transistors, [5,6] flexible displays, [7,8] energy devices, [9][10][11] mechanical sensors, [12][13][14][15][16] etc. Stretchable conductive fibrous composites as a vital part of stretchable devices are very promising for wearable electronics in the near future as they can be easily manufactured in abundance and facilely knitted into garments. [17,18] Currently, stretchable fibers are requested to possess high sensitivity and stretchability to meet the applications such as health monitoring, and e-skins. [19,20] Here, the main arguments accounting for the properties of strain sensors are sensitivity, stretchability, and stability.Fibrous strain sensors have gained great development on the tuning of microstructure and sensing properties, recently. [21] Zhang et al. prepared a carbonized silk fiber as the main component of a wearable and ultra-stretchable strain sensor (500% workable strain). [22] Compared with the natural stretchable fibers, wet-spinning is a universal method for industrial manufacture of serial fibers for many decades, providing a general strategy for producing high performance fibers. [23] Previously, Tang et al. constructed an Ecoflex/multi-walled carbon nanotubes (MWCNTs) coresheath fiber, which exhibited high stretchability (above 300% strain), good stability (over 10 000 cycles), low hysteresis, and favorable hydrophobicity. [20] Lee et al. fabricated a thermoplastic As a crucial element for wearable devices, high-performance strain sensors have been spotlighted as an ideal strategy to develop machine-human interfaces and healthcare systems. It still remains a huge challenge to construct flexible strain sensors with equational response in a broad range. Herein, highly stretchable multi-walled carbon nanotubes (MWCNTs)-decorated thermoplastic polyurethane (TPU) fibers with a porous microstructure are produced through a scalable and facile strategy by wet-spinning and ultrasonication. The fiber is composed of pure TPU fibers with MWCNTs decorated on the surface. The porous fiber is then assembled as a strain sensor. Interestingly, the effective MWCNTs distribution on the TPU fiber enables exponential sensing over the whole strain range. The sensor possesses a high gauge factor (GF, 102 at 300% strain), very large workable sensing range (300% strain), excellent durability (10 000 cycles), light weight (0.85 g cm −3 ), and fast response (200 ms). The as-prepared strain sensor exhibits excellent insensitive properties toward buckling, torsion, temperature, and humidity stimuli. Based on the high sensing performance, the fiber-shaped strain sensor detects human movements precisely by directly attaching to skin or embedding in garments, demonstrating huge potential in human-machine interfaces, health monitoring application, etc.Recently, stretchable devices have attracted lots of researchers on the basis of their significant impact and promotion in various fields, including wearable electronics, [1,2] actuators, [3,4] Adv.
