Research On Pressure-sensitive Characteristics Of Conductive Rubber And Sensor

Conductive polymer material is a new functional material, whose conductivity range is between the insulator and metal. Conductive polymer material is an important material for preparing a flexible sensor with good force-sensitive, thermal and other features. As one of conductive polymer composite materials, Conductive rubber is a core component of the flexible pressure sensor and its performance is directly related to the practicality of the sensor. This paper described the conductivity mechanism of conductive rubber, studied the piezoresistive properties and sensing properties of conductive rubber, and on its basis a flexible array sensor was designed.In order to study the piezoresistive properties and sensing properties of conductive rubber, acetylene carbon black filled conductive rubber was prepared in lab. Before experiments, experimental program, preparation process, experiment material and equipment were determined. The impact of different amount of acetylene carbon black filled on the resistivity of conductive rubber was analyzed. The study found that8%of acetylene black content of conductive rubber could be used as flexible sensor sensitive material. By scanning electron microscopy (SEM), it found that the carbon black particles dispersed evenly in the interior of the conductive rubber.The capacitance-Frequency characteristics of conductive rubber was studied, and it was found that these were obvious capacitance and inductance characteristics for conductive rubber. Therefore, it was proposed that the impedance of conductive rubber was constituted by resistance, capacitance and impedance of the series-parallel structure. A new conductive network structure was put forward, and the corresponding circuit model was established. The paper further studied the influence of amount of carbon black filled and pressure on pure resistance, capacitance and inductance coefficient of conductive rubber. Piezoresistive effect of conductive rubber includes body piezoresistive effect and surface piezoresistive effect. The regularities of surface piezoresistive response and body piezoresistive response were researched. Results have shown that the sensitivity of surface resistance response was higher than that of body resistance response. By the method of applying pressure or the surface of the conductive rubber coated conductive silver paste could effectively reduce the impact of contact resistance on the body piezoresistive effect. When a conductive rubber sensor was designed, in order to improve the sensitivity of the sensor, the surface piezoresistive effect of conductive rubber should be taken advantage of. Based on the effective medium universal equation, the relationship between body resistance value and the axial strain of conductive rubber was derived.Conductive rubber sensor performance was studied, including measurement range, sensitivity, repeatability, hysteresis and relaxation properties. By measuring the force-sensitive response of different thickness of conductive rubber, it found that the measurement range increased as the thickness increased. It was determined that for4mm thickness of conductive rubber, the internal of force-sensitive was0.2-3N. The resistance sensitivity of conductive rubber included volume resistance sensitivity and surface resistance sensitivity, and the latter was relatively high. With the increase of the carbon black filler, the resistance sensitivity of the conductive rubber relatively reduced. Conducted through pressure on conductive rubber or by repeated loading would improve the repeatability of piezoresistive curve. Proper applying pressure or loading-uninstall could reduce the resistance lagging for conductive rubber, and help to improve the stability of conductive rubber. Conductive rubber had obvious resistance relaxation behavior. In the flow range, increasing the amount of carbon black would reduce the resistance relaxation time. While increasing the thickness of the sample would increase the resistance relaxation time. As the pressure increased, the relaxation time reduced for the conductive rubber. Influence of ambient temperature on the resistance relaxation time is more complex and in the turning point of the positive and negative temperature effect, resistance had the longest relaxation time.Based on the study of the performance of conductive rubber, a new array unit of conductive rubber sensor was designed, compared to the usual array sensor unit. Matlab software was applied to fit the piezoresistive curve of the new array sensor unit. Through the fitting comparison finally choose cubic curve fitting, and obtained the best fitting equation. Conductive rubber sensor array structure was designed, and analyzed the principles of signal acquisition.