In dedicated chapters, crucial components needed to realize flexible and wearable devices are discussed which include transistors and sensors and deal with memory, data handling and display. Additionally, suitable power sources based on photovoltaics, thermoelectric energy and supercapacitors are reviewed. A special chapter treats implantable flexible sensors for neural recording.
The book editor concludes with a perspective on this rapidly developing field which is expected to have a great impact on healthcare in the 21st century.
Table of Contents
Preface xiii
1 History of Flexible and Stretchable Devices 1
Kuniharu Takei
References 4
2 Carbon Nanotube Based Flexible and Stretchable Electronics 7
Le Cai and ChuanWang
2.1 Introduction 7
2.2 Carbon Nanotube Networks for Applications in Flexible Electronics 10
2.2.1 Thin-Film Transistors (TFTs) 10
2.2.2 Integrated Circuits 11
2.2.3 Active Matrix Backplanes for Flexible Display, E-Skin and Imager 16
2.3 Carbon Nanotube Networks for Applications in Stretchable Electronics 19
2.3.1 Stretchable Conductors 21
2.3.2 Stretchable Strain Sensor 23
2.3.3 Stretchable Thin-Film Transistors 27
2.4 Scalable Fabrication Process - Printing 35
2.4.1 Digital Printing - Inkjet and Aerosol Jet 36
2.4.2 Gravure Printing 41
2.4.3 Printed ComplementaryMetal–Oxide Semiconductor (CMOS) Devices 41
2.5 Conclusions and Outlook 44
References 45
3 Organic-Based Transistors and Sensors 53
Aristide Gumyusenge, Tianbai Xu, XiaozhiWang, and Jianguo Mei
3.1 Introduction 53
3.2 Materials Consideration for Flexible Organic-Based Transistors 54
3.2.1 How Flexibility is Achieved 54
3.2.1.1 Flexible Substrates 54
3.2.1.2 Flexible Electrodes 55
3.2.2 Organic Dielectric Layer 56
3.2.3 Organic Functional Layer 57
3.3 State-of-the-Art Designs and Fabrication of Organic-Based Transistors 57
3.3.1 Organic Field-Effect Transistors 58
3.3.1.1 Structure 58
3.3.1.2 Performance and Characterization 59
3.3.2 Modifications of OFETs for Sensing Applications 60
3.3.2.1 Electrolyte-Gated and Ion-Sensitive Organic Field-Effect Transistors 60
3.3.2.2 Organic Electrochemical Transistors 62
3.3.2.3 Operating Mechanisms 63
3.4 Fabrication Techniques for Organic-Based Transistors and Sensors 63
3.5 Flexible Organic Transistor-Based Sensors 65
3.5.1 Flexible Organic Strain Sensors 65
3.5.2 Flexible Organic Pressure Sensors 67
3.5.3 Flexible Organic Temperature Sensors 69
3.5.4 Flexible Organic Biosensors 70
3.5.5 Flexible Organic Optical Sensors 73
3.6 Summary and Outlook 74
References 75
4 Printed Transistors and Sensors 83
Kenjiro Fukuda
4.1 Introduction 83
4.2 Printing Technologies for Electronics 84
4.2.1 Inkjet Printing 85
4.2.2 Gravure Printing 86
4.2.3 Reverse-Offset Printing for High-Resolution Patterning 87
4.3 Printed Transistors 88
4.3.1 Fabrication of Fully Printed Transistors 88
4.3.2 Profile Control of Inkjet-Printed Electrodes 89
4.3.3 Mechanical Stability 91
4.3.3.1 Calculation of Strain in the Devices 91
4.3.3.2 Improvement of Adhesion 91
4.3.4 Printed Organic Transistors with Uniform Electrical Performance 93
4.3.5 Ultraflexible and Fully Printed Organic Circuits 94
4.4 Printed Biosensors 97
References 99
5 Flexible Photovoltaic Systems 105
Lichen Zhao, Deying Luo, and Rui Zhu
5.1 Introduction 105
5.1.1 Introduction of Flexible Photovoltaics 105
5.1.2 Principles of Photovoltaics 106
5.1.3 The Flexible Substrates 109
5.1.3.1 Metals and the Alloys 109
5.1.3.2 Polymers 110
5.1.4 The Types of Flexible Photovoltaic Systems 110
5.2 Flexible Inorganic Photovoltaic Systems 110
5.2.1 Flexible Silicon Photovoltaics 110
5.2.2 Flexible Copper Indium Gallium Selenide Photovoltaics 113
5.3 Flexible Organic Photovoltaic Systems 115
5.3.1 Fundamental Properties of OPV Materials 115
5.3.2 Device Structure andWorking Mechanisms 116
5.3.3 Materials and Methods for OPV 118
5.3.4 Recent Advances in Flexible OPV 119
5.4 Flexible Organic–Inorganic Hybrid Photovoltaic Systems 122
5.4.1 Fundamental Properties of Perovskites 123
5.4.2 Device Structure andWorking Mechanisms 124
5.4.3 Materials and Methods for Flexible PerSCs 125
5.4.4 Recent Advances for Flexible PerSCs 128
5.5 Summary and Conclusion 132
References 133
6 Materials Design for Flexible Thermoelectric Power Generators 139
Yoshiyuki Nonoguchi
6.1 Introduction 139
6.2 General Principles 140
6.2.1 The Basic Principles of Thermoelectricity 140
6.2.2 Density of State and the Seebeck Coefficient 141
6.2.3 Energy Conversion Efficiency and Dimensionless Thermoelectric Figure of Merit ZT 142
6.2.4 A Classical Requirement for Efficient Module Design 144
6.3 Thermoelectric Materials Design 145
6.3.1 Organic Solids and Conducting Polymers 145
6.3.2 Carbon Nanotubes and Related Matters 149
6.3.3 Useful Survey Methods for Discovering Efficient Thermoelectric Materials 154
6.3.4 Prototype Thermoelectric Generators and Applications 154
6.4 Outlook for Flexible Thermoelectric Generators 155
References 156
7 Flexible Supercapacitors Based on Two-Dimensional Materials 161
Dianpeng Qi and Xiaodong Chen
7.1 Introduction 161
7.2 Flexible Supercapacitors Based on 2D Materials 162
7.2.1 2D Electrode Materials for Flexible EDLCs 163
7.2.2 2D Materials for Pseudocapacitive Supercapacitors 171
7.2.3 2D Electrode Materials for Hybrid Flexible Supercapacitors 176
7.3 Conclusions 179
References 181
8 Organometal Halide Perovskites for Next Generation Fully Printed and Flexible LEDs and Displays 199
Thomas Geske, Sri Ganesh R. Bade, MattWorden, Xin Shan, Junqiang Li, and Zhibin Yu
8.1 Introduction 199
8.1.1 General Background for LEDs 200
8.1.2 Fundamentals of Halide Perovskites 201
8.1.3 Multilayer Perovskite LEDs 203
8.2 Single Layer Perovskite LEDs 206
8.3 Current Challenges 208
8.4 Conclusions and Outlook 211
Acknowledgments 211
References 211
9 Flexible Floating Gate Memory 215
Ye Zhou, Su-Ting Han, and Arul Lenus Roy Vellaisamy
9.1 Introduction 215
9.2 Device Operation of Floating Gate Memory 216
9.3 Charge Injection Mechanism in Floating Gate Memory 217
9.3.1 The Hot-electron Injection Mechanism 217
9.3.2 Fowler–Nordheim (F-N) Tunneling Mechanism 218
9.3.3 Direct Tunneling Mechanism 219
9.4 Flexible Nanofloating Gate Memory 219
9.5 Characterization of Floating Gate Memory 221
9.6 Flexibility of Floating Gate Memory 223
9.7 Conclusion 225
References 225
10 Flexible and StretchableWireless Systems 229
Aftab M. Hussain and Muhammad M. Hussain
10.1 Introduction 229
10.2 The Basics ofWireless Systems 230
10.2.1 Wireless Systems 230
10.2.2 Antennas 231
10.2.3 Antenna Parameters 233
10.3 Flexible, Stretchable Circuits 234
10.3.1 Flexible, Stretchable Silicon Circuits 234
10.3.2 Non-Silicon-Based Channels 236
10.4 Flexible Antennas 239
10.4.1 Micromachined Flexible Antennas 240
10.4.2 Inkjet-Printed Antennas 240
10.5 Stretchable Antennas 242
10.5.1 Material Stretchability 242
10.5.2 Design Stretchability 244
10.6 Future Outlook 246
References 247
11 Conductive Nanosheets for Ultra-Conformable Smart Electronics 253
Kento Yamagishi, Silvia Taccola, Shinji Takeoka, Toshinori Fujie, Virgilio Mattoli, and Francesco Greco
11.1 Introduction 253
11.2 Fabrication of Conductive Nanosheets 255
11.2.1 Spin-Coating-Processed Conductive Nanosheets 255
11.2.2 Roll-to-Roll (R2R) Gravure-Printing-Processed Conductive Nanosheets 258
11.3 Characterization of Conductive Nanosheets 260
11.3.1 Electrical Properties of Conductive Nanosheets 260
11.3.2 Structural Properties of Conductive Nanosheets 262
11.3.3 Mechanical Properties of Conductive Nanosheets 263
11.3.4 Electrochemical Properties of Conductive Nanosheets 267
11.4 Applications of Conductive Nanosheets 269
11.4.1 Surface Electromyogram (EMG) Recording Using Conductive Nanosheets 269
11.4.2 Humidity Sensors 272
11.4.3 Microactuators 272
11.4.4 Tattoo Conductive Nanosheets for Skin-Contact Applications 274
11.5 Concluding Remarks 277
Acknowledgments 278
References 278
12 Flexible Health-Monitoring Devices/Sensors 287
Minjeong Ha, Seongdong Lim, and Hyunhyub Ko
12.1 Introduction 287
12.2 Flexible Sensors for Health Monitoring 288
12.2.1 Detection Approaches for Physical Bio-Signals 289
12.2.1.1 Pressure and Strain Sensors for Health Monitoring 289
12.2.1.2 Temperature Sensors for Health Monitoring 293
12.2.2 Detection Approaches for Biochemical Signals 295
12.2.2.1 Flexible pH Sensors 297
12.2.2.2 Flexible Blood Sugar Sensors 299
12.2.2.3 Flexible Pulse Oximeters 299
12.2.2.4 Other Flexible Chemical Sensors to Detect Volatile Organic Compounds 302
12.2.3 Detection Approaches for Electrophysiological Signals 304
12.3 Multifunctional Flexible Sensors for Multiple Bio-Signals 306
12.4 Practical Applications of Flexible Health-Monitoring Devices 309
12.4.1 Sports and Fitness 309
12.4.2 Prosthetics and Rehabilitation 309
12.4.3 WoundTherapy 311
12.4.4 Telemedicine and Self-Diagnosis of Disease 311
12.5 Conclusions and Future Perspective 312
References 312
13 Stretchable Health Monitoring Devices/Sensors 323
Xian Huang
13.1 Introduction 323
13.2 Materials for Stretchable Health Monitoring Devices 323
13.2.1 Physically Soft and Stretchable Materials 324
13.2.2 Unique Stretchable Structures 324
13.3 Health Monitoring Applications of Stretchable Devices 326
13.3.1 Skin Sensors 326
13.3.1.1 Skin Biophysical Signal Monitoring 329
13.3.1.2 Biomolecule Analysis 332
13.3.2 Implantable Devices 336
13.3.2.1 Brain and Neural Probes 336
13.3.2.2 Cardiovascular Monitoring 337
13.3.3 BodyWearable Devices 337
13.3.3.1 Rehabilitation 337
13.3.3.2 Daily Health Tracking 341
13.4 Future of Stretchable Electronic Devices 341
References 342
14 Flexible/Stretchable Devices for Medical Applications 351
GwanJin Ko, JeongWoong Shin, and Suk-Won Hwang
14.1 Introduction 351
14.2 Materials, Synthesis and Composites for Flexible/Stretchable Systems 352
14.3 Electronic/Optoelectronic Devices, Sensors and Systems 355
14.4 Multifunctional Electronic Sensors and Power Scavenging Circuit for the Heart 358
14.5 Electrophysiology and Optogenetics for the Brain 362
14.6 Communication and Regulation for the Nervous System 364
14.7 Skin-Like Electronics/Optoelectronics 367
14.8 Transient, Bioresorbable Systems 370
14.9 Conclusion and Outlook 373
References 373
15 Implantable Flexible Sensors for Neural Recordings 381
Shota Yamagiwa, Hirohito Sawahata, and Takeshi Kawano
15.1 Introduction 381
15.1.1 Neuronal Signal Recordings 383
15.1.1.1 EEG 383
15.1.1.2 ECoG 384
15.1.1.3 LFPs and Spikes 384
15.1.2 Electrode Materials 385
15.1.3 Electrode Impedance in Neural Recordings 385
15.2 Flexible Needle Electrodes 387
15.3 Flexible ECoG Electrodes 391
15.4 Functionalities of Flexible Substrates 395
15.4.1 Active Matrixes 395
15.4.2 Dissolvable Films 395
15.4.3 Stretchable Films 399
15.4.4 Other Functionalities 403
15.5 Flexible Devices for Chronic Applications 403
15.5.1 Tissue Damage 403
15.5.2 Packaging Technologies 405
15.5.2.1 Rivet-Like Electric and Mechanic Interconnections 405
15.5.2.2 Anisotropic Conductive Paste/Films 407
15.5.3 Wireless Technologies 407
15.6 Summary 407
References 408
16 Perspective in Flexible and Stretchable Electronics 411
Kuniharu Takei
Index 413
