简介：Itiswellknownthatsurfaceroughnesshasaveryimportanteffectonsuperhydrophobicity.TheWenzelandCassie-Baxtermodels,whichcorrespondtothehomogeneousandheterogeneouswettingrespectively,arecurrentlyprimaryinstructionsfordesigningsuperhydrophobicsurfaces.However,theparticulardropshapethatadropexhibitsmightdependonhowitisformed.Awaterdropcanoccupymultipleequilibriumstates,whichrelatetodifferentlocalminimalenergy.Insomecases,bothequilibriumstatescanevenco-existonasamesubstrate.Thustheapparentcontactanglesmayvaryandhavedifferentvalues.WediscusshowtheWenzelandCassie-Baxterequationsdeterminethehomogeneousandheterogeneouswettingtheoretically.Contactangleanalysisonhierarchicalsurfacestructureandcontactanglehysteresishasbeenputspecificattention.Inparticular,westudytheenergybarrieroftransitionfromCassie-BaxterstatetoWenzelstate,basedonexistingachievementbypreviousresearchers,todeterminethepossibilityofthetransitionandhowitcanbeinterpreted.Ithasbeendemonstratedthatsurfaceroughnessandgeometrywillinfluencetheenergyrequiredforadroptogetintoequilibrium,nomatteritishomogeneousorheterogeneouswetting.

简介：Whencharacterizingflowsinminiaturizedchannels,thedeterminationofthedynamiccontactangleisimportant.Bymeasuringthedynamiccontactangle,theflowpropertiesoftheflowingliquidandtheeffectofmaterialpropertiesontheflowcanbecharacterized.Amachinevisionbasedsystemtomeasurethecontactangleoffrontorrearmenisciofamovingliquidplugisdescribedinthisarticle.Inthisresearch,transparentflowchannelsfabricatedonthermoplasticpolymerandsealedwithanadhesivetapeareused.Thetransparencyofthechannelsenablesimagebasedmonitoringandmeasurementofflowvariables,includingthedynamiccontactangle.Itisshownthatthedynamicanglecanbemeasuredfromaliquidflowinachannelusingtheimagebasedmeasurementsystem.AnimageprocessingalgorithmhasbeendevelopedinaMATLAB?environment.Im-agesaretakenusingaCCDcameraandthechannelsareilluminatedusingacustommaderinglight.Twofittingmethods,acircleandtwoparabolas,areexperimentedandtheresultsarecomparedinthemeasurementofthedynamiccontactangles.