Development and Characterization of Silicon Micromachined Nozzle Units for Continuous Ink Jet Printers

Abstract

The design of a silicon micromachined nozzle unit to be used in continuous ink jet printers is suggested and characterized. A truncated pyramid shaped nozzle geometry was obtained by anisotropic etching and p–n junction etch stop processing of <100> silicon wafers. The pyramid shaped nozzle, with the exit on the front side of the silicon die, has a square orifice, which connects to the center of a 10 mm × 0.7 mm × 30 μm (L × W × D) channel situated on the backside of the die. The channel was sealed by an anodically bonded glass lid, which provided in- and outlet via drilled holes. The flow through option, given by the connection of the in- and outlet to each end of the channel, facilitates cleaning at the end of the manufacturing process as well as de-clogging of the nozzle during operation. The stimulation of the jet, to attain constant droplet size and distance between droplets, was achieved with the aid of a piezoelectric element that was glued to the glass lid on the backside of the nozzle unit. The piezoelectric element was positioned adjacent to the orifice of the nozzle to secure a good acoustic coupling to the jet. A jet emerged from a nozzle (10 μm × 10 μm orifice) with a velocity of 50 m/s at a flow rate of 0.22 ml/min when a pressure of 10 bar was used to force the ink through the nozzle unit. The droplet flight stability was characterized by an in-house developed optical measurement system. The results showed that the nozzle unit generated droplets with high droplet flight stability (less than 15° standard deviation in droplet period width measured at 7 mm from the orifice) in a large stimulation frequency region around the desired frequency of 1 MHz.