Soft robotics inspired by the movement of living organisms, with excellent adaptability and accuracy for accomplishing tasks, are highly desirable for efficient operations and safe interactions with human. With the emerging wearable electronics, higher tactility and skin affinity are pursued for safe and user-friendly human-robot interactions. Fabrics interlocked by fibers perform traditional static functions such as warming, protection, and fashion. Recently, dynamic fibers and fabrics are favorable to deliver active stimulus responses such as sensing and actuating abilities for soft-robots and wearables. First, the responsive mechanisms of fiber/fabric actuators and their performances under various external stimuli are reviewed. Fiber/yarn-based artificial muscles for soft-robots manipulation and assistance in human motion are discussed, as well as smart clothes for improving human perception. Second, the geometric designs, fabrications, mechanisms, and functions of fibers/fabrics for sensing and energy harvesting from the human body and environments are summarized. Effective integration between the electronic components with garments, human skin, and living organisms is illustrated, presenting multifunctional platforms with self-powered potential for human-robot interactions and biomedicine. Lastly, the relationships between robotic/wearable fibers/fabrics and the external stimuli, together with the challenges and possible routes for revolutionizing the robotic fibers/fabrics and wearables in this new era are proposed.

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Functional Fibers and Fabrics for Soft Robotics, Wearables, and Human-Robot Interface.

The emergence of new applications, such as in artificial intelligence, the internet of things, and biotechnology, has driven the evolution of stress sensing technology. For these emerging applications, stretchability, remoteness, stress distribution, a multimodal nature, and biocompatibility are important performance characteristics of stress sensors. Mechanoluminescence (ML)-based stress sensing has attracted widespread attention because of its characteristics of remoteness and having a distributed response to mechanical stimuli as well as its great potential for stretchability, biocompatibility, and self-powering. In the past few decades, great progress has been made in the discovery of ML materials, analysis of mechanisms, design of devices, and exploration of applications. One can find that with this progress, the focus of ML research has shifted from the phenomenon in the earliest stage to materials and recently toward devices. At the present stage, while showing great prospects for advanced stress sensing applications, ML-based sensing still faces major challenges in material optimization, device design, and system integration.

Mechanoluminescence Rebrightening the Prospects of Stress Sensing: A Review.

Textile triboelectric nanogenerator (TENG) is a kind of smart textile technology that integrates traditional flexible and wearable textile materials with emerging and advanced TENG science, which not only embraces the capabilities of autonomous energy harvesting and active self-powered sensing, but also maintains original wearability and desired comfortability. With the help of the burden-free and self-sufficient wearable intelligent system, individuals can achieve convenient acquisition and efficient utilization of electric energy, which will help to promote the future development of human-oriented on-body electronics and artificial intelligence. Here, some fundamental knowledge and core elements, including the operational modes and corresponding service occasions, charge generation and transfer mechanisms, remaining challenges and potential solutions are comprehensively summarized and systematically discussed. Based on these analyses, a roadmap toward the scientific research and large-scale commercial application of textile TENGs in the next decade is highlighted at the end of the article. We believe that textile TENGs will become an indispensable part of daily clothing in the future, thus benefiting all humankind and human civilization.

Smart textile triboelectric nanogenerators: Current status and perspectives

The seamless integration of emerging triboelectric nanogenerator (TENG) technology with traditional wearable textile materials has given birth to the next‐generation smart textiles, i.e., textile TENGs, which will play a vital role in the era of Internet of Things and artificial intelligences. However, low output power and inferior sensing ability have largely limited the development of textile TENGs. Among various approaches to improve the output and sensing performance, such as material modification, structural design, and environmental management, a 3D fabric structural scheme is a facile, efficient, controllable, and scalable strategy to increase the effective contact area for contact electrification of textile TENGs without cumbersome material processing and service area restrictions. Herein, the recent advances of the current reported textile TENGs with 3D fabric structures are comprehensively summarized and systematically analyzed in order to clarify their superiorities over 1D fiber and 2D fabric structures in terms of power output and pressure sensing. The forward‐looking integration abilities of the 3D fabrics are also discussed at the end. It is believed that the overview and analysis of textile TENGs with distinctive 3D fabric structures will contribute to the development and realization of high‐power output micro/nanowearable power sources and high‐quality self‐powered wearable sensors.

Advances in High‐Performance Autonomous Energy and Self‐Powered Sensing Textiles with Novel 3D Fabric Structures

Piezoelectric materials for flexible and wearable electronics: A review

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.

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

Bright-Multicolor, Highly Efficient, and Addressable Phosphorescent Organic Light-Emitting Fibers: Toward Wearable Textile Information Displays

Light‐emitting fibers have been intensively developed for the realization of textile displays and various lighting applications, as promising free‐form electronics with outstanding interconnectivity. These advances in the fiber displays have been made possible by the successful implementation of the core technologies of conventional displays, including high optoelectronic performance and essential elements, in the fiber form‐factor. However, although white organic light‐emitting diodes (WOLEDs), as a fundamental core technology of displays, are essential for realizing full‐color displays and solid‐state lighting, fiber‐based WOLEDs are still challenging due to structural issues and the lack of approaches to implementing WOLEDs on fiber. Herein, the first fiber WOLED is reported, exhibiting high optoelectronic performance and a reliable color index, comparable to those of conventional planar WOLEDs. As key features, it is found that WOLEDs can be successfully introduced on a cylindrical fiber using a dip‐coatable single white‐emission layer based on simulation and optimization of the white spectra. Furthermore, to ensure durability from usage, the fiber WOLED is encapsulated by an Al2O3/elastomer bilayer, showing stable operation under repetitive bending and pressure, and in water. This pioneering work is believed to provide building blocks for realizing complete textile display technologies by complementing the lack of the core technology.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/advs.202104855

High‐Performance and Reliable White Organic Light‐Emitting Fibers for Truly Wearable Textile Displays

Smart displays have been integrated into our daily life, providing new concepts of interconnections between humans and interactivity with close collaboration between users. As a centerpiece of this integration, textile displays that can be worn like clothes are being intensively developed and are poised to provide a more intimate and closer connection. Among various light sources that have been used in the field of textile displays, organic light‐emitting diodes (OLEDs) have attracted considerable attention as one of the promising candidates for realizing truly wearable textile displays (i.e., wearing displays) in that they have shown the highest level of technical maturity, including high optoelectronic performance and flexibility, which can provide not only clear visual information and versatility regardless of the surrounding environment but have also been industrially proven. This review introduces the recent progress in OLED‐based textile displays and related technologies, with the discussion of challenges and limitations of the fiber‐ and fabric‐based approaches. Additionally, specific opinions are provided on research opportunities for organic light‐emitting textile displays, which can contribute to realizing truly wearable textile displays with a complete platform in the future.

Organic light‐emitting fibers and fabrics for truly wearable smart displays: Recent progress and future opportunities

Abstract Increasing demand for real-time healthcare monitoring is leading to advances in thin and flexible optoelectronic device-based wearable pulse oximetry. Most previous studies have used OLEDs for this purpose, but did not consider the side effects of broad full-width half-maximum (FWHM) characteristics and single substrates. In this study, we performed SpO 2 measurement using a fiber-based quantum-dot pulse oximetry (FQPO) system capable of mass production with a transferable encapsulation technique, and a narrow FWHM of about 30 nm. Based on analyses we determined that uniform angular narrow FWHM-based light sources are important for accurate SpO 2 measurements through multi-layer structures and human skin tissues. The FQPO was shown to have improved photoplethysmogram (PPG) signal sensitivity with no waveguide-mode noise signal, as is typically generated when using a single substrate (30–50%). We successfully demonstrate improved SpO 2 measurement accuracy as well as all-in-one clothing-type pulse oximetry with FQPO. 

/pdf/fiber-based-quantum-dot-pulse-oximetry-for-wearable-health-172oykn7.pdf

Yong Ha Hwang

Papers

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

Bright-Multicolor, Highly Efficient, and Addressable Phosphorescent Organic Light-Emitting Fibers: Toward Wearable Textile Information Displays

High‐Performance and Reliable White Organic Light‐Emitting Fibers for Truly Wearable Textile Displays

Organic light‐emitting fibers and fabrics for truly wearable smart displays: Recent progress and future opportunities

Fiber-based quantum-dot pulse oximetry for wearable health monitoring with high wavelength selectivity and photoplethysmogram sensitivity