Science-3D打印技术新发展

18.X.-G.Wang,T.CarringtonJr.,J.Chem.Phys.129,234102(2008).24.M.P.Deskevich,A.B.McCoy,J.M.Hutson,D.J.Nesbitt,

therawdataarearchivedattheUniversityofCologneand19.T.Oka,J.Mol.Spectrosc.228,635–639(2004).

J.Chem.Phys.128,094306(2008).

areavailableuponrequest.

20.HereJdenotestherotationalquantumnumbercomprising

end-over-endrotationRandinternalrotation.

ACKNOWLEDGMENTS

21.P.Bunker,B.Ostojić,S.Yurchenko,J.Mol.Struct.695–696,

WethankT.Carrington,P.Bunker,D.Nesbitt,P.Jensen,andSUPPLEMENTARYMATERIALS

253(2004).

U.MantheforfruitfuldiscussionsontheoreticalaspectsofCHwww.sciencemag.org/content/347/6228/1346/suppl/DC15+,22.HereweusethequantumnumberJinsteadofR,becausethe

aswellasJ.Kriegintheinitialstageoftheexperiment.SupportedMaterialsandMethodsrotationalmotioninthestateisnotpurelytheend-over-endbyDeutscheForschungsgemeinschaftgrantSCHL341/6-1.TablesS1andS2rotation.

WegratefullyacknowledgethesupportoftheworkshopsoftheReference(25)

23.M.Kolbuszewski,P.R.Bunker,J.Chem.Phys.105,39

I.PhysikalischesInstitut.Thetwolinelists(for10Kand4K)21November2014;accepted21January2015(1996).associatedwithFig.1areavailableassupplementarymaterial;10.1126/science.aaa3304

ADDITIVEMANUFACTURINGingsuctionforcesthatconstantlyrenewreactiveliquidresin.Thisnonstopprocessisfunda-Continuousmentallydifferentfromtraditionalbottom-upstereolithographyprinters,whereUVexposure,productionofliquid3Dobjectsinterfaceresinrenewal,andpartmovementmustbecon-ductedinseparateanddiscretesteps(fig.S2).Evenforinvertedtop-downapproachesinwhichphotopolymerizationoccursatanair-resinin-JohnR.Tumbleston,1DavidShirvanyants,1NikitaErmoshkin,1RimaJanusziewicz,2terface[i.e.,thepartissuccessivelyloweredintoAshleyR.Johnson,3DavidKelly,1KaiChen,1RobertPinschmidt,1JasonP.Rolland,1aresinbathduringprinting(16,19)],thesestepsAlexanderErmoshkin,1*EdwardT.Samulski,1,2*JosephM.DeSimone1,2,4*mustbeconductedsequentiallyfortheformationofeachlayer.Becauseeachsteptakesseveralsec-Additivemanufacturingprocessessuchas3Dprintingusetime-consuming,stepwiseondstoimplementforeachlayer,andbecauselayer-by-layerapproachestoobjectfabrication.Wedemonstratethecontinuousgenerationeachlayerofaparthasatypicalthicknessof50ofmonolithicpolymericpartsuptotensofcentimetersinsizewithfeatureresolutionto100mm,verticalprintspeedsarerestrictedtobelow100micrometers.Continuousliquidinterfaceproductionisachievedwithanafewmillimetersperhour(16).Bycontrast,theoxygen-permeablewindowbelowtheultravioletimageprojectionplane,whichcreatesaprintspeedforCLIPislimitedbyresincurerates“deadzone”(persistentliquidinterface)wherephotopolymerizationisinhibitedbetweenandviscosity(discussedbelow),notbystepwisethewindowandthepolymerizingpart.Wedelineatecriticalcontrolparametersandlayerformation.Forexample,thegyroidandar-showthatcomplexsolidpartscanbedrawnoutoftheresinatratesofhundredsofmillimetersgylestructuresshowninFig.1Bwereprintedatperhour.Theseprintspeedsallowpartstobeproducedinminutesinsteadofhours.500mm/hour,reachingaheightof~5cminlessAthan10min(moviesS1andS2).Anadditionaldditivemanufacturinghasbecomeause-caneitherquenchthephotoexcitedphotoinitia-benefitofacontinualprocessisthatthechoicefultechniqueinawidevarietyofapplica-tororcreateperoxidesbycombiningwiththeof3Dmodelslicingthickness,whichaffectsparttions,includingdo-it-yourself3Dprintingfreeradicalfromthephotocleavedphotoinitiatorresolution,doesnotinfluenceprintspeed,as(1,2),tissueengineering(3–5),materials(fig.S1).IftheseoxygeninhibitionpathwayscanshownintheramptestpatternsinFig.1C.Becauseforenergy(6,7),chemistryreactionwarebeavoided,efficientinitiationandpropagationofCLIPiscontinuous,therefreshrateofprojected(8),molecularvisualization(9,10),microfluid-polymerchainswillresult.Whenstereolithographyimagescanbeincreasedwithoutalteringprintics(11),andlow-density,high-strengthmate-isconductedaboveanoxygen-permeablebuildspeed,ultimatelyallowingforsmooth3Dobjectsrials(12–15).Currentadditivemanufacturingwindow,continuousliquidinterfaceproductionwithnomodelslicingartifacts.

methodssuchasfuseddepositionmodeling,(CLIP)isenabledbycreatinganoxygen-containingEstablishinganoxygen-inhibiteddeadzoneselectivelasersintering,andstereolithography“deadzone,”athinuncuredliquidlayerbetweenisfundamentaltotheCLIPprocess.CLIPuses(2,16)areinordinatelyslowbecausetheyrelythewindowandthecuredpartsurface.Weshowanamorphousfluoropolymerwindow(Teflononlayer-by-layerprintingprocesses.Amacro-thatdeadzonethicknessesontheorderoftensofAF2400)withexcellentoxygenpermeabilityscopicobjectseveralcentimetersinheightcanmicrometersaremaintainedbyjudiciousselection(1000barrers;1barrer=10–10cm3(STP)cmcm–2takehourstoconstruct.Foradditivemanufactur-ofcontrolparameters(e.g.,photonfluxandresins–1cmHg–1)(20),UVtransparency,andchemicalingtobeviableinmassproduction,printspeedsopticalandcuringproperties).Simplerelationshipsinertness.Deadzonethicknessmeasurementsmustincreasebyatleastanorderofmagnitudedescribethedeadzonethicknessandresincuringusingadifferentialthicknesstechnique(fig.S3)whilemaintainingexcellentpartaccuracy.Al-process,and,inturn,resultinastraightforwarddemonstratetheimportanceofbothoxygensup-thoughoxygeninhibitionoffreeradicalpolym-relationshipbetweenprintspeedandpartresolu-plyandoxygenpermeabilityofthewindowinerizationisawidelyencounteredobstacletotion.WedemonstratethatCLIPcanbeappliedtoestablishingthedeadzone.Figure2showsthatphotopolymerizingUV-curableresinsinair,wearangeofpartsizesfromundercutmicropaddlesthedeadzonethicknesswhenpureoxygenisshowhowcontrolledoxygeninhibitioncanbewithstemdiametersof50mmtocomplexhand-usedbelowthewindowisabouttwicethethick-usedtoenablesimplerandfasterstereolithography.heldobjectsgreaterthan25cminsize.

nesswhenairisused,withthedeadzonebecom-Typically,oxygeninhibitionleadstoincom-Figure1Aillustratesthesimplearchitectureingthinnerastheincidentphotonfluxincreasespletecureandsurfacetackinesswhenphoto-andoperationofa3Dprinterthattakesadvan-(seebelow).Whennitrogenisusedbelowthewin-polymerizationisconductedinair(17,18).Oxygen

tageofanoxygen-inhibiteddeadzone.CLIPpro-dow,thedeadzonevanishes.Adeadzonealso1Carbon3DInc.,RedwoodCity,CA94063,USA.2DepartmentceedsviaprojectingacontinuoussequenceofUVdoesnotformwhenTeflonAF2400isreplacedofChemistry,UniversityofNorthCarolina,ChapelHill,NCimages(generatedbyadigitallight-processingbyamaterialwithverypooroxygenpermeability,27599,USA.3JointDepartmentofBiomedicalEngineering,imagingunit)throughanoxygen-permeable,UV-suchasglassorpolyethylene,evenifoxygenispre-UniversityofNorthCarolinaatChapelHillandNorthtransparentwindowbelowaliquidresinbath.sentbelowthewindow.WithoutasuitabledeadCarolinaStateUniversity.4DepartmentofChemicalandBiomolecularEngineering,NorthCarolinaStateUniversity,Thedeadzonecreatedabovethewindowmain-zone,continuouspartproductionisnotpossible.Raleigh,NC27695,USA.

tainsaliquidinterfacebelowtheadvancingpart.Forthecaseofambientairbelowthewindow,*Correspondingauthor.E-mail:alex@carbon3d.com(A.E.);Abovethedeadzone,thecuringpartiscontin-Fig.3Ashowsthedependenceofdeadzonethick-et@unc.edu(E.T.S.);desimone@email.unc.edu(J.M.D.)

uouslydrawnoutoftheresinbath,therebycreat-nessonincidentphotonflux(F0),photoinitiator

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140DZ Thickness (µm)120100806040200024681012x10152Photon Flux (#/s cm) Oxygen Air NitrogenFig.2.Thedeadzoneiscreatedbyoxygenper-meationthroughthewindow.Deadzonethick-nessisshownasafunctionofincidentphotonflux.Whenpureoxygenisusedbelowthegas-permeablewindow,thedeadzonethicknessincreases.Ifni-trogenisused,thedeadzonevanishes,resultinginadhesionofthecuredresintothewindow.ErrorbarsrepresentSDof10measurementsofthesameconditions.doesnotproduceradicals)butcontributestooverallresinabsorptionviaa=aPI+adye.Notethataistheinverseofthecharacteristicopticalabsorptionheight(hA)oftheresin:

Fig.1.CLIPenablesfastprintspeedsandlayerlesspartconstruction.(A)SchematicofCLIPprinterwherethepart(gyroid)isproducedcontinuouslybysimultaneouslyelevatingthebuildsupportplatewhilechangingthe2Dcross-sectionalUVimagesfromtheimagingunit.Theoxygen-permeablewindowcreatesadeadzone(persistentliquidinterface)betweentheelevatingpartandthewindow.(B)Re-sultingpartsviaCLIP,agyroid(left)andanargyle(right),wereelevatedatprintspeedsof500mm/hour(moviesS1andS2).(C)Ramptestpatternsproducedatthesameprintspeedregardlessof3Dmodelslicingthickness(100mm,25mm,and1mm).

hA¼

1að3Þ

absorptioncoefficient(aPI),andresincuringdosage(Dc0).Thesethreecontrolparametersarerelatedtodeadzonethicknessaccordingto󰀁󰀂F0aPI−0:5

Deadzonethickness¼C

Dc0

ð1Þ

whereF0isthenumberofincidentphotonsattheimageplaneperareapertime,aPIistheproductofphotoinitiatorconcentrationandthewavelength-dependentabsorptivity,Dc0quantifiestheresinreactivityofamonomer-photoinitiatorcombination(fig.S4),andCisaproportionalityconstant.Thisrelationshipissimilartotheonethatdescribesphotopolymerizableparticlefor-mationinmicrofluidicdevicesthatuseoxygen-permeablechannelwalls(21,22).Thedeadzonethicknessbehavesasfollows:IncreasingeitherF0oraPIincreasestheconcentrationoffreerad-icalsintheresin(fig.S1)anddecreasestheini-tialoxygenconcentrationbyreaction.Additionaloxygendiffusesthroughthewindowandintotheresinbutdecayswithdistancefromthewin-dow,sothatfreeradicalswilloverpowerinhib-itingoxygenatsomedistancefromthewindow.Atthethresholddistancewherealloxygeniscon-sumedandfreeradicalsstillexist,polymerizationwillbegin.Increasingthereactivityoftheresin(i.e.,decreasingDc0)causesthepolymerizationthresholddistancefromthewindowtoalso

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shrink,thusmakingthedeadzonethinner.TheproportionalityconstantCinEq.1hasavalueof~30forourcaseof100-mm-thickTeflonAF2400withairbelowthewindow,andhasunitsofthesquarerootofdiffusivity.Thefluxofoxygenthroughthewindowisalsoimportantinmain-tainingastabledeadzoneovertime,whichiscommonlydescribedintermsoftheratiooffilmpermeabilitytofilmthickness(23).Usingtheserelationshipsenablescarefulcontrolofthedeadzone,whichprovidesacriticalresinrenewallayerbetweenthewindowandtheadvancingpart.Abovethedeadzone,photopolymerizationoccurstoacertaincuredthicknessthatdependsonF0aPI/Dc0alongwithexposuretime(t)andtheresinabsorptioncoefficient(a)accordingtotherelationship

󰀁󰀂1F0aPIt

Curedthickness¼ln

aDc0

ð2Þ

ThevalueofhA,inconjunctionwiththemodel

slicingthickness(Fig.1C),projectedpixelsize,andimagequality,determinesthepartresolution.Theprojectedpixelsize(typicallybetween10and100mm)andimagequalityarefunctionsoftheimagingsetupanddeterminelateralpartreso-lution.Aswithslicingthickness,hAaffectsverticalresolutionbutisapropertyoftheresin.IfhAishigh,thenpreviouslycured2Dpatternswillcon-tinuetobeexposed,causingunintentionalover-curingand“print-through,”whichinturnresultsindefectsforundercutandoverhanggeometries.Fromtheexpressionsfordeadzonethick-nessandcuredthickness,asimplerelationshipamongprintspeed,hA(i.e.,resolution),andF0aPI/Dc0isderived:

SpeedF0aPI

º

Dc0hA

ð4Þ

Figure3Bshowscuredthicknessforthreedif-ferentresinswithvaryinga(holdingaPIconstant)

wherethicknessesweremeasuredfordifferentUVphotondosages(productsofF0andt)(fig.S3).Thesecurvesareakintotheso-called“work-ingcurves”usedinstereolithographyresinchar-acterization(16,19).Fortheseresins,aisvariedbyadjustingtheconcentrationofanabsorbingdyeorpigmentthatpassivelyabsorbslight(i.e.,

Corrected 23 March 2015; see full text.

(seesupplementarymaterials).Figure3CshowsacontourplotofspeedasafunctionofhAandtheratioF0aPI/Dc0;thedeadzonethickness(Eq.1)isindicated.ForagivenhA,speedcanbeincreasedbyincreasingF0oraPIorbyusingaresinwithlowerDc0.However,asspeedincreases,deadzonethicknessdecreasesandwilleventuallybecometoothinfortheprocesstoremainstable.ForCLIP,theempiricallydeterminedminimumdeadzonethicknessis~20to30mm.Partpro-ductionwithadeadzonethicknessbelowthisminimumispossiblebutcanleadtowindowadhesion–relateddefects.Oncetheminimumdeadzonethicknessisreached,theprintspeedcanonlybeincreasedbyrelaxingtheresolution(i.e.,usingaresinwithhigherhA).

sciencemag.orgSCIENCE

RESEARCH|REPORTS

Fig.3.Atradeoffexistsbetweenprintspeedandpartresolution.(A)Liquidinterfacedeadzone(DZ)thicknessasafunctionofF0aPI/Dc0.Theseparametershavetypicalranges:5×1014cm−2s–1Fig.4.AvarietyofpartscanbefabricatedusingCLIP.(A)Micropaddleswithstems50mmin

diameter.(B)EiffelTowermodel,10cmtall.(C)Ashoecleat>20cmin

length.Eveninlargeparts,finedetailisachieved,asshownintheinsetof(B)wherefeatures<1mminsizeareobtained.Themicropaddleswere

printedat25mm/hour;theEiffelTowermodelandshoecleatwereprintedat100mm/hour.

Thisanalysisshowsthatforadeadzonethick-nessof20mm,speedsinexcessof300mm/hourwithhA=100mmareaccessible.ByincreasinghAto300mmandsacrificingresolution,speedsgreaterthan1000mm/hourarereadilyachieved.ThetradeoffbetweenspeedandresolutionisdemonstratedinFig.3DwithresolutiontestpatternsusingtheresinswithdifferenthAfromFig.3B(allhaveequivalentF0aPI/Dc0anddeadzonethickness).Asdyeloadingisincreased,hAisreduced,leadingtolessprint-throughandul-timatelyhigherresolution.However,dyeabsorp-tiondoesnotproducefreeradicals,soresinswithlowerhArequiregreaterdosagestoade-quatelysolidify;thatis,partsmustbeelevatedmoreslowlyforconstantphotonflux.Ontheotherhand,theresinwithoutdyeandwiththehighesthAcanbeprintedatthegreatestspeedbutwithpoorresolution(asshownbyuninten-tionalcuringoftheoverhangsinthetestpattern).Usingthisprocesscontrolframework,Fig.4showsanarrayofexpedientlyproducedpartsrang-inginsizefromundercutmicropaddleswithstemdiametersof50mm(Fig.4A)tofull-sizeshoecleats25cminlength(Fig.4C).TheEiffelTowermodelinFig.4Billustratesthatfinedetailisachievedeveninmacroscaleparts:Thehorizon-talrailingposts(diameter<500mm)areresolvedonthis10-cm-tallmodel.Thisratioofscales(1:200)confirmsthattheCLIPprocessenablesrapidproductionofarbitrarymicroscopicfeaturesoverpartshavingmacroscopicdimensions.Fortheseparts,thespeed-limitingprocessisresincuring(Eq.4);however,forotherpartgeometries,thespeed-limitingprocessisresinflowintothebuildarea.Forsuchgeometrieswithcomparativelywidesolidcrosssections,parametersthataffect

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resinflow(e.g.,resinviscosity,suctionpressuregradient)becomeimportanttooptimize.

PreliminarystudiesshowthattheCLIPpro-cessiscompatiblewithproducingpartsfromsoftelasticmaterials(24,25),ceramics(26),andbiologicalmaterials(27,28).CLIPhasthepoten-tialtoextendtheutilityofadditivemanufacturingtomanyareasofscienceandtechnology,andtolowerthemanufacturingcostsofcomplexpolymer-basedobjects.

REFERENCESANDNOTES

PALEOANTHROPOLOGYEarlyHomoat2.8MafromLedi-Geraru,Afar,EthiopiaBrianVillmoare,1,4,6*WilliamH.Kimbel,2*ChalachewSeyoum,2,7ChristopherJ.Campisano,2ErinN.DiMaggio,3JohnRowan,2DavidR.Braun,4JRamónArrowsmith,5KayeE.Reed2OurunderstandingoftheoriginofthegenusHomohasbeenhamperedbyalimitedfossilrecordineasternAfricabetween2.0and3.0millionyearsago(Ma).HerewereportthediscoveryofapartialhomininmandiblewithteethfromtheLedi-Geraruresearcharea,AfarRegionalState,Ethiopia,thatestablishesthepresenceofHomoat2.80to2.75Ma.ThisspecimencombinesprimitivetraitsseeninearlyAustralopithecuswithderivedmorphologyobservedinlaterHomo,confirmingthatdentognathicdeparturesfromtheaustralopithpatternoccurredearlyintheHomolineage.TheLedi-GerarudiscoveryhasimplicationsforhypothesesaboutthetimingandplaceoforiginofthegenusHomo.1.J.M.Pearce,Science337,1303–1304(2012).

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ACKNOWLEDGMENTS

ThisworkwassponsoredbyCarbon3DInc.J.R.T.,D.S.,N.E.,D.K.,R.P.,J.P.R.,A.E.,E.T.S.,andJ.M.D.allhaveanequitystakeinCarbon3DInc.,whichisaventure-backedstartupcompany.ContinuousliquidinterfaceprintingisthesubjectofpatentprotectionincludingPatentCooperationTreatypublicationnumbersWO2014/126837A2,WO2014/126830A2,andWO2014/126834A2,andothers.

SUPPLEMENTARYMATERIALS

iftyyearsaftertherecognitionofthespe-ciesHomohabilisastheearliestknownrep-resentativeofourgenus(1),theoriginofHomoremainsclouded.Thisuncertaintystemsinlargepartfromalimitedfossilrecordbetween2.0and3.0millionyearsago(Ma),especiallyineasternAfrica.Sometaxafromthistimeperiod,suchasAustralopithecusafricanus(~2.8to2.3Ma)andthelesswellknownA.garhi(~2.5Ma)andA.aethiopicus(~2.7to2.3Ma),ap-peartoospecializedcraniallyand/ordentallytorepresenttheprobableproximateancestralconditionsforHomospeciesknowninAfricaby~2.0Ma(H.habilisandH.rudolfensis).Thisleavesathinscatterofisolated,variablyinform-ativespecimensdatedto2.4to2.3MaastheonlycrediblefossilevidencebearingontheearliestknownpopulationsofthegenusHomo(2,3).Herewedescribearecentlyrecoveredpartialhomininmandible,LD350-1,fromtheLedi-Geraruresearcharea,AfarRegionalState,Ethiopia,thatextendsthefossilrecordofHomobackintimeafurther0.4millionyears.Thespecimen,securelydatedto2.80to2.75Ma,combinesderivedmor-phologyobservedinlaterHomowithprimitivetraitsseeninearlyAustralopithecus.Thediscov-eryhasimplicationsforhypothesesconcerningthetimingandplaceofHomoorigins.

TheLD350localityresidesintheLeeAdoytaregionoftheLedi-Geraruresearcharea(Fig.1).GeologicresearchatLeeAdoyta(4)identifiedfault-boundedsedimentarypackagesdated2.84to2.58Ma.TheLD350-1mandiblewasrecov-eredonthesurfaceoffinelybeddedfossiliferous

DepartmentofAnthropology,UniversityofNevadaLasVegas,LasVegas,NV1,USA.2InstituteofHumanOriginsandSchoolofHumanEvolutionandSocialChange,ArizonaStateUniversity,Tempe,AZ85287,USA.3Departmentof

Geosciences,PennsylvaniaStateUniversity,UniversityPark,PA16802,USA.4CenterfortheAdvancedStudyofHomininPaleobiology,GeorgeWashingtonUniversity,Washington,DC20052,USA.5SchoolofEarthandSpaceExploration,ArizonaStateUniversity,Tempe,AZ85281,USA.6DepartmentofAnthropology,UniversityCollegeLondon,LondonWC1H0BW,UK.7AuthorityforResearchandConservationofCulturalHeritage,AddisAbaba,Ethiopia.

*Correspondingauthor.E-mail:brian.villmoare@unlv.edu(B.V.);wkimbel.iho@asu.edu(W.H.K.)

1Fwww.sciencemag.org/content/347/6228/1349/suppl/DC1MaterialsandMethodsSupplementaryTextFigs.S1toS4MoviesS1andS2Reference(29)

5November2014;accepted3February201510.1126/science.aaa2397

silts10mconformablyabovetheGurumahaTuff(Fig.1).Thematrixadherenttothespeci-menisconsistentwithithavingerodedfromthesesilts[fordetailsonstratigraphyanddepo-sitionalenvironment,see(4)].TheGurumahaTuffisradiometricallydatedto2.822T0.006Ma(4),adatethatisconsistentwiththenormalmagneticpolarityoftheGurumahasection,pre-sumablytheGaussChron.AnupperboundingageforLD350-1isprovidedbyanadjacentdown-faultedyoungerblockthatcontainsthe2.669T0.011MaLeeAdoytaTuff.Amagnetostratigraphicreversal12mconformablyabovetheLeeAdoytaTuffisinferredtobetheGauss/Matuyamabound-aryat2.58Ma(4).BecausenosignificanterosionaleventsintervenebetweentheGurumahaTuffandthefossiliferoushorizon,theageofLD350-1canbefurtherconstrainedbystratigraphicscaling.Applyingasedimentationrateofeither14cmperthousandyears(ky)fromtheLeeAdoytafaultblockor30cm/kyfromtheHadarFormation(5)providesageestimatesof2.77and2.80mil-lionyears(My),respectively,forLD350-1.BasedonthecurrentchronostratigraphicframeworkforLedi-Geraru,weconsidertheageofLD350-1tobe2.80to2.75My.

Thehomininspecimen,foundbyChalachewSeyoumon29January2013,comprisestheleftsideofanadultmandibularcorpusthatpreservesthepartialorcompletecrownsandrootsofthecanine,bothpremolars,andallthreemolars.Thecorpusiswellpreservedfromthesymphysistotherootoftheascendingramusandretromolarplatform.Surfacedetailisverygoodtoexcellent,andthereisnoevidenceofsignificanttransport.Theinferiormarginofthecorpusandthelingualalveolarmarginareintact,butthebuccalalveolarmarginischippedbetweenP3andM1.TheP4,M2,andM3crownsarecompleteandwellpre-served,buttheC,P3,andM1crownsareincom-plete(Fig.2andtextS2).Theanteriordentitionisrepresentedbythebrokenrootofthelateralincisorandthealveolusofthecentralincisor.Givenitslocationandage,itisnaturaltoaskwhethertheLD350-1mandiblerepresentsalate-survivingpopulationofA.afarensis,whose

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Corrected 23 March 2015; see full text.

Continuous liquid interface production of 3D objectsJohn R. Tumbleston et al.Science 347, 1349 (2015);

DOI: 10.1126/science.aaa2397

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