This paper describes a device in which the DEP electrodes form the channel walls. This is achieved by fabricating microfluidic channel walls from highly doped silicon so that they can also function as DEP electrodes. The device is fully enclosed and there is no fluidic leakage due to lead-outs. The electrode arrangement minimized the electrical dead volumes such that the DEP force is always sufficient to overcome Stoke's force and concentrate the cells and beads at the nominal operating potential of 25 V p–p. The device has been tested successfully with yeast cells. When the actuation signal was increased to 13 V p–p, cells began to move towards the tip of the DEP electrodes, where the electric field gradient was highest. As the actuation voltage increased, the cells moved faster. For 25 V p–p, a stable equilibrium of cell concentration pattern was achieved in 10–13 s.