Antibacterial stainless steel

A quick glance at your cutlery shows it’s made of stainless steel, as are most surgical instruments but they eventually succumb to wear and tear, and are not resistant to bacteria

Antibacterial stainless steel

Antibacterial surgical equipment could be finding its way into the theatre

But researchers in Bristol have moved a step closer towards making these everyday utensils resistant to bacteria by adding silver or copper into the steel surface.

“Previous attempts to make stainless steel resistant to bacteria have not been successful as these have involved coatings which are too soft and not hard-wearing,” said Hanshan Dong, professor of surface engineering. “Thin anti-bacterial coatings can be easily worn down when interacting with other surfaces, which leads to a low durability of the antibacterial surface.”

They have developed a novel surface alloying technology using Active Screen Plasma (ASP) with a purpose designed composite or hybrid metal screen. The exact mechanism involved is not completely understood, but researchers believe the combined sputtering, back-deposition and diffusion introduces silver or copper into the stainless steel surface, along with nitrogen and carbon.

“We chose silver and copper because biologically active Ag/Cu ions are the most effective antimicrobial agents against bacteria, viruses and other eukaryotic microorganisms,” Dong told Laboratory News. “They can inactivate bacteria by interacting with the thiol groups of bacteria proteins and enzymes.”

Nitrogen and carbon make the stainless steel much harder and durable. Researchers replicated the cleaning process for medical instruments in hospitals, and found that after 120 cycles the antibacterial properties of the stainless steel were still intact and the surface still resistant to wear.

Dong’s team are confident the technique could be scaled up and used in the manufacturing of stainless steel products – they have already used the technique to surface engineer items measuring 2m by 2m in the lab.

“Further research in this area is towards application of this novel technology for medical devices, body implants and food processing equipment made from stainless steel,” said Dong.

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