SUMMARY

Complimentary acoustic metamaterials (CMMs) are designed to enable acoustic transmission through highly mismatched impedance barriers. In biomedical applications, CMMs facilitate acoustic transmission through skull to realize noninvasive brain imaging and neural ultrasound therapies. However, CMMs do not account for the skull’s internal porosity that dissipates energy as a function of propagation distance. To resolve this issue, we propose a non-Hermitian complementary acoustic metamaterial (NHCMM) that counteract skull attenuation with active circuits for high acoustic transmission at high frequencies. Full-wave simulations show near-perfect transmission from either side of the skull while preserving imaging information and enhancing focused acoustic energy for ultrasound therapies. Additional simulations evaluate the effectiveness of NHCMMs for realistic skull geometries with curvature and imperfections. The ultimate goal of this project is to fabricate a NHCMM that enhances acoustic transmission through real human skull in a one-dimensional transmission line experiment. The proposed NHCMM design consists of two sensor-transducer pairs on both sides of the metamaterial that detects incident waves and superimposes an active acoustic signal on an otherwise passive unit cell. By facilitating two-way acoustic transmission through the skull with NHCMMs, we lay the foundation for noninvasive brain imaging and treatment for neural disorders.