Magneto Rheological Gels are analogous materials to Magneto Rheological Fluids and Magneto Rheological Elastomers. They are also composed of micron-sized magnetic particles but unlike Magneto Rheological Fluids and Magneto Rheological Elastomers the magnetic particles in Magneto Rheological Gels are dispersed in a gel. This feature of MRG helps intrinsically to overcome the distinct shortcomings shown by Magneto Rheological Fluids e.g. the settling of the magnetic material in time due to the density mismatch and the small response ratio that Magneto Rheological Elastomers shows due to limited movement of the particles within a polymeric matrix.
Gel Matrix: Magneto Rheological Gels are conventionally prepared by dispersing the magnetic particles within a fluid that can be gellated with gelator agents (i.e. water, polymers, etc). A gel is obtained at room temperature and upon heating or cooling it melts to obtain a fluid: this is a fully reversible process. A feature of Magneto Rheological Gels is that they respond to more than just one stimulus: i.e. magnetic field and temperature or pressure. These effects can be used for applications that depend on certain temperature ranges. This will avoid settling of the particles while it is liquid at high or low temperature. Ionic liquids’ properties can ensure a good temperature range of operation at low risk (not flammable, not toxic, and not volatile) while adding value by having a high ionic and electric conductivity.
Stimuli effect: Magneto Rheological Gels may be (semi-) solid at room temperature (or at selected temperature) behaving as a Magneto Rheological Elastomers or may be liquid and having the performance of a Magneto Rheological Fluids, depending on the gelling system used. When such (an)isotropic Magneto Rheological Gels are exposed to an external magnetic field, the elastic modulus or viscosity (if melted) in a certain direction (x,y,z) of the material will change according to the strength of the applied magnetic field and its direction These characteristics enable the possibility to make materials with different properties at each phase (gel and liquid) and temperature.
Applications: Magneto Rheological Gels can be utilized in several engineering applications that involve variable stiffness, and moreover they can also work in an environment in which temperature responsiveness is important. The use of IL in Magneto Rheological Gels can enable the development of new sensors for ionic and electric conductivity and sense modification of a magnetic field and/or temperature range.