Recent Progress of Fiber Shaped Lighting Devices for Smart Display Applications—A Fibertronic Perspective

Advances in material science and nanotechnology have fostered the miniaturization of devices. Over the past two decades, the form-factor of these devices has evolved from 3D rigid, volumetric devices through 2D film-based flexible electronics, finally to 1D fiber electronics (fibertronics). In this regard, fibertronic strategies toward wearable applications (e.g., electronic textiles (e-textiles)) have attracted considerable attention thanks to their capability to impart various functions into textiles with retaining textiles' intrinsic properties as well as imperceptible irritation by foreign matters. In recent years, extensive research has been carried out to develop various functional devices in the fiber form. Among various features, lighting and display features are the highly desirable functions in wearable electronics. This article discusses the recent progress of materials, architectural designs, and new fabrication technologies of fiber-shaped lighting devices and the current challenges corresponding to each device's operating mechanism. Moreover, opportunities and applications that the revolutionary convergence between the state-of-the-art fibertronic technology and age-long textile industry will bring in the future are also discussed.     

Large‐Area All‐Textile Pressure Sensors for Monitoring Human Motion and Physiological Signals

Wearable pressure sensors, which can perceive and respond to environmental stimuli, are essential components of smart textiles. Here, large‐area all‐textile‐based pressure‐sensor arrays are successfully realized on common fabric substrates. The textile sensor unit achieves high sensitivity (14.4 kPa^?1), low detection limit (2 Pa), fast response (≈24 ms), low power consumption (<6 µW), and mechanical stability under harsh deformations. Thanks to these merits, the textile sensor is demonstrated to be able to recognize finger movement, hand gestures, acoustic vibrations, and real‐time pulse wave. Furthermore, large‐area sensor arrays are successfully fabricated on one textile substrate to spatially map tactile stimuli and can be directly incorporated into a fabric garment for stylish designs without sacrifice of comfort, suggesting great potential in smart textiles or wearable electronics.     

Stretchable Transparent Conductive Films from Long Carbon Nanotube Metals

Flexible transparent conductors are an enabling component for large‐area flexible displays, wearable electronics, and implantable medical sensors that can wrap around and move with the body. However, conventional conductive materials decay quickly under tensile strain, posing a significant hurdle for functional flexible devices. Here, we show that high electrical conductivity, mechanical stretchability, and optical transparency can be simultaneously attained by compositing long metallic double‐walled carbon nanotubes with a polydimethylsiloxane substrate. When stretched to 100% tensile strain, thin films incorporating these long nanotubes (≈3.2 µm on average) achieve a record high conductivity of 3316 S cm^?1 at 100% tensile strain and 85% optical transmittance, which is 194 times higher than that of short nanotube controls (≈0.8 µm on average). Moreover, the high conductivity can withstand more than 1000 repeated stretch‐release cycles (switching between 100% and 0% strain) with a retention approaching 96%, whereas the short nanotube controls exhibit only 10%. Mechanistic studies reveal that long tubes can bridge the microscale gaps generated during stretching, thereby maintaining high electrical conductivity. When mounted on human joints, this elastic transparent conductor can accommodate large motions to provide stable, high current output. These results point to transparent conductors capable of attaining high electrical conductivity and optical transmittance under mechanical strain to allow large shape changes that may take place in the operation and use of flexible electronics.     

Laser-Triggered Degradation of Silicon Circuits by Lithiation and Moisture Uptake for On-Demand Transient Electronics

Data security risks of unauthorized access of confidential information have attracted considerable attention. Transient electronics capable of physical disappearance or disintegration upon external stimuli could potentially offer an alternative solution at the device level. Despite great advances, smart, efficient, wireless, and nonrecoverable degradation of foundry-compatible silicon (Si)-integrated circuit (IC) chips remains a challenge. Herein, a laser-triggered degradation of Si circuits by lithiation and moisture uptake is proposed. By integrating IC chips with a small amount of lithium sources and a fluidic reservoir consisting of hygroscopic materials, on-demand, wireless, rapid, and complete degradation of Si IC chips built at 600 nm node is achieved upon activation by laser irradiation. This work paves a new route to accomplish smart, tether-free, and thorough degradation of devices compatible with existing foundry processes, offering an essential baseline for the development of intelligent transient electronics for secured hardware.     

Visually Imperceptible Liquid‐Metal Circuits for Transparent,Stretchable Electronics with Direct Laser Writing

A material architecture and laser‐based microfabrication technique is introduced to produce electrically conductive films (sheet resistance = 2.95 Ω sq^?1; resistivity = 1.77 × 10^?6 Ω m) that are soft, elastic (strain limit >100%), and optically transparent. The films are composed of a grid‐like array of visually imperceptible liquid‐metal (LM) lines on a clear elastomer. Unlike previous efforts in transparent LM circuitry, the current approach enables fully imperceptible electronics that have not only high optical transmittance (>85% at 550 nm) but are also invisible under typical lighting conditions and reading distances. This unique combination of properties is enabled with a laser writing technique that results in LM grid patterns with a line width and pitch as small as 4.5 and 100 µm, respectively—yielding grid‐like wiring that has adequate conductivity for digital functionality but is also well below the threshold for visual perception. The electrical, mechanical, electromechanical, and optomechanical properties of the films are characterized and it is found that high conductivity and transparency are preserved at tensile strains of ≈100%. To demonstrate their effectiveness for emerging applications in transparent displays and sensing electronics, the material architecture is incorporated into a couple of illustrative use cases related to chemical hazard warning.     

Conductive and Elastic 3D Helical Fibers for Use in Washable and Wearable Electronics

Due to the intrinsic properties of fabrics, fabric-based wearable systems have certain advantages over elastomeric material-based stretchable electronics. Here, a method to produce highly stretchable, conductive, washable, and solderable fibers that consist of elastic polyurethane (PU) fibers and conductive Cu fibers, which are used as interconnects for wearable electronics, is reported. The 3D helical shape results from stress relaxation of the prestretched PU fiber and the plasticity of the Cu fiber, which provides a predictable way to manipulate the morphology of the 3D fibers. The present fibers have superior mechanical and electrical properties to many other conductive fibers fabricated through different approaches. The 3D helical fibers can be readily integrated with fabrics and other functional components to build fabric-based wearable systems.     

Smart Textile-Integrated Microelectronic Systems for Wearable Applications

The programmable nature of smart textiles makes them an indispensable part of an emerging new technology field. Smart textile-integrated microelectronic systems (STIMES), which combine microelectronics and technology such as artificial intelligence and augmented or virtual reality, have been intensively explored. A vast range of research activities have been reported. Many promising applications in healthcare, the internet of things (IoT), smart city management, robotics, etc., have been demonstrated around the world. A timely overview and comprehensive review of progress of this field in the last five years are provided. Several main aspects are covered: functional materials, major fabrication processes of smart textile components, functional devices, system architectures and heterogeneous integration, wearable applications in human and nonhuman-related areas, and the safety and security of STIMES. The major types of textile-integrated nonconventional functional devices are discussed in detail: sensors, actuators, displays, antennas, energy harvesters and their hybrids, batteries and supercapacitors, circuit boards, and memory devices.     

Self-Powered Integrated Sensing System with In-Plane Micro-Supercapacitors for Wearable Electronics

Self-powered integrated sensor with high-sensitivity physiological signals detection is indispensable for next-generation wearable electronic devices. Herein, a Ti₃C₂T_x/CNTs-based self-powered resistive sensor with solar cells and in-plane micro-supercapacitors (MSCs) is successfully realized on a flexible styrene–ethylene/butylene–styrene (SEBS) electrospinning film. The prepared Ti₃C₂T_x/CNTs@SEBS/CNTs nanofiber membranes exhibit high electrical conductivity and mechanical flexibility. The laser-assisted fabricated Ti₃C₂T_x/CNTs based-MSCs demonstrate a high areal energy density of 52.89 and 9.56 µWh cm⁻² with a corresponding areal power density of 0.2 and 4 mW cm⁻². Additionally, the MSCs exhibit remarkable capacity retention of 90.62% after 10 000 cycles. Furthermore, the Ti₃C₂T_x/CNTs based-sensor exhibits real-time detection capability for human facial micro-expressions and pulse single under physiological conditions. The repeated bending/release tests indicate the long-time cycle stability of the Ti₃C₂T_x/CNTs based-sensor. Owing to the excellent sensing performance, the sensing array was also fabricated. It is believed that this work develops a route for designing a self-powered sensor system with flexible production, high performance, and human-friendly characteristics for wearable electronics.     

Bioinspired Fluffy Fabric with In Situ Grown Carbon Nanotubes for Ultrasensitive Wearable Airflow Sensor

Recently, electronic skin and smart textiles have attracted considerable attention. Flexible sensors, as a kind of indispensable components of flexible electronics, have been extensively studied. However, wearable airflow sensors capable of monitoring the environment airflow in real time are rarely reported. Herein, by mimicking the spider's fluff, an ultrasensitive and flexible all-textile airflow sensor based on fabric with in situ grown carbon nanotubes (CNTs) is developed. The fabric decorated with fluffy-like CNTs possesses exceptionally large contact area, endowing the airflow sensor with superior properties including ultralow detection limit (≈0.05 m s⁻¹), multiangle airflow differential response (0°–90°), and fast response time (≈1.3 s). Besides, the fluffy fabric airflow sensor can be combined with a pristine fabric airflow sensor to realize highly sensitive detection in a wide airflow range (0.05–7.0 m s⁻¹). Its potential applications including transmitting information according to Morse code by blowing the sensors, monitoring increasing and decreasing airflow velocity, and alerting blind people walking outside about potential hazard induced by nearby fast-moving objects are demonstrated. Furthermore, the airflow sensor can be directly integrated into clothing as stylish designs without sacrificing comfortness. It is believed that the ultrasensitive all-textile airflow sensor holds great promise for applications in smart textiles and wearable electronics.     

A review on structures,materials and applications of stretchable electrodes

With the rapid development of wearable smart devices,many researchershave carried out in-depth research on the stretchable electrodes.As one of the corecomponents for electronics,the electrode mainly transfers the electrons,which plays animportant role in driving the various electrical devices.The key to the research for thestretchable electrode is to maintain the excellent electrical properties or exhibit theregular conductive change when subjected to large tensile deformation.This articleoutlines the recent progress of stretchable electrodes and gives a comprehensiveintroduction to the structures,materials,and applications,including supercapacitors,lithium-ion batteries,organic light-emitting diodes,smart sensors,and heaters.Theperformance comparison of various stretchable electrodes was proposed to clearly showthe development challenges in this field.We hope that it can provide a meaningfulreference for realizing more sensitive,smart,and low-cost wearable electrical devices inthe near future.