How does the leaf margin make the lotus surface dry as the lotus leaf floats on water?

Abstract

A smart role of the leaf margin makes the lotus surface dry when a lotus leaf floats on the water’s surface. It is mainly attributed to anisotropic topography composed of flat folds at the margin, which are quite different from the upper surface of the lotus leaf including the micro-papillae. The flat folds around the leaf margin forms a ring-band, which introduces a strong energy barrier against water that tends to return to the surface of leaf. As a result, the water underneath the lotus surface hardly overflows onto the upper surface by getting across the energy barrier of the margin. Thanks to the ultra narrowness of the margin, water on the upper surface can still be shed from the surface through the margin. This finding helps the understanding of the structure effect of the margin on many natural nonwetting surfaces of aqueous biology. It can inspire us to design a smart margin that can be applied to micro-devices on water.