Applications for drop ejectors range from ink jet printing to drug delivery systems. MEMS (Micro-Electro-Mechanical Systems) fabrication techniques, particularly surface micromachining, allow production of small monolithic structures that can be adapted to many applications. We report on the design, fabrication, and testing of a surface micromachined MEMS liquid ejection system for printing applications. The ejectors were fabricated using the SUMMiT™ process,1 a surface micromachining technique. The only assembly required is electrical connection and attachment of a fluid reservoir. The process features three, four or five layers of structural polysilicon, separated by layers of sacrificial silicon dioxide. The final step of the fabrication process is the removal of the oxide to release the “machined” structure. The ejector produces small volume (2 – 4 picoliters), satellite-free drops traveling at 5 – 10 m/s. To eject a drop a piston is drawn rapidly towards a plate containing a nozzle through which the drop is ejected. The piston is electrostatically actuated. Since the electric field acts across the liquid bath, device operation is sensitive to the dielectric strength, breakdown voltage and conductivity of the fluid.
A. Gooray, G. Roller, P. Galambos, K. Zavadil, R. Givler, F. Peter, J. Crowley, "Design of a MEMS Ejector for Printing Applications" in Journal of Imaging Science and Technology, 2002, pp 415 - 421, https://doi.org/10.2352/J.ImagingSci.Technol.2002.46.5.art00004