Handheld plasma flashlight wipes out bacteria on the skin

An international team of researchers from Huazhong University of Science and Technology (Wuhan, China), CSIRO Materials Science and Engineering (Clayton, South Australia), the University of Sydney in Australia, and the City University of Hong Kong have developed a handheld, 12 V battery-powered, plasma-producing flashlight that can rid skin of bacteria instantly. The device could be used in ambulance emergency calls, natural disaster sites, military combat operations, and other instances in remote locations that require treatment.

In the experiment, the plasma flashlight effectively inactivated a thick biofilm of one of the most antibiotic- and heat-resistant bacteria, Enterococcus faecalisa—which often infects the root canals during dental treatments.

The team created the biofilms by incubating the bacteria for seven days. The biofilms were around 25 µm thick and consisted of 17 different layers of bacteria; each one was treated for five minutes with the plasma flashlight and then analyzed 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. For individual bacteria, inactivation time could be just tens of seconds, says Professor Kostya (Ken) Ostrikov of the Plasma Nanoscience Centre Australia, CSIRO Materials Science and Engineering, who co-authored the study.

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°–230°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. What's more, the device costs less that $100 to produce, says Ostrikov, and miniaturization and engineering design to make the device more appealing for commercialization is in the works as well.

The full work has been published in the Journal of Physics D: Applied Physics; please visit http://iopscience.iop.org/0022-3727/45/16/165205.

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