Complementary Acoustic Metamaterial for Penetrating Aberration Layers.

Impedance-matched acoustic materials were developed to improve ultrasound penetration through the aberration layer. The traditional ultrasound layer matching material is called a couplant, which can only enhance ultrasound transmission to soft biological media such as the cartilage and muscle but cannot penetrate hard media such as the bone. Here, we propose a phase-modulated complementary acoustic metamaterial based on the principle of impedance matching, which enables ultrasound to penetrate the bone, and use the equivalent parameter technology of acoustic metamaterials for parameter design. Ultrasonic layer adjustment is performed through 3D printing and corrects bone aberrations. Several configurations were investigated through numerical simulations and experiments in non-reflecting tanks. Specifically, the bone matching layer can be optimally designed for a specific bone thickness and a specific operating frequency of the ultrasound probe, thereby amplifying the ultrasound to penetrate the matching layer and bone. The experimental and simulation results show that the proposed acoustic metamaterial can improve the transmission efficiency of ultrasound through the aberration layer.