Modelling and simulation of micro-optical switches for dynamic and static loading

Inertial Measurement Units (IMUs) using MEMS (Micro Electro Mechanical Systems) sensors, to detect rotation and acceleration, are extremely sensitive to vibration and shock. Because these IMUs are used in aircraft, missiles, and even in gun launched projectiles, the vibration and shock levels can be extremely high. We have been successful in designing isolation systems that protect the MEMS sensors from these harsh environments. These isolation systems attenuate the shock and vibration in frequency ranges that would otherwise degrade IMU performance and even damage the sensors. In designing an isolation system, for an IMU with MEMS devices, the designer must first acquire a good definition of the shock and vibration environment to which the IMU will be exposed. Then the designer must determine the frequencies and levels to which the MEMS devices are sensitive. Finally the designer must have knowledge of IMU properties such as resonant frequencies, mass properties, clock frequencies, etc. By knowing all of this information, and how it affects IMU performance, the designer can determine the proper parameters for the isolation system. A well designed isolation system using these parameters will be capable of protecting the MEMS devices while maintaining IMU performance through out all specified environments.

Chapter 44 - MEMS reliability

If you've not been involved in MEMS (MicroElectroMechanical Systems) technology or had the cause to use MEMS devices, then you may wonder what all the fuss is about. What are MEMS anyway? What's the difference between MEMS and MST (MicroSystems Technology)? What are the advantages over existing technologies? If you have ever found yourself pondering over such questions, then this book may be for you. As the title suggests, the main aim is to provide an introduction to MEMS by describing the processes and materials available and by using examples of commercially available devices. The intended readership are those technical managers, engineers, scientists and graduate students who are keen to learn about MEMS but have little or no experience of the technology. I was particularly pleased to note that Maluf has dedicated a whole chapter to the important (and often difficult) area of packaging. The first three chapters provide a general overview of the technology. Within the first three pages we are introduced to the MEMS versus MST question, only to discover that the difference depends on where you live! The United States prefer MEMS, while the Europeans use the handle MST. (Note to self: tell colleagues in MEMS group at Southampton). A good account is given of the basic materials used in the technology, including silicon, silicon oxide/nitride/carbide, metals, polymers, quartz and gallium arsenide. The various processes involved in the creation of MEMS devices are also described. A good treatment is given to etching and bonding in addition to the various deposition techniques. It was interesting to note that the author doesn't make a big issue of the differences between bulk and surface micromachined devices; the approach seems to be `here's your toolbag - get on with it'. One of the great strengths of this book is the coverage of commercial MEMS structures. Arising as they have, from essentially a planar technology, MEMS devices are often elaborate three-dimensional creations, and 2D drawings don't do them much justice. I have to say that I was extremely impressed with the many aesthetic isometric views of some of these wonderful structures. Pressure sensors, inkjet print nozzles, mass flow sensors, accelerometers, valves and micromirrors are all given sufficient treatment to describe the fundamental behaviour and design philosophy, but without the mathematical rigour expected for a traditional journal paper. Chapter 5 addresses the promise of the technology as a means of enabling a new range of applications. The concept of using MEMS devices as key elements within complex systems (or even microsystems!) is explored. The so-called `lab-on-a-chip' approach is described, whereby complex analytical systems are integrated onto a single chip together with the associated micropumps and microvalves. The design and fabrication of MEMS devices are important issues by themselves. A key area, often overlooked, is that of packaging. Painstaking modelling and intricate fabrication methodologies can produce resonator structures oscillating at precisely, say, 125 kHz. The device is then mounted in a dual-in-line carrier and the frequency shifts by 10 kHz because of the additional internal stresses produced. Packaging issues can't be decoupled from those of the micromachined components. Many of these issues, such as protective coatings, thermal management, calibration etc, are covered briefly in the final chapter. Overall, I found this book informative and interesting. It has a broad appeal and gives a good insight into this fascinating and exciting subject area. Neil White

Stress distribution is one of the main factors influencing the reliability of MEMS (Micro Electro Mechanical System) structure. In most cases, MEMS devices work in motion state, the dynamic stress often affects the performances of the MEMS devices. For the first time, dynamic streses were measured by means of Raman spectroscopy and high-frequency modulation technology, the measurement result shows that dynamic stress at a certain point in silicon micro-resonator is in agreement with the analysis of theory.

Integrated TiC coatings for moving MEMS

In this study we describe a novel system for measuring the distribution of inhomogeneous mechanical properties of microelectromechanical system (MEMS) devices. Such inhomogeneous properties are important because they can decrease the reliability of MEMS devices. Our technique involves measuring the variation in the relative position and angle between single molecule markers sprayed on a MEMS device, which indicates the amount of local deformation. The distribution of the deformation on the surface of a MEMS device is calculated from local displacements measured using the system. To simultaneously measure the three-dimensional (3D) position and orientation of the markers, we developed a 3D orientation measurement system that consists of an epifluorescence microscope and a polarization mode converter (PMC). We also detected the 3D displacement and orientation of the torsion bar in a MEMS mirror device.

A variation of local point interpolation method ( vLPIM) for analysis of microelectromechanical systems (MEMS) device

MEMS (micro electro mechanical systems) products have significant growth potential, and are being used in an increasing number of applications. One issue with MEMS devices is manufacture, as current MEMS manufacturing processes not standardized. Design techniques were developed to allow a single MEMS manufacturing flow to meet a wide range of accelerometer specifications. One technique is Metal on proof this is a design method that adds thermally dissimilar materials (such as metal) to the accelerometer proof mass, and isolates the proof mass from resulting thermal stresses. Another technique is variable gap sense capacitance, which uses two different sensing gaps in capacitive transducers. This allows z-axis transducers to provide increased output and improved linearity.

This paper investigates the possibilities of measuring vehicle deceleration using modern devices based on GPS (Global Positioning System) and MEMS (Micro Electro Mechanical System) technologies, with the aim of replacing traditional inertial devices. The experiments were carried out on a passenger vehicle and a construction machine, using three different measuring devices: an inertial decelerometer, a GPS device (Racelogic DriftBox) and a MEMS accelerometer. The measurement results show good mutual agreement between recorded results from devices used for this paper, with an emphasis on the precision and ease of use of modern devices. The conclusion emphasizes the justification of using GPS and MEMS devices in testing the dynamic characteristics of vehicles due to their high frequency of data acquisition, simple processing, absence of the need for calibration, and greater practicality. This research suggests that such devices will be increasingly used in the future to analyse vehicle dynamics.

We present efficient computational methods for scattered point and meshless analysis of electrostatic microelectromechanical systems (MEMS). Electrostatic MEM devices are governed by coupled mechanical and electrostatic energy domains. A self-consistent analysis of electrostatic MEMS is implemented by combining a finite cloud method-based interior mechanical analysis with a boundary cloud method (BCM)-based exterior electrostatic analysis. Lagrangian descriptions are used for both mechanical and electrostatic analyses. Meshless finite cloud and BCMs, combined with fast algorithms and Lagrangian descriptions, are flexible, efficient, and attractive alternatives compared to conventional finite element/boundary element methods for self-consistent electromechanical analysis. Numerical results are presented for MEM switches, a micromirror device, a lateral comb drive microactuator, and an electrostatic comb drive device. Simulation results are compared with experimental and previously reported data for many of the examples discussed in this paper and a good agreement is observed.

This review article through light on a highly promising & demanding technology, which is set to revolutionize nearly every product category in present era, while discussing the Concept, Design & Development, Fabrication techniques and applications of micro electro-mechanical systems (MEMS) based Devices or systems. Microelectromechanical system discloses outstanding flexibility and adaptability in miniaturization devices followed by their compact dimension, low power consumption, and fine performance. The MEMS devices have numerous and very high potentials of creating a new field of applications for mobile equipment’s with increased flexibility & more reliability. This work deals with research carried out for the development of MEMS based sensors & Actuators and appropriate uses of MEMS. This work carries information’s regarding subsequent commercial and real life applications of MEMS and discusses various recent technological innovations carried out with their advantages & disadvantages. This work also describes the historical development of micro-electromechanical system (MEMS) sensor technology.

This dissertation explores the feasibility of using integrated optical waveguides to measure the motion of microelectromechanical structures (MEMS). MEMS are a class of silicon devices which are being developed as sensors and actuators. Because these free moving structures are fabricated using processes similar to microfabrication, MEMS devices and traditional electronics can be integrated on the same substrate. This merging of the technologies will allow the miniaturization of large scale mechanical systems. A difficulty with MEMS devices is determining the submicron motion. One method of noninvasive measurement is optical measurement. Research focused on the characterization of one particular MEMS device, a linear comb resonator. Linear comb resonators displace linearly along a single axis when drive with a sinusoidal voltage signal. This research presents how single mode and multimode guided waves have potential to yield significant positional information. Using optical fibers to create a bulk optical metrology probe, the displacement and operating frequency of this device was characterized. Integration of this an optical probe structure with the MEMS devices can create integrated optical metrology (IOM), which is an in-situ method of device characterization and can represent an enabling technology for MEMS. Co-integration of the two technologies can be achieved through either processing or post processing of integrated waveguides with the MEMS devices. The fabrication process for co-integration of polymer optical waveguides has been experimentally defined in this dissertation, however final results indicate guides wave IOM would best be explored through process interruption or hybrid techniques given existing polymer materials. Analysis yields that the co-integration of inorganic waveguide structures first requires optimization of the design of the microprobe layout.

In developing micro electro mechanical systems (MEMS), finite element analysis (FEA) is usually relied upon to study these micro-structures in determining stress, deformation, resonance, temperature distribution, electromagnetic interference, and electrical properties. With this kind of approach, the performance of the devices can be easily expanded, as well as reducing the time and cost of MEMS production. This paper focuses on the modelling of silicon MEMS accelerometer in an attempt to design a surface micro-machined accelerometer that satisfies certain pre-determined specifications.

In this paper, we first present an efficient physical level simulation method for the dynamic analysis of electrostatic micro-electromechanical systems (MEMS). This method is then used to analyze MEMS dynamics. Stiffness hardening or softening of MEM structures has been shown to depend both on the applied voltage and the geometry. The existence of multiple resonant peaks in the frequency response diagram has been presented. We have shown that a DC bias along with an appropriate AC bias can give fast switching at a considerably less peak power requirement. Finally, a reduced order model has been developed based on Karhunen-Loeve decomposition for the dynamic simulation of MEMS. Reduced order models are cheap in terms of memory and computational time and are needed to perform fast and efficient system-level composite circuit and micro-mechanical simulations.

There is strong experimental evidence for the existence of strange modes of failure of microelectromechanical systems (MEMS) devices under mechanical shock and impact. Such failures have not been explained with conventional models of MEMS. These failures are characterized by overlaps between moving microstructures and stationary electrodes, which cause electrical shorts. This work presents modeling and simulation of MEMS devices under the combination of shock loads and electrostatic actuation, which sheds light on the influence of these forces on the pull-in instability. Our results indicate that the reported strange failures can be attributed to early dynamic pull-in instability. The results show that the combination of a shock load and an electrostatic actuation makes the instability threshold much lower than the threshold predicted, considering the effect of shock alone or electrostatic actuation alone. In this work, a single-degree-of-freedom model is utilized to investigate the effect of the shock–electrostatic interaction on the response of MEMS devices. Then, a reduced-order model is used to demonstrate the effect of this interaction on MEMS devices employing cantilever and clamped–clamped microbeams. The results of the reduced-order model are verified by comparing with finite-element predictions. It is shown that the shock–electrostatic interaction can be used to design smart MEMS switches triggered at a predetermined level of shock and acceleration.