A portable and high-resolution optomechanical accelerometer employing a deformable grating-based micro-electro-mechanical system (MEMS) interferometer is presented in this Letter. The movable reflective mirror of this interferometer is realized by a low-frequency vertical sensing structure with a three-dimensional (3D)-spring construction, which, to the best of our knowledge, is first proposed and fabricated in this work. All the components of the sensor are packaged in a metal case with a compact size of 4 cm×6 cm×3.15 cm. The micrometer-scale springs permit the device to have a high mechanical sensitivity of 893.23 µm/g and a resultant self-noise below 2 n g / H z from 2 to 7 Hz. Meanwhile, the measured voltage responsivity is as high as 15,874 V/g, demonstrating it is one of the most sensitive accelerometers reported to date.

Presented in the paper is the design, the simulation, the fabrication and the experiment of a new z-axis resonant accelerometer based on the electrostatic stiffness. The new z-axis resonant micro-accelerometer, which consists of a torsional accelerometer and two plane resonators, decouples the sensing movement of the accelerometer from the oscillation of the plane resonators by electrostatic stiffness, which will improve the performance. The new structure and the sensitive theory of the acceleration are illuminated, and the equation of the scale factor is deduced under ideal conditions firstly. The Ansys simulation is implemented to verify the basic principle of the torsional accelerometer and the plane resonator individually. The structure simulation results prove that the effective frequency of the torsional accelerometer and the plane resonator are 0.66 kHz and 13.3 kHz, respectively. Then, the new structure is fabricated by the standard three-mask deep dry silicon on glass (DDSOG) process and encapsulated by parallel seam welding. Finally, the detecting and control circuits are designed to achieve the closed-loop self-oscillation, to trace the natural frequency of resonator and to measure the system frequency. Experimental results show that the new z-axis resonant accelerometer has a scale factor of 31.65 Hz/g, a bias stability of 727 µg and a dynamic range of over 10 g, which proves that the new z-axis resonant micro-accelerometer is practicable.

Traditional seismometers and gravimeters normally have large volumes and entail high manufacturing costs. Aiming at the miniaturization of such geophysical instruments, a portable microelectromechanical systems (MEMS) accelerometer applicable to seismic-grade measurements is fabricated and characterized in this work. This accelerometer is operating on the deformable grating-based MEMS interferometer, where a new MEMS out-of-plane sensing chip employing double layers of 10- $\mu \text{m}$ -thickness spring is first proposed. The simulation results show that this geometry has a low natural frequency of 52.23 Hz and undergoes a low stress of 26.94 MPa under the gravitational acceleration. The test of the fabricated prototype is implemented in a quiet environment for tracking the inherent microseismic peaks of Earth. The evaluation results demonstrate that the fabricated prototype has achieved a voltage sensitivity of 510.6 V/g. Furthermore, the noise estimation indicates that the self-noise of this sensor has reached 20 ng/ $\sqrt {\text {Hz}}$ from 0.3 to 20 Hz, and a bias stability of 235.4 ng is obtainable at room temperature. Combined with the compact package size of 40.5 cm ³ , the proposed device exhibits a promising prospect in the seismic-grade applications.

The design, simulation, fabrication, and experiments of a novel flow sensor based on resonant sensing with a two-stage microleverage mechanism are presented in this paper. Different from the conventional detection methods for flow sensors, two differential resonators are adopted to implement air flow rate transformation through two-stage leverage magnification. The proposed flow sensor has a high sensitivity since the adopted two-stage microleverage mechanism possesses a higher amplification factor than a single-stage microleverage mechanism. The modal distribution and geometric dimension of the two-stage leverage mechanism and hair are analyzed and optimized by Ansys simulation. A digital closed-loop driving technique with a phase frequency detector-based coordinate rotation digital computer algorithm is implemented for the detection and locking of resonance frequency. The sensor fabricated by the standard deep dry silicon on a glass process has a device dimension of 5100 μm (length) × 5100 μm (width) × 100 μm (height) with a hair diameter of 1000 μm. The preliminary experimental results demonstrate that the maximal mechanical sensitivity of the flow sensor is approximately 7.41 Hz/(m/s)² at a resonant frequency of 22 kHz for the hair height of 9 mm and increases by 2.42 times as hair height extends from 3 mm to 9 mm. Simultaneously, a detection-limit of 3.23 mm/s air flow amplitude at 60 Hz is confirmed. The proposed flow sensor has great application prospects in the micro-autonomous system and technology, self-stabilizing micro-air vehicles, and environmental monitoring.