Durable surface coating eliminates SARS-CoV-2 and other germs in minutes
Engineers and immunologists from the University of Michigan (U-M) have developed a material coating that maintains its antibacterial power for months, capable of killing almost 99.9% of bacteria and viruses even after repeated cleaning and abrasion. The coating combines two types of oil and polyurethane, and can be used on frequently-touched surfaces such as keyboards and cell phone screens.
U-M Professor of Material Science and Engineering, Anish Tuteja, said the durable coating could be a game changer in traditionally germ-laden public spaces like airports and hospitals.
“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 antimicrobial molecules in the clear coating are derived from tea tree oil and cinnamon oil, both used for centuries as safe and effective germ killers that work in under two minutes. Polyurethane is added to give the coating durability – polyurethane is a tough, varnish-like sealer commonly used on surfaces like floors and furniture.
The U-M team combined the oil and polyurethane via cross-linking, a process that uses heating to link materials together at the molecular level. The smaller oil molecules readily combined with the cross-linking polymer molecules, forming a stable matrix.
But to kill germs, the oil molecules need to penetrate their cell walls, which they can’t do if they’re tightly tethered into the matrix.
The team eventually found a middle ground by partially cross-linking the materials, but just enough to keep some of the oil molecules free to do their work, while the others remained bound tightly to the polyurethane.
“The free oil tends to stay with the oil that’s cross-linked into the matrix, helping the coating last longer,” Tuteja added.
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. However, the coating can be recharged by wiping it with fresh oil; the new oil is reabsorbed by the surface, starting the cycle again.
Toxicity testing also revealed the coating’s ingredients were safe to use compared to many microbials currently in the market.
Tuteja has estimated that the technology would be commercially available in a year’s time; it has been licensed to Hygratek, a spinoff company that Tuteja founded with assistance from U-M Innovation Partnerships.
