Modeling Perfluorinated Polyether-Based MR Fluids

This study investigates the field-induced rheological characteristics of PFPE-based MR fluids. Four PFPE-based MR fluid samples were prepared, each with a different solid loading. All samples contain a single grade of carbonyl iron powder with an average particle diameter of 2 µm. The PFPE base fluid enhances sedimentation stability and its composition and qualities are introduced in the article. The magnetization characteristics of the iron powder and a fluid sample are measured. Its magnetic properties are compared to known models from the literature. The shear-yield stress in all fluid samples is investigated experimentally, as a function of solid loading and the magnetic flux density. The results are compared to established shear stress models for MR fluids. Model parameters are set to conform to the PFPE-based MR fluids. The PFPE-based MR fluids are shown to have a comparable shear-yield stress, when compared to commercially available MR fluids with a comparable particle loading and particle size. An application for the PFPE-based MR fluids is introduced. This application is an adaptive MR prosthetic knee, utilizing the fluid in shear mode.