3 research outputs found
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Thermal conductivity measurements of Summit polycrystalline silicon.
A capability for measuring the thermal conductivity of microelectromechanical systems (MEMS) materials using a steady state resistance technique was developed and used to measure the thermal conductivities of SUMMiT{trademark} V layers. Thermal conductivities were measured over two temperature ranges: 100K to 350K and 293K to 575K in order to generate two data sets. The steady state resistance technique uses surface micromachined bridge structures fabricated using the standard SUMMiT fabrication process. Electrical resistance and resistivity data are reported for poly1-poly2 laminate, poly2, poly3, and poly4 polysilicon structural layers in the SUMMiT process from 83K to 575K. Thermal conductivity measurements for these polysilicon layers demonstrate for the first time that the thermal conductivity is a function of the particular SUMMiT layer. Also, the poly2 layer has a different variation in thermal conductivity as the temperature is decreased than the poly1-poly2 laminate, poly3, and poly4 layers. As the temperature increases above room temperature, the difference in thermal conductivity between the layers decreases
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Development and characterization of a miniaturized PEM fuel-cell for MEMS applications
In order to create autonomous mechatronics systems enabled with advanced MEMS sensors and actuators, long lasting, small, and efficient power sources are needed. Microproton exchange membrane fuel-cells (PEMFCs) have the potential to define such power sources due to their relatively high chemical to electrical energy conversion efficiency. This paper presents results of our investigations on the effects of miniaturization of PEMFCs for use in MEMS. We developed analytical and computational models to determine the performance of scaled PEMFCs. These models use the Maxwell-Stefan equations, Darcy's Law, Ohm's Law, and Tafel's equation to account for species transport and diffusion, current distribution, and other governing phenomena. It was found that miniaturization of PEMFCs can increase their efficiency because of the dominance of surface area to volume ratio effects. Furthermore, miniaturization decreases ohmic losses due to reduction of the effective electrical path length, increases flux of the reactants due to decrease in gas diffusion layer thickness, and helps increase the effective pressure. Using the results of our analytical and computational models, the dimensions of similarly designed PEMFCs having a power output on the order of 1.8 mW, suitable to drive a MEMS accelerometer, were obtained. PEMFCs were constructed, characterized, and their performance compared with analytical and computational results. Coupled with sufficient background investigation, the results culminate in a recommendation for fabrication of micro-PEMFCS
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Copenhagen Carshare -- Carsharing Technology Study
This report concerns a project for the nonprofit organization Copenhagen Carshare investigating issues relating to booking, billing and car access. Presently the systems in use are insufficient for the needs of the management and rapidly growing membership. Extensive research and discussion with members, coordinators and suppliers has analyzed commercial and custom development of wireless access systems and updated booking and billing software. The final recommendations present proposals to the carshare for integration of such technology into the carsharing process