Nippon Paint imitates tuna development antifouling bottom coating

It is said that large tuna can swim at speeds of up to 80km/h in the ocean. The shape of the tuna does belong to the streamlined shape of the fast speed, but in addition, there should be other flaws that reduce the frictional resistance of the water. The advent of a product is derived from this idea. That is the anti-fouling bottom coating “LF-Sea” developed by Kobe’s Nippon Nippon Marine Coatings.

The secret lies in the mucous membrane of the surface

The tuna that swims at high speed does not have fish scales, and its body surface is covered with a sticky and smooth mucous membrane. Although the details are still unknown, there is a perception that under the action of this mucosa, the frictional resistance of the boundary layer in the turbulent state will be weakened. In fact, studies have shown that after adding a very small amount of polymer to the liquid, the turbulent liquid frictional resistance will be weakened (Toms effect), which may be the same phenomenon on the body surface of the tuna.

“Because I am engaged in the development of ship bottom coatings, I often think about the inspiration for developing products from fish and marine life.” Shan Shengzhi, executive director of Nippon Marine Coatings Technology Division, has set his sights on tuna. When the ship is sailing, the bottom surface friction of the seawater accounts for 50-80% of the total resistance. According to Shan Sheng's idea, if the ship can achieve liquid-liquid contact between the mucous membrane and seawater, instead of solid (the bottom of the ship) in direct contact with seawater, it should be able to reduce the resistance.

To this end, Shansheng has adopted a method of incorporating a highly hydrophilic and viscous hydrogel into the bottom coating, thereby reducing friction with water. The bridged polymer in the hydrogel can form a three-dimensional mesh early enough to store water in the mesh. In daily life, kelp soup and agar also fall into this category.

In this way, the LF-Sea, which does not impair the basic purpose of the bottom coating to prevent the attachment of aquatic organisms such as barnacles, and which can weaken the frictional resistance of seawater, has emerged. It has been confirmed that the ferry using this coating can save fuel consumption by about 3.4%. Although only 3.4% of the area can be converted into fuel costs, it can save about 10 million to 20 million yen. Therefore, since it was put into production in 2008, it has been adopted by more than 600 vessels.