Abstract
Smart fluids are stimuli-responsive materials whose rheological properties can be changed drastically by applying either an external electric or magnetic field strength. Smart fluids are dispersions comprised of dispersed particles in a carrier liquid that transform from liquid-like state to solid-like state within milliseconds reversibly with an application of external field due to the structural chain formation of the dispersed particles. Owing to this outstanding controllable transformation capability, smart fluids are utilized in various potential applications where an electro/magneto-mechanical interface is required, such as dampers, clutches, shock absorbers, robotics, haptic devices, microfluidics, etc. Various kinds of materials have been proposed and used by researchers for applications that require the electrorheological (ER) and magnetorheological (MR) effects. Polyaniline (PAn) is considered a remarkable material as a dispersed phase of ER fluids due to its easy synthesis, low cost, adjustable conductivity through doping/de-doping processes, and excellent environmental stability. PAn is an attractive material in MR fluids as well due to its contribution to the improvement of dispersion stability and protection against corrosion and oxidation of the soft-magnetic particles. In this chapter, the recent advances in the usage of various kinds of PAn-based materials as electric and magnetic field responsive materials and their ER/MR behaviors are summarized.