Preparation And Performance Of Stretchable Temperature Sensing Hybrid Electronic Yarn

Body temperature is an important indicator of human health monitoring,which can reflect the key information of human life activities and plays an important role in daily monitoring and clinical medicine.Compared with the traditional temperature monitors,the temperature sensing yarns have the advantages of softness,sensitivity and light,which have attracted more and more attention.What’s more,the temperature sensing hybrid electronic yarn is a kind of electronic yarn with good concealment and comfort,which combines the traditional rigid and small temperature sensing element with the flexible circuit,and overcomes the defects of material separation and positioning measurement,suitable for measuring skin surface temperature.At present,the basic preparation process and performance of electronic temperature sensing yarn have been studied,but the relationship between yarn material,structure and sensing performance has not been studied,nor has the heat transfer model of sensing yarn been established during temperature monitoring.Meanwhile,the elongation of yarn is low,and the sensing part is prone to tensile fracture failure,which cannot fully satisfy the textile characteristics requirements of yarn.In view of the problems such as low elongation of hybrid electronic yarn and easy failure of sensing area,this topic uses spandex as core yarn and copper enameled wire as covered yarn,connects thermistor and wire by interconnection technology,and makes stretchable temperature sensing hybrid electronic yarn by encapsulation and coating method,then discusses the influence of preparation technology on the sensing performance of yarn.According to the existing heat transfer theory,the theoretical model of electronic yarn is built to illustrate the influence of material and structure on sensing performance.The main research contents and conclusions are as follows:(1)Using the copper wire spiral structure to overcome the low stretchability of hybrid electronic yarn and the corresponding hybrid electronic interconnect technology,then choose the optimal interconnect technology and determine bending fatigue behavior at interconnect interface.In order to realize the helical structure of copper wire and be compatible with the traditional textile process,this paper proposes to use the wrapping method to prepare the stretching composite wire,that is,the spandex as the core yarn and copper enameled wire as the covered yarn,which obtains the composite wire by spiral winding.The influence of the resistance and ambient temperature of the composite wire is evaluated.Then,the interconnect method of mixed electrons is studied,and the two component conductive adhesive,melt welding and heat pressure welding are used to interconnect the thermistors and wires to fabricate three kinds of hybrid electronic sensing yarns.Finally,the sensitivity,maximum hysteresis error and response time of these three sensing yarns were tested,and the influence of bending on the contact resistance of interconnect interface was evaluated.The results show that the resistance of the composite wire is not sensitive to the ambient temperature.When the temperature increases by 1 ℃,the change of the resistance of the wire only accounts for0.024% of the change resistance of the sensing yarn,that is,the composite wire does not affect the change of the resistance and temperature of the sensing yarn;three kinds of interconnecting temperature sensing yarns all have good sensing performance,and can be used to measure the surface temperature of human skin;by further comparing the appearance and sensing performance of three kinds of sensing yarns,it is determined that heat pressing welding is the best interconnection technology for temperature sensing hybrid electronic yarns.At the same time,according to the bending fatigue test results,it can be seen that the thermal pressure interconnection sensing part is less affected by bending.Thus,it is determined that the traditional wrapped yarn technology and hot press interconnect technology are suitable for the preparation of hybrid electronic sensing yarn.(2)Studying the stable packaging process of the interconnection structure on the temperature sensing hybrid electronic yarn and its influence on the sensing performance.It is found that the packaging structure affects the sensing response time of the thermistor.The interconnect structure formed by thermistor and composite wire through heat pressure interconnection has low connection strength,poor insulation and water resistance in application,which will reduce the service life of temperature sensing yarn.Therefore,the packaging technology of the interconnect structure is studied here.The transparent silicone tube is used as the packaging mold and PUA,PDMS and Ecoflex are selected as the packaging materials.Then,the curing and demoulding are carried out by UV curing or thermal curing.Finally,the apparent morphology,sensitivity,maximum hysteresis error and response time of three kinds of packaging sensing yards are observed and tested to explore the impact of packaging technology on the performance of temperature sensing yards.The results show that the thermistor is easily mislocated in the packaging process,and the contact distance between the thermistor and the heating platform increases;the edge of the packaging structure is easily affected by tension and friction during demoulding;the packaging structure has no significant effect on the sensitivity and hysteresis of the sensing yarn,but has the greatest effect on the sensing response time.After heat shrink packaging,the packaging diameter of the sensing unit is smaller than that of the mold packaging,the distance between the thermistor and the measured surface is shortened,and the sensing performance of yarn is improved.Hence,this paper determines that the heat shrink packaging technology is suitable for protecting the interconnect structure of temperature sensing hybrid electronic yarn.(3)Researching the enveloping process of the temperature sensing hybrid electronic yarn and its influence on the sensing performance and cyclic tensile resistance.It is found that the coating structure affects the response time and response hysteresis of the temperature sensor,and the influence mechanism of the enveloping structure is defined by the classical heat transfer theory.In order to improve the softness and comfort of the yarn,the traditional spinning technology is used to cover the hybrid electronic sensing yarn by wrapping and braid.The influences of different wrapping layers and braid angles on the diameter of the sensing area and yarn elongation are investigated.Then,the parameters of the two coating processes are compared and determined,and the transmission and cyclic tensile properties of the two electronic yarns are tested.Moreover,according to the existing heat transfer model,the heat transfer process of the hybrid electronic yarn is determined,and the relationship between the sensing performance and the packaging and coating structure is analyzed.The results show that the number of wrapping layers has a greater effect on the yarn elongation,and the yarn elongation decreases with the increase of the number of wrapping layers;the braiding angle has a significant effect on the diameter of the sensing area and the elongation of the yarn,both of which decrease with the decrease of the braiding angle;the coating technology has no significant effect on the sensitivity of the sensing yarn,but has influence on the hysteresis and response time;the coating method has no significant influence on the sensitivity and hysteresis,but has the greatest influence on the response time,and the influence on the sensing performance of the two coated sensing yarns is small after cyclic stretching;the higher the thermal conductivity and volume fraction of the packaging and coating materials,the better the sensing performance of the temperature sensing hybrid electronic yarn.Therefore,this paper determines that the traditional spinning coating technology is suitable for the preparation of temperature sensing hybrid electronic yarn.(4)Verifying the feasibility of applying temperature sensing hybrid electronic yarn to human body surface temperature monitoring and defining the sensing relationship of electronic yarn and good performance of real-time temperature monitoring.In order to determine the relationship between resistance and temperature of the hybrid electronic sensing yarn,Steinhart-Hart equation is used to calibrate.In addition,the woven sensing yarn is made into a temperature sensitive wrist guard,and the resistance response of the wrist guard wear on the wrist and at room temperature is tested.The results show that the resistance values obtained in different environmental tests are different;the maximum temperature difference between the test temperature and the actual temperature after conversion is 0.3 ℃,which is less than the temperature test accuracy of diabetic foot ulcer and could monitor the surface skin temperature.Based on the above discussion and analysis,this paper prepares a kind of stretchable hybrid electronic sensing yarn suitable for real-time monitoring of human body surface temperature,and proposes the spiral structure and interconnect,encapsulation and coating technology compatible with traditional textile technology,which satisfies the stretchability in practical application,basically maintains the flexibility and comfort,and realizes the concealment of electronic components.In addition,this electronic yarn can give new tools for temperature monitoring in clinical medicine and sports,and also can provide theoretical guidance for the optimization of temperature sensing yarn and the industrial production.