Modeling Studies of Atmospheric Pressure Microplasmas: Plasma Dynamics, Surface Interaction

Technologies based on atmospheric-pressure microplasmas (APMs) have been widely developed due to their unique nature such as its non-equilibrium state and capability for high pressure operation. Electrophotographic printing, sensors, surface functionalization and plasma medicine are typical applications of APMs. However, obtaining accurate measurements of key plasma parameters is challenging due to the complicated plasma dynamics and the small spatial and temporal scales. In this work, results from a computational investigation of APMs using a two-dimensional, multi-fluid simulation platform are discussed with the goal of improving our fundamental understanding of the nonlinear plasma kinetics of APMs, and to provide design rules for the devices of interest. In this thesis, the following problems are discussed: Micro-dielectric barrier discharges (mDBD’s) consist of micro-plasma devices (10-100 μm diameter) are finding continued use in the printing technologies. In a print head used for ionography, for example, a third electrode is desirable to extract electron current out of the mDBD. As a result, the physical structure of micro-DBD and the electron emitting properties are important to its operation. The characteristics of mDBD current extraction for frequencies from 2.5 to 25 MHz are discussed. After an electron avalanche in the mDBD cavity, the plasma can be attracted to the bottom dielectric or expelled from the mDBD’s cavity towards the extraction electrode as the rf voltage varies. The electron current extraction and charge collection can be controlled by choice of rf frequency, rf driving voltage and permittivity of the dielectric barrier.