An inexpensive, plasma-producing flashlight powered by a 12 V battery and able to kill skin bacteria instantly could help first responders treat victims of emergencies in remote locations. In experiments, the handheld device—created by an international team from Huazhong University of Science and Technology (Wuhan, China), CSIRO Materials Science and Engineering (Clayton, South Australia), the University of Sydney (Australia), and the City University of Hong Kong—proved able to effectively inactivate a 25-µm-thick film of one of the most antibiotic- and heat-resistant bacteria, Enterococcus faecalisa, which often infects root canals during dental treatments. This is the thickest reported biofilm inactivated using room-temperature air plasmas, according to the researchers.1
The team created the biofilms by incubating the bacteria for seven days and applying 17 different layers of bacteria. After treating each biofilm for five minutes with the plasma flashlight—which produces room-temperature plasma in self-repetitive discharges with current pulses of ~100 ns duration, current peak amplitude of ~6 mA, and repetition rate of ~20 kHz—the researchers analyzed the samples. 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 at CSIRO, who co-authored the study.
The researchers found that highly reactive nitrogen- and oxygen-related species dominated the results. The device costs less than $100 to produce; miniaturization and engineering work is ongoing to prepare the device for commercialization.
1. X. Pei et al., J. Phys. D: Appl. Phys., 45, 165205 (2012).
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