Study on factors influencing the durability of conductive yarns and flexible sensors
The rapid development of wearable smart textiles has led to in-depth research on conductive yarns and flexible sensors.The most common conductive yarn on the market is metal-based conductive yarn.Such a yarn and the functional fabrics thereof have excellent electrical conductivity and play an important role in wearable applications.However,various external factors may affect its structure and electrical conductivity in the actual use process.The durability is an important indicator for evaluating such smart textiles.In this paper,to explore the factors affecting the durability of conductive yarns and flexible sensors,five typical metal conductive yams were selected.Firstly,the effects of washing times,heat setting temperature,and oxidation time on the resistance of conductive yams were analyzed.The influence of these three factors on the durability of each conductive yarn was expressed by analyzing the change in the resistance of each sample compared with the original resistance at different lengths.Then,considering the difficulty of weaving each yarn and the requirements of fabric performance,77 dtex silver-plated conductive yarn was selected to weave flexible sensors of different sizes.It was subjected to 30 washing tests,and the active navy blue BF-DB was used for dyeing treatment.By comparing with the original sample,the influence of washing and dyeing on the performance of the sensor was analyzed by the change of equivalent resistance under different horizontal and vertical lines of the flexible sensor.The results show that the three factors have the greatest influence on the electrical conductivity of copper fibers,while the durability is the worst.The copper wire and stainless steel conductive yam,as a single component of metal filaments,have the smallest resistance change rate and stable electrical conductivity after multiple washing,heat drying under different temperatures and treatment of different oxidation times,indicating that they have good washing resistance,heat resistance and oxidation resistance.The mechanical force of washing will cause damage to the conductive layer on the surface of the metal-coated yam.When the coating is defective,with the increase in washing times,the resistance of two silver-plated conductive yarns with different densities increases to a certain extent.The thermal shrinkage of nylon-based silver-plated yams occurs after the heat setting temperature increases.When the yarn is shortened,the contact degree of each particle in the conductive layer increases,so the resistance decreases and the heat resistance is satisfactory.After 20 days of oxidation treatment,the conductivity is significantly weakened,so the oxidation resistance of the silver-plated conductive yarns is poor.The surface morphology of the flexible sensor woven by the 77 dtex silver-plated conductive yarn changes after multiple washing treatments,but its equivalent resistance value decreases due to the reduction of vertical and horizontal dimensions,so its washing resistance is satisfactory.When dyed with reactive dyes,the flexible sensor is in a high-temperature and high-humidity environment.The coil becomes larger after the fiber expands,and the fiber shrinks after cooling to make its size smaller.The equivalent resistance value is reduced to a certain extent,and it can still maintain stable conductivity,indicating that it has excellent dyeing resistance.The experimental results of this paper can provide reference for subsequent research on the factors influencing the durability of conductive materials,and inspiration for the selection of suitable conductive yarns to develop more excellent and stable wearable sensors.
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