Ferrofluid can be defined as one of typical “nano-materials” as the basic composition is a blend of real “nm” controlled substances. The history of ferrofluid is more than half century and there are some specific fields where ferrofluid has dedicated to support the key commercial technologies as like HDD, speaker, semi-conductor, smartphone, recycle unit and biomedical manners. Recently we can see more candidate applications adapting ferrofluid to develop new business area. The latest trend of some typical applications is introduced in this paper.

　Bio-robotics is a research field that learns from the structural and control systems acquired by living organisms in the process of evolution and makes use of them in robotics. When imitating living organisms, it is still difficult to completely imitate their components such as muscles and skeletal structures, and trial and error is being carried out by applying various methods. Magnetic smart fluids are also attracting attention in bio-inspired robotics because not only they are liquids but also able to generate displacements and their properties by an external magnetic field. In this paper, we explain the earthworm-type robot and the variable viscoelastic joint system which is a bio-inspired robot using magnetic smart fluid.

　We will explain the development of MR materials that have evolved sequentially from MRfluid, MR-elastomer, to Permanent magnetized elastomers. With the application of paint technology, MR fluid has solved the fatal problem of sedimentation. Then, by solidifying the MR fluid, we created an MR elastomer that shows a unique movement. Finally, a permanent magnetized elastomer was created by magnetizing the MR elastomer using a special magnetic powder. All of these are materials that are expected to be applied to advanced mechanisms such as robots. We will introduce examples of actual applications and introduce the current status and future of MR materials.

　Magnetorheological fluid (MRF) which is one kind of magnetic functional fluids has a great potential to improve components in robotic systems, including actuators, dampers, clutches, and so on, by enhancing existing functions and adding new functions. The application of the MRF could bring the intrinsic backdrivablity and high responsiveness to those robot components. Therefore, this paper introduces several examples of application of the MRF to robot components by focusing on powerfulness, backdrivability, and responsiveness.

　HOPG means highly oriented graphite. The HOPG plate is effective for realizing a non-controlled diamagnetic magnetic levitation motor at room temperature. The authors have found a way to improve the HOPG disk required for non-controlled diamagnetic magnetic levitation to further enhance axial stability. It was demonstrated that the stability in the radial direction is increased by composing the HOPG disc with two types of HOPG block in which the orientation of the HOPG block differs by 90 degrees. This discovery was made possible by deriving an equation that approximates the benzene ring of graphite to a ring current.