A report discusses the continuing development of a normally closed, piezoelectrically actuated valve fabricated mostly by micromachining of silicon. The design and operation of the microvalve as described in the instant report are basically the same as those of the version described in “Improved Piezoelectrically Actuated Microvalve” (NPO-30158), NASA Tech Briefs, Vol. 26, No. 1 (January 2002), page 29. Major elements of design described in both the instant report and the cited prior article include (1) a pressure-aided sealing configuration that contributes to the desired normally-closed mode of operation and (2) knife-edge sealing rings that reduce susceptibility to trapping of particles and the consequent leakage. The report also presents additional information concerning details of design and fabrication, including, notably, additional justification for knife-edge (in contradistinction to blunt-cross-section) sealing rings: The knife-edge sealing rings provide greater sealing pressure at a given sealing force, thereby reducing the leak rate and even making it possible to achieve an adequate seal with a hard seat. A potential additional advantage of the knife-edge/hard-seat design is that contact pressures may be high enough to crush contaminant particles, thereby reducing the leakage attributable to contaminants.
This work was done by Eui-Hyeok Yang, Larry Wild, and Nishant Rohatgi of Caltech for NASA’s Jet Propulsion Laboratory. To obtain a copy of the report, “A Micro Valve for High Pressure Applications,” access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Mechanics category.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to Intellectual Assets Office JPL Mail Stop 202-233 4800 Oak Grove Drive Pasadena, CA 91109 (818) 354-2240 E-mail:
This Brief includes a Technical Support Package (TSP).
Improvements in a Piezoelectrically Actuated Microvalve
(reference NPO-30338) is currently available for download from the TSP library.
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Overview
The document is a NASA Technical Support Package detailing advancements in piezoelectrically actuated microvalves, primarily for microspacecraft propulsion systems. It highlights the need for highly miniaturized and integrated propulsion components due to the small size of microspacecraft. Traditional propulsion systems often struggle with the precise control of very small thrust levels and impulse bits, necessitating the development of microvalves that can manage minimal propellant flow rates.
The report discusses the limitations of existing commercial MEMS (Micro-Electro-Mechanical Systems) valves, which typically do not meet the stringent requirements for space applications. These valves often suffer from issues such as high leak rates and inadequate pressure handling capabilities. The document emphasizes the potential of piezoelectric and electromagnetic actuation concepts, which are seen as more suitable for micropropulsion applications compared to thermal or magnetic actuation methods.
A key innovation presented is the design of a normally closed microvalve that utilizes a pressure-aided sealing configuration. This design enhances the sealing capability and reduces susceptibility to leakage caused by contaminants. The valve features knife-edge sealing rings that provide greater sealing pressure and can crush contaminants, further minimizing leakage. The report also addresses the integration of these microvalves with driver and power conditioning electronics, as well as material compatibility with liquid propellants.
The document outlines the challenges faced in developing these microvalves, including the need for sufficient seat pressures and the integration of various components into a compact system. It suggests that successful development could lead to tightly integrated micropropulsion modules ideally suited for microspacecraft.
Overall, the report underscores the importance of advancing microvalve technology to enable the next generation of microspacecraft propulsion systems. It highlights ongoing research efforts and the potential for significant improvements in performance and reliability, which are critical for the success of future space missions. The work is attributed to researchers Eui-Hyeok Yang, Larry Wild, and Nishant Rohatgi from Caltech, conducted under NASA's Jet Propulsion Laboratory.
