Metasurface Matching Layers for Enhanced Electric Field Penetration Into the Human Body

The use of electromagnetic elds applied to human tissues has proven to be benecial in several applications, such as monitoring physiological parameters and delivering medical treatments. Often applications rely on targeted energy deposition into the tissue, or rely on wireless powering of implanted devices. In such cases, the system energy efciency, the stability of the eld, and ultimately the process safety could all benet from minimizing the mismatch at the air-skin interface. In this article, the maximization of the electric eld transmitted into the muscle tissue is initially addressed by optimizing a dielectric-only matching layer in terms of thickness and relative dielectric permittivity, and under realistic constraints on low-cost available materials. The propagation of the electromagnetic eld inside a multilayered medium that represents the body is evaluated by using the wave-transmission chain matrix approach. Furthermore, an innovative solution, based on the application of a metasurface matching layer (MML), is proposed to signicantly improve the performance of the matching, thus enhancing the electromagnetic elds reaching the targeted muscle tissue. A thorough assessment of the performance is carried out considering both the presence of an air gap, and the case of plane waves impinging at oblique incidence.