Method and apparatus using traveling wave potential waveforms for separation of opposite sign charge particles

An apparatus for developing a latent image recorded on an imaging surface, comprising:

• a donor member, spaced from the imaging surface, for transporting toner on the surface thereof to a region opposed from the imaging surface, said donor member includes an electrode array on the outer surface thereof, said array including a plurality of spaced apart electrodes extending substantial across width of the surface of the donor member;
• means for loading toner onto said donor member;
• a multi-phase voltage source operatively coupled to said electrode array, said multiphase voltage source generating a waveform which creates an electrodynamic wave pattern for moving toner particles of one polarity to and from a development zone and preventing toner particles of the opposite polarity from moving on to said development zone, said waveform generates an ambipolar bi-directional wave mode wherein toner particles of said first polarity and toner particles of the opposite polarity are transported in opposite directions from each other.