Lotus is an ornamental plant that lives in shallow water and also has practical value. In addition to its graceful and elegant flowers, the beauty of its leaves is no less impressive than that of its flowers. The petioles of lotus leaves are very long, lifting the leaves above the water surface, like a row of green umbrellas that open up, adding a beautiful landscape to the lake and mountains.
When it comes to lotus leaves, many people have noticed this phenomenon: after rainy days and sunny weather, the rainwater on lotus leaves always forms round water droplets, like shining pearls rolling in a green jade plate. Why do water droplets become so beautiful and charming when they fall on lotus leaves? The usual explanation is that the surface of lotus leaves has a very fine layer of soft hairs, which makes it difficult for falling water droplets to spread out. In fact, if you observe lotus leaves under a microscope, you will find that the surface of lotus leaves is not smooth, but has many papillary structures and a layer of wax. The simultaneous action of these two characteristics makes the surface of lotus leaves extremely hydrophobic. Water sprinkled on the leaf surface will automatically gather into water droplets, and the rolling of water droplets will also adsorb and roll off the dust and mud on the leaf surface, keeping the leaf surface clean. This is the famous "lotus self-cleaning effect".
Scientists further studied the microscopic structure of lotus leaves and found that in addition to the wax component, the "lotus effect" is related to two structures of lotus leaves: one is a micron-sized protrusion, and the other is a nanometer-sized hair-like structure. Lotus leaves containing these two structures have a contact angle of 142° on the surface of water. If the lotus leaves only contain micron-sized structures, the contact angle is 126°; or if the lotus leaves only contain a wax surface, the contact angle is 74°. Scientists believe that due to the nanometer-sized hair-like structure of lotus leaves, the contact angle of water on the leaf surface increases, that is, the hydrophobicity of the lotus leaf surface increases, and these two structures are the main causes of the "lotus effect".
In fact, similar ultra-micro and nano-structures with self-cleaning effects are not only found in lotus leaves, but also widely exist in other plants. They are not only conducive to self-cleaning, but also help prevent a large number of harmful bacteria and fungi in the atmosphere from invading plants. The self-cleaning effect even exists in many animals. For example, when it rains, human hair or the fur of cats and dogs are easily wet by rainwater, while the feathers of ducks will not be wet. Even if they are doused with water, they can shake off the water with a flap of their wings. This is because the contact angle of water on human hair or cats and dogs' fur is very small, while on duck feathers, it is very large.