Principal Investigator: Vitali F. Nesterenko, Professor, MAE Department, UCSD Co-Principal Investigator: Sungho Jin, Professor, MAE Department, UCSD
Research in linear elastic phononic materials is an active area of basic research with important applications for development of band filters for environmental or industrial noise, delay lines, designing vibration free environment and transducers. They also represent a class of man-designed materials with evolving understanding of their properties and applications. Their properties are different than properties of traditional materials and are based on periodic arrangement of components with elastic contrast unavailable in normal conditions. However, the major part of research is performed with so to speak model structures rather than materials. For example the most favorable configuration for obtaining large acoustic band gaps is a periodic array of water cylinders in mercury. All examples of phononic materials are based on linear wave dynamics in periodic structures. As a result these structures can be tuned only due to an awkward rearrangement in the periodic array of components. Also because sound speed of solid materials is in the range 2 - 10 km/s the tunability of band gaps is limited. It is therefore desirable to design and study new materials, which are capable of significant nonlinear tuning by convenient and viable methods. The objectives of this proposal are therefore to (1) design and process strongly nonlinear tunable phononic crystal (NTPC) materials; (2) characterize their properties and (3) identify areas of their practical applications. The proposed work has 3 unique aspects. First, unlike other approaches it is based on emerging strongly nonlinear wave dynamics in periodic structures based on solid theoretical, numerical and experimental results. Secondly, the work proposed focuses on processing of clearly identified examples of NTPC materials. Thirdly, the team synergistically combines unique expertise in the nonlinear wave dynamics of "sonic vacuum" and in processing of materials supported by full scale of processing equipment. The work will prompt theoretical and experimental research in the diverse area of strongly nonlinear wave dynamics creating a broader impact not only in acoustic but in such areas as photonics and electrical transmission lines and signal processing. The design and investigation of unique materials will most likely lead to a discovery of new phenomena (like new type of waves, violations of Snell's law, travelling metal insulator transition induced by small amplitude waves or pressure induced transparency to sound wave) and an establishment of new mechanisms of wave processes. Potential applications may include (1) design of a sound scrambler/decorder for secure voice communications for military and national security personnel, (2) improved invisibility of submarines to acoustic detection signals, (3) noise and shock wave mitigation for protection of vibration sensitive devices such as head mounted vision devices, (4) drastic compression of acoustic signals into centimeter regime impulses for artificial ear implants, hearing aid and devices for ease of conversion to electronic signals and processing, and acoustic delay lines for communication applications.
