Granular crystals are close-packed arrays of elastic particles, and are effective at tailoring acoustic wave propagation. However, so far granular crystals are typically constructed at macroscopic length scales and designed to affect sonic frequency acoustic waves. This grant provides funding for the study of the nonlinear contact-based dynamics of micro to nanoscale granular crystals. Extending granular crystals to the microscale and nanoscale has the potential to enable granular-based devices that operate at megahertz and gigahertz frequencies. The size scale is also important, as effects which are negligible at the macroscale, such as adhesion, become significant at microscales. Granular crystal will be manufactured by self-assembly. Photoacoustic techniques will be utilized to study the fundamental contact-based dynamics of micro- and nanoparticles, as well as to study nonlinear wave propagation in more complex microscale granular systems. The experimental findings will be modeled using a combination of techniques drawn from the areas of nonlinear dynamical systems, solid mechanics, and acoustic metamaterials. Nonlinearities in locally-resonant granular-elastic metamaterial configurations will be explored.
This project has the potential for significant societal impact, as micro- to nanoscale granular crystals and locally-resonant granular-elastic metamaterials may have potential future applications to areas such as signal processing, non-destructive evaluation and adhesion characterization, and biomedical ultrasound imaging and therapy. It is also anticipated that this project will establish the fundamental understanding of nonlinear wave propagation in microscale granular media. The research efforts will be combined with a significant educational component, and will provide a diverse student group with a unique interdisciplinary educational opportunity in the classroom and the laboratory. The proposed research will be incorporated into a newly developed course led by the PI, and simplified versions of relevant experiments will be developed to generate increased interest in science and engineering through outreach activities.
