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.
Lars Palm, Lars Wallman, Thomas Laurell, Johan Nilsson, "Development and Characterization of Silicon Micromachined Nozzle Units for Continuous Ink Jet Printers" in Journal of Imaging Science and Technology, 2000, pp 544 - 551, https://doi.org/10.2352/J.ImagingSci.Technol.2000.44.6.art00012