applications, and smart sportswear. [13][14][15][16][17] In this regard, stretchable and wearable electronic devices in the 1D form, which can be directly integrated into daily clothes without any inconsistency, are greatly promising for future wearable electronics. [18][19][20][21][22][23] In addition, the hierarchical property of the fibrous structures (fiber: a small and short piece of a strand, filament: a long strand, yarn: an intertwined 1D structure of fibers or filaments, and fabric: a flexible substance consisting of a network of yarns) makes 1D electronic devices and systems remarkably suitable for advanced wearable electronics. The 1D assemblies including the 1D electronic devices also have unique characteristics appropriate to wearable electronics such as softness, stretchability, breathability, and high tolerance to damage. [3] Stretchability, in particular, is one of the most important properties for practical wearable applications because smart clothes or textiles including such 1D electronic devices should be covered on soft and curved human body. [24] Furthermore, some parts of clothes are frequently stretched and deformed during natural movements in daily life, thereby increasing the importance of stretchability of 1D electronic devices. Although many of existing clothes have achieved certain stretchability with only rigid yarns through specific textile structures such as woven or knitted structures, the stretchability resulting from such textile structures is insufficient to cover high stretchability desired in specific applications. For example, high stretchability of textiles is highly required for sportswear in order to achieve a form-fitting property, high comfortability, and elasticity during exercise. For such purpose, various stretchable yarns such as spandex have been widely used in textile industry. These properties of textiles are also essential for various sensing applications of wearable and textile electronic, resulting that high stretchability should be achieved for the 1D electronic devices. [25,26] In addition, the high stretchability resulting from the use of stretchable conductive yarns can successfully prevent a bagging issue of smart textiles which degrades stability and reproducibility of the smart textiles. For achieving the 1D stretchable electronic devices and systems, the development of 1D stretchable electrodes such as conductive yarns or filaments with high electrical conductivity and stretchability is basically essential above other things. In this regard, recent advances toward developing various high-performance Research on wearable electronic devices that can be directly integrated into daily textiles or clothes has been explosively grown holding great potential for various practical wearable applications. These wearable electronic devices strongly demand 1D electronic devices that are light-weight, weavable, highly flexible, stretchable, and adaptable to comport to frequent deformations during usage in daily life. To this end, the development of 1D electrodes wit...

Conductive fibers, which are highly adaptable to the morphologies of the human body, are attractive for the development of wearable systems, smart clothing, and textronics to detect various biological signals and human motions. A fiber‐based conductive sensor interconnected with hierarchical microhairy architectures, exhibiting remarkable stretchability (<200%) and sensitivity for various stimuli (pressure, stretching, and bending), is developed. For distinguishability of multiple gestures, two hierarchical hairy conductive fibers are twisted to fabricate a fiber‐type sensor, which monitors distinct waveforms of electrical signals retrieved from pressure, stretching, and bending. This sensor is highly robust under repeated appliances of external stimuli over multiple cyclic tests of various modes (<2200 cycles for each stimulus). Upon formation of a self‐assembled monolayer, it exhibits stable performance even under wet conditions. For practical applications, this sensor can be weaved into a smart glove to demonstrate a pressure and gesture‐discernible wearable controller for virtual reality (VR) interface, shedding light on advances in wearable electronics with medical and healthcare functionalities and VR systems.

In article number 1902532, Taeyoon Lee and co‐workers review the recent progress of stretchable fiber‐based electronic devices. They consider not only representative conductive materials and fabrication techniques for stretchable conductive fibers, but also designs and applications of various stretchable fiber‐based electronic devices, including mechanical sensors and energy devices.

Advances in electronic textiles (E-textiles) for next-generation wearable electronics have originated from making a balance between electrical and mechanical properties of stretchy conductive fibers. Despite such progress, the trade-off issue is still a challenge when individual fibers are woven and/or stretched undesirably. Time-consuming fiber weaving has limited practical uses in scalable E-textiles. Here, a facile method is presented to fabricate ultra-stretchable Ag nanoparticles (AgNPs)/polyurethane (PU) hybrid conductive fibers by modulating solvent diffusion accompanied by in situ chemical reduction and adopting a tough self-healing polymer (T-SHP) as an encapsulation layer. First, the controlled diffusivity determines how formation of AgNPs is spatially distributed inside the fiber. Specifically, when a solvent with large molecular weight is used, the percolated AgNP networks exhibit the highest conductivity (30 485 S cm −1) even at 300% tensile strain and durable stretching cyclic performance without severe cracks by virtue of the efficient strain energy dissipation of T-SHP encapsulation layers. The self-bondable properties of T-SHP encapsulated fibers enables self-weavable interconnects. Using the new integration, mechanical and electrical durability of the self-bonded fiber interconnects are demonstrated while stretching biaxially. Furthermore, the self-bonding assembly is further visualized via fabrication of a complex structured E-textile.

The need for wearable electronic devices continues to grow, and the research is under way for stretchable fiber-type sensors that are sensitive to the surrounding atmosphere and will provide proficient measurement capabilities. Currently, one-dimensional fiber sensors have several limitations for their extensive use because of the complex structures of the sensing mechanisms. Thus, it is essential to miniaturize these materials with durability while integrating multiple sensing capabilities. Herein, we present an ultrasensitive and stretchable conductive fiber sensor using PdNP networks embedded in elastomeric polymers for crack-based strain and H 2 sensing. The fiber multimodal sensors show a gauge factor of ∼2040 under 70% strain and reliable mechanical deformation tolerance (10,000 stretching cycles) in the strain-sensor mode. For H 2 sensing, the fiber multimodal sensors exhibit a wide sensing range of high sensitivity: −0.43% response at 5 ppm (0.0005%) H 2 gas and −27.3% response at 10% H 2 gas. For the first time, we demonstrate highly stretchable H 2 sensors that can detect H 2 gas under 110% strain with mechanical durability. As demonstrated, their stable performance allows them to be used in wearable applications that integrate fiber multimodal sensors into industrial safety clothing along with a microinorganic light-emitting diode for visual indication, which exhibits proper activation upon H 2 gas exposure.