A 3-axis accelerometer and strain sensor system for building integrity monitoring

SensorsandActuatorsAxxx (2011) xxx–xxx

ContentslistsavailableatSciVerseScienceDirect

Sensors

and

Actuators

A:

Physical

j our na l h o me p a g e :w w w . e l s e v i e r . c o m / l o c a t e / s n a

A

3-axis

accelerometer

and

strain

sensor

system

for

building

integrity

monitoring

J.

Santana

_{, R.}

_van

_den

_Hoven

_{, C.}

_van

_Liempd

_{, M.}

_Colin

_{, N.}

_Saillen

_,

_D.

_Zonta

_,

_D.

_Trapani

_,

_T.

_Torfs

_,

C.

Van

Hoof

a_{imec-HolstCentre,Eindhoven,TheNetherlands} b_{MEMSCAP,Grenoble,France}

c_{ThermoFisherScientific,Enschede,TheNetherlands} d_{UniversityofTrento,Italy}

e_{IMEC,Leuven,Belgium}

a

r

t

i

c

l

e

i

n

f

o

Articlehistory: Received9August2011 Receivedinrevisedform 10November2011 Accepted11November2011 Available online xxx Keywords: Signal-to-Noiseratio Linearity Bandwidth Sensitivity

Integratednumberofpulses Residualmotion

a

b

s

t

r

a

c

t

AnUltra-Low-PowerreadoutarchitectureforcapacitiveMEMS-basedaccelerometersandstrainsensors

ispresented.Thesystemcanreadbothaccelerometersandstrainsensorsinahalf-bridgeconfiguration.

AnaccurateVerilogAmodelofthesensorwasmadetoimprovesimulations.Thegainofthesystemis

controlledbyintegratingpulsesfromtheexcitationcircuitallowingaccuratecontrolofthe

Signal-to-Noiseratio.AFigure-of-Meritof4.41×10−20_F√_{(W/Hz)wasachievedforasensorrangeof±2.0gand}

±20,000␮␧ overa100Hzbandwidth.Aminimumof440nWpowerconsumptionwasrecorded.Residual

motionartifactsarealsocancelledbythesystem.

© 2011 Elsevier B.V. All rights reserved.

1. Introduction

Anaccuratesensingofsignalsrequiresinnovative,flexibleand powerefficientreadoutarchitectures. Infieldssuchas building integritywhichuseawiderangeofcapacitiveMEMS/NEMS-based devices,suchasaccelerometersandstrainsensorswithdifferent actuationvoltages,sensitivitiesandresolutions,thespecifications ofthesensorandsystemareincreasinglydemanding.Resolutions of1mgand10_␮␧arerequiredfortheaccelerometerandstrain sen-sorrespectivelyandarangeof±2.0gand±20,000␮␧overa100Hz bandwidthtosenseaccelerationsandstresses.Thisisessentialfor theassessmentofstructuresduringandafterseismicevents.

ThisworkintroducesauniqueUltra-Low-Powersystemwhich canbeappliedtoMEMS-basedcombfingercapacitive accelerome-tersorstrainsensorsinahalf-bridgeconfiguration[1].Anaccurate behavioralmodelofthesensor(inVerilogAlanguage)wasmade inordertosimulatethefullsystemandimproveitsperformance. In comparison with current modulation–demodulation readout techniquesthegainofthesystemcanbesetbythenumberof inte-grationpulsesNcomingfromtheexcitationvoltage,optimizing

∗ Correspondingauthor.Tel.:+31404020548;fax:+31404020699. E-mailaddress:juan.santana@imec-nl.nl(J.Santana).

thenSNRandbandwidthwithpower.Inadditionthearchitecture suppressesmotionartifacts[2,3]suchasresidualmotion.

2. Sensors

Theaccelerometersensorconsistsof2transversecombfinger structures(XandYaxis)and,apendulatingonefortheZaxis(Fig.1). Thesensorsare madeusinga capstructure (Fig.2), its pur-poseistwofold;itprotectstheMEMSstructureandalsoformsthe counterelectrode fortheZsensor.Innovativecapthrough con-nectionswereused.ThecapitselfismountedtotheMEMSwafer byusingametal–siliconeutecticbondingprocesses.Themetalfor thesealingringisalsousedtorealizetheelectricalconnections betweenthecapandtheMEMSwafer.Theaccelerometerwas fab-ricatedwithasurfacemicro-machinedprocessfromaSOIwafer 85␮mthick.Thesensorhas78fingerswithatotalsensitivityof 2.02pF/g.TheZsensorhasanareaof2.17mm2_perplate.

The main tradeoff in thedesign of theaccelerometer is the sensitivity–bandwidth–linearityinallthreeaxes,achallengefor thedesigngiventhedifferentusedstructures.

Thestrainsensorisalongitudinalcombfingercapacitor(Fig.3). Thesensorconsistsofthreeparts:theconnectorarea(for connec-tiontothereadout),theflexiblearea(tosustainthestrainandstress ofthebars)andthesensorarea(theactivedevice).Thestrainsensor 0924-4247/$–seefrontmatter © 2011 Elsevier B.V. All rights reserved.

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Fig.1.3-Axisaccelerometerarrangement.

Fig.2.Crosssectionoftheaccelerometersensor.

Fig.3.3Drepresentationofthestrainsensor.

fabricationusesaSOIwaferwitha500␮mthickhandle,50␮m thickfingersand2␮mthickoxidelayerwith400fingersinthe sensorandithasasensitivityof0.133fF/␮␧.

Twoanchorswereetched-outofthesurfacetocreatethe neces-saryclampstoattachthesensortotherebarofapillar.Thefingers areprotectedwitha borosilicateclasscap.Thespecificationsof theMEMS-basedsensorsusedinthisworkaregiveninTable1. Thevoltagevs.frequencyresponseoftheaccelerometeras func-tionofpressureisshowninFig.4.Theplotshowsthetransition oftheaccelerometerfromanover-dampedsystem(at820Torr)to anunder-dampedsystem(at3Torr).Thetemperaturedependence oftheaccelerometerandstrainsensoriscompensatedbyusinga temperaturesensorclosetotheaccelerometer/strainsensorand usinglookuptablesforcalibration.Nolongtermdriftisexpected becauseofthegoodagingpropertiesofsiliconinthecapwafer. Fineleakscouldappearinthebondinglayerswhichwillmakethe

Table1

Accelerometerandstrainsensorspecifications.TheX,YaxissensorsandZaxisare givenseparate.

Parameter Accelerometer Strainsensor

Basic 20pF(X,Y) 5.3pF

Capacitance 20pF(Z)

0.34mg(X,Y) –

0.5mg(Z)

Mechanicalsensitivity 0.4–0.06␮m/g 3nm/␮␧ Electricalsensitivity 0.23–2.02pF/g(X,Y) 0.133fF/␮␧

0.38–0.94pF/g(Z)

Resonant 785–2080Hz(X,Y) 56kHz

Frequency 780–1015(Z)

Pull-involtage 2.3–5.4V(X,Y) –

0.95–1.3V(Z)

Fingergap 3␮m 4␮m

pressuretoriseinsidetheMEMScavitybuttheseissuesarebeyond thescopeofthepaper.

Fig.5 showsthefabricatedsensorsandthereadoutASIC.As mentionedinpreviousparagraphsthesamereadoutASICisused forboththeaccelerometerandstrainsensors,makingthisa cost-effectivesolutionwhencomparedtoothersystems.

3. Behavioralmodelofthesensor

AsmentionedinSection1anaccuratemodelofthesensoris necessaryinordertooptimizethedesignofthereadout.Asthe trendforlow-powercontinuestorequirepowersavingsystems anoptimumtrade-offbetweensensorsandreadoutisnecessary toreachsuchdemandingexpectations,thereforeaccurate mod-elsofthesensorswhichcanbeusedalonginthetransistor-level simulationsarerequired.Suchmodelshavebeenknownfor sev-eralyearsandinseveralforms,look-uptables,behavioralmodels, macro-models,etc.Inthisstudyabehavioraldescriptionlanguage waschosentomodelthesensor,namelyVerilogA,mainlybecause itisatoolincludedintheuseddesignenvironment.

Avariablecapacitorwiththreeterminalswasmadeto simu-latethesensors;thethirdterminalsimulatesthedisplacementof themasswhenanexternalforceisappliedtotheaccelerometer, suchasthatcomingfromanearthquake,orstressinthecaseofthe stresssensor.Ineithercasethemodelcanbeeasilycustomizedto eachsensor,aparameterizedmodelwasdevelopedsotobeeasily adaptedtodifferentrequirements.

J.Santanaetal./SensorsandActuatorsAxxx (2011) xxx–xxx 3

Fig.5.Microphotographoftheaccelerometer,strainsensorandreadoutASICchip.

4. Readoutarchitecture

Thereadoutarchitectureofthesystemhasbeendescribed else-where[10].Itsmaincharacteristicsaresummarizedinthenext paragraphs.Theprincipleofoperationisbasicallytheonedepicted inFig.6.Whenanaccelerationforceappearsinthesensor,Fig.6(a), theanti-phaseactuationvoltagesappliedtothecapacitorsshown inFig.6(b)aremodulated.Currentpulsesflowintwodirections,as showninFig.6(c).AteveryrisingedgetheswitchesS1andS2are openwhiletheINTEGRATEswitchisclosed(Fig.7).

Thecurrent pulseis integrated inthefeedback capacitorCf, showninFig.6(d).Thesystemhasseveraladvantagesthathelpto compensateproblemsrelatedwiththesensorsuchasoffsets, non-linearity,intrinsicgain,sensor’smismatch,etc.Varyingtheduty cycleoftheactuationvoltage,forexample,cansettheoptimum SNRandgainforthesensorsinvolved.Varyingtheamplitudeofone oftheexcitationvoltageswithrespecttotheothercancompensate foroffsetsornon-linearities.Forthecaseofthestrainsensorsimilar behaviorissimulatedwiththeonlydifferencethatthefrequency ofthesignalisclosetoDCandthemassofthesensorissmall.

Fig.6. Variablecapacitorelectricalmodelresults.(a)Proof-massdisplacementattheinputofthemodel,(b)excitationvoltages,(c)currentpulsesatoutputofhalf-bridge, and(d)onlypositivepulsesareintegrated.

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Fig.7.ArchitectureofasinglechannelofthereadoutASICandsin(x)/xresponseofthesystem(inset).

Fig.7showssinglechannelarchitecturereadoutaswellasthe sin(x)/xsystemresponse.Itdiffersfromcommonlyuseddesigns

[2,3]bydecouplingtheoutputofthesensorfromtheinputofthe

chargeamplifier(OTA)byaseriescapacitorC1andswitches con-nectedtoarbitraryvariablereferencevoltagesVREF1andVREF2. Thefunctionof C1is levelshifting, toallowa different operat-ingpotential betweentheoutput of thesensors and theinput of the OTA. In this way the excitation voltages of the sensor canbeunipolar, while still allowingDC signalprocessing from thesensorssignals.Thearchitecturedifferssignificantlyfromthe modulation–demodulationapproach,whichisregularlyusedfor similardevicesandusesmorepower.

Architectureshavebeenreported[1–4]inwhichlinearity, res-olution,bandwidthor gain isalwaysmatched totheparticular typeof device.In somedesignsthechannel architectureis tai-loredtothepropertiesofthesensorand,althoughsomeflexibility is added as shown in [7–9], its performance is not optimum (FOM=1.0×10−18F√(W/Hz)).

Inthisworkthenumberofpulses(N)canhoweverbe arbitrar-ilysetdependingonthedesiredSNR,bandwidthorgain.Tofirst ordertheseparametersarerelatedbythefollowingrelationships: thegainisproportionalwithN,sinceallNintegratedpulsesare added.ThebandwidthisproportionaltotheinverseofN,sincethe samplingtimeisproportionaltoNandtheSNRisproportionalto thesquarerootofNbecausegainisincreasingwithNandnoiseis onlyincreasingwithsquarerootofN.Thisisoneofthekeyissuesof theproposedarchitecture,itsolvestheissueofsettingthegainof thesystembyincreasing/decreasingthenumberofpulsesinstead ofswitchingbetweenintegratingcapacitorsofdifferentsizes.The readoutgainhaslittletemperaturedependency,non-linearityand hysteresis,sincetheintegratedcapacitorCf,theOTAperformance andclockfrequencyareverystable.

Thedevelopedsystemhastheaddedadvantagethatthesame readoutcanbeusedtosenseaccelerationandstrainwiththe pur-poseof reducing powerconsumption and making it more cost effective,thereisnoneedtofabricatetwodifferentreadoutsto processtheinformationcomingfromthetwotypesofsensors.In principlethesignalsfromthetwotypesofsensorscouldbe mul-tiplexedattheinputofthereadout,thus usingonlyonesingle channeltoamplifytheirsignalsbyalternatingthereadingofthe sensorsinapredeterminedsequence.Neverthelessthe accelerom-eterhas tobe alwaysswitched-on. One way toovercome this

requirementisbyoperatingthereadoutinalow power(lower bandwidthandSNR)modeandswitchedtohighresolution acqui-sitionmodeincaseofanearthquakeevent.Thestrainsensoris usedforcertainperiodsoftimeandatime-sharingschemewould makethedecisiontoalternatebetweentheaccelerometerandthe strainsensorwithoutjeopardizingthedataacquisitionbandwidth andSNRimmediateafteranearthquakeoccurred.

4.1. Measurements

Forthepurposeofsimulationofthewholesystembothsensors weremodeledinahighleveldescriptionlanguage,namely Ver-ilogA,asapairofvariablecapacitorsproducinga10%Cfullscale. Themodelallowsthedesignertoaccuratelyassessthegain,noise, sensitivityandmotionartifactswithinthecircuitdesign environ-mentwithlesscomputationaleffort.Resultsareingoodagreement withsimulations;thenextparagraphsshowthemeasurements.

Fig.8showsthemeasurementsoftheaccelerometersensorwith theproposedreadout.Inthefigurethreechannelsareplotted cor-respondingtoX,YandZdirectionsandcomparedtocommercially available accelerometers, namely PCB piezoelectric transducers model393-B12and393-B31[11].TheWLdatacorrespondstothe sensorsandreadoutdesignforthisworkwhereastheBdata corre-spondtothecommercialdevices.Bothsystemsandobtaineddata complywithspecificationsforbuildingintegrity monitoringbut thedevelopedreadoutconsumeslesspowerthanthecommercial one.

Asshownin[10]theresolutionis80dB(13-bit)forvibration tonesbetween10and100Hzandnon-linearity<1%.The accelera-tionmeasurementsaremeantforrecordingthebuilding’sresponse during an earthquake event; the measured system noise floor (readoutplussensor)of70␮g/√Hziswellinlinewiththepurpose oftheapplicationanddoesnotdegradetheexpectedperformance ofthesystemasshownin[13].MEMS-basedaccelerometerslike theSTMicroelectronicsLIS3L02ALhavea50␮g/√Hznoisefloor fora±2grange[14]andtheCrossbowCXL10TG3a20␮g/√Hzfor a±2grange[15]buttheirpowerconsumptionisintheorderof mW,smalleraccelerationrangeandarelargerinsize,therefore notsuitableforoperationoverextendedperiodsoftimewithout rechargingorreplacingbatteries.

ThereadoutisDCcoupledthereforeabletoreadverylow fre-quencysignals.Thisrepresentsanadvantagecomparedtostandard

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Table2

PowerconsumptionatVDD=1.6V.

Current Power Amplitude Non-linearity

2.51␮A 4.00␮W 57.1mV/g 1.24%

0.44␮A 0.70␮W 52.7mV/g 1.05%

0.33␮A 0.52␮W 43.5mV/g 1.73%

0.19␮A 0.30␮W 21.6mV/g 6.30%

modulation–demodulationschemes,whicharealwayslimitedtoa specificlowfrequencyvalue,thusallowingforthereadoutof sig-nalssuchasthosefromastrainsensor.Fig.9showstheresultsof strainsensormeasurementswhenmountedonatestrebar.

Testsweretakenoveratimespanofover2000sunder con-tinuoustensilestrainandreleasetosimulatethestraincondition expectedinthesteelreinforcementofaconcretebuildingduringan

earthquakeaction.Thesteelbarwastakenbeyonditselasticlimit, correspondingtoaloadcapacityofapproximately140kNanda yieldstrainof2000␮␧.Thedatawerecomparedtocommercially availablesystemscompliantwiththespecifications.More specif-icallythereferencesensorsareresistivemetalfoilstraingauges HBMmodel LY41-3/700[12].Consistentlywithpreviousresults

[10],thetestconfirmsthatsensorsandreadoutareableto mea-sureoverarangeof±20,000␮␧,whichcorrespondstotheultimate designstrainconditionofsteelreinforcementundersevereseismic action.

Fig.10showsthemeasurementsofthesensitivityversusthe integratednumberofpulsesNfortheaccelerometer.Asexpected thesensitivityofthereadoutisproportionaltothenumberofpulses N,whiletheintegratednoiseisproportionalto√N.The measure-mentsweretakenwitharateof200samples/s.

Fig.8.MeasuredaccelerationsignalsforX,YandZchannelscomparedtocommercialdevices(N=24pulses).

Fig.9. (a)Testrebarmountingofthestrainsensoralongwiththereferencegauge(topright).(b)Loadvs.strainplotfortest(WLdata)andreferencesensors(SGdata).(c) Strainvs.timehistorymeasurements.Thepositionofthesensorintherebarisalsoshownintheinset.

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Table3

Comparisonwithstate-of-the-artcapacitivereadouts.

Parameter Denison[5] Paavola[6] Thiswork

Accel/strainsensorrange ∼±1g ±2g ±2.5g

±20,000␮␧

Supplyvoltage 1.7–2.2V 1.0V 1.6/3.0V

Power 1.5␮W 1.5␮W 440nW/15␮W

Sensitivity 125mV/g – Variable

Noisefloor(acceler.) 1mg/√Hz 704␮g/√Hz 70␮g/√Hz

Non-linearity <1% – <1%(accel.)

<0.6%(strainsensor)

Bandwidth 10Hz 1Hz 100Hz

Figure-of-Merit 8.1×10−22_F√_{(W/Hz) 4.41×10}−20_F√_(W/Hz)

1400␮W␮g/Hz 881␮W␮g/Hz

Technology 0.8␮mCMOS 0.25␮mCMOS 0.25␮mCMOS

Activearea – 2.25mm2 _2mm2

Fig.10.Measuredsensitivityandtotalintegratednoisefortheaccelerometervs. numberofpulsesN.

Thesensitivityandrangeofacceleration(orstrain)canbeset accordingtothedeviceandapplicationspecifications.Alternative methodshavebeenreportedelsewhere;thesettingsof reconfig-urablebuildingblockscreateanadaptablegenericarchitecturefora widerangeofcapacitivesensors[9].Neverthelesspower consump-tionremainshighandnotadequateforlowpowerapplications.In thisworkthereadoutwasdesignedtooptimizepower consump-tion.Previousresultsshownin[10],withVDD=3.0Vshowapower

consumptionof15␮W.Withabiasvoltageof1.6V,improved lev-elsofpowerconsumptionforthereadoutcircuitcanbereachedas showninTable2.

Theamplitudeofthesignaldecreasesbyafactorof10butthe powerconsumption decreasesbyafactorof 100while keeping therestoftheparametersasinthecaseof3.0V.Theresultsin thetableshowalsothenon-linearityvalueswhicharestillwithin specifications.Attheminimumpowerconsumptionof330nWthe non-linearityincreasesto6.30%whichistheextremecaseofthe operatingrangeofthesensorsystem.Theexperimentalresultsare showninFig.11.

Inspiteoftheamplitudeofthesignalbeinglowerthesystemcan compensatebyintegratingmorepulses,asmentionedinprevious paragraphs,andthereforerestoretheDynamicRangetofull rail-to-rail.Thesystemresponsetimewilldecreasebutforthetarget applicationsthisdoesnotrepresentamajorproblem.

5. Conclusions

Results show that the readout architecture can work with Ultra-Lower-Powerconsumptionwhilekeepinglinearityunderthe expectedperformance.Batterylifetimeisthenextended to sev-eralyears’operation.Comparedtothefiguresofmeritproposed

in[5,6]thisworkhas4.41×10−20F√(W/Hz)and881␮W␮g/Hz,

Fig.11.Signalamplitudeat1.6Vforseveralbiascurrentvalues.

respectively.Theproposedarchitecturehasthelowestreported equivalentaccelerationnoiselevel,highestbandwidthandhasthe uniqueadvantageofofferingtradeoffbetweenSNR,bandwidthand power.Whencomparedtocommercialaccelerometersandstrain sensorsthereadoutofferstheusercompetitivespecifications.The designwasfabricatedonTSMC0.25␮mCMOSwithM-i-M capac-itors.Thetotalpowerconsumptionof the3channelsis15␮W. The clock and excitation voltages for the sensors are external. Recentmeasurementsshowthatthearchitecturecanworkwith lesspowerconsumption(0.52␮W)stillwithintheexpectedrange ofaccelerationandstrain(Table1).

Table 3 shows thebenchmarking of the proposed

architec-ture.No similarsystem hasbeenreportedwhich handles both accelerometers and strain sensors with a minimum of power consumption,lownoisefloor,variablesensitivityandlarger band-width.Mostofthesystemsreportedarecustom-madesystemsfor aparticularsensor(whichusuallyhasalargesensitivityina nar-rowband)withlow-powerconsumption.AlsoshowninTable3is thelowestpowerconsumptionmeasurementreported.

The presentedsystem candeal withdifferent sensors with-outjeopardizingthepowerconsumption,importantin building integritymonitoringwhichrequiresbatteryoperatedsystemsfor severalyears.Italsorepresentsaverycosteffectivesolutionsince thesamereadoutcanbeusedforaccelerometersorstrainsensors, makingtheintegrationofthefinalmonitoringsystemsimplerand cheaper.

Flexibilityis alsoa majorassetfor thesystem,sensors with differentsensitivities,offsetsandmismatchcanbeeasilyreadout modifyingthetiminganddutycycleoftheexcitationpulsesand thenumberofintegratedones.Asinglereadoutsystemforboth accelerometersand strain sensorsmakesthesystemmore cost effectiveandpowersaving.

J.Santanaetal./SensorsandActuatorsAxxx (2011) xxx–xxx 7

Acknowledgments

ThisworkispartoftheHuman++Programofimec-HolstCentre, TheNetherlands,andpartiallyfundedbytheMEMSCONproject (EC SeventhFramework ProgrammeGrant Agreement n. CP-TP 212004-2).

References

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Biographies

JuanSantanaobtainedhisPhDinSemiconductorDevicesfromtheUniversityof Lancaster,U.K.andin1992joinedtheengineeringdepartment.In1997hejoined CINVESTAV,aresearchcentreinMexico.From1998to2001hedirectedthe Semi-conductorTechnologyCentre(CTS)ofCINVESTAV.Heworkedasacommissioned engineerinseveralASICprojectsforautomotiveapplicationsforATMELCorp.,in Columbia,Maryland.In2001hejoinedtheMotorolaCenterforSemiconductor Tech-nology.Since2006heworksforHolstCentre,TheNetherlands.Hehaspublished morethan30papersininternationaljournals,supervisedseveralM.Sc.dissertations andholdsonepatent.

RichardvandenHovenstudiedElectronicsattheTechnicalUniversityin Eind-hoven,wherehegraduatedin2006atthegroupMixedSignalMicroElectronics on“Apre-correctionmethodforimprovedstaticlinearityusingparallelDACs”.In

2006hejoinedPhilipsSemiconductors(NXP)inEindhoven,theNetherlands.Since 2007heworksforHolstCentreintheNetherlands,onASICdesignofAnalogto Dig-italconversionandcapacitivereadout.Hehaspublishedtwopapersandholdsone patent.

ChrisvanLiempdisaSeniorResearcheratHolstCentresince2009.Hehasbeen systemarchitectatPhilipsSemiconductors,NXPandSunext.In1998hebecame partofthePhilipsOpticalStoragegroupandplayedamajorroleinseveralprojects inthisgroup.Hehasmorethan30yearsexperienceinanalogelectronics engi-neering.Heis currentlyworkingonDC–DCand AC–DCconvertersforpower managementandenergyharvesting.Hehaspublishedseveralpapersandholds patents.

MikaelColinreceivedaPostgraduatedegreeinOpticsin2000fromthe Univer-sityofSaint-Etienne,France.HesubsequentlyjoinedBookhamTechnologies,UK (2000),andOpsitech,France(2002),asanR&Dengineerwherehemainlyworked indesigningintegratedcomponentsforOpticalNetworks.In2004,hemovedto Memscap,France,asaMEMSdesigner.Hisworkmainlyfocusedonthedesign ofinertialcomponentsforMilitary,Space,BiomedicalandIndustrialapplications andonEnergyscavengingsolutionsusingtheMEMStechnology.Since2011,he worksonthedevelopmentofimplantableenergyscavengersattheTIMAlaboratory, France.

NicolasSaillenisaMEMSProductEngineerwithaM.Sc.degreeinMicroSystems EngineeringfromEPFL,Lausanne.Hehas5yearsexperienceinMSTprocess,product development,andinternationalprojectmanagementatThermoFisherScientific (previouslyC2V).Hisworkinvolves,amongotherthings,thedevelopmentofmicro componentssuchas:aflowsensor,forcesensor,apiezodriveninkjetnozzle,and fluidicvalves.

DanieleZontaachievedhisDoctorateinStructuralMechanicsattheUniversity ofBolognain2000.HeworkedasaPost-DoctoralresearcherattheUniversityof California,SanDiego,intheperiod2000–2001.Hehasbeenvisitingscholaratthe UniversityofMichigan(2010)andatPrincetonUniversity(2009and2011).Since 2001,heisAssistantProfessorofStructuralEngineeringattheUniversityofTrento, teachingprecastconcretebridgedesignandsmartstructures.Hisresearchactivity includes:bridgemanagement;Bayesiandecision-making,structuralhealth moni-toring;fiberopticsandsmartsensortechnologies;allasappliedtocivilstructures. Heisauthorofoveronehundredtechnicalpublications.

DavideTrapanigraduatedin2010incivilengineeringattheUniversityofTrento.He iscurrentlyResearchAssistantintheIntelligentInfrastructuregroupatthesame Universityworkingonthelaboratoryvalidationofsmartsensortechnologies.He authoredfourtechnicalpapers.

TomTorfsreceivedthedegreeofIndustrialEngineerinElectronics,specialization DesignTechnologyin2001fromDeNayerInstitute,Belgium.Heissince2001a systemsdesignengineerinthesensorelectronicsgroupatIMEC.Hehasdesigneda rangeoflowpowerwirelesssensormodules,withafocusonbiopotentialacquisition systemsforbodyareanetworksandautonomoussystems.Hehasalsobeenactive indevelopingdemonstratorsusingIMEC’s3Dand2Dintegrationtechnologyaswell asparticipatinginthedesignofa3Dmodularneedlearrayforinvivoapplications (NeuroprobesEUproject).

ChrisVanHoofisProgramDirectorofMorethanMooreSIPSystemsatIMECin Leuven.HeisalsoAssociateDepartmentDirectorofInterconnect,Packagingand SystemIntegration.HereceivedaPhDinElectricalEngineeringfromtheUniversity ofLeuvenin1992.AtIMEC,hebecamesuccessivelyheadofthedetectorsystems group,DirectoroftheMicrosystemsDepartmentandIntegratedSystems Depart-ment,andProgramDirector.Hisresearchconcernsautonomoussensornodes, focusingonadvancedpackagingandinterconnecttechnologyandsystem integra-tion.Since2000heisaprofessorattheUniversityofLeuvenadvising12doctoral students.