Micro and Nanosystems - Volume 6, Issue 4, 2014

The discovery of graphene, a single-atom thin sheet of carbon, led to the worldwide race for the discovery of similar two-dimensional materials of other elements, especially of common semiconductor materials such as silicon and germanium. Although graphene may be electrically the most conductive material, it is not suitable for making a transistor because of the lack of an energy band gap. In contrast, silicene and germanene, single-atom layers of silicon and germanium, pose a small band gap that can be used for making nanoelectronic transistors. A recent work has demonstrated the proof of concept of this transistor, which is made of a single layer of silicon atoms.

A method that utilizes vibration velocity signal and differential combs to improve the equivalent Q factor of MEFS is proposed in this study to address charge accumulation on the metal cap surface of an MEMS-based electric field sensor (MEFS) with vacuum package. The MEFS system is characterized by a high degree of nonlinearity, so the averaging method is used to analyze system stability and vibration amplitude. Theoretical and simulation results show that the proposed method is feasible. Experiment results indicate that the larger is the referenced voltage, the larger is the zoom stable vibration amplitude, and the shorter is the transient time. The resulting signal-to-noise ratio is about 92 dB, and the vibration amplitude shows a deviation of 0.2% in 6 min.

A system of multiple organs integrated on a single chip or human on a chip (HUC) has a great potential for drug discovery. Such a system helps to advance the fundamental understanding of diseases as well as the complex interactions between cells, tissues and organs. HUC models will potentially overcome the shortcomings of traditional animal models such as high cost, incompatibility with human physiology, the inability to control and manipulate the microenvironment in vivo and the lack of efficacy. The matching length scale of biological structures and micromachined components makes a microfluidic chip the ideal platform to investigate physiological events. This paper presents an overview of the state of the art of the development of HUC. The paper also provides a perspective on the integration of cell culture on a chip to create an ethical human model and to provide insights into the sensitivity of different cell constructs on drugs.

We demonstrate a simple method to fabricate elastic magnetic membrane which could be used to enhance mixing in microwells of a microtitre plate. The magnetic membrane was fabricated using an off-the-shelf flexible magnetic sheet and the elastomer polydimethylsiloxane (PDMS). In order to demonstrate the concept, the membrane was integrated in a single microwell to act as an actuator for improved mixing. A customized electromagnet was used to allow contactless and robust actuation. The membrane can achieve a unidirectional deflection of about 120 µm when a 3 A direct current (DC) is applied. Periodic deflection is achieved by applying a square wave alternating current (AC) of 100 Hz and ±3 A. In the dynamic case, the membrane follows the square wave with the same frequency and provides a peak-to-peak deflection of about 115 µm. The observed oscillation was able to mix the fluorescent dye and an aqueous solution within 18 seconds. The proposed method has the potential to be implemented in microtiter plate arrays to improve mixing.

Zn doped Ba germanate nanorods have been prepared by the hydrothermal process and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and solid UV-vis diffuse reflectance spectroscopy. XRD analysis shows that the Zn doped Ba germanate nanorods consist of hexagonal Ba2Ge5O12 and rhombohedral ZnGeO3 phases. The size and band gap of the Zn doped Ba germanate nanorods depend on the Zn doping mass percentage. The band gap of the 1wt.% Zn doped Ba germanate nanorods is 4.07 eV which is smaller than that of undoped and Zn doped Ba germanate nanorods with the Zn doping mass percentage of 3%, 5% and 10%. The role of the irradiation time and content of the nanorods in aqueous solution has been analyzed. The 1wt.% Zn doped Ba germanate nanorods show the highest photocatalytic activity under UV light irradiation. The photocatalytic activity has been greatly enhanced by the Zn doping.

In the present work Repaglinide loaded ammonio methacrylate copolymer nanoparticles were developed by modified solvent emulsion technique using high pressure homogenizer. An effect of numerous organic solvents, surfactant concentration, drug-polymer ratios and combination of polymers on encapsulation efficiency as well as drug release profile were studied. Sustained released nanoparticles were obtained in the size of less than 400 nm. FE-SEM showed smooth and rigid surface of Eudragit RS nanoparticle’s while porous surface nature was observed in Eudragit RL nanoparticles. No drug-polymer interaction was found. X-RD revealed that the crystallinity of repaglinide was decreased when processed with Eudragit polymers. Eudragit RSPO retained drug for more time than other copolymers. Most of the formulations followed zero order kinetics. Prepared nanoparticles can be used for the treatment of type 2 diabetes mellitus by minimizing dose rate, reducing adverse effects and enhancing patient fulfillment.