Abstarct: This thesis invetigates numerically the motion of a rigid particle, which is affected by two constant DC electric fields, and uses its results in particle sorting and drug delivery scope. Because of the dependence of the hydrodynamic force in the electrokinetics and its subcategories to the electric current and the Zeta potential, particle control is possible by using these two parameters. In this thesis, the two-dimensional and time-dependent motion of a rigid particle in a microchannel has been studied. The effects of different parameters such as electric current, particle diameter and particle geometry on the path of motion have been investigated. Finally, an effective way of particle separation is is introduced. The introduced method in this thesis, due to its dependence on electric current, is in the branch of active methods of particle separation. In this method, the particles are classified regardless of their geometry; Previously the particle seperarion was influenced by their geometry, but by using the microchip which is presented in this study, particles can be separated from each other by different Zeta potentials. It should be noted that by changing the electric field applied to the microchip, different particles could be classified and there is no need to make a new microchip for the separation of new particles. The microchip has a particle collecting chamber. In two constant electric fields, the path of particle motion changes with the increase of the particle to the channel wall Zeta potential ratio, and therefore particles with higher Zeta potential ratio than the critical value can be collected into the chamber. In the following, the ratio of the two electrical currents is discussed, the results of which can be said to have no effect on the Zeta potential ratio much less than the critical value. Geometry and particle dimensions are among the subjects studied in this study. It is found that, the effect of geometry and particle size on the result of separation is negligible and can not be ignored.