Electrorotation of dense colloidal suspension

When a strong electric field is applied to a colloidal or biological cells suspension, the induced dipole force will cause an aggregation of the suspended particles in response to the field. In the case of a rotating electric field, the electrorotation (ER) spectrum can be modified due to the local field effects arising from the many-particle systems. To capture the local field effect, we invoke the Maxwell-Garnett approximation for the dielectric response. The hydrodynamic interactions between the suspended particles will modify the spin friction, which is a key to determine the angular velocity of ER. By invoking the spectral representation approach, we derive the analytic expressions for the characteristic frequency at which the maximum angular velocity of ER occurs. We report a detailed investigation of the dependence of the characteristic frequency and the dispersion strength of ER oil various material parameters.