Flexible Strain Sensor of Core–Shell Composite Structure Based on Polyamide/Spandex Wrapped Yarn

The flexible strain sensors based on wrapped yarn have attracted wide attention in the field of smart textiles due to their excellent sensitivity and wide detection range. In this article, the polyamide/spandex wrapped yarn was prepared by using a fancy twisting machine, and the polyamide/spandex wrapped yarn flexible strain sensor was prepared by in situ polymerization and dip-coating process. Through studying the influence of process parameters on the properties of the yarn and the performance of the sensor, it was found that the wrapped yarns with a twist of 2500 T/m have a better performance. When the concentration of Py is 0.08% and the concentration of MWCNT is 9%, the sensor shows a maximum influence factor of 2.44 when the stretching range is less than 175%. Its resistance change rate is not affected by the stretching frequency and has outstanding repetition stability and washing resistance. The results show that the proposed strain sensor shows great potential for healthcare-related applications such as disease diagnosis, preventive healthcare, and rehabilitation care in the fields of health monitoring and smart textiles.