MEMS micro-valve for space applications

34th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 1998

A feasibility investigation for a newly proposed microfabricated, normally-closed i s o l a t i o n valve was initiated. The micro-isolation valve is silicon based and relies on the principle of melting a doped plug, opening, an otherwise sealed flow passage. This valve may thus s e r v e a similar role as a conventional pyrovalve and is intended for use in micropropulsion systems onboard future microspacecraft, having wet masses of no more than 10-20 kg, a s well as in larger scale propulsion systems having only low flow rate requirements, such a s ion propulsion or Hall thruster systems. Two key feasibility issuesmelting of the plug and pressure handling capability were addressed. Thermal finite element modeling showed that valves with plugs having widths between 10 and 50 pm have power requirements of only 10 -30 Watts to open over a duration of 0.5 ms or less. Valve chips featuring 50 micron p l u g s were burst pressure tested and reached maximum pressure values of 2850 psig (19.4 Mpa).

2010

Based on a previously developed piezoelectric membrane actuator a normally closed piezoelectric micro valve is designed. The principle of this novel actuator is explained in this paper as well as the possible design of a normally closed piezoelectric micro valve. The actuator operates with surface electrodes. The thus generated electric field causes an inhomogeneous mechanical stress distribution within the piezoelectric material. Because of this the piezoelectric material is forced to deflect without any supporting passive membrane. If this actuator is placed smartly in a micro valve device a normally closed piezoelectric micro valve can be created, as will be shown in this paper.

The advent of remote sensing satellites is gaining vital importance for national resource surveys. The control systems required for such satellites call for stringent propulsion systems with high precision actuators. These satellites use monopropellant propulsion systems which need to deliver impulses as less as 30 mNs with an actuator (thruster) on time of 30ms for day to day attitude corrections or even to extended period of operating up to a few thousand seconds firing of the actuators for major orbital plane corrections which may have to be carried out few time during the life span of the satellite. Further the propellant delivery to the actuators is by actuation of a solenoid valve which plays a vital role on the overall capability of the propulsion system. Any minute leakage though these valves could generate continuous thrust of a few mN which could affect the quality of the imagery obtained by the on board remote sensing devices. Extreme leak tightness through the valve is an important criterion for design.

2010

Based on a previously developed piezoelectric membrane actuator a normally closed piezoelectric micro valve was designed. The presented paper briefly explains the principle of this novel actuator and continues with the possible design of a normally closed piezoelectric micro valve. The actuator operates with surface electrodes. The thus generated electric field causes an inhomogeneous mechanical stress distribution within the piezoelectric

Sensors and Actuators A-physical, 2005

Microfuel cell systems require microvalves that are chemically tolerant of hydrogen, have thermally insensitive activation mechanisms, and tight geometric constraints. A planar bulk-micromachined piezoelectric valve for portable fuel cell system is proposed. The actuating diaphragm and the valve seat are etched on silicon wafers. A piezoelectric bimorph disc is glued to the actuating diaphragm to lift the diaphragm and open the valve. The pressure differential between the valve chamber and the outlet and the initial pressure caused by the deformed tethers are employed to increase the sealing force. The actuating device with four Z-tethers attached to the actuating diaphragm is thermally insensitive and can reduce thermally induced deflection at the center and avoid clamping effect at circumferential edge. The proposed actuating diaphragm with Z-tethers shows good thermal stability and excellent actuating performance through the finite element method (FEM) analyses. The prototype valve of 20 mm in diameter and 2 mm thick was fabricated and tested as a regulator. Using compressed air, the flow characteristics for the prototype valve were measured at different inlet pressure and elevated air temperature. The design, fabrication, simulation and characterization of the prototype valve are described. Crown

Proceedings of the International Solid-State Sensors and Actuators Conference - TRANSDUCERS '95, 2000

Journal of Microelectromechanical Systems, 1999

Technologies for fabricating silicone rubber membranes and integrating them with other processes on silicon wafers have been developed. Silicone rubber has been found to have exceptional mechanical properties including low modulus, high elongation, and good sealing. Thermopneumatically actuated, normally open, silicone rubber membrane valves with optimized components have been designed, fabricated, and tested. Suspended silicon nitride membrane heaters have been developed for low-power thermopneumatic actuation. Composite silicone rubber on Parylene valve membranes have been shown to have low permeability and modulus. Also, novel valve seats were designed to improve sealing in the presence of particles. The valves have been extensively characterized with respect to power consumption versus flow rate and transient response. Low power consumption, high flow rate, and high pressure have been demonstrated. For example, less than 40 mW is required to switch a 1-slpm nitrogen flow at 33 psi. Water requires close to 100 mW due to the cooling effect of the liquid. [427]

Acta Astronautica, 2003

Development of MEMS (Microelectromechanical Systems) micropropulsion at the Jet Propulsion Laboratory (JPL) is reviewed. This includes a vaporizing liquid micro-thruster for microspacecraft attitude control, a micro-ion engine for microspacecraft primary propulsion or large spacecraft fine attitude control, as well as several valve studies, including a solenoid valve studied in collaboration with Moog Space Products Division, and a piezoelectric micro-valve. The solenoid valve features much faster actuation (as little as 1.5 ms to open) than commercially available MEMS valves and showed no detectable leak (< 10-4 sccs GN 2) even after 1 million cycles. The solenoid valve weighs 7 gram and is about 1 cm 3. A micro-isolation valve, aimed at sealing propulsion systems at zero leak rates, was able to show burst pressures as high as 3,000 psi even though entirely machined from silicon and Pyrex. It could be actuated with energies as little as 0.1 mJ. I. INTRODUCTION: THE MICROSPACECRAFT BACKGROUND Propulsion is a key subsystem to most spacecraft, having significant impacts on spacecraft volume and mass. Small (<100 kg) or microspacecraft (<20 kg), however, appear to have been an exception in this regard in the past, often making do with either no propulsion system at all, or requiring only very limited propulsive capability 1. As small and microspacecraft continue to develop, however, one might expect such spacecraft to exhibit increasing degrees of capability and complexity, mirroring similar such trends in virtually every branch of technology. Specifically, small and microspacecraft will likely continue to evolve beyond the status of mere technology demonstrators, which represent a fair fraction of today's microspacecraft (see below). They increasingly may have actual primary missions to fulfill that may require high degrees of maneuverability, necessitating the use of propulsion systems. For example, small and microspacecraft may be deployed in constellations for earth observation or communication, as in the case of the Air Force TechSat 21 mission 2,3 , consisting of a multitude of 100-kg class spacecraft (Fig. 1). Microspacecraft may also be deployed for "tensormapping" missions 1 , such as magnetic field mapping around Earth (see Fig. 2), the Sun, or other planets, as currently envisioned in the National Aeronautics and Space Administration's (NASA's) Sun-Earth Connection theme of

Electronic and Photonic Packaging, Electrical Systems and Photonic Design, and Nanotechnology, 2003

There is a need for small valves which control flow at high temperature and pressure for a number of commercial and military applications. However, traditional solenoid actuated valves are typically expensive, heavy and subject to undesirable electrical and mechanical failure modes. Micromachining techniques, commonly used in the electronics industry, are finding more and more applications for Micro Electro Mechanical Systems (MEMS). Most of the previous work in the area of MEMS valves has been limited to low pressure/low temperature flows at ambient conditions. In this presentation, the development and testing of a two stage MEMS diaphragm valve that is capable of operating at high temperature and pressure gas flows is presented. Valve requirements, tolerances and thermal management are considered in the design. Valve fabrication processes, such as Reactive Ion Etching (RIE) and laser ablation, are discussed in detail. Issues related to the actuation of the microvalve are also disc...

Micromanufacturing and Nanotechnology