Bio-inspired Artificial Helical Chromatophore for Stealth Mode

Stealth technology has been very usefully applied in the military fields and is now becoming more prominent as a strategic technology. In nature, the firefly squid can protect itself from enemies using camouflage as a stealth mode. On the other hand, it is able to send fluorescent signals to attract prey by switching into a bright mode. Despite the development of many existing biomimetic materials, there are significant constraints related to their color-changeable velocity and mobility. Herein, we have developed a bio-inspired artificial thermochromic material system, which can reversibly switch between stealth and bright modes and thus provide a means to adapting to one’s environment analogous to the strategy applied by firefly squids. Through vertical contraction, a helically coiled yarn artificial muscle, selectively coated by Rhodamine B and TiO₂, can switch between fluorescent and stealth modes with a maximum speed of 0.31 cm/s. Upon external thermal impulse, artificial thermochromic muscle can spin up to 309° and achieve a negative strain of 84.6%. In addition, this research demonstrates thermochromic effects even in underwater aqueous conditions, showing applicability toward underwater robotics. With the cost-effectiveness of the demonstrated system, the developed artificial thermochromic muscles can be implemented into a variety of applications, such as colorimetric sensors and aqueous color-changeable soft robotics.