As one of the most important field-responsive intelligent and smart soft matter materials, magnetorheological (MR) fluids, consisting of magneto-responsive magnetizable particles suspended in non-magnetic fluids, have drawn a lot of attentions in both academia and industry as their physical and rheological characteristics can be controlled with external magnetic field strength. In this highlight, preparation methods and MR properties of various magnetic composites with soft magnetic particles and polymers are reviewed. In addition, some industrial applications, such as a MR dampers and a MR polishing, are briefly summarized.

This highlight aims to report electrorheological (ER) materials in state-of-the art polymeric particles and their various nanocomposites with clay, mesoporous inorganics and carbon nanotubes along with their potential application. ER fluids, suspensions of these particles having higher dielectric constant or electrical conductivity than the low-viscosity fluids in which they are suspended, are currently regarded as a smart/intelligent material, because their structural and rheological properties can be systematically tuned by controlling electric field strengths. In this highlight, various conducting polymers, including polyaniline, polypyrrole, poly(p-phenylene), poly(naphthalene quinone) and copolyaniline, are introduced and different types of polymer nanocomposites are emphasized. Flow curves for shear stress of the ER fluids are also examined.

An electrorheological fluid, a special type of suspension with controllable fluidity by an electric field, generally contains semiconducting or polarizable materials as electro-responsive parts. These materials align in the direction of the applied electric field to generate a solid-like phase in the suspension. These electro-responsive smart materials, including dielectric inorganics, semiconducting polymers and their hybrids, and polymer/inorganic composites, are reviewed in terms of their mechanism, rheological analysis and dielectric characteristics.