I keep asking them to enhance their scientific tastes and make the first‐class research, not only so‐called original science or technology. I will try my best to help them to publish their results at top journals, which is important for their future development. During the whole training process, the most important thing I hope to achieve is enjoying science, at least feel successful. It is obviously not easy. Sometimes we make it, and sometimes we fail. We always work for the better full of hope. I sincerely hope that every student, after graduation, will have a good memory at my lab.What is the most important personality for scientific research?I think there are two very important characteristics. One is brave. A scientist should be brave to solve the most difficult problem in the field. The other is imagination. Science is pretty similar to arts in many aspects. We may fix the gap sometimes through imagination. However, it is particularly challenging to train scientists for good imagination in science.

Electroconductive and Anisotropic Structural Color Hydrogels for Visual Heart-on-a-Chip Construction.

Heart‐on‐a‐chip plays an important role in revealing the biological mechanism and developing new drugs for cardiomyopathy. Tremendous efforts have been devoted to developing heart‐on‐a‐chip systems featuring simplified fabrication, accurate imitation and microphysiological visuality. In this paper, the authors present a novel electroconductive and anisotropic structural color hydrogel by simply polymerizing non‐close‐packed colloidal arrays on super aligned carbon nanotube sheets (SACNTs) for visualized and accurate heart‐on‐a‐chip construction. The generated anisotropic hydrogel consists of a colloidal array‐locked hydrogel layer with brilliant structural color on one surface and a conductive methacrylated gelatin (GelMA)/SACNTs film on the other surface. It is demonstrated that the anisotropic morphology of the SACNTs could effectively induce the alignment of cardiomyocytes, and the conductivity of SACNTs could contribute to the synchronous beating of cardiomyocytes. Such consistent beating rhythm caused the deformation of the hydrogel substrates and dynamic shifts in structural color and reflection spectra of the whole hybrid hydrogels. More attractively, with the integration of such cardiomyocyte‐driven living structural color hydrogels and microfluidics, a visualized heart‐on‐a‐chip system with more consistent beating frequency has been established for dynamic cardiomyocyte sensing and drug screening. The results indicate that the electroconductive and anisotropic structural color hydrogels are potential for various biomedical applications.

Directional, Low-Energy Driven Thermal Actuating Bilayer Enabled by Coordinated Submolecular Switching.

The authors reveal a thermal actuating bilayer that undergoes reversible deformation in response to low‐energy thermal stimuli, for example, a few degrees of temperature increase. It is made of an aligned carbon nanotube (CNT) sheet covalently connected to a polymer layer in which dibenzocycloocta‐1,5‐diene (DBCOD) actuating units are oriented parallel to CNTs. Upon exposure to low‐energy thermal stimulation, coordinated submolecular‐level conformational changes of DBCODs result in macroscopic thermal contraction. This unique thermal contraction offers distinct advantages. It's inherently fast, repeatable, low‐energy driven, and medium independent. The covalent interface and reversible nature of the conformational change bestow this bilayer with excellent repeatability, up to at least 70 000 cycles. Unlike conventional CNT bilayer systems, this system can achieve high precision actuation readily and can be scaled down to nanoscale. A new platform made of poly(vinylidene fluoride) (PVDF) in tandem with the bilayer can harvest low‐grade thermal energy and convert it into electricity. The platform produces 86 times greater energy than PVDF alone upon exposure to 6 °C thermal fluctuations above room temperature. This platform provides a pathway to low‐grade thermal energy harvesting. It also enables low‐energy driven thermal artificial robotics, ultrasensitive thermal sensors, and remote controlled near infrared (NIR) driven actuators.

Multi-Functional Film Based on Aligned CNT Sheet for Liquid Crystal Display Application

Carbon nanotube (CNT), an extremely long hollow cylinder with nanometer-sized diameter, is a promising carbon material with unique thermal, electrical, and physical properties. Due to their peculiar and fascinating properties, CNTs have been studied and used in various industries since their discovery. The CNTs are potentially viable alternatives for conventional materials in electric devices considering their mechanical resilience, high electrical conductivity, and optical transparency. The alignment of CNTs into ordered structures garnered a special interest as it enhances electrical conductivity and optical transparency, and generates a new intriguing anisotropic optical absorption property. The optical properties of highly oriented CNT sheets have been investigated to apply as optical polarizer and polarized light source. Further, the flexible electrodes derived from an aligned CNTs have unveiled applications in super-capacitors, solar cell, and lithium-ion battery. Therefore, to utilize CNTs in LCD and many other flexible electronic device applications it is essential to attain highly ordered CNTs which should be static even under external stresses such as bending, pressing, and strain.In this work, we fabricated the aligned CNT sheet films (a-CSFs) in which the grown CNTs are stretched unidirectionally on the substrate and its orientation is fixed via polymerization of a coated monomer and then measured its optical and mechanical properties, testing feasibility of its application for multi-functioning films such as polarizer, electrode, and liquid crystal (LC) alignment. The fabricated a-CSF exhibits polarization efficiency (PE) (87.23% of 10 layers of a-CSF), sheet resistance (361.7 Ω/sq), and an excellent aligning capability of LC molecules as shown in Fig. 1 (a~c). Besides, flexibility and stability test of a-CSF via repeating bending test of 1,000 cycles at bending radius of 2 mm exhibited very low variation in the change ratio of sheet resistance and transmittance less than 8% and 10%, respectively.Utlilizing the mutifunctionalty of a-CSF, a liquid crystal display (LCD) with a twisted nematic(TN) mode was fabricated and exhibited feasibility of dynamic swicthing between bright and dark states on application of voltage off/on even without using conventional components of LCD such as transparent electrode, film-type polarizer, and polyimide-type alignment layer. We measured the voltage-dependent transmittance of both devices based on the a-CSF with 5 layers and 8 layers. The threshold voltage (Vth) and operating voltage (Vop) are defined as the voltage required to achieve 90% and 10% of transmittance relative to maximum transmittance, respectively. The measured Vth of both devices with 5 and 8 layers are 1.7 Vrms and 1.3 Vrms, respectively and the measured Vop of both devices are 7.6 Vrms and 4.3 Vrms, respectively. In the case of 8 layers, it shows slightly lower Vth and Vop, which is mainly due to the lower sheet resistance of a-CSF with 8 layers than 5 layers as shown Fig 2.In conclusion, we fabricated the multi-functional a-CSF with properties of the electrode, polarizer, and alignment layer based on the a-CSF using the simple fabrication process. We confirmed the a-CSFs exhibit better conductivity and PE in the visible regime. Furthermore, it has the excellent grooved morphology along the drawn direction of a-CS for homogeneous alignment of LC molecules. We carried out the bending test to confirm the stability of the films from mechanical stress. It showed excellent stability after bending tests of 1,000 cycles. The performance of the fabricated TN cells using a-CSFs were considerably working good. Figure 1

A High Energy Density 2D Microsupercapacitor Based on an Interconnected Network of a Horizontally Aligned Carbon Nanotube Sheet

Highly aligned carbon nanotubes (HACNT sheets) have recently attracted great attention in developing high-performing ultrathin supercapacitors, which take advantage of the long-range alignment to improve electrochemical performance. While there are investigations into sandwich electrode CNT sheet devices, there are no known reports on interdigitated electrode (IDE) HACNT sheet microsupercapacitors (MSCs). This paper reports a facile method for rapidly fabricating high energy density ultrathin HACNT sheet-based MSCs with IDE planar configuration. Increasing the electrode thickness from 32 nm (5 layers) to 300 nm (50 layers) results in an approximately three times factor in performance. The 50 layer devices (MSC-50L) yield a top energy density of 10.52 mWhcm-3 and power density of 19.33 Wcm-3, making its performance comparable to those of microbatteries with potential for further improvement. Additionally, incorporation of MnO2 nanoparticles (NPs) within the MSCs-50L improves specific capacitance (242 Fcm-3), energy density (33.7 mWhcm-3), and power density (31 Wcm-3), outperforming current thin-film MSCs and matching the performance of 3D MSCs. MSCs also demonstrate a long cycle life (7000 charge-discharge cycles) with less than 5% capacitance fade. These findings suggest that HACNT sheets have substantial potential as active electrode materials for ultrathin high energy density microscale power sources.

Orientation-dependent impedance response of highly aligned carbon nanotube sheets

Highly aligned carbon nanotube (CNT) sheets have been successfully applied to a number of interesting devices because of their distinctive properties. In this paper, aligned CNT sheets were fabricated and their orientation-dependent impedance properties were investigated in detail. Perpendicularly aligned CNT sheets showed both resistive and capacitive responses, which differed from those of horizontally aligned CNT sheets. Moreover, CNT-CNT junction dominant electrical transport is discussed, and a new concept for a capacitive-impedance sensor is also demonstrated. This work contributes to better understanding of the orientation-dependent impedance characteristics of aligned CNT sheets, and should facilitate practical applications.

Electricity-Triggered Self-Healing of Conductive and Thermostable Vitrimer Enabled by Paving Aligned Carbon Nanotubes.

Electrically conducting films are important for the development of modern electronics. However, most of these conducting films become susceptible to structure fractures under complex deformations or accidental damages, causing the devices to fail to work. Inspired by the self-healing capability of creatures, we developed a self-healing, thermostable, and electrically conducting film that can be healed by electricity by paving aligned carbon nanotube (CNT) sheets onto the surface of liquid crystal elastomer composite films. The aligned CNT sheets make the composites conductive, so the composites can be healed not only by light but also by electricity after breaking. The scratches on the self-healing film can be healed easily under a voltage of 1.18 V/mm because of the electro-thermal effect of aligned CNT sheets. The healed film has almost the same mechanical properties compared to the pristine sample. The electrical and mechanical self-healing of the film is derived from the electrical reconnection of carbon nanotubes and transesterification-induced topology change of the network, respectively. We further demonstrated soft actuators and high-performance supercapacitors based on the prepared self-healing conducting films. This method for preparing self-healing conducting films enables the development of self-healing electronics.

Anomalous Negative Resistance Phenomena in Twisted Superconducting Nanowire Yarns.

We report unusual absolute negative resistance phenomena in twisted superconducting yarns consisting of niobium-nitride (NbN) nanowires formed on a template of aligned carbon nanotube (CNT) sheets. In the vicinity of the superconducting critical temperature and critical current, the electrical resistance with a standard four-probe configuration exhibits negative values for many wire-shaped twisted yarns. This anomalous behavior at the superconducting transition stage is analyzed using a simplified circuit model, where the charge conduction is determined by the combination between the intra- and internanofiber transports inside the yarn. The superconducting transition of intrafibrillar transport along CNT-templated NbN nanowires was distinguished from that of an interfibrillar one, where the latter exhibits the ensemble property of superconducting weak links among adjacent NbN nanowires. Furthermore, the topological similarity between the sheet of an aligned array of nanowires and the yarn of twisted nanofibrils enables the occurrence of this anomaly. This study indicates that the quantitative network-based approach is effective for the analysis of anomalous charge conduction through nanowire-based anisotropic materials.

An active carbon-nanotube polarizer-embedded electrode and liquid-crystal alignment.

We report a method for constructing an active optical polarizer using an aligned carbon nanotube (CNT) sheet that is flexible, bendable, transparent, conductive, and also serves to anchor liquid-crystal (LC) molecules. A horizontally aligned CNT sheet was obtained by mechanical stretching from a vertically grown CNT forest, which was then transferred onto a substrate. A liquid polymer was infiltrated into the CNT sheet followed by UV curing, while a part of the CNT sheet was still exposed on the film surface without polymer coating. The polymer-embedded CNT sheet (P-ECS) film with 10 layers of CNT sheets exhibited a good polarization efficiency of 87%, a sheet resistance of 340 Ω□-1, and excellent ability to align LC molecules. The high stability of the P-ECS film was confirmed from the very low variation of sheet resistance (2%) and transmittance (10%) observed during a bending test of 1000 cycles. In addition, a twisted nematic LC device constructed using the P-ECS films shows a good bright-dark switching performance. The P-ECS film functions simultaneously as a transparent electrode, a film-type polarizer, and a LC alignment layer, demonstrating the multi-functionality of the active CNT film. This study thus highlights a wide range of possible applications for active polarizers and flexible displays.

High-Performance, Wearable Thermoelectric Generator Based on a Highly Aligned Carbon Nanotube Sheet

A high-performance, wearable thermoelectric generator (TEG) was fabricated with a highly aligned carbon nanotube (CNT) sheet. The aligned CNT sheet exhibits extraordinary electrical conductivity co...

All-in-one stretchable coaxial-fiber strain sensor integrated with high-performing supercapacitor

Ever-increasing attempts have recently been focused on exploring stretchable fiber-shaped integrated wearables, owing to their multi-functionalities and mechanical flexibilities. However, a rational design and effective integration of multi-functional components, such as strain sensor and high-performing energy storage, into one single fiber remains a great challenge. Herein, we have achieved an all-in-one stretchable coaxial-fiber sensing system simultaneously integrating strain detection and power supporting supercapacitor. The asymmetric stretchable coaxial-fiber supercapacitor is made on an elastic fiber, with a maximum working voltage of 1.8 V, by adopting manganese dioxide and polypyrrole deposited on aligned carbon nanotube sheets as the positive and negative electrode, respectively. Benefiting from the unique coaxial-fiber integrated architecture and advanced electrode design, the optimized device delivers a high stack volumetric energy density of 1.42 mWh cm−3, and an outstanding flexibility with 85.1% capacitance retention after stretching for 6000 cycles at a strain of 200%. The all-in-one stretchable coaxial-fiber strain sensing system shows consistent self-supported performance with a superior stability and durability at repeatedly unloading/loading of 40% applied strain for 10000 cycles, after one single charge. The present work demonstrates the new proof-of-concept for integration of strain element with energy storage into a single stretchable fiber for the next generation wearables.

High temperature carbon nanotube – Nanofiber hybrid filters

Novel hybrid filters composed of aligned carbon nanotube (CNT) sheets, sandwiched between electrospun polyimide (PI) nanofiber membranes serving as the supporting layers, were fabricated for the capture of fine particles. The CNT sheets and PI nanofiber membranes were thermally bonded together by melting electrospun polyetherimide (PEI) nanofibers. Two different kinds of filter structures were prepared, where multiple layers of aligned CNT sheets were either stacked together on top of each other or separated from each other by a PEI layer. The filtration performance tests showed that the filtration efficiency increased with increasing number of CNT sheets. The maximum filtration efficiency reached 99.99% at 5.3 cm/s face velocity for 0.3 μm particles by the 4-layer CNT filter, while the pressure drop was only 120 Pa. In mechanical testing, the CNT sheets also reinforced the hybrid filters, even though the PI nanofiber membrane already had relatively high mechanical properties. The tensile strength of the 4-layer CNT hybrid filters was 9 MPa, reaching the highest tier of strength reported for nanofiber membranes. In addition to high efficiency and low pressure drop, the hybrid all-nanofiber filters are also targeted for use in hot gas filtration applications where temperatures reach 200–250 °C.

Effects of high-temperature thermal annealing on properties of aligned multi-walled carbon nanotube sheets and their composites

ABSTRACTAligned multi-walled carbon nanotube (MWCNT) sheets were thermally annealed at high temperatures of 1800°C, 2200°C, and 2600°C. Pristine and thermally annealed MWCNT/epoxy composites were fabricated using hot-melt prepreg processing. Effects of thermal annealing on properties of aligned MWCNT sheets and their composites were examined. Transmission electron microscope images and Raman spectra measurements of the aligned MWCNT sheets showed an improvement of the MWCNT nanostructure after high-temperature thermal annealing. High-temperature thermal annealing did not cause the change in microstructural morphologies of the MWCNT sheets. Although the strength of the MWCNT sheets after high-temperature thermal annealing did not improve, their stiffness enhanced significantly. Particularly, high-temperature thermal annealing increased markedly both the tensile strength and elastic modulus of the aligned MWCNT/epoxy composites. The enhancement in the tensile strength and elastic modulus of the composites is mainly attributed to significant improvement of the MWCNT nanostructure by high-temperature thermal annealing. Generally, high-temperature thermal annealing improved the stiffness of the aligned MWCNT sheets and their composites considerably.

Miniaturized Electrochemical Supercapacitor with Patterned Horizontally Aligned Carbon Nanotube Sheets

Introduction: Miniaturized energy storage systems have emerged as a promising approach to address the growing demands to power electronic devices on small footprint area. Microsupercapacitors have become a crucial part of this advancement and have drawn much attention in the research communities. Designing a microstructure and choosing the electroactive materials are two significant factors that greatly affect the performance of the device. Here, we report for the first time the successful fabrication and characterization of a microsupercapacitor with interdigitated structure based on carbon nanotube sheets (CNT sheet). Carbon nanotube sheet is a novel structure which is spun directly from the as-grown carbon nanotube forest. Horizontally aligned structure of CNT sheet offering excellent conductivity and large surface area enabled us to develop a light micro-device with higher electrochemical performance than other CNT-based counterparts in aqueous electrolyte. Materials and process: Spinnable carbon nanotube was grown via chemical vapor deposition (CVD) in a horizontal furnace at temperature of 780°C using acetylene as hydrocarbon and iron as metal catalyst. Multi-sheets of 5, 10, 20, 30 and 50 layers on two different substrates (glass slide and silicon wafer) and were patterned with reactive ion etch (RIE). CNT sheet was used as both active material and current collector. Interdigital structure (IDE) with gap size of 145 um, electrode width of 300um and the length of 5mm were fabricated. The effect of active material thickness on the device performance including specific capacitance and rate capability was studied. Furthermore, long-term stability of the devices was investigated using cyclic voltammetry technique at scan rate of 100mV/s for 10,000 cycles. Results: Thickness dependent specific capacitance of 5 mF/cm2 at the scan rate of 50 mV/s per footprint area of the device was obtained for multi-sheet of 50 layers. Stability and performance of the device was tested using an aqueous PVA-H3PO4 gel electrolyte that also offers desirable electrochemical capacitive properties. High Coulombic efficiency (around 95%), great rate capability (1.2 mF/cm2 at scan rate of 5V/s) and excellent capacitance retention (less than 12%) over 10,000 cycles were obtained. Conclusion: We have fabricated a long-term stable planar microsupercapacitor using horizontally aligned carbon nanotube sheets and achieved a noticeable specific capacitance and high rate capability which demonstrates the potential of CNT sheet for future thin film micro scale energy storage devices. Figure 1

Stacked double-walled carbon nanotube sheet electrodes for electrochemically harvesting thermal energy

Nanocarbon based electrodes have led to remarkable improvements in the performance of thermoelectrochemical cells (TECs), which are able to electrochemically harvest low-grade waste thermal energy. However, the highly tortuous ionic pathways of the electrodes limit the output current from the TECs by reducing the reaction rate inhibited by a concentration gradient in the electrode. In this work, we investigate an electrode structure that facilitates efficient ion transport by sequentially stacking highly aligned double-walled carbon nanotube (DWCNT) sheets. The performance of the TEC is evaluated with respect to the number of DWCNT stacks and the lamination orientation in a parallel or orthogonal direction. As the number of stacks increases from 1 to 3 layers oriented in parallel, the output power increases from 113 to 187 mW/m2 at a small temperature difference of 22 °C. The output power with 3-layer DWCNT sheets can be further improved to 200 mW/m2 by implementing an orthogonal lamination. The significance of electrode tortuosity presented here would be useful in electrode design as a way to improve energy harvesting performance. The results should also provide a basis for devising electrochemical devices with highly porous nanocarbon electrodes.

Hybrid Carbon Nanotube Fabrics with Sacrificial Nanofibers for Flexible High Performance Lithium-Ion Battery Anodes

Silicon is one of the most promising anode materials for lithium-ion batteries because of its highest known theoretical charge capacity (4,200 mAh g−1). However, it has found limited application in commercial batteries because of the significant volume change (up to 400%) of silicon during cycling, which results in pulverization and capacity fading. Here, we present a new method to develop a silicon - carbon nanotube (CNT) hybrid anode architecture using CNT-polymer nanofiber hybridization method. The anode material is produced by electrospinning PMMA-Si nanofibers onto aligned CNT sheets, which are drawn on a grounded, rotating take-up roller, and then subsequently decomposing the PMMA electrospun fibers at elevated temperature to create a uniform distribution of Si particles within the CNT sheets. The whole structure is then coated with pyrolytic carbon via chemical vapor deposition (CVD). The architecture provides sufficient space to accommodate the volume expansion of the Si nanoparticles. The CVD pyrolytic carbon coating helps to anchor the Si nanoparticles within CNT sheets and stabilize solid-electrolyte-interface (SEI) formation. The novel freestanding, binder free CNT-Si-C sheet hybrid exhibited improved performance in terms of excellent cycling capacity (1470 mAh g−1), high coulombic efficiency (98%), and good capacity retention of 88% after 150 cycles.