Microelectromechanical Systems Research Articles

Accuracy and reliability improved GNSS partial ambiguity resolution assisted by a MEMS inertial measurement unit

Traditional partial ambiguity resolution (PAR) methods based on integer least-squares (ILS-PAR) assume that the ambiguity terms are unbiased integers, which is seldomly true in challenging environments of the Global Navigation Satellite System (GNSS). The bias will lead to unreliable positioning solutions. This study proposes a reliable PAR method based on the tightly coupling of GNSS and inertial navigation system (INS) and the solution separation with external solution (SSE) statistical testing algorithm. First, the inertial measurement unit (IMU) mechanization results are compensated using the latest fixed real-time kinematic (RTK) solutions, thus high-accuracy INS predictions are obtainable at the current GNSS epoch. Second, the SSE method based on double-differenced (DD) carrier-phase measurements are applied to select and validate the ambiguity subset and perform the GNSS/INS integration. A dynamic vehicular experiment with a low-cost microelectromechanical systems (MEMS) device has been conducted and the results indicate that the proposed method can ensure good performance of both accuracy and reliability.

Design and Analysis of MEMS-Based Capacitive Power Inverter Using Electrostatic Transduction

In this study, a capacitive microelectromechanical system (MEMS) based DC/AC power inverter design for renewable energy applications is proposed, modeled, and analyzed. In the proposed approach, electrostatic actuation is preferred to develop a DC/AC power inverter with varying phase overlap lengths for solar energy systems. The operating voltage required during the analysis is applied to the active part as the tensile stress. Thus, the maximum displacement is achieved with less instability. The developed inverter is based on MEMS to achieve miniaturized performances, producing smooth sine wave output, efficiently obtaining the signal frequency, and low power consumption. The proposed inverter has a thickness of 325 μm, an active settlement area of 45x45x0.585 mm3, and an initial capacitance value of 2.9 pF. In addition, a 50 Hz mechanical resonance frequency was used to be compatible with the frequency of the city network. It can convert voltage values between 0.5V and 24V DC with a MEMS power inverter. Since the inverter is based on a capacitive structure, it provides near-zero power consumption. The frequency and waveform of the converted DC/AC signal match the AC signal of a power grid with an efficiency of 5%.

Research on Adaptive Closed-Loop Control of Microelectromechanical System Gyroscopes under Temperature Disturbance.

Microelectromechanical System (MEMS) gyroscopes are inertial sensors used to measure angular velocity. Due to their small size and low power consumption, MEMS devices are widely employed in consumer electronics and the automotive industry. MEMS gyroscopes typically use closed-loop control systems, which often use PID controllers with fixed parameters. These classical PID controllers require a trade-off between overshoot and rise time. However, temperature variations can cause changes in the gyroscope's parameters, which in turn affect the PID controller's performance. To address this issue, this paper proposes an adaptive PID controller that adjusts its parameters in response to temperature-induced changes in the gyroscope's characteristics, based on the error value. A closed-loop control system using the adaptive PID was developed in Simulink and compared with a classical PID controller. The results demonstrate that the adaptive PID controller effectively tracked the changes in the gyroscope's parameters, reducing overshoot by 96% while maintaining a similar rise time. During gyroscope startup, the adaptive PID controller achieves faster stabilization with a 0.036 s settling time, outperforming the 0.06 s of the conventional PID controller.

A Detailed Analysis of the Dynamic Behavior of a MEMS Vibrating Internal Ring Gyroscope.

This paper presents the development of an analytical model of an internal vibrating ring gyroscope in a Microelectromechanical System (MEMS). The internal ring structure consists of eight semicircular beams that are attached to the externally placed anchors. This research work analyzes the vibrating ring gyroscope's in-plane displacement behavior and the resulting elliptical vibrational modes. The elliptical vibrational modes appear as pairs with the same resonance frequency due to the symmetric structure of the design. The analysis commences by conceptualizing the ring as a geometric structure with a circular shape possessing specific dimensions such as thickness, height, and radius. We construct a linear model that characterizes the vibrational dynamics of the internal vibrating ring. The analysis develops a comprehensive mathematical formulation for the radial and tangential displacements in local polar coordinates by considering the inextensional displacement of the ring structure. By utilizing the derived motion equations, we highlight the underlying relationships driving the vibrational characteristics of the MEMS' vibrating ring gyroscope. These dynamic vibrational relationships are essential in enabling the vibrating ring gyroscope's future utilization in accurate navigation and motion sensing technologies.

Monolithic finite element modeling of compressible fluid‐structure‐electrostatics interactions in MEMS devices

AbstractThis work presents a monolithic finite element strategy for the accurate solution of strongly‐coupled fluid‐structure‐electrostatics interaction problems involving a compressible fluid. The complete set of equations for a compressible fluid is employed within the framework of the arbitrary Lagrangian–Eulerian (ALE) fluid formulation on the reference configuration. The proposed numerical approach incorporates geometric nonlinearities of both the structural and fluid domains, and can thus be used for investigating dynamic pull‐in phenomena and squeeze film damping in high aspect‐ratio micro‐electro‐mechanical systems (MEMS) structures immersed in a compressible fluid. Through various illustrative examples, we demonstrate the significant influence of fluid compressibility on the dynamics of MEMS devices subjected to constrained geometry and/or high‐frequency electrostatic actuation. Moreover, we compare the proposed formulation with the nonlinear compressible Reynolds equation and highlight that, particularly at low pressures and high fluid viscosity, the Reynolds equation fails to provide a reliable approximation to the complete set of equations utilized in our proposed formulation.

Ultrahigh Electrostrictive Effect in Lead-Free Sodium Bismuth Titanate-Based Relaxor Ferroelectric Thick Film.

In recent years, the development of environmentally friendly, lead-free ferroelectric films with prominent electrostrictive effects have been a key area of focus due to their potential applications in micro-actuators, sensors, and transducers for advanced microelectromechanical systems (MEMS). This work investigated the enhanced electrostrictive effect in lead-free sodium bismuth titanate-based relaxor ferroelectric films. The films, composed of (Bi0.5Na0.5)0.8-xBaxSr0.2TiO3 (BNBST, x = 0.02, 0.06, and 0.11), with thickness around 1 μm, were prepared using a sol-gel method on Pt/TiO2/SiO2/Si substrates. By varying the Ba2+ content, the crystal structure, morphology, and electrical properties, including dielectric, ferroelectric, strain, and electromechanical performance, were investigated. The films exhibited a single pseudocubic structure without preferred orientation. A remarkable strain response (S > 0.24%) was obtained in the films (x = 0.02, 0.06) with the coexistence of nonergodic and ergodic relaxor phases. Further, in the x = 0.11 thick films with an ergodic relaxor state, an ultrahigh electrostrictive coefficient Q of 0.32 m4/C2 was achieved. These findings highlight the potential of BNBST films as high-performance, environmentally friendly electrostrictive films for advanced microelectromechanical systems (MEMS) and electronic devices.

Key Technologies in Developing Chip-Scale Hot Atomic Devices for Precision Quantum Metrology.

Chip-scale devices harnessing the interaction between hot atomic ensembles and light are pushing the boundaries of precision measurement techniques into unprecedented territory. These advancements enable the realization of super-sensitive, miniaturized sensing instruments for measuring various physical parameters. The evolution of this field is propelled by a suite of sophisticated components, including miniaturized single-mode lasers, microfabricated alkali atom vapor cells, compact coil systems, scaled-down heating systems, and the application of cutting-edge micro-electro-mechanical system (MEMS) technologies. This review delves into the essential technologies needed to develop chip-scale hot atomic devices for quantum metrology, providing a comparative analysis of each technology's features. Concluding with a forward-looking perspective, this review discusses the future potential of chip-scale hot atomic devices and the critical technologies that will drive their advancement.

An Ionization-Based Aerosol Sensor and Its Performance Study.

In recent years, with the rapid development of new energy vehicles, the safety issues of lithium-ion batteries have attracted attentions from all sectors of society. Research has found that during the thermal runaway process of lithium-ion batteries, aerosol emissions usually occur earlier than other gases. Accurate and timely measurement of these aerosol concentrations can help to warn the power battery pack fires. However, existing aerosol sensors are unable to meet the requirements of real-time monitoring and high precision. This article proposes an ionization mechanism based aerosol sensor that works at principles of field emission, field charging and gas discharge, and investigates its static and dynamic response characteristics. The sensor is manufactured and assembled using Microelectro Mechanical Systems processing technology. The sensor exhibits superior performances in terms of range, sensitivity, nonlinearity, repeatability, response time, and other aspects. The study provides a new solution for current aerosol detection with great potential for application.

Development and Integration of an Ultraminiaturized Gas Chromatograph Prototype Based on Lab-on-a-Chip Microelectromechanical Systems for Space Exploration Missions

Development and Integration of an Ultraminiaturized Gas Chromatograph Prototype Based on Lab-on-a-Chip Microelectromechanical Systems for Space Exploration Missions

On a parabolic equation in microelectromechanical systems with an external pressure

The parabolic problem on a bounded domain of with Dirichlet boundary condition models the microelectromechanical systems (MEMS) device with an external pressure term. In this paper, we classify the behavior of the solutions to this equation. We first show that under certain initial conditions, there exist critical constants and such that when , there exists a global solution, while for or , the solution quenches in finite time. The estimates of voltage , quenching time , and pressure term are investigated. The quenching set is proved to be a compact subset of with an additional condition on , provided is a convex bounded set. In particular, if is radially symmetric, then the origin is the only quenching point. Furthermore, we not only derive the two‐sided bound estimate for the quenching solution but also obtain its asymptotic behavior near the quenching time.

Optimizing the Electrode Geometry of an In-Plane Unimorph Piezoelectric Microactuator for Maximum Deflection

Piezoelectric microactuators have been widely used for actuation, sensing, and energy harvesting. While out-of-plane piezoelectric configurations are well established, both in-plane deflection and asymmetric electrode placement have been underexplored in terms of actuation efficiency. This study explores the impact of asymmetric electrode geometry on the performance of slender unimorph actuators that deflect in-plane, where actuator length is much larger than width or thickness. After validating the finite element modeling method against experimental data, the geometric parameters of the proposed unimorph model are manipulated to explore the effect of different electrode geometries and layer thicknesses on actuation efficiency. Four key findings were that (1) the fringing field within the piezoelectric material plays a measurable role in performance, (2) symmetry in electrode placement is generally nonoptimal, (3) optimal electrode geometry is independent of scale, and (4) the smaller the ratio of width to thickness, the larger the deflection. The findings contribute to the development of efficient design strategies that optimize the performance of planar actuators for potential implications for microelectromechanical systems (MEMS). To aid designers of piezoelectric unimorph actuators in determining the optimal electrode geometry, three types of parameterized figures and two types of simulation apps are provided.

3D printing cross‐scale mold for manufacturing micromixers

AbstractNowadays, the methods of manufacturing microfluidic mixers were not flexible enough to customize and manufacture special sizes. Hence, a novel electrohydrodynamic jet printing method was proposed to fabricate cross‐scale mold for manufacturing micromixers in one step. Polyvinylpyrrolidone (PVP)/polycaprolactone (PCL) composite ink was prepared, and various printing parameters were investigated for fabricating varieties of 2D structures and 3D regular molds. A cross‐scale spiral mixer was successfully printed, various diameter ratio of 5.6, aspect ratio of 7.2. The PVP/PCL lines were direct printed, size of 66 nm deep and 743 nm wide. The circles were size of 564 nm deep and 7.02 μm wide. The mixing conditions of micromixers with different width ratios were simulated and analyzed; and the better mixing effect of micromixers with width ratio of 2:1 was proved, improved the mixing efficiency by 15.6% compared with micromixer without cross‐scale channels. The cross‐scale micromixers are promising for skin chip sensor and drug metabolite analysis, and the printing method proposed in this paper has great application potential in micro‐electro‐mechanical systems (MEMS).

3D Printing of Metals with sub-10µm Resolution.

The ability to manufacture 3D metallic architectures with microscale resolution is greatly pursued because of their diverse applications in microelectromechanical systems (MEMS) including microelectronics, mechanical metamaterials, and biomedical devices. However, the well-developed photolithography and emerging metal additive manufacturing technologies have limited abilities in manufacturing micro-scaled metallic structures with freeform 3D geometries. Here, for the first time, the high-fidelity fabrication of arbitrary metallic motifs with sub-10µm resolution is achieved by employing an embedded-writing embedded-sintering (EWES) process. A paraffin wax-based supporting matrix with high thermal stability is developed, which permits the printed silver nanoparticle ink to be pre-sintered at 175°C to form metallic green bodies. Via carefully regulating the matrix components, the printing resolution is tuned down to ≈7µm. The green bodies are then embedded in a supporting salt bath and further sintered to realize freeform 3D silver motifs with great structure fidelity. 3D printing of various micro-scaled silver architectures is demonstrated such as micro-spring arrays, BCC lattices, horn antenna, and rotatable windmills. This method can be extended to the high-fidelity 3D printing of other metals and metal oxides which require high-temperature sintering, providing the pathways toward the design and fabrication of 3D MEMS with complex geometries and functions.

MEMS-based meta-emitter with actively tunable radiation power characteristic

We propose a meta-emitter based on micro-electro-mechanical system (MEMS) technology. The main structure of the meta-emitter unit cell is composed of four symmetrically split crosses of Au and SiO2 bilayer cantilevers. By changing the size of the cantilevers, this MEMS-based meta-emitter can realize the tunable perfect absorption, and the absorption spectrum is within the longwave infrared (LWIR) wavelength from 8.90 to 11.90 µm. When the surface temperature of the meta-emitter rises, the electrothermal actuation mechanism is performed through the different thermal expansion coefficient (TEC) of the bilayer cantilevers. Therefore, the cantilevers will be bent downward and the bending height of the cantilevers decreases linearly. In such case, the peak value of thermal radiation power can be tuned from the wavelength of 9.52 µm to 10.48 µm when the temperature of meta-emitter is increased from 293 to 1290 K. This proposed MEMS-based meta-emitter is an excellent LWIR light source and has potential application prospects in gas sensing, infrared spectroscopy analysis, medical care and so on.

Development of Highly Sensitive and Thermostable Microelectromechanical System Pressure Sensor Based on Array-Type Aluminum-Silicon Hybrid Structures.

In order to meet the better performance requirements of pressure detection, a microelectromechanical system (MEMS) piezoresistive pressure sensor utilizing an array-type aluminum-silicon hybrid structure with high sensitivity and low temperature drift is designed, fabricated, and characterized. Each element of the 3 × 3 sensor array has one stress-sensitive aluminum-silicon hybrid structure on the strain membrane for measuring pressure and another temperature-dependent structure outside the strain membrane for measuring temperature and temperature drift compensation. Finite-element numerical simulation has been adopted to verify that the array-type pressure sensor has an enhanced piezoresistive effect and high sensitivity, and then this sensor is fabricated based on the standard MEMS process. In order to further reduce the temperature drift, a thermodynamic control system whose heating feedback temperature is measured by the temperature-dependent structure is adopted to keep the working temperature of the sensor constant by using the PID algorithm. The experiment test results show that the average sensitivity of the proposed sensor after temperature compensation reaches 0.25 mV/ (V kPa) in the range of 0-370 kPa, the average nonlinear error is about 1.7%, and the thermal sensitivity drift coefficient (TCS) is reduced to 0.0152%FS/°C when the ambient temperature ranges from -20 °C to 50 °C. The research results may provide a useful reference for the development of a high-performance MEMS array-type pressure sensor.

TiO2-based nitrogen dioxide gas sensor with transparent ordered micro-hollow bump structure prepared by 3D heterogeneous integration technology

This study produces the TiO2 membrane for a transparent ordered micro-hollow-bump (TOMHB) structure using a micro electro mechanical system (MEMS) and 3D heterogeneous integration (HI). The SEM image shows that the diameter and depth of each MHB are 12.5 μm and 8.5 μm. The TEM image shows that a 70 nm-thick TiO2 membrane is uniformly coated onto the MHB using atomic layer deposition (ALD). For NO2 gas sensing, the TiO2 TOMHB gas sensor is measured with and without UV irradiation at a working temperature for the sensor of room temperature, and a measurement time from NO2 injection to exhaust of about 5 min. Without UV irradiation, the gas response is good but the response time is slow and difficult-recoverable. With UV irradiation, the TiO2 TOMHB gas sensor has a fast response and recovery time. Four consecutive stability experiments show that the sensor response has an average value of 9.5 % for NO2 4.25 ppm. The average response time is 7 s and the average recovery time is 144 s. In addition, the TiO2 TOMHB gas sensor is a good selective for NO2 gas. These results show that the TiO2 TOMHB NO2 gas sensor has good stability, reproducibility and selectivity.

Enhancing Flexible Neural Probe Performance via Platinum Deposition: Impedance Stability under Various Conditions and In Vivo Neural Signal Monitoring.

Monitoring neural activity in the central nervous system often utilizes silicon-based microelectromechanical system (MEMS) probes. Despite their effectiveness in monitoring, these probes have a fragility issue, limiting their application across various fields. This study introduces flexible printed circuit board (FPCB) neural probes characterized by robust mechanical and electrical properties. The probes demonstrate low impedance after platinum coating, making them suitable for multiunit recordings in awake animals. This capability allows for the simultaneous monitoring of a large population of neurons in the brain, including cluster data. Additionally, these probes exhibit no fractures, mechanical failures, or electrical issues during repeated-bending tests, both during handling and monitoring. Despite the possibility of using this neural probe for signal measurement in awake animals, simply applying a platinum coating may encounter difficulties in chronic tests and other applications. Furthermore, this suggests that FPCB probes can be advanced by any method and serve as an appropriate type of tailorable neural probes for monitoring neural systems in awake animals.

Enhanced dipole-interaction in Nd-Dy-Fe-Co-B/Fe composite thick stacked trilayer

It is crucial to better understand the magnetization reversal process between soft and hard magnets and to achieve a high maximum energy product in thick composite multilayers. In this study, we find that the exchange interactions dominate in soft–hard-magnetic composite bilayers, while dipole interactions are predominant in soft–hard-magnetic composite trilayers. Based on the first-order reversal curve, magnetization reversal models are developed for both the thick composite bilayer and trilayer. Dipole interactions play an important role in the long range, resulting in higher coercivity and remanence in the thick trilayer. A multilayer in a stacked trilayer structure is achieved, which is composed of thick films with a perpendicular magnetic anisotropy at a thickness of up to 16 μm. The enhanced dipole interactions lead to a remanent polarization of 1 T and a maximum energy product of 22.5 MGOe. This work contributes to the preparation of thick films with a high maximum energy product for applications in magnetic microelectromechanical systems.

Comparative study of the sensitivity of H2S and NO2 in CuInSe2 gas sensors that are fabricated using screen printing and MEMS Integration

This study compares the gas response efficiency of a gas sensor substrate that is produced using screen-printing (SP) and micro-electro-mechanical systems (MEMS) technology, followed by deposition of CuInSe2 (CIS) film layers by radio-frequency (RF) sputtering and hyperthermal annealing for gas sensing applications. The SP substrates are used for CIS film deposition for RF sputtering, followed by various hyperthermal annealing treatments. SEM observations of the CIS film surfaces after annealing show surface particles with a size distribution of 155 to 30 nm, which demonstrate a phenomenon that is similar to Ostwald ripening and which creates structural variation and unevenness after annealing. The CIS film/MEMS substrates (MEMSs) gas sensor substrates are evaluated using a NIR thermal camera to determine the optimal operating temperature for direct annealing, which is 203.2 °C. Gas sensing response tests show that only H2S or NO2 gas rapidly and significantly elicit a response but a CIS film/SPs gas sensor exhibits significant resistance signal noise. The CIS film/MEMSs gas sensor is more stable than CIS film/SPs (after annealing) so it is more suitable for gas sensing. SEM images confirm that the film remains intact, so it is suitable for gas sensing applications.

On-chip multi-degree-of-freedom control of two-dimensional materials.

Two-dimensional materials (2DM) and their heterostructures offer tunable electrical and optical properties, primarily modifiable through electrostatic gating and twisting. Although electrostatic gating is a well-established method for manipulating 2DM, achieving real-time control over interfacial properties remains challenging in exploring 2DM physics and advanced quantum device technology1-6. Current methods, often reliant on scanning microscopes, are limited in their scope of application, lacking the accessibility and scalability of electrostatic gating at the device level. Here we introduce an on-chip platform for 2DM with in situ adjustable interfacial properties, using a microelectromechanical system (MEMS). This platform comprises compact and cost-effective devices with the ability of precise voltage-controlled manipulation of 2DM, including approaching, twisting and pressurizing actions. We demonstrate this technology by creating synthetic topological singularities, such as merons, in the nonlinear optical susceptibility of twisted hexagonal boron nitride (h-BN)7-10. A key application of this technology is the development of integrated light sources with real-time and wide-range tunable polarization. Furthermore, we predict a quantum analogue that can generate entangled photon pairs with adjustable entanglement properties. Our work extends the abilities of existing technologies in manipulating low-dimensional quantum materials and paves the way for new hybrid two- and three-dimensional devices, with promising implications in condensed-matter physics, quantum optics and related fields.