Abstract: A device capable of manipulating, sorting, separating and measuring the properties of charged species particles by physical interaction via electrostatic forces. The device operates on charged species particles ranging from small molecular species to intact mammalian cells. The device has a semiconductor substrate serving as an electrode. A dielectric layer overlays the substrate. A chamber holds a fluid which contains the charged species particles. The fluid in the chamber is placed in physical contact with the dielectric layer. A control electrode of metal is disposed opposite the dielectric layer and is also in physical contact with the fluid. A voltage source establishes an electric field between the electrodes which extends into the liquid. Charged species particles are either attracted to or repelled from the dielectric layer surface. The device structure readily provides for precise and continuous control of the electric field at the dielectric layer-fluid boundary interface.