One step fabrication of aligned carbon nanotubes using gas rectifier.

We report the one-step fabrication of aligned and high-quality carbon nanotubes (CNTs) using floating-catalyst chemical vapor deposition (FCCVD) with controlled fluidic properties assisted by a gas rectifier. The gas rectifier consists of one-dimensional straight channels for regulating the Reynolds number of the reaction gas. Our computational fluid dynamics simulation reveals that the narrow channels of the gas rectifier provide steady and accelerated laminar flow of the reaction gas. In addition, strong shear stress is induced near the side wall of the channels, resulting in the spontaneous formation of macroscopic CNT bundles aligned along the direction of the gas flow. After a wet-process using chlorosulfonic acid, the inter-tube voids inherently observed in as-grown CNT bundles are reduced from 16 to 0.3%. The resulting CNT fiber exhibits a tensile strength of 2.1 ± 0.1 N tex-1 with a Young's modulus of 39 ± 4 N tex-1 and an elongation of 6.3 ± 0.6%. FCCVD coupled with the strong shear stress of the reaction gas is an important pre-processing route for the fabrication of high-performance CNT fibers.

Development of Pure Silica CHA Membranes for CO2 Separation.

Thin pure-silica chabazite (Si-CHA) membranes have been synthesized by using a secondary growth method on a porous silica substrate. A CO2 permeance of 2.62 × 10-6 mol m-2 s-1 Pa-1 with a CO2/CH4 permeance ratio of 62 was obtained through a Si-CHA membrane crystallized for 8 h using a parent gel of H2O/SiO2 ratio of 4.6. The CO2 permeance through the Si-CHA membrane on a porous silica substrate was twice as high as that through the membrane synthesized on a porous alumina substrate, which displayed a similar zeolite layer thickness.

Blood compatibility and tissue responsiveness on simple and durable methylsiloxane coating.

This study was conducted to evaluate the blood compatibility and tissue responsiveness of methylsiloxane (MS)-coated inorganic (glass and metal) substrates both in vitro and in vivo. MS was prepared from methyltriethoxysilane (MTES) through hydrolysis of a sol-gel solution at 80 °C. The adhesive strength of the MS coating was evaluated by using a tear-off test, revealing that the MS strongly adhered to the surface of the inorganic substrates. Blood compatibility was evaluated by assessing platelet adhesion and blood plasma coagulation time. The platelet aggregation ratio of the MS-coated glass tube was reduced to 10%, which was much smaller than that of the coating-free glass tubes (99%) and conventional blood-compatible polystyrene (PS) tubes (18%). Coagulation time was measured by active partial thromboplastin time (APTT) test, which showed that MS coating is as inert as PS in activating blood coagulation factor XII. Tissue responsiveness to the bulk MS sample, evaluated by animal test, showed a desirable compatibility comparable to that of the control titanium sample. This study indicated that MS coating is readily available to convert inorganic materials to useful biomaterials that have suitable mechanical strength and are compatible with blood and tissue.

Regulation of the protein-loading capacity of hydroxyapatite by mercaptosuccinic acid modification.

Loading and releasing protein in a controllable way is extremely important for the protein vehicles used in bone tissue engineering. To obtain a suitable carrier material for basic proteins, such as BMP or bFGF, hydroxyapatite particles containing mercaptosuccinic acid (mercaptosuccinic acid (Mer), (Mer-HAp)) were synthesized. Physicochemical evaluation of Mer-HAp suggested that Mer was contained in HAp particles: it either simply adsorbed onto HAp crystals or was trapped among the HAp crystals. A protein adsorption study using basic and acidic model proteins indicated that the synthesized Mer-HAp had selective loading properties of the basic protein. The loaded protein was gradually released from Mer-HAp in phosphate buffered saline. The protein release rate was different in each Mer-HAp synthesized with a different concentration of Mer. In addition, the protein release from Mer-HAp showed a similar profile with the Ca dissolution in different pH solutions, indicating that the Mer-HAp dissolution was concerned with the protein release from Mer-HAp. Thus, Mer-HAp is a useful candidate for the basic protein carrier because it has properties which enable the loading and releasing of protein in a controllable way.

Bioactive titanate nanomesh layer on the Ti-based bulk metallic glass by hydrothermal-electrochemical technique.

Titanate nanomesh layers were fabricated on Ti-based bulk metallic glass (BMG) to induce bioactivity in the form of apatite-forming ability. Titanate nanomesh layers were prepared by hydrothermal-electrochemical treatment at 90 degrees C for 2 h, with an aqueous solution of NaOH as an electrolyte. A constant electric current of 0.5 mA cm(-2) was applied between the BMG substrate and a Pt electrode acting as the anode and cathode, respectively. A nanomesh layer, consisting of nanowires (approximately 20 nm in diameter) formed on the BMG. An immersion test in simulated body fluid for 12 days revealed that the titanate nanomesh layer on the BMG promoted the growth of bone-like hydroxyapatite.