A team at the University of Hong Kong have developed the first anti-pathogen stainless steel that kills infectious viruses, including COVID-19, on its surface.
The high copper content of the new metal means that it "exhibits significant antiviral properties," according to the researchers.
The new metal can reduce 99.75% of viable COVID-19 on its surface within three hours, and 99.99% within six hours, with no trace of the virus present after 24 hours, the scientists found.
The metal also kills the H1N1 influenza A virus — the virus strain behind swine flu — and E. coli bacteria.
The team launched the project as a response to evidence that large virus-laden droplets and direct or indirect contact with touching surfaces contaminated by respiratory secretions can be critical paths for COVID-19 to be transmitted from person to person, posing a high risk of virus transmission via surface touching in public areas.
Stainless steel is used extensively in public areas such as hospitals, schools, and public transport for surfaces which are frequently touched, such as lift buttons, doorknobs, and handrails, because of its excellent mechanical properties, corrosion resistance, and workability.
However, the researchers found that traditional stainless steel does not have antibacterial or antiviral properties. On the contrary, the COVID-19 virus shows "strong stability" on the surface of conventional stainless steel, with infectious virus detected even after two days, according to the University of Hong Kong.
Researchers found that infectious pathogenic viruses and bacterias could still be detected on the surface of traditional stainless steel after typical cleaning procedures such as wiping with water and liquid soap.
The scientists discovered that pure copper exhibits an excellent antiviral efficiency towards COVID-19 and other viruses. But, replacing stainless steel products with pure copper in public areas is impractical due to its high cost, low strength, and lower corrosion-resistant capability.
However, an alloy of stainless steel with 20% weight copper proved to be extremely effective.
Stainless steel is a corrosion-resistant mix of iron, chromium and, in some cases, nickel and other metals. It is also classified as a “green material" as it is infinitely recyclable.
The scientists also tested pure silver and an alloy of stainless steel with silver, as the metal is renowned for its antibacterial properties. However, silver and stainless steel containing silver did not prove to be effective in killing COVID-19.
The team has been liaising with industrial partners to create prototypes of public stainless steel products such as lift buttons, doorknobs, and handrails for further tests and trials, according to the University of Hong Kong.
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