mres are typically prepared by curing process for polymers. the polymeric material (e.g. silicone rubber) in its liquid state is mixed with iron powder and several other additives to enhance their mechanical properties. the entire mixture is then cured at high temperature. curing in the presence of a magnetic field causes the iron particles to arrange in chain like structures resulting in an anisotropic material. if magnetic field is not applied, then iron-particles are randomly distributed in the solid resulting in an isotropic material. recently, in 2017, an advanced technology, 3d printing has also been used to configure the magnetic particles inside the polymer matrix.