05 April 2012

Portable Handheld Plasma Flashlight Sterilizes and Kills Bacteria in an Instant

Plasma Light Gun
Plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Compared to gasses, the atoms of plasma are different because they are made up of free electrons and ions of the element. The word "PLASMA" was first applied to ionized gas in 1929 by American chemist and physicist, Dr. Irving Langmuir.

A common example of plasma can be found in fluorescent light bulbs and neon signs. Inside the long tubes of the sign and the bulb is a gas. Electricity flows through the tube when the light is turned on. The electricity acts as that special energy and charges up the gas. This charging and exciting of the atoms creates glowing plasma inside the bulb.

Plasma Medicine

Plasma medicine combines physics, life sciences and clinical medicine to apply plasma in therapeutic and medical applications. Plasma can be effective in sterilizing living tissue without affecting surrounding cells and can also stimulate tissue regeneration. Based on research on plasma-tissue interaction, first therapeutic applications in wound healing, dermatology and dentistry will be opened.

Plasma is also a source of UV-photons. These plasma-generated active species are useful for several bio-medical applications such as sterilization of implants and surgical instruments. Sensitive applications of plasma, like subjecting human body or internal organs to plasma treatment for medical purposes, are also possible.

Handheld plasma flashlight rids skin of notorious pathogens

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 which was presented April, in IOP Publishing's 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.

Video: Sterilizing Food With Plasma Technology

The biofilms were created by incubating the bacteria for seven days. The biofilms were around 25 micrometres 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 our skin.

"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 of seconds."

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 anti-bacterial 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 theorised 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 20-230C, 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 US dollars to produce. Of course, some miniaturisation and engineering design may be needed to make it more appealing and ready for commercialisation," 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.


Institute of Physics
Journal of Physics D: Applied Physics
CSIRO Materials Science and Engineering
The University of Sydney
City University of Hong Kong
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