By Jason Palmer
Science and technology reporter, BBC News
The prototype device can kill off bacteria, viruses, and fungi in just seconds
Researchers have demonstrated a prototype device that can rid hands, feet, or even underarms of bacteria, including the hospital superbug MRSA.
The device works by creating something called a plasma, which produces a cocktail of chemicals in air that kill bacteria but are harmless to skin.
A related approach could see the use of plasmas to speed the healing of wounds.
Writing in the New Journal of Physics, the authors say plasmas could help solve gum disease or even body odour.
Plasmas are known as the fourth state of matter, after solid, liquid, and gas. They are a soup of atoms that have had their electrons stripped off by, for example, a high voltage.
Plasmas are common elsewhere in the cosmos, where high-energy processes produce them, and they are even posited as a potential source of fusion energy. Their properties have recently been harvested for use in plasma televisions.
But the new research focuses on so-called cold atmospheric plasmas.
Rather than turning a whole group of atoms into plasma, a more delicate approach strips the electrons off just a few, sending them flying.
Collisions with nearby, unchanged atoms slows down the electrons and charged atoms or ions they leave behind.
It has been known for some time that the resulting plasma is harmful to bacteria, viruses, and fungi - the approach is already used to disinfect surgical tools.
"It's actually similar to what our own immune system does," said Gregor Morfill, of the Max Planck Institute for Extraterrestrial Physics, who led the research.
"The plasma produces a series of over 200 chemical reactions that involve the oxygen and nitrogen in air plus water vapour - there is a whole concoction of chemical species that can be lethal to bacteria," he told BBC News.
Professor Morfill and his colleagues have worked out the precise details of the plasma production that effectively kills off such bugs without doing harm to skin, and demonstrated a number of prototype devices that do the job efficiently.
"To produce plasmas efficiently at low cost so you can really mass produce these things for hospitals, that's the big breakthrough of the last year," Professor Morfill said.
The team says that an exposure to the plasma of only about 12 seconds reduces the incidence of bacteria, viruses, and fungi on hands by a factor of a million - a number that stands in sharp contrast to the several minutes hospital staff can take to wash using traditional soap and water.
Professor Morfill said that the approach can be used to kill the bacteria that lead to everything from gum disease to body odour.
Hospital staff can spend hours cleaning hands by traditional means
"The idea is scalable to any size, it can be produced in any shape; it's very flexible," he said.
"You can even make it battery-operated so you can use small devices - I have one in my hand right now."
A similar approach, using the element argon instead of plain air, has been demonstrated for application directly to wounds, and initial indications are that it speeds healing.
Michael Kong, a bioelectrics engineering researcher at Loughborough University, said it remains unclear whether those effects are through the chemical cocktail that the plasma produces, or simply from the effect of reducing the number of bacteria crowding a wound.
"Either way, it is still a very important breakthrough," Professor Kong told BBC News.
"The ideas are not new - but only recently, collectively, has this community of researchers come up with plasma sources that achieve disinfection but also have minimal impact on skin cells."
Professor Morfill said that more testing of the devices is necessary before they end up in widespread use, but he said that there is already significant interest from industry.