Typical Microelectromechanical Systems Research Articles

Radially symmetric stationary solutions for a MEMS type reaction–diffusion equation with fringing field

Radially symmetric stationary solutions for a micro-electro-mechanical system (MEMS) type reaction–diffusion equation with fringing field are considered. This equation arises in the study of the MEMS devices. This paper is devoted to the study of the existence of these solutions, information about their shape, and their asymptotic behaviour. These are studied by applying the framework that combines Poincaré type compactification, classical dynamical systems theory, and geometric methods for desingularization of vector fields called the blow-up technique.

An Artificial Neural Network Method for High-Accurate and High-Efficient MEMS Pressure Sensor Design

Microelectromechanical system (MEMS) devices have numerous advantages including small sizes, high performance, and easy integration capability and thus have been widely used in the Internet of Things (IoT). A typical MEMS device usually includes a set of performance parameters, and each parameter is sensitive to the device geometries but with different regularities and weights, thus resulting in the complexity of MEMS device design. The conventional design method is mainly based on iterative finite-element (FE) simulation and optimization, which is time-consuming and inefficient. To address the above issues, a bidirectional artificial neural network (ANN)-based method is explored and used as the design method by using an MEMS pressure sensor as a design example. First, a forward ANN with the geometries and performance as the input and output, respectively, is trained and constructed, which can accurately predict the performance. Then, an inverse ANN with the performance and geometries as the input and output, respectively, is also investigated. By means of a tandem network, the nonuniqueness issue of the inverse ANN caused by a one-to-many response from the input to the output can be well addressed. This tandem network can output the corresponding geometries instantly according to the target performance. This work demonstrates the great potential of the ANN as a new and facile strategy in MEMS device design.

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.

Field-programmable gate array (FPGA) based programmable digital emulator of vibratory microelectromechanical systems (MEMS) gyroscopes.

This paper presents a hardware emulator of microelectromechanical systems (MEMS) vibratory gyroscopes that can be used for characterization and verification of control/interface electronics by means of hardware-in-the-loop testing, thus speeding up design cycles by decoupling these tasks from the often longer MEMS design and fabrication cycles. The easily re-configurable hardware emulator is completely synthesized on a field-programmable gate array board. The emulator is shown to successfully model the Coriolis effect along with the prominent error sources present in typical MEMS gyroscopes, namely, quadrature error, spring nonlinearity, and thermo-mechanical, electronic, and environmental noise. Preliminary experimental results characterizing the noise and nonlinearity models based on a prototype with user-controllable device parameters synthesized on the Xilinx Zynq®-7020 SoC (Digilent ZYBO Z7 board) are presented.

Carrier-Phase-Based Initial Heading Alignment for Land Vehicular MEMS GNSS/INS Navigation System

For a micro-electromechanical system (MEMS)-based inertial navigation system (INS) and global navigation satellite system (GNSS) integrated system in land vehicular applications, rapid and accurate initial heading alignment is still a challenge. We propose an initial heading alignment method for MEMS INS using the GNSS carrier-phase measurement, based on the basic principle of trajectory similarity. The proposed method performs “trajectory matching” in the line-of-sight direction of satellites, where the angle is obtained by comparing the actual observed time-differenced carrier phase (TDCP) and INS-derived TDCP. Experimental results show that the initial heading could be determined accurate to 0.65° and 1.68° at a 95% confidence level within 5 s under open sky conditions and in typical urban environments, respectively, using a typical MEMS inertial measurement unit (e.g., STIM300, Safran Sensing Technologies Norway) and high-quality GNSS receiver (NovAtel OEM6). The proposed method is also verified using low-cost GNSS receivers and low-cost IMU chip under different environment. The proposed method performs better than existing approaches in terms of both time efficiency and accuracy.

100km wear-free sliding achieved by microscale superlubric graphite/DLC heterojunctions under ambient conditions.

Wear-free sliding between two contacted solid surfaces is the ultimate goal in the effort to extend the lifetime of mechanical devices, especially when it comes to inventing new types of micro-electromechanical systems where wear is often a major obstacle. Here we report experimental observations of wear-free sliding for a micrometer-sized graphite flake on a diamond-like-carbon (DLC) surface under ambient conditions with speeds up to 2.5 m/s, and over a distance of 100 km. The coefficient of friction (COF) between the microscale graphite flake, a van der Waals (vdW) layered material and DLC, a non-vdW-layered material, is measured to be of the order of n}{}{10^{ - 3}}, which belongs to the superlubric regime. Such ultra-low COFs are also demonstrated for a microscale graphite flake sliding on six other kinds of non-vdW-layered materials with sub-nanometer roughness. With a synergistic analysis approach, we reveal the underlying mechanism to be the combination of interfacial vdW interaction, atomic-smooth interfaces and the low normal stiffness of the graphite flake. These features guarantee a persistent full contact of the interface with weak interaction, which contributes to the ultra-low COFs. Together with the extremely high in-plane strength of graphene, wear-free sliding is achieved. Our results broaden the scope of superlubricity and promote its wider application in the future.

Investigation of Potting-Adhesive-Induced Thermal Stress in MEMS Pressure Sensor

Thermal stress is one of the main sources of micro-electro-mechanical systems (MEMS) devices error. The Wheatstone bridge is the sensing structure of a typical piezoresistive MEMS pressure sensor. In this study, the thermal stress induced by potting adhesive in MEMS pressure sensor was investigated by experiments, calculated by analytics and analyzed by simulations. An experiment system was used to test the sensor at different air pressures and temperatures. The error becomes greater with the decrease in pressure. A set of novel formulas were proposed to calculate the stress–strain on Wheatstone bridge. The error increases with the temperature deviating from 25 °C. A full-scale geometric model was developed, and finite element simulations were performed, to analyze the effect of the stress on MEMS pressure sensor induced by different temperatures and thicknesses of potting adhesive. Simulation results agree well with the experiments, which indicated that there is a 3.48% to 6.50% output error in 0.35 mm potting adhesive at 150 °C. With the thickness of potting adhesive increasing, the variations of output error of the Wheatstone bridge present an N-shaped curve. The output error meets a maximum of 5.30% in the potting adhesive of 0.95 mm and can be reduced to 2.47%, by increasing the potting adhesive to 2.40 mm.

An efficient electro‐thermo‐mechanical model for the analysis of V‐shaped thermal actuator connected with driven structures

AbstractV‐shaped thermal actuators are popular in many types of microelectromechanical systems' (MEMS) devices. In the rapidly growing applications of V‐shaped thermal actuators, there are usually complex driven structures, in which the Joule heat may transfer, connecting to the V‐beams. However, their influence on the temperature distribution has not been included in existing analytical models. An electro‐thermo‐mechanical model is presented to tackle this problem. By dividing the thermal actuator into a set of short beams, a two‐dimensional network is constructed. Besides, the driven structure can be analyzed as an equivalent circuit of thermal resistances. Then, circuit‐like node equations can be acquired for this heat flow network to solve the heat distribution. On this basis, the heat expansions of the shuttle beam are taken into consideration to predict the displacements and forces under different driving voltage and ambient temperature. Taking a test structure as an example, this model is proved to be accurate by comparing the results with finite element analysis. This model can be served as an effective analysis technique for MEMS devices containing V‐shaped thermal actuators.

An ARMA-Based Digital Twin for MEMS Gyroscope Drift Dynamics Modeling and Real-Time Compensation

The applications of Inertial Measurement Unit (IMU) based on Micro Electro Mechanical System (MEMS) are widely used because of its low-cost, small volume and low energy consumption. Unlike the accelerometers and magnetometers, which are respectively sensitive to vibrations and ferrous materials interference, MEMS type gyroscope is able to provide stable orientation information for a short period of time. Compared with these two sensors, gyroscopes are neither disturbed by vibrations nor affected by metallic materials, and therefore it would be one of the primary sensors for industrial applications. Reviewing the most recently related works, accurate attitude estimations are usually obtained by fusing gyro integration. However, it is well known that series drifts will be induced after a long-term integration. Furthermore, according to the literature and the associated experiments, they all demonstrated that MEMS type gyroscopes have strong temperature correlation because of the silicon structure. Put it simply, the temperature variations will give rise to gyro drifts severely and thereby degrade the orientation estimation precision. To address this problem, this article proposed a temperature modeling technique and a real-time drift pre-compensation procedure by applying autoregressive moving average (ARMA) technology. Different from the traditional modeling methods, the proposed method is able to describe transient drifting behaviors as well as steady state ones. Moreover, comparison studies using artificial neural networks (ANNs) are also presented. Experiments show that the proposed method provides a stable and reliable temperature-caused gyroscope drift pre-compensation. The developed method is also very suitable for the realization in a low-cost embedded system.

A dual hybrid virtual element method for plane elasticity problems

A dual hybrid Virtual Element scheme for plane linear elastic problems is presented and analysed. In particular, stability and convergence results have been established. The method, which is first order convergent, has been numerically tested on two benchmarks with closed form solution, and on a typical microelectromechanical system. The numerical outcomes have proved that the dual hybrid scheme represents a valid alternative to the more classical low-order displacement-based Virtual Element Method.

Developments of MEMS Gas Sensors Based on Tin Oxide semiconductors: Application to Battery-Powered Household Gas Alarms

Developments of MEMS Gas Sensors Based on Tin Oxide semiconductors: Application to Battery-Powered Household Gas Alarms

Development Trends and Perspectives of Future Sensors and MEMS/NEMS.

With the fast development of the fifth-generation cellular network technology (5G), the future sensors and microelectromechanical systems (MEMS)/nanoelectromechanical systems (NEMS) are presenting a more and more critical role to provide information in our daily life. This review paper introduces the development trends and perspectives of the future sensors and MEMS/NEMS. Starting from the issues of the MEMS fabrication, we introduced typical MEMS sensors for their applications in the Internet of Things (IoTs), such as MEMS physical sensor, MEMS acoustic sensor, and MEMS gas sensor. Toward the trends in intelligence and less power consumption, MEMS components including MEMS/NEMS switch, piezoelectric micromachined ultrasonic transducer (PMUT), and MEMS energy harvesting were investigated to assist the future sensors, such as event-based or almost zero-power. Furthermore, MEMS rigid substrate toward NEMS flexible-based for flexibility and interface was discussed as another important development trend for next-generation wearable or multi-functional sensors. Around the issues about the big data and human-machine realization for human beings’ manipulation, artificial intelligence (AI) and virtual reality (VR) technologies were finally realized using sensor nodes and its wave identification as future trends for various scenarios.

IMPLEMENTASI SENSOR MEMS AKSELEROMETER SEBAGAI ALAT PENGUKUR GETARAN PADA TURBIN ANGIN

Many techniques are available in the market to measure and analyze vibrations caused by rotating machines and the structure of the machine itself, but require expensive resources to identify the problem of damage. Generally these expensive equipment use conventional sensors such as eddy-current sensors, swing coil velocity sensors and piezoelectric transducer sensors to measure vibration. The implementation of a vibration measuring device in the form of an accelerometer sensor with a type of Micro Electro Mechanical System (MEMS) and a signal processing unit (Arduino Mega microcontroller) is used to measure vibrations that occur in small-scale horizontal type wind turbine blades. Experiments were carried out to check the accelerometer's ability to detect vibration response on wind turbine blades with the free vibration position. Then the signal in the form of the time domain will be converted into the frequency domain to get the dominant frequency value of the turbine blade, which is then analyzed to be compared with the B & K VibroPort 80 vibration meter. The experimental results show that the MEMS type accelerometer sensor can be applied to measure the free vibration conditions on wind turbine blades with an error percentage below 6%.

Full Custom MEMS Design: 2.5D Fabrication-Process Simulation for 3D Field-Solver-Based Circuit Extraction

Due to the lack of sophisticated component libraries for microelectromechanical systems (MEMS), highly optimized MEMS sensors are currently designed using a polygon-driven design flow. The advantage of this design flow is its accurate mechanical simulation, but it lacks a method for an efficient and accurate electrostatic analysis of parasitic effects of MEMS. In order to close this gap in the polygon-driven design flow, we present a customized electrostatic analysis flow for such MEMS devices. Our flow features a 2.5D fabrication-process simulation, which simulates the three typical MEMS fabrication steps (namely deposition of materials including topography, deep reactive-ion etching, and the release etch by vapor-phase etching) very fast and on an acceptable abstraction level. Our new 2.5D fabrication-process simulation can be combined with commercial field-solvers such as they are commonly used in the design of integrated circuits. The new process simulation enables a faster but nevertheless satisfactory analysis of the electrostatic parasitic effects, and hence simplifies the electrical optimization of MEMS.

Modeling of Multifunctional Thermoresistive Transduser Used Heat Exchange Technology

The physical and technical characteristics, structural and topological aspects of the micromechanical thermo-resistor active heating transdusers synthesis for fluid (gas and liquid) parameters determination are considered. All transducers are based on a single MEMS (Micro Electro Mechanical System) structure and differ in functionality due to different operating modes and different principles for determining fluid parameters. It allows the development of multifunctional sensors based on a single hardware, which includes a typical MEMS structure and mass production microprocessor, for example, PSoC (Programmable System On Chip). The transducers mathematical models acceptable for the COMSOL simulation library and designing of information electronics devices with the registration of various physical parameters are proposed. The analytical calculations on the basis of the proposed models for a gas flow sensor of the temperature dependence from the fluid flow velocity in the MEMS structure was performed. The proposed models can be used for the operation analytical description and computing of devices based on the use of thermoelectric processes in micro-scale structures. Ref. 29, fig. 3.

Computational viscothermal acoustic study of micro-electro-mechanical systems (MEMS) perforated plates

Micro-perforated plates (MPP) are widely used as sound absorption materials in many noise control applications. Acoustic properties of the MPPs have been theoretically and experimentally studied for many years. The results of these studies are often used in the studies of MEMS devices with perforated plates. However, there exist differences in the physical dimensions of MPPs and MEMS perforated plates. The typical MPP perforation radius is in the range of 1 mm to 1 cm. For these dimensions and audio frequencies, the shear wave-number is much larger than 1. The dimensionless shear wave-number, which is an unsteady Reynolds number, is a measure for the ratio between inertial and viscous effects. Hence for typical MMPs, the inertial effects are dominant. However, the typical hole radius in the MEMS perforated plates is below 20 µm corresponding to subunit shear wave-numbers. Therefore, in MEMS perforated plates, the viscous effects are the dominant part of the impedance. In addition, typical MPPs have low porosities on the order of 1%, whereas typical MEMS perforated plates have high porosities in the range of 25% to 75%. In this work, viscous and thermal losses and also the end effects of the MEMS perforated plates are studied using the finite element method.Micro-perforated plates (MPP) are widely used as sound absorption materials in many noise control applications. Acoustic properties of the MPPs have been theoretically and experimentally studied for many years. The results of these studies are often used in the studies of MEMS devices with perforated plates. However, there exist differences in the physical dimensions of MPPs and MEMS perforated plates. The typical MPP perforation radius is in the range of 1 mm to 1 cm. For these dimensions and audio frequencies, the shear wave-number is much larger than 1. The dimensionless shear wave-number, which is an unsteady Reynolds number, is a measure for the ratio between inertial and viscous effects. Hence for typical MMPs, the inertial effects are dominant. However, the typical hole radius in the MEMS perforated plates is below 20 µm corresponding to subunit shear wave-numbers. Therefore, in MEMS perforated plates, the viscous effects are the dominant part of the impedance. In addition, typical MPPs have low po...

Analytical, Numerical and Experimental Study of a Horizontal Electrothermal MEMS Microgripper for the Deformability Characterisation of Human Red Blood Cells.

Microgrippers are typical microelectromechanical systems (MEMS) that are widely used for micromanipulation and microassembly in both biological and micromanufacturing fields. This paper presents the design, modelling, fabrication and experimental testing of an electrothermal microgripper based on a ‘hot and cold arm’ actuator design that is suitable for the deformability characterisation of human red blood cells (RBCs). The analysis of the mechanical properties of human RBCs is of great interest in the field of medicine as pathological alterations in the deformability characteristics of RBCs have been linked to a number of diseases. The study of the microgripper’s steady-state performance is initially carried out by the development of a lumped analytical model, followed by a numerical model established in CoventorWare® (Coventor, Inc., Cary, NC, USA) using multiphysics finite element analysis. Both analytical and numerical models are based on an electothermomechanical analysis, and take into account the internal heat generation due to the applied potential, as well as conduction heat losses through both the anchor pads and the air gap to the substrate. The models are used to investigate key factors of the actuator’s performance including temperature distribution, deflection and stresses based on an elastic analysis of structures. Results show that analytical and numerical values for temperature and deflection are in good agreement. The analytical and computational models are then validated experimentally using a polysilicon microgripper fabricated by the standard surface micromachining process, PolyMUMPs™ (Durham, NC, USA). The microgripper’s actuation is characterised at atmospheric pressure by optical microscopy studies. Experimental results for the deflection of the microgripper arm tips are found to be in good agreement with the analytical and numerical results, with process-induced variations and the non-linear temperature dependence of the material properties accounting for the slight discrepancies observed. The microgripper is shown to actuate to a maximum opening displacement of 9 m at an applied voltage of 3 V, thus being in line with the design requirement of an approximate opening of 8 m for securing and characterising a RBC.

A Novel Macroscale Acoustic Device for Blood Filtration.

Retransfusion of a patient's own shed blood during cardiac surgery is attractive since it reduces the need for allogeneic transfusion, minimizes cost, and decreases transfusion related morbidity. Evidence suggests that lipid micro-emboli associated with the retransfusion of the shed blood are the predominant causes of the neurocognitive disorders. We have developed a novel acoustophoretic filtration system that can remove lipids from blood at clinically relevant flow rates. Unlike other acoustophoretic separation systems, this ultrasound technology works at the macroscale, and is therefore able to process larger flow rates than typical micro-electromechanical system (MEMS) scale acoustophoretic separation devices. In this work, we have first demonstrated the systematic design of the acoustic device and its optimization, followed by examining the feasibility of the device to filter lipids from the system. Then, we demonstrate the effects of the acoustic waves on the shed blood; examining hemolysis using both haptoglobin formation and lactate dehydrogenase release, as well as the potential of platelet aggregation or inflammatory cascade activation. Finally, in a porcine surgical model, we determined the potential viability of acoustic trapping as a blood filtration technology, as the animal responded to redelivered blood by increasing both systemic and mean arterial blood pressure.

(Invited) How to Integrate MEMS on Foundry-Fabricated CMOS Backplanes

A large variety of new applications for Internet of Things (IoT), Industrie 4.0 and other consumer products are pushing volume and manufacturing of microelectromechanical systems (MEMS) into a new phase. Due to massive use of these sensors and actuators in mobile and industrial applications smaller systems combined with low power consumption and higher versatility are required. MEMS are transducers that sense or control physical, chemical or optical quantities creating devices for applications in the area of 3D-motion tracking, pressure sensing, light shaping or detection of irradiation. The combination of MEMS with an application specific integrated circuit (ASIC) based on CMOS technology enables the entire system to interact with outside world. These ASICs are providing required features such as analog-to-digital conversion, amplification, filtering, information processing and storage as well as communication to the outside world. There are different solutions available to combine MEMS with customized CMOS circuits. One choice known as system-in-package (SiP) is the manufacturing of MEMS and CMOS on separate wafers and its subsequent integration in a multi-chip module using interposer/ rewiring technologies. Key advatanges of this technique are high flexibility, high modularity and a complete decoupled manufacturing of CMOS and MEMS. This enables a rapid development and leads to low development costs. And, there is no impact of different sizes between CMOS and MEMS chip. In order to enhance the integration density, to drive system feature size down, to suppress potential parasitic capacitances and to reduce power consumption an integrated manufacturing on the same substrate is a must and known as system-on-chip (SoC) solution. On one hand this approach can be still realized by a multi-wafer processing and a final integration using bonding technologies. This technology is often named as heterogeneous integration. Key advantage of multi-wafer technology is the possibility to use high-performance MEMS materials such as monocrystalline silicon as actuation/sensing material and its integration on CMOS wafers. Disadvantages are the required alignment accuracies when using a metallic bond or limitation for integration densities when using via-last approach. A more consistent way is a complete monolithic integration of MEMS on CMOS substrates. Especially when large transducer arrays are required (e.g. bolometers, micro-mirror arrays, CMUT arrays) a monolithic integration of MEMS on CMOS is the best solution. All advantages are now on hand – high integration densities, low parasitic capacitances and an effective usage of CMOS area. Fraunhofer IPMS applies surface and bulk micromachining technologies for the integration of MEMS on customized CMOS backplanes. To reduce development costs and time-to-market IPMS combines standard CMOS processes offered from CMOS foundries with a subsequent integration of MEMS part in our MEMS fab. Due to the application specific design of the CMOS backplane this concept allows a perfect match between ASIC and MEMS functionalities. In a typical project flow CMOS and MEMS will be manufactured and tested in parallel to shorten development time. After ASIC design is finished it will be tested using Multi- Project- Wafer run (MPW) in a CMOS foundry. Using these MPW runs a complete characterization of CMOS functionality can be realized in an early project state at low costs. Parallel to CMOS testing an entire process development of MEMS part can be done on passive devices in our MEMS fab. If CMOS and MEMS characterization is completed the MEMS part will be monolithically integrated on these customized CMOS backplanes. But there are still some challenges for the integration of MEMS on foundry fabricated CMOS backplanes, e.g.: Modifications of last CMOS/ interconnect/ ILD layers to realize an appropriate interface to MEMS Clarification of PCM (process control monitoring) test environment, depth of test structures and possible arising contamination issues In-chip surface topology after interconnect processing to define necessary actions to achieve required planarity for further processing Tuning mix-and-match lithography to achieve high overlay accuracies (Picture 1: Reached overlay accuracy between last 0,18µm CMOS and first MEMS layer of about 30- 40nm after correction step using i-line stepper) Required chip design features when using sacrificial layer technology IPMS offers a wide range of surface and bulk micromachining technologies which are particularly suitable for the fabrication of sensors and actuators on pre-fabricated CMOS wafers using monolithic integration. Especially surface micromachining using inorganic sacrificial layer technology allows the realization of rather complex MEMS structures on CMOS backplanes. Based on examples such as spatial light modulators (SLM) and capacitive micromachined ultrasonic transducers (CMUT) we will present solutions for the integration of surface micromachined MEMS on customized CMOS substrates. Figure 1

MEMS IMU stochastic error modelling

ABSTRACTLow cost inertial measurement units (IMU) are comprised of micro-electro-mechanical systems (MEMS) gyroscopes and accelerometers. These inertial sensors have high random noise and time varying bias. Hence, an accurate stochastic error model is necessary to predict performance and also to implement an attitude and heading reference system or a navigator. The parameters of this stochastic model are classically obtained via Allan Variance analysis. In this paper, two modern approaches, based on autoregressive moving average model and Kalman Filter, respectively, are investigated and their performances are unveiled via sensitivity analysis, realistic simulations with typical MEMS parameters and also with experimental data. Basic equations for the estimation problem are developed and the solution sensitivity to data and parameters is discussed. It is shown that the deficiency with the online methods can be traced back to the difficulty in estimating the parameters B (bias instability) and K (rate random walk for gyros, acceleration random walk for accelerometers) separately under high measurement noise N (angular random walk for gyros, velocity random walk for accelerometers), which is typical of MEMS IMU.