A transparent electrorheological (ER) fluid was fabricated by dispersing urea-modified silica nanopartides in a mixture of halocarbon oil and silicone oil, whose refractive index could be tuned to be the same as that of the dispersed particles. The ER fluid showed considerable enhancement in shear stress and shear viscosity, as determined by a rotational rheometer, as well as improved dielectric spectra measured using a LCR meter. Morphological and thermal characterization by scanning electron microscopy and thermal gravimetric analysis confirmed the modification by urea. The potential applications of the transparent ER fluid as haptic displays were also investigated. (C) 2013 Elsevier Inc. All rights reserved.