Integration Of Carbon Nanotubes Research Articles

Organic solar cell efficiency improvement through architecture engineering by integrating carbon nanoring – SCAPS 1D modelling

This research work aims to investigate on improving the performance of organic solar cells (OSC) by proposing new architectures that progressively integrate carbon nanotubes. This contribution takes into account the exceptional properties of carbon nanotubes (CNT) highlighted in recent work, with the aim of addressing the current challenges of materials used in the manufacture of conventional OSCs, such as reactivity with the ambient medium, stability over time, better transport of charge carriers, etc. Using a reference OSC cell with the following structure: PEDOT/BHJ/PDINO and the numerical one-dimensional simulation tool SCAPS, which helps in validating the modelling approach, we gradually replace each layer with a CNT-based material exhibiting superior properties. In this respect, we carry out calculations on the different cells architectures, to better visualize energy-level alignment profiles, the different current-voltage (J-V), and quantum efficiency (QE) characteristics. Approaches toward efficiency improvement were discussed, by investigating the effects of active layer thickness, the doping level, the charge carriers mobility, defect density, and external parameters such as temperature. After numerous calculations and modelling, very promising results were finally achieved with a full CNT-based solar structure with the following recorded performances: VOC=0.87V, JSC=27.81mA/cm2, FF=80.91%, and PCE=19.63%. These results are the first theoretical report for a complete CNT-based modelled OSC and, given the reliability and robustness of the approach adopted, they can be considered as relevant for future theoretical and experimental work. The integration of CNT as functional layers is a remarkable step forward in OSC architectures engineering for efficiency enhancement. CNT are good candidates for light harvesting applications.

Superior Anodic Lithium Storage in Core–Shell Heterostructures Composed of Carbon Nanotubes and Schiff‐Base Covalent Organic Frameworks

Covalent organic frameworks (COFs) after undergoing the superlithiation process promise high‐capacity anodes while suffering from sluggish reaction kinetics and low electrochemical utilization of redox‐active sites. Herein, integrating carbon nanotubes (CNTs) with imine‐linked covalent organic frameworks (COFs) was rationally executed by in‐situ Schiff‐base condensation between 1,1′‐biphenyl]‐3,3′,5,5′‐tetracarbaldehyde and 1,4‐diaminobenzene in the presence of CNTs to produce core–shell heterostructured composites (CNT@COF). Accordingly, the redox‐active shell of COF nanoparticles around one‐dimensional conductive CNTs synergistically creates robust three‐dimensional hybrid architectures with high specific surface area, thus promoting electron transport and affording abundant active functional groups accessible for electrochemical utilization throughout the whole electrode. Remarkably, upon the full activation with a superlithiation process, the as‐fabricated CNT@COF anode achieves a specific capacity of 2324 mAh g−1, which is the highest specific capacity among organic electrode materials reported so far. Meanwhile, the superior rate capability and excellent cycling stability are also obtained. The redox reaction mechanisms for the COF moiety were further revealed by Fourier‐transform infrared spectroscopy in conjunction with X‐ray photoelectron spectroscopy, involving the reversible redox reactions between lithium ions and C=N groups and gradual electrochemical activation of the unsaturated C=C bonds within COFs.

Synergistic Interaction of Ionic Liquid Grafted Poly(vinylidene Fluoride) and Carbon Nanotubes to Construct Water Treatment Membranes with Multiple Separation Properties.

In this study, the dual strategy of 1-butyl-3-vinylimidazolium bromide ionic liquid (IL) grafting and carbon nanotubes (CNTs) nanocomposition was applied to modify poly(vinylidene fluoride) (PVDF)-based membranes. The highly hydrophilic/oleophobic and fouling-resistant PVDF-g-IL/CNTs membranes with excellent separation efficiency were obtained by the nonsolvent-induced phase separation method with ethanol-water mixed solution as the coagulation bath. The grafted IL not only generated hydrophilic groups on PVDF chains but also acted together with the CNTs to induce the formation of hydrophilic β-crystalline phase of PVDF, which significantly improved the hydrophilicity and pore structure of the modified PVDF membranes. As a result, the pure water flux of the optimal membrane increased up to 294.2 L m-2 h-1, which was 5.2 times greater than that of the pure PVDF membrane. Simultaneously, the electrostatic interaction of the positive IL and the integration of CNTs enhanced adsorption sites of the membranes, producing exceptional retention and adsorption of dye wastewater and oil-water emulsion. This study presents a straightforward and efficient approach for fabricating PVDF separation membranes, which have potential applications in the purification of various polluted wastewater.

Bio-based epoxy resin/carbon nanotube coatings applied on cotton fabrics for smart wearable systems

Electroactive coatings for smart wearable textiles based on a furan bio-epoxy monomer (BOMF) crosslinked with isophorone diamine (IPD) and additivated with carbon nanotubes (CNTs) are reported herein. The effect of BOMF/IPD molar ratio on the curing reaction, as well as on the properties of the crosslinked resins was first assessed, and it was found that 1.5:1 BOMF/IPD molar ratio provided higher heat of reaction, glass transition temperature, and mechanical performance. The resin was then modified with CNT to prepare electrically conductive nanocomposite films, which exhibited conductivity values increased by eight orders of magnitude upon addition of 5 phr of CNTs. The epoxy/CNT nanocomposites were finally applied as coatings onto a cotton fabric to develop electrically conductive, hydrophobic and breathable textiles. Notably, the integration of CNTs imparted efficient and reversible electrothermal behavior to the cotton fabric, showcasing its potential application in smart and comfortable wearable electronic devices.

Novel mushroom-like cotton-based evaporator for simultaneous freshwater production and salt harvesting via edge-preferential crystallization

Solar-driven interfacial evaporation (SDIE) has emerged as a promising technology to alleviate the global freshwater scarcity. However, the simultaneous collection of water and salt as resources while maintaining stable evaporation rate without salt contamination at the evaporation interface remains a huge challenge. Herein, we report a novel mushroom-like cotton-based evaporator, inspired by the vertical stem and inclined caps of mushrooms, for simultaneous freshwater production and salt harvesting. By depositing polyaniline (PANI) and carbon nanotubes (CNTs) onto the cotton fabric (CF), an evaporation rate of 1.88 kg m−2h−1 and a high solar evaporation efficiency of 99.4 % can be achieved in 3.5 wt% NaCl solution under one solar irradiation. Furthermore, a significant water collection efficiency of 70.2 % and a high salt harvesting rate of 42.1 g m−2h−1 can be derived. Even exposed to high-concentration (15 wt%) brine, our design still effectively prevents salt contamination. The distinctive edge-preferential crystallization not only avoids the salt contamination but also promotes the salt harvesting, due to the capillary force, the criss-cross water channels from the nature of cotton cloth, as well as the gravity-assisted water transport of the “mushroom cap” during evaporation. In addition, the low thermal conductivity (0.163 W m−1 K−1) of the photothermal layer with the integration of PANI and CNTs, as well as the vertical water upward transport via the “mushroom stem” effectively reduce the heat loss. This research holds great potential for seawater desalination applications with the comprehensive utilization of seawater resources.

Noncovalent cross-linked engineering hydrogel with low hysteresis and high sensitivity for flexible self-powered electronics

In this study, the hydrogel network was reinforced by covalent-like hydrogen bonding, and the strong binding ability of boron–nitrogen coordination served as the main driving force. Among them, acrylamide (AM) and 3-acrylamidophenylboronic acid (AAPBA) were the main body, and the numerous hydroxyl groups in the trehalose (Treh) molecule and other polymer groups formed strong hydrogen bonding interactions to improve the mechanical properties of the PAM/PAAPBA/Treh (PAAT) hydrogel and ensured the simplicity of the synthesis process. The hydrogel possessed high strain at break (1239%), stress (64.7 kPa), low hysteresis (100% to 500% strain, corresponding to dissipation energy from 1.37 to 7.80 kJ/m3), and outstanding cycling stability (retained more than 90% of maximum stress after 200 tensile cycles). By integrating carbon nanotubes (CNTs) into PAAT hydrogel (PAATC), the PAATC hydrogel with excellent strain response performance was successfully constructed. The PAATC conductive hydrogel exhibited high sensitivity (gauge factor (GF) = 10.58 and sensitivity (S) = 0.304 kPa−1), wide strain response range (0.5%–1000%), fast response time (450 ms), and short recovery time (350 ms), excellent fatigue resistance, and strain response stability. Furthermore, the PAATC-based triboelectric nanogenerator (TENG) displayed outstanding energy harvesting performance, which shows its potential for application in self-powered electronic devices.

The dielectric properties of silicone-multiwall carbon nanotubes nanocomposite in the frequency range from 0.5 to 20 GHz

Integrating carbon nanotubes (CNTs) into a polymer matrix can significantly modify its physical properties, providing that the challenges associated with CNT dispersion are successfully resolved. In this work, we investigate the enhancement of the dielectric properties of silicone when multiwall carbon nanotubes (MWCNTs) are introduced to its polymer matrix as a filler in the frequency range from 0.5 to 20 GHz. An optimized procedure is used to prepare nanocomposites with MWCNTs concentrations by weight of 0%, 0.5%, 1.0%, 1.5%, and 2.0%. The investigated dielectric properties for the prepared nanocomposites are the real dielectric constant ɛ′, the imaginary dielectric constant ɛ″, the loss tangent tan δ, and the AC conductivity σAC. The dispersion of the MWCNTs in the silicone matrix is confirmed using the Fourier-transform infrared (FTIR) spectroscopy and the scanning electron microscope. This study shows that the dielectric properties of the nanocomposite are enhanced as the MWCNT’s concentration is increased over the entire frequency range. For example, the enhancement in ɛ′ value was from 3.2 up to 21.6 at 0.5 GHz and from 2.5 to 10.6 at 20 GHz as the concentration increased from 0% to 2.0%. For the ɛ″ value, the enhancement was from less than 0.1 to 8.6 at 0.5 GHz and to 2.0 at 20 GHz, respectively. Based on the obtained tanδ values, the nanocomposites with MWCNTs of 0.5% and 1.0% can be classified as low-loss dielectrics, while the other nanocomposites with MWCNTs of 1.5% and 2.0% are classified as lossy dielectrics.

Corrosion behaviour of plasma-sprayed baghdadite bioceramic coatings reinforced with carbon nanotubes

Bioceramics have been extensively used for the restoration and replacement of hard tissues, such as bones and teeth due to their physicochemical resemblance to these tissues. This study focuses on enhancing the properties of plasma-sprayed bioceramic coatings with the addition of carbon nanotubes. The coatings deposited include hydroxyapatite, baghdadite, and baghdadite with carbon nanotube reinforcement. The effect of incorporating carbon nanotubes into baghdadite coatings is thoroughly investigated in terms of microstructural, mechanical, and electrochemical properties. Multiple characterization techniques such as scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry, and Raman spectroscopy have been employed to reveal microstructural details, elemental composition, and phase constituents of the deposited coatings. The results indicate that baghdadite coatings exhibit higher porosity compared to hydroxyapatite coatings. However, the addition of carbon nanotubes as reinforcement into baghdadite coatings effectively reduces porosity by integrating carbon nanotubes within the inter-lamellae structure and filling voids within the inter-splat regions. This integration also mitigates common post plasma spray defects including porosity, voids, and microcracks. The incorporation of 2 wt% carbon nanotubes into the baghdadite matrix results in a substantial 80% reduction in corrosion current density(Icorr). This reduction is attributed to the combined effects of reduced porosity, and improved structural integrity due to carbon nanotubes. Furthermore, the carbon nanotubes reinforced baghdadite coatings have indicated the healthy development of the MC3T3-E1 osteoblast cell line.

Radio frequency-assisted curing of on-chip printed CNT/silicone heatsinks produced by material extrusion 3D printing

With the rapid development of high-power integrated electronic devices, many polymer-based thermal management devices have been developed to address the problem of overheating and to improve the reliability and lifetime of electronic devices. Here we demonstrate the material extrusion 3D printing of carbon nanotube (CNT)/silicone heatsinks directly onto electronic devices. CNTs were used as a conductive nanofiller and a rheological modifier to improve thermal and electrical conductivities and the printability of the silicone inks, respectively. Additionally, CNTs are also a radio frequency (RF) susceptor, so the integration of CNTs into the silicone matrix allowed for rapid out-of-oven curing by applying RF heating. Specifically, at a CNT loading of 14 wt%, the CNT/silicone heatsinks could be printed and RF cured with shape retention; the heatsinks’ performance was comparable to that of commercial heatsinks. More importantly, the CNT/silicone heatsinks could be printed and cured directly onto a chip attached to a circuit board. This printing approach can eliminate the use of thermal interface materials and the step of heatsink assembly while reducing the number of thermal interfaces between the chip and the heatsink. The results suggest that material extrusion 3D printing combined with RF-assisted curing can be an effective approach to fabricate high-performance polymer-based heatsinks with reduced production time and energy requirements.

Self-Healable and Reprocessable Silicon Elastomers Based on Imine-Boroxine Bonds for Flexible Strain Sensor.

Silicon elastomers with excellent self-healing and reprocessing abilities are highly desirable for the advancement of next-generation energy, electronic, and robotic applications. In this study, a dual cross-linked self-healing polysiloxane elastomer was facilely fabricated by introducing an exchangeable imine bond and boroxine into polydimethylsiloxane (PDMS) networks. The PDMS elastomers exhibited excellent self-healing properties due to the synergistic effect of dynamic reversible imine bonds and boroxine. After healing for 2 h, the mechanical strength of the damaged elastomers completely and rapidly recovered at room temperature. Furthermore, the prepared PDMS elastomers could be repeatedly reprocessed multiple times under milder conditions without significant degradation in mechanical performance. In addition, a stretchable and self-healable electrical sensor was developed by integrating carbon nanotubes (CNTs) with the PDMS elastomer, which can be employed to monitor multifarious human motions in real time. Therefore, this work provides a new inspiration for preparing self-healable and reprocessable silicone elastomers for future flexible electronics.

Strength and Electrical Properties of Cementitious Composite with Integrated Carbon Nanotubes

The main objective of this work was to study the effects of carbon nanotubes (CNTs) on the strength and electrical properties of cement mortar. Molecular dynamic simulations (MDSs) were carried out to determine the mechanical and electrical properties of a cementitious composite and its associated mechanisms. To model the atomic structure of a calcium silicate hydrate (C-S-H) gel, tobermorite 11Å was chosen. Single-walled carbon nanotubes (SWCNTs) embedded in a tobermorite structure were tested numerically. In particular, it was concluded that a piezoelectric effect can be effectively simulated by varying the concentration levels of carbon nanotubes. The deformation characteristics were analyzed by subjecting a sample to an electrical field of 250 MV/m in the z-direction in a simulation box. The results indicated a progressively stronger converse piezoelectric response with an increasing proportion of carbon nanotubes. Additionally, it was observed that the piezoelectric constant in the z-direction, denoted by d33, also increased correspondingly, thereby validating the potential for generating an electrical current during sample deformation. An innovative experiment was developed for the electrical characterization of a cementitious composite of carbon nanotubes. The results showed that the electrostatic current measurements exhibited a higher electric sensitivity for samples with a higher concentration of CNTs.

Proof-of-Concept Vacuum Microelectronic NOR Gate Fabricated Using Microelectromechanical Systems and Carbon Nanotube Field Emitters.

This paper demonstrates a fully integrated vacuum microelectronic NOR logic gate fabricated using microfabricated polysilicon panels oriented perpendicular to the device substrate with integrated carbon nanotube (CNT) field emission cathodes. The vacuum microelectronic NOR logic gate consists of two parallel vacuum tetrodes fabricated using the polysilicon Multi-User MEMS Processes (polyMUMPs). Each tetrode of the vacuum microelectronic NOR gate demonstrated transistor-like performance but with a low transconductance of 7.6 × 10-9 S as current saturation was not achieved due to a coupling effect between the anode voltage and cathode current. With both tetrodes working in parallel, the NOR logic capabilities were demonstrated. However, the device exhibited asymmetric performance due to differences in the CNT emitter performance in each tetrode. Because vacuum microelectronic devices are attractive for use in high radiation environments, to test the radiation survivability of this device platform, we demonstrated the function of a simplified diode device structure during exposure to gamma radiation at a rate of 45.6 rad(Si)/second. These devices represent a proof-of-concept for a platform that can be used to build intricate vacuum microelectronic logic devices for use in high-radiation environments.

Integrated carbon nanotube and triazine-based covalent organic framework composites for high capacitance performance.

As a rising class of crystallographic organic polymers, covalent-organic frameworks (COFs) have high specific surface areas, ordered pore structures, and designability, which exhibit broad application prospects in the energy storage sector. However, their low electrical conductivity hinders their potential use in supercapacitors. To improve the electrical conductivity, we introduced carboxylated multi-walled carbon nanotubes to obtain a series of carbon nanotube@COF composites by a facile one-pot method, in which 2D TFA-COFs are in situ grown on the surface of carboxylated multi-walled carbon nanotubes. Among them, the CNT@TFA-COF-3 composite exhibits good crystallinity, regular pores, excellent stability and a specific surface area of 1034 m2 g-1. As expected, as a capacitive electrode material, the CNT@TFA-COF composite shows improved electrochemical performance. Notably, the value of specific capacitance of the CNT@TFA-COF-3 composite (338 F g-1) is about 8.5, 4.9, and 7.5 times higher than those of TFA-COFs, CNTs, and the CNT/TFA-COF physically mixed complex at a current density of 1.0 A g-1, respectively. Furthermore, the CNT@TFA-COF-3 supercapacitor exhibits long-term cycle chemical stability and splendid rate capability even after 7000 charge-discharge cycles. The successful preparation of the CNT@TFA-COF-3 composite can provide new ideas for the construction of new COF-based composites and the development of new materials for energy storage.

Efficient charge separation and transfer in a one-dimensional carbon nanotube/tungsten oxide p-n heterojunction composite for solar energy conversion.

Efficient and cost-effective photocatalysts for solar energy conversion represent a rapidly advancing and compelling area of research. In our study, we employed theoretical calculations to design a novel composite material consisting of a one-dimensional (1D) carbon nanotube (CNT) and tungsten oxide (W18O49) p-n heterojunction. This composite material was successfully synthesized using a straightforward solvothermal method, and we thoroughly investigated the charge separation and transfer mechanism. Our findings revealed that the composite material exhibited a superior photocurrent response. Notably, the CNTs/W18O49-2 sample demonstrated a significantly higher photocurrent under both AM 1.5G and infrared light irradiation, outperforming the individual components under AM 1.5G by a substantial factor of 30. This remarkable enhancement in performance can be attributed to the efficient charge separation and transfer facilitated by the built-in electric field created at the interface through the p-n heterojunction. Our study introduces a pioneering integration of CNTs and 1D tungsten oxide, resulting in a composite structure with a p-n heterojunction-a concept that has not been extensively explored previously. The results confirmed the formation of this unique one-dimensional structure and a p-n heterojunction, which has outstanding properties for various applications. These findings provide a robust foundation for the design of photocatalytic interfaces and offer a fresh approach to the development of high-performance photocatalysts.

Toughening two-dimensional hybrid materials by integrating carbon nanotubes

Graphene (Gr) has ultra-high intrinsic strength and elastic modulus, but it is fragile and has low fracture toughness. It is extremely difficult to evaluate the mechanical properties of two-dimensional (2D) materials because of brittleness. Contrary to expectation, a high fracture toughness of 2D hybrid materials with effective crack deflection is therefore established here by regularly integrating carbon nanotubes (CNTs). Our combined finite element theory and molecular dynamics simulations confirm that embedded CNTs divert and bridge the propagating crack and provide a different toughening effect for the different region of 2D hybrid material. "Toughening zone effect" explain the asymmetric edge elastic properties at the crack tip and edge swapping during crack propagation. The preparation of 2D hybrid materials with CNTs opens up a new idea for other 2D materials, and can be mechanically customized according to the application requirements of its flexible equipment.

Microwave Gas Sensor Based on Carbon Nanotubes Loaded on Open Loop Ring Resonators

This letter presents a microwave gas sensor based on planar coupled open loop ring resonators (OLRRs) embedded with carbon nanotube sensing film for ammonia gas sensing. The sensing area adopts the interdigitated electrode patterns to provide a larger contact area for better sensitivity. By integrating carbon nanotube films as the local variable resistors into a microwave sensor platform, the platform can transduce the gas concentration to its electromagnetic properties. According to the step response of NH3 from 100 to 1000 ppm, the sensitivity is estimated as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 11~\mu $ </tex-math></inline-formula> dB/ppm and −232 Hz/ppm for the insertion losses and resonant frequency variations, respectively. The sensor repeatability and reversibility are also measured by maintaining the concentration from 300 to 700 ppm and repeating ten cycles with the average value of each concentration consistent with the step response. The results show a linearly response and a high repeatability of OLRRs via the real-time detection for gas sensing at high frequency and room temperature. Microwave gas sensors can be further integrated in the IoT or RF front-end system, offering low-cost, lightweight, reliable, and power efficient system for remote monitoring.

Pillar[n]arene-Mimicking/Assisted/Participated Carbon Nanotube Materials.

The recent progress in pillar[n]arene-assisted/participated carbon nanotube hybrid materials were initially summarized and discussed. The molecular structure of pillar[n]arene could serve different roles in the fabrication of attractive carbon nanotube-based materials. Firstly, pillar[n]arene has the ability to provide the structural basis for enlarging the cylindrical pillar-like architecture by forming one-dimensional, rigid, tubular, oligomeric/polymeric structures with aromatic moieties as the linker, or forming spatially “closed”, channel-like, flexible structures by perfunctionalizing with peptides and with intramolecular hydrogen bonding. Interestingly, such pillar[n]arene-based carbon nanotube-resembling structures were used as porous materials for the adsorption and separation of gas and toxic pollutants, as well as for artificial water channels and membranes. In addition to the art of organic synthesis, self-assembly based on pillar[n]arene, such as self-assembled amphiphilic molecules, is also used to promote and control the dispersion behavior of carbon nanotubes in solution. Furthermore, functionalized pillar[n]arene derivatives integrated carbon nanotubes to prepare advanced hybrid materials through supramolecular interactions, which could also incorporate various compositions such as Ag and Au nanoparticles for catalysis and sensing.

Biomass hydrogels combined with carbon nanotubes for water purification via efficient and continuous solar-driven steam generation

Solar vapor generation is a promising, environmentally friendly solution for water purification. The development and design of new materials and supporting devices for efficient energy conversion and clean water production are essential for the practical application of solar-driven desalination and water purification. In this study, an environmentally friendly and economical biomass hydrogel-based solar evaporator with a controllable shape was developed in a simple method by integrating carbon nanotubes (CNTs) into a sodium alginate (SA) hydrogel network. The evaporator had a high solar absorption rate (94.3%) and satisfactory hydrophilicity and could effectively avoid salt crystallization during the desalination process. This study took advantage of the aforementioned merits, and a high evaporation rate of 1.699 kg m-2 h-1 and a conversion efficiency of 86% were achieved under 1.0 sun irradiation. The evaporator could efficiently remove Na+, K+, Ca2+, and Mg2+ from seawater with a removal rate of up to 99.3% and a good decolorization effect on methylene blue (MB) and methyl orange (MO) dye wastewater, whose colour could be completely removed. This study provides a simple, practical, and economical method to prepare hydrogel-based evaporators that utilize abundant solar energy for large-scale desalination and wastewater treatment.

Molecular Dynamics Simulation of Carbon Nanotube Reinforced Rubber Composites

The mechanical characteristics of nitrile butadiene rubber (NBR) and carbon nanotube (CNT) nanocomposites were investigated using molecular dynamics (MD) simulations in this study. The crystal with CNT is created with a volume fraction of about 2.47% and 4.86%. The constant strain method was used to calculate the young's modulus, shear modulus, and bulk modulus of the nanocomposite. The integration of CNT inside the rubber composite matrices increased the mechanical properties. The simulation results show that the young’s, bulk, and shear modulus of NBR 2-CNT were enhanced by about 47.10%, 28.39 %, and 17.86 % respectively when compared to the pure NBR.

The Demonstration of High-Quality Carbon Nanotubes as Through-Silicon Vias (TSVs) for Three-Dimensional Connection Stacking and Power-Via Technology

With the usage of gas ferrocene Fe(C₅H₅)₂ as a reactant, which is different from the traditional thin Fe film, to grow the high-quality carbon nanotubes (CNTs) in the high aspect ratio (AR) trench structure, it has many advantages to be the through-silicon vias (TSVs) material for the three-dimensional (3-D) stacking technology. In this work, we successfully demonstrate the full process flow, including CNT growing, chemical&#x2013;mechanical planarization (CMP), and wafer temporary bonding for CNTs as TSVs in the 3-D stacking connection. The flexibility for this demonstrated process flow makes the integration of real high dense devices and CNTs as TSVs for the 3-D connection more easily.