Patent ID: 7805095

Claim:
A charging device, comprising: a first electrode and a second electrode that are arranged to form a charging zone therebetween, wherein the first electrode and the second electrode each have a plate configuration and the first electrode and the second electrode are substantially parallel to each other; a plurality of nanostructures disposed on the first and second electrodes; a charging voltage supply operatively coupled to the first and second electrodes; wherein the charging voltage supply is arranged to provide an alternating-current waveform comprising a square wave shape that provides a time average voltage at or near zero with a peak magnitude of from about 50 to about 750 Volts, or a peak-to-peak magnitude of from about 100 to about 1500 Volts; a gas supply unit for storing gaseous material and being arranged to supply the gaseous material to the charging zone to produce gaseous ions; and an aperture electrode or grid downstream from and proximate to the charging zone and coupled to an included grid control voltage supply, the grid control voltage supply arranged to control a flow of the gaseous ions from the charging zone through the aperture electrode or grid to thereby charge a receptor located proximate to the aperture electrode or grid, wherein the grid control voltage supply supplies a voltage output to provide a negative DC voltage bias on the aperture electrode or grid, the negative DC bias establishes an electric field between the charging device and the receptor, and charging of the receptor with the gaseous ions ceases when a surface potential of the receptor becomes approximately equal to the voltage output of the grid control voltage supply.