Preparation And Application Of Strain Sensor Based On SEBS

Flexible strain sensor is a new type of electronic equipment.It has attracted much attention in various fields due to its flexibility,deformability,light weight,multiple functions,low cost and so on.At present,the research of strain sensor mainly devoted to the improvement of working range,sensitivity,response time,working range,and so on.In this paper,electrospun styrene ethylene butene styrene（SEBS）was used as the substrate,and multi wall carbon nanotubes（MWCNTs）with good conductivity and mechanical properties were used as the conductive fillers to prepare flexible strain sensor.In order to improve the adsorption fastness and content of MWCNTs on SEBS fiber,SEBS fiber was modified with dopamine（DA）（PDA@SEBS）,active groups were formed on the surface of SEBS to improve the combination of SEBS and MWCNTs.MWCNTs were deposited on the surface of SEBS by vacuum filtration,coating and ultrasound（PDA@SEBS/MWCNTs）.In order to obtain a strain sensor with high sensing performance,the process parameters（spinning solution concentration,spinning voltage and spinning distance）of electrospun SEBS substrate were explored firstly,and then MWCNTs were loaded on the substrate surface with two-dimensional structure SEBS（membrane）and one-dimensional structure SEBS（yarn）.So as to prepare two different types of strain sensors.Next,the influence of substrate structure on variable sensing performance was researched.It was found that the sensor with one-dimensional structure has high mechanical properties,higher sensitivity and faster response speed.Therefore,one-dimensional structure was selected as the structure of the sensor.However,the working range of the one-dimensional structure sensor is small.In order to further improve the sensing performance of the strain sensor,the structure of one-dimensional structure sensor was made into a tube,and finally a strain sensor with excellent performance was obtained.（1）The spinnability of SEBS substrate was explored.The effects of spinning solution concentration,spinning voltage and spinning distance on fiber morphology and diameter were explored.It was found that the concentration of spinning solution was 25 wt.%When,the fiber evenness was also relatively uniform;When the spinning voltage was 10 k V,the fiber diameter was small and the evenness was uniform;When the receiving distance is 15 cm,the spinning solution has more time to volatilize,long drawing time and smaller diameter.（2）SEBS fiber membrane（two-dimensional structure）was spun by electrospinning,and then crimped and twisted to form SEBS yarn（one-dimensional structure）.The substrate with two-dimensional structure and one-dimensional structure were modified by DA.The surface morphology characterization,EDS and XPS tests showed that DA successfully modified SEBS substrate.By the conductivity test of the material,the best preparation process was obtained.Comparing the mechanical and electromechanical properties of these two composites with different structures,it was found that the PDA@SEBS/MWCNTs with one-dimensional structure has higher stress(σ=20 MPa,ε_{at break}=1093.14%),higher sensitivity（1.13×10⁵）,smaller response time（30 ms）.In addition,the sensor with one-dimensional structure had excellent working stability.It exhibited excellent durability and repeatability during 15000 cycles at the strain of 0-50%.（3）Selecting SEBS with one-dimensional structure as the substrate,then the structure was designed into a tube,and its interior was coated with a layer of PDMS/MWCNTs solution.The surface was modified with DA and then coated with MWCNTs.Its working range can reach 306%and the sensitivity can reach 3.62×10⁵.It also had excellent working stability,excellent durability and repeatability during 15000 cycles at the strain of 0～50%.When it was applied to human activity monitoring,such as pulse beat,finger joint bending,elbow joint bending and knee joint bending,it can get good response.