Simulation, Reliability and Optimal Design of Micro-Electro-Mechanical (MEM) Structures

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9321508 MACDONALD Micro-electro-mechanical (MEM) devices consist of integrated movable micro-structures with electronics. With structural elements having high aspect ratios and being in the size range of 0.1 - 100{SYMBOL 109 \f "Symbol"}m , significant forces and/or deformations can be obtained with the application of low voltages ({SYMBOL 187 \f "Symbol"} 10 volts). The guiding principle here is to fabricate integrated, movable microstructures for precision motion and actuation. Fabrication techniques for MEM structures are closely related to very large scale integration (VLSI) technology. Primary application areas are in micro-sensors and micro-actuators. Possible applications of this technology are very diverse. It is believed that entire new classes of mechanical , optical, fluid, thermal and chemical machines can be fabricated with MEMS technology. The research focus is development of a better understanding of micro-electro-mechanical (MEM) structures and involves simulation, reliability analysis and optimal design. The research team is interdisciplinary, involving an electrical engineer with primary expertise in experimental research in the area of nanostructures, two mechanical engineers with primary expertise in computer simulation in applied mechanics, including optimization problems, and an expert in the area of fracture mechanics. The research team also includes a collaboration between academia and industry. It is expected that the diversity of the research team will lead to a cross-fertilization of ideas leading to significant advances in the knowledge base in this challenging research area. In addition, the presence of an industrial researcher, who is resident at a university campus, will greatly facilitate the process of "technology transfer" to industry. The project has three primary focus areas. The first is the efficient and accurate simulation of static as well as dynamic behavior of MEM structures, subjected to electric fields, and hence electrostatic forces . Nonlinear behavior-geometric, as well as, where relevant, material, will be included in the simulation. A state of the are coupling of an exterior boundary element method (BEM) for electrical analysis and interior finite element method (FEM) for mechanical analysis, will be employed for this purpose. A second task is reliability analysis of MEM structures subjected to cyclic, dynamic loading. Here, a representative problem to be studied is time-dependent crack growth in a vibrating beam and its effect on the natural frequencies and mode shapes of the beam. Finally, the third task is optimal shape design of MEM structures. Here, the shapes of variable cross-section vibrating beams will be designed to have desired natural frequency characteristics. Every aspect of the research will have a balance of experiment and analysis. Thus, for example, measured frequency versus time curves on a progressively cracking beam will be used to solve the inverse problem of crack identification, and optimally designed MEM beams will be fabricated and their performance tested against beams of other shapes. ***