Current Issue : October - December Volume : 2012 Issue Number : 4 Articles : 5 Articles
Biological cilia are found on surfaces of some microorganisms and on surfaces of many eukaryotic cells where they interact with\r\nthe surrounding fluid. The periodic beating of the cilia is asymmetric, resulting in directed swimming of unicellular organisms or in\r\ngeneration of a fluid flow above a ciliated surface in multicellular ones. Following the biological example, externally driven artificial\r\ncilia have recently been successfully implemented as micropumps and mixers. However, biomimetic systems are useful not\r\nonly in microfluidic applications, but can also serve as model systems for the study of fundamental hydrodynamic phenomena in\r\nbiological samples. To gain insight into the basic principles governing propulsion and fluid pumping on a micron level, we investigated\r\nhydrodynamics around one beating artificial cilium. The cilium was composed of superparamagnetic particles and driven\r\nalong a tilted cone by a varying external magnetic field. Nonmagnetic tracer particles were used for monitoring the fluid flow\r\ngenerated by the cilium. The average flow velocity in the pumping direction was obtained as a function of different parameters,\r\nsuch as the rotation frequency, the asymmetry of the beat pattern, and the cilium length. We also calculated the velocity field\r\naround the beating cilium by using the analytical far-field expansion. The measured average flow velocity and the theoretical\r\nprediction show an excellent agreement...
The VLS (vapor-liquid-solid) method is one of the promising techniques for growing vertical III-V compound semiconductor\r\nnanowires on Si for application to optoelectronic circuits. Heterostructures grown in the axial direction by the VLS method and\r\nin the radial direction by the general layer-by-layer growth method make it possible to fabricate complicated and functional threedimensional\r\nstructures in a bottom-up manner. We can grow some vertical heterostructure nanopillars with flat tops on Si(111)\r\nsubstrates, and we have obtained core-multishell Ga(In)P/GaAs/GaP nanowires with flat tops and their air-gap structures by using\r\nselective wet etching. Simulations indicate that a high-Q factor of over 2000 can be achieved for this air-gap structure. From\r\nthe GaAs growth experiments, we found that zincblende GaAs without any stacking faults can be grown after the GaP nanowire\r\ngrowth. Pillars containing a quantum dot and without stacking faults can be grown by using this method. We can also obtain\r\nflat-top pillars without removing the Au catalysts when using small Au particles....
Ordered mesoporous, crystalline MgTa2O6 thin films with a mesoscopic nanoarchitecture were synthesized by evaporation-induced\r\nself-assembly (EISA) in combination with a solââ?¬â??gel procedure. Utilization of novel templates, namely the block copolymers KLE\r\n(poly(ethylene-co-butylene)-b-poly(ethylene oxide)) and PIB6000 (CH3C(CH3)2(CH2C(CH3)2)107CH2C(CH3)2C6H4O-\r\n(CH2CH2O)100H), was the key to achieving a stable ordered mesoporous structure even upon crystallization of MgTa2O6 within the\r\nmesopore walls. The effect of the calcination temperature on the ability of the mesoporous films to assist the photodegradation of\r\nrhodamine B in water was studied. As a result, two maxima in the photocatalytic activity were identified in the calcination temperature\r\nrange of 550ââ?¬â??850 Ã?°C, peaking at 700 Ã?°C and 790 Ã?°C, and the origin of this was investigated by using temperature-dependent\r\nX-ray scattering. Optimal activity was obtained when the mesoporous film was heated to 790 Ã?°C; at this temperature, crystallinity\r\nwas significantly high, with MgTa2O6 nanocrystals of 1.6 nm in size (averaged over all reflections), and an ordered mesoporous\r\nstructure was maintained. When considering the turnover frequency of such photocatalysts, the optimized activity of the present\r\nnanoarchitectured MgTa2O6 thin film was ca. four times that of analogous anatase TiO2 films with ordered mesopores. Our study\r\ndemonstrated that high crystallinity and well-developed mesoporosity have to be achieved in order to optimize the physicochemical\r\nperformance of mesoporous metal-oxide films....
We review the use of self-assembled, vertically oriented one-dimensional (1D) titania nanowire and nanotube geometries in several\r\nthird-generation excitonic solar cell designs including those based upon bulk heterojunction, ordered heterojunction, F�¨orster\r\nresonance energy transfer (FRET), and liquid-junction dye-sensitized solar cells (DSSCs)....
We report a low-cost, mask-free, reduced material wastage, deposited technology using transparent, directly printable, air-stable\r\nsemiconductor slurries and dielectric solutions.We have demonstrate an emerging process for fabricating printable transistors with\r\nZnO nanoparticles as the active channel and poly(4-vinylphenol) (PVP) matrix as the gate dielectric, respectively, and the inkjetprinted\r\nZnO TFTs have shown to exhibit the carrier mobility of 0.69 cm2/Vs and the threshold voltage of 25.5V. We suggest that\r\nthe printable materials and the printing technology enable the use of all-printed low-cost flexible displays and other transparent\r\nelectronic applications....
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