Virginia Tech Mechanical Engineering Annual Report 2019 Annual Report | Page 20

An ultrasonic solution for wireless powering of biomedical implants Shima Shahab Assistant Professor Research Focus: To design a new genera- tion of smart autonomous biomedical sys- tems that lead to new medical diagnostics and treatments. Contactless ultrasonic power transfer (UPT) is a new technology that eliminates impracticali- ties associated with wired electrical connec- tions. In biomedical implants (e.g. cardiac pacemakers and wireless networks of sensors such as artificial retina and cancer detectors), the UPT concepts are the biocompatible methods which are effective at larger distanc- es and offer frequency-wise flexibility. This technology, which is based on the reception of acoustic waves at ultrasonic frequencies by piezoelectric receivers, can be used to wire- lessly charge low to high-power electronics. MInDS Laboratory investigates the use of acoustic holograms to create multifocal pres- sure patterns and power an array of piezoelectric receivers. The technical approach based on the combination of the nonlinear acoustic field with transmitter and receiver electroelastic nonlineari- ties, verified with controlled experiments, are studied to explore and understand the effects of various parameters on the coupled system for performance enhancement of UPT. We also per- form a system-level investigation of through-wall high-power UPT dynamics to lay the founda- tion for its implementation in next-generation acoustic-based wireless devices including enclosed electronic devices operating in armor or other environments, such as autonomous unmanned aerial and underwater vehicles. State-of-the-art experiments and mathematical models of UPT focus on the transmitter, receiver, medium, geometric and material parameters. This project was awarded by NSF. Heat transfer: Metal foams as heat sinks With the increasing demand for higher performance and progressive miniaturiza- tion of electronic packages, power densities and the attendant thermal dissipation requirements continue to escalate. Innovative ther- mal solutions are needed to ensure reliable operation at the device and die (chip) level. To this end, Professor Mahajan and his research team in the Department of Mechanical Engineering have embarked upon a multi- pronged, interdisciplinary research that explores novel thermal interface materi- als and highly porous metal foams as heat sinks. Accord- ing to Professor Mahajan, his team focuses not only enhancing our understand- ing of the underlying physics of the transport phenomena in such devices, but equally importantly on the end goal of developing engineering solutions. 20 Revised and Corrected, Nov. 2019 Roop Mahajan Lewis A. Hester Chair Professor Illustration of heat pathways of gra- phene/silicone Thermal Interface Mate- rial composites in between heat genera- tor and heat spreader. Research Focus: Advanced electronic cool- ing; Two-phase flows; Porous media synthesis and application of graphene, derivatives and composites; Biomedical devices; Emerging and Black Swan technologies