Recently, the phenomenon of “returning to the south” in some areas of the southern my country has appeared. Netizens have said that “it feels like living in the water curtain hole” and “the walls in the family are crying.” The reason for this phenomenon is because the outdoor temperature, low indoor temperature, and water mist produced by indoor water vapor condensation are covered with walls and floor surfaces, which are the same as the foggy of winter glasses. For the general public, just wait for the weather to continue warming, and “returning to the south” will naturally pass. However, for medical workers and some special operators, it is critical to avoid fogging on the surface of the equipment. On the surface anti -fog, the doorway here is deep; and the water -proof soap, and the waterproof mosquito, perhaps the secret weapon we defeat the “back to the south”.


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Wang Wei

(Professor of Harbin University of Technology (Shenzhen))


Return to Nantian and Fog

On Saturday morning, I thought I arrived at the bathhouse for a moment: the walls and windows in the corridor were hanging water droplets, and the ground was as humid as it was sprinkled with water. The downstairs of the community is even more exaggerated: some shade positions, water on the tile floor can be splashed out of water.

The author’s corridor. No one dragged the ground and wiped the wall.

It turns out, annual

“Back to Nantian

“here we go again.

With pictures source: Shenzhen Health Commission public account

Students in Fujian, Guangdong may be no stranger to “returning to the south”. simply put,

The reason for this phenomenon is that the outdoors suddenly warmed and the humidity was large, but the indoor was still cool, and there would be water vapor on the interior surface.


Picture source: China Weather Network Public Account

Based on the same reason, we go to the bathhouse in winter or from the air -conditioned room to the outdoors in the summer, and the glasses are easy to fog. In addition, sitting in a closed car in winter, the inside of the window will fog; in the summer, the side of the window of the air -conditioned car is also prone to fog.

Image source:

It is good to return to the south, and the fog on the eyes and glass may only bring some inconvenience to our lives. However, for medical staff, workers who operate key instruments and equipment, etc., the sudden fog on the goggles and glasses will make the sight blur, which will bring huge hidden safety hazards; May cause serious traffic accidents. therefore,

Development of anti -fog materials has great practical significance

Image source:

Anti -fog is also of great significance in nature. For example, for the small flying insects such as butterflies, mosquitoes, etc., if there are water droplets condensed in their wings, eyes, or other parts of the body, they may bring a disaster.

Image source:

If you want to avoid fog, you must first understand that there are three elements on the surface of the object on the surface of the object:

The air with high humidity, the surface of low temperature, and small water droplets need to be formed.

Therefore, by dehumidifying the air, or heating the surface, you can fundamentally avoid fog.

Photo source: Author drawing

However, no matter the air exhaled or the environment where the insect is located, the water vapor is constantly steaming; whether it is the doctor’s goggles, or the mosquito’s eyes and wings, it cannot be heated at will. Is there any way to prevent fog goggles and mosquitoes?

Let’s review the three elements of the fog. Since the surface cannot be heated and the air humidity cannot be reduced, we can only make an article on the water drop. in other words,

You can allow the condensation of the water, but as long as you avoid generating water droplets

Essence Starting from this idea, there are two types of anti -fog strategies, which are “hydrophilization” strategies that allow water to form a uniform water film, and the “hydrophobicization” strategy that condenses the water into a large water droplet.


One of the anti -fog strategies: hydrophilic surface

Artificial anti -fog materials usually use the first method, that is,

By chemically modify the surface, cover some “hydrophilic” substances

, Make the condensed water spread into a uniform water film

Essence Such a water film is transmitted like glass, so it will not interfere with sight.

This “hydrophilicization” can be achieved through special instruments. For example, the “oxygen and other ions” bombard the surface of the glass to produce a group containing oxygen atoms, which greatly improves the hydrophilicity of the glass surface, so that the water can be fully wet and form a water film.

You can also achieve “hydrophilization” by covering a special layer of coating. For example, researchers at Xiangya Hospital of Central South University have developed a composite coating containing organic silicon oxidation compounds and acrylic acid, which have good hydrophilicity and light transmission rate, and can be closely integrated with optical lenses.

Now, many anti -fog goggles made of similar ideas are already able to buy in the market. However, in the early days of the outbreak, medical staff may not be able to use this anti -fog goggles in large quantities due to prices and supply. Is there a cheaper and more affordable way to make the goggles “currently prevent fog”?



Plasma for soap

In addition to plasma treatment and coating, “hydrophilization” can also be called by smearing


Chemicals are realized. Such molecules are divided into two ends: one end is the head that likes water, usually contains atoms and groups that can be closely integrated with water molecules; the other end does not like water

(“Water Shui”)

The tail is usually a long organic molecular chain. Soap


(Lanches, laundry powder, etc.)

The molecule is a typical surfactant. They pull the oil from the surface of the clothes and dishes from the surface of the clothes and dishes with a hydrophobic terminal and dissolve them into the water.

After applying the surfactant to the surface of the object, one end of their hydrophobic will be attached to the surface of the object, and the other end will be combined with water molecules to help the water molecule spread to form a water film.


As a result, a folk remedy that prevents glasses from fog in winter: “Solk the detergent, soap, toothpaste, or egg white in water, and then soak the lens in it … , Is it amazing? “


The core of this method is

Apply a layer of surfactant molecules on the surface of the glasses, so that the condensed water forms a transparent water film.


Instead of hindering a small droplet.

Don’t look at this method seemingly old, but during the period when the new crown was raging two years ago, this is the most urgent “card neck technology” for many medical workers. Published in 2020 in a paper in “Chinese Eye Optics and Visual Sciences”

, Team from Wenzhou Medical University Affiliated to the Eye Vision Hospital investigated the seven methods to solve the problem of anti -fog problems, including hand washing solution, soap detergent, anti -fog ointment, iodine, automotive glass water, swimming mirror anti -fog agent Wait. They found, “Antibacterial toiletting fluids can be seen everywhere around the medical staff. Apply the hand -wash liquid in the inside of the goggles, then rinse it with water, and dry it.


(Note: Do not dry with gauze or paper towels)

In this way, the goggles have anti -fog function. This method is convenient and practical. One of the authors of this article, the three ward medical teams led by Nurse Zheng Xiuyun, who assisted Wuhan, used this method to prevent fog. The effect was stable and lasting. “


In fact, whether it is a low -cost soapy water, or the “swimming mirror anti -fog agent” that sounds tall, and even the “eye mirror anti -fog coating technology” developed by some scientific research teams, the principle is the same:

Surface active agent molecules condense water into a water film instead of water droplets.

Because these methods are the same in nature, there are similar disadvantages: these “anti -fog” molecules are only attached to the surface of the object, encountering mechanical power

(For example scraping)

It is easy to fall off, this is why the above paper specifically reminds “avoid drying with gauze or paper towels.” On the other hand, these surfactants are essentially soluble in water. Therefore, water condensation is also taken away by these molecules, so this kind of anti -fog means will fail after a day.


Second of the anti -fog strategy: ultra -hydrophobic surface


As mentioned above, in order to avoid small water droplets when the water is condensed on the surface, it can be physical treatment on the surface, or covered with hydrophilic coating, so that the surface becomes hydrophilic, so that the water condenses into a clear and translucent water film. Do not interfere with sight. However, such coatings are easily contaminated by oil, dust, etc. in the air, and become less hydrophilic, and it is easy to fall off and dissolve. Therefore, the goggles made by this “hydrophilic” strategy often do not have a long life.

For our daily use, maybe it is not a big deal to do anti -fog treatment once a day. However, for the creatures that must fight with water vapor in the air every day, these anti -fog methods above are not only inconvenient, but if the hydrophilic coating fails, it will become a major problem of life and death. Therefore, nature needs a stable, lasting and reliable anti -fog strategy.

The lotus flowers that “out of the sludge but not dyed” made us realize that

There is also a “hydrophobic” anti -fog strategy that is completely different from human “hydrophilic”

Essence The reader may be familiar with the water sparseness characteristics of the lotus leaf: water droplets will not only stick to the surface of the lotus leaf, but will turn into the center of the lotus leaf like the surface of the non -stick pan. Since the 1970s in the 1970s, German botanist William Bartalot

(Wilhelm Barthlott)

Since studying the surface of the lotus leaf under the microscope for the first time, people have basically recognized the principle of hydrophobic dredging of lotus leaves: In simple terms, there are many raised on the surface of the lotus leaf more than a few tens of times smaller than the hair, and the surface coverage Water with hydrophobic. The water cannot be wet, and it is forced to form large water droplets; when the lotus leaves are slightly inclined, the water droplets roll up cheerfully.

Image source: Source: ENSIKAT, H. J.; Ditsche-kuru, P.; Neinhuis, C.; BARTHLOTT, W. Beilestein J. Nanotechnol. 2011, 2, 152–16161


Do not like to be wet insects also use this micro -nano structure to prevent fog. For example, the wings of butterflies have a special groove, which is similar to the raised size on the surface of the lotus leaf. The water could not be opened, but formed a drop of water. What’s even more amazing is that the droplets that rolled down can also take away the dirt on the wings and the surface of the eyes, thereby ensuring the dryness and cleaning of the insect’s body.

Image source: leave-to-lab/


The research on bionic anti -fog materials based on ultra -hydrophobic surfaces is a very prosperous research field. Scientists in my country have also achieved the world’s leading research results in this field. Interested readers can read references [4], [5]

(Editor’s Note: See “


From nature to bionic: the past and present life of ultra -hydrophobic materials


Essence You may be thinking that since nature provides us with such a good strategy, can this ultra -hydrophobic structure be used in anti -fog mirrors, windshields, and glasses? Unfortunately, this method has not yet been used in production and life. The reason is that on the one hand, it is necessary to prepare such a fine structure in micro -nano -standard and produce in large quantities, which may be very cost -effective and complicated; on the other hand, our requirements for anti -fog surfaces are not as high as insects. The demand for long -term and stable fog materials is not so urgent.

In addition, there is a fatal defect based on this ultra -hydrophobic surface based on a micro -nano structure: not abrasion. Once such a fine structure is destroyed, it will fundamentally lose the “magic” of hydrophobic. However, the team of Professor Deng Xu of the University of Electronic Science and Technology has jointly developed a new strategy with collaborators

Using a micro -structure “armor” with excellent mechanical stability to protect the surface of the ultra -hydrophobic surface, which greatly solves the problem of wear on the super hydrophobic surface. Maybe we can quickly see waterproof, self -cleaning walls, glass and even solar panels entering millions of households.

Who would have thought that mosquitoes and butterflies may be our key little helper to defeat back to Nantian?



Li Jian, Liu Jiayi, Zhang Yangde, a new type of nanometer transparent fogging film on the surface modification of optical lenses, Chinese organizational engineering research, 2011, 15 (3): 445-449


“What should I do if we wear masks and glasses in winter? Let me teach you 5 little tricks.” Netease


Huang Xiaoqiong, Qu Jia, Chen Yanyan, et al.. New coronary virus pneumonia’s epidemic situation and anti-fog guidance of goggles.


“Summary: The progress and challenge of ultra -moisturizing and imitating fog materials” “



“Wang Pengwei, Liu Mingjie, Jiang Lei. Bionic multi -scale super -infiltrated interface materials.


DEHUI Wang, qiangqiang Sun, Matti J. HOKKENEN, Chenglin zhang, Fan-Yen Lin, qiang liu, shun-peng zhu, tianfeng zhou, office Deng, nature, 2020, 582, 55–59,

Reprinted content only represents the author’s point of view


Does not represent the position of the Institute of Physics of the Chinese Academy of Sciences


Photo source: Author drawing

Photo source: Author drawing

Photo source: Author drawing

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Source: Hui Pu

Edit: Muyu