Donald A. Nixon

Viscoelastic Properties of Magneto- and Electro-Rheological Fluids

This paper examines the transition area between elastic and viscous behavior for a conventional electro-rheological (ER) fluid and a state-of-the-art magneto-rheological (MR) fluid through the use of oscillatory rheometry techniques. A comparison between the yield behavior (strain and stress) measured for these two different types of controllable fluids is presented. The data obtained for MR fluids represents the initial characterization of the pre-yield properties exhibited by this type of material. Finally, a recommendation as to a key area for future R&D is highlighted.

ER Fluid Inks: A Rainbow of Possibilities

The concept of using electrorheological (ER) fluids as inks originated with the design of several electroviscous recording devices some 25 years ago.1,2 The colored, ER active pigments used in these early inks included carbon black, copper phthalocyanine derivatives (Skyline Blue & Monstral Green B), flavanthrone (Indofast yellow toner), quinacridone (Quindo Magenta), 3,4,9,10-bis(n,n′-(p-methoxyphenyl)-imido)perylene (Indofast Brilliant Scarlet toner), and 1,2,5,6-di-(c,c′-diphenyl)thiazole anthraquinone. In addition to utilizing colored pigments in an ink, the possibility of coloring conventional ER fluids (i.e., those prepared by W. Winslow3, etc.) through the addition of dyes also was suggested.1,4 Examples of the oil soluble dyes used to colorize known ER fluids included Oil Yellow AB, Oil Red, Oil Blue G Extra and Oil Black.