Design and fabrication of a micromachined electrostatically suspended gyroscope

The current paper describes the design and fabrication of a micromachined electrostatically suspended gyroscope. Electrostatic levitation is employed to suspend the rotor, eliminating the mechanical bearing and thus friction effects between the rotor and the substrate, hence improving long-term stability. The rate of rotation can be measured by detecting the torque-induced displacement of the spinning rotor using capacitive interface circuits. The device structure and its basic operating principle are described, as well as theoretical background and design considerations. The fabrication process of the gyroscope relies on glass/silicon/glass stack bonding and deep dry etching and is outlined in detail. Initial prototypes realized with this fabrication process are presented and described

MEMS velocity sensor using direct velocity feedback

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Design and simulation of a spring-less micro switch

This paper reports on the design of an ultra low actuation voltage microelectromechanical systems (MEMS) switch. The mechanical design of the spring-less switch is presented. The theoretical actuation voltage of the switch is shown to be as low as 0.34 V. The concept is tested using an electrostatic levitated disc accelerometer, reconfigured to operate as a MEMS switch. Experimental and theoretical data for the dynamic behaviour of these devices are also presented. The results of this paper validate the feasibility of realising ultra low-voltage MEMS switches using electrostatic levitation. Key words: Low actuation voltage, microelectromechanical systems (MEMS) switches, electrostatic actuation, no mechanical spring

Behavior of Freezable Bound Water in the Bacterial Cellulose Produced by Acetobacter xylinum: An Approach Using Thermoporosimetry

The aim of the study is to examine thermal behavior of water within reticulated structure of bacterial cellulose (BC) films by sub-ambient differential scanning calorimetry (DSC). BC films with different carbon source, either manitol (BC (a)) or glycerol (BC (b)), were produced by Acetobacter xylinum using Hestrin and Shramm culture medium under static condition at 30 ± 0.2°C for 3 days. BC samples were characterized by electron scanning microscopy and X-ray diffraction spectroscopy. The pore analysis was done by B.H.J. nitrogen adsorption. The pre-treated with 100% relative humidity, at 30.0 ± 0.2°C for 7 days samples were subjected to a between 25 and −150°C-cooling–heating cycle of DSC at 5.00°C/min rate. The pre-treated samples were also hydrated by adding 1 μl of water and thermally run with identical conditions. It is observed that cellulose fibrils of BC (a) were thinner and reticulated to form slightly smaller porosity than those of BC (b). They exhibited slightly but non-significantly different crystalline features. The freezable bound water behaved as a water confinement within pores rather than a solvent of polymer which is possible to use thermoporosimetry based on Gibb–Thomson equation to approach pore structure of BC. In comparison with nitrogen adsorption, it was found that thermoporosimetry underestimated the BC porosity, i.e., the mean diameters of 23.0 nm vs. 27.8 nm and 27.9 nm vs. 33.9 nm for BC (a) and BC (b), respectively, by thermoporosimetry vs. B.H.J. nitrogen adsorption. It may be due to large non-freezable water fraction interacting with cellulose, and the validity of pore range based on thermodynamic assumptions of Gibb–Thomson theory