A group of Chinese and Australian scientists
have developed a handheld, battery-powered plasma-producing device that can rid
skin of bacteria in an instant.
The device could be used in ambulance emergency
calls, natural disaster sites, military combat operations, and many other
instances where treatment is required in remote locations.
The plasma flashlight, presented in Journal of Physics D: Applied Physics, is driven by a 12-V battery and
doesn’t require any external generator or wall power; it also doesn’t require
any external gas feed or handling system.
In the experiment, the plasma flashlight
effectively inactivated a thick biofilm of one of the most antibiotic- and
heat-resistant bacteria, Enterococcus faecalis—a bacterium which often infects the
root canals during dental treatments.
The biofilms were created by incubating the
bacteria for seven days. The biofilms were around 25 um thick and consisted of
17 different layers of bacteria. Each one was treated for five minutes with the
plasma flashlight and then analysed to see how much of the bacteria survived.
Results showed that the plasma not only
inactivated the top layer of cells, but penetrated deep into the very bottom of
the layers to kill the bacteria.
Co-author of the study, Professor Kostya (Ken)
Ostrikov, from the Plasma Nanoscience Centre Australia, CSIRO Materials Science
and Engineering, 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
“In this study we chose an extreme example to
demonstrate that the plasma flashlight can be very effective even at room
temperature. For individual bacteria, the inactivation time could be just tens
Plasma—the fourth state of matter in addition
to solids, liquids, and gases—has previously shown its worth in the medical
industry by effectively killing bacteria and viruses on the surface of the skin and in water.
Although the exact mechanism behind the antibacterial
effect of plasma is largely unknown, 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.
The researchers ran an analysis to see what
species were present in the plasma and found that highly-reactive nitrogen- and
oxygen-related species dominated the results. Ultraviolet radiation has also
been theorized as a reason behind plasma’s success; however, this was shown to
be low in the jet created by the plasma flashlight, adding to the safety aspect
of the device.
The temperature of the plume of plasma in the
experiments was between 20 C to 23 C, which is very close to room
temperature and therefore prevents any damage to the skin. The device itself is
fitted with resistors to stop it heating up and making it safe to touch.
“The device can be easily made and costs less
than 100 U.S. dollars to produce. Of course, some miniaturization and
engineering design may be needed to make it more appealing and ready for
commercialization,” Ostrikov continued.
The device was created by an international team
of researchers from Huazhong University of Science and Technology, CSIRO
Materials Science and Engineering, The University of Sydney, and the City
University of Hong Kong.