Weavable sensing fibers with superior mechanical strength and sensing functionality are crucial for the realization of wearable textile sensors. However, in the fabrication of previously reported wearable sensing fibers, additional processes such as reduction, doping, and coating were essential to satisfy both requirements. The sensing fibers should be continuously synthesized in a scalable process for commercial applications with high reliability and productivity, which was challenging. In this study, we first synthesize mass-producible wearable sensing fibers with good mechanical properties and sensing functionality without additional processes by incorporating carbon nanotubes (CNTs) into distinct nanocellulose. Nanocellulose extracted from tunicate (TCNF) is homogeneously composited with single-walled CNTs, and composite fibers (TCNF/CNT) are continuously produced in aligned directions by wet spinning, facilitating liquid-crystal properties. The TCNF/CNT fibers exhibit a superior gas (NO 2 )-sensing performance with high selectivity and sensitivity (parts-per-billion detection). In addition, the TCNF/CNT fibers can endure complex and harsh distortions maintaining their intrinsic sensing properties and can be perfectly integrated with conventional fabrics using a direct weaving process. Our meter-scale scalable synthesis of functional composite fibers is expected to provide a mass production platform of versatile wearable sensors.

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Transition metal dichalcogenides (TMDs) have attracted significant interest as one of the key materials in future electronics such as logic devices, optoelectrical devices, and wearable electronics. However, a complicated synthesis method and multistep processes for device fabrication pose major hurdles for their practical applications. Here, we introduce a direct and rapid method for layer-selective synthesis of MoS 2 and WS 2 structures in wafer-scale using a pulsed laser annealing system (λ = 1.06 μm, pulse duration ∼100 ps) in ambient conditions. The precursor layer of each TMD, which has at least 3 orders of magnitude higher absorption coefficient than those of neighboring layers, rigorously absorbed the incoming energy of the laser pulse and rapidly pyrolyzed in a few nanoseconds, enabling the generation of a MoS 2 or WS 2 layer without damaging the adjacent layers of SiO 2 or polymer substrate. Through experimental and theoretical studies, we establish the underlying principles of selective synthesis and optimize the laser annealing conditions, such as laser wavelength, output power, and scribing speed, under ambient condition. As a result, individual homostructures of patterned MoS 2 and WS 2 layers were directly synthesized on a 4 in. wafer. Moreover, a consecutive synthesis of the second layer on top of the first synthesized layer realized a vertically stacked WS 2 /MoS 2 heterojunction structure, which can be treated as a cornerstone of electronic devices. As a proof of concept, we demonstrated the behavior of a MoS 2 -based field-effect transistor, a skin-attachable motion sensor, and a MoS 2 /WS 2 -based heterojunction diode in this study. The ultrafast and selective synthesis of the TMDs suggests an approach to the large-area/mass production of functional heterostructure-based electronics.