Preparation Of Sandwich-type Capacitance Sensor With Large Strain And Its Application In Motion Detection

In recent years,with the rapid development of flexible strain sensors in the fields of human motion detection,electronic skin and robots,it has become a hotspot of current research.In order to improve the performance of flexible strain sensors and maintain good mechanical properties,conductive fillers with excellent conductivity and compatibility and the matrix with good flexibility,high elasticity are often required.In this paper,flexible composites of conductive polyaniline/poly(styrene-ethylene-butadiene-styrene)(SEBS)were prepared by solution blending method,and large strain capacitive sensors with good sensing properties were prepared by hot pressing with the dielectric layer.The sensing properties of capacitive strain sensors in uniaxial and cyclic tension were studied.Then the bending motion of human joints was detected by capacitance strain sensor.The main contents of this paper are as follows:(1)With dodecylbenzenessulfonic acid as dopant and emulsifier,the soluble conductive polyaniline was synthesized by emulsion polymerization,and conductive polyaniline/SEBS flexible composite was prepared by blending PANI with SEBS through solution blending method.The structure of the flexible composite material was characterized by Fourier transform infrared spectroscopy(FT-IR),Raman spectroscopy(Raman),energy dispersive spectrometry(EDS)and high-resolution transmission electron microscopy(HR-TEM).The properties of the flexible composites were tested by thermogravimetric analysis(TGA),universal tension tester and DC low resistance tester.The results show that conductive polyaniline(PANI·DBSA)doped with dodecylbenzenesulfonic acid is well compatible with SEBS and uniformly dispersed in SEBS.The diameter of PANI·DBS A particles are between 10 and 100nm and the flexible composite materials have stable thermal properties below 150?.When the content of conductive polyaniline is 20.00wt%,the flexible composites have good conductivity and the elongation at break can still reach about 700%.In addition,flexible composites exhibit good reversibility and stability during the initial 10 cyclic of stretching at different strain ranges and tension rates.(2)Copper calcium titanate/SEBS dielectric layer was prepared by blending CCTO with SEBS solution,and a "sandwich" type capacitive strain sensor was fabricated with two dielectric layers and 20.OOwt%conductive polyaniline/SEBS flexible material.The dielectric layer and capacitive strain sensor were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),broadband dielectric instrument and stretching strain sensor measurement system.The results show that the dielectric constant of the dielectric layer increases by 58.6%when the content of CCTO is 20.00wt%.The prepared capacitive strain sensor still shows good stability.Within 100%strain range,the capacitance values of capacitive strain sensors with different dielectric layers increase monotonously,and show a good linear relationship.In addition,capacitive strain sensors with different electrode widths have good stability and durability in different strain ranges and tension rates.(3)The "sandwich" capacitive strain sensor is applied to the human motion parts to detect the bending motion of fingers,elbows and knees.The results show that the relative capacitance of capacitive strain sensor changes with the bending motion of human joints,and the motion of human body can be effectively detected.In addition,in order to realize the mass storage and processing of the test data,the test data is stored in the designed database.Through the specific retrieval conditions,the corresponding data and curves can be retrieved and automatically compared.The difference of each human motion between the previous motion can be known and judged.