Abstract: Respiration is an uninterrupted and important biomechanical behavior that occurs throughout human′s whole life, and is used as a diagnostic signal for a variety of diseases. With the development of wearable flexible sensors, new ideas are provided for the design of respiratory sensors that real-timely, non-invasively and comfortably monitor human respiratory motion. Compared to other types of sensors, triboelectric sensors have been widely adopted for self-powered respiration monitoring owing to their compelling features, such as decent biocompatibility, wearing comfort, low-cost, and high sensitivity to respiration activities in the aspect of low frequency and slight amplitude motion. Among them, yarn-based triboelectric sensors have attracted attention for their comfort and high flexible integration. However, most of the researches on triboelectric sensing yarns for respiration monitoring focus on structural design. How structural parameters affect their performance remains unclear, hindering the industrial production of triboelectric sensing yarns.
In order to meet the needs of daily long-term monitoring of human respiratory motion and large-scale production, a braided core-sheath triboelectric sensing yarn based on a single-electrode working mode was designed. According to its structure and process characteristics, the effects of the stretchable electrode twist and the braiding parameters of the outer braided layer on the performance of the sensing yarn are discussed. Firstly, six stretchable electrodes with different twists were prepared with the same structural parameters of the outer braided layer, and their tensile and electrical properties were tested. On this basis, the stretchable electrodes with the best performance were selected, and the sensing yarns with different braiding parameters were prepared by changing the number of braided yarns and the braiding angle. In order to satisfy the application in daily garments, the first step is to select the braiding parameters with stable structure and to meet the requirements of tensile properties. Then, investigating the effects of braiding parameters on the electrical property of the sensing yarns. In this paper, the effects of stretchable electrode yarn twist and braided layer parameters on the dielectric layer thickness, surface morphology and compression deformation of the braided core-sheath triboelectric sensing yarn are investigated. Moreover, correlation analysis was used to investigate the relationship between these factors and the electrical property of the sensing yarns. The results show that the elastic elongation of the sensing yarn gradually increases with the increase of stretchable electrode yarn twist, and the elastic recovery rate and short-circuit current decrease. For the braiding parameters, the elastic recovery rate of the sensing yarn is mainly affected by the braiding angle, and the electrical property by the multiple effects of the braiding parameters. The maximum short-circuit current is obtained when the number of braided yarns is 10 and the braiding angle is 45˚. In the contact-separation frequency range of 0.15~1.2 Hz, the short-circuit current of this sensing yarn increases with frequency and has good output stability during 2000 cycles of motion. The sensing yarn can respond to different respiratory states when it is worn on the human abdomen. The results show that the braided sensing yarn based on the knitting/twisting process can be used for human respiratory status monitoring, which is of great significance for the production of triboelectric respiratory monitoring sensors.
Generally, the effects of braided core-sheath yarn structural parameters on the performance of triboelectric sensing yarns are determined, and the application potential of this sensing yarns for human respiratory status monitoring is tested. The research results provide guide for the subsequent production of triboelectric respiratory monitoring sensors.

Key words: triboelectric sensing yarn, core-sheath braided yarn, structural parameter, respiratory motion monitoring, wearable

摘要： 为满足人体呼吸运动日常长时监测的需要，设计了一种可拉伸编织芯鞘型摩擦发电传感纱，探究拉伸电极包缠捻度和编织层等结构参数对传感纱性能的影响。结果显示：增加可拉伸电极包缠捻度，传感纱的弹性伸长率随之增大，弹性回复率和短路电流减小；传感纱弹性回复率主要受编织角影响，电学性能受编织参数多效应影响，当编织根数为10、编织角为45˚时获得最大的短路电流，达到(0.06±0.01) nA；该传感纱在0.15~1.2 Hz频率范围内的短路电流随频率加快而增大，并在2000次循环运动过程中有良好的输出稳定性；将传感纱佩戴在人体腹部时能对不同的呼吸状态产生响应。测试结果表明，该编织芯鞘型摩擦发电传感纱可用于人体呼吸状态监测，对摩擦电式呼吸监测传感器的生产具有一定的借鉴意义。

关键词: 摩擦发电传感纱, 芯鞘型编织纱, 结构参数, 呼吸运动监测, 可穿戴