关键词: SBS, 导电纤维, 高弹性, 碳纳米管, 湿法纺丝, 应变传感

Abstract: In recent years, with the progress of science and technology, wearable electronic products have been used more and more in portable medical monitoring devices, electronic skin, portable electronic devices and other fields. Strain sensors, as the core components of intelligent wearable devices, have received extensive attention. Traditional strain sensors based on metal and semiconductor materials have poor extensibility and unstable conductivity, which limits their use in the intelligent wearable field. Conductive polymer composite fiber, with the advantages of being easy to bend, can be attached to skin, and can be braided, so its application in strain sensors has been rapidly developed.
In order to prepare flexible strain sensors with good tensile property, the SBS/CNTs elastic conductive composite fiber was prepared by wet spinning, using polystyrene butadiene styrene triblock thermoplastic elastomer (SBS) with good tensile property as the matrix and carbon nanotubes (CNTs) with high conductivity, good mechanical properties and flexibility as the conductive filler. The influence of the mass ratio of CNTs with two different aspect ratios on the morphology, mechanical properties, electrical conductivity and tensile resistance response of SBS/CNTs elastic conductive composite fibers were studied. The results showed that the cross section of SBS/CNTs elastic conductive composite fiber was bean-shaped, and porous structure appeared near the fiber center due to solvent exchange during wet spinning. When the ratio of long CNTs (10~30 µm) to short CNTs (0.5~2.0 µm) was 4:1, the conductivity of SBS/CNTs elastic conductive composite fiber was the highest (0.04065 S/m). The maximum inductive strain of the strain sensor based on this fiber was 70.2%, and it had good sensitivity and stability. The strain sensor based on SBS/CNTs elastic conductive composite fiber showed good response behavior in monitoring various human body activities including the knee, wrist, finger and elbow.
Although the conductive polymer composite fiber based strain sensor has more excellent tensile properties, there are still some problems to be solved. For example, carbon nanotubes and other nano sized conductive fillers are easy to agglomerate in the polymer matrix. How to improve their dispersion by surface modification or adding compatibilizers, and how to improve their interfacial bonding with the polymer matrix are problems to be solved. In addition, the performance of the fiber is affected not only by the material performance, but also by the spinning process parameters. Through the optimization of the spinning process, it is expected to prepare conductive composite fibers with better performance. The solution of these problems will better promote the practical application of flexible strain sensors.

Key words: SBS, conductive fiber, high elasticity, carbon nanotubes, wet spinning, strain sensing