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EXPERIMENTAL

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EXPERIMENTALEXPERI

    EXPERIMENTAL

CHrNESEJ0URNAL0FMECHANICALENGrNEERrNG

    ;vo1.21,No.3,2008?87?

    ;HEYong

    ;FUJianzhong

    ;CHENZichen

    ;CollegeofMechanicalandEnergy

    ;Engineering,

    ;ZhejiangUnviersity,

    ;Hangzhou310027,China

    ;OINTRoDUCTIoN

    ;EXPERIMENTALSTUDYONTHEHOT

    ;EMBOSSINGPOLYMER

    ;MICROFLUIDICCHIP

    ;Abstract:Experimentsareusedtostudythefabricationofpolymermicrofluidicchipwithhot

    ;embossingmethod.Thepa~emfidelitywithrespecttotheprocessparametersisanalyzed. ;Experimentresultsshowthattherelationshipbetweentheimprinttemperatureandthemicrocharmel

    ;widthisapproximatelyexponentia1.However,thedepthofmicrocharmelisn’tsensitivetotheimprint

    ;temperature.Whentheimprintpressureislargerthan1MPaandtheimprinttimeislongerthan2

    ;min.theincreasingofimprintpressureandholdingtimehas1ittleimpactonthemicrochanne1width.

    ;Sooverlongholdingtimeisnotneededinhotembossing.Basedontheexperimentanalysis.aseries

    ;ofoptimizationprocessparametersisobtainedandafinemicrofluidicchipisfabricated.The

    ;electrophoresisseparationexperimentareusedtoverifythemicrofluidicchipperformanceafter

    ;bondingTheresultsshowthat100bp.1adderDNAsamplecanbeseparatedin1essthan5min

    ;successfully.

    ;Keywords:MicrofluidicchipHotembossingChanne1sizesPatternfidelity ;Inthepastdecades.micro.electro.mechanical-systems

    ;rMEMS)includingmicrofluidicdeviceshavebeenfabricated

    ;almostexclusivelyinsiliconorglassbecausesimilartechnologies

    ;areavailableinthemicroelectronicsindustry.Nowadays.the

    ;MEMSapplicationsinthelifescience(suchasmicrofluidicchips.

    ;1abonachip)areingreatdemandLIJ_Silicon.basedMEMS ;productshavegoodsurfacequalitybutareusuallyexpensiveand ;arenotsuitablefor1ow.costandmassproduction.Inaddition. ;silicon.basedmaterialofteninducesproblemssuchaslackof ;opticalclarity,lowimpactstrengthandpoor-compatibility,thus ;limitingitswidespreadusageinMEMSproducts.Polymer.based ;materialsofferawiderangeofphysicalandchemicalproperties ;(suchaslowelectricalconductivityandhighchemicalstability). ;andbecamethepopularmaterialsinmicrofabriation.Among ;themicrofabricationmethodswiththepolymer,hotembossing ;methodisoneofanlmportant,prormslngtechnologyrecently ;developedJ.Asitisasuitableandflexibleprocessforthe ;fabricationofpolymermicrofeaturedcomponents,itgradually ;showsthecommercialpotentia1.particularlyinthefieldof ;microfluidic/biomedicalandmicroopticalproductsL. ;Anumberofstudieshavebeenconductedinrecentyearsto ;investigatethehotembossingprocessforthefabricationof ;polymericmicrofluidicchips”J.Tbavoidtheincrease/decease

    ;temperaturetimeinhotembossing.fabricationofmicrochannel ;withroomtemperaturewasusedt.LEE.etalL/J,reportedtheir ;experimentsaboutDNAseparationanddetectionwim ;microfluidicchipsfabricatedwithhotembossing.Anewmicro ;replicationprocesswithphoto-.etchableglass..ceramicstampsand ;polymerswaspresentedbyKIM_oJ.Thisprocesshastwomain ;advantages:arapidmasterfabricationwithalaserprocessanda ;flexiblereplicationprocesscomparedwithconventionalmicro ;replicationtechniqueonpolymers.Amethodwasdescribedthatis ;suitabletorapidlyarriveatoptimalconditionsformolding ;microstructuresforagivenmoldinsertandpolymerbyDATTA. ;etal[9].

    ;Althoughhotembossinghasbeenusedinmicrofabrication ;fo’rseveralyears,effectofembossingconditionsonthereplication

    ;accuracyofmicrofluidicchannelhasnotyetbeenfully ;investigatedsystematically.Particularly,therelationsbetweenthe ;ThisprojectissupposedbyNationalHitechResearchandDevelopment

    ;ProgramofChina(863Program,No.2002AA421150)andResearch ;FoundationofDoctorialProjectofMinistryofEducation,China(No. ;20030335091).ReceivedJune8,2007;receivedinrevisedformApril10, ;2008;acceptedApril22,2008

    ;processparametersofhotembossingprocessandthe ;microchannelsizeswereseldomstudied.Toourknowledge,only ;CHIENIJJstudiedtheinfluenceoftheimprintforceonthe ;imprinttemperatureonthequalityofreplica.Buttheimprint ;temperaturewasabove16O.Cinhisexperiments.wherehigh

    ;temperaturewasseldomusedinthefabricationofmicrofluidic ;chips.Thetimeusedinheating/coolingnearlyaccountsforabout ;5O%ofthetotalcycletimeinhotembossing.Sowhenthe ;microfluidicchipisfabricatedinmass.highimprinttemperature ;willinducetolowembossingefficiency.InthisPapeaseriesof ;hotembossingexperimentswiththeprocessparameterschanged ;werecarriedouttoanalysistheembossingansferftdelityinthe

    ;temperaturenear.Thenelectrophoresisseparationexperiment ;onthemicrofluidicchipwasusedtotestifythechipperformance. ;1HoTEMBOSSINGEXPERIMENTS

    ;1.1Hotembossingprocess

    ;AtypicalhotembossingprocessisdemonstratedinFig.1. ;Withaprepressurep,thepolymerisheatedfromtheinitial

    ;temperaturetototheimprinttemperaturete,whichshouldbe ;higherthanitsglasstransitiontemperature.Thenthepolymeris ;pressedbythemoldwiththeimprintpressurePe.Afterholding ;thepressurewiththetimeofth,thepolymeriscooleddowntothe ;demoldingtemperaturetd,thenthepressureisreleased.Afterthe ;molddetachedfromthepolymer,afinishedproductwithpattern ;transferredfromthemoldcanbegot.

    ;1

    ;,.

    ;7

    ;tltl+tht3

    ;Embossingtimef

    ;Fig.1Schemaofhotembossingprocess

    ;

    ;:g?.量叫2:?ls.

    ;

    ;?88?HEYong

    ;,etal:Experimentalstudyonthehotembossingpolymermicrofluidicchip ;1.2Experimentprocess

    ;Thesiliconmoldwasformedbywetchemicaletching.The ;hotembossingmachineusedinthisexperimentwasdesignedby ;ourlab.whichisdemonstratedinFig.2.Ahydraulicpressure ;systemwasdesignedtoapplypressure.Ahighlyefficientsystem ;forincrease/decreaseoftemperatureisneededtoprovidegood ;throughput.Soaheating/coolingsystembasedonthePeltier ;effectwasdesignedLlZ1.Itcouldincreasethetemperatureom

    ;20.Cto140.Cinlessthan2minanddecreasethetemperature ;from140.Cto20.Cinlessthan2.2min.Thetemperature. ;vacuumandimprintpressurewereallcontrolledbyaprogram

    ;mablelogiccontrollerfPLC).Forconvenienceofsettingthe ;processparameters,apersonalcomputerwasusedasthehostfor

;thehuman.machineinterface.

    ;Fig.2Hotembossingmachinedesignedbyourlab

    ;PMMAfilmsfromZhenjiangChi.MeiCo.wereusedas

    ;polymersubstrate,featuringaglasstransitiontemperatureof ;1O5.C,PiecesofPMMAplates,30[nrnX30mmx1miTt.werecut ;fromaPMMAsheetwithaCNCmachine,Thekeyprocess

    ;parameters,Te,Peandth,werechangedintheexperimentsto ;studytheirimpactonpattevilfidelity,Atierembossing.thesizes ;ofmicrochannelweremeasuredinthesameplacebya

    ;profilometer(Alpha.step200,TencorInstruments).Dataobtained ;fromtheprofilometerwereusedtoanalyzetherelationsbetween ;theprocessparametersandthemicrocharmelsizes.Each ;experimentwiththesameprocessparameterswascarriedout ;threetimesandtheaveragesizeswereusedinthefollowin2 ;analysis.

    ;2RESUISANDDISCUSSIONS

    ;Fig.3showsthecrosssectionofthesiliconmoldandthe ;microfluidicchanne1.TheaveragewidthoftrapeziformsectionW ;andchanneldepthDareusedtoevaluatetheembossingquality. ;Theimprinttemperaturewithrespecttothereplicaqualityis ;studiedwithafixedimprintpressureof0.85MPa.

    ;(a)Siliconmold(b)Polymermicrochanne

    ;Fig.3Crosssectionofthesiliconmoldandthe

    ;microfluidicchannel

    ;Graphicaldisplaysontheaccuraciesofchannelsizesat ;differenttemperaturecanbefoundinFig.4.Itcanbeseenthatthe ;widthaccuracyincreaseswiththeimprinttemperatureinitially, ;butitscontributiononchannelwidthdecreaseswhenthe ;temperatureishigherthanl25.C.Thechannelsizesarehardto ;becontrolledanddistortionmayhappenwhenthetemperatureis ;higherthan.Fig.5showsatypicaldistortionwhentheimprint ;temperaturereachesl40.C.Itisinterestingthatthechanneldepth ;isnotsensitivetothelmprinttemperatureandkeepsclosetothe ;heightofsiliconstamps.AstheCTEfcoefficientofthermal ;expansion)ofPMMAisabout6e5/K.theshrinkofthechannel

    ;widthisonlyabout2.7gm.whichissmallerthanthewidth ;replicationerror.Sothemainreasonofthewidtherrorisnot ;thermalshrinkbuttherecoilofPMMA.Withthetemperature ;increasing,theviscoproportioninpolymerincreasesandthe

    ;recoiIisrestrained.

    ;

    ;

    ;rJ

    ;Imprinttemperature/?

    ;Fig.4Relationsbetweentemperatureandchannelsizes ;Fig.5Distortionhappenswhentheembossingtemperature ;ishighe=0.85MPa,th=3rain,Ta=60.C,=140.C)

    ;Theholdingtimewithrespecttothereplicaqualitywas ;alsostudiedwithafixedimprintpressureofO.85MPaanda ;constantimprinttemperatureof105.C.AsshowninFig.6.wim ;increasingholdingtime.thechannelwidthincreasesslowlyand ;thechannelheightnearlykeepsthesame.Whentheholdingtime ;increasesom1minto15min.thechannelwidthonlyincreases ;l0pm.FromFig.6.wecanseethatthechannelsizesarenot ;sensitivetoholdingtime.Aslongholdingtimeresultsinlow ;embossingefficiencyandcan’timprovethepatternfidelity

    ;observably,longholdingtimeisn’tnecessaryinthefabricationof

    ;polymermicrofluidicchips.

    ;

    ;

    ;;

    ;

    ;

    ;

    ;Imprinttimet}min

    ;Fig.6Relationshipbetweentimeandchannelsizes ;Fig.7demonstratestherelationshipbetweentheimprint ;pressureandthechannelsizes.ThepressurehasliRleimpacton ;thechangeofchanneldepth.Butthechannelwidthincreases ;rapidlywhentheimprintpressureincreasesfrom0.75MPato ;1.0MPa.Whentheimprintpressureishigherthan1.0MPa.the ;channelwidthnearlykeepsthesame.Thisresultisinversedto ;CHIEN’sll”report.maybeduetothelowertemperaturethan

    ;CHIENused.

    ;Basedontheexperimentsonthechannelsizeswithdifferent ;processparametersinhotembossing,aseriesofoptimization ;processparameterswasobtained(po=0.85MPa,th=3min,rd= ;60.c,tierbondingwithaPMMAfilmforitscover,a ;microfluidicchipwasgot.asshowninFig.8b.T0verifythe ;labricatedmicrofluidicchipperformance,electrophoresissepara. ;tionDNAexperimentwascarriedout.Theexperimentresults ;showthatitcanseparatelsegmentsinlessthan5min

    ;successfullywhichisdemonstratedinFig.9(sievingmatrix: ;3%HPMCinl1~TBE.pH8.3,DNAconcentration:25p/mL, ;electricfieldstrength:139V/cm).

    ;1mpn~pressure/MPa

    ;Fig.7Relationshipbetweenpressure

    ;andchannelsizes

;

    ;

    ;

    ;

    ;

    ;(a)CrosssectionofamicrocharmelwithSEM

    ;(pc=0.85MPa,th3min,Td=70.C,=120.C)

    ;(b)CCDimageofthemicrofluidicchip

    ;afterbonding

    ;Fig.8Finemicroftuidicchipfabricated

    ;byhotembossingmethod

    ;0l2O240360

    ;Separationtimet/s

    ;Fig.9ElectrophoregramofDNAladder

    ;3CoNCLUSIoNS

    ;f11Hotembossingappliedtomicrofluidicchipshasbeen ;carriedoutbyusingthesiliconstampfabricatedbywetchemical ;etching.Theprocessparameterswithrespecttothereplication ;accuracyareinvestigatedwithhotembossingexperiments. ;f21Basedonthemeasuredresults,someconclusionscanbe ;made:boththeimprintpressureandimprinttemperatureare ;foundtoaffectthechannelwidthsignificantly.Withtheholding ;timeincreasing.thechanne1widthincreasesslowly.Whilethese ;parametersseemtohaveliRleimpactonthechanneldepth.DNA ;separationexperimentsaleusedforverifyingthepolymericmicro

    ;fuidicchipperformance.Theexperimentsshowthefabricated ;chipshavegoodseparationcapacity.

    ;[2]

    ;[3]

    ;[4]

    ;[5]

    ;[6]

    ;[7]

    ;[8]

    ;[9]

    ;[1O]

    ;[12]

    ;Rererences

    ;TORSTENVDIRKJ.ANDREASM.Microfofalanalysissystems ;recentdevelopments[J].AnalyticalChemistry,2oo4(76):33733386.

    ;STEPHENRO,AXELS.Frommicro.tonanofabricationwithsoft ;materials[J].Science,2000,290(24):l536l540.

    ;HECKELEM.SCHOMBURGWK.Reviewonmicromoldingof ;thermoplasticpolymers[J].JournalofMicromechanicsand

;Microengineering,2004,14(20):114.

    ;HOLGERB.LAURIEEL.Polymermicrofluidicdevices[J].Talanta. ;2002(56):267287.

    ;HOLGERB.CLAUDIAG.Polymermicrofabricationmethodsfor ;microftuidicanalyticalapplications[J].Electrophoresis,2000(21): ;l2l6.

    ;XUJ,LOCASCIOL,GAITANM,eta1.Roomtemperatureimprinting ;methodforplasticmicrochanne1fabrication[J].AnalyticalChemistry, ;2000,72(6):l93Ol933.

    ;LEEGB,CHENSH,HUANGGR,eta1.Microfabricatedplasticchips ;byhotembossingmethodsandtheirapplicationsforDNAseparation ;anddetection[J].SensorandActuatorsB,200l,75(1):l42l48.

    ;KIMJ.Replicationofmicrochannelstructuresinpolymersusinglaser ;fabricatedglass?ceramicstamp[J].OpticsandLasersinEngineering, ;2007,45(8):890897.

    ;DATTAP.GOETTERTJ.Methodforpolymerhotembossingprocess ;development[J].MicrosystemTechnology,2007(13):265270.

    ;CHIENRD.Micromoldingofbiochipdevicesdesignedwithmicroch. ;armels[J].SensorsandActuatorsA,2006,l28(2):238247.

    ;CHIENRD.HotembossingofmicroftuidicplatformlJ].Intemational ;CommtmicationsinHeatandMassTransfer,2006,33(5):645653.

    ;FUJZ,CHENZC,HEeta1.Micro/nanoimprintdevicewithPeltier ;effect:China,2004l0053401.XP1.2006.11O1.

    ;Biographicalnotes

    ;HEYongiscurrentlyapostdoctorinCollegeofMechanicalandEnergy ;Engineering,ZhejiangUniversity,China.HereceivedhisPhDdegreefrom ;ZhejiangUniversity,China,in2007.Hisresearchinterestsareinthefabdcafion ;technologyofMEMSandnumericalcontrol,etc.

    ;Tel:+8657187951907;E?mail:yongqin@zju.edu.cn

    ;FUJianzhongiscurrentlyaprofessorinZhejiangUniversity,China.He ;receivedhisPhDdegreefromZhejiangUniversity,China,in1996.His ;researchinterestsincludemicroelectro?mechanicalsystems(MEMS),thermal ;deformationandnumericalcontroltechnology.

    ;Tel:+86571?87951906;E?mail:0z@zju.edu.cn

    ;CHENZicheniscurrentlyaprofessorinZhejiangUniversity,China.He ;receivedhisPhDdegreefromZhejiangUniversity,China,in1989.His ;researchinterestsincludethermaldeformation,numericalcontro[标签:快照]

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