From Metamaterials to Smart Materials - Overview of meta-concepts in microwave applications

Marko Bosiljevac
University of Zagreb, Faculty of Electrical Engineering and Computing

Speculations about materials that could have negative electromagnetic parameters and strange properties started in 1940s and 1960s, but it wasn’t until year 2000 that these ideas truly came to life with the first demonstrations of metamaterials. Although various artificial electromagnetic structures were developed also before, the idea of metamaterials or “beyond” materials developed in 2000 initiated a major evolution in the field of electromagnetics resulting in many new communication and microwave devices and applications. Metamaterial is defined as any material which has been engineered to have properties not found in naturally occurring materials and usually it is a composite of different materials arranged in some kind of periodic lattice where the period is much smaller than the operating wavelength. This concept has resulted in many various demonstrations that were later extended and converted to actual applications, such as super-lenses with infinite resolution, electromagnetic "invisibility cloaks”, miniaturization of waveguides, resonators, antennas and other communication and microwave components. Also, the original term of metamaterials diversified in many other directions in electromagnetics, and today there are passive and active metamaterials, metasurfaces, higher-symmetry metamaterials and many other concepts. This overview will summarize the most important results achieved in the past, present applications and on-going projects and highlight future research activities leading to a concept popularly known as “smart materials”.