Ingenious: Bacteria Zapper

The Tribo-sanitzer’s design was inspired by lightning. (Image by Fred Zwicky)

During thunderstorms, electric charges build up within and between clouds, as well as between clouds and the ground. When the difference in charges between the clouds and the ground grows big enough, pent-up electricity “leaps” across the gap between them in the form of lightning.

Inspired by this natural phenomenon, U. of I. researchers have developed a food sanitizer that takes advantage of “electrical leaps” across air gaps to boost its power.

“We were looking to build a device that converts mechanical energy into electricity,” says Yi-Cheng Wang, assistant professor of food safety and engineering. He and his team wanted to create a portable food sanitizer that could generate mechanical energy through physical motion, as well as through the ambient environment, such as wind or moving water.

Their invention, the Tribo-sanitizer, uses ultraviolet-C (UVC) light to inactivate bacteria. That light is generated by cranking a handle on the device that rubs two surfaces together, building up static electricity. When enough electricity accumulates, it leaps across an air gap between the device and its UVC lamp—much the way lightning does, but on a smaller scale. Most significantly, the Tribo-sanitizer requires no external power source, giving it immense value for disaster or conflict zones where electricity may be undependable or nonexistent.

The Tribo-sanitizer’s air gap gives it an extra spark to create stronger irradiation, boosting its ability to inactivate bacteria. Researchers focused on the two most common foodborne pathogens—Escherichia coli O157:H7 (E. coli) and Listeria monocytogenes (L. monocytogenes)—to see how well the sanitizer killed bacteria on plastic wrap, apple peels and romaine lettuce.

Together, Yi-Cheng Wang (center), Zhenhui Jin (left), and Longwen Li developed a Tribo-sanitizer, which is a lamp that has food-safety applications.

When the researchers exposed plastic wrap to UVC light, the device reduced E. coli by 99.999 percent. But it’s trickier with lettuce and apple peels because bacteria can more easily hide in their uneven surfaces, Wang says.

Nevertheless, in first-round testing, the Tribo-sanitizer inactivated 99.98 percent of E. coli and 99.9 percent of L. monocytogenes bacteria on apple peels, as well as 99.8 percent of E. coli and 98 percent of L. monocytogenes on romaine lettuce.

Wang says that if they redesign the Tribo-sanitizer to shine UVC light at different angles, it might be able to eliminate an even greater percentage of bacteria, but it also needs to decrease the time it takes to do so—in initial trials, it took 90 minutes.

“Our ongoing research shows we can dramatically reduce that time,” Wang says. Indeed, the researchers have already sped up sanitization to less than an hour, but their goal is 10 minutes or less.

The Tribo-sanitizer represents just one of many food-safety innovations Wang’s team is working on. For instance, it also is developing smart packaging for milk products, in which a color indicator on the carton could signify when the product is spoiled.

“We’re about making devices—and making a difference,” Wang says.