外文翻译-实验室的一个显示器：使用液晶显示器（LCD）的新的微粒操纵平台

0外文文献Lab-on-a-display:anewmicroparticlemanipulationplatformusingaliquidcrystaldisplay(LCD)WonjaeChoiSe-HwanKimJinJangJe-KyunParkReceived:20June2006/Accepted:8September2006/Publishedonline:11October2006Springer-Verlag2006AbstractThispaperreportsanewportablemicrofluidicplatform,lab-on-a-display,thatmicroparticlesaremanipulatedbyoptoelectronictweezers(OET)onaliquidcrystaldisplay(LCD).TheOEThasbeenconstructedbyassemblingagroundlayer,aliquidchamber,andaphotoconductivelayer.Withoutlensoropticalalignments,theLCDimagedirectlyformsvirtualelectrodesonthephotoconductivelayerfordielectrophoreticmanipulation.Thelab-on-a-displaywasfirstrealizedbyaconventionalmonochromaticLCDmoduleandalightsourcebrighterthan5,000lux.Itwassuccessfullyappliedtotheprogrammablemanipulationof45mpolystyrenebeads;morethan100particlesweretransportedwithanopticalimage-drivencontrol,followingthemovingedgeoftheimageateverymoment.Theeffectsofbeadsizeandbiasvoltageonthemanipulationspeedwerealsoinvestigated.Duetotheportabilityandcompatibilityfordisposableapplications,thisnewplatformhaspotentialforprogrammableparticlemanipulationorchip-basedbioprocessingincludingcellseparationandbead-basedanalysis.KeywordsMicrofluidics,Lab-on-a-display，Liquidcrystaldisplay(LCD),Optoelectronic,tweezers,Dielectrophoresis,Particlemanipulation1IntroductionThemanipulationofbiologicalcellsandmicroparticlesplaysanimportantroleinmany1biologicalapplications(Verpoorte2003;DittrichandManz2006).Dielectrophoresis(DEP)isafavorablephenomenonforthemanipulationofvariousdielectricparticles(Hughes2002;Krupkeetal.2003;Washizuetal.1994).Generally,DEPutilizestheinteractionforcebetweennonuniformelectricfieldandtheinduceddipolemomentoftheparticle.Duetoitsabilitytohandlecellsorparticleswithoutanymodificationofthem,ithasbecomeoneofthemostattractivemanipulationtechniquesinamicrofluidicdeviceoralab-on-a-chip.Inrecentstudies,manyresearchgroupshaverevealedthedielectricpropertiesofpolystyrenemicrobeads(Abeetal.2004;ChoiandPark2005),DNA(LaoandHsing2005),bacteria(LiandBashir2002;Lagallyetal.2005),yeast(Perch-Nielsenetal.2003;DohandCho2005),leukocytes(Wangetal.2000),anderythrocytes(Minericketal.2003).Thedielectrophoreticforceisdescribedasfollows:whereaisthediameterofmicroparticle;m,permitivityofmedia;fCM,theClausius-Mossotifactor;*,complexpermittivity(*=-j/);,theconductivity;istheelectricfieldfrequency.AprogrammableDEPelectrodearrayhasbecomeoneofthekeyissuesinDEP-basedmanipulationtechniques.Manaresietal.(2003)reportedacomplementarymetal-oxide-semiconductor(CMOS)circuit-driventechnique.ItwasdemonstratedthattheprogrammableDEPmanipulatorwithindividuallyaddressabletwo-dimensionalelectrodearraycouldbeusedfortheparallelmanipulationsofbiologicalcellsandmicroscopicparticles.Sincetheactivatedelectrodepatternsaremovableandreconfigurable,ithasmanyadvantagessuchassingle-particleaddressingandselection,grap-and-dragmotion,parallelmanipulation,robustnessfromcloggingandchannel-lessstructure.However,ithasapotentialdrawbackfordisposableapplicationsduetohighmanufacturingcost.Integrationofon-chipcircuitsincreasesthecostofthedevice,makingitlessattractivefordisposableapplications.2Todealwiththisdrawback,optoelectronictweezers(OET)wereproposedbyreplacingthepatternedelectrodeswithapattern-lessphotoconductivelayer(Chiouetal.2005).Intheirapproach,light-inducedvirtualelectrodesonaphotoconductivelayerwereusedtomakeaDEPforcebyusingthetransmittedlightsignalgeneratedfromadigitalmicro-mirrordevice(DMD).Thistechniqueispotentiallyusefulforbiomedicalapplications,becausetheOETpartcanbeusedasadisposablecartridge-typeforsamplehandling.TheonlyelectricalconnectionsfortheOETpartwouldbetwowirestosupplyanACbias.However,theopticalstructureforDMDprojectionleadstodifficultiesinportableapplications.Thereflectivestructureresultedincomplexstructure.Additionally,theopticallensbetweenDMDandOETrequiresopticalalignmenttofocustheprojectedimageonthephotoconductivelayer.Thispaperaimstodemonstrateanewlab-on-a-displayplatformformicroscopicparticlemanipulationusinganewopticalstructure.UnliketheprojectiondisplaymethodbasedonDMD,weutilizedirectimagetransferonaliquidcrystaldisplay(LCD).Alab-on-a-displayhasnoopticalcomponentbetweendisplay(LCD)andOET,thustheOETpartisjustplacedonthedisplaydevice.Duetotheeliminationoflensandopticalalignment,itwouldbemoresuitableforportableapplications.Inaddition,thisplatformisrelativelythinandtoleranttovibrationsinrealworldapplication.Inthisstudy,thelab-on-a-displaywasfirstrealizedbyaconventionalmonochromaticLCDmodule.Priortoconductingthemanipulationofmicroparticles,thefeasibilityofthelab-on-a-displaywasevaluatedbyelectricalfieldsimulation.WehavealsoinvestigatedvariousOETpropertieswhichdependonthelightsource,theLCDtype(colorormonochromatic),biasvoltage,andmicroparticlesize.Detailedexperimentalproceduresandresultsofthelab-on-a-displayprototypearereportedherein.2Materialsandmethods2.1Designandmicrofabricationofalab-on-a-displayFigure1showstheschematicconfigurationofalab-on-a-display,whichhasanOETpartonthetopofaLCD.IntheOET,theliquidcontainingmicroparticlesissandwiched3betweenthephotoconductivelayerandthegroundlayer.WhenanACbiasvoltageisappliedbetweentwolayers,theLCDrepresentsanimageandtransmitsittothephotoconductivelayer.Consequently,theimageformsvirtualelectrodesonthesurfaceofphotoconductivelayer,resultinginanelectricfieldgradientintheliquid.Thiselectricfieldgradientgeneratesdipolemomentsofneutralparticles,whichcausesaDEPforceformicroparticlemanipulation.Thetransparentandconductivegroundlayerwasanindiumtinoxide(ITO)layer.Glasssubstratescoatedwitha180nmthickITOlayerwerepurchasedfromSamsung-CorningPrecisionGlass(Asan,Korea).Afterdicinginto37.5mm25.0mmsize,awrappingwirewasconnectedforbiasingasagroundlayer.Thephotoconductivesurfaceonaglasssubstratewascomprisedoffourlayers:a180-nm-thickITOlayer,a50-nm-thickn+dopedhydrogenatedamorphoussilicon(n+a-Si:H)layer,a1-m-thickintrinsichydrogenatedamorphoussiliconlayer(intrinsica-Si:H,photocon-ductor),anda20-nm-thicksiliconnitride(SiNx)layer(Table1).Triplelayersofn+a-Si:H,intrinsica-Si:H,andSiNxwereconsecutivelydepositedbyplasmaenhancedchemicalvapordeposition(PECVD)methodonanITO-coatedglasssubstrateinasinglechamberreactor.Then+a-Si:Hwasdepositedfromagasratioof1.5%PH3inSiH4andthenintrinsica-Si:Hwasdepositedfromagasmixtureof20%SiH4/He=300sccmandH2=100sccmat280oC.TheSiNxlayerwasdepositedbyaSiH4,NH3andN2mixture.Then,someregionswereetchedbyreactiveionetch(RIE)toexposetheITOlayerforbiasconnections.Afterdicingthephotoconductivelayer,awirewasconnectedforbiasinglikethegroundlayer.4Fig.1Schematicofalab-on-a-display.Microparticles-containingliquidwassandwichedbetweenthemiddlephotoconductivelayerandthetopgroundlayer.AbottomLCDmakesanimageandtransmitsittothephotoconductivelayer.WhenanACbiasvoltageisappliedbetweenthephotoconductiveandthegroundlayers,thisimageformsvirtualelectrodesonthesurfaceofphotoconductivelayer,whichresultsintheelectricfieldgradientforDEPmanipulation2.2ExperimentalsetupAfilmmaskmadefromsilverhalideemulsiononapolyesterfilmsubstrate(Han&AllTechCo.,Ansan,Korea)wasusedasastaticimagepattern.TwotypesofLCDwereinvestigatedinthisstudy.AcolorLCD(8003480pixelarraywith100300-mpixelsize)waspickedoutfroma7-inLCDpanel(TX18D11VM1CAA;Hitachi,Japan).Itsdimensionswere102mminlengthand163mminwidth.ThethicknessofthecolorLCDwithoutbacklightandwithbacklightwas2and11mm,respectively.A1.3-inmonochromaticLCD(800600pixelarraywith33mpixelpitch)modulewastakenoutofaconventionalprojector(EMP-5300;Epson,Japan).Itsdimensionswere42mminlength,40mminwidth,and5mminthickness.TheLCDmodulewasoperatedbytheLCDdrivercircuitoftheprojector.TheimageareaoftheLCDmodulewas26.4mm19.6mm,andtheLCDimages5weredrawnbyusingstandardpresentationsoftware(MicrosoftPowerPointTM)onacomputer.Plainpolystyrenebeads(PolySciences,PA,USA)wereusedforparticlemanipulation.Thesamplewaspreparedbydilutionwithdeionizedwatertothefinalconcentrationofabout2.5105particles/mL.Asampledropletof5-7Lwassandwichedbetweenthegroundlayerandthephotoconductivelayerusingdouble-sticktapeasaspacer,ensuringtheliquidchamberof120mthick.Theelectricbiasvoltageproducedfromafunctiongenerator(MXG-9802A;SeowonFamilyCo.,KoreaorAGF3022;Tektronix,USA)wasappliedacrossthegroundlayerandthephotoconductivelayerofthelab-on-a-display.Themovementsofbeadswereobservedandrecordedusinganuprightmicroscope(ZeissAxioskop40;CarlZeiss,Germany)withacamera(Coolpix5400;Nikon,Japan).Weusedtwoilluminationofthemicroscope:oneforactuationandtheotherforobservation(Fig.2).Thedownsideilluminationwithhighintensitywasusedforactuation,i.e.,tocreatetheimageforvirtualelectrodes.Theupsideilluminationwithlowintensitywasusedforobservation,becauseitwasdifficulttoseeparticlesinadarkregionwithoutthisupsideillumination.Toinvestigatetheeffectsofbiasvoltageandbeadsizeonthebeadvelocity,werecordedthebeadmovementsandanalyzedthevideoimagesframebyframe.Thebeadspeedwascalculatedfromatleasttenbeads.6Fig.2Experimentalsetup.Theimagewasdrawnusingpresentationsoftware(MicrosoftPowerPoint)onacomputer.TheimageiselectronicallytransferredfromthecomputertotheLCDmodule.Themovementsofbeadswereobservedusinganuprightmicroscopewithtwoilluminations:oneforactuationandtheotherforobservation.Avoltageproducedfromafunctiongeneratorwasappliedacrossthegroundlayerandthephotoconductivelayer3Resultsanddiscussion3.1SimulationofelectricfielddistributionAsaproof-of-concept,wesimulatedanelectricfielddistributionintheliquidlayerofthelab-on-a-display.TheelectricfieldwascalculatedbyusingacommercialCFDsolver(CFD-ACE+;ESIUSR&DInc.,Huntsville,AL,USA)intheconditionof22VACbiasat100kHz.Becausethephotoconductivityofhydrogenatedamorphoussiliconphotoconductorwaslargerthanthedarkconductivityformorethanthreeordersofmagnitude(Ryuetal.2001),weassumedtheilluminatedregionandnon-illuminatedregionofphotoconductivelayerasaconductorandaninsulator,respectively.Figure3aisacross-sectionalviewoflab-on-a-displaywhentheLCDdisplaysanimage,7whichtheleftandrightsideoftheLCDisbrightanddark,respectively.Itwasnoticedthattheelectricfieldgradientwasrelativelylargeratthelocalizedregionaroundtheimageedge.SinceDEPforceisproportionaltothegradientofthesquareoftheelectricfield,theDEPforceattheedgesoftheimageisstrongerthanelsewhere.Therefore,particlescanmovefasterintheseregionsthanotherregions.InnegativeDEPcondition,microparticleswouldmoveinthedirectionfromtheilluminatedsidetothenon-illuminatedside(rightwarddirectioninthefigure).ThereisalsoaverticaldifferenceofDEPvelocity.Atthesamelateralposition,theparticlesatdifferentverticalpositionswouldmovewithdifferentvelocities;theparticlesnearthetopgroundlayer(e.g.,90mabovethephotoconductivelayer)wouldmoveslowerthanotherparticlesnearthephotoconductivelayer(e.g.,30mabove).Inordertotransporttheparticleacrossalongdistance,theLCDimageshouldbechangeddynamicallyaccordingtoaproperprogramsequence.Iftheimageisstatic,aparticlewouldmoveonlyforalimiteddistance.Foralongmovementtheimagepatternneedstobecontinuouslychangedbecauseatrappedparticlewouldmoveaccordingtotheedgeofmovingimage.Forexample,aparticlecanmovefromtheleftendtotherightendoftheliquidchamberiftheimageedgemovesfromthelefttotherightoftheLCD.Figure3bshowstheliquidlayersatthreesequentialmomentswhilethebrightimageextendsfromtheleftsidetotherightside.8Fig.3Distributionofthesquareoftheelectricheldintheliquidlayerofthelab-on-a-display.AAcross-sectionalviewoflab-on-a-displaywhenthephotoconductivelayerisilluminatedbyLCDimage,wheretheleftsideisbrightandtherightsideisdark.BSchematicviewsrepresentingtheliquidlayersatthreesequentialmomentswhilethebrightimageextendsfromtheleftsidetotherightside.TheelectricfieldwascalculatedbyusingCFD-ACE+,andtheDEPforceisproportionaltothegradientofthisdistribution.3.2Light-inducedvirtualelectrodegenerationThephotoconductivityofhydrogenatedamorphoussiliconwascharacterizedusingatestdevice,inwhichtwocoplanaraluminumelectrodeswerefabricatedonthehydrogenatedamorphoussiliconlayer(Fig.4a).Here,thedistancebetweenelectrodeswas360m,theelectrodewidthwas4.9mm,andtheintrinsica-Si:Hthicknesswas400nm.A9whitelightsourcewithuniformintensitywasusedforthemeasurement.Figure4bshowsthemeasuredphotoconductivityversuslightintensity.Thedarkconductivitywas1.0x10-9S/cm,whichwasincreasedbyalmost10,000timesunderilluminationoflightwithanintensityof20,000lux.Thisconductivitydifferencemakesthevirtualelectrodelight-induciblebecausetheconductivityofphotoconductivelayerintheilluminatedregionsismuchlargerthanthatinthenon-illuminatedregions.Thevirtualelectrodesareabletocreatenon-uniformelectricfieldstomanipulateparticlesbyDEPforces.FromtheresultshowninFig.4b,weselectedthelightintensityofmorethan5,000luxinordertoinducevirtualelectrodeseffectively.Toconfirmthegenerationofvirtualelectrodesonthefabricatedphotoconductivelayer,thelight-inducedDEPexperimentswereconductedusingastaticimagepatterncreatedbyafilmmask.Thebeadsinliquidlayerweresuccessfullymovedinthisexperiment(datanotshown).Fig.4Photoconductivitymeasurementofhydrogenatedamorphoussiliconlayer.aA10testdeviceusedforthemeasurementofphotoconductivityandbphotoconductivityversuslightintensityToinvestigatethegenerationofvirtualelectrodesusingcolorandmonochromaticLCDs,light-inducedDEPexperimentswerealsoconductedinasimilarway.InFig.5,theleftfiguresareschematicandtherightfiguresshowthetransmittedimagethroughtheglasssubstrate(theupperside)orthephotoconductivelayer(thelowerside).Atfirst,weutilizedthecolorLCDwithitsbacklight(Fig.5a).Therewasnovisiblepixelthroughthephotoconductivelayer,whileallpixelsthroughtheglasssubstratewerevisible.Thisresultindicatesthatthebacklightisweak,whichisnotintenseenoughtomakevirtualelectrodes.Therefore,weutilizedthecolorLCDwithanexternallightsource,makingtheilluminationintenseenoughtopassthroughthephotoconductivelayer(Fig.5b).Whenwhitelightwasilluminated,eachpixeloftheLCDrepresentedoneofthreecolors(red,green,andblue)duetocolorfiltersinsidetheLCD.Throughthephotoconductivelayer,however,onlyredpixelswerevisible.Thereasonwhyonlytheredlightamongthreecolorswasvisiblewasthoughttobethatthelightabsorptionthroughtheamorphoussiliconlayerdependsonitswavelength.Itseemsthattheredlightwithalongerwavelengthwasrelativelylessabsorbed.WhenanACvoltagewasapplied,thebeadsaroundthevisibleredpixelweremovedwiththedirectionawayfromtheredpixel(datanotshown).AlthoughtheLCDlight-inducedDEPwassuccessful,itwashardtoimplementthebeadmovementacrossseveralpixelssincetwothirdsofLCDpixels(greenandblue)didnotmakevirtualelectrodes.11InsteadofthecolorLCD,wethustestedamono-chromaticLCDmodulewhichhasnocolorfilter(Fig.5c).TheLCDimagewasvisiblethroughboththeglasssideandthephotoconductiveside,andthebeadsweretransportedbytheLCDlight-inducedDEP.Whenwhitelightwasilluminated,thecolorofbrightregionsthroughthephotoconductivesidewasalsored.Here,themonochromaticLCDgavetwoadditionalchangessuchasthereductionoftheLCDpixelsizeandunwantedimagepattern.Sincethepixelsizewasshrinkedfrom100m300mto33m33m,smallervirtualelectrodeswouldenablemoreprecisecontrolofposition.AsshowninFig.5c,theimagepattern(I)ontheLCDmodulewasnotthesamewiththeintendedimagepattern.Twopixelsineverysixpixelswerealwaysbrightanddark,respectively,whiletherestfourpixelsineverysixpixelswerecontrollableaccordingtotheprogrammedimagebyacomputer.Inaddition,thedarkpixelsoutoftheimagepatternwerevisibleasablackverticallinethroughthephotoconductivelayer;however,thebrightpixelsintheimagepatternwereinvisiblethroughthephotoconductivelayer.ThedifferenceofthismicroscopicimagepatternwasinferredtohaveitsoriginintheLCDdrivercircuits,becausetheimagewithout12microscopelookedliketheoriginaloncomputerscreen:theblackverticalfinesbythedarkpixelswereinvisible.Fig.5ComparisonofvirtualelectrodesusingvariousLCDs.Leftfiguresareschematicandrightfiguresshowthetransmittedimagethroughtheglasssubstrate(theupperside)orthephotoconductivelayer(thelowerside).aUsingcolorLCDwithitsbacklight,thelightintensityofLCDbacklightwasnotenoughtopassthroughthephotoconductivelayer.bUsingcolorLCDandexternallightsource,onlyredlightamongthreecolors(red,greenandblue)passedthroughthehotoconductivelayer.cWhilewhitelightwasilluminatedbymonochromaticLCDandexternallightsource,thecolorofilluminatedphotoconductiveregionwasred.3.3MicroparticlemanipulationusingdynamicLCDimagepatternAsademonstrationofalab-on-a-displaymanipulation,anumberof45mdiametersizebeadsweretransportedtofinallyformaletter.Thered(bright)imagewasmadeonthe22VACbias.During60s,theimagegraduallyappeared,finallymakingtheletterIof1.8mm2.4mminsize(Fig.6).Itwasobservedthatthebeadsfollowedthemovingedgeoftheimageateverymoment.UndernegativeDEPregime,particlesinthelab-on-a-displaytraveledfromthebrightregiontothedarkregion.Thesemovementswereoccurredatthelocalizedregionneartheedgeoflightpatternasexpectedinthesimulation.Aftercontinuoustransportationfor60s,morethan100beadsweregatheredtomakeanarrangementoftheletterIastheimageonLCD.Aftertheimagedisappeared(at65s),thebeadsstayedinthesameplaceandrepresentedthealphabetletter.Somebeadswerehardtomanipulatealthoughthemostofbeadsweremanipulatedaccordingtothemovingimageedgewithaspeedof7m/s.Possiblereasonsforthisphenomenonareexplainedasfollows:theverticaldifferencesofelectricfielddistributionandstickingofbeadtothesubstrate.1314中文翻译实验室的一个显示器：使用液晶显示器（LCD）的新的微粒操纵平台Wonjae彩世焕锦张JE-筠园收稿日期：2006年6月20日/接受日期：2006年9月8日在线/发布时间：2006年10月11日施普林格出版社2006摘要:报道了一种新型便携式微流体平台，“实验室的一个显示器”，即微粒的液晶显示器（LCD）上操纵光电镊子（OET）。该OET已构建通过组装一个接地层，液体腔室，和一个光电导层。不包括镜头或光学比对，LCD图像直接形成光导层的介电泳操纵虚拟电极。该实验室在一个显示器首次由一个传统的单色液晶显示模块和光源亮度超过5,000lux.It被成功地应用于可编程操控45微米的聚苯乙烯珠实现;超过100个颗粒被运送用光学图像驱动的控制，下面的图像中的每一个时刻的移动力。还研究珠尺寸和偏置电压上的操作速度的影响。由于便携性和兼容性为一次性应用，这个新平台有潜力的可编程粒子操纵或芯片为基础的生物处理，包括细胞分离和珠为基础的分析。关键词微流体，实验室在一个显示器，液晶显示器（LCD），光电，镊子，介电泳，粒子操纵1引言生物细胞和微粒的操纵中起着许多生物学应用（Verpoorte2003;迪特里希和2006曼茨）具有重要作用。介电电泳（DEP）是用于各种电介质粒子的处理有利的现象（2002休斯;Krupke等人，2003;。鹫津等人，1994）。通常，DEP利用非均匀电场和粒子的诱导偶极之间的相互作用力。由于它处理的细胞或颗粒没有它们的任何修改的能力，它已经成为在微流体装置或实验室在一个芯片上的最有吸引力的操作技术之一。在最近的研究中，许多研究小组已经发现聚苯乙烯微球的介电性能（Abeet人，2004年;彩和2005年公园），脱氧核糖核酸（老挝和Hsing2005），细菌（Li和巴希尔2002年Lagally等al.2005），酵母（鲈鱼-Nielsen等，2003;卫生署和Cho2005），白细胞（Wang等人2000），和红细胞（Minerick等人，2003）。介电电泳力的