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1、ARTICLEpubs.acs.org/LangmuirAreSuperhydrophobicSurfacesBestforIcephobicity?†,‡†‡§§StefanJung,MarkoDorrestijn,DominikRaps,ArindamDas,ConstantineM.Megaridis,and,†DimosPoulikakos*†LaboratoryofThermodynamicsinEmergingTechnologies,MechanicalandProcessEngineeringDepartment,ETHZurich,8092Zurich,Sw
2、itzerland‡Dept.IW-MS,EADSInnovationWorks,81663Munich,Germany§MechanicalandIndustrialEngineeringDepartment,UniversityofIllinoisatChicago,Chicago,Illinois60607,UnitedStatesbSSupportingInformationABSTRACT:Iceformationcanhavecatastrophicconsequencesforhumanact-ivityonthegroundandintheair.Herewe
3、investigatewaterfreezingdelaysonuntreatedandcoatedsurfacesrangingfromhydrophilictosuperhydrophobicandusethesedelaystoevaluateicephobicity.Supercooledwatermicrodropletsareinkjet-depositedandcoalesceuntilspontaneousfreezingoftheaccumulatedmassoccurs.Surfaceswithnanometer-scaleroughnessandhigh
4、erwettabilitydisplayunexpectedlylongfreezingdelays,atleast1orderofmagnitudelongerthantypicalsuperhydrophobicsurfaceswithlargerhierarchicalroughnessandlowwettability.Directlyrelatedtothemainfocusonheterogeneousnucleationandfreezingdelayofsupercooledwaterdroplets,theobservedensuingcrystalliza
5、tionprocessconsistedoftwodistinctphases:oneveryrapidrecalescentpartialsolidificationphaseandasubsequentslowerphase.Observationsofthedropletcollisionprocessemployedforthecontinuousliquidmassaccumulationuptothepointoficeformationrevealapreviouslyunseenatmospheric-pressure,subfreezing-temperatu
6、reregimeforliquid-on-liquidbounce.Onthebasisoftheentropyreductionofwaternearasolidsurface,weformulateamodificationtotheclassicalheterogeneousnucleationtheory,whichpredictstheobservedfreezingdelaytrends.Ourresultsbringtoquestionrecentemphasisonsuperwater-repellentsurfaceformulationsforiceform
7、ationretardationandsuggestthatanti-icingdesignmustoptimizethecompetinginfluencesofbothwettabilityandroughness.6,7’INTRODUCTIONdropletsplaceduponsubfreezingsurfacesandforsuper-5cooledwaterpouredontosurfaces.However,theimpactandThesafetyandperformanceofmode