Abstract: The invention relates to an electrorheological fluid comprising fine silica particles, to which an alcohol-modified silicone oil is bonded, compounded with a nonconducting liquid, to which a polarizing agent is added as necessary. Use of fine silica particles of which the surface is modified by an alcohol-modified silicone oil according to the invention provides an electrorheological fluid which have low initial viscosity, high viscosity increase ratio and excellent dispersion stability.

Abstract: An electrode for applying voltage to electroviscous fluid, particularly where the electroviscous fluid has electrically insulating fluid and porous solid particles, the ER effect can be stably maintained up to a high temperature range and high durability can be obtained by laminating an insulating layer on the surface of the electrode in contact with the electroviscous fluid.

Abstract: In an electroviscous fluid comprising electrically insulating fluid as the dispersant and porous solid particles as the dispersed phase, at lease one substance selected from acid, salt and base and at least one substance selected from polyhydric alcohol and water, and further containing dispersing agent, antioxidant and/or corrosion inhibitor are added to obtain the better effects such as high responsiveness in wide temperature range up to high temperature, high reproducibility, excellent electroviscous effect and the higher durability.Therefore, the electroviscous fluid by this invention is useful, for example, for the control systems utilizing viscosity change, and it is capable to increase the control accuracy, particularly in the operation at high temperature.