Haptic interfaces based on magnetorheological fluids

In this paper we present an innovative application of magnetorheological (MR) fluids to haptic interfaces. These materials consist of a suspension of a micron-sized, magnetizable particles in a synthetic oil. Exposure to an external magnetic field induces in the fluid a change in rheological behaviour turning it into a near-solid in few milliseconds. Just as quickly, the fluid can be returned to its liquid state by the removal of the field. MR fluids are already present on the market, used in devices such as valves, brakes, clutches, and dampers. In this paper we investigate the possibility of using MR fluids to mimic the compliance, damping, creep (in other terms, the rheology) of materials in order to realize a haptic display and we propose two different implementations. Here we only outline the first scheme, whose experimental results have been reported in our previous work, and will describe the second one. In this latter scheme we set up a psychophysical protocol where a group of volunteers were asked to interact with the MR fluid duly excited and qualitative results are discussed.