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...

Stretchable interconnects with invariable conductivity and complete elasticity, which return to their original shape without morphological hysteresis, are attractive for the development of stretchable electronics. In this study, a polydimethylsiloxane‐coated multifilament polyurethane‐based helical conductive fiber is developed. The stretchable helical fibers exhibit remarkable electrical performance under stretching, negligible electrical and mechanical hysteresis, and high electrical reliability under repetitive deformation (10 000 cycles of stretching with 100% strain). The resistance of the helical fibers barely increases until the applied strain reaches the critical strain, which is based on the helical diameter of each fiber. According to finite element analysis, uniform stress distribution is maintained in the helical fibers even under full stretching, owing to the fibers' true helix structure. In addition, the stretchable helical fibers have the ability to completely return to their original shapes even after being fully compressed in the vertical direction. Cylinder‐shaped connecting pieces made using 3D printing are designed for stable connection between the helical fibers and commercial components. A deformable light‐emitting diode (LED) array and biaxially stretchable LED display are fabricated using helical fibers. A skin‐mountable band‐type oximeter with helical fiber‐based electrodes is also fabricated and used to demonstrate real‐time detection of cardiac activities and analysis of brain activities.

There is currently a high demand for smart wearable and flexible electronics for high‐sensitivity strain sensors with good transparency, stretchability, and water‐repellent characteristics. The demand for such devices, especially those that demonstrate superhydrophobicity, is constantly increasing because of their prospective wearable applications. A stretchable, superhydrophobic, and transparent polydimethylsiloxane/carbon nanotube strain sensor is fabricated by directly spraying a carbon nanotube solution onto a polydimethylsiloxane nanowrinkle substrate. Applying this coating not only provides many substrate materials with a superhydrophobic surface, but also responds to stretching, bending, and torsion—properties that benefit flexible sensor applications. The strain sensor shows high optical transparency (over 70%) and displays excellent superhydrophobicity (a water contact angle of 165 ± 2°). It shows a good response, with over 5000 stretching–relaxing cycles and 10 000 cycles with twisting angles from 0° to 20°, and is able to sense strain for stretching of up to 80%, bending of up to 140°, and rotation of up to 90°. These findings demonstrate the validity of this approach for fabricating transparent superhydrophobic materials with excellent stretchability and conductivity characteristics. Such materials show great potential for wearable devices to detect human motion, including large‐scale movements, without affecting the appearance of the device.

Major concerns in the development of wearable textile electronics are exposure to moisture and contamination. The exposure can cause electrical breakdown of the device and its interconnections, and thus continuous efforts have been made to fabricate textile electronics which are free from moisture and pollution. Herein, we developed a highly conductive and waterproof fiber with excellent electrical conductivity (0.11 Ω/cm) and mechanical stability for advanced interconnector components in wearable textile electronics. The fabrication process of the highly conductive fiber involves coating of a commercial Kevlar fiber with Ag nanoparticle-poly(styrene- block-butadiene- block-styrene) polymer composites. The fabricated fiber then gets treated with self-assembled monolayer (SAM)-forming reagents, which yields waterproof and self-cleaning properties. To find optimal SAM-forming reagents, four different kinds of reagents involving 1-decane thiol (DT), 1 H,1 H,2 H,2 H-perfluorohexanethiol, 1 H,1 H,2 H,2 H-perfluorodecyltrichlorosilane, 1 H,1 H,2 H,2 H-perfluodecanethiol (PFDT) were compared in terms of their thiol group and carbon chain lengths. Among the SAM-forming reagents, the PFDT-treated conductive fiber showed superior waterproof and self-cleaning property, as well as great sustainability in the water with varying pH because of nanoscale roughness and low surface energy. In addition, the functionality of the conductive fiber was tested under mechanical compression via repeated washing and folding processes. The developed conductive fiber with waterproof and self-cleaning property has promising applications in the interconnector operated under water and textile electronics.

Superomniphobic surfaces showing extremely liquid-repellent properties have received a great amount of attention as they can be used in various industrial and biomedical applications. However, so far, the fabrication processes of these materials mostly have involved the coating of perfluorocarbons onto micro- and nanohierarchical structures of these surfaces, which inevitably causes environmental pollution, leading to health concerns. Herein, we developed a facile method to obtain flexible superomniphobic surfaces without perfluorocarbon coatings that have shape-tunable mushroom-like micropillars (MPs). Inspired by the unique structures on the skin of springtails, we fabricated mushroom-like structures with downward facing edges (i.e., a doubly re-entrant structure) on a surface. The flexible MP structures were fabricated using a conventional micromolding technique, and the shapes of the mushroom caps were made highly tunable via the deposition of a thin aluminum (Al) layer. Due to the compressive residual stress of the Al, the mushroom caps were observed to bend toward the polymer upon forming doubly re-entrant–MP structures. The obtained surface was found to repel most low-surface-tension liquids such as oils, alcohols, and even fluorinated solvents. The developed flexible superomniphobic surface showed liquid repellency even upon mechanical stretching and after surface energy modification. We envision that the developed superomniphobic surface with high flexibility and wetting resistance after surface energy modification will be used in a wide range of applications such as self-cleaning clothes and gloves.

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.

A hybrid composite photodetector based on cesium lead bromine perovskite (CsPbBr3) nanosheets and carbon nanodots (CDs) was fabricated on a quartz substrate by a one-step method of spin-coating and hot-plate annealing. The responsivity of the CsPbBr3/CD hybrid composite photodetector was 608 mAW−1 (under a 520-nm laser diode source applied at 0.2 mWcm−2), almost three times higher than that of a CsPbBr3-based photodetector (221 mAW−1). The enhanced performance of the CsPbBr3/CD photodetector is attributable to the high band alignment of the CDs and CsPbBr3, which significantly improves the charge extraction at the CsPbBr3/CD interface. Moreover, the hybrid CsPbBr3/CD photodetector exhibited a fast response time with a rise and decay time of 1.55 and 1.77 ms, which was faster than that of a pure CsPbBr3 based photodetector, indicating that the CDs accelerate the extraction of electrons and holes trapped in the CsPbBr3 film.