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37Biomimetics:BiomimeticsinNanotechnologyIlleC.
GebeshuberandManfredDrackINTRODUCTIONThischapterdealswiththebiomimeticmethodinnanosci-enceandnanotechnology.
Predictabilityonthebasisofsci-entificunderstandingisapreconditionfortechnology.
Theaimsofsciencearetoexplainandunderstandandtoorganizeknowledge.
Withasolidscientificbasis,itshallbepossibletomakepredictions,forexample,aboutthemovementofplanetsorasteroids,molecules,waterflowaroundpillars,oremer-gentpropertiessuchasbirdflockflyingpatternsandswarmintelligenceinants.
Toachievethis,varioustechniquesandmethodsareapplied.
Nanoscienceandnanotechnologytoolsandtechniqueshaverapidlydevelopedsincethe1980s.
Currenttoolsandtechniquesforcharacterization,manipulation,andfabri-cationofmatteratthenanoscalearemanifold.
Thefourmajorgroupsofnanoscaleprobingtoolsarescanningprobemicroscopy,(includingscanningtunnelingmicros-copy,atomicforcemicroscopy(AFM),andscanningnearfieldopticalmicroscopy),aswellaselectronmicroscopy,x-raymethods,andopticaltechniques(Bhushan2010).
Thecoretool,theAFM,wasinventedin1986(Binnigetal.
1986).
Thislenselessmicroscopehassubnanometerreso-lution,canbeusedforimagingaswellasmanipulationdowntothesingleatomlevel,andworksinvariousenvi-ronmentssuchasvacuum,air,water,buffersolutions,andoil(Haugstad2012).
Thismakesitsointerestingforappli-cationsregardingtheinvestigationofbiologicalsamples(Parotetal.
2007).
Evenlivecells(Henderson1994)orprotein–proteininteractionsonthesingleproteinlevelcanbeimagedwiththisdeviceinrealtimeatunprecedentedresolution(Vianietal.
2000).
Nanotechnologicalproductsandprocessescanbedevel-opedonthegroundsofnanofabrication(labscale),molec-ularmanufacturing(manufactureofcomplexnanoscalestructuresbymeansofnonbiologicalmechanosynthesisandsubsequentassembly),andnanomanufacturing(indus-trialscale)(Bhushan2010).
Insuchproductsandprocesses,nanotechnologycanbeembeddedinnumerousaspectsofthemanufacturingprocesses.
Whilethephysicsitselfisthesameacrossalllengthscales,materialsandstructureshaveuniquesize-dependentproperties(thatmaybeverydifferentfromthepropertiesofbulkmaterial).
Also,thesmallerthesize,themorerelevantthestructureofthematerialbecomes.
Singleatoms,moleculesandnanostructuresexhibitunusualphysi-cal,chemical,andbiologicalpropertieswhencomparedtothebulkmaterial.
Gold,forexample,hasgoldencolorationatthemacroscaleandisknownasahighlyinertmaterial;nano-goldcolloids,however,exhibitdifferentcolorsatdifferentsizesandconcentrations,andtheyarenotbio-inert(Brownetal.
2008).
Theideasfornewnanotechnologicalproductsandpro-cessesareoftenrootedinphysicsorinorganicchemistry.
Thereis,however,alsoaconsiderableandexpandingbodyofknowledgeatthenanoscaleinbiology.
Suchknowledgeaboutmaterials,structuresandfunctionsinlivingnaturecanbeappliedindifferentways.
Onepossibilityistousemacromoleculesororganismsdirectly,likeinbiotechnol-ogy.
Anotherwayistostrivefortheunderstandingofprin-ciplesbehindparticularphenomenaandtoapplythemindistinctareas,likeinbiomimetics.
Thefollowingfocusesonbiomimetics.
Whatwedescribehereisperhapsasmallbutprobablysig-nificantmethodfornanotechnology,becausetherolemodelsCONTENTSIntroduction37CommonGroundofBiomimeticsandNanotechnology38WhatIsBiomimetics38WhatIsNanotechnology39FieldsofCommonPotential40TechnologyPull41BiologyPush41ReverseBiomimetics41MetascientificConsiderations41ConclusionsandOutlook43Acknowledgments44References4438Biomimetics:BiomimeticsinNanotechnologythatcanbefoundinlivingnaturehavebeentestedinevolu-tionsincebillionsofyears.
COMMONGROUNDOFBIOMIMETICSANDNANOTECHNOLOGYMostoftenbiologyandengineeringdonottouchoneachother(Figure30).
Thereis,however,anintersectionofbothfields.
Differentdisciplinesarefoundinthisintersection,suchasthetwodistinctfieldsofbiotechnologyandbiomimetics.
Biotechnologyisnotourconcernhere;weonlydealwithbiomimetics.
Theintersectionitselfcanbeslicedintopiecesaccordingtotheirscale.
Bydoingso,thefielddiscussedinthischaptercanbeillustratedlikeinFigure30.
Inthefollowing,thefieldsofbiomimeticsandnanotech-nologyarecharacterizedinordertoinvestigatehowthefor-mercancontributetothelatter.
WhatIsBiomimeticsBiomimeticsisabouttransferringprinciplesfrombiologytoengineeringtoenhanceandbringupnewproductsandpro-cessesforhumanneeds.
Althoughthenameandthescientificfieldwereonlyestablishedinthelastdecades,themethodisanoldone.
LeonardodaVinciandhisstudiesofbirdflight,forexample,eventuallyhaveledtoairplanes.
Attheendofthetwentiethcentury,thefieldofbiomimeticsbecameestab-lishedbothmethodicallyandinstitutionally,leadingtoanever-increasingnumberofapplications.
Inthisrecentdefinition,themainaspectsarecovered:"Biomimeticscombinesthedisciplinesofbiologyandtech-nologywiththegoalofsolvingtechnicalproblemsthroughtheabstraction,transfer,andapplicationofknowledgegainedfrombiologicalmodels"(VDI62202012).
Atthecore,biomimeticsisaboutunderstandingfunc-tionaloroperationalprinciplesthatareatworkinbiologyandresultsintheabstractionsoftheminordertofindoutiftheymightalsoworkinengineering.
Thisprocedureisdifferentfrombiotechnology,whichisnotnecessarilyabouttransfer-ringprinciples.
Biomimeticsworksbecausebiologicalandengineeringentitiesarepartofthesameworldandthereforeunderliethesamenaturallaws.
Hence,principlesinlivingorganismscanalsoworkintechnicalapplications.
Nevertheless,therearelargedifferencesbetweenentitiesfromtherespectivefields.
Onedifferenceisthedevelopmentthroughoutwhichafertilizedeggturnsintoanembryoandeventuallyintoamatureorganism.
Thisiscompletelydifferentfromproduc-tiondevicesormachinesinengineering.
Anotherdifferenceisthateverymachinehasitsengineerwhobuildsit,whereasorganismsdonot.
Butthisparadigmisslowlychanging,withthedevelopmentofengineeredself-replicatingmachines(see,e.
g.
,Griffithetal.
2005).
Basically,twowaysofworkinginbiomimeticscanbedis-tinguished.
Theyarereferredtoastechnologypull(alsocalledtop-downbiomimeticsandbiomimeticsbyanalogy)andbiol-ogypush(alsocalledbottom-upbiomimeticsandbiomimeticsbyinduction)(see,e.
g.
,GebeshuberandDrack2008).
Technologypullbiomimeticsisproblembased:itstartswithaprobleminengineering.
Thenextstepistoseeifsimilar"problems"occurinlivingnature.
Dragreduction,forinstance,isaproblemforshipbuildersandsimilarlyforfish.
Aftersuchequalproblemsarefound,thebiologicalrolemodelsareinvestigatedwiththetoolsandmethodsofengi-neering.
Theterm"technicalbiology"(TechnischeBiologie)wasintroducedbyNachtigalltonamethismethodicalpartofbiomimetics(cf.
Nachtigall1998).
Inthedragreductioncase,forexample,theengineerwouldmeasurerelevantparam-etersofthefishandlookatthesurface,shape,andsoon.
Indoingso,theresearchermightfindinterestingfeatures,sofarnotthoughtaboutinengineering.
Theprocessoffindingoutmoreabouttheprinciplesstartswiththepotentialresultofanabstractionthatcanbetransferredandappliedinhuman-builtdevicesormachines.
Biologypushbiomimeticsstartswithbasicresearchinbiology,withouthavinganapplicationinmind.
Duringoraftersuchwork,itmightturnoutthatthefoundresultsarealsousefulforengineering(solution-basedbiomimetics).
Thefoundprinciplesarethentransferredandapplied.
Technologypull,ingeneral,hasalargepotentialforfind-ingwithinashorttimeprinciplesthatareusefulforparticularproblems.
Utilizationofsuchprinciplesisusuallyrestrictedtoasmallareaofapplication.
Incontrast,biologypushbiomi-meticshasalowerpotentialforimmediateapplications,butthechanceforfindingrevolutionaryorgenericprinciplesismuchhigher.
Whetheraproductortechnologyistheresultofbiomimet-icsornotfollowsfromthedescriptionofthemethod.
Threenecessaryconditionshavetobefulfilled(i.
e.
,answeredwithyes)tolegitimatelyspeakaboutbiomimetics(Freyetal.
2011,VDI62202012):1.
Rolemodelfrombiology:Didtheinspirationcomefromlivingnature(biology)2.
Abstractionfrombiologicalrolemodel:Wasthereanabstraction(ofaprinciple)ofthenaturalroleBiomimeticsatthenanoscaleEngineeringBiologyMilliBiomimeticsNanoMicroFIGURE30Biomimeticsandbiotechnologyaresomeofthefewareasattheintersectionofengineeringandbiology.
Biomimeticsatthenanoscaleisasmallbutprobablysignificantmethodinnanotechnology.
39Biomimetics:BiomimeticsinNanotechnologymodelWasthebiologicalknowledgeanalyzedandabstractedstepbystep(withanunderstandingoftheprinciple)3.
Transfertotechnicalapplication:WastheprincipleappliedinengineeringThescopeofbiomimeticsisbroad.
Mostoftheestablishedknowledgetransferwasdoneinthefieldofconstructions.
However,processesinlivingnaturearealsoofinter-est,forexample,photosynthesis.
Furthermore,informa-tionprocessinglikeinneuronalnetworksoroptimizationwithgeneticalgorithmscanbereferredtoasbiomimetics(Gruberetal.
2011).
Aswehaveseen,researchinbiomimeticscanleadtoapplicationsinengineering.
Additionally,theprocessofdoingbiomimeticscanalsorevealnewinsightsforbiol-ogy,besidesthoseaccomplishedwithtechnicalbiology.
Thiscanbetermedasreversebiomimetics(cf.
Masselteretal.
2012,p.
380).
Oneexampleistheevolutionarystrat-egyofRechenberg(1994).
Heintroducedalgorithmsforoptimizationinengineeringbasedontheconceptsofmuta-tion,selection,andrecombinationfromevolutionarybiologyandachievedgoodresultsinengineering.
Analyzingthosealgorithmsinturnwasofinterestforevolutionarybiology(cf.
WagnerandAltenberg1996).
WhatIsNanotechnologyAccordingtoISOdefinitionISO/TS80004-1:2010,nanotech-nologyisthe"applicationofscientificknowledgetomanipu-lateandcontrolmatterinthenanoscale[…]inordertomakeuseofsize-andstructure-dependentpropertiesandphenom-ena,asdistinctfromthoseassociatedwithindividualatomsormoleculesorwithbulkmaterials.
"Inanotetothisentry,ISOstatesthatmanipulationandcontrolincludesmaterialsynthesis.
Nanotechnologyhasfunctionalpartsintherangeofnanometerstosomehundredsofnanometers.
Theriseofnanotechnologybeganwhenwewereablenotjusttoimagebutalsotomanipulatematteronthenanometerscale.
Thesepossibilitiesweregreatlyenhancedwiththeincreasingavail-abilityofscanningprobemicroscopesforthescientificcom-munity(Meyeretal.
2004/2012).
OneoftheearlyexamplesofnanotechnologicalmanipulationisthespellingofthecompanynameIBMbyDonEiglerandcoworkersfromIBMAlmadenwithjust35xenonatomsonasingle-crystalnickelsurface(EiglerandSchweizer1990).
Thegrouptherebydem-onstratedtailoredmanipulationofsingleatoms.
Thetwomajorapproachesforobtainingnanotechno-logicalproductsandprocessesaretermedtopdownandbottomup(nottobeconfusedwiththetermsasusedinbiomimetics).
Intop-downapproaches,nanoobjectsareconstructedfromlargerentitieswithoutatomic-levelcontrol.
Top-downapproachescompriselithography,deposition,andetching.
Inbottom-upapproaches,materialsanddevicesarebuiltfrommolecularcomponentsthatassemblethemselveschemicallybyprinciplesofmolecularrecognition.
Bottom-upmethodsinclude(self-)assemblyofatomicandmolecularbuildingblockstoformnanostructures.
Thismethodiswidelyusedinsol-gelandchemicalvapordeposition.
Innature,self-assemblyhasexistedforbillionsofyears,fromsimplebiomoleculestocompleteorganisms.
Gebeshuberetal.
(2010)Thehistoryofnanomaterialscanbedatedbacktopre-Columbiantimes:Thefirstpermanentorganicbluepigment,MayaBlue,isaresultofancient"nanotechnology"(Chiarietal.
2008).
FurtherexamplesofhistoricalnanomaterialsaretheLycurgusCupintheBritishMuseum,datingbacktothelateRomanEmpire,andstainedglassesinMedievalEurope(Francis2010).
Propertiesofnanomaterialsareresponsiblefortherespectiveeffectsdescribedinthispara-graph.
Itremainstobediscussedifitisjustifiedtocallsuchancientapproaches"nanotechnology,"sincethepeoplebackthendidnotknowthereasonfortherespectivematerialproperties.
Ingeneral,nanosciencedealswithresearchonmaterials,structures,andprocessesonthenanometerscale,andnano-technologydealswiththedevelopmentofmaterials,struc-tures,andprocesseswherethefunctionalunitsareinthenanometerrange(generallyfromafewnanometerstosomehundredsofnanometers).
Nanoscienceandnanotechnologycanratherbeassociatedwithtools,techniques,andmethodsthanwithestablishedresearchfields.
Mostresearchinthesefieldsisratherinterdisciplinaryandtouchesuponpureandappliedmathematics,physics,chemistry,materialsscience,engineering,andlifesciences.
Themethods,concepts,andgoalsoftherespectivefieldsconverge.
Thisinherentinter-disciplinarityofnanotechnologyposesachallengeandoffersanenormouspotentialforfruitfulcross-fertilizationamongspecialistareas.
Thepropertiesofmanymaterialschangewhentheyexistasnanosizedparticles.
Besidesthechemistry,surfacephysicsbecomesincreasinglyimportant,andnotjustthematerialitselfbutalsoitsstructureisofrelevanceforitsmechanical,electrical,catalytic,optical,andtoxicproperties.
Furthermore,quantumeffectssuchasthetunnelingeffect,confinementproperties,spineffects,andquantumcoherenceareimportant.
Thescopeofnanotechnologyistoindividuallyaddress,control,andmodifystructures,materials,anddeviceswithnanometerprecisionandtosynthesizesuchstructuresintosystemsofmicro-andmacroscopicdimensionssuchasmicroelectromechanicalsystems-baseddevices.
Forthis,weneedtoestablishathoroughunderstandingofthefundamen-talphysics,chemistry,biology,toxicologyandtechnologyofnanoscaleobjects(nanomaterials,nanoparticles,nanostruc-tures),therespectivefabrication,diagnosticsandanalyticsandofhowsuchobjectscanbeusedinareassuchascom-putation,cosmetics,engineering,medicine,nanobiotechnol-ogy,nanostructuredmaterials,optics,resourcesustainability,science,sensors,textiles,andmanymore.
40Biomimetics:BiomimeticsinNanotechnologyFIELDSOFCOMMONPOTENTIALPhenomenaoflifeoccurondifferenthierarchicallevels,downtothenanoscale.
Themicro-andnanoscaleareofspecificimportanceinlivingsystems.
Singlemolecules,theirinter-actions,andemergentpropertiesonlargerlengthscalesaretheveryconstituentsoflife.
Thecomplexityofasinglecellinthehumanbodybyfarexceedsanycurrentengineereddevice.
Acell'sactivitiessuchassensing,actuation,energyconversion,orinformationstoragearecarriedoutwiththecontributionofbiomolecules,suchasproteins.
Proteinsizesrangefromabout1toabout20nm;therearemillionsofdifferentproteins.
Biologicalmaterialsareamazing:therearetoughmaterials,"smart"materials,adaptivematerials,functionalmaterials,materialswithmolecularprecision,hierarchicalmaterials,andmultifunctionalmaterials.
Manyfunctionalitiesonthemacroscalearebasedonfunctionalitiesonthenanoscale.
Themoreweunderstandandabstractdeepprinciplesofbiologyontheselengthscales,themoresuccess-fulcanthebiomimeticmethodtransferknowledgefrommate-rials,structures,andprocessesinlivingnaturetoengineering,forindependenttechnologicalapplicationsanddevices.
Withincreasinglypowerfulmicroscopes,researchershavestartedtoseeamazingorder,structure,andfunctionalitiesofbiologicalmaterials,downtoverysmallscales.
Biomolecular"machines"suchastheribosome,builtwithatomicprecision(Yusupovetal.
2001),powerfulcompositessuchastheAbaloneshell(Smithetal.
1999)orthecrystaleyesofbrittlestars(Aizenbergetal.
2001),biomineralizedbeautifullystructuredlittlegemssuchasdiatoms(GebeshuberandCrawford2006,Roundetal.
1990/2007),optimizedbiotribologicalproperties,forexample,decreasingthefrictioncoefficienttonumberssolowthatlubricationengineersareamazed(Gebeshuber2007)andfunctionalsurfaceswithnanoscalepropertiesresponsibleforexcitingtrickssuchasincreasedantireflectiveproperties(Stavengaetal.
2006)oriridescentcolorationinplantsandmicroorganismsbasedonnanostructures(GebeshuberandLee2012)arejustsomeexamplesforthepropertiesoforgan-ismsthatarealsointerestingforengineering.
Currently,mergingofnanoscienceandnanotechnologywiththelifesciences,especiallybiology,biotechnology,bio-mimetics,nanomedicine,geneticengineering,andsyntheticbiology,canberecognized(see,e.
g.
,Bainbridge2007,ChenandHo2006,Ulvick2010).
Thisnewandemergingfieldwithenormouscreativepotentialiscallednanobioconvergence.
AndreasLymberisfromtheEuropeanCommission,InformationSocietyandMediaDirectorate-General,describesconvergingmicro-andnanobiotechnologiestowardintegratedbiomedicalsystemsasresearchanddevelopmentattheconvergenceofmicroelec-tronics,nano-materials,biochemistry,measurementtechnol-ogyandinformationtechnologythatisleadingtoanewclassofbiomedicalsystemsandapplications,e.
g.
,molecularimag-ing,pointofcaretesting,genetherapyandbionics(includingonandinsidethebodysensorsandotherminiaturisedsmartsystems)whichareexpectedtorevolutionisethehealthcareprovisionandqualityoflife.
Inparticulartheyareexpectedtoidentifydiseasesattheearliestpossiblestage,intervenebeforesymptomaticdiseasebecomesapparentandmonitorboththeprogressofthediseasesandtheeffectofinterventionandtherapeuticprocedures.
Lymberis(2008)Nanobioconvergenceisanemergingfield,andnorigiddefini-tionhasbeenestablishedyet.
Onepotentialdefinitionisthefollowing:"Nanobioconvergencedenotesthemergingoflifesciences,especiallybiologyandbiotechnology,withnanosci-enceandnanotechnology,focusingonthetechnicaloutputfromtheconnectionsoftheseparticularfieldsaswellasontheunifiedopportunitiesandchallengestheypresenttohumannatureandourvalues"(Gebeshuberetal.
2013).
Biotechnology(geneticengineering,engineeringofproteins,etc.
),bionano-science(focusingonmolecularbuildingblocksoflivingcells),andbiomimeticsformimportantconstituentsofnanobiocon-vergence.
Biomimeticscanbedoneonmanylengthscales,butbecauseofthehierarchicalorganizationoforganisms,withmanypropertiesbasedonfunctionalitiesoriginatingfromthenanoscale,biomimeticsisespeciallyrewardingwhentakingintoaccountnanoscalepropertiesoflife.
Sinceallthesefieldsarecurrentlyemerging,thereisstillalotofdefiningandcategorizinggoingon.
Whatonesetofresearcherswouldplaceinbiotechnology,otherscategorizeasbiomimetics.
Researchtowardproducingspidersilkisacaseinpoint.
Thecategoriescanalsochangewithtime.
Sarikayaandcoworkers,forexample,wroteintheir2003paper"Molecularbiomimetics:nanotechnologythroughbiology"(Sarikayaetal.
2003):"Molecularbiomimeticsisanemergingfieldinwhichhybridtechnologiesaredevelopedbyusingthetoolsofmolecu-larbiologyandnanotechnology.
Takinglessonsfrombiology,polypeptidescannowbegeneticallyengineeredtospecifi-callybindtoselectedinorganiccompoundsforapplicationsinnano-andbiotechnology.
"Eightyearslater,thegroupreportsthefabricationofhierarchicalhybridstructuresusingbioen-abledlayer-by-layerself-assembly,functionalhybridnanoma-terialswithwell-definedhierarchicalandspatialorganization(Hnilovaetal.
2012)—somethingonewouldnowadaysrathercallbiotechnologythanbiomimetics.
Biomimetictechniquesappliedtonanotechnologycom-prisetechnologypullandbiologypush.
Examplesforbio-mimeticsinnanotechnologyareprinciplesofself-assembly(Valéryetal.
2003),self-repairingmaterials(dynamicbreak-ingandrepairof"sacrificial"bonds)(Fantneretal.
2005),bioinspiredsensors(Barthetal.
2012),massproductionofnanostructures(GuozhongandYing2011),andartificialpho-tosynthesis(Razeghifard2013).
Onamoreabstractlevel,WernerNachtigall,thedoyenofbiomimeticsinGermany,identified10generalprinciplesofbio-mimeticsthatcanbeappliedbyeverybodyworkinginthefield,evenbypeoplewhoarenot(orwhodonotwanttobe)involvedinbiologyatall(Nachtigall2009).
Theseprinciplesareasfollows:1.
Integrationinsteadofadditiveconstruction2.
Optimizationofthewholeinsteadofmaximizationofasinglecomponentfeature41Biomimetics:BiomimeticsinNanotechnology3.
Multifunctionalityinsteadofmonofunctionality4.
Fine-tuningregardingtheenvironment5.
Energyefficiency6.
Directandindirectusageofsolarenergy7.
Limitationintimeinsteadofunnecessarydurability8.
Fullrecyclinginsteadofpilingwaste9.
Interconnectednessasopposedtolinearity10.
Developmentviatrial-and-errorprocessesNachtigall'sgeneralprinciplesareofhighrelevanceforbiomimeticsthatdrawsitsinspirationfromnanoscalepropertiesoflivingmatter.
Oneexamplefor"fine-tuningregardingtheenvironment"isnavigationinhoneybees.
Theseanimalsorientthemselveswiththehelpofthepolarizationoftheskylight.
Abstractionofthedeepprin-ciplesofpolarizedskylight-basednavigationleadstothedevelopmentoftechnicalnavigationsystems(producedwithmicro-andnanofabricationtechniques)thatarecom-pletelyindependentfromthenormallyusedGPSsystems(reviewedinKarmanetal.
2012).
Biomimeticsatthenanoscalehasasintegralpartsabstrac-tionoftheprinciplesoftheinvestigatednanomaterials,nano-structures,andnanoprocesses,followedbyprincipletransfertonanotechnology.
Intheremainderofthissection,weillus-trateintwoexamplesthetechnologypullandbiologypushmethodsofbiomimeticnanotechnology.
TechnologyPullTheCarinthiaUniversityofAppliedSciencesinAustriaofferstheMSccourse"BiomimeticsinEnergySystems.
"Oneoftheauthorsofthischapter(ICG)supervisedtheMScthesis"Biomimeticpotentialofspongespicules"byEhret(2012).
Theworkperformedinthisthesisshallnowserveasanexamplefor"technologypull.
"Bioinspiredimprove-mentofdaylight-guidancesystemsinbuildingswastheprobleminengineeringonwhichthethesisisbased.
Glasssponges(animals)wereselectedasmodelorganismswithsimilar"problems"inlivingnature.
Thesilicaspiculesofglassspongesserveaslightguides,providinglighttothephotosynthesizingmicroorganismsandalgaethatliveincloseassociationwiththe"glassfiber"intheinteriorfromthesponge.
Detaileddescriptionofinvestigationsofthebiologicalrolemodel,theglasssponges,withtoolsandmethodsfromengineering,includingdynamicalmechani-calanalysis,lighttransmissionstudies,andthepropagationofultrashortlaserpulses,leadtothefollowingabstractionsthatcansubsequentlybetransferredtoengineering:self-assemblyofmetaloxidesonfunctionalizedsurfaces,themanufacturingoflayeredorganic-inorganiccompositeswithenhancedmechanicalproperties,andthetuningofopticalandmechanicalpropertiesbymeansofnanostructuringandhierarchicalarchitecture.
Applicationoftheseabstractionsinconstructionofdaylight-guidancesystemsshallyieldmoreconvenientlyilluminatedworkspacesinofficesproof(Figure31).
BiologyPushOneexampleforsuccessful"biologypush"isnanoscalestruc-turesonmotheyes(Figure32).
Theeyesofcertainmothsarecoveredwithnipple-likearrays,whichbasicbiologicalresearchrevealedtobeantireflective(VukusicandSambles2003).
Thenipplearraygraduallymatchestheopticalimped-anceofonemediumwiththatofitsneighboracrosstheinter-face.
Suchapropertyisofparamountinterestinengineeringapplications,forexample,forlenssurfacesofcameraandphotographicequipment.
Principletransfertoengineeringisstraightforward,sincethepropertyinquestionisdepen-dentonthestructureratherthanonthematerial.
Man-madesimilarnanofabricatedstructures(ReflexiteTM)yieldamazingantireflectivepropertiesinawidebandwidth,from400to700nm(BodenandBagnall2006,Figure32).
ReverseBiomimeticsProminentexamplesforreversebiomimeticsatthenanoscaleremaintobeseen.
Nevertheless,thereisaconsiderablepoten-tialforsuchexamples.
Thoughnotintherealmofreversebiomimetics,thediscoveryofthemechanismofATPproduc-tioninmitochondriacanserveasanillustration.
ATPisauniversalcarriermoleculeofenergyinorganisms.
PeterD.
MitchellproposedthechemiosmotictheorytoexplainhowATPproductioncouldwork,forwhichhereceivedtheNobelPrize.
FortheproductionofATP,anelectrochemical(proton)gradientacrossthemembraneofthemitochondrionwaspro-posed.
ExperimentstosupportthistheorywereperformedbyRackerandStoeckenius(1974).
Theyartificially"built"vesiclesthatcontainedATPase(theenzymethatcatalyzethedecompositionofATPintoADPandafreephosphateion)intheirmembranesandthroughsomeothermeanstheyprovidedforaprotongradient.
Thearrangementofthesecomponentsturnedouttobecausallysufficienttoexplaintheprocessesintheorganism(Weber2005).
Similarly,onecanthinkoffutureexampleswhere,bybuildingofbiomimeticnanoprod-ucts,knowledgecanbegainedinbiology.
METASCIENTIFICCONSIDERATIONSInthissection,wedealwithfurtherconsiderationsthataredeemedimportantwhendescribingbiomimeticsinnanotech-nology:thegoalandfutureofnanotechnology,ethical,legal,andsocialissues(leadingtogovernanceandriskresearch)andeducationalaswellasaccessibilityissuesinanageofconvergingtechnologies.
AccordingtotheForesightInstitute(PaloAlto,California),thegoalofnanotechnologyis"toimproveourcontroloverhowwebuildthings,sothatourproductscanbeofthehighestquality[…]whilecausingthelowestenvironmentalimpact.
"(ForesightInstitute2015).
However,itneedstobeensuredthatnanotechnologythatisintendedtocausethelowestenviron-mentalimpactisnotonlyupfront"green"withnegativesideeffectsonourselves,furtherorganisms,andtheenvironment.
Somehumanactionsandtechnologicaldevelopmentsmight42Biomimetics:BiomimeticsinNanotechnologyhaveshort-termbenefitsontheenvironment,butcomewithunforeseeablelong-termeffectsthatarehardandimpossibletopredictforthecomplexsystemweareallembeddedin.
Theprogressofnanoscienceandnanotechnologyisaccom-paniedbyimportantethical,health,environmental,andsocialissues.
Becauseofthehugeenvisagedimpactofscienceandtechnologyonsociety,increasinglyalsosocialscientistsandtechnologyassessmentspecialistsdealwithnanoscienceandnanotechnology.
Prospects,problems,andpotentialrisksrequirefocusedconsiderationbythirdpartiessuchasparliaments,NGOs,sociologists,philosophers,insurancecompanies,lawenforcementagencies,orscientificresearchersfromotherfields.
Technological,environmental,societal,health,andsafetyissuesmustbeaddressedinresearch,societalstudies,regulatorymea-sures,andgovernmentpolicies(Holsappleetal.
2005,HolsappleandLehman-McKeeman2005,Huber2010,Powersetal.
2006,ThomasandSayre2005,Thomasetal.
2006a,b,Tsujietal.
2006).
Societalimplicationsofnanoscienceandnanotechnol-ogyshouldbejudgedusingabalancedapproachbetweenthepotentialachievements(leadingtoenvisionedsocietalben-efits)andpotentialhazardousconsequences(whichcouldbeacombinationofunexpectedbenefitsandrisks)(Roco2003).
"Futures"intermsofvisions,expectations,scenarios,fears,andhopesincreasinglydominatescienceoutreachandthegps(a)(b)DiuserLowerpipeInsulationAttic(orplenum)spaceMiddlepipeRoofCollectorUpperpipeCeiling(c)FIGURE31(a)Amemberofthe1910–1913BritishArcticexpeditionwithaglasssponge.
Someglassspongeshavehydratedsilicaspiculesthatare3mlong.
Basedonfunctionalitiesonthenanoscale,suchspiculescanbeveryeffectivefracture-resistantlightguides.
(CopyrightPontingCollection,ScottPolarResearchInstitute,Cambridge,U.
K.
,http://www.
spri.
cam.
ac.
uk/.
)(b)Thelargestbiosilicastruc-tureonEarth:thegiantbasalspiculefromthedeep-seaglassspongeMonorhaphischuni.
(ReproducedfromWang,X.
etal.
,Evid.
BasedCompl.
Altern.
Med.
,540987,14,Copyright2011.
Withpermission.
)(c)Principleofdaylightguidinginbuildings.
(CopyrightDr.
AzizLaouadi,NationalResearchCouncilCanada,Ottawa,Ontario,Canada.
)43Biomimetics:BiomimeticsinNanotechnologydriveandmotivationofscientists(Grunwald2007).
Futuresaresociallyconstructed.
Especiallyconcerningnanoscienceandnanotechnologies,theongoingdebateisverymuchadebateaboutfutures.
Thevisionsforthefutureofnanotechnologyhaveawidebandwidth,rangingfrom"expectationsofsalvationandanticipationsofparadise"(Grunwald2010)totheannounce-mentofthe"ultimatecatastrophe"(Grunwald2010)—bothextremesbeingbasedonthesamefuturistictechnicalground.
Thehighdegreeofinterdisciplinarityinnanoscienceandnanotechnologyposesagrandchallengeaswellasprovidesgreatopportunitiestotoday'smainlyspecialistscientists.
Tofullyexploitthepotentialofbiomimeticsintheageofnanotechnology,scientistsandengineerswillhavetosubstan-tiallychangetheirwaysofthinking,especiallyontheleveloffundamentalresearchandeducation(CasertandDeboelpaep2006,GebeshuberandMajlis2010,Roco2002).
Still,manyresearchersusefortheirresearchonaspecificfieldinnanotech-nologyjusttheinstrumentstheyortheirclosecollaboratorshaveattheirdisposal,whicharenotalwaysthebest-suitedones.
Wehavetomovefromtool-basednanotechnologytounderstand-ing-basednanotechnology.
MartinReesfromTrinityCollegeinCambridgedescribesinhisforewordtoJamesLovelock's2010bookthecurrentwayofdoingscienceas"thespecial-izedquasi-industrialstyleinwhichmostresearchisconducted"(Rees2009).
Insuchaway,trueinterdisciplinaritycannotbeobtained.
Interdisciplinaryscientificprinciplesandconceptsthatallowspecialistscientiststounderstandcomplexphenom-enaneedtobedevelopedtowardaunificationofscience(RocoandBainbridge2002).
Toallowforproper,accessibleorganiza-tionofknowledge,thespecialistresultsthatcurrentlyappearinincreasinglyspecialistjournalsneedtoberearrangedandconnectedacrossfields(GebeshuberandMajlis2010).
CONCLUSIONSANDOUTLOOKOneoftheparamountadvantagesofthebiomimeticmethodasopposedtootherinnovationmethodsinnanotechnologyisthatwehavebiological"bestpractice"examplesandknowthatthey700600Wavelength(nm)Low-costARirditerationmotheyePMMAFirstiterationmotheyeWidebandAR500400(a)(A)(B)(B)(b)(A)5.
004.
003.
002.
001.
000.
00Reectance(%)2μmFIGURE32Antireflectivesurfacesonmotheyes(a)andtherespectiveengineeredbiomimeticantireflectivestructures(b).
(a):(A)SEMofamotheye,showingnipple-likestructures.
Inset:Moth.
Scalebar,1μm.
(B)Similarstructuresontransparentwingsofhawkmoths.
Scalebar,1μm.
Inset:Singlenipple.
Scalebar,100nm.
(b):(A)Reflectancemeasurementsonengineeredantireflectivesurfacestructures.
Forthesurfacecalled"thirditerationmotheye,"reflectanceisbelow1%forthewholespectrumthatisvisibletohumans.
(B)Biomimeticstructure,machinedinsilico.
Scalebar,2μm.
(a:ReproducedbypermissionfromMacmillanPublishersLtd.
Nature,Vukusic,P.
andSambles,J.
R.
,Photonicstructuresinbiology,424,852–855,CorrigenduminNature,429,680,Copyright2003;b:Boden,S.
A.
andBagnall,D.
M.
,Biomimeticsubwavelengthsurfacesfornear-zeroreflectionsunrisetosunset,ProceedingsoftheFourthIEEEWorldConferenceonPhotovoltaicEnergyConversion,Waikoloa,HI,pp.
1358–1361,2006IEEE.
)44Biomimetics:BiomimeticsinNanotechnologywork.
However,duetotheintegratedmultifunctionalityofbio-logicalmaterials,structures,andprocesses,itmightsometimesbehardtoidentifytherespectiveprinciplesresponsibleforonesingletechnologicalaspectthatwewanttotransfertoresearchanddevelopment.
Inthebiomimeticmethodappliedtonanosci-enceandnanotechnology,wehavetheoptiontogoalongtworoads:eithertotakethetypicalWesternscienceapproachandtrytodissectthebestpracticemodelsinlivingnaturetovari-oussingle,unrelatedproperties,someofwhichmaybehighlyintriguingandsuccessfulforimmediateapplicationincommonproducts,butthatmightcomewithunintendedlong-termeffects,ortotakeamoreholisticapproachandappreciatethebestprac-ticemodelsasawhole,tryingtodevelopadeepunderstandingwhylifeasweknowithasdevelopedthewaywecurrentlyexpe-rienceitandtodevelopakindofengineeringandwayofmanag-ingresourcesthatisclosertothewaynaturedoesit—biomimeticnanotechnologywiththestriveforsustainability.
Organismsshowus,forexample,acompletelydifferentwayofresource"management"asopposedtotheonewecurrentlyhaveinengineeringandconstruction.
Theypredominantlyusewater-basedchemistry,aresubjecttolimitsandboundaries,andareinastateofdynamicnonequilibrium.
Theyarelocallyattunedandresponsive(theyharvestlocally,usecommonmaterials,etc.
),integratecyclicprocessesviafeedbackloops,cross-pollinateandmutate,andareresilient(diverse,decen-tralizedanddistributed,redundant)(Biomimicry3.
82014).
Biomimeticsisperhapsasmallbutprobablysignificantmethod,becausetherolemodelsthatcanbefoundinlivingnaturehavebeentestedinevolutionsincebillionsofyearsandpromisegreatnanoscienceandnanotechnology-basedinnovations.
Tosumup,biomimeticsinnanotechnologyhasgreatpotentialforexcitingnanoscienceandnanotechnology-basedinnovations.
ACKNOWLEDGMENTSPartofthisworkwasfundedbygrantUKM-AP-NBT-16-2010(UniversityKebangsaanMalaysia)andgrantFRGS/1/2013/TK02/UKM/01/1(GovernmentofMalaysia).
ResearchofMDwasfundedbytheAustrianScienceFund(FWF):P22955-G17.
PartofthisworkwasfundedbyDeutscheForschungsgemeinschaft(DFG)grantSFB-TRR141.
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