"A drop of dew on the autumn lotus, falling from the clear night into the celestial realm. On the jade plate in the future, one might not realize its roundness until then." This poem "Ode to Dewdrops" by the Tang Dynasty poet Wei Yingwu depicts a beautiful scene unfolding in a lotus pond: on a cool autumn night, a drop of dew glistens on the lotus leaf under the moonlight, as if falling from the heavens. Song Dynasty scholar Zhou Dunyi also praised the lotus in "A Treatise on the Love of Lotus": "Growing out of the mud but unstained by it, washed by clear water yet not tainted by its impurities." Later generations used the lotus to metaphorically symbolize the noble character of a gentleman who remains uncorrupted by worldly influences in adverse environments.
The Lotus Leaf Effect Why doesn't the lotus leaf get stained by "mud while growing out of it"? In 1997, German botany professor Basler at the University of Bonn studied plant leaves using an electron microscope and unraveled the mystery. It turned out that the lotus leaf surface is covered with numerous bumps about 5-9 micrometers in height and 12 micrometers apart. Each bump is further covered with wax-like protrusions 200 nanometers in diameter, forming a "micro-nanostructure" on the "micron-scale structure." These "micro-nanostructures" on the lotus leaf surface appear like densely packed "small pillars." Combined with the repellent effect of the wax, water droplets cannot penetrate the gaps between the "small pillars" and can only roll around on their tops. Thus, the water droplets and the lotus leaf surface exhibit repellency, which we call the "Lotus Leaf Effect" or the "Hydrophobic Effect." When pollutants fall on the lotus leaf surface, they are easily swept away with the water droplets. This is the secret behind the lotus's "growing out of mud without being stained."
Surfaces with the Lotus Leaf Effect possess self-cleaning properties. If the repellent effect between the surface and water droplets is extremely strong, it is called a "super-hydrophobic surface," which also has excellent drag reduction effects. If the wax on the lotus bumps is lost, its super-hydrophobic properties will be destroyed. However, the lotus can continuously secrete wax, and with the replenishment of wax, the super-hydrophobic properties can be restored. Similarly, most plants in nature with excellent super-hydrophobic surfaces also have micro-nanostructures. According to incomplete statistics, there are about 1,200 species of insects in nature that can walk on water, and their legs also have micro-nanostructures. The Institute of Chemistry of the Chinese Academy of Sciences has studied the leaf and petal surfaces of various plants in nature, not only synthesized many super-hydrophobic materials, but also produced self-cleaning clothing, making significant contributions to the field of super-hydrophobicity.