Spatially confined air microplasmas in an array of microcavity devices with asymmetric air flow geometry

Summary form only given. Arrays of microcavity devices designed for the operation in a forced flow of laboratory air. Microcavities having a diameter of 100 ~300 μm and are encapsulated and protected with a Al₂O₃ ring-shaped dielectric for the protection from plasma sputtering. With a micropatterning process by simple lithography and a microfabrication technique for microcavity formation, precise control of microcavity and its array geometry was obtained with an accuracy of less than 5 %. In particular, to control the plasma properties and flow dynamics of air inside the microcavities of device, the shape of microcavity has been modified to be asymmetric between electrodes. The device was stably operated in air with flow rate of 180-6000 cfm which are equivalent to the velocity of 2.5-7 m/s. Confinement of air plasma inside the microcavity was measured by optical microscopy and ozone generation from the array was measured quantitatively by calibrated UV absorption spectroscopy. Detailed performance and spatial distribution of microdischarges in different air flow rates will discussed in this presentation.