Elastic metamaterials and phononic crystals are artificially structured composite materials that can manipulate and control elastic waves. While they are proven to be useful in many ultrasonic applications, their wave functionality is limited to the low frequency regime. Since a significant amount of energy is carried by low frequency waves propagating in mechanical or civil systems, it is crucial to develop compact structures enabling broadband control of low frequency elastic waves without the need for further structural modifications. This grant will support research that will answer how to effectively tailor low frequency elastic waves within a small footprint and advance the state-of-art via reconfigurable metasurface concepts. The reconfigurable metasurfaces will enable broadband wave focusing and high-power energy harvesters converting low frequency vibrations into usable electricity, overcoming the energy related limitations of the wireless sensor networks. This award supports fundamental research and advances applications in mechanical, civil, and aerospace systems to achieve next-generation wave devices that are compact and easy to integrate within existing structures. Therefore, results from this research will benefit the U.S. economy and broader society. The integrated education program will also help broaden participation of underrepresented groups in research and features a K-12 outreach module for the Girls in Science and Engineering Camp at the U-M.
The research goal of this is to manipulate and control low frequency elastic waves (~hundreds of Hz) via compact reconfigurable metasurfaces which can adapt to environmental conditions to achieve greater dynamic wave functionalities such as steering and focusing in a broadband frequency range. This research will introduce active elastic metasurfaces and nonlinear elastic metasurfaces which will be tuned by external electrical and mechanical loads, respectively. The key idea is to leverage the linear/nonlinear dynamics of the elastic/electro-elastic unit cells and tailor elastic wavefronts over a broad range of frequencies using the existing structure. A theoretical framework will be established to implement the required phase gradient for achieving desired dynamic wavefront shapes. While manipulating the elastic wave propagation by tailoring the refraction properties of the metasurface, wave reflections will be minimized to ensure maximum wave transmission through the active/nonlinear metasurface layer. The research will create next-generation metasurfaces to modulate low frequency wavefronts in high impact applications in mechanical, civil, and aerospace systems.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
