Abstract
Inthispaperwepresentanovelmicrofluidicchipcapableofcontinuous multi-sampleswitchingandinjectionforbio-analyticalapplications.The innovativedeviceintegratestwoimportantmicrofluidicphenomena,including hydrodynamicfocusingandvalvelessflowswitchinginsidemulti-ported microchannels.Themultiplesamplescanbepre-focusedtonarrowstreamsand canthenbecontinuouslyinjectedintodesiredoutletports. Inthisstudy,a theoreticalmodelbasedonthe‘flow-rate-ratio’methodisfirstproposedtopredict theperformanceofthemicrofluidicdevice.Then,asimplebutreliableone-mask micromachiningprocessisdevelopedtofabricatethepre-focusedM×Nflow switchonaquartzsubstrate.Themulti-sampleswitchingandinjectionisthen verifiedexperimentallywiththeuseofmicroscopicvisualizationofwatersheath flowsanddye-containingsampleflows.Theexperimentaldataindicatethatthe multi-sampleflowscanbehydrodynamicallypre-focusedandthenguidedintothe desiredoutletportspreciselybasedonrelativesheathandsampleflowrates.The datapredictedbytheproposedtheoreticalmodelarehighlyconsistentwiththe experimentalresults. Itisalsonotedthatthe‘pre-focusing’functionaddedprior tomulti-sampleflowswitchingiscrucialforprecisesampleinjection.Thenovel microfluidicchiphasgreatpotentialforhigh-throughputchemicalanalysis,cell fusion,fractioncollection,fastsamplemixingandmanyotherapplicationsinthe fieldofmicro-total-analysissystems.