Researchers showcase their novel artificial camouflage skin in a biomimetic chameleon soft robot, demonstrating its excellent capacity for high-resolution crypsis and real-time concealment.
Being invisible sounds like a power only superheroes could have, but a new artificial camouflage skin developed by researchers from Seoul National University may turn our imagined fantasies into a reality.
Artificial camouflage is a functional mimicry of natural concealment technologies that exist in the natural world, such as the ones found in chameleons and octopuses. In recent years, camouflage technology has garnered significant attention for its widespread military applications – from improving survivability to simplifying the identification of anonymous objects. In the field of medicine, artificial camouflage is also emerging as an important area for soft robotics, electronic skin, and wearable devices.
However, existing artificial camouflage devices are often pixelated, resulting in lowered concealment efficiency. This is problematic as live backgrounds usually require patterns smaller than an individual pixel. Furthermore, although the practical application of camouflage devices requires real-time background sensing ability, this is a feature that active camouflage technologies have yet to realise due to the sheer complexity of the required system.
Now, a team of researchers led by Professor Seung Hwan Ko at Seoul National University has recently announced the development of a wearable artificial chameleon skin that can conceal itself immediately by detecting the surrounding background in real-time. They overcame the problems of earlier models with the help of thermochromic liquid crystal ink and silver nanowire heaters to construct a more practical, scalable, and high-performance artificial camouflage at a complete device level.
As its name suggests, thermochromic liquid crystals can change colour depending on temperature. In particular, they have a reflective spectrum that can be controlled over a wide range of the visible spectrum through minor temperature changes. This gives them their characteristic tuneable colouration, even when made into ink form. Knowing this, Ko and his colleagues strategised to layer thermochromic liquid crystal ink onto their new artificial camouflage skin. However, to allow for its colourful camouflage, the researchers had to find a way to control the temperature of the device.
In search of a solution, the researchers tested a variety of heaters before finally concluding that silver nanowire heaters worked best to accurately manipulate temperature. These nanowire heaters not only show excellent electrical and mechanical stability, but also enable the expression of fine patterns without associating the lateral pixelation scheme. They also found that displaying images do not need individually addressable lateral pixels. Therefore, they arranged the silver nanowire heaters in a vertically-stacked multilayer fashion.
With this new arrangement, the team successfully reduced the complexity of the system. But more importantly, they were able to achieve colourful camouflage since the researchers can activate either a single layer selectively or multiple layers simultaneously to show a wide range of colours and patterns. The team also addressed the issue of real-time concealment by incorporating a real-time sensing system that can quickly blend into the background.
Having addressed the limitations of past models, the team sought to demonstrate the efficacy of their novel creation. To do this, they integrated the proposed silver nanowire and thermochromic-based Artificial Chameleon Skin with colour sensors and feedback control systems. Combined, they completed the artificial camouflage device. When tested on a chameleon model, it was revealed that the “skin” could successfully detect the local background colour and match its colouration in real-time, demonstrating its potential to become a scalable and practical next-generation camouflage technology.
Source: Kim et al. (2021). Biomimetic chameleon soft robot with artificial crypsis and disruptive coloration skin. Nature Communications, 12, 4685.