Super-strong magnetorheological fluids

Magnetorheological (MR) fluids, which can rapidly be changed from a liquid state to a solid state and vice versa by a magnetic field, have the potential to revolutionize several industrial sectors. The key issue is to enhance their yield shear stress. This paper reviews the physical mechanism and microstructure of MR fluids. It finds that the weak points of the MR microstructure under a shear force are at the chains' ends. Hence, a general technique, a compression-assisted-aggregation process, is developed to change the induced MR structure to a structure that consists of robust thick columns with strong ends. The scanning electronic micrographic (SEM) images confirm such a structure change. With this approach, MR fluids become super-strong. The enhanced yield stress of MR fluids reaches 800 kPa at a moderate magnetic field.