Pore performance: RMIT/CSIRO team develop new copper type with remarkable antibacterial properties

A team of researchers has boosted the effectiveness of copper against bacteria, acting 120 times faster in killing golden staph, which they believe could lead to a diverse set of product applications.

The team from RMIT University and CSIRO published their work, titled ‘Robust bulk micro-nano hierarchical copper structures possessing exceptional bactericidal efficacy,in the journal Biomaterials. 

A statement from the university said that a “special copper mould casting process” was used to form an alloy of copper and manganese — “arranging copper and manganese atoms into specific formations” — with manganese atoms then removed using “dealloying” and leaving microscale and nanoscale cavities. 

The process was cheap and scalable, according to RMIT, and patents for it are pending in Australia, the US and China.

Lead author, Dr Jackson Leigh Smith, said the porousness was key effectiveness in rapidly killing bacteria. The copper was made of “comb-like microscale cavities” said Smith, and within each tooth of the comb structure were much smaller nanoscale cavities creating a massive surface area.

Picture: The copper magnified 500,000 times under a scanning electron microscope shows its tiny nano-scale pores. (Supplied)

“The pattern also makes the surface super hydrophilic, or water-loving, so that water lies on it as a flat film rather than as droplets,” said Smith.  

“The hydrophilic effect means bacterial cells struggle to hold their form as they are stretched by the surface nanostructure, while the porous pattern allows copper ions to release faster.

“These combined effects not only cause structural degradation of bacterial cells, making them more vulnerable to the poisonous copper ions, but also facilitates uptake of copper ions into the bacterial cells… It’s that combination of effects that results in greatly accelerated elimination of bacteria.”   

RMIT’s Distinguished Professor Ma Qian said that regular copper killed 97 per cent of golden staph within four hours, though the team’s specially-designed copper surface destroyed over 99.99 per cent of cells in just two minutes, and without the use of any drugs.  

“So not only is it more effective, it’s 120 times faster.”  

The team sees potential applications ranging from antimicrobial doorhandles and other touch surfaces to antimicrobial filters in respirators or air ventilation systems, as well as face masks.  

Next steps include investigating the copper’s effectiveness against the virus behind Covid-19, SARS-COV-2, including assessing 3D-printed samples.

The antibacterial qualities of regular copper have previously seen it used by Australian companies for anti-Covid purposes in facemasks and 3D printed door coatings.

Main picture: A copper door handle (via www.bauers.com.au)

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