PATTERN TRANSITIONS INDUCED BY THE SURFACE-PROPERTIES OF SUSPENDED MICROSPHERES IN ELECTRORHEOLOGICAL FLUID

In our previous Letter [Phys. Fluids 8, 2789 (1996)] we reported a new kind of netlike structure formed by metal microspheres suspended in s ilicon oil. In this paper we present further experimental results show ing that different patterns are formed depending on whether metal, sem iconducting, or dielectric microspheres are presented in the electric field. In addition, several experiments are performed on the surface p roperties of suspended microspheres and it is found that a pattern tra nsition occurs when the surface conductivity of the solid phase is cha nged. This phenomenon can also be observed in a glass/oil ER fluid if the glass particles absorb enough water. (C) 1997 American Institute o f Physics.