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:200512,:200653(No.05JC14019)33e2mail:qhlu@sjtu.edu.cn333(200240),,,,:O64715:A:10052281X(2006)1121425209AdvanceofWettingBehaviorResearchontheSuperhydrophobicSurfacewithMicro2andNano2StructuresXuJianhaiLiMeiZhaoYanLuQinghua33(SchoolofChemistryandChemicalTechnology,ShanghaiJiaoTongUniversity,Shanghai200240,China)AbstractInthispaper,advanceofwettingbehaviorresearchonthesuperhydrophobicsurfacewithmicro2andnano2structuresisreviewed,includingfabricationmethodsofsuperhydrophobicsurfaceswithmicro2andnano2structures,influenceofthemicro2andnano2structuresonwettingbehavior,superhydrophobiccriterionsofsurfaceswithperiodicstructures,contactanglehysteresisandfunctionalizationofsuperhydrophobicsurfaces.Problemsexistedinthisresearchfieldandpossibleprospectsofsuperhydrophobicsurfacewithmicro2andnano2structuresarediscussed.Keywordscontactangle;superhydrophobicsurfaces;surfaceswithmicro2andnano2structures;contactanglehysteresis1,150[13],,160,,(lotuseffect)2070,,2004Nature[4],,[5,6][7][8],[6,9,10]1811200611PROGRESSINCHEMISTRYVol.18No.11Nov.,2006,[11],,,,2:,,,,[12];2,,[13,14];(AKD,)[15];,[16];,[17];[18]P,(photolithographymethods)(non2photolithographymethods)[19],,250nm,(193nmArF157nmF2)100nm[20],,100nm,[21][22,23][24,25][26,27][28][29,30][31][32][33,34](softlithography)[19],,,,,[35,36][37,38][39][40][41],(PDMS),Sun[42]PDMS,,PDMS,,,Hosono[43](bottom2upprocess)2(brucite2typecobalthydroxide2laurate,BCH2LA)(1),178ab(FE2SEM),c(TEM),d[44](PTFE)93%97%190%,118165[45](layer2by2layerself2assemblytechnology),1(a,b)BCH2LAFE2SEM;(c)BCH2LATEM;(d)[43]Fig.1(a,b)FE2SEMimagesoftheBCH2LAfilmsobservedfromthetopandside,respectively;(c)TEMimagesoftheBCH2LAfilms;(d)Asimplemodelofthefilmwiththefractalstructure[43],[46]2(solvent-nonsolvent);2(PS2b2PDMS)624118,PDMS,[47]3311,,,()Wenzel[48]Cassie[49],Wenzel,(2a),,Wenzel:coswr=rcosewr,e,r()Wenzel,,,WenzelCassie,,(2b),,:coscr=scose+s-1cr,s2(a);(b)[2]Fig.2(a)Adropfillsthegroovesoftheroughsurface;(b)Thedropsitsonthecrestsoftheroughpatternformingacompositesurface[2]Jopp[50](replicationmoldingprocess)4(3),Wenzel[48]Cassie[49],,,,,,,34[50]Fig.3Sketchesofthefourtypesofmicrostructuresusedforthewettingexperiments[50]41mgrc,50m,100m[21]Fig.4Shapesof1mgwaterdropletsonpreparedpillarstructures,correspondingwatercontactangles,roughnessfactorsr,andpillarheightsc.Pillarwidthsare50mandgroovewidthsare100minallsamples[21]Yoshimitsu[21](4),,,,,,,,,724111Shiu[51],(5),,190nm,168,Cassie[52]560SEM(a)400nm,135,(b)360nm,144,(c)330nm,152,(d)190nm,168,1m[51]Fig.5SEMimages(60)ofthesize2reducedpolystyrenebeadsandthewatercontactanglemeasurementonthecorrespondingmodifiedsurfaces(insets).Thediametersofpolystyrenebeadsandwatercontactanglesonthesesurfacesweremeasured:(a)400nm,135,(b)360nm,144,(c)330nm,152,and(d)190nm,168.bar:1m[51][29],A(DMF),,(micro2nano2binarystructure),20%50%75%,132101541016118(6),,,,,,[53](LDPE)6(a)20%,(b)50%,(c)75%SEM,(d)(c)[29]Fig.6SEMimagesofcoatingscastatroomtemperaturewithdifferentRHof(a)20%,(b)50%,(c)75%.(d)sideviewofcoating(c)[29]LDPELDPELDPE,LDPE,,,LDPE,,25170215,119[54],,,170,,CH2(7),,7PVASEMPVA[54]Fig.7Cross2sectionalSEMimageoftheas2synthesizedPVAnanofibersandconformationmodesofthePVAmoleculesattheairPsolidinterface[54]Extrand[55]8824118,:,;,,,812:(a);(b)[55]Fig.8Asmallcircularpatchofmaterial2onasubstrateconsistingofmaterial1:(a)planview;(b)sideview[55],312Extrand:[1],[56]Extrand9,[1],c,:c=-gV1P3{[(1-cosa)Psina]{3+[(1-cosa)Psina]2}}2P3P[(36)1P3cos(a,0+-90)]a,V,a,0,,c,,,,;,c,,,9(xz):(a),yP2,,;(b),[1]Fig.9Schematicdepictionofasurfacecoveredbyahexagonalarrayofsquareasperitiesofwidthxandheightz:(a)Planview,thesquaregridhasalineardimensionofyP2,thedashedlinedefinesasingleunitcell,thecrosshatchedareasarethetopsoftheasperities;(b)Sideview,theanglesubtendedbythetopedgesoftheasperitiesis,andtheriseangleoftheirsidesis[1]10;d,z,2b,a,0,d[56]Fig.10Amagnifiedsideviewofasuspendedliquidprotrudingtoadepthd,betweentwomodelasperities.Theasperitieshaveaheightofzandamaximumdistancebetweenthemof2b.Theliquidexhibitsitstrueadvancingvalue,a,0onthesidesoftheasperities.distheanglebetweenthehorizontalplaneandtheprotrudingliquid[56]Yoshimitsu[57]Extrand[56]Zc,:Zc=btan[(a,0+-180)P2]b,,,c,d,Zd(ZZc)(10)924111Patankar[5],(11),,11:(a);(b);(c)[5]Fig.11Amodelroughnessgeometryfortheoreticalanalysis(a)Thefinescaleroughness:thefirstgeneration;(b)Thefinescaleroughnessformsthesurfaceofthecoarsescalepillars:thesecondgenerationofroughness;(c)Thepillargeometryatbothscalesisassumedperiodic[5]313,,,,,,,[58],[59,60],[61]Furmidge[61]:mgsin=kwlv(cosr-cosa)m,g,k,,ar,lv,,,,,Qur[63,64],,,,Yoshimitsu[57],,,,,12(a)L,D,(b)(a),(c)(b),,[65]Fig.12(a)SurfacetexturebasedonsquaresofsidelengthsDembeddedinasquarearrayofrepeatsizeL,(b)equivalenttextureto(a)butwithsidelengthandarraylengthhalved,and(c)afurtherhalvingofthedimensionsin(b).Ineachcase,thesolidsurfacefractionisthesame,whiletheperimeterdoubleseachtime,thedimensionsarehalved[65]Wenzel,,Cassie,McHale[65](12),,Wenzel,,,;Cassie,,,034118Wenzel,,Cassie,McCarthy[17],,Fang[66]Neumann2Good[67],13GibbsG2,G2G,,,1,5