Development of MR Fluid for Running Shoes with an Active Damping System

Sporting shoes, in particular those for running, must fulfill two requirements: on one hand they must assure the maximum utilization of the biomechanical energy, while on the other hand they must protect the athlete from functional overload pathologies due to isolated trauma or by repeated microtraumas over time. To satisfy these conditions, materials or devices must able not only to reduce the maximum values of the impact strength, but also absorb the micro-vibrations. The damping cannot be excessive because it negatively affects the athletic performance; therefore there is the need to reach a compromise between two opposite demands; this can be achieved using smart fluids able to modify in real time the damping coefficient according to needs. Thereby to design a running shoe with an active damping system based on magnetorheological (MR) fluids it is necessary first of all to know the viscoelastic and damping properties of the fluid. We have studied the characteristics of the MR fluid made in our laboratory, with a reference comparison with commercial MR fluids. We have chosen to prepare the fluid ourselves because in this way we have been able to determine the influence of each element of the MR fluid. These preliminary results seem to show promise for MR fluids for this kind of application; for the future the target is improve their properties and develop an efficient prototype for preindustrial application.