Electric field detachment of a uniformly charged dielectric sphere on a dielectric coated electrode

In the electrophotographic process, charged toner particles are transferred from one surface to another with an electric field. To enable electric field transfer of toner, the externally applied field strength must be greater than a threshold value so that the coulombic force can overcome the toner adhesion force at the residing surface. In this work, the threshold field strength to detach a uniformly charged dielectric sphere and the electrostatic adhesion force are determined efficiently by using the Galerkin finite element method to simultaneously solve the Laplace equation for the field distribution and an overall constraint equation for the force balance. This computational method is applicable to various problem configurations. For illustrative purposes, however, the authors consider the axisymmetric problem of electric field detachment of a uniformly charged dielectric sphere on a dielectric coated electrode. Their analysis is particularly focused on the dependence of the threshold detachment field strength and electrostatic adhesion force on the dielectric coating thickness and gap between electrodes.