Performance Evaluation of Embroidered Honeycomb Resistive Textile Strain Sensors

The rise of soft wearable sensors has opened the door for less obtrusive sensing during upper limb rehabilitation. Many studies have proposed different methods of fabrication for these sensors, but the simplest ones include those made using knitting, stitching, or embroidering to create resistive strain sensors. However, the reliability of these sensors is influenced by the amount of contact points of the conductive thread used at any given time. These contact points can suffer from deformations due to forces applied during each stretching cycle, which can affect the sensor response and produce erroneous measurements. These issues can be avoided by creating embroidered sensors with patterns that do not affect the contact points of the stitches. Still, forces applied directly to the conductive thread can cause irreparable damage to the sensor. Therefore, in this study a novel embroidered strain sensor is created using a honeycomb pattern. This pattern has two main purposes: a distribution of the axial forces across the walls of the pattern to protect the conductive thread; and the addition of stretchiness to the embroidered sensor. Sensors created using this pattern were embroidered onto an elastic band and then attached to a strain divider system to increase the stretchability of the sensor further. After 50 stretching cycles, sensors showed good linearity, an average gauge factor of 0.24, an average hysteresis of 36.85% and a 55.56% working range. These results show that the proposed sensor is robust to thread damages, thus making it a viable alternative for strain sensing applications.