Polar molecule dominated electrorheological effect

The yield stress of our newly developed electrorheological (ER)fluids consisting of dielectric nano-particles suspended in silicone oilreaches hundreds of kPa, which is orders of magnitude higher than that ofconventional ones. We found that the polar molecules adsorbed on theparticles play a decisive role in such new ER fluids. To explain this polarmolecule dominated ER (PM-ER) effect a model is proposed based on theinteraction of polar molecule-charge between the particles, where the localelectric field is significantly enhanced and results in the polar moleculesaligning in the direction of the electric field. The model can well explainthe giant ER effect and a near-linear dependence of the yield stress on theelectric field. The main effective factors for achieving high-performancePM-ER fluids are discussed. The PM-ER fluids with the yield stress higherthan one MPa can be expected.