<p> Magnetic Responsive Soft Composite with Variable Elasticity and Its Application</p><p>Tetsu MITSUMATA *,1,2 1Graduate School of Science and Technology, Niigata University, Niigata, Japan 2JST-ALCA, Japan</p><p>Magnetic responsive soft composite that alters the viscoelastic properties in response to the magnetic field has been investigated. The magnetic soft composite consists of magnetic particles and polymer matrix such as polymer gels or elastomers, which is called magnetic elastomer in this study. Typical for MR soft composites, the diameter of magnetic particles is in several microns. When a magnetic soft composite is put in a magnetic field, the elastic modulus increased. The storage modulus for the magnetic elastomer without magnetic fields (0 mT) was ~104 Pa and it rapidly increased to ~1.5 MPa when a magnetic field of 500 mT was applied. The magnetic elastomer exhibited a reversible increase by factors of 277 of the storage modulus and 96 of the loss modulus upon the magnetic field, which were nearly the same level with magnetic hydrogels demonstrating the giant magnetorheology. This MR effect maintained the magnetic field response for half year after the synthesis. In addition, the magnetic elastomer underwent high mechanical toughness with a breaking strain exceeding 0.8, and did not show a permanent deformation after removing the strain. We have also tried to improve the MR property of magnetic elastomers. A typical example is bimodal magnetic elastomers mimetic to sea cucumber, which consist of magnetic particles (iron) and nonmagnetic particles (ZnO). The relative change in the Young’s modulus at 320 mT for the monomodal magnetic elastomer was 1.8 and it was raised to 5.8 only by mixing with the nonmagnetic particles of 9.6 vol%, originating from the stress transfer by the additional chains of magnetic particles via nonmagnetic particles. The MR property of various magnetic soft composites and their recent applications as actuators will be presented.</p>