Preparation And Strain Response Behavior Of SEBS/MWCNTs Conductive Composite Fibers

Strain sensor is a kind of sensor that can convert mechanical deformation into electrical signal.It has important application value in the fields of human health monitoring,electronic skin and flexible robot.It has become an important direction of the development of intelligent devices in the future.In recent years,strain sensors based on flexible polymer composites have been widely studied,but it is still a difficult problem to obtain flexible strain sensors with large working range,high sensitivity and reliable stability.In this study,a conductive composite fiber based on poly（styrene-b-ethylene-ran-butylene-b-styrene）（SEBS）/multi wall carbon nanotubes（MWCNTs）was prepared by wet spinning,and its application as a flexible strain sensor in human activity monitoring was explored.（1）SEBS fiber was prepared by wet spinning method.The effect of SEBS spinning solution concentration on the surface morphology and mechanical properties of the fiber was explored.It was found that when the spinning concentration was 25%,the breaking strength was 50.46±1.44 MPa and the elongation at break was 1626.68±29.99%.The comprehensive properties of the fiber were excellent.（2）SEBS/MWCNTs conductive composite fiber was prepared by wet spinning with SEBS as matrix and MWCNTs as conductive filler.The effects of MWCNTs content and aspect ratio（L/D）on the morphology,structure,mechanical properties,electrical properties and electromechanical properties of SEBS/MWCNTs composite fibers were studied.The results show that for MWCNTs with the same aspect ratio,with the increase of MWCNTs content,the tensile strength and elongation at break of SEBS/MWCNTs conductive composite fiber decrease,and the conductivity and strain sensing range increase.When the MWCNTs content is the same,SEBS/MWCNTs composite fiber filled the MWCNTs with the lowest L/D（length 0.5-2μm/diameter 10-20 nm）has the highest tensile strength and elongation at break;While SEBS/MWCNTs composite fiber filled the MWCNTs with the maximum L/D（length 10-30μm/diameter10-20 nm）showed the highest conductivity,strain sensing range（0-506%）and sensitivity（58.274 at 0%-275%and 197.944 at 275%-506%）.（3）SEBS/MWCNTs composite fiber filled with MWCNTs with L/D（length 10-30μm/diameter 10-20 nm）was used to prepare the strain sensor,and its tensile and bending strain sensing properties were explored.The results show that SEBS/MWCNTs tensile strain sensor can respond to tensile strain as low as 1.0%and as high as 700%.The response speed is about 133 ms,the tensile strain recovery response time is 33510 ms,and it maintains good repeatability and stability in 2500 tensile release cycles.The results of bending strain sensing show that with the decrease of chord length,the relative resistance of SEBS/MWCNTs bending sensor increases linearly,showing a stable bending response,and the bending sensitivity is 0.093 rad^-1.（4）The application of SEBS/MWCNTs sensor in human activity monitoring is explored.The results show that the sensor based on SEBS/MWCNTs can well monitor the small and large movements of human elbow,back of hand,neck,fingers,knees and so on.SEBS/MWCNTs fiber can bear the tension applied in the knitting process,weave into knitted fabric,and has the ability to monitor human activities.