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HomeTechnologyInnovative Water-Repellant Coatings: The Rise of Structural Color Shields

Innovative Water-Repellant Coatings: The Rise of Structural Color Shields

In an advancement towards creating innovative materials for functional coatings, a research team from Japan has unveiled a technology that merges structural color coatings with exceptional water-repellent features. Unlike traditional paints, structural color coatings maintain their vibrancy and possess self-cleaning abilities. This was accomplished through the utilization of hydrophobic melanin particles that impart both structural color and water resistance. This breakthrough represents a significant step forward in the field of advanced materials for coatings and paints.

Have you ever marveled at the striking blue shades of peacock feathers or the glimmering chitin on beetles? These natural phenomena are known as structural colors— where microscopic structures create stunning and enduring hues. Motivated by these natural wonders, a research group from Japan has been investigating structural colors. Their previous work revealed that utilizing melanin particles to create structural color materials imitates the coloration techniques found in peacock feathers. Armed with this knowledge, the team aimed to produce a coating material that showcases the brilliance of structural colors through melanin particles, resulting in non-iridescent color visible from multiple angles.

The research team, including Professor Michinari Kohri and Ms. Yui Maejima of Chiba University’s Graduate School of Science and Engineering, collaborated with Dr. Shin-ichi Takeda from Takeda Colloid Techno-Consulting Co., Ltd., and Dr. Hiroshi Fudouzi from the National Institute for Materials Science. Their discoveries were published in Macromolecular Reaction Engineering on December 18, 2024. Professor Kohri shares his research motivation, We have spent years studying melanin-based structural color materials inspired by nature. Our goal was to enhance the practicality of these materials by quickly creating structural color while incorporating functional features such as water repellency.

To realize this goal, the team developed polystyrene particles in three different sizes. They coated these with polydopamine (which modifies melanin particles), followed by adding hydrophobic octadecyl groups— composed of 18 carbon atoms—via a Michael addition reaction. This reaction facilitates the introduction of negative chemical groups to an α, β-unsaturated carbonyl compound, leading to enhanced water resistance without the use of environmentally damaging fluorine compounds.

The newfound hydrophobicity of the particles was verified through the time-domain nuclear magnetic resonance (TD-NMR) technique. Once treated, the particles were suspended in hexane for quick and efficient application onto surfaces like glass and melamine laminate. After drying, the coatings exhibited a contact angle exceeding 160 degrees, vibrant hues, and a self-cleaning effect known as the lotus effect, which allows water droplets to bead and roll off without leaving any residues.

The hydrophobic melanin particles that were coated with octadecyl groups demonstrated hydrophobic characteristics comparable to those of fluorine-coated particles renowned for their exceptional water resistance. Commenting on the team’s notable findings, Ms. Maejima, the lead author, states, We found that super-hydrophobic structural color coatings can be achieved by integrating the hydrophobic qualities of the particle surfaces with their hierarchical assembly structure in a matter of minutes.

The team emphasized the importance of creating a simple and scalable method, allowing for swift application of the coatings without requiring complex equipment or processes. Ms. Maejima highlights the practical implications of their research, stating: “This technology could represent the future of coating materials, ideal for uses such as wallpaper or outdoor surfaces, and it avoids the fading associated with traditional pigments. Its efficient application makes it well-suited for industrial adoption.”

Structural color coatings show great potential for various uses. Unlike standard pigments, these colors originate from physical interaction with light, guaranteeing endurance and resistance to fading. Their combination of durability and self-cleaning characteristics makes them especially suitable for exterior applications. For instance, walls covered with this material may stay vibrant and clean for many years, greatly minimizing repainting and maintenance expenses.

As long as the structure of periodic arrangements is preserved, the structural color coatings retain their hue. The proposed methodology is effective and does not rely on harsh chemicals. Structural color coatings can also be applied across diverse fields, including food, pharmaceuticals, cosmetics, and industrial products, presenting opportunities for sustainable, enduring designs.

Looking ahead, the research team is focusing on improving the adhesion and durability of these coatings to enhance their versatility across a range of surfaces. As this technology progresses, it has the potential to revolutionize coating materials, seamlessly merging aesthetics, functionality, and environmental considerations. This innovation emphasizes the impact of research in creating solutions that are not only avant-garde but also align with the demand for a sustainable future.