Enhancing yield stress of electrorheological fluids with liquid crystal additive

The enhancement of yield stress of NaY/insulating oil electrorheological (E R) fluid is found by adding a liquid crystal additive with a higher dielect ric constant than that of the carrier fluid. The yield stress increases wit h additive's concentration and saturates at high concentrations. A polariza tion model has been suggested to understand the role of the additives. The theoretical calculations agree with our experiments very well. We show that adding a small amount of additive with a high dielectric constant can dras tically improve the yield stress even in a 'dry' ER fluid if the conductivi ty or dielectric constant of the additive is still much smaller than that o f the dispersed particles.