Since 1960, electronics has played an important role in modern society, either as computing, sensing devices for information collection or as mobile terminates for data exchange. Further wider applications essentially require overcoming the restriction of traditional rigid, unsustainable power sources, thereby promoting the favorable properties of stability, high‐output, being maintenance‐free, flexibility, or even stretchability for the most sophisticated electronics. Quantitative comparison and qualitative analysis prove that emerging triboelectric nanogenerators (TENGs), invented by Zhonglin Wang of the Georgia Institute of Technology in 2012, can be a powerful and promising approach to address these challenges. Mostly, the TENG is fabricated by polymer‐based materials which make it flexible and stretchable naturally. More than a traditional energy harvester, the TENG can not only scavenge the mechanical energy from an ambient environment, based on the combination of contact electrification and electrostatic induction, but also serve as an active sensor from its rich information output with external stimulation. With all these merits, TENGs are developed as a flexible and stretchable self‐powered system for many applications.

In this book, we introduce in four parts the principle and progress of flexible and stretchable devices based on the triboelectric nanogenerator – the fundamentals of TENGs, approaches to flexible and stretchable structures, self‐powered smart systems, and their applications in various areas. The major contents of each part are listed as follows.

PART I: Fundamentals of triboelectric nanogenerators, including principle, working modes and structures, fabrication technologies, characterization, and power management.

PART II: Approaches to flexible and stretchable, including commonly used materials (0D, 1D, 2D nanomaterials) and unconventional 3D structural design and other recent progresses.

PART III: Self‐powered smart systems, including active and hybrid sensors, smart actuators, electronic skin, and all‐in‐one self‐powered microsystems.

PART IV: Applications of self‐powered smart systems, including biomedical systems, Internet of Things and artificial intelligence, environmental monitoring/protection, etc.

Therefore, this book provides a coherent viewpoint of this attractive field that is difficult to obtain solely by reading individual journal papers. The book also gives comparisons between methods, designs, and materials that typically do not appear in journal publications. The book will act as a resource to those who aspire to further extend either the science and technologies of flexible and stretchable electronics and self‐powered systems or future applications.

This book was written based mainly on numerous journal papers we and our collaborators have authored since 2012. I thank Alice Wonderlab's current and former members and partners who have made countless contributions in relative fields (list not in any particular order): Xiaosheng Zhang, Mengdi Han, Haotian Chen, Zongming Su, Xiaoliang Cheng, Xuexian Chen, Mayue Shi, Hanxiang Wu, Jinxin Zhang, Liming Miao, Yu Song, Bo Meng, Hang Guo, Ji Wan, Chen Xu, Haobin Wang, Wen Liu, Fuyun Zhu, Quan Yuan, Wei Tang, Xuming Sun, Xiuhan Li, Hangbo Zhao, Cunman Liang, Yanyuan Ba, Zhaohui Wu, Danliang Wen, B N Chandrashekar, Smitha A S, Jianbo Fu, and Zijian Song, etc. We thank our collaborators and coworkers worldwide: John A Rogers, Juergen Brugger, Jingfu Bao, Zhongfan Liu, Zhihong Li, Shuxiang Dong, Tianling Ren, and Wei Gao, etc. Particularly, I express my thanks to Prof. Zhonglin Wang for his continuous support and encouragement in the past 10 years, for me Prof. Wang is not just an outstanding scientist in research, a great mentor in career, but also a living model in life.

In addition, I thank my iCAN team, Yiqing Wang, Zhonghua Yu, Baoqin Chen, Jianping Xing, Yalin Ren, Xiangjun Xin, Jiaxin Cui, Sulan Li, Esashi Masayoshi, Chihming Ho, and others. iCAN is the original force in my mind, to make something different, to make something great, and to make something meaningful. With your long‐term support and co‐efforts, we are on the way to make this great dream come true. This book is a demonstration in academy.

Last but not least, I thank my harmonious four‐generation family, my dearest grandmother, and my father and mother, my husband Herbert and my daughter Lily, without their powerful support and full understanding nothing would have come out in my life. This book is my sincere gift to all of you.