Living things appear on Earth and various survival techniques that have evolved over hundreds of millions of years are being incorporated into human life in various ways. The product of this evolution has been studied in biomimetic technology and has become an important key to solving various engineering problems. Through many outstanding studies, we have been in awe of the products of natural evolution. However, understanding and mimicking the complex mechanisms of living things was sometimes impossible or inefficient.

Representatively, one of mother nature’s most clever approaches to stealth and safety is Chameleon's color-changing ability which protects themselves using their muscle cells of the skin. There have been various applied researches to imitate this unique camouflage tactic, but a technology that can perform a perfect camouflage by recognizing the real-time surrounding environment and changing one's own color and pattern has not yet been developed.

We propose a thin and flexible artificial concealment device based on thermochromic liquid crystal (TLC) and silver nanowire network heaters for an intuitive and effective color change biomimetic concealment technique. (Nature Communications volume 12, 4658, 2021) TLC shows R, G, and B colors depending on the temperature and is coated on the outermost surface. Since the vertically stacked silver nanowire network heater has a unique pattern for each layer, various colors and patterns expressed from the TLC on the surface can be realized through a single pattern or overlapping patterns. In addition, through the precise heater control using the thermal resistance coefficient (TRC) of the silver nanowire and the fast heater activation control through the feedback control system, a device capable of fast and accurate color expression without being affected by external environmental disturbances is realized.

This biomimetic artificial camouflage skin can be effectively concealed from the surrounding background with a combination of appropriate patterns, and by applying this to the chameleon robot, the robot was effectively blended into the background and concealed through patterns and colors similar to the surrounding environment in the artificial natural environment.

In addition, for real-time ambient background detection, a color sensing system was added to the camouflage skin with a simple configuration. This integrated camouflage device is attached to the chameleon robot to recognize the surrounding color and successfully concealed itself from the ambient environment in real-time. As the robot walks through the various color background, it changes its skin color in real-time to match the changing surrounding background color. (Check the supplementary video of this paper) This new device is not only a military wearable camouflage device, but also an active color-changing flexible device that can be applied to various fields such as architecture, art, and clothing.

The paper:

Hyeonseok Kim, Joonhwa Choi, Kyun Kyu Kim, Phillip Won, Sukjoon Hong, Seung Hwan Ko, “Biomimetic chameleon soft robot with artificial crypsis and disruptive coloration skin”, Nature Communications, 12, 4658, 2021.     

Lab website: http://ants.snu.ac.kr/

Twitter handle: @SeungHwanKo1