Soft magnetorheological elastomers as active materials in novel valves

The actuation behavior of soft silicone-based magnetorheological eleastomers (MRE) in magnetic fields of variable strength was investigated. An inhomogeneous magnetic field gives rise to a reversible actuation effect, which is the result of the competition between magnetic and elastic forces in the material. MRE are capable to perform more sophisticated deformations than known rigid actuator materials. In this connection, the actuation behavior of MRE ring-shaped bodies in a valve-type device for the control of an air flow is demonstrated. For this purpose, MRE rings with different hardness were prepared and used in the valve. Additionally, the actuation of anisotropic MRE was compared with that of isotropic samples. The inhomogeneity of the magnetic field at the MRE material which is required for the actuation could be strongly influenced by the shape of the magnetic yoke. In the study, the closing characteristics of the valve with different yoke shapes and MRE materials were evaluated by measuring the dependence of the air flow rate on the magnetic field strength. It is demonstrated that the air flow through the valve can be controlled by the current in the field-generating coil, which yields the base for a new type of magnetic valves.