This document is intended as a primer for first time users of ink-jet dispensing technology. It is written with the assumption that at least the ink-jet dispensers are purchased from MicroFab Technologies. The document discusses the needs of the “low temperature” dispensers and several approaches to fulfill them. The “high temperature” devices are only sold with their associated printhead and are not discussed here.
The set-up concentrates on “drop-on-demand” (DOD) operation, even though a set-up as described later on could be used for “continuous” ink-jet. In continuous ink-jet processes, drops are generated all the time and the ones that are used are selected from the stream of droplets. Drop-on-demand ink-jet can generate any desired number of drops (down to a single drop) whenever they are needed and thus provides better control. A separate document describes in more detail the basics of drop generation, approaches in identifying appropriate operational conditions, and troubleshooting.
The main components of a basic set-up for ink-jet dispensing are:
- Ink-jet microdispenser or micro jet: piezoelectrically actuated droplet generator
- Fluidics (tubing, connectors and reservoir): Feeds the liquid to be dispensed from the reservoir to the dispenser
- Drive electronics: The ink-jet microdispensers discussed here employ a piezoelectric actuator to transmit the energy required by the drop generation. The drive electronics generate the electrical signal/pulse required to generate a drop.
- Backpressure control & purging: Controls the pressure in the space above the liquid in the reservoir to a level that maintains the liquid flush with the orifice. By applying pressure to the reservoir, the solution is “purged” through the orifice. The purge is used to fill up the tubing after filling up the reservoir and to eliminate air bubbles and contamination smaller than the orifice.
- Observation camera & video monitor: Allows the visualization of the drop formation together with a LED that is turned on synchronously with the drop generation.
- Mechanical mounting: Mounts the various components and aligns them with respect to each other.
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