Microelectromechanical Systems Devices Research Articles

Global Bifurcation Behaviors and Control in a Class of Bilateral MEMS Resonators

The investigation of global bifurcation behaviors the vibrating structures of micro-electromechanical systems (MEMS) has received substantial attention. This paper considers the vibrating system of a typical bilateral MEMS resonator containing fractional functions and multiple potential wells. By introducing new variations, the Melnikov method is applied to derive the critical conditions for global bifurcations. By engaging in the fractal erosion of safe basin to depict the phenomenon pull-in instability intuitively, the point-mapping approach is used to present numerical simulations which are in close agreement with the analytical prediction, showing the validity of the analysis. It is found that chaos and pull-in instability, two initial-sensitive phenomena of MEMS resonators, can be due to homoclinic bifurcation and heteroclinic bifurcation, respectively. On this basis, two types of delayed feedback are proposed to control the complex dynamics successively. Their control mechanisms and effect are then studied. It follows that under a positive gain coefficient, delayed position feedback and delayed velocity feedback can both reduce pull-in instability; nevertheless, to suppress chaos, only the former can be effective. The results may have some potential value in broadening the application fields of global bifurcation theory and improving the performance reliability of capacitive MEMS devices.

Application of DC-DC Converter in Sensor and MEMS Device Integration and Packaging

DC-DC (direct current controlled direct current) converter is the core control circuit in the field of power electronics technology. Based on the theory of sensors and MEMS (microelectromechanical systems), this paper constructs a DC-DC converter device integration and packaging model and proposes an enhanced current equalization technology with offset correction function suitable for two-phase DC-DC converters. Aiming at the generation mechanism of the output ripple of the two-phase DC-DC converter, the model adopts the ripple elimination technology based on the interleaved synchronous clock and the self-calibration interleaved time generator, so that each phase of the converter is accurately staggered within the full-load range, and the problem of output ripple amplitude is solved. During the simulation process, a high-performance two-phase DC-DC converter chip is designed and implemented, which includes an adaptive on-time control logic based on ripple feedback, a self-calibrating zero-current turn-off circuit, and a robust power switch transistor drive logic. The experimental results show that the full-load current of the chip reaches 6A, the peak efficiency is 91%, the phase-to-phase current error is <0.6%, and the output ripple is <9 mV. In the 90.265 V AC input, 0-10 W load range, the output voltage error is less than 0.96%, when the load is switched between no-load and full-load, and the system response speed is less than 200 ps, which effectively improves the overall performance of the DC-DC converter.

Vibration analysis of the rotating multilayer piezoelectric Timoshenko nanobeam

The vibration behavior of multilayers piezoelectric nanobeam is investigated in this study. The governing equations of rotating piezoelectric beams are obtained by utilizing the Timoshenko beam theory. The nonlocal continuum theory along with surface elasticity theory are handled to derive the differential governing equation of motion. The differential governing equation of motions is solved by employing the DQM. The results show a great correlation between the numerical results and the presented results in the literature. The results are obtained for four different boundary conditions such as cantilever nanobeam (clamped-free or CF), simply-simply (SS), clamped-simply (CS), and clamped-clamped (CC). The reaction of vibration frequencies to the change of different parameters such as the external voltage, the thermal stress, the angular velocity, etc. is investigated. The results show that the boundary condition type, thermal stress, and external voltage have a vital consequence on the vibration frequency. The results of this study can be appropriated to design and fabricated the nanodevices such as nanomotors, nano turbines, biosensors, nano-electromechanical systems, and micro-electromechanical systems (NEMS/MEMS) devices.

Micro 3D printing of a functional MEMS accelerometer

Microelectromechanical system (MEMS) devices, such as accelerometers, are widely used across industries, including the automotive, consumer electronics, and medical industries. MEMS are efficiently produced at very high volumes using large-scale semiconductor manufacturing techniques. However, these techniques are not viable for the cost-efficient manufacturing of specialized MEMS devices at low- and medium-scale volumes. Thus, applications that require custom-designed MEMS devices for markets with low- and medium-scale volumes of below 5000–10,000 components per year are extremely difficult to address efficiently. The 3D printing of MEMS devices could enable the efficient realization and production of MEMS devices at these low- and medium-scale volumes. However, current micro-3D printing technologies have limited capabilities for printing functional MEMS. Herein, we demonstrate a functional 3D-printed MEMS accelerometer using 3D printing by two-photon polymerization in combination with the deposition of a strain gauge transducer by metal evaporation. We characterized the responsivity, resonance frequency, and stability over time of the MEMS accelerometer. Our results demonstrate that the 3D printing of functional MEMS is a viable approach that could enable the efficient realization of a variety of custom-designed MEMS devices, addressing new application areas that are difficult or impossible to address using conventional MEMS manufacturing.

XPS investigation of 5N purity Al thin foils for MEMS devices

Thin Al foils are promising materials for applications in devices of microelectromechanical systems (MEMS). In this work, three foils of high purity (5N) Al with different thickness (10, 50, and 125 μm) were analyzed by means of X‐ray photoelectron spectroscopy (XPS), before and after annealing (720 K for 30 min). XPS surface analysis and depth profiling of chemical composition were performed to investigate the distribution of Al oxide. Electron energy loss spectroscopy (EELS) measurements were also carried out in order to identify the plasmon losses and chemical state of Al. The loss peaks in the 5N‐Al thin foils were compared with those of an Al foil of commercial purity (99.95 wt%). The thickness of the oxide layer on the sample surface of all the samples is not constant and oxide is thicker in the samples of high purity than in those of commercial quality. Moreover, the thinnest foils of 5N‐Al (10 μm) exhibit the thinnest oxide layer. These findings have been discussed by considering the size effect, that is, mechanical properties of thin foils are improving as the thickness decreases. The complex morphology of the metal‐oxide interface may contribute to enhance the mechanical performances of Al foils with a thickness below ~50 μm, because the free dislocations pile up against the interface which represents an obstacle for their motion hindering plastic deformation. Obtained results suggest that Al foils to be used in MEMS devices should be of high purity and annealed to get a surface completely covered by the oxide layer.

A MEMS Device Integrating Multiple Cantilever Displacement Sensors to Evaluate Flat Machined Surfaces

Multi-point scanning measurement, which is effective in eliminating motion errors of the stage in on-machine profile measurement, requires multiple displacement sensors of equal pitch to measure displacements simultaneously. However, it is not easy to arrange small sensors with high alignment accuracy when applying the multi-point method at a narrow pitch. In addition, if many sensors can be arranged in parallel, improvement in measurement accuracy can be expected. Therefore, a new micro electro mechanical system (MEMS) device for straightness measurement, one that integrates 10 cantilever displacement sensors, has been proposed. This device can be expected to solve the problem involved in the multi-point method because of the characteristics of MEMS, as the semiconductor processing method can make mechanical structures with high accuracy and it can easily make the device with many identical structures. The device is designed to measure waviness less than 100 μm in height. Ten cantilevers of 11 mm length are fabricated in parallel with 1.8 mm pitch on a side of a base substrate 20 mm square. The strain induced by a displacement of the probe placed near the front edge of the cantilever is detected as a change in the resistance of the piezo resistor at the foot of the cantilever. In the fabrication process of this device, crystal anisotropic etching is performed for 12 hours to form probes 250 μm high. A new fabrication process is also proposed in which a protective process is added to prevent damage to the circuits already formed during the etching. A prototype is investigated, and it is found that the resistance value increases about 0.45% in proportion to the displacement of 100 μm. It is therefore confirmed that this device has the basic ability to detect displacement.

Periodic Oscillations in MEMS under Squeeze Film Damping Force

We provide sufficient conditions for the existence of periodic solutions for an idealized electrostatic actuator modeled by the Liénard-type equation x ¨ + F D x , x ̇ + x = β V 2 t / 1 − x 2 , x ∈ − ∞ , 1 with β ∈ ℝ + , V ∈ C ℝ / T ℤ , and F D x , x ̇ = κ x ̇ / 1 − x 3 , κ ∈ ℝ + (called squeeze film damping force), or F D x , x ̇ = c x ̇ , c ∈ ℝ + (called linear damping force). If F D is of squeeze film type, we have proven that there exists at least two positive periodic solutions, one of them locally asymptotically stable. Meanwhile, if F D is a linear damping force, we have proven that there are only two positive periodic solutions. One is unstable, and the other is locally exponentially asymptotically stable with rate of decay of c / 2 . Our technique can be applied to a class of Liénard equations that model several microelectromechanical system devices, including the comb-drive finger model and torsional actuators.

KNN lead-free piezoelectric films grown by sputtering

Potassium sodium niobate [(K,Na)NbO3, KNN] films are promising lead-free piezoelectric materials for microelectromechanical systems (MEMS) devices. We previously developed technologies for forming high-quality KNN films by sputtering, which showed excellent piezoelectric properties comparable to lead zirconate titanate (PZT) films. In the present study, we addressed several challenges with the aim of introducing KNN films into commercialized MEMS devices. First, we optimized the dielectric and piezoelectric properties to realize a suitable performance for actuator and sensor devices. The sensor-type KNN films had a low dielectric constant (248) and a self-poling function, which are greatly beneficial for sensor device performance and the fabrication process. The actuator-type KNN films had a very high e31 value of −13.5 C/m2, which is almost comparable to the top level of PZT films. Next, we found that the DC stress lifetime of KNN films strongly depended on the material used for the adhesion layer of the top electrode. When we used a Pt/RuO2 top electrode, the actuator-type KNN films had a long lifetime (>130 000 s, 300 kV/cm and 200 °C), which is long enough to be used for commercialized MEMS devices. Furthermore, we realized 8-in. KNN wafers with good thickness uniformity across the wafer (±3.5%) by introducing a mass-production-ready sputtering tool: the EB-2500 produced by Canon Anelva. In the near future, these promising results will open the way to replace PZT with KNN in the piezoMEMS industry.

Investigation on magnetic properties of W-doped diamond via first-principles

The electronic and magnetic properties of W-doped diamond were investigated by first-principles calculation. The results revealed that the substitutional site was more favorable than interstitial site for W atom in diamond. The W-doped diamond exhibited the half metallic behavior and stable ferromagnetism with a magnetic moment of 2 μB, while the intrinsic diamond was non-magnetic. The density of states implied that magnetism originated from the p-d hybridization between the W-5d and C-2p states. The spin charge density and magnetic moment of W-doped diamond stemmed from the W atom and the surrounding C atoms. Therefore, the W-doped diamond would be a promising novel type of dilute magnetic semiconductor and could possess a great potential application in spintronic and micro-electromechanical system devices.

Impacts of noise on quenching of some models arising in MEMS technology

In the current work, we study a stochastic parabolic problem. The presented problem is motivated by the study of an idealised electrically actuated MEMS (Micro-Electro-Mechanical System) device in the case of random fluctuations of the potential difference, a parameter that actually controls the operation of MEMS device. We first present the construction of the mathematical model, and then, we deduce some local existence results. Next for some particular versions of the model, relevant to various boundary conditions, we derive quenching results as well as estimations of the probability for such singularity to occur. Additional numerical study of the problem in one dimension follows, which also allows the further investigation the problem with respect to its quenching behaviour.

Application of Micro Electrical Discharge Machining and Electrochemical Machining in Manufacturing of Micro‐Electromechanical Systems: A Review

AbstractThe paper deals with the classification, applications, and advantages of microelectromechanical systems (MEMS), materials, and technologies used. This area of production represents one of the most promising technologies of 21st century, with a big impact in manufacturing 4.0. Nowadays, MEMS fabrication methods have a very big influence in the area of medicine, and therefore the review applications of utmost importance like micromechanical stents or antenna stents are related. The study presents information about MEMS based micro‐EDM, regarding working parameters and some examples of techniques used to realize MEMS devices. These have the purpose to minimize the cost together with the increase of the output technological parameters. The process capabilities of micro‐ECM, associated with working parameters are also treated, and the potential applications in industries like automotive, aerospace, biomedical, security, communication, etc. Finally, some future challenges of MEMS application in the specified fields are exposed.

Towards Reliable Parameter Extraction in MEMS Final Module Testing Using Bayesian Inference.

In micro-electro-mechanical systems (MEMS) testing high overall precision and reliability are essential. Due to the additional requirement of runtime efficiency, machine learning methods have been investigated in recent years. However, these methods are often associated with inherent challenges concerning uncertainty quantification and guarantees of reliability. The goal of this paper is therefore to present a new machine learning approach in MEMS testing based on Bayesian inference to determine whether the estimation is trustworthy. The overall predictive performance as well as the uncertainty quantification are evaluated with four methods: Bayesian neural network, mixture density network, probabilistic Bayesian neural network and BayesFlow. They are investigated under the variation in training set size, different additive noise levels, and an out-of-distribution condition, namely the variation in the damping factor of the MEMS device. Furthermore, epistemic and aleatoric uncertainties are evaluated and discussed to encourage thorough inspection of models before deployment striving for reliable and efficient parameter estimation during final module testing of MEMS devices. BayesFlow consistently outperformed the other methods in terms of the predictive performance. As the probabilistic Bayesian neural network enables the distinction between epistemic and aleatoric uncertainty, their share of the total uncertainty has been intensively studied.

Recent Advances in Flexible RF MEMS.

Microelectromechanical systems (MEMS) that are based on flexible substrates are widely used in flexible, reconfigurable radio frequency (RF) systems, such as RF MEMS switches, phase shifters, reconfigurable antennas, phased array antennas and resonators, etc. When attempting to accommodate flexible deformation with the movable structures of MEMS, flexible RF MEMS are far more difficult to structurally design and fabricate than rigid MEMS devices or other types of flexible electronics. In this review, we survey flexible RF MEMS with different functions, their flexible film materials and their fabrication process technologies. In addition, a fabrication process for reconfigurable three-dimensional (3D) RF devices based on mechanically guided assembly is introduced. The review is very helpful to understand the overall advances in flexible RF MEMS, and serves the purpose of providing a reference source for innovative researchers working in this field.

Low-Temperature Ammonia Gas Sensor Based on NiO/ZnO Heterojunction Nanosheet on MEMS Devices

A double layered nanosheet structure of NiO over ZnO incorporated on Micro electro mechanical system (MEMS) device consisting of heater electrodes and sensing electrodes were investigated for gas sensing characteristics of Ammonia (NH3) gas. This process was achieved by combining 2 different deposition processes which are hydrothermal for ZnO and sputtering for NiO. From the synthesized samples, a series of different structural and morphological properties were analyzed such as X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM) and Energy dispersive spectroscopy (EDS). Sensing properties of ammonia gas are investigated with two different thicknesses of NiO and at different temperatures in order to find the best possible sensing response properties. The inspection of NiO/ZnO loaded samples sensing properties with ammonia gas ranging from 2.25 ppm to 18 ppm, revealed that 20 nm thickness of NiO with ZnO at 35 °C is the optimal sensing condition for the study. 18 ppm of ammonia gas recorded 55.8% sensing response at 35 °C with a response time of 8 s. Selectivity of the NiO/ZnO sensor is tested with 6 different gases such as CO, H2, H2S, NO2, SO2 and NH3, sensor demonstrated good selectivity for ammonia gas and showed excellent repeatability property.

Dimensionality Nanostructures Classification on Scanning Electron Microscopy Images Using Two-Stage Hybrid Classification Algorithm

Nanoscience is increasingly focusing on artificial intelligence approaches to handle the complexities of everyday living demands. Imaging approaches for the categorization of nanomaterials with specified attributes to meet the needs of applications are of interest to researchers in both academia and industry. Machine-learning advancements have been utilized to improve computers’ ability to understand scanning electron microscopy (SEM) images. The aim of the work is to classify the SEM images based on their dimensionality using a two-stage hybrid classification technique. In two-stage hybrid classification, the support vector machine (SVM) is employed in the first stage of classification. Based on the result of SVM classifier, [Formula: see text]-nearest neighbor ([Formula: see text]-NN) is used for final classification. The proposed classification algorithm was able to successfully classify 86.5% of test data into six categories including particles, powders, fibers, wires, thin-films and micro-electromechanical systems (MEMSs) devices. The performance of the proposed method is measured in terms of overall accuracy, class accuracy, precision, recall and [Formula: see text]1-score.

Design and Applications of Integrated Transducers in Commercial CMOS Technology

Monolithic integration of Microelectromechanical Systems (MEMS) directly within CMOS technology offers enhanced functionality for integrated circuits (IC) and the potential improvement of system-level performance for MEMS devices in close proximity to biasing and sense circuits. While the bulk of CMOS-MEMS solutions involve post-processing of CMOS chips to define freely-suspended MEMS structures, there are key applications and conditions under which a solid, unreleased acoustic structure composed of the CMOS stack is preferred. Unreleased CMOS-MEMS devices benefit from lower barrier-to-entry with no post-processing of the CMOS chip, simplified packaging, robustness under acceleration and shock, stress gradient insensitivity, and opportunities for frequency scaling. This paper provides a review of advances in unreleased CMOS-MEMS devices over the past decade, with focus on dispersion engineering of guided waves in CMOS, acoustic confinement, CMOS-MEMS transducers, and large signal modeling. We discuss performance limits with standard capacitive transduction, with emphasis on performance boost with emerging CMOS materials including ferroelectrics under development for memory.

Integrated 1 × 3 MEMS silicon nitride photonics switch.

We present a 1 × 3 optical switch based on a translational microelectromechanical system (MEMS) platform with integrated silicon nitride (SiN) photonic waveguides. The fabricated devices demonstrate efficient optical signal transmission between fixed and suspended movable waveguides. We report a minimum average insertion loss of 4.64 dB and a maximum average insertion loss of 5.83 dB in different switching positions over a wavelength range of 1530 nm to 1580 nm. The unique gap closing mechanism reduces the average insertion loss across two air gaps by a maximum of 7.89 dB. The optical switch was fabricated using a custom microfabrication process developed by AEPONYX Inc. This microfabrication process integrates SiN waveguides with silicon-on-insulator based MEMS devices with minimal stress related deformation of the MEMS platform.

Optimization of an amplification mechanism enabling large displacements in MEMS-based nanomaterial testing devices

In this paper we report on the optimization of an amplification mechanism to enable large displacements in microelectromechanical systems (MEMS). As a case study, we considered a MEMS-based platform for the mechanical testing of nanomaterials, but the results we obtained can be extended to other devices, too. The studied device consists of a couple of V-shaped thermal actuators, heat sink beams, comb drives for sensing the displacements delivered by the actuators to the sample to be tested, and an amplification stage capable of amplifying the produced displacements to tens of micrometers. Regarding the amplification stage, three different schemes were designed and simulated in order to identify the optimal solution. To this aim, static structural analyses have been carried out to predict the performance of the amplification mechanism with respect to geometrical parameters, such as inclination angle, length or width of the beams embedded in the amplification stage. An amplification factor as large as 50 is found. The numerical results show good agreement with those obtained from analytical models. The performance of the complete device is also evaluated through 3D steady-state static thermal-electrical analyses under variable voltage applied to the actuators. • Different types of amplification mechanisms have been analyzed in order to enable large displacements in MEMS devices. • The mechanism consisting of a V-shaped beam provided the best performance. • The final device was designed as able to deliver a displacement of ~1 μm to the sample, while not overcoming 81 °C.

Zn2SnO4 Thin Film for Ozone Gas Sensor Developed on MEMS Device and Synthesized by HiPIMS Co-sputtering

The sensing film of Zn2SnO4 is developed and synthesized by High Power Impulse Magnetron Sputtering (HiPIMS) co-sputtering system which is integrated on the Microelectromechanical Systems (MEMS) gas sensor. The experimental results revealed that the optimal annealing temperature is at 600 °C and optimal operating temperature is at 100 °C which has the best sensing performance for Ozone sensing. It is found that 0.3 ppm of O3 gas concentration gas the response value (Ra/Rg) 39.03 and at 0.05 ppm of low concentration, the sensing response recorded to be 8.03. In the selectivity test, with 5 other gases like CO, NO2, C3H4O3, C2H5OH and H2S, sensor exhibited high selectivity for O3 gas. The Zn2SnO4 sensing film have quickly responded to O3 gas with 6 s response time and the 18 s recovery time. In the current study, the Zn2SnO4 film in MEMS gas sensor shown good detection performance at low gas concentrations and has potential applications in environmental sensing.

Catalytic effect of Ag embedded with ZnO prepared by Co-sputtering on H2S gas sensing MEMS device

Ag doped ZnO thin films are deposited on a micro electromechanical systems (MEMS) device incorporating a microheater and sensing electrodes using a co-sputtering system. Structural properties and sensing properties were tested with pure Zn alongside with 0.15%, 0.3%, 0.5%, 1% and 2% Ag doping concentrations. The H2S gas sensing performance of the MEMS-based devices is evaluated for H2S concentrations in the range of 0.2–1.0 ppm and heating temperatures of 150–300 °C. The optimal sensing performance is obtained with a Ag concentration of 0.5% and a working temperature of 250 °C. For an H2S gas concentration of 1 ppm, the sensor achieves a sensing response of 16% and a response time of 3 s. The sensor additionally shows good selectivity for H2S gas compared to that for CO, NO2, NH3 and SO2, respectively. Finally, different response time phenomenon is explained due to the formation of Ag+ on doped ZnO surface.