Research On Flexible And Wide-range Strain Sensing Of Carbon Nanotube Fiber

Carbon nanotube fiber(CNTF)is a continuous fibrous material made of carbon nanotubes(CNTs)with a micron diameter.Due to the excellent characteristics,such as high strength,low density,good flexibility,self-supporting and high conductivity,CNTF can be widely used in structural materials,sensitive materials and batteries,super capacitors,drivers and other fields.Based on the piezoresistive effect of carbon nanotube fiber,this paper focused on the strain sensing characteristics,and explored the application in smart wearable devices.Firstly,the conductive principle of the carbon nanotube fiber was studied by analyzing its micro structures.On this basis,in order to develop a flexible wide-range sensor,a twisted carbon nanotube fiber(TCNTF)was proposed,and the deformation of CNTF and the variation of its resistance during stretching process were analyzed.Through the research,the mechanism of the piezoresistive effect of CNTF was clarified,which provides theoretical support for the research of sensing properties and application of CNTF in strain sensing field.Secondly,twisted carbon nanotube fiber was developed by twisting carbon nanotube fiber,and the processing technology of CNTF composites and TCNTF composites were introduced.Experiments were conducted to study the piezoresistive effect of CNTF and TCNTF.The experimental results showed that the resistance of TCNTF during stretching process can be divided into three stages:elastic stage,plastic stage and fracture stage.The strain range of each stage was obtained,and the reason was analyzed.The experimental results proved the theoretical results of the piezoresistive effect.Thirdly,the sensing characteristics of twisted carbon nanotube fibers were studied.Experiments were carried out on the volt-ampere characteristics,the repeatability,the measuring range and the creep properties of TCNTF,which proved that TCNTF was feasible in strain sensing.Moreover,the optimal range of the TCNTF was determined.On this basis,further experiments were conducted to compare TCNTF's sensing properties with carbon fibers'.The results clarified the differences of sensing characteristics and applications between TCNTF and carbon fibers.Finally,experiments on applications of twisted carbon nanotube fiber were carried out.The feasibility of twisted carbon nanotube fiber was proved by the accuracy experiment.On this basis,we explored the application of TCNTF in wearable devices.Fingers motion detection tests and respiration rate measurement test showed that the TCNTF had good flexibility,good ductility and a larger strain range.Therefore,TCNTF was suitable for the wearable device applications,and had large prospects in this field.Based on the piezoresistive effect,good flexibility and ductility of twsited carbon nanotube fiber,the paper probed into the flexible and wide-range sensing technology.The research results provided a new idea and method for self-monitoring of stress and strain in nanostructures and functional composites.