Flexible and Wearable Electronics: Design and Fabrication Techniques

The objective of this book is to provide a comprehensive guide to the state of the art technologies and methods applied in the realization of flexible and wearable electronics. The targeted readers of this book include but not limited to college professors, Research and Development scientists, practicing electronics and material engineers, in addition to all the enthusiasts interested in modern technological advancements. Moreover, the book serves as an extensive resource for graduate students working on topics related to wearable and flexible electronics. This book, organized into eleven chapters, introduces the latest research findings and trends related to the design, fabrication processes and techniques used in the realization of wearable and flexible electronics. Chapter One shows how recent developments in wireless, flexible, fully-printable, and sensor technologies are paving the way for the emergence of ubiquitous sensing capabilities, in the form of "Smart Skins" and the Internet of Things (IoT). The chapter also presents a brief review of state-of-the-art implementations of flexible chemical sensing components technologies; and reviews the latest advances in wireless interrogation techniques for such devices. Chapter Two presents the incremental Latin Hypercube Sampling (LHS) technique which is aimed at speeding up the circuit simulations while considering process variation and aging effects. Two automated robust design optimization techniques are introduced for the analog circuits with flexible Thin Film Transistors. Chapter Three presents the advantages and suitability of semiconducting Nano Wires (NWs) for flexible and large area electronics. Various aspects of NWs such as physical and chemical properties, synthesis methods, processing, and applications are reviewed with examples. Chapter Four discusses how to fabricate flexible/stretchable piezoelectric devices by the use of electrohydrodynamical direct-writing technique. Furthermore, this chapter provides detailed engineering design rules and paves a cost-effective and high-efficiency manufacturing pathway for applications in wearable and bio-integrated electronics. Chapter Five explores chief approaches towards the development of flexible silicon electronics. The chapter reports some of the most promising methodologies for converting rigid silicon substrates into flexible electronics through the use of silicon-based nanomaterials, etch-release processes, and stress-based wafer spalling. Chapter Six focuses on the use of inkjet printing technique of conductive tracks and electrode patterns on textile substrates. The chapter also reports a two-step fabrication process using UV barrier channels and low viscosity functional inks. Chapter Seven provides an overview of existing wearable technologies for Intra-Body Communication (IBC); it also addresses their potential and challenges, and discusses future directions. Chapter Eight presents the design of a flexible antenna structure operating at multiple frequencies covering WLAN, WiMaX, GPS, and ISM applications. Chapter Nine discusses the design of Near Field Communication (NFC) wearable antennas. The chapter examines the design of such antennas especially for small gadgets like wristbands, watches, and rings. Chapter Ten reports recent advances in the fabrication, structure, mechanism and electrical output performances of various fiber-based and textile-based flexible generators, including piezoelectric, triboelectric and electret generators. Moreover, discussions are provided regarding newfangled applications, current challenges and future directions. Last but not least, the appropriate choice of the electronic elements of wearable sensor nodes including the power source, sensors, digital signal processing components, and transceivers to build up an energy-efficient wearable body area network is discussed in Chapter Eleven.