The significant advancements within the electronics miniaturization field have shifted the scientific interest towards a new class of precision devices, namely microelectromechanical systems (MEMS). Specifically, MEMS refers to microscaled precision devices generally produced through micromachining techniques that combine mechanical and electrical components for fulfilling tasks normally carried out by macroscopic systems. Although their presence is found throughout all the aspects of daily life, recent years have witnessed countless research works involving the application of MEMS within the biomedical field, especially in drug synthesis and delivery, microsurgery, microtherapy, diagnostics and prevention, artificial organs, genome synthesis and sequencing, and cell manipulation and characterization. Their tremendous potential resides in the advantages offered by their reduced size, including ease of integration, lightweight, low power consumption, high resonance frequency, the possibility of integration with electrical or electronic circuits, reduced fabrication costs due to high mass production, and high accuracy, sensitivity, and throughput. In this context, this paper aims to provide an overview of MEMS technology by describing the main materials and fabrication techniques for manufacturing purposes and their most common biomedical applications, which have evolved in the past years.

https://www.mdpi.com/2072-666X/13/2/164/pdf?version=1643089600

Microelectromechanical Systems (MEMS) for Biomedical Applications

The micro-electro-mechanical systems (MEMS)-based sensor technologies are considered to be the enabling factor for the future development of smart sensing applications, mainly due to their small size, low power consumption and relatively low cost. This paper presents a new structurally and thermally stable design of a resonant mode-matched electrostatic z-axis MEMS gyroscope considering the foundry constraints of relatively low cost and commercially available silicon-on-insulator multi-user MEMS processes (SOIMUMPs) microfabrication process. The novelty of the proposed MEMS gyroscope design lies in the implementation of two separate masses for the drive and sense axis using a unique mechanical spring configuration that allows minimizing the cross-axis coupling between the drive and sense modes. For frequency mismatch compensation between the drive and sense modes due to foundry process uncertainties and gyroscope operating temperature variations, a comb-drive-based electrostatic tuning is implemented in the proposed design. The performance of the MEMS gyroscope design is verified through a detailed coupled-field electric-structural-thermal finite element method (FEM)-based analysis.

https://www.mdpi.com/2076-3417/11/3/1129/pdf

A Dual-Mass Resonant MEMS Gyroscope Design with Electrostatic Tuning for Frequency Mismatch Compensation

In this paper we present an innovative approach to the automatic design of MEMS gyroscopes, based on structural size optimization A novel design environment, called feMEMS, is fully developed in Matlab: it allows the parametric generation of the structure geometry, the simulation of its behaviour and the layout optimization by means of gradient based techniques The gyroscope layout is parametrized by a set of design variables, that describe the geometry and position of the mechanical elements composing the structure, namely the internal masses and flexure springs The dynamic behaviour of the gyroscope is simulated through a finite element discretization, focusing on the computation of the structure resonant frequencies and of the mechanical response to the external angular rate Also, the use of substructuring techniques based on static reduction is suggested, in order to reduce the computational cost of the simulations and of the optimization procedure The working scheme of feMEMS is demonstrated considering the mechanical design of a triaxial beating-heart MEMS gyroscope Two possible formulations of the optimization problem are presented and compared: the design objectives are respectively the maximization of the sensor response to the external angular rate and the maximization of spurious modes frequencies, while constraints are imposed to properly tune the drive and sense resonant frequencies and to satisfy the requirements on the available design space

Size optimization of MEMS gyroscopes using substructuring

Micro-electromechanical systems (MEMS) vibrating gyroscopes have gained a lot of attention over the last two decades because of their low power consumption, easy integration, and low fabrication cost. The usage of the gyroscope equipped with an inertial measurement unit has increased tremendously, with applications ranging from household devices to smart electronics to military equipment. However, reliability issues are still a concern when operating this inertial sensor in harsh environments, such as to control the movement and alignment of mini-satellites in space, tracking firefighters at an elevated temperature, and assisting aircraft navigation in gusty turbulent air. This review paper focuses on the key fundamentals of the MEMS vibrating gyroscopes, first discussing popular designs including the tuning fork, gimbal, vibrating ring, and multi-axis gyroscopes. It further investigates how bias stability, angle random walk, scale factor, and other performance parameters are affected in harsh environments and then discusses the reliability issues of the gyroscopes.

/pdf/a-review-of-mems-vibrating-gyroscopes-and-their-reliability-3pnbsicv.pdf

A Review of MEMS Vibrating Gyroscopes and Their Reliability Issues in Harsh Environments

This paper presents a design optimization approach for a single-drive, 3-axis Microelectromechanical Systems (MEMS) gyroscope. Mathematical models for springs are obtained and a simplified structure for single-drive, 3-axis MEMS gyroscope is proposed. In the proposed structure, concentrated spring architecture was exploited to critical mechanical elements in order to mitigate the fabrication imperfections in the design and the effect of unwanted frequencies. The number of elastic elements was also reduced, while increasing the active area efficiently. The proposed simplified, single-drive, 3-axis MEMS gyroscope is using mode split approach, having a drive resonant frequency of 
$$25443\mathrm{H}\mathrm{z},$$

 with the 
$$x-\mathrm{s}\mathrm{e}\mathrm{n}\mathrm{s}\mathrm{e}, y-\mathrm{s}\mathrm{e}\mathrm{n}\mathrm{s}\mathrm{e}, \mathrm{a}\mathrm{n}\mathrm{d}\mathrm\ z-\mathrm{s}\mathrm{e}\mathrm{n}\mathrm{s}\mathrm{e}$$

 being 
$$25529\mathrm{H}\mathrm{z}$$

, 
$$25612\mathrm{H}\mathrm{z}$$

, and 
$$25621\mathrm{H}\mathrm{z},$$

 respectively. The drive and desired sense resonant frequencies are separated by a frequency difference of less than 300
$$\mathrm{H}\mathrm{z}$$

, while the unwanted ones are above 
$$3 \mathrm{k}\mathrm{H}\mathrm{z}$$

.

Modelling and optimization of single drive 3-axis MEMS gyroscope

This paper presents the design, fabrication, and characterization of a highly sensitive, single drive multi-axis gyroscope. The multi-axis gyroscope allows for a wide bandwidth in all three axes (X, Y, Z) and exhibits high linearity. The fabricated multi-axis gyroscope was fabricated with a structural thickness of 30 µm and packaged at 100 mtorr using wafer level packaging. The fabricated multi-axis gyroscope has a small footprint of 1426 × 1426 µm2, making it one of the smallest multi-axis gyroscopes. A custom printed circuit board (PCB) was designed for the evaluation of the multi-axis gyroscope. The experimental results demonstrate that the gyroscope has a high sensitivity of 12.56 μ V / dps , 17.13 μ V / dps and 25.79 μ V / dps in the roll (X-sense), pitch (Y-sense) and yaw (Z-sense) modes respectively. The scale-factor non-linearity of the gyroscope is less than 0.2 % for roll and pitch mode and 0.001 % for the yaw mode, in the full-scale range of ± 1500 deg / s . The multi-axis gyroscope demonstrates an angle random walk of 2.79 dps / Hz , 2.14 dps / Hz , and 1.42 dps / Hz , for the roll, pitch and yaw rate with the in-run bias stability 1.62 deg / s , 1.14 deg / s and 0.84 deg / s respectively.

https://www.mdpi.com/2072-666X/10/6/410/pdf

Single Drive Multi-Axis Gyroscope with High Dynamic Range, High Linearity and Wide Bandwidth.

In this paper, a COMSOL Multiphysics-based methodology is presented for evaluation of the microelectromechanical systems (MEMS) gyroscope. The established finite element analysis (FEA) model was successfully validated through a comparison with analytical and Matlab/Simulink analysis results. A simplified single-drive, 3-axis MEMS gyroscope was analyzed using a mode split approach, having a drive resonant frequency of 24,918 Hz, with the x-sense, y-sense, and z-sense being 25,625, 25,886, and 25,806 Hz, respectively. Drive-mode analysis was carried out and a maximum drive-displacement of 4.0 μm was computed for a 0.378 μN harmonic drive force. Mechanical sensitivity was computed at 2000 degrees per second (dps) input angular rate while the scale factor for roll, pitch, and yaw was computed to be 0.014, 0.011, and 0.013 nm/dps, respectively.

https://www.mdpi.com/2072-666X/11/12/1030/pdf

Sensitivity Analysis of Single-Drive, 3-axis MEMS Gyroscope Using COMSOL Multiphysics

In this paper, a new design technique is presented to estimate and reduce the cross-axis sensitivity (CAS) in a single-drive multi-axis microelectromechanical systems (MEMS) gyroscope. A simplified single-drive multi-axis MEMS gyroscope, based on a mode-split approach, was analyzed for cross-axis sensitivity using COMSOL Multiphysics. A design technique named the “ratio-matching method” of drive displacement amplitudes and sense frequency differences ratios was proposed to reduce the cross-axis sensitivity. Initially, the cross-axis sensitivities in the designed gyroscope for x and y-axis were calculated to be 0.482% and 0.120%, respectively, having an average CAS of 0.301%. Using the proposed ratio-matching method and design technique, the individual cross-axis sensitivities in the designed gyroscope for x and y-axis were reduced to 0.018% and 0.073%, respectively. While the average CAS was reduced to 0.045%, showing a reduction rate of 85.1%. Moreover, the proposed ratio-matching method for cross-axis sensitivity reduction was successfully validated through simulations by varying the coupling spring position and sense frequency difference variation analyses. Furthermore, the proposed methodology was verified experimentally using fabricated single-drive multi-axis gyroscope.

/pdf/design-approach-for-reducing-cross-axis-sensitivity-in-a-43mv1jc67m.pdf

Design Approach for Reducing Cross-Axis Sensitivity in a Single-Drive Multi-Axis MEMS Gyroscope

In this letter, a design technique is presented to reduce the cross-axis sensitivity (CAS) in single-drive multi-axis microelectromechanical systems (MEMS) gyroscope. A design technique based on resonant mode ordering concerning drive-displacement amplitudes ratio and frequency differences ratio was proposed. A simplified single-drive multi-axis MEMS gyroscope, based on the mode-split approach, was analyzed for cross-axis sensitivity. The designed gyroscope utilizing a driving scheme based on a simple folded coupling spring has equal x and y – axes drive-displacement amplitudes of 3.892 μ m respectively. The proposed resonant mode ordering technique was used, and an equal sense-frequency difference of 184 Hz was achieved with respect to drive-mode frequency. The designed gyroscope having common resonant mode order was analyzed, and CAS of x and y – axes was computed to be 0.241% and 0.387% respectively. The proposed resonant mode order technique successfully reduced the cross-axis sensitivity in the designed gyroscope. The reduced cross-axis sensitivities of x and y – axes were 0.025% and 0.076% respectively. Comparison of both designs showed a reduced rate of 89.627% and 80.362% in x and y – axes respectively. The main sensitivities of x and y – axes were computed to be 0.055 nm/dps respectively. Furthermore, the significance of the proposed technique was experimentally verified.

Hussamud Din

Papers

Single Drive Multi-Axis Gyroscope with High Dynamic Range, High Linearity and Wide Bandwidth.

Modelling and optimization of single drive 3-axis MEMS gyroscope

Sensitivity Analysis of Single-Drive, 3-axis MEMS Gyroscope Using COMSOL Multiphysics

Design Approach for Reducing Cross-Axis Sensitivity in a Single-Drive Multi-Axis MEMS Gyroscope

Mode ordering of single-drive multi-axis MEMS gyroscope for reduced cross-axis sensitivity