Metamaterials are designed and artificially crafted composite materials that derive their properties from internal microstructure, rather than chemical composition found in natural materials.
The core concept of metamaterials is to craft materials by using artificially designed and fabricated structural units (e.g. oscillators) to achieve the desired properties and functionalities. These structural units – the constituent artificial 'atoms' and 'molecules' of the metamaterial – can be tailored in shape and size, the lattice constant and interatomic interaction can be artificially tuned, and 'defects' can be designed and placed at desired locations.
By engineering the arrangement of these nanoscale unit cells into a desired architecture or geometry, one can tune the refractive index of the metamaterial to positive, near-zero or negative values. Thus, metamaterials can be endowed with properties and functionalities unattainable in natural materials.
The fascinating functionalities of metamaterials typically require multiple stacks of material layers, which not only leads to extensive losses but also brings a lot of challenges in nanofabrication. Many metamaterials consist of complex metallic wires and other structures that require sophisticated fabrication technology and are difficult to assemble. The unusual optical effects do not necessarily imply the use of the volumetric (3D) metamaterials.
You can also manipulate the light with the help of two-dimensional (2D) structures – so-called metasurfaces (or flat optics). Metasurfaces are thin-films composed of individual elements that have initially been developed to overcome the obstacles that metamaterials are confronted with.
According to the Coherent Market Insights, the global metamaterials market was valued at US$ 238.9 million in 2018 and is projected to exhibit a CAGR of 39.5% over the forecast period (2019 – 2027).
Some examples of start-ups here:
Take a look at this paper: Intelligent metasurface imager and recognizer
In this article, we present a proof-of-concept intelligent metasurface working at ~2.4 GHz (the commodity Wi-Fi frequency) to experimentally demonstrate its capabilities in obtaining full-scene images with high resolution and recognizing human-body language and respiration with high accuracy in a smart, real-time and inexpensive way. We experimentally show that our ANN-driven intelligent metasurface works well in the presence of passive stray Wi-Fi signals, in which the programmable metasurface supports adaptive manipulations and smart acquisitions of the stray Wi-Fi signals. This intelligent metasurface introduces a new way to not only “see” what people are doing but also “hear” what people talk without deploying any acoustic sensors, even when multiple people are behind obstacles. In this sense, our strategy could offer a new intelligent interface between humans and devices, which enables devices to remotely sense and recognize more complicated human behaviors with negligible cost.
In principle, the concept of the intelligent metasurface can be extended over the entire EM spectrum, which will open up a new avenue for future smart homes, human-device interaction interfaces, health monitoring, and safety screening.