“Plasma Pencil” Holds Promise For Medical Use

By Jim Raper

Since the mid-1990s, Mounir Laroussi has been at the forefront of research involving the production of low-temperature plasmas, and last fall his development of a “plasma pencil” or “saber” only added to his reputation as a pioneer in the field of cold plasmas.

The plasma pencil represents Laroussi’s latest achievements in the production of cheap and reliable cold plasma. His easy-to-handle device is about 5 inches long and 1 inch in diameter, and produces a plasma jet or plume that is adjustable from one-half to 2 inches in length.

He envisions the device being used to disinfect small articles or surfaces, to treat wounds and even to attack plaque-making bacteria in the mouth. He believes that one day such a device could destroy tumors without damaging surrounding tissue.

Laroussi is an associate professor of electrical and computer engineering and a researcher at the Frank Reidy Research Center for Bioelectrics, which is operated by Old Dominion and Eastern Virginia Medical School. He was assisted in the development of the plasma jet by Xin Pei Lu, a postdoctoral researcher at the Reidy Center. Wayne Hynes, associate professor of biological sciences, and Fred Dobbs, associate professor of ocean, earth and atmospheric sciences, also were project collaborators.

Plasmas, sometimes called the fourth state of matter along with solids, liquids and gases, are generated anywhere atoms are stripped of electrons, creating soups of neutral particles, charged ions and electrons. Plasmas can be found in solar flares and around lightning bolts, and, in fact, make up 99 percent of the known universe because of their common presence in interstellar space. In the denser Earth’s atmosphere, most plasmas are super hot and hard to control.

Cold plasmas are generated when an electrical source is tailored to kick lighter electrons into high speeds without doing the same for heavier ions. This can be done with electricity that is turned on and off – or pulsed – thousands of times a second. The relative inactivity of the ions eliminates the high heat that plasmas can develop in the Earth’s atmosphere and gives researchers the more manageable cold plasmas.

Unlike other hand-held plasma jets, Laroussi’s device poses no risk of arcing or heating up during prolonged use. Its plume produces only a slight tingle, and no harm, when it is directed at human skin. Nevertheless, highly reactive oxygen atoms in the plume can attack bacteria. The Reidy Center is developing and experimenting with technologies that would allow the precise elimination of cancer cells.

Laroussi said he liked the description of his new plasma device used on the Nature.com Web site. “The writer called it a light saber. And that is just what it looks like, a saber to kill bad cells.” His research was also highlighted in a February 2006 National Geographic story, “The fourth state of matter.”

Mohammad A. Karim, ODU vice president for research, said Laroussi “has significantly advanced the state of the art. His plasma pencil is very small and can work at least eight hours at a time. While surgical blades often damage surrounding tissues, the plasma pencil can be suitably adapted to kill cancer cells, only a few layers at a time.”

Laroussi has developed larger cold-plasma generators in the last five years, and applications on scales larger than the pencil could revolutionize sterilization processes for hospitals, industry and the military, he said.

He also received a patent in February 2005 for a new type of ultraviolet lamp – UV and fluorescent lamps also utilize plasma – that is ultra-efficient and can be used to disinfect articles and purify water. Patents are pending on his cold plasma innovations.

Last summer, Laroussi was interviewed by the Discovery Channel about potential use of cold plasmas for defensive shields in space. A plasma field enveloping an aircraft, a missile or a satellite could, theoretically, neutralize bursts of microwaves or particle beams fired by an enemy from Earth or an aircraft. The same kind of field may someday “cloak” aircraft by redirecting enemy radar.