The plasma pencil is a dielectric tube where two disk-shaped electrodes of about the same diameter as the tube are inserted, and are separated by a small gap. Each of the two electrodes is made of a thin

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

ring attached to the surface of a centrally perforated

dielectric In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the mate ...

disk. The

plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral), a green translucent silica mineral * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood pla ...

is ignited when nanoseconds-wide high voltage pulses at kHz repetition rate are applied between the two electrodes and a gas mixture (such as

helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...

and

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

) is flown through the holes of the electrodes. When a plasma is ignited in the gap between the electrodes, a plasma plume reaching lengths up to 12 cm is launched through the aperture of the outer electrode and into the surrounding room air. The cold plasma plume emitted by the plasma pencil can be used to kill

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

without harming skin tissue. Applications of the plasma pencil are in

wound A wound is a rapid onset of injury that involves laceration, lacerated or puncture wound, punctured skin (an ''open'' wound), or a bruise, contusion (a ''closed'' wound) from blunt force physical trauma, trauma or compression. In pathology, a '' ...

healing, killing of oral bacteria, and in controlled surface modification of heat-sensitive materials. The plasma pencil was invented by

Mounir Laroussi Mounir Laroussi (born August 9, 1955) is a Tunisian-American scientist. He is known for his work in plasma science, especially low temperature plasmas and their biomedical applications. Biography Early life Mounir Laroussi was born and rais ...

, a plasma science professor at Old Dominion University, Norfolk, VA, USA.

Sources

* *{{cite journal , last1=Laroussi , first1=Mounir , last2=Tendero , first2=Claire , last3=Lu , first3=Xinpei , last4=Alla , first4=Sudhakar , last5=Hynes , first5=Wayne L. , title=Inactivation of Bacteria by the Plasma Pencil , journal=Plasma Processes and Polymers , publisher=Wiley , volume=3 , issue=6–7 , date=2006-08-15 , issn=1612-8850 , doi=10.1002/ppap.200600005 , pages=470–473

External links

* https://abcnews.go.com/health/ColdandFluNews/story?id=5987227&page=7
www.nature.com/news/2005/050919/full/news050919-13.html
Dielectrics