Abstract

Passive acoustic structures can be used to engineer wavefronts in many practical applications. By tuning its topology, the local refraction, scattering or inner resonances can be tailored for a particular functionality. We report the use of metasurfaces to synthesize wavefronts by tuning subwavelength 3D-printed elastic resonators for ultrasonic frequencies. These structures are shown to be remarkably flexible for spatially-coding arbitrary phase-conjugated fields corresponding to the ones used for selected biomedical ultrasound applications. In this way, by tuning the hologram inner structure, we can synthesize high-intensity acoustic images with unprecedent resolution, which are currently being applied to focus therapeutic ultrasound beams and treat several diseases in a non-invasive, non-ionizing, localized and low-cost manner.