4. Artificial materials: metamaterials

Metamaterials are artificial materials whose properties (electronic, mechanical, thermal, etc.) can be controlled by adjusting their parameters and geometric structures. This applies to electromagnetism, but could be applied to all physical properties of materials. The beginning of metamaterials is often cited as E. Yablonovitch's 1991 proposal for photonic crystals, whose geometric structure is inspired by natural crystalline materials. . However, the same type of periodic arrangement of dielectric or metallic rods can be found in a Microwave Handbook dating from 1945. And the antenna patented by Marconi in 1919 uses a metal grid...