Transformation acoustics for beamforming in anisotropic media

Acoustic wave propagation in anisotropic media like tissue and other biomaterials is important for biomedical acoustics, as ultrasound is commonly used as a technique for non-invasive surgeries and diagnostic imaging purposes. These ultrasound applications require beamformed signals to target specific regions of the body. However, the anisotropic properties of the body (e.g., muscle fibers) distort the beamformed wavefronts, detrimental to the performance of ultrasound therapies and imaging. Here, we propose and experimentally demonstrate a unique transformation acoustic technique that corrects the anisotropic distortive effects to beamform an arbitrarily desired propagation pattern. The experimental measurements demonstrate the effectiveness of this transformation acoustic correction for arbitrary focusing and selfbending beams. Our work provides an important method to suppress undesired anisotropic effects on beamformed waves, to improve upon the precision and effectiveness of medical treatments and diagnostics facilitated by noninvasive ultrasound therapies and imaging.