Drop-on-demand ink jet printer with controlled fluid flow to effect drop ejection

摘要

A drop on demand microfluidic ink jet printing system includes an ink flow chamber having a nozzle opening in a wall of the flow chamber through which ink droplets are ejected when ink in the flow chamber is at or above a predetermined positive pressure. An inlet channel opens into the flow chamber to supply thermally-responsive ink to the flow chamber at or above the predetermined pressure. A microfluidic outlet channel communicates the flow chamber with a low pressure ink reservoir such that thermally-responsive ink is normally transported from the flow chamber at a flow velocity sufficient to maintain ink in the flow chamber at a pressure less than the predetermined positive pressure. A valve selectively restricts the flow of the thermally-responsive ink through the microfluidic outlet channel sufficiently to cause an increase in ink pressure in the flow chamber to at least the predetermined positive pressure, the valve including a heater in contact with at least a portion of the associated microfluidic outlet channel, whereby the viscosity of the thermally-responsive ink can selectively be increased by heat from the heater to restrict the flow of the thermally-responsive ink from the flow chamber such that an ink droplet is ejected through the nozzle opening.