Fiber-Based Generator for Wearable

ARTICLEFiber-BasedGeneratorforWearableElectronicsandMobileMedicationJunwenZhong,†,^YanZhang,‡,§,^QizeZhong,†,^QiyiHu,†BinHu,†ZhongLinWang,‡,andJunZhou†,*WuhanNationalLaboratoryforOptoelectronicsandSchoolofOpticalandElectronicInformation,HuazhongUniversityofScienceandTechnology,Wuhan,430074,China,‡BeijingInstituteofNanoenergyandNanosystems,ChineseAcademyofSciences,Beijing,China,§InstituteofTheoreticalPhysicsandKeyLaboratoryforMagnetismandMagneticMaterialsofMOE,LanzhouUniversity,Lanzhou730000,China,andSchoolofMaterialsScienceandEngineering,GeorgiaInstituteofTechnology,Atlanta,Georgia30332-0245,UnitedStates.^J.-W.Zhong,Y.Zhang,andQ.-Z.Zhongcontributedequallytothiswork.)†)ABSTRACTSmartgarmentsformonitoringphysiologicalandbiomechanicalsignalsofthehumanbodyarekeysensorsforpersonalizedhealthcare.However,theytypicallyrequirebulkybatterypacksorhavetobepluggedintoanelectricpluginordertooperate.Thus,asmartshirtthatcanextractenergyfromhumanbodymotionstorunbody-wornhealthcaresensorsisparticularlydesirable.Here,wedemonstratedametal-freefiber-basedgenerator(FBG)viaasimple,cost-effectivemethodbyusingcommoditycottonthreads,apolytetrafluoroethyleneaqueoussuspension,andcarbonnanotubesassourcematerials.TheFBGscanconvertbiomechanicalmotions/vibrationenergyintoelectricityutilizingtheelectrostaticeffectwithanaverageoutputpowerdensityof∼0.1μW/cm2andhavebeenidentifiedasaneffectivebuildingelementforapowershirttotriggerawirelessbodytemperaturesensorsystem.Furthermore,theFBGwasdemonstratedasaself-poweredactivesensortoquantitativelydetecthumanmotion.KEYWORDS:electrostaticinduction.fiber-basedgenerator.mobilemedicationsystemmartgarmentsformonitoringphysio-logicalandbiomechanicalsignalsofthehumanbodyarekeysensorsforpersonalizedhealthcare.However,theyty-picallyrequirebulkybatterypacksorhavetobepluggedintoanelectricpluginordertooperate.Thus,asmartshirtthatcanextractenergyfromhumanbodymotionstorunbody-wornhealthcaresensorsisparticularlydesirable.Here,wedemon-stratedametal-freefiber-basedgenerator(FBG)viaasimple,cost-effectivemethodbyusingcommoditycottonthreads,apolyte-trafluoroethyleneaqueoussuspension,andcarbonnanotubesassourcematerials.TheFBGscanconvertbiomechanicalmotions/vibrationenergyintoelectricityutilizingtheelectrostaticeffectwithanaverageoutputpowerdensityof∼0.1μW/cm2andhavebeenidentifiedasaneffectivebuildingele-mentforapowershirttotriggerawirelessbodytemperaturesensorsystem.Further-more,theFBGwasdemonstratedasaself-poweredactivesensortoquantitativelydetecthumanmotion.Wearableelectronicsrepresentsapara-digmshiftinconsumerelectronicsforap-plicationssuchasintegrationwithhumanbodyandhealth/wellnessmonitors,surgicalZHONGETAL.Stools,andbodysensornetworks(BSN).1À4Thevisionofnoninvasive,automatedperso-nalizedhealthcareusingwearablewirelessmedicaldevicesisanewandfast-growingmultidisciplinaryresearcharea.5Forexam-ple,continuousmonitoringofhumanbloodpressureinpatientswithhyperten-sioncansignificantlyincreasemedicationcompliance;6real-timemonitoringofelec-trocardiographtracescanbeveryeffectiveatrevealingearlystagesofheartdiseases.7Althoughsensinggarments(withthecom-mercialnameofSmartshirt)formonitoringphysiologicalandbiomechanicalsignalsofthehumanbodyhavealreadybeenin-ventedforhealthcare8andsportstraining,9theytypicallyrequirebulkybatterypacksorhavetobepluggedintoanelectricpluginordertooperate,whichmaylimitthewide-spreadusageofsmartgarments.10À13Indeed,fueledbytherapiddevelopmentofmicro-andnanotechnologies,lowerpowerconsumptionandevenself-poweredsystemshaveprofoundimpactsforbiome-dicalandportableelectronics.14Biomecha-nicalenergyrepresentsatypical,universallyavailable,andfeasiblesourceofcontinuouspowerforwearabledevices.ThehumanbodyisasurprisinglyrichsourceofenergyVOL.8’*Addresscorrespondencetojun.zhou@mail.hust.edu.cn.ReceivedforreviewMarch30,2014andacceptedApril26,2014.PublishedonlineApril26,201410.1021/nn501732zC2014AmericanChemicalSocietyNO.6’6273–6280’2014www.acsnano.org6273ARTICLEFigure1.Fabricationoffiber-basedgenerator(FBG).(a)SchematicdiagramillustratingthefabricatingprocessofanFBG.SEMimagesofacarbonnanotubecoatedcottonthread(CCT)with(b)lowand(c)highmagnification,respectively.SEMimagesofpolytetrafluoroethylene(PTFE)andcarbonnanotubecoatedcottonthread(PCCT)with(d)lowand(e)highmagnification,respectively.DigitalphotographyofFBGs(f)withlinearshape,(g)withcurvedshape,and(h)wovenintofabric.includingwalking,armswinging,fingermotion,andmonitorsystem.Moreover,theFBGsweredemonstratedbreathing.Itisestimatedthatharvestingeven1À5%oftoquantitativelymonitorhumanbodymotion.Thisworkthebody'spowerwithoutsignificantlyincreasingtheestablishesthefirstproof-of-conceptthattheFBGcanloadtothehumanbodywouldbesufficienttorunbewovenintofabricsandexploitthebiomechanicalmanybody-worndevices.15Thus,devicesthatexploitmotionsasnaturalenergysourcesforwearableelectro-biomechanicalmotionsasnaturalsourcesofenergynicsandmobilemedicationapplications.canbeparticularlydesirable.Inthepasttwodecades,researchershavedevelopedmultipleroutesinclud-RESULTSANDDISCUSSIONingelectromagneticfields,16,17thepiezoelectricFabricationofFiber-BasedGenerators.Thesourcemate-effect,18À27theelectrostaticeffect,28,29andthetribo-rialsfortheFBGsarecommoditycottonthreads,aPTFEelectriceffect30À32towardtransformingbiomechanicalaqueoussuspension,andcarbonnanotubeink.Themotionintoelectricalpower.detailedfabricationprocessisschematicallyshownIdeally,iftheenergyharvesterswereimplementedinFigure1aandsupplementarymethods.Thecottonastextile-fiberstructures,suchfiberswouldprovidethreadswerefirsttreatedbyethanolflametoeliminateperfectbuildingelementsforasmartshirt,astheyredundantfibers(SupplementaryFigureS1aandb)couldbenaturallyintegratedintofabricsduringtheandtreatedbyanitricacidsolutiontoincreasetheweavingprocesswithoutaffectingcomfort,flexibility,hydrophilicity.Thepretreatedcottonthreadswerethenairpermeability,andmaneuverability.Qinetal.de-coatedwithmultiwalledcarbonnanotubesbyusingamonstratedananogeneratorbasedonthepiezoelectrichomemadeCNTinkviaa“dippinganddrying”methodeffectusinghybrid-structuredmicrofiber-ZnOoxidetomakethemconductive(Figure1aII).11Comparednanowires,20butitsstructurewasveryfragileandthewithmetalelectrodes,CNTshavebetteradhesionwithpoweroutputwassolowthatthiskindofnanogeneratorcellulosesduetotheirmutualstrongchemicalbonds.33isnotfeasibletobeintegratedintotextilesforsmartMoreover,comparedwiththethermalevaporationgarments.14Hereweintroduceacost-effective,metal-method,whichisnormallyutilizedtodepositmetalfree,fiber-basedgeneratorthatcanconvertbiomecha-electrodes,“dippinganddrying”isasimpleandcost-nicalmotions/vibrationenergyintoelectricitybytheeffectivemethod.Scanningelectronmicroscopy(SEM)electrostaticinductioneffect.TheFBGconsistsoftwoimagesshowninFigure1bandcrevealthatthesurfaceentangledmodified-cottonthreads:oneisacarbonofthecottonthreadwithadiameterof∼240μmwasnanotube(CNT)coatedcottonthread(CCT),andthefullycoveredbyCNTs,withamassloadingdensityotherisapolytetrafluoroethylene(PTFE)andcarbonof∼0.207mg/cm.ThefinalCCTshaveagoodflexibi-nanotubecoatedcottonthread(PCCT).TheFBGscanlityandconductivitywithaconstantresistanceofbewovenintoacommercialtextiletoforma“power∼0.4kΩ/cminbothstraightandcurvingconditionshirt”andusedtotriggerawirelessbodytemperature(SupplementaryFigureS2a).ThemaximumtensileZHONGETAL.VOL.8’NO.6’6273–6280’2014www.acsnano.org6274

ARTICLEFigure2.PowergenerationmechanismoftheFBG.(a)SchematicdiagramillustratingthepowergenerationmechanismoftheFBGwithanexternalloadofRwhenthedeviceisat(I)theoriginal,(II)stretching,and(III)releasingstates,respectively.ThecorrespondingoutputcurrentÀtimecurves(d)whenforward-connectedtothemeasurementsystemand(c)whenreverse-connectedtothemeasurementsystem.stressthatcanbebornebytheCCTandFBGiscottonthreads.Inourstudy,theFBGscanbeeasily∼180and∼210MPa,respectively(Supplementarywovenintofabrictoforma“powershirt”(Figure1h).FigureS2b).ProposedPowerGenerationMechanismoftheFiber-PCCTswerepreparedbycoatingCCTswithPTFEviaBasedGenerators.AlthoughtheFBGhasacomplexa“dippinganddrying”method(Figure1aIII)followed“double-helix”structure,theFBGcanbeapproximatelybyasequenceannealingprocesstoenhancetheregardedasnumerousparallel-wirecapacitorscon-adhesion.Asoneoftherepresentativeelectretmateri-nectedinparallelbyignoringtheedgeeffect.Inaalsforpowergenerators,29PTEFcantheoreticallysimplifiedmodel,theequivalentcircuitoftheFBGwithretainelectrostaticchargesonitssurfacesforoveranexternalloadofRisillustratedinFigure2a.Inthetensofyears.34Thetopviewandcross-sectionalvieworiginalstate(Figure2a,I),thePTFEsurface,theouterSEMimagesshowninFigure1dandFigureS1dreveallayerofthePCCT,waschargedwithnegativeelectro-acoreÀshell-structuredcharacterwithadiameterofstaticchargesofQwhiletheCCTwasgrounded,∼500μm.TherearesomeminorcracksonthesurfaceandtheCNTlayersinboththePCCTandCCTwouldofthePCCTs,whichmaybeduetothestress-releasingproducepositivechargesofQ1andQ2,respectively,process.TheformationofthecrackscanenhancetheduetotheelectrostaticinductionandconservationflexibilityofthePCCTs.Ahigh-resolutionSEMimageofcharges,whereQ=À(Q1þQ2).32Therefore,theshowninFigure1eindicatesthatthePTFElayerwaschargesQonPTFEcouldbeconsideredasanelectriccomposedofoval-likenanoparticleswithdiametersoffieldsource.lessthan200nm.ThePCCTswerepolarizedviaoxygenWhentheFBGwasstretched(Figure2a,II),aplasmatreatmentandresultedinnetnegativeelectro-shrinkageoftheinterfibergapdistancedbetweenstaticcharges(Q)onthePTFEsurface,and40minCCTandPCCTwouldresultinmoreinducedpositiveofpolarizationcandramaticallyincreasethesurfacechargesaccumulatingintheCNTlayeroftheCCTpotentialofPCCTsfromca.À9Vforfreshsamplestobecauseoftheelectrostaticinduction.Accordingly,ca.À660V(SupplementaryFigureS3a).ThesurfacefreeelectronsofCCTwouldflowtotheCNTlayerpotentialdecreasedto∼470Vin30handcouldalmostofPCCTinordertobalancethefieldfromQ.Thus,thismaintainthisvalueformorethan20days.ThehighprocessproducesaninstantaneouspositivecurrentstabilityofthesurfacepotentialinPCCTsisbeneficial(Figure2b)(wedefinedaforwardconnectionforforlong-termsustainableapplicationsofthedevice.measurementasaconfigurationwiththepositiveFinally,aCCTandaPCCTwereentangledwitheachendoftheelectrometerconnectedtotheCNTelec-othertoformalightweight,flexibleFBGwithdouble-trodeofthePCCT).Itisnecessarytonotethatthehelixstructure(Figure1aIV,Figure1fandg).ThehelixchargeQonPTFEwillnotbeannihilatedevenwhenturnsandleavinggapsoftheFBGcanbeadjusted,itcontactswiththeCNT-coatedfiber,becausetheandthetwoendsoftheFBGwerefixedbycommodityelectrostaticchargesarenaturallyimpregnatedintoZHONGETAL.VOL.8’NO.6’6273–6280’2014www.acsnano.org6275

ARTICLEFigure3.PowergenerationperformanceofasingleFBGthoughanexternalloadof80MΩunderdifferenttestingconditions.(a)OutputcurrentÀtimecurveand(b)thecorrespondingtotalchargetransferofaFBGvariedwithstimulationstrainsof0,0.54%,1.08%,1.61%,and2.15%foragivenfrequencyof5Hz.(c)OutputcurrentÀtimecurveand(d)thecorrespondingtotalchargetransferofaFBGvariedwithstimulatefrequenciesof1.3,2,3,4,and5Hzforagivenstrainof2.15%.(f)Fivehours(∼90000cycles)continuouspowergenerationoftheFBGand(g)thevariationofpeakoutputcurrentovertime.theinsulatorPTFE.Inthereversecase,whentheFBGatagivenfrequencyof5Hz.Nocurrentsignalwaswasreleased(Figure2aIII),thedevicewouldrecoverdetectedwhentherewasnostimulationappliedonbacktoitsoriginalshapeandtheinternalgapdistheFBG.Generally,anincreaseofstrainincreasedtheincreased,resultinginanincreaseofQ1andadecreasepeakoutputcurrent,from3.98nAat0.54%to11.22nAofQ2;thus,aninstantaneousnegativecurrentcouldat2.15%(FigureS5b).Theintegrationofeachcurrentbeproduced(Figure2b).Therefore,astretchingÀpeakcangivethetotalchargestransferredbetweenreleasingprocessoftheFBGwillgenerateanalternat-theelectrodes,asshowninFigure3bandFigureS5c,ingcurrent(ac)throughtheload.indicatingthatthetotalamountofchargestransferredAstheelectrostaticchargesremainstable(Sup-increasedwiththeincreaseofstrain,whichisconsis-plementaryFigureS3b)forarelativelongtimeontentwithourmodeldiscussedabove.TheoutputthePCCTsurface,theFBGcanbethoughtofasatypecurrentofanFBGvariedwithstimulationfrequenciesofvariable-capacitancegenerator.Switchingpolarityof1.3,2,3,4,and5Hzforagivenstrainof2.15%istestswerealsocarriedouttoconfirmthatthemea-showninFigure3c,revealingaclearincreasingtrendsuredoutputsignalsweregeneratedfromtheFBGwiththeincreaseoffrequency.Theintegrationsofratherthanfromthemeasurementsystem(Figure2c).eachcurrentpeakfromeachofthefivedifferentPowerGenerationPerformanceofaSingleFiber-BasedstimulationfrequenciesareshowninFigure3dandGenerator.ThetypicalpowergenerationperformanceFigureS5d,indicatingthatthetotalamountoftheoftheFBGwithalengthof∼9.0cmandeightchargestransferredalmoststaysconstantat∼0.16nChelixturnswassystematicallystudiedbyperiodicallyatagivenstrainof2.15%.ThisstudyindicatesthatthestretchingandreleasingtheFBGwithcontrolledpeakoutputcurrentisrelatedtoboththestimulationfrequenciesandstrains.Themeasuringsystemissche-frequencyandmagnitudeofstrain,whiletheamountmaticallyshowninFigureS4;oneendoftheFBGofthetransferredchargesisrelatedonlytotheappliedwasfixedonanx-y-z3Dmechanicalstagethatwasstrain.mountedtightlyonanopticaltable,whiletheotherThecharacterizationcurveofthedependenceofendwasfixedonavibrationsourcewithcontrolledtheoutputpowerontheexternalloadisshowninfrequency.TheoutputcurrentthroughanexternalFigureS6a.Itwasmeasuredatagivenfrequency(5Hz)loadof80MΩwascontinuouslymonitored.anddegreeofdeformation(2.15%strain).Theinstan-Figure3ashowstheoutputcurrentofanFBGwithtaneousoutputpeakpowervalueis11.08nW,corre-anappliedstrainof0,0.54%,1.08%,1.61%,and2.15%spondingtoanoptimalexternalloadof100MΩ.ZHONGETAL.VOL.8’NO.6’6273–6280’2014www.acsnano.org6276

ARTICLEFigure4.FBGasaself-poweredactivesensorforbodymotiondetection.(a)CurrentÀtimeresponsecurveand(b)thecorrespondingchangetransferthroughan80MΩexternalloadoftheFBGthatwasfixedonanindexfingeratfiThevedidownfferentinsetsbendingin(a)ÀlabeledreleasingasfiI,ngerII,III,motionIV,andamplitudes.Vdemon-stratethefivefinger-motionstates.Toruleoutthepossibleartifacts,themeasurementoftheoutputcurrentwascarriedoutwhentwoFBGswereconnectedinparallelwithanexternalloadof80MΩunderthesamefrequencyanddeformationcontrol.AsshowninFigureS6b,thetotaloutputcurrentwasenhanced,indicatingthattheelectricityoutputoftheFBGssatisfiedalinearsuperpositioncriterioninthebasiccircuitconnections.ThestabilityoftheFBGisanessentialfactortoensureitspracticalapplications.Inourstudy,theFBGwascontinuouslyoperatedfor90000cyclesatastimulationstrainof2.15%andfrequencyof5Hz.Typicaldatain1minforeveryhourareshowninFigure3e,andonlyasmallvariationofpeakoutputcurrentisseeninFigure3f,indicatingthehighlystablepowergenera-tionoftheFBG.Thisfeaturemaybeattributedtotherobustnessofthedevice,asnonoticeablesurfacemorphologydegradationofthePCCTandCCTafterthetestwasprovenfromtheSEManalysis(FigureS7).Fiber-BasedGeneratorasanActiveSensorforBodyMotionDetection.AsingleFBGwasfixedonasubject'sindexfinger.Wecheckedtheoutputcurrentflowingthroughanexternalloadof80MΩatfivedifferentbend-ingÀreleasingmotionstatesthatwerelabeledasstateI,II,III,IV,andV,respectively(insetsinFigure4a).Ineachmotionstate,thefingerwasbenttothesameampli-tudeandthenreleasedforthreecycles.ItcanbeseenthatacoupleofoutputcurrentsignalswithoppositepolaritywouldbegeneratedineverybendingÀreleasingmotioncycle(Figure4a).TheinstantaneousoutputpowergeneratedbytheFBGwithsmall-scalefingermotioncouldreach∼0.91μW(averageareapowerdensityof∼0.1μW/cm2,SupplementaryNote1),whichwasZHONGETAL.Figure5.Electricitygenerationofthe“powershirt”.(a)Outputcurrentofthe“powershirt”with(blackcurve)andwithout(redcurve)rectificationwhenthelabcoatwasbeingshaken.Theinsetdepictstheequivalentloopcircuitforstoringtheelectricalenergyproducedbythe“powershirt”andlightingtheLED.(b)Voltagechargingcurveofa2.2μFcommercialcapacitorbythe“powershirt”.Theupperinsetshowsanenlargedplotduringcharging.ThelowerinsetdepictsdigitalphotographyofalightedLEDpoweredbythechargedcapacitor.enoughtopoweranelectronicdevicesuchasaliquidcrystallinedisplay(LCD)withsmallpowerconsumption(SupplementaryVideo1andFigureS8).Asdiscussedabove,thepeakoutputcurrentsweredecidedbybothmotionspeedandmotionamplitude.However,inourexperiments,thefingermotionspeedwasmanuallycontrolled;thus,asmallfluctuationispossible(FigureS9a).Asthetotalchargetransfercorrespondsonlytothemotionamplituderegardlessofthemotionspeed,wehaveintegratedeachpositivecurrentpeakforfivedifferentmotionstates,asshowninFigureS9bandFigure4b,indicatingthatthetotalamountofchargestransferredincreasedwiththeincreaseofmotionam-plitude,fromwhichthemotionstateswerequantita-tivelyidentified.ThisbehaviorindicatesthattheFBGcanbeusedasaself-poweredactivesensor28,35À37fordetectingtinymusclemotion/stretchingwithoutanexternalpoweratleastforthesensorunitandhaspotentialapplicationsinpatients'rehabilitationtrainingandsportstraining.PowerShirtforHealthMonitoring.Forthisdemonstra-tion,eightFBGswerewovenintoafabricandcon-nectedinparallel(Figure1h),thenthefabricwassewonalabcoattofabricatea“powershirt”(Figure6b).Whenthelabcoatwasshaken,analternatingoutputcurrentwouldbegenerated(blackcurveinFigure5a).VOL.8’NO.6’6273–6280’2014www.acsnano.org6277

ARTICLEFigure6.Wirelessbodytemperaturesensorsystemtriggeredbythe“powershirt”.(a)Schematicdiagramand(b)digitalphotographyofawirelessbodytemperaturemonitorsystemtriggeredbythepowerclothes.Modulatedanddemodulatedsignalsthatrepresentthetemperaturesdetectedbythesensorwhenthewristbandwasplaced(c)onadeskor(e)onahumanwrist.Thecorrespondingtemperaturevaluesof(d)22°Cforroomtemperatureand(f)37°Cforbodytemperatureareshowninthedisplayscreen.Additionally,anapproachtoprovetheelectricityanalogÀdigital(AD)module.Then,thedigitalsignalsgeneratedbyFBGshasalsobeenimplemented.AswereloadeddirectlyintoasquarewavegeneratedillustratedinFigureS10,whenshakingonlytheelec-bytheMCUinwhichthehalf-periodofthewavetrodesthatwerefixedonthelabcoat,therewerenoindicatedthetemperaturevalueandwastransmittedsignalsdetectedbythemeasuringinstrument.Thebyaninfrareddiode.Finally,thereceiverinfraredoutputelectricsignalswerefirstrectifiedbyabridgediodesimultaneouslycapturedthesignalsthatwererectifier(insetinFigure5a),transformingalternatingdemodulatedbyanotherMCUandidentifiedthecurrenttodirectcurrent(redcurveinFigure5a)andtemperaturevalue,andsenttheinformationtothechargingthecapacitorcontinuously(Supplementarydisplayscreen.Videos2).Thechargingcurveofthe2.2μFcommercialInourstudy,theactivebodytemperaturemonitorcapacitorisshowninFigure5b.Thecapacitorcouldsystemdetectedthesurroundingtemperaturewherebechargedto2.4Vinaround27s,andeverystepofthewristbandwaswornwhenshakingthelabcoatvoltageincreasecorrespondedtoeachvibrationof(SupplementaryVideos3).Themodulatedsignalsthelabcoat(upper-leftinsetinFigure5b).AftertheshowninFigure6canderepresentthedetectedtemp-capacitorwasfullycharged,itcouldlightuparedlighteratureswhenthewristbandwasplacedonadeskemittingdiode(LED),asshowninthelower-rightinsetoronthehumanwrist,respectively.Meanwhile,theofFigure5b,indicatingthattheelectricitygeneratedcorrespondingtemperaturevaluesof22°Cforroombythe“powershirt”canbestoredinastoragecellandtemperatureand37°Cforbodytemperaturearepowercommercialelectronics.showninthedisplay(Figure6dandf).Furthermore,the“powershirt”hadsuccessfullytriggeredahomemadewirelessbodytemperatureCONCLUSIONSmonitoringsystem.TheworkingprincipleoftheInsummary,wehavefabricatedaflexibleandmetal-wirelessbodytemperaturemonitorsystemissche-freeFBGviaacost-effectivemethodbyusingcom-maticallyshowninFigure6aandFigureS11.Themoditycottonthreads,aPTFEaqueoussuspension,“powershirt”wasusedtochargea10nFcapacitor;andcarbonnanotubesassourcematerials.TheFBGwhenthevoltageofthecapacitorreachedathresh-canconvertbiomechanicalmotions/vibrationenergyoldof2.4V,itwouldwakeupamicrocontrollerunitintoelectricityutilizingtheelectrostaticeffectwithan(MCU,Atmega168V-10PI,withapowerconsump-averageoutputpowerdensityof∼0.1μW/cm2.Thetionof0.18μWinstandbymodeand27μWinFBGwasdemonstratedasaself-poweredactivesensoractivemode)thatwasdrivenbyanexternalpowertoquantitativelydetecthumanmotion.Furthermore,source.TheMCUissuedinstructionstothethermistorFBGshadbeenidentifiedasaneffectivebuildingintegratedintothewristbandtodetectsurround-elementforapowershirtthatcouldtriggerawirelessingtemperatureandconvertedthedetectedtem-homemadebodytemperaturesensorsystem.Thisperatureanalogsignalsintodigitalsignalsbyanworkestablishesthefirstproof-of-conceptthatFBGsZHONGETAL.VOL.8’NO.6’6273–6280’2014www.acsnano.org6278

ARTICLEcanbewovenintotextilesandextractenergyfrombiomechanicalmotionsforpoweringmobilemedicalsystems,makingtheself-poweredsmartgarmentpossible.EXPERIMENTALSECTIONFabricationofCNTInk.First,CNTsweretreatedwith5Mnitricacidfor30mintoincreasethehydrophilicity.Then20mg/mLSupportingInformationAvailable:Moredetailedinformationaboutcalculations,sensorworkingprinciple,IÀVcurveofCCT,surfacepotentialofPTFE,supportingmovies1À3,etc.ThismaterialisavailablefreeofchargeviatheInternetatacidpretreatedCNTsand40mg/mLsodiumdodecylbenzene-sulfonate(SDBS)weredispersedindeionizedwater.Last,themixturewassonicatedfor20minusinganultrasoniccelldisruptor(KeshengSonicsVibraCell,550F).FabricationofCCT.Sincethesurfaceofthecommercialcottonthreadswasfibrous,thecottonthreadswerefirsttreatedwithanethanolflametoeliminateredundantfibers.Thentheywerecleanedbyacetone,ethanol,anddeionizedwaterseveraltimes,followingbyimmersinginto5Mnitricacidsolutionfor1htoincreasethehydrophilicity.ThecottonthreadswerecoatedbyCNTsbyusingtheCNTinkmentionedabovethroughthe“dippinganddryingalternately”method.38Specifically,thetreatedcottonthreadsweredippedintotheCNTinkanddriedat80°Cinanoven.Afterthisprocesswasrepeatedseveraltimes,theconductivecottonthreadskeptdryat80°Cinanovenfor2h.FabricationofPTFEandPCCT.ThePCCTwasfabricatedthroughthe“dippinganddrying”methodaswell.Typically,theCCTwasimmersedintoPTFEsolution(Aladdin,60%wt,aqueous)for30sandthendriedat60°Cfor5min.The“dippinganddrying”processwasrepeatedthreetimestoensurethattheCCTwascompletelycoatedbyPTFE.TheresultingPCCTwasthenannealedat150°Cinanovenfor12h.Finally,thePCCTswerepolarizedviatheplasmamethodwithaservicepowerof120Wfor40min.AssemblyofFBGandthe“PowerShirt”.ACCTandaPCCTwereentangledwitheachothertoformadouble-helix-structuredevice.ThehelixturnsandleavinggapsoftheFBGcanbeadjusted,andthetwoendsoftheFBGwerefixedbycommoditycottonthreads.ThentheFBGswerewovenintothefabrictoforma“powershirt”.Characterization.Themorphologyofthesampleswasprobedbyahigh-resolutionfieldemissionscanningelectronmicro-scope(FEINovaNanoSEM450).TheconductanceoftheCCTwasstudiedbyaKeithley2400sourcemeter.ThemechanicalpropertyoftheCCTwascharacterizedbyanelectronicuniversalmaterialtestingmachine(RGM-4005T,Reger,China).Theplas-mapolarizationmethodwascarriedoutwithaPDC-MGgasplasmadrycleaner(Hengming,China).ThesurfacepotentialofPTFEwasdetectedbyanelectrometer(EST102,HuajingBeijing,China).TheperiodicstretchingÀreleasingprocessoftheFBGwasstimulatedbyaresonator(JZK,Sinocera,China),whichwascontrolledbyasweptsignalgenerator(YE1311-D,Sinocera,China).Thepowergenerationperformancemeasurementsys-temoftheFBGisschematicallyshowninFigureS4,inwhichoneendoftheFBGwasfixedonanx-y-zmechanicalstagethatwasmountedtightlyonanopticaltable,whiletheotherendwasfixedontheresonator.Duringthemeasurementprocess,asingleFBGwasperiodicallystretchedandreleasedwithdiffer-entdegreesofstrainandfrequencybytheresonator(JZK).Simultaneously,thecurrentsignalsthroughanexternalloadof80MΩweremeasuredbyaStanfordlow-noisecurrentpre-amplifier(modelSR570).ThemodulatedanddemodulatedsignalsgeneratedbythewirelessbodytemperaturesensorsystemweremonitoredbyanAgilentDSOX-2014oscilloscope.ConflictofInterest:Theauthorsdeclarenocompetingfinancialinterest.Acknowledgment.ThisworkwasfinanciallysupportedbytheNationalNaturalScienceFoundationofChina(51322210,51002056),aFoundationfortheAuthorofNationalExcellentDoctoralDissertationofPRChina(201035),theFundamentalResearchFundsfortheCentralUniversities(HUST:2012YQ025,2013YQ049,2013TS160),andtheseedprojectofWuhanNationalLaboratoryforOptoelectronics.TheauthorswouldliketothankProf.J.TangandDr.F.R.Fanfortheirconstructivesuggestions.ZHONGETAL.http://pubs.acs.org.REFERENCESANDNOTES1.Rogers,J.A.Electronics:ADiversePrintedFuture.Nature2010,468,177–178.2.Yamada,T.;Hayamizu,Y.;Yamamoto,Y.;Izadi-Najafabadi,A.;Futaba,D.N.;Hata,K.AStretchableCarbonNanotubeStrainSensorforHuman-MotionDetection.Nat.Nano-technol.2011,6,296–301.3.Wang,C.;Hwang,D.;Yu,Z.;Takei,K.;Park,J.;Chen,T.;Ma,B.;Javey,A.User-InteractiveElectronicSkinforInstanta-neousPressureVisualization.Nat.Mater.2013,12,9–904.4.Lipomi,D.J.;Vosgueritchian,M.;Tee,B.;Hellstrom,S.L.;Lee,J.A.;Fox,C.H.;Bao,Z.Skin-LikeSensorsofPressureandStrainEnabledbyTransparent,ElasticFilmsofCarbonNanotubes.Nat.Nanotechnol.2011,6,788–792.5.Ross,P.ManagingCarethroughtheAir.IEEESpectrum2004,6,26–31.6.Flowerday,A.;Smith,R.LessonsLearntfromLong-TermChronicConditionMonitoring.Proc.1stInt.WorkshopWearableImplantableBodySensorNetwork2004,48.7.Needham,P.;Gamlyn,L.ArrhythmiaAnalysisintheCom-munity.Proc.1stInt.WorkshopWearableImplantableBodySensorNetwork2004,49–50.8.Wolffenbuttel,M.R.;Regtien,P.P.L.PolysiliconBridgesfortheTealizationofTactileSensors.Sens.Actuators,A1991,26,257–2.9.Chu,Z.;Sarrob,P.M.;Middelhoeka,S.SiliconThree-AxialTactileSensor.Sens.Actuators,A1996,54,505–510.10.Jost,K.;Stenger,D.;Perez,C.R.;McDonough,J.K.;Lian,K.;Gohotsi,Y.;Dion,G.KnittedandScreenPritedCarbon-FiberSupercapacitorsforApplicationsinWearableElec-tronics.EnergyEnviron.Sci.2013,6,2698–2705.11.Hu,L.;Pasta,M.;Mantia,F.L.;Cui,L.;Jeong,S.;Deshazer,H.D.;Choi,J.;Han,S.;Cui,Y.Porous,andConductiveEnergyTextiles.NanoLett.2010,10,708–714.12.Lee,Y.;Kim,J.;Lee,J.;Kim,H.;Choi,S.;Seo,J.;Jeon,S.;Kim,T.;Lee,J.;Choi,J.WearableTextileBatteryRechargeablebySolarEnergy.NanoLett.2013,13,5753–5761.13.Chen,T.;Qiu,L.;Yang,Z.;Cai,Z.;Ren,J.;Li,H.;Lin,H.;Sun,X.;Peng,H.AnIntegratedEnergyWireforBothPhotoelectricConversionandStorage.Angew.Chem.,Int.Ed.2012,51,11977–11980.14.Qi,Y.;McAlpine,M.C.Nanotechnology-EnabledFlexibleandBiocompatibleEnergyHarvesting.EnergyEnviron.Sci.15.2010Starner,,3,1275T.Human-Powered–1285.WearableComputing.IBMSyst.J.1996,35,618–629.16.Rome,L.C.;Flynn,L.;Goldman,E.M.;Yoo,T.D.GeneratingElectricityWhileWalkingwithLoads.Science2005,309,1725–1728.17.Donelan,J.M.;Li,Q.;Naing,V.;Hoffer,J.A.;Weber,D.J.;Kuo,A.D.BiomechanicalEnergyHarvesting:GeneratingElectricityduringWalkingwithMinimalUserEffort.Science18.2008Nelson,,319L.;,807Bowen,–810.C.;Stevens,R.;Cain,M.;Stewart,M.ModellingandMeasurementofPiezoelectricFibersandInterdigitatedElectrodesfortheOptimisationofPiezofiberComposites.SPIEConf.Proc.2003,5053,556–567.19.Wang,Z.L.;Song,J.PiezoelectricNanogeneratorsBasedonZincOxideNanowireArrays.Science2006,312,242–246.VOL.8’NO.6’6273–6280’2014www.acsnano.org6279

ARTICLE20.Qin,Y.;Wang,X.;Wang,Z.L.Microfibre-NanowireHybridStructureforEnergyScavenging.Nature2008,451,809–813.21.Qin,Y.;Jafferis,N.T.;Lyons,K.;Christine,J.;Lee,M.;Ahmad,H.;McAlpine,M.C.PiezoelectricRibbonsPrintedontoRubberforFlexibleEnergyConversion.NanoLett.2010,10,524–528.22.Park,K.;Lee,M.;Liu,Y.;Moon,S.;Hwang,G.;Zhu,G.;Kim,J.;Kim,S.;Kim,D.;Wang,Z.L.;etal.FlexibleNanocompositeGeneratorMadeofBaTiO3NanoparticlesandGraphiticCarbons.Adv.Mater.2012,24,2999–3004.23.Lee,K.;Kumar,B.;Seo,J.;Kim,K.;Sohn,J.;Cha,S.;Choi,D.;Wang,Z.L.;Kim,S.P-TypePolymer-HybridizedHigh-PerformancePiezoelectricNanogenerators.NanoLett.24.2012Chang,,12C.;,1959Tran,–V.19.H.;Wang,J.;Fuh,Y.K.;Lin,L.Direct-WritePiezoelectricPolymericNanogeneratorwithHighEnergyConversionEfficiency.NanoLett.2010,10,726–731.25.Persano,L.;Dagdeviren,C.;Su,Y.;Zhang,Y.;Girarod,S.;Pisignano,D.;Huang,Y.;Rogers,J.A.HighPerformancePiezoelectricDevicesBasedonAlignedArraysofNano-fiCommun.bersofPoly(vinylidene2012,4,1633.fluoride-co-trifluoroethylene).Nat.26.Lee,B.;Zhang,J.;Zueger,C.;Chung,W.;Yoo,S.Y.;Wang,E.;Meyer,J.;Ramesh,R.;Lee,S.Virus-BasedPiezoelectricEnergyGeneration.Nat.Nanotechnol.2012,7,351–356.27.Sun,C.;Shi,J.;Bayerl,D.J.;Wang,X.PVDFMicrobeltsforHarvestingEnergyfromRespiration.EnergyEnviron.Sci.28.2011Zhong,,4,Q.4508Z.;Zhong,–4512.J.W.;Hu,B.;Hu,Q.;Zhou,J.;Wang,Z.L.Paper-BasedNanogeneratorAsPowerSourceandActiveSensor.EnergyEnviron.Sci.2013,6,1779–1784.29.Boland,J.;Chao,Y.;Suzuki,Y.;Tai,Y.C.MicroElectretPowerGenerator.Proc.16thIEEEInt.Conf.MEMS2003,538–541.30.Fan,F.;Tian,Z.;Wang,Z.L.FlexibleTriboelectricGenerator.NanoEnergy2012,1,328–334.31.Zhang,X.;Han,M.;Wang,R.;Zhu,F.;Li,Z.;Wang,W.;Zhang,H.Frequency-MultiplicationHigh-OutputTriboelectricNanogeneratorforSustainablyPoweringBiomedicalMicrosystems.NanoLett.2013,13,1168–1172.32.Post,E.R.;Waal,K.ElectrostaticPowerHarvestinginTextiles.Proc.ESAAnn.Meet.Electrost.2010,PaperG1.33.Hu,L.;Choi,J.;Yang,Y.;Jeong,S.;Mantia,F.L.;Cui,L.;Cui,Y.P.HighlyConductivePaperforEnergy-StorageDevices.Natl.Acad.Sci.U.S.A.2009,106,21490–21494.34.Malecki,J.A.LinearDecayofChargeinElectrets.Phys.Rev.B1999,59,9954–9960.35.Lee,S.;Hinchet,R.;Lee,Y.;Yang,Y.;Lin,Z.;Ardila,G.;Montes,L.;Mouis,M.;Wang,Z.L.UltrathinNanogenera-torsasSelf-Powered/ActiveSkinSensorsforTrackingEyeBallMotion.Adv.Funct.Mater.2013,24,1163–1168.36.Hu,Y.;Yang,J.;Jing,Q.;Niu,S.;Wu,W.;Wang,Z.L.Tribo-electricNanogeneratorBuiltonSuspended3DSpiralStructureasVibrationandPositioningSensorandWaveEnergyHarvester.ACSNano2013,7,10424–10432.37.Lin,L.;Xie,Y.;Wang,S.;Wu,W.;Niu,S.;Wen,X.;Wang,Z.L.TriboelectricActiveSensorArrayforSelf-PoweredStaticandDynamicPressureDetectionandTactileImaging.ACSNano2013,7,8266–8274.38.Liu,N.S.;Ma,W.Z.;Tao,J.Y.;Zhang,X.H.;Su,J.;Li,L.Y.;Yang,C.X.;Gao,Y.H.;Golberg,D.;Bando,Y.Cable-TypeSupercapacitorsofThree-DimensionalCottonThreadBasedMulti-GradeNanostructuresforWearableEnergyStorage.Adv.Mater.2013,25,4925–4931.ZHONGETAL.VOL.8’NO.6’6273–6280’2014www.acsnano.org6280