**1. Introduction**

20 Will-be-set-by-IN-TECH

[2] N. Takesue, H. Asaoka, J. Lin, M. Sakaguchi, G. Zhang and J. Furusho, Development and Experiments of Actuator Using MR Fluid, Proceedings of 2000 IEEE International Conference on Industrial Electronics, Control and Instrumentation, pp.1838-1843, 2000. [3] T. Kiyota, N. Sugimoto and M. Someya, 3D-Free Rescue Robot System, Proceedings of the 2006 IEEE International Conference on Robotics and Automation (ICRA'06),

[4] K. Berk Yesin, Philipp Exner, Karl Vollmers and Bradley J. Nelson, Design and Control of In-Vivo Magnetic Microrobots, Proc. of Medical Image Computing and

[5] Mathieu, Jean-Baptiste Martel, Sylvain, Magnetic Steering of Iron Oxide Microparticles Using Propulsion Gradient Coils in MRI, 28th Annual International Conference of the

[7] N.TAKESUE, J.FURUSHO, M.SAKAGUCHI, Improvement of Response Properties of MR-Fluid Actuator by Torque Feedback Control, Proceedings of the 2001 IEEE

[8] J.Furusho and T.Kikuchi, A 3-D rehabilitation System for Upper limbs EMUL and a 6-DOF Rehabilitation System Robotherapist and Other Rehabilitation System with High Safety, Rehabilitation Robotics, I-Tech Education and Publishing, pp.115-136, 2007. [9] Nokata,M. Kitamura,S. Nakagi,T. Inubushi,T. Morikawa,S., Capsule type medical robot with magnetic drive in abdominal cavity, Proc. of Biomedical Robotics and Biomechatronics, 2008 (BioRob 2008). 2nd IEEE RAS & EMBS International Conference,

[10] CapsuleEndoscopy, Given Imaging Ltd., http://www.capsuleendoscopy.org/ [11] K.Ishiyama, M.Sendoha, A.Yamazakia, K.I Arai: Swimming micro-machine driven by magnetic torque, Sensors and Actuators A: Physical, Vol. 91, Issues 1-2, pp.141-144, 2001. [12] A.Chiba, M.Sendoh, K.Ishiyama, K.Arai: Magnertic Actuator for capusle endoscope navigation system INTERMAG Asia 2005: Digest of the IEEE International Magnetics

[13] M. Shikanai et al.: Development of robotic endoscope that locomotes in the colon with flexible helical fin, The 31st Annual International Conference of the IEEE Engineering in

[14] P. Glass, E. Cheung, and M. Sitti: A legged Anchoring Mechanism for Capsule Endoscopes Using Micropatterned Adhesives, IEEE Transactions on Biomedical

[15] Eugene Cheung, Mustafa Emre Karagozler, Sukho Park, Byungkyu Kim, and Metin Sitti: A New Endoscopic Microcapsule Robot using Beetle Inspired Microfibrillar Adhesives, Proceedings of the 2005 IEEE/ASME International Conference on Advanced Intelligent

[16] M.Nokata et al.: Capsule Type Medical Robot with Magnetic Drive in Abdominal Cavity, IEEE RAS / EMBS International Conference on Biomedical Robotics and

[17] M.Nokata et al.: New magnetic rotational drive by use of magnetic particles with specific gravity smaller than a liquid, 2010 IEEE International Conference on Robotics

[18] T.Fukuda: Characteristic and application development of TECBALL, KINZOKU, vol.79,

IEEE Engineering in Medicine and Biology Society (EMBS'06), pp.472-475, 2006. [6] CHIBA ATSUSHI, SENDO MASAHIKO, ISHIYAMA KAZUSHI, ARAI KEN'ICHI, Moving of a Magnetic Actuator for a Capsule Endoscope in the Intestine of a Pig, Journal

International Conference on Robotics & Automation, pp.3825-3830, 2001.

Computer-Assisted Intervention (MICCAI2005), pp.819-826, 2005.

of Magnetics Society of Japan, Vol.29, No.3 pp. 343-346, 2005.

pp.3983-3988, 2006.

pp. 348-353, 2008.

Conference.

Medicine and Biology Society (EMBC2009).

Mechatronics, pp.551-557,2005.

and Automation (ICRA2010).

No.11, 2009 (in Japanese).

Engineering, Vol.55, No.12, pp. 2759-2767, 2008.

Biomechatronics (BioRob 2008), pp.348-353, 2008.

Magnetic materials, that is to say, materials which respond to external magnetic fields, have attracted great interest since around 5th century BC. The ability of materials such as iron or magnetite to be attracted by permanent magnets has always involved some kind of mystery, although magnetism principles are well understood nowadays, especially after J.C. Maxwell stated the basis of electromagnetism in 1865. Magnetism plays a crucial role in our lives these days, being present in many technological applications surrounding us. Nevertheless, only solid magnetic materials can be found in nature. In the search for new ones that could be used in novel technological applications, scientists in the 18th century tried to prepare field-responsive liquids by dispersing particles of magnetic materials in liquid carriers. Actually, the first attempt can be attributed to G. Knight (1779), who suspended iron filings in water that quickly settled (Popplewell, 1984). The preparation of magnetic fluids has undergone great development since then, and magnetic fluids with particles of different nature, size or shape and a wide range of liquid carriers have been reported in the literature.

In this chapter an overview of magnetic fluids and their applications is made, focusing on the latest developments in the field. More specifically, the use of novel ionic liquids as carrier fluids is described. The interest in doing so lies in the fact that ionic liquids may give rise to a new generation of magnetic fluids with promising technological applications.
