Fig. 1: Schematic viewing of SML applications.
From: Soft Metalens for Broadband Ultrasonic Focusing through Aberration Layers

A Medical ultrasound in brain tumor treatment, B underwater sonar ranging in AUV, C urban pipeline inspection. A generalized SML for all applications is established by universal full-wave equations in non-uniform layered medium to derive the phase accumulation of SML, and ensure the ultrasound wave for penetrating through AL.