Actuation with Magnetoactive polymers

Magnetoactive polymers (MAP) are a relatively new class of smart composite materials, which change their mechanical properties in a magnetic field. They consist of magnetisable particles dispersed in a soft elastomer matrix. Besides possible applications in vibration reduction, they exhibit also excellent actuation capabilities, which is demonstrated with various examples in this paper. MAP actuators with linear deformation are predestined for human-machine interfaces with haptic feedback and for pumping devices with sensitive control of the transport of liquid media as well. However, especially interesting are MAP actuators, which perform a radial expansion of a ring-shaped MAP body as an outstanding actuation mode. Such radial MAP actuators can be beneficially exploited for valves with rotational symmetry as well as for seals under rotational loads, which offer a solution for the existing trade-off between the objectives of high tightness and low friction. Furthermore, another useful application of radial MAP actuators are new locking devices, which smoothly block a rotational motion by the radial expansion of an MAP ring in the magnetic field.