Bio-inspired electrochromic skin based on tungsten oxide

Some animals, such as the chameleon, have great capability of camouflage by changing their skin color to avoid detection. This outstanding property have inspired researchers to develop the ability of the materials and devices to mimic chameleon for applications in intelligent wearable and camouflage devices. Tungsten oxide (WO₃), switching between blue and transparent, is widely studied due to its large optical modulation but it is difficult to obtain multicolor and flexibility. Here, we design a bio-inspired chameleon skin electrochromic device (ECD) assembled by inorganic electrochromic materials WO₃, which can achieve the reversible color changes from yellow, light green to dark green according to subtractive color mixture theory. The flexible ECD exhibits a high optical reflectance modulation of 38.9% at voltage of ± 1.5 V in the wavelength range of 250–2500 nm. Fast response speed of 0.32 s for both coloring and bleaching process is obtained which can be attributed to the porous structure of the WO₃ electrochromic layer. The ECD keeps excellent electrochromic performance even under bending conditions, indicating the great flexibility. The inorganic bio-inspired chameleon skin ECD opens new avenues for the design of intelligent and wearable devices.