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Microelectromechanical Systems, Journal of

Issue 4 • Date Dec 1994

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Displaying Results 1 - 5 of 5
  • Silicon-micromachined gas chromatography system used to separate and detect ammonia and nitrogen dioxide. I. Design, fabrication, and integration of the gas chromatography system

    Page(s): 134 - 146
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    A miniature gas chromatography (GC) system was designed and developed using silicon micromachining and integrated circuit (IC) processing techniques. The micromachined gas chromatography (MMGC) system is composed of a miniature sample injector incorporating a 10-μm-long sample loop; a 0.9-m-long, rectangular-shaped (300 μm width and 10 μm height) capillary column coated with a 0.2-μm-thick copper phthalocyanine (CuPc) stationary phase, and a dual-detector scheme based upon a CuPc-coated chemiresistor and a 125-μm-diameter thermal conductivity detector (TCD) bead. Silicon micromachining was employed to fabricate the interface between the sample injector and the GC column, the GC column itself, and the dual-detector cavity. A novel processing technique was developed to sublime a homogeneous CuPc stationary-phase coating on the GC column walls. The complete MMGC system package is approximately 4 in, square and 100 mils (2.5 mm) thick, [96] View full abstract»

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  • Silicon-micromachined gas chromatography system used to separate and detect ammonia and nitrogen dioxide. II. Evaluation, analysis, and theoretical modeling of the gas chromatography system

    Page(s): 147 - 154
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    A miniature gas chromatography (GC) system was designed and developed using silicon micromachining and integrated circuit (IC) processing techniques. The MMGC system can separate parts-per-million (ppm) ammonia and nitrogen dioxide concentrations in less than 30 minutes when isothermally operated (80°C) at 40 psi. The heat of adsorption of nitrogen dioxide (0.38 eV) on a CuPc thin film (0.2 μm thick) was also independently established. As a result of the MMGC system's performance evaluation, several of the assumptions invoked in the initial design were re-investigated, and a refined technique for optimizing the MMGC system's operation and performance was developed View full abstract»

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  • A simple fabrication process for polysilicon side-drive micromotors

    Page(s): 126 - 133
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    A simple fabrication process for rapid prototyping of side-drive polysilicon micromotors has been developed. This process uses three low-pressure chemical vapor depositions and three photolithography steps, and it enables fabrication of new micromotors and flange bearing designs. An important feature of this process is that the rotor, stator, and rotor/stator gap pattern definition is the first photolithography step and is performed over a flat surface. As a result, excellent linewidth resolution is possible for defining the rotor/stator gaps. Conventional wobble and salient-pole micromotors fabricated with this process have been operated for months after release, For wobble micromotors with 3-μm-thick rotor/stator polysilicon films, minimum operating voltages have been 25 V across 1.5-μm rotor/stator gaps; maximum operating speeds have been 1000 rpm. limited by the power supply. Corresponding salient-pole micromotors have had minimum operating voltages of 50 V; their maximum operating speeds have been near 5000 rpm View full abstract»

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  • Coupled electrostatic and mechanical FEA of a micromotor

    Page(s): 162 - 171
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    The electrostatic forces occurring in a novel double stator axial-drive variable capacitance micromotor (VCM) are studied as a function of rotor-stator overlap, applied voltage, rotor support morphology, and rotor thickness. Analytical equations are developed using parallel plate assumptions, and results are compared with those obtained with 3D Finite Element Analysis (FEA) for tangential, axial, and radial electrostatic forces. The influence of the axial forces on the rotor deflections are studied using iterative indirect coupled field analysis, where the axial forces obtained from the electrostatic 3D FE model are iteratively applied to a structural FE model until stable rotor deflections are obtained. It was found that the axial forces, taking the rotor deflection into account, are twice as high as those obtained by analytical evaluation neglecting rotor deflections and about 70 times higher than the radial forces at a typical operating voltage of 100 V. Inclusion of bushing supports results in lower axial forces and decreases the influence of rotor tilt. Tangential forces likely to be exerted on the rotor at start-up are also examined and compared with analytical predictions. The study demonstrates that FEA provides more accurate results than analytical equations due to the geometry and field simplifications assumed in the latter View full abstract»

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  • Electronically controlled etch-mask for silicon bulk micromachining

    Page(s): 155 - 161
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    Wafers that are to be submitted to anisotropic etching in aqueous KOH are conventionally passivated with a silicon dioxide or nitride layer in which backside windows are etched to define the microstructures. A different method to mask the backside of a silicon wafer for this purpose is presented. The method makes use of the phenomenon that silicon is not etched in KOH when biased above the passivation potential. The mask is defined by applying a set of bias voltages to the front of the wafer instead of patterning a deposited passivation layer at the backside, for which an accurate double-sided alignment is required. The feasibility of the method was demonstrated with the fabrication of membranes and suspended masses of various sizes View full abstract»

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Aims & Scope

The topics of interest include, but are not limited to: devices ranging in size from microns to millimeters, IC-compatible fabrication techniques, other fabrication techniques, measurement of micro phenomena, theoretical results, new materials and designs, micro actuators, micro robots, micro batteries, bearings, wear, reliability, electrical interconnections, micro telemanipulation, and standards appropriate to MEMS. Application examples and application oriented devices in fluidics, optics, bio-medical engineering, etc., are also of central interest.

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Meet Our Editors

Editor-in-Chief
Christofer Hierold
ETH Zürich, Micro and Nanosystems