Methicillin-resistant Straphylococcus aureus (MRSA) is antibiotic-resistant and spread by hand-to-surface contact with metal surfaces, often leading to hospital patient infection. Copper (Cu) and silver (Ag) possess anti-microbial capability due to the release of either oxidized Cu or Ag ions via electrochemical processes in response to complex surface environments formed during deliquescence of perspiration salt deposits in humid air. Cu surfaces are not presently favored in hospitals due to rapid tarnishing caused by hand perspiration. A Cu alloy that has antimicrobial capability and color stability is highly desirable for high touch surfaces where stainless steel is now used but has no antimicrobial capabilities. The ideal alloy surface releases Cu ions at rates mediated via alloying. However, there is a gap in scientific understanding of electrochemical Cu oxidation, passivity and release from copper alloys. Few past studies focus on the role of major and minor alloying elements on Cu release from alloys. Prior research on commercial alloys confirms the complex effects of alloying elements; alloying elements may either suppress or enhance release of Cu ions by mechanisms which are presently unknown. The objective is to elucidate the Cu release characteristics and mechanisms in selected Cu alloys as mediated by systematic variation of alloying elements. The effects of alloying on copper release, passivity and color stability will be investigated using binary and ternary Cu alloys synthesized with systematic additions of selected alloying elements. Corrosion/release behavior will be connected with atomic scale measurements of the fate of alloying elements during oxidation. Both global and high resolution surface and atomic scale experimental studies using a variety of techniques will track the fate of Cu in the metal, the oxide as well as the flux released. Intellectual merits include new solid/liquid interfacial understandings of the role of major and minor alloying elements on these processes. A foundation for functional alloy design that improves trial and error approaches will emerge.
NON-TECHNICAL SUMMARY: This project concerns developing the materials science which enables better design of copper and silver based alloys that have anti-microbial functionality as a way to ultimately control hospital acquired infections. For instance, Methicillin-resistant Straphylococcus aureus (MRSA) is antibiotic-resistant and spread by hand-to-surface contact, often leading to infection. Copper (Cu) and silver (Ag) metallic alloys possess anti-microbial function due to the release of metal ions in response to complex chemical environments such as human sweat. Cu is not favored in hospitals due to rapid tarnishing caused by hand perspiration. Stainless steels resist tarnishing but do not possess any antimicrobial capability. This project seeks to identify and understand factors controlling alloy properties that enable both antimicrobial function and color stability. These properties are highly desirable for high touch surfaces. This project will conduct research to define the Cu release characteristics and mechanisms in selected Cu alloys as mediated by selected alloying elements. Intellectual merits include new understandings of the role of alloying elements on copper alloy oxidation/ion release in human perspiration. This will enable intelligent design of alloy compositions for ideal anti-microbial function and minimal tarnishing. Broader implications include development of the insight necessary to enable use of multi-functional copper alloys in anti-microbial applications to reduce the spread of disease-causing bacteria. This can positively affect world health, and also contribute to understanding of metal release in other applications. Significant human resource development will occur in the fields of materials science and engineering as well as corrosion science - crucial gaps in STEM training and a national need identified by the US National Academy. Graduate students in the materials science area will be educated and fully integrated with all research tasks. Undergraduate as well as high school students will also participate. Collaboration is underway with the Copper Development Association of America and various copper alloy producers.
