This antiviral stainless steel can inactivate 99.75 per cent of SARS-CoV-2 virus within three hours and is expected to replace frequently touched stainless steel products in public areas to reduce the risk of accidental infection.
A team of researchers led by Professor Mingxin Huang at the Department of Mechanical Engineering of the Faculty of Engineering of the University of Hong Kong (HKU) has collaborated with Professor Leo Lit Man Poon’s research team at the Centre for Immunity and Infection of the LKS Faculty of Medicine of HKU to develop the first anti-COVID-19 stainless steel that can kill not only SARS-CoV-2 on its surface, but also inactivate the H1N1 virus and E.coli.
While the spread of pathogenic bacteria and viruses in public areas has long been a public health issue, its importance has been highlighted during the current COVID-19 pandemic. To minimise the risk of infections, health authorities continuously warn the public of the most critical routes of human-to-human transmissions of pathogens such as large virus-laden droplets and direct or indirect contact with surfaces that have been contaminated by respiratory secretions.
Amongst the many surfaces that pathogens can contaminate, stainless steel objects have become a matter of concern as conventional stainless steel possesses no inherent antimicrobial properties despite it being one of the most widely and frequently touched materials in public areas and hygiene facilities. In fact, SARS-CoV-2 has been found to display strong stability on standard stainless-steel surfaces with viable viruses detected even after three days.
To overcome the limitations of conventional stainless steel, scientists have been exploring a variety of alternatives. Copper and silver have become the two most popular inorganic antimicrobial elements because they pose low toxicity to animal cells and are well-known to inactivate a broad spectrum of bacteria and viruses. However, replacing stainless steel products with pure copper in public areas is not feasible due to its high cost, low strength, and poor resistance to corrosion. Attempts to introduce antimicrobial properties into standard stainless steel by surface coating and ion implantation have also been largely unsuccessful as the thickness of coatings is limited and damage on coatings can severely affect the antimicrobial properties of the stainless steel.
“In this latest breakthrough, the inactivation of pathogen microbes (especially the SARS-CoV-2) on [stainless steel] surface is achieved by tuning the chemical composition and microstructure of regular [stainless steel]. The breakthrough also found interesting points about [silver] and [copper] as the allying elements to prepare anti-pathogen stainless steel. Pathogen viruses like H1N1 and SARS-CoV-2 exhibit good stability on the surface of pure [silver] and [copper]-contained [stainless steel] of low [copper] content (e.g., ≤ 5wt per cent) but are rapidly inactivated on the surface of pure [copper] and [copper]-contained [stainless steel] of high copper content (e.g., ≥ 10 wt per cent),” explained Professor Mingxin Huang.
The researchers have also filed a patent for their research findings and are liaising with industrial partners to produce prototypes of public stainless-steel products like doorknobs, handrails, and lift buttons for additional tests and trials. As an initial demonstration, elevator “floor buttons” have been successfully created using stainless steel of high copper content (20wt per cent).
“Massive [copper]-rich precipitates are permanently present in the [stainless steel] matrix. Thus, this anti-COVID-19 [stainless steel] can chronically inactivate pathogen microbes even though its surface is continuously damaged,” said Litao Liu, the first author of the study and a PhD student supervised by Professor Huang.
“The present anti-COVID-19 [stainless steel] can be mass-produced using existing mature technologies. They can replace some of the frequently touched [stainless steel] products in public areas to reduce the risk of accidental infection and fight the COVID-19 pandemic,” added Professor Huang optimistically. [APBN]
Source: Liu et al. (2021). Anti-pathogen stainless steel combating COVID-19. Chemical Engineering Journal, 133783.