Plasma, the fourth state of matter, is a powerful tool for critical cleaning, controlling contamination, and achieving the appropriate surface quality. A wide range of applications are in use; even more have been proposed. Examples include removing minute traces of contamination from semiconductor wafers, preparing surfaces for coatings, removing masks and markings, decontaminating and sterilizing medical devices, and skin rejuvenation.

In the previous column we explained that plasma is a mixture of atoms, ions, and electrons that result when sufficient energy (heat or voltage) is applied to a gas. The efficacy of plasma for surface modification and cleaning is due to the energy of the plasma particles and/or the ultraviolet light they emit as well as from chemical interaction of plasma constituents with surface molecules.

There is versatility provided by plasma parameters including the choice of gas and the pressure mode, vacuum or atmospheric. Two out of many areas of applicability include medical device cleaning and surface preparation for bonding and coating.

MEDICAL DEVICE PROCESSING
Because plasma can destroy as well as remove protein, there is potential utility in biomedical applications, including cleaning of reusable medical instruments such as forceps and dental drills. Plasma cleaning could be inserted as an added step between washing and autoclaving for high risk situations. A result of research conducted at The University of Edinburgh¹ indicates that plasmas can destroy and remove proteins, including prions that are believed to cause Transmissible Spongiform Encephalopathy (TSE) or “Mad Cow Disease.”