Electrorheological resonance observed in a colloidal suspension

Measurements of rheological properties of a suspension containing rutile (${\mathrm{TiO}}_2$) particles are made under applications of ac electric fields. When the shear stress is measured as a function of frequency of the ac field, a peak in the shear stress is observed with the peak frequency shifting linearly with the shear rate. The effects of the shear rate and the amplitude of the field on the peak indicate that the peak is due to a resonance that occurs when the angular velocity of rotating particles matches the angular frequency of the ac field. The resonance makes this suspension behave as a non-Newtonian fluid.