Super-aligned Carbon Nanotube Research Articles

Electron Beam Interaction with Carbon Nanotubes in Scanning Electron Microscope: Mechanisms and Applications

AbstractA comprehensive understanding of the interaction between electron beams and carbon nanotubes (CNTs) in scanning electron microscope (SEM) can be challenging due to the complex surface charging behavior and various nanostructures formed by CNTs. Herein, an overview of the challenges and potential solutions are provided for achieving high‐resolution imaging of nanomaterials, such as CNTs, in SEM systems. First, imaging mechanisms of CNTs on conducting, insulating, and hybrid substrates are summarized, with morphology, material type, and charging effect covered. Second, measuring the conductivity, bandgap, and diameter of a CNT by SEM method is introduced. Finally, the utilization of super‐aligned CNT (SACNT) films for observing insulators and vertically aligned CNT arrays (VACNTAs) as electron blackbodies are discussed separately. New techniques for imaging and characterizing nanostructures will ultimately lead to the advancement of CNT‐based technologies.

High Sensitivity and Rapid Response Optomechanical Uncooled Infrared Detector From Self-Assembled Super-Aligned Carbon Nanotubes Film

High Sensitivity and Rapid Response Optomechanical Uncooled Infrared Detector From Self-Assembled Super-Aligned Carbon Nanotubes Film

Microheater Chips with Carbon Nanotube Resistors.

The specific and excellent properties of the low-dimensional nanomaterials have made them promising building blocks to be integrated into microelectromechanical systems with high performances. Here, we present a new microheater chip for in situ TEM, in which a cross-stacked superaligned carbon nanotube (CNT) film resistor is located on a suspended SiNx membrane via van der Waals (vdW) interactions. The CNT microheater has a fast high-temperature response and low power consumption, thanks to the micro/nanostructure of the CNT materials. Moreover, the membrane bulging amplitude is significantly reduced to only ∼100 nm at 800 °C for the vdW interaction between the CNTs and the SiNx membrane. An in situ observation of the Sn melting process is successfully conducted with the assistance of a customized flexible temperature control system. The uniform wafer-scaled CNT films enable a high level of consistency and cost-effective mass production of such chips. The as-developed in situ chips, as well as the related techniques, hold great promise in nanoscience, materials science, and electrochemistry.

Electricity-Driven Strategies for Bioinspired Multifunctional Swimming Marangoni Robots Based on Super-Aligned Carbon Nanotube Composites.

Marangoni actuators that are propelled by surface tension gradients hold significant potential in small-scale swimming robots. Nevertheless, the release of "fuel" for conventional chemical Marangoni actuators is not easily controllable, and the single swimming function also limits application areas. Constructing controllable Marangoni robots with multifunctions is still a huge challenge. Herein, inspired by water striders, electricity-driven strategies are proposed for a multifunctional swimming Marangoni robot (MSMR), which is fabricated by super-aligned carbon nanotube (SACNT) and polyimide (PI) composite. The MSMR consists of a Marangoni actuator and air-ambient actuators. Owing to the temperature gradient generated by the electrical stimulation on the water surface, the Marangoni actuators can swim controllably with linear, turning, and rotary motions, mimicking the walking motion of water striders. In addition, the Marangoni actuators can also be driven by light. Importantly, the air-ambient actuators fabricated by SACNT/PI bilayer structures demonstrate the function of grasping objects on the water surface when electrically Joule-heated, mimicking the predation behavior of water striders. With the synergistic effect of the Marangoni actuator and air-ambient actuators, the MSMR can navigate mazes with tunnels and grasp objects. This research will provide a new inspiration for smart actuators and swimming robots.

Continuously‐Tunable and Ultrawide‐Range Thermal Regulator Based on Superaligned Carbon Nanotube Aerogels for Dynamic Thermal Management of Batteries and Buildings

AbstractEfficient heat transfer control is highly demanded for dynamic thermal management of equipment and buildings especially when the environmental temperature dramatically changes. Thermal switches, the current approach of heat transfer control, suffer from the issues of low switching ratios below eight and sharp state transition between “on” and “off”. Herein, a continuously‐tuned thermal regulator with an ultrahigh thermal‐conductivity change ratio of 43 based on superaligned carbon nanotube aerogel is reported, which works on the regulation of both thermal interfacial resistance and conduction pathways by compressive deformation‐induced microstructure evolution. This thermal regulator can stabilize the device temperature at 25 °C when the environmental temperature varies by 7 and 11 °C under the natural convection and forced convection conditions, respectively. Toward practical application, the thermal regulator with flexibility is wrapped around a cylindrical lithium‐ion battery to control the operation temperature within the optimal range of 20–40 °C for enhanced discharging performance even at an environmental temperature of −20 °C. Besides, by combining the thermal regulator with radiative cooling film, the house model temperature can be lowered by 2.7 °C during daytime and raised by 1.1 °C during nighttime compared with the bare one. This efficient thermal regulation approach offers an effective solution for practical thermal management.

Self-assembled hierarchical porous carbon nanotube sponge bioanode for energy harvesting and gaseous toluene removal

Microbial fuel cells (MFCs) have emerged as a promising technology with potential for volatile organic compounds (VOCs) treatment and energy recovery. However, the low efficiency of electron transfer between microorganisms and electrodes has limited their degradation ability and power output. To address this issue, we designed a macroscopic hierarchical porous super-aligned carbon nanotube (SACNT) sponge bioanode. The hierarchical structure of the SACNT anode exhibited an appropriate distribution of macro/mesopores. The large pores facilitated biofilm formation and mass transfer, enhancing direct electron transfer between bacteria and SACNTs. The abundant mesopores augmented adsorption and electrochemical reaction sites, thereby enhancing flavin-mediated indirect electron transfer. This hierarchical pore structure induced the formation of biofilms mainly composed of electroactive bacteria and toluene-degrading bacteria, promoting toluene removal and power generation. The MFC demonstrated an exceptional power density of 726.18 mW m−2, surpassing existing toluene-fueled MFCs, while achieving the toluene elimination capacity of 61.29 g m−3 h−1.

Advanced lightweight lightning strike protection composites based on super-aligned carbon nanotube films and thermal-resistant zirconia fibers

We fabricated a composite laminate consisting of 1000 layers of SA-CNTFs and 1 layer of zirconia fiber, effectively shielding CFRP from 100 kA lightning strikes. Furthermore, the lightning strike protection mechanism was thoroughly investigated.

An on-chip vacuum triode based on thermionic electron emission from super-aligned carbon nanotube films

An on-chip vacuum triode based on thermionic electron emission from suspended super-aligned carbon nanotube films is realized via microfabrication technology.

Superaligned carbon nanotube film/quartz fiber composites towards advanced lightweight lightning strike protection

Due to poor electrical conductivity, carbon fiber-reinforced plastic (CFRP) is easily damaged by lightning strikes. In this paper, highly conductive superaligned carbon nanotube films (SA-CNTFs) and new isolation layers (quartz fibers) were combined to fabricate advanced lightweight lightning strike protection (LSP) composites. We verified that the isolation layer indeed has an LSP effect and demonstrated for the first time that quartz fibers are a better alternative isolation layer material candidate than conventional glass fibers due to their high thermal resistance. The “complementary effect” between the conductive layer and the isolation layer is revealed. The preliminarily optimized laminate composites made of SA-CNTF/quartz fiber can sustain 100 kA simulated lightning strike. Compared with typical CNT-based LSP laminate samples made of buckypaper/Boron Nitride/epoxy layer or SA-CNTF/glass fiber, the weight can be reduced by at least ∼30% and ∼38%, respectively.

Highly Efficient Visible-Blind Ultraviolet Photodetector Based on Scalably Produced Titanium Dioxide Nanowire Arrays.

Here, we report a novel, feasible, and cost-effective method for the preparation of one-dimensional TiO2 nanowire arrays using a super-aligned carbon nanotube film as a template. Pure-anatase-phase TiO2 nanowires were scalably prepared in a suspended manner, and a high-performance ultraviolet (UV) photodetector was realized on a flexible substrate. The large surface area and one-dimensional nanostructure of the TiO2 nanowire array led to a high detectivity (1.35 × 1016 Jones) and an ultrahigh photo gain (2.6 × 104), respectively. A high photoresponsivity of 7.7 × 103 A/W was achieved under 7 μW/cm2 UV (λ = 365 nm) illumination at a 10 V bias voltage, which is much higher than those of commercial UV photodetectors. Additionally, by taking advantage of its anisotropic geometry, we found the TiO2 nanowire array showed polarized photodetection. The concept of using nanomaterial systems shows the potential for realization of nanostructured photodetectors for practical applications.

High Ampacity On-Chip Wires Implemented by Aligned Carbon Nanotube-Cu Composite.

With the size of electronic devices shrinking to the nanometer scale, it is of great importance to develope new wire materials with higher current carrying capacity than traditional materials such as gold (Au) and copper (Cu). This is urgently needed for more efficient, compact and functional integrated chips and microsystems. To meet the needs of an atom chip, here we report a new solution by introducing super-aligned carbon nanotubes (SACNTs) into Cu thin films. The microwires exhibit an ultra-high current carrying capacity beyond the limit of the traditional Cu wires, reaching (1.7~2.6) × 107 A·cm-2. The first-principles calculation is used to obtain the band structural characteristics of the CNT-Cu composite material, and the principle of its I-V characteristic curve is analyzed. Driven by the bias voltage, a large number of carriers are injected into the CNT layer from Cu by the strong tunneling effect. Moreover, a variety of microwires can be designed and fabricated on demand for high compatibility with conventional microelectronics technology. The composite structures have great potential in high-power electronic devices, high-performance on-chip interconnecting, as well as other applications that have long-term high-current demands, in addition to atom chips.

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.

Rapidly Modulated Wide‐Spectrum Infrared Source Made of Super Aligned Carbon Nanotube Film for Greenhouse Gas Monitoring (Adv. Funct. Mater. 4/2023)

Rapidly Modulated Wide‐Spectrum Infrared Source Made of Super Aligned Carbon Nanotube Film for Greenhouse Gas Monitoring (Adv. Funct. Mater. 4/2023)

Rapidly Modulated Wide‐Spectrum Infrared Source Made of Super Aligned Carbon Nanotube Film for Greenhouse Gas Monitoring

AbstractNon‐dispersive infrared (NDIR) gas monitoring has advantages of environment stability, convenient operation and maintenance, wide detection range, and multi‐gas‐detection capability. However, the conventional IR sources for NDIR gas monitoring, such as miniature lamps, microelectromechanical system (MEMS) light sources, and light‐emitting diodes (LEDs), can only work at narrow modulation frequency and spectral range, or require complicated design and fabrication, because of the constraint of materials and work principle. These issues cause low data acquisition rate, poor anti‐interference ability and limited gas compatibility to NDIR. Here, the super‐aligned carbon nanotube (SACNT) film is developed as an IR source in NDIR gas monitoring system. It has a wide spectral range (0.2–334 µm), a facile fabrication method, and can work up to a high frequency ≈150 kHz. A mechanical‐chopper‐free and wide‐concentration‐range monitoring equipment for CO2 and CH4 greenhouse gases is demonstrated with SACNT film IR source. The concentration ranges for CO2 and CH4 investigated in this paper are 0.0195–20.10% (v/v) and 0.10–17.11% (v/v), respectively. It can be easily applied to monitor other kinds of gases as well.

Nonpolar cross-stacked super-aligned carbon nanotube membrane for efficient wastewater treatment

Nonpolar cross-stacked super-aligned carbon nanotube membrane for efficient wastewater treatment

Terahertz and infrared transmission properties of super-thin periodic multi-walled carbon nanotube gratings

Super-aligned multi-walled carbon nanotube arrays on Si wafer were synthesized by low press chemical vapor deposition. The super-thin multi-walled carbon nanotube films were obtained by a drawing process on the side of the vertically aligned carbon nanotubes. The as-synthesized samples were characterized by scanning electron microscopy and optical microscopy. Terahertz time-domain measurements showed that anisotropic transmission properties were observed. The multi-walled carbon nanotube films with various two-dimensional periods and thicknesses displayed remarkably enhanced transmission at the terahertz range. Comparing experimental results with theoretical calculations revealed that the excitation of surface plasmon polaritons on the carbon nanotubes/Si interface was the key mechanism responsible for the enhanced transmission. The resonance peaks were red shifted with increasing period. In the infrared region, no obvious resonance peaks were observed.

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.

Super-aligned carbon nanotubes and GelMA hydrogel composite scaffolds promote spiral ganglion neuron growth and orientation

Sensorineural hearing loss caused by the damage and degeneration of spiral ganglion neurons (SGNs) is a common disease. So, the regeneration and directional growth of spiral ganglion neurons (SGNs) is vital for the treatment of sensorineural hearing loss. In this study, we combined methacrylated gelatin (GelMA) hydrogel and super-aligned carbon nanotubes sheets (SACNTs) to form a composite material (GelMA-SACNT) that combined the good biocompatibility of GelMA hydrogel with the conductivity of carbon nanotubes. The prepared composite material retained the topological structure of SACNTs and thus provided a suitable platform for neural cell culture. SGNs grown on GelMA-SACNT showed well orientation, increased length of neurites and filopodia and increased area of the axon growth cone. Furthermore, neural network activity on the GelMA-SACNT was increased. These results clearly show that the prepared GelMA-SACNT can promote the growth of SGNs and the formation of anisotropic neural networks and thus has potential for the treatment of sensorineural hearing loss.

Investigation and optimization of polarization properties of self-assembled carbon nanotube films

Super-aligned carbon nanotubes (CNTs) film has strong anisotropy to light propagation. In order to better integrate the self-assembled CNTs into microelectromechanical system (MEMS) for polarization applications, some inherent impacts on polarization properties of CNT film were investigated. We described the polarization effects of the film thickness variation in detail, giving an optimum thickness range which is around 700–800 nm. The amorphous carbon content of CNT film was reduced by oxidation process where the transmittance increased by almost 4 folds. The alignment of CNT arrangement was optimized from 0.41 (Chebyshev orientation parameter) to 0.54 by manipulating the C2H4 flow rate from 54 to 80 sccm. More specifically, a sample possessing a degree of polarization up to 99% and transmittance over 45% was obtained through proper regulations. The validated optimization makes the aligned CNT films more feasible and valuable for the integration of the CNT polarimeters with MEMS technology.

Active terahertz liquid crystal device with carbon nanotube film as both alignment layer and transparent electrodes

Liquid crystal (LC) materials are a good candidate for active phase and polarization devices. However, they also encounter significant challenges in the lack of transparent electrodes and the difficulty of LC alignment due to the thick LC cell for sub-mm wavelength in the terahertz (THz) regime. Here, we presented a strategy to overcome these difficulties, that is, using a super-aligned carbon nanotube (CNT) film with dual functions for both transparent electrodes and the aligning layer for THz LC cell. The LC molecules are uniformly aligned along the orientation direction of the CNT film because of its surface anchoring effect. The experiment results show that the active THz polarization conversions are controlled by the bias voltage tuning from 0 to 30 V between the upper and lower CNT films, and the output polarization state is converted between linear polarization and circular polarization. This work may pave a simple and flexible path toward the development of various active THz liquid crystal devices for spatial light modulation, dynamic imaging, and wavefront control.