Biomimetic coating technology is a technical science that provides new design ideas, working principles and system composition for coating engineering technology through the structure, traits, principles, behaviors and interactions of biological systems. The coating industry looks to the biological world for inspiration and simulation in order to promote the technological level of the coating industry, which is an important development direction to promote coating science in the direction of microscopic, systematic, intelligent, fine and clean as well as to enhance the original innovation capability of coating science and technology. Translated with www.DeepL.com/Translator (free version)
In the 1970s, the botanist Barthelot from the University of Bonn, Germany, discovered the lotus leaf effect when studying the foliage of plants, i.e., the residual pollutants on the foliage of many plants were more than 40%, while the residual percentage of pollutants on the foliage of lotus leaves was less than 5%. The surface of the lotus leaf has tiny waxy particles and is covered with numerous micron-sized protrusions, which in turn are covered with even finer villi of only a few hundred nanometers in diameter. In 1999, a research group at the University of Bonn, in cooperation with ISPO, used the water repellency of silicone resins to produce Lotusan coatings that mimic the microstructure of the lotus leaf surface and have remained self-cleaning for more than five years.
In 2000s, the Institute of Chemistry of Chinese Academy of Sciences prepared the micron and nano dual structure of polymer by molecular design, and used the principle of self-aggregation, surface tension and phase separation of polymer in the process of solvent evaporation to construct the polymer surface with micro and nano dual structure similar to lotus leaf by direct film formation under room temperature and atmospheric conditions in one step, and obtained the bionic coating with superhydrophobic and oleophobic properties, and the contact angle of water and oil can be as high as 166° and 140° respectively. The contact angles of water and oil can be as high as 166° and 140°, respectively, and the rolling angle of water on the bionic surface of the coating is only 3.4±2.0°, which can roll freely and has a self-cleaning effect similar to that of a lotus leaf surface. This kind of technology has very good effect when applied to the production of architectural coatings, clothing fabrics, kitchenware panels and other coating products that require dirt resistance.
In a collaboration with AkzoNobel, Wageningen University in the Netherlands, and Cambridge University in the UK, inspired by the inner wall properties of pigweed, Audrey has developed a conceptual pigweed bionic ultra-slick coating (without pesticides) that is conceptually designed to make the surface so smooth that ants cannot climb it. Ants climb walls by using a combination of microscopic claws and sticky feet (they also expel a liquid that acts like glue). Therefore, the paint design idea was to use a particle that was small enough that the ants’ microscopic claws could not attach to it, while at the same time these particles could detach from the paint and stick to the ants’ claws so that they could not stick to anything else, making them no longer sticky and therefore fall off the wall. The study showed that as the experimental coating was gradually optimized, no ants could crawl on surfaces coated with this paint. Harvard scientists have also designed and produced a transparent coating that can be used economically on a variety of objects, including the hull of a ship, by mimicking the inner skin of the pigweed. The coating, developed by mimicking the skin structure of hogweed, can heal itself almost immediately even when the coating is scraped off with a knife or razor blade, and is able to cope with environmental contaminants and degradation, achieve self-healing capability and damage tolerance that can be applied in extreme temperature and high pressure environments.
Researchers in the United States, France, Japan and other countries have attached great importance to the study of chameleon-style camouflage coatings. In order to prevent being hurt by other animals and to facilitate hunting, chameleons can automatically change color to conceal themselves with the change of environment. This is because the cells of the chameleon’s multi-layered skin contain green pigments that can move, sometimes gathering into a point and sometimes spreading out, thus changing the body color. A camouflage expert in the United States asserts that chameleon-style camouflage will enter the practical stage in 15 years. The representative of this kind of research in Europe is France. It is reported that the French National Center for Scientific Research and Arcueil Technology Center under the contract of the French General Directorate of Armaments have researched three major types of chameleon coatings, collectively known as “X-chameleon” coatings, including photochromic, thermochromic and electrochromic. All of them are in the visible and infrared range, and although each has its own characteristics, they have the commonality of color change for a variety of applications.
The self-layered gradient anti-corrosion coating designed according to the lotus root structure bionic can be self-layered after spraying, and the layered coating surface is hydrophobic and self-cleaning and anti-UV, the bottom layer has strong adhesion and corrosion resistance, and the middle layer plays a stabilizing role to get a high anti-corrosion intelligent gradient bionic coating. When PU/EP:fluorosilicon modified PAA=1:1, the contact angle reaches 96.0°, flexibility is 0.5 mm, impact resistance is 50 cm, adhesion grade is 1, and light loss rate is reduced to 19%; when butyl acetate (NBAC):n-butanol (NBA) = 4:6, the delamination of the coating film is good, contact angle reaches 107.7°, water resistance does not change when immersed in water for 48 h, and light loss rate is reduced to 17%. SEM-EDS and infrared spectroscopy analysis showed that the top layer of the self-layered coating film was fluorosilicone modified PAA, the bottom layer was PU/EP, and there was a transition coating in the middle, and the ─COOH, ─OH and epoxy groups in the two resins in the transition layer reacted to make the whole coating more stable. By EIS analysis, after 40 days of immersion in 3.5% NaCl solution, the corrosive medium did not penetrate the coating film to reach the substrate metal interface.
AkzoNobel recently launched MoodPaint, a color-shifting paint using bionic technology, which contains a modified thermogenic liquid crystal that responds to pheromones from nearby bodies, absorbing or reflecting different wavelengths of light waves to present different coating colors as the crystal moves. moodPaint is a smooth eggshell white that can start working within hours, as long as someone is in the room, it will seamlessly change color. Research has long shown that color may have an effect on human mood and behavior. soft blues can soothe hospital patients, vibrant yellows can stimulate your appetite in the kitchen, and neutrals can make people feel comfortable in their living areas. moodPaint allows one coating to bring out multiple colors at your fingertips.
Coating biomimetic technology has great potential and opportunities. Under the inspiration of natural organisms, many new research fields will emerge in coating science, and more high-performance, highly functional and highly intelligent coating technologies will be successful in the future.
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