1、ISSCC 2024SESSION 25Invited:Innovations from Outside the(ISSCCs)Box25.1 Short-Reach Silicon Photonic Interconnects with Quantum Dot Mode Locked Laser Comb Sources John E.Bowersjbowersucsb.eduAndy Netherton,Mario Dumont,Zach Nelson,Luke TheogarajanJ Castro,B Dong,M Dumont,K Feng,J Guo,R Koscica,M Li,

2、T Morin,J Peters,P Pintus,C Shang,T Steiner,University of California Santa Barbara,California,USAwww.optoelectronics.ece.ucsb.eduFunded by DARPA MTO(PIPES)and CUBICDavid Plant,McGill UniversityKerry Vahala,CaltechLin Chang Peking UniversityISSCC Feb.21,2024Outline Economic drivers:high volume applic

3、ations Laser integration platforms Comb generation:Mode locked lasers Nonlinear combs Impact of combs on high capacity interconnects 2 Tbps,12 Tbps and 58 Tbps demonstrations Narrow linewidth lasers from injection locking produces arrays of high power DFBs,which were used in 58 Tb/s transmission wit

4、h a significant reduction in DSP powerArray of narrow linewidth lasers integrated with SiN microresonator comb sources 2024 IEEE International Solid-State Circuits ConferenceHigh Volume Silicon Photonic Applications3LIDARBiosensors for glucose,oxygen,AR/VRDatacom/TelecomOptical GyroscopesOptical and

5、 Quantum Computing 2024 IEEE International Solid-State Circuits ConferenceTransformerELMoBERT LargeGPT-1RoBERTa LargeMegatronALBERT xxlMicrosoft T-NLGGPT-31101001,00010,000100,0001,000,00010,000,000100,000,0001,000,000,00010,000,000,000100,000,000,0001101001,00010,000100,0001,000,00010,000,000100,00

6、0,0001,000,000,00010,000,000,000100,000,000,0001,000,000,000,00020020202242025202620272028POWER(KW)TOTAL TFLOPS TO TRAINYEARTransformer:750 x/2 yrsPower(KW)Current requirements(power)trajectory is un-sustainableWhitney Zhao and Dheevasta Mudigere,“Challenges and Opportunities i

7、n DC-scale AI Cluster Design”,OCP Summit 2021Data Center Growth Driver:AI TrainingMore efficient optical interconnects required 2024 IEEE International Solid-State Circuits ConferenceMore Fiber Optic Interconnects RequiredComputeStorageAI/MLBandwidth Increase at Rack Level:Scale-upClustering:Scale-o

8、ut 2024 IEEE International Solid-State Circuits Conference6More lanes means more photonic integration 2024 IEEE International Solid-State Circuits ConferenceCopper Traces are Lossy at High SpeedsOptical interconnects dominate today for distances longer than 10 m.Soon,optical interconnects will domin

9、ate for distances longer than 1 mm 2024 IEEE International Solid-State Circuits Conference VCSELs dominated data center transmission until 2015.100 Gbps/wavelength demonstrated for distance 1 km 10 GHz km bandwidth distance product is the problem with multimode fiberVCSELs were used for interconnect

10、s,but Bandwidth Distance Product:Drive to 1.3 micron single mode fiber10 GHz kmVCSELVCSEL transceiverMultimode fiberVCSELs 2024 IEEE International Solid-State Circuits Conference VCSELs dominated data center transmission until 2015.100 Gbps/wavelength demonstrated for distance 1 dB/cm 2024 IEEE Inte

11、rnational Solid-State Circuits ConferenceNature 2022,Optica 202326High temperature lasing(185 C)2 kHz fundamentallinewidthWide tuning range(10 THz)LUMOS and GRYPHON fundedGaNGaAs(high-bandgap)InPSiNVISIBLENEAR-INFREREDnmNexus Photonics Heterogeneous SiN Platform0.00010.08000160

12、010210010-210-4WG Loss(dB/cm)GaAsLUMOS focus 2024 IEEE International Solid-State Circuits ConferenceNexus Photonics27Nexus Foundry Process for Heterogeneous GaAs lasers and PICs:780,980 nmLUMOS and GRYPHON fundedNature 2022,Optica 2023 2024 IEEE International Solid-State Circuits ConferenceNexus Pho

13、tonics28Heterogeneous GaAs lasers and PICs87Rb D1 and D2 absorption spectra measured by sweeping one tunable laser across the corresponding wavelength range.Foundry process:High yield(99%)High uniformityHigh functionalityMore than just a laser!500 out of 500 lasers500 out of 500 photodetectorsLUMOS

14、and GRYPHON fundedNature 2022,Optica 2023 2024 IEEE International Solid-State Circuits ConferenceComb Based High Capacity Data Link Demonstrations Yesterday:K.Omirzakhov and F.Aflatouni,“Monolithically integrated sub-63fJ/b 8-channel 256Gb/s optical transmitter with autonomous wavelength locking in

15、45nm CMOS SOI,“IEEE ISSCC,paper 12.1(2024).UCSB Comb source and collaborators:1 Tbps,0.5 pJ/bit intensity modulated 2 Tbps,intensity modulated 12 Tbps coherent using just two lasers:1 transmit,1 receive 68 Tbps coherent with SIL DFBs29 2024 IEEE International Solid-State Circuits ConferenceOFC W6A.3

16、:A.MalikBowers.“Low power consumption silicon photonics datacenter interconnects enabled by a parallel architecture”,OFC(2021).Xiang.Bowers,“High performance Silicon Photonic Circuits Using Heterogeneous Integration”,JSTQE(2022).30300mmPICEICUCSB/AIM/AP/Ciena:PIPES:Project to build 10 Tbps link with

17、 0.2 pJ/bit efficiencyTransmitReceive20 wavelengths x 27 Gbit/s x 2 Pol=1 TbpsPassive Quantum Dot Mode Locked Lasers with Saturable Absorbers 2.5 dB Flatness21 linesExactly 60.0 GHz spacing140 mW total electrical powerAdvantage of Quantum dot mode locking:1)Higher FWM allows better locking and even

18、self mode locking(no saturable absorber)2)Lower linewidth enhancement factor results in reduced reflection sensitivity(no isolator required)0.1 pJ/bitDongBowers“Broadband quantum-dot frequency-modulated comb laser”Light Science and Applications 12,182(2023).2024 IEEE International Solid-State Circui

19、ts Conference322 Tbps DWDM Comb Experiment2 Tbps20 wavelengthsPAM-450 GbaudH.Shu et al.,“Microcomb-driven silicon photonic systems”Nature(2022)PKU 2024 IEEE International Solid-State Circuits Conference12 Tbps Coherent Transmission Using 2 QD Mode locked lasers33DP-IQM 1DP-IQM 2DP-IQM 3DP-IQM 26 Fre

20、quency Comb12326.12326.12326.12326.10 km SSMFO-band123.2612326.12326.Local OscillatorFrequency CombCRx 1CRx 2CRx 3CRx 26JointSignalProcessingCh 1Ch 2Ch 3Ch 26OpticalRF1 comb source for transmitter1 comb source for receiver26 wavelengths0.47 Tbps/wavelength64 QAM Bernal,Bowers,and Plant,“12.1 Terabit

21、/Second Data Center Interconnects Using O-band Coherent Transmission with Frequency Combs”OFC 2024).2024 IEEE International Solid-State Circuits ConferenceCoherent transmission system experiments using a comb as carrier.34Bernal,Bowers,and Plant,“12.1 Terabit/Second Data Center Interconnects Using O

22、-band Coherent Transmission with Frequency Combs”OFC 2024).2024 IEEE International Solid-State Circuits Conference35High Power Coherent Comb SourcesZhangBowers,Wang,Chang,unpublishedDFB self injection locked to SiN cavityTurnkey DFB/SiN single soliton comb sourceDFB array injection locked to comb li

23、nesThe comb power is boosted by 60 dB on chip with no degradation in coherence.PKU/UCSB 2024 IEEE International Solid-State Circuits Conference58 Tbps Comb Driven Coherent Link36Xuguang ZhangJohn E.Bowers,Xingjun Wang,Lin Chang,unpublishedCoherent link of 58 Tb/s:6 cores of 10 Tb/s each2 Polarizatio

24、ns34 comb lines32-QAM at 30 Gbaud30Gbaud x 5 x 2 x 32 x 6=58 TbpsNarrow linewidth reduces coherent related DSP consumption by 99.999%PKU/UCSB 2024 IEEE International Solid-State Circuits ConferenceMargalit,Xiang,Bowers,Bjorlin,Blum,and Bowers,“Perspective on the Future of Silicon Photonics and Elect

25、ronics”,Applied Physics Letters,(2021)Photonic Moores LawYear#Silicon Photonics PapersNumber of Silicon Photonics Papers 2024 IEEE International Solid-State Circuits ConferenceMargalit,Xiang,Bowers,Bjorlin,Blum,and Bowers,“Perspective on the Future of Silicon Photonics and Electronics”,Applied Physi

26、cs Letters,(2021)Photonic Moores LawThanks to my group,particularly Joel Guo,Chen Shang,Ted Morin,Andy Netherton,Paolo Pintus,Kaiyin Feng,Josh Castro,Trevor Steiner,Rosalyn Koscica,Mingxiao Li,BozhangDong,Eammon Hughes.Thanks to former group members,particularly Lin Chang,Chao Xiang,Warren Jin,Yatin

27、g Wan,Rich Mirin,Alex Fang,Alan Liu,Tin Komljenovic,Chong Zhang,Mike Davenport,Alex Spott,Alexis Bjorlin,Eric Stanton.Thanks to DARPA MTO for fundingComplicated,high performance PICs are being commercialized on silicon substrates(Intel,Cisco,Broadcom,Juniper Networks,)in high volume.2024 IEEE Intern

28、ational Solid-State Circuits Conference39Please Scan to Rate Please Scan to Rate This PaperThis Paper25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference1 of 41Extreme Wave-basedMetastructuresFebruary 21,2024Nader EnghetaUniversity of PennsylvaniaPhiladelphi

29、a,PA 1910425.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference2 of 41Research Interests/Programs/ProjectsPhotonic Analog ComputingMZIs for Information Processing4D OpticsQuantum NZI OpticsPhotonic DopingThermal Diffusion with Spatiotemporal StructuresENZ Ele

30、ctric-LevitationTopological MetastructuresPTD-Symmetry MetastructuresMagnet-Free NonreciprocityMemristor MetastructuresENZ NonlinearityNear-Zero-Index PhotonicsNonlocal Metasurfaces()g u()(),bag v K u v dv()g u()inIu12N25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circui

31、ts Conference3 of 41Research Interests/Programs/ProjectsPhotonic Analog ComputingMZIs for Information Processing4D OpticsQuantum NZI OpticsPhotonic DopingThermal Diffusion with Spatiotemporal StructuresENZ Electric-LevitationTopological MetastructuresPTD-Symmetry MetastructuresMagnet-Free Nonrecipro

32、cityMemristor MetastructuresENZ NonlinearityNear-Zero-Index PhotonicsNonlocal Metasurfaces()g u()(),bag v K u v dv()g u()inIu12N25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference4 of 42Metamaterials that function as analog computing machines25.2 Extreme Wa

33、ve-Based Metastructures 2024 IEEE International Solid-State Circuits Conference5 of 42Back to 20 years ago:Optical Lumped Circuit ElementsLCRNano-Optics?Radio Frequency(RF)electronics25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference6 of 41Optical Lumped C

34、ircuit Elements:Modularized PhotonicsDiEt=()()OpticalVoltage EZOptical Displacement D=Electronicsa()Re0C()Re0EHL()Im0EHREHEngheta,Science,317,1698(2007)Engheta,Salandrino,Alu,Phys.Rev.Lett.95(2005)Engheta,Physics World,23(9),31(2010)MetatronicsSun,Edwards,Alu,Engheta,Nature Materials,March 2012Cagla

35、yan,Hong,Edwards,Kagan,Engheta,Phys.Rev.Lett.(2013)25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference7 of 41Modularized Photonics for InformaticsLCRTra()Re0()Re0()Im0MetatronicsRRCCCLLLCElectronic ProcessorA.Silva,F.Monticone,G.Castaldi,V.Galdi,A.Alu,N.Eng

36、heta,Science(2014)N.Engheta,“Math Operations/Processing with Structured Materials”a section in A.Urbas et al.,J.Optics(2016)?25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference8 of 42Goals and Basic Questions forMetamaterial Photonic Processors f x,y,z;t()M

37、etastructureg x,y,z;t()25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference9 of 42?A.Silva,F.Monticone,G.Castaldi,V.Galdi,A.Alu,and N.Engheta,Science(2014)Performing Math Operations with Waves in Metamaterials25.2 Extreme Wave-Based Metastructures 2024 IEEE

38、International Solid-State Circuits Conference10 of 42Materials that Become Analog Computing Machines()g u()(),bag v K u v dv()g u()inIu12NN.Mohammadi Estakhri,B.Edwards,N.Engheta,Science(2019)M.Camacho,B.Edwards,N.Engheta Nature Communications(2021)D.Tzarouchis,M.J.Mencagli,B.Edwards,N.EnghetaLight:

39、Science&Applications(2022)25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference11 of 41N.Mohammadi Estakhri,B.Edwards,N.Engheta,Science(2019)Metasurfaces that Can Solve EquationsInput=0,0,1,0,0Input=0,0,0,1,0Input=0,0,0,0,125.2 Extreme Wave-Based Metastructur

40、es 2024 IEEE International Solid-State Circuits Conference12 of 42Metasurface Analog Computing in Si-Photonic PlatformSi Photonics Near IR(in collaboration with Firooz Aflatouni)V.Nikkhah,A.Pirmoradi,F.Ashtiani,B.Edwards,F.Aflatouni,N.Engheta,Nature Photonics,in press25.2 Extreme Wave-Based Metastru

41、ctures 2024 IEEE International Solid-State Circuits Conference13 of 42Metasurface Analog Computing in Si-Photonic PlatformSi Photonics Near IR(in collaboration with Firooz Aflatouni)V.Nikkhah,A.Pirmoradi,F.Ashtiani,B.Edwards,F.Aflatouni,N.Engheta,Nature Photonics,in press25.2 Extreme Wave-Based Meta

42、structures 2024 IEEE International Solid-State Circuits Conference14 of 42Metagrating/Metasurface for Optical Analog Computing”Open”Geometry with Metasurface(in collaboration with Albert Polman(AMOLF)and Andrea Al(CUNY)Design,simulations,Experiments:A.Cordaro AMOLFSi on Al2O3500 nmNanofabrication an

43、d experimentation at AMOLFA.Cordaro,B.Edwards,V.Nikkhah,A.Al,N.Engheta,A.Polman.Nature Nanotechnology(2023)metasurfaceSemi-transparent mirror25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference15 of 42“Mathematics at the Speed of Light”Collaboration with Alb

44、ert Polman(AMOLF)and Andrea Al(CUNY)A.Cordaro,B.Edwards,V.Nikkhah,A.Al,N.Engheta,A.Polman.Nature Nanotechnology(2023)25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference16 of 42Reconfigurability and ProgrammabilityD.Tzarouchis,M.J.Mencagli,B.Edwards,N.Enghet

45、a,Light:Science and Applications(2022)D.Tzarouchis,B.Edwards,N.Engheta,submitted,under review,ArXiv:2301.02850(2022)25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference17 of 41Mach-Zehnder-Interferometer(MZI)-based PlatformDavid Millers MZI unit“Top”“Left”“B

46、ottom”“Right”22+cos2sin2TBLRiTRLBittierrie=()()()(),inbagKdyg yyyyyI=+D.Tzarouchis M.J.Mencagli,B.Edwards,N.Engheta,Light:Science and Applications(2022)David Miller,Opt.Express 21,6360-6370(2013)David Miller,Science(2015)David Miller,Photon.Res.(2013)25.2 Extreme Wave-Based Metastructures 2024 IEEE

47、International Solid-State Circuits Conference18 of 42Solving Equations with MZI PlatformsReconfigurable MZI Platforms for Analog ComputingCollection of MZIsD.Tzarouchis,M.J.Mencagli,B.Edwards,N.Engheta,Light:Science and Applications(2022)Hermite EquationAiry EquationHelmholtzEquation25.2 Extreme Wav

48、e-Based Metastructures 2024 IEEE International Solid-State Circuits Conference19 of 42Experimental Platforms:Reconfigurable KernelsD.Tzarouchis,B.Edwards,N.Engheta,submitted,under review,ArXiv:2301.0285025.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference20

49、of 42Example 1:Root findingD.Tzarouchis,B.Edwards,N.Engheta,submitted,under review,ArXiv:2301.0285025.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference21 of 42Example 2:Inverse Design“A metastructure that can design metastructures”D.Tzarouchis,B.Edwards,N.En

50、gheta,submitted,under review,ArXiv:2301.0285025.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference22 of 42Near-Zero-Index Photonics25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference23 of 42What-if questionTime-Harmo

51、nic Macroscopic Maxwell EquationsH=-iweE E=iwmH0=H0n=E=0Spatial Distribution:“Static-like”Temporal Variation:“Dynamic”A.Mahmoud and N.Engheta,Nature Communications,Dec 2014M.Silveirinha&N.Engheta,Phys.Rev.Lett.97,157403,Oct 2006N.Engheta,Science,340,286(2013)R.Ziolkowski,PRE(2004)n()vg c25.2 Extreme

52、 Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference24 of 42ENZ Supercoupling25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference25 of 42PECPECPECHinca1PECEinca2PECPECHincEincM.Silveirinha&N.Engheta,Phys.Rev.Lett.97,157403,Oct 2

53、006ENZ Supercoupling25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference26 of 42PECPECPECHinca1PECEinca2PECPECHincEince0ENZ Supercouplingr=a1-a2()+ik0mrADa1+a2()-ik0mrADM.Silveirinha&N.Engheta,Phys.Rev.Lett.97,157403,Oct 200625.2 Extreme Wave-Based Metastruc

54、tures 2024 IEEE International Solid-State Circuits Conference27 of 42Simulation Results:2D scenario1ch=0.5ch=0.001ch=0.1ch=25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference28 of 42Epsilon-Near-Zero(ENZ)and Near-Zero-Index(NZI)Examples From:A.Boltasseva(Pu

55、rdue)Bi1.5Sb0.5Te1.8Se1.2 From:J.Caldwell(Vanderbilt)TCO SiC From:N.Zheludev(Southmapton)WireSEM from:Zayat&Podolskiy SEM from:Polmans&Enghetas StackSEM from:Polman&Engheta From:CT Chans Kimet al.,Optica(2016)Kimet al.,Optica(2016)Ouet al.,Nat.Commun.(2014)Mass et al.,Nat.Photon.(2013)Vesseur et al.

56、,PRL(2013)Pollard et al.,PRL(2009)Huang et al.,Nat.Mater.(2011)()Re0 From:E.Mazurs Liet al.,Nat.Photon.(2015)25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference29 of 42Experimental VerificationLachB.Edwards,A.Al,M.Young,M.Silveirinha,N.EnghetaPhys.Rev.Lett.

57、100,033103(2008)25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference30 of 42ENZ-based Supercoupling:ExperimentsB.Edwards,A.Al,M.Silveirinha,N.EnghetaJ.Appl.Phys(2009)A.Al,M.Silveirinha,N.Engheta Phys.Rev.E.(2008)LachB.Edwards,A.Al,M.Young,M.Silveirinha,N.Eng

58、hetaPhys.Rev.Lett.(2008)25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference31 of 42Geometry-Independent Cavity“Flexible Photonics”25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference32 of 41wnwnwnConventional Cavity

59、25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference33 of 42ENZ-based“Open Cavity”0pI.Liberal and N.Engheta,Optics and Photonics News(OPN),2016I.Liberal and N.Engheta,Science Advances,201625.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-S

60、tate Circuits Conference34 of 42Flexible“Open”Cavity Three degenerate eigenmodes(spherical defect)Eigenfrequency variation t1+dSummary of Some of Our WorkPacheco-Pena&Engheta,Light:Science and Applications,(2020)Temporal AimingTemporal Brewster AnglePacheco-Pena&Engheta,PRB,2021Pacheco-Pena&Engheta,

61、New J.Phys,(2021)Temporal DeflectionAR Temporal CoatingPacheco-Pena&Engheta,Optica(2020)xkxykyqt()xyTemporal TwistronicsPtitcyn&Engheta,manuscript in preparationAsymmetric DiffusionM.Camacho,B.Edwards,&N.Engheta,Nature Communications,July 202025.2 Extreme Wave-Based Metastructures 2024 IEEE Internat

62、ional Solid-State Circuits Conference41 of 41SummaryExtreme wave-based metastructures can provide a versatile platform for enhanced wave-matter interaction()g u()(),bag v K u v dv()g u()inIu12N25.2 Extreme Wave-Based Metastructures 2024 IEEE International Solid-State Circuits Conference42 of 41Pleas

63、e Scan to Rate Please Scan to Rate This PaperThis Paper25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference1 of 34Toward Exponential Growth of Therapeutic NeurotechnologyJacob T.Robinson1,2,Joshua E.Woods1,Kaiyuan Yang1Rice University1

64、Motif Neurotech,Inc.2Josh WoodsKaiyuan YangReferences25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference2 of 34Jon Nelson25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Confer

65、ence3 of 34Jon Nelson25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference4 of 34Alternative neurotech for depressionTravel to clinic 5-days a week6 weeks of therapyMedian time to relapse only 11 monthsDifficult to Access25.3 Toward Exp

66、onential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference5 of 34Neurotech LandscapeNot ScaryWorks Awesome25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference6 of 34Neurotech LandscapeNot Sca

67、ryWorks Awesome25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference7 of 34Neurotech LandscapeNot ScaryWorks AwesomeFuture Neurotech25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circui

68、ts Conference8 of 34Exponential growth in clinical neuromodulation=more awesome25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference9 of 34Smaller neurotech=less scary25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IE

69、EE International Solid-State Circuits Conference10 of 34Battery-free=extreme miniaturizationVishnu Nair,Ashley N Dalrymple,Zhanghao Yu,Gaurav Balakrishnan,Christopher J Bettinger,Douglas J Weber,Kaiyuan Yang,Jacob T Robinson Science(2023)Vishnu Nair25.3 Toward Exponential Growth of Therapeutic Neuro

70、technology 2024 IEEE International Solid-State Circuits Conference11 of 34Wireless power is improvingPoon LabRogers LabMaharbiz&MullerGlowacki LabRobinson&Yang Labs25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference12 of 34Tradeoffs f

71、or Bioelectronics WPT25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference13 of 34Tradeoffs for Bioelectronics WPTAmanda Singer25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Co

72、nference14 of 34PiezoelectricMagnetostrictiveMagnetoelectrics as an efficient wireless power source for bioelectronics25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference15 of 34Magnetoelectrics as an efficient wireless power source fo

73、r bioelectronicsInductive CoilrMagnetic FieldMagnetic FieldMagnetoelectricsMagnetic InductionW.Kim,C.A.Tuppen Robinson(J.App.Phys.2023)2A=AreaAA25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference16 of 34Magnetoelectrics as an efficien

74、t wireless power source for bioelectronicsInductive Coilr Magnetic FieldMagnetic FieldMagnetoelectrics 2Magnetic Inductionflux suxW.Kim,C.A.Tuppen Robinson(J.App.Phys.2023)PowerAreaPowerArea0.50.50.5A=AreaAA25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-S

75、tate Circuits Conference17 of 34Magnetoelectrics as an efficient wireless power source for bioelectronicsW.Kim,C.A.Tuppen Robinson(J.App.Phys.2023)MagnetoelectricOther methodsInductive Coilr Magnetic FieldMagnetic FieldMagnetoelectrics 2Magnetic InductionA=AreaAA25.3 Toward Exponential Growth of The

76、rapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference18 of 34Magnetoelectrics as an efficient wireless power source for bioelectronicsW.Kim,C.A.Tuppen Robinson(J.App.Phys.2023)Inductive Coilr Magnetic FieldMagnetic FieldMagnetoelectrics 2Magnetic InductionA=AreaAA25.3 Towa

77、rd Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference19 of 34Bi-directional data linkYu and Alrashdan et al.,ACM MobiCom,2022Woods and Singer et al.,Sci.Adv.,2024Fatima AlrashdanJosh Woods25.3 Toward Exponential Growth of Therapeutic Neurotechno

78、logy 2024 IEEE International Solid-State Circuits Conference20 of 34electronicselectrodeshermetic packagingmagnetoelectricantenna25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference21 of 34Commercialization of battery-free neuromodulat

79、ion600k patients per year with severe TRD(US)2.3M patients per year with TRD(US)1 in 5 have a mental health disorderPea-sized implant.No brain surgery.Access therapy at home.25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference22 of 342

80、5.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference23 of 34Smallest brain stimulator demonstrated in humansWoodsRobinson,Science Adv.(2024)Amanda SingerJosh Woods25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE I

81、nternational Solid-State Circuits Conference24 of 34$18.75M Series A for clinical trial by 2026motifneuro.tech|confidential2002222Pre-clinical milestones12See Motif Data Room for more infoValidated prototypes in animals and humansDeep Brain Stimulator in RodentsNerve Stimulator in Large A

82、nimalsFirst Magneto-electric Brain Stimulator in Humans20 Singer Robinson,Neuron(2020)2 Chen Robinson,Nature BME(2022)3.Woods Robinson(2023)Motif Founded$15M DARPA&NIH Funding3Begin clinical trials by 2026Closed$18.75M Series A202425.3 Toward Exponential Growth of Therapeutic Neurotechnol

83、ogy 2024 IEEE International Solid-State Circuits Conference25 of 34Toward closed-loop cardiac devicesStimulation2 V0.2 sWoods,Singer Yang,Robinson,in prepRecordingFatima AlrashdanJosh Woods*With Medhi Ravavi Lab25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Sol

84、id-State Circuits Conference26 of 34Wireless networks of implantsWoods,Alrashdan Yang,Robinson,in prepJosh WoodsZhanghao YuKaiyan YangFatima Alrashdan25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference27 of 34Networked spinal cord sti

85、mulation25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference28 of 34Outlook for commercial neurotech25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference29 of 342004201420

86、342024InvestmentCommercial prototypeAdoption25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference30 of 342004201420342024InvestmentCommercial prototypeAdoptionInvestmentCommercial prototypeAdoption?25.3 Toward Exponential Growth of Ther

87、apeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference31 of 34Accelerating the development cycleISSCC 2024(with Kaiyuan Yang):17.1:Wei Wang33.6:Zhanghao Yu&Huan-Cheng Liao25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circui

88、ts Conference32 of 34Wishlist SoCs that support emerging WPT solutions AND standalone chipsets to support small low-power individual functions Low power comms pJ/bit 5-200 kbps at distances of 1-8 cm Energy efficient bio-signal recording+pre-processing to reduce data rates Programmability to meet va

89、rying clinical needs Needs to support real-world operating conditions(e.g.misalignment)25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference33 of 3425.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International So

90、lid-State Circuits Conference34 of 34AcknowledgementsReferences25.3 Toward Exponential Growth of Therapeutic Neurotechnology 2024 IEEE International Solid-State Circuits Conference35 of 34Please Scan to Rate Please Scan to Rate This PaperThis Paper25.4 Liquid Metal Polymer Composites for Stretchable

91、 Circuits,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference1 of 29Liquid Metal-Polymer Composites for Stretchable Circuits,Soft Machines,and Thermal Management Carmel MajidiCarnegie Mellon University25.4 Liquid Metal Polymer Composites for Stretchable Circu

92、its,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference2 of 29Outlinen Overview of Liquid Metal n Digital Circuits with Liquid Metal n LM-Embedded Elastomersn Printable LM-based Inksn Applicationsn Summary&Conclusions25.4 Liquid Metal Polymer Composites for S

93、tretchable Circuits,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference3 of 2925.4 Liquid Metal Polymer Composites for Stretchable Circuits,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference4 of 29of adhesion as well

94、as understanding the materialsevolution.Has natural selection optimized b-keratin forfibrillar adhesion,or do geckos possess the sameb-keratin as their ancestors?Although the helicalb-sheet structure of b-keratin is thought to beconserved,the underlying amino acids are not.Recentwork by Alibardi(Ali

95、bardi&Toni 2005)suggests thatgeckos and birds converged independently on theirkeratinous fibrils(setae and feathers,respectively)byevolving low molecular weight b-keratins that are thenpolymerized into long filaments.Keratin filaments arein turn cross-linked together longitudinally by disulfidebonds

96、(Rizzo et al.2006).Increased cross-linkage couldincrease the material stiffness(Parbhu et al.1999).Stiffness has also been found to depend on orientation ofthe keratin fibrils along the feather rachis(Cameronet al.2003).Without direct measurements,thereremains the possibility of variation in both th

97、e tensileand the bending moduli depending on what types ofb-keratin molecules are manufactured and how they areassembled in the animal.Geckos have diverged ecologically such that theyinhabit humid tropical as well as arid desert environ-ments,and encompass both diurnally and nocturnallyactive specie

98、s.If the material properties of setalb-keratin are variable,some species could conceivablybenefit from evolutionary pressure driving changes instiffness or viscoelasticity(e.g.through increased ordecreased degrees of cross-linkage)to compensate forthe effects of extreme environments.Alternatively,if

99、material properties are constrained across gekkonids,that pressure could drive structural changes instead.Another important consideration is how setae age;depending on the species,a gecko must use the samesetae for weeks or months between moults.Setae arenot adhesive in their resting state,but must

100、deform bybending to generate adhesive force(Autumn et al.2000;Autumn&Hansen 2006).If material properties changesignificantly over time,this bending(and thereforeadhesive function)may be compromised towards theend of the moulting cycle.The objective of our experiment is to quantify thematerial proper

101、ties of gekkonid setal keratin from twospecies:Gekko gecko,a well-studied tropical species,and Ptyodactylus hasselquistii,a desert dweller.Ourprinciple aim is to determine how b-keratin varies instiffness between birds and lizards.However,we havechosen these species with the reasoning that,if anygec

102、kos exhibit differences in elastic modulus due totheir ancestral environment,we should see a differencebetween two species from greatly disparate habitats.2.METHODS2.1.AnimalsWe harvestedsetae fromfourindividuals ofG.gecko andfourindividualsofP.hasselquistii.AnimalswerecaredforbytheOfficeofLaborator

103、yAnimalCareattheUniversityof California,Berkeley,and seta removal was performedin accordance with Animal Use Protocol no.R137.2.2.Data collectionIndividual setae were isolated and mounted at the baseto the tip of a pin with Gapper gap-filling adhesive(Partsmaster,Dallas,TX).A 250 mm diameter glasssp

104、here(Jaygo,Inc.,Union,NJ)wasthenmountedtothetip(branched end)of the seta.When the glue hardened,only the stalk was exposed and deformable,while baseand branched tips were rigidly fixed(figure 4).Wecollecteddatafor410setaefromeachindividualgecko.The mounted seta was placed in front of a PhotronFastCa

105、m-X 1024 PCI high-speed camera(PhotronUSA,Inc.,San Diego,CA)with a custom microscopeattachment and illuminated with Fiberlite Series 180fibre optic lights(Dolan-Jenner Industries,Inc.,Lawr-ence,MA).The seta was then perturbed(by flicking)several times from the left and the right.We recordedthe resul

106、tant motion at 500 or 1000 fps.We thendetermined the natural frequency by counting thenumber of frames between the initial release and theinstant closest to the return to initial position anddividing 2p by this time period.We recorded relativetoeclawscansorssetaespatulaeFigure 1.Generalized structur

107、e of an adhesive gecko foot.1kPa1GPa1TPa1MPatackynon-tacky100 kPadiamondbonesteel-keratin(feather)concretespider silkresilintapemesogleabeetle setaeadipose tissue-keratin(wool)cellulosesoft insect cuticleFigure 2.Representative materials along a continuum ofYoungs moduli.Materials with Youngs modulu

108、s over 1 MPaare not considered sticky according to the Dahlquist criterionfor tack.mammalsbirdscrocodileslizards and snakes-keratinFigure 3.Origin of b-keratin among amniotes.1072Elastic modulus of gecko setal b-keratinA.M.Peattie et al.J.R.Soc.Interface(2007)Peattie,Majidi,Corder,Full,J.R.Soc.Inter

109、f.(2007)SOFT MATTER SOFT MATTER ENGINEERING 2016 WILEY-VCH Verlag GmbH&Co.KGaA,WeinheimCOMMUNICATIONfrequency of 100 kHz and 0%strain.The plot shows that as the concentration of LM increases,the effective relative permittivity increases nonlinearly.For the silicone system,the effective relative perm

110、ittivity of the sample with =50%increases to over 400%as compared to the unfi lled system over the entire 1200 kHz frequency range(Figure 2 b).In order to evaluate the ability of the dielectric to store charge,we measure its dissipa-tion factor(D)for the same range of frequencies(Figure 2 c).Also ca

111、lled the loss tangent,D corresponds to the ratio of elec-trostatic energy dissipated to that stored in the dielectric.13 For LMEEs,the dissipation factor is measured to be similar to or less than that of the unfi lled material(D (1a)123311LL=where rm is the matrix relative permittivity at =0%,p =r 3

112、/r 1 is the aspect ratio of the ellipsoids,and is the angle between the axis along which permittivity is being calculated and the prin-cipal axis corresponding to the dimension r 3.For our materials,the average aspect ratio of the LM inclusions measured through particle analysis is p =1.49 0.36(Tabl

113、e S1,Supporting Infor-mation)and =1/3 for randomly orientated ellipsoids.Adv.Mater.2016,DOI:10.1002/adma.201506243www.advmat.dewww.MaterialsVAchieve robotic and computing functionality with condensed soft matter:Elastomers Gels Fluids Granular mediaMajidi,Soft Matter Engineering for Soft RoboticsSof

114、t Matter Engineering for Soft Robotics,Adv.Mater.Tech.(2019)25.4 Liquid Metal Polymer Composites for Stretchable Circuits,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference5 of 29LIQUID METAL LIQUID METAL EUTECTIC GALLIUM INDIUMEutectic Gallium IndiumEutecti

115、c Gallium Indium75 wt%Gallium25 wt%Indium3x106 S/m conductivityLow viscosity(2 cP)Negligible vapor pressureNon-toxicapproaches,materials properties,and creative applications for LM-based wearable electronics and mate-rials,further improving the quality of life and society(Figure 1).The first section

116、 of this report will cover thestrategiesfor circuit fabrication bycategorizing them into three architecturesto describeitsadvantage andchallenges and also shows material properties that exhibit with LM inclusions.Furthermore,the recentlyreported LM-based wearable applications including various senso

117、rs,energy-harvesting/storage devices,antenna,and even implantable devices will be further explored.Finally,the summary and outlook forLM-based wearable electrics and materials for unexplored areas and emerging applications are discussed.STRATEGIES FOR FABRICATING LM-BASED STRETCHABLE CONDUCTORSTreme

118、ndous different approaches to fabricate LM-based conductor and materials have been reportedrecently,making advantages and options out of its unique rheological property.Among all these,threerepresentative strategies for LM-based conductor can be categorized into i)microfluidic elastomers,ii)biphasic

119、 alloys and iii)LM-embedded elastomers(LMEEs).All these strategies are discussed andcompared in the following section(Figure 2).MICROFLUIDIC ELASTOMER CONDUCTORMicrofluidic elastomers have been the most universal technique of using LM alloy for electronic sensorsand circuit components with many othe

120、r approaches including injection,direct writing,and contact print-ing(Figure 2A).(Khoshmanesh et al.,2017;Neumann and Dickey,2020;Silva et al.,2020a)Unlike otherFigure 1.Overview of recent advances in liquid-metal-based wearable electronicsMicrofluidic elastomer.Reproduced with Permission(Gao et al.

121、,2017).Copyright,Wiley-VCH.Miniaturized fabrication.Reproduced with Permission(Kim et al.,2020d).Copyright,Springer Nature.Liquid-metal-embedded elastomer.Reproduced with Permission(Markvicka et al.,2018).Copyright,Springer Nature.Electronic vessel.Reproduced withPermission(Cheng et al.,2020).Copyri

122、ght,Cell Press.Artificial eye.Reproduced with Permission(Gu et al.,2020).Copyright 2020,SpringerNature.Multifunctionalelectronics.Reproduced with Permission(Lopeset al.,2021).Copyright,American Chemical Society.Electrochemical sensor.Reproduced with Permission(Silva et al.,2020b).Copyright,Wiley-VCH

123、.Wireless communication.Reproduced with Permission(Alberto et al.,2020).Copyright,Springer Nature.Electronictattoo.Reproduced with Permission(Tavakoli et al.,2018).Copyright,Wiley-VCH.Electronic textile.Reproduced withPermission(Dong et al.,2020).Copyright,Springer Nature.Thermal conductive.Reproduc

124、ed with Permission(Bartlettet al.,2017).Copyright,Proceedings of National Academy of Science.EMI shielding.Reproduced with Permission(Yaoet al.,2020).Copyright,Wiley-VCH.Transparency.Reproduced with Permission(Pan et al.,2018).Copyright,Wiley-VCH.Energy storage.Reproduced with Permission(Liu et al.,

125、2019a).Copyright,Wiley-VCH.Thermoelectric generator.Reproduced with Permission(Zadan et al.,2020).Copyright 2020,American Chemical Society.llOPEN ACCESS2iScience 24,102698,July 23,2021iSciencIndium CorpWon,Jeong,Majidi,Ko iScience(2021)25.4 Liquid Metal Polymer Composites for Stretchable Circuits,So

126、ft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference6 of 291950s-presentWhitney Strain GaugeFloat SwitchTilt SwitchFlame SensorMercury Displacement RelayMercury Wetted RelayMercury Contact Relay 1949 Reginald WhitneyWhitney,R.J.,“The measurement of changes in hu

127、man limb-volume by means of a mercury-inrubber strain gauge.”The Journal of physiology,109(1-2)(1949)LIQUID METAL LIQUID METAL HISTORY2000s2000s“Microsolidics”and Ga-based LM electronics developed in the George Whitesides Group(Michael DickeyMichael Dickey,Ryan Chiechi,Adam Siegel,et al.)Majidi,Brar

128、d,Wood,unpublished(2009).25.4 Liquid Metal Polymer Composites for Stretchable Circuits,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference7 of 29C.Pan,K.Kumar,J.Li,E.J.Markvicka,P.R.Herman,C.Majidi,Advanced Materials 30 1706937(2018)LASER PATTERNING LASER PAT

129、TERNING FOR LM CIRCUIT FABRICATION25.4 Liquid Metal Polymer Composites for Stretchable Circuits,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference8 of 29IC CHIP INTEGRATION IC CHIP INTEGRATION WITH VAPOR-BASED SOLDERINGOzutemiz,et al.,Advanced Materials Inte

130、rfaces(2018)25.4 Liquid Metal Polymer Composites for Stretchable Circuits,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference9 of 29Ozutemiz,et al.,Advanced Materials Interfaces(2018)25.4 Liquid Metal Polymer Composites for Stretchable Circuits,Soft Machines,

131、and Thermal Management 2024 IEEE International Solid-State Circuits Conference10 of 29Ozutemiz,et al.,Advanced Materials Interfaces(2018)LIQUID METAL MICROFLUIDICS LIQUID METAL MICROFLUIDICS CHALLENGES&LIMITATIONS Challenges with robust microelectronics interfacing Failure at the chip-electrode inte

132、rface Direct ink write(DIW)is possible but not practical No reliable technique of interfacing DIW-printed LM with surface mounted 2018 WILEY-VCH Verlag GmbH&Co.KGaA,Weinheim1701596(4 of 13)www.advmatinterfaces.dethat 40.9 m of the resistance measured corresponds to the copper interconnects while the

133、 remaining value corresponds to the soldercomponent interface and the component itself.Figure 3B shows the shape of the liquid metal at the com-ponentLM interface before and after HCl vapor application.Figure 3A shows the side views of a surface-mount resistor in contact with LM-coated Cu contact pa

134、ds with and without HCl treatment.As a reference,a side view of an SMDCu connec-tion obtained using conventional solder paste is also provided.Before the HCl treatment,the component rests on the LM-coated Cu pads and has a limited contact area.When HCl vapor is applied,liquid metal surrounds the com

135、ponent pins(com-posed of Sn-plated Cu).This not only increases the interfacial contact area,potentially reducing the contact resistance,but also produces a better mechanical connection between the LM and microelectronic component.Referring to the figures,the HCl treated LMcomponent interface resembl

136、es the conven-tional soldercomponent interface.There are clear benefits to using HCl vapor to solder the packaged components to the terminals of the LM circuit.Referring to Figure 2,we observed that immediate and reli-able electrical connectivity requires the application of HCl vapor.If vapor is not

137、 applied,then electrical contact is still possible but may take hours or days to form.Considering that the component pins are tin coated,this time-dependent connectivity in the absence of HCl is likely governed by the reactive wetting observed between EGaIn and Sn presented by Kramer et al.57Referri

138、ng to these results,we conclude the following:(i)Without HCl treatment,robust LMcomponent interfaces cannot be reliably obtainedi.e.,they have a low yield(9/20 did not work),exhibit significant changes of conductivity in time,and show considerable variations in conductivity.(ii)When treated with HCl

139、,LMcomponent interfaces become conduc-tive immediately and maintain a stable contact resistance,with very low variability over time.(iii)Moreover,with HCl treat-ment,the interface conductance is similar to that of a conven-tional solder joint.Referring to Figure 3A,B,the interfacial contact area is

140、larger in the treated versus nontreated case and this likely corresponds to a lower contact resistance between the component pins and the LM leads.2.2.Self-Alignment of Components through HCl TreatmentFigure 3B shows the top and side views of the EGaIn drops applied on the Cu pads,initial placement

141、of a component on the pads,and the component after the HCl treatment.Although the component was placed in a misaligned manner with respect to the layout of contact pads,we observed that HCl vapor exposure causes the component to self-align itself with respect to the contact pads.The high surface ten

142、sion of liquid metal caused the components to self-align.This is a phenom-enon observed in reflow soldering,58 but demonstrated here for the first time for EGaInmicroelectronic interfacing.Video S2 (Supporting Information)demonstrates this behavior on sur-face-mount resistorLM interface.To quantify

143、this self-alignment phenomenon,an evalua-tion of the self-alignment was conducted for placement of nine components.For this purpose,the misalignment of the components both before and after the application of the HCl vapor was measured.The test design used in this experiment was composed of two LM-co

144、ntact pads patterned on a Si-wafer backed PDMS substrate.The component(zero-ohm resistor)was placed on these pads manually.The details of the sample fabrication and the experimental settings are given in the Adv.Mater.Interfaces 2018,5,1701596Figure 3.Effect of HCl treatment on self-aligning.A)Side

145、view images of electrical interface test circuits on rigid PCB board.B)Side and top view images of self-alignment test designs on PDMS before/after component placement and before/after HCl vapor 2018 WILEY-VCH Verlag GmbH&Co.KGaA,Weinheim1701596(9 of 13)www.advmatinterfaces.decomponents.Gallium and

146、its alloys are known to significantly cor-rode Al6365 through intergranular diffusion,and can alloy with and diffuse into Cu.19,66,67 One concern with bringing LM into direct contact with component pins is how this interfacing may affect the lifetime of the IC components.For EGaIn and Gal-instan,res

147、pectively,Tang et al.19 and Ralphs et al.66 reported that when Cu and LM are brought into contact,a CuGa2 inter-metallic compound is formed and In(and Sn in case of Galin-stan)is dispersed into the LM solution without alloying with Cu.To understand the distribution and penetration of EGaIn at the co

148、mponent pin interface,we analyzed an analog accelerom-eter chip from a 4-month-old LM circuit and a digital IMU chip from a 6-month-old LM circuit kept at room temperature.The removed ICs were cleaned,cross-sectioned,and polished for energy-dispersive X-ray spectroscopy(EDS)analysis.Fresh ICs with n

149、o EGaIn were also prepared in the same way and their elemental maps were also obtained using EDS for comparison.Figures S12 and S13(Supporting Information)show the ele-mental maps of the component pin cross-sections for the analog accelerometer and digital IMU ICs,respectively.Referring to Figure S1

150、2(Supporting Information),the analog accelerometer IC has a layered structure consisting of Au,Ni,Cu,Al,and Si.A thin layer of Au(as commonly used in ICs)is at the pin surface and Ni is used as a diffusion barrier between Au and Cu.When we investigated the same layered structure for the EGaIn inter-

151、faced chip,we observed that Ga is penetrated into Au and AuGa layer on the pin surface remains intact through the cleaning and sectioning steps.We also observed that penetrated Ga dif-fused through Au layer all the way to the Ni layer.However,Ga penetration was seen to stop at the Ni layer and no Ga

152、 is observed in the remaining layers.Moreover,no In is observed in the obtained elemental map.Referring to Figure S13 (Supporting Information),the digital IMU IC has a layered structure consisting of Ni and Cu.According to the manufac-turers datasheet,the pin surface has a AuPdNi finish(Au:350 nm,Pd

153、:20100 nm,Ni:500 nm2 m in thickness,as reported by manufacturer),however,the amounts of Au and Pd were not in the reliable detection range for EDS.The elemental map of the EGaIn interfaced IMU chip shares a similar trend with the accelerometer chip,i.e.,Ga was intact on the compo-nent pin surface,Ga

154、 penetration seemingly stopped at the Ni layer,and no In was observed.These results indicate that Ni is acting as a diffusion barrier between Ga and Cu,as reported in ref.63 for EGaInAl and Adv.Mater.Interfaces 2018,5,1701596Figure 7.Component package architectures and functional circuits.A)Photos s

155、howing the pin architecture of QFN,SoT,LGA packages and a thick film resistor from the bottom view.Scale bars:1 mm.B)Photo on the left shows the bottom view of soft digital IMU+temperature sensor circuit and the photo on the right shows the bottom view of soft analog accelerometer circuit.C)Represen

156、tative images of functioning analog accelerometer circuit with real-time animated block.Animated blocks orientation information comes from the accelerometer circuit.Photos show orientation sensing in roll and pitch angles under bending and stretching.D)Representative images of functioning IMU+temper

157、ature sensor circuit with real-time animated block.Animated blocks orientation infor-mation comes from the IMU while the color of the block shows the temperature sensed from the sensor.(Top row)Photos show orientation sensing in roll,pitch,and yaw angles.(Bottom row)Photos show orientation and tempe

158、rature sensing.E)Representative images that show the circuits tested until failure at different applied strains.(Top row)Tensile testing of analog accelerometer circuit.(Bottom row)Tensile testing of digital IMU+temperature sensor circuit.25.4 Liquid Metal Polymer Composites for Stretchable Circuits

159、,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference11 of 29LMEELMEE LIQUID METAL EMBEDDED ELASTOMER 2016 WILEY-VCH Verlag GmbH&Co.KGaA,WeinheimCOMMUNICATIONfrequency of 100 kHz and 0%strain.The plot shows that as the concentration of LM increases,the effecti

160、ve relative permittivity increases nonlinearly.For the silicone system,the effective relative permittivity of the sample with =50%increases to over 400%as compared to the unfi lled system over the entire 1200 kHz frequency range(Figure 2 b).In order to evaluate the ability of the dielectric to store

161、 charge,we measure its dissipa-tion factor(D)for the same range of frequencies(Figure 2 c).Also called the loss tangent,D corresponds to the ratio of elec-trostatic energy dissipated to that stored in the dielectric.13 For LMEEs,the dissipation factor is measured to be similar to or less than that o

162、f the unfi lled material(D (1a)123311LL=where rm is the matrix relative permittivity at =0%,p =r 3/r 1 is the aspect ratio of the ellipsoids,and is the angle between the axis along which permittivity is being calculated and the prin-cipal axis corresponding to the dimension r 3.For our materials,the

163、 average aspect ratio of the LM inclusions measured through particle analysis is p =1.49 0.36(Table S1,Supporting Infor-mation)and =1/3 for randomly orientated ellipsoids.Adv.Mater.2016,DOI:10.1002/adma.201506243www.advmat.dewww.MaterialsVMichael Bartlett,et al.Adv.Mater.201625.4 Liquid Metal Polyme

164、r Composites for Stretchable Circuits,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference12 of 29 Composite elasticity governed by properties of elastomer matrix LM loading has little influence on strain limit and Youngs modulus Composites exhibit pronounced“

165、Mullins effect”Michael Bartlett,et al.PNAS 2017.Kazem,et al.Adv.Mater.2018.Speed=32x EGaIn-Silicone CompositeELASTICITY&FRACTURE TOUGHNESSELASTICITY&FRACTURE TOUGHNESS25.4 Liquid Metal Polymer Composites for Stretchable Circuits,Soft Machines,and Thermal Management 2024 IEEE International Solid-Stat

166、e Circuits Conference13 of 29Bartlett et al.Bartlett et al.PNAS PNAS 20172017Kazem et al.Kazem et al.Adv.Mater.Adv.Mater.20172017was measured at high LM volume fraction(66%by vol.;92.5%byweight),these samples exhibited an increased stiffness(Youngsmodulus increased from 0.65 MPa to 3.3 MPa)and reduc

167、edstretchability(strain limit decreased from 150 to 50%),which limitsthe ability to elongate LM droplets in situ.Comparing previous re-sults with the exceptional performance reported here(Fig.1E)highlights the critical importance of LM microstructure(and not justmaterial composition)in enabling elas

168、tomers to exhibit metal-likethermal conductivity without altering their natural elasticity.Experimental ResultsTheLMembeddedelastomer(LMEE)iscomposedof aPt-catalyzedsilicone elastomer embedded with a randomly distributed,polydisperse suspension of nontoxic(21),liquid-phase eutecticgalliumindium(EGaI

169、n)microdroplets(19,20,22).As shown in Fig.1D and Movie S1,stretched and twisted strips of LMEE exhibit rapidthermal dissipation compared with adjacent strips of unfilled elastomersubject to the same initial heating.Compared with previous attemptswith LM-filled elastomers(12),we have discovered that

170、strain createsthermally conductive pathways through the in situ elongation of thedeformable liquid inclusions,which significantly enhances thermalconductivity in the stretching direction.For permanent(stress-free)and strain-controlled elongation of the LM inclusions,thisenhanced k is nearly 25 to 50

171、 greater than the unfilled elasto-mer(0.20 0.01 Wm1K1)and approaches the limit for theparallel rule of mixtures of an EGaInsilicone composition(23)without the aid of percolating networks.Referring to Fig.1E,theexceptional combination of high thermal conductivity,low elasticmodulus,and high strain li

172、mit allows the LMEE composites tooccupy an uncharted region of the material properties space.The thermal composite is fabricated by shear mixing EGaIn alloy(75%Ga,25%In,by weight;Gallium Source)with an uncuredsilicone elastomer(Ecoflex 00-30;Smooth-On)(see Methods formaterial fabrication).During mix

173、ing,the LM droplets form aself-passivating Ga2O3coating that helps prevent coalescenceand eliminates the need to add surfactants or other dispersingagents(24).The droplets have a statistically uniform spatialdistribution and are polydisperse,with a median diameter of15 m(19).Thermal conductivity is

174、measured using the tran-sient hotwire(THW)method in which an embedded wire si-multaneously acts as a resistive heat source and thermometerthat measures the change in temperature(T)as a function oftime(t),which is related to thermal conductivity through the cy-lindrical heat diffusion equation(Method

175、s and Fig.S1).Experi-mental measurements are presented in Fig.2A and show that,asLM volume fraction()increases,thermal conductivity increases(Fig.S2).These values are in good agreement with theoreticalpredictions obtained from the Bruggeman effective medium theory(EMT)formulation(25)for a uniform di

176、spersion of sphericalEGaIn inclusions k=26.4 Wm1K1(23)in a silicone matrix(k=0.20 Wm1K1).We further configure the THW method to enable directionalmeasurements of thermal conductivity upon deformation bylaminating LMEE strips around wires that are parallel(axial)and perpendicular(transverse)to stretc

177、h,as shown in Fig.2B.Ellipsoidal heat spreading yields effective anisotropic thermalconductivities in the axial and transverse directions that can betransformed to measure the orthotropic(kx,ky,kz)bulk values(see EMT for derivation)(26,27).This configuration enablesexamination of the thermalmechanic

178、al coupling between thermalconductivity and deformation.We find that,upon stretching theunfilled(=0%)homogenous elastomer,the thermal conductivityin the direction of stretch(ky 0.20 Wm1K1)remains largelyunchanged(Fig.2C).However,when stretching the =50%LMEE,the thermal conductivity in the longitudin

179、al direction(ky)dramatically increases and reaches a value of 9.8 0.8 Wm1K1at 400%strain(Figs.S3 and S4).This represents an increase of50 relative to the unfilled material and a value that approachesFig.1.Soft,thermally conductive composite.(A)Highly deformable LMEE.(scale bars,25 mm.)(B)EGaIn alloy

180、 is liquid at room temperature and shows fluidcharacteristics as demonstrated by falling droplets.(Scale bar,10 mm.)(C)Schematic illustration of the LMEE composite where LM microdoplets are dispersed inan elastomer matrix and,upon deformation,the LM inclusions and elastomer elongate in the direction

181、 of stretching.(D)Alternating strips of LMEE and unfilledelastomer are heated with a heat gun,and the IR photo time sequence shows the LMEE dissipating heat more rapidly than the elastomer(images correspond to t=0,5,10,and 15 s after the heat source is removed).(Scale bar,25 mm.)(E)The =50%LMEE comp

182、osites described here occupy a unique region of the materialproperties space when comparing thermal conductivity with the ratio of strain limit to Youngs modulus.(Data points are from refs.2,9,12,and 14.)2 of 6|www.pnas.org/cgi/doi/10.1073/pnas.1616377114Bartlett et al.LM-embedded elastomers(LMEEs)w

183、ith high EGaIn content exhibit metal-like thermal conductivityThermal conductivity scales according to Effective Medium TheoryB.Mozooni,“Effective Medium Theory”(2015).interactions,a self-consistent dierential eective mediumtheory188is developed to calculate the composite thermalconductivity:kp?kckp

184、?kmkmkcL=1?,(2.2)where kcis the composite thermal conductivity,kpis the LMthermal conductivity,kmis the elastomer thermal conduc-tivity,?is the LM volume ratio,and L is the depolarizationfactor,which depends on the strain.117,185As shown in Fig.5F,the increase in thermal conductivity is in good agre

185、ementwith this adaptation of the Bruggeman formulation.3Connected LM NetworksDepending on volume fraction and spatial distribution,theembedded LM can form a connected network that supportselectrical conductivity.These networks can be ordered,forexample a 3D grid or periodic lattice,or random.The lat

186、terincludes gels or foams with open pores that are filled withliquid metal.3.1Ordered NetworksAn embedded LM network is“ordered”if the shape of theinclusions is uniform and their spacing is periodic in three-dimensions.When connected,these inclusions form a con-ductive network that gives the composi

187、te an eective bulkelectrical conductivity.One example is a grid-like open foamthat is back-filled with liquid metal.The mechanical integrity,elasticity,and electrical properties of such a system is gov-erned by LM-elastomer interfacial wetting and 3D architec-ture.The latter is limited by available

188、fabrication methods,which in general involves either direct elastomer 3D printingor molding techniques in which a sacrificial template/scaold(negative)is used for casting elastomer.Park et.al introduced a photolithography technique to pro-duce a 3D polymer template using proximity-field nanopat-tern

189、ing(PnP).2This sacrificial template is used to castPDMS and is removed by a water-based developer after theelastomer is cured.Scanning electron microscope images showa fairly consistent 3D grid-like elastomer microstructure(Fig.6A).Next,the PDMS is vacuum injected with EGaIn,creat-ing conductive int

190、erconnected 3D channels throughout.Thistechnique has been shown to support a simple LED circuit(Fig.6B)with a conductivity of approximately(2.4106S/m)and minimal degradation over many loading cycles.3.2Random NetworksAn open foam elastomer can also be produced by filling sugarcubes with a polydimeth

191、ylsiloxane(PDMS)prepolymer andthen dissolving away the sugar after the elastomer cures.Thisresults in a sponge with random pores that can then be filledwith liquid metal(Fig.6C,D).1The presence of liquid metaldoes not significantly interfere with the ability to deform thePDMS sponge under light comp

192、ression(Fig.6E,F).Depend-ing on the sponge porosity,the eective volumetric conduc-tivity of the bulk system can be as high as 1.6106S/m,sim-ilar to that of the ordered network2.The advantage of thisfacile technique is that it eliminates the need for PnP-basedtemplating or other specialized technique

193、s for 3D elastomerpatterning.Random LM networks in an open foam matrix can also beaccomplished with“mechanical sintering”techniques that in-volve the application of highly localized pressure to an LMEEcomposite.In the case of EGaIn nanodroplets produced withultrasonication,it has been previously sho

194、wn that high pres-sure can rupture the Ga2O3skin and cause droplets to co-alesce into conductive traces(Fig.6G).150Droplet ruptureand coalescence can also be accomplished with laser-based sin-tering using a CO2laser engraver(Fig.6H).135For certainLMEE compositions,mechanically sintering can be used

195、topermanently transform the composite from an electrical insu-lator into a conductor.It has been shown that stier LMEEcomposites composed of highly cross-linked PDMS(Sylgard184;Dow-Corning)with 50%(by vol.)loading EGaIn can ex-hibit permanent electrical conductivity(104S/m)when sub-ject to intense p

196、ressure with a roller or ball-point pen(Fig.6I).116Moreover,electrical resistance of the trace does notchange significantly when stretched to 125%strain.This ap-parent departure from Ohms law is likely related to the gov-erning role of contact resistance between LM droplets,whichis not expected to c

197、hange significantly with stretch.In general,electrical conductivity can be accomplished withpercolative networks in which the fluid exhibits long-rangeconnectivity throughout the volume of the composite.Fora liquid dispersion with statistically uniform spatial distri-bution,percolation typically req

198、uires a high volume fraction?such that the inclusions are packed su?ciently tight andin physical contact.189Even in the absence of direct con-tact,electrical connectivity is still possible through electricaltunneling over interfacial gaps of 0.1-1 nm.190In the spe-cial case of embedded spherical inc

199、lusions with fixed diameterand periodic spatial distribution,the percolation threshold?0can be determined for a variety of lattice geometries,includ-ing cubic,body-centered,and face-centered.191193However,electrical conductivity may not be significant even when?0isexceeded.This could be on account o

200、f the insulating Ga2O3skin covering the LM droplets126,194or conformal wetting ofthe elastomer.4Connected LMPA NetworksAs with LM-based composites,connected LMPA networksembedded in elastomer can also be categorized into orderedor random.In both cases,the LMPA-elastomer system canbe engineered to fu

201、nction as a rigidity-tuning composite thatundergoes dramatic change in stiness when the embedded al-loy melts.Such phase change can be controlled with externalheating or by internal Joule heating with electrical current.Stiness tuning can also be accomplished with shape mem-ory alloys195,shape memor

202、y polymers139,196,thermoplas-tics197199,and a variety of other techniques.200,201How-ever,LMPAs remain attractive due to the dramatic changein mechanical compliance from a rigid solid(modulus 10GPa)to fluidic.8the thermal conductivity of some metals like bismuth and stainlesssteel.These measurements

203、,which were taken at room tempera-ture,are in good agreement with tests performed on samples thatwere either cooled to 0 C or heated to 60 C(Fig.S5).In addition,the material is robust to cyclical loading,with only a slight increasein thermal conductivity measured after 1,000 cycles of 200%strain(Fig

204、.S6).Furthermore,we can“program”the material to achievepermanently elongated LM inclusions in a stress-free state bystretching a virgin sample of LMEE to 600%strain and thenunloading to zero stress.An unrecoverable plastic strain of 210%isinduced,enabling elongated inclusions in an unloaded(stress-f

205、ree)state(Methods and Fig.S7).As shown in Fig.2A,thermal con-ductivity of the programmed LMEE sample in the longitudinaldirection(ky)is 4.7 0.2 Wm1K1,which is 25 greater thanthat of the base elastomer(Fig.2D).It is important to note that,when unstrained,both the =0 and 50%samples exhibit values ofk

206、that are typically observed in other polymeric composites(12,28).Such an unprecedented enhancement in k arises from thediscovery of a unique thermalmechanical coupling in which thedeformable LM inclusions elongate into needle-like micro-structures along the prestrained or mechanically loaded directi

207、onto create enhanced thermally conductive pathways(Fig.2E).This is further demonstrated in Fig.2F,in which compositionswith =30%and 50%EGaIn(by volume)are subject to strainsranging from 0 to 400%in increments of 100%(Methods andFigs.S3 and S4).As shown,the thermal conductivity in the y(stretching)di

208、rection increases by greater than a factor of 5beyond 300%strain.To theoretically capture this behavior,wecreate an EMT model based on the Bruggeman formulation toexplain the relative increase in directional thermal conductivityas a function of axial strain()(see EMT for details).As seen inFig.2F,we

209、 find good agreement between the experimentallymeasured values(markers)and our theoretical predictions(curves),which capture the large increase in thermal conductivityin the stretching direction(ky)and the slight decrease in theorthogonal directions(kz,kx).The agreement with theory isachieved withou

210、t data fitting and supports the claim that theobserved anisotropic thermalmechanical response is controlledby the directional change in aspect ratio of the LM inclusions(Fig.1C).Lastly,for all volume fractions,the composite mate-rials have an elastic modulus less than 90 kPa(Fig.S8)and cansupport un

211、iaxial strains above 600%,properties that are similarto those of the homogeneous elastomer(Fig.2G).The modestincrease in elastic modulus(20%)for the LMEE compositescan be attributed to surface tension at the liquidsolid interface.For liquid inclusions in a compliant matrix,Style et al.(29)haveprevio

212、usly shown that surface tension can induce mechanical re-sistance to droplet deformation and result in an overall stiffening ofthe composite.Together,these results show that the EGaIndroplets greatly enhance thermal conductivity of soft materialsFig.2.Thermalmechanical behavior of the LMEE composite

213、.(A)Thermal conductivity versus LM volume fraction()in the stress-free state.The programmed samplerefers to a composite that has been stretched to 600%strain and then relaxed to an unloaded state.Here the symbols are the experimental measurements,and thesolid curve represents the theoretical predict

214、ion from the Bruggeman EMT formulation(n=100 volume fraction dependence,n=5 programmed samples).(B)Schematic of the THW method to measure anisotropic thermal conductivity under deformation.(C)Plot of thermal conductivity in the stretch direction versus strain forthe elastomerandthe LMEEcomposites.Up

215、onstretching,theLMEE approachesthe thermal conductivityof stainlesssteel and is 50greater thanthe unfilledelastomer(n=5).(D)Thermal conductivity comparison for different LM volume fractions()and stress states(n=5).(E)Optical micrographs of the 30%LMEE microstructureduring stretching,with the images

216、corresponding to 0 to 400%strain in 100%increments(from top to bottom).(F)Normalized thermal conductivity as a function ofstrain(blue open symbols are =30%,and cyan closed symbols are =50%;n=5).The solid line represents the predicted behavior for they direction,and the dashedline is the prediction f

217、or the x and z direction from our model.The images are representative images of the LM inclusions during the deformation process.(G)Me-chanical properties of the LMEE composites with elastic modulus on the left axis and strain at break on the right axis(n=3).All error bars represent 1 SD.Bartlett et

218、 al.PNAS Early Edition|3 of 6APPLIED PHYSICALSCIENCESthe thermal conductivity of some metals like bismuth and stainlesssteel.These measurements,which were taken at room tempera-ture,are in good agreement with tests performed on samples thatwere either cooled to 0 C or heated to 60 C(Fig.S5).In addit

219、ion,the material is robust to cyclical loading,with only a slight increasein thermal conductivity measured after 1,000 cycles of 200%strain(Fig.S6).Furthermore,we can“program”the material to achievepermanently elongated LM inclusions in a stress-free state bystretching a virgin sample of LMEE to 600

220、%strain and thenunloading to zero stress.An unrecoverable plastic strain of 210%isinduced,enabling elongated inclusions in an unloaded(stress-free)state(Methods and Fig.S7).As shown in Fig.2A,thermal con-ductivity of the programmed LMEE sample in the longitudinaldirection(ky)is 4.7 0.2 Wm1K1,which i

221、s 25 greater thanthat of the base elastomer(Fig.2D).It is important to note that,when unstrained,both the =0 and 50%samples exhibit values ofk that are typically observed in other polymeric composites(12,28).Such an unprecedented enhancement in k arises from thediscovery of a unique thermalmechanica

222、l coupling in which thedeformable LM inclusions elongate into needle-like micro-structures along the prestrained or mechanically loaded directionto create enhanced thermally conductive pathways(Fig.2E).This is further demonstrated in Fig.2F,in which compositionswith =30%and 50%EGaIn(by volume)are su

223、bject to strainsranging from 0 to 400%in increments of 100%(Methods andFigs.S3 and S4).As shown,the thermal conductivity in the y(stretching)direction increases by greater than a factor of 5beyond 300%strain.To theoretically capture this behavior,wecreate an EMT model based on the Bruggeman formulat

224、ion toexplain the relative increase in directional thermal conductivityas a function of axial strain()(see EMT for details).As seen inFig.2F,we find good agreement between the experimentallymeasured values(markers)and our theoretical predictions(curves),which capture the large increase in thermal co

225、nductivityin the stretching direction(ky)and the slight decrease in theorthogonal directions(kz,kx).The agreement with theory isachieved without data fitting and supports the claim that theobserved anisotropic thermalmechanical response is controlledby the directional change in aspect ratio of the L

226、M inclusions(Fig.1C).Lastly,for all volume fractions,the composite mate-rials have an elastic modulus less than 90 kPa(Fig.S8)and cansupport uniaxial strains above 600%,properties that are similarto those of the homogeneous elastomer(Fig.2G).The modestincrease in elastic modulus(350kPa to NickleStra

227、in at break exceeding 200%25.4 Liquid Metal Polymer Composites for Stretchable Circuits,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference16 of 29 For certain compositions,LMEEs can be electrically conductive Requires“mechanical sintering”Composites have neg

228、ligible electromechanical couplingFasslerFassler&Majidi&Majidi Adv.Mater.Adv.Mater.20152015.MarkvickaMarkvicka et al.et al.Nature Mater.Nature Mater.2018.2018.Pouillets Law:DR/R0=l2 1LMEE CompositeELECTRICAL CONDUCTIVITYELECTRICAL CONDUCTIVITY25.4 Liquid Metal Polymer Composites for Stretchable Circ

229、uits,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference17 of 29ARTICLESNATURE MATERIALSefforts in LMEE synthesis2427,3032,34 resulted in material composi-tions and microstructures that achieved electrical conductivity only at very high volume loadings 50%(if

230、 at all)and did not exhibit autonomous self-repair.In addition,light pressure(2.8 GPa);however,conductivity is initially inter-rupted after damage and self-healing was limited to a single event as the LM is depleted during healing21.By combining recent work on LM,fluidic self-healing and mechanical

231、sintering,we are able to demonstrate a soft,stretchable circuit that is electrically stable under typical operational load-ing conditions but capable of instantaneous electrical self-healing under multiple,extreme damage events.In contrast to previous work,the material composition and LM microstruct

232、ure presented 2 cm200 mClockDataVccGNDMicrocontrollerTimer displayLM microdropsElastomerSelectively create conductive pathwaysCircuit reconfigures around severe damageAutonomous self-healingNon-self-healingextra-wideNon-self-healingredundantabcdModerate resistance increase:R R0Significant resistance

233、 increase:R R0ARTICLESNATURE MATERIALSefforts in LMEE synthesis2427,3032,34 resulted in material composi-tions and microstructures that achieved electrical conductivity only at very high volume loadings 50%(if at all)and did not exhibit autonomous self-repair.In addition,light pressure(2.8 GPa);howe

234、ver,conductivity is initially inter-rupted after damage and self-healing was limited to a single event as the LM is depleted during healing21.By combining recent work on LM,fluidic self-healing and mechanical sintering,we are able to demonstrate a soft,stretchable circuit that is electrically stable

235、 under typical operational load-ing conditions but capable of instantaneous electrical self-healing under multiple,extreme damage events.In contrast to previous work,the material composition and LM microstructure presented 2 cm200 mClockDataVccGNDMicrocontrollerTimer displayLM microdropsElastomerSel

236、ectively create conductive pathwaysCircuit reconfigures around severe damageABABABAutonomous self-healingNon-self-healingextra-wideNon-self-healingredundantabcdModerate resistance increase:R R0Significant resistance increase:R R0 LM circuits remain intact when mechanical damaged Electrical self heal

237、ing achieved through“autonomous”formation of new conductive LM pathwaysMarkvicka et al.Nature Mater.2018.ELECTRICAL“SELFELECTRICAL“SELF-HEALING”HEALING”25.4 Liquid Metal Polymer Composites for Stretchable Circuits,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conf

238、erence18 of 29LMLM-LCELCE LIQUID METAL+LIQUID CRYSTAL ELASTOMERstimulation(Fig.1G).Critically,the LCE retains the abilityto actively shape morph even for cases when up to 50 vol%(83wt%)of the composite is filled with the mechanically passiveLM droplets.Immediately after synthesis,the composites are

239、inherentlyelectrically insulating due to the native oxide shell that formsaround the LM microparticles,which contributes to stabilizing theLM microparticle dispersion(17).In this state,the compositesexhibit a high thermal conductivity that improves heat distributionand response to thermal stimulatio

240、n.Electrical conductivity can beinduced by mechanical sintering(18),which irreversibly formspercolating LM pathways.Electrical conductivity in the compositecan autonomously reconfigure when conductive traces are mechan-ically damaged(Fig.1E).More generally,the composites elec-trical conductivity ena

241、bles the creation of internally Joule-heatedactuators,transducers for touch sensing,and circuit wiring forsurface-mounted electronic components(Fig.1H).Joule-heatedlinear actuation of LMLCEs can be excited at rates faster than2 Hz and cycled to 50%reversible strain 15,000 times at 0.007 Hz(and 2.5%r

242、eversible strain 100,000 times at 1 Hz while stillretaining 90%of its original shape change).Together,theseproperties enable the composite to display a rich diversity offunctionalities that allows it to simultaneously exhibit sensingand dynamic responses(e.g.,Fig.1H).Results and DiscussionLCEs were

243、synthesized from a simple,one-pot methodologyusing commercially available precursors(SI Appendix,Fig.S1)(19).LM microparticles were introduced by shear mixing withan overhead mixer before curing the elastomer to form drop-lets of 200 to 500 m in size(Fig.1D).The stressstraincharacteristics of all co

244、mposites measured were comparable toAEGHBFCDLM dropletsLCE matrixMesogen:RM 257 Spacer:EDDET Cross-linker PETMP Photoinitiator:HHMP Filler:EGaIn 50 vol%Michael Ford,Ambulo,Kent,Markvicka,Pan,Malen,Ware,Majidi,PNAS 201925.4 Liquid Metal Polymer Composites for Stretchable Circuits,Soft Machines,and Th

245、ermal Management 2024 IEEE International Solid-State Circuits Conference19 of 29BIPHASIC CONDUCTIVE INKS BIPHASIC CONDUCTIVE INKS LM+SILVER+POLYMERSoft and stretchable conductive ink EGaIn liquid metalSilver microflakesSIS co-polymer elastomerwww.advmattechnol.de2200534(2 of 7)2022 The Authors.Advan

246、ced Materials Technologies published by Wiley-VCH GmbHdevices as the inner diameter of the extruder needle used is too large(500 m).Recently,we reported a bi-phasic ink synthesized by mixing silver(Ag)microflakes,EGaIn alloy,and SIS tri-block copolymer as a soft elastomeric binder.21 This ink is esp

247、ecially promising for printed soft electronics because of its high stretchability,high conductivity,elimination of sintering or other forms of postprocessing steps,and compatibility with low-cost extrusion-based printers.Without any sintering by heat or pressure,this ink overcomes the additional pos

248、tprocessing steps required for previous inks composed of percolating LM droplets.In this way,it is particularly well-suited for applications in printed soft electronics that require rapid and scalable manufacturing.However,there still remains a gap in the systematic study of these AgInGa-SIS inks,an

249、d further study is required to develop a stronger understanding of how the composition of inks,spe-cifically the choice of Ag microflakes,influences their electrical and electromechanical properties.In this article,we examine the influence of material com-position on the performance of a previously

250、reported class of conductive elastomer composites.This systematic study leads to the discovery of a digitally printable biphasic composite with an exceptional combination of high electrical conductivity(highest value:6.38 105Sm1),high stretchability(1000%),extremely low electromechanical coupling(10

251、00%),extremely low electromechanical coupling(2%resistance change at 100%strain),and promising durability on stretching.The stretchable SIS block copolymer is used as a soft elasto-meric binder for embedding solid-phase Ag microflakes and liquid phase EGaIn alloy that electrically anchors to the Ag

252、microflakes(Figure 1a).This enables rapid and automatic fab-rication of stretchable printed circuit boards through the direct ink writing(DIW)technique(Figure1b).For Ag fillers,Leeetal.22 reported that among Ag micro-flakes,Ag microparticles,and Ag nanoparticles,the Ag micro-flakes showed the highes

253、t conductivity and the best consistency under stretch among these Ag particle types.For these reasons,we focused our study on the use of various commercially avail-able Ag microflakes.In particular,we report our observations on varying Ag microflakes with different chemical finishings,surface areas,

254、and dimensions contributed to different stretch-ability,conductivity,and other electromechanical properties of the AgInGa-SIS conductors.Figure1c presents a comparison of the performance of these inks versus other printable soft conductors.For some formulations,the AgInGa-SIS stands out for its exce

255、ptional combination of high stretchability and con-ductivity,making them especially well-suited for applications in stretchable coils(Figure1d)and circuits,robotic sensing skins,and epidermal electronics for wearable health monitoring.To highlight the potential application scenarios of this elastic

256、conductor,we demonstrate a digitally printed adhesive patch for wearable electrocardiography(ECG).As shown in Figure1e,the circuit can be printed on thin,flexible,and stretchable films,including medical-grade adhesive films that are certified for applications over the human skin.For ECG monitoring,t

257、he ink is used both as bioelectrodes for bio-potential acquisition,and as electrical interconnects for interfacing to an external circuit Figure 1.Digitally printable elastic conductors.a)Ink synthesis process.b)Close-up photograph showing ink deposition on the TPU substrate.c)Conductivity at 0%stra

258、in and maximum strain of elastic conductor synthesized with different Ag flakes compared to other classes of nonliquid print-able conductive materials.d)Photograph of a Joule heating coil with a double-spiral pattern on a piece of SIS substrate under a relaxed and stretched state.e)Photograph of a f

259、ully integrated electrocardiography system consisting of digitally printed elastic conductor serving as skin-interfacing elec-trodes on both sides to detect heart pulses and interconnects to connect the ECG patch(up)with the microcontroller patch(bottom)to light up the blue LED on the bottom left wh

260、en a heart pulse is detected.Adv.Mater.Technol.2022,7,2200534 2365709x,2022,12,Downloaded from https:/ by Carnegie Mellon University,Wiley Online Library on 25/08/2023.See the Terms and Conditions(https:/ Wiley Online Library for rules of use;OA articles are governed by the applicable Creative Commo

261、ns License25.4 Liquid Metal Polymer Composites for Stretchable Circuits,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference21 of 29Zu et al.Adv.Mater.Tech.(2022)Carneiro et al.Adv.Funct.Mater.(2022)2205956(9 of 15)2022 The Authors.Advanced Functional Material

262、s published by Wiley-VCH GmbHFigure 6E and Video S3(Supporting Information)depict in red the three leads acquired from the EASI montage (AS,ES,AI)and the derived 12-lead ECG in green.Features such as the QRS complex(normal sinus rhythm)can be observed in all signals,and as well the RR interval shows

263、 to be regular in all traces.These are characteristics of a normal adult 12-lead electrocardiogram,as stated in.67 Apart from the regular RR interval(indicating the absence of arrhythmia67),the heart rate can also be calculated to be 77bpm,between the 60 and 100 lower and upper boundaries considered

264、 normal.67 The equation and coefficients to perform the transformation between the EASI and the 12-lead ECGs are presented in the Experimental section.2.3.3.Electroencephalography,Electrooculography,and Facial EMGA patch containing ten electrodes was fabricated for recording brain activity,eye movem

265、ent,and facial muscle activity.Figure 7A depicts the placement and function of each elec-trode.Figure7B shows a user wearing the patch on their fore-head and face.The simple and inexpensive digital fabrication process enables the fabrication of patient-specific patches with precise electrode positio

266、ns and a custom layout that fits each user perfectly.Figure7C shows an example of a recorded EEG signal in which the Berger effect68 can be observed.This effect consists of suppression of the Alpha rhythm(813Hz)when the user opens their eyes,leading to a lower amplitude signal when compared to the b

267、rain activity while keeping their eyes closed.FigureS12A,B(Supporting Information)shows the frequency spectrums for the open and closed eyes signals,respectively,and a frequency peak can be observed 10Hz when the user closes his eyes but is suppressed when the eyes are open.This observable differenc

268、e in the two signals enables a clear separation between the two states.Although it is usually more noticeable in electrodes placed on the back of the scalp,we were still able to observe this with a signal acquired from the users forehead.Figure7D and VideoS4(Supporting Information)depict EOG signals

269、 that were acquired.We can observe that the left and right electrodes show opposite polarities when lateral eye movement is detected.On the other hand,eye blinks,predominantly vertical movements,are detected with higher amplitude by the EOG electrode placed below the users eye.These are characterize

270、d by their high amplitude and low frequency.Finally,sEMG artifacts derived from masticatory movement(Figure7E)are detected in the face by the electrode placed near the masseter muscle.These are characterized by both high amplitude and high frequency.Overall,possible applications of this patch includ

271、e fast deployable EEG exams for emergency or ambulatory settings,sleep monitoring,and staging or human/brainmachine inter-faces.Moreover,the possibility of recording muscle activity in the face(and specifically near the jaw),has relevance for monitoring orthodontia-related conditions such as bruxism

272、 or temporomandibular joint disorder,as discussed in Ref.692.3.4.Electromyography and Hand Pose SignatureFigure8A shows an EMG patch with 17 electrodes.The patch is composed of 16 recording electrodes connected to eight Adv.Funct.Mater.2022,2205956PHYSIOLOGICAL MONITORINGPHYSIOLOGICAL MONITORING W/B

273、IPHASIC INK2205956(2 of 15)2022 The Authors.Advanced Functional Materials published by Wiley-VCH GmbHAs well,despite the progresses,there have been limited efforts to create fully-functional systems instead,most studies focus on the synthesis and characterization of standalone elec-trodes.10,13,15,5

274、1,52,55,57 Furthermore,in cases where a fully standalone patch is presented,it is typically limited to a single predefined application.3,4,7,12,20In this work,we demonstrate a novel architecture of materials and methods for implementation of thin-film multielectrode adhesive patches for long-term an

275、d reliable monitoring of elec-trophysiological signals and digital biomarkers(Figure1A,B).We show that by using a bi-phasic Ag-EGaIn composite we previously developed32(Figure1C),and a multi-layer thin film(210 m)implementation,one can,thanks to a digital fabri-cation process,rapidly develop patient

276、-specific multi-electrode biostickers that seamlessly conform to the natural roughness and contours of the human skin and can be used for a range of biopotential recording applications.Referring to Figure1A,this includes single-lead ECG,which is also used to determine the respiration rate of the sub

277、ject,multi-lead ECG,EOG,EEG,and EMG,during several days,while withstanding everyday activi-ties such as jogging or bathing.This is a fully standalone system,with the e-patch(Figure1D)is connected to a small-sized analog front-end(Figure1E)that also rests on the skin surface,allowing for true wireles

278、s biopo-tential monitoring of up to 16 electrodes.A comprehensive study with ten subjects shows that these electrodes provide a signal quality better than Ag/AgCl elec-trodes or than the same composite without liquid metal.Although these electrodes are solid-like and non-smearing,48 the inclusion of

279、 EGaIn droplets into the composite contributes to lower electrode-skin impedance,making this material an excellent choice for wearable epidermal electrodes as it com-bines the advantages of wet electrodes in terms of signal quality and skin-interfacing,and of dry electrodes(printability,low thicknes

280、s and easy implementation).2.Results2.1.FabricationFigure 1B presents the layered structure of the multielectrode biopotential recording system.Referring to the figure,the system is composed of a soft patch attached to a rigid acquisition board.The active layer of the biosticker consists of the prin

281、ted conductive lines and skin interfacing electrodes made of AgInGaSIS polymer.32 The circuit is readily printed through direct ink writing and can be taylor-made for each user.The ink and electrodes can be printed with a resolution of 300m and thickness 50m,thus allowing for implementation of high-

282、res-olution multi-electrode bioelectronics.The active conductive layer is aligned with a thin,flexible interfacing printed circuit board and encapsulated between two layers of thermoplastic urethane(TPU;50m thickness each)of the desired shape.All layers are fused together seamlessly through a heat p

283、ressing process sim-ilar to that which is used in t-shirt stamping.A pre-cut medical-grade skin-compatible acrylic adhesive(60m thickness)with a backing paper liner is laminated to serve as the skin-adhesion layer prior to fusion.In the TPU and adhesive layers,holes were pre-patterned in the electro

284、de locations to allow direct electrical contact between the ink and the skin.The rigid acquisition board consists of the analog front end(AFE),processor,and wireless communication module.The interface between the electronics and the patch is established through solder joints enabling a reli-able mec

285、hanical and electrical connection between both.A conformal and robust bond with the human skin is achieved by removing the adhesives release liner and applying light pressure to the e-skin patch.As seen in Figure 1A,depending on the shape and placement of the e-skin in the human body,various distinc

286、t signals can be recorded,such as heart activity,brain activity,eye movement,respiration,or muscle activity in different locations.Detailed material listing Adv.Funct.Mater.2022,2205956Figure 1.A)Depending on its shape and placement in the body,the proposed adhesive patches can be used for detection

287、 of multiple electrophysi-ological signals:brain waves(EEG),eye movement(EOG),neuromuscular activity(EMG),cardiac activity(ECG),and respiration.B)The various layers and components that compose the e-patch.C)Schematic model of the trinary microstructure of the biphasic conductive polymer.Adapted with

288、 permission from Ref.29.Copyright 2021 American Chemical Society.D)Fully printed flexible adhesive patch on a patterned background,evidencing the transparency of the substrate.E)Rigid analog front end.Multimodal physiological sensing with printed LM-Ag-SIS bioelectrodes25.4 Liquid Metal Polymer Comp

289、osites for Stretchable Circuits,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference22 of 29Zhou,et al.Nature Electronics 2023LMLM-AgAg-ORGANOGEL ORGANOGEL SELF-HEALING CONDUCTORNature ElectronicsArticlehttps:/doi.org/10.1038/s41928-023-00932-0Fig.2b.The degre

290、e of physical entanglement is impacted by the freez-ing time,which affects mechanical properties of the composite such as Youngs modulus and stretchability.The longer freezing time leads to more physical entanglements,and thus a higher energy is required to deform the polymer chains,which is reflect

291、ed by the tensile modulus(the tensile moduli of samples in the thawed state after having been frozen for 10,20 and 30min are 17.1kPa,23.6kPa and 42.3kPa,respec-tively).The physical entanglements also restrict the reconfiguration and straightening of the polymer chains,which degrades the stretch-abil

292、ity(the maximum strain of samples after having been frozen for 10,20 and 30min are 439.9%,358.1%and 319.8%,respectively).Embedding metal fillers,in this case Ag flakes and EGaIn droplets,alters both the tensile and rheological properties of the material(Supplementary Figs.57).However,because the vol

293、ume fraction of the metal fillers is relatively low(23%vol),the composite still exhibits a low elastic modulus and high flexibility.For many applications,the material is expected to sustain multi-ple loading cycles during usage.To test the cyclic performance of the composite,it was first stretched b

294、y 20%strain and then relaxed to its original length,then the strain was increased by 20%up to 100%for each successive cycle,as shown in Fig.2c.A hysteresis loop between loading and unloading cycles is observed,which is a typical feature of 020406080100Strain healing eficiency(%)2103104105

295、106Electrical conductivity(S m1)Ionic gelRigid particle-hydrogel compositeLM-hydrogel compositeThis workacbiiiCrosslinkingDry annealingiiiSelf-healingMixingAgflakes MixingPVACutBorax solutionAg-LM-PVA compositeAg micro flakeEGaIn micro dropletPVA polymer chainHydrogen bondHealed hydrogen bondEthylen

296、e glycol OriginalStretchHeal10 mmSelf-healingd10 mmef50 mmFig.1|Self-healing,electrically conductive organogel.a,Overview of the AgLMPVA composite:(i)schematic of the fabrication process,(ii)dry annealing and(iii)self-healing mechanism.b,Ashby-style plot highlighting the combination of high electric

297、al conductivity and high self-healing efficiency of the AgLMPVA composite.References for the literature are listed in the Supplementary Information.c,Demonstration of composite stretchability and self-healing.d,Snail-inspired crawling robot demonstrating the properties of the composite.e,Reconfigura

298、ble circuit for powering a toy car and LED.f,Composite utilized as an electrode for EMG.Nature ElectronicsArticlehttps:/doi.org/10.1038/s41928-023-00932-0Fig.2b.The degree of physical entanglement is impacted by the freez-ing time,which affects mechanical properties of the composite such as Youngs m

299、odulus and stretchability.The longer freezing time leads to more physical entanglements,and thus a higher energy is required to deform the polymer chains,which is reflected by the tensile modulus(the tensile moduli of samples in the thawed state after having been frozen for 10,20 and 30min are 17.1k

300、Pa,23.6kPa and 42.3kPa,respec-tively).The physical entanglements also restrict the reconfiguration and straightening of the polymer chains,which degrades the stretch-ability(the maximum strain of samples after having been frozen for 10,20 and 30min are 439.9%,358.1%and 319.8%,respectively).Embedding

301、 metal fillers,in this case Ag flakes and EGaIn droplets,alters both the tensile and rheological properties of the material(Supplementary Figs.57).However,because the volume fraction of the metal fillers is relatively low(23%vol),the composite still exhibits a low elastic modulus and high flexibilit

302、y.For many applications,the material is expected to sustain multi-ple loading cycles during usage.To test the cyclic performance of the composite,it was first stretched by 20%strain and then relaxed to its original length,then the strain was increased by 20%up to 100%for each successive cycle,as sho

303、wn in Fig.2c.A hysteresis loop between loading and unloading cycles is observed,which is a typical feature of 020406080100Strain healing eficiency(%)26Electrical conductivity(S m1)Ionic gelRigid particle-hydrogel compositeLM-hydrogel compositeThis workacbiiiCrosslinkingDry anne

304、alingiiiSelf-healingMixingAgflakes MixingPVACutBorax solutionAg-LM-PVA compositeAg micro flakeEGaIn micro dropletPVA polymer chainHydrogen bondHealed hydrogen bondEthylene glycol OriginalOriginalCutHeal10 mmSelf-healingd10 mmef50 mmFig.1|Self-healing,electrically conductive organogel.a,Overview of t

305、he AgLMPVA composite:(i)schematic of the fabrication process,(ii)dry annealing and(iii)self-healing mechanism.b,Ashby-style plot highlighting the combination of high electrical conductivity and high self-healing efficiency of the AgLMPVA composite.References for the literature are listed in the Supp

306、lementary Information.c,Demonstration of composite stretchability and self-healing.d,Snail-inspired crawling robot demonstrating the properties of the composite.e,Reconfigurable circuit for powering a toy car and LED.f,Composite utilized as an electrode for EMG.25.4 Liquid Metal Polymer Composites f

307、or Stretchable Circuits,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference23 of 2925.4 Liquid Metal Polymer Composites for Stretchable Circuits,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference24 of 29ENERGY HARVEST

308、ING ENERGY HARVESTING FOR WEARABLE ELECTRONICSZadan et al.,Multifunctional Materials(2020).LMEEs for energy harvestingPower wearable haptics using soft generatorsHarvest energy from body motion,friction,and 2016 WILEY-VCH Verlag GmbH&Co.KGaA,WeinheimCOMMUNICATIONfrequency of 100 kHz and 0%strain.The

309、 plot shows that as the concentration of LM increases,the effective relative permittivity increases nonlinearly.For the silicone system,the effective relative permittivity of the sample with =50%increases to over 400%as compared to the unfi lled system over the entire 1200 kHz frequency range(Figure

310、 2 b).In order to evaluate the ability of the dielectric to store charge,we measure its dissipa-tion factor(D)for the same range of frequencies(Figure 2 c).Also called the loss tangent,D corresponds to the ratio of elec-trostatic energy dissipated to that stored in the dielectric.13 For LMEEs,the di

311、ssipation factor is measured to be similar to or less than that of the unfi lled material(D (1a)123311LL=where rm is the matrix relative permittivity at =0%,p =r 3/r 1 is the aspect ratio of the ellipsoids,and is the angle between the axis along which permittivity is being calculated and the prin-ci

312、pal axis corresponding to the dimension r 3.For our materials,the average aspect ratio of the LM inclusions measured through particle analysis is p =1.49 0.36(Table S1,Supporting Infor-mation)and =1/3 for randomly orientated ellipsoids.Adv.Mater.2016,DOI:10.1002/adma.201506243www.advmat.dewww.Materi

313、alsV25.4 Liquid Metal Polymer Composites for Stretchable Circuits,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference25 of 29Zadan,Malakooti,Majidi,ACS Appl.Mater.Inter.2020Chapter 1.Wearable Thermoelectric Generators for Self-Powered Medical SensingFigure 1.

314、1:a,Open-circuit voltage vs temperature comparing the voltage(a)and voltage density(b)for HA-LD,HA-HD,and LA-HD devices.b,Open-circuit voltage density vs temperature.c,Open-circuit voltage vs temperature comparing HA-LD,HA-LD+Thubber,and HA-LD+ControlEpoxy devices.d,Power output vs external load res

315、istance for HA-LD+Thubber TEG at 20,40,60T.e,Power output vs external load resistance for HA-HD+Thubber TEG at 20,40,60T.f,Comparison of peak power outputs for HA-LD+Thubber and HA-HD+Thubber generators.1.3Thermoelectric Device Performance with VaryingParameters1.3.1Semiconductor Aspect Ratio Perfor

316、mance ComparisonTo better understand the influence of semiconductor aspect ratio on holding a temperaturedifferential and generating a high voltage output,devices with high and low aspect ratiosemiconductors were compared.Both devices had a high fill factor of 42%and 39%butwith two different semicon

317、ductor dimensions selected:1.41.41.6 mm and 1.41.44 mm respectively.These devices are referred to as Low-Aspect High-Density(LA-HD)shown in Figure 1.2a and High-Aspect High-Density designs(HA-HD)shown in Figure 1.2b.Fabrication follows the same steps as before but with the LA-HD substrate having a 1

318、.6 mmhigh solid infill.In comparison,the HA-HD substrate is 4 mm tall and open in the center6Chapter 1.Wearable Thermoelectric Generators for Self-Powered Medical SensingFigure 1.1:a,Open-circuit voltage vs temperature comparing the voltage(a)and voltage density(b)for HA-LD,HA-HD,and LA-HD devices.b

319、,Open-circuit voltage density vs temperature.c,Open-circuit voltage vs temperature comparing HA-LD,HA-LD+Thubber,and HA-LD+ControlEpoxy devices.d,Power output vs external load resistance for HA-LD+Thubber TEG at 20,40,60T.e,Power output vs external load resistance for HA-HD+Thubber TEG at 20,40,60T.

320、f,Comparison of peak power outputs for HA-LD+Thubber and HA-HD+Thubber generators.1.3Thermoelectric Device Performance with VaryingParameters1.3.1Semiconductor Aspect Ratio Performance ComparisonTo better understand the influence of semiconductor aspect ratio on holding a temperaturedifferential and

321、 generating a high voltage output,devices with high and low aspect ratiosemiconductors were compared.Both devices had a high fill factor of 42%and 39%butwith two different semiconductor dimensions selected:1.41.41.6 mm and 1.41.44 mm respectively.These devices are referred to as Low-Aspect High-Dens

322、ity(LA-HD)shown in Figure 1.2a and High-Aspect High-Density designs(HA-HD)shown in Figure 1.2b.Fabrication follows the same steps as before but with the LA-HD substrate having a 1.6 mmhigh solid infill.In comparison,the HA-HD substrate is 4 mm tall and open in the center6Chapter 1.Wearable Thermoele

323、ctric Generators for Self-Powered Medical SensingFigure 1.2:a,Image and Peltier cooling and heating performance of LA-HD TED at 0.25 A,0.50 A,and 0.75 A.b,Image and Peltier cooling and heating performance of HA-HD TED at 0.25 A,0.50 A,and 0.75 A.c,Image and Peltier cooling and heating performance of

324、 HA-LD TED at 0.25 A,0.50 A,and 0.75 A.d,Image and Peltier cooling and heating performance of HA-LD+Thubber TED at 0.25A,0.50 A,and 0.75 A.-3.90.6 C at 3.5 s and-4.80.7 C at 2.8 s respectively for LA-HD compared to-10.70.5 Cat 13.0 s and-13.00.6 C at 8.8 s respectively for HA-HD.Heating performance

325、confirmsthis trend with temperature increases at 0.50 A and 0.75 A of 21.51.9 C and 49.14.0 Crespectively for LA-HD compared to 39.90.5 C and 84.84.0 C respectively at 45 s forHA-HD.While Seebeck and Peltier performance increases with the HA-HD device,mechanical per-formance decreases due to the inc

326、rease in bending moment.Figure 1.3a-b gives a comparisonof compression-force and corresponding electrical performance under 20%compressive loadfor both devices for 10 cycles.Eulers critical load(Pcr)and flexural rigidity(EI)increasesfromPcr=1.06Nand 5.68105Pam4for LA-HD toPcr=3.47Nand 1.86104Pam4for

327、HA-HD with elastic and plastic regimes appearing in both curves.Eulers critical load is8Seebeck effect for thermoelectric energy harvesting0.8V&3 mW/cm2 60C differentialTHERMOELECTRIC ENERGY GENERATORTHERMOELECTRIC ENERGY GENERATORZadan,et al.manuscript in review(2024)25.4 Liquid Metal Polymer Compo

328、sites for Stretchable Circuits,Soft Machines,and Thermal Management 2024 IEEE International Solid-State Circuits Conference26 of 29Zadan,et al.manuscript in review(2024)HAHA-LDLDHAHA-LDLDw/LMEEw/LMEEw/LMEEw/LMEEPeltier HeatingPeltier HeatingPeltier CoolingPeltier CoolingPeltier Cooling/Heating-10C/6

329、0C 0.75AFigure A.2:Additional images of completed Low-Aspect High-Density Device24CONCLUSIONIn summary,we present a 3D printable LM-embeddedelastomer(LMEE)that is highly soft and can be engineeredto be thermally or electrically conductive.This approach is well-suited to rapid prototyping of LMEE str

330、uctures with complexgeometries that cannot be produced using stencil lithography,laser ablation,or other planar fabrication methods.By selectingthe appropriate rheology of the LMEE emulsion,we can printwithresolutionsaslowas180mandcreatestructureswithasmany as 50 printed layers.As part of this appro

331、ach,we alsointroduced a method to transform 3D printed LMEE structuresfrom electrically insulating to conductive.This is accomplishedby encasing the structure in a highly viscoelastic gel that is thenused to deliver a shockwave.With these advances in materials rheology,direct ink writing(DIW),and fa

332、cile postprocessing,we can create LMEE systemsthat exhibit improved electrical and thermal properties.This isdemonstrated with use cases related to emerging applications ofLMEEs for triboelectric energy harvesting and wearablethermoelectric cooling/heating.In summary,this work uses athorough examina

333、tion of LMpolymer rheology to address keychallenges in DIW-based printing of LMEEs and presents aframework for creating 3D LMEE structures that achieveenhanced triboelectric and heat dissipating properties throughgeometry.METHODSPreparation of 3D Printable Liquid Metal EmbeddedElastomer Ink.The LMEE ink was prepared by mixing a mixture ofeutecticgalliumindium(EGaIn;75%galliumand25%indiumbymass;bot