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The Growing Necessity for Continuing Education: The Short Course Option

Description: Continuing education is a critical issue in the workplace. Rapid change, the emergence of new technology, and the lack of trained individuals make continuing education an imperative for employers. The desire for individual growth and marketability make it an imperative for the employee also. While there are many options for continuing education, an increasingly popular vehicle is the short course. Time, cost efficiency and instruction by those experienced in real industrial practice are key factors in the success of this educational format. Over the past couple of decades, short course offerings and the number and type of sponsoring organizations have grown significantly. Within the scientific community, courses in basic disciplines (e.g., materials characterization), emergent technologies (e.g., Micro-Electro- Mechanical Systems), equipment operation (e.g., electron microscopes) and even business practices (e.g., ES&H, proposal writing) have emerged and are taught by universities, technical societies and equipment manufacturers. Short course offerings and formats are evolving. Presently, it is possible to find series of courses which define specific curricula. These curricula set the stage for new developments in the future, including increased certification and licensing (e.g., technologists). Along with such certifications will come the need for accreditation. Who will offer such programs, and especially, who will accredit them are significant questions. Perhaps the most dramatic changes will occur with the integration of advanced information technology. While satellite-based remote offerings are available, the use of the web for educating a dispersed group is just beginning to emerge. In its simplest forms, this offers little advantage over a video or a real-time satellite course, but the eventual emergence of tele-operation of experimental equipment will revolutionize remote teaching.
Date: February 2, 1999
Creator: McWhorter, P.J. & Romig, A.D.
Partner: UNT Libraries Government Documents Department

Performance tradeoffs for a surface micromachined microengine

Description: An electromechanical model of Sandia`s microengine is developed and applied to quantify critical performance tradeoffs. This is done by determining how forces impact the mechanical response of the engine to different electrical drive signals. To validate the theoretical results, model-based drive signals are used to operate actual engines, where controlled operation is achieved for the following cases: (1) spring forces are dominant, (2) frictional forces are dominant, (3) linear inertial forces are dominant, (4) viscous damping forces are dominant, and (5) inertial load forces are dominant. Significant improvements in engine performance are experimentally demonstrated in the following areas: positional control, start/stop endurance, constant speed endurance, friction load reduction, and rapid actuation of inertial loads.
Date: October 1, 1996
Creator: Miller, S.L.; Sniegowski, J.J.; LaVigne, G. & McWhorter, P.J.
Partner: UNT Libraries Government Documents Department

Friction in surface micromachined microengines

Description: Understanding the frictional properties of advanced Micro-Electro- Mechanical Systems (MEMS) is essential in order to develop optimized designs and fabrication processes, as well as to qualify devices for commercial applications. We develop and demonstrate a method to experimentally measure the forces associated with sliding friction of devices rotating on a hub. The method is demonstrated on the rotating output gear of the microengine recently developed at Sandia National Laboratories. In-situ measurements of an engine running at 18300 rpm give a coefficient of friction of 0.5 for radial (normal) forces less than 4 {mu}N. For larger forces the effective coefficient of friction abruptly increases, suggesting a fundamental change in the basic nature of the interaction between the gear and hub. The experimental approach we have developed to measure the frictional forces associated with the microengine is generically applicable to other MEMS devices.
Date: March 1, 1996
Creator: Miller, S.L.; Sniegowski, J.J.; LaVigne, G. & McWhorter, P.J.
Partner: UNT Libraries Government Documents Department

Dynamical modeling and characterization of a surface micromachined microengine

Description: The practical implementation of the surface micromachined microengine [1,2] to perform useful microactuation tasks requires a thorough understanding of the dynamics of the engine. This understanding is necessary in order to create appropriate drive signals, and to experimentally measure fundamental quantities associated with the engine system. We have developed and applied a dynamical model of the microengine and used it to accomplish three objectives: (1) drive inertial loads in a controlled fashion, i.e. specify and achieve a desired time dependent angular position of the output gear,( 2) minimize stress and frictional forces during operation, and (3) as a function of time, experimentally determine forces associated with the output gear, such as the load torque being applied to the output gear due to friction.
Date: January 1, 1996
Creator: Miller, S.L.; Sniegowski, J.J.; LaVigne, G.L. & McWhorter, P.J.
Partner: UNT Libraries Government Documents Department

Hidden Challenges to MEMS Commercialization: Design Realization and Reliability Assurance

Description: The successful commercialization of MicroElectroMechanical Systems (MEMS) is an essential prerequisite for their implementation in many critical government applications. Several unique challenges must be overcome to achieve this widespread commercialization. Challenges associated with design realization and reliability assurance are discussed, along with approaches taken by Sandia to successfully overcome these challenges.
Date: January 20, 1999
Creator: McWhorter, P.J.; Miller, S.L.; Miller, W.M.; Rodger, M.S. & Yarberry, V.R.
Partner: UNT Libraries Government Documents Department

Advanced micromechanisms in a multi-level polysilicon technology

Description: Quad-level polysilicon surface micromachining technology, comprising three mechanical levels plus an electrical interconnect layer, is giving rise to a new generation of micro-electromechanical devices and assemblies. Enhanced components can not be produced through greater flexibility in fabrication and design. New levels of design complexity that include multi-level gears, single-attempt locks, and optical elements have recently been realized. Extensive utilization of the fourth layer of polysilicon differentiates these latter generation devices from their predecessors. This level of poly enables the fabrication of pin joints, linkage arms, hinges on moveable plates, and multi-level gear assemblies. The mechanical design aspects of these latest micromachines will be discussed with particular emphasis on a number of design aspects of these latest micromachines will be discussed with particular emphasis on a number of design modifications that improve the power, reliability, and smoothness of operation of the microengine. The microengine is the primary actuation mechanism that is being used to drive mirrors out of plane and rotate 1600-{mu}m diameter gears. Also discussed is the authors most advanced micromechanical system to date, a complex proof-of-concept batch-fabricated assembly that, upon transmitting the proper electrical code to a mechanical lock, permits the operation of a micro-optical shutter.
Date: August 1, 1997
Creator: Rodgers, M.S.; Sniegowski, J.J.; Miller, S.L.; Barron, C.C. & McWhorter, P.J.
Partner: UNT Libraries Government Documents Department

Gas-driven microturbine

Description: This paper describes an invention which relates to microtechnology and the fabrication process for developing microelectrical systems. It describes a means for fabricating a gas-driven microturbine capable of providing autonomous propulsion in which the rapidly moving gases are directed through a micromachined turbine to power devices by direct linkage or turbo-electric generators components in a domain ranging from tenths of micrometers to thousands of micrometers.
Date: June 27, 1996
Creator: Sniegowski, J.J.; Rodgers, M.S.; McWhorter, P.J.; Aeschliman, D.P. & Miller, W.M.
Partner: UNT Libraries Government Documents Department

Monolithic geared-mechanisms driven by a polysilicon surface-micromachined on-chip electrostatic microengine

Description: We have previously described a practical micromachined power source: the polysilicon, surface-micromachined, electrostatically actuated microengine. Here we report on 3 aspects of implementing the microengine. First, we discuss demonstrations of the first-generation microengine actuating geared micromechanisms including gear trains with elements having dimensions comparable to the drive gear (about 50 {mu}m) and a relatively large (1600-{mu}m-diameter) rotating optical shutter element. These configurations span expected operating extremes for the microengine and address the coupling and loading issues for very-low-aspect-ratio micromechanisms which are common to the design of surface-micromachined devices. Second, we report on a second-generation of designs that utilize improved gear teeth design, a gear speed-reduction unit, and higher force-per-unit-area electrostatic comb drives. The speed-reduction unit produces an overall angular speed reduction of 9.63 and requires dual-level compound gears. Third, we discuss a dynamics model developed to accomplish 3 objectives: drive inertial loads in a controlled fashion, minimize stress and frictional forces during operation, and determine as a function of time the forces associated with the drive gear (eg load torque on drive gear from friction).
Date: May 1, 1996
Creator: Sniegowski, J.J.; Miller, S.L.; LaVigne, G.F.; Rodgers, M.S. & McWhorter, P.J.
Partner: UNT Libraries Government Documents Department

Routes to failure in rotating MEMS devices experiencing sliding friction

Description: Gear systems rotating on hubs have been operated to failure using Sandia`s microengine as the actuation device. Conventional failure modes such as fatigue induced fracture did not occur, indicating that the devices are mechanically extremely robust. The generic route to failure observed for all rotating devices involves sticking of structures that are in sliding contact. This sticking evidently results from microscopic changes in the sliding surfaces during operation. The rate at which these changes occur is accelerated by excessive applied forces, which originate from non-optimized designs or inappropriate drive voltages. Precursors to failure are observed, enabling further understanding of the microscopic changes that occur in the sliding surfaces that ultimately lead to failure.
Date: August 1, 1997
Creator: Miller, S.L.; LaVigne, G.; Rodgers, M.S.; Sniegowski, J.J.; Waters, J.P. & McWhorter, P.J.
Partner: UNT Libraries Government Documents Department

Intricate Mechanisms-on-a Chip Enabled by 5-Level Surface Micromachining

Description: Surface micromachining generally offers more design freedom than related technologies, and it is the technology of choice for most microelectromechanical applications that require multi-level structures. However, the design flexibility that surface micromachining offers is not without limitations. In addition to determining how to fabricate devices in a planar world, the designer also needs to consider issues such as film quality, thickness, residual stress, topography propagation, stringers, processing limitations, and concerns about surface adhesion [1]. Only a few years ago, these were the types of issues that limited design complexity. As the technology improved, the number of mechanical layers available to the designer became the dominant constraint on system functionality. In response, we developed a 5-level polysilicon fabrication technology [2] that offers an unprecedented level of microelectromechanical complexity with simultaneous increases in system yield and robustness. This paper outlines the application that was the driving force behind this work and describes the first devices specifically designed for and fabricated in this technology. The 5-level fabrication technology developed to support this program is known as SUMMiT-V. Four mechanical layers of polysilicon referred to as polyl, poly2, poly3, and poly4 are fabricated above a polyO electrical interconnect and ground plane layer [2,4]. PolyO is 0.3 pm thick, polyl is 1.0 pm, poly 2 is 1.5 pm, and both poly3 and poly4 are 2.25 pm. All films except polyl and poly2 are separated by 2-pm thick depositions of sacrificial oxide. A 0.5-m sacrificial oxide between polyl and poly2 typically defines the clearance between close mating parts such as hubs and hinges. This entire stack is built on a single crystal substrate with a dielectric foundation of 0.8 pm of nitride over 0.63 m of oxide. Seventeen drawing layer are combined to generate the 14 photolithographic masks used to pattern these films during a 240-step ...
Date: March 30, 1999
Creator: Allen, J.J.; McWhorter, P.J.; Miller, S.L.; Rodgers, M.S.; Smith, J.H. & Sniegowski, J.J.
Partner: UNT Libraries Government Documents Department

Microelectro-optical devices in a 5-level polysilicon surface micromachining technology

Description: The authors recently reported on the development of a 5-level polysilicon surface micromachine fabrication process consisting of four levels of mechanical poly plus an electrical interconnect layer and its application to complex mechanical systems. This paper describes the application of this technology to create micro-optical systems-on-a-chip. These are demonstration systems, which show that five levels of polysilicon provide greater performance, reliability, and significantly increased functionality. This new technology makes it possible to realize levels of system complexity that have so far only existed on paper, while simultaneously adding to the robustness of many of the individual subassemblies.
Date: August 1, 1998
Creator: Smith, J.H.; Rodgers, M.S.; Sniegowski, J.J.; Miller, S.L.; Hetherington, D.; McWhorter, P.J. et al.
Partner: UNT Libraries Government Documents Department