Preface xiii
Session I Soft Sensors for Diagnosis 1
1 Mechanics Design of Flexible Sensors 3
li Yuhang, Zhao Zhao, and Wu Wenbin
1.1 Design of Stretchable Flexible Device Structure 3
1.1.1 Ripple Method 3
1.1.2 Island Bridge Structure-Curved Line 12
1.1.3 Island Bridge Structure-Serpentine Line 15
1.1.4 2D Spiral Interconnects 26
1.1.5 3D Spiral Interconnects 32
1.1.6 2D Fractal Structure 35
1.2 Structural Design of Substrate 38
1.2.1 Surface Structure Designs 39
1.2.2 Cellular Substrate Designs 40
1.2.3 Curvilinear Substrate Designs 43
1.3 Structural Designs for Spatial Integration of Device Systems 45
1.3.1 Strategy of Folding-Based Origami 45
1.3.2 Strategy of Buckling-Guided 3D Assembly 51
1.3.3 Stacked Multilayer Designs 57
References 59
2 Epidermal Wearable Biosensors 67
Xingcan Huang, Yanli Jiao, Yawen Yang, and Jiyu li
2.1 Wearable Biosensing Technology 67
2.1.1 History of Wearable Biosensors 67
2.1.2 Wearable Enzymatic Biosensors 68
2.1.3 Wearable Immunosensors 69
2.1.4 Wearable Ion Biosensors 70
2.2 Epidermal Wearable Biosensors 73
2.2.1 Introduction 73
2.2.2 Flexible and Stretchable Epidermal Sensors 74
2.2.3 Self-powered Sweat Sensors 76
2.3 Ocular Wearable Sensors 79
2.3.1 Ocular Biomarkers 79
2.3.2 Wearable Ocular Sensors 80
2.3.2.1 Contact Lens Sensor 81
2.3.2.2 Capsule-based Tear Sensors 87
2.3.2.3 Wearable Eye Patch 87
2.3.2.4 Eyeglass Sensor 88
2.3.3 Conclusion 88
2.4 Wound Sensor 88
List of Abbreviations 91
References 92
3 Soft Sensors for Disease Diagnosis 101
Huihui Hu, Yuyan Su, and Kewang Nan
3.1 Introduction 101
3.2 Materials and Structures of Flexible Sensors 103
3.2.1 Materials 103
3.2.1.1 Nanomaterials 103
3.2.1.2 Liquid Conductors 105
3.2.1.3 Elastomer 106
3.2.1.4 Conductive Polymer 106
3.2.1.5 Hydrogel 107
3.2.1.6 Textile 108
3.2.2 Structures 109
3.2.2.1 Serpentine Structure 109
3.2.2.2 Mesh Structure 110
3.2.2.3 Kirigami Structure 111
3.2.2.4 Fractal Structure 112
3.2.2.5 Coiled Structure 112
3.2.2.6 Wave Structure 113
3.2.2.7 Three-Dimensional Porous Structure 114
3.3 Application of Flexible Sensors in Disease Diagnosis 114
3.3.1 Diagnosis of Cardiovascular Diseases 115
3.3.1.1 Heart Rate 115
3.3.1.2 Blood Pressure 117
3.3.1.3 Blood Oxygen Saturation 117
3.3.2 Diagnosis of Brain Disease 118
3.3.2.1 Soft Sensor Materials for Brain Interfaces 119
3.3.2.2 Applications 121
3.3.3 Diagnosis and Self-management of Chronic Disease 123
3.3.3.1 Flexible Sensors for Diabetes 123
3.3.3.2 Flexible Sensors for Chronic Inflammatory Diseases 125
3.3.3.3 Flexible Sensors for Chronic Respiratory Diseases 126
3.3.3.4 Flexible Sensors for Cancers 127
List of Abbreviations 128
References 129
4 Wearable Chemical Sensors for Noninvasive Monitoring 147
Hnin Yin Yin Nyein, Asmita Veronica, Yanan Li, and Yue Guo
4.1 Introduction 147
4.2 Biofluids of Interest for Wearable Chemical Sensors 150
4.2.1 Dermal Biofluids 153
4.2.1.1 Sweat 153
4.2.1.2 Interstitial Fluid 155
4.2.2 Oral Biofluids 157
4.2.2.1 Saliva 157
4.2.2.2 Gcf 160
4.3 Biofluid Enabled Platforms: Traditional to Wearable 161
4.3.1 Need for Noninvasive Wearable Chemical Sensing 161
4.3.2 Potential Challenges in Wearable Chemical Sensors 162
4.4 Sampling and Detection Strategies for Biofluid-Based Wearable Sensors 163
4.4.1 Sweat Sampling and Induction Methods 163
4.4.2 ISF Sampling Methods 165
4.4.3 Saliva Sampling Methods 168
4.4.4 Detection Mechanisms for Noninvasive Wearable Sensors 169
4.5 Outlook 172
References 174
5 Flexible Electrode for Noninvasive Brain–Computer Interfaces 181
Sen Lin
5.1 Introduction 181
5.2 Development of Noninvasive BCIs 182
5.3 Electrode Technologies for Noninvasive BCIs 183
5.3.1 Rigid Electrodes 183
5.3.1.1 Wet Electrodes 184
5.3.1.2 Dry Electrode 184
5.3.2 Flexible Electrodes 186
5.3.2.1 Flexible Dry Electrodes 186
5.3.2.2 Semi-dry Electrode 189
5.4 Challenges 191
5.5 Conclusion 193
References 194
6 Chronic Neural Interfaces 203
Enming Song, Yifei Lu, and Hehua Zhang
6.1 Introduction 203
6.2 Architectures for Mechanical Compliance and Biocompatibility 204
6.3 Advanced Chronically Stable Materials for Neural Interfaces 209
6.4 Encapsulation for Stable Operation 211
6.5 Engineering Strategies for Chronic Active Sensing 220
6.6 Multimodal Functions of Long-Term Stable Implants 225
6.7 Challenges and Future Directions 228
References 229
7 Mechanical Sensors (Transducers) for Motion Detection of Humans and Organs 235
Chengfeng Pan
7.1 Introduction 235
7.2 Classification of Stretchable Mechanical Sensors 236
7.2.1 Resistive Sensors 236
7.2.2 Capacitive Sensors 236
7.2.3 Piezoelectric Sensors 237
7.2.4 Triboelectric Sensors 237
7.2.5 Electromagnetic Sensors 238
7.3 Material Architectures 238
7.3.1 Flexible/Stretchable Matrix Materials 239
7.3.2 Electrically Conductive Materials 241
7.4 Sensing Mechanisms 244
7.4.1 Geometrical Effect 244
7.4.2 Piezoresistive Effect 245
7.4.3 Disconnection Mechanism 246
7.4.4 Crack Propagation 247
7.4.5 Tunneling Effect 247
7.5 Representative Applications 248
7.5.1 Small Strain Detection 248
7.5.2 Large Motion Monitoring 250
References 252
8 Smart Optoelectronics in Health Monitoring and Human-Machine Interactions 257
Leilei Gu, Yuanjing Lin, and Qianpeng Zhang
8.1 Fundamentals on Photodetectors 257
8.1.1 Figures-of-Merit of Photodetectors 257
8.1.2 Classification of Photodetectors 259
8.1.3 Material Advances in Photodetectors 261
8.1.3.1 2D Materials 262
8.1.3.2 Quantum Dots 262
8.1.3.3 Perovskites and Other Organic Materials 263
8.1.3.4 Nanostructure-based Photodetectors 264
8.2 Integrated Optoelectronic Systems 264
8.2.1 Integration of Photodetectors with LEDs 266
8.2.2 Photodetectors Integrated with Energy Storage Devices 267
8.2.3 Self-powered Optoelectronic Systems 268
8.2.4 Integration Strategies 270
8.3 Flexible Integrated Systems Based on Photodetectors for Advanced Applications 273
8.3.1 Clinical Diagnostic 273
8.3.1.1 Lab-on-a-Chip Systems for Diagnostics 273
8.3.1.2 Wearable Biosensing for Daily Health Monitoring 275
8.3.1.3 Optoelectronics for Advanced Human-Machine Interaction 277
8.3.1.4 Autopilot Systems 280
8.4 Future Trend of Photodetectors for Soft Electronics 282
References 283
9 Wearable Sensor for Bioimaging 287
Cunman Liang, Zhou Jiang, Ni Zhao, Puxiang Lai, and Yingying Zhou
9.1 Introduction 287
9.2 Wearable Ultrasound Bioimaging Sensor 288
9.2.1 Overall Description 288
9.2.2 Imaging Principles 289
9.2.3 Structures and Materials 290
9.2.4 Typical Devices and Applications 292
9.2.4.1 1D Transducer Array 292
9.2.4.2 2D Transducer Array 294
9.2.4.3 Orthogonal Transducer Array 296
9.2.5 Summary 298
9.3 Wearable Photoacoustic Imaging Sensor 299
9.3.1 Overall Description 299
9.3.2 Imaging Principles 299
9.3.3 Structures and Materials 301
9.3.4 Typical Devices and Applications 302
9.3.5 Summary 304
9.4 Wearable Electrical Impedance Tomography 305
9.4.1 Overall Description 305
9.4.2 Imaging Principles 305
9.4.3 Structures and Materials 306
9.4.4 Typical Devices and Applications 307
9.4.4.1 Pulmonary Imaging 307
9.4.4.2 Cancer Detection 309
9.4.4.3 Gesture Recognition 310
9.4.5 Summary 312
9.5 Wearable Terahertz Imaging Sensor 312
9.5.1 Overall Description 312
9.5.2 Imaging Principles 313
9.5.3 Structures and Materials 313
9.5.4 Typical Devices and Applications 314
9.5.5 Summary 316
9.6 Wearable Bioimaging Device for Biomedical Applications 316
9.6.1 Ultrasound Imaging 316
9.6.2 Photoacoustic Imaging 327
9.7 Conclusion 329
References 330
Session II Soft Sensors for Therapy 333
10 Thermotherapy (Resistive Heaters, Photothermal Nanomaterials, Textile Devices, Cryotherapy, etc.) 335
Xiao Yang and Zuankai Wang
10.1 Introduction 335
10.2 Resistive Heaters 336
10.2.1 Metal Wire 336
10.2.2 Two-Dimensional (2D) Materials 339
10.2.3 Conductive Polymers 341
10.2.4 Conclusion 343
10.3 Photothermal Nanomaterials 343
10.4 Textile Devices 348
10.5 Cryotherapy 354
List of Abbreviations 355
References 356
11 Soft Electronics for Drug Delivery 361
Lelun Jiang and Jingbo Yang
11.1 Introduction 361
11.2 Skin Structure 362
11.3 Soft Electronics-Assisted TTDS for Drug Delivery 364
11.3.1 MNs for Passive Drug Delivery 364
11.3.2 Soft Electronics-MNs Systems for Active Drug Delivery 367
11.3.3 Soft Electronics-MN Systems for Closed-Loop Drug Delivery 372
11.3.4 Soft Electronic Systems for Closed-Loop Drug Delivery 375
11.4 Conclusions and Perspectives 379
List of Abbreviations 380
References 380
12 Wearable and Implantable Drug Delivery System 387
Xinran Jiang, Han Wu, Ao Xiao, Ya Huang, Xinge Yu, and Lingqian Chang
12.1 Introduction 387
12.2 Categories of Soft Electronics for Drug Delivery 389
12.2.1 Wearable Systems 390
12.2.2 Implantable Systems 394
12.3 Challenges and Prospects 399
References 400
13 Soft Robotic Sensing and Medicine 403
Dengfeng li
13.1 Introduction 403
13.2 Soft Robotic Tactile Sensing 403
13.3 Soft Robotic Environmental Sensing 406
13.4 Miniature Robotic In Vivo Medicine 409
References 410
Session III Soft Sensors for Interaction 415
14 Integration System 417
Chun Ki Yiu, Pengcheng Wu, Jingkun Zhou, and Park Wooyoung
14.1 Power Supply Strategy of Soft Electronics 417
14.1.1 Introduction 417
14.1.2 Power Source 418
14.1.3 Regulation 419
14.2 Encapsulation 422
14.3 Communication 424
14.4 Closed-Loop Control (AI, Deep Learning, Microcontroller Unit, etc.) 427
List of Abbreviations 432
References 432
15 Self-powered Sensors 437
Binbin Zhang and Zhiming Lin
15.1 Introduction 437
15.2 Piezoelectric Sensor 439
15.3 Triboelectric Sensor 441
15.4 Piezoionic Sensor 445
15.5 Electromagnetic Sensor 446
15.6 Thermoelectric Sensors 448
15.7 Potentiometric Ion Sensors 453
15.8 Conclusion 455
References 457
Index 461
