Design of Helically Double-Leveled Gaps for Stretchable Fiber Strain Sensor with Ultralow Detection Limit, Broad...

Flexible strain sensors have attracted extensive attention in electronic skins and health monitoring systems. To date, it remains a great challenge for the development of a multifunctional strain sensor with simultaneous ultralow detection limit, broad sensing range, and high repeatability. In this paper, we report a new carbon nanotube/flexible fiber-shaped strain sensor. The fiber substrate has a novel microstructure where a highly elastic rubber fiber core is tightly wound by a continuous spring-like polypropylene fiber as the shell. Our sensor offers combined sensing performances of ultralow detection limit of 0.01% strain, wide sensing range of 200% strain, and high repeatability of 20 000 cycles by designing double-leveled helical gaps. This strain sensor shows a rapid response time of 70 ms under both stretching and releasing. In addition, it is available for a variety of other deformations such as bending and torsion. Due to the unique fiber structure, it can extend the torsion detection range to 1000 rad m^-1. On the basis of the superior sensing performances, our sensor demonstrates to efficiently work for both subtle physiological activities and vigorous human motions. This work provides a general and effective strategy for designing smart wearable devices with high performance.