Several devices and measurement approaches have recently been developed to perform ballistocardiogram (BCG) and seismocardiogram (SCG) measurements. The development of a wireless acquisition system (hardware and software), incorporating a novel high-resolution micro-electro-mechanical system (MEMS) accelerometer for SCG and BCG signals acquisition and data treatment is presented in this paper. A small accelerometer, with a sensitivity of up to 0.164 µs/µg and a noise density below 6.5 µg/ $\sqrt{\mathrm{Hz}}$ is presented and used in a wireless acquisition system for BCG and SCG measurement applications. The wireless acquisition system also incorporates electrocardiogram (ECG) signals acquisition, and the developed software enables the real-time acquisition and visualization of SCG and ECG signals (sensor positioned on chest). It then calculates metrics related to cardiac performance as well as the correlation of data from previously performed sessions with echocardiogram (ECHO) parameters. A preliminarily clinical study of over 22 subjects (including healthy subjects and cardiovascular patients) was performed to test the capability of the developed system. Data correlation between this measurement system and echocardiogram exams is also performed. The high resolution of the MEMS accelerometer used provides a better signal for SCG wave recognition, enabling a more consistent study of the diagnostic capability of this technique in clinical analysis.

Here, a frequency modulated MEMS accelerometer encapsulated in vacuum is presented. The small size (0.25 mm ² ) and the capability of encapsulation at low pressures (≈ 150 Pa) are the main advantages reported. A high sensitivity (85 Hz/g) for a single double-ended tuning fork (DETF) resonator is achieved due to the addition of a force amplification mechanism, fully optimized through finite-element method analysis (FEM). Since a differential approach, composed by two DETF resonators, is implemented, the sensitivity is doubled to approximately 170 Hz/g. The structures have been fabricated using a commercial process (19 μm thickness active layer) and later characterized to validate the design. Device sensitivity, its temperature dependence (2 Hz/°C) and dynamic behavior have been experimentally measured.

A very high-resolution SOI (silicon-on-insulator) MEMS (Micro-Electro-Mechanical Systems) accelerometer for geodetic space grade applications using pull-in time measurements is presented here. Parallelplates implemented in the handle-layer are used to provide the necessary squeeze-film damping, while increasing the effective-mass. Large mass (126 mg) devices with low-Q (quality factor of 0.53) have been fabricated and tested using time transduction. The high measured sensitivity of 1.9 ns/ng enables the use of the device in ultra-high resolution and low-dynamic range applications.

In this paper, we present a bi-directional extended range parallel-plate electrostatic actuator using feedback linearization control. The actuator can have stable displacements up to 90% of the full-gap (limited by mechanical stoppers) on both directions, i.e., the device can move ±2μm within a ±2.25μm gap. The system has successfully tracked references until 1kHz (limited by the dynamics of the device) and it presents a capacitor tuning range of 17, using an actuation voltage from 0 to 10V. The results presented here are a clear advance in respect to the current state-of-the-art in terms of tracking capabilities, total stable displacement and tuning range.