Micro and Nanosystems - Volume 5, Issue 4, 2013

Transparent conductive ZnO:Al:Mo films with a constant molar ratio of Zn: Al: Mo=99:0.99:0.01 were deposited on quartz glass substrate by a template-assisted sol-gel process and characterized by X-ray diffraction, atomic force microscopy, and UV-vis and luminescent spectrophotometries. The organic templates in precursor solution have induced the formation of nanorod microstructure with different aspect ratio for the films. The films with rodlike morphology show obviously blue shift and enhanced transmittance in the UV-visible light range. The PEG-1000 and PEG- 2000 have a better effect than the PEG-4000 and PVP as their addition amounts are equiponderant. The films a l so show strong ultraviolet, violet and bluish violet emissions. The templates lead to more native defects and thereby enhance photoluminescence at different degrees.

This paper presents analytical modeling of slip liquid flow in parallel-plate microchannels, and can be divided in two parts. In the first part, classical relationships describing velocity, flow rate, pressure gradient, and shear stress are extended to the more general cases where there exist two different values of the yet-unknown slip lengths at the top and bottom walls of the channel. These formulations can be used to experimentally determine the values of slip length on the channels fabricated from two different hydrophobic walls. In the second part, the emphasis is given on the quantification of the slip length analytically. Generating mechanism of slip is attributed to the existence of a low-viscosity region between the liquid and the solid surface. By extending the previous works, the analytical values of slip length are determined using exact, rather than empirical, values of air gap thickness at different ranges of air flow Knudsen number. In addition to the exact expressions of air gap thickness, the corresponding ranges of the channel height where slip flow can be induced are also found analytically. It is found that when the channel height is larger than 700 μm, air flow is in continuum regime and no-slip boundary condition can be used. For the case where the channels height is smaller than 700 μm, and larger than 7.5 μm, slip boundary condition should be used to model the air flow in the channel. Finally, for the channel with the height smaller than 7.5 μm, Navier-Stokes equation cannot be used to model the air flow, and instead molecularbased approaches should be implemented. The results of this paper can be used as a guideline for both experimentalists and theoreticians to study the slip flow in parallel-plate microchannels.

Mn vanadate microrods have been synthesized via a simple hydrothermal method using Mn acetate and sodium metavanadate as the raw materials, polyvinyl pyrrolidone (PVP) as the surfactant. X-ray diffraction (XRD) and scanning electron microscopy (SEM) observations show that the Mn vanadate microrods are composed of monoclinic MnV2o6 phase. The diameter of the microrods increases from 250 nm to 1µm with the increase of the PVP concentration from 0.1 to 10wt.%. Hydrothermal temperature plays an important role in the formation of the Mn vanadate microrods. The growth process of the Mn vanadate microrods has also been discussed according to a PVP-assisted growth process. Photocatalytic degradation of Rhodamine B (RB) is analyzed using the Mn vanadate microrods under visible light irradiation. RB is degraded about 55.42% after visible light irradiation for 4 h using 20 mg Mn vanadate microrods in 10 ml 2.5 mgL-1 RB solution.

Electrochemical machining has the potential to allow machining at the nanometer scale. A nano electrode is an essential tool in nano-electrochemical machining. In this paper, the mechanism of liquid membrane electrochemical etching is studied, and a processing platform is developed. The processing voltage, initial tungsten diameter and electrolyte concentration are control factors in nano electrode fabrication. An orthogonal experiment was conducted using these three processing parameters. Experimental results showed that the electrolyte concentration had the most significant effect on nano electrode fabrication, where the optimal machining parameters are the following: processing voltage of 6 V, initial tungsten diameter of 200 μm and potassium hydroxide electrolyte concentration of 1 mol/L. Using these optimal machining parameters, an 85 nanometers diameter tool electrode with an aspect ratio of 20 was obtained in several minutes. Successful nano electrode fabrication provides technological support and a theoretical basis for future research in nanoelectrochemical machining.

Three different power densities and fixed irradiation times have been used to prepare porous silicon using laserinduced etching process to control the size and shape of nanostructure. There are new optical properties of porous silicon. Scanning electron microscopy was used to study surface morphology after the etching process. Porous silicon was characterized using spectroscopic studies. There is shift in Raman peak position as a result of the increase of power densities. The photoluminescence spectra (PL) tend to blue shift in peak position due to etching conditions. Raman and PL data were explained using appropriate dimensional confinement of size and size distributions of nanocrystallites. There has been an agreement between the results of Raman and PL spectroscopic studies of the PS samples.

Nanotechnology is the study, design, creation, synthesis, manipulation, and application of functional materials, devices, and delivery systems through control of matter at the nanometer scale. These include nanovectors, nanotubes, nanosensors, nanowires and nanocantilever arrays, nanopores and nanoformulations. These advances will lead to significant applications relevant to the diagnosis, management, and in the treatment of many diseases. The application of nanotechnology has attracted much interest as a new approach to deliver poorly soluble drugs in the form of colloidal nano-dispersion “nanosuspension” due to flexibility in processing during manufacturing and benefits like, improvement in oral bioavailability, high drug loading, and targeting capabilities and so on. Nanosuspensions formulation was found to be an efficient delivery system for oral as well as non oral routes like parenteral, ocular, pulmonary and targeted delivery. In this article, we will highlight formulation aspects of nanosuspensions in the light of a brief introduction to the pharmaceutical technology and will summarize the application of nanosuspensions via a variety of administration routes.

The advent of nanotechnology has reignited interest in the lungs as a major route of drug delivery for both systemic and local treatments. As the end organ for the treatment of local diseases or as the route of administration for systemic therapies, the lung is a very attractive target for drug delivery. The large surface area and the minimal barriers impeding access to the lung’s periphery make this organ a suitable portal for a variety of therapeutic interventions. Pulmonary drug delivery is an alternative method to subcutaneous injection, and also intravenous injection. Pulmonary drug delivery system is also used for delivery of peptides and some sensitive drugs. It provides direct access to disease in the treatment of respiratory diseases, while providing an enormous surface area and a relatively low enzymatic, controlled environment for systemic absorption of medications. The formulation most commonly used for pulmonary delivery includes nanoparticles, liposomes, niosomes and microspheres. Among these, on one hand a lots of attention has been focused to improve the bioavailability of marketed drugs intended for respiratory diseases and to develop new concepts for pulmonary administration of drugs and, on the other hand, the pulmonary route used for systemic diseases. Nanoparticle formulations have many advantages over traditional dosage forms, such as potential to achieve relatively uniform distribution of drug dose among the alveoli, improved solubility of the drug, reduced dosing frequency, improvement in patient compliance, decrease in incidence of side effects, enhanced dissolution properties and the potential for intracellular drug delivery. Polymers have also been used to improve therapeutic effect, while minimizing side effect. Specifically, pure drug nanoparticles and polymeric nanoparticles offer some encouraging results for delivering drugs through the lungs. Traditional techniques such as spray drying, supercritical fluid extraction, precipitation and solvent extraction have been employed to produce nanoparticulate formulations for pulmonary delivery. Here, we review various aspects of nanoparticulate formulation along with characterization and their applications with recent review.

Shear- and pressure-driven gas flows are encountered in several Micro-Electro-Mechanical-Systems (MEMS) applications, where the fluid is usually trapped under or around the vibrating micromechanical structure in extremely narrow gaps. The thin gas film is responsible for damping in these oscillating microstructures and its properties are of great importance to design, optimize and fabricate improved minute devices. Under such conditions, when the smallest characteristic length of MEMS is comparable with (or smaller than) the mean free path of the gas molecules, the traditional computational fluid dynamics methods, based on the Euler or the Navier-Stokes equations, fail in predicting the flows related to these devices. Therefore, in the present investigation, we solve directly the linearized Boltzmann equation in order to evaluate the damping forces exerted on a general two-dimensional configuration of a real biaxial accelerometer where different sets of plates induce a Poiseuille-like flow (microstructures that move in the direction perpendicular to their surfaces) as well as a Couette-like flow (microstructures that move in the direction parallel to their surfaces). A set of numerical experiments has been carried out in order to predict the scaling of damping forces by varying the relative dimensions of the geometrical configuration of the microdevice and the properties of the particular gas flowing through it, at different working pressures.