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Here, we report a generic synthetic approach to rationally design multiply connected and hierarchically branched nanopores inside anodic aluminum oxide templates. By using these nanochannels, we controllably fabricate a large variety of branched nanostructures, far more complex than what exists today. These nanostructures include carbon nanotubes and metallic nanowires having several hierarchical levels of multiple branching. The number and frequency of branching, dimensions, and the overall architecture are controlled precisely through pore design and templated assembly. The technique provides a powerful approach to produce nanostructures of greater morphological complexity, which could have far-reaching implications in the design of future nanoscale systems.T he design and controlled synthesis of complex nanowire (1-5) and carbon nanotubes (CNTs) (6-8) will impact developments in nanotechnology applications. The present synthesis approaches, however, limit the degree of complexity that can be controllably configured into these structures. Fabrication inside rationally designed porous templates [such as anodic aluminum oxide (AAO) templates] is ideal to produce nanowire morphologies, but this feat has been accomplished controllably only for linear (9-15) and Y-shaped (6, 7) architectures. The creation of controlled pore structure, with various levels of complexity, inside these templates provides a powerful way to produce predesigned multiply connected and branched nanowires and nanotubes. We have developed a rational approach for creating hierarchically branched nanoporous AAO templates and have fabricated a whole generation of branched nanowires and nanotubes inside these templates. As a suitable example, we detail the case of CNT structures in this work, but other material systems can also be made into similar architectures, as highlighted for the case of metallic nanowires in Materials and Methods. Materials and MethodsPreparation of AAO Templates. AAO templates were prepared by using a modified two-step anodization process (6, 16). The first-step anodization was the same for all templates. High-purity Al foils were anodized in 0.3 M oxalic acid solution at 8-10°C under a constant voltage (in the range of 40-72 V dc ) for 8 h. Then, the formed anodic aluminum layer was removed. In the second-step anodization, templates with different pore architectures underwent different processes of anodization as follows. AAO Templates with Multiple Generations of Y-Branched Pores.We reduced the anodizing voltage multiple times in the second-step anodization. Initially, the anodization was performed under the same conditions as those in the first step to create the primary stem pores; then, the anodizing voltage was reduced by a factor of 1͞ ͌ 2 to form Y-branched pores. Two-, three-, and fourgeneration Y-branched pores can be obtained by further sequential reduction of anodizing voltages. It is noted that if a subsequent anodizing voltage is Յ25 V, after any prior anodization, the samples should be washed in deionized w...

The present study demonstrates that novel nanocomposites consisting of blends of polylactic acid and carbon nanotubes effectively can be used to expose cells to electrical stimulation. When osteoblasts cultured on the surfaces of these nanocomposites were exposed to electric stimulation (10 microA at 10 Hz) for 6 h/day for various periods of time, there was a 46% increase in cell proliferation after 2 days, a 307% increase in the concentration of extracellular calcium after 21 consecutive days, and upregulation of mRNA expression for collagen type-I after both 1 and 21 consecutive days. These results provide evidence that electrical stimulation delivered through novel, current-conducting polymer/nanophase composites promotes osteoblast functions that are responsible for the chemical composition of the organic and inorganic phases of bone. Furthermore, this evidence elucidates aspects of the cellular/molecular-level mechanisms involved in new bone formation under electrical stimulation.

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This paper investigates the change in contact angle of droplets of fluid containing dispersed nanoparticles (nanofluid) functionalized with thioglycolic acid molecules as a function of the concentration and size of nanoparticles, and the quality and composition of the substrate material. Bismuth telluride nanoparticles with an average size ranging from 2.5 to 10.4 nm and functionalized with thioglycolic acid groups were grown by a microemulsion method and dispersed in water. Experimental measurements of the contact angle of nanofluid droplets cast on smooth glass and silicon substrates show that the contact angle depends strongly on nanoparticle concentration. Moreover, smaller size nanoparticles lead to larger changes in contact angle at the same mass concentration. These findings contribute to understanding the role of functionalized nanoparticles in surface wettability.