Nanotube Membranes Research Articles

Preparation of reduced graphene oxide-carbon nanotubes membranes for conductive heating membrane distillation treatment of humic acid

Membrane distillation (MD) has attracted extensive attention as a technology to solve water scarcity in the fields of desalination. Surface-heated membrane distillation techniques that have emerged in recent years have improved flux due to the elimination of temperature polarization, but still suffer from membrane fouling. The use of electrochemical techniques for in-situ cleaning of membrane fouling in MD is expected to be an effective solution. Herein, electroactive membranes were prepared by loading mixtures of reduced graphene oxide (rGO) and carbon nanotube (CNT) with four mass ratios on polytetrafluoroethylene (PTFE) hydrophobic membranes. A series of analytical methods, such as scanning electron microscopy, atomic force microscopy, pore size analysis, water contact angle, Raman spectroscopy, membrane surface zeta potential, and cyclic voltammetry curve, were employed to characterize the properties of the rGO-CNT membranes. The best separation performance and conductivity were achieved at a 2:1 mass ratio of rGO to CNTs (R2 membrane). Then, the rGO-CNT membranes were applied to a conductive heating vacuum membrane distillation system to treat humic acid (HA). Compared with the PTFE membrane, the four rGO-CNT membranes showed a significant improvement in the rejection of HA. Using the rGO-CNT membranes as the cathode and the titanium as the anode, after a certain potential was applied, the flux decreases slowly. The fluxes of all rGO-CNT membranes were maintained over 9.5 kg/(m2·h) for 10 h of continuous operation. An increase in potential helps to increase change by alleviating membrane fouling. The highest flux and HA rejection reached 13 kg/(m2·h) and 99.8 %, respectively, with R2 membrane and −5 V potential applied. The mechanism of antifouling included electrostatic repulsion and electrocatalytic oxidation.

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

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

In-situ photothermal activation of peroxydisulfate in a carbon nanotubes membrane-based flow-by reactor toward degradation of contaminants.

The energy-induced peroxydisulfate (PDS) activation is a green and effective approach for pollutant degradation, while the huge energy consumption would significantly increase the cost of wastewater treatment. In this study, by taking carbon nanotubes (CNTs) membrane as the light to heat (LTH) conversion materials, we developed a photothermal PDS activation process for degradation of organic contaminants in a flow-by reactor, with hydroxyl radicals (•OH) and sulfate radicals (SO4•-) as the main reactive species. This system has excellent in-situ LTH conversion performance and heat transfer ability. As a result, various pollutants are degraded with an efficiency higher than 90%. More importantly, the LTH device exhibits satisfying stability and could be used for pollutant (i.e., methyl orange (MO)) removal under solar irradiation. In addition, some important factors (i.e., irradiation distance, residence time, solution pH, and PDS dosage) that might significantly influence the removal efficiency of pollutants are optimized. This work provides a novel perspective for the activation of PDS via CNTs as photothermal materials for pollutant degradation with a flow-by reactor.

Performance and mechanism of removal of antibiotics and antibiotic resistance genes from wastewater by electrochemical carbon nanotube membranes.

Electrochemical carbon nanotube (CNT) and carboxylated carbon nanotube (CNT-COOH) membranes were prepared by vacuum filtration for the removal of antibiotics and antibiotic resistance genes (ARGs) from water. Scanning electron microscopy and energy-dispersive spectroscopy were used to analyze the performances of the two electrochemical membranes in the removal of antibiotics and ARGs, to determine the effects of different factors on removal rates, and to explore the mechanisms of the removal of antibiotics and ARGs. The results showed that CNT-COOH formed a porous mesh structure on the surface of polytetrafluoroethylene membrane and contained more oxygen than CNT. The electrochemical CNT-COOH membrane showed higher antibiotic and ARG removal rates than the electrochemical CNT membrane, with an antibiotics removal rate of 82% after 60 min of reaction and an ARGs concentration decrease by 1.85 log. The removal rate of antibiotics and ARGs increased with the increase in electrolyte concentration and anode voltage but decreased with the increase in the influent flow rate. The removal rate of antibiotics decreased with the increase in pH, while the best removal rates of ARGs were observed in a neutral environment. The degradation mechanism of antibiotics on the electrochemical CNT-COOH membrane was analyzed, and possible antibiotic degradation pathways were proposed. The removal of antibiotics and ARGs mainly occurred through electrochemical degradation, where hydroxyl radicals (-OH) played a dominant role.

Carbon nanotube membranes for the separation of Li+ and Mg2+ ions: Effect of functional groups with charges

Non-equilibrium molecular dynamics simulations were employed to explore the Mg2+/Li+ separation efficiency of pristine and functionalized carbon nanotubes (CNT) for the MgCl2/LiCl solution. It is initially found that the dehydration degree of the first shell of Li+ near the mouth of pristine CNT membrane is greater than that of Mg2+, so the energy barrier for Mg2+ entering CNT membrane is generally smaller than the counterpart of Li+, emphasizing the potential of CNTs for the separation of Mg2+/Li+. Further, Mg2+ experiences greater attraction from the CNT membrane coated with carboxyl groups relative to Li+, which further enhances the permeability of Mg2+ over Li+. Therefore, the carboxyl-CNT membrane demonstrates enhanced Mg2+/Li+ selectivity compared to the pristine CNT membranes. Nevertheless, for the CNT membrane grafting with amino groups, the Mg2+ undergoes enhanced repulsion from the CNT mouth relative to Li+, so the retention time of Mg2+ at the fluid-CNT interface is increased, which makes the amino-CNT membrane to preferentially passing through Li+. Consequently, the Mg2+/Li+ selectivity is reduced in amino-CNT membrane, with respect to the pristine CNT membrane. It is also found that while the selectivity of Mg2+/Li+ increases with the external driving force for the pristine and carboxyl-CNT membranes, the amino-CNT membrane undergoes an opposite trend with the driving force. We note that in all the cases considered, the CNT membranes mounted with carboxyl groups deliver the best Mg2+/Li+ separation efficiency for carrying negative charges at the pore mouth. Our findings could facilitate the development in membrane design for efficient Mg2+/Li+ separation.

Renewable single-walled carbon nanotube membranes for extreme ultraviolet pellicle applications

We propose a facile, cost-efficient, environmentally friendly, and scalable process to renew single-walled carbon nanotube membranes serving as extreme ultraviolet (EUV) protective pellicles. The method comprises of high-temperature treatment of the membrane by Joule (resistive) heating at temperatures higher than 1000 °C and pressure below 0.3 Pa. Using model Sn aerosol nanoparticles, the primary contaminant from extreme ultraviolet light sources, we demonstrate the proposed method to clean the membrane with the power consumption as low as 20 W/cm2. We show the proposed method to cause no harm to carbon nanotube structure, opening a route towards multiple membrane renovation. We confirm the applicability of the approach using in situ deposition from the semi-industrial EUV light source and subsequent Sn-based contaminant removal, which restores the EUV-UV-vis-NIR transmittance of the film and, therefore, the light source performance. The proposed method supports pulse-cycling opening an avenue for enhanced protection of the lithography mask and stable performance of the EUV light source. Additionally, the approach suits other composite contaminants based on such species as Pb, In, Sb, etc.

Multiwalled Carbon Nanotube-Based Freestanding Filters for Efficient Removal of Fine Particulate Matters (PM0.3), Microplastics (MP0.3), and Bioaerosols

Air pollution caused by various hazards such as particulate matters (PM), microplastics (MP), bioaerosols (BA), etc. has become a global concern for public health across the globe. In recent decades, nanofiltration-based air purification techniques have rapidly evolved as a viable solution to address worldwide air pollution challenges. Herein, we report a simple, cost-effective, and scalable technique for the fabrication of lightweight, freestanding, and flexible multiwalled carbon nanotube (MWCNT) membranes for air filter applications. The developed membrane filter possesses excellent capturing efficiency of more than 99% for PM0.3, MP0.3, and BA. Additionally, the developed membrane has also been well investigated in terms of hydrophobic behavior (contact angle ∼148 ± 7°), narrow pore size (∼16 nm), packing density (∼0.65 g/cc), porosity (∼56%), pressure drop (∼139.7 Pascal), flexibility, and reusability, reflecting its self-cleaning feature, physical sieve characteristics, adaptability, and commercialization. Thus, the filter developed in this work shows its potential utility toward the removal of indoor pollution and in air filter industries as well.

The Cation Role in Ion Transport Selectivity of Gold-Plated Nanotubes

Ion permselectivity is an important ionic transport property exhibited in nanopores and nanotubes. Permselectivity develops due to the strong interactions between ions in solution and the nanopore/nanotube surfaces. Here, we study the ion permselectivity of gold-plated nanotube membranes. Gold-plated membranes were obtained by using an electroless gold plating method to deposit gold nanotubes into the pores and on the faces of track-etched polycarbonate membranes. These membranes have the potential to display cation permselectivity due to the excess surface charge density present on the membrane from chemisorbed Cl- anions. The cation permselectivity of membranes with 9.9 + 0.6 nm diameter nanotubes was studied potentiometrically by using a concentration cell. A new Debye-sphere based model was presented here to describe the extent of permselectivity. However, some ion specific effects with the gold-plated membrane are observed that cannot be interpreted by Debye theory. These ion-specific surface interactions lead to a reduction in the negative surface charge, causing no permselectivity for some cations as demonstrated by their lower than ideal cation transference numbers. Quantification of the surface charge density by XPS indicated the gold-plated membranes are highly charged due to Cl- chemisorption with a surface charge density of ~ 5.3 uC per cm2 corresponding to 3.3 x 1013 Cl--ions per cm2.

Highly specific differentiation of MSCs into neurons directed by local electrical stimuli triggered wirelessly by electromagnetic induction nanogenerator

Transdifferentiation of mesenchymal stem cells (MSCs) into neurons provides a practical way for neurodegenerative diseases as alternatives to neural stem cells, but is confronted with challenges to get well-differentiated and mature neurons. In this work, a wirelessly triggered local electrical stimulation system was established to specifically induce neuronal differentiation from rat bone-marrow-derived MSCs (rBMSCs) by coupling a highly conductive and flexible multi-wall carbon nanotube (MWCNT) membrane with a rotating magnetic field. Without nerve-inducing factors, a nearly 100% yield of differentiated neurons was realised without the presence of astrocyte cells by the localized electrical stimuli mediated from electromagnetic induction nanogenerator. Neuronal functions were revealed by rapid spontaneous [Ca2+] i-transient peaks under neurotransmitter action. This novel therapeutic strategy for neurodegenerative disease was further demonstrated in vivo, where the successful neural differentiation of exogenous rBMSCs driven by external magnetic-filed accelerated the brain recovery. This wireless electric stimulation system shows promising effects on neuron differentiation and offers a new perspective in nerve repair without glial scarring.

Effects of modification groups and defects on the desalination performance of multi-walled carbon nanotube (MWNT) membranes

Like single-wall carbon nanotubes (SWNTs), multi-wall carbon nanotubes (MWNTs) have channels for selective separation of ions. Moreover, MWNTs have the advantages of simpler preparation and lower cost, potentially allowing wider applications in the desalination industry. In this study, the transport of water and ions inside two types of MWNTs, i.e., double-wall carbon nanotubes (DWNTs) and tri-wall carbon nanotubes (TWNTs) were investigated using non-equilibrium molecular dynamics simulations. Modification groups, including carbon chains of different lengths and types with hydrophilic groups like carboxylate anion (COO–), and ammonium (NH3+), were used to improve the salt rejection performance. The simulation results suggest that 100% salt rejection could be achieved by adding different modification groups to various MWNTs ranging from 13 to 20 Å. More importantly, this study demonstrates that MWNT membranes with 100% desalination have water fluxes that are 10–30% greater than that of SWNT membranes with 100% desalination, implying the greater potential of MWNTs as building blocks towards next-generation desalination membranes. Additionally, even though all real-world carbon nanotubes (CNTs) have a certain amount of defects from the production process, most previous molecular model studies of water and ions transport in CNTs assumed that CNTs were perfect and defect-free. This study shows for the first time that CNTs with defects have improved salt rejection rates than perfect carbon nanotubes, although the former have lower water fluxes than the latter.

Interception of volatile organic compounds through CNT electrochemistry of electrified membrane surface during membrane distillation

The unimpeded transport of volatile organic compounds (VOCs) in the membrane distillation (MD) greatly restricts its application in treating industrial wastewater treatment. Herein, an electrically MD process (E-MD) was conducted by coupling electrified carbon nanotube (CNT) membrane for the VOCs intercept test. This work systematically investigated membrane characteristic, the intercept efficiency and mechanism of VOCs in the E-MD. The results showed that CNT significantly promoted conductivity and permeate performance of the membrane. The transport of 7 VOCs across the membrane was highly correlated with their molecular weights and hydrophobicity. By applying a low voltage of 3.0 V on the membrane surface, the distilled VOCs concentrations were efficaciously reduced. Meanwhile, the distilled phenol concentration was only 0.15 mg/L in the E-MD, 62 times lower than that in standard MD. Moreover, the cathodic CNT and anodic CNT modes were adopted, which exhibited different intercept efficiencies. Compared with the cathodic CNT, the anodic CNT mode was superior in intercepting VOCs but with poor stability due to electrochemical byproducts induced CNT fouling. As revealed by mechanism investigation, direct electrooxidation and electropolymerization contributed to the VOCs intercept under the anodic CNT mode. By contrast, the favorable intercept efficiency under the cathodic CNT mode was mainly ascribed to the locally elevated pH near the CNT surface achieved through water electrolysis. At an elevated pH, phenol compounds were substantially ionized, and were therefore more favorably intercepted by the electronegative CNT networks of membrane surface. This study emphasizes the application potential of electrified MD membranes in reducing noxious VOCs of the cold stream.

Molecular simulation of modified large interstice outer wall carbon nanotube membrane and its desalination behavior

Large size interstices of carbon nanotube arrays have been proved to exhibit extremely higher water permeation. However, ion retention is still a big problem if the gap is to be used in desalination. Herein, nonequilibrium molecular dynamics simulations were applied to investigate water and ions transport among the different-size (9 Å, 11 Å, 13 Å, and 15 Å) interstices of outer wall membrane of the (10, 10) CNT array. Modifications were performed to improve salt rejection. The modifications included different lengths and types of carbon chains with hydrophilic COO– or NH3+. Simulation results revealed that 100% salt rejection can be achieved by using different functional groups for the outer wall CNT membrane with 9 Å, 11 Å, 13 Å and 97.24% for 15 Å interstices. Importantly, the water fluxes through the interstice (9 Å, 11 Å, 13 Å, and 15 Å) of the outer wall CNT membrane with high desalination were 3.43, 4.52, 5.95 and 5.49 times higher of than that of closely packed modified (10,10) CNT membrane with 100% desalination, respectively, implying the great potential of the interstice array of CNT as building blocks for the preparation of next-generation desalination membranes.

Filtration and adsorption of tetracycline in aqueous solution by copper alginate-carbon nanotubes membrane which has the muscle-skeleton structure

Recently, removal of antibiotic contaminants such as tetracycline (TC) from wastewater has been widely studied. In this study, we innovatively used copper alginate as the substrate and carbon nanotubes (CNTs) as the framework to obtain copper alginate-carbon nanotubes (CA-CNTs) composite membrane which has the “muscle-skeleton” structure after vacuum freeze-drying, cross-linking reaction and natural drying. Its performance on TC removal was verified from both filtration and adsorption. As shown by various analytical methods, the prepared composite membranes have good filtration and adsorption performance, with a maximum filtration removal rate of 95.03 % and a maximal adsorption capacity of 230.17 mg·g−1 at 318 K. The adsorption equilibrium data were well in accordance with the Langmuir isothermal model and the pseudo-second-order kinetic model. In addition, the thermodynamic analysis showed that the adsorption action of TC by CA-CNTs membranes was spontaneous and endothermic. In terms of principle and mechanism, copper alginate (CA) and CNTs were mainly bonded by hydrogen bonds, and the adsorption of TC was mainly accomplished by hydrogen bonds, cation bonding bridges and n-π EDA interactions. Meanwhile, it still had good adsorption performance after five regeneration cycles. Therefore, the prepared composite membrane has a good prospect in the application of TC removal.

Effect of the presence of various natural organic matters on anodic oxidation of electrified carbon nanotube membrane.

The widespread adoption of electrified carbon nanotube membranes (ECM) requires to better understand process effectiveness according to limiting phenomena of natural organic matters (NOMs). In this study, the influences of various NOM fractions were investigated on the oxidative degradation of Rhodamine B (RhB) in ECM. The results showed the decolorizing efficiencies of RhB in the presence of humic acid (HA) were still above 96%, while bovine serum albumin (BSA) reduced firstly and then increased the decolorizing efficiencies of RhB. The decolorizing efficiencies of RhB with alginate (AA) were over 98% at the first 15 min but decreased gradually to 76% after 150 min. These different performances of HA, BSA and AA were mainly due to their influences on the electrochemical reactivity characterization of ECM. ECM with the BSA depositing layer showed the highest exchange current density (j0), while the AA depositing layer restrained electron-transfer activity of ECM. Cyclic voltammetry (CV) experiments showed that the partial electrooxidation of BSA would occur in ECM with its degradation product observed in the effluent. The variation of electrochemical reactivity characterization of ECM resulted into its electri-oxidation and electri-adsorption rates to be the largest with BSA, followed by AA and HA.

Coupled electrochemical transformation and filtration of water pollutants by cathodic-carbon nanotube membranes

This study aimed at evaluating the concomitant electrochemical reduction and separation of organic and inorganic model contaminants from water. A highly conductive (40,000 S/m) support free carbon nanotube (CNT) membrane was used as a cathode in a three-electrode electrochemical crossflow membrane filtration system. Diatrizoate (DTZ), a recalcitrant iodinated contrast media; resazurin (RZ), a redox indicator; and hexavalent chromium ion (Cr(VI)), a ‘gold’ standard for characterization of reducing systems, were tested as model contaminants. Voltages of −0.6 to −1.0 V were enough to remove between 90% and 95% of the three model contaminants tested. Removal of Cr(VI) proceeded by reduction to Cr(III) followed by adsorption onto the cathode, which could be efficiently regenerated (up to 95%) applying reversal (anodic) potential. Preliminary findings applying AC current (0.6–1.5 V, 10 Hz-1 kHz) suggest that it could be a feasible approach for detoxification with minimization of membrane clogging. Resazurin was immediately transformed into resorufin to near completion which was in turn further reduced to dihydroresorufin. The reductive transformation of DTZ resulted in almost complete deiodination, leading to the accumulation of 3,5-diacetamidobenzoic acid as the main end-product. Although other five secondary transformation products were detected, four of them were fully deiodinated. Concluding, the proposed electrochemical filtration cell equipped with a highly conductive CNT-cathodic membrane can be regarded as a potential technique for water decontamination and effective dehalogenation of organic compounds.

Asymmetric Cellulose/Carbon Nanotubes Membrane with Interconnected Pores Fabricated by Droplet Method for Solar-Driven Interfacial Evaporation and Desalination.

Solar-driven interfacial water purification and desalination have attracted much attention in environmentally friendly water treatment field. The structure design of the photothermal materials is still a critical factor to improve the evaporation performance such as evaporation rate and energy conversion efficiency. Herein, an asymmetric cellulose/carbon nanotubes membrane was designed as the photothermal membrane via a modified droplet method. Under 1 sun irradiation, the evaporation rate and energy efficiency of pure water can reach up to 1.6 kg m−2 h−1 and 89%, respectively. Moreover, stable reusability and desalination performance made the cellulose/carbon nanotubes membrane a promising photothermal membrane which can be used for solar-driven desalination.

Polyethersulfone Blended with Titanium Dioxide Nanoribbons/Multi-Wall Carbon Nanotubes for Strontium Removal from Water.

Nanofiltration methods were used and evaluated for strontium removal from wastewater. The phase inversion method was used to create a variety of polyethersulfone (PES)/TiO2 nanoribbons (TNRs)–multi-walled carbon nanotubes (MWCNTs) membranes with varied ratios of TNR-MWCNT nanocomposite. The hydrothermal technique was applied to synthesize the nanocomposite (TNRs-MWCNTs), which was then followed by chemical vapor deposition (CVD). The synthesized membranes were characterized by scanning electron microscopy (SEM), transmission electron microscopy, and FTIR. TNR macrovoids are employed as a support for the MWCNT growth catalyst, resulting in a TNR-MWCNT network composite. The hydrophilicity, mechanical properties, porosity, filtration efficiency of the strontium-containing samples, water flux, and fouling tendency were used to assess the performance of the synthesized membranes. The effect of feed water temperature on water flux was investigated as well as its effect on salt rejection. As the temperature increased from 30 to 90 °C, the salt rejection decreased from 96.6 to 82% for the optimized 0.7 PES/TNR-MWCNT membrane, whereas the water flux increased to ≈150 kg/m2. h. Double successive filtration was evaluated for its high efficiency of 1000 ppm strontium removal, which reached 82.4%.

Preparation of structured N-CNTs/PSSF composite catalyst to activate peroxymonosulfate for phenol degradation

Four different types of structured nitrogen-doped carbon nanotube membranes (C50, NC25, NC50, N25C25) were used as metal-free catalysts for phenol degradation. Firstly, nitrogen-doped carbon nanotubes were prepared on paper-like sintered stainless steel fibers (PSSF) by chemical vapor deposition using melamine and acetylene as dual precursors, then the nitric acid was used to remove amorphous carbon and catalyst particles in the tubes. Subsequently, TEM, XPS, N2 adsorption and desorption and other characterization techniques were used to investigate the structure and morphology of the catalysts. Characterization results showed that the use of dual precursor could well adjust the nitrogen content in carbon nanotubes, and nitrogen doping could change the hollow structure of carbon nanotubes into rough bamboo-like and corrugated structure. Meanwhile, acid treatment significantly increased the specific surface area, among which the value of HN25C25 reached 38.15 m2/g. Pristine and acid-treated catalysts were then used to activate peroxymonosulfonate (PMS) in a structured fixed bed reactor. NC25 and N25C25 were able to mineralize 46% and 17.5% of phenol at 1 h, but the TOC conversion rate only maintained at about 10% in the subsequent reaction time. After acid treatment, HNC25 and HN25C25 were able to mineralize up to 76% and 84% of phenol, and the TOC conversion rate maintained at about 70% within 7 h. the high leaching of Fe in the acid-treated catalysts could be attributed to the formation of small carboxylic acids and the destruction of the PSSF support during the reaction. At last, radical inhibition experiments and ESR spectra showed that sulfate radicals and hydroxyl radicals were the main active species in the reaction. The increase in the proportion of active nitrogen species and the improvement in contact efficiency could explain the higher mineralization efficiency of phenol catalyst after acid treatment.

Development of Carbon Nanotubes (CNTs) Membrane from Waste Plastic: Towards Waste to Wealth for Water Treatment

Plastic, a non-biodegradable material has always been a concern to the environment and people. This single-use item generates waste to landfills and it persists for centuries once disposed. The urge of transforming such material into a highly valuable product has sought attention from many researchers. This study emphasizes on a nanotechnological approach to synthesize vertically-aligned carbon nanotubes (CNTs) on a substrate template using commercially available plastic bags as carbon precursor. CNTs are grown inside a hexagonally arranged nanoporous anodic alumina membranes (NAAMs). CNTs are liberated by wet chemical etching to dissolve the alumina matrix. The resulting CNTs are used as adsorption media filters for water treatment purpose. The high adsorption affinity towards heavy metals, organic matters and microbes, ability to antifouling and self-cleaning function have made CNTs a better choice over others. This article briefly discusses the catalyst-free synthesis, growth mechanism, characterization and functionalization of CNTs for water treatment application.

Single-Walled Carbon Nanotube Membranes Accelerate Active Osteogenesis in Bone Defects: Potential of Guided Bone Regeneration Membranes.

Carbon nanotubes (CNTs) are potentially important biomaterials because of their chemical, physical, and biological properties. Our research indicates that CNTs exhibit high compatibility with bone tissue. The guided bone regeneration (GBR) technique is commonly applied to reconstruct alveolar bone and treat peri-implant bone defects. In GBR, bone defects are covered with a barrier membrane to prevent the entry of nonosteogenic cells such as epithelial cells and fibroblasts. The barrier membrane also maintains a space for new bone formation. However, the mechanical and biological properties of materials previously used in clinical practice sometimes delayed bone regeneration. In this study, we developed a CNT-based membrane for GBR exhibiting high strength to provide a space for bone formation and provide cellular shielding to induce osteogenesis. The CNT membrane was made via the dispersion of single-walled CNTs (SWCNTs) in hyaluronic acid solution followed by filtration. The CNT membrane assumed a nanostructure surface due to the bundled SWCNTs and exhibited high strength and hydrophilicity after oxidation. In addition, the membrane promoted the proliferation of osteoblasts but not nonosteogenic cells. CNT membranes were used to cover experimental bone defects made in rat calvaria. At 8 weeks after surgery, more extensive bone formation was observed in membrane-covered defects compared with bone defects not covered with membrane. Almost no diffusion of CNTs was observed around the membrane. These results indicate that the CNT membrane has adequate strength, stability, and surface characteristics for osteoblasts, and its shielding properties promote bone formation. Demonstration of the safety and osteogenic potential of the CNT membranes through further animal studies should facilitate their clinical application in GBR.