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.
