We cook in stainless steel skillets, ride steel subway cars over steel rails to our offices in steel-framed building. Steel screws hold together broken bones, steel braces straighten crooked teeth and steel scalpels remove tumors. Most of the goods we consume are delivered by ships and trucks built of steel.

While various grades of steel that have been developed over the past 50 years, steel surfaces have remained largely unchanged. The steel of today is still vulnerable to the corrosive effects of water and salt and abrasive materials. Steel surgical tools still carry microorganisms that cause deadly infections. 

Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have demonstrated a way to make steel stronger, safer and more durable. Their new surface coating, made from rough nano-porous tungsten oxide, is supposedly  the most durable anti-fouling and anti-corrosive material to date. They claim it is capable of repelling any kind of liquid even after sustaining severe abuse. 

The new material joins the portfolio of other non-stick, anti-fouling materials developed in the lab of Joanna Aizenberg, the Amy Smith Berylson Professor of Materials Science and core faculty member of the Wyss Institute for Biologically Inspired Engineering at Harvard University. Aizenberg's team developed “Slippery Liquid-Infused Porous Surfaces” in 2011 and since then they have  demonstrated a broad range of applications for the super-slick coating, known as “SLIPS”. The new SLIPS-enhanced steel is described in the scientific peer-reviewed publication Nature Communications. 

"Our slippery steel is several orders of magnitude more durable than any anti-fouling material that has been developed before," said Aizenberg. "So far, these two concepts of mechanical durability and anti-fouling were at odds with each other. We need surfaces to be textured and porous to impart fouling resistance but rough nano-structured coatings are intrinsically weaker than their bulk analogs. 

This research shows that careful surface engineering allows the design of a material capable of performing multiple functions, without performance degradation. 

The material could have far-ranging applications and avenues for commercialization, including non-fouling medical tools and devices, such as implants and scalpels, nozzles for 3D printing and, potentially, larger-scale applications for buildings and marine vessels.