22nd August 2021

Artificial camouflage on a robot chameleon

South Korean researchers have created a new material that instantly reacts to match the colour of its surroundings. This has been demonstrated on the skin of a soft robot – and could one day have military or other uses.

Artificial camouflage that imitates concealment methods existing in the natural world – such as those used by chameleons and octopuses – has attracted much attention in recent years. Future applications may include the disguising of military equipment, suits, and other wearable devices, as well as robots.

In previous studies, however, the devices used have been too pixelated – reducing the concealment efficiency in settings where a pattern smaller than an individual pixel is required. In addition, for practical application as a camouflage device, real-time background sensing ability is essential, but this instant effect has proved difficult to implement due to system complexities.

This month, a team at Seoul National University in South Korea, led by Professor Seung Hwan Ko, has demonstrated a wearable artificial skin that can blend onto a surface immediately by detecting the surrounding background in real-time.

Professor Ko and his colleagues developed a layer of thermochromic liquid crystal (TLC) ink, which combines with silver nanowire heaters, stacked vertically in multiple layers. This overcomes the problems from earlier concepts and provides "a more practical, scalable, and high-performance artificial camouflage at a complete device level," according to the team. Their research is published as an open access paper in Nature Communications.

The TLC ink changes the light reflectance based on the device temperature, which is controlled by the extremely thin nanowire heaters. These measure less than 100 nanometres in diameter. Since these vertically stacked elements have a different pattern for each layer, it is possible to activate either a single layer selectively or multiple layers simultaneously to exhibit a wide range of colours and patterns.

In addition to the skin's high resolution, it has a real-time sensing system that enables blending into the background immediately. Ko's team demonstrated this advanced feature with a chameleon robot that is able to instantly camouflage itself across surfaces with different colours and patterns.

The effect is somewhat reminiscent of the OctoCamo depicted in stealth video game, Metal Gear Solid 4. Perhaps, like many concepts that once appeared to be science fiction, this technology will soon find its way into real life applications.

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