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Improving the Sensitivity and Bandwidth of In-Plane Capacitive Microaccelerometers Using Compliant Mechanical Amplifiers

TitleImproving the Sensitivity and Bandwidth of In-Plane Capacitive Microaccelerometers Using Compliant Mechanical Amplifiers
Publication TypeJournal Article
Year of Publication2014
AuthorsKhan, S, Ananthasuresh, GK
JournalJournal of Microelectromechanical Systems
Date PublishedAug
KeywordsAcceleration, accelerometers, amplifiers, axial sensitivity measurement, Bandwidth, bandwidth improvement, Capacitive sensors, compliant mechanical amplifier, Compliant mechanism, cross-axis sensitivity, DaCM, displacement amplification, displacement amplifying compliant mechanism, dual axis accelerometer, dual-axis micromachined accelerometer, frequency 920 Hz, frequency measurement, in-plane axes, in-plane capacitive microaccelerometer, in-plane orthogonal axes, interfinger gap, Mathematical model, microfabrication process, micromachining, micropackaging, microsensors, natural frequency measurement, Resonant frequency, Sensitivity, sensitivity enhancement, sensitivity enhancement., sensitivity improvement, size 25 mum, suspension, Suspensions, suspensions (mechanical components)

This paper presents a method to enhance both the sensitivity and bandwidth of in-plane capacitive micromachined accelerometers by using compliant mechanical amplifiers, and thus obviating the compromise between the sensitivity and bandwidth. Here, we compare one of the most sensitive single-axis capacitive accelerometers and another with large resonant frequency reported in the literature with the modified designs that include displacement-amplifying compliant mechanisms (DaCMs) occupying the same footprint and under identical conditions. We show that 62% improvement in sensitivity and 34% improvement in bandwidth in the former, and 27% and 25% in the latter can be achieved. Also presented here is a dualaxis accelerometer that uses a suspension that decouples and amplifies the displacements along the two in-plane orthogonal axes. The new design was microfabricated, packaged, and tested. The device is 25-μm thick with the interfinger gap as large as 4 μm. Despite the simplicity of the microfabrication process, the measured axial sensitivity (static) of about 0.58 V/g for both the axes was achieved with a cross-axis sensitivity of less than ±2%. The measured natural frequency along the two in-plane axes was 920 Hz. Displacement amplification of 6.2 was obtained using the DaCMs in the dual-axis accelerometer.