Based On The Flexible Sensor Of Conductive Fiber Knitted Fabric Respiratory Monitoring Research

In recent years the rapid development of mobile Internet, makes the wearable devices become hot. Industry supporters indicate that this is a revolution bound to come, it will be all over in people’s work and life, fitness and health and other fields. Smart textiles are still a very new field as a wearable device, almost all the researches and developments are still in a preliminary exploration stage. In both software and hardware aspects, intelligence textiles are still a big room to improve. With the continuous improvement of living standards, portable respiratory monitoring equipment becomes the first selection of prevention, clinical, and treatment of related diseases. Conductive fabric soft sensor as a representative of the smart textiles has been widely concerned, some research institutes lining the conductive fibre into the clothes in order to produce knitted flexible sensors, use pressure resistance change of sensors to reaction breathing, reach the respiratory monitor. But also in a basic experimental exploration stage, such as reliability, stability and durability of the knitted flexible sensor has not reached the commercial standard; and the effect of internal and external causes for using knitted flexible sensors did not do a detailed theoretical study.This paper started research at the microstructure and electrical conductivity of conductive fiber s, explor ing weaving and electric conductivity of knitted fabric which based on conductive fibers, etc. Studied the washing performance, heat setting conditions of knitted flexible sensor, and use the sensor to monitor respiratory, the concrete research contents are as follows:1. By using SEM and EDS to analysis the microstructure of several kinds conductive fibers, testing the basic performance of conductive fibers and focus on analyzing the electric conductivity.2. Choose the conductive fibers knit weft plain, full rib on computer flat knitting machine, a total of 10 kinds of flexible sensor samples. To discuss the possibility of weaving, prepare for further research.3. In addition to the basic performance test of the fabric samples, this part focus on studying its conductivity. Analysis the equivalent resistance change law of those different samples and tissues, the same longitudinal with different number of the row.4. Explore two external impact factors of knitted flexible sensor equivalent resistance: washing times and heat setting process. Observe the change of fabric size and equivalent resistance after washing 5~30 times and 40~140 ℃ heat setting, draw a conclusion according to the change rule of each sample.5. Select volunteers using knitted flexible sensors for breathing test. Text the breathing rate of 5 minutes quiet breathing and 1 minute breathing after jogging 5 minutes. Compare the breathing rate captured by the DM3068 and count by the researchers, to confirm the reliability and stability of the sample.Through this series experiments and researches, the results are as follows: silver plating fiber is based on the nylon filaments, it was twisted by 24 or 36 monofilaments; Copper fiber created by copper sulfide particles deposit on the surface, monofilament section is polygon; Stainless steel wire and copper wire are made by high-tech treatment. The different yarn strength are as follows: 100 D silver-plated fiber > copper fiber > 70 D silver-plated fiber > stainless steel microfilament > copper wire. 5 conductive fibers all possess higher linear fitting, and lowest resistivity can reach 1.4954·10-5 Ω·cm, the electrical conductivity is very well. Through mixing the five electrical conductivity fiber, inc luding s ilver-plating yarn, stainless steel wire, copper wire and copper fiber, with viscose and nylon/spandex core-spun elastic yarn, weft-knitted flexible sensors are knitted on the computerized flat knitting machine, it can be see that the conducting fibers are knittable. After weaving the average total density is nearly 1350 coil/25cm2; average permeability of the samples is about 700 L/m2·s, despite the embedded weave conductive fiber, but little inf luence on the gas permeability. Based on the resistance hexagonal model, the 40·40 coil equivalent circuit contains 3160 current loops. At the same time by using KVL and loop current method to calculate the circuit equations, and through using Matlab to calculate the equivalent resistance of 40·40; though the measuring data of local resistance, it is almost in conformity with the resistance hexagon model, which is apply to the five kinds of conductive fiber and be better used in the theoretical analysis. with the increase of number of washing, the longitudinal size of silver-plated knitted fabric decreased after the lateral size decreased, then the equivalent resistance of conductive knitted fabric decrease first and then increase to stable. The resistance of stainless steel wire and copper wire amplif ied. We can chose 100℃ or 120℃ as the setting temperature to more reasonable and stable Resistance value. Observing the equivalent resistance of 40×40 weft-knitted flexible sensors, it changed very small of the times of washing and heat setting temperature, it can be see that weft-knitted flexible sensors are laundering durability and thermal stability. Through compare the breathing rate captured by the DM3068 and count by the researchers, effectively confirmed that based on the flexible sensor of conductive fiber knitted fabric respiratory monitoring is reliability and stability.The experiment analys is and researches of this paper are provide theoretical reference basis for the follow-up research, and have more important practical signif icance meaning to the conductive fiber knitted fabric.