Drop-on-demand ink jet printing with controlled fluid flow during drop ejection

摘要

A drop-on-demand ink jet printing system includes an ink channel having a nozzle orifice through which ink droplets are ejected when ink in the ink channel is subjected to a momentary positive pressure wave. An ink feed passage opens into the ink channel to transport ink into the channel from an ink reservoir. A selectively-actuated valve, associated with the ink feed passage, restricts the flow of ink through the ink feed passage when actuated. The valve is actuated in timed association with the momentary pressure wave, whereby flow of ink past the valve from the ink channel towards the reservoir is inhibited. The ink feed passage may be a microfluidic channel, and the selectively-actuated valve a heater in thermal contact with at least a portion of the associated microfluidic channel, whereby thermally-responsive ink in the ink feed passage can selectively be heated by the heater such that the thermally-responsive ink will be caused to increase in viscosity to thereby restrict backward ink flow through the ink feed passage. The ink may be comprised of a carrier having a tri-block copolymer of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide).