Japan has developed a physical mosquito repellent that can stop mosquitoes from flying within seconds with just one spray. How does this new technology work?

According to media reports, new research by Japan's Kao Corporation and the RIKEN Institute of Physical and Chemical Research found that using aqueous solutions of surfactants with low surface tension can hinder the normal flight of mosquitoes, and using liquids with even lower surface tension can suffocate mosquitoes and cause them to lose their ability to move. This has led to the development of a new physical mosquito repellent technology that does not require pesticides.

Mosquitoes are virus-spreading killers

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Mosquitoes have existed on Earth for at least hundreds of millions of years. Their size alone is not scary, but they are important vectors of viruses. In the process of sucking blood from different organisms, female mosquitoes can spread some extremely harmful diseases, such as malaria, yellow fever, chikungunya, West Nile fever, dengue fever, filariasis, Japanese encephalitis, Zika disease and other viruses.

Bill Gates once said: If measured by "how many people it kills each year", the most dangerous animal in the world is the mosquito.

It is estimated that mosquito-borne diseases such as malaria and dengue fever kill 700,000 people worldwide each year. Malaria alone infected 280 million people in 2018, killing 410,000 people.

It can be seen that it is really necessary to prevent and control mosquitoes.

Common mosquito repellent and mosquito killing products contain slightly toxic ingredients

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In order to prevent mosquito bites, businesses have developed a variety of mosquito repellent and mosquito killing products, from the mosquito coils that need to be ignited at the beginning, to electric mosquito coils, electric mosquito coil liquid, and later wearable mosquito repellent bracelets, etc. At the same time, more and more people are using floral water to refresh themselves and repel mosquitoes.

The main effective substances for repelling mosquitoes in these various products are DEET and picolinate. DEET can volatilize around the skin, and by forming a vapor barrier, it interferes with the chemical sensors of mosquito antennae, making it impossible for mosquitoes to sense volatile substances on the human body surface, thereby achieving the purpose of preventing people from being bitten by mosquitoes. picolinate is less toxic than DEET.

DEET is slightly toxic, and its side effects are absorbed through the skin into the bloodstream and are irritating to the eyes. However, for adults, it is not a problem as long as they do not accidentally ingest it.

What is the principle of surfactant in killing mosquitoes?

Researchers have not given up their exploration in pursuit of safe and efficient mosquito control.

According to the Japanese company, by spraying a liquid containing water and surfactants, the mosquito's ability to fly will be severely hindered within a few seconds. Experiments have found that spraying liquid containing surfactants can prevent the mosquito's feathers from functioning properly, causing it to fall quickly. In contrast, spraying pure water has no effect on the mosquito's flight.

The surfactant mentioned here, also known as surface active agent, refers to a substance that can significantly change the interfacial state of its solution system when added in a small amount.

In terms of composition, surfactant molecules have a typical two-end structure: one end is a hydrophilic and lipophilic group, which is easily soluble in water and is called a hydrophilic group; the other end is a lipophilic and hydrophobic group, which is insoluble in water but soluble in oil and is called a hydrophobic group. The two types of molecular fragments or groups with completely opposite structures and properties are located at the two ends of the same molecule and connected by chemical bonds, forming an asymmetric, polar structure, thus giving this special molecule the characteristics of being both hydrophilic and lipophilic, but not hydrophilic or lipophilic as a whole.

If the common symbol of a rectangle plus a circle is used to represent a surfactant molecule, as shown in the figure, the rectangle represents the lipophilic group, and the circle represents the hydrophilic group.

When the surfactant is dissolved in water, the hydrophilic groups of the surfactant molecules are on the water side, while the hydrophobic groups are repelled from the water, forming a directional arrangement of surfactant molecules. This directional arrangement of surfactant molecules weakens the attraction between surface water molecules, which can strongly reduce the surface tension of water, thereby increasing the wetting and penetration of water into the wings and body surface of mosquitoes, affecting the wing flapping and making it difficult for them to maintain a normal flying posture.

At the same time, there are tiny holes on the body surface of mosquitoes and other insects for taking in oxygen from the air, which are called spiracles. Liquids containing water and surfactants can block the spiracles, suffocating mosquitoes to death.

Compared with the mechanism of traditional insecticides, the advantage of this new physical technology is that it is less likely for mosquitoes to develop resistance.

I hope that in the coming summers, people can stay away from the "harassment" of mosquitoes.