Design and application of thermally drawn multimaterial electronic fiber devices for smart sensing

<sec><p indent="0mm">The applications of fiber materials span a wide array of fields, ranging from traditional textiles to multifunctional composites, as well as waveguide functionalities, flexible electronic fabrics, and other critical components in various devices. The extreme environments in which electronic devices operate, coupled with the trends of miniaturization and flexibility, have resulted in increasingly complex and diverse functional requirements. This shift necessitates higher, broader, and more sophisticated standards for the preparation and performance of fiber-integrated devices. It is becoming evident that current fiber materials often lack versatility in composition, geometry, and feature sizes. As a result, researchers are actively exploring the limits of fiber functionality and applications. This paper provides a comprehensive review of the thermally drawn process, specifically focusing on a unique method of fiber production: Thermally drawing from preformed rods. The preformed thermally drawn technique, which allows for the simultaneous drawing of metals, polymers, and semiconductors into fibers, is a well-established approach for manufacturing advanced functional electronic fibers, thereby unlocking new opportunities for sensing applications. The review highlights four key application areas for smart sensing fibers produced using thermally drawn fiber technology: Mechanomechanical sensing, acoustic sensing, bioelectrical signal sensing, and optical signal sensing. In mechanomechanical sensing, thermally drawn fibers demonstrate high sensitivity and reliability in detecting strain and pressure changes, which are subsequently converted into electrical signals by detectors. In acoustic sensing, these specialized fabrics can transform acoustic pressure signals into electrical signals, facilitating real-time monitoring of environmental sounds with extensive potential applications. In the realm of bioelectrophysiological signal sensing, thermally drawn fibers can interface with biological tissues, capturing electrical signals from the human body and converting ionic currents into electronic currents. This capability holds significant promise for healthcare monitoring and diagnostics, including the measurement of electrocardiograms (ECG), electroencephalograms (EEG), electromyograms (EMG), and electrooculograms (EOG). </sec><sec> For optical sensing applications, the stretching of semiconductor and metallic materials, in conjunction with fiber feeding, allows these fibers to respond to variations in optical signals, making them suitable for integration into optical detection fiber devices. The paper begins with an overview of the fundamental principles underlying the thermally drawn process. It then synthesizes the operational principles and design concepts of existing thermally drawn fiber sensors, categorizing them by function. This section outlines critical elements in the design of smart sensing fibers, including material selection and the design of prefabricated structures to construct diverse functional thermally drawn fiber sensors. Following this, a review of the development of thermally drawn smart sensing fibers across various fields is presented, emphasizing the importance of integrating structure-function design between prefabricated rods and fibers to enhance sensor performance. Finally, the advantages and challenges of thermally drawn fiber sensors in diverse applications are discussed, underscoring their potential and areas for further research. </sec>