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Yarn-based strain sensor is an emerging candidate for the fabrication of wearable electronic devices. The intrinsic properties of yarn, such as excellent lightweight, flexibility, stitchability, and especially its highly stretchable performance, stand out the yarn-based strain sensor from conventional rigid sensors in detection of human body motions. Recent advances in conductive materials and fabrication methods of yarn-based strain sensors are well reviewed and discussed in this work. Coating techniques including dip-coating, layer by layer assemble, and chemical deposition for deposition of conductive layer on elastic filament were first introduced, and fabrication technology to incorporate conductive components into elastic matrix via melt extrusion or wet spinning was reviewed afterwards. Especially, the recent advances of core–sheath/wrapping yarn strain sensor as-fabricated by traditional spinning technique were well summarized. Finally, promising perspectives and challenges together with key points in the development of yarn strain sensors were presented for future endeavor.

• Durable core-sheath electro-thermochromic CNT/cotton composite yarn was fabricated. • The yarn shows excellent mechanical properties and thermochromic performance. • The yarn exhibits excellent electrified heating performance with stability. • The yarn is durable against mechanical deformations, washing and chemicals. • The color of the yarn can be tuned by changing the applied current for design. A core-sheath nanocomposite yarn, with CNT/cotton composite yarn (CCY) as the core and nanofibrous polyurethane/temperature sensitive ink as the sheath, was fabricated to generate highly robust and durable electro-thermochromic performance. Due to its novel core-sheath nanocomposite structure, the as-fabricated electro-thermochromic composite yarn (ECCY) brought together the excellent mechanical properties and electrothermal properties together with electrochromic performance. The ECCY exhibited excellent electrified heating performance with stability even after 100 cycles of heating/cooling. Moreover, the ECCY showed excellent durability against repeated bending, twisting and stretching, washing and even soaking in acid and alkali solutions. The color of ECCY was successfully tuned via changing the applied current. In addition, the ECCY was used to design different patterns and to form a fabric, resulting in color conversion patterns/fabrics when applying/releasing a current. This work provides a novel strategy of developing electro-thermochromic composite yarn by designing the core-sheath micro-nano fibrous composite structure. The highly robust and durable performance of yarn will benefit its applications as wearable electronics. [ABSTRACT FROM AUTHOR]

With fiber-based wearable electronics being developed and widely used in various fields, the safety and durability of nanomaterials in fibrous system become big concerns due to the leakage of nanomaterials and possible failure in functionality. To date, it is still challenging to fabricate wearable strain sensors with sensitivity and durability. Herein, we report a simple strategy for large-scale fabrication of core-sheath nanocomposite yarn (CSCY) based wearable sensor with high sensitivity and superior durability. By dispersing aqueous CNT ink into braided composite yarns as the core (BYs-CNT) and electrospun polyurethane (PU) nanofibers as the sheath, a unique core-sheath micro-nanofibrous structure was fabricated to grant the yarn with extremely high sensing sensitivity (maximum GF up to 980), long-term stability and great durability (against washing and dilute hydrochloric acid). The as-developed CSCY strain sensor was demonstrated to monitor real-time subtle and vigorous human activities. The present work provides insights for developing reliable and stable, highly sensitive, flexible and durable wearable electronics with potential applications in different areas. Image 1 [ABSTRACT FROM AUTHOR]