Current Microelectromechanical Systems Research Articles

Characterization of Sand and Dust Pollution Degradation Based on Sensitive Structure of Microelectromechanical System Flow Sensor.

The effect of sand and dust pollution on the sensitive structures of flow sensors in microelectromechanical systems (MEMS) is a hot issue in current MEMS reliability research. However, previous studies on sand and dust contamination have only searched for sensor accuracy degradation due to heat conduction in sand and dust cover and have yet to search for other failure-inducing factors. This paper aims to discover the other inducing factors for the accuracy failure of MEMS flow sensors under sand and dust pollution by using a combined model simulation and sample test method. The accuracy of a flow sensor is mainly reflected by the size of its thermistor, so in this study, the output value of the thermistor value was chosen as an electrical characterization parameter to verify the change in the sensor's accuracy side by side. The results show that after excluding the influence of heat conduction, when sand particles fall on the device, the mutual friction between the sand particles will produce an electrostatic current; through the principle of electrostatic dissipation into the thermistor, the principle of measurement leads to the resistance value becoming smaller, and when the sand dust is stationary for some time, the resistance value returns to the expected level. This finding provides theoretical guidance for finding failure-inducing factors in MEMS failure modes.

Analysis of Coupled Vibration Characteristics of Linear-Angular and Parameter Identification

Abstract A steady-state sinusoidal and distortion-free excitation source is very important for the accuracy and consistency of the calibration parameters of micro-electro-mechanical systems (MEMS) inertial sensors. To solve the problem that the current MEMS inertial measurement unit (IMU) calibration device is unable to reproduce the spatial motion of linear and angular vibration coupling, research topics on the coupling vibration characteristics and parameter identification for an electromagnetic linear-angular vibration exciter are proposed. This research paper used Ampere’s law and Lorentz force to establish the analytical expressions for the electromagnetic force and electromagnetic torque of the electromagnetic linear-angular vibration exciter. Then, the main purpose of this paper is to establish uniaxial and coupled vibration electromechanical analogy models containing mechanical parameters based on the admittance-type electromechanical analogy principle, and the parameter identification model is also obtained by combining the impedance formula with the additional mass method. Finally, the validity of the coupling vibration characteristics and the parameter identification model are verified by the frequency response simulation and the additional mass method, and the relative error of each parameter identification is within 5% in this paper.

Ultra-compact and high-performance suspended aluminum scandium nitride Lamb wave humidity sensor with a graphene oxide layer.

The utilization of Microelectromechanical Systems (MEMS) technology holds great significance for developing compact and high-performance humidity sensors in human healthcare, and the Internet of Things. However, several drawbacks of the current MEMS humidity sensors limit their applications, including their long response time, low sensitivity, relatively large sensing area, and incompatibility with a complementary metal-oxide-semiconductor (CMOS) process. To address these problems, a suspended aluminum scandium nitride (AlScN) Lamb wave humidity sensor utilizing a graphene oxide (GO) layer is firstly designed and fabricated. The theoretical and experimental results both show that the AlScN Lamb wave humidity sensor exhibits high sensing performance. The mass loading sensitivity of the sensor is one order higher than that of the normal surface acoustic wave (SAW) humidity sensor based on an aluminum nitride (AlN) film; thus the AlScN Lamb wave humidity sensor achieves high sensitivity (∼41.2 ppm per % RH) with only an 80 nm-thick GO film. In particular, the as-prepared suspended AlScN Lamb wave sensors are able to respond to the wide relative humidity (0-80% RH) change in 2 s, and the device size is ultra-compact (260 μm × 72 μm). Moreover, the sensor has an excellent linear response in the 0-80% RH range, great repeatability and long-term stability. Therefore, this work brings opportunities for the development of ultra-compact and high-performance humidity sensors.

Strong piezoelectricity of the nm-thick flexible Hf0.5Zr0.5O2 ferroelectric film

Integrated nanoelectromechanical systems (NEMS) exhibit enormous potential for replacing current microelectromechanical systems in various fields, such as 5G/6G wireless communication, in the future. However, their advancement is impeded by the challenge of achieving nanometer-thick ferroelectric oxide films with a high piezoelectric coefficient of d33. Herein, the nm-thick flexible Hf0.5Zr0.5O2 (HZO) films were deposited on mica substrates, and they exhibited a remnant polarization of ≥ 8.1 μC/cm2 at 25–320 °C and a high d33 value of 37.8 pC/N at 25 °C. After the HZO films with inter-digitated electrodes were fully polarized, the flexible HZO film with a dynamic bending strain of 0.102 % at 4 Hz produced an open-circuit voltage of 1.1 V. This HZO film with strong piezoelectricity can promote the development of novel NEMS and flexible piezoelectric sensors.

Extended Higher-Order Elements with Frequency-Doubled Parameters: The Hysteresis Loops Are Always of Type II.

Current MEMS (Micro Electro Mechanical Systems) can be modeled by state-dependent elements that exhibit hysteretic behavior. Examples include capacitors and inductors whose capacitances and inductances are dependent on the instantaneous state of the electromechanical system, resistors whose resistances exhibit temperature changes when the elements are actually heated, etc. Regardless of the physical background, such hysteresis manifestations can be studied uniformly in the broader framework of generic and extended higher-order elements, in which a classification of hysteretic loops into types I and II is established. The loop type is an important dynamical parameter of an element, having the potential to indicate, for example, its (in)volatility. Thus far, there is no reliable criterion to determine the type of steady loop from the defining relations of an element. This work reports on one special class of extended elements that produces type II loops under all circumstances. The paper presents hitherto unpublished connections between the frequency-doubling parameters of an element and the type of its hysteresis loop. The new findings are expressed by several theorems that allow the type of hysteresis to be inferred from the frequency behavior of the element parameter or state, and vice versa. These procedures are demonstrated with examples and verified by computer simulations.

Serial and Parallel Connections of Micromechanical Resonators for Sensing: Theories and Applications

The mass-spring-damper resonator is the basic mechanical component of current microelectromechanical systems (MEMS) sensors. It is typically implemented in various forms of micromechanical cantilevers, beams, diaphragms, rings, etc. In the classical sensing paradigm, the amplitude, frequency, or phase change of a single degree-of-freedom (1-DoF) resonator is used to perform sensing applications. This paper presents the basic theories and applications for serial and parallel connections of 1-DoF micromechanical resonators for sensing. In the serial connection, the amplitude ratio of the two outer resonators is typically selected as the output metric and the mode-localization phenomenon is especially used to mechanically amplify the signal and suppress common-mode noises. Then the signal-to-noise ratio (SNR) of sensors can be improved. In the parallel connection, resonators are combined by an optimal filter to suppress random noises and the SNR can be further improved. Unknown disturbances can also be suppressed by differential sensing in the parallel connection. In a short summary, the serial and parallel connection provide calculation of summation, subtraction, and division, thus enabling further sensing performance improvement. And full compatibility to current MEMS processes provides a new sensing paradigm to improve the performance of MEMS sensors. 2021-0158

Nanometer-Sized Te Pistons in Carbon Cylinders as Nano-Motor Prototypes: Implications for Nano-Electromechanical Device Fabrication

Manipulation of nano-objects is fascinating as it not only facilitates the understanding of the essential properties of nanomaterials but also enlightens the design of future nano-devices beyond current micro-electromechanical systems. In this paper, a piston-cylinder-configured nano-motor prototype is designed and fabricated, in which nanometer-sized Te segments are electrically controlled to reciprocate inside the carbon cylinder serving as nano-pistons. The nano-motor prototype has a length of ∼550 nm, an outer diameter of ∼150 nm, and a piston diameter of ∼30 nm. Electron-wind and thermal expansion are two reciprocal forces that create a dynamic equilibrium on the Te pistons and enable the circulating motions. With bias control, a circulating rate of 0–4.3 counts per second has been achieved. This prototype is the smallest piston-cylinder-type nano-motor that has ever been reported and can provide new insights into investment casting-assisted nano-electromechanical device fabrication.

Design, fabrication and test of a bulk SiC MEMS accelerometer

The application of micro accelerometer in extremely high temperature environment has become an urgent problem to be solved. However, current microelectromechanical system (MEMS) Si-based accelerometer cannot adapt to higher temperatures than 500 °C. Because of its excellent properties in high temperature environments, silicon carbide (SiC) shows promising potential in development of high temperature MEMS sensors, and it is a good alternative to Si for developing accelerometers. Due to the difficulty of bulk-SiC fabrication process and the complex structure of MEMS accelerometers, there are few studies on bulk SiC accelerometers and few test data of the performance. In this study, in order to solve the problem of fabrication, a MEMS accelerometer based on bulk SiC processing technology is designed, and fabricated. The sensor is fabricated using a 4H-SiC wafer and adopts the classic elastic beam-proof mass structure. The top surface of the wafer is a doped N-type SiC epitaxial layer that is used as piezoresistive material to develop sensitive resistance. Ultra-thin (20 μm) elastic beams obtained using dry etching form the sensitive mechanical structure to realize a high-sensitivity output in low/medium-g-value environments. The static flip and dynamic vibration experiments show that the final sensor can test low/medium-g-value acceleration signals precisely. Finally, the dynamic sensitivity obtained is 0.21 mV/g under 5 V input voltage and the linearity is 99.8%. This work has potential value for promoting the practical application of fabrication of bulk micromachined SiC in accelerometer, and the test data can provide guidance for future design of bulk SiC piezoresistive sensors.

Effects of Sample Geometry and Grain Size on Mechanical Property of Electrodeposited Gold Evaluated By Micro-Bending Test

In recent years, MEMS (microelectromechanical systems) devices are required to have high functionality and small size, especially for MEMS acceleration sensors, and sensitivity of a MEMS acceleration sensor is highly dependent on the Brownian noise [1,2]. The Brown noise is known to be inversely proportional to mass of movable parts in the sensor, and the noise is lowered by increasing the mass [1,2], which implies a number of volume is needed to ensure high sensitivity. However, increasing size of the component is not preferable. Because of this, a design of gold-based MEMS acceleration sensor is proposed. The density of gold is 19.3 g/cm3, and gold has high corrosion resistance and chemical stability. Most importantly, gold electrodeposition process can be easily integrated with current MEMS fabrication process.Mechanical properties of the material are essential informtion for design of MEMS components. For instance, the yield stress is needed to guarantee elastic deformation of the material during operation of the MEMS device. Mechanical properties of metallic materials are known to change with size of the sample used in a mechanical property characterization becomes smaller than micrometer scale, which is known as the sample size effect [3]. Therefore, mechanical property characterization of materials toward MEMS should be conducted using samples having the same dimensions as those used in MEMS. Various micro-mechanical testing methods have been developed to characterize micro-specimens, such as micro-compression test, micro-tensile test, and micro-bending test. Among them, micro-bending test is suggested to be the most suitable method to evaluate materials for applications in MEMS when compared with micro-compression and micro-tensile tests since cantilever-like structure is commonly utilized in movable components, such as the micro-spring in MEMS accelerometers. On the other hand, micro-cantilevers are reported to have the sample geometry effect [4], which the sample size effect is only observed when varying thickness of the micro-cantilever. Also, it has been reported that the sample size effect is dependent on ratio of the sample diameter to the average grain size, and materials prepared by electrodeposition are usually polycrystal. Thus, relationship between the sample geometry effect and the average grain size is investigated in this study.Two gold films were electrodeposited at different current density to change the average grain size. The average grain size was determined by electron backscatter diffraction, and the average grain size of film A and B were 1.2~1.3 and 0.6 μm, respectively. Samples used in the micro-bending test were micro-cantilevers fabricated from the gold films by focus ion beam. Thicknesses of the micro-cantilever were ranged from 6.0 to 13 μm. The micro-bending tests are conducted using a test machine specially designed for micro-specimens developed in our group as shown in Fig. 1.The yield stresses were in a range of 428 to 553MPa, which were all higher than that of the bulk gold (55 to 220 MPa). Table 1 shows the detailed dimensions and yield stress of all samples. Yield stresses were plotted against the log scale of thickness shown in Fig. 2. At first, the sample geometry effect was confirmed in samples fabricated from both film A and B. Then, the yield stresses of samples fabricated from film B were all higher than those of film A, which was a result of the Hall-Petch relationship. In Fig. 2, the slop was steeper for film A indicating the sample geometry effect was more obvious in samples composed of larger grains. [1] D. Yamane, T. Konishi, T. Matsushima, K. Machida, H. Toshiyoshi, and K. Masu, Appl Phys Lett 104 (2014) 074102[2] K. Machida, T. Konishi, D. Yamane, H. Toshiyoshi, K. Masu, ECS Trans. 61 (2014) 21-39.[3] J.R. Greer and J.Th.M. De Hosson: Plasticity in small-sized metallic systems: Intrinsic versus extrinsic size effect. Prog. Mater. Sci. 56, 654 (2011).[4] K. Suzuki, “Sample Geometry Effect on Mechanical Property of Electrodeposited Gold Evaluated by Micro-Bending Test", 45th International Conference on Micro & Nano Engineering (MNE2019), Rhodes Greece, Sep. 2019 Figure 1

Fabrication and testing of PMOS current mirror-integrated MEMS pressure transducer

PurposeThis paper aims to describe the fabrication, packaging and testing of a resistive loadedp-channel metal-oxide-semiconductor field-effect transistor-based (MOSFET-based) current mirror-integrated pressure transducer.Design/methodology/approachUsing the concept of piezoresistive effect in a MOSFET, three identicalp-channel MOSFETs connected in current mirror configuration have been designed and fabricated using the standard polysilicon gate process and microelectromechanical system (MEMS) techniques for pressure sensing application. The channel length and width of thep-channel MOSFETs are 100 µm and 500 µm, respectively. The MOSFET M1 of the current mirror is the reference transistor that acts as the constant current source. MOSFETs M2 and M3 are the pressure-sensing transistors embedded on the diaphragm near the mid of fixed edge and at the center of the square diaphragm, respectively, to experience both the tensile and compressive stress developed due to externally applied input pressure. A flexible square diaphragm having a length of approximately 1,000 µm and thickness of 50 µm has been realized using deep-reactive ion etching of silicon on the backside of the wafer. Then, the fabricated sensor chip has been diced and mounted on a TO8 header for the testing with pressure.FindingsThe experimental result of the pressure sensor chip shows a sensitivity of approximately 0.2162 mV/psi (31.35 mV/MPa) for an input pressure of 0-100 psi. The output response shows a good linearity and very low-pressure hysteresis. In addition, the pressure-sensing structure has been simulated using the parameters of the fabricated pressure sensor and from the simulation result a pressure sensitivity of approximately 0.2283 mV/psi (33.11 mV/MPa) has been observed for input pressure ranging from 0 to 100 psi with a step size of 10 psi. The simulated and experimentally tested pressure sensitivities of the pressure sensor are in close agreement with each other.Originality/valueThis current mirror readout circuit-based MEMS pressure sensor is new and fully compatible to standard CMOS processes and has a promising application in the development CMOS-MEMS-integrated smart sensors.

Mems Technology Quality Requirements as Applied to Multibeam Echosounder

Abstract Small, lightweight, power-efficient and low-cost microelectromechanical system (MEMS) inertial sensors and microcontrollers available in the market today help reduce the instability of Multibeam Sonars. Current MEMS inertial measurement units (IMUs) come in many shapes, sizes, and costs - depending on the application and performance required. Although MEMS inertial sensors offer affordable and appropriately scaled units, they are not currently capable of meeting all requirements for accurate and precise attitudes, due to their inherent measurement noise. The article presents the comparison of different MEMS technologies and their parameters regarding to the main application, namely Multibeam Echo Sounders (MBES). The quality of MEMS parameters is crucial for further MBES record-processing. The article presents the results of undertaken researches in that area, and these results are relatively positive for low-cost MEMS. The paper undertakes some vital aspect of using MEMS in the attitude and heading reference system (AHRS) context. The article presents a few aspects of MEMS gyro errors and their estimation process in the context of INS processing flow, as well as points out the main difficulties behind the INS when using a few top MEMS technologies.

A reliable MEMS switch using electrostatic levitation

In this study, a microelectromechanical system (MEMS) beam is experimentally released from pull-in using electrostatic levitation. A MEMS cantilever with a parallel plate electrode configuration is pulled-in by applying a voltage above the pull-in threshold. An electrode is fixed to the substrate on each side of the beam to allow electrostatic levitation. Large voltage pulses upwards of 100 V are applied to the side electrodes to release the pulled-in beam. A large voltage is needed to overcome the strong parallel plate electrostatic force and stiction forces, which hold the beam in its pulled-in position. A relationship between bias voltage and release voltage is experimentally extracted. This method of releasing pulled-in beams is shown to be reliable and repeatable without damaging the cantilever or electrodes. The proposed approach is of great interest for any MEMS component that suffers from the pull-in instability, which is usually irreversible and permanently destroys the device, as electrostatic levitation allows pulled-in structures to be released and reused. It has a promising application in MEMS switches by creating a normally closed switch as opposed to current MEMS switches, which are normally open.

A Low Contact Resistance 4-Terminal Mems Relay: Theoretical Analysis, Design, and Demonstration

A 4-terminal microelectromechanical systems (MEMS) relay has long been sought for signal switching applications because it allows de-coupling of the actuation (body and gate) and signal (source and drain) components unlike a 3-terminal MEMS relay. However, the contact resistance still remains a serious problem in current 4-terminal MEMS relays compared with the 3-terminal MEMS relays. In this paper, using theoretical analysis, we first determined that the two-contact design, which was the most common design in the 4-terminal MEMS relay, was the origin of the high contact resistance. We subsequently developed a 4-terminal MEMS relay with a novel single-contact design. The fabricated 4-terminal MEMS relay with the single-contact design exhibited a contact resistance of 18 $\text{m}\Omega $ . To the best of our knowledge, this result is the lowest value among 4-terminal MEMS relays. In addition, we demonstrated that the two-contacts are the origin of the high contact resistance using measurement. The relay operated up to $1.1\times 10^{6}$ cycles at 1 V / 50 mA in air and hot switching conditions. Finally, the proposed 4-terminal MEMS relay was hermetically packaged for use in commercial applications. [2017-0183]

Exploiting Partial Reconfiguration through PCIe for a Microphone Array Network Emulator

The current Microelectromechanical Systems (MEMS) technology enables the deployment of relatively low-cost wireless sensor networks composed of MEMS microphone arrays for accurate sound source localization. However, the evaluation and the selection of the most accurate and power-efficient network’s topology are not trivial when considering dynamic MEMS microphone arrays. Although software simulators are usually considered, they consist of high-computational intensive tasks, which require hours to days to be completed. In this paper, we present an FPGA-based platform to emulate a network of microphone arrays. Our platform provides a controlled simulated acoustic environment, able to evaluate the impact of different network configurations such as the number of microphones per array, the network’s topology, or the used detection method. Data fusion techniques, combining the data collected by each node, are used in this platform. The platform is designed to exploit the FPGA’s partial reconfiguration feature to increase the flexibility of the network emulator as well as to increase performance thanks to the use of the PCI-express high-bandwidth interface. On the one hand, the network emulator presents a higher flexibility by partially reconfiguring the nodes’ architecture in runtime. On the other hand, a set of strategies and heuristics to properly use partial reconfiguration allows the acceleration of the emulation by exploiting the execution parallelism. Several experiments are presented to demonstrate some of the capabilities of our platform and the benefits of using partial reconfiguration.

3-D Micro and Nano Technologies for Improvements in Electrochemical Power Devices

This review focuses on recent advances in micro- and nano-fabrication techniques and their applications to electrochemical power devices, specifically microfabricated Lithium-ion batteries, enzymatic and microbial fuel cells (biofuel cells), and dye-sensitized solar cells (DSSCs). Although the maturity of these three technologies ranges from market ready (batteries) to fundamental research (biofuel cells) to applied research (DSSCs), advances in MEMS (Micro-Electro-Mechanical Systems) and NEMS (Nano-Electro-Mechanical Systems) techniques, particularly modifications in surface area and surface chemistry, and novel genetic and molecular engineering techniques, significantly improve the electrochemical activity of these technologies across the board. For each of these three categories of power-MEMS devices the review covers: (1) The technical challenges facing the performance and fabrication of electrochemical power devices; (2) Current MEMS and NEMS techniques used to improve efficiency; and (3) Future outlook and suggested improvements of MEMS and NEMS for implementation in electrochemical power devices.

An Assessment of Bulk Metallic Glasses for Microelectromechanical System Devices

Metallic glasses were born purely of academic interest and earlier commercial attempts were limited due to the low thickness of the samples. However, with the successful fabrication of bigger samples using multicomponent system, there has been renewed interest in the commercial applicability of bulk metallic glasses (BMGs) as they offer promising mechanical, tribological and other properties which make the commercialization aspect lucrative. Through this study, an attempt has been made to assess the applicability of bulk metallic glasses as a material for Microelectromechanical System (MEMS) applications. Ranking and comparison, with the current MEMS material set, has been made using multiple criteria decision making (MCDM) approach. Performance index (PIs) was calculated using Ashby approach and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) was used to rank the materials on a collective basis. Additional features have been investigated to assess their suitability as a MEMS material. It was observed that BMGs offer promising prospects as a suitable MEMS material based on their overall performance when compared to the current material set being used for MEMS applications.

AUGMENTED FAST ORTHOGONAL SEARCH/KALMAN FILTERING (FOS/KF) POSITIONING AND ORIENTATION SOLUTION USING MEMS-BASED INERTIAL NAVIGATION SYSTEM (INS) IN DRILLING APPLICATIONS

Due to the advantages of small size and low cost, micro-electro-mechanical system (MEMS) inertial navigation systems (INS) show good prospects for use as a part of measurement-while-drilling (MWD) equipment to guarantee proper directional drilling procedure. Since current MEMS sensors have inaccurate measurements, an update aiding solution is developed using the Kalman filtering (KF) technique. However, because of the inherent poor behavior of MEMS sensors, KF technique with its linearized models has limited capability in providing accurate solution through the entire surveying process. In addition, certain realistic problems from the rugged environment would interrupt the updates in KF, without which the performance of the inertial system would deteriorate badly. This research proposes a fast orthogonal search (FOS)/KF solution where the FOS (a nonlinear modeling technique) method is proposed to augment KF. The experimental results illustrate that the FOS/KF solution outperforms the KF-only solution. Velocity and position performance are greatly enhanced during the interruptions of measurement updates.

Batch production of single-crystal diamond bridges and cantilevers for microelectromechanical systems

The utilization of single-crystal diamond offers a way to achieve extreme semiconductor and mechanical properties of diamond for microelectromechanical systems (MEMS). However, current diamond MEMS devices are limited to polycrystalline or nanocrystalline films. In this paper, we report on the batch fabrication and mechanical operation of single-crystal diamond bridges/cantilevers. The bending of these bridges/cantilevers is achieved by nanoindentation with atomic force microscopy. The resonant vibration of the cantilevers is demonstrated by using a piezoelectric actuation method with direct optical readout. These bridges/cantilevers exhibit high-quality single crystal. The maximum measured Young's modulus of the diamond bridges/cantilevers is more than 1000 GPa. The air gap between the diamond bridges/cantilevers and the substrate guarantees the application of single-crystal diamond to the MEMS.

MEMS-based high speed scanning probe microscopy

The high speed performance of a scanning probe microscope (SPM) is improved if a microelectromechanical systems (MEMS) device is employed for the out-of-plane scanning motion. We have carried out experiments with MEMS high-speed z-scanners (189 kHz fundamental resonance frequency) in both atomic force microscope and scanning tunneling microscope modes. The experiments show that with the current MEMS z-scanner, lateral tip speeds of 5 mm/s can be achieved with full feedback on surfaces with significant roughness. The improvement in scan speed, obtained with MEMS scanners, increases the possibilities for SPM observations of dynamic processes. Even higher speed MEMS scanners with fundamental resonance frequencies in excess of a megahertz are currently under development.

Architectures of Translational Parallel Mechanism for MEMS Fabrication

Manufacturing techniques, especially in the microscale, determine the type of joints, links, and actuators available for the designer, and as a result, the possible kinematic architectures of the designed mechanism. This paper discusses the design constraints imposed by current microelectromechanical system (MEMS) fabrication techniques, and how they affect the feasible kinematic architectures of microrobots. In particular, three degree-of-freedom translational mechanisms are investigated, and all possible nonoverconstrained kinematic architectures under limitations imposed by MEMS fabrication techniques are derived.