Bionic Composite Material Simulating the Optical Spectra of Plant Leaves

Though many physical models have been proposed to simulate the spectra of plant leaves, there are few reports on the material simulation of plant leaves. In order to prepare a material that could simulate the reflectance spectra of plant leaves, the spectral reflectance characteristics of plant leaves and their forming mechanism were analyzed. The study indicated that the reflectance spectra of plant leaves exhibits four common characteristics, which were determined by the spongy inner structure and biochemical contents (chlorophyll, water) of plant leaves. In our procedure, the chlorophyll was concealed into the high-oxygen-barrier polyvinyl alcohol (PVA) film to improve its photostability, and the water was sealed into the bag of high-vapor-barrier polyvinylidene chloride (PVDC) to prevent its vaporization loss. Subsequently, taking the structures of plant leaves and petals as simulating models and considering the limits of PVA film and PVDC bag, a novel bionic composite material constituted with three layers was designed and prepared. The spectral tests and endurance experiment show that the bionic composite material exhibits almost the same reflectance spectrum with those of green leaves, and its spectrum changes little after sunlight treatment for three months, which proves a good sunlight endurance of this bionic composite material.