WHY THIS MATTERS IN BRIEF

Metamaterials are odd, they’re freaks of nature, and now they’re going digital which opens up an amazing number of possibilities.

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As you’ll know by now I follow a huge number of technologies, and one of those that I track are metamaterials – a funky class of materials that have properties not found in nature which help them bend light and sound to create the first prototype cloaking devices as well as a huge range of other applications that include morphing plane wings and the ability to turn your car into its own airbag.

Metamaterials are artificially crafted composite materials whose properties come from patterns or small microstructures on their surface, and it’s the prefix “meta” that indicates that the unique characteristics of these materials exist outside of what is observed in nature. And in my view it’s these characteristics that make them so interesting, particularly as we race into the future.

Schematic of the coding metallic metasurface, which can modulate the scattering properties of EM and acoustic fields simultaneously.

Imagine, for example, being able to tune a materials refractive index for light or sound in order to obscure it from detection – an “invisibility” cloak. Metamaterials, which are artificial 2D materials made up of subwavelength-structured architectures, enable this because of their enhanced ability to fine tune and control the propagation of electromagnetic, optical, and acoustic waves. And as a result research into the weird materials has recently become a topic of considerable interest.

Now though a team from Southeast University in Nanjing in China have combined the best of metamaterials with information technologies (ICT) to create a digital material – the first so called Digital Coding Metamaterial (DCM). The new metamaterial has patterned sequences on its surface that resemble a digital circuit design that let the team use “digital componentry” to “carry out complicated functions” that are achieved by bending, steering, focusing, and scattering of electromagnetic waves.

In short, they’ve found a way to digitise metamaterials, and as anyone involved with regular digital technologies will tell you that opens up the door to a huge range of new applications and possibilities.  It’s a game changer that will help researchers in the future create tunable metamaterials that can morph to their environment and take on new properties in real time – something that could be useful for everything from military jets to robots and beyond.

So far the team have used the concept to control these DCM’s response to specific electromagnetic wavelengths such as the microwave frequencies, terahertz radiation, as well as the acoustic spectrum, but the new materials will, over time, become even more interesting when they are used to simultaneously manipulate multiple electromagnetic wavelength ranges all at once which will let them achieve multiple physical responses at the same time. Imagine, for example, a military jet that can detect specific electromagnetic wavelengths and dynamically cloak itself from enemy detection systems and you’ll get the idea – and that’s just the tip of the iceberg.

In this sense these new DCM’s can be interpreted as a key factor of our “multiphysics world”, where a single device can be controlled by different chemical and physical phenomena that all work simultaneously and cooperatively.

In a recent study published in Advanced Intelligent Systems, Professor Tie Jun Cui at the university and his team have recognised this potential and proposed a method to implement metasurfaces in simultaneously manipulating electromagnetic and acoustic waves.

This was achieved by tuning the geometric features of the “unit cell” created on the surface of the device, allowing the researchers to create 3-bit digital sequences which tune the metamaterial to specific incident wavelengths. The coding states were used to create a “reflecting array” metamaterial capable of scattering and reflecting incident waves of both electro-magnetic and acoustic energy, thus effectively creating a light and sound cloaking device that shields them from detection.

These mutli-physics effects were only previously possible using complex composites or multiple-materials-configuration designs. However, in the present study, the researchers demonstrate similar results using just a single material – aluminium. This not only simplifies the fabrication and design complexity of such devices, but thanks to the inherent features of aluminium, the device showed high strength, good flexibility, and high temperature resistance.

These characteristics make the device easily compatible with the outer skins of aircraft or ships, which might one day use them as advanced cloaking or signalling devices. The authors hope that future endeavours will involve safety detection or target exploration in complex scenarios.

Source: Nature