Anthony Petrovich

Fluid damping in resonant flexural plate wave device

Fluid damping models are developed for resonant (standing wave) flexural plate wave (FPW) devices, which are rectangular plates or diaphragms with structural layers, a piezoelectric layer, and interdigitated conducting combs for driving and sensing. This configuration is often used in micromechanical chemical, biological, or nonvolatile residue sensors. Where much of the previous work on fluid effects in FPW devices focused on delay lines, this effort investigates resonant devices both analytically and experimentally. The fluid model is based on closed-form solution of a wide beam vibrating into a semi-infinite fluid volume and is mated directly into the beam equation. While the fluids pressure versus wave motion solution has been reported previously, the application to the resonant FPW is mathematically rigorous and leads to a greater understanding of the FPW damping regimes. Frequency responses of FPW devices constructed from silicon with deposited piezoelectric aluminum nitride and operating in water and alcohol compared well with analytic results with some discrepancies noted.

Detection of proteins and intact microorganisms using microfabricated flexural plate silicon resonator arrays

We are developing biosensor arrays that are based on microfabricated silicon flexural plate wave (FPW) resonators coated with molecular recognition chemistry. The resonators within the micro-chemical analysis array (CANARY) are micro-electromechanical (MEM) sensors that have been miniaturized to allow many independently addressable sensors to be integrated within a single silicon chip. The target analyte of an individual sensor within the chip is selectively detected by depositing molecular recognition component (or “coating”) onto the sensor surface, and monitoring changes in the frequency and phase of the resonance as the coating interacts with the analyte. The ultimate goal of this project is integration of hundreds of miniature resonators within a single chip for detection of biological species. As proof of concept demonstration, we describe here the detection of proteins and intact microorganisms using 2-element and 8-element CANARY sensor chips and address electronics. Preliminary results of sensitivity, selectivity, and surface regeneration methods of the sensor are presented. Detection of proteins and microorganisms with the CANARY sensor were confirmed by optical measurements.

Vibrating wheel micromechanical gyro

Silicon micromechanical gyro performance has progressed to the threshold of useful initial applications, at least 1 deg/s. The vibrating wheel on a gimbal (VWOG) is a new gyro design with the promise of improved manufacturability. With a variety of accelerometers from which to choose, the advent of the silicon gyro begins the era of silicon micromechanical inertial guidance.

Microwave resonator accelerometer

A microwave resonator accelerometer including a microwave resonant cavity having a predetermined resonant frequency; the cavity including a flexible portion; a proof mass fixed to the flexible portion for changing the geometry and establishing a new resonant frequency of the cavity in response to an acceleration force on the proof mass; a microwave frequency signal at or approximately at the predetermined resonant frequency coupled to the cavity; and a discrimination circuit, responsive to the reflected microwave signal from the cavity, for discriminating a shift in the predetermined resonant frequency of the cavity to a new resonant frequency effected by the change in geometry of the cavity resulting from the acceleration force on the proof mass.

Recent developments in flexured mass accelerometer technology

The flexured mass accelerometer (FMA) is being developed for high performance guidance applications. The focus of the present development is an accelerometer with the capability of meeting strategic missile thrust axis requirements but with a cost an order of magnitude lower than that for current thrust axis accelerometers and a mean time between failure (MTBF) in excess of fifteen years. The FMA uses a microwave readout to measure the deflection of a proof mass. Critical to the performance of this device is the bias stability of the flexured mass under loading. The flexure is mechanically open loop so there are stringent requirements on the flexure material and structural support. Candidate structural materials are reviewed. Specific requirements on the flexure support are identified. Modeling of the readout errors for the FMA indicate the specific requirements on the data sampling and the compensation algorithm. Error modeling and calculations include the effect of cross axis inputs as well as shock and vibration. Projections are made regarding the nuclear hardenability and circumvention requirements. Calibration requirements are reviewed.