Passive and Active Mixing in Microfluidic Devices

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1、Macromol.Symp.2009,279,201–209DOI:10.1002/masy.200950530201PassiveandActiveMixinginMicrofluidicDevicesHanE.H.Meijer,*MrityunjayK.Singh,TaeGongKang,JaapM.J.denToonder,PatrickD.AndersonSummary:InmicrofluidicstheReynoldsnumberissmall,preventingturbulenceasatoolformixing,whilediffusionisthatslo

2、wthattimedoesnotyieldanalternative.Mixinginmicrofluidicsthereforemustrelyonchaoticadvection,aswell-knownfrompolymertechnologypracticewhereonmacroscalethehighviscositymakestheReynoldsnumberslowanddiffusionslow.Themappingmethodisusedtoanalyzeandoptimizemixingalsoinmicrofluidicdevices.Weinvest

3、igatepassivemixerslikethestaggeredherringbonemicromixer(SHM),thebarrierembeddedmicromixer(BEM)andathree-dimensionalserpentinechannel(3D-SC).Activemixingisobtainedviaincorporatingparticlesthatintroduceahyperbolicflowine.g.twodimensionalserpentinechannels.Magneticbeadschains-upinaflowafterswi

4、tchingonamagneticfield.Rotatingthefieldcreatesaphysicalrotormovingtheflowfield.TheMasonnumberrepresentstheratioofviscousforcestothemagneticfieldstrengthanditsvaluedeterminesthefateoftherotor:asingle,analternatingsingleanddouble,oramultiplepartchain-rotorresults.Thetypeofrotordeterminesthemixin

5、gqualitywithbestresultsinthealternatingcasewherecrossingstreamlinesintroducechaoticadvection.Finally,anactivemixingdeviceisproposedthatmimicstheciliainnature.Thetransverseflowinducedbytheirmotionindeedenhancesmixingatthemicroscale.Keywords:BEM;cilia;magneticbeads;serpentine;SHMIntroduction

6、herringbonemixerandthebarrier-embeddedmixer.ThelastpassivemixerMostoftheefficientmicro-mixerspro-dealtwithisthe3DserpentinechannelthatposedinthelastdecadearebasedononlyfunctionsatReynoldsnumberslargerpressuredrivenflowsthatincludethethanone.Sometimesamoreactiveact-baker’stransformationaskno

7、wnfromtheuationmaybedesirablewiththeadvantageworkingprincipleofstaticmixersfre-thatbothflowandmixingcanbecontrolled,quentlyappliedindifferentpolymerpro-i.e.rangingfromalmostnomixingfromcessingoperations.Themechanismtointermediatelevelstocompletemixing.achieveeffectiv