Electrorheological (ER) response of biocompatible particles suspended in an insulating silicone oil, was investigated under several different applied external electric field strengths. Chitosan, a biodegradable polysaccharide, was used as anhydrous ER materials. The effect of particle volume concentration on their ER response was examined by focusing on the measurement for theological and electrical properties. The yield stress of chitosan suspended in silicone oil system as a function of applied electric field strength showed different value of slopes for different particle concentrations, however, all data points collapse onto a universal scaling function. (c) 2005 Elsevier Ltd. All rights reserved.