Optimization-of-Passive-Air-Damping-of-MOEMS-Vibration-Senso

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Procedia Engineering 87 ( 2014 )440 – 443

EUROSENSORS2014,theXXVIIIeditionoftheconferenceseries

OptimizationofPassiveAirDampingof

MOEMSVibrationSensors

A.Kainza, ,W.Hortschitzb,M.Stifterb,J.Schalkoa,F.Keplingera

bCenteraInstitute

ofSensorandActuatorSystems,ViennaUniversityofTechnology,Vienna,AustriaforIntegratedSensorSystems,DanubeUniversityKrems,WienerNeustadt,Austria

Abstract

WereportondesignrulesforthepassiveairdampingoflaterallyoscillatingMOEMS[1].Theyallowforatailormadecharac-teristicofthetransferfunctionofamicrosensorforagiven eldofapplication.Measurementsinairatatmosphericpressureaswellasinvacuumatapressureof10 4to10 1mbarwereaccompaniedby nitevolumemethodcomputational uidmechanicssimulationsusingtheopensourcesoftwareOpenFOAM®.Thesewerecombinedwithanalyticmodelstoidentifyandquantifytheimportantparametersoftheairdampingofamicromachinedvibrationsensorwithopticalread-out.Ourresultsprovethatthedesireddampingcanbeachievedwithhighprecision.ThisimportantfactcannowbeusedtodesignawiderangeofMOEMSwithawell-de nedqualityfactorQ,e.g.forresonantsensing(highQ,lowfrequencyrange)orvibrationsensing(lowQ,highfrequencyrange).

©2014TheAuthors.PublishedbyElsevierLtd.(/licenses/by-nc-nd/3.0/).

Peer-reviewunderresponsibilityofthescienti ccommiteeofEurosensors2014.Peer-review under responsibility of the scientific committee of Eurosensors 2014

© 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

Keywords:Damping;AirDamping;MOEMS;CFD;OpenFOAM;FVM;VibrationSensor;LateralOscillator

1.Introduction

Manyoftoday’ssensorsinvolveoscillatingmicrostructures.Ingeneral,theycanbedescribedasharmonicoscil-latorsthataredrivenbya(periodic)externalforceFext=Keiωtanddampedbyaforceproportionaltothevelocityof

˙(t)=dvstr.Thefactorofproportionalitydiscalleddampingparameter.ItisconnectedtothethestructureFd=dx

dissipationofkineticenergyoftheoscillatorandthusplaysakeyroleforthefrequencycharacteristicsofthesensingelement.Whilethesti nesskandthemassmoftheoscillatormainlydeterminetheresonancefrequencyω0,theheightandrelativewidthoftheresonanceisdeterminedbyd.Ahighdampingparametercorrespondstoalowqualityfactorandtoawideresonancepeakinthetransferfunctionofthemicro-opto-electromechanicalsystem(MOEMS).Incontrasttothat,aweakdampingresultsinahighresonancepeakaswellasahighQ-factor.

Themainsourceforenergydissipationinmicrostructuresoscillatinginambientpressureisthedampinginducedbythesurrounding uid,i.e.airinthepresentpaper[2].Otherdissipatingmechanismssuchasanchorlossorthermoelasticdampingareovershadowedbyfar.Theybecomedominantonlyintheabsenceofasurrounding uid,

Corresponding

author.

E-mailaddress:andreas.kainz@tuwien.ac.at

1877-7058 © 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

(/licenses/by-nc-nd/3.0/).

Peer-review under responsibility of the scientific committee of Eurosensors 2014doi: 10.1016/j.proeng.2014.11.326