Electrorheological fluids of coated microspheres

We study model electrorheological (ER) fluids which consist of three material components in an attempt to explain recent experimental results, in which the ER effects can be promoted by adding some water. At low water concentration, the droplets tend to aggregate on the surfaces of the dispersed particles, forming coated microspheres. The ER effects are analyzed via spectral representation, and the experimental conditions for optimal ER responses are obtained. At low frequencies, it is found that by tuning the thickness and dielectric properties of the coating materials, it is possible to enhance the effective dielectric constant, thereby increasing the applicability of the ER fluids.