Alternating current induced-charge electrophoresis of leaky dielectric Janus particles

Abstract

We hereby provide a semi-analytic and numerical solution for the nonlinear, induced-charge electrophoretic motion of an electrically inhomogeneous Janus sphere—comprising two hemispheres with differing dielectric permittivities—under the application of a uniform, time-dependent (ac) electric field. No assumptions are made regarding the size of the electric double layer (EDL) and thus the analysis remains valid even in the case of nanoparticles where the particle radius can be of the same order as the EDL thickness. We consider a number of practical and realistic configurations of metallic and dielectric hemispheres and predict the variations in particle mobility as a function of the conductivity of the two hemispheres and the electrolyte, the frequency of the applied electric field and the EDL length. It is determined that there exist critical values for the conductivity of each hemisphere and the frequency of the applied field, which when exceeded, can cause the mobility to decay rapidly to zero.