A handheld plasma blaster that can beam away 17 layers of bacteria could be used in medical emergencies to clean skin and wounds, said a physics boffin presenting the device in the Journal of Physics D: Applied Physics today.

The plasma gun or "flashlight" requires just a 5V battery to produce enough cold plasma to kill even heat-resistant and antibiotic-resistant bacteria such as Enterococcus faecalis (a nasty gastrointestinal bug). Because the plasma's heat ranges from 20 to 23°C (68 to 73°F), it doesn't damage the skin. The bacteria-busting raygun - the work of scientists from China and Australia - costs just $100 to manufacture.

In the experiment, five minutes of exposure to the plasma ray burned through 25 micrometres of 17 different layers of bacteria. The plasma not only inactivated the top layer of cells, but penetrated deep into the very bottom layers to kill the bacteria.

Co-author of the study, Professor Kostya Ostrikov, from the Plasma Nanoscience Centre Australia said:

The bacteria form thick biofilms, which makes them enormously resistant against inactivation which is extremely difficult to implement. High temperatures are commonly used but they would obviously burn our skin. In this study we chose an extreme example to demonstrate that the plasma flashlight can be very effective even at room temperature.

The action of plasma on bacteria is not fully understood, but it is thought that reactions between the plasma and the air surrounding it create a cocktail of reactive species that are similar to the ones found in our own immune system.

Ostrikov said that the bacteria-blasting raygun might need to be made a bit smaller and redesigned to make it more useful in the field, but it would have obvious benefits for killing bacteria in medical emergencies, for operations in far-flung places or in warzones and natural disaster sites.

The device was created by an international team of researchers from China's Huazhong University of Science and Technology, Australia's CSIRO Materials Science and Engineering, the University of Sydney and the City University of Hong Kong. ®

Inactivation of a 25.5 µm Enterococcus faecalis biofilm by a room-temperature, battery-operated, handheld air plasma jet was published April 5 in The Journal of Physics D: Applied Physics