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Abstract

A droplet generator is provided that is particularly adapted for generating micro droplets of ink on demand in an inkjet print head having a plurality of nozzles. The droplet generator includes a droplet separator formed from the combination of a droplet assistor and a droplet initiator. The droplet assistor is coupled to ink in each of the nozzles and functions to lower the amount of energy necessary for an ink droplet to form and separate from an ink meniscus extending across the nozzle outlet. The droplet assistor may be, for example, a heater or surfactant supply mechanism for lowering the surface tension of the ink meniscus. Alternatively, the droplet assistor may be a mechanical oscillator such as a piezoelectric transducer that generates oscillations in the ink sufficient to periodically form convex ink menisci across the nozzle outlets, but insufficient to cause ink droplets to separate from the outlets. The droplet initiator cooperates with the droplet assistor and selectively causes an ink droplet to form and separate from the ink meniscus. The droplet initiator may be, for example, a thermally-actuated paddle. The droplet separator increases the speed and accuracy of ink micro droplets expelled from the print head nozzles.

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First Claim