On a daily basis, our requirements for technology become more innovative and creative and the field of electronics is helping to lead the way to more advanced appliances. This book gathers and evaluates the materials, designs, models, and technologies that enable the fabrication of fully elastic electronic devices that can tolerate high strain. Written by some of the most outstanding scientists in the field, it lays down the undisputed knowledge on how to make electronics withstand stretching. This monograph provides a review of the specific applications that directly benefit from highly compliant electronics, including transistors, photonic devices, and sensors. In addition to stretchable devices, the topic of ultraflexible electronics is treated, highlighting its upcoming significance for the industrial-scale production of electronic goods for the consumer. Divided into four parts covering: * Theory * Materials and Processes * Circuit Boards * Devices and Applications An unprecedented overview of this thriving area of research that nobody in the field - or intending to enter it - can afford to miss.

Table of Contents:
Preface xv List of Contributors xvii Part I Theory 1 1 Theory for Stretchable Interconnects 3 Jizhou Song and Shuodao Wang 1.1 Introduction 3 1.2 Mechanics of Stretchable Wavy Ribbons 5 1.2.1 Small-Deformation Analysis 5 1.2.2 Finite-Deformation Analysis 8 1.2.3 Ribbon Width Effect 12 1.3 Mechanics of Popup Structure 15 1.4 Mechanics of Interconnects in the Noncoplanar Mesh Design 19 1.4.1 Global Buckling of Interconnects 19 1.4.2 Adhesion Effect on Buckling of Interconnects 21 1.4.3 Large Deformation Effect on Buckling of Interconnects 24 1.5 Concluding Remarks 27 References 27 2 Mechanics of Twistable Electronics 31 Yewang Su, Jian Wu, Zhichao Fan, Keh-Chih Hwang, Yonggang Huang, and John A. Rogers 2.1 Introduction 31 2.2 Postbuckling Theory 31 2.3 Postbuckling of Interconnect under Twist 33 2.4 Symmetric Buckling Mode 34 2.5 Antisymmetric Buckling Mode 36 2.6 Discussion and Concluding Remarks 38 References 38 Part II Materials and Processes 41 3 Graphene for Stretchable Electronics 43 Chao Yan, Seoung-Ki Lee, Houk Jang, and Jong-Hyun Ahn 3.1 Introduction 43 3.2 Production of Graphene Films 44 3.2.1 Large-Area Graphene Synthesis by CVD 44 3.2.2 Exfoliation Methods 47 3.2.3 Epitaxial Growth Methods 48 3.3 Fabrication of Graphene Films on Substrates 50 3.3.1 Solution-Based Method 50 3.3.2 Transfer Printing 52 3.4 Applications in Flexible and Stretchable Electronics 54 3.4.1 Interconnect for Integrated Circuits 57 3.4.2 Flexible Electronics 60 3.4.2.1 Graphene Electrodes for Flexible FETs 60 3.4.2.2 Graphene Electrodes for Flexible OPVs 64 3.4.2.3 Graphene Electrodes for OLEDs 66 3.4.2.4 Graphene Film for Flexible Touch Screen Panels 70 3.4.3 Stretchable Electronics 71 3.5 Concluding Remarks 75 References 76 4 Stretchable Thin-Film Electronics 81 Stéphanie P. Lacour 4.1 Introduction 81 4.2 Silicone Rubber as a Substrate 82 4.2.1 Elastomers 82 4.2.2 Silicone Rubber – Polydimethylsiloxane (PDMS) 83 4.2.2.1 PDMS Surface Chemistry 83 4.2.2.2 PDMS Mechanical Properties 84 4.2.2.3 Dielectric Properties 85 4.2.2.4 Other Properties 86 4.2.3 Photosensitive Silicones 86 4.3 Mechanical Architecture 87 4.3.1 Preserving the Mechanical Integrity of Thin-Film Structures 88 4.3.1.1 Small Platforms (<500 μm Side) 89 4.3.1.2 Large Platforms (>500 μm Side) 90 4.3.2 Ensuring Smooth Strain Gradient across Interconnects 91 4.4 Stretchable Metallization 93 4.4.1 Morphology of Thin Gold Films on PDMS 94 4.4.2 Electromechanical Response 95 4.4.2.1 Uni-axial (1D) Stretching 96 4.4.2.2 Multi-axial (2D) Stretching 98 4.4.3 Printed Films on PDMS Substrate 99 4.5 Integrated Stretchable Thin-Film Devices 100 4.5.1 Soft Neural Electrode Arrays 100 4.5.2 Stretchable Capacitive Sensors 101 4.5.3 Stretchable Antennas 102 4.5.4 Stretchable Thin-Film Transistors 103 4.5.5 Stretchable Organic Lasers 105 4.6 Outlook 106 References 107 5 Stretchable Piezoelectric Nanoribbons for Biocompatible Energy Harvesting 111 Yi Qi, Thanh D. Nguyen, Prashant K. Purohit, and Michael C. McAlpine 5.1 Energy Harvesting and Piezoelectric Materials 111 5.1.1 Introduction to Biomechanical Energy Harvesting 111 5.1.2 Piezoelectric Materials and Lead Zirconate Titanate (PZT) 112 5.2 PZT Nanofabrication and Interfacing with Stretchable Substrates 116 5.2.1 Wafer-Scale PZT Nanowire Fabrication 116 5.2.2 Transfer Printing onto Stretchable Substrates 117 5.2.3 Stretchable Wavy and Buckled PZT Nanoribbons 120 5.3 Piezoelectric Characterization and Electrical Measurements 126 5.3.1 Piezoelectric Characterization 126 5.3.2 Electrical Measurements 130 5.4 Summary 133 References 134 Part III Circuit Boards 141 6 Modeling of Printed Circuit Board Inspired Stretchable Electronic Systems 143 Mario Gonzalez, Yung-Yu Hsu, and Jan Vanfl eteren 6.1 Technology Development Considerations 143 6.2 Modeling and Simulation 145 6.2.1 Optimization of Metal Conductor Shape 146 6.2.1.1 Description of the Model 146 6.2.1.2 Material Properties 146 6.2.1.3 Stress/Strain Comparison of Different Conductor Shapes 147 6.2.1.4 Optimization of the Horseshoe Shape of Conductor 149 6.2.2 Influence of Substrate Stiffness on the Plastic Strain of the Conductor 151 6.2.3 Induced Mechanical Interaction on Multitracks 152 6.2.4 Polyimide-Supported Stretchable Interconnect 155 References 158 7 Materials for Stretchable Electronics Compliant with Printed Circuit Board Fabrication 161 Matthias Adler, Ruth Bieringer, Thomas Schauber, and Jürgen Günther 7.1 Introduction 161 7.1.1 Silicones 161 7.1.1.1 Fundamentals of Silicones 161 7.1.1.2 Silicone Elastomers 163 7.1.1.3 Durability 166 7.1.1.4 Processing 168 7.1.1.5 Fields of Application 170 7.1.2 Polyurethanes 171 7.1.2.1 Fundamentals of Polyurethanes 171 7.1.2.2 Properties of Polyurethanes 175 7.1.2.3 Thermoplastic Polyurethanes 176 7.1.2.4 Cast Polyurethanes 177 7.1.2.5 Commercial Raw Materials 179 7.1.2.6 Applications of Polyurethanes 181 7.1.2.7 Excursion Conductive Pastes (Developed during the STELLA Project) 182 References 184 Further Reading 185 8 Technologies and Processes Used in Printed Circuit Board Fabrication for the Realization of Stretchable Electronics 187 Frederick Bossuyt and Thomas Löher 8.1 Lamination Technology 187 8.1.1 Process Concept 187 8.1.2 Polyurethane Films 188 8.1.3 Printed Circuit Board Cu Foils 189 8.1.4 Lamination of Copper Foils to Polyurethane Films 189 8.1.5 Substrate Fabrication 190 8.1.6 Component Assembly and Interconnection 193 8.1.7 Encapsulation of Components 194 8.1.8 Outline Cutting of Circuits on the Fabrication Board and Release 195 8.1.9 Lamination to Textiles or Other Substrates 195 8.2 Molding Technology 196 8.2.1 General Introduction of the Process 196 8.2.2 Copper as Electrical Conductor 197 8.2.3 Polyimide as Mechanical Support 199 8.2.4 Lamination of Polyimide–Copper Sheet on Rigid Substrate Using a Temporary Adhesive 199 8.2.5 Copper Patterning 200 8.2.6 Solder Mask Application 200 8.2.7 Copper Finish Application 201 8.2.8 Assembly of Components 201 8.2.9 Encapsulation by Molding 202 8.2.10 Application to Textiles 203 References 205 9 Reliability and Application Scenarios of Stretchable Electronics Realized Using Printed Circuit Board Technologies 207 Jan Vanfl eteren, Frederick Bossuyt, Thomas Löher, Yung-Yu Hsu, Mario Gonzalez, and Jürgen Günther 9.1 Application Considerations 207 9.2 Reliability 209 9.2.1 Results and Discussion of Single and Cyclic Elongation Tests 209 9.2.2 One-Time Stretch Tests 210 9.2.3 Cyclic Endurance Tests of Laminated and Molded Test Samples 211 9.2.3.1 Pure Copper Tracks 211 9.2.3.2 PDMS Encapsulated Parallel PI Supported Meander Tracks 212 9.2.4 Failure Analysis 214 9.2.4.1 In Situ Observation of the Deformation Behavior and Failure Mechanism of Encapsulated/Nonencapsulated Stretchable Interconnects 214 9.2.4.2 In Situ Electromechanical Measurement for One-Time-Stretching Reliability 216 9.2.4.3 Correlation between Numerical and Experimental Results 218 9.2.4.4 Fatigue Failure of Copper Meanders 219 9.2.4.5 Lifetime Prediction by FEM 221 9.2.5 Washability – An Introduction 222 9.3 Application Scenarios 223 9.3.1 Temperature Sensor 223 9.3.2 Wireless Power Circuit 224 9.3.3 Fitness Sensor 225 9.3.4 Pressure Senors in a Shoe Insole 226 9.3.5 Bandage Inlay for Compression Therapy 227 9.3.6 Baby Respiration Monitor Demonstrator 227 9.3.7 LED Matrix 229 9.3.8 RGB Led Matrix (SMI by Laser) 230 9.3.9 Thermoforming of Printed Conductors – Single Stretching 231 Reference 233 Further Reading 233 Part IV Devices and Applications 235 10 Stretchable Electronic and Optoelectronic Devices Using Single-Crystal Inorganic Semiconductor Materials 237 Dae-Hyeong Kim, Nanshu Lu, and John A. Rogers 10.1 Introduction 237 10.1.1 Materials Selection for High-Performance Stretchable Electronics 237 10.1.2 Monocrystalline Inorganic Semiconductors in Stretchable Designs 238 10.1.3 Bio-integrated Electronics 240 10.2 Stretchable Circuits 240 10.2.1 Wavy Electronic Devices and Circuits 240 10.2.2 Noncoplanar Electronic Devices and Circuits 242 10.2.3 Electronic Circuits with Serpentine Interconnects 244 10.2.4 Stretchable Electronic Devices on Unconventional Substrates 244 10.3 Application of Stretchable Designs to Microscale Inorganic Light Emitting Diodes (μ-ILEDs) 247 10.3.1 Stretchable μ-ILED Arrays 247 10.3.2 Lighting Devices on Substrates of Unconventional Materials and Shapes 249 10.4 Biomedical Applications of Stretchable Electronics and Optoelectronics 253 10.4.1 Encapsulation Strategy 253 10.4.2 Bio-applications of μ-ILEDs: Suture Threads and Proximity Sensors 253 10.4.3 Minimally Invasive Surgical Tools: Instrumented Balloon Catheters 256 10.4.4 Epidermal Electronic System (EES) 259 10.5 Stretchable Digital Imagers and Solar Modules 261 10.5.1 Hemispherical Electronic Eye Camera 261 10.5.2 Curvilinear Imagers and Stretchable Photovoltaic Modules with High Fill Factors 263 10.5.3 Hemispherical Electronic Eye Camera with Adjustable Zoom Magnification 264 10.6 Conclusions 265 References 267 11 Stretchable Organic Transistors 271 Tsuyoshi Sekitani and Takao Someya 11.1 Introduction 271 11.2 Perforated Organic Transistor Active Matrix for Large-Area, Stretchable Sensors 272 11.2.1 Simultaneous Sensing of Pressure and Temperature 274 11.3 Rubber-Like Stretchable Organic Transistor Active Matrix Using Elastic Conductors 275 11.3.1 Integration of Elastic Conductors with Printed Organic Transistors 276 11.3.1.1 Integration Process 276 11.3.2 Electrical and Mechanical Performances 278 11.4 Rubber-Like Organic Transistor Active Matrix Organic Light-Emitting Diode Display 280 11.5 Future Prospects 283 Acknowledgments 283 References 283 12 Power Supply, Generation, and Storage in Stretchable Electronics 287 Martin Kaltenbrunner and Siegfried Bauer 12.1 Introduction 287 12.2 Radio Frequency Power Supplies 287 12.3 Power Generation 289 12.3.1 Dielectric Elastomer Generators 290 12.3.2 Piezoelectric Energy Generation 292 12.3.3 Solar Cells 294 12.4 Power Storage 297 12.4.1 Supercapacitors 297 12.4.2 Batteries 299 12.5 Summary 301 Acknowledgments 301 References 301 13 Soft Actuators 305 Kinji Asaka 13.1 Introduction 305 13.2 Conducting Polymers 306 13.3 Ionic Polymer Metal Composites (IPMCs) 308 13.4 Nanocarbon Actuators 310 13.4.1 Carbon Nanotube (CNT) Actuators 310 13.4.2 CNT Actuators Based on Ionic-Liquid-Based Bucky-Gels 311 13.4.3 Materials of Bucky-Gel Actuators 313 13.4.4 Modeling of the Nanocarbon Actuators 315 13.5 Applications 319 13.6 Conclusion 319 References 320 14 Elastomer-Based Pressure and Strain Sensors 325 Benjamin C.K. Tee, Stefan C.B. Mannsfeld, and Zhenan Bao 14.1 Introduction 325 14.2 A Brief Elastomers Overview 326 14.3 Important Sensor Characteristics 327 14.3.1 Sensitivity 328 14.3.2 Hysteresis 329 14.3.3 Temporal Resolution 329 14.3.4 Sensitivity to Environmental Factors 330 14.3.5 Mechanical Durability 330 14.4 Elastomeric Force Sensors 330 14.4.1 Piezoresistive Sensors 331 14.4.1.1 Conductive Fillers in Elastomeric Composites 331 14.4.2 Elastomer as a Dielectric Material 335 14.4.2.1 Plain Elastomers 336 14.4.2.2 Foam 338 14.4.2.3 Microstructured Elastomers 339 14.4.3 Piezoelectric Films 341 14.4.4 Optical Pressure Sensors 342 14.5 Active Pressure/Strain Sensors Systems 343 14.6 Applications 348 14.7 Outlook 348 References 350 15 Conformable Active Devices 355 Robert A. Street and Ana Claudia Arias 15.1 Introduction 355 15.2 Printing Processes for Organic TFTs 356 15.2.1 Printing Considerations for Metals, Semiconductors, and Dielectrics 356 15.2.2 Printed Organic CMOS TFTs 359 15.2.3 Alternative Material Choices 360 15.2.4 Self-Assembly of TFTs from Solution 361 15.3 Sensing and Memory Devices Based on Piezoelectric Polymer 363 15.3.1 Pressure Sensor and Accelerometer 363 15.3.2 Chemical Sensors 364 15.3.3 Nonvolatile Printed Memory 365 15.3.4 Printed Memristor 366 15.3.5 Photodiodes and Other Devices 367 15.4 Electronic Circuits 368 15.4.1 All-Printed Organic TFT Display 369 15.4.2 Inverter, Ring Oscillator, and Shift Register 371 15.4.3 Self-Stabilized Amplifier Circuits 372 15.5 Curved Conformal Devices by a Cut-and-Bend Approach 374 15.6 Summary 375 Acknowledgments 376 References 376 16 Stretchable Neural Interfaces 379 Woo Hyeun Kang, Wenzhe Cao, Sigurd Wagner, and Barclay Morrison, iii 16.1 Introduction 379 16.2 Overview of MEAs 380 16.2.1 Advantages of Stretchable MEAs 381 16.3 Classes of SMEAs 382 16.3.1 Planar SMEAs 382 16.3.2 Cuff SMEAs 389 16.4 Common Limitations for All SMEAs 394 16.5 Future Directions in Stretchable Neural Interfaces 394 16.6 Conclusion 395 References 396 17 Bio-based Materials as Templates for Electronic Devices 401 Christian Müller and Olle Inganäs 17.1 Introduction 401 17.2 Polysaccharide-Based Templates 402 17.2.1 Cellulose: Paper Substrates 402 17.2.2 Cellulose: Nanofiber Networks 403 17.2.3 Cellulose Fibers: Cotton, Lyocell, and Viscose 407 17.2.4 Vascular Bundles 407 17.2.5 Polysaccharide Hydrogels 408 17.3 Protein-Based Templates 409 17.3.1 Wool and Silk Fibers 409 17.3.2 Silk Fibroin Films 410 17.3.3 Protein Fibrils: Rhapidosomes, Microtubules, Actin Filaments, and Amyloid Fibrils 413 17.3.4 Collagen and Gelatin 415 17.4 DNA Templates 415 17.4.1 Intrinsic Electrical Properties of DNA 415 17.4.2 Decorated DNA 416 17.5 Virus Templates: Tobacco Mosaic Virus and M13 Bacteriophage 418 17.6 Summary 419 References 420 18 Organic Integrated Circuits for EMI Measurement 431 Makoto Takamiya, Koichi Ishida, Tsuyoshi Sekitani, Takao Someya, and Takayasu Sakurai 18.1 Introduction 431 18.2 Stretchable EMI Measurement Sheet 432 18.2.1 Overview of Stretchable EMI Measurement Sheet 432 18.2.2 2 V Organic CMOS Decoder 434 18.2.3 Stretchable Interconnects with CNTs 436 18.3 Silicon CMOS LSI for EMI Detection 437 18.4 Experimental Results and Discussion 440 18.4.1 Direct Silicon–Organic Circuit Interface 440 18.4.2 Comparison of Conventional and Proposed EMI Measurements 442 18.4.3 Calibration for EMI Measurement LSI 443 18.5 Conclusion 446 Acknowledgments 447 References 447 Index 449