Piezoresistivity Of Magnetorheological Elastomer And Its Application

As a new type of smart material, magnetorheological elastomers (MREs) have some controllable performances in a certain condition. So, it has become a research focus in recent years. Current researches are mainly targeted at its mechanical properties, and lots of its relevant theories and applications have been proposed. However, its piezoresistive property has seldom been studied and reported. Due to its sensitive piezoresistivity and good linear relationship between the resistivity of the MRE and the applied pressure in a certain range, it is potentially capable to substitute the traditional sensing element for tactile sensors and a variety of force-sensitive components.Based on this situation, this thesis attempts to carry out the testing and application research of piezoresistivity of MRE. In order to achieve good experimental results, we designed and made a mold for preparing MRE, and prepared a large number of MRE samples with good appearance and density in different content proportions, using different soft magnetic materials and different thicknesses.By analyzing the electric conduction mechanism of MRE, this thesis suggests that it is jointly determined by the conductive channel mechanism and the tunneling current theory. Based on this assumption, it then deduced the model of piezoresistivity for magnetorheological elastomers. The model shows that, the resistance of magnetorheological elastomer exhibits pressure dependence significantly.On this basis, we designed a test rig to study the piezoresistivity of magnetorheological elastomers, and test the pizeoresitivity for the prepared MRE samples in different groups. A subsequent experimental study shows that, the resistance of magnetorheological elastomer samples decreased in exponential order as responding to an axial pressure, which matches the results given by the proposed theoretical model, thus providing a qualitative verification of the model. The thesis also obtained several key parameters which affect the pizeoresistivity of MRE significantly, then analyzed the trend of piezoresistivity change of MRE when these parameters vary.With the above research results, the thesis then points out that it is feasible to make tactile sensor with MRE and it has some advantages such as strong sensitivity, simple preparation and so on, hence it is worthy of further studying for application. According to the piezoresistivity of MREs, we have designed a unit structure model for tactile sensor based on MRE, which provides a new approach for the application of MRE, for example, being used as a tactile sensor for three-dimensional force in robots.