A team of corrosion experts from the University of Virginia has advanced a new way of understanding the antiviral properties of copper and its compounds. Their editorial explores the incorporation of copper oxidation products as antiviral agents into face masks, air filters, fabrics and clothing. John R. Scully, Charles Henderson Chaired Professor of Materials Science and Engineering at the University of Virginia, Mike Hutchison (Ph.D., MSE '18) and R. J. Santucci, Jr. (Ph.D., MSE '19), a post-doc in mechanical engineering at the U.S. Naval Academy, seek to inform public dialogue regarding the important role of protective gear in preventing the spread of COVID-19. A number of strategies have been offered to improve face masks, beyond their use as a physical barrier to transmission. These strategies all involve materials science principles, with a few governed by electrochemical corrosion processes. The team pursued “what if†scenarios as they searched for the science behind copper's antiviral properties—whether self-cleaning functions could be built-in to personal protective equipment, whether airborne particles could be inactivated upon contact with the outside layer of a mask, or whether exhaled saliva could be disinfected when landing on the inside layer. “Numerous patents exist that describe the use of various copper compounds as antibacterials and antivirals, but rarely does the supporting literature explain the governing factors—what matters and what doesn't,†Scully said. The team employed chemical stability diagrams to illustrate the thermodynamic principles behind copper release from copper compounds. Their early findings imply that some copper compounds have longer or shorter disinfection times, a function of the dissolved copper concentration in equilibrium with the corrosion product and the pathogen's sensitivity to “free†copper, or the fraction of dissolved copper which is not bound to other chemicals. To maintain effective antimicrobial function within a practical time frame, compounds or compound mixtures that actively dissolve, i.e., that are less stable in water, are preferable in order to supply the free copper ions needed. “It is imperative to investigate and define windows of effective operation, where metallic cations are successful in reducing virus viability to the point where human transmission by aerosols and droplets is reduced by a significant amount,†Santucci said. More research is needed to optimize the chemical dissolution of copper-based compounds for virus inactivation. A balance between speed and durability may be necessary. A highly dispersed, quickly dissolving compound may be effective, but might deplete itself within a short time such that it is “used up quickly†or its effectiveness may be weakened by repeated washing. “To truly understand whether a given copper compound and environment create the circumstances where antiviral properties are operative when needed, we need to track the fate of copper—whether oxidized and retained in the solid oxide, dissolved in a droplet deposited on a mask, or somewhere else,†Hutchison said. Whereas overnight cleaning might permit an inactivation time as long as 12 hours, an aerosol residing on a mask fabric layer for a limited period of time before inhalation might demand a faster inactivation time. A range of temperatures, surface conditions and relative humidity could be investigated to identify the key combinations of conditions where copper alloys and oxidized copper compounds are effective. Cleaning and wash solutions applicable to personal protective equipment might also be studied, the authors said. “These factors serve as design considerations and some products might take these into account. The societal benefits are well worth the investments into further research and understanding,†Scully said. The team published their findings,Understanding the Efficacy of Oxidized Copper Compounds in Suppressing Infectious Aerosol-based Virus Transmission, as an editorial in the April 2021 issue ofCORROSIONJournal. This is the second in a series of editorials exploring the COVID-19 pandemic and the antimicrobial function of copper and silver enabled by corrosion. Scully authored the first editorial,Can Antimicrobial Copper-Based Alloys Help Suppress Infectious Transmission of Viruses Originating from Human Contact with High-Touch Surfaces?, published in June 2020, calling on fellow experts to pursue research and experimentation directed at virus transmission on high touch surfaces that can be mitigated by anti-microbial copper materials. Both editorials indicate that the community has many opportunities to offer solutions based on the extensive materials science that is known and yet to be discovered. TheCenter for Electrochemical Science and Engineeringwithin UVA's Department of Materials Science and Engineering is dedicated to this endeavor. Research conducted at the Center arises from real-world corrosion issues that resist easy solutions. Faculty and students working in the Center pursue fundamental research to identify the crux of the problem and find methods to remedy it, with support from major government research laboratories. Collaborations with private sector partners enable testing and evaluation of proposed solutions against operational needs and requirements.