Bionic coating imitating reflection characteristics of plant leaf in solar spectrum waveband for hyperspectral camouflage

Imitating the reflection characteristics of plant leaves in solar spectrum waveband with bionic coatings can effectively counter the hyperspectral detection technology in the vegetation background. Herein, inspired by the formation mechanisms of the reflection characteristics of plant leaves, a bionic coating containing chromium oxide (Cr2O3) particles and a hydrophilic inorganic salt dispersed in a polyvinyl alcohol (PVA) matrix is prepared on metal plates, and a theoretical model was constructed to clarify the bionic mechanisms. Results show that the Cr2O3 particles exhibit absorption characteristics similar to those of chlorophyll and scattering characteristics similar to those of multilayer cells in plant leaves, thereby enabling the bionic coating to imitate the reflection characteristics in the visible and near-infrared waveband. Meanwhile, the hydrophilic inorganic salt can absorb moisture molecules in the air when the bionic coating is placed in natural environments, thereby absorbing incident radiation and imitating the water absorption valleys. Moreover, it was found that there is only non-freezing bound water in the bionic coating with a differential scanning calorimeter, thus the moisture absorption processes associated with the hydrophilic hydroxyl groups in PVA matrix were considered when determining the mass transfer characteristics in a natural environment. In the whole solar spectrum, the bionic coating can significantly suppress the high reflectance of the metal plates when the volume fraction of Cr2O3 particles is 0.81 % and the coating thickness is greater than 0.2 mm. Increasing the surface roughness of the metal plates can further improve the suppressing performance in the range from 800 to 1300 nm, achieving a better similarity of the reflection curves between the bionic coating and the plant leaves. The outstanding imitation performance of the key reflection characteristics of the plant leaves confirms the remarkable application potential of the bionic coating in the field of hyperspectral camouflage.