Mechanism of the Electrorheological Effect: Evidence from the Conductive, Dielectric and Surface Characteristics of Water-Free Electrorheological Fluids

Mechanism is clarified of the electrorheological (ER) effect of particle-dispersed ER fluids. The conductive, dielectric and surface properties of several water-free polymer or inorganic material based ER fluids, as well as their response times, are discussed to elucidate the physical ground of the elctrorheological effect. It is found that the slow polarization, especially the interfacial polarization rather than Debye polarization, is responsible for observed phenomena. A possible ER mechanism is proposed as follows: a large interfacial polarization would facilitate the particles to attain a large amount of charges on the surface, then leading to the turn of particles along the direction of an electric field to form a fibrillation structure; the strength of fibrillation chains is thus determined by the particle polarization force, i.e. the particle dielectric constant. The rationality that the marked interfacial polarization would likely drive the particles to turn is theoretically addressed on the basis of experimental results.