MEMS Resonators Research Articles

A Bent-TBTF Resonant MEMS Accelerometer Using Auxiliary Supporting Beams

A Bent-TBTF Resonant MEMS Accelerometer Using Auxiliary Supporting Beams

Characterization of Three-Mode Combination Internal Resonances in Electrostatically Actuated Flexible–Flexible Microbeams

Abstract Nonlinear intermodal coupling based on internal resonances in MEMS resonators has advanced significantly over the past two decades for various real-world applications. In this study, we demonstrate the existence of various three-mode combination internal resonances between the first five flexural modes of electrostatically actuated flexible–flexible beams and dynamic modal interaction between three modes via internal resonance. We first calculate the natural frequencies of the beam as a function of the stiffnesses of the transverse and rotational springs of the flexible supports, utilizing both analytical formulation and finite element analysis (FEA). Following this, we identify six combination internal resonances among the first five modes and use applied DC voltage to validate the exactness of one commensurable internal resonance condition (ω2=ω5−ω4). Subsequently, we studied a detailed forced vibration analysis corresponding to this resonance condition by solving the five-mode coupled governing equations through numerical time integration and the method of multiple scales. The results compellingly exhibit three-mode intermodal coupling among the second, fourth, and fifth modes as a function of excitation amplitude and frequency. Alongside this, intriguing nonlinear phenomena such as threshold behavior, saturation phenomena, and autoparametric instability are observed. Finally, this paper provides a systematic methodology for investigating three-mode combination internal resonances and related nonlinear dynamics, offering significant insights that could be used in observing phonon or mechanical lasing phenomena in MEMS resonators.

Sensitivity enhancement of nonlinear micromechanical sensors using parametric symmetry breaking

The working mechanism of resonant sensors is based on tracking the frequency shift in the linear vibration range. Contrary to the conventional paradigm, in this paper, we show that by tracking the dramatic frequency shift of the saddle-node bifurcation on the nonlinear parametric isolated branches in response to external forces, we can dramatically boost the sensitivity of MEMS force sensors. Specifically, we first theoretically and experimentally investigate the double hysteresis phenomena of a parametrically driven micromechanical resonator under the interaction of intrinsic nonlinearities and direct external drive. We demonstrate that the double hysteresis is caused by symmetry breaking in the phase states. The frequency response undergoes an additional amplitude jump from the symmetry-breaking-induced parametric isolated branch to the main branch, resulting in double hysteresis in the frequency domain. We further demonstrate that significant force sensitivity enhancement can be achieved by monitoring the dramatic frequency shift of the saddle-node bifurcations on the parametric isolated branches before the bifurcations annihilate. Based on the sensitivity enhancement effect, we propose a new sensing scheme which employs the frequency of the top saddle-node bifurcation in the parametric isolated branches as an output metric to quantify external forces. The concept is verified on a resonant MEMS charge sensor. A sensitivity of up to 39.5 ppm/fC is achieved, significantly surpassing the state-of-the-art resonant charge sensors. This work provides a new mechanism for developing force sensors of high sensitivity.

A novel high-Q Lamé mode bulk acoustic resonator

This study introduces a novel high-Q Lamé mode MEMS resonator, optimized through support beam structures and etching hole distributions to minimize anchor losses and thermal elastic dissipation (TED). Fabricated using a Silicon-On-Insulator (SOI) process, the resonators achieved Q values of 129,200 and 102,100 in different designs, demonstrating significant improvements in vacuum conditions and highlighting air damping as a key loss mechanism. Nonlinear analysis revealed material nonlinearity dominance. These findings offer valuable guidelines for developing high-end MEMS devices, such as low phase noise oscillators and high-resolution sensors, by showcasing substantial reductions in energy dissipation and enhanced Q factors through structural optimizations.

Static and dynamic characteristics of electrostatically coupled MEMS beams under asymmetric actuation conditions

Abstract Electrostatically actuated microbeams have gained prominence due to their applications as micro-actuators and ultrasensitive sensors. In this study, we investigate the dynamic behavior of electrostatically coupled microbeams, specifically focusing on the effects of asymmetric actuation conditions. Our investigation encompasses both static and dynamic characteristics of the coupled microbeam system, considering various gap ratios between the beams and the fixed electrodes. Within the coupled system, two doubly clamped microbeams are positioned between two fixed electrodes. We develop a reduced-order model (ROM) to investigate static and dynamic responses of the coupled system. To validate the ROM, we rigorously compare its results with finite element (FE) simulations. Our findings reveal that the gap ratios play a pivotal role in shaping the system’s response. Notably, first two natural frequencies are important for design of micro-resonators and they exhibit complex variation with respect to the applied DC voltage. Moreover, we explore resonance frequency tunability and investigated interplay between geometric nonlinearity and nonlinear electrostatic actuation forces. These insights contribute significantly to the efficient design of MEMS resonators.

Piezoelectrically and Capacitively Transduced Hybrid MEMS Resonator with Superior RF Performance and Enhanced Parasitic Mitigation by Low-Temperature Batch Fabrication

Piezoelectrically and Capacitively Transduced Hybrid MEMS Resonator with Superior RF Performance and Enhanced Parasitic Mitigation by Low-Temperature Batch Fabrication

High sensitivity, thermal noise-driven aluminum-based resonant MEMS humidity sensor

The integration of connected devices and the Internet of Things in the era of Industry 4.0 has led to the transformation of various sectors. Sensors, particularly for humidity measurement, play a pivotal role in applications such as respiration and wound monitoring, human–machine interfaces, fuel cells, and circuit failure detection. While conventional humidity sensors dominate the market, gravimetric-based sensing offers promise but faces challenges due to complex fabrication, high cost, and nonlinearity. This study explores gravimetric platforms for humidity sensing and proposes linear and nonlinear schemes to detect humidity. The linear sensors exhibit consistent frequency shifts with humidity changes, while the nonlinear sensors introduce a turn-around point where nonlinear effects counteract mass-loading. We address this limitation by splitting the dynamic range into low and high ranges on either side of this point, thereby creating one-to-one relationships. Both sensor types demonstrate high sensitivity (from 39068 to −23568 ppm/%RH for nonlinear and 5809 ppm/%RH for linear) and repeatability, emphasizing their suitability for real-time humidity monitoring. Moreover, the thermal noise-driven resonators underlying the sensors do not require external input, thereby enhancing their suitability for low-power applications. These findings provide a foundation for innovative real-time sensing applications and offer insights into optimizing sensitivity and stability in humidity sensing and other applications.

Exploiting Nonlinearities of Electrostatic MEMS Resonators for Tunable Low Pressure Sensing

In this paper, we demonstrate the potential functionalization of inherent nonlinearities associated with electrostatic MEMS resonators for low air pressure applications, with operating ranges as low as 0.65-295 mbar. The proposed pressure sensor is made of a polysilicon microplate subject to electrostatic actuation via an underneath electrode and attached to two cantilever microbeams. The pressure sensing mechanism relies on the motion-induced current method, a transduction mechanism that converts the dynamic alteration of the microplate due to pressure variations into an electrical signal detected via a lock-in amplifier. The experimental study showed evidence of the possible tunability of the pressure sensor via the deployment of different detection mechanisms to achieve superior performance in terms of sensitivity and low pressure operating range. These mechanisms rely on nonlinear dynamic features that result from the strong coupling between the microplate and the surrounding fluid along with the electrostatic actuation. These include dynamic pull-in instability, bifurcation and softening behavior associated with the elastic effect of the squeeze-film damping. The experimental results revealed that tracking the bifurcation frequency allows for the detection of low pressure levels, in the range of a few millibars. This capability is not provided by the resonance frequency shift method, which, while offering higher sensitivity, does not achieve the same low-pressure detection.

Design, Fabrication, and Dynamic Analysis of a MEMS Ring Resonator Supported by Twin Circular Curve Beams.

In this paper, we present a compressive study on the design and development of a MEMS ring resonator and its dynamic behavior under electrostatic force when supported by twin circular curve beams. Finite element analysis (FEA)-based modeling techniques are used to simulate and refine the resonator geometry and transduction. In proper FEA or analytical modeling, the explicit description and accurate values of the effective mass and stiffness of the resonator structure are needed. Therefore, here we outlined an analytical model approach to calculate those values using the first principles of kinetic and potential energy analyses. The natural frequencies of the structure were then calculated using those parameters and compared with those that were simulated using the FEA tool ANSYS. Dynamic analysis was performed to calculate the pull-in voltage, shift of resonance frequency, and harmonic analyses of the ring to understand how the ring resonator is affected by the applied voltage. Additional analysis was performed for different orientations of silicon and assessing the frequency response and frequency shifts. The prototype was fabricated using the standard silicon-on-insulator (SOI)-based MEMS fabrication process and the experimental results for resonances showed good agreement with the developed model approach. The model approach presented in this paper can be used to provide valuable insights for the optimization of MEMS resonators for various operating conditions.

Investigation of a MEMS resonator model with quintic nonlinearity

Investigation of a MEMS resonator model with quintic nonlinearity

Differential capacitive mass sensing based on mode localization in coupled microbeam arrays

In this paper, we developed a multi-physics model of an electrostatic MEMS resonator made of an array of mechanically-coupled beams and investigate its potential use for mass detection applications. Experiments were conducted on two- and three-coupled beams under electrostatic actuation to verify the capability of the model to predict the mechanical response of coupled beam arrays. The fabricated device, comprising polysilicon-coupled microbeams, is produced using the Multi-User MEMS Processes, followed by an experimental investigation. Numerical results were found in good agreement with their experimental counterparts. The developed model was used to demonstrate the possible adjustment of the electrostatic actuation to enhance the sensitivity of the dynamic response of the coupled MEMS resonator to mass perturbations. By leveraging the mode localization phenomenon and incorporating a novel differential capacitance sensing mechanism, a notable 84% improvement in sensitivity when switching from two-beam to three-beam system while operating near the second mode in the linear regime. Actuating the MEMS device at higher voltages enabled to achieve higher sensitivity thanks to the activation of nonlinear effects such as bifurcation and softening. We observed the transition from nonlinear to nearly-linear dynamic response of the coupled beams upon the addition of mass and demonstrated how bifurcations that cause a sudden shift to a high-amplitude motion can be utilized in differential capacitance-based mass sensing. Additionally, the suggested detection mechanism allows for overcoming the inherent parasitic capacitance, thereby mitigating low signal-to-noise ratios.

Enhanced anchor quality factor of an aluminium nitride-on-silicon MEMS resonator using support tethers based on compound leaf-shaped one dimensional phononic crystal

Enhanced anchor quality factor of an aluminium nitride-on-silicon MEMS resonator using support tethers based on compound leaf-shaped one dimensional phononic crystal

Single-structure 3-axis Lorentz force magnetometer based on an AlN-on-Si MEMS resonator

This work presents a single-structure 3-axis Lorentz force magnetometer (LFM) based on an AlN-on-Si MEMS resonator. The operation of the proposed LFM relies on the flexible manipulation of applied excitation currents in different directions and frequencies, enabling the effective actuation of two mechanical vibration modes in a single device for magnetic field measurements in three axes. Specifically, the excited out-of-plane drum-like mode at 277 kHz is used for measuring the x- and y-axis magnetic fields, while the in-plane square-extensional mode at 5.4 MHz is used for measuring the z-axis magnetic field. The different configurations of applied excitation currents ensure good cross-interference immunity among the three axes. Compared to conventional capacitive LFMs, the proposed piezoelectric LFM utilizes strong electromechanical coupling from the AlN layer, which allows it to operate at ambient pressure with a high sensitivity. To understand and analyze the measured results, a novel equivalent circuit model for the proposed LFM is also reported in this work, which serves to separate the effect of Lorentz force from the unwanted capacitive feedthrough. The demonstrated 3-axis LFM exhibits measured magnetic responsivities of 1.74 ppm/mT, 1.83 ppm/mT and 6.75 ppm/mT in the x-, y- and z-axes, respectively, which are comparable to their capacitive counterparts.

Directional Multi-Resonant Micro-Electromechanical System Acoustic Sensor for Low Frequency Detection.

This paper reports on the design, modeling, and characterization of a multi-resonant, directional, MEMS acoustic sensor. The design builds on previous resonant MEMS sensor designs to broaden the sensor's usable bandwidth while maintaining a high signal-to-noise ratio (SNR). These improvements make the sensor more attractive for detecting and tracking sound sources with acoustic signatures that are broader than discrete tones. In-air sensor characterization was conducted in an anechoic chamber. The sensor was characterized underwater in a semi-anechoic pool and in a standing wave tube. The sensor demonstrated a cosine-like directionality, a maximum acoustic sensitivity of 47.6 V/Pa, and a maximum SNR of 88.6 dB, for 1 Pa sound pressure, over the bandwidth of the sensor circuitry (100 Hz-3 kHz). The presented design represents a significant improvement in sensor performance compared to similar resonant MEMS sensor designs. Increasing the sensitivity of a single-resonator design is typically associated with a decrease in bandwidth. This multi-resonant design overcomes that limitation.

Fabrication of low-resonant-frequency inertial MEMS using through-silicon DRIE applied to silicon-on-glass

This paper reports on a fabrication process suitable for ultra-low resonant frequency inertial MEMS sensors. The low resonant frequency is achieved by electrically tunable springs and a heavy mass formed by through-silicon deep reactive-ion etching (DRIE) applied to a silicon-on-glass. A thermal issue of through-silicon DRIE (TSD) stemming from the low-resonant-frequency structure is circumvented by two methods: introducing cooling time between the DRIE steps, and adopting a metal hard mask. A blade dicing method suited for this process is also presented. To monitor the verticality of TSD, a non-destructive taper detection method that utilizes a capacitance–voltage (CV) curve is proposed and verified.

Aluminum Nitride MEMS Resonant Pressure Gauges Without Vacuum Packaging

Aluminum Nitride MEMS Resonant Pressure Gauges Without Vacuum Packaging

Highly Reliable Diamond MEMS Dual Sensor for Magnetic Fields and Temperatures with Self‐Recognition Algorithms

AbstractNearly all sensors inevitably suffer from environmental influence such as temperature fluctuation. To precisely process the external signals, independent temperature compensation devices or electronic circuits are usually required, making the overall system and algorithms sophisticated. Especially, when the environment temperature is as high as over 200 °C, both the sensors and temperature‐compensation devices encounter the reliability problem. In this work, an intelligent multifunctional sensor utilizing single‐crystal diamond (SCD) microelectromechanical (MEMS) resonators is demonstrated that can sense both magnetic fields and temperatures up to 300 °C, independently. The strategy is to integrate a magnetostrictive thin film and a non‐magnetic thin film on different diamond MEMS resonators on the same diamond chip for simultaneous magnetic field sensing and temperature monitoring, respectively. The multi‐resonators based on diamond MEMS offer a promising platform for multi‐parameter sensing immune to environment interference.

Design and Optimization of MEMS Resonant Pressure Sensors with Wide Range and High Sensitivity Based on BP and NSGA-II.

With the continuous progress of aerospace, military technology, and marine development, the MEMS resonance pressure sensor puts forward the requirements of not only a wide range but also high sensitivity. However, traditional resonators are hardly compatible with both. In response, we propose a new sensor structure. By arranging the resonant beam and the sensitive diaphragm vertically in space, the new structure improves the rigidity of the diaphragm without changing the thickness of the diaphragm and achieves the purpose of increasing the range without affecting the sensitivity. To find the optimal structural parameters for the sensor sensitivity and range, and to prevent the effects of modal disturbances, we propose a multi-objective optimization design scheme based on the BP and NSGA-II algorithms. The optimization of the structure parameters not only improved the sensitivity but also increased the interference frequency to solve the issue of mode interference. The optimized structure achieves a sensitivity and range of 4.23 Hz/kPa and 1-10 MPa, respectively. Its linear influence factor is 38.07, significantly higher than that of most resonant pressure sensors. The structural and algorithmic optimizations proposed in this paper provide a new method for designing resonant pressure sensors compatible with a wide range and high sensitivity.

A Q-factor Boost Strategy for High-Order Width-Extensional Mode MEMS Resonators by Varied Unit Length

A Q-factor Boost Strategy for High-Order Width-Extensional Mode MEMS Resonators by Varied Unit Length

Dynamical Analysis, Circuit Design, and Fuzzy Prescribed Performance Backstepping Control of the FO Weakly Coupled MEMS Resonators

Dynamical Analysis, Circuit Design, and Fuzzy Prescribed Performance Backstepping Control of the FO Weakly Coupled MEMS Resonators