Why do water drops have light spots on lotus leaves?

There are nanostructures on the surface of lotus leaves.

This structure can make the lotus leaf have double hydrophobic effect, that is, it does not touch water or oil, that is, the oil-water contact angle on the lotus leaf is greater than 90. It is reported that this structure has a strong ability to absorb air and will form on its interface.

An air film prevents water and oil from contacting lotus leaves. Jiang Lei of Institute of Chemistry, Chinese Academy of Sciences also thinks that lotus leaf has double hydrophobic effect.

But all the lotus leaves that can be touched are used for verification experiments. Results Lotus leaves are not oleophobic, and both engine oil and edible oil can invade.

Moistening lotus leaves can produce capillary phenomenon on the lotus leaves.

There is shiny reflection on the lower layer of the lotus leaf water drop, indicating that there is a layer of air between the water drop and the lotus leaf, and the reflection on the lower layer of the water drop is produced when the light shines into the water drop and reflects on the lower layer of the water drop. Observing the surface of lotus leaf with microscope and electron microscope, we can see whether there are cauliflower-like transparent and whitish spots on the surface of lotus leaf, which are temporarily called wax spots. Observing the total reflection surface of water droplets on the lotus leaf with a microscope, we will find that the reflection surface of water droplets on the lotus leaf is uneven, and there are many non-reflective protrusions on the reflection surface, which correspond to wax points. The protruding points occupy a small part of the reflection surface, between the wax points, and are arc-shaped. Through observation, it can be judged that the thickness of air dripping from lotus leaves is very different, about 0-20 microns. If it is the air adsorbed by nano-materials, the thickness of the adsorbed air should be consistent on the macro level. Make a big hole with a diameter of 3 mm on the dried lotus leaf, or make a small hole with a needle, so that the water drops on the lotus leaf can stay above the hole and will not flow out of the hole.

There are also wax spots on the dried lotus leaves, and water can also form shiny drops on them. When fresh lotus makes a hole, liquid seeps from the edge of the leaf hole, and water will leak out of the hole. ) There is no nanostructure in the hole of the lotus leaf, which is empty. Dongdong water quality institute

It doesn't flow down because the wax spots around the hole are hydrophobic, which holds the water on the lotus leaf, and the water in the middle of the hole is pulled by the surface tension of water, so the water can't leak out. The distance between wax spots of lotus leaves is about 10-20 microns, and water is at the wax spots.

In addition, it will be pulled by the surface tension of water, so that it can not enter the gap between wax points, so that the gap between wax points is occupied by air, forming a small reflection surface that can be totally reflected. Smooth wax block, PTFE

The vinyl sheet is hydrophobic, and the water droplets on it have no total reflection layer. Rough wax blocks and PTFE sheets found at random have not been treated with nanostructures, but they can form shiny water droplets with total reflection of light, that is, water.

There is air under the beads. All these indicate that there is air dripping from lotus leaf water, which may not be caused by nano-structure adsorption.