Method enables development of bacteria-resistant surfaces

Materials scientists at Birmingham University have devised a way of making stainless steel surfaces resistant to bacteria in a project funded by the EPSRC.

By introducing silver or copper into the steel surface (rather than coating it onto the surface), the researchers claim to have developed a technique that not only kills bacteria but that is very hard and resistant to wear and tear during cleaning.

According to a statement, bacteria-resistant surfaces could be used in hospitals to prevent the spread of superbug infections on stainless steels surfaces, as well as in medical equipment such as instruments and implants. They would also be of use to the food industry and in domestic kitchens.

The team is said to have developed a novel surface alloying technology using active screen plasma (ASP) with a purpose-designed composite or hybrid metal screen.

The combination of sputtering, back deposition and diffusion allows the introduction of silver into a stainless steel surface, along with nitrogen and carbon. The silver acts as the bacteria-killing agent and the nitrogen and carbon make the stainless steel much harder and more durable.

The researchers replicated the cleaning process for medical instruments in hospitals. After cleaning the treated instruments 120 times, they found that the antibacterial properties of the stainless steel were still intact and the surface still resistant to wear.

Hanshan Dong, professor of surface engineering at the university and lead investigator, said: ‘Previous attempts to make stainless steel resistant to bacteria have not been successful as these have involved coatings that are too soft and not hard-wearing.

‘Thin antibacterial coatings can be easily worn down when interacting with other surfaces, which leads to a low durability of the antibacterial surface. Our technique means that we avoid coating the surface; instead, we modify the top layers of the surface.’

Prof Dong’s team is said to be confident that this technique could be used in the manufacturing of stainless steel products as it is already able to surface engineer items of up to 2 x 2m in the laboratory.