Resistive network model of the weft-knitted strain sensor with the plating stitch-Part 2: Resistive network model during the elongation along course direction

Abstract

Based on the static resistive network investigated in Part 1 of this series, the resistive network model of the weft-knitted strain sensor with the plating stitch is explored under the elongation along course direction, and it changes with the conductive loops’ configuration and contact situation. Since the voltage is applied at both ends of the course, under a specific stretching state, the resistive network model can be reduced to a resistance network connected in series in the course direction and parallel in the wale direction, which determines that the sensor’s equivalent resistance increases with the growth of the conductive wale number, and decreases with the raise of the conductive course number. Through experiment and model calculation, it can be obtained that in the initial stage of stretching, the contact resistances’ changes are the main factors affecting the mechanical–electrical performance of the sensor. Then as the sensor is further stretched, the length-related resistances of the conductive yarn segments begin to affect the sensor’s properties due to yarns’ slippage and self-elongation. In addition, the weft jacquard plating technology makes the strain of the sensor reach about 32% before yarns’ slippage and self-elongation, which expands the sensor’s measurable strain range, and avoids irreversible deformation of the sensor after repeated use in this range. It can be verified that the sensor’s gauge factor can be improved by reducing the conductive course number and increasing the conductive wale number. It should be noted that the ground yarn will reduce the gauge factor of the sensor during stretching, so it is necessary to choose a ground yarn with a smaller fineness than the conductive face yarn and good elasticity in practical.

Design of Electro-Thermal Glove with Sensor Function for Raynaud’s Phenomenon Patients

“…A single loop knitted structure contains three parts, termed the head, side limbs, and sinker loop, and different knitted structures have a different loop assembly and contact [ 30 , 31 , 32 ]. Hence, the length of the loop and the contact between each loop can be the main contributor affecting the resistance change and stable sensing ability of the conductive knitted fabric [ 25 , 33 ]. The change in resistance of the four different sample structures was examined to evaluate the sensitivity and stability under minimal tensile elongation.…”

Dynamic Equivalent Resistance Model of Knitted Strain Sensor under In-Plane and Three-Dimensional Surfaces Elongation

“… When the force is stretched until loops are separated from each other, the resistance is constant at the maximum value. When the fabric continues to be stressed, according to the contact resistance [ 23 , 24 ] theory as given in Equation (2), the contact pressure between the loops increases and the resistance decreases. where ( ), ( ), , and ( ) are the electrical resistivity, material hardness, number of contact points, and contact pressure between the conductive yarn, respectively.…”

“…(2) When the force is stretched until loops are separated from each other, the resistance is constant at the maximum value. (3) When the fabric continues to be stressed, according to the contact resistance [23,24] theory as given in Equation ( 2), the contact pressure between the loops increases and the resistance decreases.…”

“…Most textile-based sensors are based on the change in resistance [ 13 , 14 , 15 , 16 ], which can be used to predict fabric deformation and mechanical properties [ 17 , 18 , 19 ]. Therefore, there is a huge need to study the basic electro-mechanical properties of conductive knitted fabric, and develop the application of knitted strain sensors [ 20 , 21 , 22 , 23 , 24 ].…”

The mechanical and electrical properties of flexible strain sensors based on carbonized cotton knitted fabric

“…Many types of research have recently reported specially treated conductive textiles as conductive elements of the flexible strain sensor. 23–26 Some attempts employed various fabrication methods, such as weaving, knitting, printing and dip-coating, by arranging the substrate and conductive materials. 27 Zhang and Long 23,28 and Wang et al.…”