A major effort in sensing technology centers about the miniaturization of sensing elements. Much investment is being expended upon the development of sensing systems that can be incorpo-rated into autonomous micro-electrical-mechanical systems (MEMS) for widespread wireless sensing needs ranging from monitoring buildings and bridges for safety, to electronic noses for detecting atmospheric chemical hazards across wide geographic areas, to electronic ears for monitoring com-munication channels just to name a few. One key to the successful deployment of such systems is overcoming the energy needs of sensor nodes. Note that sensors need power not only to sense but also to communicate. An attractive technology for dealing with many of these issues is bulk-acoustic wave resonators (BAWRs); at the MEMS scale of a few microns these devices operate in the GHz range (cell phone frequencies). BAWRs can be used as high quality frequency references in chemical sensors, elements of signal processing filter networks, and as elements of wireless com-munication systems all at very low power compared to alternate technologies. Much of the promise of such devices has been seen in proof-of-concept experiments that have recently been published. However, a careful reading of these publications shows that while the general operating principles of BAWRs are known, there is a distinct lack of accuracy to which resonant-based MEMS sensor designers understand expected system behavior. This proposal intends to help rectify this defi-ciency and to promote more rapid development of successful BAWR devices by developing freely available computer aided design (CAD) tools. This interdisciplinary team of researchers intends to not only develop a CAD tool but to also conduct experiments to verify its accuracy. Their CAD software is designed to accurately predict resonator quality degradation from thermoelastic damping, intrinsic material losses, and anchor (or clamping) losses. They will tackle the problem in a new way for the MEMS community by looking directly to the governing partial differential equations (PDEs) for the resonator behavior and then abstracting small, accurate, and fast models for design level computations using advanced Krylov model reduction methods. Novel aspects in their approach include a modeling system that will automatically separate different damping effects from each other and make possible new virtual experiments for the creation of heretofore unknown BAWRs. Key to this last point is their proposal to develop an optimization module for the CAD tool that will allow for the optimization of targeted performance parameters, such as transfer functions, that are needed for higher level sensor node design. Integral to the proposed work will be the fabrication of poly- and single-crystal BAWRs that will test the models, help refine them, and test new concepts in coupled resonator designs. The team make-up includes experts in material modeling, scientific computing, and MEMS design and fabrication. They intend to build upon their past successes in creating new MEMS devices and in creating and disseminating MEMS design software. The scientific questions to be addressed in this proposal are of a critical importance to the community. But beyond these merits, it is noted that the proposal will have the broader impact of developing the community's research infrastructure as the software to be developed will be dis-tributed freely. On the human resource side the proposers will fill a broader objective by training students in an highly interdisciplinary field by combining training in semi-conductor engineering with mechanical modeling and scientific computing. Such graduates are sorely needed in the com-munity. The proposers additionally plan to recruit from the successful Summer Undergraduate Program in Engineering Research at Berkeley (SUPERB). This program aims to reach out to under-represented groups in engineering and provide them with a high quality research experience and encourage them to aspire to graduate degrees. The PIs have successfully participated in this program in the past.
