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F. S. DENES, Dept. of Biological Systems Engineering, Univ. of Wisconsin, Madison, 460 Henry Mall, Madison, WI 53706 Broadly the plasma state can be considered to be a gaseous mixture of oppositely-charged particles with a zero net electrical charge. Sir William Crooks suggested the concept of the “fourth state of matter” (1879) for electrically discharged matter and Irving Langmuir used first the term “plasma” to denote the state of gases in discharge tubes. Most electrical discharge processes are initiated and sustained by electron impact ionization phenomena. The plasma-state is created when “omni-present” free electrons in a gas environment are accelerated by an electric or an electromagnetic field to energy levels when ionization and molecular fragmentation processes occur through non-elastic collision mechanisms. Cold plasmas are composed of low temperature particles (charged and neutral molecular and atomic species) and relatively high temperature electrons and they are associated with low degrees of ionization (10-4-10 %). The energy levels of plasma-species are comparable with the common bond-energies of organic compounds and organic compounds containing main-group elements, and accordingly these species can interact and alter all chemical bonds of gas- and liquid-phase molecules, and molecular structures of surface layers of solid-phase materials. This plasma-enhanced, dry-chemistry approach opens up a non-conventional way for the functionalization of various material surfaces, covalent implantation of active biomolecules and for the deposition of bioactive macromolecular thin layers on selected substrate surfaces. In this presentation, cold-plasma-enhanced surface-fnctionalization, implantation of active biomolecules (e.g. enzymes and DNA), plasma-enhanced deposition of PEG-type anti-fouling thin layers, and generation of material surfaces that kill bacteria on contact will be discussed. The potentials of non-equilibrium plasma approach will be discussed.
Session 51, Biofilms in the food environment: Current approaches and findings
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