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See detailA Micro-Macroapproach to Predict Stiction due to Surface Contact in Microelectromechanical Systems
Wu, Ling ULg; Noels, Ludovic ULg; Rochus, Véronique et al

in IEEE/ASME Journal of Microelectromechanical Systems (2011), 20(4), 976-990

Stiction, which results from contact between surfaces, is a major failure mode in micro electro-mechanical systems (MEMS). Indeed microscopic structures tend to adhere to each other when their surfaces ... [more ▼]

Stiction, which results from contact between surfaces, is a major failure mode in micro electro-mechanical systems (MEMS). Indeed microscopic structures tend to adhere to each other when their surfaces enter into contact and when the restoring forces are unable to overcome the interfacial forces. Since incidental contacts cannot be completely excluded and since contacts between moving parts can be part of the normal operation of some types of MEMS, stiction prediction is an important consideration when designing micro and nano-devices. In this paper a micro-macro multi-scale approach is developed in order to predict possible stiction. At the lower scale, the unloading adhesive contact-distance curves of two interacting rough surfaces are established based on a previously presented model [L. Wu et al., J. Appl. Phys. 106, 113502, 2009]. In this model, dry conditions are assumed and only the van der Waals forces as adhesion source are accounted for. The resulting unloading adhesive contact-distance curves are dependant on the material and on surface properties, such as, elastic modulus, surface energy and on the rough surfaces topography parameters; the standard deviation of asperity heights and the asperities density. At the higher scale, a finite element analysis is considered to determine the residual cantilever beam configuration due to the adhesive forces once contact happened. Toward this end, the adhesive contact-distance curve computed previously is integrated on the surface of the finite elements as a contact law. Effects of design parameters can then be studied for given material and surface properties. [less ▲]

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See detailModeling and finite element analysis of mechanical behavior of flexible MEMS components
Pustan, Marius ULg; Paquay, Stéphane; Rochus, Véronique et al

in Microsystem Technologies (2011), 17(4), 553-562

This paper describes the studies of the mechanical characteristics of flexible MEMS components including theoretical approaches, finite element analysis and experimental investigations. Modeling and ... [more ▼]

This paper describes the studies of the mechanical characteristics of flexible MEMS components including theoretical approaches, finite element analysis and experimental investigations. Modeling and finite element analyses together with theoretical and experimental investigations are performed to estimate the elastic behavior of MEMS components as microcantilevers, microbridges and micromembranes. Finite element analysis of microcomponents deflections under different loading and the stress distribution in beams are determined and compared with the experimental measurements performed using an atomic force microscope. The modeling of a micromembrane supported by four hinges that enable out-of-plane motion is presented. Finite element analysis and experimental investigations are performed to visualize the deflection of the mobile part of the micromembrane under an applied force and the stress distribution in hinges. In additional, this paper provides analytical relations to compute the stiffness and the stress of the investigated flexible MEMS components. [less ▲]

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See detailEffects of the electrode positions on the dynamical behaviour of electrostatically actuated MEMS resonators
Pustan, Marius ULg; Paquay, Stéphane; Rochus, Véronique et al

(2011, April 18)

The influence of the lower electrode positions on the dynamic response of polysilicon MEMS resonators is studied and presented in this paper. The change in the frequency response of investigated MEMS ... [more ▼]

The influence of the lower electrode positions on the dynamic response of polysilicon MEMS resonators is studied and presented in this paper. The change in the frequency response of investigated MEMS resonators as function of the lower electrode positions is measured using a vibrometer analyzer. The decrease in the amplitude and velocity of oscillations if the lower electrode is moved from the beam free-end toward to the beam anchor is experimental monitored. The measurements are performed in ambient conditions in order to characterize the forced-response Q-factor of samples. A decrease of the Q- factor if the lower electrode is moved toward to the beam anchor is experimental determined. Different responses of MEMS resonators may be obtained if the position of the lower electrode is modified. Indeed the resonator stiffness, velocity and amplitude of oscillations are changed. [less ▲]

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See detailNANOMATERIAL BEHAVIOUR OF A GOLD MICROCANTILEVER SUBJECTED TO PLASTIC DEFORMATIONS
Pustan, Marius ULg

in Digest Journal of Nanomaterials & Biostructures [=DJNB] (2011), 6(1), 285-290

The nanomechanical material behaviour of a gold microcantilever subjected to plastic deformations is presented in this paper. Using an atomic force microscope, experimental investigations are performed in ... [more ▼]

The nanomechanical material behaviour of a gold microcantilever subjected to plastic deformations is presented in this paper. Using an atomic force microscope, experimental investigations are performed in order to determine the dependence between bending deflections of sample versus applied forces and to estimate the maximum stress in the beam structure. During testing, the force has successive positions on microcantilever, starting from the beam free-end and moving toward to the anchor. The plastic deformation of microcantilever occurs when the force is applied close to the beam anchor and performed large deflections. Finite element analysis is used to visualize the deflection of microcantilever and to estimate the maximum stress. [less ▲]

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See detailDynamic investigations of paddle MEMS cantilevers used in mass sensing applications
Pustan, Marius ULg; Belcin, Oliviu; Golinval, Jean-Claude ULg

in Arghir, Mariana (Ed.) Acta Technica Napocensis of The Technical University of Cluj-Napoca (2011)

The dynamic behaviour of paddle MEMS cantilever oscillators under electrostatic actuation is investigated and presented in this paper. The scope is to estimate the influence of the geometrical dimensions ... [more ▼]

The dynamic behaviour of paddle MEMS cantilever oscillators under electrostatic actuation is investigated and presented in this paper. The scope is to estimate the influence of the geometrical dimensions and operating conditions on the frequency response of mechanical paddle cantilevers fabricated from polysilicon. Theoretical approach and finite element analysis are developed considering the multiphysics coupling between the electrical field and the mechanical structure of oscillators. The;experimental tests are performed under ambient condition and in vacuum in order to characterize the effect of operating condition on the frequency response of paddle cantilevers. [less ▲]

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See detailDesign of Microswitch Systems Avoiding Stiction due to Surface Contact
Wu, Ling ULg; Noels, Ludovic ULg; Rochus, Véronique et al

in Proulx, Tom (Ed.) MEMS and Nanotechnology, Volume 2 (2011)

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 ▲]

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See detailNANOTRIBOLOGICAL AND NANOMECHANICAL CHARACTERIZATIONS OF MEMS MATERIALS
Pustan, Marius ULg; Rochus, Veronique; Golinval, Jean-Claude ULg

Poster (2010, December)

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See detailGeometrical Effects on the Dynamical Behavior of MEMS structures
Pustan, Marius ULg; Golinval, Jean-Claude ULg; Rochus, Véronique ULg

(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 ▲]

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See detailModeling and Finite Element Analysis of Mechanical Behavior of Flexible MEMS Components
Pustan, Marius ULg; Paquay, Stéphane; Rochus, Véronique ULg 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 ▲]

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See detailEvaluation of Tribo-Mechanical Properties of Thin Films Using Atomic Force Microscope
Pustan, Marius ULg; Rochus, Véronique ULg; Wu, Ling ULg 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 ▲]

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See detailDesign of Microswitch Systems Avoiding Stiction due to Surface Contact
Wu, Ling ULg; Noels, Ludovic ULg; Rochus, Véronique ULg 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 ▲]

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See detailNanomechanical properties of sensing microcomponents
Pustan, Marius ULg; Golinval, Jean-Claude ULg; Rochus, Véronique ULg

Scientific conference (2009)

Detailed reference viewed: 41 (16 ULg)