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Record for a UF thesis. Title & abstract won't display until thesis is accessible after 2015-05-31.

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Permanent Link: http://ufdc.ufl.edu/UFE0045601/00001

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Title: Record for a UF thesis. Title & abstract won't display until thesis is accessible after 2015-05-31.
Physical Description: Book
Language: english
Creator: Feng, Xuhui
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2013

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Subjects / Keywords: Chemical Engineering -- Dissertations, Academic -- UF
Genre: Chemical Engineering thesis, M.S.
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theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
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Electronic Thesis or Dissertation

Notes

Statement of Responsibility: by Xuhui Feng.
Thesis: Thesis (M.S.)--University of Florida, 2013.
Local: Adviser: Butler, Jason E.
Electronic Access: INACCESSIBLE UNTIL 2015-05-31

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Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2013
System ID: UFE0045601:00001

Permanent Link: http://ufdc.ufl.edu/UFE0045601/00001

Material Information

Title: Record for a UF thesis. Title & abstract won't display until thesis is accessible after 2015-05-31.
Physical Description: Book
Language: english
Creator: Feng, Xuhui
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2013

Subjects

Subjects / Keywords: Chemical Engineering -- Dissertations, Academic -- UF
Genre: Chemical Engineering thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Statement of Responsibility: by Xuhui Feng.
Thesis: Thesis (M.S.)--University of Florida, 2013.
Local: Adviser: Butler, Jason E.
Electronic Access: INACCESSIBLE UNTIL 2015-05-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2013
System ID: UFE0045601:00001


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FABRICATIONANDIMAGINGANALYSISOFMICROFLUIDICDEVICESByXUHUIFENGATHESISPRESENTEDTOTHEGRADUATESCHOOLOFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENTOFTHEREQUIREMENTSFORTHEDEGREEOFMASTEROFSCIENCEUNIVERSITYOFFLORIDA2013

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c2013XuhuiFeng 2

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Ilovinglydedicatethisthesistomyparents,whosupportedmeeachstepoftheway. 3

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ACKNOWLEDGMENTS Iwouldliketothankallofthosepeoplewhomadethisthesispossibleandanunforgettableexperienceforme.Firstofall,Iwouldliketoexpressmydeepestsenseofgratitudetomyresearchadviser,Dr.JasonE.Butler,forhiscontinuoussupportofmymaster'sstudyandresearch.Hisguidancehelpedmeinallthetimeofresearchandwritingofthisthesis.Ithankhimforthesystematicguidanceandgreateffortheputintotrainingmeinthescienticeld.Specialthankstomycommittee,Dr.JasonE.ButlerandDr.YiiderTseng,fortheirguidanceandhelpfulsuggestions.TheirguidancehasservedmewellandIowethemmyheartfeltappreciation.IthankDr.AnthonyJ.C.Laddforhishelpandsuggestionsinconductingexperiments;IthankDr.MeganA.HahnattheParticleEngineeringResearchCenterattheUniversityofFloridaforconductingtheAFMexperiments.Ialsothankmembersinmygroup,MertArca,PhongPhamandBradenSnookfortheirhelpandencouragements.IwouldliketosendmyspecialthankstoMertArca:thankyouforhelpingmeinmyresearchandcourseworkaswellaseverydaylife.Finally,Itakethisopportunitytoexpresstheprofoundgratitudefrommydeephearttomybelovedparents,FengQiushengandGuoJunzan,fortheirloveandcontinuoussupport-bothspirituallyandmaterially.Ialsowouldliketothankmygirlfriend,WuXuanzhen,forherencouragementandsupport. 4

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TABLEOFCONTENTS page ACKNOWLEDGMENTS .................................. 4 LISTOFTABLES ...................................... 7 LISTOFFIGURES ..................................... 8 ABSTRACT ......................................... 9 CHAPTER 1MICROFLUIDICDEVICES ............................. 10 1.1ExamplesofMicrouidicDevicesApplications ................ 10 1.1.1ApplicationsofMicrouidicDevicesinCellCultureandControl .. 10 1.1.2ApplicationsofMicrouidicDevicesforStudiesofDNAandProteins 11 1.2MethodsofFabricatingMicrouidicDevices ................. 11 1.2.1Softlithography ............................. 11 1.2.1.1Microcontactprinting .................... 13 1.2.1.2Moldingoforganicpolymers ................ 13 1.3BriefIntroductionofThisWork ........................ 14 2FABRICATIONOFMICROFLUIDICDEVICES .................. 16 3IMAGINGFLOWSINTHEMICROFLUIDICDEVICES .............. 22 3.1MaterialsandExperimentSetup ....................... 22 3.1.1SolutionofMicrospheres ........................ 22 3.1.2ImagingSet-upandProcedures .................... 22 3.2ExperimentResult ............................... 23 4ANALYSISANDTESTINGOFFABIRCATEDCHANNELS ............ 32 4.1PolymerizationProcessofPDMS ....................... 32 4.2AtomicForceMicroscopy(AFM)Result ................... 34 4.3AnalysisofChannelAlignment ........................ 35 5CONCLUSIONS ................................... 41 APPENDIX AMICROFLUIDICDEVICEDATA ........................... 43 A.1GeneralInformationofMicrouidicDevices ................. 43 A.2MicrouidicDeviceErrorAnalysisData ................... 45 5

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BDETAILEDEXPERIMENTPROCEDURE ..................... 50 B.1DetailedExperimentProcedure ........................ 50 B.2ProductCategory ................................ 51 REFERENCES ....................................... 55 BIOGRAPHICALSKETCH ................................ 58 6

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LISTOFTABLES Table page 2-1Materialsforfabricationofmicrouidicdevices. .................. 19 3-1Materialsforimagingexperiments. ......................... 26 A-1Listofmetalsquare80mm-inner-diameterdevices. ................ 43 A-2Listofround100mm-inner-diameterdevices. ................... 43 A-3Listofsquare50mm-inner-diameterdevices. ................... 43 A-4Listofcoatedsquare80mm-inner-diameterdevices. ............... 43 A-5Listofsquare80mm-inner-diameterdevices. ................... 44 A-6Listofcoatedmetalsquare80mm-inner-diameterdevices. ........... 44 A-7Erroranalysisdata,forFOV-1andFOV-2. ..................... 45 A-8Erroranalysisdata,forFOV-3andFOV-4. ..................... 46 A-9Erroranalysisdata,forFOV-5andFOV-6. ..................... 47 A-10Erroranalysisdata,forFOV-7andFOV-8. ..................... 48 A-11Erroranalysisdata,forFOV-9andFOV-10. .................... 49 7

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LISTOFFIGURES Figure page 2-1Corestepsforfabricationofmicrouidicdevices. ................. 20 2-2InterfacebetweenPDMSandairinmicrocapillary. ................ 21 3-1Imagingexperimentalequipment. .......................... 26 3-2Exampleofaframeintheanalyzedmovie. .................... 27 3-3Fittedcurvefromthemodel. ............................. 28 3-4Velocityofparticles. ................................. 29 3-5Actualandeffectiveheight. ............................. 30 3-6Effectiveheightversusmaximumvelocity. ..................... 31 4-1Schematicsofmicrouidicdevice. ......................... 37 4-2Elasto-capillarythinningexperiment. ........................ 38 4-3TherheologicalphaseangleofPDMSwithrespecttotimeat50Cduringpolymerization. .................................... 39 4-4Surfaceimagesandprolesmicrocapillarydeviceswithcircularandsquarecrosssections. .................................... 40 4-5Schematicofatiltedchannel(angle)withtheprojectionimagefrombrighteldmicroscopy. ................................... 40 B-1Microuidicdevicewithplastictubing. ....................... 52 B-2Microuidicdevicewithmetaltubing. ........................ 53 B-3Microuidicdevicewithcopperwiretwinedmetaltubing. ............. 54 8

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AbstractofThesisPresentedtotheGraduateSchooloftheUniversityofFloridainPartialFulllmentoftheRequirementsfortheDegreeofMasterofScienceFABRICATIONANDIMAGINGANALYSISOFMICROFLUIDICDEVICESByXuhuiFengMay2013Chair:JasonE.ButlerMajor:ChemicalEngineeringAnewmethodtofabricatemicrouidicdeviceshasbeendeveloped.Thismethodcreateschannelsforimagingapplicationsusingasimpleprocessthatisinexpensive.Detailedprocessesoffabricationformicrouidicdevicesaredescribedinthisthesis,includinganalysisoftheviscoelastictestthatdenesthecriticaltimefortheplacementofsilicamicrocapillaries.Thestructuresofmicrouidicdevicesarepicturedandillustrated.Thepositionofthesilicamicrocapillariesonthedeviceshasbeenveriedbyatomicforcemicroscopy(AFM),andtheorientationofthesilicamicrocapillariesonthemicrouidicdeviceshasbeendeterminedfromthedatacollectedbyutilizingbright-eldmicroscopy.Thedevicescanbeproducedforaround$2.00eachusingcylindricalandrectangularmicrocapillaries.Researchgroupsthatneedsimplechannelsforimagingapplicationscanbenetfromthisapproachwithoutinvestinginexpensiveandcomplexequipment. 9

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CHAPTER1MICROFLUIDICDEVICESMicrouidicchipsystems,generallyknownaslab-on-a-chipsystems,wererstintroducedbyManzandWidmer[ 1 ]asapartofmicro-totalchemicalanalysissystem(knownasmTAS).Microuidictechnologyintegratesunitoperationsinbiologicalandchemicalprocess,suchassamplepreparation,reaction,separationanddetection,ontoasquarecentimeterlevelchips.Nowadays,microuidicanalysischip,especiallyhighlevelintegratedmicrouidicdevices,areplayingimportantrolesineldsofchemistryandbiochemistry[ 2 4 ].Comparedtomacro-levelreactors,microuidicstechniquesignicantlyreducessampleconsumption,increasesreactionproductivity,andloweringwasteproducedduringexperiment,furtherlowerspollutiontotheenvironment.Microuidicdevicesarewidelyusedduetotheirexibility,highresolution,andotheradvantages.Somerepresentativeapplicationsarereviewedinthenextsection.Methodsusedtomanufacturechipsarediscussedinsection1.2. 1.1ExamplesofMicrouidicDevicesApplications 1.1.1ApplicationsofMicrouidicDevicesinCellCultureandControlCellsarethefundamentalunitoflifeandtheirstudyitisthefoundationofcellularbiology.Oneofthefundamentallaboratoryoperationsintheareaofcellbiologyisthecultivationofcells.Currentmethodsofcellcultivationhavemanylimitations[ 5 ].Forexample,theprocessesareexpensiveandenergyconsuming[ 6 ],cellsaredifculttoobserveandanalyzewithinsystem[ 7 ],anditisnotpossibletoregulatethegrowthanddifferentiatecellswithdifferentfunctions[ 8 ].Advancingcellbiologyrequiresthestudyofsinglecells[ 9 ],andhenceimprovedmethodsforcultivationareneeded.Applicationofmicrofuidictechnologiestothisareaofneedispromising.Thesizesofmostcellsareonthescaleofafewmicrons,whichtsthedimensionofmicrouidicdevicesverywell.Microuidicdevicescanthushelptocontrolthecellular 10

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microenviornment.Generally,thecellularmicroenvironmentisdenedbythechemicalandphysicalparametersthateffectcellularactivities.Inconventionalcellcultures,theseenvironmentalparametersareeasilycontrolledforapopulationofcells,butcannotbeaddressedlocallytoindividualcells[ 10 ].Microuidicdevicescanprovideafavorablemicroenvironmentandadjustthemicroenvironmentdynamicallyandautomaticallyforsinglecells[ 10 ].Microuidicstechniquehelpstocontrolandstudyofsinglecells.Theadvantagesofusingmicrouidicdevicestoconductsinglecellanalysishasbeenstudiedbyscientists[ 11 13 ].Welldevelopedmicrouidicdevicesintegratesingle-cellinjection,cellularanalysis,separationofitscomponents,anduorescenceormassspectrometerdetection[ 14 ]. 1.1.2ApplicationsofMicrouidicDevicesforStudiesofDNAandProteinsDNAandproteinsareamongthemostimportantbiologicalmacromolecules:researchonthestructureandfunctionofDNAandproteinshaslaidthefoundationstounderstandandmanipulatelifeatthemolecularlevel.Technically,usingmicrouidicdeviceshasmanyadvantagesforthestudyofDNAandproteins.Sampleconsumptionwithinmicrouidicdevicesisminimal[ 15 ],thereforeitisnotveryexpensivetoincreasetheconcentrationofbiologicalmolecules,thereforestudyingDNAandproteincanbeeasierduetothehigherconcentrations.Thescaleofmicrouidicdevicesisatthemicronlevel[ 8 ],inwhichmasstransferanddiffusionprogressquickly.Microuidicstechniqueallowsintegrationofmanychemicalandbiochemicalprocessesontoasmallmicrochip[ 16 ],helpingtosimplifyexperimentalprocessesandincreasesensitivityofdetection[ 17 ]. 1.2MethodsofFabricatingMicrouidicDevices 1.2.1SoftlithographySoftlithographyhasprovidedresearcherswithaneconomicandeasywaytofabricatemicrochannelsandmicrocapillaries.ItwasrstintroducedbyG.M.Whitesides 11

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etal[ 18 ].Takingself-assemblymonolayertechniques,elastomericstampstechniques,andmoldingoforganicpolymerstechniquesasfoundations,Whitesidesandhisco-workersdevelopedthiscost-effectivemethods.Thecoretechniqueofsoftlithographyisfabricationofgraph-transportcomponent,whichisknowaselastomericstamps.Forthepreparationoftheelastomericstamps,theoptimalpolymerispolydimethyl-silicane(PDMS)becauseofitsfavoredopticalandmechanicalpropertiesanditssimplemanufacturebyrapidprototyping[ 19 ].LiquidprepolymerofPDMSismadebymixingsiliconelastomerwithcuringagentataratioof10:1.AftercuringofthePDMSprepolymerwhichiscastedontothemastermaterials,PDMSshouldbecarefullypeeledfrommasterwafer.InadditionaltoPDMS-basedmicrochannels,microchannelsmanufacturedbyothermaterialsareeasytondinliteratures.Forexample,DeSimoneetal[ 20 ]developedaseriesofmicrocapillariesbyreplacingPDMSwithphotocurableperuoropolyethers(PFPEs),onetypeofmaterialthatnotonlypossessesfavorablepropertiessimilartoPDMS,butisalsochemicallyresistant.AsimilarexampleisthefabricationmicrochannelswithbiodegradablepolymersasreportedbyBorenstein[ 21 ].Softlithographytechnology,whichisbasedonamoldingtechnique,hasanumbersofadvantagesoverothermicromanufacturingtechniques.Itmakesmanufacturingofmicrochannelsinlaboratoryeasy,economicallyefcient.Inaddition,softlithographyalsopossesshighdelityofreplication.Besidesmanufacturingmicrochannels,softlithographyalsocontributesfabricatingmicrostructuresonsurfacesofmaterialssuchaspolymers,inorganic/organicsaltsaswellascarbonandceramics.Numbersofwaystomakeuseofthesoftlithographytechniquehasbeendeveloped,amongthemaremicrocontactprinting(alsoknownasmCP)andmoldingoforganicpolymers. 12

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1.2.1.1MicrocontactprintingMicrocontactprintingisasimplemethodtocontrolchemicalandphysicalpropertiesofsurfaceofmicrochannels[ 22 ].Numbersofresearchershavealreadyprovenitspotentialinareasofbiosensor[ 23 ]andmicromanufacturing[ 18 24 ].Thetermmicrocontactprintingmeansthetechnologythatcombineselastomericstampandself-assemblymonolayertechnologytoprintgraphsonatorcurvesurfaces.Self-assemblymonolayerisonetypeoflayerthatisformedbylongchainmoleculesthatcontainssomecertainfunctiongroupsspontaneouslyarrayformingaregularstructureonasuitablemastertoensureminimumfreeenergyofthesystem.Examplesofwell-knownself-assemblymonolayercombinationsarealkylthiolonthesurfacesofgoldandsilver,alkylsiloxaneonthesurfacesofglass,siliconandsilicondioxide.ElastomericstampscanbeobtainedpouringPDMSontomoldspreparedbyutilizinglithographytechnology.Byapplyingalkylthiolinkontheelastomericstamp,itispossibletomakemicrographsonsurfaceofsomecertainmetals,namelygoldandsilver.Duringtheprocess,alkylthiolmoleculesautomaticallyarraytoformaregularstructuretoensureaminimumoffreeenergyofthesystem,thereisatrendtohealdefectautomaticallyduringtheprocess,whichdecreasesprintingerrorsandensuresclearanceofpainting. 1.2.1.2MoldingoforganicpolymersMoldingoforganicpolymersmethodscontainstechniquessuchasmicromoldingincapillaries(MIMIC)[ 25 ],microtransfermolding(mTM)[ 26 ]andreplicamolding[ 27 ].AccordingtotheprocedureofMicromoldinginCapillarymethoddescribedbyWhitesidesandhisco-workers[ 28 ],capillarychannelsareformedbetweenasupportandanelastomericmoldmadeofPDMSthatcontainscertainrecessedpatternsintherststep.Thephysicalpropertiesmakesconformalcontactandeasyseparationbetweenmoldandsupportpossible.Thestepisfollowedbyplacingadropofuid 13

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containsmaterials(polyurea,forexample)usedtobepatternattheentranceofpatternsofthemold.Afterthematerialintheuidhascrystalized,reactedorbeenabsorbedbythesupport,separatetheelastomericmoldfromthesupport,microstructuresonthemasterarethenreplicatedfromtheelastomericmaterialstothesurfaceofthesubstrate.However,thelimitationofMIMICisthatitcanonlyhelptofabricatemicrostructuresconnectingtotheentranceoftheelastomericmold[ 29 ].Procedureofmicrotransfermoldinginvolvesfabricationofelastomericmoldwithareliefstructureonitssurface,asdescribedinliterature[ 30 ],whichisfollowedbypouringprepolymeronthesurfaceonwhichdrawnpatterns.Afterremovingexcessprepolymerfromtheelastomericmold,keepthemoldcontactedwithsubstrate.Separatemoldandsubstrateaftertheprepolymerisfullyabsorbedonthesubstrate.Anotherpracticalprocedureisreplicamolding[ 31 ],thisprocedurerequirescastprepolymer,usuallyliquidPDMS,ontoamasterwithpatternedgraphonitssurface.Aftergettingdried,solidPDMSshouldbecarefullyseparatedfromtheoriginalmaster.ThesurfaceofPDMSwillbepatternedwiththecomplementarygraphofthatontheoriginalmaster.ThisstepisfollowedbytakingthePDMSasmasterandcastrigidpolymer,polyurethan(PU)forexample,ontothesurfaceofthesolidPDMSforre-replicating. 1.3BriefIntroductionofThisWorkThisworkdescribesamethodtoassemblesinglechannelmicrouidicdevicesbyembeddingsilicamicrocapillariesontothesurfaceofpolydimethylsiloxane(PDMS).Thismethodtakesadvantageofinexpensiveandeasily-obtainedsilicamicrocapillariesandPDMStoproducestraightsilicamicrochannels.Softlithographyisawidelyusedtechniqueforfabricationofmicrouidicdevices,however,PDMSbasedmicrouidicdevices,whicharemadefromsoftlithography,lackmechanicalstability[ 32 ]andhavepoorcompatibilityoforganicsolvents[ 33 ].Themicrouidicdevicesmadeinthisworktakeadvantageofsilicamaterialstobuildthechannelsofthedevices,thereforethe 14

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microuidicdevicesinthisworkaremechanicallystableandcompatiblewithorganicsolvents. 15

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CHAPTER2FABRICATIONOFMICROFLUIDICDEVICESThemicrouidicdevicefabricationmethodintroducedinthisthesisusesanumberofinexpensiveandeasilyobtainedmaterialssuchassilicamicrocapillaries,PDMS,andplastictubingtoproducestraightsilicamicrouidicdevices.Themethodintroducedinthisthesisisalsoeasyandefcientsincefabricatingthedevicesconsistsofonlyafewsteps:namely,preparationofPDMSpolymer,embeddingofsilicamicrocapillaries,andassemblyofthemicrouidicdevice.Thematerialsandstepsforthefabricationaredescribedinthischapter.MaterialsusedfortheconstructionofthechannelsarelistedinTable 2-1 .Thereareelevenitems,thersteightofwhichcanbeobtainedfromanumberofsourcessincethematerialsarefairlygeneric.Thelastthreeitemsarethesilicamicrocapillariesthemselves,whicharemoredifculttolocate.Theyare,however,availableinawiderangeofshapesandsizes.ThemanufacturerandcatalognumbersarelistedinTable 2-1 .Inthiswork,squareandcylindricalsilicamicrocapillariesareused,squaresilicamicrocapillariesareavailablewith50&80mmininnerdiameter,whilecylindricalsilicamicrocapillariesareavailablein100mmininnerdiameter.Therststepofthemicrochannelfabricationrequiresmixing10gramsofsiliconeelastomerbaseand1gramofsiliconeelastomercuringagent.Aftermixingthetwomaterialswell,thesampleinplacedavacuumsystemat0.1torrfor15minutestoeliminategasbubbles.Afterfullydegassing,thePDMSprepolymeristransferredontoasilicasubstrate.Heatthesystemataround50Cfor20-30minutes;notethattheexactheatingtimedependsonvariablessuchasratioofsiliconeelastomerbaseandsiliconeelastomercuringagent,heatingtemperature,andtheambienttemperature.Duringtheheatingprocedure,testtheviscosityofthePDMSpolymerbyusinganeedletoprobethemixtureconditions.Theneedleshouldbeinsertedtothebottomof 16

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thePDMSsolutionandraised1.0cmabovethesurfaceofthemixture.ThePDMSwillformathinlamentthatwillpersistforupto2-3seconds.Keepheatingthesampleuntilthefavorableviscosityisreachedandthenplacefourofthesquarecapillariesontothesurfaceofthesemi-solidstatePDMS,seeFigure2-1.Toplacemicrocapillaries,aspoonwithsomePDMSmixturedippedonitisused.MicrocapillariesarestuckbythePDMSonthespoon.MicrocapillariesareplacedonthesurfaceofPDMSwiththespoon.ThisstepmustbedonewithextremecaretoassurethattheuppersurfaceofthesilicamicrocapillaryisnotcoveredbyPDMS.Otherwise,thesilicamicrocapillarywillsinktothebottomofthePDMS.Keepthesystemheatedat50Corroomtemperatureovernightfortotalsolidi-cationofthePDMSpolymer.However,experienceshowsthatthetemperatureappliedheredoesnotmaketoomuchdifferenceintheoverallqualitiesofthePDMSormicrouidicdevices.OncethePDMS-capillarypartisprepared,thePDMSisremovedfromthesiliconwaferandputonamicroscopeslide.Toavoidbreakingmicrocapillaries,thePDMSshouldbepeeledfromthelongersideofthePDMSbase.Alsobeforetransferringontothemicroscopicslides,thebottomofthePDMSshouldbetreatedwithplasmafor45secondstoactivemoleculesonthesurfaceofthePDMSsothatitwilladheretotheslidematerial.Sincethemicrocapillariesareverythin,capillaryforcesaresignicant.PlacementofsilicamicrocapillariesontothesurfaceofPDMSwhenPDMSisstillintheliquidstatecausesasmallamountofliquidPDMStoinevitablyowintoandblockthechannelsafterthePDMSsolidies.Therefore,cuttingthepluggedportionsofthecapillariesisnecessary.Withthehelpofamicroscope,theblockedpartiseasytolocate.Figure2-2showstheinterfaceofsolidiedPDMSandairinsidemicrocapilliries.Afterremovingtheblockedpartoftheglasscapillary,trimtheblockofPDMSinordertomakethedimensionsofthePDMS-capillarypartapproximatelyequalto40mm10mm. 17

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Tubingofvarioussizescanbeusedtoconnectthesquarecapillariesdiscussedabove.Forourwork,TygonS-54-HLmicroboretubingandmetalneedlewereused.ThemetaltubingwasobtainedfromTerumoneedles.Therststepisremovingtheplasticpartsoftheneedles,followedbygrindingbothendsofthemetaltube.Inourwork,someofthemetaltubingistwinedwithcopperwiresbeforeconnectingtotheglasscapillaries;thesecopperwireshelptoconductelectricityandestablishtheelectriceldinsidetheglasscapillaries.Fabricationproceduresformicrouidicdeviceswiththesekindsoftubingareverysimilar.Allofthemrequireconnectingtubingwithcapillariesandsealingthegapbetweenthesilicamicrocapillaries,PDMSbase,andtubingwithsiliconesealant.Aftersealing,keepthemicrochannelsatroomtemperatureovernightuntilthesiliconesealantdries.DetailedstepsformicrouidicdevicefabricationandpicturesoffabricatedmicrouidicdevicesaregiveninAppendix. 18

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Table2-1. Materialsforfabricationofmicrouidicdevices. Item#MaterialManufacturerCatalog# 1SiliconeslastomerbaseDowCorningSylgard-1842SiliconeelastomercuringagentDowCorningSylgard-1843PlainmicroscopeslidesFisherScientic12-544-14PolishedprimewaferCematSiliconV7010015MicroboretubingTygonS-54-HL6SiliconewaterproofsealantLoctite9085707SyringeneedleTerumo21G18TeontapeNeiko1/26009SquaresilicamicrocapillariesVitrocell8505-5010SquaresilicamicrocapillariesVitrocell8508-5011CylindricalsilicamicrocapillariesVitrocellCV1017 19

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Figure2-1. (a)PreparePDMSmixtureliquid.(b)MakeacontainerforPDMSwithasilicawaferandaluminafoil.(c)PlaccsilicamicrocapillaryonPDMSatcriticaltime,aspoonisdippedwithalittlePDMSviscousliquid,silicamicrocapillaryisstickonthespoon.(d)AfterPDMSisfullypolymerized,peelthePDMSwithsilicamicrocapillaryoffandplaceontoamicroscopicslide.(e)TrimexcessPDMS.(f)Preparemetalmicrotubesfromsyringeneedles.(g)Readytoassemble.(h)Connectsilicamicrocapillarywithmetalmicrotubeandsealtheconnectionwithsilicone,andcoverthesiliconewithteontape.(i)Peeloffteontapeafterplacethedeviceovernight. 20

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Figure2-2. MicroscopyimageshowingtheinterfacebetweenPDMSandairinsideofasilicamicrocapillary.Thisportionofthedevicemustbecut-awayfromtherestofthemicrocapillarytoallowtheintroductionofuid. 21

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CHAPTER3IMAGINGFLOWSINTHEMICROFLUIDICDEVICESImagingexperimentsareconductedforcharacterizingtheowinthemicrouidicdevices.Asolutionofuorescentmicrospheresisusedasindicatorsofow.Inthischapter,alldiscussionisbasedupontheresultsofexperimentsconductedonasquaremicrochannelwithaninnerdiameterof80mm. 3.1MaterialsandExperimentSetupAftermakingthemicrouidicdevices,theabilitytoimageowsbyexaminingthemotionofmicrosphereswithinthesystemwastested.Inthissection,theexperimentsaredescribed.Thematerialsusedintheexperimentsareeasytoobtain.Preparationofthemicrospheresolutionandsetupforgeneratingowarestatedinthissection. 3.1.1SolutionofMicrospheresThesolutionoforescentmicrospheresispreparedbyusingthemethoddescribedelsewhere[ 34 ].ThemicrospheresolutionobtainedfrominvetrogenisdilutedwithTAEbuffersolutionataratioof1:1,000,000.ThecompositionoftheTAEbuffersolutionincludes90%Nanopurewater,10XTAEBufferandsaltaccordingattheionicconcentration.The40mlofsolutionisequallydistributedbetweentwo50mlreservoirs. 3.1.2ImagingSet-upandProceduresFigure3-1showstheschematicoftheexperiment.Tworeservoirsarehorizontallyequilibrated,whichcanbeveriedbyobservationofmovementofmicrospheresinsidethemicrouidicdevicebymicroscopicmethods.Horizontalequilibriumcanbeconrmedwhenthemicrospheresarerandomlymovingwithoutanypreferreddirections.Avelocityeldcanbeachievedbyslightadjustingtheheightofoneofthereservoirs.ThemicrospheresareimagedbyusingaNikondiaphot200orescentinvertedmicroscopewithQImagingRetigaSRVCCDcamerausingaCarlZeissobjectiveat63x.Experimentswereperformedatvedifferentowrates,orrelativeheights,andeachexperimentmeasured3000frameswitha0.2secondtimedelay.Thesystemuses 22

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NikonElementssoftware,imagesaresavedin.aviformat,andthetimeoftheeachframearesavedinanexcelspreadsheet. 3.2ExperimentResultByimagingthemovementofmicrospheres,criticalpropertiesofthemicrouidicdevices,suchasthepressuredrop,owraterelationship,canbedetermined.Inthispart,asolutionofmicrospheresispreparedandusedasanindicatorofvelocity,sincethemotionofmicrospheresinmicrouidicdevicescanbeconsideredtofollowthestreamlines.Velocityprole,velocitydistributionoftheparticlesovertime,andvelocitydistributionalongthex-andy-axisareobtained;theresultofimagingexperimentsshowsthatpressuredropalongthemicrouidicchannelislinearlydependentontheheightdifferencebetweenthetworeservoirsshowninFigure3-1asexpectedfromthetheoryofcreepingow.Thisworkusesawell-knownprogramfortrackingparticlesandcalculatingthevelocities[ 35 ].Programrun.mistheshelltorunotherfunctions.Theprogramhasvemainpartswhicharempretrack,mpretrackinit,particlespeedandplotparticles.Theparametersarewelloptimizedtofulllthetrackingrequirements.Therstpartisthempretrackinit.mfunctionwhichndstheacceptedfeaturesforoptimizingtheparameters.Figure3-2showstheoutputimagefromoneoftheexperimentsprocessedwithmpretrackinit.m:greencirclesshowtheacceptedmicrospheresandreddotsaretherejectedfeatureswhichareignoredintheanalysis.Onceparametersintheprogramareoptimized,theimagesareprocessedwiththempretrackfunction,whichreturnsalecontainingthepositionsoftheparticleswithtime,fromframetoframe.Thisprocessisfollowedbylinkingtheparticlesusingthefancytrackfunction.Thefunctionrequiresthemaximumalloweddisplacement,whichiscalculatednumericallybysolving @2U(x,y) @x2+@2U(x,y) @y2=gh L,(3) 23

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whereisthedensityofuid,gisgravitationalacceleration,histheeffectiveheight,Listhelengthofsilicamicrocapillary,istheviscosityofsolution.Boundaryconditionforequation( 3 )aretheno-slipconditionsonallwalluidinterfaces.Thenalstepoftheprogramisbinningthedistributionusingaresolutionof5mm.Meanvelocityoftheparticlesfallingintoeachbiniscalculatedfromthedataasafunctionofreservoirheight.Sinceequation( 3 )scaleslinearlywithheight,amodelforheightvelocityisgenerated(heightt.m)and,basedonexperimentalparticlespeeds,thetheoreticalparticlespeediscalculated.Figure3-3showsthevelocityproleobtainedbyobservingmotionsofmicrospheresisapproximatelyaparabola,whichisinagreementwiththetheoreticalcalculatedvelocityproleandshowsthattheowinthismicrouidicdeviceiswelldeveloped.Figure3-4demonstratesthevelocityofeachparticleafterusingthefancytrackfunction.Thefunctionlinksthemicrosphereswiththeclosestoneineachconsecutiveframe.Notetheowisgeneratedalongthexaxisandthechannelisviewedfromxyplane.InFigure3-4themaximumspeedoftheparticlesremainsapproximately40mm/s,whichindicatesthatthevelocitydistributionoftheparticlesdoesnotdecayovertime.Therefore,byapplyingaheightdifferenceaconstantpressuredrivenowcanbegenerated.Thevaluesthatarehigherthan40mm/sareduetotrackingprogramerrorswhichwillbexedinfuturerevisions.Aparabolicowproleisformedwhichisinagreementwithwiththetheoreticallycalculatedvelocityprole.Againoutlinesintheparticlespeeddistribution(Figure3-4rightside)isduetotrackingprogramerrors.Therandommotionoftheparticlesarecalculatedwithequation =kBT 6at,(3) 24

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wherex(t)isthepositionofamicrosphereattimet,kBistheBoltzmannconstant,Tisthetemperature,istheviscosityofsolution,aistheradiusofmicrospheres,tisasmallvalueoftime.Equation( 3 )showsthatvarianceintheparticlesshouldbe0.45mm.Howeveraveragerandommovementcalculatedfromexperimentaldatais1mm/s.InordertocorrectthesemeasurementerrorsextensiveanalysisofTaylordispersionisrequired.Aftertheowforallvedifferentheightsaremeasuredandcalculated,actualheightandtheeffectiveheightarecompared.Thisexperimentisconductedontwomicrouidicdevices,bothofwhoseinnerdiameteris80mm.Pressuredropinthesystemisfoundbyttingy=ax+blines,whichareshowninFigure3-5,whichillustratesthelinearcorrelationofactualheightandeffectiveheight.Byutilizingthemaximumvelocityandeffectiveheightobtainedfromexperimentsonbothmicrouidicdevices,aneffectiveheightversusmaximumvelocityisobtainedinFigure3-6.Figure3-6illustratesthatthelineardependentofmaximumvelocityonactualheightinexperiment.ThemaximumvelocityiscalculatedfromEquation( 3 ).Theplotinthisgraphshowsthatthelinearcorrelationoftheactualheightandmaximumvelocity,theactualheightscaleslieanrlywiththemaximumvelocity. 25

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Table3-1. Materialsforimagingexperiments. Item#MaterialManufacturerCatalog# 1NanopurewaterPERCattheUniversityofFloridaN/A210XTAEBufferLifeTechnologiesAM98693FluorescentmicrosphereLifeTechnologiesF-8813 Figure3-1. Schematicfortheexperimentalowarraratus:(a)Fixedstage,(b)Reservoir,(c)Voltagegenerator,(d)MicrouidicDevice,(e)Objective,(f)Movingstage. 26

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Figure3-2. Exampleofadataframeanditsanalysis.Reddotsshowthefeaturesthatarenotacceptedandthegreencirclesshowacceptedmicrospheres. 27

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Figure3-3. Fittedcurvefromthemodel.Particlesarebinnedandbarsrepresentsthestandarddeviationinvelocity. 28

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Figure3-4. Velocityofparticles.Lefthandside:Velocitydistributionoftheparticlesovertime.Righthandside:Velocitydistributionalongthexandyaxis. 29

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Figure3-5. Therelationshipbetweenactualandeffectiveheightofthetwomicrouidicdevicesanalyzedarelinearlydependent.Therelationshipbetweenactualandeffectiveheight,theeffectiveheightinthesystemisttedinastraightline. 30

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Figure3-6. Therelationshipbetweeneffectiveheightandmaximumvelocityinthetwomicrouidicdevices.TherelationshipbetweenthetwotermsaregivenbytheNavier-StokesEquation(Equation( 3 )). 31

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CHAPTER4ANALYSISANDTESTINGOFFABIRCATEDCHANNELSByusingthemethodformakingmicrouidicdevicesdescribedinChapter2,anumberofmicrouidicdeviceshavebeenproduced.Tablesthatrecorddetailedinformation,namely,microuidicDeviceIDnumber,innerdiameter,andsilicamicrocapillarylength,canbefoundintheAppendix.Inthischapter,imagesofthemicrolfuidicdevicesareacquiredandillustrated.Twomethodstodeterminethetimingfortheassemblyofthedevices,elasto-capillarythinningtestandrheologicalmeasurement,aredescribedinSection4.1.ResultsofAFManalysisandorientationerroranalysisforsquaremicrouidicdevicesaredescribedanddiscussedinSection4.2andSection4.3.Figure4-1showsaschematicofthedevicewhichincludesfourmaincomponents:amicroscopicslide,aPDMSmount,asilicamicrocapillary,andtubing.ThesilicamicrocapillaryisonthesurfaceofPDMS(seeSection3.3fordetails),whichmakesimagingpossible.ChemicalbondsonthebottomofthePDMSmountareactivatedbyplasmatreatmenttoincreaseadhesionbetweenPDMSandmicroscopicslidestoassureofadhesionthePDMSmountonmicroscopicslide.Thelengthofsilicamicrocapillarywasmeasuredandwritteninmillimetersoneachmicroscopicslidetofacilitatethecalculationoftheelectriceld.Thejunctionamongsilicamicrocapillary,tubing,andsiliconeiscarefullyassembled.AtlastanIDnumberofamicrouidicdeviceisassigned(MS8-1inFigure4-1,forexample). 4.1PolymerizationProcessofPDMSThecriticalstepinfabricatingthechannelsisthetimingfortheplacementofthesilicamicrocapillariesonthesurfaceofthePDMS.PlacingthesilicamicrocapillariesonthePDMStoosoonresultsintheirsubmersion,astheywillsinkthroughtheviscousmaterial.Atlatertimes,themicrocapillarywillsimplysitontopofthePDMSandnotbeattached.Consequentlyinthissection,therheologyofPDMS,heatedat50C,is 32

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studiedintimeandtheresultsarecorrelatedwiththeoptimumtimeforplacingthesilicamicrocapillariesonthePDMS.PDMSispreparedbymixingapproximately10gramsofbaseandapproximately1gramofcuringagent.Airbubblesappearafterfullymixingthebasewiththecuringagent.Toremoveanyairbubbles,themixtureisdegassedinavacuumchamberat0.1torrforatleast15minutes.Thenthemixtureispouredontoaatplatewhichismaintainedatatemperatureof50C.Theheatingprocesslastsfor20-30minutesbeforeplacementofthesilicamicrocapillaries.Beforetheplacementofsilicamicrocapillaries,thematerialshouldbetestedinordertoidentifythetimeatwhichtoplacethesilicamicrocapillariesontothePDMS.Asimpletestoftheelasto-capillarythinningbehaviorofthepolymersufcestoidentifythepropertiming.Inthistest,aneedleisslowlydippedtothebottomofthePDMSmixture,asshowninFigure4-2a,andthenslowlyelevatedto1cmaboveofthePDMS.DuetotheviscoelasticityofPDMS,alamentisformedbetweentheneedleandthesurfaceofPDMS,asshowninFigure4-2b.Beforethecriticaltime,eithernolamentisformedorthelamentisabletolastthanless2seconds.Atthecriticaltime,thelamentcanlastfor2-3seconds,whichisshowninFigure4-2c.Alastingtimeoflamentthatisshorterthan2secondsorlongerthan3secondsindicatesaninappropriatetimeforsilicamicrocapillary'splacement.AmoredetailedtesttodeterminecriticaltimeofsilicamicrocapillariesplacementhasbeenconductedbymeasuringtheviscoelasticityofPDMSduringpolymerization.AnARESLS-1straincontrolledrheometer(TAInstrument)wasusedwithacone-and-plategeometry.Themeasuringtemperaturewascontrolledtomaintainthesystemat501C,whichisthepolymerizationtemperatureusedinthefabricationofthedevices.Oscillatoryshearwasconductedatafrequencyof50rad/secandastrainamplitudeof25%. 33

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Figure4-3showstherelationshipbetweenthephaseangle,whichisameasureoftheoverallviscoelasticnatureofthesample[ 36 ],andthetimefromthepointofcontactingthepolymerwiththeheatedplates.Figure4-3istheresultthatisobtainedbycomparingtherheometerdatawithphenomenaobservedinfabricationexperiment.IntheFigure4-3,thephaseangleisapproximately90intherst20minutes(regiona).TheregionaiscalledviscousregionduetotheviscouspropertyofPDMSinthisregion.Itisfoundthatviscousregionisrelativelyearlyforplacementofmicrocapillarieswhencomparingtherheometerdatawithexperimentalfabricationprocedure.PlacementofsilicamicrocapillariesinthisregionisgoingtocausesilicamicrocapillariestosinktothebottomofthePDMSlayer.Fromthe20thminutetothe30thminute(regionb),themixturebeginstoshowelasticproperties,whenthephaseanglechangesfrom87to75.Thisregioniscalledthetransitionregion.Itisfoundthatinthetransitionregion,theviscoelasticitybeginstoincreasefasterthanintheviscousregion.Aftercomparingthephenomenaobservedinfabricationexperiment,itisconcludedthatthetransitionregioniscorrespondingtothecriticaltimeregion,whichisthebesttimerangefortheplacementofsilicamicrocapillaries.ThisconclusioncoincidesthefastdecreasingphaseangleinFigure4-3.Beginningat30minutes(regionc),thephaseanglecontinuestodeclinelinearly.Itisfoundthatinexperiment,theelasticityofPDMSinthisregionbecomesmoresignicantthanthoseinregionaandregionb.Theregioncisalsocalledtheelasticregion,duetotheelasticitybecomingsignicant.PlacementofsilicamicrocapillariesatthistimeresultsinmicrocapillariesnotbeingembeddedinthePDMS. 4.2AtomicForceMicroscopy(AFM)ResultThissectionfocusesondetailingtheexactlocationofthesilicamicrocapillarieswhichareembeddedonthesurfaceofthePDMS.ThesurfaceofthemicrocapillarydevicesarecharacterizedwithAFMtodeterminetheexactpositionofthechannelas 34

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embeddedonthePDMS.Forimagingpurposes,AFMexperimentsareperformedina15non-contactmodeusinganAsylumResearchMFP3D-BioAFMwithAC240TScantilever.BrighteldimageswerecollectedusingaQImaging25RetigaSRVCCDcameraattachedtoaNikondiaphot200invertedmicroscopewithaLeitzWetzlarExtraFlat(63X/0.85)objective.Figure4-4showsthatthesilicamicrocapillaryislocatedonthesurfaceofPDMS,with1to4mmofthesilicamicrocapillaryprotrudingthroughthesurface.Figure4-4aand4-4bshowmicroscopeimagesofacircularandasquarechannelembeddedinPDMSandmarkstheregionsonthesurfacesthatwereinterrogatedusingAFM.Figures4-4cand4-4dshowboththetopographyandthephaseangle;thetopographyrevealstheheightofthefeaturesandthephaseangledifferentiatesthematerial(PDMSorsilica)exposedonthesurface.Thecurvatureofthecylindricalmicrocapillary(Figure4-4c)extendsadistanceof4mmabovetheplanarsurfaceofthePDMS,wherethecurvedregionisidentiedastheharderglassmaterialfromthelargerphaseangleascomparedtothesurroundingPDMSsurface.Likewise,Figure4-4dshowsthatthetopplaneofthesquaremicrocapillaryisexposedtotheatmosphereandsitsapproximately1mmabovethesurfaceofthePDMS.Theresultshowsthattheuppersurfaceisexposedtotheatmosphere,whichisgoodfortheimaginganalysis.Thefocaldistanceoftheobjectiveusedinimaginganalysisisapproximately60mm,nocoverageofPDMSontheuppersurfaceofsilicamicrocapillaryensurenoextradistancebetweenobjectiveandsilicamicrocapillary. 4.3AnalysisofChannelAlignmentNoactivemethodisemployedforcontrollingthealignmentofsquaresilicamicrocapillariesduringtheirplacementontothesurfaceofthePDMS.YetthequalityoftheimagesdependscriticallyupononeofsideofthecapillarylayingcoplanarwiththesurfaceofthePDMS.Inthissection,methodstomeasureandcalculatetheorientationerrorofthesilicamicrocapillariesaredemonstratedanddiscussed. 35

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Figure4-5ashowsamicroscopicimageofachannelthathasanorientationerrorof=15.Theorientationerrormakesitdifculttoseethenear-wallarea.Thecalculationoforientationerrorofeachmicrouidicdeviceisbasedontenimageseachalongthelengthofvemicrouidicdeviceswithaninnerdiameterof50mmandtwelvewith80mm.Theangleforeachchannelateachpositioncanbemeasuredfromthemicroscopeimage(seeFigure4-5a)from=tan)]TJ /F9 7.97 Tf 6.59 0 Td[(1(M2=M1),whereM1=L0cos()andM2=L0sin().Afterthedeterminationoftheangle,itispossibletocalculateL0fromM1,whichcanbecomparedwithL,thewidthofthesilicamicrocapillariesasreportedbythemanufacturer.ThereisnoneedtoconsidertheconversionfrompixeltophysicallengthsinceM2=M1isadimensionlessnumber.Figures4-5band4-5cshowallofthedata.Thedottedlinerepresentstheaverageoftheorientationerror.Thestandarddeviationofanglealongeachmicrouidicdeviceislessthan2,whichismostlikelyaresultfrommeasurementerrors.ItisshownthattheaveragetiltofthechannelsinFigure4-5cis7,whichaddsonly1%totheoverallerror(cos(7)=0.992).Thestandarddeviationofthenormalizedlengththroughoutthechannelislessthan0.02(2%ofthechannel).TheaverageerrorfortheL0is2%(Figure4-5adottedline),whichislessthantheerrorof10%,asspeciedbythemanufacturer. 36

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Figure4-1. Schematicsofthemicrouidicdevicefrom(1)they-zplaneand(2)thex-zplanealongwithanimageofthechannel(3)fromthex-yplane.Thelabelsonthegurerefertothe(a)microscopicslide,(b)PDMS,(c)silicamicrocapillary,and(d)microscopeobjective. 37

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Figure4-2. Thispictureillustrateselasto-capillarythinningexperiment.(a)AneedleisslowlydippedtothebottomofPDMS,(b)alamentisformedbetweentheneedleandthesurfaceofPDMS,(c)a1-cm-longlamentcanlastfor2-3secondsatcriticaltime,(d)lamentdisappearsafteratmost3secondsofformationatcriticaltime. 38

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Figure4-3. TherheologicalphaseangleofPDMSwithrespecttotimeat50Cduringpolymerization.TherheologyofPDMStransitionsfromviscous(regiona)tostronglyelastic(regionc)duetothepolymerization.Introducingthecapillaryduringthetransitionperiod(regionb)resultsinthenaldepthandalignment,withouttheneedtomanuallycontroleitherparameter. 39

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Figure4-4. Microscopicimagesinthex-yplaneofthe(a)roundand(b)squaremicrochannelsareshownandtheregionsprobedbyAFMaremarked.TheAFMresults,showingboththetopographyandphaseangle,aregivenforthe(c)roundand(d)squarechannels.Diagrams(e)and(f)showanend-view(yzplane)ofthetopography. Figure4-5. (a).NormalizedlengthL0=L(b)andangle(c)from10measurementsalongeachchannel.Thedottedlinesdesignatetheaveragevaluescalculatedusingallofthemeasurements. 40

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CHAPTER5CONCLUSIONSInthiswork,amethodtofabricatestraightmicrouidicchannelsforuseinimagingapplicationshasbeendemonstrated.Theprocedureformakingthedevicesissimpleandinexpensive,inpartowingtotheuseofoff-the-shelfsilicamicrocapillaries.Assuch,themethodproposedherehassignicantadvantagesoverothermethodsthatrelyonaccesstoexpensiveequipmentandmaterials,solongasthegoalistofabricatemicrouidicchannelsforimagingapplications,andnotamorecomplexdevice.DetailedprocessesoffabricatingthemicrouidicchannelswereclearlystatedandillustratedinChapter2.ThetimingoftheplacementofthesilicamicrocapillaryonthesurfaceofpolymerizingPDMSwasarguedtobetheonecriticalissuewithregardtothedeviceconstruction.However,asimpletechniquefordeterminationofthetimingcanbeutilized.Inthismethod,theviscoelaticityofthePDMSisprobedbyinsertinganeedletothebottomofthePDMSandthenobservingthelamentafterelevatingtheneedle1cmabovethesurface.Itwasfoundthatthepersistenceofthelamentforaperiodofafewsecondssigniesthecorrecttime.Afullrheologicaltesttodeterminethetimingwasalsoperformed.Bothmethodsshowthatthebesttimerangeforplacementofthesilicamicrocapillariesrangesfromtwentytothirtyminutesafterinitiatingthepolymerization.Channelsfabricatedusingthedescribedmethodalsowerecharacterizedandtested.Measurementsofpositionandalignmentofthechannelsweremadeusingatomicforcemicroscopy(AFM)andbrighteldmicroscopy.Useofthechannelswasdemonstratedbymakingvelocitymeasurementsfortracerspheres.TheAFMmeasurementswereusedtoinvestigatethetopographyoftheuppersurfaceofthesilicamicrocaipillaryandPDMSmaterial.TheAFMimagesshowthattheuppersurfaceofthesilicamicrocapillary,whethercircularorsquareincross-section,areslightlyabove(approximately1and4mm,forsquareandcylindrical,respectively)thesurfaceofPDMS.Theuppersurfacesofboththecylindricalandsquarechannels 41

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areexposedtotheatmosphere,whichmakesobservationbymicroscopeeasysincethefocaldistanceisapproximately60mm.Errorintheorientationofthesquaremicrouidicdeviceswerecalculatedbyanalyzingimagescollectedfrombrighteldmicroscopy.Tenmeasurementsaretakenalongeachmicrouidicdevicetocalculateanaverageorientationerrorofeachmicrouidicdevice.Theresultfrom17ofthemicrouidicdevicesmeasuredinthisworkshowsthattheorientationerrorofthemeasuredmicrouidicdevicesvariesfrom4.55to9.71.Theaveragevalueoforientationerrorforallofthemicrouidicdevicesmeasuredinthisworkis7.52,whichisacceptableintheimagingapplicationofmicrouidicdevices.TherawdatafororientationerrormeasurementsareshowninAppendixA.2.Imagingofmicrospheresowingthroughthemicouidicdeviceswasalsodescribedinthiswork.Thesuccessfulmeasurementofthevelocitydistributioninthechannelconrmsthatthechannelscanbeusedforimagingstudiesofowingparticulates.Therelationshipbetweentheheightdifferentialandtheowrateswasalsoattainedfromtheexperiments;asexpectedforcreepingows,therelationshipbetweentheheightandowislinear. 42

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APPENDIXAMICROFLUIDICDEVICEDATA A.1GeneralInformationofMicrouidicDevices TableA-1. Listofmetalsquare80mm-inner-diameterdevices. MicrouidicDeviceID#InnerDiameter/mmSilicaMicrocapillaryLength/mm MS8-18049.78MS8-28050.26MS8-38048.06MS8-48047.18MS8-58050.25MS8-68046.05MS8-78048.45MS8-98045.97 TableA-2. Listofround100mm-inner-diameterdevices. MicrouidicDeviceID#InnerDiameter/mmSilicaMicrocapillaryLength/mm r-110036.67r-210038.30 TableA-3. Listofsquare50mm-inner-diameterdevices. MicrouidicDeviceID#InnerDiameter/mmSilicaMicrocapillaryLength/mm S5-15047.88S5-25036.87S5-35044.12S5-45042.32S5-55048.00S5-65042.54S5-75045.28S5-85041.30S5-95047.25 TableA-4. Listofcoatedsquare80mm-inner-diameterdevices. MicrouidicDeviceID#InnerDiameter/mmSilicaMicrocapillaryLength/mm CS8-18045.11CS8-28047.21CS8-38045.44CS8-48046.93CS8-58038.23 43

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TableA-5. Listofsquare80mm-inner-diameterdevices. MicrouidicDeviceID#InnerDiameter/mmSilicaMicrocapillaryLength/mm S8-18047.50S8-28044.34S8-38044.30 TableA-6. Listofcoatedmetalsquare80mm-inner-diameterdevices. MicrouidicDeviceID#InnerDiameter/mmSilicaMicrocapillaryLength/mm MS8-88048.66 44

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A.2MicrouidicDeviceErrorAnalysisData TableA-7. Erroranalysisdata,forFOV-1andFOV-2. ChannelIDFOV-1M1/PixelM2/PixelFOV-2M1/PixelM2/Pixel MS8-1469.4361.80459.2463.45MS8-2468.4938.87468.6733.32MS8-3447.1478.75458.6866.64MS8-4458.2567.81454.6469.27MS8-6462.7462.16466.6757.36MS8-7475.6848.53475.8642.33MS8-8465.2959.40465.2158.20S8-1449.8071.90440.0775.89S8-3457.7669.70458.4572.88S5-1265.8838.10265.0336.58S5-3293.1138.56293.4537.26S5-4279.4930.94278.1636.10S5-5283.3338.67285.6339.35S5-6289.2434.66284.6043.58S5-7308.3635.47305.9034.49 FOVFocusofView. 45

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TableA-8. Erroranalysisdata,forFOV-3andFOV-4. ChannelIDFOV-3M1/PixelM2/PixelFOV-4M1/PixelM2/Pixel MS8-1469.3764.64464.8668.57MS8-2457.7939.39464.6840.30MS8-3456.8963.76460.4167.15MS8-4458.3069.06456.9469.24MS8-6464.4563.41463.4264.19MS8-7465.1053.54474.8447.99MS8-8459.4871.18469.4758.26S8-1442.0178.34453.1776.42S8-3456.0672.44462.5964.16S5-1265.7035.77266.3936.89S5-3294.6038.17300.9035.22S5-4274.1637.44277.0533.45S5-5282.6239.55290.5736.03S5-6290.7237.44287.9338.75S5-7308.9234.99308.7236.10 46

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TableA-9. Erroranalysisdata,forFOV-5andFOV-6. ChannelIDFOV-5M1/PixelM2/PixelFOV-6M1/PixelM2/Pixel MS8-1467.9461.82466.2258.97MS8-2470.1840.21469.1838.58MS8-3463.5574.52472.0567.48MS8-4450.4571.13449.1472.00MS8-6568.8362.00459.8162.30MS8-7479.4649.97471.6841.16MS8-8466.1863.22471.9955.74S8-1445.6274.71354.6472.19S8-3467.0368.43464.8875.89S5-1267.7738.12269.6638.25S5-3292.5939.95295.1639.97S5-4285.5631.91281.1936.76S5-5289.0038.90285.3938.18S5-6293.2236.03291.7536.91S5-7313.3331.74316.1731.91 47

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TableA-10. Erroranalysisdata,forFOV-7andFOV-8. ChannelIDFOV-7M1/PixelM2/PixelFOV-8M1/PixelM2/Pixel MS8-1469.6460.27468.5759.74MS8-2464.6335.32475.6233.27MS8-3465.5467.66456.3176.01MS8-4455.1870.58466.7666.41MS8-6471.3060.32480.3862.11MS8-7469.0248.02468.4051.98MS8-8459.5266.28466.1254.86S8-1451.6674.31444.4780.38S8-3465.7373.60455.3770.24S5-1268.7237.01265.1835.98S5-3296.2840.33299.8839.58S5-4282.8038.22298.2637.46S5-5279.6838.20291.6534.97S5-6294.6134.26291.6937.23S5-7307.4936.45310.0337.46 48

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TableA-11. Erroranalysisdata,forFOV-9andFOV-10. ChannelIDFOV-9M1/PixelM2/PixelFOV-10M1/PixelM2/Pixel MS8-1466.8365.07470.1161.57MS8-2472.2737.24467.2039.91MS8-3464.8865.22453.8276.37MS8-4458.2166.18462.0567.60MS8-6464.4062.29462.6962.18MS8-7473.4148.98478.2748.85MS8-8457.5169.80456.3965.99S8-1454.0670.01444.8972.19S8-3450.6375.77453.6965.45S5-1268.6738.53267.1037.46S5-3298.0643.30291.9640.43S5-4289.5239.24293.2438.48S5-5290.3738.26287.6836.37S5-6290.6635.20293.0437.12S5-7302.6535.52314.2333.42 49

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APPENDIXBDETAILEDEXPERIMENTPROCEDURE B.1DetailedExperimentProcedureStepOne:Mixture10gramsofsiliconeelastomerand1gramofsiliconeelastomercuringagent,duringthisprocess,ahugenumberofslightairbubbleswillappearinthemixture.StepTwo:Degasthesiliconemixtureat0.1torrfor15minutestoeliminatealloftheairbubblesinthemixture.StepThree:Duringtheprocessofdegassing,prepareacontainerforPDMSmixturewithasilicawaferandapieceofaluminafoil.StepFour:Afterfullydegassing,PDMSmixtureispouredintothecontainerdescribedinStepThree,thisstepshouldbedonewithcaretoavoidanypossibleoccurrenceofairbubbles.StepFive:Begintoheatthecontainerat50ConahorizontalatafterPDMSmixtureisfullyspreadoutonsilicawafer.Thisprocessmighttake20minutestoaslongas80minutes,dependingonenvironmentaltemperature,beforecriticaltimeisreached.StepSix:Whilewaitingforcriticaltime,takesquaremicrocapillaryontoapieceofmicroscopicslide.Atcriticaltime,useaspoontodipalittlePDMSviscousliquid,whichhelpstostickmicrocapillary.Stickamicrocapillarywiththespoon,carefullyputthemicrocapillaryonthethesurfaceofPDMS.RepeatthestepforthreetofourtimestohavethreetofourmicrocapillariesembeddedonthesurfaceofPDMSelastomer.StepSeven:KeepthePDMSelastomeratroomtemperatureovernight,carefullypeelPDMSwithmicrocapillaryoutfromsilicawaferandputitonamicroscopicslide.StepEight:UsemicroscopetoseekforinterfaceofairandPDMSinsidemicrocapillaryandcutthemicrocapillaryatapositionthatisbehindtheinterface.CutextraPDMSoffandconnectmicrocapillaryandtubingtogether. 50

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StepNine:Sealtheconnectionbetweenmicrocapillaryandtubingwithsilicone,keepthechipatroomtemperatureovernight.StepTen:Testtightnessoftheconnectionbypumpingwaterinthechip. B.2ProductCategoryInthissection,onlymicrouidicdeviceswith80mmareshown,astheappearanceofboth50-mmand80-mmarealmostthesame. 51

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FigureB-1. Microuidicdevicewithplastictubing.Themostsimplemicrouidicdeviceinthiswork.Thiskindofdeviceistherstinventedandcanbeusedformicrosphereimaging,whichhelpstounderstandpropertiesofsilicamicrocapillaryandmicrouidicdevices. 52

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FigureB-2. Microuidicdevicewithmataltubing.Themetaltubingconnectedtosilicamicrocapillarywasaddedastwoelectrodesthathelpstoprovidestableelectricaleldinsidesilicamicrocapillary. 53

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FigureB-3. Microuidicdevicewithcopperwiretwinedmetaltubing.Twocopperwiresweretwinedontwoelectrodesofthisdevice,thisimprovementmakeiteasytoestablishastableelectricaleldascopperwiresareexibleandeasytoconnecttoanyelectrodes. 54

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BIOGRAPHICALSKETCH XuhuiFengwasborninShijiazhuang,HebeiProvinceinP.R.China,wherehespenthisrst19years.OnSeptemberof2007,helefthishomecitytoBeijingtostudyforhisbachelor'sdegreeinappliedchemistryatBeijingUniversityofChemicalTechnology.Aftergraduatingwithhisbachelor'sdegreein2011,hejoinedtheUniversityofFloridainGainesvilleforhismaster'sdegreeinchemicalengineering.HisresearchisfocusedonfabricationofmicrouidicdevicesHewasadvisedbyDr.JasonE.Butler. 58