Takahashi, Koji; Sakai, Hirofumi; Nagayama, Kunihito; Baba, Akihito; Makihira, Kenji; Asano, Tanemasa

AIAA Thermophysics Conference, 35th, Anaheim, CA, June 11-14, 2001

A vaporization microchamber is fabricated by the MEMS technology in order to improve and check the concept of a vaporizing liquid microthruster for a nanosatellite. This chamber is a part of microchannel with 2-10-micron height made by silicon and glass substrates. The nozzle is fabricated in silicon just above a thin film ITO heater deposited on glass. Liquid propellant is repetitively pulse-heated by the heater, and the flow pattern is recorded thorough glass and ITO by a high-speed video camera. Four types of flow patterns are found depending on the employed voltage, pulse width, and frequency. For example, large heat flux per pulse of high frequency does not allow the liquid to fill the chamber. Even with lower heat flux, no droplet emission from the nozzle is observed because the nozzle itself is sufficiently heated in this geometry. The nanoscale cavity or roughness on the heating surface is found to play an important role for the nucleation in the microchannel. The preferable thermal design for the microthruster is also discussed. (Author)

Ayazi, Farrokh; Najafi, Khalil

Journal of Microelectromechanical Systems (1057-7157), vol. 10, no. 2, Jun. 2001, p. 169-179

This paper presents the design, fabrication, and testing of an 80-micron-thick, 1.1-mm-diameter high aspect-ratio (20:1) polysilicon ring gyroscope (PRG). The vibrating ring gyroscope was fabricated through the high aspect-ratio combined poly and single-crystal silicon MEMS technology (HARPSS). This all-silicon single-wafer technology is capable of producing electrically isolated vertical electrodes as tall as the main body structure with various size air-gaps ranging from submicron to tens of microns. A detailed analysis has been performed to determine the overall sensitivity of the vibrating ring gyroscope and identify its scaling limits. An open-loop sensitivity of 200micro-V/deg s in a dynamic range of +/- 250 deg/s was measured under low vacuum level for a prototype device tested in hybrid format. The resolution for a PRG with a quality factor (Q) of 1200, drive amplitude of 0.15 micron, and sense node parasitic capacitances of 2 pF was measured to be less than 1 deg/s in 1 Hz bandwidth, limited by the noise from the circuitry. Elimination of the parasitic capacitances and improvement in the quality factor of the ring structure are expected to reduce the resolution to 0.01 deg/s sq rt Hz. (Author)

Voronka, Nestor; Johnson, Derek; Benny, Richard J; Millette, William L, Jr

AIAA Aerodynamic Decelerator Systems Technology Conference and Seminar, 16th, Boston, MA, May 21-24, 2001

Cybernet Systems, a small research firm based in Ann Arbor, MI, is exploring the feasibility of a military reserve parachute Automatic Activation Device (AAD). Commercial AADs are currently available to civilian jumpers, but are designed only for high-altitude jumps and are prohibitively expensive. Cybernet's AAD utilizes inexpensive MEMS which are being developed for the automotive industry. Cybernet uses these sensors, including accelerometers and pressure transducers, to create a modified inertial navigation system. This inertial navigation system is then used to feed a sophisticated decision process, which decides, in real time, if the jumper wearing the AAD has encountered a malfunction. If a malfunction is detected, the AAD activates the jumper's reserve parachute by firing a pyrotechnic device, which pulls the reserve ripcord. The most up-to-date decision algorithm created by Cybernet has proven 100 percent effective upon a limited data set. Cybernet is currently preparing to expand the data set to include special scenarios such as when a jumper is towed by the aircraft and to further test the decision algorithm. (Author)

Gad-el-Hak, Mohamed

Journal of Aircraft (0021-8669), vol. 38, no. 3, May-June 2001, p. 419-429

Micro-air-vehicles (MAV) are small, autonomous, aerial vehicles designed for reconnaissance and difficult to reach missions. Microelectromechanical systems (MEMS) are extremely small machines in which electronic and mechanical components are combined on a single silicon chip using photolithographic micromachining techniques. The question of whether MEMS can help improve the performance of futuristic MAV is pondered. The treatment focuses on the lifting and control surfaces of MAV, particularly the fixed-wing type. Two additional ideas are advanced to improve the performance of the lifting surfaces of MAV: (1) effecting chaotic mixing to energize the laminar boundary layer and thus delay separation and (2) using genetic algorithms to optimize the shape of the airfoil section. (Author)

Liang, Y C; Lin, W Z; Lee, H P; Lim, S P; Lee, K H; Feng, D P

Journal of Micromechanics and Microengineering (0960-1317), vol. 11, no. 3, May 2001, p. 226-233

This paper proposes a neuro-network-based method for model reduction that combines the generalized Hebbian algorithm (GHA) with the Galerkin procedure to perform the dynamic simulation and analysis of nonlinear MEMS. An unsupervised neural network is adopted to find the principal eigenvectors of a correlation matrix of snapshots. It has been shown that the extensive computer results of the principal component analysis using the neural network of GHA can extract an empirical basis from numerical or experimental data, which can be used to convert the original system into a lumped low-order macromodel. The macromodel can be employed to carry out the dynamic simulation of the original system resulting in a dramatic reduction of computation time while not losing flexibility and accuracy. Compared with other existing model reduction methods for the dynamic simulation of MEMS, the present method does not need to compute the input correlation matrix in advance. It needs only to find very few required basis functions, which can be learned directly from the input data, and this means that the method possesses potential advantages when the measured data are large. The method is evaluated to simulate the pull-in dynamics of a doubly clamped microbeam subjected to different input voltage spectra of electrostatic actuation. The efficiency and the flexibility of the proposed method are examined by comparing the results with those of the fully meshed finite-difference method. (Author)

Witherspoon, Scott R; Tung, Steve; Roe, Larry A

AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference and Exhibit, 42nd, Seattle, WA, Apr. 16-19, 2001

Inflatable structures are susceptible to damage in orbit from effects, such as radiation and small holes caused by micrometeoroids. Health monitoring of the structures is important for knowing the condition of the structure and to provide early warning of impending failure. Traditional sensor packages can be bulky, expensive, and rigid, making them unsuitable for the flexible surfaces and contours of inflatable structures. We are currently developing a MEMS-based sensor module that is low-cost, low-mass, and flexible. To achieve low cost, the sensor suite utilizes commercial-off-the-shelf sensors for monitoring physical quantities, such as temperature, strain, pressure, and acceleration. The sensors are packaged together on a flexible polyimide substrate providing ample flexibility. The double-sided substrate consists of copper traces allowing backside leads and contacts. Through matching contacts on the surface of the inflatable structure, it will be possible to install the health-monitoring module by simple attachment methods. Integration of sensors and actuators was investigated and initial assessments were made. The incorporation of supporting electronics with flexible actuators will move the module toward autonomy and active control of the inflatable structure. (Author)

Meller, David M; Reiter, Joel; Terry, Mason; Boehringer, Karl F; Campbell, Mark

AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference and Exhibit, 42nd, Seattle, WA, Apr. 16-19, 2001

Microelectromechanical system (MEMS) technology promises to improve performance of future spacecraft components while reducing mass, cost, and manufacture time. Arrays of microcilia actuators offer a lightweight alternative to conventional docking systems for miniature satellites. Instead of mechanical guiding structures, such a system uses a surface tiled with MEMS actuators to guide the satellite to its docking site. This report summarizes work on an experimental system for precision docking of a "picosatellite" using MEMS cilia arrays. Microgravity is simulated with an aluminum puck on an airtable. A series of experiments is performed to characterize the cilia, with the goal of understanding the influence of normal force, picosat mass, docking velocity, cilia frequency, interface material, and actuation strategy ("gait") on the performance of the MEMS docking system. We demonstrate a 4 sq cm cilia array capable of docking a 45 g picosat with a 2 sq cm contact area with micrometer precision. It is concluded that current MEMS cilia arrays are useful to position and align miniature satellites for docking to a support satellite. (Author)

Gorinevsky, Dimitry; Hyde, Tupper; Cabuz, Cleopatra

AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference and Exhibit, 42nd, Seattle, WA, Apr. 16-19, 2001

This paper discusses how an efficient control of a gossamer structure shape can be achieved using large distributed actuator arrays. Advanced algorithms using only local information about errors and actuation for collocated and neighboring positions in each of the distributed computational elements allow achieving required control performance. A gossamer structure with built-in distributed actuators, sensors, and computational elements can be made scalable to a very large size. Of course, integrating thousands of actuators in a structure in a practically affordable way requires actuators that are mass producible. MEMS technologies based on electrostatic actuation and implemented on compliant plastic substrates represent a highly attractive proposition thanks to their very low areal density. A distributed surface control approach is a key enabler for future gossamer space apertures. (Author)

Arney, Susanne

MRS Bulletin (0883-7694), vol. 26, no. 4, Apr. 2001, p. 296-299

The author reviews MEMS (microelectromechanical systems) reliability-physics issues and MEMS-specific test methodologies, failure modes, and solutions. The examples emphasize electrostatically actuated MEMS and materials choices deriving from silicon or silicon-compatible fabrication techniques leveraged from the microelectronics industry. (CSA)

Kahn, H ; Heuer, A H ; Ballarini, R

MRS Bulletin (0883-7694), vol. 26, no. 4, Apr. 2001, p. 300, 301

Fracture-toughness results are presented for MEMS-fabricated Si specimens with varying microstructures. Sharp pre-cracks were produced by indentation in micron-scale specimens. Results suggest that only the characteristics of the Si-Si chemical bonds immediately in front of the pre-crack are involved in initiating fracture. (CSA)

de Boer, M P ; Mayer, T M

MRS Bulletin (0883-7694), vol. 26, no. 4, Apr. 2001, p. 302-304

An effort has been made to acquire an understanding of MEMS (microelectromechanical systems) tribology over a borad range of length scales, from the macroscopic to the molecular. Integrated interferometry and finite element modeling in concert with optimized test structure design have been used to determine thin-film and interfacial properties. (CSA)

Sullivan, J P ; Friedmann, T A ; Hjort, K

MRS Bulletin (0883-7694), vol. 26, no. 4, Apr. 2001, p. 309-311

The authors first examine the materials requirements for surface-micromachined MEMS (microelectromechanical systems) and amorphous diamond MEMS. They then examine the characteristics of nanocrystalline and polycrystalline diamond MEMS. They conclude that carbon, with its remarkable diversity of structure and exceptional materials properties, shows considerable potential for future MEMS devices. (CSA)

Elders, Job ; Spiering, Vincent ; Walsh, Steve

MRS Bulletin (0883-7694), vol. 26, no. 4, Apr. 2001, p. 312-315

The authors suggest that microsystems technology (MST) is a potentially disruptive technology, offering factor improvement over sustaining technologies when the applications can take advantage of miniaturization and other critical performance features not currently supported by the existing technology /product paradigm. Some of the industries that MST has the potential to revolutionize are discussed, with attention given to MST applications in connection with fluidic systems, optical systems, sensors for process instrumentation, and RF MEMS. (CSA)

Richards, Randy J; De Los Santos, Hector J

Microwave Journal (0192-6225), vol. 44, no. 3, Mar. 2001, p. 20, 24, 28 (4 ff)

Microelectromechanical systems (MEMS) technology is on the verge of revolutionizing RF and microwave applications (De Los Santos, 1999). The requirements of present-day and future RF/microwave systems for lower weight, volume, power consumption, and cost with increased functionality, frequency of operation, and component integration are driving the development of new RF/microwave MEMS components and system architectures. (Author)

Saari, H; Sillanpaa, T; Eiden, M; Kugel, U

Preparing for the Future (1018-8657), vol. 11, no. 1, Mar. 2001, p. 8-9

There is a demand in space applications for a low-cost light controllable axial fine-pointing mirror with a large bandwidth. Microelectromechanical system (MEMS) techniques are very suitable for space applications, offering devices with reduced size, mass, and power consumption. In 1997, VTT Automation, Measurement Technology of Finland started an internally funded project to develop a scanning micromechanical mirror. In 1998 this work was continued under ESA funding. The feasibility of this technology for a fine-pointing mirror of an intersatellite link was assessed, and a prototype was designed, manufactured, and tested. The two-axis mirror has a gimbal design and is electrostatically actuated. Capacitive readout provides high-accuracy measurement of the mirror angles. The design details and the results of the tests are discussed in this article. (CSA)

Mihailovich, R E; Kim, M; Hacker, J B; Sovero, E A; Studer, J; Higgins, J A; DeNatale, J F

IEEE Microwave and Wireless Components Letters (1531-1309), vol. 11, no. 2, Feb. 2001, p. 53-55

We describe a microelectromechanical (MEM) relay technology for high-performance reconfigurable RF circuits. This microrelay, fabricated using surface micromachining, is a metal contact relay with electrical isolation between signal and drive lines. This relay provides excellent switching performance over a broad frequency band (insertion loss of 0.1 dB and isolation of 30 dB at 40 GHz), versatility in switch circuit configurations (microstrip and coplanar, shunt, and series), and the capability for monolithic integration with high-frequency electronics. In addition, this MEM relay technology has demonstrated yields and lifetimes that are promising for RF circuit implementation. (Author)

Green, Amanda A

AIAA, Aerospace Sciences Meeting and Exhibit, 39th, Reno, NV, Jan. 8-11, 2001

The recent interest in the space community for small, highly integrated microspacecratt has driven the design and development of the Free Molecule Micro-Resistojet (FMMR) as a new type of micro-thruster. The FMMR combines microelectromechanical systems fabrication techniques with simple, lightweight construction. It is powered by a patterned, thin-film heater on a 400-micron thick silicon chip (13x42 mm). Resistive heating of the device imparts energy to a propellant gas prior to its expansion through several (40) narrow width (-100 p.m), long (l cm) slots to produce thrust. In this design, the FMMR thrust is proportional to the temperature of the heated device. The project design goal was to minimize device heat transfer through a wide range of operating conditions for a device design that is low cost and easy to manufacture. Requirements for a proposed mission on an Arizona State University microspacecratt will require a power-to-thrust ratio of approximately 1-2 W/mN. Recent results and calculations indicate that the current FMMR design requires approximately 1 W/mN, an improvement of almost a factor of five over previous designs for the operating condition of 600 K. This manuscript details the developments in design, fabrication and testing of initial FMMR devices, emphasizing the design improvements that will further minimize power consumption. (Author)

Tung, Steve; Maines, Brant; Jiang, Fukang; Tsao, Tom

AIAA, Aerospace Sciences Meeting and Exhibit, 39th, Reno, NV, Jan. 8-11, 2001

A MEMS-based flow control system was designed to minimize transonic flow separation over the deflected trailing edge flap of a wing. The main components of the control system are MEMS-based shear stress sensors and MEMS-based balloon actuators. Up to date, we have successfully verified our concept in wind tunnel experiments using a trailing edge ramp model instrumented with the MEMS transducers. The instrumented model was installed in the wind tunnel and tested at a series of Mach numbers between 0.2 and 0.6. Within this Mach number range, output from both the shear stress sensors and a pressure probe indicated that the balloon actuators improved the separation characteristics of the ramp model. When the micro balloons were deployed, the sensor data showed that the shear stress level on the trailing ramp increased substantially, which coincided with an enhancement in pressure recovery from the wall out to the freestream. This result demonstrated the effectiveness of MEMS transducers in both sensing and controlling flow separation. Currently, the wind tunnel data are being applied toward the development of a revolutionary closed loop separation control system applicable to existing and future high-performance aircraft. (Author)

Huang, Adam; Folk, Chris; Silva, Chris; Christensen, Brian; Chen, Yih-Far; Ho, Chih-Ming; Jiang, Fukang; Grosjean, Charles; Tai, Yu-Chong

AIAA, Aerospace Sciences Meeting and Exhibit, 39th, Reno, NV, Jan. 8-11, 2001

About six years ago, we conceived the idea of using MEMS-based transducers for aircraft maneuvering. By using micro-actuators as effectors, micro-sensors to detect the optimal actuation location, and microelectronics to provide close loop feedback decisions, a low power control system has been developed for controlling a UAV-sized aircraft. This paper covers the evolution a MEMS controlled delta wing UAV (christened Gryphon), from concept to application, and the transonic testing of the sensors and actuators. Furthermore, recent concepts have been developed to further simplify and add robustness to the control scheme. (Author)

Wereley, S T; Gui, L; Meinhart, C D

AIAA, Aerospace Sciences Meeting and Exhibit, 39th, Reno, NV, Jan. 8-11, 2001

The recent explosive increase in the use of fluidic micro-electromechanical systems (MEMS) has subsequently driven the development of fluidic measurement techniques capable of measuring velocities at length scales small enough to be of use in characterizing and optimizing these new devices. Recently, several techniques have demonstrated spatial resolutions smaller than 100 microns but larger than 10 microns. These techniques include X-Ray microimaging, molecular tagging velocimetry, and micro-laser Doppler velocimetry. However, measurements with spatial resolutions smaller than 10 microns are necessary for making measurements in many MEMS applications. Only micro-PIV has demonstrated this high spatial resolution. By using a combination of advanced imaging and processing techniques that are described here, spatial resolutions on the order of single microns can be achieved. (Author)

Cass, Stephen

IEEE Spectrum (0018-9235), vol. 38, no. 1, Jan. 2001, p. 72, 73

Microelectromechanical systems (MEMSs) would allow better front-end analog-frequency filtering than present-day filters, with much smaller components. Their sensitivity would enable channel selection within bands, which could be revolutionary for wireless. (CSA)

Neukermans, Armand; Ramaswami, Rajiv

IEEE Communications Magazine (0163-6804), vol. 39, no. 1, Jan. 2001, p. 62-69

The explosion of the Internet has brought about an acute need for broadband communications, which can only be filled with optical networking. This in turn has resulted in an unprecedented interest in optical microelectromechanical systems. Since the early days of fiber optics, it has been recognized that micro-optics is a fertile ground for the applications of MEMS. MEMS-based products offer substantial cost and performance advantages for optical networking applications in the area of switching fabrics, variable attenuators, tunable lasers, and other devices. This article provides a review of various types of MEMS technologies for optical networking applications. (Author)

Mueller, Juergen; Pyle, David; Chakraborty, Indrani; Ruiz, Ronald; Tang, William; Marrese, Colleen; Lawton, Russell

IN:Micropropulsion for small spacecraft, Reston, VA, American Institute of Aeronautics and Astronautics, Inc. (Progress in Astronautics and Aeronautics. Vol. 187), 2000, p. 303-334

The feasibility of microfabricated grid designs is investigated from the standpoint of the obtainable grid breakdown voltages. The material used in the study is silicon dioxide, a typical insulator material used in the microfabrication field. Although the motivation for this investigation was the evaluation of this material as a grid insulator in ion engine accelerator systems, data obtained in this study may also be applicable to other micropropulsion systems. (CSA)

Bay, Robert L; Breuer, Kenneth S

IN:Micropropulsion for small spacecraft, Reston, VA, American Institute of Aeronautics and Astronautics, Inc. (Progress in Astronautics and Aeronautics. Vol. 187), 2000, p. 381-397

The performance of extruded two dimensional micronozzles is analyzed. The nozzle are fabricated by deep reactive ion etching and tested for thrust and mass flow as a function of chamber pressure. Performance predictions are obtained through a numerical analysis and compared with the experimental results. The impact of viscous losses on the thrust performance is evaluated, and this is quantified as thrust efficiency, which is established as a function of the throat Reynolds number. (CSA)

Mueller, Juergen; Vargo, Stephen; Bame, David; Chakraborty, Indrani; Tang, William

IN:Micropropulsion for small spacecraft, Reston, VA, American Institute of Aeronautics and Astronautics, Inc. (Progress in Astronautics and Aeronautics. Vol. 187), 2000, p. 399-422

The currently available MEMS valve technology, as provided by the nonaerospace industry, does not meet many of the requirements of spaceflight applications with respect to leakage rates, valve actuation times, required bus voltages, or robustness of design. Here, a micro-isolation valve concept is proposed which is designed to address these shortcomings, in particular, with respect to leakage rates. The key feasibility issues are identified, and initial tests and analysis aimed at addressing these issues are discussed. (CSA)

Mueller, Juergen

IN:Micropropulsion for small spacecraft, Reston, VA, American Institute of Aeronautics and Astronautics, Inc. (Progress in Astronautics and Aeronautics. Vol. 187), 2000, p. 449-476

MEMS microvalve technologies are essential for propulsion systems featuring a high degree of miniaturization and integration. Here, the currently available MEMS valves are reviewed and evaluated from the standpoint of microspacecraft applications. Several technology needs are identified, indicating the need for substantial additional development efforts if this valve technology is to be considered a candidate for future micropropulsion designs. (CSA)

Gonglewski, John D, Ed; Vorontsov, Mikhail A, Ed; Gruneisen, Mark T, Ed

Bellingham, WA, Society of Photo-Optical Instrumentation Engineers ( SPIE Proceedings. Vol. 4124), 2000

The present volume on high-resolution wavefront controls dicusses phase modulation devices and adaptive wavefront control systems phase modulation devices, phase modulation devices and adaptive wavefront control systems, LC-phase modulation devices for wavefront phase distortion modeling and control, phase modulation devices and adaptive wavefront control systems wavefront analysis, novel algorithms and adaptive system architectures, laser-based sensing, and dynamic measurement and correction of severely aberrated large optics compensation of severe dynamic aberrations. Attention is given to a micromachined deformable mirror for optical wavefront compensation, prospects for liquid crystals for adaptive optics applications, high-resolution curvature sensing, adaptive wavefront control using a nonlinear Zernike filter, long-range laser-illuminated imaging, real-time holographic compensation of large optics for deployment in space, object detection against the background of scattering layer media, and imaging with heterodyne laser radar and reflection tomography. (CSA)

Liou, W W; Fang, Y C

CMES - Computer Modeling in Engineering & Sciences (1526-1492), vol. 1, no. 4, 2000, p. 119-128

A simple implicit treatment for the low speed inflow and outflow boundary conditions for the direct simulation Monte Carlo (DSMC) of the flows in MEMS is proposed. The local mean flow velocity, temperature, and number density near the subsonic boundaries were used to determine the number of molecules entering the computational domain and their corresponding velocities at every sample average step. The proposed boundary conditions were validated against micro-Poiseuille flows and micro-Couette flows. The results were compared with analytical solutions derived from the Navier-Stokes equations using first-order and second order slip-boundary conditions. The results show that the implicit treatment of the subsonic flow boundaries is robust and appropriate for use in the DSMC of the flows in MEMS. (Author)

Malczewski, A; Eshelman, S; Pillans, B; Ehmke, J; Goldsmith, C L

IEEE Microwave and Guided Wave Letters (1051-8207), vol. 9, no. 12, Dec. 1999, p. 517-519

Development of a low-loss RF microelectromechanical (MEMS) 4-bit X-band monolithic phase shifter is presented. These microstrip circuits are fabricated on 0.021-in-thick high-resistivity silicon and are based on a reflection topology using 3-dB Lange couplers. The average insertion loss of the circuit is 1.4 dB with the return loss greater than 11 dB at 8 GHz. To the best of our knowledge, this is the lowest reported loss for X-band phase shifter, and promises to greatly reduce the cost of designing and building phase arrays. (Author)

Pillans, B; Eshelman, S; Malczewski, A; Ehmke, J; Goldsmith, C L

IEEE Microwave and Guided Wave Letters (1051-8207), vol. 9, no. 12, Dec. 1999, p. 520-522

As the need for low-loss phase shifters increases, so does the interest in RF MEMS as a solution to provide them. In this paper, progress in building low-loss Ka-band phase shifters using RF MEMS capacitive switches is demonstrated. Using a switched transmission line 4-bit resonant phase shifter, an average insertion loss of 2.25 dB was obtained with better than 15-dB return loss. A similar 3-bit phase shifter produced an average insertion loss of 1.7 dB with better than 13-dB return loss. Both devices had a phase error of less than 13 in the fundamental states. To our knowledge, these devices represent the lowest loss Ka-band phase shifters reported to date. (Author)

Lyshevski, Sergey E

IN:IEEE Conference on Decision and Control, 38th, Phoenix, AZ, Dec. 7-10, 1999, Proceedings. Vol. 3 (A00-48501 14-63), Piscataway, NJ, Institute of Electrical and Electronics Engineers, Inc., 1999, p. 2611-2616

New advances in micro-machining, micro-, nano- and meso-scale electromechanical devices and ICs, when combined, provide enabling benefits and capabilities to manufacture MEMS. Critical issues to be solved are to improve power and thermal management, circuitry and actuator/sensor integration, and embedded electronically controlled micro-actuator assemblies. Very large scale IC and micromachining silicon, germanium, and gallium arsenic technologies have been developed and used to manufacture ICs and micro-actuators. In order to improve the performance, the motion control problem must be addressed and solved, particularly in prospective applications of MEMS in aerospace and automotive industry, where micro-actuators, multistable relays, micro-connectors, micro-propulsion, and micro-optical systems, as well as active control micro-devices are used. The solution of a spectrum of problems in nonlinear analysis, design, and optimization of MEMS lead to the development of superior MEMS. Analytical, numerical, and experimental results are presented to demonstrate the methods and algorithms applied in nonlinear analysis, design, and control. (Author)

Balogh, Andras; Liu, Wei-Jiu; Krstic, Miroslav

IN:IEEE Conference on Decision and Control, 38th, Phoenix, AZ, Dec. 7-10, 1999, Proceedings. Vol. 3 (A00-48501 14-63), Piscataway, NJ, Institute of Electrical and Electronics Engineers, Inc., 1999, p. 2869-2874

We stabilize the parabolic equilibrium profile in a 2D channel flow using actuators and wall-shear-stress sensors only at the wall. The control of channel flow was previously considered by Speyer et al. and Bewley et al., who derived feedback laws based on linear optimal control and implemented by wall-normal actuation. With the objective of achieving global Liapunov stabilization, we arrive at a feedback law using tangential actuation (using teamed pairs of synthetic jets) and only local measurements, allowing one to embed the feedback in MEMS hardware without the need for wiring. This feedback is shown to guarantee global stability in at least the H2 norm, which by Sobolev's embedding theorem implies continuity in space and time of both the flow field and the control (as well as their convergence to the desired steady state). (Author)

von Flotow, Andy

IN:Active 99; Proceedings of the International Symposium on Active Control of Sound and Vibration, Fort Lauderdale, FL, Dec. 2-4, 1999. Pt. 2 (A01-14401 02-71), Washington, DC, Institute of Noise Control Engineering of the USA, Inc., 1999, p. 1279-1290

This paper outlines the problem of high cycle fatigue (HCF) in turbomachinery, and introduces an approach for active control of HCF. The actuation requirements are described. MEMS construction techniques for such actuators are reviewed. The most promising MEMS approaches are detailed and contrasted against alternative ways of building the required actuators. (Author)

Gill, John J; Ho, Ken; Carman, Gregory P

IN:Adaptive structures and material systems - 1999; Proceedings of the Symposium, 1998 ASME International Mechanical Engineering Congress and Exposition, Nashville, TN, Nov. 14-19, 1999 (A00-42276 11-31), New York, American Society of Mechanical Engineers (ASME Aerospace Div./Materials Div., AD-Vol. 59/MD-Vol. 87), 1999, p. 125-131

A novel two-way thin film NiTi shape memory alloy actuator is presented. Thin film shape memory alloy is sputter-deposited onto a silicon wafer in an ultra high vacuum system. Transformation temperatures of the deposited NiTi film are measured by residual stress measurement at temperatures from 25 C to 120 C. Test results show that the Mf (the Martensite Finish Temperature) is around 60 C and Af (the Austenite Finish Temperature) is around 110 C. A free standing NiTi membrane (10 mm x 10 mm and 3 microns thick) is fabricated using MEMS technology. We found that a mixture of HF, HNO3, and DI (deionized) water with thick photo resist mask works best for the fabrication process. The membrane is hot-shaped in different shapes such as dome shape, pyramidal shape, and cylindrical shape. Results indicate that when the temperature of the NiTi film exceeds Af, the NiTi membrane transforms into the trained hot-shape. When the temperature cools down to room temperature, the membrane returns to the initial flat shape. (Author)

Pochiraju, Kishore

IN:Adaptive structures and material systems - 1999; Proceedings of the Symposium, 1998 ASME International Mechanical Engineering Congress and Exposition, Nashville, TN, Nov. 14-19, 1999 (A00-42276 11-31), New York, American Society of Mechanical Engineers (ASME Aerospace Div./Materials Div., AD-Vol. 59/MD-Vol. 87), 1999, p. 213-218

This paper presents a sandwich composite architecture suitable for embedding MEMS-based accelerometers for long-term vibration monitoring or to act as sensors in adaptive structures. This architecture is designed around multi-axis accelerometers and temperature sensors that are commercially available. These devices also integrate sophisticated sensor compensation and data acquisition hardware into a single integrated circuit chip package. The paper presents the stiffness modeling of a sandwich composite with embedded accelerometers based on classical lamination theory. The fast order shear deformation theory is used to compute the free vibration response of the sandwich composite. Solutions are presented for the free-vibration response of the sandwich beam under fixed-free boundary conditions. Results presented also include the response obtained from the MEMS-accelerometer when coupled to a thick cross-ply laminate under fixed-free boundary conditions. (Author)

Mehregany, M; Roy, S

IN:Microengineering aerospace systems (A00-20551 04-31), El Segundo, CA/Reston, VA, Aerospace Press/American Institute of Aeronautics and Astronautics, Inc., 1999, p. 1-28

An overview of MEMS technology is presented, with attention given to both the potential and limitations of this technology. The discussion covers the historical background, silicon pressure sensor technology, micromachining, fabrication technologies, MEMS components, commercial applications, and recent trends in MEMS technology. Finally, a summary of journals and conferences dealing with MEMS technology is presented. (AIAA)

Michalicek, M Adrian; Comtois, John H; Schriner, Heather K

IN:Spatial light modulators; Proceedings of the Conference, San Jose, CA, Jan. 28, 29, 1998 (A98-29776 07-74), Bellingham, WA, Society of Photo-Optical Instrumentation Engineers (SPIE Proceedings. Vol. 3292), 1998, p. 71-80

This paper describes the design and characterization of several types of micromirror devices to include process capabilities, device modeling, and test data resulting in deflection vs applied potential curves and surface contour measurements. These devices are the first to be fabricated in the state-of-the-art four-level planarized polysilicon process available at Sandia National Laboratories known as the Sandia Ultra-planar Multi-level MEMS Technology (SUMMiT). This enabling process permits the development of micromirror devices with near-ideal characteristics which have previously been unrealizable in standard three-layer polysilicon processes. This paper describes such characteristics as elevated address electrodes, various address wiring techniques, planarized mirror surfaces using Chemical Mechanical Polishing (CMP), unique post-process metallization, and the best active surface area to date. (Author)

Ho, Chih-Ming; Tai, Yu-Chong

IN:Annual review of fluid mechanics. Vol. 30 (A98-30501 07-34), Palo Alto, CA, Annual Reviews, Inc., 1998, p. 579-612

The micromachining technology that emerged in the late 1980s can provide micron-sized sensors and actuators. These micro-transducers can be integrated with signal conditioning and processing circuitry to form MEMS that can perform real-time distributed control. This capability opens up a new territory for flow control research. On the other hand, surface effects dominate the fluid flowing through these miniature mechanical devices because of the large surface-to-volume ratio in micron-scale configurations. We need to reexamine the surface forces in the momentum equation. Owing to their smallness, gas flows experience large Knudsen numbers, and therefore boundary conditions need to be modified. Besides being an enabling technology, MEMS also provide many challenges for fundamental flow-science research. (Author)

Krishnamoorthy Mali, Raji; Bifano, Thomas G; Vandelli, Nelsimar; Horenstein, Mark N

Optical Engineering (0091-3286), vol. 36, no. 2, Feb. 1997, p. 542-548

The development of a silicon-based microelectromechanical deformable mirror is reported, with emphasis placed on design, fabrication, device characterization, and system integration issues. The mirror parameters are derived from theoretical and empirical models of adaptive optics. Sufficient yield is demonstrated with a standard robust actuator. Processing issues for obtaining a planar mirror surface are currently being addressed. A 20-channel electronic control circuit is used for the high-speed control of a segmented mirror array. Applications for this MEMS deformable mirror include adaptive optical imaging and projection systems as well as optical correlators for pattern recognition systems. (AIAA)

Dickey, Fred M; Holswade, Scott C; Smith, Norman F; Miller, Samuel L

IN:Miniaturized systems with micro-optics and micromechanics II; Proceedings of the Meeting, San Jose, CA, Feb. 10-12, 1997 (A97-30496 07-31), Bellingham, WA, Society of Photo-Optical Instrumentation Engineers (SPIE Proceedings. Vol. 3008), 1997, p. 52-61

Understanding the mechanisms that impact the performance of microelectromechanical systems (MEMS) is essential to the development of optimized designs and fabrication processes, as well as the qualification of devices for commercial applications. Silicon micromachines include engines that consist of orthogonally oriented linear comb drive actuators mechanically connected to a rotating gear. These gears are as small as 50 microns in diameter and can be driven at rotation rates exceeding 300,000 rpm. Optical techniques offer the potential for measuring long term statistical performance data and transient responses needed to optimize designs and manufacturing techniques. We describe the development of micromachine optical probe (MOP) technology for the evaluation of micromachine performance. The MOP approach is based on the detection of optical signals scattered by the gear teeth or other physical structures. We present experimental results obtained with a prototype optical probe and micromachines developed at Sandia National Laboratories. (Author)

Hornak, L A; Brown, K S; Taylor, B J; Barr, J C

IN:Miniaturized systems with micro-optics and micromechanics II; Proceedings of the Meeting, San Jose, CA, Feb. 10-12, 1997 (A97-30496 07-31), Bellingham, WA, Society of Photo-Optical Instrumentation Engineers (SPIE Proceedings. Vol. 3008), 1997, p. 124-135

This paper explores issues confronting the integration of waveguide technologies within the surface micromachined MEMS environment. Specific focus is placed on initial efforts developing processes for guided wave polymer optics cointegration with the Multi-User MEMS Process Service (MUMPS) surface micromachining process. Efforts studying the cointegration of polyimide waveguides with MEMS for integrated optical metrology and state feedback applications are highlighted. (Author)

Gabriel, Kaigham J

IN:1997 IEEE Aerospace Conference, Aspen, CO, Feb. 1-8, 1997, Proceedings. Vol. 3 (A97-44051 12-99), Piscataway, NJ, Institute of Electrical and Electronics Engineers, Inc., 1997, p. 9-43

A graphical presentation is given for the status and prospects of MEMS being developed under the aegis of the Defense Advanced Projects Agency; these devices, which can be either electrical or mechanical, or both, merge computation with sensing and actuation in microdimensional packages. Attention is here given to MEMS fabrications technologies derived from microelectronics manufacturing, the MEMS industry and market structure, MEMS military applications, and such representative devices as inertial measurement units, multiple device chips, optomechanical displays, environmental monitors, optical components, and a monolithic free-space optical disk pickup head. (AIAA)

De Los Santos, Hector J; Kao, Yu-Hua; Caigoy, Arturo L; Ditmars, Eric D

IN:1997 IEEE Aerospace Conference, Aspen, CO, Feb. 1-8, 1997, Proceedings. Vol. 3 (A97-44051 12-99), Piscataway, NJ, Institute of Electrical and Electronics Engineers, Inc., 1997, p. 235-254

Microelectromechanical systems (MEMS) technology is expected to impact such aerospace systems as phased-array antennas, frequency multiplexers, spacecraft guidance and navigation, onboard communications, autonomous health monitoring and safety, space structures, thermal control, and on-board system reconfigurability. One of the most ubiquitous components enabled by MEMS technology is the electrostatic microelectromechanical (MEM) switch; due to its simplicity and high performance potential, this is poised to become the pioneering MEMS component for microwave signal processing-related applications in space-based communications systems. This paper discusses the impact of microwave performance specifications of the MEM switch on its mechanical structure and design. A quantitative discussion of switch parameters (actuation voltage, actuation frequency, insertion loss, and isolation) is presented. (Author)

Lee, Gwo-Bin; Jiang, F K; Tsao, Thomas; Tai, Y C; Ho, C M

IN:1997 IEEE Aerospace Conference, Aspen, CO, Feb. 1-8, 1997, Proceedings. Vol. 3 (A97-44051 12-99), Piscataway, NJ, Institute of Electrical and Electronics Engineers, Inc., 1997, p. 255-263

During the past few years, microelectromchanical systems (MEMS) have emerged as a major enabling technology across the engineering disciplines. The possibility of applying MEMS to the aerodynamics field is explored. We demonstrate that microtransducers can be used to control the motion of a delta wing in a wind tunnel and can even maneuver a scaled aircraft in flight tests. The main advantage of using microactuators to replace the traditional control surface is the significant reduction of radar cross-sections. At a high angle of attack, a large portion of the suction loading on a delta wing is contributed by the leading edge separation vortices which originate from thin boundary layers at the leading edge. We used microactuators with a thickness comparable to that of the boundary layer in order to alter the separation process and thus achieved control of the global motion by means of minute perturbations. (Author)

Ho, Chih-Ming; Tung, Steve; Lee, Gwo-Bin; Tai, Yu-Chong; Jiang, Fukang; Tsao, Thoma

AIAA, Aerospace Sciences Meeting & Exhibit, 35th, Reno, NV, Jan. 6-9, 1997

A technology, Micro-Electro-Mechanical Systems (MEMS), emerged in the late 1980s which enables us to fabricate mechanical parts on the order of microns. Micromachining technology is suitable for developing new transducers or improving existing transducer designs. Due to the dramatic reduction in size, micro transducers can outperform traditional ones by orders of magnitude. Furthermore, MEMS is a fundamental technology which has the potential to influence advancements in many fields. In the automobile, electronics, bio-medical and television industries, MEMS products have already made appreciable impacts. In this paper, the applications of MEMS for aerodynamic control are presented. (Author)

Bishop, David; Giles, Randy; Roxlo, Charles

Photonics Spectra (0731-1230), vol. 34, no. 3, Mar. 2000, p. 167-169

The most pervasive of the bottlenecks for communications carriers are the switching and cross-connect fabrics that switch, route, multiplex, demultiplex, and restore traffic in optical networks. Transmission systems move information as photons, but switching and cross-connect fabrics until now have largely been electronic, requiring costly time-consuming bandwidth-limiting optical-to-electronic-to-optical conversions at every network connection and crosspoint. This article discusses the recently developed MicroStar cross-connect fabric, unveiled by Bell Labs, which is based on micro-optoelectromechanical system device fabrication. This process enables the construction of micromachines that are finding increasing acceptance in such application categories as communications, automotive, aerospace, and consumer electronics. MicroStar comprises 256 mirrors, each one 0.5 mm in diameter, spaced 1-mm apart, and covering a total of less than 1 sq in. of silicon. The mirrors sit within the router so that only one wavelength can illuminate any one mirror. Each mirror can tilt independently to pass its wavelength to any of 256 input and output fibers. The mirror arrays are made using a self-assembly process that causes a frame around each mirror to lift from the silicon surface and lock in place, positioning the mirrors high enough to allow a range of movement. MicroStar is part of Lucent Technology's LambdaRouter, a cross-connect system aimed at helping carriers deliver vast amounts of data unimpeded by conventional bottlenecks. The all-optical-format LambdaRouter is commercially available in June 2000 and offers a total switching capacity of more than 10 Tb/s, enabling communications providers to route more than 10 times the current Internet traffic in one second. (AIAA)