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Electrostatic Simulation using XFEM for Conductor and Dielectric Interfaces Rochus, Véronique ; ; Van Miegroet, Laurent et al in International Journal for Numerical Methods in Engineering (2011), 85(10), 12071226 ManyMicro-Electro-Mechanical Systems (e.g. RF-switches, micro-resonators and micro-rotors) involve mechanical structures moving in an electrostatic field. For this type of problems, it is required to ... [more ▼] ManyMicro-Electro-Mechanical Systems (e.g. RF-switches, micro-resonators and micro-rotors) involve mechanical structures moving in an electrostatic field. For this type of problems, it is required to evaluate accurately the electrostatic forces acting on the devices. Extended Finite Element (X-FEM) approaches can easily handle moving boundaries and interfaces in the electrostatic domain and seem therefore very suitable to model Micro-Electro-Mechanical Systems. In this study we investigate different X-FEM techniques to solve the electrostatic problem when the electrostatic domain is bounded by a conducting material. Preliminary studies in one-dimension have shown that one can obtain good results in the computation of electrostatic potential using X-FEM. In this paper the extension of these preliminary studies to 2D problem is presented. In particular a new type of enrichment functions is proposed in order to treat accurately Dirichlet boundary conditions on the interface. [less ▲] Detailed reference viewed: 143 (25 ULg)Geometrical Effects on the Dynamical Behavior of MEMS structures Pustan, Marius ; Golinval, Jean-Claude ; Rochus, Véronique (2010, May 16) The influence of geometrical dimensions on the dynamical behavior of polysilicon MEMS structures configurations is studied and presented in this paper. Electrostatically actuated MEMS components as ... [more ▼] The influence of geometrical dimensions on the dynamical behavior of polysilicon MEMS structures configurations is studied and presented in this paper. Electrostatically actuated MEMS components as microbridges and microcantilevers are used to investigate the coupled electro-mechanic effect, frequency responses and the dynamic bending stress. The electrostatic principle is common in sensing and acting devices and there are many MEMS structures subjected to electrostatic forces. [less ▲] Detailed reference viewed: 29 (10 ULg)Modeling and Finite Element Analysis of Mechanical Behavior of Flexible MEMS Components Pustan, Marius ; ; Rochus, Véronique et al in Courtois, Bernard (Ed.) DTIP 2010 (2010, May 05) This paper describes the studies of the mechanical characteristics of flexible MEMS components including theoretical approach, finite element analysis and experimental investigations. Modeling and finite ... [more ▼] This paper describes the studies of the mechanical characteristics of flexible MEMS components including theoretical approach, finite element analysis and experimental investigations. Modeling and finite element analyses together with theoretical and experimental investigations are performed to estimate the mechanical behaviour of MEMS components as microcantilevers, microbridges and micromembranes. The finite element analysis of microcomponents deflections under different loading and the stress distribution in beams is determined and compared with the experimental measurements performed using atomic force microscope. The modeling of a micromembrane supported by four hinges that enable out-of-plane and in-plane motions is presented. Finite element analysis and experimental investigations are performed to estimate the deflection of the mobile plate of the micromembrane under an applied force and to visualize the distribution of the stress in hinges. In additional, this paper provides analytical relations for stiffness and stresses of the investigated flexible MEMS components. [less ▲] Detailed reference viewed: 38 (8 ULg)Prediction of Stiction in Microswitch Systems Wu, Ling ; Rochus, Véronique ; Noels, Ludovic et al in EUROSIME 2010 (2010) Stiction is a major failure mode of MEMS as microscopic structures tend to adhere to each other when their surfaces enter into contact. Although increasing the restoring forces of switch devices could ... [more ▼] Stiction is a major failure mode of MEMS as microscopic structures tend to adhere to each other when their surfaces enter into contact. Although increasing the restoring forces of switch devices could overcome the stiction effect, this is not practical, as in turn, it also increases the actuation voltage. Therefore stiction prediction is important to be considered when designing micro- and nano- devices. In this paper, the numerical prediction of stiction for capacitive MEMS switches is considered. Toward this end, a micro-adhesive-contact law is derived from previous work and combined with a finite-element model. [less ▲] Detailed reference viewed: 96 (32 ULg)Evaluation of Tribo-Mechanical Properties of Thin Films Using Atomic Force Microscope Pustan, Marius ; Rochus, Véronique ; Wu, Ling et al in First European Conference on Nanofilm ECNF2010 (2010) Experimental investigations of mechanical and tribological properties of thin films using an atomic force microscope and its combination with nanoidentation are presented in this paper. The normal mode of ... [more ▼] Experimental investigations of mechanical and tribological properties of thin films using an atomic force microscope and its combination with nanoidentation are presented in this paper. The normal mode of an atomic force microscope is used to measure the stiffness and hardness of thin films which are tribologically characterized by roughness, nano-scale adhesion forces and friction forces. The friction forces are measured using the lateral force mode of atomic force microscope. In order to measure the adhesion forces of thin films, spectroscopy in point with atomic force microscope was performed. Direct measurement of tribological and mechanical behaviour of thin films is important to increase the lifetime of microstructures which use thin films for friction and stiction reduction of microsystems. [less ▲] Detailed reference viewed: 89 (24 ULg)Design of Microswitch Systems Avoiding Stiction due to Surface Contact Wu, Ling ; Noels, Ludovic ; Rochus, Véronique et al in SEM 2010 Annual Conference & Exposition on Experimental and Applied Mechanics (2010) Stiction which results from contact between surfaces is a major failure mode in micro electro-mechanical systems (MEMS). Increasing restoring forces using high spring constant allows avoiding stiction but ... [more ▼] Stiction which results from contact between surfaces is a major failure mode in micro electro-mechanical systems (MEMS). Increasing restoring forces using high spring constant allows avoiding stiction but leads to an increase of the actuation voltage so that the switch’s efficiency is threatened. A statistical rough surfaces interaction model, based on Maugis’ and Kim’s formulations is applied to estimate the adhesive forces in MEMS switches. Based on the knowledge of these forces, the proper design range of the equivalent spring constant, which is the main factor of restoring force in MEMS switches, can be determined. The upper limit of equivalent spring constant depends mainly on the expected actuator voltage and on the geometric parameters, such as initial gap size and ,thickness of dielectric layer. The lower limit is assessed on the value of adhesive forces between the two contacting rough surfaces. It mainly depends on the adhesive work of contact surfaces and on the surfaces’ roughness. In order to study more complicated structures, this framework will be used in a multiscale model: resulting unloading micro adhesive contact-distance curves of two rough surfaces will be used as contact forces in a finite-element model. In this paper the extraction of these curves for the particular case of gold to gold micro-switches is pursued. [less ▲] Detailed reference viewed: 160 (43 ULg)Effects of the geometrical dimensions on stress and strain of electrostatically actuated MEMS resonators at pull-in and stiction positions Pustan, Marius ; Golinval, Jean-Claude ; Rochus, Véronique in EuroSimE 2010 (2010) Detailed reference viewed: 18 (12 ULg)Introduction to Electromechanical Coupling Rochus, Véronique in Computer and Experimental Simulations in Engineering and Science [=CESES] (2010), (7), This paper is dedicated to the physical understanding of electrostatic forces with a one-dimensional reference problem. First a non-dimensional analysis prescribes the kind of assumptions to consider for ... [more ▼] This paper is dedicated to the physical understanding of electrostatic forces with a one-dimensional reference problem. First a non-dimensional analysis prescribes the kind of assumptions to consider for the electric field model. An analytical study of electro-mechanical coupling is then performed to understand the type of non-linearity added by electrostatic forces, and static and dynamic analysis are used to define new characteristic parameters. To come closer to more realistic problems, cubic mechanical stiffness is added to account for the large displacement hypothesis prescribed for certain types of MEMS and damping effects are studied. [less ▲] Detailed reference viewed: 89 (17 ULg)A Xylophone Bar Magnetometer for micro/pico satellites ; Niyonzima, Innocent ; Rochus, Pierre et al in Acta Astronautica (2010), 67(7-8), 793-809 The Belgian Institute of Space Aeronomy (BIRA-IASB), "Centre Spatial de Liège" (CSL), "Laboratoire de Techniques Aéronautiques et Spatiales" (LTAS) of University of Liège, and the Microwave Laboratory of ... [more ▼] The Belgian Institute of Space Aeronomy (BIRA-IASB), "Centre Spatial de Liège" (CSL), "Laboratoire de Techniques Aéronautiques et Spatiales" (LTAS) of University of Liège, and the Microwave Laboratory of University of Louvain-La-Neuve (UCL) are collaborating in order to develop a miniature version of a xylophone bar magnetometer (XBM) using Microelectromechanical Systems (MEMS) technology. The device is based on a classical resonating xylophone bar. A sinusoidal current is supplied to the bar oscillating at the fundamental transverse resonant mode of the bar. When an external magnetic field is present, the resulting Lorentz force causes the bar to vibrate at its fundamental frequency with an amplitude directly proportional to the vertical component of the ambient magnetic field. In this paper we illustrate the working principles of the XBM and the challenges to reach the required sensitivity in space applications (measuring magnetic fields with an accuracy of approximately of 0.1 nT). The optimal dimensions of the MEMS XBM are discussed as well as the constraints on the current flowing through the bar. Analytical calculations as well as simulations with finite element methods have been used. Prototypes have been built in the Microwave Laboratory using Silicon on Insulator (SOI) and bulk micromachining processes. Several methods to accurately measure the displacement of the bar are proposed. [less ▲] Detailed reference viewed: 137 (28 ULg)Dual approach for an accurate estimation of pull-in voltage Rochus, Véronique ; Lemaire, Etienne ; Geuzaine, Christophe in Proceedings of the IVth European Conference on Computational Mechanics (ECCM 2010) (2010) Detailed reference viewed: 29 (21 ULg)Simulation of Particle Levitation due to Dielectrophoresis Rochus, Véronique ; ; Golinval, Jean-Claude et al in EuroSimE 2010 (2010) The aim of the research is to model accurately dielectrophoresis using different numerical tools and compare them to experimental results. The dielectrophoresis phenomenon consists in the creation of ... [more ▼] The aim of the research is to model accurately dielectrophoresis using different numerical tools and compare them to experimental results. The dielectrophoresis phenomenon consists in the creation of electrostatic forces on nano or micro particles due to a gradient of electric field. The aim of such a setup is to control the motion of micro or nano particles for MEMS applications, for instance, for bioanalysis devices. To validate the numerical results, some prototypes have been fabricated at TU Delft. Using these simulations, a design of microstructure has been chosen to levitate Silica micro-particles. Experimental measurements have been performed and some characteristic behaviours of particle depending on the amplitude and the frequency of the applied voltage have been identified. The measurements are compared to the numerical simulation. [less ▲] Detailed reference viewed: 41 (3 ULg)Influence of Adhesive Rough Surface Contact on Micro-Switches Wu, Ling ; Rochus, Véronique ; Noels, Ludovic et al in Journal of Applied Physics (2009), 106(11), 113502 Stiction is a major failure mode in micro electro-mechanical systems (MEMS). Undesirable stiction, which results from contact between surfaces, threatens the reliability of MEMS severely as it breaks the ... [more ▼] Stiction is a major failure mode in micro electro-mechanical systems (MEMS). Undesirable stiction, which results from contact between surfaces, threatens the reliability of MEMS severely as it breaks the actuation function of MEMS switches for example. Although it may be possible to avoid stiction by increasing restoring forces using high spring constants, it follows that the actuation voltage has also to be increased significantly, which reduces the efficiency. In our research, an electrostatic-structural analysis is performed to estimate the proper design range of the equivalent spring constant which is the main factor of restoring force in MEMS switches. The upper limit of equivalent spring constant is evaluated based on the initial gap width, the dielectric thickness, and the expected actuation voltage. The lower limit is assessed on the value of adhesive forces between the two contacting rough surfaces. The MEMS devices studied here are assumed to work in a dry environment. In these operating conditions only the Van der Waals forces have to be considered for adhesion. A statistical model is used to simulate the rough surface, and the Maugis’s model is combined with Kim’s expansion to calculate adhesive forces. In the resulting model, the critical value of the spring stiffness depends on the material and surface properties, such as the elastic modulus, surface energy and surface roughness. The aim of this research is to propose simple rules for design purposes. [less ▲] Detailed reference viewed: 138 (53 ULg)Influence of the material model on local pull-in in electromechanical microdevices topology optimization Lemaire, Etienne ; Van Miegroet, Laurent ; Duysinx, Pierre et al in PLATO-N International Workshop - Extended Abstracts (2009, September) The appearance of local pull-in modes has been noticed during electromechanical microdevices topology optimization. The goal of the present research is to study the influence of material properties ... [more ▼] The appearance of local pull-in modes has been noticed during electromechanical microdevices topology optimization. The goal of the present research is to study the influence of material properties (mechanical and electrical) modeling for intermediate densities to see if an appropriate choice allows avoiding such local modes. At first, a simple 1D model is developed to study the influence of the material properties interpolation. Finally, we evaluate if the conclusions from the 1D model can help to prevent the appearance of local modes for a 2D topology optimization problem. [less ▲] Detailed reference viewed: 48 (5 ULg)Electromechanical FEM models and electrostatic forces near sharp corners ; ; et al E-print/Working paper (2009) Accounting for multiphysical coupling in models of Micro Electro Mechanical Systems (MEMS) is essential for accurate simulations. One essential multiphysical effect in MEMS is the electromechanical ... [more ▼] Accounting for multiphysical coupling in models of Micro Electro Mechanical Systems (MEMS) is essential for accurate simulations. One essential multiphysical effect in MEMS is the electromechanical coupling since electrostatic forces are often used for actuation or sensing in those devices. Often MEMS are designed such that their shape exhibits many corners. In this paper two different numerical approaches are used to model this coupling using the Finite Element Method: the electrostatic forces are either derived from the variational approach or a local approach based on the Maxwell stress tensor such as implemented in commercial Finite Element codes. The evaluation of electrostatic forces near corners is investigated in detail and in this paper the two approaches are compared around corners. Although the issue of numerical models around singularities is not new, the question addressed here is related to the computation of electric forces in the vicinity of corners. Since those forces are quadratic functions of the electric field, namely the gradient of the electric potential, here the primal unknown, computing those forces accurately is a challenge in itself. Elements which use special shape functions are used to discretize the field near this corner singularity as well. In the work presented here, it is shown that a significant discrepancy appears in the electrostatic force computed around a corner depending on the discretization approach considered, and we conclude that the variational approach or equivalently the full Maxwell tensor should be used to properly evaluate electrostatic forces around corners. [less ▲] Detailed reference viewed: 97 (6 ULg)Influence of Adhesive Rough Surface Contact on Micro-Switches Wu, Ling ; Rochus, Véronique ; Noels, Ludovic et al Scientific conference (2009) Detailed reference viewed: 52 (21 ULg)A Xylophone Bar Magnetometer for micro/pico satellites Rochus, Véronique ; ; et al in Materials and Structures Symposium (C2.8): Specialised Technologies, including Nanotechnology (2009) Detailed reference viewed: 79 (20 ULg)Dual Approach for Electromechanical Coupling in MEMS Rochus, Véronique ; Golinval, Jean-Claude ; Geuzaine, Christophe (2009) In this paper we present an approach for the computation of coupled electromechanical problems in micro-electromechanical systems based on a vector potential formulation of the electrostatic problem. This ... [more ▼] In this paper we present an approach for the computation of coupled electromechanical problems in micro-electromechanical systems based on a vector potential formulation of the electrostatic problem. This formulation is the dual of the scalar potential approach commonly used in the literature. We present an analytic derivation of the force computed using this dual method based on the virtual work principle, and compare the primal and dual approaches on the finite element solution of simple twodimensional test-cases. [less ▲] Detailed reference viewed: 67 (14 ULg)Electrostatic Forces Computed with Extended Finite Element Rochus, Véronique ; Golinval, Jean-Claude ; Van Miegroet, Laurent et al (2009) Detailed reference viewed: 36 (4 ULg)High Vibration Sensors: Modelling, Design and Integration Rochus, Véronique ; ; Golinval, Jean-Claude et al in Proceedings of Thermal, Mechanical and Multiphysics Simulation and Experiments in Micro-Electronics and Micro-systems EuroSime (2009) Since many years, the University of Liège is involved in micro-electronics and microelectromechanical systems modelling, design and integration. Recently, the University of Liege had received the ... [more ▼] Since many years, the University of Liège is involved in micro-electronics and microelectromechanical systems modelling, design and integration. Recently, the University of Liege had received the opportunity to build a brand new infrastructure (clean rooms – ISO 7) with specific equipments for packaging and MEMS characterisation. This new facility (clean rooms and equipments) enables the University to be very well positioned in the nano/micro-electronics modelling, analysis and packaging world and is now able to answer specific research and related industrial needs. In this paper we consider the design of a vibration sensor in its significantly vibrating surroundings and investigate in its dynamical behaviour. Environmental vibrations affect the sensor part of the MEMS device and influence the choice of the “best” packaging methods for the application. Within the framework of packaging, we consider a simple test application ensuring best interconnection technology. Dynamical investigations include a preliminary analysis of the packaging and a separate finite-element analysis of the MEMS device (inside the package), testing the device under the condition of a harsh environment (high vibration spectral level). Computations are proposed in combination with experimental observations. [less ▲] Detailed reference viewed: 70 (14 ULg)Smart Sensors and MEMS for all over Industrial Application Niches Saint-Mard, Michel ; Heusdens, Bruno ; Haudry, Fabrice et al in Smart Systems Integration (2009) Detailed reference viewed: 73 (10 ULg) |
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