This research program will investigate new theoretical and practical knowledge on the application of nonlinearity, asymmetry, and mixed scales to design and fabricate ground-breaking materials and devices. The approach will yield materials which overcome traditional bounds on time-reversal symmetry and acoustic reciprocity. These transformative reciprocity-breaking materials and systems are expected to find wide application in diverse fields, including noise-mitigating transportation systems; medical ultrasound devices; atomic force microscope (AFM) sensing; acoustic filters and logic devices; sonar; and energy control and redirection. The research will also broadly impact education through planned curriculum development and outreach activities aimed at increasing exposure of engineering students, and the public, to the exciting physics of acoustic materials. At the same time, these activities will promote interest in science, technology, engineering, and mathematics. Planned activities will include a multidisciplinary collaborative course on non-traditional acoustic materials; broadening opportunities with outreach organizations on campus by inviting high school students and teachers to develop lab modules and earn continuing education credits; a collaboration with Clark Atlanta University to engage faculty and underrepresented undergraduate students in research tasks; and industrial collaboration with the Hughes Research Laboratory to enhance and facilitate technology transfer.
This research investigates a new class of reciprocity-breaking acoustic systems characterized by nonlinear internal structures, asymmetry and mixed scales. These systems exhibit directed cross-scale energy transfers which break time reversibility and reciprocity both locally (within each of the system subunits) and globally (for the entire system viewed a whole). Non-reciprocal, large-to-small scale energy transfers mimic analogous nonlinear energy transfer cascades in nature (e.g., turbulence). The research aims to be transformative in the field of nonlinear acoustics, promoting a new paradigm for predictive design with nonlinear non-reciprocity through (i) the theoretical and experimental understanding of acoustic systems with nonlinear hierarchical internal structures; (ii) the uncovering of the combined role of asymmetry, disorder, nonlinearity and cross-scale directed energy transfers on non-reciprocity; (iii) the development of new approaches for fabricating, characterizing and experimentally testing non-reciprocal lattice materials combining multiple macro-to-nano scales; and (iv) the translation of these materials to new technologies and acoustic devices that exploit and showcase transformative capabilities.