Researchers have discovered a new method to develop ultrathin surface coatings strong enough to resist scratch and dings. The new material was created by combining thin films and self-healing technologies.
University of Illinois researchers have developed a new ultrathin waterproof coating with self-healing abilities that may help steam power plants run more efficiently in the future. From left, graduate student Ellie Porath, professor Nenad Miljkovic, professor Christopher Evans, and graduate research assistant Jingcheng Ma. Image Credit: L. Brian Stauffer.
The material has an extensive range of potential applications, such as self-cleaning, anti-fouling, anti-icing, anti-bacterial, anti-fogging and improved heat exchange coatings.
The new study observed that the rapid evaporative character of a specialized polymer comprising a network of dynamic bonds in the backbone facilitates the formation of a water-resistant, self-healing coating of nanoscale thickness.
Headed by University of Illinois Urbana-Champaign mechanical science and engineering professor Nenad Miljkovic and materials science and engineering professor Christopher Evans, the study was published in the Nature Communications journal.
As part of the study, the key focus of the Miljkovic group was to increase the efficiency of steam power plants, which are the largest generators of electricity in the world, by employing these kinds of coating in their condensers.
The coatings, when applied to the surfaces of the condensers, make them more water-resistant and efficient at forming water droplets, which optimizes heat transfer.
Jingcheng Ma, Study Co-Lead Author and Graduate Research Assistant, University of Illinois at Urbana-Champaign
According to the researchers, thin coatings utilized in steam power plants can run into various durability problems. Coatings can wear off in a week’s time and sometimes even in hours. Such a short lifetime makes the real-world application of the coating a challenging task.
This has been a basic issue in mechanical and material sciences for about eight decades. Although thicker coatings are more durable, they decrease heat transfer and erode the underlying advantages of the coating.
Earlier studies have revealed that a majority of ultrathin coatings face tiny pinhole defects after they get cured on the surface. Steam penetrates through these defects, resulting in the gradual delamination of the coating. Therefore, the objective of the researchers was to develop a pinhole-free, water-resistant thin film and improve the overall energy efficiency of steam power plants by many folds.
Self-healing materials can recycle and reprocess themselves. We found that we can successfully utilize the healing enabled by the dynamic bonds, allowing the coatings to self-repair in response to scratching or to prevent pinholes from growing.
Christopher Evans, Professor, Materials Science and Engineering, University of Illinois at Urbana-Champaign
The material is named dyn-PDMS and is simple to dip-coat onto materials in nanoscale layers on several surfaces like silicon, aluminum, copper or steel.
One of the reasons we can get such thin layers is because the solvents used in the reaction evaporate very quickly, leaving only the polymer. Also, once cured, the material repairs itself from scratches very fast — so fast that it is difficult to observe in real time. We do not see this behavior in large, bulk samples of the material — only in the thin-film, and that is a question we are trying to answer now.
Christopher Evans, Professor, Materials Science and Engineering, University of Illinois at Urbana-Champaign
The researchers note that the ultrathin coatings designed in this research provide a solution for sustainable water-resistant materials and lead to open scientific questions within materials science and fluid mechanics that remain unanswered.
The study was supported by the Office of Naval Research, the International Institute for Carbon-Neutral Energy Research, the Air Force Office of Scientific Research, and the National Science Foundation.
Miljkovic and Evans are both affiliated with the Materials Research Laboratory. Miljkovic is also affiliated with electrical and computer engineering. Evans is also affiliated with the Beckman Institute for Advanced Science and Technology and chemical and biomolecular engineering.
Journal Reference:
Ma, J., et al. (2021) Ultra-thin self-healing vitrimer coatings for durable hydrophobicity. Nature Communications. doi.org/10.1038/s41467-021-25508-4.