Magnetorheological fluid, Electrorheological fluid and ferro fluids are the smart fluids known today. These fluids are either electrically conductive or non conductive. They do not exhibit variable electrical resistance or switching behavior. Of recent interest to researchers has been the development of new types of magnetoresistive materials. Such materials can be of large practical importance, as they will change their electrical resistance in the presence of a magnetic field. However, most materials only exhibit appreciable magnetoresistance under extreme conditions, such as high magnetic fields or low temperatures. A smart fluid whose electrical resistance can be varied by several orders of magnitude under nominal level of magnetic field is reported in this paper (designated MARSONPOL). In the absence of a magnetic field the fluid is an insulator having electrical resistance in the order of 10⁸ ohm-meter and in the presence of a magnetic field the resistance of the material reduces to less than 1 ohm-meter, at room temperature of 30°C. The sharp and reversible change in resistivity makes the material transform from an insulator to conductor, rendering properties characteristic of either state, within a fraction of a second. Fluids with such characteristics are not reported in the literature making this development a breakthrough and opening up potentials for the development of several smart devices. One such device is the magnetic field sensor probe currently under development at NPOL. A capsule of MARSONPOL forms the basic sensor element. Depending on the strength of the Magnetic field, the electrical resistivity of the capsule undergoes changes. The present paper will discuss details of the smart fluid as well as features of the magnetic field sensor.

Date Published: 14 October 2003
PDF: 6 pages
Proc. SPIE 5062, Smart Materials, Structures, and Systems, (14 October 2003); doi: 10.1117/12.514554

Published in SPIE Proceedings Vol. 5062:
Smart Materials, Structures, and Systems
S. Mohan; B. Dattaguru; S. Gopalakrishnan, Editor(s)