Invited Paper PS+EM-MoM5
Cold Atmospheric Microplasma Arrays for Processing of Flexible Materials

Monday, October 29, 2012, 9:40 am, Room 24

Microplasmas offer a pathway to atmospheric pressure plasma processing using low-temperature, low-cost substrates. Unlike arc and torch technologies, the atmospheric microplasma typically operates near room temperature. Corona discharges share this distinction, but modern microplasma devices produce electron densities that are several orders of magnitude greater than the corona. The combination of low gas temperature and high electron density suggests that a unique process window exists for deposition, etching, and surface modification of flexible materials at atmospheric pressure. In this lecture, we describe the plasma physics of a steady-state microplasma excited by 1 GHz microwave power. Spatially resolved laser diode absorption, imaging spectroscopy, and electrical probe measurements show that the individual microdischarge has an intense inner core surrounded by a cooler region that is rich in metastable atoms. These physical insights are combined with data from deposition experiments using acetylene mixed with a helium gas flow. High densities of electrons and energetic species produced by steady-state microplasmas are believed to be crucial to quality film formation at one atmosphere. Finally, we explore scaling the microplasma toward roll coating geometries. Linear arrays of microplasmas are excited from a single microwave power source through the use of resonant energy sharing. This technique allows over 100 microplasmas to operate in parallel without the usual problem of instabilities induced by ionization overheating and negative differential discharge resistance. This work was supported in part by the U.S. Department of Energy under award No. DE-SC0001923 and by the National Science Foundation under Grant No. CBET-0755761.