基于长银纳米线的应变传感与电热双功能包芯纱的制备及其性能

Strain⁃sensing and electrothermal difunctional core⁃spun yarn based on long silver nanowires

针对柔性应变传感器目前存在的灵敏度低、应变范围窄、反复拉伸后性能不稳定、功能单一等问题,采用预拉伸浸渍法以商用弹性包芯纱为柔性基体、水性聚氨酯(WPU)为分散剂和黏合剂、长银纳米线(AgNWs)为导电材料制备了具有应变传感与电热双功能的包芯纱。借助X射线衍射仪、扫描电子显微镜、数字万用表、万能试验机、菲力尔热像仪对AgNWs的晶体结构及双功能包芯纱的形貌结构、电学性能、力学性能、电热性能进行表征和分析。结果表明:当弹性包芯纱的预拉伸应变量为30%且AgNWs的负载量为15%时,制备的双功能包芯纱的鞘层棉纤维上形成了致密的AgNWs导电网络;在宽应变范围(0%~70%)内呈现明显的应变传感性能,灵敏度最高可达12.8,反复拉伸后的应变传感和力学性能稳定;在手指的运动监测中,手指发生小幅度和大幅度的弯曲变化,双功能包芯纱均能做出相应的电信号响应,体现了高灵敏度;5 V电压下,静态拉伸范围为0%~50%时,双功能包芯纱的温度变化范围为49.8~65.7℃,体现了优异的电热性能。

Objective Strain sensing is one of the important functions of a smart fabric,which can transform the external stress(or strain)into visible electrical signals and monitor the physiological and motion characteristics of human body.At present,the flexible strain sensor has some problems,such as low sensitivity,small strain range and unstable performance after multiple stretching.Method AgNO3 was used as silver source material,NaCl and NaBr as nucleating agent,polyvinylpyrrolidone as ending agent,ethylene glycol as solvent and reducing agent in the reaction to prepare long silver nanowires.The commercial elastic core-spun yarn with single spandex fiber as inner layer,polyester fiber as sheath as flexible matrix,water-borne polyurethane(WPU)as dispersing agent and binder,and long silver nanowires(AgNWs)as conductive material was prepared by pre-stretch impregnation method with dual functions of strain sensing and electric heating.Results AgNWs prepared by polyol method have uniform morphology,uniform dispersion,length up to 155μm,diameter only 146 nm,and aspect ratio up to 1000(Fig.1(b)).When the mass ratio of AgNWs/WPU is 2∶1 and the core-spun yarn is pre-stretched by 30%,AgNWs can adhere to a single cotton fiber to form a stable and dense AgNWs conductive network(Fig.2).When the load of AgNWs was 15%,the percolation threshold is reached,and the conductivity value became 466 S/m(Fig.3(a)).During stretching,the conductive network formed by AgNWs was deformed together with the inner spandex fiber,and the core-spun yarn exhibited a Gauge factor value of 12.7 at the highest within a wide strain range of 0%-70%.When the core-spun yarn was drawn,the stress gradually increases with the deformation.When the tensile length reached 25 mm,i.e.,the elongation of 250%,the polyester fiber began to break.The cyclic tensile mechanical properties of core-spun yarns under 10%strain were further tested(Fig.5(b)).The deformation of core-spun yarns could be quickly recovered after repeated stretching for at least 10 times,showing good mechanical stability.At 5 V voltage,when the static tensile range was increased from 0%to 50%,the conductive network structure formed by AgNWs is destroyed,resulting in a continuous decrease in its electrical conductivity.The maximum temperature range is 49.8-65.7℃,which reflects excellent electrothermal performance.Conclusion In this paper,a strain sensing electrothermal core-spun yarn with elastic core-spun yarn as flexible substrate,WPU as dispersing agent and binder,and AgNWs as conductive material was prepared by the method of multiple impregnation of 30%of pre-drawn elastic core-spun yarn.The results show that when AgNWs/WPU(mass ratio of 2∶1)mixed emulsion is prepared,AgNWs can be uniformly dispersed and AgNWs/WPU film is formed only on the surface of a single cotton fiber.The cotton fiber is completely dispersed by using the 30%impregnation method of pre-drawn core-spun yarn.Dense AgNWs conductive network is formed on the single cotton fiber of the yarn sheath layer,and the electrical conductivity reaches the extreme value.When the load of AgNWs is 15%,the strain range of AgNWs core-spun yarn is wide(0%-70%),and the sensitivity is up to 12.8.After repeated stretching,the strain sensing and mechanical properties of AgNWs yarn are stable.At 5 V voltage,when the static tensile range is 0%-50%,the maximum temperature variation range is 49.8-65.7℃,which reflects the excellent electric heating performance.The AgNWs strain sensing electrothermal cored yarn made by pre-stretch impregnation is expected to be an ideal method for large-scale production of wearable smart devices.