A leaf-mimic material based on polyurethane microcapsules and Cr2O3 for hyperspectral stealth

Targets can achieve invisibility in the vegetation environments by simulating the reflection spectra of plant green leaves. However, balancing the accuracy and stability of simulation effects, particularly in simulating spectral features caused by water in the leaves, is often challenging. Herein, polyurethane microcapsules encapsulating liquid water (W-PUMCs) were prepared by inverse emulsion polymerization, then mixed with Cr2O3 in specific proportions into the epoxy resin matrix to obtain a material capable of simulating the reflection spectra of green leaves in the visible and near-infrared bands. The normalized similarity (NS) between the spectrum of this material and that of plant (cherry) green leaf can reach 0.9779 in the range of 400–2500 nm. W-PUMCs are used to simulate the spectral characteristics caused by water in the leaves because the spectral NS between W-PUMCs and the green leaf in the 1100–2200 nm range is 0.9930. Cr2O3 is employed to simulate the other major spectral features of green leaves. This strategy guarantees simulation accuracy while simplifying the preparation process and reducing production costs and providing solutions to spectral simulation in the fields of military stealth and ecological protection.