Micro-total-analytical systems for analyzing chemical/biological substances are now used across a wide variety of applications ranging from biological warfare agent detection to the Healthcare industry. The first step in the operation of such systems consists of concentrating and separating the analytes of interest from the background matrix and positioning these analytes into selected locations for subsequent analysis. Electro-kinetic and electro-hydrodynamic techniques for manipulating particles in suspension are highly used in microsystems eliminating the need for movable parts. In addition, because of the high surface to volume ratio there is efficient dissipation of Joule heating. Here, we analyze the electric field distribution and particle motion in microfluidic devices with a variety of electrode configurations. First, we consider the particle motion and electric field gradient in our recently developed technique of dielectric gating. We consider the particle motion and numerical simulation results using the Computational Fluid Dynamics Research Corporation (CFDRC) code in 2D designs. In addition, the electrothermal effects within the channel are examined. Next, we consider triangular and trapezoidal electrode configurations as well as single stream particle delivery. We study the particle motion, electric field gradients, and electrothermal effects in these designs. Computer simulations and experimental results are compared.