Ejectors applications range from ink-jet printing to drug delivery. MEMS (Micro-Electro-Mechanical Systems) fabrication techniques, particularly surface micromachining, allow production of small monolithic structures that can be adapted to many applications. We will 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 (www.sandia.mdl/Micromachine), a surface micromachining process. The only assembly required is electrical connection and attachment of a fluid reservoir. The process includes 3 layers of structural polysilicon (poly), separated by layers of sacrificial silicon dioxide (oxide). The final step of the fabrication process is the removal of the oxide to release the poly structure.The system ejects small volume (3-4 picoliters), satellite free drops at approximately 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 ejectors are electrostatically actuated. Since the electric field is across the ejected fluid, 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, "A MEMS Ejector for Printing Applications" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP17), 2001, pp 278 - 286, https://doi.org/10.2352/ISSN.2169-4451.2001.17.1.art00061_1