In this article we demonstrate methods of transporting micro-objects in fluids using microelectromechanical system electrode arrays to generate nonuniform electric fields. We show the ability to control fluid flow through ac electro-osmosis and the ability to move micro-objects through dielectrophoresis where the velocity is a function of the frequency, voltage, and spacing of arrays. Velocities in excess of 600 mum/s have been achieved with ac voltages as low as 7 V-pp. In addition to one-dimensional arrays that provide single axis control, here we also investigate a two-dimensional array capable of planar control. (C) 2004 American Vacuum Society