Focusing Ultrasound with an Acoustic Metamaterial Network

TLDR

The study experimentally demonstrates focusing ultrasound waves using a flat acoustic metamaterial lens composed of a planar network of subwavelength Helmholtz resonators. The experiment achieved a half‑wavelength‑wide focus at 60.5 kHz, matched simulation predictions, showed frequency‑dependent focal length, and demonstrates the potential for compact, lightweight ultrasound imaging elements.

Abstract

We present the first experimental demonstration of focusing ultrasound waves through a flat acoustic metamaterial lens composed of a planar network of subwavelength Helmholtz resonators. We observed a tight focus of half-wavelength in width at 60.5 kHz by imaging a point source. This result is in excellent agreement with the numerical simulation by transmission line model in which we derived the effective mass density and compressibility. This metamaterial lens also displays variable focal length at different frequencies. Our experiment shows the promise of designing compact and lightweight ultrasound imaging elements.