Acoustic metamask for enhanced ultrasound transmission and focusing through stiff barriers
Phys. Rev. Applied 25, 034048 – Published 13 March, 2026
DOI: https://doi.org/10.1103/718f-7w8s
Abstract
Efficient ultrasound transmission and focusing through acoustic barriers are crucial for advancing high-resolution imaging, targeted therapy, and acoustic manipulation. However, impedance mismatch and the geometric complexity of practical barriers, particularly stiff solids such as metal or bone, lead to strong reflections, wave-front distortion, and substantial energy loss. This work introduces an acoustic metamask that enhances transmission and enables flexible focusing through a stiff, curved barrier. The patterned surface structure of the metamask enables strong acoustic-solid coupling, where incident ultrasound excites resonant Lamb modes, and these guided modes subsequently reradiate the energy into the surrounding medium. This process mitigates impedance mismatch and enhances transmission, while the patterned structure simultaneously enables phase-modulated wave control for focusing. Full-wave simulations of curved brass shells reveal that the proposed metamask achieves a peak focal intensity over 2 orders of magnitude greater than that of a bare barrier, while maintaining 58.5% of the intensity observed in the barrier-free case and simultaneously producing a subwavelength focus. Our findings further demonstrate that the metamask design adapts to barriers with nonuniform thickness and complex geometries, enabling flexible multifocal control through stiff barriers. By utilizing the patterned structure to enhance acoustic-solid coupling, the design conceptually transforms the barrier into a functional acoustic device, facilitating efficient ultrasound transmission through acoustically opaque structures without requiring physical openings. The work establishes a design framework for wave manipulation through complex media, with broad potential implications for therapeutic ultrasound, nondestructive evaluation, and other advanced acoustic technologies.
