Applications of Microplasmas and Microreactor Technology

During the last decade a number of microcavity plasma devices have been developed. Examples are microhollow cathode (MHC) discharges and cathode boundary layer (CBL) discharges proposed by Schoenbach, capillary plasma electrode (CPE) discharges proposed by Kunhardt and Becker, and micro-structured electrode arrays (MSEs) introduced by Gericke and Penache. Arrays of microplasmas based on silicon, ceramic, or metal/polymer structures were investigated by Eden, Frame, Park and coworkers. A breakthrough in the life expectancy of such devices was achieved when all metal electrodes were covered by dielectrics, thus combining dielectric-barrier discharge technology with microcavity plasma devices. The advantage of this technology is that large numbers of miniature atmospheric-pressure non-equilibrium discharges can be operated in parallel. Applications include emitters for visible and UV radiation, photodetectors, sensors, decontamination, surface modification, etching, film deposition, generation of nanoparticles. Operated in different gas mixtures many of these devices proved to be efficient emitters of ultraviolet excimer radiation. If a small gas flow is fed through these microplasmas applications for plasmachemical synthesis and pollution control become feasible. Novel applications are expected from the combination of microreactor technology with non-equilibrium plasma chemistry. Doping or coating of the dielectric surfaces results in additional catalytic effects.