Bionic Leaves Imitating the Transpiration and Solar Spectrum Reflection Characteristics of Natural Leaves

A novel thin film organic bionic leaf was prepared by a solution-casting method to simulate the thermal effect of transpiration and solar spectrum reflection characteristics of plant leaves. The main components of the bionic leaf are polyvinyl alcohol (PVA), lithium chloride (LiCl) and chromium sesquioxide (Cr2O3). The thin film was modified by chemical cross-linking, and its surface was modified by alkylsilane to prevent excessive swelling. The thin film can simulate the thermal effect of natural leaf transpiration because that the hygroscopic PVA and LiCl can absorb and desorb water due to the high and low humidity of the ambient air at night and day, respectively. The thin film has the similar solar spectrum reflection characteristics to those of plant leaves due to the Cr2O3 and the water content of the hygroscopic materials. The measured diurnal maximum radiation temperature difference between the organic bionic leaf and the Osmanthus fragrans leaf was only 0.55 °C. In addition, the solar spectrum reflection measurements revealed that the organic bionic leaf could precisely simulate the key solar spectrum reflection characteristics of plant leaves.