Micro and Nanosystems - Volume 4, Issue 1, 2012

It has been three years since the first issue of Micro and Nanosystem was published. The mission of this journal has been providing a forum for interdisciplinary science and technology in micro and nanoscale. Despite its youth, the journal has been indexed by MediaFinder®-Standard Periodical Directory, Compendex, Genamics JournalSeek, Scopus and J-Gate. Our commitment to the readers of this journal is to provide the most updated research and trend of the field. Our commitment to the contributors of this journal is to provide a high-impact forum with a wide readership. To this end, we need to further improve the quality of the journal by a stringent peer-review process and to offer a wider access to the published articles. With this first issue of the 4th volume, I would like to thank the Editor in Chief, our contributors and the board members for the past success. As the newly appointed Co-Editor in Chief, I wish that our contributors and board members will continue to promote the journal in their other publications and international conferences. Their continued support in the years to come will be decisive for the future success of Mircro and Nanosystem.

We demonstrate the microfabrication of a low-noise silicon (Si) chip as a platform for suspending mechanically stable bilayer lipid membranes (BLMs). Microapertures with smoothly tapered edges were formed by isotropic etching in a silicon nitride layer deposited on a Si substrate. The surface of the Si chip was coated with insulator layers of Teflon and SiO2. The insulator coating worked to reduce the total capacitance, leading to noise reduction (1-2 pA in peak-to-peak after low-pass filtering at 1 kHz) and elimination of current transients (< 0.5 ms). Since the tapered edges were necessary to maintain mechanically stable BLMs, the entire chip except for the aperture was coated with the insulators. Owing to this process, the BLMs formed in the Si chips still showed high mechanical stability after coating with the insulator layers. The membranes withstood high applied voltage (±1 V) and mechanical shocks during solution exchanges. The mechanically stable BLMs having electric properties suitable for recording activities of biological channels will open up a variety of applications including high-throughput analysis of ion-channel proteins.

Isolated nanodots of ZnO of at least 100 nm in size were deposited on transparent conducting substrate (Indium Tin Oxide coated quartz) by aqueous chemical growth technique. The nanodots have polycrystalline character and their crystallinity improves due to annealing in vacuum and oxygen atmosphere. The ultraviolet sensing property of the ZnO nanodot was investigated by current-voltage measurement. Under ultraviolet irradiation, the photo current was observed to be higher for the nanodots having higher volume density of point defects.

The electrohydrodynamic and stress instability of the interface between two viscous fluids with different electrical properties under tangential electric fields in a microchannel is analytically and experimentally investigated. In the analytical model, the two-layer system is subjected to a tangential electric field. There is no assumption on the magnitude of the ratio of fluid to electric time scales, and thus the linear Poisson-Boltzmann equation are solved using separation of variable method for densities of bulk charge and surface charge; the electric field and fluid dynamic are coupled only at the interface through the stress balance equations. Under constant flowrates, the fractions of the fluids are calculated for different parameters. Using the calculated fractions, the stability of the system can be determined according to the linear perturbation theory. In the experiments, two immiscible fluids, aqueous NaHCO3 (conducting fluid) and silicone oil (non-conducting fluid) are pumped into a PMMA microchannel. The tangential electric field is added to the aqueous NaHCO3 using a high voltage power supply. The results are recorded using a CCD camera. The results show that the electric field can have either destabilizing or stabilizing effect depending on the ratios of viscosity of the two fluids. The flowrates, zeta potential, and dimension of the microchannel affect the growth rate of the perturbation. Both experimental and analytical results show a good agreement.

We propose a model to study self-diffusion of fluid confined between two rough walls. The model is based on microscopic considerations wherein the configuration space of the body systems is divided into cells. Within the cell, it executes harmonic motion unless it finds a saddle point on potential energy hypersurface. Results are obtained for Lennard Jones fluid for different order of rectangular and sinusoidal roughness of confining walls. It is found that the roughness of wall significantly affects the motion of fluid and reduces the average diffusion of particles in agreement with simulation results. The reduction is more for rectangular than for sinusoidal roughness. The study has applicability for fluids flowing in biological systems.

An exact closed form solution is presented for a case of combined loading of an initially imperfect double walled carbon nanotube. A continuum mechanics based thin shell model is used which accounts for the presence of Van der Waals forces between the walls in an approximate way. This exact solution is used to investigate the effects of axial load distribution, initial imperfections, and the transverse loading on axisymmetric buckling. It is found that the axisymmetric buckling behaviors of single walled and double walled carbon nanotubes are qualitatively similar.

The photocatalytic hydrogen generation from H2O/H2O2/MnO2 system and H2O2 concentration dependence of the efficiency were studied for the first time. The MnO2 powder was synthesized by an aqueous reaction followed by low temperature calcination. The powder appeared very stable in water. The absorption edge of the MnO2 powder was ∼1248 nm, corresponding to a band gap of ∼0.68eV. The experiment results of the hydrogen generation revealed that the efficiency was very high and increased as increase in H2O2 concentration. A mechanism for the hydrogen generation was mainly discussed.

This study investigates lysozyme immobilization on modified detonation nanodiamonds (MND) adapted for biomedical research purposes. Catalytic activity of lysozyme was evaluated after the enzyme was immobilized on MND through nonspecific adsorption or covalent binding. The enzyme adsorbed on MND particles or covalently conjugated to them exhibited catalytic activity and lysed Gram-positive and Gram-negative bacterial cells, but the activity of the immobilized enzyme was lower than the activity of the free lysozyme in both variants. The lysozyme covalently conjugated to MND was more resistant towards the proteolytic action of pepsin under acidic conditions than the adsorbed enzyme. The present study has only looked at a small proportion of the potential activity and applicability of associating lysozyme with MND. It therefore seems probable that further development will yield valuable insights.

In order to study the dynamic characteristics of microstructures under high-g acceleration and harsh temperature environment, dynamic measurement techniques were presented and the corresponding testing systems were established. For testing in high-g acceleration environment, the acceleration was generated by high speed rotation plate, and over 10000 g acceleration environment was created. The base excitation device designed with piezoelectric ceramic (PZT) was used to excite the microstructures. Piezoresistive cantilevers with typical beam-proof mass structure were designed and fabricated for obtaining the vibration signal. For testing in harsh temperature environment, two instruments were designed to realize the low temperature environment and high temperature environment, respectively. A thermoelectric refrigerator was modified to vary the temperature of microstructures from room temperature down to -55 oC. A small alumina ceramics heater (MCH) was used to heat microstructures up to 350 °C. The base excitation device with PZT was also used to excite microstructures under harsh temperature environment. Laser Doppler Vibrometer (LDV) was adopted to obtain the vibration signals through the viewport of these instruments. The dynamic characteristics of silicon microcantilevers were tested under these harsh environment. The results show that the resonance frequencies of microcantilevers increase with the elevated external high load as soon as the deformation of micro-beam is in the geometrically nonlinear state, and also the resonance frequencies slightly and linearly decrease with the increasing temperature.

In this paper, we present the need for concurrent engineering in Microelectromechanical System (MEMS) device and product development. MEMS system is considered as six subsystems: micromachined element design subsystem, microelectronics circuit design subsystem, fabrication subsystem, packaging subsystem, materials subsystem and environment subsystem. Design for ‘X’ abilities is addressed by considering six subsystems/abilities. A concurrent model is developed using graph theory to show the interaction between subsystems. This work utilizes the advantages of the graph theoretic approach to consider all design aspects together in a single methodology with the help of a multinomial defined using matrix algebra. The design index developed using the proposed methodology shows the interaction among the subsystems and indicates whether the overall design is acceptable or not, by considering all the aspects related to micromachined element design, microelectronics circuit design, fabrication, packaging, materials, environment etc. A MEMS based RF power sensor is designed and the proposed methodology is explained. Simulated results of the RF MEMS power sensor are presented to validate the proposed methodology. A power sensor with VSWR of 1.08002 is reported.

An aqueous phase sonication technique method was developed for the rapid preparation of four kinds of Chinese herbs (Licorice, Tuckahoe, Rhizoma Atractylodis Macrocephalae and Ginseng) nanoparticles. The nanoparticles were characterized by the laser particles size analyzer, infrared spectroscopy and scanning electron micrograph. The particle size of 95% nanoparticles was nearly 200nm. Moreover, the nanoparticles had very similar chemical composition with primary particles, despite slight changes. Therefore, this preparation technique was demonstrated to be a simple, available and effective method to get high quality nanoparticles of Chinese herbs.

Size-controlled CdS quantum dots are successfully synthesized in PVP matrix through chemical route. The obtained particles are characterized with XRD, UV/VIS and HRTEM. Nearly spherical and well dispersed particles of size 3-20 nm are obtained. The size of the prepared quantum dots can be readily tuned depending on temperature, stirring rate and concentration in the reaction system. This particle size produces a quantum confinement observed from blue shifted absorption edge at 211nm in UV/VIS absorption spectroscopy.