Control of ion activation energy delivered to tissue and sensitive materials in atmospheric pressure plasmas using thin porous dielectric sheets

Abstract

In atmospheric pressure discharges, such as dielectric barrier discharges (DBDs), it is common to have transient sheaths having electric fields of hundreds of kV cm−1. With these sheaths, even with short mean free paths, it may be possible to deliver short pulses of energetic ions (tens to hundreds of eV) to surfaces. The energies of these ions can be controlled to some extent by selecting the relative permittivity (ε/ε0) of the underlying surface. In using DBDs to treat sensitive materials or tissue in plasma medicine where control of ion energies may be desirable, one has a very limited ability, if any, to modify the dielectric properties of the tissue. In this paper, we use results from a computational study to propose a method to control the characteristics of the transient sheath formed at the surface of sensitive materials or biological tissue by using a thin porous film placed on top of the surface. By controlling the transient sheath, one can control the ion energies delivered to the surface. We show that ion energies delivered to the underlying surface through the pores can be controlled by the capacitance and thickness of the film and the width of the pore. Results are discussed for streamer penetration and ion energies delivered to the surface when the plasma filament directly strikes the pore and is offset from the pore.