简介：Wehavecarriedoutanexperimentalstudyofliquiddropimpactonsuperhydrophobicsubstratescoveredbyacarpetofchemicallycoatednano-wires.Themicro-structureofthesurfaceissimilartosomebiologicalones(Lotusleafforexample).Inthissituationthecontactanglecanthenbeconsideredasequalto180degrees,withnohysteresis.Duetoitsinitialinertia,thedropexperiencesaflatteningphaseafterithitsthesurface,takingtheshapeofapancake.Onceitreachesitsmaximallateralextension,thedropbeginstoretractandbouncesback.Wehaveextractedthelateralextensionofthedrop,andweproposeamodelthatexplainsthetrend.Wefindalimitinitialvelocitybeyondwhichthedropprotrudesintothenano-wirecarpet.Wediscusstherelevanceofpracticalissuesintermsofself-cleaningsurfacesorspray-cooling.

简介：Twenty-ninespeciesofbutterflieswerecollectedforobservationanddeterminationofthewingsurfacesusingaScanningElectronMicroscope(SEM).Butterflywingsurfacedisplaysstructuralanisotropisminmicro-,submicro-andnano-scales.Thescalesonbutterflywingsurfacearrangelikeoverlappingrooftiles.Therearesubmicrometricverticalgibbosities,horizontallinks,andnano-protuberancesonthescales.First-incline-then-dripmethodandfirst-drip-then-inclinemethodwereusedtomeasuretheSlidingAngle(SA)ofdropletonbutterflywingsurfacebyanopticalContactAngle(CA)measuringsystem.Relativelysmallerslidinganglesindicatethatthebutterflywingsurfacehasfineself-cleaningproperty.SignificantlydifferentSAsinvariousdirectionsindicatetheanisotropicself-cleaningpropertyofbutterflywingsurface.TheSAsonthebutterflywingsurfacewithoutscalesareremarkablylargerthanthosewithscales,whichprovesthecrucialroleofscalesindeterminingtheself-cleaningproperty.Butterflywingsurfaceisatemplatefordesignandfabricationofbiomimeticmaterialsandself-cleaningsubstrates.Thisworkmayofferinsightsintohowtodesigndirectionalself-cleaningcoatingsandanisotropicwettingsurface.

简介：Thecontactanglesofdistilledwaterandmethanolsolutiononthewingsofbutterfliesweredeterminedbyavisualcontactanglemeasuringsystem.Thescalestructuresofthewingswereobservedusingscanningelectronmicroscopy,Theinfluenceofthescalemicro-andultra-structureonthewettabilitywasinvestigated.Resultsshowthatthecontactangleofdistilledwateronthewingsurfacesvariesfrom134.0°to159.2°.Highhydrophobicityisfoundinsixspecieswithcontactanglesgreaterthan150°.Thewingsurfacesofsomespeciesarenotonlyhydrophobicbutalsoresistthewettingbymethanolsolutionwith55%concentration.OnlytwospeciesinParnassiuscannotresistthewettingbecausethemicro-structure(spindle-likeshape)andultra-structure(pinnule-likeshape)ofthewingscalesareremarkablydifferentfromthatofotherspecies.Theconcentrationofmethanolsolutionfortheoccurrenceofspreading/wettingonthewingsurfacesofdifferentspeciesvariesfrom70%to95%.Afterwettingbymethanolsolutionfor10min,thedistilledwatercontactangleonthewingsurfaceincreasesby0.8°-2.1°,showingthepromotionofcapacityagainstwettingbydistilledwater.

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简介：Thispaperpresentsamoleculardynamicssimulationofthebehavioursofnon-polardropletsmergingandalsothefluidmoleculesinteractingwithahydrophobicsurface.Suchbehavioursandtransportphenomenaarepopularingeneralmicro-channelflowboilingandtwo-phaseflow.ThedropletsareassumedtobecomposedofLennards-Jonestypemolecules.Periodicboundaryconditionsareappliedinthreecoordinatedirectionsofa3-Dsystem,wherethereexisttwoliquiddropletsandtheirvapour.Thetwodropletsmergewhentheycomewithintheprescribedsmalldistance.Themergingoftwodropletsapartfromeachotheratdifferentinitialdistancesistestedandthepossiblelarger(orcritical)non-dimensionaldistance,inwhichdropletsmergingcanoccur,isdiscussed.TheevolutionofthemergingprocessissimulatednumericallybyemployingtheMolecularDynamics(MD)method.Forinteractionswithhydrophobicsolidwall,asystemwithfluidconfinedbetweentwowallsisusedtostudythewettingphenomenaoffluidandsolidwall.Theresultsarecomparedwiththoseofhydrophilicwalltoshowtheuniquecharacteristicsofhydrophobicinteractionsbymicroscopicmethods.

简介：Themicromorphologiesofsurfacesofseveraltypicalplantleaveswereinvestigatedbyscanningelectronmicros-copy(SEM).Differentnon-smoothsurfacecharacteristicsweredescribedandclassified.Thehydrophobicityandanti-adhesionofnon-smoothleafsurfaceswerequantitativelymeasured.Resultsshowthatthemorphologyofepidermalcellsandthemor-phologyanddistributiondensityofepicuticularwaxdirectlyaffectthehydrophobicityandanti-adhesion.Thesurfacewithuniformlydistributedconvexunitsshowsthebestanti-adhesion,andthesurfacewithregularlyarrangedtrellisunitsdisplaysbetteranti-adhesion.Incontrast,thesurfacewithrandomlydistributedhairunitsperformsrelativelybadanti-adhesion.Thehydrophobicmodelsofpapilla-ciliaryandfold-setalnon-smoothsurfacesweresetuptodeterminetheimpactsofgeometricparametersonthehydrophobicity.Thisstudymayprovideaninsightintosurfacemachinemoldingandapparentmorphologydesignforbiomimeticsengineering.

简介：Bionicnon-smoothsurfaces(BNSS)canreducedrag.Muchattentionhasbeenpaidtothemechanismofshearstressreductionbyriblets.Themechanismofpressureforcereductionbybionicnon-smoothsurfacesonbodiesofrevolutionhasnotbeenwellinvestigated.InthisworkCFDsimulationhasrevealedthemechanismofdragreductionbyBNSS,whichmayworkinthreeways.First,BNSSonbodiesofrevolutionmaylowerthesurfacevelocityofthemedium,whichpreventsthesuddenspeedupofaironthecrosssection.Sothebottompressureofthemodelwouldnotbedisturbedsharply,resultinginlessenergylossanddragreduction.Second,themagnitudeofvorticityinducedbythebionicmodelbecomessmallerbecause,duetothesculpturing,thegrowthoftinyairbubblesisavoided.Thusthelargemomentofinertiainducedbylargeairbubbleisreduced.Thereductionofthevorticitycouldreducethedissipationoftheeddy.Sothepressureforcecouldalsobereduced.Third,thethicknessofthemomentumlayeronthemodelbecomeslesswhich,accordingtotherelationshipbetweenthedragcoefficientandthemomentumthickness,reducesdrag.

简介：Thebodysurfaceofsomeorganismshasnon-smoothstructure,whichisrelatedtodragreductioninmovingfluid.Toimitatethesestructures,modelswithanon-smoothsurfaceweremade.Inordertofindarelationshipbetweendragreductionandthenon-smoothsurface,anorthogonaldesigntestwasemployedinalowspeedwindtunnel.Sixfactorslikelytoinfluencedragreductionwereconsidered,andeachfactortestedatthreelevels.Thesixfactorsweretheconfiguration,diameter/bottomwidth,height/depth,distribution,thearrangementoftheroughstructuresontheexperimentalmodelandthewindspeed.Itwasshownthatthenon-smoothsurfacecausesdragreductionandthedistributionofnon-smoothstructuresonthemodel,andwindspeed,arethepredominantfactorsaffectingdragreduction.Usinganalysisofvariance,theoptimalcombinationandlevelswereobtained,whichwereawindspeedof44m/s,distributionofthenon-smoothstructureonthetailoftheexperimentalmodel,theconfigurationofriblets,diameter/bottomwidthof1mm,height/depthof0.5mm,arrangedinarhombicformation.Attheoptimalcombinationmentionedabove,the99%confidenceintervalfordragreductionwas11.13%to22.30%.

简介：Lasermultipleprocessing,i.e.lasersurfacetexturingandthenLaserShockProcessing(LSP),isanewsurfaceprocessingtechnologyforthepreparationofbionicnon-smoothsurfaces.Basedonengineeringbionics,samplesofbionicnon-smoothsurfacesofstainlesssteel0Crl8Ni9weremanufacturedintheformofreseaustructurebylasermultipleprocessing.Themechanicalproperties(includingmicrohardness,residualstress,surfaceroughness)andmicrostructureofthesamplestreatedbylasermultipleprocessingwerecomparedwiththoseofthesampleswithoutLSPTheresultsshowthatthemechanicalpropertiesofthesesamplesbylasermultipleprocessingwereclearlyimprovedincomparisonwiththoseofthesampleswithoutLSPThemechanismsunderlyingtheimprovedsurfacemicrohardnessandsurfaceresidualstresswereanalyzed,andtherelationsbetweenhardness,comnressiveresidualstressandroughnesswerealsopresented.

简介：Fivekindsof45#steelsampleswithconcavefeaturesonthesurfaceweremanufacturedusingLaserTexturingTechnology(LTT).Optimumdesigntheorywasusedtodesigntheexperiment,andatwo-levelorthogonaltable-L16(215)designwasadopted.Micro-wearandmicro-frictionexperiencedbysampleswithconcavesurfacefeaturesandsampleswithsmoothsurfaceswerecomparedexperimentally.Thewearresistanceofsampleswithconcavesurfacefeatureswasincreasedmost,anddifferentsurfacemorphologieshaddifferenteffectsonfrictionandwearproperties.