氧化锌纳米线阵列压电式纳米压电发电机

ZnONanowireArrayPiezoelectricNanogeneratorOutlineIntroductionPiezoelectricityPiezo-:derivedfromGreekmeaningpressorsqueezeElectricitygenerationbymechanicalstressReversibleDirectPZeffectandconversePZeffectFirstdemonstrationbyPierreCurieandJacquesCuriein1880inthecourseofstudyingforpyroelectricityGoverningequation:E=ε/dwhereE:electricfieldε:straind:PZcoefficient://resources.edb.gov.hk/physics/articleIE/smartmaterials/SmartMaterials_e.htmPiezoelectricGeneratorHarvestsenergyusingPZeffectExample“CrowdFarm”–electricitygenerationfromhumanfootstepsinplacessuchastrainstations1LightflickeringshownonYouTube1Wright,SarahH(2007-07-25).MITduoseespeople-poweredCrowdFarm.MITnews.MassachusettsInstituteofTechnologyBiologicalapplication:In-situreal-timemonitoringnanosensorsandnanorobotsAllowsself-poweredPiezoelectricnanogeneratorusingzincoxidenanowirearraysAdvantageouspropertiesofZnOPiezoelectricSemiconductiveBiologicallysafeandbiocompatibleDiverseandabundantNano-applicationsNWs,Nanobelts,Nanosprings,nanorings,nanobows,nanohelicesSchottkybarrierbetweenthemetalandZnOFabricationofNanoarraysZnONanowiresgrownoncplane-orientedα-Al2O3usingAuasacatalystbyvapor-liquid-solid(VLS)processAllZnONWsareverticallyalignedSinglecrystalanduniformNWgrowsalongthe[0001]direction{01-10}surfaceonthesideAuevaporatesduringthegrowthorremovedbythetipoftheatomicforcemicroscope(AFM)duringscanningNanowiresareplacedverticallyonAgplateandgroundedSEM(left)andTEM(right)imageWang.Z.L.,et.al.MeasurementMethodZnOnanowiremovedbyAFMtipandstrainedTensileonoutersurfaceCompressiveoninnersurfaceAFMtipisPtcoveredSiconeat70°Electricfieldalongthez-directionwithintheNWiscreatedduetothePZeffectPZfielddirectionisparalleltothezaxisattheoutersurfaceandantiparalleltothezaxisattheinnersurfaceAFMscanoverthenanowireWang.Z.L.,et.al.ResultsSimulatedstraincontourandSchottkyeffectWang.Z.L.,et.al.ResultsMeasuredPZeffectAveragepeakheight:~6to9mVPeakdensity:~8/µm2(capturedbyAFM)Nanowiredensity:~20/µm2Efficiency:~8/20≈40%(withscanningAFMtip)Wang.Z.L.,et.al.ResultsPowergeneration~0.5pWpertipx20/µm2≈10pW/µm2ANWarrayofsize10µmx10µmwouldyieldappreciablepowerforanano-device(~1nW)ChangingtheMaterialDirect-writepiezoelectricpolymericnanogeneratorwithhighenergyconversionefficiencyInplaceofZnO,Polyvinylidenefluoride(PVDF)usedAdvantagesHigherflexibilityReducedphysicalresistanceGoodPZChemicalstabilityDisadvantagesα-,β-,andγ-crystallinephasesexistβ-PVDFisusedforbestPZeffectMustbemechanicallystretchedandelectricallypoledChangingthematerialMethodDirectlywrittenbynear-fieldelectrospinning(NFES)toproducenanofibersonsubstratewithinsitumechanicalstretchingandelectricalpolingChang,C.,et.al.ChangingthematerialResults5-30mVat0.5-3nA=2.5-90pWEnergyconversionefficiency~12.5%average~21.8%peakChang,C.,et.al.ReferencesWang,Z.L.,Song,J.,PiezoelectricNanogeneratorsBasedonZincOxideNanowireArrays.Science,2006,312(5771),242-246.Chang,C.,Tran,V.H.,Wang,J.,Fuh,Y.,Lin,L.,Direct-WritePiezoelectricPolymericnanogeneratorwithHighEnergyConversionEfficiency.NanoLetters,2010,10,726-731.Questions?G6Rebuttal:PiezoelectricityJungHwanWooComments•Thankyouallforconstructivecomments.Iwillworkhardertoprovidefutureresearchsuggestionsandtoincludemorecurrentresearchbeingcarriedout.Iwillalsoincludesuggestionstohowtheexperimentisperformedtoimprovetheresults.Q&A•Q:Whysolittleadvanceinthetopicfrom2006-2010(judgingforthepresentation)?Thereisafundamentalobstacle?Haveothernanoarraysbetested?Isthisthebestalternativetoharvestenergyatthenanoscale?•A:Ibelievethatthelimitationcomesfromthenatureofthematerial.Thepiezoelectricitycanonlyyieldlittlepowerperarea.Increaseinthedimensionofthearraycouldyieldhigherpowerbutitwilleliminatethesegeneratorsfornanotechnologicaluse.However,itiscertainthatthismethodisoneofthebetterwaystoharvestenergyfornanorobotsastheexternalpowersourceiscompletelyeliminated.•Q:Istheonlyworkdone?Aretheremanyotherpeopleworkingonthis?Wasthepresentedworkabreakthrough?•A:Thistopicisahotresearchtopicthesedays.Therearemanymorepapersoutthere,thoughtheSciencepaperwasabrightoriginalideathatsuggestednewstrategyinpoweringnano-devices.Q&A•Q:CouldyoubetterexplainwhycurrentismeasuredwhenAFMtipexertsstressonnanowiresandhowitismeasured?•A:Forafree-standingpiezoelectricnanowireunderstress,onesidewillbecompressivelystrainedandtheothertensilelystressed.Thisproducesaflowofelectroninaclockwise(orcounter-clockwise)directionina2Dmodel.Ifthereisasourceofelectron,inthiscasetheAFMtip,electronsfromthissourcewillbepulledtothesamedirectionastheelectronmovementsduetotheelectricfield.Atthesametime,AFMcouldalsomeasurethecurrentoutoftheAFMtip.G1PiezoelectricNanogeneratorReviewEdsonP.BellidoSosaThepresenterdescribethebasicconceptsaboutpiezoelectricityandhowthisphenomenonisbeingusedatmacro-scale.HealsodescribedwhyZnOisbeingusedforthisapplication.Heexplainedthesynthesisprocessandth