A micrornachined vapor jet pump

Initial results from a micro-pump based on the principle of macroscopic vapor-jet- and diffusion-pumps are presented. A mathematical description of the underlying gas dynamics is given and equations for the calculation of pump geometry are derived. Several planar microvapor jet pumps with different geometries were designed and fabricated by means of silicon micromachining (STS Advanced Silicon Etch (TM)). The pumps consist of two Laval nozzles and water-cooled sidewalls. Pumping was achieved via momentum transfer of externally supplied nitrogen gas and water vapor respectively after expanding through the nozzles. To derive key parameters for future designs, various pump configurations with different geometries were tested. Based on the results of the measurements, it is proven that the pump principle can be transferred to micro-systems. It is shown that a differential pressure between the fore vacuum side and the high vacuum side is achieved due to the pumping effect of the supersonic jet. (c) 2004 Elsevier B.V. All rights reserved.