Coating Makes Steel Tougher, Keeps Microbes From Sticking

More and more objects are getting superhydrophobic coatings that make liquids bounce right off. Surfaces with complex nanoscopic structures that prevent wetting will soon be deployed on wind turbine blades and aircraft wings to prevent ice from sticking, and even concrete is being doped with superhydrophobic compounds to help it last decades longer.

Much still needs to be done, though, to strengthen these coatings because any damage can remove the ability to repel liquids. Such an advance is hugely important since there are potentially life-saving healthcare applications if this hurdle could be overcome with a stable, nontoxic coating for steel. Just imagine if implants, scalpels and other tools used on patients had a surface impossible for infection-causing microbes to cling to.

Now, Joanna Aizenberg and her colleagues at Harvard’s Wyss Institute for Biologically Inspired Engineering have demonstrated a possible solution. They’ve been able to coat stainless steel with nanoporous tungsten oxide, which repels all liquids. What’s more, the surface is extremely tough, maintaining superhydrophobicity even after being scratched with sharp steel objects and diamond.

“So far, these two concepts - mechanical durability and anti-fouling - were at odds with each other,” Aizenberg said in a statement. “This research shows that careful surface engineering allows the design of a material capable of performing multiple, even conflicting, functions, without performance degradation. Our slippery steel is orders of magnitude more durable than any anti-fouling material that has been developed before.“



Her team was able to deposit the tungsten oxide directly onto the steel using a standard electrochemical deposition process. It formed separate islands on the steel’s surface. These islands mean that neighboring islands can be physically damaged without hindering the overall repellency of the coating. The researchers also unexpectedly found that the material actually strengthened the steel it was deposited on.

They found the treated surgical tools and pieces of naval construction steel were able to completely repel liquids even after battering them with sand, ultraviolet light and extreme temperatures. Their results were published recently in the journal Nature Communications.

“Because we show that this material successfully repels bacteria and blood, small medical implants, tools and surgical instruments like scalpels and needles that require both significant mechanical strength and anti-fouling property are high value-added products we are exploring for application and commercialization,” said study coauthor Philseok Kim.



All gifs created from videos courtesy of Tesler et al./Nature Communications.