Unlocking ultrasound manipulation by laser-engineered hierarchical nanostructures

The precise manipulation of underwater acoustic waves in the ultrasonic frequency domain using lightweight materials, encompassing both bio-compatible and synthetic substrates, holds significant promise for diverse applications across medicine, defense, pharmaceutics, and industry. This study investigates the application of femtosecond laser micro-nanofabrication to enhance the acoustic performance of submerged steel metasurfaces featuring multi-scale hierarchical architectures and controlled wettability. Laser surface engineering reveals the latent potential of superimposing periodic nanostructures onto precisely defined micro-structured morphologies to achieve a notable broadband (0.5-1.5 MHz) attenuation of transmitted ultrasound, concurrently exhibiting a distinct frequency-dependent reflection profile. This approach offers a versatile methodology for tailoring underwater wave propagation characteristics through the creation of unconventional surface functionalities, thus opening new avenues for the design of advanced acoustic metasurfaces.