Dr. Morfill and his colleagues have tested their devices on hands and feet. “It works on athlete’s foot,” he said. “And the nice thing is, you don’t have to take your socks off. They are disinfected, too.” (The cleaning takes a bit longer when socks are added to the job, he said  about 25 seconds. “And it doesn’t yet work through shoes,” he added.)

Image A prototype hand sanitizer, left, designed by Gregor Morfill. Credit... Phil Wilson

Plasmas engineered to zap microorganisms aren’t new. During the last decade, they have come into use to sterilize some medical instruments. But using them on human tissue is another matter, said Mark Kushner, director of the Michigan Institute for Plasma Science and Engineering and a professor at the University of Michigan in Ann Arbor. “Many thousands of volts drive the generation of plasma,” he said, “and normally one doesn’t want to touch thousands of volts.” But the design of the new hand sanitizers, he said, protects people from doing so. Reassured by that design, about five years ago he put his naked thumb into a jet of microbe-destroying plasma at the lab of another plasma researcher.

“It was just one of those leaps of faith,” he said. (His thumb survived just fine.)

Research in the field of plasma medicine has grown quickly in the last decade, with at least 50 groups worldwide working on medical uses, Professor Kushner estimated.

He said that there were many documented cases of plasmas being applied for sanitizing skin or other body parts, and “for speeding the rate of blood clotting in wound healing.”

“Plasmas turn out to have beneficial effects,” he said.

Dr. Morfill, who has a plasma research laboratory inside the international space station, took an unusual route to studying medical uses of plasmas. He was researching the natural plasmas of space, including the charged dust in Saturn’s rings, and decided to develop plasmas for health on earth.