A hand-held torch-like device zaps dangerous germs, offering a boon for workers battling infection risks in wars and disaster zones, say scientists.
The "plasma flashlight" delivers a charged, or ionised, jet of gas to zap germs, a team of researchers in China, Australia and Hong Kong said in a specialised journal.
Hot plasma sterilisers are already used to disinfect surgical instruments, but they are expensive, refrigerator-sized devices that operate at high temperatures.
Sterilisers that operate at cooler temperatures require external power such as a wall electrical supply or a generator, as well as a gas feed, in order to keep working.
But the new device is driven by a 12-volt battery and does not need a gas feed, according to the study, which appears in a British publication, the Journal of Physics D: Applied Physics.
Its inventors said they tested it on a thick mat of Enterococcus faecalis, a germ that is resistant to heat treatment and antibiotics, sometimes causing infections in dental surgery.
"In this study, we chose an extreme example to demonstrate that the plasma flashlight can be very effective even at room temperature," said Ken Ostrikov, from the Plasma Nanoscience Centre in Australia.
"For individual bacteria, the inactivation time could be just tens of seconds."
The goal is a simple gadget that can kill surface bacteria in settings where clean water and medications are scarce.
With technical modifications and economies of scale, the device could be made for less than $100, Ostrikov said.
The plasma in the experiments was measured at between 20 and 23 degrees Celsius (68-73 degrees Fahrenheit), which means it is close to room temperature and does not burn the skin.
Why the jet has an anti-bacterial effect is unclear, Britain's Institute of Physics, which publishes the journal, said in a press release.
It could be that there is a reaction between the plasma and the surrounding area which creates types of oxygen molecules to which E. faecalis germs are especially vulnerable.
The invention is one of several prototypes aimed at placing easy-to-use cold-plasma sterilisers in the hands of medical workers and even consumers.
Last year, the Max Planck Institute for Extraterrestrial Physics in Germany said a similar flashlight-shaped device, tested in a laboratory, destroyed samples of a notorious food bug -- the O104:H4 strain of Escherichia coli.