Significant enhancement of the electrorheological effect by non-straight electrode geometry.

In contrast to the commonly used straight electrodes with electrorheological (ER) fluid, here, we studied the effect of non-straight electrodes comprising the sides of a microchannel, on the ER fluid response. A more than one order of magnitude enhancement of the apparent viscosity was observed for non-straight electrode geometries, where castellated and sawtooth electrode geometries were used merely as an example, relative to that measured for straight electrodes. The enhancement increased with increasing applied voltage and exhibited a distinct maximum in the frequency range of 5-10 Hz. Experimental analyses demonstrated that positive dielectrophoresis-driven attraction of the chain ends to the sharp tips of the electrode underlies the ER enhancement. Hence, introducing such uniformity breakage of the electric field through non-straight electrode geometries is of practical importance for enhancement of the ER response.