CAREER: Robust Thin Film Shape Memory Alloys for Microelectromechanical Systems (MEMS)

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This Career award to Yale University is to study shape memory alloys (such as NiTi), which have the unique ability of "remembering" their original shape when heated and can be used as thin film actuators for microelectromechanical systems (MEMS). Among the actuation modes in MEMS, shape memory alloys produce the largest actuation force and will benefit applications such as microvalves, micropumps, and micromanipulators. Despite these potential uses, integration of shape memory alloys in MEMS is limited, because their behavior is plagued with an acute compositional sensitivity. In addition, details of their thin film mechanical behavior, which often departs from bulk, remains largely unexplored. This award will study the affects of alloying on phase transformation temperature, hysteresis behavior, microstructure, actuation properties, and mechanical properties. In addition, the award will explore the behavior of thin film NiTi shape memory materials; improve their integration into the MEMS process; and broaden the understanding of thin film mechanical properties, by examining materials that exhibit elastic non-linearities. Structure-property relationship will be examined by observing the microstructure of shape memory alloys with electron microscopy; actuation properties with MEMS cantilevers; and transformation temperature behavior with differential scanning calorimetry and wafer curvature techniques. Proposed collaborations with industry, partner universities, and Brookhaven National Labs (BNL) would provide the fundamental understanding the properties of thin film shape memory alloys and their applications. Shape memory alloys and MEMS also provide a significant educational platform for they are compelling to both students and lay audiences. In addition to this research, a new undergraduate MEMS class will be developed as well as an outreach program that will encourage students to explore science through hands-on activities. A lecture series that showcases diverse scientists and fun science events will encourage all students, particularly women and minority students, to consider science. Other educational mechanisms include a web-based demonstration site, popular science writing, and collaborations with the National Science Resource Center (an arm of the Smithsonian Institute and the National Academies).