Abstract:

Significance The good conductivity of the material is the basis of manufacturing smart wearable devices. Because textile material is light, soft and good in air permeability and shape adaptability, textile-based flexible smart wearable devices have been attracting extensive attention from researchers. In recent years, the researchers have been using various techniques to integrate conductive materials with textile materials for manufacturing textile flexible intelligent wearable device for real-time monitoring of human health, friction power generation, personal thermal management, energy storage and so on. Conductive yarn is one of textile intelligent wearable materials, in order to further study the low-resistance and multi-performance conductive yarn for smart wearable devices, textile yarns was taken as the object. The methods of preparing conductive yarn materials were reviewed in relation to spinning technology, coating, coating combined with spinning technology and electrostatic spinning technology and application of the conductive yarns in electromagnetic protection, sensing device, energy storage device, transmission and power supply, artificial muscle, electric heating and thermal management device in recent years.

Progress The advantages and disadvantages of conductive preparation methods are analyzed. Both conventional textile fibers and conductive fibers are spun into yarns by blending or wrapping using spinning technology, which can produce conductive yarns in batches. Besides, the yarn has excellent textile characteristics. However the conductive yarn is seldom used in resistance strain sensing. It is difficult for the mass production of conductive yarn prepared by coating technology, and the yarn has poor performance stability and poor weaving property, the preparation process is complicated and coating waste liquid may cause environmental pollution. Compared with the spinning technology, the method of preparing conductive yarn by coating is flexible, and the yarn has wide application. The auxiliary technology of electrostatic spinning nanofibers plays an important role in developing conductive yarns, and the conductive yarn with sheath-core structure prepared by electrostatic spinning technology overcomes some problems existing in conventional conductive coating. However, it is difficult to mass-produce conductive yarn by this method. The conductive yarn prepared by coating combined with spinning technology has good textile characteristics, but the conductive coating waste liquid of textile fiber materials may also cause environmental pollution.

Conclusion and Prospect The future research and development trends of conductive yarn materials are proposed by combining the performance stability and the environmental safety of conductive yarn in its life cycle. It is proposed that the stability and service life of sensing performance under large strain needs to be further improved for the conductive yarn prepared used for resistance strain sensor. The conductive yarn needs additional flame retardant function,elasticity function and flexibility for their use in electric heating products so as to improve the use safety and wearing comfort. It is necessary to further study the change law of yarn conductivity under special environmental conditions (such as wet environment, high temperature environment, low temperature environment), so as to develop textile-based flexible smart wearable devices to be used in different temperature and humidity environments. It is still a research focus to develop conductive yarn materials with textile characteristics and lower linear resistance and good linear resistance uniformity. In order to popularize the practical application of textile flexible intelligent wearable devices, a development goal is that the whole life cycle of manufacturing, using and discarding of the conductive yarn has no negative impact on human health and environment. It is necessary to further optimize the structure of conductive yarn and innovate the integration technology of conductive materials and textile fiber materials, and improve the durability, sensibility, weaving property, biodegradability and mass production capacity of the conductive yarn.

Key words: smart wearable device, conductive yarn, spinning technology, coating, electrostatic spinning