Biomimetic Aqueous Microcapsules for Simulating NIR Spectral Reflectance of Foliage.

The spectral reflectance of plant leaves contains physiological and biochemical information, which can be effectively captured using hyperspectral imaging technology. This capability is valuable for applications in agriculture, reconnaissance, and beyond. Consequently, there is a growing demand for materials that can accurately simulate the spectral reflectance of leaves. One significant challenge in designing such materials lies in stably retaining water to mimic the reflectance features caused by water absorption in plant leaves within the 1400-2200 nm wavelength range. In this work, inspired by the cellular structure of foliage, we propose biomimetic aqueous microcapsules (BioA-MCs) to address this challenge. In these BioA-MCs, lithium chloride with robust water-retaining properties was added to the cores encapsulated by a shell of hydrophobic polyurea resin. Spectral characterization results indicate that the BioA-MCs achieve a similarity coefficient of 98.6% and a spectral Euclidean distance of 0.7269 compared to the reflectance spectrum of plant leaves within the wavelength band of 1400-2200 nm. The BioA-MCs demonstrated a minimal reflectance variation of less than 0.03 after 250 hours of exposure at 50 °C and 50% relative humidity. In this study, BioA-MCs successfully simulate near-infrared (NIR) spectral reflectance of plant leaves and hold promise for applications in hyperspectral camouflage.