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Articles 1 - 30 of 46
Full-Text Articles in Engineering
Simultaneous Actuation And Sensing Of Electrostatic Mems, Jacob E. Song
Simultaneous Actuation And Sensing Of Electrostatic Mems, Jacob E. Song
Theses and Dissertations
Micro-Electro-Mechanical Systems (MEMS) are devices that play important roles of sensing and actuation in many different industries including automation, electronics, medical, communications, and defense. In order to make full use of these devices, it is important to understand the peripherals that enable these devices. Simultaneous actuation and control of MEMS devices is an important area of research as it enables feedback control of these device and allows devices to maintain performance as devices depreciate over their lifetime. The aim of this thesis is to perform a design space analysis on an electrostatic MEMS simultaneous actuation and sensing circuit that is …
Feasibility Study Of Radio Frequency Microelectromechanical Filters For Space Operation, Karanvir Singh
Feasibility Study Of Radio Frequency Microelectromechanical Filters For Space Operation, Karanvir Singh
Theses and Dissertations
Piezoelectric contour mode resonator technology has the unique advantage of combining low motional resistance with the ability to define multiple frequencies on the same substrate. Contour mode resonators can be mechanically coupled together to form robust band-pass filters for the next generation of GPS satellites with extreme size reduction compared to electrically coupled filters. Piezoelectric zinc oxide (ZnO) contour mode resonators have the potential for monolithic integration with current ZnO transistor further reducing size, power consumption, and cost of filter modules. Barium strontium titanate (BST) contour mode resonators have incredible frequency tunability due to the fundamental nature of the thin …
Robust Scandium Aluminum Nitride Mems Resonators For L Band Operation In Orbital Environments, Israel W. Dunk
Robust Scandium Aluminum Nitride Mems Resonators For L Band Operation In Orbital Environments, Israel W. Dunk
Theses and Dissertations
This thesis investigates AlN alloyed with scandium in a variety of resonator architectures including WEM, overtone WEM, LEM, and SAW that have the potential to achieve high levels of electrical performance and environmental robustness. SAW resonators operating near 370 MHz are fabricated on polycrystalline Sc.37Al.63N, and AlN with the resulting devices compared and conclusions drawn as to the merits of each material. The design and fabrication of SAW devices is discussed in detail, with the operating characteristics of these resonators then tested both electrically and mechanically. Mechanical characterisation includes analysis of vibration and shock effects on …
Characterization Of Reactive Ion Etch Chemistries Using Direct Write Lithography, Dylan T. Martin-Abood
Characterization Of Reactive Ion Etch Chemistries Using Direct Write Lithography, Dylan T. Martin-Abood
Theses and Dissertations
The DoD requires a variety of COTS and number of custom microelectronics to provide important functionality to critical military systems. Photolithography and DRIE are two techniques commonly used in the development of deep anisotropic features for the fabrication and modification of microelectronics and MEMS. However, standard photolithography techniques are ineffective for unique substrate geometries and DRIE processes require a chemical passivation step only applicable to Si substrates. This work confirmed the capability of RIE using DWL to perform deep, highly selective, anisotropic etching on elevated, non-circular substrates.
Micro-Contacts With 3-D Surfaces Made With Grayscale Lithography, Paul L.J. Michaud
Micro-Contacts With 3-D Surfaces Made With Grayscale Lithography, Paul L.J. Michaud
Theses and Dissertations
MEMS switches show advantages over FET transistors and PIN diodes for switching applications due to low contact resistance, high linearity, low power use, better isolation and lower insertion loss. The switches have not replaced FETs or PIN diodes due to perceived limitations in their reliability and the need for stable contact resistance. In order to create switches acceptable for industry applications, research on micro-contact physics and failure mechanisms of micro-contacts is necessary to develop durable contact surfaces. The aim of this research was to design and fabricate micro-contacts with three-dimensional surfaces using grayscale lithography. The goal was to create devices …
Event-Based Visual-Inertial Odometry On A Fixed-Wing Unmanned Aerial Vehicle, Kaleb J. Nelson
Event-Based Visual-Inertial Odometry On A Fixed-Wing Unmanned Aerial Vehicle, Kaleb J. Nelson
Theses and Dissertations
Event-based cameras are a new type of visual sensor that operate under a unique paradigm. These cameras provide asynchronous data on the log-level changes in light intensity for individual pixels, independent of other pixels' measurements. Through the hardware-level approach to change detection, these cameras can achieve microsecond fidelity, millisecond latency, ultra-wide dynamic range, and all with very low power requirements. The advantages provided by event-based cameras make them excellent candidates for visual odometry (VO) for unmanned aerial vehicle (UAV) navigation. This document presents the research and implementation of an event-based visual inertial odometry (EVIO) pipeline, which estimates a vehicle's 6-degrees-of-freedom …
A Mems Dual Vertical Electrometer And Electric Field-Mill, George C. Underwood
A Mems Dual Vertical Electrometer And Electric Field-Mill, George C. Underwood
Theses and Dissertations
Presented is the first iteration of a Microelectromechanical System (MEMS) dual vertical electrometer and electric field-mill (EFM). The device uses a resonating structure as a variable capacitor that converts the presence of a charge or field into an electric signal. Previous MEMS electrometers are lateral electrometers with laterally spaced electrodes that resonate tangentially with respect to each other. Vertical electrometers, as the name suggests, have vertically spaced electrodes that resonate transversely with respect to each other. The non-tangential movement reduces damping in the system. Both types demonstrate comparable performance, but the vertical electrometer does so at a fraction of the …
Increasing The Sensitivity Of Surface Acoustic Wave (Saw) Chemical Sensors And Other Chemical Sensing Investigations, Nina R. Smith
Increasing The Sensitivity Of Surface Acoustic Wave (Saw) Chemical Sensors And Other Chemical Sensing Investigations, Nina R. Smith
Theses and Dissertations
The work involves the fabrication and testing of three different surface acoustic wave (SAW) device designs, an investigation of nanowires sensitive to chemicals and preconcentrator prototypes to include with chemical sensors. The SAW chemical sensor designs include modifications to a basic SAW device to see if the sensitivity of the SAW device is increased. The modifications consist of etched trenches along the propagation field, coating the device with carbon nanotubes (CNTs) under the chemically sensitive layer and coating CNTs on top of the chemically sensitive layer. SAW devices are coated with Nafion®, a polymer sensitive to ethanol. The tests indicate …
Investigation Of Thermal Management And Metamaterials, Calvin T. Roman
Investigation Of Thermal Management And Metamaterials, Calvin T. Roman
Theses and Dissertations
Thermal metamaterials are materials composed of engineered, microscopic structures that exhibit unique thermal performance characteristics based primarily on their physical structures and patterning, rather than just their chemical composition or bulk material properties. The heat transfer performance attributes of a thermal metamaterial are such that similar performance cannot be obtained using conventional materials or compounds. Thermal metamaterials are an emerging technology, and are just now beginning to be acknowledged and developed by the microelectronics and material sciences community. This thesis effort analyzed the current state of thermal metamaterial research, examined the physics and theory of heat transfer and electrical conductivity …
Investigation Into Contact Resistance And Damage Of Metal Contacts Used In Rf-Mems Switches, Kevin W. Gilbert
Investigation Into Contact Resistance And Damage Of Metal Contacts Used In Rf-Mems Switches, Kevin W. Gilbert
Theses and Dissertations
This research examines the physical and electrical processes involved in lifecycle failure of Microelectromechanical (MEMS) Radio-Frequency (RF) cantilever beam ohmic contact switches. Failures of these switches generally occur at the contact, but complete details of performance of microcontacts are difficult to measure and have not been previously reported. This study investigated the mechanics of microcontact behavior by designing and constructing a novel experimental setup. Three representative contact materials of varying microstructure (Au, Au5%Ru, Au4%V2O5) were tested and parameters of contact during cycling were measured. The Au4%V2O5, a dispersion strengthened material developed at …
Conceptual Mems Devices For A Redeployable Antenna, Virginia Miller
Conceptual Mems Devices For A Redeployable Antenna, Virginia Miller
Theses and Dissertations
Micro-Electro-Mechanical Systems (MEMS) are becoming an integral part of our lives through a wide range of applications, including MEMS accelerators for air bag deployment in vehicles, micromirrors in projection devices, and various sensors for chemical/biological applications. MEMS are a key aspect of ever-increasing significance in a myriad of commercial and military applications. Because of this importance, this thesis utilizes MEMS devices that can deploy and retract an antenna suitably sized for placement on an insect or microrobot for communication purposes. A target monopole antenna with a length of 1 mm was used as a test metric. From this requirement, several …
Characterization Of Intercalated Graphite Fibers For Microelectromechanical Systems (Mems) Applications, Bryan W. Winningham
Characterization Of Intercalated Graphite Fibers For Microelectromechanical Systems (Mems) Applications, Bryan W. Winningham
Theses and Dissertations
Research was accomplished to characterize the electrical and physical characteristic changes of the Thornel® P-100 carbon fiber and five variants when intercalated with 96% sulfuric acid and incorporated the use of Microelectromechanical Systems (MEMS) structures for testing purposes. The five fiber variants were oxidized in 1 M nitric acid at 0.5 A for 30 seconds, 1 and 2 minutes, the last two samples were detreated at 1150 °C for one hour prior to the nitric acid treatment. The fibers were mounted onto a MEMS die, placed into a chip carrier, sulfuric acid added, the chip carrier sealed and testing accomplished. …
Characterizationn Of Polumer-Based Mems Pyroelectic Infrared Detector, Mark E. Allard
Characterizationn Of Polumer-Based Mems Pyroelectic Infrared Detector, Mark E. Allard
Theses and Dissertations
AFRL/MLPJE had developed a novel thermal sensing material termed protein-impregnated-polymer (PIP). Thus far, a proof-of-concept has been demonstrated using a macro-sized pixel (0.64 mm2) as a bolometric detector. In an effort to better characterize this novel thermal sensing material, experimental data was used to determine figures of merit (FOMs) comparative to off-the-shelf thermal detectors. Microelectromechanical (MEMS) pixels were designed and used as the support structure for an inkjet-deposited droplet of the PIP. During the material characterization, two observations were made: PIP is a pyroelectric material, and the polymer (polyvinyl alcohol (PVA)) without the protein was found to be …
Toward A Flying Mems Robot, Nathan E. Glauvitz
Toward A Flying Mems Robot, Nathan E. Glauvitz
Theses and Dissertations
The work in this thesis includes the design, modeling, and testing of motors and rotor blades to be used on a millimeter-scale helicopter style flying micro air vehicle (MAV). Three different types of motor designs were developed and tested, which included circular scratch drives, electrostatic motors, and comb drive resonators. Six different rotor designs were tested; five used residual stress while one design used photoresist to act as a hinge to achieve rotor blade deflection. Two key parameters of performance were used to evaluate the motor and rotor blade designs: the frequency of motor rotation and the angle of deflection …
Characterization Of Stress In Gan-On-Sapphire Microelectromechanical Systems (Mems) Structures Using Micro-Raman Spectroscopy, Francisco E. Parada
Characterization Of Stress In Gan-On-Sapphire Microelectromechanical Systems (Mems) Structures Using Micro-Raman Spectroscopy, Francisco E. Parada
Theses and Dissertations
Micro-Raman (µRaman) spectroscopy is an efficient, non-destructive technique widely used to determine the quality of semiconductor materials and microelectromechanical systems. This work characterizes the stress distribution in wurtzite gallium nitride grown on c-plane sapphire substrates by molecular beam epitaxy. This wide bandgap semiconductor material is being considered by the Air Force Research Laboratory for the fabrication of shock-hardened MEMS accelerometers. µRaman spectroscopy is particularly useful for stress characterization because of its ability to measure the spectral shifts in Raman peaks in a material, and correlate those shifts to stress and strain. The spectral peak shift as a function of stress, …
Power-Scavenging Mems Robots, Daniel J. Denninghoff
Power-Scavenging Mems Robots, Daniel J. Denninghoff
Theses and Dissertations
This thesis includes the design, modeling, and testing of novel, power-scavenging, biologically inspired MEMS microrobots. Over one hundred 500-μm and 990-μm microrobots with two, four, and eight wings were designed, fabricated, characterized. These microrobots constitute the smallest documented attempt at powered flight. Each microrobot wing is comprised of downward-deflecting, laser-powered thermal actuators made of gold and polysilicon; the microrobots were fabricated in PolyMUMPs® (Polysilicon Multi-User MEMS Processes). Characterization results of the microrobots illustrate how wing-tip deflection can be maximized by optimizing the gold-topolysilicon ratio as well as the dimensions of the actuator-wings. From these results, an optimum actuator-wing configuration was …
Microelectromechanical Systems (Mems) Interrupter For Safe And Arm Devices, Steven S. Mink
Microelectromechanical Systems (Mems) Interrupter For Safe And Arm Devices, Steven S. Mink
Theses and Dissertations
This thesis addresses the development of a new micro-scale interrupter mechanism for a safe and arm device used in modern weapon systems. The interrupter mechanism often consists of a physical barrier that prevents an initial source of energy, in an explosive train, from being transferred to subsequent charges. In general, when the physical barrier is removed, the weapon is considered armed, and the charge is allowed to propagate. Several issues facing current safe and arm devices systems are the shrinking industrial base for manufacturing these devices and the desire for modern safe and arm devices to be compatible with next …
Protein Impregnated Polymer (Pip) Film Infrared Sensor Using Suspended Microelectromechanical Systems (Mems) Pixels, Tetsuo Kaieda
Protein Impregnated Polymer (Pip) Film Infrared Sensor Using Suspended Microelectromechanical Systems (Mems) Pixels, Tetsuo Kaieda
Theses and Dissertations
The Air Force Research Laboratory Materials and Manufacturing Directorate have developed a novel protein impregnated polymer (PIP) suspension that changes resistivity as a function of absorbed infrared radiation. Due to this property, the PIP is a potential material for use as an uncooled bolometer, or thermal sensor. In this research, a thermally-isolated pixel design, sensor characterization methods, and sensor fabrication and processing steps were developed. To create a microbolometer, the PIP was applied to two prototype micro-electro-mechanical systems (MEMS) surface micro-machined structures. The first is a raised cantilever pixel array that uses residual stress polysilicon and metal film arms to …
Insulator Charging In Rf Mems Capacitive Switches, Jay F. Kucko
Insulator Charging In Rf Mems Capacitive Switches, Jay F. Kucko
Theses and Dissertations
While capacitive radio frequency microelectromechanical (RF MEM) switches are poised to provide a low cost, high isolation, low power alternative to current RF switch technologies, there are still reliability issues limiting switch lifetime. Previous research identified insulator charging as a primary cause of switch failure. Changes in switch pull-in and release voltages were measured to provide insight into the mechanisms responsible for charging and switch failure. A spatial and temporal dependent model was developed to describe silicon nitride's time-dependent charging as a function of applied bias. This model was verified by applying constant biases to metal-silicon nitride-silicon capacitors and tracking …
Head Tracking For 3d Audio Using A Gps-Aided Mems Imu, Jacque M. Joffrion
Head Tracking For 3d Audio Using A Gps-Aided Mems Imu, Jacque M. Joffrion
Theses and Dissertations
Audio systems have been developed which use stereo headphones to project sound in three dimensions. When using these 3D audio systems, audio cues sound like they are originating from a particular direction. There is a desire to apply 3D audio to general aviation applications, such as projecting control tower transmissions in the direction of the tower or providing an audio orientation cue for VFR pilots who find themselves in emergency zero-visibility conditions. 3D audio systems, however, require real-time knowledge of the pilot's head orientation in order to be effective. This research describes the development and testing of a low-cost head …
Detection Of Residual Stress In Sic Mems Using Μ-Raman Spectroscopy, John C. Zingarelli
Detection Of Residual Stress In Sic Mems Using Μ-Raman Spectroscopy, John C. Zingarelli
Theses and Dissertations
Micro-Raman (µ-Raman) spectroscopy is used to measure residual stress in two silicon carbide (SiC) poly-types: single-crystal, hexagonally symmetric 6H-SiC, and polycrystalline, cubic 3C-SiC thin films deposited on Si substrates. Both are used in micro-electrical-mechanical systems (MEMS) devices. By employing an incorporated piezoelectric stage with submicron positioning capabilities along with the Raman spectral acquisition, spatial scans are performed to reveal areas in the 6H-SiC MEMS structures that contain residual stress. Shifts in the transverse optical (TO) Stokes peaks of up to 2 cm-1 are correlated to the material strain induced by the MEMS fabrication process through the development of phonon …
Using Multiple Mems Imus To Form A Distributed Inertial Measurement Unit, Ryan D. Hanson
Using Multiple Mems Imus To Form A Distributed Inertial Measurement Unit, Ryan D. Hanson
Theses and Dissertations
MEMS IMUs are readily available in quantity and have extraordinary advantages over conventional IMUs in size, weight, cost, and power consumption. However, the poor performance of MEMS IMUs limits their use in more demanding military applications. It is desired to use multiple distributed MEMS IMUs to simulate the performance of a single, more costly IMU, using the theory behind Gyro-Free IMUs. A Gyro-Free IMU (GF-IMU) uses a configuration of accelerometers only to measure the three accelerations and three angular rotations of a rigid body in 3-D space. Theoretically, almost any configuration of six distributed accelerometers yields sufficient measurements to solve …
Electrostatic Radio Frequency (Rf) Microelectromechanical Systems (Mems) Switches With Metal Alloy Electric Contacts, Ronald A. Coutu Jr.
Electrostatic Radio Frequency (Rf) Microelectromechanical Systems (Mems) Switches With Metal Alloy Electric Contacts, Ronald A. Coutu Jr.
Theses and Dissertations
RF MEMS switches are paramount in importance for improving current and enabling future USAF RF systems. Electrostatic micro-switches are ideal for RF applications because of their superior performance and low power consumption. The primary failure mechanisms for micro-switches with gold contacts are becoming stuck closed and increased contact resistance with increasing switch cycles. This dissertation reports on the design, fabrication, and testing of micro-switches with sputtered bi-metallic (i.e., gold (Au)-on-Au-(6.3at%)platinum (Pt)), binary alloy (i.e., Au-(3.7at%)palladium (Pd) and Au-(6.3at%)Pt), and ternary alloy (i.e., Au-(5at%)Pt-(0.5at%)copper (Cu)) contact metals. Performance was evaluated, in-part, using measured contact resistance and lifetime results. The micro-switches with …
A Tightly-Coupled Ins/Gps Integration Using A Mems Imu, Jonathan M. Neu
A Tightly-Coupled Ins/Gps Integration Using A Mems Imu, Jonathan M. Neu
Theses and Dissertations
Micro-Electro-Mechanical Systems (MEMS) technology holds great promise for future navigation systems because of the reduced size and cost of MEMS inertial sensors relative to conventional devices. Current MEMS devices are much less accurate than standard inertial sensors, but they can still be useful. In this thesis, data was recorded from an inexpensive MEMS inertial measurement unit and integrated with GPS measurements using a tightly-coupled Kalman filter. The overall goal of this research is to investigate the usefulness of MEMS sensors for a small, real-time, low-cost INS/GPS integration. A golf cart was used to collect dynamic data, along with a commercial …
Demonstrating Optothermal Actuators For An Autonomous Mems Microrobot, Francis R. Szabo
Demonstrating Optothermal Actuators For An Autonomous Mems Microrobot, Francis R. Szabo
Theses and Dissertations
There are numerous applications for microrobots which are beneficial to the Air Force. However, the microrobotics field is still in its infancy, and will require extensive basic research before these applications can be fielded. The biggest hurdle to be solved, in order to create autonomous microrobots, is generating power for their actuator engines. Most present actuators require orders of magnitude more power than is presently available from micropower sources. To enable smaller microrobots, this research proposed a simplified power concept that eliminates the need for on-board power supplies and control circuitry by using actuators powered wirelessly from the environment. This …
Thin Film Encapsulation Of Radio Frequency (Rf) Microelectromechanical Systems (Mems) Switches, Eric D. Marsh
Thin Film Encapsulation Of Radio Frequency (Rf) Microelectromechanical Systems (Mems) Switches, Eric D. Marsh
Theses and Dissertations
Microelectromechanical systems (MEMS) radio frequency (RF) switches have been shown to have excellent electrical performance over a wide range of frequencies. However, cost-effective packaging techniques for MEMS switches do not currently exist. This thesis involves the design of RF-optimized encapsulations consisting of dielectric and metal layers, and the creation of a novel thin film encapsulation process to fabricate the encapsulations. The RF performance of several encapsulation designs are evaluated with an analytical model, full wave electromagnetic simulation, and laboratory testing. Performance degradation due to parasitic and reflection losses due to the package is considered, and RF feed-throughs of the transmission …
Mechanical Computing In Microelectromechanical Systems (Mems), Kenneth C. Bradley
Mechanical Computing In Microelectromechanical Systems (Mems), Kenneth C. Bradley
Theses and Dissertations
Mechanical computing devices in polysilicon-based microelectromechanical systems (MEMS) were designed with the goal of developing computing devices for harsh environments, such as those with high dose radiation and high temperatures, as well as devices that may be able to interface with molecular or biological computer systems. The devices that were designed include both analog and digital computing devices. The analog devices include integrators, differentials (summers), multipliers, and those that perform trigonometric functions. The digital devices that were designed are inverters, NAND, NOR, and XOR logic gates. Analog-to-digital (A-to-D) and digital-to-analog (D-to-A) converters were also designed. The designs were submitted to …
The Effects Of Ionizing Radiation On Microelectromechanical Systems (Mems) Actuators: Electrostatic, Electrothermal, And Residual Stress, Jared R. Caffey
The Effects Of Ionizing Radiation On Microelectromechanical Systems (Mems) Actuators: Electrostatic, Electrothermal, And Residual Stress, Jared R. Caffey
Theses and Dissertations
The effects of ionizing radiation on the operation of polysilicon mmicroelectromechanical system (MEMS) electrostatic actuators, electrothermal actuators, and residual stress cantilevers were examined. Pre-irradiation, in-situ, and post-irradiation measurements were taken for the electrosatic and electrothermal actuators. The residual stress cantilevers were characterized before and after irradiation. All devices were irradiated to a total ionizing does of 1 megarad(Si) using both the Air Force Research Laboratory's low energy X-ray source and Co-60 gamma source.
Characterization Of Residual Stress In Microelectromechanical Systems (Mems) Devices Using Raman Spectroscopy, Lavern A. Starman
Characterization Of Residual Stress In Microelectromechanical Systems (Mems) Devices Using Raman Spectroscopy, Lavern A. Starman
Theses and Dissertations
Due to the small scale of MEMS devices, the inherent residual stresses during the deposition processes can affect the functionality and reliability of the fabricated devices. Residual stress often causes device failure due to curling, buckling, or fracture. Currently, few techniques are available to measure the residual stress in MEMS devices. In this dissertation, Raman spectroscopy is used to measure and monitor the residual and induced stresses in MUMPs polysilicon MEMS devices. Raman spectroscopy was selected since it is nondestructive, fast, and provides potential in situ stress monitoring. Raman spectroscopy scans on unreleased and released MEMS fixed-fixed beams, cantilevers, and …
Fabrication Techniques For Iii-V Micro-Opto-Electro-Mechanical Systems, Jeremy A. Raley
Fabrication Techniques For Iii-V Micro-Opto-Electro-Mechanical Systems, Jeremy A. Raley
Theses and Dissertations
This thesis studies selective etching techniques for the development of AlxGa1-xAs micro-opto-electro-mechanical systems (MOEMS). New MEMS technology based on materials such as AlxGa1-xAs enables the development of micro-systems with embedded active micro-optical devices. Tunable micro-lasers and optical switching based on MOEMS technology will improve future wavelength division multiplexing (WDM) systems. WDM vastly increases the speed of military communications and sensor data processing. From my designs, structures are prepared by molecular beam epitaxy. I design a mask set for studies of crystal plane selectivity. I perform a series of experiments on the selective …