NEW USE FOR PLASMA PENCIL REPORTED BY LAROUSSI

The plasma pencil that Mounir Laroussi created more than five years ago was hailed in publications throughout the world, including National Geographic, as an easy-to-use, miniature light saber for germ-killing applications. Now, in an article published by AIP (American Institute of Physics) Advances, the Old Dominion University electrical engineering professor is reporting an innovative new use for the pencil: the ignition of a large-volume cold plasma.

Both cold and conventional plasmas have been shown to kill germs, but the cold version has gotten more attention for bio-medical applications because it is safer and easier to use. Laroussi's new application uses the plasma pencil, which is about the size of an electric toothbrush, to ignite a much larger volume of cold plasma.

In recent laboratory experiments, Laroussi and graduate student ArdaAkman shot the plume from the pencil into a Pyrex chamber. A vacuum tube connected to the chamber allowed the pressure to be regulated inside. By lowering the pressure, fewer air molecules would interact with the helium gas in the plasma jet, theoretically producing a longer plume.

But strange things happened as they took the pressure down.

"The sudden shortening of the plume, immediately followed by the ignition of a large-volume, uniform plasma is an intriguing new observation and constitutes an interesting transition mode (from jet) that beckons further detailed investigations, which can lead to various interesting applications," Laroussi and Akman wrote in the article, which was given highlight treatment this month in AIP Advances.

Laroussi said in an interview that the "neat" innovation he and Akman are reporting is the way such a large volume of plasma can be created so easily and cheaply. "Another way to generate a comparable large volume of plasma would be to launch high-power microwaves or radio-frequency power to ignite a gas in an evacuated chamber, but RF and microwave circuitry are quite complicated, expensive and require special skills to operate. In our case, the igniter is a little plasma plume generated by simple means."

Plasma-filled chambers have been proposed to sterilize all sorts of containers and products headed for market. Experiments have shown them to be useful for sterilization, treatment of disease and wound healing.