Abstract: A printing method and apparatus is disclosed wherein the printhead has a linear array of nozzles oriented in an axis, and drops of a liquid are printed at a particular location from first and second nozzles of the printhead at a first location. In an embodiment, the nozzles are arranged in groups, each group of nozzles being used to superpose spots of a particular liquid at a different location. A further method is described wherein the printhead is triggered by transferring printing triggers from a processing module to a printhead at print intervals representative of a plurality of fixed units of spatial displacement of the printhead. The present invention is particularly advantageous for the cycling of print nozzles, superposition of spots in linear arrays and fine control of spot positioning. The invention has particular application in the field of printing DNA microarrays.

Abstract: A method is described of operating an ink jet printhead having one or more manifolds each connected to more than one chamber, each chamber being associated with a nozzle and capable of ejecting drops therefrom: a number of different liquids larger than the number of manifolds is introduced into the printhead via the nozzles; and the volume of the liquid subsequently printed from each nozzle is less than the volume of the chamber associated with that nozzle, and also less than the volume of liquid introduced into that chamber. By this means the printhead prints more different liquids than is conventionally possible without mixing them.