We report a new silicon Microelectromechanical systems (MEMS) accelerometer based on differential frequency modulation (FM) with experimentally demonstrated thermal compensation over a dynamic temperature environment and μg-level Allan deviation of bias. The sensor architecture is based on resonant frequency tracking in a vacuum packaged siliconon-insulator (SOI) tuning fork oscillator. To address drift over temperature, the MEMS sensor die incorporates two identical tuning forks with opposing axes of sensitivity. Demodulation of the differential FM output from the two simultaneously operated oscillators eliminates common mode errors and provides an FM output with continuous thermal compensation. The first SOI prototype with quality factor of 350000 was built and characterized over a temperature range between 30 °C and 75 °C. Temperature characterization of the FM accelerometer showed less than a 0.5% scale-factor change throughout a temperature range from 30 °C to 75 °C, without any external compensation. This is enabled by an inherently differential frequency output, which cancels common-mode influences, such as those due to temperature. Allan deviation of the differential FM accelerometer revealed a bias instability of 6 μg at 20 s, along with an elimination of any temperature drift due to increases in averaging time. After comparing the measured bias instability with the designed linear range of 20 g, the sensor demonstrates a wide dynamic range of 130 dB. A second design iteration of the FM accelerometer, vacuum-sealed with getter material, was created to maximize Q-factor, and thereby frequency resolution. A Q-factor of 2.4 million was experimentally demonstrated, with a time constant of >20 min.

Due to restrictive tolerancing in microfabrication, structural imperfections that reduce performance of fabricated micro devices are typical. In microelectromechanical vibratory gyroscopes, feedback control is a common strategy in attempting to correct the imperfections. However, a purely feedback control can be insufficient for compensation of all the errors, requiring post processing in the form of laser trimming to achieve higher levels of performance. In this paper, we explore another alternative: the design and implementation of a dual stage control architecture with self-calibration and feedback capabilities. The self-calibrative portion of the control identifies and electronically "trims" large imperfections, while the feedback control compensates for remaining small nonidealities and in-operation perturbations. Presented here is an algorithm for in-situ imperfection identification based on the dynamic response of the device. A realization of the dual stage control architecture is proposed for a gyroscope using nonlinear electrostatic parallel plate actuators. Modeling and simulation results which demonstrate successful compensation of imperfections with the proposed architecture for a device with 10% fabrication error appearing in the form of stiffness nonidealities and subjected to further 1% in-run perturbations are presented.

A fabrication process for the simultaneous shaping of arrays of glass shells on a wafer level is introduced in this paper. The process is based on etching cavities in silicon, followed by anodic bonding of a thin glass wafer to the etched silicon wafer. The bonded wafers are then heated inside a furnace at a temperature above the softening point of the glass, and due to the expansion of the trapped gas in the silicon cavities the glass is blown into three-dimensional spherical shells. An analytical model which can be used to predict the shape of the glass shells is described and demonstrated to match the experimental data. The ability to blow glass on a wafer level may enable novel capabilities including mass-production of microscopic spherical gas confinement chambers, microlenses, and complex microfluidic networks

This paper presents analysis, design, realization, and experimental demonstration of a bistable switch actuated dynamically utilizing mechanical resonance phenomenon. We demonstrated that if a bistable structure is driven into a resonance near one of its states, it may achieve a large enough amplitude of vibration, sufficient to switch between its stable states. Using energy analysis, we concluded that dynamic switching of bistable structures may provide significant energy advantages over conventional static-switching approaches. To confirm the results, we derived analytically the closed-form actuation conditions guaranteeing switching between the states of a bistable structure and applied these conditions to experimental devices. Micromachined prototypes of dynamically actuated bistable switches were designed, fabricated, and characterized. We demonstrated experimentally that resonant dynamic switching provides energy saving of around 60% at atmospheric pressure with proportional increase in efficiency as the pressure decreases.