Bistable origami thermal switch with high switching ratios

Domain: physics
Published: 2026-02-25
Editorial outcome: major_revision

Abstract
EffectivethermalmanagementiscriticalforpowerelectronicsinAIandrobotics,highlightingtheneedfordynamic,reversiblethermalswitches.Achievingahighswitchingratioremainschallenging.Here,wepresentabis-tableorigami-inspiredthermalswitchthatswitchrapidlybetweendistinctthermalconductionstateswithoutexternalenergyorsensoryinput.Fabri-catedfromathinfilmthroughprecisecut-and-fold,itachievesthermalswitchingratiosof13,984invacuumand1360inambientair,significantlyhigherthanexistingapproaches.Switchingisdrivenbysnap-throughinstability,actuatedbyacombinationofshape-memoryalloyandelasticsprings.Theenergylandscapecanbetunedthroughgeometricvariationstoadjusttriggeringtemperatureandswitchingratio.Wedemonstratestable,repeatablethermalregulationacrossmultiplescenarios,offeringapathwaytowardpassive,programmablethermalmanagement.

Introduction
Modulatingheatflowwithprecision-akintoelectronicanalogs—hasbeen a long-standing aspiration in thermodynamic engineering,which holds the promise of advancing technologies ranging fromphononic logic circuits to functional thermal devices1,2. However,achievingactiveandreversiblecontrolofthermalconduction(i.e.,thermalswitch)remainsaformidablechallengeduetothedifficultyofsimultaneouslymeetingessentialcriteria,includinghighswitching ratio, robust cyclic reliability, passive operation, and bistablefunctionality. Advances in nanotechnology have extended ourunderstanding of heat carrier transport and enabled innovativeapproachestoitsmanipulation3–6.Overthepastdecades,significantefforts have been dedicated to tuning room-temperature thermaltransport in solids through temperature/light triggered phasetransitions7,8,electrochemicalscatteringmotionofions9,10,orelectrical/magnetic field-driven structural modulation11,12. While thesestrategieshaveshownpromise,theysufferfromcriticallimitations:lowswitchingratios(<13)7–12,severeperformancedegradationafterlimited cycles9,10, and the need for continuous external energyinput11,12, complicating system design and reducing energyefficiency.

Analternativeapproachinvolvesthermalswitchesbasedontheopeningandclosingofamacroscopicinterface.Thisstrategytypicallyleveragesdifferentialthermalexpansionbetweenmaterialstoinducegeometricchanges,exploitingthestronglynon-linearbehaviorofthermalconductanceasinterfacialgapsclose13,14.Throughdevelopinga shape memory alloy (SMA) actuation configuration to close aninterfacialgap,aswitchingratioof~40inairisachieved,whichbooststo~2000undervacuumbyeliminatingnaturalconvection15.However,the switching ratio is still impractical under ambient environment.More importantly, thermal switching strategies developed to date(bothnanoscalestructuralengineeringandmacroscopicgapclosing)failtoaddressacriticalgap:thelackofbistableoperation.Bistablefunctionality, essential for binary representation (0 and 1) akin todigital electronics, ensures clear state differentiation, resistance toexternal perturbations, and threshold-based switching for reliableoperationeveninnoisyenvironments.

To address the aforementioned challenges, we seek solutionsfromorigami,theancientartofpaperfolding16,17.Inrecentyears,origamihassignificantlyinfluencedscienceandengineering,impactingvarious fields including condensed matter physics18, materialscience19–22, mechanical engineering23–29, robotics30–33, biomedicalengineering34,35,andarchitecture36,37.Atits core,origami transformsflattwo-dimensionalmaterialsintointricatethree-dimensionalstructures through precise cuts and folds. In particular, by leveragingcarefully engineered crease patterns38–40, origami leads to bistablestructuresthatcanreliablyswitchbetweentwogeometricconfigurations with distinct thermal conductance. These bistable systemsexhibit remarkable mechanical properties, enabling them to snaprapidlyfromonestatetoanotherwithprogrammableenergyinput41–43.

Leveraging the inherent bistability of origami, we introduce anovelpassivethermalswitchwithunprecedentedswitchingratio.Forinstance,thepassiveswitchcanbeappliedtoapowersupplyarray,allowing pixelated regulation of the temperature of each individualbattery (Fig. 1a). Specifically, our design utilizes a bistable origamiarchitecture that enables rapid, reversible switching between twodrastically different thermal conduction states, leading to ultrahighswitching ratio (Fig. 1b). The origami structure undergoes flat-stateactuation,duringwhichtheupperplateremainsparalleltothebase,suchthatintimatecontactismaintainedwitheitherthedeviceortheheatsink.Thestateswitchingenergyisprovidedbyinnovativethermalactuators,whichtakeadvantageofthethermalresponsivenessofSMAandtheelasticityoftailoredsprings.Theorigamimetastructurecanthenlocallycontrolthecontactofadevicetotheheatsinktodisplaceheatornotbyshapetransition.Asaresult,theproposedswitchregulates the device’s temperature between designated temperatures,turningonandoffautomaticallywithouttheneedforexternalsensoryinformationandenergyinput.Ourresultsdemonstrateasignificantenhancement in thermal modulation performance, with robust andenergy-efficientoperationunderambientconditions,pavingthewayfornext-generationthermalmanagementsystems.

Results
The ultra-high switching ratio originates from the bistable origamiswitch (BOS) from the two distinct stable states: the flat state (ONstate)andtheelevatedstate(OFFstate).Thetwostablestatesdisplayhuge difference in thermalconductance (Fig. 1b). When the hosteddevice is heated up, the heat drives the origami metastructure toovercometheenergybarriertoshiftfromitselevatedstatetoitsflatstate,andturnontheheatexchangewiththeheatsink(Fig.1a).Whenthedevicecoolsdown,theelasticforcerecoverstheorigamimetastructure to the elevated state and turn off the heat exchange. Bycontinuouslyrepeatingthesesteps,thetemperatureofadeviceiskeptwithintheproperrangepassively.

TheorigamipatternoftheBOSisillustratedinFig.1c,whichiscomposedoffiveaxisymmetricarmsandapentagoncentralpanel.Adesignparadigmforthegeometryisproposed,asillustratedinFig.S1(SupplementaryNote1).Itisgeneratedfromthreeconcentricpolygons with different radius and the connection lines between theircorrespondingvertices.Itisaspecialorigamistructurethatfeaturesdevelopabilityandchiralgeometry,knownastheRotationalErectionSystem44.Countingthedegreesoffreedomoftheorigamistructuresuggests that it is over constrained, leading to inherent bistability.Whenthearmsstandupfromtheinitialflatconfiguration,thepentagonpanelisrotatedandelevatedevenly(SupplementaryVideo1).Thearmsareundercompressionduringtheelevationprocess,whichcontributestotheenergybarrierbetweenthetwostablestates.Theorigamipatternisdesignedunderfourparameters:a,c,α1,andα2,asshowninFig.1c.Theparametersaandcarederivedfromtheoveralldimensionsofthedeviceandtheswitch.Theparametersα1andα2determinetheheightandthearmwidthofthestructure,asillustratedinFig.S2.

Thepolyimidesheetwithathicknessof0.2mmwasselectedasthebasedmaterialtofabricatethestructure.WemeasuredtheYoung’smodulusofthepolyimidesheettobe4000MPa,asshowninFig.S4(SupplementaryNote3).Theorigamistructureisfabricatedinthreesteps(Fig.1d).First,weusealasercuttertocutthepolyimidesheetfollowing the origami pattern, with all folding creases and cuttingedges trimmed off. Second, we use pre-glued polyimide tape(0.06mm)tocoatthepolyimidepanelsandreconnectthecreasesandedges.Finally, the polyimide tape is trimmed again only along thecutting edges. By this way, the rotational stiffness of the foldingcreasesisextremelyreduced(0.0285N·mm/rad,Fig.S5).Resultsfromthemechanicaltestoftheorigamistructuresshowconsistentbistablecharacteristics, including peak forces and location of the instabilitypoint, across different fabrication batches (Fig. S6, SupplementaryNote 3),attesting to the repeatabilityofthe manufacturing processandtherobustnessofthedesign.

Afterequippedwiththethermalactuatorsandtheregulator,weobtainthefunctionalBOS(Fig.1e).FigureS3(SupplementaryNote2)presents the specific components employed and the detailed compositionalprocedure.Eacharmisembeddedwithacustomthermalactuatortodrivetheswitchinginresponsetoexcessiveheatoverthetemperaturethreshold.

ToexperimentallymeasurethethermalconductanceofthetwostatesoftheBOS,weemployedthewidelyrecognizedreferencebarmethod45. A high-vacuum steady-state thermalconduction platformwasconstructedincompliancewiththeASTM-5470standard,anda schematicoftheexperimentalsetupisillustratedinFig.2a.TheBOSwaspositionedbetweentwostainless steel reference bars—serving asheat source and sink—each embedded with three equidistant high-precision thermocouples along their lengths to ensure a one-dimensionalheat flow. Photographsoftheexperimentalsetupalongwithacorresponding close-upimageare illustrated in Fig.S9 (SupplementaryNote4).Figure2b,cshowphotographicimagesofthetestapparatus in its ON and OFF states, as well as the correspondingtemperature-timeprofilesrecordedbythethermocouples.Figure2dpresentsthe steady-state temperature distributions along the referencebars in both switching states.

Thethermalconductancevalues(G on=off)werecalculatedusingFourier’slaw,G on=off=q=ΔT on=off,where the interfacial temperaturedrop ΔT on=off was determined by linear extrapolation of bartemperatureprofiles,andtheheatfluxqwasderivedfromthetemperaturegradientinthelowerbar.Thethermalswitchingratio(ρ=G on =G off)serves as a key performance metric. In the OFF state, a substantialtemperature discontinuity of ΔT=41.87°C was observed across theBOS, corresponding to an ultralow thermal conductance ofG off =2.0W/m2·K. Upon switching to the ON state, the origami-enabled mechanical contact significantly reduced the interfacialresistance,resultinginΔT=0.189°Candanexceptionallyhighconductance of G on=27,968W/m2·K. These values yield an unprecedented switching ratio of ρ=13,984 under vacuum conditions—thehighestreportedtodateforapassivethermalswitch.Finiteelementsimulations (Fig. 2e) further corroborate the experimental findings,showingdistinctandconsistenttemperaturedistributionsfortheONandOFFstateswithinthereferencebarassembly.Toassessreal-worldapplicability, the same measurements were conducted under atmospheric conditions. Despite the presence of parasitic heat transferthroughairconductionandconvection,whichleadstotheOFFstateconductance to G on=51,685W/m2·K and G off =38W/m2·K (Fig. S10,Supplementary Note 5), respectively, the BOS achieved a switchingratioof1360—stillseveralordersofmagnitudegreaterthanexistingpassivethermalswitchingsolutions.

To elucidate the physical origins of the exceptionally highswitchingratiooftheBOS,wedevelopedatheoreticalthermalconductance model based on the reference bar experimental setup(Supplementary Note 6). Under vacuum conditions, heat transferbetweentheupperandlowerbarsoccursthroughtwoprimarypathways: radiative heat exchange and solid conduction via the BOS(Fig. S11,TableS1).The modelpredicted anOFF state thermal conductanceofG off=1.75W/m2·Kandaswitchingratioρ=15982,closelyaligning with the experimental value of 13,984. The remaining discrepancyisprimarilyattributedtouncertaintiesinestimatingsurfaceemissivity.DecompositionofG off revealsthatsolidconductioncontributes only 0.37W/m2·K—approximately 18.5% of the total—significantly lower than that of state-of-the-art contact-based thermalswitches. For comparison, a typical SMA-spring thermal regulatorexhibits G off =3.98W/m2·K, with solid conduction accounting for83.9%ofthetotal15;arepresentativemagneticthermaltransistorshowsG off =8.0W/m2·K,with84.0%attributedtosolidconduction46(Fig.2f,TableS2).WefurtherevaluatedmultiplecandidatebasematerialsfortheBOSwithdifferentthermalconductivities(e.g.,PC,PVC,PET,PS,and silica aerogel, summarized in Fig. S11). Each of these materialsshows a high switching ratio, ranging from 1.6×104 to 2.0×104 invacuum,whichconfirmsthebroadmaterialcompatibilityoftheBOSdesign.

Unlike prior designs with immediate connection between thethermalreservoirsviathermallyconductivesolidelements(e.g.,SMAorpolymerpins),theBOSemploysabistableorigamimetastructureinwhichtheSMAhingesareisolatedatthefoldingcreasesanddonotbridgethehotandcoldsurfaces.Thus,thethermalpathintheoff-stateisdominatedbythethinpolyimidefilm(withultralowthermalconductivity,k=0.2W/m·K)andalargespatialgap(16mm),effectivelysuppressingbothheatconductionandconvection.Moreover,theBOSdesignfeaturesgeometricallytunableparameters—suchasarmwidth,length,andheight—thatallowforprogrammingoftheswitchingratioacrossabroadrange(ρ=15,425to16,771,Figs.2g,S12).Combinedwithitsrelativelyfastresponsetime,theBOSnotonlyoutperformsexistingpassivethermalswitchesbutalsoexceedstheperformanceofmanyactiveones(Fig.2handTableS2),demonstratingitstransformativepotentialfornext-generationthermalmanagementapplications.

Toswitchbetweenthetwostablestates,anenergybarriermustbeovercomebythethermalactuators.Wedevelopedananalyticalmodeltostudytheenergyevolutionoftheorigamistructureduringdeformation(SupplementaryNotes7and8).Themodelaccountsforthefoldingenergylocalizedatthehingesandthebendingenergyalongthearms.Theanalysisbeganbyexaminingthekinematicsofthehingesandtheupperplate.Theresultsconfirmthatthefoldingatthebottomhinges,alongwiththeresultingdisplacementandrotationoftheupperplate,undergoesrigid-bodymotion,asshowninFig.S13.Incontrast,thefoldingattheupperhingesisaffectedbythebendingofthearms.Toinvestigatethebendingenergy,thearmoftheorigamistructure is simplified as a beam element and analyzed usingTimoshenkobeamtheory.Thebeammodel,employedtosimulatethearmundershearorcompression,yieldsresultthatcloselymatchthefinite element simulations (Figs. S14–S16). The stress distributionresultsfromthefiniteelementsimulationsarepresentedinFig.S17,revealingsignificantlocalized stress intensityinthe arm and creaseregions.Thestressconcentrationsmainlyoccuratthebottomcreases,reachingamaximumVonMisesstressof129MPa.Furthermore,fiveorigami samples with different geometrical parameters were fabricatedtovalidatetheanalyticalmodelexperimentally(Fig.S18).

Throughquantitativeanalysisbytheanalyticalmodel,weinvestigatethebistableenergylandscapeandthedesignscopeoftheorigamistructure(SupplementaryNote9).Thegeometricparameterα2,whichgovernsthefoldingdirectionofthearms,directlydetermineswhetherthestructureexhibitsbistability.Asα2increases,theenergybarrier of bistability emerges, increases, then decreases, and finallydisappears (Fig. S19). Along with the geometric parameter α1, theenergybarriervariesfrom0mJto1mJ.Toachieveahigherbarrier,theradiusofthemiddlepentagon(Fig.S1)canbeincreased,raisingtheenergybarrierto4mJ.Fig.S20furtherillustratesthebistableorigamistructurewithinthe(α1andα2)parameterspace:armwidthisbounded between 15–21.5mm, while standing height ranges from 16to26.3mm.

Meanwhile,theanalyticalmodelverifiesthattheorigamistructureexhibitsadeformationpatternwithapproximatelyonedegreeoffreedom.Actuatinganyhingecandrivetheentirestructureforstatetoggling. We select the folding creases between the arms and thepentagonpaneltoinstallthethermalactuators(Fig.3a)sothattheyareclosetothehosteddevice(i.e.,heatsource)forefficientheating.Theactuationforcebythethermalactuatorsvariesasthetemperatureandtheelevatedheight(δ)changes,demonstratingaverticaldrivingforceof1.2Nat80°Cand−0.5Nat25°C(Fig.3b).TheexperimentalsetupformeasuringtheactuationforceisprovidedinFig.S8(SupplementaryNote3).Inthisprocedure,theBOSisclampedinafixedposition.Theactuatorsarethenheatedbyaheater,andtheverticalloadismeasuredconcurrently.

Thethermalactuatorcomposesofanickeltitanium(NiTi)SMAwireandanelastictorsionalspring(Fig.3c),whichprovidesbidirectional driving torque at low and high temperature thresholds. ThedrivingtorqueisfromthedifferenceofthetorquesoftheSMAwireandthetorsionalspring.TheSMAwirehasaninitialZ-shapeatlowtemperatureandtwists90°towardsaU-shapeuponheatingaboveitsphasetransitiontemperature.ThemaximumactuationtorqueoftheSMA wire is measured to be 5N·mm at 70°C (Fig. 3d). When thetemperature of SMA wire decreases below 25°C, the active drivingtorquevanishes,andtheSMAwireisleftwithanearlyconstantpassiveresistanceof0.86N·mm.Ontheotherhand,thetorsionalspringhasanelastictorqueof1.9N·mm/radwitharestangleattheelevatedOFFstate.ItselastictorqueiscapableofuntwistingtheSMAwirebacktoitsZ-shape. However, as γ decreases towards the elevated state, theelastictorqueofthetorsionalspringdecreaseslinearly,andreachesanequilibriumwiththeresistanceoftheSMAwireat147°(Fig.3d).

Furthermore,takingintoaccountthebistableenergybarrieroftheorigami structure, it is clear that the driving force of the thermalactuatoratlowtemperatureisnotenoughtopushtheBOSfromONstatetoOFFstate.Toaddressthisproblem,anelasticregulator(i.e.aTPU cord) is adopted to adjust the energy barrier of the origamimetastructure. The regulator is connected between the ends of theupperplateandthebase(Fig.3a).WhentheBOSswitchesfromtheelevatedtotheflatstate,theupperplaterotatesrelativetothebase,stretchingtheregulatorandincreasingitstensilestrainfrom0to0.19(Fig.S21,SupplementaryNote10).Thus,atlowtemperatureandtheONstate,theregulatoraddsextraforcetopulltheBOSup,andequivalently,reducesthecriticalforcerequiredtoovercometheenergybarriertoelevate(i.e.,turningOFF).AsshowninFig.3e,byincreasingtheprestrainoftheregulatorattheelevatedstateoftheBOS,thecriticalstructural force of the BOS is effectively reduced for switchingOFF (Supplementary Video 1). The experimental setup for measuring thestructuralforceandthepreloadingstrainoftheregulatorisdepictedinFig.S7(SupplementaryNote3).TheinfluenceoftheregulatorontheenergybarriersoftheBOSisillustratedinFigs.S21andS22.Theresultsdemonstratethattheregulatornotonlyreducesthefirstenergybarrierbutalsostrengthensthesecondone,therebyenablinganextensionofthebistableenergylandscapebyupto40%.

TorealizefullcyclesoftheBOS,thedrivingforceofthethermalactuators and the resistance of the origami metastructure must becarefullycalibrated(Fig.3f).Wemustensurethattheactuationforcesatboththehighandlowswitchingtemperaturesarelargerinmagnitudethanthecriticalstructural forces to overcome bistable energybarrier.Inotherwords,thestructuralforcecurvemustbeclampedbythetwoactuationforcecurves,asshowninFig.3f.Whentheactuationforceexceedsthenegativepeakforce(M’),thethermalactuatorspushtheBOStosnapdownandturnON.Conversely,whenthetemperaturebecomes lower than 25°C, the reverse actuation force exceeds thepositivepeakforce,andtheBOSiselevatedandturnedOFF.

TuningtheprestrainoftheregulatorchangesthestructuralforceprofileoftheBOS(Fig.3e),andthusadjuststheswitchingtemperatures. To elaborate, as the prestrain of the regulator increases, thecritical peak force linearly increases (Fig. S23), and the requiredactuation force increases accordingly, leading to higher switchingtemperature (Fig. 3g). In addition to the prestrain of the regulator,customizableswitchingtemperaturescanalsobeachievedbychangingthephasetransitiontemperatureoftheSMA.Forexample,ifwechange the phasetransition temperature ofthe SMAfrom 60°Cto47°C,thehighswitchingtemperaturedecreasesfrom73°Cto63°C(Fig.S26andSupplementaryVideo2).

In our experimental demonstration (Fig. 4, SupplementaryVideo 2), the low and high switching temperatures are set as 25°C(ON→OFF)and72°C(OFF→ON),respectively(Figs.3e,S24,SupplementaryNote11).ThesetupisinambientairandcomposedoftheBOS,aheater,andaheatsink(Fig.4a).Theheatsinkisa2cm × 2cmwater-cooledcopperplatewithaconstanttemperaturecontrolledat4°C.An1mm-thick,aluminumnitride-filledthermalconductivesiliconesheetisappliedonthecopperplatetoenhancethermalcontactwiththehosteddeviceatONstate.TotestthecyclicperformanceoftheBOS,astandardceramicJouleheaterisfirstused,under5V-appliedvoltage.TheBOSautomaticallytogglesONandOFFaccordingtotheswitchingtemperatures(Fig.4b).Figure4cillustratestheheattransferfromtheheatertothethermalactuatorviathecopperpanel.Thisdesignresultsin a temperature difference of 7°C between the heater and theactuatorwhentheheaterisheatedto70°C.

Therelationshipbetweenthedrivingangleofthethermalactuator and the vertical displacement of the upper plate is plotted inFig.4d.Duringoperation,theactuatorundergoesatotaldrivingangleofapproximately40degreesateachstroke.Itfirstfoldsby20degreestobuildupactuationforce,thendrivestheBOSupwardordownwardthroughthesubsequent20degrees.ThisbehaviorconfirmsthattheBOS effectively locks into position at both the ON and OFF states,withoutgettingstuckinsomeintermediatestates.Figure4edisplaysthereal-timetemperaturesanddisplacementcurvesoftheBOS.ThedatashowthattheBOSremainsstableineithertheONorOFFstateuntil the temperature reaches the switching threshold. The subsequentstatetransitionexhibitsaresponsetimeof~10sandaverticalspeedof0.66mm/s(Fig.S25).Thetemperatureregulationfunctionisuncompromised after 100 cycles of continuous test, demonstratingoutstandingreliabilityoftheBOS(Fig.4f).Duringtherepeatedcycles,thehighandlowswitchingtemperaturesremainverystable,measuredas71.7±1.7°Cand28.2±3.4°C,respectively.Therepeatabilityofthefabricationprocessishighlightedbythebatch-to-batchconsistencyobservedintheswitchingtemperatureandoperationalcharacteristics,asshowninFig.S27.

The switching speed of the BOS is influenced by a number offactors,includingtraveldistancebetweentheONandOFFstates,thenumberofthermalactuators,heatsinktemperature,theheatingrate,andthebearingmassontheupperplate.ItwasfoundthatthetraveldistanceplaysaprimaryroleaffectingtheswitchingspeedoftheBOS.Usingahigh-speedcamera(X190,Revealer,China)tocapturethepurestructuralsnap-throughtransitionoftheorigamistructure(Fig.5a),weobserve that traveling from the instability point to any stable staterequireslessthan90ms.Toexploitthisproperty,weequippedtheBOSwithalimiterthatconstrainstheupperplatetobecome3mmclosertoitsinstabilitypointthanbefore(Fig.5b).Withthelimiterandtwo thermal actuators, the BOS achieves two-way operation with aswitching time of 200ms (Fig. 5c), with switching temperatureat83.6°C.

The influence of the number of thermal actuators on theswitchingspeedispresentedinFig.5d.Theresultsindicatethatagreaternumber ofactuatorsleads toanincreaseintheswitchingtime,owingtotheincreasedresistanceforceofthesystem.Aslow-motionvideooftheBOSequippedwithfiveactuatorsisprovidedinSupplementaryVideo3.FortheBOSequippedwithonlyonethermalactuator,thegeneratedactuationforcewasinsufficienttodrivethebistableswitching.Influencesoftheheatsinktemperature,theheatingrate,andthebearingmassontheupperplateareshowninFig.5e-g.Whilechangingtheheatsinktemperatureandtheheatingrateexhibitnosignificanttrend,wefindthatlargerbearingmassonthe upper plate leads to slower transition, likely due to largerinertia.

To investigate the influence of bearing mass, we conducted aseries of experiments by adding calibrated weights onto the upperplateoftheBOS.Astheloadincreased,thetransitionfromtheONtoOFFstatebecamemorechallengingduetotheincreasedweightandinertia.Toaddressthis,wecanraisethepre-strainintheregulator,therebyboostingtherestoringforceattheONstatetosupportheavierloads.Asaresult,evenunderatotalmassof20g,theBOSmaintainedafunctionalsnap-throughtransition,withaswitchingtimeof470ms,aspresentedinFig.5gandtheSupplementaryVideo4.

ToshowcasetheversatilityoftheBOSinrealworldapplications,weexperimenttheBOSfortemperatureregulationofsomecommonlyused electric devices, including battery, power amplifier, Bluetoothchip,LED,andDC-DCconverter(Fig.6a,SupplementaryVideo5).TheBOSdisplaysitspassive,automaticswitchingfunctiontothesedevices, and successfully regulates the temperature of the devices in acertain range (Fig. 6b–e). The designated temperaturerange of thepoweramplifier,LED,andDC-DCconverteraretunedtobearound24–77°C.SincetheheatingeffectoftheBluetoothchipismuchhigher,themaximumswitchingtemperatureisincreasedto114.5°C.Incontrast,thelithium-ionbatteryhasstringenttemperaturerequirementstoavoidpermanentdamage.Asaresult,thethermalactuatorisbuiltwithlowtemperatureSMAof47°C,suchthatthecorrespondingBOSmaintainsasteadytemperatureregulationaround27–67°C(Fig.6f).The BOS design also shows quite consistent thermalswitching performancewithdifferentnumbersofarms,asshowninFig.6g-handSupplementaryVideo6.Theswitchingtimeofthefour-armandsix-armBOSare7.2sand90ms,respectively,demonstratinganotabledecreaseasthenumberofarmsincreasesintherangethatwehavetested.Duringthesnap-throughtransition,thetopplateremainedflatrelativetothegroundgivendifferentnumberofarms.

Methods
Samplefabrication
A0.2-mm-thickpolyimidefilm(GuangzhouShibeiDragonElectronicsCo.,Ltd.,China)isselectedasthebasematerial.Thefilmislaser-cutalongtheorigamipattern(Fig.1d)usinga16Wlasercutter.Thedesignparameters of the origami pattern are set as a=20mm, b=25mm,c=40mm, α1=59.2°, and α2=55°. Cut pieces are bonded usingpolyimidetape(3M™7418FHeat-ResistantPolyimideProcessTape).Fifteen1-mm-diameterholesaredrilledintotheinnerpentagonpanel(threeholesateachedge).

The thermal actuator (Fig. 3c) comprises a U-shape SMA wire(Beijing GEE SMA Technology Co., Ltd., China) and a stainless-steeltorsionalspring(WenzhouHeliSpringManufacturingCo.,Ltd.,China).TheU-shapeSMAwirehasalengthof7.5mm,widthof5mm,andwirediameterof0.5mm.Itistwisted180°aboutitsmajoraxisandinstalledconcentricallywithinthetorsionalspring.Thetorsionalspringhasawirediameterof0.4mm,outerdiameterof3mm,9coils,andaninitialangleof180°.

To mount the thermal actuator and facilitate heat transfer, acopperbaseisfabricatedusinga0.1-mm-thickcopperplate(XinghuaFanglingMetalProductsCo.,Ltd.,China)andcoppersleeves(TaizhouXuehuaStainlessSteelProductsCo.,Ltd.,China).Thecopperplateiscut to size matching the dimensions and arrangement of the innerpentagonpane.Coppersleeves(height:3mm,innerdiameter:1mm,outerdiameter:2.2mm)areweldedovertheseholes.Thesleeveboresarethenfilledwithsiliconegrease(Shin-EtsuChemical7921),anda0.8-mm-diameter TPU elastic cord (MIYUKI H3198E, length: 50mm) isfastenedtoacornersleeve.Thisintegratedassemblyofcopperplate,sleeves,andTPUcordconstitutestheregulator.

Finally,theregulator’ssleevesandTPUcordaresecuredtothepolyimidefilm.Thethermalactuatorsareinstalledbyinsertingtheirwire ends into the copper sleeves, while the opposite ends engagemountingtubes.ThesemountingtubesaresectionsofTeflontubing(inner diameter: 1.8mm, outer diameter: 2.6mm) cut to length of5mm.TheTeflontubesarepermanentlyaffixedtotheorigamiarmsviarivetedconnections.

Thermalswitchingratiomeasurements
Thethermalcharacterizationofthebistableorigamiswitch(BOS)isconductedusingacustom-builttestingplatform(Fig.2aandFig.S9),designedinaccordancewithASTM-5470standards.Measurementsareconducted inside a sealed aluminum vacuum chamber under high-vacuum conditions of ~10-3Pa. The setup consists of two verticallyalignedstainless steel reference bars (20×20×50mm) with precision-groundsurfaces(Ra≤0.025)tominimizeradiationlosses.Thelowerbarisfixedtothechamberbase,whilebothbarsareinstrumentedwiththree T-type thermocouples (±10mK accuracy, 254μm diameter)spaced 15mm apart to record temperature gradient. Temperaturedata isrecorded bytwoYET-640X four-channel thermometers. TheBOSsampleistightlyalignedbetweenthereferencebarsusingpress-fit assembly, ensuring flush contact with the bar ends for efficientthermalcoupling.Analumina-basedceramicheaterismountedonthetop surface of the upper reference bartoprovideacontrolledheatinput.ForOFF-statemeasurements,theupperbarissuspendedusingnylonthreadstoeliminatecontact(Fig.S9A).ForON-statemeasurements,itisloweredintodirectcontactwiththelowerbar(Fig.S9B).Toenhance interfacial thermal conductance, a thin (~100μm) layer ofApiezonHhigh-vacuumgreaseisappliedatthecontactinterface.

ThethermalconductanceoftheBOSinambientairismeasuredusing the same experimental platform and protocol as in vacuumconditions,withtwokeyproceduralmodifications.First,thevacuumchamberisventedtoatmosphericpressure(1atm)whilemaintainingahermetically sealed environment. Second, the thermal interfacematerial(TIM)is changed. For vacuum measurements,a low-vapor-pressureTIM(ApiezonH)witharelativelylowthermalconductivityof0.216W/m·Kisusedtoavoidoutgassing.Incontrast,air-basedmeasurementsallowtheuseofhigh-performanceTIMs,suchasShin-EtsuX-23-7921-5, a commercially available thermal grease with a significantlyhigherthermalconductivity(>6W/m·K),therebyminimizinginterfacialthermalresistance.

Itisnoteworthythatthermalradiationlossesalongthereferencebars are proportional to the fourth power of local temperature,resulting in slight non-uniformities in vertical heat flux. Due to itscloser proximity in temperature to the ambient environment, thelowerreferencebarexperiencesreducedradiativelossandmoreclosely satisfies the assumption of a linear temperature distribution.Therefore,the temperaturegradient used to compute thermalconductanceviaFourier’slawG=Q=ΔTisobtainedfromalinearfitofthetemperature distribution along the lower bar. Detailed temperaturedistributions, extracted thermal conductance values, and correspondingswitchingratiosundervacuumconditionsarepresentedanddiscussedinthemaintext.

Structuralforcemeasurements
To measure axial force while accommodating twist coupling in theBOS,wefabricatedalow-frictionrotationalcouplingbetweentheBOSandtestingmachineclamp(Fig.S6).Thecouplingconsistsofapentagonalcopperplatemountedattheterminusofaslenderbolt,constrained by locking nuts and washers. During testing, the BOS isinitializedinitsflatstate,andthenbeingverticallydeployedat10mm/minviatheclamp.Throughoutdeployment,axialdisplacementandforcearerecorded.

ThesameexperimentalsetupisusedtomeasurestructuralforcesontheBOSwithregulator.Oneendoftheregulatorissecuredtoa corner of the BOS pentagon panel, while the opposite end passesthroughabaseplatemountinghole.Asteelcaliperisfixedtothebaseplate serves as the measurement reference. During testing, pre-determined prestrain isapplied by stretching the regulator to alignwith the caliper’s target scale. Final positioning of the regulator ismaintainedusingtwomechanicalclamps.

Actuationforcemeasurements
Tomeasurethermalactuationforcesacrosstemperatures,theBOSisequippedwithaheater,fivethermalactuators,andathermocouple.Thetestingmachineoperatesinposition-holdingmode,loweringtheBOStoapredeterminedheightδandtaringtheforcesensor.Aconstant 5V voltage is applied to the heater while force-time andtemperature-time profiles are synchronously recorded. Force-temperature curves are generated by cross-referencing the time-synchronized datasets. This procedure is repeated for multiple displacementsetpoints δ to characterize the temperature-dependentforceresponse.

Toobtaintheactuationforce-displacementcurveoftheBOSat25°C,wefirstmeasuretheforce-displacementcurveoftheBOSwiththermal actuators at 25°C, then subtract the baseline structuralresponsewithoutthermalactuators.

Dataavailability
ThedatathatsupportthefindingsofthisstudyareprovidedinthemaintextandtheSupplementaryInformation.Sourcedataareprovidedwiththispaper.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The manuscript presents an interesting design for ultra-high ratio passive thermal switching based on a bistable origami metastructure. The key contribution lies in achieving a record thermal switching ratio (13,984 in vacuum and 1,360 in air) through a purely passive, energy-free mechanism. By integrating the snap-through bistability of an origami structure with the temperature-responsive behavior of shape memory alloys and elastic springs, the authors have introduced a novel architecture capable of reversible, autonomous, and energy-efficient thermal regulation. The idea is quite original and validated through experiments. The various demonstrations show its potential for real-world impact. The manuscript is generally well-written and easy to follow. With further clarifications and broader contextual discussion, it would make an excellent contribution to the field.\nI have the following questions to the authors:\n1.The origami structure is interesting. However, I wonder how reproducible is the switching temperature across different fabrication batches, given the manual assembly and sensitivity to crease geometry? What is the success rate during experiments?\n2.Can the authors comment on the possible miniaturization limits of the origami metastructure—how small could such switches be made while retaining functionality? This design would be very useful if it can be put on advanced chips.\n3.If the origami base is made with materials other than the polymide film, would the design still maintain high switching ratio? Some theoretical or numerical analysis on this material-dependency is suggested.\n4.The manuscript mentions ~10 s response time. Can the authors provide an analysis of the switching kinetics—what limits the response (SMA heating/cooling, mechanical inertia, or contact formation)? Could the switching speed be enhanced (e.g., by thinner SMA wires, or reduced thermal mass)?\n5.Page 4: “The origami pattern of the BOS is illustrated in Fig. 1c, which composes of five axisymmetric arms…” The verb “composes of” should be “is composed of.”\n6.Be consistent with figure references: sometimes written as “Fig. 1b” and elsewhere as “Figure 1b.”\n7.Ensure consistent units (W m⁻² K⁻¹ vs W/m²K) and correct symbols for temperature differences.\n8.Page 6: “The ultra-high switching ratio originates of the bistable origami switch.” The word after “originates” should be “from” instead of “of.”\n9.Include scale bars in all optical/IR images (Figs. 1e, 2b, 4b).", "reviewer_2": "The manuscript reports a bistable origami-based passive thermal switch achieving an exceptionally high thermal switching ratio. The system exploits a snap-through instability between two distinct mechanical states, enhancing the difference in thermal contact. Passive actuation is realized by integrating shape-memory alloy actuators at the hinge regions, while a TPU elastic wire introduces pre-strain to ensure reversible ON/OFF switching. The concept demonstrates an elegant combination of structural mechanics and thermal actuation, potentially valuable for autonomous thermal management.\nWhile the overall framework is interesting and the fabrication appears well executed, I believe the novelty and clarity of the work are somewhat limited for a high-impact journal. Bistable origami structures and snap-through–based mechanisms have been widely utilized in various mechanical and functional systems, including actuators, reconfigurable devices, and thermal switches. The current manuscript primarily adapts this well-known concept to a thermal regulation context without introducing substantial mechanistic or material-level innovation.\nFurthermore, many details—particularly regarding the actuator design, dynamic operation, and local stress behavior—are confined to the Supplementary Information and only briefly summarized in the main text. The work would benefit from clearer visualization, quantitative actuation analysis, and expanded discussion of physical limits and applications. For these reasons, I would recommend “Reject or Reject and Resubmit after Major Revision.”\nBelow are my questions and suggestions to improve paper.\n1. The structure is not clearly visible. Please provide close-up images of important regions.\n2. The sequential deformation process should be better illustrated in the main text. Using a high-speed camera or slow-motion video would help visualize the snap-through transition.\n3. Although the limitation comes from the temperature-based actuation, the switching speed appears slow. What happens if the heating and cooling rates are increased?\n4. Although the authors varied the folding angles and arm lengths, the design is still limited to a five-fold symmetric (pentagonal) structure. It would be desirable to demonstrate the same concept in other geometries or configurations.\n4-1. The current design has five arms. Is it possible to design with fewer or more arms?\n4-2. If the arm lengths differ, would the top plate tilt relative to the ground, creating an inclined surface?\n5. What happens if only part of the SMA actuators are heated instead of all of them?\n6. Many results are only summarized in the manuscript just as ‘Supplementary Notes’. Each Supplementary Figure should be described or cited in the text with corresponding explanations.\n7. The simulation is too macroscopic. More detailed modeling of the hinge regions or local stress distribution is needed. Are the forces acting only on the legs?\n8. What is the maximum load that the BOS top plate can support while still maintaining functional snap-through switching?"}, "author_response": "Re: Manuscript NCOMMS-25-58894-A “Ultra-High Ratio Passive Thermal Switching via\nBistable Origami Metastructure” by B. Tan, J. Lyu, F. Yang, K. Xu, S. Qiao, B. Song, L.\nYang, K. Liu\nResponse to the Editor and Reviewers\nWe sincerely thank the Editor and the Reviewers for thoroughly reading our manuscript and\nproviding constructive comments and suggestions. In this response letter, we address these\ncomments point-by-point. For convenience, we mark the corresponding modifications in our\nrevised manuscript in blue fonts.\nReviewer: 1\nThe manuscript presents an interesting design for ultra-high ratio passive thermal switching\nbased on a bistable origami metastructure. The key contribution lies in achieving a record\nthermal switching ratio (13,984 in vacuum and 1,360 in air) through a purely passive, energy-\nfree mechanism. By integrating the snap-through bistability of an origami structure with the\ntemperature-responsive behavior of shape memory alloys and elastic springs, the authors have\nintroduced a novel architecture capable of reversible, autonomous, and energy-efficient thermal\nregulation. The idea is quite original and validated through experiments. The various\ndemonstrations show its potential for real-world impact. The manuscript is generally well-\nwritten and easy to follow. With further clarifications and broader contextual discussion, it\nwould make an excellent contribution to the field.\nResponse: We thank the reviewer for the positive comments about our work. In this work, we\npropose a purely passive, energy-free thermal switch that, via the bistable mechanism, achieves\nan unprecedented switching ratio and switching speed, reliable repeatability, and integrated\nself-powered and self-sensing capabilities. To enhance clarity, Figs. 1 and 4 have been revised\nto more clearly illustrate the structure and its operational mechanism. Furthermore, two new\nfigures (Figs. 5 and 6) have been added to demonstrate the advantages of the bistable design\nand to verify the BOS concept across different configurations. The Discussion Section has been\nsignificantly expanded to provide a more in-depth analysis of the findings and contributions.\nWe address other comments from the reviewer below.\nI have the following questions to the authors:\n1. The origami structure is interesting. However, I wonder how reproducible is the switching\ntemperature across different fabrication batches, given the manual assembly and sensitivity to\ncrease geometry? What is the success rate during experiments?\nResponse: We thank the reviewer for this important question, which give us an opportunity to\nhighlight the repeatability of our research. The origami structure is fabricated using\nstandardized manufacturing, where laser cutting of the creases is sufficient to maintain high\ngeometric accuracy of the main structure. Thus, the mechanical properties of the origami\nstructure---particularly bistability---remain consistent across different batches, as shown in Fig.\nS6B. In case manual assembly introduces some errors into the switching behavior, the regulator\ncan be adjusted to maintain a consistent performance. As a result, all of our tested samples\ndemonstrated stable switching temperature ( 1.5℃), as presented in Fig. S27. Among the\nfabricated samples, Numbers 1 to 3 are clas±sified as early-stage prototypes. The real-time\nperformance data for Sample No. 1 is plotted in Fig. 4e. Sample No. 4 serves as the test\nspecimen for cycle testing (also presented in Fig. 4f), while Sample No. 5 is dedicated to\nswitching speed evaluation (Fig. 5). The functional demonstrations for various devices hosted\nby Sample No. 6 and 7 are provided in Fig. 6a-f.\nFig. S6. Measurement of mechanical properties of BOS. (A) Photo of the experimental set-\nup. (B) Sequential pictures during tension deformation. (C) Measured force and related\nenergy versus displacement. The bistable transition generates an energy barrier at the\nsecond equilibrium. ∆𝑈𝑈2\nFig. S27. Switching temperature of BOS under different fabrication batches.\nTo address the reviewer’s comment, we have commented on the repeatability of the bistable\norigami switch in the main text:\nPage 6:\n“Results from the mechanical test of the origami structures show consistent bistable\ncharacteristics, including peak forces and location of the instability point, across different\nfabrication batches (Fig. S6, Supplementary Note 3), attesting to the repeatability of the\nmanufacturing process and the robustness of the design.”\nPage 17:\n“The repeatability of the fabrication process is highlighted by the batch-to-batch consistency\nobserved in the switching temperature and operational characteristics, as shown in Fig. S27.”\n2. Can the authors comment on the possible miniaturization limits of the origami\nmetastructure—how small could such switches be made while retaining functionality? This\ndesign would be very useful if it can be put on advanced chips.\nResponse: We thank the reviewer for this critical comment. The bistability of the origami\noriginates from its geometric design, where the compression and release of the arms induces\nenergy barrier between the two stable states. Consequently, the origami structure is scale\nindependent, which can be freely scaled up and down before the quantum effect kicks in.\nConsidering the fabrication and assembly of thermal actuators, in the micro-scale, the torsion\nsprings may be replaced by the inherent elasticity of the origami hinges, and the SMA wires\ncan be replaced by other printable or depositable stimuli-responsive materials [Ref. 56, 57]. We\nare currently working with our collaborators for miniaturizing our bistable origami switch (BOS)\nin the size of less than 100 microns.\nTo address the reviewer’s comment, we have added more comments on the scalability of the\nproposed thermal switch in the Discussion Section:\n“Furthermore, as the bistable behavior mainly comes from geometry, our solution is inherently\nscale-independent, which can be potentially scaled up and down from meters to micrometers33,56.\nConsidering the fabrication and assembly of thermal actuators, in the micro-scale, the torsion\nsprings may be replaced by the inherent elasticity of the origami hinges, and the SMA wires\ncan be replaced by other printable or depositable stimuli-responsive materials56,57. Future work\nis still needed to unleash the high suitability of the BOS for integration in advanced chip\narchitectures.”\n3. If the origami base is made with materials other than the polymide film, would the design\nstill maintain high switching ratio? Some theoretical or numerical analysis on this material-\ndependency is suggested.\nResponse: We thank the reviewer for this valuable suggestion. It is meaningful to clarify the\nmaterial dependence of the BOS switching ratio. The effect by the material could be\ninvestigated by our simplified one-dimensional steady-state thermal conduction model (see\nSupplementary Note 6 for details). The model explicitly clarifies how the base material\nparticipates in the thermal-resistance network of the BOS (Fig. S11A, B): as the main structural\nbody of the BOS, the base material constitutes a key parasitic heat-leak pathway in the OFF\nstate. The thermal conductivity of the base material affects the OFF-state heat conduction\nprimarily by modulating R and R (marked in Fig. S11a). Following the suggestion of the\narm bottom\nreviewer, we have evaluated multiple candidate base materials with different thermal\nconductivities (e.g., PC, PVC, PET, PS, and silica aerogel, summarized in Fig. S11C). All of\nthose base materials show a high switching ratio, ranging from 1.6 × 104 ~ 2.0 × 104 in vacuum.\nThese results confirm that the BOS design can preserve a high switching ratio across different\nmaterial choices, and further demonstrate its flexibility in material selection, broad applicability,\nand robust thermal regulation capability.\nFig. S11. Base-material dependence of the BOS switching ratio. A~B, Schematic\nillustration of the thermal-resistance network for solid-state heat conduction in the BOS\nunder vacuum in the OFF state. C, Thermal conductivity and the corresponding switching\nratio for representative base materials (PC, PVC, PET, PS, and silica aerogel).\nTo address the reviewer’s comment, we have commented on the material dependence of the\nBOS switching ratio in Results Section, page 10:\n“We further evaluated multiple candidate base materials for the BOS with different thermal\nconductivities (e.g., PC, PVC, PET, PS, and silica aerogel, summarized in Fig. S11). Each of\nthese materials shows a high switching ratio, ranging from 1.6 × 104 to 2.0 × 104 in vacuum,\nwhich confirms the broad material compatibility of the BOS design.”\n4. The manuscript mentions ~10 s response time. Can the authors provide an analysis of the\nswitching kinetics—what limits the response (SMA heating/cooling, mechanical inertia, or\ncontact formation)? Could the switching speed be enhanced (e.g., by thinner SMA wires, or\nreduced thermal mass)?\nResponse: The reviewer raised a valuable point, which helps us to better showcase our work.\nWe now thoroughly investigated the factors that affect the switching speed of the BOS, as\nshown in the new Fig. 5. According to our new experiments, the switching speed is primarily\nlimited by the travel distance between the ON and OFF states and the system’s resistance force.\nIn the previous design, to intuitively achieve higher switching ratio, the OFF state was set at\nthe second equilibrium point of the origami structure, which is far from the critical point of\ninstability (Fig. 4a and Fig. 5b). However, this design is not optimal for high switching speed.\nConsequently, the origami structure was slowly driven toward the instability point by the\nactuators, a process that consumed 95% of the time, before the fast snap-through happened. In\nthe new experiments, to minimize the response time, we employed a limiter that displaces the\nupper plate downward by 3 mm to set the OFF state closer to the instability point. Additionally,\nwe reduced the number of actuators from five to two to lower the elasticity they impose on the\nbistable transition of the origami structure. This modification reduces the response time to as\nlow as 200ms. At the same time, the switching ratio is minimally affected by this reduced travel\ndistance, owing to the minor contribution from increased air convection. We also found that the\nheating rate, heat sink temperature and the bearing mass influence the switching speed, but their\neffect are not as significant as the travel distance of the upper plate, as shown in Fig. 5d-g.\nFig. 4a. Photograph of the customized Fig. 5b. Setup for the switching speed test.\nexperimental setup. The heat source is hosted An additional limiter is used to investigate\non the copper panel of the BOS. A water- the influence of bistable position.\ncooled copper plate is installed underneath the\nBOS.\nFig. 5. Factors affecting the switching speed of the BOS. a, Video frames of the snap-\nthrough transition of the origami structure only, captured by high-speed camera. b, Setup for\nthe switching speed test. A weight is added on the upper plate to investigate the influence of\nbearing weight. An additional limiter is used to investigate the influence of bistable position.\nc, Real-time temperature profile and vertical displacement of the two-way switching. (d~g)\nFactors that affect the switching speed, including: number of actuators, heat sink\ntemperature, heating rate, and bearing mass.\nIn addition, the following content is added to the main text (Results Section, page 19):\n“The switching speed of the BOS is influence by a number of factors, including travel distance\nbetween the ON and OFF states, the number of thermal actuators, heat sink temperature, the\nheating rate, and the bearing mass on the upper plate. It was found that the travel distance plays\na primary role affecting the switching speed of the BOS. Using a high-speed camera (X190,\nRevealer, China) to capture the pure structural snap-through transition of the origami structure\n(Fig. 5a), we observe that traveling from the instability point to any stable state requires less\nthan 90ms. To exploit this property, we equipped the BOS with a limiter that constrains the\nupper plate to become 3mm closer to its instability point than before (Fig. 5b). With the limiter\nand two thermal actuators, the BOS achieves two-way operation with a switching time of\n200ms (Fig. 5c), with switching temperature at 83.6°C.\nThe influence of the number of thermal actuators on the switching speed is presented in Fig.\n5d. The results indicate that a greater number of actuators leads to an increase in the switching\ntime, owing to the increased resistance force of the system. For the BOS equipped with only\none thermal actuator, the generated actuation force was insufficient to drive the bistable\nswitching. Influences of the heat sink temperature, the heating rate, and the bearing mass on the\nupper plate are shown in Fig. 5e-g. While changing the heat sink temperature and the heating\nrate exhibit no significant trend, we find that larger bearing mass on the upper plate leads to\nslower transition, likely due to larger inertia.”\n5. Page 4: “The origami pattern of the BOS is illustrated in Fig. 1c, which composes of five\naxisymmetric arms…” The verb “composes of” should be “is composed of.”\nResponse: The verb “composes of” is now corrected to “is composed of.”\n6. Be consistent with figure references: sometimes written as “Fig. 1b” and elsewhere as\n“Figure 1b.”\nResponse: We thank the reviewer for pointing this out. All figure references are now unified.\n7. Ensure consistent units (W m⁻² K⁻¹ vs W/m²K) and correct symbols for temperature\ndifferences.\nResponse: We thank the reviewer for pointing this out. We have gone through the manuscript,\nand ensured that all units and symbols are consistent.\n8. Page 6: “The ultra-high switching ratio originates of the bistable origami switch.” The word\nafter “originates” should be “from” instead of “of.”\nResponse: We thank the reviewer for pointing out our mistakes. This sentence has been\ncorrected to “The ultra-high switching ratio originates from the bistable origami switch.”\n9. Include scale bars in all optical/IR images (Figs. 1e, 2b, 4b).\nResponse: We thank the reviewer for this valuable suggestion. Scale bars are now inserted to\nall optical/IR images.\nReviewer: 2\nThe manuscript reports a bistable origami-based passive thermal switch achieving an\nexceptionally high thermal switching ratio. The system exploits a snap-through instability\nbetween two distinct mechanical states, enhancing the difference in thermal contact. Passive\nactuation is realized by integrating shape-memory alloy actuators at the hinge regions, while a\nTPU elastic wire introduces pre-strain to ensure reversible ON/OFF switching. The concept\ndemonstrates an elegant combination of structural mechanics and thermal actuation, potentially\nvaluable for autonomous thermal management.\nResponse: We thank the Reviewer for the positive comments about our work. We especially\nthank the reviewer for recognizing the “elegant combination of structural mechanics and\nthermal actuation” in our work. Indeed, simply adding SMA wires to a bistable origami\nstructure would not produce the same thermal switching functionality. Therefore, the core\ninnovation of our work is the proposed design that “elegantly” orchestrate smart materials and\nsmart structures to enable a repeatable, high-performance, passive thermal switch.\nWhile the overall framework is interesting and the fabrication appears well executed, I believe\nthe novelty and clarity of the work are somewhat limited for a high-impact journal. Bistable\norigami structures and snap-through–based mechanisms have been widely utilized in various\nmechanical and functional systems, including actuators, reconfigurable devices, and thermal\nswitches. The current manuscript primarily adapts this well-known concept to a thermal\nregulation context without introducing substantial mechanistic or material-level innovation.\nResponse: We are sorry that our previous submission did not impress the reviewer for its\nnovelty. However, we must respectfully disagree with the reviewer’s statement about the\nnovelty of our work. By thoroughly searching academic databases, we did not find any similar\nprevious work as the reviewer indicated. Thus, we would like to ask the reviewer to point out\nthe exact literature that has reported using a bistable origami structure for thermal switching,\nso that we can compare or cite. We acknowledge that bistable origami and snap-through\nstructures have been widely utilized for other areas, but it is not fair to conclude that everything\nfollowing such mechanical design is not novel.\nRegarding thermal switches, to the best of our knowledge, we have not found any paper\nreporting a bistable origami thermal switch. We have collected most related papers that we can\nfound to compare with our work, as shown in the table below. Current thermal switches\ntypically depend on external fields, rely on slow phase-change processes, or fail to provide a\nstrong binary response. Our approach addresses all of these limitations and attains a record\nswitching ratio across all reported thermal switch designs.\nIt may be helpful for us to reiterate the novel contribution of our work.\n(1) To the best of our knowledge, we are the first work to report a mechanical thermal switch\nusing bistable origami structure with record-high switching ratio. In previous research,\nattempts of using SMA for thermal switching have only achieved best switching ratio of\n2070 (Ref [15], nature energy, https://doi.org/10.1038/s41560-018-0243-8), owing the fact\nthat SMA itself is of high thermal conductivity. Using the proposed bistable origami design,\nwe are able separate the SMA from the device and the heat sink, such that no heat flow\nleaks through the SMA wires when the switch is toggled OFF. In addition, the bistability\nof the BOS helps to maintain a steady thermal conductivity whenever the switch is ON or\nOFF, achieving clear binary effect.\n(2) The repeatable passive thermal regulation cycle that we reported represents substantial\nmechanistic innovation, beyond simply adding SMA to bistable origami. It may be easy\nto push a bistable structure from its original state to the other state, however, it is extremely\ndifficult to bring it back to the original states without external help. In this work, we\nachieved this by carefully optimizing the combined forces of the bistable origami, the SMA\nwire, the rotational springs, and elastic regulators. As shown in Fig. 3, when the temperature\nof the device rises to the designated degree, the actuation force of SMA wires suppresses\nthe resistant forces from the elastic components and pushes the BOS down (turning ON).\nIn this state, the thermal load is critical for maintaining the driving force of the SMA wires.\nWithout the thermal load, the BOS cannot stay at this state, and it will automatically spring\nback to its original state (turning OFF). Therefore, the complete BOS is no longer\nmechanically bistable as traditionally defined --- it becomes bistable as a system under\nthe thermal load. By simply adding SMA to the bistable origami, it is impossible to achieve\nthe repeatable thermal regulation cycles without external sensing and actuation.\nTo reflect on the reviewer’s comment, we have made the following changes to the main text in\norder to highlight and clarify the novel contributions of this work:\nIn Discussion Section:\n“The novelty of this work is two-fold: (1) This work reports a mechanical thermal switch using\nbistable origami structure that produces record-high switching ratio among all types of thermal\nswitches (Fig. 2, Supplementary Table S2); (2) The repeatable passive thermal regulation cycles\nhighlight that the complete BOS is no longer mechanically bistable in the conventional sense;\nrather, its bistability emerges at the system level under thermal loading (Fig. 3).”\nFurthermore, many details—particularly regarding the actuator design, dynamic operation, and\nlocal stress behavior—are confined to the Supplementary Information and only briefly\nsummarized in the main text. The work would benefit from clearer visualization, quantitative\nactuation analysis, and expanded discussion of physical limits and applications. For these\nreasons, I would recommend “Reject or Reject and Resubmit after Major Revision.”\nResponse: We thank the Reviewer for the detailed suggestions. We have now substantially\nrevised our manuscript according to the reviewer’s comments. The following major changes\nare made:\n(1) The details of the actuator design and its installation are shown in Fig. 1e.\n(2) The BOS design is optimized for switching speed, which becomes less than 200ms. Factors\nthat affect the switching speed are analyzed in the new Fig. 5.\n(3) The snap-through transition was captured using a high-speed camera and is presented in\nFig. 5a and Supplementary Video 3.\n(4) The dynamic operation of the actuators and corresponding close-up views are presented in\nFig. 4d.\n(5) A new finite element model incorporating 3D solid elements and hinge modelling is\ndeveloped. The resulting local stress distribution is presented in Fig. S17.\n(6) All supplementary figures are referenced in the main text, where their content is described\nin detail.\n(7) Two new switches, based on the four-arm and six-arm origami designs, were fabricated\nand experimentally evaluated (Fig. 6g and h).\n(8) Expanded discussion of novelty, physical limits, and applications are added in the\nDiscussion Section.\nWe hope that with these revisions, the reviewer could appreciate the novelty and impact of our\nwork.\nBelow are my questions and suggestions to improve paper.\n1. The structure is not clearly visible. Please provide close-up images of important regions.\nResponse: We thank the reviewer for this constructive comment. The close-up images about\nactuators, regulator, and creases are now added into Fig. 1.\nThe new Fig. 1 is attached below:\nFig. 1. Design and fabrication of the bistable origami switch (BOS). a, Application and\nschematics of the BOS. Left: the BOS for pixelated thermal regulation of a battery pack.\nRight: a passive thermal regulation cycle. Heating the device over temperature threshold\ndrives the BOS to overcome the energy barrier and transition from OFF to ON state,\nactivating heat exchange with the sink, while cooling reverses it via elastic force, turning off\nthe heat exchange. b, Real-time temperature profile at the ON and OFF states, respectively.\nc, Origami crease pattern design. The thin black lines refer to folding creases, and the thick\nwhite lines are cutting edges. d, Fabrication of the BOS using a laser cutter. e, Photograph of\na BOS at the OFF state with zoom-in views of the details.\n2. The sequential deformation process should be better illustrated in the main text. Using a high-\nspeed camera or slow-motion video would help visualize the snap-through transition.\nResponse: We thank the reviewer for this constructive comment. We have recorded the\nswitching process using high-speed camera and reported the sequential deformation process of\nthe snap-through transition in the new Fig. 5(a). This new figure helps to explain the\ndeformation of the origami structure during the snap-through transition. A slow-motion video\nof the BOS during the snap-through transition is provided in Supplementary Video 3. The new\nSupplementary Video 3 illustrates the sequential deformation process of the BOS equipped\nwith five thermal actuators, played at a playback speed of 0.1 of the real-time. Additionally,\nclose-up images illustrating the torsion angles of the actuators are presented in Fig. 4d.\nThe new Fig. 4 and 5 is attached below:\nFig. 4. Demonstration of the functionality and switching of BOS. a, Photograph of the\ncustomized experimental setup. The heat source is hosted on the upper plate of the BOS. A\nwater-cooled plate is installed underneath the BOS as the heat sink. b, Video frames and IR\nimages of the BOS during one cycle of temperature regulation. c, Schematic of the heat flow\non the upper plate, and the temperature changes of the heater and the actuator. d, Hinge\nactuation process for switching recorded as vertical displacement (H- ) vs. dihedral angle\n( ), where H is the initial height of the device at the elevated OFF𝛿𝛿 state. e, Real-time\nte𝛾𝛾mperature profile and vertical displacement (H- ) of the hosted device, f, Repeatability test\nof the BOS up to 100 times. The temperature of𝛿𝛿 the Joule heater is well controlled within\n28.2~71.7oC.\nFig. 5. Factors affecting the switching speed of the BOS. a, Video frames of the snap-\nthrough transition of the origami structure only, captured by high-speed camera. b, Setup for\nthe switching speed test. A weight is added on the upper plate to investigate the influence of\nbearing weight. An additional limiter is used to investigate the influence of bistable position.\nc, Real-time temperature profile and vertical displacement of the two-way switching. (d~g)\nFactors that affect the switching speed, including: number of actuators, heat sink\ntemperature, heating rate, and bearing mass.\n3. Although the limitation comes from the temperature-based actuation, the switching speed\nappears slow. What happens if the heating and cooling rates are increased?\nResponse: The reviewer raised a valuable point, which helps us to better showcase our work.\nWe have further optimized our design, and the switching speed is now significantly improved.\nBy optimizing the structural parameters, the switching time can now be decreased to as low as\n200ms, and generally less than 1s.\nThe switching speed is primarily related to the distance between the ON and OFF states. In the\nprevious design, to intuitively achieve higher switching ratio, the OFF state was set at the\nsecond equilibrium point of the origami structure, which is far from the critical point of\ninstability (Fig. 4a and Fig. 5b). However, this design is not optimal for high switching speed,\nas the origami structure was slowly driven toward the instability point by the actuators, a\nprocess that consumed 95% of the time, before the fast snap-through happened. In the new\nexperiments, to minimize the response time, we employed a limiter that displaces the upper\nplate downward by 3 mm to set the OFF state closer to the instability point. Additionally, we\nreduced the number of actuators from five to two to lower the elasticity they impose on the\nbistability of the origami metastructure. This modification reduces the response time to as low\nas 200ms. The switching ratio is minimally affected by this reduced travel distance due to slight\nincrease of heat convection through air. We conducted a batch of new experiments to\ncharacterize the switching time of the BOS, and detailed analyses of the influencing factors are\nreported in the new Fig. 5 (see previous response). The effects of heating and cooling rates on\nthis performance are analyzed in the new Fig. 5(e) and (f). The results indicate that the heating\nand cooling rates had a minimal effect on its performance, and the switching performance is\nlargely governed by the structural design of the BOS.\nFig. 4a. Photograph of the customized Fig. 5b. Setup for the switching speed test.\nexperimental setup. The heat source is hosted An additional limiter is used to investigate\non the copper panel of the BOS. A water- the influence of bistable position.\ncooled copper plate is installed underneath the\nBOS.\nIn addition to the new Fig. 5, the following content is added to the main text (Results Section,\npage 19):\n“The switching speed of the BOS is influence by a number of factors, including travel distance\nbetween the ON and OFF states, the number of thermal actuators, heat sink temperature, the\nheating rate, and the bearing mass on the upper plate. It was found that the travel distance plays\na primary role affecting the switching speed of the BOS. Using a high-speed camera (X190,\nRevealer, China) to capture the pure structural snap-through transition of the origami structure\n(Fig. 5a), we observe that traveling from the instability point to any stable state requires less\nthan 90ms. To exploit this property, we equipped the BOS with a limiter that constrains the\nupper plate to become 3mm closer to its instability point than before (Fig. 5b). With the limiter\nand two thermal actuators, the BOS achieves two-way operation with a switching time of\n200ms (Fig. 5c), with switching temperature at 83.6°C.\nThe influence of the number of thermal actuators on the switching speed is presented in Fig.\n5d. The results indicate that a greater number of actuators leads to an increase in the switching\ntime, owing to the increased resistance force of the system. For the BOS equipped with only\none thermal actuator, the generated actuation force was insufficient to drive the bistable\nswitching. Influences of the heat sink temperature, the heating rate, and the bearing mass on the\nupper plate are shown in Fig. 5e-g. While changing the heat sink temperature and the heating\nrate exhibit no significant trend, we find that larger bearing mass on the upper plate leads to\nslower transition, likely due to larger inertia.”\n4. Although the authors varied the folding angles and arm lengths, the design is still limited to\na five-fold symmetric (pentagonal) structure. It would be desirable to demonstrate the same\nconcept in other geometries or configurations.\n4-1. The current design has five arms. Is it possible to design with fewer or more arms?\n4-2. If the arm lengths differ, would the top plate tilt relative to the ground, creating an inclined\nsurface?\nResponse: We thank the reviewer for this critical comment. We adopted the five-fold origami\nin our initial design because it provided a relatively rounded upper plate to host devices while\nkeeping a small number of arms for structural simplicity. Nevertheless, it is absolutely possible\nto make the BOS to have different numbers of arms. The adopted bistable origami design (aka.\nRotational Erection System) shows quite consistent bistable performance with different\nnumbers of arms (from 3 to more than 10) as reported in the literature (Refs. [41, 56]). The RES\ndesign is also known for keeping a flat, leveled upper plate during deformation, and that is why\nit is originally proposed by architect Yoshinobu Miyamoto as an “erection system.” Therefore,\nthe top plate will not tilt relative to the ground given different number of arms. Differing the\narm lengths would lead to complex consequences including loss of bistability and tilting of the\ntop plate. However, it is unclear to us why we should do this for the thermal switch. The main\nfocus of this paper is not a sole study of the RES origami.\nTo address the reviewer’s comment, we have made new switches based on the four-arm and\nsix-arm origami. The test results are shown in the new Figs. 6 (g and h) and the new\nSupplementary Video 6. We have not observed any tilting of the top plate during our\nexperiments, as can be seen in the slow-motion frames (Fig. 5a).\nThe new Fig. 6 is attached below:\nFig. 6. Effectiveness of the BOS for temperature regulation. (a~f) Demonstration of the\nBOS hosting various devices, including battery, power amplifier chip, Bluetooth chip, LED,\nand DC-DC converter chip. (g~h) Functionality of the BOS with four-arm and six-arm\nconfigurations.\nIn addition to Fig. 6g-h, the following content is added to the main text (Results Section, page\n21):\n“The BOS design also shows quite consistent thermal switching performance with different\nnumbers of arms, as shown in Figs. 6g-h and Supplementary Video 6. During the snap-through\ntransition, the top plate remained flat relative to the ground given different number of arms.”\n5. What happens if only part of the SMA actuators are heated instead of all of them?\nResponse: We thank the reviewer for this critical comment. To answer the reviewer’s question,\nwe conducted a series of additional experiments with 1, 2, 3, 4, and 5 thermal actuators. In the\nexperiments, we fabricated a new BOS starting with no thermal actuator, then gradually\nincreased the number of actuators and tested the structure under device heating. The results are\nshown in the new Fig. 5(b, c, d) (see previous response), a configuration with only two actuators\nsuccessfully achieved snap-through switching, but the switching temperature increased to\n83.6oC. We conclude that fewer actuators lead to faster switching speed but higher switching\ntemperature to generate adequate actuation force. For the BOS equipped with only one thermal\nactuator, the actuation force was insufficient to drive the switch, and the experiment was\nunsuccessful.\nTo address the reviewer’s comment, we have added the following content to the main text\n(Results Section, page 19):\n“The influence of the number of thermal actuators on the switching speed is presented in Fig.\n5d. The results indicate that a greater number of actuators leads to an increase in the switching\ntime, owing to the increased resistance force of the system. For the BOS equipped with only\none thermal actuator, the generated actuation force was insufficient to drive the bistable\nswitching.”\n6. Many results are only summarized in the manuscript just as ‘Supplementary Notes’. Each\nSupplementary Figure should be described or cited in the text with corresponding explanations.\nResponse: We thank the reviewer for this constructive comment. We acknowledge that by\nputting so much content in the Supplementary Information (SI), we increased the effort of our\nreaders to understand the main paper. We have now moved a portion of the information from\nthe SI to the main text, as listed below:\n1. “A design paradigm for the geometry is proposed, as illustrated in Fig. S1 (Supplementary\nNote 1). It is generated from three concentric polygons with different radius and the\nconnection lines between their corresponding vertices.”\n2. “The parameters a and c are derived from the overall dimensions of the device and the\nswitch. The parameters and determine the height and the arm width of the switch,\nas illustrated in Fig. S2.”𝛼𝛼 1 𝛼𝛼2\n3. “Fig. S3 (Supplementary Note 2) presents the specific components employed and the\ndetailed compositional procedure.”\n4. “The polyimide sheet with a thickness of 0.2 mm was selected as the based material to\nfabricate the structure. We measured the Young's modulus of the polyimide sheet to be\n5. “By this way, the rotational stiffness of the folding creases is extremely reduced (0.0285\nN·mm/rad, Fig. S5). Results from the mechanical test of the origami structures show\nconsistent bistable characteristics, including peak forces and location of the instability\npoint, across different fabrication batches (Fig. S6, Supplementary Note 3), attesting to the\nrepeatability of the manufacturing process and the robustness of the design.”\n6. “The experimental setup for measuring the structural force and the preloading strain of the\nregulator is depicted in Fig. S7 (Supplementary Note 3).”\n7. “The experimental setup for measuring the actuation force is provided in Fig. S8\n(Supplementary Note 3). In this procedure, the BOS is clamped in a fixed position. The\nactuators are then heated by a heater, and the vertical load is measured concurrently.”\n8. “Photographs of the experimental setup along with a corresponding close-up image are\nillustrated in Fig. S9 (Supplementary Note 4).”\n9. “…, which leads to the OFF state conductance to = 51685 W/m2·K and = 38\nW/m2·K (Fig. S10, Supplementary Note 5), respect𝐺𝐺iv𝑜𝑜e𝑜𝑜ly, …” 𝐺𝐺𝑜𝑜𝑜𝑜𝑜𝑜\n10. “Under vacuum conditions, heat transfer between the upper and lower bars occurs through\ntwo primary pathways: radiative heat exchange and solid conduction via the BOS (Fig.\nS11, Table S1).”\n11. “We further evaluated multiple candidate base materials for the BOS with different\nthermal conductivities (e.g., PC, PVC, PET, PS, and silica aerogel, summarized in Fig.\nS11). Each of these materials shows a high switching ratio, ranging from 1.6 × 10⁴ to 2.0\n× 10⁴ in vacuum, which confirms the broad material compatibility of the BOS design.”\n12. “Moreover, the BOS design features geometrically tunable parameters—such as arm width,\nlength, and height—that allow for programming of the switching ratio across a broad range\n( = 15425 to 16771, Fig. 2g and Fig. S12).”\n13. “𝜌𝜌The results confirm that the folding at the bottom hinges, along with the resulting\ndisplacement and rotation of the upper plate, undergoes rigid-body motion, as shown in\nFig. S13. In contrast, the folding at the upper hinges is affected by the bending of the arms.”\n14. “The beam model, employed to simulate the arm under shear or compression, yields result\nthat closely match the finite element simulations (Figs. S14, S15, S16).”\n15. “The stress distribution results from the finite element simulations are presented in Fig.\nS17, revealing significant localized stress intensity in the arm and crease regions. The\nstress concentrations mainly occur at the bottom creases, reaching a maximum Von Mises\nstress of 129 MPa.”\n16. “Furthermore, five origami samples with different geometrical parameters were fabricated\nto validate the model experimentally (Fig. S18).”\n17. “As increases, the energy barrier of bistability emerges, increases, then decreases, and\nfinall𝛼𝛼y2 disappears (Fig. S19).”\n18. “Fig. S20 further illustrates the bistable origami structure within the ( and )\nparameter space: arm width is bounded between 15–21.5 mm, while sta𝛼𝛼n1ding hei𝛼𝛼g2ht\nranges from 16 to 26.3 mm.”\n19. “The regulator is connected between the ends of the upper plate and the base (Fig. 3a).\nWhen the BOS switches from the elevated to the flat state, the upper plate rotates relative\nto the base, stretching the regulator and increasing its tensile strain from 0 to 0.19 (Fig.\nS21, Supplementary Note 10).”\n20. “The influence of the regulator on the energy barriers of the BOS is illustrated in Figs. S21\nand S22. The results demonstrate that the regulator not only reduces the first energy barrier\nbut also strengthens the second one, thereby enabling an extension of the bistable energy\nlandscape by up to 40%.”\n21. “To elaborate, as the prestrain of the regulator increases, the critical peak force linearly\nincreases (Fig. S23), …”\n22. “In our experimental demonstration (Fig. 4, Supplementary Video 2), the low and high\nswitching temperatures are set as 25℃ (ON→OFF) and 72℃ (OFF→ON), respectively\n(Fig. 3e, Fig. S24, Supplementary Note 11).”\n23. “The subsequent state transition exhibits a response time of approximately 10 s and a\nvertical speed of 0.66 mm/s (Fig. S25).”\n24. “For example, if we change the phase transition temperature of the SMA from 60℃ to\n47℃, the high switching temperature decreases from 73℃ to 63℃ (Fig. S26 and\nSupplementary Video 2).”\n25. “The repeatability of the fabrication process is highlighted by the batch-to-batch\nconsistency observed in the switching temperature and operational characteristics, as\nshown in Fig. S27.”\nIn addition, we have carefully checked the main text to ensure that all SI Notes and Figures are\ncited in the appropriate locations of the main text.\n7. The simulation is too macroscopic. More detailed modeling of the hinge regions or local\nstress distribution is needed. Are the forces acting only on the legs?\nResponse: We thank the reviewer for this comment. We have developed a high-fidelity finite\nelement model to simulate the deformation of the origami structure. Given that the origami\nstructure is comprised of a 0.2 mm thick polyimide film and a 0.06 mm thick adhesive layer,\nthe most accurate representation is a geometrically identical (1:1 scale) replica of the physical\nassembly. In the model, the PI film was discretized using 3D solid elements, while the adhesive\nlayer—functioning as the hinge—was represented with 2D shell elements, a choice justified by\nits minimal thickness, ensuring computational efficiency while accurately capturing its\nbending-dominated behavior. The two components were connected via shared nodes at their\ninterface. Validation confirms that the new model reproduces previous results while providing\nsignificantly improved resolution of the stress distribution near the hinge regions. The stress\ncontour plot, presented in Fig. S17, clearly shows that the applied load is transmitted primarily\nthrough the structural arms.\nTo address the reviewer’s comment, the following content is added to the main text (Results\nSection, page 12):\n“The stress distribution results are presented in Fig. S17, revealing significant localized stress\nintensity in the arm and crease regions. The stress concentrations mainly occur at the bottom\ncreases, reaching a maximum Von Mises stress of 129 MPa.”\nThe following content is added to Supplementary Note 8:\nFig. S17. Stress distribution of the origami structure from the finite element simulation.\n8. What is the maximum load that the BOS top plate can support while still maintaining\nfunctional snap-through switching?\nResponse: We thank the reviewer for this critical comment. To answer the reviewer’s question\nregarding the load-bearing capacity, we conducted a series of experiments utilizing calibrated\nweights (1 g, 2 g, and 5 g) incrementally placed on the upper plate of the BOS. As the load\nincreased, the transition from the ON to OFF state became more challenging due to the\nincreased weight and inertia. To address this, we raised the pre-strain in the regulator, thereby\nboosting the restoring force at the ON state to support heavier loads. As a result, even under a\ntotal mass of 20g, the BOS maintained a functional snap-through transition, with a switching\ntime of 470ms, as presented in Fig. 5g and the Supplementary Video 4.\nTo reflect on the reviewer’s comment, the following content is added to the main text (Results\nSection, page 19):\n“While changing the heat sink temperature and the heating rate exhibit no significant trend, we\nfind that larger bearing mass on the upper plate leads to slower transition, likely due to larger\ninertia.\nTo investigate the influence of bearing mass, we conducted a series of experiments by adding\ncalibrated weights onto the upper plate of the BOS. As the load increased, the transition from\nthe ON to OFF state became more challenging due to the increased weight and inertia. To\naddress this, we can raise the pre-strain in the regulator, thereby boosting the restoring force at\nthe ON state to support heavier loads. As a result, even under a total mass of 20g, the BOS\nmaintained a functional snap-through transition, with a switching time of 470ms, as presented\nin Fig. 5g and the Supplementary Video 4.”"}, {"round": 2, "reviewer_comments": {"reviewer_1": "The authors have replied to my question and I recommended it published.", "reviewer_2": "I have carefully read the authors’ responses, and overall they are well addressed. I only have a few minor comments and questions as outlined below.\n1. Regarding the literature discussion, my original comment was intended to encourage mentioning other applications of snap-through mechanisms enabled by origami structures, particularly in the context of actuators and robotics. Relevant examples include, but are not limited to, the following works:\nPNAS, 118, 36, e2110023118 (2021)\nNat. Commun., 14, 4329 (2023)\nAdv. Funct. Mater., 32, 35, 2201891 (2022)\nIEEE/ASME Transactions on Mechatronics, 30, 6, 7019–7030 (2025)\n2. With respect to the leg length, altering the orientation of the top plate could make the system interesting for other applications, such as robotic arms. If flat-state actuation is a key advantage of this design, I suggest emphasizing this point more clearly in the Introduction.\n3. In Figures 6g and 6h, the slope of the H–δ relationship appears to vary depending on the number of legs, and the actuation speed also seems to differ in the videos. Are there corresponding differences in the response time or required actuation force as a function of the leg number?\n4. There is a typo in Figure 1d.\nAdhensive -> adhesive"}, "author_response": "Re: Manuscript NCOMMS-25-58894-A “Ultra-High Ratio Passive Thermal Switching via\nBistable Origami Metastructure” by B. Tan, J. Lyu, F. Yang, K. Xu, S. Qiao, B. Song, L.\nYang, K. Liu\nResponse to the Editor and Reviewers\nWe sincerely thank the Editor and the Reviewers for thoroughly reading our manuscript and\nconsidering accepting our paper. In this response letter, we address these comments point-by-\npoint. For convenience, we mark the corresponding modifications in our revised manuscript in\nblue fonts.\nReviewer: 2\nI have carefully read the authors’ responses, and overall they are well addressed. I only have a\nfew minor comments and questions as outlined below.\nResponse: We sincerely thank the Reviewer for appreciating our revised manuscript.\n1. Regarding the literature discussion, my original comment was intended to encourage\nmentioning other applications of snap-through mechanisms enabled by origami structures,\nparticularly in the context of actuators and robotics. Relevant examples include, but are not\nlimited to, the following works:\nPNAS, 118, 36, e2110023118 (2021)\nNat. Commun., 14, 4329 (2023)\nAdv. Funct. Mater., 32, 35, 2201891 (2022)\nIEEE/ASME Transactions on Mechatronics, 30, 6, 7019–7030 (2025)\nResponse: We thank the Reviewer for pointing out these relevant papers. We have now\nincluded them in our list of references [30-33] and provided proper credits in the writing of the\nmanuscript.\nThe corresponding changes can be found in page 3 of the main text:\nIn recent years, origami has significantly influenced science and engineering, impacting various\nfields including condensed matter physics18, material science19-22, mechanical engineering23-29,\nrobotics and actuators30-33, biomedical engineering34,35, and architecture36,37.\nThe added references are:\n[30] Zhang, C., Zhang, Z., Peng, Y., Zhang, Y., An, S., Wang, Y., Zhai, Z., Xu, Y. & Jiang, H.\nPlug & play origami modules with all-purpose deformation modes. Nat Commun 14, 4329\n(2023).\n[31] Wu, S., Ze, Q., Dai, J., Udipi, N., Paulino, G. H. & Zhao, R. Stretchable origami robotic\narm with omnidirectional bending and twisting. Proceedings of the National Academy of\nSciences 118, e2110023118 (2021).\n[32] Melancon, D., Forte, A. E., Kamp, L. M., Gorissen, B. & Bertoldi, K. Inflatable Origami:\nMultimodal Deformation via Multistability. Adv Funct Mater 32, 2201891 (2022).\n[33] Chen, P., Liu, Y., Huang, J., Shi, W., Deng, Z. & Ding, Q. Design and Fabrication of\nBistable Actuators With High Load Capacity Based on Origami. IEEE/ASME Transactions on\nMechatronics 30, 7019-7030 (2025).\n2. With respect to the leg length, altering the orientation of the top plate could make the system\ninteresting for other applications, such as robotic arms. If flat-state actuation is a key advantage\nof this design, I suggest emphasizing this point more clearly in the Introduction.\nResponse: We thank the reviewer for pointing this out. This advantage of flat-actuation is now\nemphasized in the Introduction.\nThe corresponding changes can be found in page 4 of the main text:\nThe origami structure undergoes flat-state actuation, during which the upper plate remains\nparallel to the base, such that intimate contact is maintained with either the device or the heat\nsink.\n3. In Figures 6g and 6h, the slope of the H–δ relationship appears to vary depending on the\nnumber of legs, and the actuation speed also seems to differ in the videos. Are there\ncorresponding differences in the response time or required actuation force as a function of the\nleg number?\nResponse: We thank the reviewer for pointing this out. The differences in the response time to\nthe leg number are added in the Result section.\nPage 21:\nThe switching time of the four-arm and six-arm BOS are 7.2s and 90ms, respectively,\ndemonstrating a notable decrease in response time as the number of arms increases within the\ntested range.\n4. There is a typo in Figure 1d.\nAdhensive -> adhesive\nResponse: We thank the reviewer for pointing out our mistakes. This word has been corrected\nto “adhesive” in Fig. 1d."}, {"round": 3, "reviewer_comments": {"reviewer_2": "The authors have adequately addressed the reviewer's comments, and I recommend publishing it. I have no further comments."}, "author_response": ""}]

Decision letter