Have you ever been caught in a sudden rain shower and had your favorite clothes soaked? You wish you had fashionable clothes that could repel water. However, there are creatures in nature that have mechanisms to avoid getting wet. For example, there is the lotus plant, which never gets soaked even though it is sticking its head out of the pond.

In the early summer mornings, the lotus flower shoots up its long stem from among the leaves that spread over the water surface, and a large flower blooms. Since it grows in the mud at the bottom of the water, the lotus has been praised as "the lotus grows out of the mud but is not stained by it," and it has been revered as a sacred flower since ancient times.

The round, sparkling droplets of water on the leaves, like a gently placed crystal ball, also remind us of the nobility of the lotus. Lotus leaves have an excellent mechanism for repelling water.

Generally, the surface of plant leaves contains a wax-like substance that has the ability to repel water (water-repellent effect). However, the surface of lotus leaves has another secret. If you look closely, you can see that what appears to be a smooth leaf is actually uneven, with countless tiny protrusions about 1/100 of a millimeter in size lined up. Each of these tiny protrusions has countless even smaller protrusions lined up on its surface.

The presence of countless microscopic projections that cannot be seen by the human eye reduces the surface area where the water droplets contact the leaf, and the air between the projections acts as a cushion to support the water droplets from below. As a result, the water droplets cannot stay on the leaf's surface and roll off. This is the lotus's super water-repellent effect .

Although lotus plants grow in environments where they are easily covered with muddy water, the rolling water droplets slide off the leaves, taking all the dirt and debris with them, allowing them to always maintain a pure appearance. For lotus plants, this microscopic structure is important because it prevents the stomata (microscopic holes that allow gas and water to pass through) in the leaves from becoming clogged with mud, which would impede photosynthesis and respiration.

This mechanism is called the "lotus effect" after the English name for the lotus flower, and did you know that it is already used in many aspects of our daily lives, such as rice spoons that prevent rice grains from sticking, yogurt lids, rain gear, and building materials?

The day may soon come when books that can be read while soaking in the bathtub and children's clothes that won't get wet even when playing in the mud will become available.

Reference: Frontiers in Plant Science 6:102 (2015) "Mechanism of leaf surface structure and water repellency"