There may soon be a new weapon in our centuries-old battle against germs: the first durable coating that can quickly kill bacteria and viruses and keep on killing them for months at a time.
Developed by a team of University of Michigan engineers and immunologists, it proved deadly to SARS-CoV-2 (the virus that causes COVID-19), E. coli, MRSA and a variety of other pathogens. It killed 99.9% of microbes even after months of repeated cleaning, abrasion and other punishment on real-world surfaces like keyboards, cell phone screens and chicken-slathered cutting boards.
The coating could be a game changer in traditionally germ-laden public spaces like airports and hospitals, according to Anish Tuteja, a professor of material science and engineering at U-M and co-corresponding author of the paper published in Matter.
“We’ve never had a good way to keep constantly-touched surfaces like airport touch screens clean,” he said. “Disinfectant cleaners can kill germs in only a minute or two but they dissipate quickly and leave surfaces vulnerable to reinfection. We do have long-lasting antibacterial surfaces based on metals like copper and zinc, but they take hours to kill bacteria. This coating offers the best of both worlds.”
The coating, which is clear and can be brushed or sprayed on, gets its durability and germ-killing power by combining tried-and-true ingredients in a new way. It uses antimicrobial molecules derived from tea tree oil and cinnamon oil, both used for centuries as safe and effective germ killers that work in under two minutes. The coating’s durability comes from polyurethane, a tough, varnish-like sealer that’s commonly used on surfaces like floors and furniture.
“The antimicrobials we tested are classified as ‘generally regarded as safe’ by the FDA, and some have even been approved as food additives,” Tuteja said. “Polyurethane is a safe and very commonly used coating. But we did do toxicity testing just to be sure, and we found that our particular combination of ingredients is even safer than many of today’s antimicrobials.”
The results of the study’s durability tests suggest that the coating could keep killing germs for six months or longer before its oil begins to evaporate and reduce its disinfectant power. But even then, Tuteja says it can be recharged by wiping it with fresh oil; the new oil is reabsorbed by the surface, starting the cycle again.
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