Characterization of the Dynamical Response of a Micromachined G-Sensor to Mechanical Shock Loading

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Daniel Jordy ◽  
Mohammad I. Younis
Keyword(s):  
Element Model ◽  
Plane Motion ◽  
Squeeze Film ◽  
Dynamical Response ◽  
Mechanical Shock ◽  
Mems Devices ◽  
Squeeze Film Damping ◽  
Out Of Plane ◽  
Gap Width

Squeeze film damping has a significant effect on the dynamic response of microelectromechanical system (MEMS) devices that employ perforated microstructures with large planar areas and small gap widths separating them from the substrate. Perforations can alter the effect of squeeze film damping by allowing the gas underneath the device to easily escape, thereby lowering damping. By decreasing the size of the holes, damping increases and the squeeze film damping effect increases. This can be used to minimize the out-of-plane motion of the microstructures toward the substrate, thereby minimizing the possibility of contact and stiction. This paper aims to explore the use of the squeeze film damping phenomenon as a way to mitigate shock and minimize the possibility of stiction and failure in this class of MEMS devices. As a case study, the performance of a G-sensor (threshold accelerometer) employed in an arming and fusing chip is investigated. The effect of changing the size of the perforation holes and the gap width separating the microstructure from the substrate are studied. A multiphysics finite-element model built using the software ANSYS is utilized for the fluidic and transient structural analysis. A squeeze film damping model, for both the air underneath the structure and the flow of the air through the perforations, is developed. Results are shown for various models of squeeze film damping assuming no holes, large holes, and assuming a finite pressure drop across the holes, which is the most accurate way of modeling. It is found that the threshold of shock that causes the G-sensor to contact the substrate has increased significantly when decreasing the holes size or the gap width, which is very promising to help mitigate stiction in this class of devices, thereby improving their reliability.

Characterization of the Dynamical Response of a Micromachined G-Sensor to Mechanical Shock Loading

2007 ◽  
Author(s):  
Daniel E. Jordy ◽  
Mohammad I. Younis
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Squeeze Film ◽  
Dynamical Response ◽  
Mems Devices ◽  
Damping Coefficients ◽  
Squeeze Film Damping ◽  
Out Of Plane ◽  
Gap Width

Squeeze film damping has a significant effect on the dynamic response of MEMS devices that employ perforated microstructures with large planar areas and small gap widths separating them from the substrate. Perforations can alter the effect of squeeze film damping by allowing the gas underneath the device to easily escape, thereby lowering the damping. By decreasing the size of the holes, the damping increases and the squeeze film damping effect increases. This can be used to minimize the out-of-plane motion of the microstructures toward the substrate, thereby minimizing the possibility of contact and stiction. This paper aims to explore the use of the squeeze-film damping phenomenon as a way to mitigate shock and minimize the possibility of stiction and failure in this class of MEMS devices. As a case study, we consider a G-sensor, which is a sort of a threshold accelerometer, employed in an arming and fusing chip. We study the effect of changing the size of the perforation holes and the gap width separating the microstructure from the substrate. We use a multi-physics finite-element model built using the software ANSYS. First, a modal analysis is conducted to calculate the out-of-plane natural frequency of the G-sensor. Then, a squeeze-film damping finite-element model, for both the air underneath the structure and the flow of the air through the perforations, is developed and utilized to estimate the damping coefficients for several hole sizes. Results are shown for various models of squeeze-film damping assuming no holes, large holes, and assuming a finite pressure drop across the holes, which is the most accurate way of modeling. The extracted damping coefficients are then used in a transient structural-shock analysis. Finally, the transient shock analysis is used to determine the shock loads that induce contacts between the G-sensor and the underlying substrate. It is found that the threshold of shock to contact the substrate has increased significantly when decreasing the holes size or the gap width, which is very promising to help mitigate stiction in this class of devices, thereby improving their reliability.

The Effect of Squeeze-Film Damping on Suppressing the Shock Response of MEMS

2009 ◽  
Author(s):  
Hadi Yagubizade ◽  
Mohammad I. Younis ◽  
Ghader Rezazadeh
Keyword(s):  
Reynolds Equation ◽  
Element Model ◽  
Squeeze Film ◽  
Beam Equation ◽  
Mechanical Shock ◽  
Shock Loads ◽  
Reduced Order ◽  
Squeeze Film Damping ◽  
Nonlinear Finite Element Model ◽  
Euler Bernoulli Beam

This paper presents an investigation into the response of a clamped-clamped microbeam to mechanical shock under the effect of squeeze-film damping (SQFD). In this work, we solve simultaneously the nonlinear Reynolds equation, to model squeeze-film damping, coupled with a nonlinear Euler-Bernoulli beam equation. A Galerkin-based reduced-order model and a finite-deference method (FDM) are utilized for the solid domain and for the fluid domain, respectively. Several results showing the effect of gas pressure on the response of the microbeams are shown. Comparison with the results of a multi-physics nonlinear finite-element model is presented. The results indicate that squeeze-film damping has more significant effect on the response of microstructures in the dynamic shock loads compared to the quasi-static shock loads.

Experimental Observation of Inertia-Dominated Squeeze Film Damping in Liquid

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Antoine Fornari ◽  
Matthew Sullivan ◽  
Hua Chen ◽  
Christopher Harrison ◽  
Kai Hsu ◽  
...  
Keyword(s):  
Drag Force ◽  
High Frequency ◽  
Power Laws ◽  
Plane Motion ◽  
Squeeze Film ◽  
Fluid Viscosity ◽  
Squeeze Film Damping ◽  
Out Of Plane ◽  
Made In

We have studied the phenomenon of squeeze film damping in a liquid with a microfabricated vibrating plate oscillating in its fundamental mode with out-of-plane motion. It is paramount that this phenomenon be understood so that proper choices can be made in terms of sensor design and packaging. The influences of plate-wall distance h, effective plate radius R, and fluid viscosity and density on squeeze film damping have been studied. We experimentally observe that the drag force is inertia dominated and scales as 1/h3 even when the plate is far away from the wall, a surprising but understandable result for a microfluidic device where the ratio of h to the viscous penetration depth is large. We observe as well that the drag force scales as R3, which is inconsistent with squeeze film damping in the lubrication limit. These two cubic power laws arise due to the role of inertia in the high frequency limit.

The Effect of Squeeze-Film Damping on the Shock Response of Clamped-Clamped Microbeams

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Hadi Yagubizade ◽  
Mohammad I. Younis
Keyword(s):  
Element Model ◽  
Squeeze Film ◽  
Beam Equation ◽  
Mechanical Shock ◽  
Computationally Efficient ◽  
Reduced Order ◽  
Squeeze Film Damping ◽  
Nonlinear Finite Element Model ◽  
Euler Bernoulli Beam ◽  
Fully Coupled

This paper presents an investigation into the nonlinear effect of squeeze-film damping on the response of a clamped–clamped microbeam to mechanical shock. In this work, we solve simultaneously the nonlinear Reynolds equation, to model squeeze-film damping, coupled with a nonlinear Euler–Bernoulli beam equation. A Galerkin-based reduced-order model and a finite-difference method are utilized for the solid domain and fluid domain, respectively. Several results demonstrating the effect of gas pressure on the response of the microbeams are shown. Comparison with the results of a fully coupled multiphysics nonlinear finite-element model is presented. The results indicate that, for devices operating in air, squeeze-film damping can be used effectively to minimize the displacements of released microstructures during shock and impact. The results also indicate that squeeze-film damping has more significant effect on the response of microstructures in the dynamic shock regime compared to the quasi-static shock regime. A computationally efficient approach is proposed to model the fluidic-structural problem more efficiently based on a nonlinear analytical expression of the squeeze-film damping.

Development of Latching Type Large Vertical-Travel Microactuator

2005 ◽  
Author(s):  
Risaku Toda ◽  
Eui-Hyeok Yang
Keyword(s):  
Plane Motion ◽  
Proof Of Concept ◽  
Test Device ◽  
Comb Drive ◽  
Pzt Actuator ◽  
Comb Drives ◽  
Out Of Plane ◽  
Sequential Activation ◽  
Vertical Travel

This paper describes design, fabrication and preliminary characterization of a proof-of-concept vertical-travel microactuator, providing linear motion and high precision positioning in space. The microactuator is capable of providing latching function when it is un-powered to maintain its position. The microactuator consists of two opposing comb drive actuator dies, a slider and bulk PZT actuators sandwiched between the dies. The slider is inserted between clutches. Comb drives are connected to the clutches to engage/disengage clutching. Sequential activation of the comb drives (in-plane motion) and the PZT actuator (out-of-plane motion) provides cumulative linear travel of the slider. The novelty of the slider insertion approach include (1) post-fabrication engagement of comb teeth enabling thick wafer DRIE process for comb drive actuators and (2) stressed tethers enabling zero-power latching. A test device was fabricated and assembled. By applying 100V∼300V DC to the electrostatic comb drive, lateral actuation of clutches was observed. Vertical actuation by PZT was also confirmed using WYKO RST plus interferometer.

The Effect of Shape and Distribution of Perforations on Squeeze-Film Damping in Parallel Plate Capacitors

2009 ◽  
Author(s):  
Weili Cui ◽  
Ronald N. Miles ◽  
Dorel Homentcovsci
Keyword(s):  
Parallel Plate ◽  
Internal Heat ◽  
Optical Switches ◽  
Squeeze Film ◽  
Mems Devices ◽  
Capacitive Sensing ◽  
Squeeze Film Damping ◽  
Squeeze Film Effect ◽  
Capacitive Mems ◽  
Stationary Plate

The effect of the shape and distribution of perforations in parallel plate capacitive MEMS devices on squeeze-film damping is presented. The squeeze film effect is the most important damping effect on the dynamic behavior of most MEMS devices that employ capacitive sensing and actuation, which typically employ narrow air gaps between planar moving surfaces [1, 2]. The stationary plate of a capacitive device is often perforated to reduce the damping and sensor noise and improve the frequency response. The formula for determining the total viscous damping in the gap contains a coefficient Cp that is associated with the geometry and distribution of the holes on the stationary plate. In this study, the coefficient Cp is determined using the finite element method using ANSYS by analogy with heat conduction in a solid with internal heat generation. Round, elliptical, rectangular, and oval holes that are distributed either aligned or offset are analyzed and compared. It is shown that the surface fraction occupied by the perforations is not the only factor that determines Cp. Both the shape and distribution strongly affect the damping coefficient [3, 4]. By using elongated perforations that are properly distributed, the squeeze film damping could be minimized with the minimum amount of perforation. The analysis performed in this work is quite general being applicable to a very large spectrum of frequencies and to various fluids in capacitive sensors. These results can facilitate the design of mechanical structures that utilize capacitive sensing and actuation, such as accelerometers, optical switches, micro-torsion mirrors, resonators, microphones, etc.

Non-Contact Mechanical Testing and Characterization of Micro-Scale Structures

2006 ◽  
Author(s):  
Jian Chen ◽  
Ganesh Subramanian ◽  
Justin Ricci ◽  
Liang Ban ◽  
Cetin Cetinkaya
Keyword(s):  
Plane Motion ◽  
Cantilever Beams ◽  
Micro Scale ◽  
New Class ◽  
Sensor Platform ◽  
Out Of Plane ◽  
Modes Of Vibration ◽  
Scale Structures ◽  
Micro Cantilever

A non-contact testing and characterization method based on air-coupled acoustic excitation and interferometric displacement measurements of micro-scale MEMS structures at room conditions is introduced. In demonstrating its potential uses in testing and characterization, the present non-contact approach is applied to (i) micro-cantilever beams and (ii) rotational disk oscillators. Air-coupled multi-mode excitation of micromechanical cantilever-type oscillators under a pulsed acoustic field generated by an air-coupled transducer is demonstrated and reported. Also, the testing and characterization of a micro-scale rotational disk oscillator developed for a new class of sensor platform is demonstrated. The main design objective of the rotational disk oscillator class is to overcome the out-of-plane motion related sensitivity limitations of the cantilever-based sensors at high frequency operations. The dynamics of the rotational disk oscillators is more complex than micro-cantilever beams due to its in-plane motion in addition to its various out-of-plane modes of vibration. The fabrication of a rotational disk oscillator requires a suspended disk whose underside is visibly inaccessible due to a narrow micro-gap. In addition to the dynamic characterization of the cantilever beams and rotational disk oscillators, the current investigation demonstrates that the presented approach can address unique structural concerns such as the verification of a gap separation of the rotational oscillator from the underlying silicon substrate. Utilizing the proposed technique, the resonant frequencies of the oscillator structures are obtained and its potential uses in the testing and characterization of micro-scale structures are discussed. The major specific advantages of the introduced approach include that (i) its noncontact nature can eliminate testing problems associated with stiction and adhesion, and (ii) it allows direct mechanical characterization and testing of components and sub-components of a micro-scale devices.

A Novel Expression for the Effective Viscosity to Model Squeeze-Film Damping at Low Pressure

2013 ◽  
Vol 390 ◽  
pp. 76-80 ◽  
Author(s):  
Maria F. Pantano ◽  
Salvatore Nigro ◽  
Franco Furgiuele ◽  
Leonardo Pagnotta
Keyword(s):  
Experimental Data ◽  
Effective Viscosity ◽  
Squeeze Film ◽  
Navier Stokes ◽  
Fluid Viscosity ◽  
The Novel ◽  
Mems Devices ◽  
Navier Stokes Equation ◽  
Experimental Procedure ◽  
Squeeze Film Damping

The Navier-Stokes equation is currentlyconsidered for modelling of squeeze-film damping in MEMS devices, also when the fluid flow associated to it is rarefied.In order to include rarefaction effects in such equation, a common approach consists of replacing the ordinary fluid viscosity with a scaled quantity, known as effective viscosity.The literature offers different expressions for the effective viscosity as a function of the Knudsen number (Kn). Such expressions were shown to work well whenKn<1, but theyresulted to be lessaccurate in case ofKn>1. In this paper a new expression is proposed to evaluate the effective viscosity for 1<Kn<40with increased reliability. Such anexpression was derivedfrom an optimized numerical-experimental procedure,developed in MATLAB® environment, using a finite element code and experimental data extracted from the literature. A comparison is finally reported and discussed between the results, in terms of damping coefficient, obtained considering previously reported effective viscosity expressions and the novel one,with reference to different squeeze film damping layouts, for which experimental data are already available.

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