Magnetorheological Fluids : From Basic Physics to Application

Magnetorheological (MR) fluids are suspensions of magnetizable micrometer particles in a liquid. The rheological properties of the fluids can be changed rapidly, reversibly and repeatedly from that of a liquid to that of a solid when an external magnetic field is applied. This tunability of the fluids comes from the microscopic structure of the particles. Different microscopic structures are observed, quantified and correlated with rheological properties. The yield stress and viscosity of MR fluids depends on the particle size and volume fraction, sample cell geometry, magnetic field strength and application rate. The application of MR fluids in cancer therapy is discussed. In-vitro experiments show that blood flow can be blocked leading to a tumor by injecting a dilute MR fluid in a blood vessel and placing a magnet on top of the tumor. Without blood supply, tumor necrosis occurs shortly.