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The development of an accurate, non-invasive method for the diagnosis of peripheral artery disease (PAD) from accelerometer contact microphone (ACM) recordings of the cardiac system.Mel frequency cepstral coefficients (MFCCs) are initially extracted from ACM recordings. The extracted MFCCs are then used to fine-tune a pre-trained ResNet50 network whose middle layers provide streams of high-level-of-abstraction coefficients (HLACs) which could provide information on blood pressure backflow caused by arterial obstructions in PAD patients. A vision transformer is finally integrated with the feature extraction layer to detect PAD, and stratify the severity level. This architecture is coined multi-stream-powered vision transformer (MSPViT). The performance of MSPViT is evaluated on 74 PAD and 21 healthy subjects.Sensitivity, specificity, F1 score, and area under the curve (AUC) of 99.45%, 98.21%, 99.37%, and 0.99, respectively, are reported for the binary classification which ensures accurate detection of PAD. Furthermore, MSPViT suggests average sensitivity, specificity, F1 score, and AUC of 96.66%, 97.34%, 96.29%, and 0.96, respectively, for the classification of subjects into healthy, mild-PAD, and severe-PAD classes. The silhouette score is calculated to assess the separability of clusters formed for classes in the penultimate layer of MSPViT. An average silhouette score of 0.66 and 0.81 demonstrate excellent cluster separability in PAD detection and severity classification, respectively.The achieved performance suggests that the proximal ACM-driven framework can replace state-of-the-art techniques for PAD detection.This study presents a fundamental step towards prompt and accurate diagnosis of PAD and stratification of its severity level.

This paper introduces a modification to the eigenmode operation of resonant gyroscopes. The so-called multi-coefficient eigenmode operation can improve cross-mode isolation due to spatially non-orthogonal imperfection, which is one of the causes of residual quadrature error in conventional eigenmode operation. A 1400µm annulus aluminum nitride (AlN) on Silicon bulk acoustic wave (BAW) resonator with gyroscopic in-plane bending modes at 2.98MHz achieves near 60dB cross-mode isolation when operated as a gyroscope using multi-coefficient eigenmode architecture. The as-born frequency mismatches in multiple devices are compensated by physical laser trimming as an alternative to the displacement feedback tunning mechanism. The demonstrated AlN piezoelectric BAW gyroscope shows a large open-loop bandwidth of 150Hz and a high scale factor of 9.5nA/°/s on a test board in a vacuum chamber. The measured angle random walk is 0.145°/√hr, and the bias instability is 8.6°/hr, showing significant improvement compared to the previous eigenmode AlN BAW gyroscope. The result from this paper proves that with multi-coefficient eigenmode operation, the piezoelectric AlN BAW gyroscopes can have a comparable noise performance as their capacitive counterpart while having the unique advantage of large open-loop bandwidth and not requiring large DC polarization voltages.

Hexagonal 4H-silicon carbide (4H-SiC) is a transversely isotropic substrate garnering interest for precision MEMS devices such as resonant gyroscopes. This paper investigates the elastic anisotropy of 4H-SiC by utilizing capacitive bulk acoustic wave (BAW) resonators with ultra-high mechanical quality factors ( $Q$ ) enabled by phononic crystals. We directly measure the value of $C_{66}$ using Lame mode resonators for the first time and numerically fit the values of $C_{11}$ and $C_{12}$ using BAW elliptical modes in center-supported solid disk resonators. We compare (0 0 0 1) 4H-SiC to (1 1 1) Si, another in-plane isotropic material and validate (0 0 0 1) 4H-SiC’s superior robustness to fabrication and design variations. Measurement of in-plane BAW elliptical modes in multiple disk resonators with as-born frequency splits as low as 3 ppm reveal (0 0 0 1) 4H-SiC’s transverse isotropy across process corners. Lame mode resonators display a temperature coefficient of frequency (TCF) three times lower compared to its Si counterpart. Finally, this paper provides a modified set of elastic constants for 4H-SiC with a view towards monocrystalline SiC MEMS devices. [2020-0254]

This work reports on the first demonstration of the frequency tuning and intrinsic polarization switching of film bulk acoustic resonators (FBARs), based on sputtered AlScN piezoelectric thin films with Sc/(Al + Sc) ratio of approx. 30%. A box-like ferroelectric hysteresis behavior of 900 nm-thick Al0.7Sc0.3N sputtered films is obtained, showing a coercive electric field at ~3 MV/cm. The fundamental thickness-mode resonance of the bulk acoustic wave (BAW) resonator is measured at 3.17 GHz frequency with an excellent electromechanical coupling coefficient ( $k_{t}^{2}$ ) of 18.1%. The FBAR frequency response is studied, in both (i) the linear tuning regime, upon application of DC electric fields below the coercive field; as well as (ii) the polarization switching regime, upon application of electric fields above the coercive field. A large linear tuning range of 215 ppm $\times \,\,\mu \text{m}$ /V is obtained in case (i), resulting from the high scandium content. The series resonance frequency of the FBARs is switched ON and OFF in (ii) upon application of 350 V unipolar waveform across the Al0.7Sc0.3N thickness. This is the first demonstration of the intrinsically switchable AlN-based FBARs with a large tuning range; and record high $k_{t}^{2}$ reported for AlN-based FBARs to date. Furthermore, this work paves the way for realization of tunable and switchable wideband acoustic filters operating at super high frequency ranges (SHF). [2020-0203]

We present a 4.4-MHz resonant accelerometer based on the electrostatic softening effect in a bulk acoustic wave (BAW) resonator, fabricated using a metal-less AlN-HARPSS process with combined piezoelectric and capacitive transduction. BAW accelerometers can be used in high-g and high-dynamic range applications with a very wide bandwidth. The fabrication process supports both piezoelectric and nanogap capacitive transduction in a micro/nanoelectromechanical device, primarily applicable to stiff high-frequency devices that use a nanoscale (

This paper presents a novel high-Q silicon distributed Lame mode resonator (DLR) for VHF timing reference applications. The DLR employs the nature of shear wave propagation to enable a cascade of small square Lame modes in beam or frame configurations with increased transduction area. Combined with high efficiency nano-gap capacitive transduction, it enables low motional impedances while scaling the frequency to VHF range. The DLR designs are robust against common process variations and demonstrate high manufacturability across different silicon substrates and process specifications. Fabricated DLRs in beam and frame configurations demonstrate high performance scalability with high Q-factors ranging from 50 to 250 k, motional impedances 90 °C in the VHF range, and are fabricated using a wafer-level-packaged HARPSS process. Packaged devices show excellent robustness against temperature cycling, device thinning, and aging effects, which makes them a great candidate for stable high frequency references in size-sensitive and power-sensitive 5 G and other IoT applications. Timing resonators are crucial components in a range of electronic devices, where they provide a time-based reference, commonly used in consumer electronics, automotive and industrial settings. Square Lame mode resonators enable a silicon-based timing resonator with high Q-factor and high-temperature stability. However, they have certain limitations, primarily at VHF ranges. Now, a team from Georgia Institute of Technology, USA, led by Farrokh Ayazi have designed and fabricated timing resonators that utilize the in-plane shear nature of the Lame mode to create distributed resonance which overcome the limitations of conventional timing resonators. Combined with high efficiency nano-gap capacitive transduction, they enable low motional impedances with increased transduction area, while scaling the frequency to VHF range. These DLR designs are robust against common process variations and demonstrate high manufacturability across different silicon substrates and process specifications.

This paper presents a digital gyroscope interface system for high-frequency bulk-acoustic-wave (BAW) gyroscopes with in-run automatic mode-matching (AMM) capability. The presented work demonstrates the design and implementation of the dual-mode (DM) operation architecture on a flexible digital platform, which allows for low-cost rapid development and evaluation of new functions and architectures. Two prototype silicon BAW gyroscopes are tested on this platform using the proposed system to verify the advantages of the DM architecture. The AMM in DM showed below 4-ppb mode split accuracy and fast converge time without overshoot or oscillation. The DM operation with in-run AMM substantially reduced the bias drift of the gyros, leading to significantly lower rate random walk (RRW) compared to conventional single-mode (SM) operation. The performance repeatability and stability over the temperature of the DM gyro system are characterized, showing as high as $50\times $ improvement compared to the SM architecture.

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 the implementation and characterization of a hermetically-sealed single-proof-mass multi-directional accelerometer contact microphone exhibiting wide operational bandwidth (>10kHz) and low noise (Brownian noise