Nano

Nanoscale patterning in block copolymer (BCP) thin films is one of the key issues in nanoscience and nanotechnology. To make useful nanoscale patterns in applications such as magnetic media, wire-grid polarizer, and opto-electronics, the control of orientation and lateral ordering of BCP microdomains is required. The generation of highly ordered and oriented cylindrical microdomains in BCP thin films will be discussed. This is followed by a review of applications of nanoscale patterns like fabrication of nanoporous templates, metallic nanowires, and the preparation of nanostructured inorganic materials.

The majority of active transport in cells is driven by two classes of intelligent nanomotors, kinesin and dynein. The intelligence of kinesin and dynein nanomotors is the key toward developing intelligent bio-nanosystems for various nanotechnological applications. The first step in this regard is the ability to determine the structure, behavior, and properties of basic bio-nanocomponents, such as proteins. Therefore, in this paper we have described structures and mechanisms of kinesin and dynein protein nanomotors. Kinesin and dynein nanomotors are multi-protein complexes which are responsible for various dynamical processes for transporting single molecules over small distances to cell movement and growth. They convert the chemical energy into mechanical work directly rather than via an intermediate energy. Kinesin and dynein protein nanomotors are self-guiding systems. They have evolved to enable movement on their polymer filaments, either on cellular or supra-cellular levels, to recognize the direction of movement. Kinesin and dynein nanomotors have different properties, but in the cell they are known to cooperate and even to compete with each others during their function. It has been indicated that kinesin and dynein nanomotors can be defined as ideal bio-nanocomponents for bio-nanorobotic systems because of their small size, perfect structure, smart and high efficiency.

In the present work, mass and position sensitivity of a nanocantilever is simulated using finite element analysis. Changes in resonant frequency of various modes of a polysilicon cantilever, with a gold coating of different thickness, area, and spatial distribution is simulated. It is found that for a uniform increase in gold coating thickness, torsional mode gives an order higher mass sensitivity than vertical bending and lateral bending modes. In other cases, sensitivity is highly dependent on the position of the coating and is explained on the basis of flexural rigidity. Apart from this, simulations were performed for a point mass (gold cube) loading at various positions along the length and width axis of the cantilever. Further, for localized mass loading, cantilever was tailored for enhanced sensitivity. It is found that by introducing a step discontinuity in thickness of the cantilever, the mass sensitivity increases by two orders of magnitude and it depends on the position of step from free end, step thickness, and step width.

Critical yarning conditions from vertically aligned carbon nanotubes (VACNTs) using a chemical vapor deposition have been investigated. VACNTs with a diameter of around 15 nm have been synthesized with a length up to 3.7 mm. The yarning was realized exclusively in a limited range of the CNT lengths of about 170–1500 μm. Although CNTs became long for longer growth times, some of the CNTs were plucked out from the bottom substrate during growth so that the CNT density decreased at later stages of growth, prohibiting continuous yarning by the suppression of interconnection between CNTs at the bottom part of VACNTs.

We perform a constructal design of nanofluid particle volume fraction for four heat-conduction systems and four types of nanofluids to address whether nanofluids with uniformly-dispersed particles always offer the optimal global performance. The constructal volume fraction is obtained to minimize the system overall temperature difference and overall thermal resistance. The constructal thermal resistance is an overall property fixed only by the system global geometry and the average thermal conductivity of nanofluids used in the system. Efforts to enhance the thermal conductivity of nanofluids are important to reduce the constructal overall thermal resistance. The constructal nanofluids that maximize the system performance depend on both the type of nanofluids and the system configuration, and are always having a nonuniform particle volume fraction for all the cases studied in the present work. Nanofluids research and development should thus focus on not only nanofluids but also systems that use them.

Naturally derived biopolymers have been widely used for biomedical applications such as drug carriers, wound dressings, and tissue engineering scaffolds. Chitosan is a typical polysaccharide of great interest due to its biocompatibility and film-formability. Chitosan membranes with controllable porous structures also have significant potential in membrane chromatography. Thus, the processing of membranes with porous nanoscale structures is of great importance, but it is also challenging and this has limited the application of these membranes to date. In this study, with the aid of a carefully selected surfactant, polyethyleneglycol stearate-40, chitosan membranes with a well controlled nanoscale structure were successfully prepared. Additional control over the membrane structure was obtained by exposing the suspension to high intensity, low frequency ultrasound. It was found that the concentration of chitosan/surfactant ratio and the ultrasound exposure conditions affect the structural features of the membranes. The stability of nanopores in the membrane was improved by intensive ultrasonication. Furthermore, the stability of the blended suspensions and the intermolecular interactions between chitosan and the surfactant were investigated using scanning electron microscope and Fourier transform infrared spectroscopy (FTIR) analysis, respectively. Hydrogen bonds and possible reaction sites for molecular interactions in the two polymers were also confirmed by FTIR analysis.

A novel approach in two-dimensional point probe electrical measurement in TEM is proposed to identify electrical properties at specific positions. This approach calls for a sharp W probe to be driven by piezo-motors in order to make contact with TEM samples and then proceeding I–V measurements are taken and then scanned with constant bias. The doping type and p–n junction interface can be identified by rectifying I–V data obtained. By applying this method to a transistor device with a 200 nm gate length, we could qualitatively distinguish the doping area from the substrate. Mapping results with scanning probe revealed a presence of a dopant spreading region 60 nm wide at the junction interface.

Cavitation is a common phenomenon in fluid systems. Cavitation includes bubbles formation and collapse due to propellants which reduce local pressure or increase local temperature. Cavitation leads harmful effects, i.e., noise and vibration, erosion, flow rate loss, and efficiency loss. In other hand, nanotechnology is spreading rapidly in different fields especially fluid systems. Some of the nanoparticles are used to increase heat transfer rate, bubble absorption, drug delivery, and so on. This kind of additive can affects cavitation occurrence. In this study, we assess influences of SiO₂ nanoparticle on cavitation initiation in a globe style valve by low frequency acceleration analysis. The study shows SiO₂ nanoparticles accelerate cavitation occurrence and in someway, force cavitation nature to relatively get away from low frequency collapsing toward high frequency one.