COATING TECHNOLOGY
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plant leaves and some insect wings, and can be sprayed onto objects to make them waterproof. “Research into bioinspired materials is
an extremely exciting area that continues to bring into the realm of man-made materials elegant solutions evolved in nature, which allow us to introduce new materials with properties never seen before,” says Joanna Aizenberg, Amy Smith Berylson Professor of Materials Science and Professor of Chemistry and Chemical Biology at SEAS. “Tis research exemplifies how uncovering these principles can lead to developing surfaces that maintain superhydrophobicity underwater.”
NEW CHARACTERISATION METHOD One of the biggest issues with plastrons is that they need rough surfaces to form, however this roughness makes the surface mechanically unstable and susceptible to any small perturbation in temperature, pressure, or tiny defect. Current techniques to assess artificially-made
Replicating long-lasting plastrons in the lab has previously been unsuccessful
superhydrophobic surfaces only take into account two parameters, which do not give enough information about the stability of the air plastron underwater. Alongside a group of researchers from
Aalto University and FAU, Aizenberg identified a larger group of parameters including information on surface roughness, the hydrophobicity of the surface molecules, plastron coverage, contact angles and more. When combined with the thermodynamic theory, these additional parameters enabled the group to figure out whether or not the air plastron would be stable. With this new method and a simple manufacturing technique, the team designed an aerophilic surface from a commonly used and inexpensive titanium alloy with a long-lasting plastron that kept the surface dry thousands of hours longer than previous experiments. “We used a characterisation method that had been suggested by theorists 20 years ago to prove that our surface is stable, which means that not only have we made a novel type of extremely repellent, extremely durable superhydrophobic surface, but we can also have a pathway of doing it again with a different material,” explains Alexander Tesler, former postdoctoral fellow at SEAS and the Wyss Institute, and lead author of the paper.
PROVING STABILITY To prove the stability of the plastron,
the researchers put the surface through its paces via bending, twisting, blasting with hot and cold water, and abrading it
with sand and steel to block the surface while remaining aerophilic. Te surface managed to survive 208 days submerged in water and hundreds of dunks in a petri dish of blood. It severely reduced the growth of E. coli and barnacles on its surface and stopped the adhesion of mussels altogether. “Te stability, simplicity and scalability of this system make it valuable for real- world applications,” adds Stefan Kolle, a graduate student at SEAS and co-author of the paper. “With the characterisation approach shown here, we demonstrate a simple toolkit that allows you to optimise your superhydrophobic surface to reach stability, which dramatically changes your application space.” In terms of applications, the
superhydrophobic surfaces could be used in biomedicine to reduce infection after surgery or as biodegradable implants such as stents. Tey could also be leveraged for underwater applications to prevent corrosion in pipelines and sensors. And, in the future, they could be used in combination with the super-slick coating known as SLIPS (Slippery Liquid-Infused Porous Surfaces), developed by Aizenberg and her team more than a decade ago, to protect surfaces even further from contamination.
More information can be found in the paper titled, ‘Long-term stability of aerophilic metallic surfaces underwater’ published the Nature journal.
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