Anthony J. Margida

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.