Robust manufacturable antimicrobial surfaces enabled by superhard plasmon-enhanced photocatalytic materials

Untreatable infections are one of the biggest modern-day dangers to society, which the current SARS-CoV-2 pandemic has highlighted.
The development of antibiotics has been one of the major medical successes of the last 100 years. However, the capacity of pathogens to evolve and acquire resistance to new antibiotics makes their effectiveness necessarily precarious. Meanwhile, studies on the spread of drug-resistant pathogens such as MRSA, respiratory syncytial virus, norovirus and CoVID-19 suggest that surfaces are a major point of transmission with CoVID-19 remaining infectious on plastic and stainless steel surfaces for up to 6 days.

Surfaces with an antimicrobial function that avoid or minimise the use of antibiotics whilst maintaining good efficacy after prolonged use are critically needed in hospitals, living spaces, and on biomedical implants, to reduce healthcare-acquired and public space-acquired infections, reduce healthcare costs, and promote healthier lives.

However standard antimicrobial surfaces are not sufficiently robust to withstand the wear and tear encountered in a biomedical implant environment and in public spaces. Sheffield Hallam University and Imperial College London aim to develop superhard nanostructured surfaces with plasmonically-enhanced photocatalysis which will enable microbial inactivation in both illuminated and dark environments whilst retaining their robustness and effectiveness in the long term and which, as a result, will lead to orthopaedic implants and anti-microbial surfaces that are more functional than those produced with the current technologies.

The innovative antimicrobial surfaces will be robust due to the use of superhard nanoscale multilayer coatings with wear rates up to 1000 times better than conventional metal alloys.

At the same time the robust antimicrobial surfaces will have a dual functionality -

(1) active, they will be able to kill microorganisms by photocatalysing the production of highly reactive singlet oxygen - one of the most effective killers of pathogens. The photocatalysis will be activated by visible light from the environment. The light will interact with a carefully prepared coating material to induce plasmonic resonance on its surface and generate high energy electrons which are needed to boost the photocatalytic reaction.

(2) passive, mimicking naturally occurring surfaces such as the cicada wing, the surfaces will contain a number of appropriately dimensioned nanopillars which will stretch and mechanically rupture the walls of microorganisms. This functionality is potent in wet, dry, illuminated or dark environments.

We have developed a new plasmonic nanoscale multilayer material which activates photocatalysis under standard (visible) light and have developed technology based on high power impulse magnetron sputtering which can produce these materials at room temperature on polymers.

We will study the plasma processes needed to produce the materials and nanopillars, their response to light activation and the effect they have on microbials. This will help us to develop a cost-effective manufacturing technology to enable large scale production by upgrading systems which are already available in industry for coating deposition and nanopatterning with a digitalised system control which is driven by artificial intelligence algorithms. Together with the local NHS hospital trust we will trial the material on metal plates for door furniture and polymer sheets to cover surfaces in hospitals (beds, seating areas).

When successful we will have some of the most exciting new developments in robust antimicrobial materials and their manufacturing and take a step closer to a world with fully effective infection control.