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In this paper, a modification to the eigenmode operation of resonant gyroscopes is introduced. The multi-coefficient eigenmode operation can improve cross-mode isolation due to electrode misalignments and imperfections, which is one of the causes of residual quadrature errors in conventional eigenmode operations. A 1400 µm annulus aluminum nitride (AlN) on a silicon bulk acoustic wave (BAW) resonator with gyroscopic in-plane bending modes at 2.98 MHz achieves a nearly 60 dB cross-mode isolation when operated as a gyroscope using a multi-coefficient eigenmode architecture. The as-born frequency mismatches in multiple devices are compensated by physical laser trimming. The demonstrated AlN piezoelectric BAW gyroscope shows a large open-loop bandwidth of 150 Hz and a high scale factor of 9.5 nA/°/s on a test board with a vacuum chamber. The measured angle random walk is 0.145°/√h, and the bias instability is 8.6°/h, showing significant improvement compared to the previous eigenmode AlN BAW gyroscope. The results from this paper prove that with multi-coefficient eigenmode operations, piezoelectric AlN BAW gyroscopes can achieve a noise performance comparable to that of their capacitive counterpart while having the unique advantage of a large open-loop bandwidth and not requiring large DC polarization voltages.

Monitoring pathological mechano-acoustic signals emanating from the lungs is critical for timely and cost-effective healthcare delivery. Adventitious lung sounds including crackles, wheezes, rhonchi, bronchial breath sounds, stridor or pleural rub and abnormal breathing patterns function as essential clinical biomarkers for the early identification, accurate diagnosis and monitoring of pulmonary disorders. Here, we present a wearable sensor module comprising of a hermetically encapsulated, high precision accelerometer contact microphone (ACM) which enables both episodic and longitudinal assessment of lung sounds, breathing patterns and respiratory rates using a single integrated sensor. This enhanced ACM sensor leverages a nano-gap transduction mechanism to achieve high sensitivity to weak high frequency vibrations occurring on the surface of the skin due to underlying lung pathologies. The performance of the ACM sensor was compared to recordings from a state-of-art digital stethoscope, and the efficacy of the developed system is demonstrated by conducting an exploratory research study aimed at recording pathological mechano-acoustic signals from hospitalized patients with a chronic obstructive pulmonary disease (COPD) exacerbation, pneumonia, and acute decompensated heart failure. This unobtrusive wearable system can enable both episodic and longitudinal evaluation of lung sounds that allow for the early detection and/or ongoing monitoring of pulmonary disease.

This paper reports on a new type of high-frequency mode-matched gyroscope with significantly reduced dependencies on environmental stimuli such as temperature, vibration, and shock. A novel stress-isolation system is used to effectively decouple an axis-symmetric bulk-acoustic wave (BAW) vibratory gyro from its substrate, minimizing the effect that external sources of error have on the offset and scale factor of the device. Substrate-decoupled (SD) BAW gyros with a resonance frequency of 4.3 MHz and Q values near 60 000 were implemented using the high aspect ratio poly and single-crystal silicon (HARPSS) process to achieve ultra-narrow capacitive gaps. Wafer-level packaged sensors were interfaced with a customized application-specific integrated circuit (ASIC) to achieve low variations in the offset across temperature (±26° s−1 from −40 to 85 °C), supreme random-vibration immunity (0.012° s−1 gRMS−1) and excellent shock rejection. With a scale factor of 800 μV (°s−1)−1, the SD-BAW gyro system attains a large full-scale range (±1250° s−1) with a non-linearity of less than 0.07%. A measured angle-random walk (ARW) of 0.39°/√h and a bias instability of 10.5°h−1 are dominated by the thermal and flicker noise of the integrated circuit (IC), respectively. Additional measurements using external electronics show bias-instability values as low as 3.5°h−1, which are limited by feed-through signals coupled from the drive loop to the sense channel, which can be further reduced through proper re-routing of the gyroscope pin-out configuration. Scientists in the USA have developed a device for measuring rotation that is resilient against shock and vibration. A team led by Diego Serrano at Qualtre Inc. fabricated a micrometer-scale gyroscope that is decoupled from motion in the substrate on which it is built. Micromachined gyroscopes usually comprise a low-frequency resonant cantilever or membrane, and rotation is detected through a corresponding change in the resonance pattern of the resonator. However, such devices are susceptible to external sources of vibrations. Serrano’s team created a device known as a bulk acoustic wave gyroscope that is made of a disk of silicon and supports high frequency resonance inherently resistant to random external vibrations. The disk is surrounded by a series of electrodes that can fine tune the properties of the disk to further improve performance.