1 STEEL A CRITICAL INDUSTRY For more than a century steel has been an integral part of daily life People prepare meals in stainless steel cookware and ride steel train cars on steel rails to work in steel-framed skyscrapers Orthodontists straighten teeth with steel braces while surgeons operate with steel scalpels As the uses for steel have expanded over the past 50 years its weaknesses have mostly remained the same Like other metals steel is vulnerable to the corrosive effects of water and salt and the abrasive effects of materials such as sand But in 2015 researchers at Harvard University announced they had found a way to improve this crucial metal The researchers created a new surface coating for steel They announced the coating could repel any type of liquid making the steel stronger and more durable This research is an example of hard core classic material science said Harvard’s Joanna Aizenberg We took a material that changed the world and asked how can we make it better 1 From cars on the streets to enormous skyscrapers modern cities are built largely from steel 5
Adding new coatings can help change the properties of steel The biggest challenge for researchers in developing the surface coating was figuring out a way to protect the steel without affecting its performance The researchers used an electrochemical technique to place an extremely thin film of small and rough patches of tungsten oxide known as islands directly onto a steel surface Tungsten oxide is a chemical compound that contains oxygen and the element tungsten which is very hard If one part of the tungsten film is destroyed or damaged the remaining tungsten oxide islands still protect the steel because the islands are not connected 6
The Harvard researchers tested the surface coating by scratching it with a variety of tools including stainless steel tweezers and instruments with diamond tips They hit it with thousands of hard heavy beads They also tested the surface coating’s ability to repel a variety of liquids including water oil fluids containing bacteria and blood and highly corrosive liquids The coating repelled all of the liquids and resisted bacterial contamination In addition the researchers discovered during their testing that steel coated with tungsten oxide was stronger than steel without the coating The Harvard surface coating could be used to improve many steel products Using it to coat steel medical tools such as implants and scalpels is one of the most promising future applications The surface coating may one day be used to improve 3-D printing Layer by layer 3-D printers build three-dimensional objects Like all steel objects the steel components of 3-D printers can become corroded When printing with thick and sticky materials the steel nozzles often clog Covering the nozzles with the new coating could help them deliver the material smoothly and evenly With less clogging the lifespan of the printer’s steel nozzles would improve The US Navy may also benefit from the steel coating Every year the navy spends millions of dollars cleaning the hulls of its ships Barnacles and algae cling to steel hulls These organisms create drag in the water which decreases the ship’s performance and increases the amount of fuel it uses Current antifouling paints contain ingredients that are harmful to the environment An improved steel coating could be a cleaner cheaper alternative 7
