Estimate of the electric stress in the liquid lying between particles of an electrorheological fluid

The electrorheological (ER) effect arises from the field induced interactions between particles of a suspension. When applying a DC field, the conduction properties of both the solid and liquid phases determine the distribution of the electric field and, therefore, the attraction force between particles in contact or nearly in contact. A crude model gives predictions for the attraction force which agree with measurements on scaled-up spheres of a slightly conducting polymer immersed into a much more insulating liquid. This model also gives estimates for the field in the liquid lying between the two spheres in the quasi-contact zone. This field ranges from 100 to 200 V/μm, values which are not much smaller than the breakdown field for small liquid gaps