Deep Reactive-Ion Etched Micro Valves for Spacecraft Propulsion

Micromanufacturing and Nanotechnology

Solid-State Sensors, …

We present MEMS polysilicon microvalves for flow control of a rapid analytical microsystem (Micro-Gas-Analyzer, MGA). All valve components (boss, seat, springs, electrodes, and stops) are surface micromachined in the SUMMiT TM microfabrication process. The valves have been characterized at high flow rate when open (60 ml/min air), low leak rate when closed (<0.0025 ml/min Hydrogen, H2), and tunable closing pressures (1 to 35 psig). Active electrostatic valves have been shown to hold closed (voltage on) against a high pressure (>40 psig) for sample loading, open for gas chromatograph (GC) loading (voltage off), and reclose against low pressure 2-5 psig.

Journal of Physics: Conference Series, 2015

Since combustion is an easy way to achieve large quantities of energy from a small volume, we developed a MEMS based solid propellant microthruster array for small spacecraft and micro-air-vehicle applications. A thruster is composed of a fuel chamber layer, a top-side igniter with a micromachined nozzle in the same silicon layer. Layers are assembled by adhesive bonding to give final MEMS array. The thrust force is generated by the combustion of propellant stored in a few millimeter cube chamber. The micro-igniter is a polysilicon resistor deposited on a low stress SiO 2 /SiN x thin membrane to ensure a good heat transfer to the propellant and thus a low electric power consumption. A large range of thrust force is obtained simply by varying chamber and nozzle geometry parameters in one step of Deep Reactive Ion Etching (DRIE). Experimental tests of ignition and combustion employing home made (DB+x%BP) propellant composed of a Double-Base and Black-Powder. A temperature of 250 °C, enough to propellant initiation, is reached for 40 mW of electric power. A combustion rate of about 3.4 mm/s is measured for DB+20%BP propellant and thrust ranges between 0.1 and 3,5 mN are obtained for BP ratio between 10% and 30% using a microthruster of 100 µm of throat wide.

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.

IEEE Transactions on Components, Packaging, and Manufacturing Technology: Part B, 1998

The advent of MEMS (microelectromechanical system) will enable dramatic changes in semiconductor processing. MEMS-based devices offer opportunities to achieve higher functionality, at lower cost, with decreased size and increased reliability. In this work, we describe the achievement of several important devices for use in the semiconductor equipment industry. They include a low-flow mass flow controller, a highprecision pressure regulator, and an integrated gas panel. Compared to current technology, the devices are ultra-small in size, thus minimizing dead volumes and gas contact surface areas. With wettable surfaces comprised of ceramic and silicon (or, silicon coated with Si3N4 or Sic), they are resistant to corrosion, and generate virtually no particles. The devices are created fiom modular components. The science and technology of these components wiU be detailed. The modules examined are: normally-open proportional valves; normally-closed, low leak-rate shut-off valves; critical orifices (to extract information of flow rate); flow models (to extract flow rate fiom pressure and temperature information); siliconbased pressure sensors; and, the precision ceramic-based packages which integrate these modules into useful devices for semiconductor processing. The work finishes with a detailed description of the low-flow mass flow controller. List of Symbols and Variables Volumetric change and initial volume of Fluorinert Temperature coefficient of expansion of Fluorinert liquid Mean and fiU temperatures of Fluorinert liquid Membrane stroke (or, membrane-to-NO-orifice gap) and radius Membrane, cavity thickness Pressure differential across the membrane Young's modulus (190,000 m a) and Poisson's ratio (0.09) for silicon Membrane stress Mass flow (typically in sccm, normalized to the STP flow at 273 IS) Inlet, outlet, intermediate (pressure sensor) pressures Flow velocity, loss coefficient Ratio of specific heats, cp / c,-/Hl + Y Gas = JZL constant in p = pRT (8314 m 2 K-sec' divided by mol. wt.

With the growth of interest in small satellites (<10kg), there is a particular need to provide a propulsion element for this class of spacecraft. Microfabricated electrospray thrusters offer a solution to this problem. By using ionic

Journal of Micromechanics and Microengineering, 2010

Recent progress in patterned microelectrode manufacturing technology and microfluidics has opened the way to a large variety of cellular and molecular biosensor-based applications. In this extremely diverse and rapidly expanding landscape, silicon-based technologies occupy a special position, given their statute of mature, consolidated, and highly accessible areas of development. Within the present work we report microfabrication procedures and workflows for 3D patterned gold-plated microelectrode arrays (MEA) of different shapes (pyramidal, conical and high aspect ratio), and we provide a detailed characterization of their physical features during all the fabrication steps to have in the end a reliable technology. Moreover, the electrical performances of MEA silicon chips mounted on standardized connector boards via ultrasound wire-bonding have been tested using non-destructive electrochemical methods: linear sweep and cyclic voltammetry, impedance spectroscopy. Further, an experimental recording chamber package suitable for in vitro electrophysiology experiments has been realized using custom-design electronics for electrical stimulus delivery and local field potential recording, included in a complete OPEN ACCESS

Sensors and Actuators B: Chemical, 1996

This investigation addresses the important question of whether or not silicon-based micromachined chemical sensors are a viable option for gas sensing in harsh, high-temperature flow applications such as automotive exhaust. Data are presented on the thermal and mechanical stability and long-term functionality of micromachined silicon devices containing ultra-thin Pt/TiOx films supported on a heated muitilayer silicon oxide/silicon nitride membrane. These gas detectors were originally designed for use in vacuum applications such as reactive ion etching systems. Significant modifications in device structure and materials are required to adapt these sensors for use in harsh thermal and chemical environments at elevated pressures. To test the long-term structural integrity of the sensors, they are subjected to a test protocol including pressure fluctuations, thermal shock, and mechanical vibrations. For characterization purposes, electrical resistance measurements, optical microscopy, atomic force microscopy (AFM), and Auger spectroscopy have been used. Our results indicate that properly designed micromachined silicon structures can survive long-term operation at high temperatures in ambient air, and can withstand rapid fluctuations of temperature, pressure, and flow rate.

We study microthrusters which can be used in various flight and underwater platforms. The MEMS-technology thrusters with Al/I 2 O 5 and Al/Bi 2 O 3 nanostructured energetic composites increase thrust-to-weight ratio and energy density, thereby ensuring enabling capabilities. The integrated micromachining ensures overall technology compatibility, scalability, simplicity, affordability, robustness, etc. These lead to advantages as compared to conventional solutions. The MEMS-technology microthrusters with solid-fuel are suitable in a wide range of applications, such as payload delivery, stabilization, guidance, navigation and other platforms.

2004

Reliable microfluidic interconnectors are one of the basic building blocks of integrated fluidic and chemical reaction systems-on-chip. Though many ideas have been proposed and implemented in the literature for creating different kinds of macro-to-micro fluidic connections, development of integrated on-chip connectors for high temperature and pressure microfluidic applications has not been properly studied. Such connectors will be indispensable in true on-chip chemical processing applications for reactions which require more severe operating conditions than those possible using currently available interconnection techniques. In this paper we present novel microfluidic interconnects that can be used in applications involving operating temperatures of up to 275 • C and pressures in excess of 315 Psi (21.43 atm). The only wetted surfaces in this design are teflon, silicon and pyrex glass, making the design inert to most chemicals. High-pressure leakage, pull-out and high-temperature durability tests conducted on the interconnect show that the connections obtained are superior to those reported in the literature using other techniques. Structural analysis of the interconnect is carried out to illustrate the effect of interconnect geometry on strength and high-pressure performance.