A Novel Strategy to Control the Effective Strain Range for Yarn-Based Resistive Strain Sensor by Braiding Technology

Yarn-based strain sensors are breaking the boundaries between flexible wearable electronics and smart clothing due to their unique functionality and weavability. The sensing strain range of most flexible strain sensors is less than its tensile range, and it is easy to exceed its sensing strain range during use, resulting in unstable performance and failure of the sensor. An effective-strain-range-controllable and wear-resistant yarn strain sensor was developed with a core-sheath braided structure with the sensing yarn as the core and the braided yarn as the shell. This design strain allows for control over the effective strain range by adjusting the core sensing yarn’s pre-stretch ratio and the outer braided layer’s structure. This prevents damage to the conductive network and sensor failure caused by excessive stretching during use. The sensitivity, linear sensing range, and hysteresis of the braided strain sensors are effectively adjusted by changing the braiding yarns’ braiding angle and the sensing yarn’s pre-stretch ratio. Additionally, the sensors’ appearance and texture can be customized by changing the colour and material of the braiding yarns, allowing these sensors to integrate seamlessly with the garment and enhance their aesthetics. Furthermore, when combined with elastic fabric bands, these sensors can be attached to various parts of the human body to monitor physiological information, such as respiration and movement. The braided structure design presents a versatile strategy that could be applied to other types of strain sensors, achieving stability, durability, and aesthetics simultaneously.